USE OF DIALKYLENE GLYCOL ESTER TO INCREASE THE OXIDATION RESISTANCE OF A LUBRICANT COMPOSITION

Abstract

The present invention relates to the use of at least one diester having formula (I) in a lubricant composition containing at least one base oil, so as to increase the oxidation resistance of said lubricant composition or to decrease the oxidation level of said lubricant composition,

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

Claims

1.-8. (canceled)

9. A method to increase the oxidation resistance of a lubricant composition comprising at least one base oil, comprising the addition to said lubricant composition of at least one diester of formula (I)
R.sup.a—C(O)—O—([C(R).sub.2].sub.n—O).sub.s—C(O)—R.sup.b   (I) where: R, each independently, are a hydrogen atom or a linear or branched alkyl group having 1 to 5 carbon atoms; s is 1 or 2; n is 1, 2 or 3, on the understanding that when s differs from 1, the n values can be the same or different; Ra and Rb, the same or different, are each independently linear or branched, saturated or unsaturated hydrocarbon groups having a linear sequence of 6 to 18 carbon atoms; provided that when s is 2, and n all the same are 2, at least one of the R groups is a linear or branched alkyl group having 1 to 5 carbons atoms; and provided that when s is 1, and n is 3, at least one of the R groups linked to the carbon at beta position of the oxygen atoms of the ester functions, represents a hydrogen atom.

10. A method for decreasing the oxidation level of a lubricant composition comprising at least one base oil, comprising the addition to said lubricant composition of at least one diester of formula (I)
R.sup.a—C(O)—O—([C(R).sub.2].sub.n—O).sub.s—C(O)—R.sup.b   (I) where: R, each independently, are a hydrogen atom or a linear or branched alkyl group having 1 to 5 carbon atoms; s is 1 or 2; n is 1, 2 or 3, on the understanding that when s differs from 1, the n values can be the same or different; Ra and Rb, the same or different, are each independently linear or branched, saturated or unsaturated hydrocarbon groups having a linear sequence of 6 to 18 carbon atoms; provided that when s is 2, and n all the same are 2, at least one of the R groups is a linear or branched alkyl group having 1 to 5 carbon atoms; and provided that when s is 1, and n is 3, at least one of the R groups linked to the carbon at beta position of the oxygen atoms of the ester functions, represents a hydrogen atom.

11. The method of claim 9, wherein when s differs from 1 all the n values are the same.

12. The method of claim 9, wherein n is 2 or 3.

13. The method of claim 9, wherein at least one of the R groups is a linear or branched alkyl group having 1 to 5 carbon atoms.

14. The method of claim 9, wherein the diester of formula (I) of the invention is a diester of following formula (I′):
R.sup.a—C(O)—O—([C(R).sub.2].sub.n—O)—([C(R′).sub.2].sub.m—O).sub.s-1—C(O)—R.sup.b   (I′) where: R and R′ each independently are a hydrogen atom or a linear or branched alkyl group having 1 to 5 carbon atoms; s is 1 or 2; n is 2; m is 2; Ra and Rb, the same or different, are each independently linear or branched, saturated or unsaturated hydrocarbon groups having a linear sequence of 6 to 18 carbon atoms; provided that when s is 2, at least one of the groups R or R′ is a linear or branched alkyl group having 1 to 5 carbon atoms.

15. The method of claim 9, wherein the diester is a compound of formula (I″a)
R.sup.a—C(O)—O—CHR.sup.1—CHR.sup.2—O—CHR.sup.3—CHR.sup.4—O—C(O)—R.sup.b   (I″a) where: one of the groups R.sup.1 and R.sup.2 is a linear or branched alkyl group having 1 to 5 carbon atoms, the other representing a hydrogen atom; one of the groups R.sup.3 and R.sup.4 is a linear or branched alkyl group having 1 to 5 carbon atoms, the other representing a hydrogen atom.

16. The method of claim 9, wherein the diester of formula (I) is added in a proportion of 10 to 70% by weight relative to the total weight of the lubricant composition.

17. The method of claim 10, wherein when s differs from 1 all the n values are the same.

18. The method of claim 10, wherein n is 2 or 3.

19. The method of claim 10, wherein at least one of the R groups is a linear or branched alkyl group having 1 to 5 carbon atoms.

20. The method of claim 10, wherein the diester of formula (I) of the invention is a diester of following formula (I′):
R.sup.a—C(O)—O—([C(R).sub.2].sub.n—O)—([C(R′).sub.2].sub.m—O).sub.s-1—C(O)—R.sup.b   (I′) where: R and R′ each independently are a hydrogen atom or a linear or branched alkyl group having 1 to 5 carbon atoms; s is 1 or 2; n is 2; m is 2; Ra and Rb, the same or different, are each independently linear or branched, saturated or unsaturated hydrocarbon groups having a linear sequence of 6 to 18 carbon atoms; provided that when s is 2, at least one of the groups R or R′ is a linear or branched alkyl group having 1 to 5 carbon atoms.

21. The method of claim 10, wherein the diester is a compound of formula (I″a)
R.sup.a—C(O)—O—CHR.sup.1—CHR.sup.2—O—CHR.sup.3—CHR.sup.4—O—C(O)—R.sup.b   (I″a) where: one of the groups R.sup.1 and R.sup.2 is a linear or branched alkyl group having 1 to 5 carbon atoms, the other representing a hydrogen atom; one of the groups R.sup.3 and R.sup.4 is a linear or branched alkyl group having 1 to 5 carbon atoms, the other representing a hydrogen atom.

22. The method of claim 10, wherein the diester of formula (I) is added in a proportion of 10 to 70% by weight relative to the total weight of the lubricant composition.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0136] FIG. 1 gives the KV40 values as a function of time for the compositions of the invention and the comparative compositions.

[0137] FIG. 2 gives the KV100 values as a function of time for the compositions of the invention and the comparative compositions.

DETAILED DESCRIPTION

[0138] The present application is now described with the aid of nonlimiting examples.

Example 1: Lubricant Compositions

[0139] The lubricant compositions described in Table 2 were prepared (CC2, CC3, CC4 and CC5 are comparative compositions, C2 and C3 are compositions of the invention).

TABLE-US-00002 TABLE 2 C2 CC2 CC3 C3 CC4 CC5 wt. (%) (wt. %) (wt. %) (wt. %) (wt. %) (wt. %) Additive 12.7  12.7  12.7  12.7  12.7  12.7  package (comprising detergent(s), dispersant(s) & antioxidant(s)) Antioxidant 0.5 0.5 0.5 0.5 0.5 0.5 MoDTC 0.5 0.5 0.5 0.5 0.5 0.5 Viscosity 4.4 4.4 4.4 4.4 4.4 4.4 modifiers Base oil KV100: 20   18   81.7  31.7  30   42.7  4.181 mm2/s Base oil KV100: 43.7  2.978 mm2/s Base oil KV100: 35   51.7  39   3.317 mm2/s Base oil KV100: 10   4.026 mm2/s Base oil KV100: 10   5.919 mm2/s C9/C12 diester 61.7  15   of propylene glycol V1-258 0.2 0.2 0.2 0.2 0.2 0.2

Example 2: Characteristics of the Lubricant Compositions

[0140] Table 3 below groups together the characteristics of the lubricant compositions in Example 1.

[0141] The KV100 and KV40 values were measured according to standard ASTMD445 and expressed in mm2/s.

[0142] VI was measured according to standard ISO2909.

[0143] HTHS was measured according to standard CEC L-036 and expressed in mPa.Math.s

TABLE-US-00003 TABLE 3 C2 CC2 CC3 C3 CC4 CC5 BOV (Base oil viscosity calculated 3.6 3.6 4.2 3.6 3.6 3.8 taking into account the mixture of viscosities and proportions of base oils contained in the composition) Noack (CEC L-40-A-93) 11.7 24.5 11.7 18.4 21.1 18.6 KV100 6.66 7.405 8.272 7.285 7.439 7.638 KV40 27.9 36.82 42.18 34.57 36.75 38.03 VI 209 172 176 183 174 175 HTHS at 150° Ravenfield 2.44 2.36

Example 3: Impact of the Diester of the Invention on Oxidation

[0144] The KV100 and KV40 values of compositions C2, CC2, CC3, C3, CC4 and CC5 were measured as a function of time according to standard ASTMD445. Measurements were taken after 3 days, 4 days, 5 days, 6 days, 7 days, 8 days and 9 dawns with the following protocol:

[0145] In a container containing the compositions to be tested, air was injected at a flow rate of 10 L.Math.h−1 throughout the entire duration of the test. Iron was also added in an amount of 100 ppm at T0 to stimulate/catalyse oxidation of the tested compositions. In addition, the container containing the tested compositions was left throughout the entire duration of the test over a hot water bath heated to 170° C.

[0146] The results are given in FIGS. 1 and 2.

[0147] As and when the polar compounds of oxidation started to form, after entry of the oxygenated compounds into the structure of the lubricant composition, the viscosity of the lubricant composition increased.

[0148] FIGS. 1 and 2 clearly show that the addition of the diester of the invention allows limiting and delaying of the increase in viscosity of the lubricant composition. Therefore, the diester of the invention allows an increase in oxidation resistance and decrease (or lowering) of the oxidation level thereof.