WO2012001041A1

WO2012001041A1 - Dielectric triglyceride fluids

Info

Publication number: WO2012001041A1
Application number: PCT/EP2011/060905
Authority: WO
Inventors: Karin Gustafsson; Tommaso Auletta; Leif Pettersson; Katarina Ohlsson
Original assignee: Abb Research Ltd
Priority date: 2010-06-30
Filing date: 2011-06-29
Publication date: 2012-01-05
Also published as: WO2012001041A9

Abstract

The present invention pertains to triglyceride-based dielectric fluids having fatty acid compositions of between approximately 25% and approximately100% fatty acids comprising at least one carbon-carbon double bond, and wherein approximately 0-100% of the carbon-carbon double bonds are chemically modified. Further, the present invention pertains to the use of the dielectric triglyceride fluids in electrical and/or power applications, electrical and/or power apparatuses comprising the dielectric triglyceride fluids, as well as methods for preparing said fluids. Moreover, the present invention relates to chemically modified triglycerides for use in dielectric fluids.

Description

Dielectric triglyceride fluids

Technical field

The present invention pertains to triglyceride-based dielectric fluids for electrical and/or power applications, methods for preparing said fluids, electrical and/or power apparatuses comprising said fluids, as well as uses of the dielectric fluids as such.

Technical background

Insulating, dielectric fluids are used in electrical apparatuses like transformers, capacitors, switchgear, bushings, etc., and have a multitude of functions. Dielectric fluids act as electrically insulating medium separating the high voltage and the grounded parts within the apparatus and function as a cooling medium to transfer the heat generated in the current-carrying conductors. Additionally, the fluids provide a medium to monitor the health of a transformer during operation.

In addition to the basic abovementioned functions, the insulating liquid should also comply with other necessary and desired requirements. The fluid should have a high efficiency, long life, and minimal environmental impact. Further, the fluid has to be compatible with the materials used in the electrical equipment and it should not constitute a hazard for the health and safety of personnel. In practice, insulating fluids should fulfill various physical, electrical, and chemical properties and all these properties are regulated through standards and specifications that stipulate the min- imum requirements for each one of the important properties.

For performing the electrical insulation function, the insulating oil must be designed to withstand the required electrical stresses as per the design specifications of the electrical apparatus. The dielectric breakdown withstand voltage under AC (50/60 Hz) and Lightning Impulse (1.2/50 μ8) is considered as the most important parameter from an electrical insulation perspective. The dielectric breakdown withstand voltage can be defined as the voltage required to obtain a flashover in the oil between two electrodes of specified shape and placed at a certain distance from each other. The standards specify the type of electrodes and the gap distances required for the tests. The breakdown withstand is essentially an indicator of the oil purity from water, conducting particles, organic acids, and other electrolytes. These unwanted impurities in oil can be inherent to the oil or can be generated over a period of time due to aging of the oil itself or from other sources. The other dielectric parameters of importance are the permittivity (which gives a measure of the electric field distribution in the system) and the dissipation factor (gives a measure of the dielectric losses). An understanding of the dielectric losses of insulating oils provides an indication of the impurity content or degradation over time of the oil in question.

Magnetic and electrical fields in a transformer are associated with losses that trans- late into heat generation. Solid insulation materials used in conjunction with insulating liquids will degrade over time and it is well known that the degradation rate is a function of temperature. In order to preserve the functionality of the insulation system and also to prolong the apparatus life, it is necessary to regulate the temperature in an electrical apparatus. For example, in a transformer, the cooling system (duct diameter, oil volume and coolers) is designed to guarantee that under normal conditions, the oil flow is adequate to dissipate the heat produced in the system. The oil properties, therefore, affect the heat dissipation and the most relevant parameters are the heat capacity, the viscosity, thermal conductivity and the flow properties. Additional important properties of an insulating fluid for applications in power and/or electrical apparatuses are pour point, impregnation capability, blendability and water solubility/max water content. In terms of the chemical properties, the fluid has to be inert with many different materials, be free of sulphur and halogens, possess high flash/fire points and should not release or absorb gasses. A negative gassing tendency is a desirable property for the prevention of partial discharge. Traditionally, petroleum-based oils have been used as the insulating fluid in oil- filled transformers mainly because of advantageous properties relating to low viscosity, low pour point, high dielectric strength, easy availability and low cost. During the last couple of decades, the transformer industry has been undergoing several changes. The market demand for compact and efficient transformers with guaranteed long-term performance coupled with the problems of corrosive sulphur and oil quality issues have warranted the need for enhancement in the properties of transformer oil. Further, strict environmental regulations towards health and safety have been steadily evolving and the huge liability risks in the case of transformer fires or outages have raised a cause for concern. Considering these factors, serious research and development efforts were directed since 1990 towards identifying alternatives to mineral oil.

Amongst the several options which are generally known, e.g., ester based fluids, si- licone fluid, chlorinated benzenes, perchloroethylene, polyalphaolefins etc., ester based fluids (both synthetic and natural) are excellent alternatives to mineral oil, primarily due to their high biodegradability (lower environmental risk) and high values of flash points and fire points (high fire safety factor). Further, natural esters based on vegetable oils, with the main constituent being triglycerides, are preferred due to their renewability. In spite of their appealing properties in terms of biodegradability and fire safety, vegetable oils are not utilized to any greater extent for power and/or electrical applications, as a result of a number of disadvantageous chemical and/or physical properties. Summary of the invention

There are consequently substantial needs in the art for improving the performance of triglyceride-based fluids for power and/or electrical applications, in order to replace the rather disadvantageous insulation fluids currently utilized within the in- dustry. Generally, all vegetable oils have a high viscosity as compared to mineral oil. If a transformer has to be operated at higher voltage levels, it may occasionally be necessary to circulate the oil inside the transformer through pumps. The high viscosity of vegetable-based liquids then poses several challenges towards the design of the transformer, especially from a cooling point of view. This leads to the requirement of a lower viscosity value for vegetable-based fluids.

Biodegradable natural ester-based liquids have high pour point temperatures as compared to mineral oil, which can be considered as a major drawback if the elec- trical apparatuses comprising the fluid have to be operated in extremely cold environments, a problem that is especially pronounced at higher voltage ratings. Further, a low pour point can cause changes in the dielectric and/or other properties of the fluid and the solid insulation impregnated with this fluid. This in turn can force design changes in the transformer which can lead to an increase in the manufacturing costs. A very low value of pour point is therefore desired for the vegetable fluid.

Oxidation behavior of the materials is an important parameter when it comes to insulation degradation in a transformer. The aging of pressboard insulation over time releases small amounts of oxygen into the oil, and therefore the oil has to withstand the oxidation-induced degradation. For natural ester fluids, the inherent stability to oxidation is highly dependent on the compositions of fatty acids in the base oil. Ester oils which are composed only of saturates (only C-C bonds in its structure) are stable against oxidation. Specific heat in combination with thermal conductivity is also an important property of dielectric fluids. A higher specific heat will cause a lower rise in the temperature of the oil and a higher thermal conductivity will ensure that even if the speed of circulation of the oil is marginally slower than what it is in the case of mineral oil, the amount of heat conducted from the hot-spot regions in the transformer will be high- er. A higher thermal conductivity can also result in an enhanced heat transfer at slightly higher temperatures because the viscosity of the ester fluid would be reduced at those temperatures.

Although several properties of the fluid, for instance viscosity, pour point and oxidation stability, can be modified or improved through the use of additives, there are certain disadvantages associated with the inclusion of any additional material into the fluid system, as this may lead to a reduction in the dielectric properties. This issue generates the need for enhancing the properties of a dielectric, triglyceride fluid without the use of any additives.

There is consequently a substantial need in the art for providing dielectric fluids, preferably derived from renewable resources, having desirable properties in terms of inter alia reduced viscosity, improved heat transfer properties, reduced pour point, improved oxidation stability, and biodegradability, allowing for improved thermal management and better impregnation of pressboard/paper insulation, increased personnel health and safety, facilitated clean-up and prolonged service life of power and/or electrical apparatuses.

The present invention fulfils the above-identified needs, as it provides, inter alia, dielectric, triglyceride fluids, comprising various chemical modifications, displaying desirable properties in terms of inter alia reduced viscosity, improved heat transfer properties, reduced pour point, improved oxidation stability, and biodegradability, allowing for improved thermal management and better impregnation of press- board/paper insulation, increased personnel health and safety, facilitated clean-up and prolonged service life of power and/or electrical apparatuses. Further, the present invention relates to processes and methods for preparing said dielectric, triglyceride fluids, as well as their uses in electrical and/or power apparatuses, in addition to electrical and/or power apparatuses per se comprising said dielectric, triglyceride fluids. In a first aspect, the present invention relates to a dielectric, triglyceride fluid having a fatty acid composition of between about 25% and about 100%> fatty acids having at least one carbon-carbon double bond. The dielectric, triglyceride fluid may be obtained by reacting 0-100% of the carbon-carbon double bonds (i.e. approximately 0- 100%o of the at least one carbon-carbon double bonds) with at least one alkyl halide and/or at least one acyl halide, resulting in the formation of a modified triglyceride having increased triglyceride fluidity.

A second aspect of the present invention pertains to a method for preparing a dielec- trie, triglyceride fluid. The method comprises the steps of providing a suitable triglyceride composition having a fatty acid composition of between about 25% and about 100%o fatty acids having at least one carbon-carbon double bond, and subsequently reacting 0-100% of the carbon-carbon double bonds with at least one alkyl halide and/or at least one acyl halide, normally in the presence of a catalyst.

In a third aspect, the present invention relates to an electrical apparatus comprising the dielectric, triglyceride fluid of the present invention. In one embodiment, the dielectric fluid functions as an insulating medium, as a result of its superior properties in terms of inter alia oxidation stability, fluidity, insulation, permittivity, reduced pour point, reduced viscosity, etc.

A fourth aspect of the present invention pertains to various uses of the dielectric, triglyceride fluid in electrical apparatuses, and/or in apparatuses for power applications, or in components utilized in said apparatuses. Apparatuses of interest as per the present invention may for instance be transformers, capacitors, switchgear, bushings, etc., as well components and/or parts utilized in power or electrical applications.

In a fifth aspect, the present invention relates to the use of chemically modified triglycerides in dielectric fluids. The chemically modified triglyceride is obtainable by reacting at least one carbon-carbon double bond of a triglyceride fatty acid moi- ety with at least one alkyl halide and/or at least one acyl halide. Preferably, 0-100%, or more preferably 5-100%, of the carbon-carbon double bonds of a triglyceride fatty acid moiety (i.e. 0-100% of the carbon-carbon double bonds of the triglyceride composition as a whole) are reacted with at least one alkyl halide and/or at least one acyl halide

Detailed Description of the Invention

The present invention pertains to dielectric, triglyceride fluids for various power and/or electrical applications, methods for preparing said fluids, electrical and/or power apparatuses and components comprising said fluids, as well as various uses of said fluids.

Where features, embodiments, or aspects of the present invention are described in terms of Markush groups, a person skilled in the art will recognize that the invention may also thereby be described in terms of any individual member or subgroup of members of the Markush group. The person skilled in the art will further recognize that the invention may also thereby be described in terms of any combination of individual members or subgroups of members of Markush groups. Additionally, it should be noted that embodiments and features described in the context of one of the aspects and/or embodiments of the present invention may also apply mutatis mutandis to all the other aspects and/or embodiments of the invention. For instance, the fatty acid compositions described in connection with one aspect/embodiment may naturally also apply mutatis mutandis in the context of other as- pects/embodiments of the invention, all in accordance with the present invention as such.

All words and abbreviations used in the present application shall be construed as having the meaning usually given to them in the relevant art, unless otherwise indicated. For clarity, some terms are however specifically defined below. As will be apparent from the description and the examples, the term "fatty acids" shall be understood to relate to any one of the three acyl moieties of a triglyceride, meaning that, for instance, in a triglyceride fluid having a fatty acid composition of approximately 25% fatty acids having one carbon-carbon double bond, approximately 25% of all the acyl moieties in the triglyceride fluid as a whole comprises one carbon-carbon double bond.

Further, the term "triglyceride fluidity" generally relates to the reciprocal of the triglyceride viscosity, i.e. in the context of the present invention it shall be understood to pertain to the dynamics and/or mobility of the triglyceride fatty acid chains.

The term "naturally derived" shall be understood to pertain to natural fluids and/or oils derived from renewable resources, for instance natural and/or genetically modified (GMO) plant vegetable seeds and/or fat from various animal sources. Said fluids and/or oils are generally comprised of triglycerides, i.e. three fatty acids linked to a glycerol moiety. The fatty acids may be saturated or un-saturated, with the unsaturations being either conjugated and/or unconjugated. Conjugation may be introduced synthetically, enzymatically, or by using any other types of physical and/or chemical means, or it may be naturally occurring.

Further, vegetable fluids and/or oils may for instance be selected from the group comprising, but that is not limited to, peanut, rapeseed, castor, olive, corn, cotton, canola, soybean, sesame, linseed, safflower, grapeseed, palm, avocado, pumpkin kernel, macadamia nut, sunflower, and any combinations and/or mixtures thereof. Additionally, fluids and/or oils may be obtained from essentially any organisms being a suitable fluid and/or oil source. Fluids and/or oils derived from animal sources may be selected from the group comprising beef tallow, fish oils, lard, and any combinations and/or mixtures thereof. Naturally, various combinations of the above fluids and/or oils may be utilized, irrespective of the source.

The fatty acids comprised in the triglycerides may be of essentially any length, having essentially any number of unsaturations, either conjugated and/or unconjugated. Fatty acids may be for instance be selected from the group comprising, but that is not limited to, oleic acid, linoleic acid, a-linolenic acid, myristoleic acid, arachidonic acid, icosapentaenoic acid, palmitoleic acid, erucic acid, and docosahexaenoic acid, butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, vaccenic acid, gamma- linolenic acid, behenic acid, erucic acid, lignoceric acid, or any other fatty acids, suitably modified, if needed, in accordance with the requirements of the present invention.

The term "alkyl" or "alkylene", as used herein, is a (Ci-C₅q)alkyl or (C_r C₅o)alkylene moiety, e.g. a (C2-C3o)alkyl or (Cio-C4o)alkylene moiety and is intended to encompass also the alkyl or alkylene portion of any functional group, e.g. an alkoxy, alkylamino, or carboxypolyoxyalkylene group. Also, any alkyl or alkylene group in accordance with the present invention may be branched or unbranched, and/or cyclic. The term "alkyl" includes the monoradical derived from a branched or unbranched and/or cyclic alkane.

The term "reacting 0-100% of the carbon-carbon double bonds" shall in the context of the present invention be understood to pertain to reacting between approximately 0%> and approximately 100%> of the carbon-carbon double bonds in a triglyceride- based dielectric fluid composition as a whole (i.e. approximately 0-100% of the at least one carbon-carbon double bonds) with a suitable agent for chemical modification, for instance at least one alkyl halide and/or at least one acyl halide. The fatty acid moieties of the triglycerides as per the present invention may be saturated or unsaturated (naturally including polyunsaturated). Further in accordance with the present invention, the interval "0-100%" shall be understood to comprise for instance 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100%, as well as any intermediate numbers and ranges, and any ranges made up of the enumerated figures.

In a first aspect, the present invention relates to a dielectric, triglyceride fluid having a fatty acid composition of between about 25% and about 100%> fatty acids having at least one carbon-carbon double bond. The dielectric, triglyceride fluid may be obtained by reacting approximately 0-100% of the carbon-carbon double bonds (i.e. 0- 100%o of the carbon-carbon double bonds of the triglyceride composition as a whole) with at least one alkyl halide and/or at least one acyl halide, resulting in the formation of a modified triglyceride having increased triglyceride fluidity.

In a further preferred embodiment, approximately 5-100%> of the carbon-carbon double bonds are reacted with at least one alkyl halide and/or at least one acyl halide.

The reaction between fatty acids having at least one carbon-carbon double bond and the at least one alkyl halide and/or at least one acyl halide may take place through a Friedel-Crafts reaction mechanism, or a radical mechanism, or through any other reaction mechanism, known and/or unknown. Said reaction between fatty acids hav- ing at least one carbon-carbon double bond and the at least one alkyl halide and/or at least one acyl halide, which essentially results in the introduction of steric hindrance between the fatty acyl chains, leads to increased triglyceride fluidity, i.e. increased dynamics and facilitated motion of the triglyceride fatty acyl chains. In one embodiment, the at least one alkyl halide and/or the at least one acyl halide may further comprise at least one moiety that further increases triglyceride fluidity. In further embodiments, said moiety increasing the triglyceride fluidity may be a saturated or unsaturated, branched, linear and/or cyclic hydrocarbon, optionally substituted with at least one heteroatom. Said moiety that further increases the triglyceride fluidity may be attached to any part of alkyl the moiety of the alkyl halide and/or any part of the acyl moiety of the acyl halide, and, in yet another embodiment, said moiety may for instance be selected from the group comprising inter alia branched or linear, and/or cyclic, (Ci-C₅o)alkyl, (Ci-C₅o)alkenyl, and (Ci- C₅₀)alkynyl, any hydrocarbyl, aromatic hydrocarbons comprising at least one aromatic ring structure, any combination of the above and all of the above optionally substituted with at least one heteroatom, selected from the group comprising inter alia nitrogen, oxygen, phosphorous, boron, silicone, etc, and optionally further comprising various functional groups and/or moieties such as carboxylic acids, car- boxylates, amines, primary amines, secondary amines, tertiary amines, quaternary amines, amides, imines, imides, azides, azo, cyanates, isocyanides, isocyanates, ni- tro, nitriles, nitrosooxy, nitrate, nitroso, pyridyl, esters, ethers, alcohols, acyl, ketones, carbonates, peroxy, carboxamide, phosphine, phosphodiester, phosphono, phosphate, phenyl, benzyl, aryl, etc., or any combinations thereof.

In a further embodiment, the at least one alkyl halide may for instance be selected from the group comprising any alkyl halide, isopropyl chloroformate, isobutyl chloroformate, butyl chloroformate, octyl chloroformate, alkyl chloroformate, alkyl haloformate, cyclohexyl chloroformate, cyclohexyl haloformate, di-tert- butylpyrocarbonate.

As per another embodiment of the present invention, the at least one acyl halide may for instance be selected from the group comprising any acyl halide, propanoyl chloride, butanoyl chloride, alkanoyl chloride, alkenoyl chloride, alkynoyl chloride, alkanoyl halogen, alkenoyl halogen, alkynoyl halogen. In one embodiment, the dielectric, triglyceride fluid may comprise inter alia a triglyceride exemplified in a non-limiting manner by the following structural formula (I), shown merely in a schematic, inexact manner for simplicity, as will be immediately recognized by a person skilled in the art:

wherein, x, y, and z may be independently selected from integers of 0-50, each R_1; R₂, and R₃ may be independently selected from the group comprising saturated or unsaturated, branched, linear, and/or cyclic (C₀-C₅₀)alkyl, each R4 and R₅ may be independently selected from hydroxy, hydroxyalkyl, hydroxyalkoxy, hydroxyalkoxyalkyl, hydroxypolyoxyalkylene, alkoxy, alkoxyalkyl, polyoxyalkylene, carboxy, carboxyalkyl, carboxyalkoxy, carboxyalkoxyalkyl, carboxypolyoxyalkylene, alkoxycarbonyl, alkoxycarbonylalkyl, alkoxycarbonylalkoxy, alkoxycarbonylalkoxyalkyl, alkoxy carbonylpolyoxyalkylene, amino, alkylamino, dialkylamino, aminoalkyl, alkylaminoalkyl, dialkylaminoalkyl, aminoalkoxy, alkylaminoalkoxy, dialkylaminoalkoxy, aminopolyoxyalkylene, alkylaminopolyoxyalkylene, dialkylaminopolyoxyalkylene, aminoalkoxyalkyl, alkylaminoalkoxyalkyl, dialkylaminoalkoxy alkyl, (amino) (carboxy)alkyl, (alkylamino) (carboxy)alkyl, (dialkylamino) (carboxy) alkyl, (amino) (carboxy) alkoxy, (alkylamino) (carboxy)alkoxy, (dialkylamino) (carboxy) alkoxy, (amino)(carboxy)alkoxyalkyl, (alkylamino)(carboxy)alkoxyalkyl, (dialkylamino) (carboxy)alkoxy alkyl, (amino)(caxboxy)polyoxyalkylene, (alkylamino)(carboxy)polyoxyalkylene, (dialkylamino)(carboxy)polyoxyalkylene, (alkoxycarbonyl)(amino)alkyl, (alkoxycarbonyl)(alkylamino)alkyl, (alkoxycarbonyl)(dialkylamino)alkyl, (alkoxycarbonyl) (amino) alkoxy, (alkoxycarbonyl)(alkylaniino)alkoxy, (alkoxycarbonyl) (dialkylamino) alkoxy, (alkoxycarbonyl) (amino) alkoxyalkyl, (alkoxycarbonyl) (alkylamino)alkoxyalkyl, (alkoxycarbonyl)(dialkylamino)alkoxyalkyl,

(alkoxycarbonyl)(amino)polyoxyalkylene,

(alkoxycabonyl)(alkylamino)polyoxyalkylene,

(alkoxycabonyl)(dialkylamino)polyoxyalkylene, acylamino, acylaminoalkyl, acylaminoalkoxy, acylaminoalkoxyalkyl, acylaminopolyoxyalkylene, acylalkylamino, acylalkylaminoalkyl, acylalkylaminoalkoxy, acylalkylaminoalkoxyalkyl, acylalkylaminopolyoxyalkylene, hydrazinocarbonyl, hydrazinocarbonylalkyl, hydrazinocarbonylalkoxy, hydrazinocarbonylalkoxyalkyl, hydrazinocarbonylpolyoxyalkylene, nitro, nitroalkyl, nitroalkoxy, nitroalkoxyalkyl, nitropolyoxyalkylene, cyano, cyanoalkyl, cyanoalkoxy, cyanoalkoxyalkyl, and cyanopolyoxyalkylene. The person skilled in the art immediately recognizes that the above structural formula may be varied, for instance in terms of inter alia the number and location of the alkyl and/or acyl moieties introduced by the reaction between fatty acids having at least one carbon-carbon double bond and at least one alkyl halide and/or at least one acyl halide (e.g. on which fatty acid chain(s) the alkyl(s) and/or acyl(s) are located, the position along the fatty acid chain(s)), the number and locations of unsaturations of the fatty acid chains (e.g. the presence of conjugated or unconjugated unsaturation(s), whether the unsaturations are located on the ester side or on the alkyl side of the introduced alkyl(s) and/or acyl(s)), and the length and the branching of the fatty acid chains (e.g. the presence of branches either on the ester side and/or on the alkyl side of the introduced alkyl(s) and/or acyl(s)), the length of the alkyl chains on the ester side and on the alkyl side of the introduced alkyl(s) and/or acyl(s)), without departing from the spirit of the present invention. The person skilled in the art moreover recognizes that additional groups and moieties not specifically mentioned above are within the scope of the present invention. The introduction of the at least one the alkyl(s) and/or acyl(s) increases the fluidity of the triglyceride, rendering the fluid inter alia less viscous as well as more oxidation stable, as well as endowing the fluid with properties such as improved permittivity, reduced pour point, and improved insulation properties. In one embodiment, the at least one second moiety that further increases the triglyceride fluidity may correspond to R4 and/or R₅, in accordance with structural formula (I) above.

In yet another embodiment, the dielectric, triglyceride fluid may comprise inter alia a triglyceride exemplified in a non-limiting manner by the following structural formula (II), shown merely in a schematic, inexact manner for simplicity, as will be immediately recognized by a person skilled in the art:

(II) wherein, x, y, and z may be independently selected from integers of 0-50, each Ri, R₂, and R3 may be independently selected from the group comprising saturated or unsaturated, branched, linear, and/or cyclic (C₀-C₅o)alkyl, each R4, R₅, R₆, R₇, and R₈ may be independently selected from hydroxy, hydroxyalkyl, hydroxyalkoxy, hydroxyalkoxyalkyl, hydroxypolyoxyalkylene, alkoxy, alkoxyalkyl, polyoxyalkylene, carboxy, carboxyalkyl, carboxyalkoxy, carboxyalkoxyalkyl, carboxypolyoxyalkylene, alkoxycarbonyl, alkoxycarbonylalkyl, alkoxycarbonylalkoxy, alkoxycarbonylalkoxyalkyl, alkoxy carbonylpolyoxyalkylene, amino, alkylamino, dialkylamino, aminoalkyl, alkylaminoalkyl, dialkylaminoalkyl, aminoalkoxy, alkylaminoalkoxy, dialkylaminoalkoxy, aminopolyoxyalkylene, alkylaminopolyoxyalkylene, dialkylaminopolyoxyalkylene, aminoalkoxyalkyl, alkylaminoalkoxyalkyl, dialkylaminoalkoxy alkyl, (amino) (carboxy)alkyl, (alkylamino) (carboxy)alkyl, (dialkylamino) (carboxy) alkyl, (amino) (carboxy) alkoxy, (alkylamino) (carboxy)alkoxy, (dialkylamino) (carboxy) alkoxy, (amino)(carboxy)alkoxyalkyl, (alkylamino)(carboxy)alkoxyalkyl, (dialkylamino) (carboxy)alkoxy alkyl, (amino)(caxboxy)polyoxyalkylene, (alkylamino)(carboxy)polyoxyalkylene, (dialkylamino)(carboxy)polyoxyalkylene, (alkoxycarbonyl)(amino)alkyl, (alkoxycarbonyl)(alkylamino)alkyl, (alkoxycarbonyl)(dialkylamino)alkyl, (alkoxycarbonyl) (amino) alkoxy, (alkoxycarbonyl)(alkylaniino)alkoxy, (alkoxycarbonyl) (dialkylamino) alkoxy, (alkoxycarbonyl) (amino) alkoxyalkyl, (alkoxycarbonyl) (alkylamino)alkoxyalkyl, (alkoxycarbonyl)(dialkylamino)alkoxyalkyl,

(alkoxycarbonyl)(amino)polyoxyalkylene,

(alkoxycabonyl)(alkylamino)polyoxyalkylene,

(alkoxycabonyl)(dialkylamino)polyoxyalkylene, acylamino, acylaminoalkyl, acylaminoalkoxy, acylaminoalkoxyalkyl, acylaminopolyoxyalkylene, acylalkylamino, acylalkylaminoalkyl, acylalkylaminoalkoxy, acylalkylaminoalkoxyalkyl, acylalkylaminopolyoxyalkylene, hydrazinocarbonyl, hydrazinocarbonylalkyl, hydrazinocarbonylalkoxy, hydrazinocarbonylalkoxyalkyl, hydrazinocarbonylpolyoxyalkylene, nitro, nitroalkyl, nitroalkoxy, nitroalkoxyalkyl, nitropolyoxyalkylene, cyano, cyanoalkyl, cyanoalkoxy, cyanoalkoxyalkyl, and cyanopolyoxyalkylene. The person skilled in the art immediately recognizes that the above structural formula may be varied, for instance in terms of inter alia the number and location of the alkyl and/or acyl moieties introduced by the reaction between fatty acids having at least one carbon-carbon double bond and at least one alkyl halide and/or at least one acyl halide (e.g. on which fatty acid chain(s) the alkyl(s) and/or acyl(s) are located, the position along the fatty acid chain(s)), the number and locations of unsaturations of the fatty acid chains (e.g. the presence of conjugated or unconjugated unsaturation(s), whether the unsaturations are located on the ester side or on the alkyl side of the introduced alkyl(s) and/or acyl(s)), and the length and the branching of the fatty acid chains (e.g. the presence of branches either on the ester side and/or on the alkyl side of the introduced alkyl(s) and/or acyl(s)), the length of the alkyl chains on the ester side and on the alkyl side of the introduced alkyl(s) and/or acyl(s)), without departing from the spirit of the present invention. The person skilled in the art moreover recognizes that additional groups and moieties not specifically mentioned above are within the scope of the present invention. The introduction of the at least one the alkyl(s) and/or acyl(s) increases the fluidity of the triglyceride, rendering the fluid inter alia less viscous as well as more oxidation stable, as well as endowing the fluid with properties such as improved permittivity, reduced pour point, and improved insulation properties. In one embodiment, the at least one second moiety that further increases the triglyceride fluidity may correspond to R4, R₅, Re, R7, and/or R₈, in accordance with structural formula (II) above.

In a further embodiment as per the present invention, the dielectric, triglyceride fluid may comprise inter alia a triglyceride exemplified in a non-limiting manner by the following structural formula (III), shown merely in a schematic, inexact manner for simplicity, as will be immediately recognized by a person skilled in the art:

(III) wherein, x, y, and z may be independently selected from integers of 0-50, each Ri, R₂, and R₃ may be independently selected from the group comprising saturated or unsaturated, branched, linear, and/or cyclic (C₀-C₅₀)alkyl, R₄ may be selected from hydroxy, hydroxyalkyl, hydroxyalkoxy, hydroxyalkoxyalkyl, hydroxypolyoxyalkylene, alkoxy, alkoxyalkyl, polyoxyalkylene, carboxy, carboxyalkyl, carboxyalkoxy, carboxyalkoxyalkyl, carboxypolyoxyalkylene, alkoxycarbonyl, alkoxycarbonylalkyl, alkoxycarbonylalkoxy, alkoxycarbonylalkoxyalkyl, alkoxy carbonylpolyoxyalkylene, amino, alkylamino, dialkylamino, aminoalkyl, alkylaminoalkyl, dialkylaminoalkyl, aminoalkoxy, alkylaminoalkoxy, dialkylaminoalkoxy, aminopolyoxyalkylene, alkylaminopolyoxyalkylene, dialkylaminopolyoxyalkylene, aminoalkoxyalkyl, alkylaminoalkoxyalkyl, dialkylaminoalkoxy alkyl, (amino) (carboxy)alkyl, (alkylamino) (carboxy)alkyl, (dialkylamino) (carboxy) alkyl, (amino) (carboxy) alkoxy, (alkylamino) (carboxy)alkoxy, (dialkylamino) (carboxy) alkoxy, (amino)(carboxy)alkoxyalkyl, (alkylamino)(carboxy)alkoxyalkyl, (dialkylamino) (carboxy)alkoxy alkyl, (amino)(caxboxy)polyoxyalkylene,

(alkylamino)(carboxy)polyoxyalkylene, (dialkylamino)(carboxy)polyoxyalkylene, (alkoxycarbonyl)(amino)alkyl, (alkoxycarbonyl)(alkylamino)alkyl, (alkoxycarbonyl)(dialkylamino)alkyl, (alkoxycarbonyl) (amino) alkoxy, (alkoxycarbonyl)(alkylaniino)alkoxy, (alkoxycarbonyl) (dialkylamino) alkoxy, (alkoxycarbonyl) (amino) alkoxyalkyl, (alkoxycarbonyl) (alkylamino)alkoxyalkyl, (alkoxycarbonyl)(dialkylamino)alkoxyalkyl,

(alkoxycarbonyl)(amino)polyoxyalkylene,

(alkoxycabonyl)(alkylamino)polyoxyalkylene,

(alkoxycabonyl)(dialkylamino)polyoxyalkylene, acylamino, acylaminoalkyl, acylaminoalkoxy, acylaminoalkoxyalkyl, acylaminopolyoxyalkylene, acylalkylamino, acylalkylaminoalkyl, acylalkylaminoalkoxy, acylalkylaminoalkoxyalkyl, acylalkylaminopolyoxyalkylene, hydrazinocarbonyl, hydrazinocarbonylalkyl, hydrazinocarbonylalkoxy, hydrazinocarbonylalkoxyalkyl, hydrazinocarbonylpolyoxyalkylene, nitro, nitroalkyl, nitroalkoxy, nitroalkoxyalkyl, nitropolyoxyalkylene, cyano, cyanoalkyl, cyanoalkoxy, cyanoalkoxyalkyl, and cyanopolyoxyalkylene. The person skilled in the art immediately recognizes that the above structural formula may be varied, for instance in terms of inter alia the number and location of the alkyl and/or acyl moieties introduced by the reaction between fatty acids having at least one carbon-carbon double bond and at least one alkyl halide and/or at least one acyl halide (e.g. on which fatty acid chain(s) the alkyl(s) and/or acyl(s) are located, the position along the fatty acid chain(s)), the number and locations of unsaturations of the fatty acid chains (e.g. the presence of conjugated or unconjugated unsaturation(s), whether the unsaturations are located on the ester side or on the alkyl side of the introduced alkyl(s) and/or acyl(s)), and the length and the branching of the fatty acid chains (e.g. the presence of branches either on the ester side and/or on the alkyl side of the introduced alkyl(s) and/or acyl(s)), the length of the alkyl chains on the ester side and on the alkyl side of the introduced alkyl(s) and/or acyl(s)), without departing from the spirit of the present invention. The person skilled in the art moreover recognizes that additional groups and moieties not specifically mentioned above are within the scope of the present invention. The introduction of the at least one the alkyl(s) and/or acyl(s) increases the fluidity of the triglyceride, rendering the fluid inter alia less viscous as well as more oxidation stable, as well as endowing the fluid with properties such as improved permittivity, reduced pour point, and improved insulation properties. In one embodiment, the at least one second moiety that further increases the triglyceride fluidity may correspond to R4, in accordance with structural formula (III) above.

The above-outlined structural formulas merely depict exemplary embodiments ac- cording to the present invention. A person skilled in the art would hence immediately realize that the above structural formulas I-III are primarily meant for illustrative purposes and that other structures and moieties not specifically mentioned and/or illustrated above are encompassed by the present invention. Further, a person skilled in the art would immediately recognize the schematic nature of the above formulas, and that additional suitable moieties may be incorporated in the formula without departing from the scope of the present invention.

In yet another embodiment, the dielectric triglyceride fluid may further comprise less than approximately 40% mono-unsaturated fatty acids, and more than approxi- mately 0% of other fatty acids, in order to endow the fluid with desirable properties in terms of oxidation stability, fluidity, insulation, permittivity, reduced pour point, reduced viscosity, etc. As per another embodiment, the dielectric triglyceride fluid may further comprise less than approximately 30% mono-unsaturated fatty acids, or less than approximately 25%, or less than approximately 20% mono-unsaturated fatty acids, or less than approximately 10% mono-unsaturated fatty acids. In accordance with yet another embodiment of the present invention, the dielectric triglyceride fluid may further comprise more than approximately 5%> of other fatty acids, or more than approximately 10% of other fatty acids, or more than approximately 15% of other fatty acids, or more than approximately 20% of other fatty acids.

The triglycerides utilized for the aspects and/or embodiment of the present invention may be naturally derived, optionally comprising synthetic modifications. Employing naturally derived triglycerides enables development of dielectric, triglyceride fluids, in line with a preferred embodiment of the present invention, for in- stance for power and/or electrical applications. The dielectric triglyceride fluids as per the present invention may exhibit reduced viscosity, improved insulation, reduced pour point, improved oxidation stability, permittivity, biodegradability, as well as other highly attractive properties, for instance resulting in improved personnel health and safety, negligible environmental impact, and facilitated and safer handling.

In another embodiment, the dielectric triglyceride fluids may have a permittivity value in the range between approximately 2.2 and approximately 4.5, in order to provide dielectric triglyceride fluids with optimized properties.

In a preferred embodiment, the present invention relates to a naturally derived triglyceride having one, two, or three carbon-carbon double bonds. Said carbon- carbon double bond of the naturally derived triglyceride may preferably be reacted with isopropyl chloroformate, cyclohexyl chloroformate, propanoyl chloride, or bu- tanoyl chloride, in order to generate a modified triglyceride having increased fluidity, implying improved properties in terms of reduced viscosity, improved insulation, reduced pour point, improved oxidation stability, permittivity, and/or biodegradability. In one embodiment, the dielectric triglyceride fluid as per the present invention may comprise at least one additive, for instance selected from the group comprising pour point depressants, antioxidants, and metal activators, and any combinations thereof, in order to further optimize the properties of the triglyceride fluid. One aspect of the present invention pertains to a method for preparing a dielectric, triglyceride fluid. The method comprises the steps of providing a suitable triglyceride composition having a fatty acid composition of between about 25% and about 100%o fatty acids having at least one carbon-carbon double bond, and subsequently reacting approximately 0-100% of the carbon-carbon double bonds (i.e. 0-100% of the carbon-carbon double bonds in the triglyceride composition per se) with at least one alkyl halide and/or at least one acyl halide, normally in the presence of a cata- lyst. In one embodiment, the catalyst is a Lewis acid, i.e. any substance capable of accepting a pair of electrons. In yet another embodiment, the Lewis acid may for instance be selected from the group comprising aluminium chloride, ethylalumin- ium dichloride, and/or ethylaluminium sesquichloride. In a further embodiment, the reaction step of the method is carried out at ambient temperature, and, in yet another embodiment, CH₂C1₂ acts as the solvent.

One aspect of the present invention relates to an electrical apparatus comprising the dielectric, triglyceride fluid of the present invention. In one embodiment, the dielec- trie fluid functions as an insulating medium, as a result of its superior properties in terms of inter alia oxidation stability, fluidity, insulation, permittivity, reduced pour point, reduced viscosity, etc.

Another aspect of the present invention pertains to various uses of the dielectric, triglyceride fluid in electrical apparatuses, and/or in apparatuses for power applications, or in components utilized in said apparatuses. Apparatuses of interest as per the present invention may for instance be transformers, capacitors, switchgear, bushings, etc., as well components and/or parts utilized in power or electrical applications. In one embodiment, the dielectric fluid may be utilized in for instance paints and coatings, printing inks, lubricants, surfactants, or within the food and/or cosmetics industry.

Yet another aspect in accordance with the present invention pertains to chemically modified triglycerides, as per any one of the above aspects/embodiments, for use in dielectric fluids. The chemically modified triglyceride is obtainable by reacting 0- 100% of the carbon-carbon double bonds of a triglyceride fatty acid moiety with at least one alkyl halide and/or at least one acyl halide. Preferably, 5-100% of the carbon-carbon double bonds of a triglyceride fatty acid moiety (i.e. 5-100% of the carbon-carbon double bonds of the triglyceride composition as a whole) are reacted with at least one alkyl halide and/or at least one acyl halide. Further in accordance with the present invention, a suitable triglyceride composition may have a fatty acid composition of between about 25% and about 100%> fatty acids having at least one carbon-carbon double bond. More preferably, approximately 5-100% of the carbon- carbon double bonds of the triglyceride composition are reacted with the at least one alkyl halide and/or at least one acyl halide.

As per a further embodiment, the at least one alkyl halide and/or the at least one acyl halide may further comprise at least one moiety that further increases triglyceride fluidity. In yet another embodiment, the at least one moiety that further increases triglyceride fluidity may comprise a saturated or unsaturated, branched, linear and/or cyclic hydrocarbon, optionally substituted with at least one heteroatom.

In another embodiment, the at least one alkyl halide may be selected from the group comprising isopropyl chloroformate, isobutyl chloroformate, and, in an additional embodiment, the at least one acyl halide may be selected from the group comprising propanoyl chloride, butanoyl chloride.

Examples

Isopropylation of triglycerides

At least one carbon-carbon double bond of a suitable triglyceride is reacted with isopropyl chloroformate at ambient temperature in the presence of ethylaluminium sesquichloride (Et₃Al₂Cl₃), with CH₂C1₂ as the solvent. After a reaction time of 2 h, triglycerides having at least one isopropyl-alkylated fatty acid chain are formed. The triglyceride generated through the alkylation reaction has increased triglyceride fluidity, rendering a composition comprising the isopropyl-alkylated triglyceride less viscous, with higher oxidation stability, increased permittivity, and reduced pour point.

The isopropylation of the carbon-carbon double bonds was in further experiments carried out to different degrees depending on for instance the triglyceride starting material and the desired properties of the resulting dielectric triglyceride fluid. Between 0% and 100% (for instance 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100%) of the carbon-carbon double bonds present in the triglyceride fluid was isopropyl- alkylated, generating triglyceride fluids exhibiting different oxidation stability, permittivity, viscosity, and pour point. In preferred examples, 5-100% of the carbon-carbon double bonds present in the triglyceride fluid were isopropyl-alkylated.

Cvclohexyl -alkylation of triglycerides

At least one carbon-carbon double bond of a suitable triglyceride is reacted with cyclohexyl chloroformate at ambient temperature in the presence of Et₃Al₂Cl₃, with CH₂C1₂ as the solvent. After a reaction time of 2 h, triglycerides having at least one cyclohexyl-alkylated fatty acid chain are formed. The triglyceride generated through the alkylation reaction has increased triglyceride fluidity, rendering a composition comprising the cyclohexyl-alkylated triglyceride less viscous, with higher oxidation stability, increased permittivity, and reduced pour point. The cyclohexyl-alkylation of the carbon-carbon double bonds was in further experiments carried out to different degrees depending on for instance the triglyceride starting material and the desired properties of the resulting dielectric triglyceride fluid. Between 0% and 100% (for instance 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100%) of the carbon-carbon double bonds present in the triglyceride fluid was cyclohexyl- alkylated, generating triglyceride fluids exhibiting different degrees of oxidation stability, permittivity, viscosity, and pour point. Butyl-pyrocarbonate-alkylation of triglycerides

At least one carbon-carbon double bond of a suitable triglyceride is reacted with di- tert-butylpyrocarbonate at ambient temperature in the presence of Et₃Al₂Cl₃, with CH₂CI₂ as the solvent. After a reaction time of 2 h, triglycerides having at least one tert-butyl-alkylated fatty acid chain are formed. The triglyceride generated through the alkylation reaction has increased triglyceride fluidity, rendering a composition comprising the tert-butyl-alkylated triglyceride less viscous, with higher oxidation stability, increased permittivity, and reduced pour point.

The butyl-pyrocarbonate-alkylation of the carbon-carbon double bonds was in fur- ther experiments carried out to different degrees depending on for instance the triglyceride starting material and the desired properties of the resulting dielectric triglyceride fluid. Between 0% and 100% (for instance 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100%) of the carbon-carbon double bonds present in the triglyceride fluid was bu- tyl-pyrocarbonate-alkylated, generating triglyceride fluids exhibiting different degrees of oxidation stability, permittivity, viscosity, and pour point.

Propanoyl chloride acylation of triglycerides

A suitable triglyceride comprising at least one carbon-carbon is reacted with pro- panoyl chloride at ambient temperature in the presence of ethylaluminium dichlo- ride. After a reaction time of 3 h, triglycerides having at least one propanoylated fatty acid chain are formed. The triglyceride generated through the alkylation reaction has increased triglyceride fluidity, rendering a composition comprising the pro- panoylated triglyceride less viscous, with higher oxidation stability, increased permittivity, and reduced pour point.

The propanoyl chloride acylation of the carbon-carbon double bonds was in further experiments carried out to different degrees depending on for instance the triglyceride starting material and the desired properties of the resulting dielectric triglyceride fluid. Between 0% and 100% (for instance 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100%) of the carbon-carbon double bonds present in the triglyceride fluid was acy- lated, generating triglyceride fluids exhibiting different degrees of oxidation stability, permittivity, viscosity, and pour point. In preferred examples, 5-100%> of the carbon-carbon double bonds present in the triglyceride fluid were acylated.

Butanoyl chloride acylation of triglycerides

A suitable triglyceride comprising at least one carbon-carbon is reacted with butanoyl chloride at ambient temperature in the presence of ethylaluminium dichlo- ride. After a reaction time of 3 h, triglycerides having at least one butanoylated fatty acid chain are formed. The triglyceride generated through the alkylation reaction has increased triglyceride fluidity, rendering a composition comprising the butanoy- lated-alkylated triglyceride less viscous, with higher oxidation stability, increased permittivity, and reduced pour point. The butanoyl chloride acylation of the carbon-carbon double bonds was in further experiments carried out to different degrees depending on for instance the triglyceride starting material and the desired properties of the resulting dielectric triglyceride fluid. Between 0% and 100% (for instance 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100%) of the carbon-carbon double bonds present in the triglyceride fluid was acy- lated, generating triglyceride fluids exhibiting different degrees of oxidation stability, permittivity, viscosity, and pour point.

Claims

1. A dielectric triglyceride fluid having a fatty acid composition of between about 25% and about 100%> fatty acids having at least one carbon-carbon double bond, characterized in that said dielectric, triglyceride fluid is obtainable by reacting 0-100% of the carbon-carbon double bonds with at least one alkyl halide and/or at least one acyl halide.

2. The dielectric triglyceride fluid according to claim 1, wherein the at least one alkyl halide and/or the at least one acyl halide further comprise at least one moiety that further increases triglyceride fluidity.

3. The dielectric triglyceride fluid according to claim 2, wherein the at least one moiety that further increases triglyceride fluidity comprises a saturated or unsaturated, branched, linear and/or cyclic hydrocarbon, optionally substituted with at least one heteroatom.

4. The dielectric triglyceride fluid according to any one of the preceding claims, wherein the at least one alkyl halide is selected from the group comprising isopropyl chloroformate, isobutyl chloroformate, butyl chloroformate, octyl chloroformate, alkyl chloroformate, alkyl haloformate, cyclohexyl chloroformate, cyclohexyl haloformate, and di-tert-butylpyrocarbonate.

5. The dielectric triglyceride fluid according to any one of the preceding claims, wherein the at least one acyl halide is selected from the group comprising propanoyl chloride, butanoyl chloride, alkanoyl chloride, alkenoyl chloride, alkynoyl chloride, alkanoyl halogen, alkenoyl halogen, and alkynoyl halogen.

6. The dielectric triglyceride fluid according to any one of the preceding claims, optionally further comprising at least one additive selected from the group comprising antioxidants, pour point depressants, and metal deactivators, and any combination thereof.

7. A method for preparing the dielectric triglyceride fluid according to any one of the preceding claims, comprising the steps of: (a) providing a triglyceride composition having a fatty acid composition of between about 25% and about 100% fatty acids having at least one carbon-carbon double bond;

(b) reacting 0-100% of the carbon-carbon double bonds with at least one alkyl halide and/or at least one acyl halide in the presence of a catalyst;

thereby obtaining said dielectric triglyceride fluid.

8. The method according to claim 7, wherein the catalyst is a Lewis acid.

9. The method according to claim 8, wherein the Lewis acid is selected from the group comprising aluminium chloride, ethylaluminium dichloride, and/or ethylaluminium sesquichloride.

10. The method according to any one of claims 7 to 9, wherein step (b) is carried out at ambient temperature.

11. An electrical apparatus comprising the dielectric triglyceride fluid according to any one of claims 1 to 6.

12. The electrical apparatus according to claim 11, wherein the dielectric triglyceride fluid functions as an insulating medium.

13. Use of the dielectric triglyceride fluid according to any one of claims 1 to 6 in an electrical apparatus.

14. Use of a chemically modified triglyceride in a dielectric fluid, wherein said chemically modified triglyceride is obtainable by reacting 0-100% of the carbon-carbon double bonds of a triglyceride fatty acid moiety with at least one alkyl halide and/or at least one acyl halide.

15. Use according to claim 14, wherein the at least one alkyl halide and/or the at least one acyl halide further comprise at least one moiety that further increases triglyceride fluidity.

16. Use according to claim 15, wherein the at least one moiety that further increases triglyceride fluidity comprises a saturated or unsaturated, branched, linear and/or cyclic hydrocarbon, optionally substituted with at least one het- eroatom.

17. Use according to any one of claims 14 to 16, wherein the at least one alkyl halide is selected from the group comprising isopropyl chloroformate, isobu- tyl chloroformate, butyl chloroformate, octyl chloroformate, alkyl chloroformate, alkyl haloformate, cyclohexyl chloroformate, cyclohexyl halofor- mate, and di-tert-butylpyrocarbonate.

18. Use according to any one of claims 14 to 17, wherein the at least one acyl halide is selected from the group comprising propanoyl chloride, butanoyl chloride, alkanoyl chloride, alkenoyl chloride, alkynoyl chloride, alkanoyl halogen, alkenoyl halogen, and alkynoyl halogen.