AU2015258763B2

AU2015258763B2 - Dielectric fluid for electrical apparatus

Info

Publication number: AU2015258763B2
Application number: AU2015258763A
Authority: AU
Inventors: Wolodymyr CIUPRYK; Gordon Parkinson; Helen SCOTT; Lorica STOREY
Original assignee: Plus Pa Pty Ltd
Current assignee: Plus Pa Pty Ltd
Priority date: 2014-05-16
Filing date: 2015-05-14
Publication date: 2019-07-04
Anticipated expiration: 2035-05-14
Also published as: WO2015172185A1; AU2015258763A1

Abstract

A dielectric fluid composition comprising a compound selected from the group defined by formula (i) and an unsaturated fatty acid-containing oil or oleochemical, wherein formula (I) is: wherein A is a 5 or 6 membered aromatic or heterocyclic ring; R

Description

Dielectric Fluid for Electrical Apparatus

TECHNICAL FIELD [0001] The present invention relates generally to dielectric fluids for use with electrical apparatus. In particular, the invention relates to dielectric fluids for use for electrical insulation and for the dissipation of heat in electrical apparatus such as electrical transformers. The invention also relates to a composition for adding to a dielectric fluid to enhance the performance of the dielectric fluid, as well as to a dielectric fluid containing the composition.

BACKGROUND ART [0002] Dielectric fluids are typically used to insulate conducting wire windings in electrical transformers from one other. Dielectric fluids are also used in electric apparatus such as capacitors, switching gears, transmission components, distribution components, switches, regulators, circuit breakers, and autoreclosers, importantly, dielectric fluids also function to transfer heat generated during use.

[0003] There are several specific functional properties characteristic of dielectric fluids. The dielectric breakdown, or dielectric strength, for example, provides an indication of a dielectric fluid’s ability to resist electrical breakdown and is measured as the minimum voltage required to cause arcing across a specified gap between two electrodes submerged in the fluid. The impulse dielectric breakdown voltage of a dielectric fluid provides an indication of its ability to resist electrical breakdown under transient voltage stresses such as lightning strikes and power surges. The dissipation factor of a dielectric fluid is a measure of the dielectric losses in the fluid; a low dissipation factor indicates low dielectric loss and a low concentration of soluble, polar contaminants.

[0004] Because one function of a dielectric fluid is to carry and dissipate heat, factors that significantly affect the relative ability of the fluid to function as a dielectric coolant include viscosity, specific heat, thermal conductivity, and the coefficient of expansion. The values of these properties, particularly in the range of operating temperatures for the equipment at full rating, must be weighed in the selection of suitable dielectric fluids for specific applications.

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PCT/AU2015/000284 [0005] When used in a transformer in particular, a dielectric fluid is required to withstand strong electromagnetic fields and increased temperatures for extended periods of time, in order to maintain their cooling properties, such fluids must also retain their fluid characteristics. However, exposure to such high voltages and variable heat causes deterioration of many dielectric fluids over time. Such deterioration results in the failure of the insulating and/or heat dissipation properties of dielectric fluids causing disruptive discharge and power loss.

[0006] An ideal dielectric fluid demonstrates chemical and thermal stability over a long service life of 20-30 years, good electric and thermal properties as described above, low flammability (i.e. high fire and flash points), low viscosity and low pour point, miscibility with existing transformer oils, and is non-corrosive and/or compatible with the electrical equipment material to which it is exposed.

[0007] Mineral oil has been used as a dielectric fluid for many years due to its high stability under transformer operating conditions and comparatively low cost. However, mineral oil does not biodegrade readily and therefore persists in the environment. The use of mineral oil as a dielectric fluid in transformers typically results in the production of large quantities of non-biodegradable waste which are costly to dispose of. Mineral oil is also relatively flammable and for this reason has regulatory restrictions imposed upon its use and containment.

[0008] Silicone has been used as an alternative dielectric fluid due to its relatively high flash point such that it is less flammable than mineral oil. However, silicone may contain methylpolysiloxanes which can generate the highly undesirable toxic by-product formaldehyde, at high temperature.

[0009] Increasingly, however, there has been concern that the ideal dielectric fluid should also be biodegradable, non-toxic and renewable so as to exhibit little or no detrimental impact on the environment. Mono-unsaturated fatty acid-containing oils may be obtained from renewable sources (such as vegetable oil, tallow, lard, milk fat, etc) and thus are attractive candidates for substituting petroleum-based dielectric fluids.

[0010] Advantageously, mono-unsaturated fatty acid-containing oils may have higher flash and fire point characteristics than mineral oils, which ensure better safety in operation, handling, storage and transportation of such oils and thus the operational

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PCT/AU2015/000284 safety of transformers using vegetable oil-based dielectric fluids. The excellent fire safety characteristics of mono-unsaturated fatty acid-containing oil-based dielectric fluids make them ideal candidates for high voltage transformers.

[0011] Notwithstanding the above advantages, mono-unsaturated fatty acid-containing oils are susceptible to oxidative degradation, and have a higher pour point, higher dissipation factor, higher acidity number, higher moisture content and significantly higher viscosity compared to mineral oils. Many of these deficiencies can be overcome by subjecting the mono-unsaturated fatty acid-containing oils to purification processes to remove water, acid, and conductive contaminants, and a winterization process to improve the mono-unsaturated fatty acid-containing oil's pour point. Additionally, antioxidants can be added to the purified mono-unsaturated fatty acid-containing oil to enhance its oxidative stability.

[0012] Plant-based and fatty acid ester oils are increasingly being used as dielectric fluids due to their ability to biodegrade and renewability of source. Currently available plant oil-based dielectric fluids include soy-based and canola-based fluids that are relatively less flammable than mineral oil. However, the use of these oils as dielectric fluids is often limited in terms of their dielectric strength, viscosity, and performance life.

[0013] The exposure of plant-based oils to high temperatures in the presence of oxygen causes oxidation and severely impacts on the insulating properties of the oil and its ability to remain in the liquid state. Over time, oxidation of plant oil-based dielectric fluids due to thermal and electrical stress causes the production of polymers or sludge precipitates which significantly compromise the dielectric strength ofthe fluid. Soy-bean oil, in its natural form, is oxidatively unstable and polymerises when used in a transformer, often thickening to the extent that it no longer possesses the fluid characteristics required for adequate heat dissipation. As such, soy-bean oil often requires costly modification before use as a dielectric fluid by, for instance, winterization, so as to improve its pour point in cold temperatures.

[0014] There remains a need for alternative high performing biodegradable bioelectric fluids from renewable sources for use in electrical apparatus, capable of withstanding the rigors of field use involving a wide range of temperatures and which exhibit good electric and thermal properties, chemical and thermal stability, low flammability, low

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PCT/AU2015/000284 pour point, miscibility with existing transformer oils and long service life of 20-30 years comparable to existing dielectric fluids based on mineral oils.

[0015] it is against this background that the present invention has been developed. The present invention seeks to provide the consumer with a useful or commercial choice of bioelectric fluid for use in electrical apparatus.

[0016] The above discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.

SUMMARY OF INVENTION [0017] The present invention provides a dielectric fluid composition comprising a compound selected from the group defined by formula (I) and an unsaturated fatty acidcontaining oil or oleochemical, wherein formula (I) is:

wherein

A is a 5 or 6 membered aromatic or heterocyclic ring;

R_a is OH, or C_mH2_m+i wherein m = 0 - 18, or a hydrocarbyl, or a hetero-substituted hydrocarbyl group;

R_b is OH, or C_mH_2m+i wherein m = 0 - 18, or a hydrocarbyl, or a hetero-substituted hydrocarbyl group;

R_c is OH, or a hydrocarbyl, or a hetero-substituted hydrocarbyl group, or (CH2)_aCOOR_gwhere a = 1 - 10 and R_g is either H or hydrocarbyl;

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R_d - OH, or C_mH₂m+i wherein m = 0 -18;

X is a divalent bridging group such as S, O or N, or an optionally substituted or unsubstituted methylene group; and n has a value of at least 4.

[0018] There is also provided a dielectric fluid composition comprising a compound selected from the group defined by formula (II) and an unsaturated fatty acid-containing oil or oleochemical, wherein formula (II) is:

wherein

X is a divalent bridging group such as S, O or N or an optionally substituted methylene group;

R_a is a hydrogen, hydroxyl, hydrocarbyl or hetero-substituted hydrocarbyl group;

R_b is a hydrogen, hydroxyl, hydrocarbyl or hetero-substituted hydrocarbyl group;

R_c is a hydrogen, hydroxyl, hydrocarbyl or hetero-substituted hydrocarbyl group;

R_d is a hydrogen, hydroxyl, hydrocarbyl or hetero-substituted hydrocarbyl group;

and wherein either R_a is hydroxyl and Rb, R_c and R_d are independently either hydrogen, hydrocarbyl or hetero-substituted hydrocarbyl, or

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Rb and Rd are hydroxyl and R_a and R_c are independently either hydrogen, hydrocarbyl or hetero-substituted hydrocarbyl, or

Rb, R_c and Rd are hydroxyl and R_a is either hydrogen, hydrocarbyl or hetero-substituted hydrocarbyl, or

R_a and R_c are hydroxyl, and Rb and Rd are independently either hydrogen, hydrocarbyl or hetero-substituted hydrocarbyl;

and n has a value of at least 4.

[0019] There is also provided a dielectric fluid composition comprising a compound selected from the group defined by formula (III) and an unsaturated fatty acid-containing oil or oleochemical, wherein formula (III) is:

wherein

R_c is C_mH_2m+i wherein m is 0 -18;

Rh is C_mH₂m+i wherein m is 0 -18; and n is 4, 5, 6, 7 or 8.

[0020] There is also provided a dielectric fluid composition comprising a compound selected from the group defined by formula (IV), and an unsaturated fatty acidcontaining oil or oleochemical, wherein formula (IV) is:

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wherein

R_a is C_mH₂m+i wherein m is 0 -18;

Rh is C_mH_2m+i wherein m is 0 -18; and n is 4, 5, 6, 7 or 8.

[0021] There is also provided a dielectric fluid composition comprising a compound selected from the group defined by formula (V) and an unsaturated fatty acid-containing oil or oleochemical, wherein formula (V) is:

wherein

R_a is C_mH_2m+i wherein m is 0 -18;

Rh is C_mH_2m+i wherein m is 0 -18; and n is 4, 5, 6, 7 or 8.

[0022] There is also provided a dielectric fluid composition comprising a compound selected from the group defined by formula (VI) and an unsaturated fatty acid-containing oil or oleochemical, wherein formula (VI) is:

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OH η

wherein

R_c is C_mH_2m+1 wherein m is 0 - 18, or SO₂Y where Y is H, or an alkali metal;

R_h is C_mH_2m+i wherein m is 0 -18;

X is S, SO₂, N, O or an optionally substituted methylene group; and n is 4, 5, 6, 7 or 8.

[0023] There is also provided a dielectric fluid composition comprising a compound selected from the group defined by formula (VII) and an unsaturated fatty acidcontaining oil or oleochemical, wherein formula (VII) is:

wherein

R_c is C_mH_2m+i wherein m is 0 - 18, or NH₂, or SO₂Y where Y is H or an alkali metal;

R_h is CmH_2m+i wherein m is 0 -18;

R_a is (CH₂)_aCOOR_g where a = 1 -12 and R_g is either H or hydrocarbyl;

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[0024] The unsaturated fatty acid-containing oil or oleochemical of the dielectric fluid composition of the present invention is preferably sourced from a naturally occurring or renewable source, including plants (including algae), animals, fungi, bacteria, etc. Preferably, the unsaturated fatty acid containing oil or oleochemical of the present invention is a mono-unsaturated fatty acid-containing oil or oleochemical.

[0025] The mono-unsaturated fatty acid content of the oil or oleochemical is preferably >60%, and most preferably about 80%. The mono-unsaturated fatty acid is preferably oleic acid.

[0026] The present invention also provides an antioxidant for use with an unsaturated fatty acid-containing oil or oleochemical to form a dielectric fluid, wherein the antioxidant is a compound selected from the group comprising: formula (I), formula (II), formula (ill), formula (IV), formula (V), formula (Vi), and/or formula (VII).

[0027] The present invention also provide a process for producing a dielectric fluid composition comprising the step of:

a) blending a volume of unsaturated fatty acid-containing oil or oleochemical with a compound selected from the group comprising: formula (I), formula (II), formula (III), formula (IV), formula (V), formula (VI), and/or formula (VII).

[0028] The present invention further provides a transformer having a housing which accommodates a transformer core/coil assembly and a dielectric fluid composition surrounding said core/coil assembly, wherein the dielectric fluid composition comprises a compound selected from the group comprising: formula (I), formula (II), formula (III), formula (IV), formula (V), formula (VI), and/or formula (VII), and a mono-unsaturated fatty acid-containing oil or oleochemical.

[0029] The present invention further provides a method of increasing the oxidative stability of a dielectric fluid comprising an unsaturated fatty acid-containing oil or oleochemical, said method comprising the step of: blending the dielectric fluid containing an unsaturated fatty acid-containing oil or oleochemical with a compound

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PCT/AU2015/000284 selected from the group comprising: formula (I), formula (II), formula (III), formula (IV), formula (V), formula (VI), and/or formula (VII).

BRIEF DESCRIPTION OF THE DRAWINGS [0030] The description will be made with reference to the accompanying drawings in which:

Figure 1 is a diagram of a transformer 110 having a housing 112 which accommodates a transformer core/coii assembly 114. The transformer core-coil assembly 114 is arranged to be immersed in a dielectric fluid composition 116 of the present invention, such that the dielectric fluid composition 116 surrounds the transformer core-coil assembly 114 and performs according to desired electrical standards.

Figure 2 is a graph showing the power factor v oxidation time for an example dielectric fluid of the present invention comprising HOSO oil and Sample 6 (p-tbutyl calix[4]arene).

DESCRIPTION OF THE INVENTION

Detailed Description of the Invention

Dielectric Fluid [0031] As discussed above, an important feature of a dielectric fluid is its oxidative stabiiity. In order to improve the oxidative stability of unsaturated fatty acid-containing plant-based oils and oieochemicals, there is need for new additives, specifically designed for use with plant-based oils and oieochemicals. Many of the previously known additives for dielectric fluids were developed for use in mineral oils, and do not perform well in the new renewable oils. For example, the food industry adds certain antioxidants in small quantities (up to 0.02%) to oils used in food processing, such as BHT (Butylated Hydroxy Toluene, also known as DBPC used in transformer oil) and BHA (Butylated Hydroxy Anisole). However, Oommen et al (1997; “Biodegradable electrical insulation fluids” Electrical Insulation Conference and Electrical Manufacturing & Coil Winding Conference; Proceedings: 465-468 (Meeting date 22-25 Sept 1997)) undertook oxidations tests using such additives with plant based oils and found that

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PCT/AU2015/000284 none of the oils compared with regular mineral oil in stability. The use of very high concentrations of anti-oxidants in dielectric fluids is not desirable because of the marked increase in electrical conductivity. Furthermore, Oommen et al (2000; “A New Vegetable Oil Based Transformer Fluid: Development and Verification” Electrical insulation and Dielectric Phenomena, 2000 Annual Report of Conference; Volume 1: 308-312 (Meeting date 15-18 Oct 2000)) found that oxidation inhibitors for mineral oils and plant based oils, such as BHT (a phenolic anti-oxidant) and TBHQ (a quinone antioxidant), were unable to protect the plant based oil from oxidation at concentrations as high as 3%. For transformer oil, the maximum level of known anti-oxidants used is generally about 0.3%.

[0032] The present invention therefore provides anti-oxidant additives for dielectric fluids that are suitable for use with unsaturated fatty acid-containing oils or oleochemicals.

[0033] The antioxidant compounds of the present invention are preferably macrocyclic or cyclic oligomers with repeating units forming a ring. Examples of the compounds of the present invention include calixarenes.

[0034] In accordance with the present invention, there is therefore provided a dielectric fluid composition comprising a compound selected from the group defined by formula (I) and an unsaturated fatty acid-containing oil or oleochemical, wherein formula (I) is;

R wherein

A is a 5 or 6 membered aromatic or heterocyclic ring;

R_a is OH, or C_mH₂m-f-i wherein m = 0 - 18, or a hydrocarbyl, or a hetero-substituted hydrocarbyl group;

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R_b is OH, or C_mH2m+i wherein m = 0 - 18, or a hydrocarbyl, or a hetero-substituted hydrocarbyl group;

R_d = OH, or C_mH_2tn+i wherein m - 0 -18;

Preferably n is between 4 and 8.

[0035] The compound of formula (I) may be provided in a number of more specific forms. The compounds of formulas (II) to (VII) are provided as preferable sub sets of the compounds of formula (I).

[0036] There is therefor also provided a dielectric fluid composition comprising a compound selected from the group defined by formula (11) and an unsaturated fatty acidcontaining oil or oleochemical, wherein formula (II) is:

wherein

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Ra is a hydrogen, hydroxyl, hydrocarbyl or hetero-substituted hydrocarbyl group;

and wherein either R_a is hydroxyl and R_b, R_c and Ra are independently either hydrogen, hydrocarbyl or hetero-substituted hydrocarbyl, or

R_b, R_c and Rd are hydroxyl and R_a is either hydrogen, hydrocarbyl or hetero-substituted hydrocarbyl, or

R_a and R_c are hydroxyl, and Rb and R_d are independently either hydrogen, hydrocarbyl or hetero-substituted hydrocarbyl;

and n has a value of at least 4.

[0037] In formula (II), X is preferably the substituted or unsubstituted methyl group (CR_eRf)_m in which R_e and Rf are independently either hydrogen or a hydrocarbyl of 1 - 6 carbons, and m is an integer which is at least one, preferably at least three, more preferably at least six. If any of R_a to Rd is a heterosubstituted hydrocarbyl, preferably the heteroatom is O, or S, or NH, interrupting a chain of carbon atoms, such as an alkoxy-alkyl group of 2 - 20 carbons.

[0038] Preferably in formula (II) Rb and Rd are hydrogen; R_c is hydrocarbyl, preferably alkyl of greater than 3, preferably 4, more preferably t-Bu. Preferably, one of R_e and Rf is hydrogen and the other is either hydrogen or alkyl, preferably hydrogen.

[0039] Preferably, n is at least 4 and more preferably 4, 5, 6 or 8.

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PCT/AU2015/000284 [0040] The term hydrocarbyi as used herein describe organic compounds or radicals consisting exclusively of the elements carbon and hydrogen. These moieties include alkyl, alkenyl, alkynyl, and aryl moieties. These moieties also include alkyl, alkenyl, alkynyl, and aryl moieties substituted with other aliphatic or cyclic hydrocarbon groups, such as alkaryi, alkenaryl and alkynaryl. Unless otherwise indicated, these moieties preferably comprise 1 to 20 carbon atoms.

[0041] The substituted hydrocarbyl moieties described herein are hydrocarbyl moieties which are substituted with at least one atom other than carbon, including moieties in which a carbon chain atom is substituted with a hetero atom such as nitrogen, oxygen, silicon, phosphorous, boron, sulfur, or a halogen atom. These substituents include halogen, heterocyclo, alkoxy, alkenoxy, alkynoxy, aryioxy, hydroxy, protected hydroxy, keto, acyl, acyloxy, nitro, amino, amido, nitro, cyano, thiol, ketals, acetals, esters and ethers.

[0042] The term heteroatom shall mean atoms other than carbon and hydrogen.

[0043] Unless otherwise indicated, the alkyl groups described herein are preferably lower alkyl containing from one to eight carbon atoms in the principal chain and up to 20 carbon atoms. They may be straight or branched chain or cyclic and include methyl, ethyl, propyl, isopropyl, butyl, hexyl and the like.

[0044] The terms heterocyclo or heterocyclic as used herein alone or as part of another group denote optionally substituted, fully saturated or unsaturated, monocyclic or bicyclic, aromatic or nonaromatic groups having at least one heteroatom in at least one ring, and preferably 5 or 6 atoms in each ring. The heterocyclo group preferably has 1 or 2 oxygen atoms, 1 or 2 sulfur atoms, and/or 1 to 4 nitrogen atoms in the ring, and may be bonded to the remainder of the molecule through a carbon atom or heteroatom. Exemplary heterocyclo include heteroaromatics such as furyl, thienyl, pyridyl, oxazolyl, pyrroiyl, indoiyi, quinolinyl, or isoquinoiinyl and the like. Exemplary substituents include one or more of the following groups; hydrocarbyl, substituted hydrocarbyl, keto, hydroxy, protected hydroxy, acyl, acyloxy, alkoxy, alkenoxy, alkynoxy, aryioxy, halogen, amido, amino, nitro, cyano, thiol, ketals, acetals, esters and ethers.

[0045] The term heteroaromatic as used herein alone or as part of another group denote optionally substituted aromatic groups having at least one heteroatom in at least

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PCT/AU2015/000284 one ring, and preferably 5 or 6 atoms in each ring. The heteroaromatic group preferably has 1 or 2 oxygen atoms, 1 or 2 sulfur atoms, and/or 1 to 4 nitrogen atoms in the ring, and may be bonded to the remainder of the molecule through a carbon or heteroatom. Exemplary heteroaromatics include furyl, thienyl, pyridyl, oxazolyl, pyrrolyl, indolyl, quinolinyl, or isoquinolinyl and the like. Exemplary substituents include one or more of the following groups: hydrocarbyl, substituted hydrocarbyl, keto, hydroxy, protected hydroxy, acyl, acyloxy, alkoxy, alkenoxy, alkynoxy, aryloxy, halogen, amido, amino, nitro, cyano, thiol, ketals, acetals, esters and ethers.

[0046] The term acyl, as used herein alone or as part of another group, denotes the moiety formed by removal of the hydroxy] group from the group -COOH of an organic carboxylic acid, e.g., RC(O)-, wherein R is R¹, R¹O-, R¹R²N-, or R¹S-, R¹ is hydrocarbyl, heterosubstituted hydrocarbyl, or heterocyclo and R² is hydrogen, hydrocarbyl or substituted hydrocarbyl.

[0047] As used herein, tBu and t-Bu means tert-butyl.

[0048] There is also provided a dielectric fluid composition comprising a compound selected from the group defined by formula (III) and an unsaturated fatty acid-containing oil or oleochemical, wherein formula (III) is:

OH wherein

R_c is C_mH₂m+i wherein m is 0 -18;

R_h is C_mH2m+i wherein m is 0 -18; and n is 4, 5, 6, 7 or 8.

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PCT/AU2015/000284 [0049] There is also provided a dielectric fluid composition comprising a compound selected from the group defined by formula (IV), and an unsaturated fatty acidcontaining oil or oleochemical, wherein formula (IV) is:

wherein

R_a is C_mH_2m+i wherein m is 0 -18;

R_h is C_mH_2m+i wherein m is 0 -18; and n is 4, 5, 6, 7 or 8.

[0050] There is also provided a dielectric fluid composition comprising a compound selected from the group defined by formula (V) and an unsaturated fatty acid-containing oil or oleochemical, wherein formula (V) is:

wherein

R_a is C_mH₂m+i wherein m is 0 -18;

Rh is C_mH_2rri+i wherein m is 0 -18; and nis4, 5, 6, 7 or 8.

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PCT/AU2015/000284 [0051] There is also provided a dielectric fluid composition comprising a compound selected from the group defined by formula (VI) and an unsaturated fatty acid-containing oil or oieochemical, wherein formula (VI) is:

wherein

R_c is C_mH_2m+i wherein m is 0 - 18, or SO₂Y where Y is H, or an alkali metal;

R_h is C_mH_2m+i wherein m is 0 -18;

[0052] There is also provided a dielectric fluid composition comprising a compound selected from the group defined by formula (VII) and an unsaturated fatty acidcontaining oil or oieochemical, wherein formula (VII) is:

wherein

R_c is C_mH₂m+i wherein m is 0 - 18, or NH₂, or SO₂Y where Y is H or an alkali metal;

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R_h is C_mH_2m+i wherein m is 0 -18;

R_a is (CH₂)_aCOOR_g where a = 1 - 12 and R_g is either H or hydrocarbyl;

[0053] The present invention also provides a dielectric fluid composition comprising an ester or acid derivative of a compound selected from the group defined by any one or more of formulas (I) to (VII) and an unsaturated fatty acid-containing oil or oleochemical. Preferably, the acid substituent has the general formula: RCOOH, where R = (CH₂)_n, with n = 1 to about 22. Preferably, the ester substituent has the general formula RCOOR’, where R and R’ = (CH₂)_n, with n = 1 to about 22. For example, the compound may be an ester or acid derivative of formula (II), wherein the ester or acid is provided at position R_c of formula (II).

[0054] Preferably, the compound selected from formula (l)-(VII) is present in the dielectric fluid in a concentration of less than 0.3%. More preferably, it is present in a concentration of between about 0.001% and 0.3%, between about 0.01% and 0.25%, between about 0.02% and 0.2%, between about 0.025% and 0.15%, between about 0.025% and 0.1%, between about 0.025% and 0.5%. The compound selected from formula (l)-(Vlli) may be present in the dielectric fluid in a concentration of 0.3%, 0.275%, 0.25%, 0.225%, 0.2%, 0.175%, 0.15%, 0.125%, 0.1%, 0.075%, 0.05%, or 0.025%, 0.02%, 0.01%, 0.005% or any value in between.

[0055] The dielectric fluids of the present invention may contain one compound selected from formula (l)-(VII), or a mixture of two or more such compounds.

Oil or Oleochemical [0056] The unsaturated fatty acid-containing oil or oleochemical of the dielectric fluid composition of the present invention is preferably sourced from a naturally occurring or renewable source, including plants (including algae), animals, fungi, bacteria, etc. The unsaturated fatty acid-containing oil or oleochemical of the present invention may be sourced from a single naturally occurring or renewable source, or may be a blend of two or more naturally occurring or renewabiy sourced unsaturated fatty acid-containing oils or oleochemical.

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PCT/AU2015/000284 [0057] Preferably, the unsaturated fatty acid containing oil or oleochemical of the present invention is a mono-unsaturated fatty acid-containing oil or oleochemical. However, the unsaturated fatty acid containing oil or oleochemical may alternatively be a poly-unsaturated fatty acid-containing oil or oleochemical.

[0058] In one embodiment of the invention, the unsaturated fatty acid-containing oil or oleochemical is a vegetable derived oil or oleochemical. However, it should be understood that non-vegetable sources of unsaturated fatty acid-containing oils and oleochemicals also fall within the scope of the present invention, such as animal fats and oils including tallow, lard, milk fat etc. The invention further contemplates that the unsaturated fatty acid-containing oil or oleochemical may be obtained from fungal sources or bacterial sources. In this respect, the fungal or bacterial source of the oil or oleochemical maybe a genetically modified organism that has been modified to produce an unsaturated fatty acid-containing oil or oleochemical that is substantially identical with an oil or oleochemical from another renewable source. For example, the bacterial source may be modified to produce an unsaturated fatty acid-containing oil or oleochemical that is substantially identical with a naturally occurring vegetable oil or oleochemical.

[0059] The oil or oleochemical from a naturally occurring or renewable source may also be combined with a minor amount of one or more mineral oils or synthetic oils, providing that the resulting blend demonstrates the beneficial properties of the naturally occurring or renewably sourced unsaturated fatty acid-containing oil or oleochemical.

[0060] While the present invention provides for the use of natural vegetable oils or oleochemical, the invention may use synthetic vegetable oils or oleochemical which have the same or similar compositional characteristics as natural vegetable oils or oleochemical, or genetically modified vegetable oils or oleochemical or a mixture thereof to provide the unsaturated fatty acid-containing oil or oleochemical.

[0061] Where the unsaturated fatty acid-containing oil or oleochemical is a vegetable derived oil or oleochemical, in one embodiment of the invention the vegetable oil or oleochemical is selected from the group comprising: natural vegetable oil, synthetic vegetable oil, genetically modified vegetable oil, oleochemicals derived from such oils and mixtures thereof.

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PCT/AU2015/000284 [0062] Typical examples of vegetable oils suitable for use in the present invention include, but are not limited to: castor oil, coconut oil, corn oil, cottonseed oil, linseed oil, olive oil, palm oil, peanut oil, grapeseed oil, canola oil, safflower oil, sunflower oil, meadowfoam oil and soybean oil, high oleic variants thereof, and mixtures thereof. One particular embodiment of the present invention employs RBD (Refined, Bleached, and Deodorised) vegetable oil. Alternatively, the vegetable oil may be RBDW vegetable oil (Refined, Bleached, Deodorised and Winterised). Oleochemical derivatives of these oils may be used in the present invention.

[0063] In the present application, the term “oleochemicai” and “oleochemicai derivative” encompasses basic oleochemical substances like fatty acids, fatty acid methyl esters (FAME), fatty alcohols, fatty amines and glycerols, derived from chemical modification of naturally occurring or renewable oils. Intermediate chemical substances may also be produced from these basic oieochemical substances; such intermediate chemical substances include alcohol ethoxylates, alcohol sulfates, alcohol ether sulfates, quaternary ammonium salts, monoacyiglycerols (MAG), diacylglycerols (DAG), structured triacylglycerols (TAG), sugar esters, and other oieochemical products derived from chemical modification of naturally occurring or renewable oils and/or from chemical modification of basic oieochemical substances derived from naturally occurring or renewable oils.

[0064] The physical and chemical stability (including oxidative stability) of any unsaturated fatty acid-containing oil or oleochemical is determined by the degree of unsaturation in the fatty acid content, while the freezing point of the oil or oleochemical is determined by chain length, degree of branching and unsaturation. While a unsaturated fatty acid-containing oii or oleochemical with a high saturated fatty acid content will demonstrate chemical stability to oxidation, it will also have a high freezing point. Typically, most fatty acids in oils such as vegetable oils have a chain length of between 16-22 carbon atoms. Therefore, a compromise between oxidative stability and freezing point characteristics is achieved by basing the dielectric fluid composition of the present invention on unsaturated fatty acid-containing oils or oleochemicals with a high (above 60%) unsaturated fatty acid content. Preferably, the high unsaturated fatty acid content is a high mono- unsaturated fatty acid content. However, the high unsaturated fatty acid content may alternatively be a high poly- unsaturated fatty acid content.

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PCT/AU2015/000284 [0065] The term “fatty acid” as used herein refers to a long chain (more than 8-10 carbon atoms) straight- or branched- saturated, mono-unsaturated or polyunsaturated hydrocarbon chain bonded to a terminal carboxyl group. It will be understood that the term “fatty acid” also encompasses the fatty acid moieties of mono-, di- and triglycerides which are the major constituents of renewable or naturally occurring oils, including vegetable oils, and oleochemical derivatives of such oils.

[0066] Saturated fatty acids are stable under mild oxidative conditions; whereas monounsaturated and, even more so poly-unsaturated fatty acids, are susceptible to oxidation. The melting point of saturated fatty acids increases with chain length such that decanoic and longer chain saturated fatty acids are solids at ambient temperature. While it is also true that the melting point of mono-unsaturated and poly-unsaturated fatty acids .increases with chain length, the rise in melting point tends to be tempered by an increase in the degree of unsaturation throughout the chain length of the fatty acids or the extent of branching throughout the chain length of the fatty acids.

[0067] The physical and chemical stability of a dielectric fluid over prolonged periods of use is an important performance requirement. Thus, in one embodiment of the present invention the unsaturated fatty acid-containing oil or oleochemical used in the dielectric fluid comprises a high unsaturated fatty acid content. Typically, the unsaturated fatty acid content is > 60%. In some forms of the invention, the unsaturated fatty acid content is > 65%. in some forms of the invention, the unsaturated fatty acid content is > 70%. In some forms of the invention, the unsaturated fatty acid content is > 75%. In one particular embodiment of the invention the unsaturated fatty acid-containing oil comprises about 80% unsaturated fatty acid content. In some forms of the invention, the unsaturated fatty acid content is > 80%.

[0068] The invention provides for the unsaturated fatty acid-containing oil or oleochemical to comprise a high mono-unsaturated fatty acid content. Typically, the mono-unsaturated fatty acid content is > 60%. In some forms of the invention, the mono-unsaturated fatty acid content is > 65%. In some forms of the invention, the mono-unsaturated fatty acid content is > 70%. In some forms of the invention, the mono-unsaturated fatty acid content is > 75%. In one particular embodiment of the invention the mono-unsaturated fatty acid-containing oil or oleochemical comprises about 80% mono-unsaturated fatty acid content. In some forms of the invention, the mono-unsaturated fatty acid content is > 80%.

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PCT/AU2015/000284 [0069] The invention also provides for the unsaturated fatty acid-containing oil or oleochemical to comprise a high poly-unsaturated fatty acid content. Typically, the polyunsaturated fatty acid content is > 60%. In some forms of the invention, the polyunsaturated fatty acid content is > 65%. In some forms of the invention, the polyunsaturated fatty acid content is > 70%. In some forms of the invention, the polyunsaturated fatty acid content is > 75%. In one particular embodiment of the invention the poly-unsaturated fatty acid-containing oil or oleochemical comprises about 80% poly-unsaturated fatty acid content. In some forms of the invention, the polyunsaturated fatty acid content is > 80%.

[0070] Preferably the unsaturated fatty acid-containing oil or oleochemical is high in a single mono-unsaturated fatty acid (>94%) with <4 % saturated fatty acid, <2% diunsaturated fatty acid and 0% tri-unsaturated fatty acid. Preferably the oil is a safflower oil with a mono-unsaturated fatty acid content of >94%; <4 % saturated fatty acid; <2% di-unsaturated fatty acid and 0% tri-unsaturated fatty acid.

[0071] The high unsaturated fatty acid content of the unsaturated fatty acid-containing oil or oleochemical may occur naturally or may be artificially enhanced. For example, an unsaturated fatty acid-containing oil or oleochemical’s unsaturated fatty acid content may be enriched with additional unsaturated fatty acids or an oil containing high quantities of such, or the concentration of the unsaturated fatty acid increased by removal of other components from the unsaturated fatty acid-containing oil or oleochemical, or non-unsaturated fatty acid components of the oil or oleochemical may be chemically converted to unsaturated fatty acids.

[0072] The unsaturated fatty acid-containing oil or oleochemical is preferably a monounsaturated fatty acid-containing oil or oleochemical. The most common monounsaturated fatty acid found in vegetable oil is oleic acid. It is found in many naturally occurring vegetable oils, such as sunflower, olive and safflower oil in relatively high proportions, although other renewable and naturally sources of mono-unsaturated fatty acid-containing oils containing oleic acid exist. Genetic modification of certain oil seed stocks, such as canola and sunflower, can generate vegetable oils with an oleic acid content of above 80%. Mono-unsaturated fatty acid-containing oils or oleochemical with a high oleic acid content are particularly suitable for use in the present invention.

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PCT/AU2015/000284 [0073] Accordingly, in a preferred embodiment of the invention, the mono-unsaturated fatty acid-containing oil or oleochemical comprises a high oleic acid content. Typically, the oleic acid content is > 60%. in some forms of the invention, the oleic acid content is > 65%, > 70%, > 75%, or > 80%. Preferably, the oleic acid content of the monounsaturated fatty acid-containing oil or oleochemical is about 80%. Alternatively, the mono-unsaturated fatty acid-containing oil or oleochemical may comprise other monounsaturated fatty acids such as eicosenoic acid, docosenoic acid, palmitoleic acid, or erucic acid.

[0074] The mono-unsaturated fatty acid-containing oil or ofeochemical may, for example, be daikon radish oil, meadowfoam seed oil, jojoba oil, meadowlactone, safflower oil or sunflower oil.

[0075] In one of the embodiments of the invention the mono-unsaturated fatty acidcontaining oil or oleochemical used in the dielectric fluid is a high oleic sunflower oil (HOSO) or oleochemical derivative of HOSO with 80% oleic acid and < 3% linoleic acid. This particular oil or oleochemical often has the following fatty acid composition: 81% mono-unsaturated fatty acid content, 11% saturated fatty acid content, and 8% polyunsaturated fatty acid content.

Antioxidant [0076] The present invention also provides an antioxidant for use with an unsaturated fatty acid-containing oil or oleochemical to form a dielectric fluid, wherein the antioxidant is a compound selected from the group comprising: formula (I), formula (II), formula (111), formula (IV), formula (V), formula (VI), and/or formula (VII).

[0077] The anti-oxidant may be an ester or acid derivative of the compound of formula (I), formula (II), formula (III), formula (IV), formula (V), formula (VI), and/or formula (VII). Preferably, the acid substituent has the general formula: RCOOH, where R = (CH₂)_n, with n = 1 to about 22. Preferably, the ester substituent has the general formula RCOOR’, where R and R’ = (CH₂)_n, with n = 1 to about 22.

Use [0078] The present invention provides the use of a composition comprising:

a) an unsaturated fatty acid-containing oil or oleochemical;

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b) a compound selected from the group comprising: formula (1), formula (li), formula (III), formula (IV), formula (V), formula (VI), and/or formula (VII) as a dielectric fluid composition.

[0079] The compound may be an ester or acid derivative of the compound of formula (I), formula (II), formula (111), formula (IV), formula (V), formula (VI), and/or formula (VII). Preferably, the acid substituent has the general formula: RCOOH, where R = (CH₂)_n, with n = 1 to about 22. Preferably, the ester substituent has the general formula RCOOR’, where R and R’ = (CH₂)_n, with n = 1 to about 22.

[0080] The invention further provides for use of a compound selected from the group comprising: formula (I), formula (II), formula (III), formula (IV), formula (V), formula (VI), and/or formula (VII) as an additive for a dielectric fluid.

[0081] Preferably, the dielectric fluid to which the compound selected from the group comprising: formula (I), formula (IS), formula (111), formula (IV), formula (V), formula (VI), and/or formula (VII) is added comprises an unsaturated fatty acid-containing oil or oleochemicai.

Alkyl Esters [0082] The dielectric fluid composition of the present invention may further comprise one or more alkyl esters. Preferably, the alkyl esters added to the dielectric fluid composition are able to act as viscosity modifiers of the dielectric fluid composition.

[0083] The alkyl esters of the present invention preferably comprise one or more fatty acid alkyl esters. The fatty acid alkyl esters are preferably organic compounds formed by an esterification or transesterification reaction between alcohols of 1 to 4 carbon atoms and fatty acids. Therefore, typically, the alkyl moiety has 1 to 4 carbon atoms. Generally, the most commonly available alkyl esters of fatty acids are produced by esterification or trans-esterification of unsaturated fatty acid-containing oils, such as mono-unsaturated fatty acid-containing oils, and other lipids with methanol or ethanol. In one embodiment of the invention the alkyl ester comprises one or more fatty acid methyl esters or fatty acid ethyl esters.

[0084] In one embodiment of the invention, the fatty acids are selected from the group comprising: saturated fatty acids, mono-unsaturated fatty acids, poly-unsaturated fatty

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PCT/AU2015/000284 acids, and mixtures thereof. Suitable examples of saturated fatty acids include, but are not limited to: butyric, valeric, caproic, caprylic, pelargonic, capric, lauric, myristic, palmitic, margaric, stearic, arachidic, behenic, lignoceric, cerotic, carboceric, montanic, melissic, lacceoic, psyilic. Suitable examples of mono-unsaturated fatty acids include, but are not limited to: obtusilic, caproleic, lauroleic, linderic, myristoleic, physeteric, tsuzuic, paimitoleic, petroselinic, oleic, vaccenic, gadoleic, gondoic, cetoleic, erucic, and nervonic. Suitable examples of polyunsaturated fatty acids include, but are not limited to: linoleic, y-iinolenic, dihomo-y-linolenic, arachidonic, α-linoleic, stearidonic 7,10,13,16docosatetraenoic, 4,7,10,13,16-docosapentaenoic, 8,11,14,17-eicosatetraenoic,

5,8,11,14,17-eicosapentaenoic (EPA), 7,10,13,16,19-docosapentaenoic (DPA), 4,7,10,13,16,19-docosahexaenoic (DHA), docosadienoic acid and 5,8,11-eicosatrienoic (Mead acid).

[0085] Typically, the viscosity of most fatty acid alkyl esters, regardless of the degree of unsaturation in the fatty acid moiety, fall in a range of about 2-6 cSt at 40°C. While it will be understood that fatty acid alkyl esters with any one of the above fatty acid moieties will be suitable for use in the dielectric fluid composition of the present invention, preferably as a viscosity modifier, a high mono-unsaturated fatty acid content of the fatty acid alkyl ester is preferred, in order to provide better chemical stability of the alkyl ester and/or to assist in protecting the dielectric fluid composition containing said alkyl esters against oxidation.

[0086] Preferably, the alkyl esters comprise a high unsaturated fatty acid content. Typically, sufficient chemical stability against oxidation is provided when the alkyl ester comprises above 60% unsaturated fatty acids. In some forms of the invention, the alkyl ester comprises above 65%, above 70%, or above 75% unsaturated fatty acids. In the preferred embodiment the alkyl ester comprises about 80% unsaturated fatty acids.

[0087] More preferably, the alkyl esters comprise a high mono-unsaturated fatty acid content. Typically, sufficient chemical stability against oxidation is provided when the alkyl ester comprises above 60% mono-unsaturated fatty acids. In some forms of the invention, the alkyl ester comprises above 65%, above 70%, or above 75% unsaturated fatty acids. In the preferred embodiment the alkyl ester comprises about 80% monounsaturated fatty acids.

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PCT/AU2015/000284 [0088] The alkyl esters employed in the present invention may be readily derived from high oleic mono-unsaturated fatty acid-containing oils which have a high concentration of mono-unsaturated fatty acids.

[0089] Preferably, the fatty acid moieties of the fatty acid alkyl esters are substantially homologous with the fatty acid content of the unsaturated fatty acid-containing oil or oleochemical of the dielectric fluid composition.

[0090] in a further embodiment of the present invention, the alkyl esters comprise fatty acid alkyl esters derived from the unsaturated fatty acid-containing oil or oleochemical of the dielectric fluid composition.

[0091] When the oil or oleochemical in the fatty acid-containing oil or oleochemical of the dielectric fluid composition is a mono-unsaturated fatty acid-containing oil or oleochemical, the fatty acid moieties of the fatty acid alkyl esters are preferably substantially homologous with the fatty acid content of the mono-unsaturated fatty acidcontaining oil or oleochemical of the dielectric fluid composition.

[0092] More preferably, when the oil or oleochemical in the fatty acid-containing oil or oleochemical of the dielectric fluid composition is a mono-unsaturated fatty acidcontaining oil or oleochemical, the alkyl esters comprise fatty acid alkyl esters derived from the mono-unsaturated fatty acid-containing oil or oleochemical of the dielectric fluid composition.

[0093] To ensure that the aikyi esters in the dielectric fluid composition conform to a similar or the same fatty acid content as the unsaturated fatty acid-containing oil or oleochemical, the alkyl esters may be conveniently be derived from the unsaturated fatty acid-containing oil or oleochemical of the dielectric fluid composition by subjecting the unsaturated fatty acid-containing oil or oleochemical to esterification or transesterification with the preferred alcohol.

[0094] Notwithstanding the preferred options described above, it will also be understood that the alkyl esters employed by the present invention, either as the viscosity modifier or as one of the components of the dielectric fluid composition, may be derived from other sources of fatty acids, including vegetable- or animal-based fats and oils or oleochemical and non-renewable sources of fatty acids such as mineral oils.

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PCT/AU2015/000284 [0095] Preferably, the addition of alkyl esters to the dielectric fluid composition of the present invention results in a viscosity of < 20 cSt at 40°C.

[0096] In one form, the viscosity of the composition is < 19 cSt at 40°C, <18 cSt at 40°C, < 17 cSt at 40°C, or < 16 cSt at 40°C. In one form, the viscosity of the composition is between 1 and 20 cSt at 40°C, between 1 and 19 cSt at 40°C, 1 and 18 cSt at 40°C, between 1 and 17 cSt at 40°C or between 1 and 16 cSt at 40°C, [0097] The dielectric fluid composition of the present invention may preferably comprise unsaturated fatty acid-containing oil or oleochemical in the range of 40 - 60 %v/v, and alkyl esters in the range of 60 - 40 %v/v. More preferably, the dielectric fluid composition comprises mono-unsaturated fatty acid-containing oil or oleochemical in the range of 40 - 60 %v/v, and alkyl esters in the range of 60 - 40 %v/v.

[0098] The present invention therefore provides a dielectric fluid composition comprising:

a) an unsaturated fatty acid-containing oil or oleochemical;

b) a compound selected from the group defined by formula (I);

c) one or more fatty acid alkyl esters, each having a fatty acid moiety and an alkyl moiety, wherein the alkyl moiety of the fatty acid alkyl esters has 1 to 4 carbon atoms;

wherein the oil or oleochemical is in the range of 40%-60% v/v of the dielectric fluid composition and the a fatty acid alkyl ester is in the range of 40%-60% v/v of the dielectric fluid composition, and wherein the viscosity of the dielectric solution is < 20 cSt at 40°C.

Additives [0099] In another embodiment of the invention, the dielectric fluid composition further comprises at least one additive, to improve or further enhance the dielectric properties and characteristics of the dielectric fluid composition of the present invention. The or each additive may be selected from the group comprising: anti-oxidants, pour point depressants, corrosion inhibitors, anti-microbial compounds, and/or viscosity modifiers.

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PCT/AU2015/000284 [00100] The pour point of the dielectric fluid composition can be improved either by the addition of pour point suppressants to the dielectric fluid composition or winterization of the dielectric fluid composition.

[00101] The pour point depressant typically contains a branched polymethacrylate backbone which encourages inclusion of the pour point depressant molecule into a growing crystal of the unsaturated fatty acid-containing oil or oleochemicai in the dielectric fluid composition. By interfering with wax crystal growth patterns, the pour point depressant increases the operational range of the dielectric fluid composition so it remains fluid at much lower temperatures. Pour point depressants such as Viscoplex® 10-310, Viscoplex® 10-930, and Viscoplex® 10-950 are suitable examples.

[00102] Winterization is the process of removing sediment which appears in oils, such as unsaturated fatty acid-containing oils, at low temperatures. The sedimentation is accompanied by a decrease in the oil or oleochemical’s viscosity. Winterization of the dielectric fluid composition is typically performed by slow cooling the dielectric fluid composition to 7°C, then filtering out any resulting crystals. The liquid filtrate subsequently undergoes another period of slow cooling in a manner as described above to remove any additional resulting crystals.

[00103] The oxidative stability of the dielectric fluid composition can be improved by addition of meta! deactivators and/or supplementary anti-oxidants to the dielectric fluid composition. However, it is a benefit of the compounds of the present invention that they may be able to chelate metal ions. Therefore, it is believed that they may be able to provide a meta! deactivating function as well as their antioxidant function. Given this, there may not be a need for additional metal deactivators to be added to the dielectric fluids. Nevertheless, the present compounds are compatible with known metal deactivators and therefore the compounds can be added to dielectric fluids already containing commercial or known metal deactivators.

[00104] Suitable examples of metal deactivators include, but are not limited to: copper deactivators such as benzotriazole and triazole derivatives. Typically, the dielectric fluid composition comprises less than 0.7 % metal deactivator.

[00105] Suitable examples of supplementary anti-oxidants include, but are not limited to: phenolic anti-oxidants such as Irganox® L109, Irganox® L64, lrganox® L94,

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PCT/AU2015/000284 and octyiated/butyiated diphenyiamine antioxidants such as lrganox® L57. Typically, the dielectric fluid composition comprises less than 0.3 % anti-oxidant.

Transformer [00106] The dielectric fluid composition developed by the inventors has comparable dielectric properties and performance to mineral oil, the standard dielectric fluid currently used in electrical distribution and power equipment, such as transformers, switching gear and electric cables. Existing transformers can be readily retro-filled with the dielectric fluid of the present invention comprising an unsaturated fatty acidcontaining oi! or oleochemical and an antioxidant compound and operated under standard conditions.

[00107] Accordingly, the present invention provides a transformer having a housing which accommodates a transformer core/coil assembly and a dielectric fluid composition surrounding said core/coil assembly, wherein the dielectric fluid composition comprises a compound selected from the group comprising: formula (I), formula (II), formula (ill), formula (IV), formula (V), formula (VI), or formula (VII), and a mono-unsaturated fatty acid-containing oil or oleochemical.

[00108] Referring to Figure 1, there is shown a transformer 110 having a housing 112 which accommodates a transformer core/coil assembly 114. The transformer corecoil assembly 114 is arranged to be immersed in a dielectric fluid composition 116 of the present invention, such that the dielectric fluid composition 116 surrounds the transformer core-coil assembly 114 and performs according to desired electrical standards.

Method [00109] The inventors have found that the compounds of formula (l)-(VII) of the present invention are able to increase the oxidative stability of dielectric fluids comprising unsaturated fatty acid containing oils or oleochemicals.

[00110] Thus, the present invention provides a method of increasing the oxidative stability of a dielectric fluid comprising an unsaturated fatty acid-containing oil or oleochemical, said method comprising the step of: blending the dielectric fluid containing an unsaturated fatty acid-containing oil or oleochemical with a compound

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PCT/AU2015/000284 selected from the group comprising: formula (I), formula (II), formula (III), formula (IV), formula (V), formula (VI), or formula (VII).

[00111] The compound may be an ester or acid derivative of the compound of formula (i), formula (II), formula (III), formula (IV), formula (V), formula (VI), and/or formula (VII). Preferably, the acid substituent has the general formula: RCOOH, where R = (CH₂)n, with n = 1 to about 22. Preferably, the ester substituent has the general formula RGOOR’, where R and R’ = (CH₂)_n> with n = 1 to about 22.

Oxidative Stability Modifier [00112] The present invention also provides an oxidative stability modifier for an unsaturated fatty acid-containing oil or oieochemical -based dielectric fluid, comprising a compound selected from the list comprising: formula (I), formula (ll), formula (III), formula (IV), formula (V), formula (VI), or formula (VII).

[00113] The oxidative stability modifier may be an ester or acid derivative of the compound of formula (I), formula (II), formula (III), formula (IV), formula (V), formula (VI), and/or formula (VII), Preferably, the acid substituent has the general formula: RCOOH, where R = (CH₂)_n, with n = 1 to about 22. Preferably, the ester substituent has the general formula RCOOR’, where R and R’ = (CH₂)_n, with n = 1 to about 22.

Process for Producing a Dielectric Fluid Composition [00114] The present invention also provide a process for producing a dielectric fluid composition comprising the step of:

a) blending a volume of unsaturated fatty acid-containing oil or oieochemical with a volume of a compound selected from the group comprising: formula (I), formula (ll), formula (III), formula (IV), formula (V), formula (VI), and/or formula (VII).

[00115] Preferably, the compound selected from formula (l)-(VII) is present in the dielectric fluid in a concentration of less than 0.3%. More preferably, it is present in a concentration of between about 0.001% and 0.3%, between about 0.01% and 0.25%, between about 0.02% and 0.2%, between about 0.025% and 0.15%, between about 0.025% and 0.1%, between about 0.025% and 0.5%. The compound selected from formula (l)-(VIII) may be present in the dielectric fluid in a concentration of 0.3%,

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0,275%, 0.25%, 0.225%, 0.2%, 0.175%, 0.15%, 0.125%, 0.1%, 0.075%, 0.05%, or 0.025%, 0.02%, 0.01%, 0.005% or any value in between.

[00116] The compound may be an ester or acid derivative of the compound of formula (I), formula (II), formula (III), formula (IV), formula (V), formula (VI), and/or formula (VII). Preferably, the acid substituent has the general formula: RCOOH, where R = (CH2)_n> with n = 1 to about 22. Preferably, the ester substituent has the general formula RCOOR’, where R and R’ = (CH₂)„, with n = 1 to about 22.

[00117] The process for producing the dielectric fluids of the present invention may involve the blending of one compound selected from formula (l)-(VII) with a volume of unsaturated fatty acid-containing oil or oleochemical, or blending a mixture of two or more such compounds with a volume of unsaturated fatty acid-containing oil or oleochemical.

[00118] The unsaturated fatty acid-containing oil or oleochemical may be sourced from a naturally occurring or renewable source, preferably from the group comprising: natural vegetable oil, synthetic vegetable oil, genetically modified vegetable oil, animal fats and oils, oleochemicais derived from such oils and mixtures thereof.

[00119] Preferably, the unsaturated fatty acid-containing oil is selected from the group comprising: castor oil, coconut oil, corn oil, cottonseed oil, linseed oil, olive oil, palm oil, peanut oil, grapeseed oil, canola oil, safflower oil, sunflower oil, and soybean oil, high oleic variants thereof, and mixtures thereof. Oleochemical derivatives of these oils may be used in the present invention.

[00120] In one form of the present invention, the unsaturated fatty acid-containing oil or oleochemical comprises a high unsafurated fatty acid content. Typically, the unsaturated fatty acid content is > 60%. In some forms of the invention, the unsaturated fatty acid content is > 65%, > 70%, > 75% or > 80%. In one particular embodiment of the invention the unsaturated acid-containing oil or oleochemical comprises about 80% unsaturated fatty acid content.

[00121] The invention provides for the unsaturated fatty acid-containing oil or oleochemical to comprise a high mono-unsaturated fatty acid content. Typically, the mono-unsaturated fatty acid content is > 60%. In some forms of the invention, the mono-unsaturated fatty acid content is > 65%, > 70%, > 75% or > 80%. In one

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PCT/AU2015/000284 particular embodiment of the invention the vegetable oii or oleochemical comprises about 80% mono-unsaturated fatty acid content.

[00122] In a preferred embodiment of the invention the mono-unsaturated fatty acid-containing oil or oleochemical comprises a high oleic acid content.

[00123] Typically, the oieic acid content is > 60%. In some forms of the invention, the oleic acid content is > 65%, > 70% or > 75%. In some forms of the invention, the oleic acid content is > 80%.

[00124] In one of the embodiments of the invention the mono-unsaturated fatty acid-containing oil is a high oleic sunflower oil (HOSO) or oleochemical derivative of HOSO with 80% oleic acid and < 3% linoleic acid. In another embodiment, the monounsaturated fatty acid-containing oil is a safflower oil with a mono-unsaturated fatty acid content of >94%; <4 % saturated fatty acid; <2% di-unsaturated fatty acid and 0% triunsaturated fatty acid.

[00125] The dielectric fluid composition provided by the above process may additionally comprise an alkyl ester. Typically the alkyl ester is blended with the unsaturated fatty acid-containing oil or oleochemical in a percentage volume ratio of 40:60 to 60:40.

[00126] The dielectric fluid composition provided by the above process may additionally comprise at least one additive, the or each additive being selected from the group comprising: anti-oxidants, pour point depressants, corrosion inhibitors, antibacterials, viscosity modifiers. Suitable examples of anti-oxidant additives comprise metal deactivators.

[00127] Therefore, there is provided a process for producing a dielectric fluid composition comprising the step of:

a) blending a volume of unsaturated fatty acid-containing oil or oleochemical with a volume of a compound selected from the group comprising: formula (I), formula (II), formula (III), formula (IV), formula (V), formula (VI), or formula (VII) to form a mixture;

b) blending the mixture of step (a) with an alkyl ester.

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PCT/AU2015/000284 [00128] There is also provided a process for producing a dielectric fluid composition comprising the step of:

a) blending a volume of unsaturated fatty acid-containing oil or oleochemical with a volume of a compound selected from the group comprising: formula (I), formula (II), formula (III), formula (IV), formula (V), formula (Vi), or formula (VII);

b) blending the mixture of step (a) with one or more additives.

[00129] There is additionally provided a process for producing a dielectric fluid composition comprising the step of:

b) blending the mixture of step (a) with an alkyl ester and one or more additives

Purification of Oil [00130] It is understood by the person skilled in the art that the dielectric fluid composition of the present invention comprising a compound of formula (I) and an unsaturated fatty acid-containing oil or oleochemical may need to undergo one or more purification processes in order to ensure that the dielectric fluid composition has the necessary performance characteristics to compare to existing mineral oil-based dielectric fluids.

[00131] For example, while it is envisaged that an oil such as RBD (Refined, Bleached and Deodorised) vegetable oil or or oleochemical derivative of RBD may be employed as the unsaturated fatty acid-containing oil component of the dielectric fluid composition of the present invention, it is acknowledged that RBD vegetable oil is typically unsatisfactory for use as a dielectric fluid. The RBD oil typically contains water and other conductive contaminants which degrade its performance properties as a dielectric fluid when used in electrical apparatus such as power and distribution transformers. For example, in respect to high oleic sunflower oil (HOSO), the dielectric

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PCT/AU2015/000284 breakdown voltage is typically > 55 kV (IEC 60156, 2 mm gap electrode), dielectric dissipation factor < 0.085 at 90 °C and 50 HZ (IEC 60247), initial acidity number <0.12 mg KOH/g (IEC 60296), initial surface tension (IFT) > 21.0 dynes/cm (ISO 6295), pour point < -15 °C (ISO 3016), and a moisture content > 380 ppm. These values are outside of acceptable dielectric performance.

[00132] Therefore, the unsaturated fatty acid-containing oil or oleochemical of the present invention and/or the dielectric fluid composition of the present invention, may need to undergo one or more purification processes.

[00133] The process may comprise the step of depleting the dielectric fluid composition of water and other conductive contaminants such as acids.

[00134] Removal of water is effected with known dehydration processes. Suitable examples of dehydration processes include but are not limited to eluting the dielectric fluid composition under gravity through adsorption media such as molecular sieves, starches, and desiccants, centrifugal separation, and vacuum dehydration. Typically, the dehydration process employed in the present invention decreases the water content of the dielectric fluid composition by more than 70%, preferably more than 80%.

[00135] Removal of other contaminants such as acids is typically accomplished by eluting the dielectric fluid composition under gravity through adsorption media including but not limited to Fuller’s earth, activated clays, and attapulgite. Typically, elution of the dielectric fluid composition through the above described adsorption media decreases the acid value of the dielectric fluid composition and increases the interfacial tension of the dielectric fluid composition to acceptable parameters.

[00136] It will be understood that the above described process may be conducted one or more times, depending on the original acid value and interfacial tension of the mono-unsaturated fatty acid-containing oil or oleochemical.

[00137] Preferably, the dielectric fluid composition is dehydrated prior to treatment with adsorption media for removal of contaminants.

[00138] Advantageously, it has been found that sequential treatment of the dielectric fluid composition with the desiccant followed by elution through the adsorption media is an effective method for also significantly improving the dielectric voltage and

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PCT/AU2015/000284 dissipation factors of the dielectric fluid composition such that after said treatment these parameters fall within acceptable standards for dielectric fluids. In one example, the dielectric fluid composition is contacted with said adsorption media by eluting the dielectric fluid composition through a column of said adsorption media. In another example, the step of purifying the dielectric fluid composition comprises eluting the dielectric fluid composition through a first adsorption medium and removing water, and then eluting the dielectric fluid composition through a second adsorption medium and removing acid.

[00139] In an alternative example, the process comprises the step of purifying the unsaturated fatty acid-containing oil or oleochemical prior to blending the oil or oleochemical with the compounds of formula (I) to form the dielectric fluid composition. Typically, purifying the unsaturated fatty acid-containing oil or oleochemical prior to blending the oil or oleochemical with the compounds of formula (I) comprises eluting the unsaturated fatty acid-containing oil or oleochemical through adsorption media to remove water and acid.

General [00140] Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications. The invention also includes all of the steps, features, compositions and compounds referred to or indicated in the specification, individually or collectively and any and all combinations or any two or more of the steps or features.

[00141] The present invention is not to be limited in scope by the specific embodiments described herein, which are intended for the purpose of exemplification only. Functionally equivalent products, compositions and methods are clearly within the scope of the invention as described herein.

[00142] The entire disclosures of all publications (including patents, patent applications, journal articles, laboratory manuals, books, or other documents) cited herein are hereby incorporated by reference. No admission is made that any of the references constitute prior art or are part of the common general knowledge of those working in the field to which this invention relates.

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PCT/AU2015/000284 [00143j Each document, reference, patent application or patent cited in this text is expressly incorporated herein in their entirety by reference, which means that it should be read and considered by the reader as part of this text. That the document, reference, patent application or patent cited in this text is not repeated in this text is merely for reasons of conciseness.

[00144] Any manufacturer’s instructions, descriptions, product specifications, and product sheets for any products mentioned herein or in any document incorporated by reference herein, are hereby incorporated herein by reference, and may be employed in the practice of the invention.

[00145] As used herein the term derived” and “derived from” shall be taken to indicate that a specific integer may be obtained from a particular source albeit not necessarily directly from that source.

[00146] As used herein, the singular forms “a,” “an” and “the” include plural references unless the context clearly dictates otherwise.

[00147] Throughout this specification, unless the context requires otherwise, the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

[00148] Other than in the operating example, or where otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term about. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. Hence “about 80%” means “about 80%’’ and also “80%”. At the very least, each numerical parameter should be construed in light of the number of significant digits and ordinary rounding approaches.

[00149] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value;

WO 2015/172185

PCT/AU2015/000284 however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements [00150] Other definitions for selected terms used herein may be found within the detailed description of the invention and apply throughout. Unless otherwise defined, all other scientific and technical terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the invention belongs.

[00151] The following examples serve to more fully describe the manner of using the above-described invention, as well as to set forth the best modes contemplated for carrying out various aspects of the invention. It is understood that these methods in no way serve to limit the true scope of this invention, but rather are presented for illustrative purposes.

EXAMPLES

Example 1: Testing Samples of Formula I to VII

Materials

Oils

HOSO - Goodman Fielder Sunola®

Envirotemp®FR3™ - Cargill

Sunflower Oil - Crisco® Sunflower Oil

Additives

Sample No	Additive	Source
1	Irgartox L57	BASF
2	Irganox L109	CIBA
3	Irgamet 30	CIBA
4	Irganox L135	BASF
5	Irgamet 39	BASF
73	Butylated hydroxytoluene, DBPC	Lanxess
74	2,6-Di-tert-butylphenol	Sigma Aldrich
76	4-tert-Butylphenol	Sigma Aldrich

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Samples

Sample No	Compound name	Source
6	p-t-butyl ca!ix[4]arene (Custom)	Manufactured for this study as described below
6	p-t-butyl calix[4]arene Sigma Aldrich 95%	Sigma Aldrich
6	p-t-butyi calix[4]arene TCI (Japan) >98%	TCI (Japan)
7	p-t-butylthia calix[4]arene	Manufactured for this study using the method of Arduini et al (1986) Tetrahedron 42: 20892100
9	p-t-butyl calix[4]arene-tetraacetic acid tetraethyl ester	Manufactured for this study using the method of Kumagai et al (1997) Tetrahedron Letters 38:3971-3972
10	meso-Octamethyicalix(4)pyrrole Sigma Aldrich 97%	Sigma Aldrich
28	4-t-butylcalix[6]arene Sigma Aldrich 95%	Sigma Aldrich
29	4-t-Butylcalix\|8]arene Sigma Aidrich 95%	Sigma Aldrich
140	p-t-butyl calix[5]arene TCI Japan >98%	TCI Japan
145	C-undecylcalix[4]resorcinarene Monohydrate TCI Japan >90%	TCI Japan

[00152] All test compounds were provided in HOSO oil as described above. Those samples tested in the presence of a metal deactivator (Sample No + MD), were tested using Irgamet 30® as the metal deactivator.

Methods [00153] The acceptable range of dielectric fluid properties for typical dielectric fluids used in power and distribution transformers is defined by the following standards: ASTM 6871 “Standard Specification for Natural (Vegetable Oil) Ester Fluids Used in Electrical Apparatus”.

Method for Testing Dielectric Dissipation Factor, Resistivity at 20°C and Resistivity at

90/100°C [00154] Testing of Dielectric Dissipation Factor (DDF), Resistivity at 20°C and Resistivity at 90/100°C was carried out on an Oil Tan-Delta and Resistivity Test System (Ajit Electronics; India). The DDF was tested at 90°C.

WO 2015/172185

PCT/AU2015/000284 [00155] To meet the ASTM 6871 criteria, the DDF at 60 Hz should be a maximum of 0.20% at 25°C and 4.0% at 100°C. The Resistivity at 20°C should be >10GOhms and Resistivity at 90/100°C should be >450MOhms.

Method for Testing Oxidative Stability [00156] The oxidative stability of the dielectric fluid composition was tested using the Rancimat Oxidation Stability test EN14112 (2003). In this test, a volume of 10L per minute air is passed through the dielectric fluid at 110°C. The end point is determined when the production of acids begins, as indicated by a conductivity increase.

[00157] To meet the EN14112 (2003) criteria, the oxidative stability should be >6 hours.

Method for Testing Oxidative Stability I EC 61125 Method B [00158] The oxidative stability of the dielectric fluid composition was tested using the IEC 61125 Method B. it measures the time taken for a phenolphthalein indicator to lose colour. At this point, volatile acidity is around 0.28mg KOH/g oil

Manufacture of Custom p-t-butyl calix[4]arene

A. Preparation of precursor.

[00159] A mixture of 100 g (0.666 mol) of p-tert-butylphenol (Aldrich Chemical Company, Inc.), 62 mL of 37% formaldehyde solution (0.83 mol of HCHO) (Fisher Chemical Company), and 1.2 g (0.03 mol) of sodium hydroxide (corresponding to 0.045 equiv with respect to phenol) in 3 mL of water is placed in a 3-L, three-necked, roundbottomed flask equipped with a mechanical stirrer. The contents of the open flask are allowed to stir for 15 min at room temperature, and then heated for 2 hr at 100-120°C by means of a heating mantle. Care should be taken not to allow the heating mantle to get so hot as to char the solid material on the walls of the flask. The reaction mixture, which is clear and colourless at the beginning, becomes light yellow after 30 min, a somewhat deeper yellow after 2 hr, and eventually changing to a thick slurry as the water evaporates and finally turning to a deep yellow or brown-yellow very viscous mass. During this period there is considerable frothing, and the reaction mixture fills most of the flask before shrinking back to the original volume. Stirring is discontinued, the reaction vessel is removed from the heating mantle, and the reaction mixture is

WO 2015/172185

PCT/AU2015/000284 allowed to cool to room temperature. To dissolve the residue 800-1000 mL of warm diphenyl ether is added to the flask and the contents are stirred, the process generally requiring at least 1 hr.

B. Pyrolysis of the precursor.

[00160] The 3-L, three-necked flask is fitted with a nitrogen inlet. The contents of the flask are stirred and heated (110-120°C) with a heating mantle while a stream of nitrogen is blown rapidly over the reaction mixture to facilitate the removal of the water as it is evolved. During this period the colour of the solution changes from yellow to a grey or a light brown. When the evolution of water subsides and a solid starts to form (prior to attaining the reflux temperature), the flask is fitted with a condenser, and the contents of the flask are stirred and heated to ca. 150-160°C for a few minutes and then at reflux for 3-4 hr under a gentle flow of nitrogen. During this phase of the reaction the solid dissolves, and a clear dark-brown to greyish-black solution is formed. The reaction mixture is cooled to room temperature (some solid separates), and the product is precipitated by the addition of1.5 L of ethyl acetate. The resulting mixture is stirred for 15-30 min and allowed to stand for at least 30 min. Filtration yields material that is washed twice with 100-mL portions of ethyl acetate, once with 200 mL of acetic acid, twice with 100-mL portions of water, and twice with 50-mL portions of acetone to yield ca. 66 g (61%) of crude product. The white-to-beige-colored crude product is dissolved in ca. 1600-1800 mL of boiling toluene that is concentrated to ca. 700-900 mL. On cooling, 61 g (49%) of product is obtained as glistening white rhombic crystals, mp 342-344°C. The product of crystallization from toluene is a 1:1 complex of p-tertbutylcalix[4]arene and toluene, from which the toluene can be removed by drying under high vacuum (< 1 mm) and high temperature (> 140°C) for an extended period of time (48 hr).

Results [00161] Table 1 shows the properties of various base oils, without additives. Although the baseline stability of pure HOSO is variable, it is clear that the oxidation stability of HOSO does not exceed 7 hours.

[00162] In all Tables, where multiple values are provided for oxidation stability, the same samples were tested on multiple days. There was often a large difference in base

WO 2015/172185

PCT/AU2015/000284 oil and base oil plus sample oxidation stability values on different days, and so the base oil plus samples were generally tested concurrently with base oil alone each time. If multiple values appear in the “Oxidative Stability”, Oxidative Stability IEC 61125 Method B” and/or “Corresponding base oil stability” columns of the Tables, the values in line with each other were determined on the same day.

[00163] Table 2 shows the properties of commercial additives for dielectric fluids, tested using HOSO as the base oil. It can be seen that the commercial additive L109, when incorporated into a dielectric fluid composition at low concentrations, does not increase the performance of the dielectric fluid composition above that of HOSO alone in terms of oxidative stability.

[00164] 2,6-Di-tert-butyl-4-methylphenol, 2,6-Di-tert-butyl-p-cresol (DBPC) and 4tert-Butylphenol are non-macrocyclic analogues of the t-But calixraenes. Addition of these compounds to HOSO does not increase the oxidative stability performance of the dielectric fluid composition significantly beyond that of pure HOSO.

[00165] Tables 3 to 7 provide results for the testing of DDF, resistivity and oxidative stability of various compounds of formulas (I) to (VII).

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Φ ω

(C co to

Φ e

φ

ΟΟ

CL

Φ _Q ¢0

H

d Stab 61125 Method B	>	3.5	4 6,5	⁵ 3.5 j	00	00	5.5	4 4.5	LTl r<
X O	u UJ
λ
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oi		1/)								t—f
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ΙΛ	X
trt 4)	o (D	un								o
cc	uS								ro
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u.		=t								cn
Q	xp os	O)								w
Q	fQ								o
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		o				O	2			_o
—		o				> C	ΠΊ tr			c “7
o		X				U-l	U-			IZ)

WO 2015/172185

PCT/AU2015/000284 (η

Φ >

TJ <

to c

o c

Φ >

f— o

O ω

Φ

Q.

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<Si

Φ £2 to

H

Corresponding base oil stability (Hours)

5 3.25

in

⁵ ! 3.25 j

in

1 ^s'⁹

OxidStab [EC 61125 Method B (Hours)

8 5.5

4.25 3.25

in in

! 15.75

4.25 3.25

5.25

m nJ tH

Γ-

Oxid Stab (Hours)

>7.0

4.4 >7.5

6.2

CO ID

Resist 90/100 °C (MOhmns)

o CM

1100

500

o in CM

O CM CM

o l£> m

310

! 510

O t-· m

o s—1 «t

Resist 20 °C (GOhms)

rs CM

ID CSl

m x—1

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1.5

in

5.8

cn r<

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S3 os p

os rH ps t—1

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ΐ£ 00 in

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s? t—1 00 τι

£ o r-s st

CM O •st

S£> os in =t •St

Cone (gm/lOOml)

Lt) C-J ό

0.25

0.025

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0.25

m CM o

0.25 |

0.025 i

0.025

0.25

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0.25

Additive

rs ul _l X 0 c ns ω

cn o t—1 _j X o c TO h&

cn o t—E —J X o c ns £?

οι o t—I -I X o c ns £?

in M tH _] X o c TO £?

Irgamet 30

Irgamet 39

| Butylated hydroxytoluene, DBRC

Butylated hydroxytoluene, DBPC

o c <u _c 0. £T □ _Q <u 4-J □ 1 ID PsT

o £ 01 X Q. S' □ _D 1 V □ to ri

2,6-Di-t-butyl phenol

4-t-Butyl phenol

Sample No

tH

f\|

CM

o + fN

St

M

in

r>

co r>

o s + r>

74

St rs

1 76

WO 2015/172185

PCT/AU2015/000284

TO =5

E

L_ o

LL

Mo (Λ

Ό

C o

Q.

E o

O o

cn c

4—>

ω

CD

I— co

CD _Q

CO

Corresponding base oil stability (Hours)
OxidStab IEC 61125 Method B (Hours)
Oxid Stab (Hours)
Resist 90/100 °C (MOhmns)	a o to co t—1 v1	o to CN
Resist 20 °C (GOhms)	; 0.48	fO	5
DDF Result (%)	CD o LO o rN t—1	7.9	o o LO «3- LO
Cone (gm/lOOml)	0.25	0.025 1	r4 o ό
Compound name i	<ZJ o £ X >- 4= ω E Π3 o o ΙΛ 0) E	CU o a. _tx cn u > _c ω E TO (J o 1 o (Λ CU E	QJ s L_ >» JQ. ΐ >» 4*1 CU E δ o 1 O VI <U E
Sample No	o T-{	o ϊ—ε	o

H

WO 2015/172185

PCT/AU2015/000284 <0

E p

o tfl

T3 c

o

CL cn .ε w

Φ 'Τ’

Φ

-Ω ro

Corresponding base oil stability (Hours)		on	on	on	ro	1/)			3.5				7.0		7.0
Oxid Stab IEC 61125 Method B (Hours)		on T—) ( CM H «4	LTl· <4·	tn co	«4 on	5.75			4.5		ro		10.5	5.25	10.5
Oxid Stab (Hours)											0 rs. LO
Resist 90/100 °C (MOhmns)	o co	610	610		730	550			1400		8000		570		700
Resist 20 °C (GOhms)	PJ l<	r\l LT)	5.2		6.0	5.7			cn		3.32		Γ. r<	LT)	7.2
u.	4.96	3.97	3.97		3.85	4.36	5.7		1.45				τ—1 LO fO	7.55	3.14
Cone (gm/lOOml)	0.25	0.25	0.25	0.125	0,025	0.025	0.25	0.25	0.025	0.025	0.025	0.025	0.025	0.025	0.025
Compound name	p-t-butyl calix[4Jarene (Custom)	p-t-butyl calix(4]arene _; (Custom)	p-t-butyl calix[4]arene Sigma Aldrich 95%	p-t-butyl calix[4]arene Sigma Aldrich 95%	p-t-butyl calix[4]arene 1 Sigma Aldrich 95% \|	p-t-butyl calix[4]arene Sigma Aldrich 95%	p-t-butyl calixI4]arene TCI (Japan) >98%	p-t-butyl calixl4]arene TCI (Japan)	p-t-butyl calix[4]arene TCI (Japan) >98%	p-t-butyl calix[4]arene TCI (Japan)	p-t-butyl calix[5]arene TCI Japan >98%	p-t-butyl calix[5]arene TCI Japan >98%	4-t-buty lea 1 ix[6] arene Sigma Aldrich 95%	0) £ se ra, fn 01 ‘x¹ -G S -0 -? £ V ,SP 'if ΪΛ	01 c CD i-2, lo 00 ΟΊ _2 o >> <r 3 (0 °P £ V ,5P 4 wn
Sample No	lo	LO	LO	LO	LO	0 + LO	LO	0 £ + LO	LO	0 + LD	¹⁴⁰	o 2 + 0 «4	00 «Ν	Q + 00 «Ν	29

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Table 5: Testing of compounds of formula (IV)

Corresponding base oil stability (Hours)	3.5
OxidStab IEC 61125 Method B (Hours)	4.5
Oxid Stab ' (Hours)
Resist 90/100 °C (MOhmns)	380
Resist 20 °C (GOhms) __	6.2
DDF (%)	5.79
Cone (gm/lOOml)	: 0.025
Compound name !	C-undecylcalix[4]resorcinarene Monohydrate TCI Japan >90%
Sample No	145

£ =3 £

o o

ω σ

ο

Ω.

co c

CD ο

Χ5 (0

I—

Corresponding base oil stability (Hours)	6-5
OxidStab IEC 61125 Method B : (Hours)	LQ
Oxid Stab (Hours)
Resist 90/100 °C (MOhmns)	o «d^- in
Ίλ * £ w «=> Ο Φ o in Q£ fM ϋ	7-5
LL Q 'Co* a	3.73 \|
1 o o C 3	Lf) ΓΝ O ό
Compound name	<u c <u <0 ic u ,^ro Ic +-· & □ -Q t M 1 Q.
Sample No	h-

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Table 7: Testing of compounds of formula (VII)

Corresponding base oil stability (Hours)
Oxid Stab 1EC 61125 Method B (Hours)
Oxid Stab (Hours)
Resist 90/100 °C (MOhmns)	ΟΊ tn
57Γ « £ o QJ Q tn ex: ϋ	0.82	S8'0	d
LL· Q Γ? O	30.1	o to o CO G <3j	O ° o in
Cone (gm/100m[)	m ό	0.025	0.01
Compound name	p-t-butyl calix[4]arenetetraacetic acid tetraethyl ester	p-t-butyl calix[4]arenetetraacetic acid tetraethyl ester	p-t-butyl calix[4]arenetetraacetic acid tetraethyl ester
Sample No	04	04

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Example 2: Further testing of p-t-butyl calix[4]arene [00166] Further testing of Sample 6 (p-t-butyl calix[4]arene) in HOSO at 0.25g/L was carried out.

Method

Testing for Oxidation Stability of insulating Oil by Pressure Vessel [00167] The procedure is performed according to ASTM test method D2112, with the modification that testing is carried out at 110°C for 64 minutes and water was not used in the sample preparation step. The test involves adding the test oil to a vessel and adding a copper catalyst. The pressure vessel was then charged with 95 psi of oxygen and rotated a specific angle in a bath set at a specific temperature. The termination of the test occurs when the pressure drops by 25 psi.

[00168] When tested using the unmodified ASTM test method D2112, the dielectric fluid comprising Sample 6 in HOSO lasted 25 minutes. When tested using the modified ASTM test method D2112, the dielectric fluid comprising Sample 6 in HOSO lasted 64 minutes.

Power Factor Valued Oxidation Testing (PFVQ) [00169] The Power Factor Valued Oxidation Testing (PFVO) periodically measures the power factor of an oil while it is being aged at 95°C in the presence of copper and air. Consequently, it indicates the dielectric-loss characteristics of insulating oil as a function of accelerated aging conditions. The resulting graph of power factor versus time characterizes a given oil. It is applicable as a continuity test, as well as a measure of oi! quality. The test is run concurrently with the Doble Sludge-Free Life test which measures the time until the oil forms sludge.

[00170] The dielectric fluid of the present invention comprising HOSO oil and Sample 6 (p-t-butyl calix[4]arene) achieved a PVFO result as provided in Figure 2. Although the power factor rose above 4.5% at the end of the testing cycle, this is considered to be quite good for a natural ester insulating liquid'

WO 2015/172185

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Doble Sludge Free Life (SFL) Testing [00171] The Sludge-Free Life of an oil, sampled at 8-hour intervals at 95°C during the PFVO test, is the number of hours which have elapsed between the start of the test and the time of taking the last sample which showed a sludge-free precipitation test. To date, standard parameters for sludge free oil life have only been developed for mineral oils, generally with BHT or DBPC included as an inhibitor. Table 8 provides the standards for such mineral oils.

[00172] Table 8: Sludge Free parameters

Oil Sample type	Requirement of Doble TPOS (hours)
Uninhibited Transformer oii	>40
Type ! oii, < 0.08% inhibitor	>64
Type ii oii, < 0.30% inhibitor	>80

[00173] The test sample of dielectric fluid of the present invention comprising HOSO oil and Sample 6 (p-t-butyl calix[4]arene) provided a sludge free life of 88 hours.

Oxidation Stability Testing [00174] The oxidation stability was performed in accordance to the modifications of the IEC61125C method as defined in [EC 62770, Annex A. The temperature was 120°C, catalyst was copper, sparging gas was air and duration of test was 48hrs.

[00175] The test sample of dielectric fluid of the present invention comprising HOSO oil and Sample 6 (p-t-butyl ca!ix[4]arene) had an oxidation stability within the limits of IEC 61125 Method C (modified).

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Table 9: Results of Oxidation Stability Testing - Sample 6 in HOSO

Standard Limits	HOSO + sample 6 result
< 0.6 mg KOH/g No requirement < 0.5 absolute Viscosity Increase, <30%	Volatile Acids: 0.07 Soluble Acids: 0,01 Total Acids: 0.08 Total Sludge: 0.01 DDF at 90°C: 0.0782 Viscosity Inc: 12.5%

Viscosity Increase Testing [00176] The sample was aged for 4 days via conditions as outlined in IEC 61125C. Viscosity testing was performed at 40°C by using the criteria outline in ASTM D445.

Table 10: Viscosity testing results - Sample 6 in HOSO

Elapsed Days of Aging	Viscosity mm2/s
0	39.48
1	41.60
2	44.40
3	49.41
4	59.62

[00177] Numerous variations and modifications will suggest themselves to persons skilled in the relevant art, in addition to those already described, without departing from the basic inventive concepts. All such variations and modifications are to be considered within the scope of the present invention, the nature of which is to be determined from the foregoing description.

1. A dielectric fluid composition comprising a compound selected from the group defined by formula (I) and an unsaturated fatty acid-containing oil or oleochemical, wherein formula (I) is:

Claims

wherein

A is a 5 or 6 membered aromatic or heterocyclic ring;

R_a is OH, or C_mH_2m+i wherein m = 0 - 18, or a hydrocarbyl, or a heterosubstituted hydrocarbyl group;

R_b is OH, or C_mH_2m+i wherein m = 0 - 18, or a hydrocarbyl, or a heterosubstituted hydrocarbyl group;

R_c is OH, or a hydrocarbyl, or a hetero-substituted hydrocarbyl group, or (CH₂)_aCOOR_g where a = 1 - 10 and R_g is either H or hydrocarbyl;

R_d = OH, or C_mH_2m+i wherein m = 0 -18;

X is a divalent bridging group such as S, O or N, or an optionally substituted or unsubstituted methylene group; and n has a value of at least 4.
2. A dielectric fluid composition according to claim 1 comprising a compound selected from the group defined by formula (II) and an unsaturated fatty acidcontaining oil or oleochemical, wherein formula (II) is:

WO 2015/172185

PCT/AU2015/000284 wherein

X is a divalent bridging group such as S, O or N or an optionally substituted methylene group;

R_a is a hydrogen, hydroxyl, hydrocarbyl or hetero-substituted hydrocarbyl group;

R_b is a hydrogen, hydroxyl, hydrocarbyl or hetero-substituted hydrocarbyl group;

R_c is a hydrogen, hydroxyl, hydrocarbyl or hetero-substituted hydrocarbyl group;

R_d is a hydrogen, hydroxyl, hydrocarbyl or hetero-substituted hydrocarbyl group;

and wherein either R_a is hydroxyl and Rb, R_c and R_d are independently either hydrogen, hydrocarbyl or hetero-substituted hydrocarbyl, or

R_b and R_d are hydroxyl and R_a and R_c are independently either hydrogen, hydrocarbyl or hetero-substituted hydrocarbyl, or

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Rb, R_c and Ra are hydroxyl and R_a is either hydrogen, hydrocarbyl or heterosubstituted hydrocarbyl, or

R_a and R_c are hydroxyl, and R_b and Rd are independently either hydrogen, hydrocarbyl or hetero-substituted hydrocarbyl;

and n has a value of at least 4.
3. A dielectric fluid composition according to claim 1 comprising a compound selected from the group defined by formula (III) and an unsaturated fatty acidcontaining oil or oleochemical, wherein formula (III) is:

wherein

R_c is C_mH2m+i wherein m is 0 -18;

R_h is C_mH_2m+i wherein m is 0 -18; and n is 4, 5, 6, 7 or 8.
4. A dielectric fluid composition according to claim 1 comprising a compound selected from the group defined by formula (IV), and an unsaturated fatty acidcontaining oil or oleochemical, wherein formula (IV) is:

WO 2015/172185 PCT/AU2015/000284 wherein

R_a is C_mH₂m+i wherein m is 0 -18;

Rh is C_mH₂m+i wherein m is 0 -18; and n is 4, 5, 6, 7 or 8.
5. A dielectric fluid composition according to claim 1 comprising a compound selected from the group defined by formula (V) and an unsaturated fatty acidcontaining oil or oleochemicai, wherein formula (V) is:

wherein

R_a is C_mH_2m+1 wherein m is 0 -18;

Rh is C_mH₂m+i wherein m is 0 -18; and n is 4, 5, 6, 7 or 8.
6. A dielectric fluid composition according to claim 1 comprising a compound selected from the group defined by formula (VI) and an unsaturated fatty acidcontaining oil or oleochemical, wherein formula (VI) is:

WO 2015/172185

PCT/AU2015/000284 wherein

R_c is C_mH_2m+i wherein m is 0 - 18, or SO₂Y where Y is H, or an alkali metal;

R_h is C_mH_2m+i wherein m is 0 -18;

X is S, SO₂, N, 0 or an optionally substituted methylene group; and n is 4, 5, 6, 7 or 8.
7. A dielectric fluid composition according to claim 1 comprising a compound selected from the group defined by formula (VII) and an unsaturated fatty acidcontaining oil or oleochemical, wherein formula (VII) is:

wherein

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R_c is C_mH_2m+i wherein m is 0 - 18, or NH₂, or SO₂Y where Y is H or an alkali metal;

R_h is C_mH_2m+1 wherein m is 0 -18;

R_a is (CH₂)_aCOOR_g where a = 1 - 12 and R_g is either H or hydrocarbyl;

X is S, SO₂, N, O or an optionally substituted methylene group; and n is 4, 5, 6, 7 or 8.
8. The dielectric fluid composition of any one of claims 1 to 7 wherein the unsaturated fatty acid-containing oii or oleochemical is sourced from a naturally occurring or renewable source, including plants (including algae), animals, fungi, bacteria, etc.
9. The dielectric fluid composition of claim 8 wherein the unsaturated fatty acidcontaining oii or oleochemical:

a) is a mono-unsaturated fatty acid-containing oil or oleochemical; and/or

b) has a mono-unsaturated fatty acid content of >60%, or about 80%; and/or

c) contains oleic acid.
10. A process for producing a dielectric fluid composition comprising the step of:

a) blending a volume of unsaturated fatty acid-containing oil or oleochemical with a compound selected from a compound selected from the group comprising: formula (I), formula (II), formula (III), formula (IV), formula (V), formula (VI), and/or formula (VII).
11. A process according to claim 10 wherein the unsaturated fatty acid-containing oil or oieochemical:

a) is a mono-unsaturated fatty acid-containing oil or oleochemical; and/or

b) has a mono-unsaturated fatty acid content of >60%, or about 80%; and/or

c) contains oleic acid.

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12. A transformer having a housing which accommodates a transformer core/coil assembly and a dielectric fluid composition surrounding said core/coil assembly, wherein the dielectric fluid composition comprises a compound selected from the group comprising: formula (I), formula (II), formula (III), formula (IV), formula (V), formula (VI), and/or formula (VII), and a mono-unsaturated fatty acid-containing oil or oleochemical.
13. A transformer according to claim 12 wherein the unsaturated fatty acid-containing oil or oleochemical:

a) is a mono-unsaturated fatty acid-containing oil or oleochemical; and/or

b) has a mono-unsaturated fatty acid content of >60%, or about 80%; and/or

c) contains oleic acid.
14. A method of increasing the oxidative stability of a dielectric fluid comprising an unsaturated fatty acid-containing oil or oleochemical, said method comprising the step of: biending the dielectric fluid containing an unsaturated fatty acidcontaining oil or oleochemical with a compound selected from the group comprising: formula (I), formula (II), formula (III), formula (IV), formula (V), formula (VI), and/or formula (VII).
15. A method according to claim 14 wherein the unsaturated fatty acid-containing oil or oleochemical:

a) is a mono-unsaturated fatty acid-containing oil or oleochemical; and/or

b) has a mono-unsaturated fatty acid content of >60%, or about 80%; and/or

c) contains oleic acid.
16. Use of a composition comprising:

a) an unsaturated fatty acid-containing oil or oleochemical;

b) a compound selected from the group comprising: formula (I), formula (II), formula (III), formula (IV), formula (V), formula (VI), and/or formula (VH),

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17. The use of claim 16 wherein the unsaturated fatty acid-containing oil or oleochemical:

a) is a mono-unsaturated fatty acid-containing oil or oleochemical; and/or

b) has a mono-unsaturated fatty acid content of >60%, or about 80%; and/or

c) contains oleic acid.
18. Use of a compound selected from the group comprising: formula (I), formula (II), formula (III), formula (IV), formula (V), formula (VI), and/or formula (VII) as an additive for a dielectric fluid.
19. An antioxidant for use with an unsaturated fatty acid-containing oil or oleochemical to form a dielectric fluid, wherein the antioxidant is a compound selected from the group comprising: formula (I), formula (II), formula (111), formula (IV), formula (V), formula (VI), and/or formula (VII).
20. The antioxidant for use according to claim 19 wherein the unsaturated fatty acidcontaining oil or oleochemical:

a) is a mono-unsaturated fatty acid-containing oil or oleochemical; and/or

b) has a mono-unsaturated fatty acid content of >60%, or about 80%; and/or

c) contains oleic acid.
21. The dielectric fluid composition of claim 1, wherein the composition further comprises one or more alkyl esters.

The dielectric fluid composition of claim 20 wherein fatty acid moieties of the fatty acid alkyl esters are substantially homologous with the fatty acid content of the unsaturated fatty acid-containing oil or oleochemical of the dielectric fluid composition, and or/ where the fatty acid moieties of the fatty acid alkyl esters are substantially homologous with the fatty acid content of the mono-unsaturated fatty acid-containing oil or oleochemical of the dielectric fluid composition.