ESTER BASED FUNCTIONAL FLUID

Abstract

The present invention relates to the use of specific esters in a functional fluid for electric vehicles.

Claims

1. Use of an ester selected from the group consisting of: esters obtainable from esterification of a saturated branched monoalcohol comprising from 5 to 16 carbon atoms, with isostearic acid; esters obtainable from esterification of 2-hexyl-1-decanol with a saturated fatty acid comprising from 7 to 18 carbon atoms; and mixtures thereof; in a functional fluid for an electric vehicle.

2. Use according to claim 1, wherein the ester is compatible with elastomer(s), elastomer NBR 1 presenting no more than 15% change in volume and/or elastomer FKM 2 presenting no more than 2.5% change in volume, when immersed in said ester during 168 hours at 100 C.; the change in volume being measured according to the standard ISO 6072.

3. Use according to claim 1, wherein the saturated branched monoalcohol is selected from the group consisting of isoamyl alcohol, 2-ethylbutyl, 2-butylhexanol, 2-butyl-1-heptanol, 2-butyl-1-octanol, 2-pentyl-1-nonanol, 2-hexyl-1-octanol and 2-hexyl-1-decanol.

4. Use according to claim 1, wherein the saturated fatty acid is selected from the group consisting of heptanoic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, isostearic acid, and mixtures thereof.

5. Use according to claim 1, wherein the ester is selected from the group consisting of: isoamyl isostearate; 2-pentyl-1-nonyl isostearate; 2-hexyl-1-decyl isostearate; 2-hexyl-1-decyl laurate; 2-hexyl-1-decyl caprylate/caprate; and 2-hexyl-1-decyl heptanoate.

6. Use according to claim 1, wherein the ester is selected from the group consisting of: 2-pentyl-1-nonyl isostearate; 2-hexyl-1-decyl isostearate; 2-hexyl-1-decyl laurate; and 2-hexyl-1-decyl caprylate/caprate.

7. Use according to claim 1, wherein the ester is 2-hexyl-1-decyl isostearate.

8. (canceled)

9. A method for lubricating and cooling one or more device(s) in an electric vehicle, comprising bringing into contact the device(s) with an ester selected from the group consisting of: esters obtainable from esterification of a saturated branched monoalcohol comprising from 5 to 16 carbon atoms, with isostearic acid; esters obtainable from esterification of 2-hexyl-1-decanol with a fatty acid comprising from 7 to 18 carbon atoms; and mixtures thereof.

10. The method according to claim 9, wherein the ester is brought into contact via a functional fluid comprising: an ester selected from the group consisting of: isoamyl isostearate; 2-pentyl-1-nonyl isostearate; 2-hexyl-1-decyl isostearate; 2-hexyl-1-decyl laurate; 2-hexyl-1-decyl caprylate/caprate; 2-hexyl-1-decyl heptanoate; and an antioxidant additive; wherein the functional fluid does not contain any diester.

Description

[0121] The invention is further described in the following examples, given by way of illustration, with reference to the FIG. 1 representing a graph relating to the evolution of the traction coefficient of different esters and of a mineral oil of Group III, according to the slide roll ratio applied.

EXAMPLE 1

Characteristics of Esters Used According to the Invention

1.1. Chemicals Used

[0122] isoamyl isostearate: was prepared by esterification of isoamyl alcohol (from Tradebe Chemicals) with isostearic acid (Radia 0905 from Oleon); [0123] 2-pentyl-1-nonyl isostearate: was prepared by esterification of 2-pentyl-1-nonanol with isostearic acid (Radia 0905 from Oleon); [0124] 2-pentyl-1-nonanol was prepared from n-heptanol as primary alcohol according to a Guerbet reaction. Such a reaction is described for example in patent U.S. Pat. No. 4,518,810 using KOH as a base and palladium as catalyst. The reaction medium was heated up to its boiling point. The crude reaction mixture was washed several times with demineralized water to remove all of the soaps. The washed product were subsequently filtered and dried under vacuum. The remaining starting primary alcohol was separated by distillation. Then, 2-pentyl-1-nonanol was isolated by distillation. [0125] 2-hexyl-1-decyl isostearate: was prepared by esterification of 2-hexyl-1-decanol (Isofol 16 from Sasol) with isostearic acid (Radia 0905 from Oleon); [0126] 2-hexyl-1-decyl laurate: was prepared by esterification of 2-hexyl-1-decanol (Isofol 16 from Sasol) with lauric acid (Radia 0653 from Oleon); [0127] 2-hexyl-1-decyl caprate/caprylate: was prepared by esterification of 2-hexyl-1-decanol (Isofol 16 from Sasol) with capric/caprylic acid (Radia 0640 from Oleon); [0128] 2-hexyl-1-decyl heptanoate: was prepared by esterification of 2-hexyl-1-decanol (Isofol 16 from Sasol) with heptanoic acid (Oleris n-heptanoic acid from Arkema).

1.2. Lubricity Property

[0129] The lubricity of a fluid is its ability to reduce friction (friction or deformation between moving parts) and/or to reduce wear on parts.

[0130] Therefore, the lubricity property of esters was evaluated and compared to a mineral oil of Group III widely used in industrial and automotive lubricants, Nexbase 3043 from Neste comprising isoparaffinic hydrocarbons, by measuring the friction reduction using a Mini Traction Machine (MTM) device under the following conditions: [0131] Material: steel ball on steel disc [0132] Load: 75N [0133] Temperature: 80 C. [0134] Rolling speed: 1000 mm/s [0135] Slide Roll Ratio: from 0 to 100%.

[0136] The curves obtained are represented in FIG. 1.

[0137] It can be observed in FIG. 1, that the traction coefficient curve of each ester (isoamyl isostearate, 2-pentyl-1-nonyl isostearate, 2-hexyl-1-decyl isostearate, 2-hexyl-1-decyl laurate and 2-hexyl-1-decyl caprate/caprylate) is lower than the traction coefficient curve of the mineral oil of Group III.

[0138] The esters used according to the invention exhibit better lubricity property than the conventional mineral oil. In particular, 2-pentyl-1-nonyl isostearate, 2-hexyl-1-decyl isostearate, 2-hexyl-1-decyl laurate and 2-hexyl-1-decyl caprate/caprylate present the lowest traction coefficients, all lower than 0.033.

1.3. Physico-Chemical Properties

[0139] Kinematic viscosities, pour points and flash points were measured for each specific ester used according to the invention.

[0140] The oxidation stability of esters was determined using the Rotating Pressure Vessel Oxidation Test (RPVOT) according to the standard ASTM D2272, with 1.5% of add-pack (ADDITIN RC 9321 from Lanxess) comprising mainly phenolic, aminic, thiadiazole and amine phosphate antioxidant additives.

[0141] Results are gathered in Table 1 below.

TABLE-US-00001 TABLE 1 Physico-chemical properties Kinematic Kinematic viscosity viscosity Pour Flash at 40 C. at 100 C. point point RPVOT (mm.sup.2/s) (mm.sup.2/s) ( C.) ( C.) (min) isoamyl isostearate 8.6 2.6 52 208 833 2-pentyl-1-nonyl 18.6 4.3 49 222 isostearate 2-hexyl-1-decyl 21.1 4.8 51 262 900 isostearate 2-hexyl-1-decyl laurate 11.5 3.1 54 240 1380 2-hexyl-1-decyl 8.5 2.5 58 226 1320 caprate/caprylate 2-hexyl-1-decyl 6.6 2.1 56 202 heptanoate

[0142] The esters used according to the invention have a kinematic viscosity lower than 30 mm.sup.2/s at 40 C. and lower than 5 mm.sup.2/s at 100 C., a pour point lower than 40 C. and a flash point greater than 200 C. They also present a good oxidation stability, since they have a value at the RPVOT test greater than 700 min. It can also be concluded that those specific esters are compatible with usual antioxidants used in the field of lubricants with mineral base oils.

1.4. Thermal Properties

[0143] The thermal conductivity was measured according to the standard ASTM 7896.

[0144] Results are gathered in Table 2 below.

TABLE-US-00002 TABLE 2 Thermal properties Thermal conductivity at 20 C. (W/m .Math. C.) isoamyl isostearate 0.137 2-pentyl-1-nonyl isostearate 0.152 2-hexyl-1-decyl isostearate 0.148 2-hexyl-1-decyl laurate 0.153 2-hexyl-1-decyl 0.148 caprate/caprylate

[0145] The esters used according to the invention present a good thermal conductivity. Since the thermal conductivity is the ability to conduct heat, those esters can be used as coolants.

1.5. Electrical Properties

[0146] The dielectric breakdown was measured according to the standard ASTM D877.

[0147] Results are gathered in Table 3 below.

TABLE-US-00003 TABLE 3 Electrical properties Dielectric breakdown at 20 C. (kV) isoamyl isostearate 40.8 2-hexyl-1-decyl isostearate 38 2-hexyl-1-decyl laurate 32 2-hexyl-1-decyl heptanoate 56.3 2-hexyl-1-decyl caprate/caprylate 55.4

[0148] The dielectric breakdown are higher than 30 kV, meaning the esters used according to the invention can each be used as a dielectric fluid.

1.6. Elastomers Compatibility Properties

[0149] The compatibility of esters with elastomers was measured according to the standard ISO 6072 by immersing each elastomer in an ester for 168 hours at 100 C.

[0150] Results are gathered in Table 4 below.

TABLE-US-00004 TABLE 4 Elastomers NBR1, HNBR and FMK2 compatibility properties NBR1 HNBR1 FMK2 Volume Volume Volume change change change (%) (%) (%) isoamyl isostearate 14.4 14 1.3 2-pentyl-1-nonyl isostearate 7.27 6.34 0.54 2-hexyl-1-decyl isostearate 5.52 4.99 2.04 2-hexyl-1-decyl laurate 7.32 0.35 2-hexyl-1-decyl caprate/caprylate 9.92 0.54 2-hexyl-1-decyl heptanoate 13.4 1.20

[0151] The esters used according to the invention present a good compatibility with elastomers. In particular, it was observed less than 15% change in volume with elastomer NBR 1, and less than 2.5% change in volume with elastomer FKM 2, when they were immersed in esters used according to the invention, change in volume being measured according to the standard ISO 6072 after 168 hours at 100 C.

[0152] The compatibility of esters with following elastomers: [0153] ethylene acrylic (AEM): Vamac 7900 from Jeantet Elastomres; [0154] polyacrylate (ACM): HyTemp ACM AR12 from Zeon Chemicals; [0155] was also measured by immersing each elastomer in an ester for 240 hours at 80 C.

[0156] The volume variations, expressed as percentages, are gathered in Table 5 below.

TABLE-US-00005 TABLE 5 Elastomers AEM and ACM compatibility properties AEM ACM Volume Volume change (%) change (%) 2-hexyl-1-decyl 1 2 isostearate

[0157] It can be seen that 2-hexyl-1-decyl isostearate has a slight effect on the volume of the elastomers AEM and ACM. It can then be concluded that 2-hexyl-1-decyl isostearate presents a good compatibility with AEM and ACM.

1.7. Plastics Compatibility Properties

[0158] The compatibility of esters with plastics was measured by immersing each plastic in an ester for 242 hours at 80 C., and comparing the mass of each plastic before and after the immersion.

Plastics Tested:

[0159] polyamide: Ertalon 6 SA PA6 (PA6) from Mitsubishi Chemical Group; [0160] epoxy: Vetronit EGS 619 from Von Roll; [0161] polyimide (PI): Kapton HN from DuPont; [0162] polyoxymethylene (POM): Tecaform AH black from Ensinger; [0163] polyethylene terephthalate (PET): Mylar A from Dr. Dietrich; [0164] Polyurethane resin (PU): Scotchcast 40 from 3M.

[0165] The mass variations, expressed as percentages, are gathered in Table 6 below.

TABLE-US-00006 TABLE 6 Plastics compatibility properties PA6 Epoxy PI POM PET PU Mass Mass Mass Mass Mass Mass change change change change change change (%) (%) (%) (%) (%) (%) 2-hexyl-1-decyl 0.9 0 0 0 0 1.5 isostearate

[0166] It can be observed that 2-hexyl-1-decyl isostearate has poor or even no effect on the mass of the plastics. It can then be concluded that 2-hexyl-1-decyl isostearate presents a good compatibility with different plastics, especially those that may be used in an electric vehicle and that may be in direct contact with them.