SACRIFICIAL ZWITTER IONS IN LOW-CONDUCTIVITY LIQUIDS

Abstract

The present invention relates to heat-transfer fluids comprising zwitterions which act as sacrificial agents when placed in contact with ion-exchange resins, thereby preventing the uptake of desired additives like corrosion inhibitors or dyes. The invention further relates to associated methods, compositions and uses.

Description

SACRIFICIAL ZWITTERIONS IN LOW CONDUCTIVE HEAT-TRANSFER FLUIDS Field of the Invention

[0001] The present invention relates to heat-transfer fluids which comprise a zwitterion. The invention further relates to methods of exchanging heat which comprises circulating heat-transfer fluids comprising a zwitterionic compound through a cooling system comprising an ion-exchange resin. The invention further relates to assemblies comprising said heat-transfer fluids and to uses thereof, for example in battery or fuel cell electric vehicles. Background Art

[0002] Heat-transfer fluids are widely employed in heat exchange systems associated with internal combustion engines, solar systems, fuel cells, electrical motors, generators, electronic equipment, battery equipment, and the like. Heat-transfer fluids are generally composed of a base fluid and one or more additives.

[0003] Historically, water has been the preferred base fluid with a view to heat-transfer properties. In many applications, antifreeze properties are needed and in such cases a base fluid consisting of water mixed with freezing point depressants like alcohols, glycols or salts is employed. The additives present in heat-transfer fluids may be employed to obtain a variety of functionalities, such as (further) lowering of the freezing point, improving the heat-exchange properties, inhibiting corrosion, et cetera. Since heat- transfer fluids are in continuous contact with metal parts (aluminium alloys, cast iron, steel, copper, brass, solder, et cetera) they nearly always contain one or more corrosion inhibitors.

[0004] The development and increased use of alternative energy technologies, such as battery electric or fuel cell electric vehicles and power plants, which are an attractive alternative to combustion engines due to their relatively low output of pollutants, brings with it the need for a new type of heat-transfer fluids.

[0005] Fuel cells are electrochemical cells in which the chemical energy stored is converted to electrical energy by controlled oxidation of the fuel. In most applications, several electrochemical cells are stacked together in series into a so-called fuel cell stack, allowing higher voltages to be generated. Heat generated by the fuel cell stack can be removed by flowing heat-transfer fluid through channels formed by the bipolar plates.

[0006] The potential difference between the positive and negative ends of the fuel cell stack may cause a shunt current to flow through the heat-transfer fluid, thus reducing the voltage of the fuel cell. In addition to the deleterious loss of voltage, shunt currents cause additional problems, such as corrosion of the separator plate near the positive end of a fuel cell stack.

[0007] Batteries are electrochemical cells in which the chemical energy stored is converted to electrical energy by redox reactions. In most applications, several electrochemical cells are placed together in series into a so-called battery pack, allowing higher voltages to be generated. Heat generated by the battery pack can be removed by flowing heat-transfer fluid through channels within, or outside the battery pack.

[0008] In case of contact between the heat transfer fluid and the current collectors (tabs) of the battery pack, safety critical events like short-circuits or electrolysis (leading to formation of flammable hydrogen gas) may occur.

[0009] In electrical machines such as electromotors, the heat transfer fluid may come in contact with current carrying parts, like copper windings. In such cases, power loss or short-circuit could lead to failure of the device.

[0010] Hence, heat-transfer fluids for use in electrical applications, such as battery and fuel cells, need to have low electrical conductivity (i.e. high electrical resistance) and should be capable of maintainingthis throughout the lifetime of the heat-transfer fluid.

[0011] Most known heat-transfer fluids (e.g. coolants) have been specifically designed for internal combustion engines and are not suitable for use in electrical applications, where low electrical conductivity is required for safety reasons, such as fuel cells, batteries, electrical machines or power electronics, because they (i) possess high electrical conductivity, or (ii) become significantly more electrically conductive upon aging, especially at increased temperatures. The increase in electrical conductivity upon aging is generally attributed to the formation of ionic compounds due to degradation of alcohols, particularly glycols, which are often used as a base fluid, due to degradation of additives, due to metal corrosion and / or due to impurities in the cooling circuit.

[0012] Hence, in recent years there has been an increased interest in developing heat-transfer fluids which are better suited for use in electrical applications, such as fuel cells, batteries, electrical machines or power electronics.

[0013] In order to maintain low conductivity for a prolonged time, in addition to employing specifically designed heat-transfer fluids, it has also become common to integrate an ion-exchange resin into the cooling circuit, such that the heat-transfer fluid passes through the ion-exchange resin when it is being circulated. The ion-exchange resin functions to remove ionic contaminants formed upon aging of the heat-transfer fluid, such as glycolates (ionic degradation products of glycols which are formed upon aging and which increase the conductivity of the heat-transfer fluid). Heat transfer fluids typically contain ionic or non-ionic additives which fulfil multiple functions such as protection against corrosion, pH control, reduction of oxidation processes in the fluid, dispersing particulate matter as well as dyes to identify the fluid. The present inventors have found that the use of such ion-exchange resins results in the undesirable removal of polar non-ionic and ionic additives from the heat transfer fluid, thereby reducing or removing the desired properties afforded by such additives. For instance, triazoles are used as red metal corrosion inhibitors but are removed from the heat-transfer fluid by the ion-exchange resin. Consequently, higher concentrations of such additives (e.g. triazoles) need to be used to compensate for the loss due to the ion-exchange resin, or the performance of the product is simply decreased.

[0014] US8951689B2 discloses a coolant circulation channel with an ion-exchange resin. As a coolant comprising an inhibitor such as mercaptobenzothiazole flows through the circulation channel, the ion-exchange resin removes and adsorbs ions generated in the coolant.

[0015] CN114214044A discloses fuel cell cooling liquid comprising N,N,N-trimethylglycine and water. The liquid is passed through an ion-exchange resin to lower the electrical conductivity to 0-5 µS / cm before it is employed as a heat-transfer fluid.

[0016] It is an object of the present invention to provide heat-transfer fluids which allow electrical conductivity of the heat-transfer fluid to be maintained.

[0017] It is an object of the present invention to provide heat-transfer fluids with improved compatibility with ion-exchange resins.

[0018] It is an object of the present invention to provide heat-transfer fluids which limit or prevent the undesirable removal or one or more additives (such as corrosion inhibitors and / or dyes) by an ion- exchange resin.

[0019] It is an object of the present invention to provide methods of exchanging heat and associated compositions which improve the compatibility of low conductive heat-transfer fluids with ion-exchange resins. Summary of the invention

[0020] The present inventors have surprisingly found that zwitterions according to formula (I-a) and / or (I-b) act as sacrificial agents when used in low conductivity heat-transfer fluids when placed in contact with ion-exchange resins. Such zwitterions prevent the uptake of desired functional additives present in the heat-transfer fluid, such as corrosion inhibitors and / or dyes. In addition, the zwitterioniccompounds do not significantly increase the electrical conductivity. Furthermore, as is shown in the appended examples, the mixtures maintain a low electrical conductivity which does not alter substantially with aging. Surprisingly, the ion-exchange resin can still perform its desired function of absorbing conductivity-increasing products which form upon aging, such as glycolates. Without wishing to be bound by theory, the present inventors believe that this is because the affinity of ion-exchange resins for the zwitterions is greater than for the additives in the heat-transfer fluid but lower than for the oxidative degradation products of the base fluid, such as glycolates. One or more objects of the invention are achieved by the different aspects of the invention described herein.

[0021] Hence, in a first aspect the present invention provides a heat-transfer fluid comprising: at least one zwitterionic compound according to formula (I-a) or (I-b);wherein Y is selected from sulfonate (-SO3-), phosphinate (-HPO2-) and phosphonate (-PO3-); R1, R2, R3, R4, R5and R6are individually selected from the group consisting of hydrogen, =O, -OH, - SH, -NH2, and optionally substituted monovalent hydrocarbon radicals having from 1 to 30 carbon atoms, preferably R1, R2, R3, R4, R5, and R6are individually selected from the group consisting of hydrogen, C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C2-C20 alkenyl, C3- C8 cycloalkyl, C4-C8 cycloalkenyl, C6-C10 aryl, C1-C20 sulfide, =O, -OH, -NH2, -SH, -OR7, -NR7R7’, - SR7, -(OCH2CH2)pCH3, -(OCHCH3CH2)qCH3, -(OCH3)rCH3, -R7OR7’, -R7(CO)R7’, -R7(COO)R7’, - R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -N=CR7R7’, -N=CR7’’, -C(O) R7; R7is selected from the group consisting of, C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 aminoalkyl, C2-C20 alkenyl, C1-C20 alkyl alcohol, -(OCH2CH2)pCH3, -(OCHCH3CH2)qCH3, -(OCH3)rCH3, preferably R7is selected from the group consisting of C1-C20 alkyl; R7’is selected from the group consisting of hydrogen, C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 aminoalkyl, C2-C20 alkenyl, C1-C20 alkyl alcohol, -(OCH2CH2)pCH3, -(OCHCH3CH2)qCH3, - (OCH3)rCH3, preferably R7’is selected from the group consisting of hydrogen, C1-C20 alkyl; R7’’is a bivalent C2-C8 alkyl radical such that -N=CR7’’is a cycloalkyl; n, m and o each are an integer individually selected from 0 to 20, preferably from 0 to 10; in each formula (I-a) and (I-b) at least one of n, m and o is > 0; p, q and r each are an integer individually selected from 1 to 30, preferably from 2-20; Z is selected from any one of Z1, Z2, Z3, Z4, Z5, Z6, and Z7, wherein Z1, Z2, Z3, Z4, Z5, Z6, and Z7are as follows:R8, R9, and R10are individually selected from the group consisting of hydrogen, and optionally substituted monovalent hydrocarbon radicals having from 1 to 30 carbon atoms, preferably R8, R9, and R10are individually selected from the group consisting of hydrogen, C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C1-C20 sulfide, -R7OR7’, -R7(CO)R7’, -R7(COO)R7’, - R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -N=CR7R7’, -N=CR7’’, -C(O) R7, more preferably R8, R9, and R10are individually selected from the group consisting of hydrogen, C1- C8 alkyl, C1-C8 haloalkyl, C1-C8 alkyl alcohol, C1-C8 aminoalkyl, C1-C8 sulfide, -R7OR7’, -R7(CO)R7’, - R7(COO)R7’, -R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -N=CR7R7’, - N=CR7’’, -C(O) R7; R11, R12, R13, R14and R15are individually selected from the group consisting of hydrogen, and optionally substituted monovalent hydrocarbon radicals having from 1 to 30 carbon atoms, preferably R11, R12, R13, R14and R15are individually selected from the group consisting of hydrogen, C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C2-C20 alkenyl, C3-C8 cycloalkyl, C4-C8 cycloalkenyl, C6-C10 aryl, C1-C20 sulfide, -R7OR7’, -R7(CO)R7’, -R7(COO)R7’, - R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -N=CR7R7’, -N=CR7’’, -C(O) R7; wherein the electrical conductivity of the heat-transfer fluid is less than 100 µS / cm, preferably less than 50 µS / cm, more preferably less than 25 µS / cm, more preferably less than 10 µS / cm, most preferably less than 5 µS / cm.

[0022] Highly preferably, the heat-transfer fluid comprises a corrosion inhibitor preferably selected from triazoles, thiazoles, triazines, diazoles and combinations thereof.

[0023] In preferred embodiments, the heat-transfer fluid comprises a base fluid consisting of water, or an alcohol, or mixtures thereof.

[0024] In preferred embodiments, the heat-transfer fluid comprises at least 0.1 wt.% of the zwitterioniccompound according to formula (I-a) or (I-b), preferably at least 0.01 wt.%, more preferably at least 0.05 wt.%, preferably at least 0.5 wt.%, more preferably at least 1 wt.% by total weight of the heat-transfer fluid.

[0025] In preferred embodiments, the zwitterionic compound of the heat-transfer fluid is selected from zwitterionic compounds having a molecular weight of less than 1000 g / mol, preferably less than 500 g / mol, preferably less than 200 g / mol.

[0026] In preferred embodiments, the heat-transfer fluid according to the invention is provided, wherein the weight ratio of the zwitterionic compound to the corrosion inhibitor (by total weight of the heat- transfer fluid) is preferably at least 5:1, preferably at least 10:1, more preferably at least 15:1.

[0027] In another aspect of the invention, there is provided a method for exchanging heat, the method comprising the steps of: a. providing a heat-transfer fluid according to the invention; b. providing a cooling system configured for thermally contacting the heat-transfer fluid with an electrical system, the cooling system comprising an ion-exchange resin; c. transferring heat from the electrical system to the heat-transfer fluid; and d. contacting the heat-transfer fluid with the ion-exchange resin.

[0028] In preferred embodiments, the volume ratio of the heat-transfer fluid to the ion-exchange resin is at least 1:99 v / v%, preferably at least 5:95 v / v%, more preferably at least 10:90 v / v% and most preferably at least 20:80 v / v%.

[0029] In a further aspect of the invention, there is provided the use of a heat-transfer fluid comprising a zwitterionic compound according to formula (I-a) or (I-b) as a heat-transfer fluid in a cooling system comprising an ion-exchange resin; wherein the electrical conductivity at 25 °C of the heat-transfer fluid is less than 100 µS / cm, preferably less than 50 µS / cm, more preferably less than 25 µS / cm, more preferably less than 10 µS / cm, most preferably less than 5 µS / cm.

[0030] In another aspect of the invention, there is provided use of a zwitterionic compound according to formula (I-a) or (I-b): • for prolonging the corrosion inhibiting properties of a heat-transfer fluid comprising a corrosion inhibitor when contacting an ion-exchange resin, preferably when used as a heat-transfer fluid in a cooling system comprising an ion-exchange resin in contact with the heat-transfer fluid; • for prolonging the coloration of a heat-transfer fluid comprising a dye when contacting an ion- exchange resin, preferably when used as a heat-transfer fluid in a cooling system comprising an ion-exchange resin in contact with the heat-transfer fluid; • for reducing the amount of corrosion inhibitor and / or dye used in a heat-transfer fluid comprising when contacting an ion-exchange resin, preferably when used as a heat-transfer fluid in a cooling system comprising an ion-exchange resin in contact with the heat-transfer fluid; • for extending the service life interval of an ion-exchange resin when contacting a heat-transfer fluid by reducing or avoiding uptake of heat-transfer fluid components, preferably when used in a cooling system comprising an ion-exchange resin in contact with the heat-transfer fluid; • for extending the service life interval of a heat-transfer fluid comprising a corrosion inhibitor (and preferably comprising an alcohol as described herein) and / or an ion-exchange resin contacting the heat-transfer fluid by o reducing, postponing or avoiding corrosion; o reducing, postponing or avoiding the formation of electrically conductive acids such as glycolates; preferably when the heat-transfer fluid is used in a cooling system comprising an ion-exchange resin in contact with the heat-transfer fluid. Description of embodiments

[0031] The expression “comprise” and variations thereof, such as, “comprises” and “comprising” as used herein should be construed in an open, inclusive sense, meaning that the embodiment described includes the recited features, but that it does not exclude the presence of other features, as long as they do not render the embodiment unworkable.

[0032] The expressions “one embodiment”, “a particular embodiment”, “an embodiment” etc. as used herein should be construed to mean that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of such expressions in various places throughout this specification do not necessarily all refer to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. For example, certain features of the disclosure which are described herein in the context of separate embodiments are also explicitly envisaged in combination in a single embodiment.

[0033] The singular forms “a,” “an,” and “the” as used herein should be construed to include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its broadest sense, that is as meaning “and / or” unless the content clearly dictates otherwise.

[0034] Whenever reference is made throughout this document to a compound which is a salt, this should be construed to include the anhydrous form as well as any solvates (in particular hydrates) of this compound, unless explicitly defined otherwise.

[0035] The term “alkyl” as used herein includes straight, branched and cyclic alkyls.

[0036] Reference is made to substances, components, or ingredients in existence at the time just before first contacted, blended, or mixed with one or more other substances, components, or ingredients in accordance with the present disclosure. A substance, component or ingredient may gain an identity, property, or character through a chemical reaction or transformation during the course of contacting, blending, or mixing if conducted in accordance with this disclosure with the application of common sense and the ordinary skills of an average chemist. Definitions of substances, components, or ingredients and their relative amounts concern the heat-transfer fluids as it is prepared at the time of first contacting the ingredients, unless expressly indicated otherwise.

[0037] Electrical conductivity as referred to herein is preferably measured in accordance with ASTM D1125-23 preferably with a Mettler-Toledo SevenExcellence Cond meter S700-Std-Kit electrical conductivity meter equipped with a SevenExcellence Cond meter S700-Std-Kit.

[0038] The term ‘thermal contact’ refers to any arrangement that allows heat produced by the electricalsystem to be transferred to the heat-transfer fluid or composition thereof by heat transfer. Heat-transfer fluid

[0039] In a first aspect of the invention, there is provided a heat-transfer fluid comprising: at least one zwitterionic compound according to formula (I-a) or (I-b);wherein Y is selected from sulfonate (-SO3-), phosphinate (-HPO2-) and phosphonate (-PO3-); R1, R2, R3, R4, R5and R6are individually selected from the group consisting of hydrogen, =O, -OH, - SH, -NH2, and optionally substituted monovalent hydrocarbon radicals having from 1 to 30 carbon atoms, preferably R1, R2, R3, R4, R5, and R6are individually selected from the group consisting of hydrogen, C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C2-C20 alkenyl, C3- C8 cycloalkyl, C4-C8 cycloalkenyl, C6-C10 aryl, C1-C20 sulfide, =O, -OH, -NH2, -SH, -OR7, -NR7R7’, - SR7, -(OCH2CH2)pCH3, -(OCHCH3CH2)qCH3, -(OCH3)rCH3, -R7OR7’, -R7(CO)R7’, -R7(COO)R7’, - R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -N=CR7R7’, -N=CR7’’, -C(O) R7; R7is selected from the group consisting of, C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 aminoalkyl, C2-C20 alkenyl, C1-C20 alkyl alcohol, -(OCH2CH2)pCH3, -(OCHCH3CH2)qCH3, -(OCH3)rCH3, preferably R7is selected from the group consisting of C1-C20 alkyl; R7’is selected from the group consisting of hydrogen, C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 aminoalkyl, C2-C20 alkenyl, C1-C20 alkyl alcohol, -(OCH2CH2)pCH3, -(OCHCH3CH2)qCH3, - (OCH3)rCH3, preferably R7’is selected from the group consisting of hydrogen, C1-C20 alkyl; R7’’is a bivalent C2-C8 alkyl radical such that -N=CR7’’is a cycloalkyl; n, m and o each are an integer individually selected from 0 to 20, preferably from 0 to 10; in each formula (I-a) and (I-b) at least one of n, m and o is > 0; p, q and r each are an integer individually selected from 1 to 30, preferably from 2-20; Z is selected from any one of Z1, Z2, Z3, Z4, Z5, Z6, and Z7, wherein Z1, Z2, Z3, Z4, Z5, Z6, and Z7are as follows:wherein R8, R9, and R10are individually selected from the group consisting of hydrogen, and optionally substituted monovalent hydrocarbon radicals having from 1 to 30 carbon atoms, preferably R8, R9, and R10are individually selected from the group consisting of hydrogen, C1-C20alkyl, C1-C20haloalkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C1-C20 sulfide, -R7OR7’, -R7(CO)R7’, -R7(COO)R7’, - R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -N=CR7R7’, -N=CR7’’, -C(O) R7, more preferably R8, R9, and R10are individually selected from the group consisting of hydrogen, C1- C8 alkyl, C1-C8 haloalkyl, C1-C8 alkyl alcohol, C1-C8 aminoalkyl, C1-C8 sulfide, -R7OR7’, -R7(CO)R7’, - R7(COO)R7’, -R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -N=CR7R7’, - N=CR7’’, -C(O) R7; R11, R12, R13, R14and R15are individually selected from the group consisting of hydrogen, and optionally substituted monovalent hydrocarbon radicals having from 1 to 30 carbon atoms, preferably R11, R12, R13, R14and R15are individually selected from the group consisting of hydrogen, C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C2-C20 alkenyl, C3-C8 cycloalkyl, C4-C8 cycloalkenyl, C6-C10 aryl, C1-C20 sulfide, -R7OR7’, -R7(CO)R7’, -R7(COO)R7’, - R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -N=CR7R7’, -N=CR7’’, -C(O) R7; wherein the electrical conductivity of the heat-transfer fluid is less than 100 µS / cm, preferably less than 50 µS / cm, more preferably less than 25 µS / cm, more preferably less than 10 µS / cm, most preferably less than 5 µS / cm.

[0040] Highly preferably, the heat-transfer fluid comprises a corrosion inhibitor, such as corrosion inhibitor selected from triazoles, thiazoles, triazines, diazoles and combinations thereof. Corrosioninhibitors are discussed in more detail herein elsewhere.

[0041] In preferred embodiments of the invention, there is provided the heat-transfer fluid comprising a base fluid wherein the base fluid consists of water, or an alcohol or mixtures thereof.

[0042] In another embodiment of the invention, there is provided a heat-transfer fluid comprising a base fluid and a zwitterionic compound according to formula (I-a) or (I-b); wherein the base fluid consists of water, or an alcohol or mixtures thereof; wherein the electrical conductivity at 25 °C of the heat-transfer fluid is less than 100 µS / cm, preferably less than 50 µS / cm, more preferably less than 25 µS / cm, more preferably less than 10 µS / cm, most preferably less than 5 µS / cm; and -wherein the heat-transfer fluid further comprises a corrosion inhibitor, preferably selected from triazoles, thiazoles, triazines, diazoles and combinations thereof, and wherein the ratio (w / w) of the zwitterionic compound to the corrosion inhibitor in the heat-transfer fluid is less than 50:1, more preferably less than 30:1; and / or -wherein the heat-transfer fluid further comprises a dye, preferably a dye as has been described herein before, and wherein the ratio (w / w) of the zwitterionic compound to the dye in the heat-transfer fluid is at least 30:1, preferably at least 50:1.

[0043] The heat-transfer fluid preferably has a pH within the range of 3-10, preferably 4-8, more preferably 4-7.5. As will be understood by the skilled person, any compound with an exchangeable hydrogen (due to acid-base functionalities) will be at equilibrium with its (de)protonated form. In accordance with the invention, at least 50 mol%, preferably at least 80 mol%, more preferably at least 99 mol% of the zwitterionic compound is in zwitterionic form at the pH of the heat-transfer fluid. Typically, the zwitterionic compound is chosen such that at least 99.9 mol%, or even 99.99 mol% of the compound is in zwitterionic form at the pH of the heat-transfer fluid. Thus, preferably at least 50 mol%, preferably at least 80 mol%, more preferably at least 99 mol% of the zwitterionic compound is in zwitterionic form at a pH within the range of 3-10, preferably 4-8, more preferably 4-7.5. In some embodiments at least least 99.9 mol%, or even 99.99 mol% of the zwitterionic compound is in zwitterionic form at a pH within the range of 3-10, preferably 4-8, more preferably 4-7.5. The zwitterionic compound

[0044] In the context of the present disclosure, and as is common in the art, the term “zwitterionic compound” refers to neutral molecules containing an equal number of positively and negatively charged groups.

[0045] In accordance with the invention, the zwitterionic compound is selected from the group consisting of to formula (I-a) or (I-b);wherein Y is selected from sulfonate (-SO3-), phosphinate (-HPO2-) and phosphonate (-PO3-);R1, R2, R3, R4, R5and R6are individually selected from the group consisting of hydrogen, =O, -OH, - SH, -NH2, and optionally substituted monovalent hydrocarbon radicals having from 1 to 30 carbon atoms, preferably R1, R2, R3, R4, R5, and R6are individually selected from the group consisting of hydrogen, C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C2-C20 alkenyl, C3- C8 cycloalkyl, C4-C8 cycloalkenyl, C6-C10 aryl, C1-C20 sulfide, =O, -OH, -NH2, -SH, -OR7, -NR7R7’, - SR7, -(OCH2CH2)pCH3, -(OCHCH3CH2)qCH3, -(OCH3)rCH3, -R7OR7’, -R7(CO)R7’, -R7(COO)R7’, - R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -N=CR7R7’, -N=CR7’’, -C(O) R7; R7is selected from the group consisting of C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 aminoalkyl, C2-C20 alkenyl, C1-C20 alkyl alcohol, -(OCH2CH2)pCH3, -(OCHCH3CH2)qCH3, -(OCH3)rCH3, preferably R7is selected from the group consisting of C1-C20 alkyl, more preferably R7is selected from the group consisting of C1-C14 alkyl; R7’is selected from the group consisting of hydrogen, C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 aminoalkyl, C2-C20 alkenyl, C1-C20 alkyl alcohol, -(OCH2CH2)pCH3, -(OCHCH3CH2)qCH3, - (OCH3)rCH3,preferably R7’is selected from the group consisting of hydrogen, C1-C20alkyl, more preferably R7’is selected from the group consisting of C1-C14 alkyl; R7’’is a bivalent C2-C8 alkyl radical such that -N=CR7’’is a cycloalkyl; n, m and o each are individually selected from 0 to 20, preferably from 0 to 10; in each formula (I-a) and (I-b) at least one of n, m and o is > 0; p, q and r each are an integer individually selected from 1 to 30, preferably from 2-20; Z is selected from any one of Z1, Z2, Z3, Z4, Z5, Z6, Z7, Z8and Z9wherein Z1, Z2, Z3, Z4, Z5, Z6, Z7, Z8and Z9are as follows:R8, R9, and R10are individually selected from the group consisting of hydrogen, and optionally substituted monovalent hydrocarbon radicals having from 1 to 30 carbon atoms, preferably R8, R9, and R10are individually selected from the group consisting of hydrogen, C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C1-C20 sulfide, -R7OR7’, -R7(CO)R7’, -R7(COO)R7’, -R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -N=CR7R7’, -N=CR7’’, -C(O) R7, more preferably R8, R9, and R10are individually selected from the group consisting of hydrogen, C1- C8 alkyl, C1-C8 haloalkyl, C1-C8 alkyl alcohol, C1-C8 aminoalkyl, C1-C8 sulfide, -R7OR7’, -R7(CO)R7’, - R7(COO)R7’, -R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -N=CR7R7’, - N=CR7’’, -C(O) R7; R11, R12, R13, R14and R15are individually selected from the group consisting of hydrogen, and optionally substituted monovalent hydrocarbon radicals having from 1 to 30 carbon atoms, preferably R11, R12, R13, R14and R15are individually selected from the group consisting of hydrogen, C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C2-C20 alkenyl, C3-C8 cycloalkyl, C4-C8 cycloalkenyl, C6-C10 aryl, C1-C20 sulfide, -R7OR7’, -R7(CO)R7’, -R7(COO)R7’, - R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -N=CR7R7’, -N=CR7’’, -C(O) R7.

[0046] In preferred embodiments of the present invention, the zwitterionic compound is selected from the group consisting of compounds according to formula (I-a) and compounds according to formula (I- b) wherein Y is selected from sulfonate (-SO3-), phosphinate (-HPO2-) and phosphonate (-PO3-); R1, R3, and R5are individually selected from the group consisting of hydrogen, =O, -OH, -SH, -NH2, and optionally substituted monovalent hydrocarbon radicals having from 1 to 30 carbon atoms, preferably R1, R3, and R5are individually selected from the group consisting of hydrogen, C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C2-C20 alkenyl, C3-C8cycloalkyl, C4-C8cycloalkenyl, C6-C10aryl, C1-C20sulfide, =O, -OH, -NH2, -SH, - -R2, R4and R6are hydrogen; R7is selected from the group consisting of C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 aminoalkyl, C2-C20 alkenyl, C1-C20 alkyl alcohol, -(OCH2CH2)pCH3, -(OCHCH3CH2)qCH3, -(OCH3)rCH3, preferably R7is selected from the group consisting of C1-C20 alkyl, more preferably R7is selected from the group consisting of C1-C14 alkyl; R7’is selected from the group consisting of hydrogen, C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 aminoalkyl, C2-C20 alkenyl, C1-C20 alkyl alcohol, -(OCH2CH2)pCH3, -(OCHCH3CH2)qCH3, - (OCH3)rCH3, preferably R7’is selected from the group consisting of hydrogen, C1-C20 alkyl, more preferably R7’is selected from the group consisting of C1-C14 alkyl; R7’’is a bivalent C2-C8 alkyl radical such that -N=CR7’’is a cycloalkyl; n, m and o each are individually selected from 0 to 20, preferably from 0 to 10; in each formula (I-a) and (I-b) at least one of n, m and o is > 0; p, q and r each are an integer individually selected from 1 to 30, preferably from 2-20; Z is selected from any one of Z1, Z2, Z3, Z4, Z5, Z6, Z7, Z8and Z9wherein Z1, Z2, Z3, Z4, Z5, Z6, Z7, Z8and Z9are as follows:R8, R9, and R10are individually selected from the group consisting of hydrogen, and optionally substituted monovalent hydrocarbon radicals having from 1 to 30 carbon atoms, preferably R8, R9, and R10are individually selected from the group consisting of hydrogen, C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C1-C20 sulfide, -R7OR7’, -R7(CO)R7’, - R7(COO)R7’, -R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -N=CR7R7’, - N=CR7’’, -C(O) R7, more preferably R8, R9, and R10are individually selected from the group consisting of hydrogen, C1-C8 alkyl, C1-C8 haloalkyl, C1-C8 alkyl alcohol, C1-C8 aminoalkyl, C1- C8 sulfide, -R7OR7’, -R7(CO)R7’, -R7(COO)R7’, -R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -C(O) R7; R11, R12, R13, R14and R15are individually selected from the group consisting of hydrogen, and optionally substituted monovalent hydrocarbon radicals having from 1 to 30 carbon atoms, preferably R11, R12, R13, R14and R15are individually selected from the group consisting of hydrogen, C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C2-C20 alkenyl, C3-C8 cycloalkyl, C4-C8 cycloalkenyl, C6-C10 aryl, C1-C20 sulfide, -R7OR7’, -R7(CO)R7’, - R7(COO)R7’, -R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -N=CR7R7’, - N=CR7’’, -C(O) R7,more preferably R11, R12, R13, R14and R15are individually selected from the group consisting of hydrogen, C1-C8 alkyl, C1-C8 haloalkyl, C1-C8 alkyl alcohol, C1-C8 aminoalkyl, C1-C8 sulfide, -R7OR7’, -R7(CO)R7’, -R7(COO)R7’, -R7(CONH)R7’, -R7(NHCO)R7’, - R7(NHCOO)R7’, -R7(NHCONH)R7’, -C(O) R7.

[0047] In highly preferred embodiments of the present invention, the zwitterionic compound is selected from the group consisting of compounds according to formula (I-a) and compounds according to formula (I-b) wherein Y is selected from sulfonate (-SO3-), phosphinate (-HPO2-) and phosphonate (-PO3-); R1, R2, R3, R4, R5, and R6are individually selected from the group consisting of hydrogen, - OH, -SH, -NH2, C1-C8 alkyl, C1-C8 haloalkyl, C1-C8 alkyl alcohol, C1-C8 aminoalkyl, C1-C8 sulfide, preferably R1, R3, and R5are individually selected from the group consisting of hydrogen, -OH, -SH, -NH2, C1-C8alkyl, most preferably R1, R3, and R5are individually selected from the group consisting of hydrogen, -OH, C1-C5 alkyl;n, m and o each are individually selected from 0 to 20, preferably from 0 to 10, more preferably from 0 to 2; in each formula (I-a) and (I-b) at least one of n, m and o is > 0; Z is selected from any one of Z1, Z2, Z3, Z4, Z5, Z6, Z7, Z8and Z9wherein Z1, Z2, Z3, Z4, Z5, Z6, Z7, Z8and Z9are as follows:R8, R9, and R10are individually selected from the group consisting of hydrogen, C1-C8alkyl, C1-C8 haloalkyl, C1-C8 alkyl alcohol, C1-C8 aminoalkyl, C1-C8 sulfide, -R7OR7’, -R7(CO)R7’, - R7(COO)R7’, -R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -C(O) R7, preferably R8, R9, and R10are individually selected from the group consisting of, C1-C8 alkyl, C1-C8 haloalkyl, C1-C8 alkyl alcohol, C1-C8 aminoalkyl, C1-C8 sulfide, -R7OR7’, -R7(CO)R7’, - R7(COO)R7’, -R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -C(O) R7, more preferably R8, R9, and R10are individually selected from the group consisting of C1-C4 alkyl, -R7OR7’, -R7(CO)R7’, -R7(COO)R7’, -R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, - R7(NHCONH)R7’, -C(O) R7; R11, R12, R13, R14and R15are individually selected from the group consisting of hydrogen, C1- C20 alkyl, C1-C20 haloalkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C2-C20 alkenyl, C3-C8 cycloalkyl, C4-C8 cycloalkenyl, C6-C10 aryl, C1-C20 sulfide, -R7OR7’, -R7(CO)R7’, -R7(COO)R7’, - R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -C(O) R7; R7is selected from the group consisting of C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 aminoalkyl, C2-C20 alkenyl, C1-C20 alkyl alcohol, -(OCH2CH2)pCH3, -(OCHCH3CH2)qCH3, -(OCH3)rCH3, preferably R7is selected from the group consisting of C1-C20 alkyl, more preferably R7is selected from the group consisting of C1-C14 alkyl; R7’is selected from the group consisting of hydrogen, C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 aminoalkyl, C2-C20 alkenyl, C1-C20 alkyl alcohol, -(OCH2CH2)pCH3, -(OCHCH3CH2)qCH3, - (OCH3)rCH3, preferably R7’is selected from the group consisting of hydrogen, C1-C20 alkyl, more preferably R7’is selected from the group consisting of C1-C14 alkyl.

[0048] In highly preferred embodiments of the present invention, the zwitterionic compound is selectedfrom the group consisting of compounds according to formula (I-a) and compounds according to formula (I-b) wherein Y is selected from sulfonate (-SO3-), phosphinate (-HPO2-) and phosphonate (-PO3-); R1, R3, and R5are individually selected from the group consisting of hydrogen, -OH, -SH, - NH2, C1-C8 alkyl, C1-C8 haloalkyl, C1-C8 alkyl alcohol, C1-C8 aminoalkyl, C1-C8 sulfide, preferably R1, R3, and R5are individually selected from the group consisting of hydrogen, - OH, -SH, -NH2, C1-C8 alkyl, most preferably R1, R3, and R5are individually selected from the group consisting of hydrogen, -OH, C1-C5 alkyl; R2, R4and R6are hydrogen; n, m and o each are individually selected from 0 to 20, preferably from 0 to 10, more preferably from 0 to 2; in each formula (I-a) and (I-b) at least one of n, m and o is > 0; Z is selected from any one of Z1, Z2, Z3, Z4, Z5, Z6, Z7, Z8and Z9wherein Z1, Z2, Z3, Z4, Z5, Z6, Z7, Z8and Z9are as follows:R8, R9, and R10are individually selected from the group consisting of hydrogen, C1-C8 alkyl, C1-C8 haloalkyl, C1-C8 alkyl alcohol, C1-C8 aminoalkyl, C1-C8 sulfide, -R7OR7’, -R7(CO)R7’, - R7(COO)R7’, -R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -C(O) R7, preferably R8, R9, and R10are individually selected from the group consisting of, C1-C8 alkyl, C1-C8haloalkyl, C1-C8alkyl alcohol, C1-C8aminoalkyl, C1-C8sulfide, -R7OR7’, -R7(CO)R7’, - R7(COO)R7’, -R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -C(O) R7, more preferably R8, R9, and R10are individually selected from the group consisting of C1-C4 alkyl, -R7OR7’, -R7(CO)R7’, -R7(COO)R7’, -R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, - R7(NHCONH)R7’, -C(O) R7;R11, R12, R13, R14and R15are individually selected from the group consisting of hydrogen, C1- C20 alkyl, C1-C20 haloalkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C2-C20 alkenyl, C3-C8 cycloalkyl, C4-C8 cycloalkenyl, C6-C10 aryl, C1-C20 sulfide, -R7OR7’, -R7(CO)R7’, -R7(COO)R7’, - R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -C(O) R7; R7is selected from the group consisting of C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 aminoalkyl, C2-C20 alkenyl, C1-C20 alkyl alcohol, -(OCH2CH2)pCH3, -(OCHCH3CH2)qCH3, -(OCH3)rCH3, preferably R7is selected from the group consisting of C1-C20 alkyl, more preferably R7is selected from the group consisting of C1-C14 alkyl; R7’is selected from the group consisting of hydrogen, C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 aminoalkyl, C2-C20 alkenyl, C1-C20 alkyl alcohol, -(OCH2CH2)pCH3, -(OCHCH3CH2)qCH3, - (OCH3)rCH3, preferably R7’is selected from the group consisting of hydrogen, C1-C20 alkyl, more preferably R7’is selected from the group consisting of C1-C14 alkyl.

[0049] In highly preferred embodiments of the present invention, the zwitterionic compound is selected from the group consisting of compounds according to formula (I-a) and compounds according to formula (I-b) wherein Y is selected from sulfonate (-SO3-), phosphinate (-HPO2-) and phosphonate (-PO3-); R1, R3, and R5are individually selected from the group consisting of hydrogen, -OH, -SH, - NH2, C1-C6 alkyl, C1-C6 haloalkyl, C1-C6 alkyl alcohol, C1-C6 aminoalkyl, C1-C6 sulfide, preferably R1, R3, and R5are individually selected from the group consisting of hydrogen, - OH, -SH, -NH2, C1-C6 alkyl, most preferably R1, R3, and R5are individually selected from the group consisting of hydrogen, -OH, C1-C4 alkyl; R2, R4and R6are hydrogen; n, m and o each are individually selected from 0 to 20, preferably from 0 to 10, more preferably from 0 to 2; in each formula (I-a) and (I-b) at least one of n, m and o is > 0; Z is selected from any one of Z1, Z2, Z3, Z4, Z5, Z6, Z7, Z8and Z9wherein Z1, Z2, Z3, Z4, Z5, Z6, Z7, Z8and Z9are as follows:R8, R9, and R10are individually selected from the group consisting of hydrogen, C1-C6 alkyl, C1-C6 haloalkyl, C1-C6 alkyl alcohol, C1-C6 aminoalkyl, C1-C6 sulfide, -R7OR7’, -R7(CO)R7’, - R7(COO)R7’, -R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -C(O) R7, preferably R8, R9, and R10are individually selected from the group consisting of, C1-C5 alkyl, C1-C5 haloalkyl, C1-C5 alkyl alcohol, C1-C5 aminoalkyl, C1-C5 sulfide, -R7OR7’, -R7(CO)R7’, - R7(COO)R7’, -R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -C(O) R7, more preferably R8, R9, and R10are individually selected from the group consisting of C1-C4 alkyl, -R7OR7’, -R7(CO)R7’, -R7(COO)R7’, -R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, - R7(NHCONH)R7’, -C(O) R7;R11, R12, R13, R14and R15are individually selected from the group consisting of hydrogen, C1- C10 alkyl, C1-C10 haloalkyl, C1-C10 alkyl alcohol, C1-C10 aminoalkyl, C2-C10 alkenyl, C3-C6 cycloalkyl, C4-C6 cycloalkenyl, C6-C8 aryl, C1-C10 sulfide, -R7OR7’, -R7(CO)R7’, -R7(COO)R7’, - R7(CONH)R7’, -R7(NHCO)R7’, -R7(NHCOO)R7’, -R7(NHCONH)R7’, -C(O) R7; R7is selected from the group consisting of C1-C10 alkyl, C1-C10 haloalkyl, C1-C10 aminoalkyl, C2-C10 alkenyl, C1-C10 alkyl alcohol, -(OCH2CH2)pCH3, -(OCHCH3CH2)qCH3, -(OCH3)rCH3, preferably R7is selected from the group consisting of C1-C10 alkyl, more preferably R7is selected from the group consisting of C1-C8 alkyl; R7’is selected from the group consisting of hydrogen, C1-C10 alkyl, C1-C10 haloalkyl, C1-C10 aminoalkyl, C2-C10 alkenyl, C1-C10 alkyl alcohol, -(OCH2CH2)pCH3, -(OCHCH3CH2)qCH3, - (OCH3)rCH3, preferably R7’is selected from the group consisting of hydrogen, C1-C10 alkyl, more preferably R7’is selected from the group consisting of C1-C8 alkyl.

[0050] In preferred embodiments, for reasons of solubility and resin compatibility it is preferred that the zwitterionic compound has a molecular weight of less than 1000 g / mol, preferably less than 500 g / mol, preferably less than 200 g / mol. Some zwitterionic compounds have been found to be particularly useful, for example because they are especially suitable to protect corrosion inhibitors such as triazoles, or because they are especially suitable to protect dyes. Thus, the preferred zwitterionic compounds will be described in more detail in the following paragraphs.

[0051] In preferred embodiments of the invention, the zwitterionic compound does not comprise a polymer. In some embodiments of the present invention, the zwitterionic compound does not comprise trimethylglycine. In some embodiments of the present invention, the heat-transfer fluid does not comprise trimethylglycine.

[0052] In some embodiments of the invention, the zwitterionic compound is selected from compounds comprising in the same molecule a positive charge from a quaternary ammonium, sulfonium or phosphonium functional group, and a negative charge from a sulfonate, phosphinate or phosphonate functional group. In highly preferred embodiments, the zwitterionic compound is selected from compounds comprising in the same molecule a positive charge from a quaternary ammonium, sulfonium or phosphonium functional group and a negative charge from a sulfonate functional group. In other embodiments, the zwitterionic compound is selected from compounds comprising in the same molecule a positive charge from a quaternary ammonium functional group, preferably trimethyl ammonium, and a negative charge from a sulfonate, phosphinate or phosphonate functional group.

[0053] In preferred embodiments, the zwitterionic compound is selected from the group consisting of 2-aminoethanesulfonic acid (taurine), 4-tert-butyl-1-(3-sulfopropyl)pyridinium hydroxide and combinations thereof.

[0054] The preferred embodiments for R1-R15and for n, m, o set out herein are explicitly envisaged in combination.

[0055] In highly preferred embodiments of the invention, the zwitterionic compound exhibits a solubility of at least 1 g / l, preferably at least 5 g / l, most preferably at least 10 g / l in a base fluid consisting of 50 vol% monoethylene glycol in water.

[0056] In preferred embodiments of the invention, the concentration of the zwitterionic compound in the heat-transfer fluid is at least 0.05 wt.%, preferably at least 0.1 wt.%, more preferably at least 0.5 wt.%, most preferably at least 1 wt.% by total weight of the heat-transfer fluid. The zwitterionic compound is typically comprised in the heat-transfer fluid at a concentration of less than 10 wt.%, preferably less than 6 wt.%, more preferably less than 4 wt.%, most preferably less than 3 wt.%, by total weight of the heat-transfer fluid. In embodiments of the invention, in particular those wherein the zwitterionic compound is selected from compounds as defined herein elsewhere, the total amount of zwitterionic compounds in the heat-transfer fluid is within the range of 0.05-10 wt.%, preferably within the range of 0.1-6 wt.%, more preferably within the range of 0.5-4 wt.%, most preferably within therange of 1-3 wt.%.

[0057] In some embodiments, the heat-transfer fluid comprises a single zwitterionic compound as described herein. The base fluid

[0058] In accordance with the invention the base fluid comprised in the heat-transfer fluid consists of water, or an alcohol or mixtures thereof. In preferred embodiments of the invention the alcohol is selected from the group consisting of monoethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, monopropylene glycol, 1,3- propanediol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, pentapropylene glycol, hexapropylene glycol, methanol, ethanol, propanol, butanol, tetrahydrofurfuryl, ethoxylated furfuryl, dimethyl ether of glycerol, sorbitol, 1,2,6-hexanetriol, trimethylolpropane, methoxyethanol, glycerol and mixtures thereof, preferably selected from the group consisting of monoethylene glycol, monopropylene glycol, 1,3-propanediol, glycerol and mixtures thereof.

[0059] In preferred embodiments of the invention, the base fluid comprises an alcohol, preferably an alcohol as described herein, and the weight ratio of the total amount of the zwitterionic compound to the alcohol is between 1:250 to 1:2, 1:100 to 1:2 preferably between 1:80 to 1:10, preferably between 1:50 to 1:20 and most preferably between 1:40 to 1:30.

[0060] In some embodiments of the invention, the base fluid comprises an alcohol, preferably an alcohol as described herein, and the weight ratio of the total amount of the zwitterionic compound to the alcohol is between 1:1000 to 1:100, preferably between 1:750 to 1:300, more preferably between 1:600 to 1:300.

[0061] As used herein, “monoethylene glycol” should be interpreted to mean “ethane-1,2-diol”, and is interchangeably referred to as “MEG”.

[0062] As used herein, “monopropylene glycol” should be interpreted to mean “propane-1,2-diol”, and is interchangeably referred to as “MPG”.

[0063] As used herein, the term “glycerol” means “propane-1,2,3-triol” and is synonymous with glycerin. In preferred embodiments of the invention the base fluid consists of water, monoethylene glycol, monopropylene glycol, 1,3-propanediol, glycerol or mixtures thereof.

[0064] In preferred embodiments of the invention the base fluid consists of water and an alcohol, wherein the alcohol is present in an amount of 10-99.5 wt.% (by weight of the base fluid), preferably 10-80 wt.%, more preferably 30-70 wt.%. In particular embodiments the alcohol is present in an amount in the range of 33-60 wt.% (by weight of the base fluid).

[0065] In some embodiments of the invention, the base fluid consists only of water, that is, 100% of the base fluid is water.

[0066] In embodiments of the invention, the base fluid comprises more than 50 wt.% water (by weight of the base fluid), preferably more than 70 wt.%, more preferably more than 85 wt.%.

[0067] In embodiments of the invention, the base fluid comprises more than 50 wt.% monoethylene glycol (by weight of the base fluid), preferably more than 70 wt.%, more preferably more than 85 wt.%, most preferably more than 95 wt.% monoethylene glycol.

[0068] In embodiments of the invention, the base fluid comprises more than 50 wt.% monopropylene glycol (by weight of the base fluid), preferably more than 70 wt.%, more preferably more than 85 wt.%, most preferably more than 95 wt.% monopropylene glycol.

[0069] In embodiments of the invention, the base fluid comprises more than 50 wt.% 1,3-propane diol (by weight of the base fluid), preferably more than 70 wt.%, more preferably more than 85 wt.%, mostpreferably more than 95 wt.% 1,3-propane diol.

[0070] In embodiments of the invention, the base fluid comprises more than 50 wt.% glycerol (by weight of the base fluid), preferably more than 70 wt.%, more preferably more than 85 wt.%, most preferably more than 95 wt.% glycerol.

[0071] In preferred embodiments of the invention, the heat-transfer fluid comprises more than 78 wt.% (by total weight of the heat-transfer fluid) of base fluid, more preferably more than 85 wt.%, even more preferably more than 90 wt.%, still more preferably more than 95 wt.% or more than 96.5 wt.% of base fluid.

[0072] As will be understood by the person skilled in the art, the base fluid is normally added to the heat-transfer fluid ‘quantum satis´. In embodiments of the invention, the heat-transfer fluid comprises less than 99.9 wt.% base fluid (by total weight of the heat-transfer fluid), such as less than 99.8 wt.%, less than 99.5 wt.% or less than 99 wt.%, less than 98 wt.% of base fluid.

[0073] In some embodiments of the invention, the base fluid is provided wherein water and the alcohol are present in a weight ratio of 95:5 to 5:95 by total weight of the heat-transfer fluid. In other embodiments, the base fluid is provided wherein water and the alcohol are present in a weight ratio of 95:5 to 5:95 by total weight of the base fluid. Corrosion Inhibitor

[0074] Cooling systems are typically configured for thermally contacting the heat-transfer fluid with metallic components which are prone to corrosion. Illustrative metals include ferrous and non-ferrous alloys such as stainless steel, aluminium, brass, braze alloy and the like. The present inventors found that the ion-exchange resins (which are employed in cooling systems of electrical systems in order to maintain a low conductivity of the coolant) are prone to removing corrosion inhibitors, even uncharged corrosion inhibitors. The present invention protects the corrosion inhibitors which may be comprised in a heat-transfer fluid from being absorbed by the ion-exchange resin and thus enables the heat-transfer fluid to maintain the benefits obtained with the use of corrosion inhibitors.

[0075] In a preferred embodiment, the heat-transfer fluid comprises a corrosion inhibitor. The corrosion inhibitor is preferably a non-ionic corrosion inhibitor. Examples of suitable non-ionic corrosion inhibitors are triazoles, thiazoles, triazines, diazoles, non-ionic polymers, silicate esters (such as Si(OR)4, wherein R is a C1 to C4 alkyl group), organic silicates (such as Si(R1)n(OR2)4-n wherein R1and R2each independently are a C1 to C6 alkyl or phenyl, and wherein n is 0, 1, 2 or 3), trimethylsilyl containing molecules (such as N,O-bis(trimethylsilyl)acetamide, N-trimethylsilylacetamide), alcohols containing an alkene or alkyne group (such as 3-butene-1-ol, 4-pentene-1-ol, 2,5-dimethyl-3-hexyne-2,5-diol) and combinations thereof, wherein the non-ionic polymers are preferably selected from the group consisting of polyvinylpyrrolidones, polyvinylalcohols, polyalkyleneoxides, polysiloxanes, C1-C18 alkyl or alkenyl ethers of polyalkyleneoxides, C1-C18 alkyl or alkenyl esters of polyalkyleneoxides, alkoxylated C1-C18 alkyl or alkenyl amines, polyvinylacetates, copolymers thereof and combinations thereof.

[0076] The corrosion inhibitor is preferably selected from triazoles, thiazoles, triazines, diazoles and combinations thereof.

[0077] In preferred embodiments of the invention, the corrosion inhibitor is selected from 1,2,3- triazoles, 1,2,4-triazoles, and combinations thereof.

[0078] In preferred embodiments of the invention, the corrosion inhibitor is selected from 1,2,4-triazole, 4H-1,2,4-triazole, 4-amino-1,2,4-triazole, 3-amino-1,2,4-triazole, 1,2,4-triazole-3-thiol, 3-amino-1,2,4- triazole-5-thiol, 3,5-diamino-1,2,4-triazole, 1H-1,2,3-triazole, benzotriazole, 2-mercaptobenzothiazole, tolyltriazole, 2-[2-hydroxyethyl-[(4-methylbenzotriazol-1-yl)methyl]amino]ethanol, 2-[2-hydroxyethyl- [(benzotriazolyl)methyl]amino]ethanol, (2-Benzothiazolylthio)acetic acid, 2,2’-[[(Methyl-1H- benzotriazol-1-yl)methyl]imino]bisethanol, N,N-bis(2-ethylhexyl)-methyl-1H-Benzotriazole-1- methanamine, and combinations thereof, more preferably selected from benzotriazole, tolyltriazole, 2-mercaptobenzothiazole, and combinations thereof.

[0079] In some embodiments of the invention, the corrosion inhibitor is a thiazole selected from 4,4'- (4(ethane-1,2-diylbis(oxy))bis(4-phenylene)dithiazol-2-amine, 2-(acetyl-ethoxycarbonyl-methyleno)-3- phenyl-4-(phenylhydrazono)-1,3-thiazolidin-5-one, 2-amino-4-(4-chlorophenyl)-thiazole, 2-Methoxy- 1,3-thiazole, 4-(4-methylphenyl)-2-thiazolamine, 2-amino-4-methyl-thiazole, 2-salicylidene amino-4- phenylthiazole, 4-[1-aza-2-(phenyl)vinyl]-3-phenyl-2- thioxo(1,3-thiazoline-5-yl), 4-(4-Methylphenyl)- 2- thiazolamine, 2-amino-4-methyl-thiazole, 2-amino-thiazole, 2,2’-dithiobis(benzothioazole), and combinations thereof.

[0080] In some embodiments of the invention, the corrosion inhibitor is a triazine selected from 1,2,3- triazine,1,2,4-triazine, 1,3,5-triazine, 6-methyl-5-[m-nitrostyryl]-3-mercapto-1,2,4-triazine, 2,4,6-tris (2- pyridyl)-1,3,5-triazine and combinations thereof.

[0081] In some embodiments of the invention, the corrosion inhibitor is a diazole selected from pyrazole, 4-nitropyrazole, 4-sulfopyrazole.

[0082] In preferred embodiments of the invention, the first corrosion inhibitor is selected from compounds according to general formula (II-a), (II-b) and / or (II-c):wherein R1represents one, two or three substituents on the six-membered ring, each substituent being independently selected from C1-C11 alkyl, amine, methoxy, ethoxy, Cl or Br; wherein X is selected from nitrogen or a C-H group; and wherein R2is selected from hydrogen, a mercapto group (-SH), or a C1-C11 alkyl, preferably methyl or ethyl; preferably wherein R1represents one, two or three substituents on the six-membered ring, each substituent being independently selected from C1-C6 alkyl, amine, methoxy, ethoxy, Cl or Br; wherein X is selected from nitrogen or a C-H group; and wherein R2is selected from hydrogen, a mercapto group (-SH), or a C1-C6 alkyl, preferably methyl or ethyl.

[0083] In preferred embodiments of the invention, the corrosion inhibitor is present in the heat-transfer fluid in an amount of at least 0.005 wt.% (by total weight of the heat-transfer fluid), preferably at least 0.01 wt.%, more preferably at least 0.05 wt.%. The corrosion inhibitor is typically present in an amount within the range of 0.005-5 wt.% (by total weight of the heat-transfer fluid), preferably 0.01-3 wt.%, more preferably 0.05-1 wt.%. The ratio (w / w) of the zwitterionic compound to the corrosion inhibitor in the heat-transfer fluid is preferably at least 5:1, preferably at least 10:1, more preferably at least 15:1. The ratio (w / w) of the zwitterionic compound to the corrosion inhibitor in the heat-transfer fluid is preferably less than 50:1, preferably less than 49:1, preferably less than 48:1, preferably less than 45:1, preferably less than 35:1, more preferably less than 30:1.

[0084] In preferred embodiments of the invention, the method is provided wherein the heat-transfer fluid comprises a corrosion inhibitor as described herein and wherein the binding affinity of the corrosioninhibitor to the ion-exchange resin is smaller than the binding affinity of the zwitterionic compound to the ion-exchange resin. Preferably, the method is provided wherein the heat-transfer fluid comprises a corrosion inhibitor as described herein and wherein the binding affinity of the corrosion inhibitor to the ion-exchange resin is smaller than the binding affinity of the zwitterionic compound to the ion-exchange resin and wherein the binding affinity of the zwitterionic compound to the ion-exchange resin is smaller than the binding affinity of glycolate to the ion-exchange resin.

[0085] To determine if the binding affinity of the corrosion inhibitor to the ion-exchange resin is smaller than the binding affinity of the zwitterionic compound to the ion-exchange resin the following protocol can be used: -prepare a mixture of 50 ml water, 50 ml monoethylene glycol, 2 ml ion-exchange resin, 2 gram zwitterionic compound and 0.1 gram corrosion inhibitor; -determine the corrosion inhibitor concentration by an appropriate method, e.g. HPLC coupled with a UV-VIS detector; -stir for 3 hours at 20 °C; and -determine the corrosion inhibitor concentration by the same method, wherein the binding affinity of the corrosion inhibitor to the ion-exchange resin is determined to be smaller than the binding affinity of the zwitterionic compound to the ion-exchange resin if the % loss in corrosion inhibitor concentration after stirring is smaller than 50%, preferably smaller than 35%.

[0086] To determine if the binding affinity of the zwitterionic compound to the ion-exchange resin is smaller than the binding affinity of glycolate to the ion-exchange resin the following protocol can be used: -prepare a mixture of 50 ml water, 50 ml monoethylene glycol, 2 ml ion-exchange resin, 2 gram zwitterionic compound and 0.01 gram glycolic acid; -determine the total combined glycolic acid and glycolate concentration by an appropriate method, e.g. ion chromatography -stir for 3 hours at 20 °C; and -determine the total combined glycolic acid and glycolate concentration by the same method, wherein the binding affinity of the zwitterionic compound to the ion-exchange resin is determined to be smaller than the binding affinity of the glycolate to the ion-exchange resin if the % loss in glycolate concentration after stirring is more than 50%, preferably more than 80%. The skilled person will understand that ion chromatography only measures glycolate ions, but that by appropriate sample preparation (addition of a strong base), all glycolic acid present in the sample can be converted to glycolate for measurement. The ion chromatography method may further be according to ASTM D5827- 22. Dye

[0087] The present inventors found that the ion-exchange resins (which are employed in cooling systems of electrical systems in order to maintain a low conductivity of the coolant) are prone to removing dyes, even very weakly ionically charged dyes or polar, uncharged dyes. The present invention protects the dyes which may be comprised in a heat-transfer fluid from being absorbed by the ion-exchange resin and thus enables the heat-transfer fluid to maintain the benefits obtained with the use of dyes.

[0088] In a preferred embodiment of the invention, the heat-transfer fluid comprises a dye. As used herein, the term “dye” should be interpreted to refer to any molecule capable of providing coloration visible to the naked eye at a concentration of 0.01 wt.% (by total weight of the heat-transfer fluid). In preferred embodiments, the dye comprises at least one of the following chromophores: anthraquinone,triphenylmethane, diphenylmethane, azo containing compounds, disazo containing compounds, trisazo containing compounds, diazo containing compounds, xanthene, acridine, indene, phthalocyanine, azaannulene, nitroso, nitro, diarylmethane, triarylmethane, methine, indamine, azine, oxazine, thiazine, quinoline, indigoid, indophenol, lactone, aminoketone, hydroxyketone, stilbene, thiazole, one or more conjugated aromatic groups, one or more conjugated heterocyclic groups, one or more conjugated carbon-carbon double bonds (e.g., carotene), and combinations thereof. In all embodiments of the invention, the dye is different from the zwitterionic compound. In one preferred embodiment, the dye comprises at least one of anthraquinone, acridine, thiazole, azo containing compounds, triarylmethane, diarylmethane, or combinations thereof. In one especially preferred embodiment, the dye comprises an azo containing compound as a chromophore. In an embodiment, the dye of the heat-transfer fluid will comprise at least one or more conjugated aromatic groups as a chromophore. In preferred embodiments, the dye is weakly ionic or non-ionic, preferably non-ionic.

[0089] In some embodiments of the invention, the chromophore of the dye comprises pendant aminic groups. Commercially available such dyes include Acid Blue 25, Reactive Blue 19, Disperse Blue 19, Disperse Blue 1, Solvent Blue 35, Crystal Violet, Malachite Green, Brilliant Green, Auramine O, Methyl Orange, Orange G, Congo Red, Direct Blue 15, Direct Red 80, Acid Red 114, Direct Black 38, Acid Black 1, Direct Red 28, Direct Blue 71, Rhodamine B, Rhodamine 6G or combinations thereof.In preferred embodiments of the invention, the dye is present in the heat-transfer fluid in an amount of less than 0.2 wt.%, preferably less than 0.1 wt.%, most preferably less than 0.05 wt.% based on the total weight of the heat-transfer fluid. In preferred embodiments of the invention, the dye is present in the heat-transfer fluid in an amount of from 0.000001 to 0.2 wt.%, preferably 0.000005 to 0.1 wt.%, preferably 0.000005 to 0.05 wt.% based on the total weight of the heat-transfer fluid. The ratio (w / w) of the zwitterionic compound to the dye in the heat-transfer fluid is preferably at least 30:1, preferably at least 50:1. In some embodiments, the ratio of zwitterionic compound to the dye in the heat-transfer fluid is preferably at least 100:1, preferably at least 200:1, more preferably at least 400:1, more preferably at least 500:1, more preferably at least 1000:1, more preferably at least 3000:1, more preferably at least 5000:1 and most preferably at least 10000:1. The ratio (w / w) of the zwitterionic compound to the dye in the heat-transfer fluid is not particularly limited (as it depends on the intensity of the dye) but may be less than 1000000:1, such as less than 500000:1, or less than 100000:1.

[0090] In preferred embodiments of the invention, the heat-transfer fluid comprises a dye as described herein and wherein the binding affinity of the dye to the ion-exchange resin is smaller than the binding affinity of the zwitterionic compound to the ion-exchange resin. Preferably, the heat-transfer fluid comprises a dye as described herein and wherein the binding affinity of the dye to the ion-exchange resin is smaller than the binding affinity of the zwitterionic compound to the ion-exchange resin and wherein the binding affinity of the zwitterionic compound to the ion-exchange resin is smaller than the binding affinity of glycolate to the ion-exchange resin.

[0091] In preferred embodiments of the invention, the method is provided wherein the heat-transfer fluid comprises a dye as described herein and wherein the binding affinity of the dye to the ion-exchange resin is smaller than the binding affinity of the zwitterionic compound to the ion-exchange resin. Preferably, the method is provided wherein the heat-transfer fluid comprises a dye as described herein and wherein the binding affinity of the dye to the ion-exchange resin is smaller than the binding affinity of the zwitterionic compound to the ion-exchange resin and wherein the binding affinity of the zwitterionic compound to the ion-exchange resin is smaller than the binding affinity of glycolate to the ion-exchange resin.

[0092] To determine if the binding affinity of the dye to the ion-exchange resin is smaller than the binding affinity of the zwitterionic compound to the ion-exchange resin the following protocol can be used: -prepare a mixture of 50 ml water, 50 ml monoethylene glycol, 2 ml ion-exchange resin, 2 gramzwitterionic compound and 0.01 gram dye; -determine the dye concentration by an appropriate method, e.g. UV-VIS absorbance -stir for 3 hours at 20 °C; and -determine the dye concentration by the same method, wherein the binding affinity of the dye to the ion-exchange resin is determined to be smaller than the binding affinity of the zwitterionic compound to the ion-exchange resin if the % loss in dye concentration after stirring is smaller than 50%, preferably smaller than 35%.

[0093] To determine if the binding affinity of the zwitterionic compound to the ion-exchange resin is smaller than the binding affinity of glycolate to the ion-exchange resin the following protocol can be used: -prepare a mixture of 50 ml water, 50 ml monoethylene glycol, 2 ml ion-exchange resin, 2 gram zwitterionic compound and 0.01 gram glycolic acid; -determine the total combined glycolic acid and glycolate concentration by an appropriate method, e.g. ion chromatography -stir for 3 hours at 20 °C; and -determine the total combined glycolic acid and glycolate concentration by the same method, wherein the binding affinity of the zwitterionic compound to the ion-exchange resin is determined to be smaller than the binding affinity of the glycolate to the ion-exchange resin if the % loss in glycolate concentration after stirring is more than 50%, preferably more than 80%. The skilled person will understand that ion chromatography only measures glycolate ions, but that by appropriate sample preparation (addition of a strong base), all glycolic acid present in the sample can be converted to glycolate for measurement. The ion chromatography method may further be according to ASTM D5827- 22. Further additives

[0094] As will be understood by the skilled person, based on teachings presented herein, the heat- transfer fluids in accordance with the invention may comprise one or more further additives, as is conventional in the art. It is within the routine capabilities of one of ordinary skill in the art to determine how much of a certain additive can be added such that the electrical conductivity of the resulting heat- transfer fluid is in accordance with the invention. As will be appreciated by those skilled in the art, non- ionic further additives are preferred. The heat-transfer fluid described herein comprises well-defined amounts of water, alcohol, zwitterionic compounds, azole-type corrosion inhibitors or dyes. Accordingly, the one or more further additives are different from water, alcohol, zwitterionic compounds, azole-type corrosion inhibitors as described herein earlier or dyes as described herein earlier.

[0095] In certain embodiments of the invention the heat-transfer fluid provided herein, comprises one or more further additives, preferably one or more further additives selected from the group consisting of corrosion inhibitors, liquid dielectrics, antioxidants, anti-wear agents, detergents and antifoam agents. In preferred embodiments, the heat-transfer fluid of further comprises one or more of said further additives in an amount within the range of 0.001-10 wt.% (by total weight of the heat-transfer fluid), preferably 0.01-5 wt.%, more preferably 0.02-3 wt.%.

[0096] In preferred embodiments the heat-transfer fluid further comprises one or more further additives selected from the group consisting of polyolefins, polyalkylene oxides, silicon oils, silicate esters (such as Si(OR)4, wherein R is a C1 to C4 alkyl group), mineral oils, monocarboxylic acids, dicarboxylic acids and tricarboxylic acids. In preferred embodiments the heat-transfer fluid of the invention further comprises one or more of said additives in an amount within the range of 0.001-10 wt.% (by total weight of the heat-transfer fluid), preferably 0.01-5 wt.%, more preferably 0.02-3 wt.%.

[0097] In preferred embodiments, the heat-transfer fluid further comprises one or more additivesselected from the group consisting of polyolefins, silicon oils, mineral oils, silicates, aliphatic monocarboxylic acids, aliphatic dicarboxylic acids, aliphatic tricarboxylic acids, molybdates, nitrates, nitrites, phosphonates and phosphates. In preferred embodiments, the heat-transfer fluid of the invention further comprises one or more of said additives in an amount within the range of 0.001-10 wt.% (by total weight of the heat-transfer fluid), preferably 0.01-5 wt.%.

[0098] In embodiments of the invention, the heat-transfer fluid comprises a defoaming agent. Preferably, the defoaming agent is selected from the group consisting of a polyolefin, or a silicon polymer (such as a 3D silicon polymer) or a silicon oil. In embodiments of the invention, a heat-transfer fluid as defined herein is provided, wherein the heat-transfer fluid further comprises the defoaming agent in an amount of more than 0.001 wt.% (by total weight of the heat-transfer fluid), preferably more than 0.005 wt.%, preferably more than 0.01 wt.% and / or less than 10 wt.%, preferably less than 5 wt.%, preferably less than 3 wt.%.

[0099] In embodiments of the invention, the heat-transfer fluid further comprises an antioxidant. Preferably, the antioxidant is selected from the group consisting of aromatic amines, such as p,p- dioctylphenylamine, monooctyldiphenylamine, phenothiazine, 3,7-dioctylphenothiazine, phenyl-1- naphthylamine, phenyl-2-naphthylamine, alkylphenyl-1-naphthatalamines and alkyl-phenyl-2-naphthal- amines, as well as sulphur containing compounds, e.g. dithiophosphates, phosphites, sulphides and dithio metal salts, such as benzothiazole, tin-dialkyldithiophosphates and zinc diaryldithiophosphates. In embodiments of the invention, a heat-transfer fluid as defined herein is provided, wherein the heat- transfer fluid further comprises the antioxidant in an amount more than 0.001 wt.% (by total weight of the heat-transfer fluid), preferably more than 0.005 wt.%, preferably more than 0.01 wt.% and / or less than 10 wt.%, preferably less than 5 wt.%, preferably less than 3 wt.%.

[0100] In certain embodiments of the invention, the heat-transfer fluid further comprises a liquid dielectric. Preferred liquid dielectrics are minerals oils, silicon oils and mixtures thereof. In certain embodiments of the invention the heat-transfer fluid provided herein comprises more than 0.0001 wt.% (by total weight of the heat-transfer fluid) of the liquid dielectric preferably more than 0.001 wt.%, preferably more than 0.01 wt.% and / or less than 10 wt.%, preferably less than 5 wt.%, preferably less than 3 wt.%.

[0101] In embodiments of the invention, the heat-transfer fluid further comprises an anionic surfactants, such as anionic surfactants which are the salt of a compound represented by R-X; wherein X represents a sulfate group, a phosphate group, a sulfonate group, or a carboxylate group, preferably a sulfate group; and wherein R is selected from: - branched or straight chain C5-C24 alkyl groups; - branched or straight chain mono-unsaturated C5-C24 alkenyl groups; - branched or straight chain poly-unsaturated C5-C24 alkenyl groups; - alkylbenzene groups comprising a C8-C15 alkyl; - alkenylbenzene groups comprising a C8-C15 alkenyl; - alkylnaphthalene groups comprising a C3-C15 alkyl; - alkenylnaphthalene groups comprising a C3-C15 alkenyl; - alkylphenol groups comprising a C8-C15 alkyl; and - alkenylphenol groups comprising a C8-C15 alkenyl.

[0102] In embodiments of the invention, the heat-transfer fluid comprises said anionic surfactant in an amount of more than 0.001 wt.% (by total weight of the heat-transfer fluid), preferably more than 0.005 wt.%, preferably more than 0.01 wt.% and / or less than 10 wt.%, preferably less than 5 wt.%, preferably less than 3 wt.%.

[0103] In embodiments of the invention, the heat-transfer fluid as defined herein is provided, wherein the heat-transfer fluid further comprises a corrosion inhibitors selected from the group consisting ofaromatic carboxylates, aliphatic monocarboxylates, aliphatic dicarboxylates, aliphatic tricarboxylates, molybdates, and phosphates. As is understood by the skilled person, the carboxylates referred to herein are typically provided in the form of a free acid which is neutralized in-situ.

[0104] In embodiments of the invention, the heat-transfer fluid further comprises an aliphatic monocarboxylate, preferably an aliphatic monocarboxylate selected from the group consisting of C4-C12 aliphatic monocarboxylates in an amount of more than 50 ppm (by weight), preferably more than 100 ppm, preferably more than 500 ppm and / or less than 5000 ppm, preferably less than 2500 ppm, preferably less than 1000 ppm. The amount of carboxylate referred to herein is calculated based on the weight of the carboxylate anion, exclusive of the weight of a cation.

[0105] In embodiments of the invention, the heat-transfer fluid further comprises an aliphatic dicarboxylate, preferably an aliphatic dicarboxylate selected from the group consisting of C6-C16 aliphatic dicarboxylates, in an amount of more than 50 ppm (by weight), preferably more than 100 ppm, preferably more than 500 ppm and / or less than 5000 ppm, preferably less than 2500 ppm, preferably less than 1000 ppm. The amount of carboxylate referred to herein is calculated based on the weight of the carboxylate anion, exclusive of the weight of a cation.

[0106] In embodiments of the invention, the heat-transfer fluid further comprises an aliphatic tricarboxylate, preferably an aliphatic tricarboxylate selected from the group consisting of C7-C18 aliphatic tricarboxylates, in an amount of more than 50 ppm (by weight), preferably more than 100 ppm, preferably more than 500 ppm and / or less than 5000 ppm, preferably less than 2500 ppm, preferably less than 1000 ppm. The amount of carboxylate referred to herein is calculated based on the weight of the carboxylate anion, exclusive of the weight of a cation.

[0107] In embodiments of the invention, the heat-transfer fluid further comprises an aromatic carboxylate, preferably an aromatic carboxylate selected from the group consisting of benzoate, benzene-1,2-dicarboxylate, benzene-1,2,3-tricarboxylate, benzene-1,2,4-tricarboxylate, benzene-1,4- dicarboxylate and combinations thereof, in an amount of more than 50 ppm (by weight), preferably more than 100 ppm, preferably more than 500 ppm and / or less than 5000 ppm, preferably less than 2500 ppm, preferably less than 1000 ppm. The amount of carboxylate referred to herein is calculated based on the weight of the carboxylate anion, exclusive of the weight of a cation.

[0108] In embodiments of the invention, the heat-transfer fluid further comprises a corrosion inhibitor which is a molybdate, preferably an inorganic molybdate in an amount of more than 1 ppm (by weight) molybdate, preferably more than 10 ppm, preferably more than 100 ppm molybdate and / or less than 10000 ppm, preferably less than 1000 ppm, preferably less than 500 ppm. If the molybdate is employed in the form of a salt, the amount of molybdate as used in this document refers to the amount of molybdate anion (i.e. exclusive of the weight of the cationic counterion).

[0109] In embodiments of the invention, the heat-transfer fluid further comprises a corrosion inhibitor which is a phosphate, preferably an inorganic phosphate in an amount of more than 10 ppm (by weight) phosphate, preferably more than 250 ppm, preferably more than 1000 ppm phosphate and / or less than 10000 ppm, preferably less than 5000 ppm, preferably less than 2500 ppm. If the phosphate is employed in the form of a salt, the amount of phosphate as used herein refers to the amount of phosphate anion (i.e. exclusive of the weight of the cationic counterion).

[0110] In embodiments of the invention, the heat-transfer fluid further comprises a corrosion inhibitor which is a silicate in an amount more than 1 ppm Si (by weight), preferably more than 10 ppm Si, most preferably more than 100 ppm Si and / or less than 10000 ppm, preferably less than 1000 ppm, preferably less than 500 ppm. Said silicate corrosion inhibitor is preferably selected from the group consisting of inorganic silicates (such as sodium metasilicate), organic silicates (such as Si(R1)n(OR2)4- n wherein R1and R2each independently are a C1 to C6 alkyl or phenyl, and wherein n is 0, 1, 2 or 3) or Silica (SiO2) nanoparticles (such as silica nanoparticles having a volume median particle size (Dv50) within the range of 10-200 nm).

[0111] In embodiments of the invention, the heat-transfer fluid further comprises a nitrate, preferablyan inorganic nitrate in an amount of more than 1 ppm (by total weight of the heat transfer fluid) nitrate, preferably more than 10 ppm, preferably more than 100 ppm nitrate and / or less than 10000 ppm, preferably less than 1000 ppm, preferably less than 500 ppm. If the nitrate is employed in the form of a salt, the amount of nitrate as used in this document refers to the amount of nitrate anion (i.e. exclusive of the weight of the cationic counterion).

[0112] In embodiments of the invention, the heat-transfer fluid further comprises a nitrite, preferably an inorganic nitrite in an amount of more than 1 ppm (by total weight of the heat transfer fluid) nitrite, preferably more than 10 ppm, preferably more than 100 ppm nitrite and / or less than 10000 ppm, preferably less than 1000 ppm, preferably less than 500 ppm. If the nitrite is employed in the form of a salt, the amount of nitrite as used in this document refers to the amount of nitrite anion (i.e exclusive of the weight of the cationic counterion).

[0113] In embodiments of the invention, the heat-transfer fluid further comprises a phosphonate, preferably an inorganic phosphonate in an amount of more than 10 ppm (by total weight of the heat transfer fluid) phosphonate, preferably more than 250 ppm, preferably more than 1000 ppm phosphonate and / or less than 10000 ppm, preferably less than 5000 ppm, preferably less than 2500 ppm. If the phosphonate is employed in the form of a salt, the amount of phosphonate as used in this document refers to the amount of phosphonate anion (i.e. exclusive of the weight of the cationic counterion).

[0114] The present inventors have found that the inclusion of certain further additives in the heat- transfer fluids of the present invention may particularly improve one or more of the composition’s properties when used as a heat-transfer fluid, in particular when considering corrosion inhibition and the capacity to maintain a low electrical conductivity upon ageing in the presence of metals, at increased temperatures, while maintaining the same performance. Such particularly preferred additives, referred to herein as “enhancing additives” include non-ionic polymers, amines, aromatic alcohols, dioxo- aromatic compound and non-ionic surfactants. These are described in more detail in the following paragraphs.

[0115] In preferred embodiments of the invention the heat-transfer fluid further comprises a non-ionic polymer selected from the group consisting of polyvinylpyrrolidones, polyvinylalcohols, polyalkyleneoxides, polysiloxanes, C1-C18alkyl or alkenyl ethers of polyalkyleneoxides, C1-C18alkyl or alkenyl esters of polyalkyleneoxides, alkoxylated C1-C18 alkyl or alkenyl amines, polyvinylacetates, copolymers thereof and combinations thereof, preferably a non-ionic polymer selected from polyvinylpyrrolidones. The non-ionic polymer preferably has a weight average molecular weight Mw in the range of 100 to 5,000,000 g / mol, preferably 500 to 2,500,000 g / mol. The polyalkelyne oxides are preferably selected from polyethylene oxides, polypropylene oxides, polybutyleneoxides, and copolymers thereof. The polyvinylpyrrolidone may be selected from polyvinylpyrrolidone homopolymer and polyvinylpyrrolidone copolymers, preferably polyvinylpyrrolidone homopolymer. Examples of suitable polyvinylpyrrolidone copolymers include polymers of N-vinylpyrrolidone in combination with at least one other monomer selected from styrene, vinyl acetate, ethylene, propylene, tetrafluoroethylene, methyl methacrylate, vinyl chloride and ethylene oxide. In such embodiments the percentage of N- vinylpyrrolidone monomers is at least 10%, more preferably at least 25%, such as at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, or at least 95%, based on the total number of monomers in the polyvinylpyrrolidone copolymer. Preferred polyvinylpyrrolidone copolymers that can be applied in the heat-transfer fluid include copolymers of N-vinylpyrrolidone and vinyl acetate, wherein the percentage of N-vinylpyrrolidone monomers is at least 25%, based on the total number of monomers in the polyvinylpyrrolidone copolymer, hydrolysed forms of copolymers of N-vinylpyrrolidone and vinyl acetate, wherein the percentage of N-vinylpyrrolidone monomers is at least 10%, based on the total number of monomers in the polyvinylpyrrolidone copolymer and copolymers of N-vinylpyrrolidone and N-vinylcaprolactam, wherein the percentage of N-vinylpyrrolidone monomers is at least 40%, based on the total number of monomers in the polyvinylpyrrolidone copolymer. The polyvinylpyrrolidone, preferably the polyvinylpyrrolidone homopolymer, preferably has a weight average molecular weight Mw in the range of 100 to 5,000,000 g / mol, preferably 500 to 2,500,000 g / mol. As appreciated by the skilledperson, the weight average molecular is the weight fraction of molecules in a polymer sample and provides the average of the molecular masses of the individual macromolecules in the polymer sample. The weight average molecular weight as defined herein is determined using the following equation: ^^^^= (∑ ^^^^^^^2^ )⁄ (∑ ^^^^^^^^) . The skilled person knows the different techniques to determine the weight average molecular weight of polymers of varying chain lengths. The weight average molecular weight and the corresponding method of measurement are typically indicated on the product data sheet of the considered polymers. In particular embodiments of the invention, the polyvinylpyrrolidone, preferably the polyvinylpyrrolidone homopolymer, has a weight average molecular weight in the range of 3,000 to 2,500,000 g / mol, preferably in the range of 5,000 to 2,250,000 g / mol, more preferably in the range of 7,500 to 2,00,000 g / mol, even more preferably in the range of 8,000 to 1,800,000 g / mol. polyvinylpyrrolidone that may be suitable used as additive can be purchased from commercial supplies such as BASF, Sigma-Aldrich or Nippon Shokubai. Examples of commercially available polyvinylpyrrolidone are Luvitec K17 (MW = 9,000 g / mol), Luvitec K30 (MW = 50,000 g / mol), Luvitec K90 (MW = 1,400,000 g / mol) and PVP K30. In embodiments of the invention, the heat-transfer fluid comprises as a further additive the non-ionic polymer in an amount of more than 0.001 wt.% (by total weight of the heat transfer fluid), preferably more than 0.005 wt.%, preferably more than 0.01 wt.% and / or less than 10 wt.%, preferably less than 5 wt.%, preferably less than 3 wt.%.

[0116] In preferred embodiments of the invention the heat-transfer fluid further comprises an amine. The amine is preferably selected from molecules consisting of the atoms C, N, H and optionally O, comprising 1 to 10 C atoms, comprising one or more amine functional groups and optionally comprising one or more hydroxyl or ether functional groups, and preferably wherein the amine is free of other functional groups than the one or more amine functional groups and optionally one or more hydroxyl or ether functional groups. In preferred embodiments the amine is selected from the group consisting of methylamine, dimethylamine, trimethylamine, ethylamine, isopropylamine, tributylamine, triethylamine, 2-dimethylaminoethanol, 2-diethylaminoethanol, monoethanolamine, 2-amino-2-methyl-1-propanol, ethoxylated caprylamine, diisopropylamine, 2-dibutylaminoethanol, 2-dipropylaminoethanol, triethanolamine, tri(isopropanol)amine, ethylenediamine, piperadine, morpholine, pyrrolidine, piperazine, diisopropyl-methylamine, 1,4-diazabicyclo[2.2.2]octane, quinuclidine, ethanolamine, diethanolamine, benzylamine, cyclohexamine, hexylamine, dicyclohexylamine, isobutanolamine, dihydroxyethylamine, 3- methoxypropylamine, p,p-dioctylphenylamine, monooctyldiphenylamine, phenyl-1-naphthylamine, phenyl-2-naphthylamine, alkylphenyl-1-naphthatalamines, alkyl-phenyl-2- naphthal-amines, alkoxylated C1-C22 hydrocarbyl amines (in particular ethoxylated caprylamine such as 2-EO-caprylamine) and combinations thereof. In embodiments of the invention, the heat-transfer fluid comprises as a further additive the amine in an amount of more than 0.001 wt.% (by total weight of the heat transfer fluid), preferably more than 0.005 wt.%, preferably more than 0.01 wt.% and / or less than 10 wt.%, preferably less than 5 wt.%, preferably less than 3 wt.%.

[0117] In embodiments of the invention the heat-transfer fluid described herein further comprises an aromatic alcohol selected from phenols, pyrogallols, gallic acid, gallate esters and combinations thereof. The phenol is preferably selected from phenol optionally having a 0, 1, 2 or 3 substituents independently selected from amino, C1-C6 alkyl. Examples of suitable and preferred phenols include 2-aminophenol, 4-aminophenol, 2-Amino-4-methylphenol, 2,6 di-t-butyl methylphenol, 4,4'-methylene-bis(2,6-di-t- butylphenol), and 4-amino-3-methylphenol. Examples of suitable and preferred gallate esters include C1-C12 alkyl esters of gallate. In embodiments of the invention, the heat-transfer fluid comprises as a further additive the aromatic alcohol in an amount of more than 0.001 wt.% (by total weight of the heat transfer fluid), preferably more than 0.005 wt.%, preferably more than 0.01 wt.% and / or less than 10 wt.%, preferably less than 5 wt.%, preferably less than 3 wt.%.

[0118] In embodiments of the invention the heat-transfer fluid further comprises a dioxo-aromatic compound selected from benzoquinones, napthoquinones, hydroquinones and catechols. The dioxo- aromatic compound is preferably selected from 1,4-benzoquinone, 1,2-benzoquinone, 1,2- napthoquinone, 1,4-napthoquinone, 1,4-dihydroxybenzene and 1,2-dihydroxybenzene, optionally having a 0, 1, or 2 substituents independently selected from amino, C1-C6 alkyl, sulphonic acid. Inembodiments of the invention, the heat-transfer fluid comprises as a further additive the dioxo-aromatic compound in an amount of more than 0.001 wt.% (by total weight of the heat transfer fluid), preferably more than 0.005 wt.%, preferably more than 0.01 wt.% and / or less than 10 wt.%, preferably less than 5 wt.%, preferably less than 3 wt.%.

[0119] In embodiments of the invention, the heat-transfer fluid further comprises a secondary antioxidant selected from thiols, thioethers, and thioesters, such as those selected from methyl mercaptan, ethyl mercaptan, n-propyl mercaptan, 2-propenethiol, butanethiol, tert-butyl mercaptan, thiophenol, thioacetic acid, dimercaptosuccinic acid, glutathione, cysteine, methyl thionobenzoate, dimethyl sulfide, methyl phenyl sulfide, 4-ethylthio-2-methylpent-2-ene, dimethyl sulfide, diethyl sulfide, diphenyl sulfide, phenyl 4-piperidyl sulfide, and thiodiglycol.

[0120] In embodiments of the invention the heat-transfer fluid further comprises a non-ionic surfactant. The non-ionic surfactant is preferably selected from the group consisting of: • fatty acid esters, such as sorbitan fatty acid esters; • polyalkylene glycols; • polyalkylene glycol esters; • copolymers and block copolymers of ethylene oxide and propylene oxide; • polyoxyalkylene derivatives of sorbitan fatty acid esters; and • alkoxylated alcohol ethers.

[0121] In embodiments of the invention, the heat-transfer fluid comprises as a further additive the non- ionic surfactant in an amount of more than 0.001 wt.% (by total weight of the heat transfer fluid), preferably more than 0.005 wt.%, preferably more than 0.01 wt.% and / or less than 10 wt.%, preferably less than 5 wt.%, preferably less than 3 wt.%.

[0122] In some embodiments of the invention, the heat-transfer fluid comprises a polymeric dye. As will be understood by the person skilled in the art, utilising such large polymeric dyes minimizes interaction with the ion-exchange resin. Commercially available examples of suitable dyes include Liquitint® Red ST or other similar polymeric colorants from Milliken Chemical of Spartanburg, S.C., USA, or colorants (e.g., Liquitint® Blue RE) from Chromatech of Canton, Mich., USA. Other illustrative colorants include the following: Liquitint Red ST, Liquitint Blue RE, Liquitint Red XC, Liquitint Patent Blue, Liquitint Bright yellow, Liquitint Bright orange, Liquitint Royal Blue, Liquitint Blue N-6, Liquitint Bright Blue, Liquitint Supra Blue, Liquitint Blue HP, Liquitint Blue DB, Liquitint Blue II, Liquitint Exp. Yellow 8614-6, Liquitint Yellow BL, Liquitint Yellow II, Liquitint Sunbeam Yellow, Liquitint Supra yellow, Liquitint Green HMC, Liquitint violet, Liquitint Red BL, Liquitint Red RL, Liquitint Cherry Red, Liquitint Red II, Liquitint Teal, Liquitint Yellow LP, Liquitint Violet LS, Liquitint Crimson, Liquitint Aquamarine, Liquitint Green HMC, Liquitint Red HN, Liquitint Red ST, as well as combinations thereof. In one exemplary embodiment, the dye will be at least one of Liquitint Red, Liquitint Yellow, Liquitint Patent Blue or combinations thereof. Concentrate

[0123] In an embodiment of the invention, the heat-transfer fluid as described herein is provided in the form of a concentrate.

[0124] In preferred embodiments, the concentrate is suitable to prepare the heat-transfer fluid described herein by addition of water and / or alcohol; preferably by addition of water, monoethylene glycol, monopropylene glycol, 1,3-propanediol and / or glycerol; most preferably by addition of water. In highly preferred embodiments, the concentrate is suitable to prepare the heat-transfer fluid solely by addition of water and / or alcohol; preferably solely by addition of water (i.e. no other ingredient needs tobe added in order to prepare the heat-transfer fluid described herein from the concentrate).

[0125] In preferred embodiments, the concentrate is provided wherein the concentration of the zwitterion is at least 5 wt.%, preferably at least 10 wt.%, more preferably at least 15 wt.% and most preferably at least 20 wt.%. Methods of preparation

[0126] In another aspect of the invention there is provided a method to prepare the heat-transfer fluid as defined herein, comprising the steps of: (i) providing a zwitterion as defined herein; (ii) providing a base fluid as defined herein; (iii) optionally providing further additives as defined herein; and (iv) combining the zwitterion of step (i), with the base fluid of step (ii) and the optional further additives of step (iii) to obtain the heat-transfer fluid.

[0127] In accordance with the invention, the order of addition of the compounds is not particularly limited.

[0128] In some embodiments, there is provided a method to prepare the heat-transfer fluid as defined herein, consisting of the following steps: (i) providing a concentrate as defined herein; (ii) providing water, alcohol or a mixture thereof; (iii) combining the concentrate of step (i) with the water, alcohol or a mixture thereof of step (ii) to obtain the heat-transfer fluid. Method of exchanging heat

[0129] In some embodiments, the invention provides a method for exchanging heat, the method comprising the steps of: a. providing a heat-transfer fluid comprising a base fluid and a zwitterionic compound; b. providing a cooling system configured for thermally contacting the heat-transfer fluid with an electrical system, the cooling system comprising an ion-exchange resin; c. transferring heat from the electrical system to the heat-transfer fluid; and d. contacting the heat transfer-fluid with the ion-exchange resin; wherein the base fluid consists of water, or an alcohol or mixtures thereof; wherein the electrical conductivity at 25 °C of the heat-transfer fluid provided in step (a) is less than 100 µS / cm, preferably less than 50 µS / cm, more preferably less than 25 µS / cm, more preferably less than 10 µS / cm, most preferably less than 5 µS / cm.

[0130] In preferred embodiments, the volume ratio of the heat-transfer fluid to the ion-exchange resin is at least 1:99 v / v%, preferably at least 5:95 v / v%, more preferably at least 10:90 v / v% and most preferably at least 20:80 v / v%.

[0131] The cooling system, heat-transfer fluid and ion-exchange resin are preferably as has been described herein in the context of the heat transfer fluid of the invention. Thus, the embodiments characterising the cooling system (in particular further components thereof), the heat-transfer fluid (in particular the conductivity, the compounds comprised therein, and the concentrations thereof) and ion- exchange resin described herein in the context of the heat transfer fluid apply mutatis mutandis to themethod of the invention. The cooling system

[0132] The cooling system of typically comprises further components such as a heat-exchanger provided for transferring heat away from the heat-transfer fluid (typically provided for exchanging heat with ambient air, such as a radiator), one or more pumps, one or more valves, and conduits for connecting various components of the cooling system. The various components of the cooling systemtogether define a flow path for the heat-transfer fluid.

[0133] In highly preferred embodiments, the ion exchange resin is positioned in the flow path of the heat-transfer fluid. In some embodiments, the cooling system of step (b) comprises the ion-exchange resin in a cartridge. In other embodiments, the ion-exchange resin may be immobilized on an inner surface of the cooling system, for instance on a porous support or bed which is fixed to the coolingsystem of step (b) in a way such that it can contact the heat-transfer fluid of step (a) during use.

[0134] In some embodiments of the invention, the cooling system of step (b) comprises a by-pass to which the heat-transfer fluid is directed towards the ion-exchange resin. In preferred embodiments, for every circulation through the coolant system, at least 10 v / v%, preferably at least 15 v / v%, more preferably at least 20 v / v% and most preferably 30 v / v% of the heat-transfer fluid flows through the ion- exchange resin. In some embodiments, such a bypass is always open such that heat-transfer fluid contacts the ion-exchange resin with every circulation through the coolant system. In other embodiments, the by-pass is closed and re-opened periodically such that the heat-transfer contacts the ion-exchange resin periodically, preferably at least once in every five circulations, preferably at least once in every 3 circulations, more preferably at least once in every 2 circulations through the coolant system.

[0135] In some embodiments of the invention, the cooling system of step (b) comprises a by-pass to which the heat-transfer fluid is directed towards the ion-exchange resin. In preferred embodiments, for every circulation through the coolant system, at least 10 v / v%, preferably at least 15 v / v%, more preferably at least 20 v / v% and most preferably 30 v / v% of the heat-transfer fluid flows through the ion- exchange resin. In some embodiments, such a bypass is always open such that heat-transfer fluid contacts the ion-exchange resin with every circulation through the coolant system. In other embodiments, the by-pass is closed and re-opened periodically such that the heat-transfer contacts the ion-exchange resin periodically, preferably at least once in every five circulations, preferably at least once in every 3 circulations, more preferably at least once in every 2 circulations through the coolant system.

[0136] The cooling system is typically designed to prevent contact between the heat-exchange fluid and air, such that inter alia decomposition of the base fluid can be avoided. Thus, the flow path for the heat-transfer fluid in the cooling system is preferably essentially isolated from air.

[0137] In some embodiments of the invention, the present method further comprises a step comprising passing the heat-transfer fluid through a heat exchanger and transferring heat away from the heat-transfer fluid.

[0138] In accordance with the invention the heat-transfer fluid is typically circulated in the cooling system such that steps (c) and (d) are continuously taking place simultaneously. However, in some embodiments the ion-exchange resin may be separated from a part of the cooling circuit with one or more valves such that step (c) can take place continuously without step (d) taking place continuously. Step (d) can then be performed at predetermined intervals, or in response to user action or sensor data, such as sensor data comprising information about the pH and / or the conductivity of the heat-transfer fluid.

[0139] In highly preferred embodiments of the invention, the electrical conductivity of the heat-transfer fluid is maintained at less than less than 100 µS / cm, preferably less than 50 µS / cm, more preferablyless than 25 µS / cm, more preferably less than 10 µS / cm, most preferably less than 5 µS / cm throughoutthe method.The electrical system

[0140] In preferred embodiments of the invention, the method further comprises a step of generatingheat in an electrical system.

[0141] The electrical system is preferably an electrical system selected from the group consisting of a solar system, a fuel cell, an electrical motor, a generator, a battery, a battery electric vehicle, DC / DC converters, DC / AC converters, a telephone transmission state, power electronics, a radio and television broadcast station, a relay station, an electrical heating or cooling device, preferably a fuel cell, battery or power electronics. The Ion-Exchange resin and pre-treatment thereof

[0142] Suitable ion-exchange resins in the context of the present invention include anion exchange resins, cation exchange resins, mixed ion exchange resins and combinations thereof. A mixed ion exchange resin as used herein denotes a resin having a combination of anion-exchange and cation- exchange functionalities. This can be provided in the same resin by chemical design, or achieved by simply mixing an anion exchange resin and a cation exchange resin. In some embodiments of the invention the resin comprises a combination of two or more resins, for example placed such that the heat-transfer fluid is first circulated through a first resin and then through a second resin, such as first through an anion-exchange resin followed by a mixed ion exchange resin.

[0143] The resin is preferably a polymeric resin. Typically the resins comprise a polymeric backbone which has ion-exchanging sites introduced after polymerisation, such as sulfonate groups, phosphonate groups, phosphinate groups, quaternary ammonium groups, carboxylate groups, etc. The polymeric backbone is preferably selected from polystyrene, polystyrene and styrene copolymers, polyacrylate, aromatic substituted vinyl copolymers, polymethacrylate, phenol-formaldehyde, polyalkylamine, and combinations thereof. In an embodiment of the invention, the polymer backbone is selected from polystyrene and styrene copolymers, polyacrylate, and polymethacrylate. In an embodiment of the invention the polymer backbone is selected from styrene divinylbenzene copolymers. In an embodiment of the invention, the ion-exchanging sites in a cation exchange resin comprise sulphonates, phosphonates and / or carboxylic acids. In some embodiments of the invention, the the ion-exchanging site is an aminic group, such as a primary, secondary and / or tertiary amino acid, and a quaternary ammonium group. In an embodiment of the invention, the ion-exchanging sites in an anion-exchange resin comprise quaternary ammonium groups. Examples of suitable quaternary ammonium groups are benzyltrimethylammonium, benzyldimethylethanolammonium, trialkylbenzyl ammonium, trimethylbenzyl ammonium, or dimethyl-2-hydroxyethylbenzyl ammonium and combinations thereof. In an embodiment of the invention, the ion-exchange resin is a cation-exchange resin comprising sulfonic acid groups (-SO3H). Such ion-exchange resins include sodium polystyrene or poly(2-acrylamido-2- methyl-1-propanesulfonic acid) (polyAMPS).

[0144] In preferred embodiments, the ion-exchange resin is a mixed ion-exchange resin comprising a combination of a cation exchange site comprising sulfonic acid, and anionic exchange site comprising trimethylammonium.

[0145] Commercially available ion exchange resins suitable for use herein are available from DuPont as Amberlite™, Amberjet™, Duolite™, and Imac™ resins, from Bayer of Leverkusen, Germany as Lewatit™ resin, from Dow Chemical of Midland, Mich. as Dowex™ resin, from Mitsubishi Chemical of Tokyo, Japan as Diaion™ and Relite™ resins, from Purolite of Bala Cynwyd, Pa. as Purolite™ resin, from Sybron of Birmingham, N.J. as Ionac™ resin, from Resintech of West Berlin, N.J., and the like. In one embodiment, a suitable commercially available ion exchange resin will be Dowex™ MR-3 LC NGMix mixed bed resin, Dowex™ MR-450 UPW mixed bed resin, Sybron Ionac™ NM-60 mixed bed resin, Amberlite™ MB-150 or AmberLiteTMIRN170 H / OH mixed bed resin, while in one exemplary embodiment, a suitable commercially available ion exchange resin will be AmberLiteTMIRN170 H / OH. References to tradenames herein should be construed as referring to the product marketed under that tradename on 01 October 2023.

[0146] The present inventors have found that resin pretreatments (e.g. by soaking the resin) are not necessary and can actually be avoided employing zwitterionic compounds as explained throughout the present description. However, in some circumstances a resin pretreatment may still be desirable. Thus, in an embodiment of the invention, the ion-exchange resin of the heat-exchange system is pre-treated by contacting the resin with a heat transfer fluid comprising the zwitterionic compound before the resin is contacted with the heat-transfer fluid. In preferred embodiments of the invention, the ion-exchange resin is contacted with the zwitterionic compound for a period of time sufficient to allow the zwitterionic compound to exchange places with at least 15 % of the total exchangeable groups, based on the total number of exchangeable ions in the ion exchange resin. In some embodiments, the ion-exchange resin is soaked in a solution comprising the zwitterionic compound, for at least 5 mins, preferably at least 20 mins, more preferably at least 12 hours and most preferably at least 24 hours. In some embodiments, at least 1 bed volume, preferably at least 2 bed volumes of a solution comprising the zwitterionic compound are circulated through a bed of the ion-exchange resin before the resin is contacted with the heat-transfer fluid. The solution comprising the zwitterionic compound preferably comprises at least 0.5 wt.% (by total weight of the solution) of the zwitterionic compound, preferably at least 1 wt.%. In some embodiments of the invention, the method is provided further comprising a step of pretreating the ion- exchange resin of the cooling system by contacting the resin with a solution comprising the zwitterionic compound, as is described herein.

[0147] As is shown in the appended examples, the present inventors have found that the zwitterionic compounds in accordance with the invention are capable of protecting a corrosion inhibitor and / or a dye from being absorbed by the resin, while still allowing ionic compounds such as glycolates to be absorbed by the resin. Without wishing to be bound by any theory, the present inventors believe that this is because the affinity of the resin for the zwitterionic compound is larger than the affinity of the resin for the corrosion inhibitor or dye, but smaller than for a charged ion such as a glycolate ion. Thus, in preferred embodiments of the invention, the method is provided wherein the binding affinity of the zwitterionic compound to the ion-exchange resin is smaller than the binding affinity of glycolate to the ion-exchange resin.

[0148] As is also shown in the appended examples, it is especially advantageous to employ a combination of two or more zwitterionic compounds as described herein, in particular when the ion- exchange resin comprises both an anion-exchange and a cation-exchange functionality. By using a combination of two or more zwitterionic compounds, optimal protection of both corrosion inhibitors and dyes can be achieved. In some preferred embodiments of the invention, in particular when the ion- exchange resin comprises both an anion-exchange and a cation-exchange functionality, the zwitterionic compound comprises a combination of a first and second zwitterionic compound, wherein the first and second zwitterionic compounds are preferably as described herein earlier for the zwitterionic compounds in general, and wherein more preferably the first zwitterionic compound comprises a trialkyl ammonium functional group, and the second zwitterionic compound comprises a sulfonic acid functional group. Cooling system of the invention

[0149] In another aspect of the invention, there is provided a cooling system comprising the heat- transfer fluid of the invention wherein the cooling system comprises an ion-exchange resin in contact with the heat-transfer fluid.

[0150] The heat-transfer fluid and ion-exchange resin are preferably as has been described hereinbefore. Thus, the embodiments characterising the heat-transfer fluid (in particular the conductivity, the compounds comprised therein, and the concentrations thereof), the methods utilising the heat-transfer fluid and ion-exchange resin described herein in before apply mutatis mutandis to the cooling system of the invention. Uses of the invention

[0151] In another aspect of the invention, there is provided the use of a heat-transfer fluid comprising a base fluid and a zwitterionic compound according to formula (I-a) or (I-b) as a heat-transfer fluid in a cooling system comprising an ion-exchange resin, wherein the base fluid consists of water, or an alcohol or mixtures thereof; and wherein the electrical conductivity at 25 °C of the heat-transfer fluid is less than 100 µS / cm, preferably less than 50 µS / cm, more preferably less than 25 µS / cm, more preferably less than 10 µS / cm, most preferably less than 5 µS / cm.

[0152] In another aspect of the invention, there is provided the use of a heat-transfer fluid comprising a base fluid and a zwitterionic compound as a heat-transfer fluid in a cooling system comprising an ion- exchange resin, wherein the base fluid consists of water, or an alcohol or mixtures thereof; and wherein the electrical conductivity at 25 °C of the heat-transfer fluid is less than 100 µS / cm, preferably less than 50 µS / cm, more preferably less than 25 µS / cm, more preferably less than 10 µS / cm, most preferably less than 5 µS / cm wherein -the base fluid comprises an alcohol selected from the group consisting of monoethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, monopropylene glycol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, pentapropylene glycol, hexapropylene glycol, methanol, ethanol, propanol, butanol, tetrahydrofurfuryl, ethoxylated furfuryl, dimethyl ether of glycerol, sorbitol, 1,2,6-hexanetriol, trimethylolpropane, methoxyethanol, glycerol and mixtures thereof, preferably selected from the group consisting of monoethylene glycol, monopropylene glycol, 1,3-propanediol, glycerol and mixtures thereof; or -the zwitterionic compound is not N,N,N-trimethylglycine, preferably the heat-transfer fluid does not comprise N,N,N-trimethylglycine; or -wherein the heat-transfer fluid further comprises a corrosion inhibitor, and wherein the ratio (w / w) of the zwitterionic compound to the corrosion inhibitor in the heat-transfer fluid is less than 50:1, more preferably less than 30:1; or -wherein the concentration of the zwitterionic compound in the heat-transfer fluid is less than 6 wt.%, more preferably less than 4 wt.%, most preferably less than 3 wt.%, by total weight of the heat-transferfluid.

[0153] The cooling system, heat-transfer fluid and ion-exchange resin are preferably as has been described herein before. Thus, the embodiments characterising the cooling system (in particular further components thereof), the heat-transfer fluid (in particular the conductivity, the compounds comprised therein, and the concentrations thereof) and ion-exchange resin described herein before apply mutatis mutandis to the uses of the invention.

[0154] The use is preferably as a heat-transfer fluid in a cooling system for an electrical system, wherein the electrical system is preferably as has been described herein before in the context of the method.

[0155] In another aspect of the invention there is provided the use of a zwitterionic compound: • for prolonging the corrosion inhibiting properties of a heat-transfer fluid comprising a corrosion inhibitor when contacting an ion-exchange resin, preferably when used as a heat-transfer fluid in a cooling system comprising an ion-exchange resin in contact with the heat-transfer fluid; • for prolonging the coloration of a heat-transfer fluid comprising a dye when contacting an ion- exchange resin, preferably when used as a heat-transfer fluid in a cooling system comprising an ion-exchange resin in contact with the heat-transfer fluid; • for reducing the amount of corrosion inhibitor and / or dye used in a heat-transfer fluid comprising when contacting an ion-exchange resin, preferably when used as a heat-transfer fluid in acooling system comprising an ion-exchange resin in contact with the heat-transfer fluid; • for extending the service life interval of an ion-exchange resin when contacting a heat-transfer fluid by reducing or avoiding uptake of heat-transfer fluid components, preferably when used in a cooling system comprising an ion-exchange resin in contact with the heat-transfer fluid; • for extending the service life interval of a heat-transfer fluid comprising a corrosion inhibitor (and preferably comprising an alcohol as described herein) and / or an ion-exchange resin contacting the heat-transfer fluid by o reducing, postponing or avoiding corrosion; o reducing, postponing or avoiding the formation of electrically conductive acids such as glycolates; preferably when the heat-transfer fluid is used in a cooling system comprising an ion- exchange resin in contact with the heat-transfer fluid.

[0156] The use is preferably as a heat-transfer fluid in a cooling system for an electrical system, wherein the electrical system is preferably as has been described herein before in the context of the method.Examples

[0157] Electrical conductivity as referred to herein is preferably measured in accordance with ASTM D1125-23 with a Mettler-Toledo SevenExcellence Cond meter S700-Std-Kit electrical conductivity meter equipped with a SevenExcellence Cond meter S700-Std-Kit.

[0158] The analysis of anions (glycolate) in the coolant was performed using ion chromatography in accordance with ASTM D5827-22 using a Thermo-Scientific Dionex ICS 6000.

[0159] UV-VIS adsorption (1 cm path length, HACH LICO 690) was used to determine concentration of Rhodamine B (535 nm) and Dye acid green 25 (650 nm).

[0160] The analysis of organic corrosion inhibitors (benzotriazole, tolyltriazole) was performed using reverse phase HPLC on a Shimadzu Prominence system employing an Agilent Zorbax Eclipse Plus C18 column with UV detection.

[0161] Heat-transfer fluids were prepared as is shown in table 1. Rhodamine B was added as a dye and tolyltriazole was added as a corrosion inhibitor to a water - monoethylene glycol base fluid. Thereafter, the heat transfer fluid was contacted with ion-exchange resin AmberliteTMMB20 HOH (2 v / v%) for 3 hours. Table 1 Comp Ex.1 Ex.2 Ex.3 Deionized water (wt.%) 49 49 49 Monoethylene glycol (wt.%) 50.75 50.75 50.75 Rhodamine B (wt.%) 0.001 0.001 0.001 Tolyltriazole (wt.%) 0.15 0.15 0.15 2-aminoethanesulfonic acid (wt.%) - 1.8 - L-Carnitine (wt.%) - - 2

[0162] Table 2 illustrates the heat-transfer fluid properties prior to and after contacting with the ion- exchange resin. The ‘eCond 25 °C prior to resin’ denotes the electrical conductivity of the heat-transfer fluid prior to contact with the ion-exchange resin. The ‘eCond 25 °C after resin’ denotes the electrical conductivity of the heat-transfer fluid after contacting the heat-transfer fluid with the ion-exchange resin. The ‘∆ Rhodamine B’ denotes the percentage change in dye concentration, the ‘∆ TTZ’ denotes the percentage change in corrosion inhibitor concentration. Table 2 Ex.1 Ex.2 Ex.3 eCond 25°C prior to resin 8.8 3.8 7.6 eCond 25 °C 0.4 1.0 2.0 after resin ∆ Rhodamine B -96% - 0 ∆ Tolyltriazole -93% -65% -

[0163] Heat-transfer fluids were prepared as is shown in table 3. Chromatint Red X4075 or Dye acid green 25 were added as dyes and benzotriazole or tolyltriazole were added as corrosion inhibitors to a water - monoethylene glycol base fluid. Thereafter, the heat transfer fluid was contacted with ion-exchange resin AmberliteTMMB20 HOH (2 v / v%) for 3 hours. Table 3 Comp. Comp. Comp. Comp. Ex.4 Ex.5 Ex.6 Ex.7 Ex.8 Ex.9 Ex.10 Ex.11 UPW (wt.%) 49 49 49 49 49 49 49 49 MEG (wt.%) 51 51 51 51 49 49 49 49 Chromatint Red X4075 (wt.%) 0.002 - - - - - - 0.002 Dye acid green 25 (wt.%) - 0.01 - - - - - - Glycolic acid (wt.%) - - 0.01 - 0.01 - - - Benzotriazole (wt.%) - - - - - 0.09 - - Tolyltriazole (wt.%) - - 0.09 - - 0.09 - 2-aminoethanesulfonic acid (wt.%) - - - - 2 2 2 - L-Carnitine (wt.%) - - - - - - - 2

[0164] Table 4 illustrates the heat-transfer fluid properties prior to and after contacting with an ion- exchange resin. The ‘eCond 25 °C prior to resin’ denotes the electrical conductivity of the heat-transfer fluid prior to contact with the ion-exchange resin. The ‘eCond 25 °C after resin’ denotes the electrical conductivity of the heat-transfer fluid after contacting the heat-transfer fluid with the ion-exchange resin. The ‘∆ Rhodamine B’ or ‘∆ Dye acid green 25’ denotes the percentage change in dye concentration, the ‘∆ benzotriazole’ or ‘∆ tolyltriazole’ denotes the percentage change in corrosion inhibitor concentration, and the ‘∆ Glycolate’ denotes the percentage change in glycolate concentration. Table 4 Comp. Comp. Comp. Comp. Ex.4 Ex.5 Ex.6 Ex.7 Ex.8 Ex.9 Ex.10 Ex.11 eCond 25°C prior to resin 0.4 1.2 28.8 0.5 25.3 1.4 4.4 4.5 eCond 25 °C 0.3 0.2 0.2 0.3 1.7 1.2 1.1 0.9 after resin ∆ Chromatint Red X4075 - 87% - - - - - - -4 ∆ Dye acid green 25 - -96% - - - - - - ∆ Glycolate - - -97% - -100% - - - ∆ Benzotriazole - - - - - -65% - - ∆ Tolyltriazole - - - -94% - - -65% -

[0165] As can be derived from the above examples and comparative examples, the inclusion of a zwitterionic compound does not adversely affect the electrical conductivity, reduces the uptake of the dyes and corrosion inhibitors by the resin, but still allows the resin to perform the desired function of removing glycolate ions.

Claims

1. A liquid heat transfer fluid containing: at least one zwitterionic compound according to formula (Ia) or (Ib): Where Y is selected from sulfonate (-SO3 - ), phosphinate (-HPO2 - ) and phosphonate (-PO3 - ); R 1 , R 2 , R 3 , R 4 , R 5 and R 6 individually selected from the group consisting of hydrogen, =O, -OH, -SH, -NH2 and optionally substituted monovalent hydrocarbon radicals containing from 1 to 30 carbon atoms, preferably R 1 , R 2 , R 3 , R 4 , R 5 and R 6 individually selected from the group consisting of hydrogen, C1-C 20 alkyl, C1-C 20 haloalkyl, C1-C 20 alkyl alcohol, C1-C 20 aminoalkyl, C2-C 20 alkenyl, C3-C8cycloalkyl, C4-C8cycloalkenyl, C6-C 10 aryl, C1-C20 sulfide, =O, -OH, -NH2, -SH, -OR 7 , -NR 7 R 7' , -SR 7 , -(OCH2CH2) p CH3, -(OCHCH3CH2) q CH3, -(OCH3) r CH3, -R 7 OR 7' , -R 7 (CO)R 7' , -R 7 (COO)R 7' , -R 7 (CONH)R 7' , -R 7 (NHCO)R 7' , -R 7 (NHCOO)R 7' , -R 7 (NHCONH)R 7' , -N=CR 7 R 7' , -N=CR 7'' , -C(O)R 7 ; R 7 selected from the group consisting of C1-C 20 alkyl, C1-C 20 haloalkyl, C1-C 20 aminoalkyl, C2-C 20 alkenyl, C1-C 20 alkyl alcohol, -(OCH2CH2) p CH3, -(OCHCH3CH2) q CH3, -(OCH3) r CH3, preferably R 7 selected from the group consisting of C1-C 20 alkyl; R 7' selected from the group consisting of hydrogen, C1-C 20 alkyl, C1-C20 haloalkyl, C1-C 20 aminoalkyl, C2-C 20 alkenyl, C1-C 20 alkyl alcohol, -(OCH2CH2) p CH3, -(OCHCH3CH2) q CH3, -(OCH3) r CH3, preferably R 7' selected from the group consisting of hydrogen, C1-C 20 alkyl; R 7'' is a divalent C2-C8 alkyl radical such that -N=CR 7'' is a cycloalkyl; each of n, m and o represents an integer individually selected from 0-20, preferably from 0-10; in each of formulas (Ia) and (Ib) at least one of n, m and o is greater than 0; each of p, q and r represents an integer individually selected from 1-30, preferably from 2-20; Z is chosen from any of Z 1 , Z 2 , Z 3 , Z 4 , Z 5 , Z 6 and Z 7 , where Z 1 , Z 2 , Z 3 , Z 4 , Z 5, Z 6 and Z 7 are presented as follows: R 8 , R 9 and R 10 individually selected from the group consisting of hydrogen and optionally substituted monovalent hydrocarbon radicals containing from 1 to 30 carbon atoms, preferably R 8 , R 9 and R 10 individually selected from the group consisting of hydrogen, C1-C 20 alkyl, C1-C 20 haloalkyl, C1-C 20 alkyl alcohol, C1-C 20 aminoalkyl, C1-C 20 sulfide, -R 7 OR 7' , -R 7 (CO)R 7' , -R 7 (COO)R 7' , -R 7 (CONH)R 7' , -R 7 (NHCO)R 7' , -R 7 (NHCOO)R 7' , -R 7 (NHCONH)R 7' , -N=CR 7 R 7' , -N=CR 7'' , -C(O)R 7 , more preferably R 8 , R 9 and R 10individually selected from the group consisting of hydrogen, C1-C8 alkyl, C1-C8 haloalkyl, C1-C8 alkyl alcohol, C1-C8 aminoalkyl, C1-C8 sulfide, -R 7 OR 7' , -R 7 (CO)R 7' , -R 7 (COO)R 7' , -R 7 (CONH)R 7' , -R 7 (NHCO)R 7' , -R 7 (NHCOO)R 7' , -R 7 (NHCONH)R 7' , -N=CR 7 R 7' , -N=CR 7'' , -C(O)R 7 ; R 11 , R 12 , R 13 , R 14 and R 15 individually selected from the group consisting of hydrogen and optionally substituted monovalent hydrocarbon radicals containing from 1 to 30 carbon atoms, preferably R 11 , R 12 , R 13 , R 14 and R 15 individually selected from the group consisting of hydrogen, C1-C 20 alkyl, C1-C 20 haloalkyl, C1-C 20 alkyl alcohol, C1-C 20aminoalkyl, C2-C 20 alkenyl, C3-C8cycloalkyl, C4-C8cycloalkenyl, C6-C 10 aryl, C1-C 20 sulfide, -R 7 OR 7' , -R 7 (CO)R 7' , -R 7 (COO)R 7' , -R 7 (CONH)R 7' , -R 7 (NHCO)R 7' , -R 7 (NHCOO)R 7' , -R 7 (NHCONH)R 7' , -N=CR 7 R 7' , -N=CR 7'' , -C(O)R 7 ; wherein the electrical conductivity of the heat transfer fluid is less than 100 μS / cm, preferably less than 50 μS / cm, more preferably less than 25 μS / cm, more preferably less than 10 μS / cm, most preferably less than 5 μS / cm; where the coolant liquid contains a corrosion inhibitor.

2. The liquid heat transfer agent according to paragraph 1, wherein the liquid heat transfer agent contains a base liquid consisting of water or alcohol or mixtures thereof.

3. The liquid heat transfer agent according to paragraph 2, wherein water and alcohol are present in a weight ratio of 95:5 to 5:95 based on the total weight of the liquid heat transfer agent.

4. The heat transfer fluid according to any one of paragraphs 2 or 3, wherein the base fluid comprises an alcohol, and wherein the alcohol is selected from monoethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, monopropylene glycol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, pentapropylene glycol, hexapropylene glycol, methanol, ethanol, propanol, butanol, tetrahydrofurfuryl, ethoxylated furfuryl, glycerol dimethyl ether, sorbitol, 1,2,6-hexanetriol, trimethylolpropane, methoxyethanol, glycerol and combinations thereof.

5. The heat transfer liquid according to any one of paragraphs 2-4, wherein the weight ratio of the zwitterionic compound and the alcohol (based on the total weight of the heat transfer liquid) is from 1:250 to 1:2, preferably from 1:100 to 1:2, preferably from 1:80 to 1:10 and most preferably from 1:50 to 1:

20.

6. The heat transfer fluid according to any one of the preceding claims, wherein the composition comprises at least 0.1 wt.% of the zwitterionic compound based on the total weight of the heat transfer fluid, preferably at least 0.01 wt.%, more preferably at least 0.05 wt.%, preferably at least 0.5 wt.%, more preferably at least 1 wt.%.

7. The heat transfer fluid according to any one of the preceding claims, wherein the weight ratio of the zwitterionic compound to the corrosion inhibitor (based on the total weight of the heat transfer fluid) is at least 5:1, preferably at least 10:1, more preferably at least 15:

1.

8. A heat transfer fluid according to any one of the preceding claims, wherein the zwitterionic compound is selected from zwitterionic compounds according to formula (Ia) or (Ib) and has a molecular weight of less than 1000 g / mol, preferably less than 500 g / mol, preferably less than 200 g / mol.

9. The heat transfer fluid according to any one of the preceding claims, wherein the heat transfer fluid comprises a corrosion inhibitor selected from triazoles, thiazoles, triazines, diazoles, nonionic polymers, silicate esters, organic silicates, molecules containing trimethylsilyl, alcohols containing an alkene or alkyne group, and combinations thereof, preferably a corrosion inhibitor selected from triazoles, thiazoles, triazines, diazoles, and combinations thereof.

10. A liquid heat transfer fluid according to any of the preceding paragraphs, having a pH in the range of 3 to 10.

11. A heat transfer fluid according to any one of the preceding claims, wherein the fluid further comprises one or more additives selected from the group consisting of antioxidants, antiwear additives, surfactants, deposit inhibitors, antifoaming agents, colorants and combinations thereof in an amount in the range of 0.001-10% by weight (based on the total weight of the heat transfer fluid).

12. A method for providing heat exchange, wherein the method includes the following steps: a. providing a liquid heat transfer agent according to any of paragraphs 1-11; b. providing a cooling system configured to provide thermal contact of a liquid coolant with an electrical system, wherein the cooling system comprises an ion exchange resin; c. ensuring the transfer of heat from the electrical system to the liquid coolant and d. bringing the liquid coolant into contact with the ion exchange resin.

13. The method according to claim 12, wherein the volume ratio of the heat transfer fluid to the ion exchange resin is at least 1:99% v / v, preferably at least 5:95% v / v, more preferably at least 10:90% v / v and most preferably at least 20:80% v / v.

14. Use of a heat transfer fluid containing a zwitterionic compound according to formula (Ia) or (Ib) as a heat transfer fluid in a cooling system containing an ion-exchange resin; wherein the electrical conductivity at 25°C of the heat transfer fluid is less than 100 μS / cm, preferably less than 50 μS / cm, more preferably less than 25 μS / cm, more preferably less than 10 μS / cm, most preferably less than 5 μS / cm.

15. Use of a zwitterionic compound according to formula (Ia) or (Ib): for prolonging the corrosion inhibiting properties of a heat transfer fluid containing a corrosion inhibitor when brought into contact with an ion exchange resin, preferably when used as a heat transfer fluid in a cooling system containing an ion exchange resin in contact with the heat transfer fluid; for prolonging the coloration or reducing the fading of a heat transfer fluid containing a dye when brought into contact with an ion-exchange resin, preferably when used as a heat transfer fluid in a cooling system containing an ion-exchange resin in contact with the heat transfer fluid; for reducing the amount of corrosion inhibitor and / or dye used in a heat transfer fluid when brought into contact with an ion exchange resin, preferably when used as a heat transfer fluid in a cooling system containing an ion exchange resin in contact with the heat transfer fluid; to increase the service life of an ion-exchange resin when brought into contact with a liquid coolant by reducing or preventing the absorption of components of the liquid coolant, preferably when used in a cooling system containing an ion-exchange resin in contact with a liquid coolant; to increase the service life of a heat transfer fluid containing a corrosion inhibitor (and preferably containing an alcohol as described herein) and / or an ion exchange resin in contact with the heat transfer fluid, by - reducing, delaying or preventing corrosion; - reducing, delaying or preventing the formation of conductive acids such as glycolates; preferably when using a liquid coolant in a cooling system containing an ion exchange resin in contact with the liquid coolant.

Images