LOW TEMPERATURE DIELECTRIC FLUID COMPOSITIONS

Abstract

The present invention relates to an ester composition that is suitable for successful operation in a dielectric fluid at extreme low temperatures, such as below about minus 50 C., without compromising the dielectric properties of the composition. The invention also relates to methods of manufacturing the ester composition and a dielectric fluid composition containing it.

Claims

1. An ester composition, wherein the ester composition comprises a plurality of esters derived from a reaction of: i) one or more polyols, wherein the one or more polyols are each independently a straight chain or branched C.sub.2-C.sub.8 polyol; and ii) two or more carboxylic acids, wherein the carboxylic acids are each independently a straight chain or branched C.sub.4-C.sub.12 carboxylic acid.

2. An ester composition according to claim 1, wherein the one or more polyols are each independently selected from straight or branched C.sub.2 to C.sub.5 polyols.

3. An ester composition according to claim 2, wherein the one or more polyols each independently have a C.sub.2 to C.sub.3 backbone and one or more C.sub.1 or C.sub.2 hydrocarbon side groups.

4. An ester composition according to any preceding claim, wherein the one or more polyols each independently comprise neopentyl glycol (NPG), glycerol, butane diol, ethylene glycol or propylene glycol.

5. An ester composition according to any preceding claim, wherein only one polyol is used.

6. An ester composition according to claim 5, wherein the polyol comprises neopentyl glycol.

7. An ester composition according to any preceding claim, wherein the one or more polyols each react only with first and second carboxylic acids.

8. An ester composition according to claim 7, wherein the first carboxylic acid comprises a C.sub.7, C.sub.8, or C.sub.9 acid.

9. An ester composition according to claim 8, wherein the first carboxylic acid comprises a branched C.sub.8 acid.

10. An ester composition according to claim 8 or claim 9, wherein the first carboxylic acid comprises 2-ethylhexanoic acid.

11. An ester composition according to any of claims 7-10, wherein the second carboxylic acid is selected from a straight chain C.sub.8, C.sub.9, or C.sub.10 acid.

12. An ester composition according to any of claims 7-11, wherein the second carboxylic acid is n-nonanoic acid.

13. An ester composition according to any preceding claim, wherein the one or more polyols comprise neopentylglycol, and the one or more polyols react only with first and second carboxylic acids, wherein the first carboxylic acid is 2-ethylhexanoic acid, and the second carboxylic acid is n-nonanoic acid.

14. An ester composition according to claim 13, wherein the one or more polyols comprise about 60-95 wt % 2-ethylhexanoic acid and about 5-40 wt % n-nonanoic acid.

15. An ester composition according to any preceding claim, wherein the one or more polyols each react with first, second and third carboxylic acids.

16. An ester composition according to claim 15, wherein the first carboxylic acid comprises a C.sub.7, C.sub.8, or C.sub.9 acid.

17. An ester composition according to claim 16, wherein the first carboxylic acid comprises a branched C.sub.8 acid.

18. An ester composition according to claim 16 or claim 17, wherein the first carboxylic acid comprises 2-ethylhexanoic acid.

19. An ester composition according to any of claims 16-18, wherein the second and third carboxylic acids are different to each other and are each independently selected from a straight chain or branched C.sub.8, C.sub.9, or C.sub.10 acid.

20. An ester composition according to claim 19, wherein the second and third carboxylic acids are different to each other and are each independently selected from n-octanoic acid, n-decanoic acid, or isononanoic acid (3,5,5-trimethylhexanoic acid).

21. An ester composition according to any preceding claim, wherein the one or more polyols comprise neopentaglycol, and the one or more polyols react with first, second and third carboxylic acids, wherein the first carboxylic acid is 2-ethylhexanoic acid, and the second and third carboxylic acids comprise a mixture of two different straight chain or branched C.sub.8, C.sub.9, or C.sub.10 carboxylic acids.

22. An ester composition according to claim 21, wherein the second and third carboxylic acids comprise a mixture of n-octanoic acid and decanoic acid.

23. An ester composition according to claim 22, wherein the second and third carboxylic acids comprise a mixture of about 50-70 wt % n-octanoic acid and about 30-50 wt % decanoic acid.

24. An ester composition according to any of claims 16-23, wherein the mixture of the first, second and third carboxylic acids comprises between about 70 to about 90 wt % of the first carboxylic acid and between about 10 to about 30 wt % of a combination of the second and third carboxylic acids.

25. A dielectric fluid composition comprising: (I) an ester composition according to any of claims 1-24; and (II) one or more additives.

26. A dielectric fluid composition according to claim 25, wherein the additives are selected from antioxidants, metal deactivators and pour point depressants, and combinations thereof.

27. A dielectric fluid composition according to claim 25, wherein the additives do not include a pour point depressant.

28. A dielectric fluid composition according to any of claims 25-27, wherein the dielectric fluid composition comprises the ester composition (I) and additives (II) in a combined amount of at least 99% by weight of the composition.

29. A dielectric fluid composition according to any of claims 26-28, wherein the dielectric fluid composition comprises an antioxidant in an amount of at least 0.0001% by weight of the composition and/or a metal deactivator in an amount of at least 0.0001% by weight of the composition.

30. An electrical apparatus containing a dielectric fluid composition according to any of claims 25-29.

31. A method of manufacturing an ester composition according to any of claims 1-24, wherein the method comprises forming a plurality of esters by reacting: (i) one or more polyols, wherein the one or more polyols are each independently a straight chain or branched C.sub.2-C.sub.8 polyol; and (ii) two or more carboxylic acids, wherein each of the carboxylic acids are independently a straight chain or branched C.sub.4-C.sub.12 carboxylic acid.

32. A method of manufacturing a dielectric fluid composition comprising an ester composition according to any of claims 1-24, wherein the method comprises combining the ester composition with an additive, wherein the ester composition comprises a plurality of esters derived from the reaction of: (i) one or more polyols, wherein the one or more polyols are each independently a straight chain or branched C.sub.2-C.sub.8 polyol; and (ii) two or more carboxylic acids, wherein each of the carboxylic acids are independently a straight chain or branched C.sub.4-C.sub.12 carboxylic acid.

33. A method according to claim 32, wherein the additives are selected from antioxidants, metal deactivators and pour point depressants, and combinations thereof.

34. A method according to claim 33, wherein the additives do not include a pour point depressant.

35. The use of an ester composition according to any of claims 1-24 and/or an ester composition manufactured according to the method of claim 25 as a dielectric fluid.

36. An ester composition, dielectric fluid composition, method of manufacturing an ester composition, method of manufacturing a dielectric fluid composition, or use of an ester composition substantially as herein described.

Description

EXAMPLE 1

[0077] Neopentyl glycol (265.6 g), 2-Ethylhexanoic acid (748 g), and an octanoic/decanoic acid blend (201.3 g, approximately 60% octanoic/40% decanoic acid) were added to a 2-Litre round bottom flask fitted with dean-stark apparatus and a condenser. The reaction mixture was stirred at 80 C. for one hour in the presence of alumina to neutralise the reaction mixture, subjected to a purifying powder treatment, and an antioxidant were added. The ester was filtered twice, a metal deactivator was added, and the ester was degassed until the moisture content of the ester was less than 80 ppm.

EXAMPLE 2

[0078] Neopentyl glycol (258.8 g), 2-Ethylhexanoic acid (745.5 g), and n-nonanoic acid blend (204.5 g) were added to a 2-Litre round bottom flask fitted with dean-stark apparatus and a condenser. The reaction mixture was stirred at 80 C. for one hour in the presence of alumina to neutralise the reaction mixture, subjected to a purifying powder treatment, and an antioxidant was added. The ester was filtered twice, a metal deactivator was added, and the ester was degassed until the moisture content of the ester was less than 80 ppm.

[0079] The properties of the ester compositions of the invention are shown in Table 1 below, together with the comparative data of the Midel 7131 commercial product.

[NOTE: I've added the example for the C9 prep. If there is anything more you would like to see taken out of the example information, let me know]

TABLE-US-00001 TABLE 1 Midel Property Units Example 1 Example 2 7131 Test Method Water content ppm 50 50 50 IEC 60814 Acid Value mgKOH/g <0.03 <0.03 <0.03 IEC 62021-2 Colour HU 100 100 125 ISO 2211 Tan delta at 90 C. and <0.03 <0.03 <0.008 IEC 60247 50 Hz Volume resistivity DC Gcm >10 >10 >30 IEC 60247 at 90 C. Breakdown voltage kV >75 >75 >75 IEC 60156 Viscosity at 100 C. cP 1.86 4.79 ISO 3104 Viscosity at 40 C. cP 6.92 26.8 Viscosity at 0 C. cP 38.6 42.1 236 Viscosity at 10 C. cP 84.4 79.4 427 Viscosity at 20 C. cP 167 172 1400 Viscosity at 30 C. cP 391 434 4229 Viscosity at 40 C. mm.sup.2 s.sup.1 1330 16090 Viscosity at 50 C. mm.sup.2 s.sup.1 5060 89160 Density at 20 C. kg dm.sup.3 0.92 0.92 0.97 ISO 3675 PMCC flash point C. 190 190 260 ISO 2719 COC fire point C. 216 220 316 ISO 2592 Pour point C. 75 72 60 ISO 3016 (modified)/ISO 3016 [NOTE: I've added the C9 data into a new column in this table, though as some of the numbers for MIdel 7131 that Francine provided earlier weren't quite the same as in the table we filed, I've left those numbers alone]
As can be seen from the above, the dielectric fluid composition of Example 1 has physical and electrical properties which render it particularly suitable for use and successful operation as a dielectric fluid in electrical apparatuses in extreme low temperatures, in contrast to the commercially available dielectric fluids which are not intended for use in such extreme conditions. In particular, the pour point is 15 C. lower for the composition of the invention, and the viscosity is significantly lower at the various temperatures at which it is measured.

[0080] Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0081] It is of course to be understood that the present invention is not intended to be restricted to the foregoing specific embodiments, which are described by way of example only. The invention extends to any novel feature, or combination of features, disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.