WO2025087963A1

WO2025087963A1 - Sacrificial zwitterions in low conductive heat-transfer fluids

Info

Publication number: WO2025087963A1
Application number: PCT/EP2024/079940
Authority: WO
Inventors: Sander Clerick
Original assignee: Arteco NV
Current assignee: Arteco NV
Priority date: 2023-10-26
Filing date: 2024-10-23
Publication date: 2025-05-01
Anticipated expiration: 2026-04-26

Abstract

The present invention relates to methods of exchanging heat with 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 compositions and uses.

Description

SACRIFICIAL ZWITTERIONS IN LOW CONDUCTIVE HEAT-TRANSFER FLUIDS

Field of the invention

[0001] The present invention relates to methods for exchanging heat which comprises circulating heat- transfer fluids comprising zwitterions through a cooling system comprising an ion-exchange resin. The invention further relates to compositions comprising an ion-exchange resin and zwitterions which are particularly useful as heat-transfer fluids. The invention further relates to assemblies comprising said compositions 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 heattransfer 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 maintaining this 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 ionexchange 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 pS/cm before it is employed as a heat-transfer fluid.

[0016] 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.

[0017] It is an objective of the present invention to provide methods of exchanging heat and associated compositions which limit or prevent the undesirable removal of one or more additives (such as corrosion inhibitors and/or dyes) by an ion-exchange resin.

[0018] It is an object of the invention to provide methods of exchanging heat and associated compositions which allow low electrical conductivity of a heat-transfer fluid to be maintained.

Summary of the invention

[0019] The present inventors have surprisingly found that zwitterionic compounds act as sacrificial agents when used in a low conductivity heat-transfer fluid which is placed in contact with an ionexchange resin, preventing the uptake by the resin of desired functional additives used in the heattransfer fluid, such as corrosion inhibitors and/or dyes. In addition, the zwitterionic compounds 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.

[0020] Hence, in a first aspect the present 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 pS/cm, preferably less than 50 pS/cm, more preferably less than 25 pS/cm, more preferably less than 10 pS/cm, most preferably less than 5 pS/cm.

[0021] In preferred embodiments, the zwitterionic compound 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; and

-comprising in the same molecule a positive charge from a quaternary ammonium, sulfonium or phosphonium functional group, and a negative charge from a carboxylate, sulfonate, phosphinate or phosphonate functional group, or comprising a nitro, nitroso or amine oxide functional group.

[0022] In another aspect of the invention there is provided a cooling system comprising a heat-transfer fluid comprising a base fluid and a zwitterionic compound, wherein the cooling system comprises an ion-exchange resin in contact with the heat-transfer fluid, wherein the base fluid consists of water, or an alcohol or mixtures thereof.

[0023] In another aspect of the invention, there is provided a composition comprising: a heat-transfer fluid comprising a base fluid and a zwitterionic compound; and an 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 is less than 100 pS/cm, preferably less than 50 pS/cm, more preferably less than 25 pS/cm, more preferably less than 10 pS/cm, most preferably less than 5 pS/cm; and 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, tetra hydrofurfury I, 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-transfer fluid. [0024] 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 ionexchange 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 pS/cm, preferably less than 50 pS/cm, more preferably less than 25 pS/cm, more preferably less than 10 pS/cm, most preferably less than 5 pS/cm.

[0025] 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 ionexchange 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 ionexchange resin in contact with the heat-transfer fluid.

Description of embodiments

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] The term “alkyl” as used herein includes straight, branched and cyclic alkyls.

[0031] 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 composition as it is prepared at the time of first contacting the ingredients, unless expressly indicated otherwise.

[0032] 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.

[0033] The term ‘thermal contact’ refers to any arrangement that allows heat produced by the electrical system to be transferred to the heat-transfer fluid or composition thereof by heat transfer.

Method for exchanging heat of the invention

[0034] In a first aspect, 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 pS/cm, preferably less than 50 pS/cm, more preferably less than 25 pS/cm, more preferably less than 10 pS/cm, most preferably less than 5 pS/cm.

[0035] The heat-transfer fluid of step (a) 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% ofthe zwitterionic compound is in zwitterionic form at the pH ofthe heat-transfer fluid. Typically, the zwitterionic compound is chosen such that at least 99.9 mol%, or even 99.99 mol% ofthe 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

[0036] 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.

[0037] The present inventors believe that the principle of employing sacrificial zwitterionic compounds which they have discovered is broadly applicable to any zwitterionic compound, although for reasons of solubility and resin compatibility it is preferred 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.

[0038] In highly 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.

[0039] 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 carboxylate, 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. In some embodiments, the zwitterionic compound is selected from compounds comprising a nitro or amine oxide functional group.

[0040] In preferred embodiments, the zwitterionic compound is selected from the group consisting of trimethylglycine, 2-aminoethanesulfonic acid, carnitine, trimethylamine N-oxide dihydrate, tris(hydroxymethyl)-nitromethane, 4-tert-butyl-1-(3-sulfopropyl)pyridinium hydroxide, dimethyl(n- octyl)(3-sulfopropyl)ammonium hydroxide, (2-hydroxyethyl)dimethyl(3-sulfopropyl)ammonium hydroxide, (methoxycarbonylsulfamoyl)triethylammonium hydroxide and combinations thereof.

[0041] In some embodiments, the heat-transfer fluid comprises at least two zwitterionic compounds, whereby the first zwitterionic compound is selected from trimethylglycine, carnitine, trimethylamine N- oxide dihydrate, tris(hydroxymethyl)-nitromethane, 4-tert-butyl-1-(3-sulfopropyl)pyridinium hydroxide, dimethyl(n-octyl)(3-sulfopropyl)ammonium hydroxide, (2-hydroxyethyl)dimethyl(3- sulfopropyl)ammonium hydroxide, (methoxycarbonylsulfamoyl)triethylammonium hydroxide and the second zwitterionic compound is selected from 2-aminoethanesulfonic acid or 4-tert-butyl-1-(3- sulfopropyl)pyridinium hydroxide. As is shown in the appended examples, optimized protection of various compounds such as corrosion inhibitors and dyes can thereby be achieved.

[0042] In preferred embodiments, the zwitterionic compound is selected from the group consisting of compounds according to formula (l-a), compounds according to formula (l-b), compounds according to formula (l-c), compounds according to formula (l-d), compounds according to formula (l-e), and combinations thereof, wherein the compounds according to formula (l-a), (l-b), (l-c), (l-d), (l-e) are as follows:

wherein

Y is selected from carboxylate (-COO ), sulfonate (-SO₃ ), phosphinate (-HPO2 ), and phosphonate (-PO₃ );

R¹, R¹’, R², R²’, R³, R³’, R⁴, R⁴’, R⁵, R⁵’, R⁶, R⁶’, R¹⁰, R¹¹, R¹² are individually selected from the group consisting of hydrogen, =0, -OH, -SH, -NH2, and optionally substituted monovalent hydrocarbon radicals having from 1 to 30 carbon atoms, preferably R¹, R¹’, R², R²’, R³, R³’, R⁴, R⁴’, R⁵, R⁵’, R⁶, R⁶’, R¹⁰, R¹¹, R¹² are individually selected from the group consisting of hydrogen, C1-C20 alkyl, C1-C20 haloalky I, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C2-C20 alkenyl, C3-C8 cycloalkyl, C4-C8 cycloalkenyl, Ce-C-io aryl, C1-C20 sulfide, =0, -OH, -NH2, -SH, -OR¹⁷, -NR¹⁷R¹⁷’, -SR¹⁷, -(OCH₂CH₂)_PCH₃, -(OCHCH₃CH₂)_qCH₃, -(OCH₃)_rCH₃, -R¹⁷OR¹⁷’, -R¹⁷(CO)R¹⁷’, - R¹⁷(COO)R¹⁷ , -R¹⁷(CONH)R¹⁷ , -R¹⁷(NHCO)R¹⁷’, -R¹⁷(NHCOO)R¹⁷’, -R¹⁷(NHCONH)R¹⁷’, - N=CR¹⁷R¹⁷ , -N=CR¹⁷ ”, -C(0) R¹⁷;

R⁷, R⁸, R⁹, R¹³, R¹⁴, R¹⁵, R¹⁶ are individually selected from the group consisting of hydrogen, and optionally substituted monovalent hydrocarbon radicals having from 1 to 30 carbon atoms, preferably R⁷, R⁸, R⁹, R¹³, R¹⁴, R¹⁵ are 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, Ce-C-io aryl, C1-C20 sulfide, -R¹⁷OR¹⁷’, -R¹⁷(CO)R¹⁷’, - R¹⁷(COO)R¹⁷ , -R¹⁷(CONH)R¹⁷ , -R¹⁷(NHCO)R¹⁷’, -R¹⁷(NHCOO)R¹⁷’, -R¹⁷(NHCONH)R¹⁷’, -C(0) R¹⁷; preferably at least one of R⁷, R⁸, and R⁹ is not hydrogen and at least one of R¹³, R¹⁴, R¹⁵ is not hydrogen;

R¹⁷ is 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 R¹⁷ is selected from the group consisting of C1-C20 alkyl; R¹⁷’ is selected from the group consisting of hydrogen, C1-C20 alkyl, C1-C20 haloalky I, C1-C20 aminoalkyl, C2-C20 alkenyl, C1-C20 alkyl alcohol, -(OCH2CH2)pCH3, -(OCHCH3CH2)qCH3, - (OCH3)rCH3, preferably R¹⁷ is selected from the group consisting of hydrogen, C1-C20 alkyl;

R¹⁷ is a bivalent C2-C8 alkyl radical such that -N=CR¹⁷ is a cycloalkyl; n, m, and 0 each are an integer individually selected from 0 to 20, preferably from 0 to 10; in each of formula (l-a) and (l-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 Z⁷ are as follows:

R¹⁸, R¹⁹, R²⁰ are individually selected from the group consisting of hydrogen, and optionally substituted monovalent hydrocarbon radicals having from 1 to 30 carbon atoms, preferably R¹⁸, R¹⁹, R²⁰ are individually selected from the group consisting of hydrogen, Ci-Cs alkyl, Ci-Cs haloalkyl, Ci-C₈ alkyl alcohol, Ci-C₈ aminoalkyl, Ci-C₈ sulfide, -R¹⁷OR¹⁷ , -R¹⁷(CO)R¹⁷ , - R¹⁷(COO)R¹⁷ , -R¹⁷(CONH)R¹⁷ , -R¹⁷(NHCO)R¹⁷’, -R¹⁷(NHCOO)R¹⁷’, -R¹⁷(NHCONH)R¹⁷’, -C(O) R²¹, R²², R²³, R²⁴, R²⁵ are individually selected from the group consisting of hydrogen, and optionally substituted monovalent hydrocarbon radicals having from 1 to 30 carbon atoms, preferably R⁷, R⁸, R⁹, R¹³, R¹⁴, R¹⁵ are 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, Ce-C-io aryl, C1-C20 sulfide, -R¹⁷OR¹⁷’, -R¹⁷(CO)R¹⁷’, - R¹⁷(COO)R¹⁷ , -R¹⁷(CONH)R¹⁷ , -R¹⁷(NHCO)R¹⁷’, -R¹⁷(NHCOO)R¹⁷’, -R¹⁷(NHCONH)R¹⁷’, -C(O) R¹⁷.

[0043] In preferred embodiments of the present invention, the zwitterionic compound is selected from the group consisting of compounds according to formula (l-a), compounds according to formula (l-b), compounds according to formula (l-c), compounds according to formula (l-d), compounds according to formula (l-e) wherein

Y is selected from carboxylate (-COO ), sulfonate (-SO3 ), phosphinate (-HPO2 ), and phosphonate (-PO3 ), preferably selected from carboxylate (-COO ), sulfonate (-SO3 ), and phosphonate (-PO3 );

R¹, R¹’, R², R²’, R³, R³’, R⁴, R⁴’, R⁵, R⁵’, R⁶, R⁶’, R¹⁰, R¹¹, R¹², are individually selected from the group consisting of hydrogen, -OH, -SH, -NH2, C1-C20 alkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C1-C20 sulfide, =0, -OR¹⁷, -NR¹⁷R¹⁷’, -SR¹⁷, -(OCH2CH₂)pCH3, -(OCHCH₃CH2)_qCH3, - (OCH₃)rCH3, -R¹⁷OR¹⁷ , -R¹⁷(CO)R¹⁷ , -R¹⁷(COO)R¹⁷’, -R¹⁷(CONH)R¹⁷’, -R¹⁷(NHCO)R¹⁷’, - R¹⁷(NHCOO)R¹⁷ , -R¹⁷(NHCONH)R¹⁷ , -N=CR¹⁷R¹⁷’, -N=CR¹⁷”, -C(O) R¹⁷, preferably R¹, R¹’, R², R²’, R³, R³’, R⁴, R⁴’, R⁵, R⁵’, R⁶, R⁶’, R¹⁰, R¹¹, R¹², are individually selected from the group consisting of hydrogen, -OH, -SH, -NH2, Ci-Cs alkyl, Ci-Cs haloalkyl, Ci-Cs alkyl alcohol, Ci-Cs aminoalkyl, Ci-Cssulfide, more preferably R¹, R², R³, R⁴, R⁵, R⁶, R¹⁰, R¹¹, R¹² are individually selected from the group consisting of hydrogen, -OH, -SH, -NH2, Ci-Cs alkyl and R¹', R²’, R³’, R⁴’, R⁵’, R⁶’ are hydrogen, most preferably R¹, R², R³, R⁴, R⁵, R⁶, R¹⁰, R¹¹, R¹² are individually selected from the group consisting of hydrogen, -OH, C1-C5 alkyl and R¹', R² , R³’, R⁴ , R⁵’, R⁶’ are hydrogen;

R⁷, R⁸, R⁹, R¹³, R¹⁴, R¹⁵, R¹⁶ are individually selected from the group consisting of hydrogen, Ci- 020 alkyl, C1-C20 haloalkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C1-C20 sulfide, -R¹⁷OR¹⁷’, - R¹⁷(CO)R¹⁷ , -R¹⁷(COO)R¹⁷ , -R¹⁷(CONH)R¹⁷ , -R¹⁷(NHCO)R¹⁷’, -R¹⁷(NHCOO)R¹⁷’, - R¹⁷(NHCONH)R¹⁷ , -C(O) R¹⁷, preferably R⁷, R⁸, R⁹, R¹³, R¹⁴, R¹⁵, R¹⁶ are individually selected from the group consisting of Ci-Cs alkyl, Ci-Cs alkyl alcohol, Ci-Cs aminoalkyl, Ci-Cs sulfide, - R¹⁷OR¹⁷ , -R¹⁷(CO)R¹⁷ , -R¹⁷(COO)R¹⁷ , -R¹⁷(CONH)R¹⁷’, -R¹⁷(NHCO)R¹⁷’, -R¹⁷(NHCOO)R¹⁷’, - R¹⁷(NHCONH)R¹⁷ , -C(O) R¹⁷; preferably R⁷, R⁸, R⁹, R¹³, R¹⁴, R¹⁵, R¹⁶ are individually selected from the group consisting of C1-C4 alkyl, -R¹⁷OR¹⁷ , -R¹⁷(CO)R¹⁷ , -R¹⁷(COO)R¹⁷ , - R¹⁷(CONH)R¹⁷ , -R¹⁷(NHCO)R¹⁷ , -R¹⁷(NHCOO)R¹⁷’, -R¹⁷(NHCONH)R¹⁷’, -C(O) R¹⁷; wherein at least one of R⁷, R⁸, and R⁹ is not hydrogen and at least one of R¹³, R¹⁴, R¹⁵ is not hydrogen, preferably wherein none of R⁷, R⁸, and R⁹ are hydrogen and none of R¹³, R¹⁴, R¹⁵ are hydrogen;

R¹⁷ is 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 R¹⁷ is selected from the group consisting of C1-C20 alkyl, more preferably R¹⁷ is selected from the group consisting of C1-C14 alkyl;

R¹⁷ 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)pCHs, -(OCHCHsCH2)qCH3, - (OCH₃)rCH3, preferably R¹⁷ is selected from the group consisting of C1-C20 alkyl, more preferably R¹⁷ is selected from the group consisting of C1-C14 alkyl;

R¹⁷ is a bivalent C2-C8 alkyl radical such that -N=CR¹⁷ is a cycloalkyl; n, m, and 0 each are an integer individually selected from 0 to 20, preferably from 0 to 10, more preferably from 0 to 2; in each of formula (l-a) and (l-b) at least one of n, m and 0 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, preferably from Z¹ wherein Z¹, Z², Z³, Z⁴, Z⁵, Z⁶, and Z⁷ are as follows:

R¹⁸, R¹⁹, R²⁰ are individually selected from the group consisting of hydrogen, C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C1-C20 sulfide, -R¹⁷OR¹⁷’, -R¹⁷(CO)R¹⁷’,

R¹⁷(COO)R¹⁷ , R¹⁷(CONH)R¹⁷ , R¹⁷(NHCO)R¹⁷’, R¹⁷(NHCOO)R¹⁷’, R¹⁷(NHCONH)R¹⁷’, -C(O) R¹⁷, preferably R¹⁸, R¹⁹, R²⁰ are individually selected from the group consisting of Ci-Cs alkyl, Ci-Cs alkyl alcohol, Ci-C₈ aminoalkyl, Ci-C₈ sulfide, -R¹⁷OR¹⁷’, -R¹⁷(CO)R¹⁷’, -R¹⁷(COO)R¹⁷’, -

R¹⁷(CONH)R¹⁷ , -R¹⁷(NHCO)R¹⁷ , -R¹⁷(NHCOO)R¹⁷’, -R¹⁷(NHCONH)R¹⁷’, -C(O) R¹⁷; preferably R¹⁸, R¹⁹, R²⁰ are individually selected from the group consisting of C1-C4 alkyl, -R¹⁷OR¹⁷ , - R¹⁷(CO)R¹⁷ , -R¹⁷(COO)R¹⁷ , -R¹⁷(CONH)R¹⁷ , -R¹⁷(NHCO)R¹⁷’, -R¹⁷(NHCOO)R¹⁷’, - R¹⁷(NHCONH)R¹⁷ , -C(O) R¹⁷; R²¹, R²², R²³, R²⁴, R²⁵ are individually selected from the group consisting of hydrogen, -OH, -SH, -NH2, C1-C20 alkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C1-C20 sulfide, =0, -OR¹⁷, -NR¹⁷R¹⁷’, - SR¹⁷, -(OCH₂CH₂)_PCH₃, -(OCHCH₃CH₂)_qCH₃, -(OCH₃)_rCH₃, -R¹⁷OR¹⁷’, -R¹⁷(CO)R¹⁷’, - R¹⁷(COO)R¹⁷ , -R¹⁷(CONH)R¹⁷ , -R¹⁷(NHCO)R¹⁷’, -R¹⁷(NHCOO)R¹⁷’, -R¹⁷(NHCONH)R¹⁷’, - N=CR¹⁷R¹⁷ , -N=CR¹⁷ ”, -C(O) R¹⁷, preferably R²¹, R²², R²³, R²⁴, R²⁵, are individually selected from the group consisting of hydrogen, -OH, -SH, -NH2, Ci-C₃ alkyl, Ci-C₃ haloalkyl, Ci-C₃ alkyl alcohol, Ci-C₃ aminoalkyl, Ci-C₃ sulfide, more preferably R²¹, R²², R²³, R²⁴, R²⁵ are individually selected from the group consisting of hydrogen, -OH, -SH, -NH2, Ci-C₃ alkyl, most preferably R²¹, R²², R²³, R²⁴, R²⁵ are individually selected from the group consisting of hydrogen, -OH, C1-C5 alkyl.

[0044] In preferred embodiments of the present invention, the zwitterionic compound is selected from the group consisting of compounds according to formula (l-a), compounds according to formula (l-b), compounds according to formula (l-c), compounds according to formula (l-d), compounds according to formula (l-e) wherein

Y is selected from carboxylate (-COO ), sulfonate (-SO₃ ), phosphinate (-HPO2 ), and phosphonate (-PO₃ ), preferably selected from carboxylate (-COO ), sulfonate (-SO₃ ), and phosphonate (-PO₃ );

R¹, R², R³, R⁴, R⁵, R⁶, R¹⁰, R¹¹, R¹², are individually selected from the group consisting of hydrogen, -OH, -SH, -NH2, C1-C20 alkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C1-C20 sulfide, =0, -OR¹⁷, -NR¹⁷R¹⁷’, -SR¹⁷, -(OCH₂CH₂)_PCH₃, -(OCHCH₃CH₂)qCH₃, -(OCH₃)_rCH₃, -R¹⁷OR¹⁷’, - R¹⁷(CO)R¹⁷ , -R¹⁷(COO)R¹⁷ , -R¹⁷(CONH)R¹⁷ , -R¹⁷(NHCO)R¹⁷’, -R¹⁷(NHCOO)R¹⁷’, - R¹⁷(NHCONH)R¹⁷ , -N=CR¹⁷R¹⁷’, -N=CR¹⁷”, -C(O) R¹⁷, preferably R¹, R², R³, R⁴, R⁵, R⁶, R¹⁰, R¹¹, R¹², are individually selected from the group consisting of hydrogen, -OH, -SH, -NH2, Ci-C₃ alkyl, Ci-C₃ haloalkyl, Ci-C₃ alkyl alcohol, Ci-C₃ aminoalkyl, Ci-C₃ sulfide, more preferably R¹, R², R³, R⁴, R⁵, R⁶, R¹⁰, R¹¹, R¹² are individually selected from the group consisting of hydrogen, -OH, -SH, -NH2, Ci-C₃ alkyl, most preferably R¹, R², R³, R⁴, R⁵, R⁶, R¹⁰, R¹¹, R¹² are individually selected from the group consisting of hydrogen, - OH, C1-C5 alkyl;

R¹', R²’, R³’, R⁴’, R⁵’, R⁶’ are hydrogen;

R⁷, R⁸, R⁹, R¹³, R¹⁴, R¹⁵, R¹⁶ are individually selected from the group consisting of hydrogen, Ci- 020 alkyl, C1-C20 haloalkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C1-C20 sulfide, -R¹⁷OR¹⁷’, - R¹⁷(CO)R¹⁷ , -R¹⁷(COO)R¹⁷ , -R¹⁷(CONH)R¹⁷ , -R¹⁷(NHCO)R¹⁷’, -R¹⁷(NHCOO)R¹⁷’, - R¹⁷(NHCONH)R¹⁷ , -C(O) R¹⁷, preferably R⁷, R⁸, R⁹, R¹³, R¹⁴, R¹⁵, R¹⁶ are individually selected from the group consisting of Ci-C₃ alkyl, Ci-C₃ alkyl alcohol, Ci-C₃ aminoalkyl, Ci-C₃ sulfide, - R¹⁷OR¹⁷ , -R¹⁷(CO)R¹⁷ , -R¹⁷(COO)R¹⁷ , -R¹⁷(CONH)R¹⁷’, -R¹⁷(NHCO)R¹⁷’, -R¹⁷(NHCOO)R¹⁷’, - R¹⁷(NHCONH)R¹⁷ , -C(O) R¹⁷; preferably R⁷, R⁸, R⁹, R¹³, R¹⁴, R¹⁵, R¹⁶ are individually selected from the group consisting of C1-C4 alkyl, -R¹⁷OR¹⁷ , -R¹⁷(CO)R¹⁷ , -R¹⁷(COO)R¹⁷ , - R¹⁷(CONH)R¹⁷ , -R¹⁷(NHCO)R¹⁷ , -R¹⁷(NHCOO)R¹⁷’, -R¹⁷(NHCONH)R¹⁷’, -C(O) R¹⁷;

R¹⁷ is 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 R¹⁷ is selected from the group consisting of C1-C20 alkyl, more preferably R¹⁷ is selected from the group consisting of C1-C14 alkyl;

R¹⁷ 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 R¹⁷ is selected from the group consisting of C1-C20 alkyl, more preferably R¹⁷ is selected from the group consisting of C1-C14 alkyl;

R¹⁸, R¹⁹, R²⁰ are individually selected from the group consisting of hydrogen, C1-C20 alkyl, C1-C20 haloalkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C1-C20 sulfide, -R¹⁷OR¹⁷’, -R¹⁷(CO)R¹⁷’, R¹⁷(COO)R¹⁷ , R¹⁷(CONH)R¹⁷ , R¹⁷(NHCO)R¹⁷’, R¹⁷(NHCOO)R¹⁷’, R¹⁷(NHCONH)R¹⁷’, -C(O) R¹⁷, preferably R¹⁸, R¹⁹, R²⁰ are individually selected from the group consisting of Ci-Cs alkyl, Ci-Cs alkyl alcohol, Ci-C₈ aminoalkyl, Ci-C₈ sulfide, -R¹⁷OR¹⁷’, -R¹⁷(CO)R¹⁷’, -R¹⁷(COO)R¹⁷’, - R¹⁷(CONH)R¹⁷ , -R¹⁷(NHCO)R¹⁷ , -R¹⁷(NHCOO)R¹⁷’, -R¹⁷(NHCONH)R¹⁷’, -C(O) R¹⁷; preferably R¹⁸, R¹⁹, R²⁰ are individually selected from the group consisting of C1-C4 alkyl, -R¹⁷OR¹⁷ , - R¹⁷(CO)R¹⁷ , -R¹⁷(COO)R¹⁷ , -R¹⁷(CONH)R¹⁷ , -R¹⁷(NHCO)R¹⁷’, -R¹⁷(NHCOO)R¹⁷’, - R¹⁷(NHCONH)R¹⁷ , -C(O) R¹⁷;

R²¹, R²², R²³, R²⁴, R²⁵ are individually selected from the group consisting of hydrogen, -OH, -SH, -NH2, C1-C20 alkyl, C1-C20 alkyl alcohol, C1-C20 aminoalkyl, C1-C20 sulfide, =0, -OR¹⁷, -NR¹⁷R¹⁷’, - SR¹⁷, -(OCH₂CH₂)_PCH₃, -(OCHCH₃CH₂)_qCH₃, -(OCH₃)_rCH₃, -R¹⁷OR¹⁷’, -R¹⁷(CO)R¹⁷’, - R¹⁷(COO)R¹⁷ , -R¹⁷(CONH)R¹⁷ , -R¹⁷(NHCO)R¹⁷’, -R¹⁷(NHCOO)R¹⁷’, -R¹⁷(NHCONH)R¹⁷’, - N=CR¹⁷R¹⁷ , -N=CR¹⁷ ", -C(0) R¹⁷, preferably R²¹, R²², R²³, R²⁴, R²⁵, are individually selected from the group consisting of hydrogen, -OH, -SH, -NH₂, Ci-C₃ alkyl, Ci-C₃ haloalkyl, Ci-C₃ alkyl alcohol, Ci-C₃ aminoalkyl, Ci-C₃ sulfide, more preferably R²¹, R²², R²³, R²⁴, R²⁵ are individually selected from the group consisting of hydrogen, -OH, -SH, -NH₂, Ci-C₃ alkyl, most preferably R²¹, R²², R²³, R²⁴, R²⁵ are individually selected from the group consisting of hydrogen, -OH, C1-C5 alkyl.

[0045] In preferred embodiments of the present invention, the zwitterionic compound is selected from the group consisting of compounds according to formula (l-a), compounds according to formula (l-b), compounds according to formula (l-c), compounds according to formula (l-d), compounds according to formula (l-e) wherein

Y is selected from carboxylate (-COO ), sulfonate (-SO₃ ), phosphinate (-HPO₂ ), and phosphonate (-PO₃ ), preferably selected from carboxylate (-COO ), sulfonate (-SO₃ ), and phosphonate (-PO₃ );

R¹, R², R³, R⁴, R⁵, R⁶, R¹⁰, R¹¹, R¹², are individually selected from the group consisting of hydrogen, -OH, -SH, -NH₂, C1-C10 alkyl, C1-C10 alkyl alcohol, C1-C10 aminoalkyl, C1-C10 sulfide, =0, -OR¹⁷, -NR¹⁷R¹⁷’, -SR¹⁷, , -(OCHCH₃CH₂)_qCH₃, -(OCH₃)_rCH₃, -R¹⁷OR¹⁷’, - R¹⁷(CO)R¹⁷ , -R¹⁷(COO)R¹⁷ , -R¹⁷(NHCO)R¹⁷’, -R¹⁷(NHCOO)R¹⁷’, - R¹⁷(NHCONH)R¹⁷ , -N=CR¹⁷ (O) R¹⁷, preferably R¹, R², R³, R⁴, R⁵ are individually selected from the group consisting of hydrogen, -OH

alkyl, Ci-C₃ haloalkyl, Ci-C₃ alkyl alcohol, Ci-C₃ aminoalkyl, Ci-C₃ sulfide, more preferably R¹, R², R³, R⁴, R⁵, R⁶, R¹⁰, R¹¹, R¹² are individually selected from the group consisting of hydrogen, -OH, -SH, -NH₂, Ci-C₃ alkyl, most preferably R¹, R², R³, R⁴, R⁵, R⁶, R¹⁰, R¹¹, R¹² are individually selected from the group consisting of hydrogen, - OH, C1-C5 alkyl;

R¹', R²’, R³’, R⁴’, R⁵’, R⁶’ are hydrogen;

R⁷, R⁸, R⁹, R¹³, R¹⁴, R¹⁵, R¹⁶ are individually selected from the group consisting of hydrogen, C1- C10 alkyl, C1-C10 haloalkyl, C1-C10 alkyl alcohol, C1-C10 aminoalkyl, Ci-Ciosulfide, -R¹⁷OR¹⁷’, - R¹⁷(CO)R¹⁷ , -R¹⁷(COO)R¹⁷ , -R¹⁷(CONH)R¹⁷ , -R¹⁷(NHCO)R¹⁷’, -R¹⁷(NHCOO)R¹⁷’, - R¹⁷(NHCONH)R¹⁷ , -C(O) R¹⁷, preferably R⁷, R⁸, R⁹, R¹³, R¹⁴, R¹⁵, R¹⁶ are individually selected from the group consisting of Ci-C₃ alkyl, Ci-C₃ alkyl alcohol, Ci-C₃ aminoalkyl, Ci-C₃ sulfide, - R¹⁷OR¹⁷ , -R¹⁷(CO)R¹⁷ , -R¹⁷(COO)R¹⁷ , -R¹⁷(CONH)R¹⁷’, -R¹⁷(NHCO)R¹⁷’, -R¹⁷(NHCOO)R¹⁷’, - R¹⁷(NHCONH)R¹⁷ , -C(O) R¹⁷; preferably R⁷, R⁸, R⁹, R¹³, R¹⁴, R¹⁵, R¹⁶ are individually selected from the group consisting of C1-C4 alkyl, -R¹⁷OR¹⁷ , -R¹⁷(CO)R¹⁷ , -R¹⁷(COO)R¹⁷ , - R¹⁷(CONH)R¹⁷ , -R¹⁷(NHCO)R¹⁷ , -R¹⁷(NHCOO)R¹⁷’, -R¹⁷(NHCONH)R¹⁷’, -C(O) R¹⁷;

R¹⁷ is selected from the group consisting of, C1-C10 alkyl, C1-C10 haloalkyl, C1-C10 aminoalkyl, C₂-Cio alkenyl, C1-C10 alkyl alcohol, -(OCH₂CH₂)_PCH₃, -(OCHCH₃CH₂)_qCH₃, -(OCH₃)_rCH₃, preferably R¹⁷ is selected from the group consisting of C1-C10 alkyl, more preferably R¹⁷ is selected from the group consisting of Ci-C₃ alkyl;

R¹⁷ is selected from the group consisting of hydrogen, C1-C10 alkyl, C1-C10 haloalkyl, C1-C10 aminoalkyl, C₂-Cio alkenyl, C1-C10 alkyl alcohol, -(OCH₂CH₂)_PCH₃, -(OCHCH₃CH₂)_qCH₃, - (OCH₃)_rCH₃, preferably R¹⁷ is selected from the group consisting of C1-C10 alkyl, more preferably R¹⁷ is selected from the group consisting of Ci-C₃ alkyl;

R¹⁷ is a bivalent C₂-C₃ alkyl radical such that -N=CR¹⁷ is a cycloalkyl; n, m, and 0 each are an integer individually selected from 0 to 20, preferably from 0 to 10, more preferably from 0 to 2; in each of formula (l-a) and (l-b) at least one of n, m and 0 is > 0; p, q and r each are an integer individually selected from 1 to 30, preferably from 2-20;

R¹⁸, R¹⁹, R²⁰ are individually selected from the group consisting of hydrogen, C1-C10 alkyl, C1-C10 haloalkyl, C1-C10 alkyl alcohol, C1-C10 aminoalkyl, Ci-Ciosulfide, -R¹⁷OR¹⁷’, -R¹⁷(CO)R¹⁷’, R¹⁷(COO)R¹⁷ , R¹⁷(CONH)R¹⁷ , R¹⁷(NHCO)R¹⁷’, R¹⁷(NHCOO)R¹⁷’, R¹⁷(NHCONH)R¹⁷’, -C(O) R¹⁷, preferably R¹⁸, R¹⁹, R²⁰ are individually selected from the group consisting of C1-C6 alkyl, C1-C6 alkyl alcohol, Ci-C₆ aminoalkyl, Ci-C₆ sulfide, -R¹⁷OR¹⁷’, -R¹⁷(CO)R¹⁷’, -R¹⁷(COO)R¹⁷’, - R¹⁷(CONH)R¹⁷ , -R¹⁷(NHCO)R¹⁷ , -R¹⁷(NHCOO)R¹⁷’, -R¹⁷(NHCONH)R¹⁷’, -C(O) R¹⁷; preferably R¹⁸, R¹⁹, R²⁰ are individually selected from the group consisting of C1-C4 alkyl, -R¹⁷OR¹⁷ , - R¹⁷(CO)R¹⁷ , -R¹⁷(COO)R¹⁷ , -R¹⁷(CONH)R¹⁷ , -R¹⁷(NHCO)R¹⁷’, -R¹⁷(NHCOO)R¹⁷’, - R¹⁷(NHCONH)R¹⁷ , -C(O) R¹⁷;

R²¹, R²², R²³, R²⁴, R²⁵ are individually selected from the group consisting of hydrogen, -OH, -SH, -NH2, C1-C10 alkyl, C1-C10 alkyl alcohol, C1-C10 aminoalkyl, Ci-Ciosulfide, =0, -OR¹⁷, -NR¹⁷R¹⁷’, -

preferably R²¹, R²², R²³, R²⁴, R²⁵, are 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, more preferably R²¹, R²², R²³, R²⁴, R²⁵ are individually selected from the group consisting of hydrogen, -OH, -SH, -NH2, Ci-Ca alkyl, most preferably R²¹, R²², R²³, R²⁴, R²⁵ are individually selected from the group consisting of hydrogen, -OH, C1-C5 alkyl.

[0046] The preferred embodiments for R¹-R²⁵ and for n, m, 0 set out herein are explicitly envisaged in combination.

[0047] In highly preferred embodiments the zwitterionic compound is selected from the group consisting of compounds according to formula (l-a), compounds according to formula (l-b), compounds according to formula (l-c), compounds according to formula (l-d), compounds according to formula (I- e), which have been described herein before, with the proviso 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, preferably less than 175 g/mol, preferably less than 150 g/mol.

[0048] 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.

[0049] In preferred embodiments of the invention, the concentration of the zwitterionic compound in the heat-transfer fluid of step (a) 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 the range of 1-3 wt.%.

The base fluid

[0050] In accordance with the invention the base fluid comprised in the heat-transfer fluid provided in step (a) of the method 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, tetra hydrofurfury I, 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.

[0051] 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, preferably between 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.

[0052] 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.

[0053] As used herein, “monoethylene glycol” should be interpreted to mean “ethane-1 ,2-diol”, and is interchangeably referred to as “MEG”.

[0054] As used herein, “monopropylene glycol” should be interpreted to mean “propane-1 ,2-diol”, and is interchangeably referred to as “MPG”.

[0055] 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.

[0056] 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).

[0057] In some embodiments of the invention, the base fluid consists only of water.

[0058] 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.%.

[0059] 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.

[0060] 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.

[0061] 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.%, most preferably more than 95 wt.% 1 ,3-propane diol.

[0062] 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.

[0063] In preferred embodiments of the invention, the heat-transfer fluid provided in step (a) 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.

[0064] 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 composition), such as less than 99.8 wt.%, less than 99.5 wt.% or less than 99 wt.%, less than 98 wt.% of base fluid.

The Ion-Exchange resin and pretreatment thereof

[0065] 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 cationexchange 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.

[0066] 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 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).

[0067] 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 tri methylammonium.

[0068] 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 lonac™ 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 NG Mix mixed bed resin, Dowex™ MR-450 UPW mixed bed resin, Sybron lonac™ NM-60 mixed bed resin, Amberlite™ MB-150 or AmberLite™ IRN170 H/OH mixed bed resin, while in one exemplary embodiment, a suitable commercially available ion exchange resin will be AmberLite™ IRN170 H/OH. References to tradenames herein should be construed as referring to the product marketed under that tradename on 01 October 2023.

[0069] The present inventors have found that resin pretreatments (e.g. by soaking the resin) are not necessary and can actually be avoided by 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 pretreated by contacting the resin with a composition comprising the zwitterionic compound before the resin is contacted with the heat-transfer fluid. In 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 ionexchange resin of the cooling system by contacting the resin with a solution comprising the zwitterionic compound, as is described herein.

[0070] In some embodiments of the invention, the method comprises a further optional step (e) wherein the ion-exchange resin is regenerated. As is known to the person skilled in the art, regeneration is a process that takes ion exchange resins that are saturated and removes ions that have been picked up during the in-service cycle such that the resin can continue to be used. Suitable regeneration steps include backwashing the resins and/or rinsing with a high concentration of regenerant chemical to restore the resin’s capacity.

[0071] 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.

[0072] 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 ionexchange 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 ionexchange 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. As is shown in the appended examples, such combination of zwitterionic compounds may provide optimal protection of various heat-transfer fluid components such as corrosion inhibitors and dyes.

Dye

[0073] 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.

[0074] In a preferred embodiment of the invention, the heat-transfer fluid provided in step (a) comprise 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). The dye is preferably non-polymeric. 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, hydroxy ketone, 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 non-ionic.

[0075] 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 1 14, Direct Black 38, Acid Black 1 , Direct Red 28, Direct Blue 71 , Rhodamine B, Rhodamine 6G or combinations thereof.

[0076] 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 heattransfer 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 .

[0077] 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.

[0078] 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 gram zwitterionic 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%.

[0079] 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.

Corrosion inhibitor

[0080] 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.

[0081] In a preferred embodiment ofthe invention, the heat-transfer fluid provided in step (a) 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 Ci to C4 alkyl group), organic silicates (such as Si(R¹)_n(OR²)4-n wherein R¹ and R² each independently are a Ci to Ce alkyl or phenyl, and wherein n is 0, 1 , 2 or 3), tri methylsilyl 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.

[0082] The corrosion inhibitor is preferably selected from triazoles, thiazoles, triazines, diazoles and combinations thereof.

[0083] In preferred embodiments of the invention, the corrosion inhibitor is selected from 1 ,2,3- triazoles, 1 ,2,4-triazoles, and combinations thereof.

[0084] In preferred embodiments ofthe 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, 1 H-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-1 H- benzotriazol-1-yl)methyl]imino]bisethanol, N,N-bis(2-ethylhexyl)-methyl-1 H-Benzotriazole-1- methanamine, and combinations thereof, more preferably selected from benzotriazole, tolyltriazole, 2- mercaptobenzothiazole, and combinations thereof.

[0085] 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.

[0086] 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- py ridy l)-1 ,3,5-triazine and combinations thereof.

[0087] In some embodiments of the invention, the corrosion inhibitor is a diazole selected from pyrazole, 4-nitropyrazole, 4-sulfopyrazole.

[0088] In preferred embodiments of the invention, the first corrosion inhibitor is selected from c

wherein R¹ represents 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 R² is selected from hydrogen, a mercapto group (-SH), or a C1-C11 alkyl, preferably methyl or ethyl; preferably wherein R¹ represents 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 R² is selected from hydrogen, a mercapto group (-SH), or a C1-C6 alkyl, preferably methyl or ethyl.

[0089] 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 , more preferably at least 20:1 . 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 40:1 , preferably less than 35:1 , more preferably less than 30:1.

[0090] 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 corrosion inhibitor 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.

[0091] 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%.

[0092] 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:

-stir for 3 hours at 20 °C; and

The cooling system

[0093] The cooling system of step (b) typically comprises further components such as a heatexchanger 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 system together define a flow path for the heat-transfer fluid.

[0094] 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 cooling system of step (b) in a way such that it can contact the heat-transfer fluid of step (a) during use.

[0095] In some embodiments of the invention, the cooling system of step (b) comprises a main circuit and a by-pass or parallel circuit in which the heat-transfer fluid is contacted with and passed through the ion-exchange resin. In preferred embodiments, the flow rate of the heat-transfer fluid through the by-pass or parallel circuit during operation of the cooling system is 1-50% of the flow rate of the heattransfer fluid through the main circuit preferably 1-30%. In some embodiments, the by-pass or parallel circuit is always open such that heat-transfer fluid is continuously passed through the ion-exchange resin during operation. In other embodiments, the by-pass or parallel circuit is closed and re-opened periodically such that the heat-transfer fluid passes through the ion-exchange resin periodically.

[0096] 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.

[0097] 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 heattransfer fluid.

[0098] 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.

[0099] In highly preferred embodiments of the invention, the electrical conductivity of the heat-transfer fluid is maintained at less than less than 100 pS/cm, preferably less than 50 pS/cm, more preferably less than 25 pS/cm, more preferably less than 10 pS/cm, most preferably less than 5 pS/cm throughout the method.

The electrical system

[00100] In preferred embodiments of the invention, the method further comprises a step of generating heat in an electrical system.

[00101] 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.

Further A dditives

[00102] As will be understood by the skilled person, based on teachings presented herein, the heattransfer fluids or compositions 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 or composition 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.

[00103] In certain embodiments of the invention the heat-transfer fluid or compositions 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 or composition), preferably 0.01 -5 wt.%, more preferably 0.02-3 wt.%.

[00104] In preferred embodiments the heat-transfer fluid or composition 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 Ci to C4 alkyl group), mineral oils, monocarboxylic acids, dicarboxylic acids and tricarboxylic acids. In preferred embodiments the heat-transfer fluid or compositions 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 or composition), preferably 0.01-5 wt.%, more preferably 0.02-3 wt.%.

[00105] In preferred embodiments, the heat-transfer fluid or composition further comprises one or more additives selected 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 or compositions 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 or composition), preferably 0.01-5 wt.%.

[00106] In embodiments of the invention, the heat-transfer fluid or composition 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 or composition as defined herein is provided, wherein the heat-transfer fluid or composition further comprises the defoaming agent in an amount of more than 0.001 wt.% (by total weight of the heattransfer fluid or composition), 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.%.

[00107] ln embodiments of the invention, the heat-transfer fluid or composition 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 or composition as defined herein is provided, wherein the heat-transfer fluid or composition further comprises the antioxidant in an amount more than 0.001 wt.% (by total weight of the heat-transfer fluid or composition), 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.%.

[00108] In certain embodiments of the invention, the heat-transfer fluid or composition 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 or composition provided herein comprises more than 0.0001 wt.% (by total weight of the heat-transfer fluid or composition) 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.%.

[00109] ln embodiments of the invention, the heat-transfer fluid or composition 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.

[00110] In embodiments of the invention, the heat-transfer fluid or composition comprises said anionic surfactant in an amount of more than 0.001 wt.% (by total weight of the heat-transfer fluid or composition), 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.%.

[00111] ln embodiments of the invention, the heat-transfer fluid or composition as defined herein is provided, wherein the heat-transfer fluid or composition further comprises a corrosion inhibitor selected from the group consisting of aromatic 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.

[00112] ln embodiments of the invention, the heat-transfer fluid or composition 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.

[00113] ln embodiments of the invention, the heat-transfer fluid or composition further comprises an aliphatic dicarboxylate, preferably an aliphatic dicarboxylate selected from the group consisting of Ce- 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.

[00114] ln embodiments of the invention, the heat-transfer fluid or composition 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.

[00115] ln embodiments of the invention, the heat-transfer fluid or composition 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.

[00116] ln embodiments of the invention, the heat-transfer fluid or composition 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).

[00117] ln embodiments of the invention, the heat-transfer fluid or composition 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).

[00118] ln embodiments of the invention, the heat-transfer fluid or composition 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 R¹ and R² each independently are a Ci to Ce 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).

[00119] ln embodiments of the invention, the heat-transfer fluid or composition further comprises a nitrate, preferably an inorganic nitrate in an amount of more than 1 ppm (by total weight of the composition) 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).

[00120] ln embodiments of the invention, the heat-transfer fluid or composition further comprises a nitrite, preferably an inorganic nitrite in an amount of more than 1 ppm (by total weight of the composition) 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).

[00121] ln embodiments of the invention, the heat-transfer fluid or composition further comprises a phosphonate, preferably an inorganic phosphonate in an amount of more than 10 ppm (by total weight of the composition) 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).

[00122]The present inventors have found that the inclusion of certain further additives in the heat- transfer fluids of step (a) 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.

[00123] In preferred embodiments of the invention the heat-transfer fluid or composition further comprises a non-ionic polymer 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, 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 A/-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 A/-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 A/-vinylpyrrolidone and vinyl acetate, wherein the percentage of A/-vinylpyrrolidone monomers is at least 25%, based on the total number of monomers in the polyvinylpyrrolidone copolymer, hydrolysed forms of copolymers of A/-vinylpyrrolidone and vinyl acetate, wherein the percentage of A/-vinylpyrrolidone monomers is at least 10%, based on the total number of monomers in the polyvinylpyrrolidone copolymer and copolymers of A/-vinylpyrrolidone and A/-vinylcaprolactam, wherein the percentage of A/-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 skilled person, 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: M_w = (2 NiMi ) / (X NiMi) . 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 composition), 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.%.

[00124] In preferred embodiments of the invention the heat-transfer fluid or composition 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 composition), 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.%.

[00125] In embodiments of the invention the heat-transfer fluid or composition 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-buty I 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 ofthe invention, the heattransfer fluid comprises as a further additive the aromatic alcohol in an amount of more than 0.001 wt.% (by total weight of the composition), 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.%.

[00126] In embodiments ofthe invention the heat-transfer fluid or composition further comprises a dioxoaromatic 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. In embodiments 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 composition), 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.%.

[00127] ln embodiments of the invention, the heat-transfer fluid or composition 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.

[00128] In embodiments of the invention the heat-transfer fluid or composition further comprises a nonionic 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.

[00129] In embodiments of the invention, the heat-transfer fluid or composition comprises as a further additive the non-ionic surfactant in an amount of more than 0.001 wt.% (by total weight of the composition), 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.%.

[00130] ln some embodiments of the invention, the heat-transfer fluid or composition 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 Liquiti nt® 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.

Cooling system of the invention

[00131] In another aspect of the invention, there is provided a cooling system comprising a heat-transfer fluid comprising a base fluid and a zwitterionic compound, wherein the cooling system comprises an ion-exchange resin in contact with the heat-transfer fluid. The electrical conductivity at 25 °C of the heat-transfer fluid is preferably less than 100 pS/cm, preferably less than 50 pS/cm, more preferably less than 25 pS/cm, more preferably less than 10 pS/cm, most preferably less than 5 pS/cm.

[00132] The cooling system, heat-transfer fluid and ion-exchange resin are preferably as has been described herein in the context of the method 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 method apply mutatis mutandis to the cooling system of the invention.

Heat-transfer fluid of the invention

[00133] In another aspect of the invention, there is provided a heat-transfer fluid comprising a base fluid and a zwitterionic compound; 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 pS/cm, preferably less than 50 pS/cm, more preferably less than 25 pS/cm, more preferably less than 10 pS/cm, most preferably less than 5 pS/cm; and

-wherein the heat-transfer fluid further comprises a corrosion inhibitor, preferably selected from triazoles, thiazoles, triazines, diazoles and combinations thereof as has been described herein before, 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 corrosion inhibitor in the heattransfer fluid is at least 30:1 , preferably at least 50:1 .

[00134] The heat-transfer fluid are preferably as has been described herein in the context of the method of the invention. Thus, the embodiments characterising the heat-transfer fluid (in particular the conductivity, the compounds comprised therein, and the concentrations thereof) described herein in the context of the method apply mutatis mutandis to the composition of the invention, unless defined otherwise.

Composition of the invention

[00135] In another aspect of the invention, there is provided a composition comprising: a heat-transfer fluid comprising a base fluid and a zwitterionic compound; and an 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 is less than 100 pS/cm, preferably less than 50 pS/cm, more preferably less than 25 pS/cm, more preferably less than 10 pS/cm, most preferably less than 5 pS/cm; and

-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, tetra hydrofurfury I, 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; and/or -wherein the zwitterionic compound is not N,N,N-trimethylg lycine, preferably the heat-transfer fluid does not comprise N,N,N-trimethylglycine; and/or

-wherein the heat-transfer fluid further comprises a corrosion inhibitor, preferably selected from triazoles, thiazoles, triazines, diazoles and combinations thereof as has been described herein before, 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 corrosion inhibitor in the heattransfer fluid is at least 30:1 , preferably at least 50:1 ; and/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-transfer fluid.

[00136]The composition may be provided in any form wherein the ion-exchange resin contacts the heat-transfer fluid. For example, the composition is created when a heat-transfer fluid as is described herein is contacted with an ion-exchange resin upon filling of a cooling system with heat-transfer fluid.

[00137]The heat-transfer fluid and ion-exchange resin are preferably as has been described herein in the context of the method of the invention. Thus, the embodiments characterising 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 method apply mutatis mutandis to the composition of the invention, unless defined otherwise.

[00138] ln another aspect of the invention, there is provided a method to prepare a composition as defined herein, comprising the steps of:

(i) providing a heat-transfer fluid comprising a base fluid and a zwitterionic compound; 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 pS/cm, preferably less than 50 pS/cm, more preferably less than 25 pS/cm, more preferably less than 10 pS/cm, most preferably less than 5 pS/cm; and wherein

-wherein the heat-transfer fluid further comprises a corrosion inhibitor, preferably selected from triazoles, thiazoles, triazines, diazoles and combinations thereof as has been described herein before, 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-transfer fluid;

(ii) providing an ion-exchange resin as described herein;

(iii) contacting the heat-transfer fluid of step (i) with the ion-exchange resin of step (ii).

Preferably, step (iii) takes place by filling a cooling system comprising the ion-exchange resin with the heat-transfer fluid. Step (ii) may comprise a further step of pre-treating the resin by contacting the resin with a composition comprising the zwitterionic compound before the resin is contacted with the heattransfer fluid, as has been described herein earlier.

Uses of the invention

[00139] 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 ionexchange 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 pS/cm, preferably less than 50 pS/cm, more preferably less than 25 pS/cm, more preferably less than 10 pS/cm, most preferably less than 5 pS/cm.

[00140] 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 ionexchange 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 pS/cm, preferably less than 50 pS/cm, more preferably less than 25 pS/cm, more preferably less than 10 pS/cm, most preferably less than 5 pS/cm wherein

[00141] -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-transfer fluid. The cooling system, heat- transfer fluid and ion-exchange resin are preferably as has been described herein in the context of the method 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 method apply mutatis mutandis to the uses of the invention.

[00142] 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.

[00143] In another aspect of the invention, there is provided the use of a zwitterionic compound

[00144] The cooling system, heat-transfer fluid and ion-exchange resin are preferably as has been described herein in the context of the method 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 method apply mutatis mutandis to the uses of the invention.

[00145] 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

[00146] Electrical conductivity was 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.

[00147]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.

[00148] 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).

[00149]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.

Examples 1 to 18

[00150] 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 DuPont Amberlite™ MB20 HOH (2 v/v%) for 3 hours.

Table 1

[00151]Table 2 illustrates the heat-transfer fluid properties prior to and after contacting with the ionexchange 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 ‘A Rhodamine B’ denotes the percentage change in dye concentration, the ‘A TTZ’ denotes the percentage change in corrosion inhibitor concentration.

Table 2

[00152] Heat-transfer fluids were prepared as is shown in table 3. Chromatint Red X4075 or Dye acid green 25 were added as dyes and benzyltriazole or tolyltriazole were added as corrosion inhibitors to a water - monoethylene glycol base fluid. Thereafter, the heat transfer fluid was contacted with ionexchange resin Dowex MR3-MB20 HOH (2 v/v%) for 3 hours.

Table 3

[00153]Table 4 illustrates the heat-transfer fluid properties prior to and after contacting with an ionexchange 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 ‘A Rhodamine B’ or ‘A Dye acid green 25’ denotes the percentage change in dye concentration, the ‘A benzotriazole’ or ‘A tolyltriazole’ denotes the percentage change in corrosion inhibitor concentration, and the ‘A Glycolate’ denotes the percentage change in glycolate concentration.

Table 4

[00154] 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.

Examples 19 to 21

[00155] Heat-transfer fluids were prepared as is shown in table 5. Rhodamine B was added as a dye and tolyltriazole was added as a corrosion inhibitor to a water - monoethylene glycol base fluid.

Povidone K17 was added as a non-ionic polymer.

Table 5

[00156]Table 6 illustrates the heat-transfer fluid properties prior to contacting with the ion-exchange resin. The ‘eCond 25 °C prior to resin’ and ‘pH’ denotes the electrical conductivity and pH of the heattransfer fluid prior to contact with the ion-exchange resin. The ‘Abs 535 nm’ denotes the UV-Vis absorbance of the dye of the heat-transfer fluid at 535 nm wavelength.

Table 6

[00157]The changes in coolant properties upon contacting with an ion-exchange resin was measured by circulating 500 mL of the heat-transfer fluids through a 50 mL glass column packed with 10 g of Amberlite™ MB20 HOH at a rate of 5 mL/min. 1 mL samples were removed according to the time periods indicated in Table 7 and the changes in dye and corrosion inhibitor were monitored.

Table 7

[00158] After 16 hours, the pump was stopped and 10 mL of a solution comprising 1 wt.% glycolic acid and 0.5 wt.% formic acid in UPW was added to the heat-transfer fluid. Sampling was resumed, and the changes in the heat-transfer fluid are shown in Table 8.

[00159] 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 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 pS/cm, preferably less than 50 pS/cm, more preferably less than 25 pS/cm, more preferably less than 10 pS/cm, most preferably less than 5 pS/cm.

2. The method according to claim 1 , wherein the ion-exchange resin of the cooling system is pre-treated by contacting the resin with a composition comprising the zwitterionic compound before the resin is contacted with the heat-transfer fluid.

3. The method according to any one of the preceding claims wherein the heat-transfer fluid has a pH within the range of 3-10.

4. The method according to any one of the preceding claims wherein the zwitterionic compound 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.

5. The method according to any one of the preceding claims, wherein 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 carboxylate, sulfonate, phosphinate or phosphonate functional group, or selected from compounds comprising a nitro, nitroso or amine oxide functional group.

6. The method according to any one of the preceding claims, wherein the concentration of the zwitterionic compound is at least 0.05 wt.%, preferably 0.1 wt.%, more preferably at least 0.5 wt.%, by total weight of the heat-transfer fluid.

7. The method according to any one of the preceding claims 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, tetra hydrofurfury I, 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; and wherein the weight ratio of the total amount of the zwitterionic compound to the alcohol is between 100:1 to 2:1 , preferably between 80:1 to 10:1 , preferably between 50:1 to 20:1 and most preferably between 40:1 to 30:1 .

8. The method according to any one of the preceding claims, wherein the heat-transfer fluid comprises a corrosion inhibitor and/or a dye, preferably wherein the heat-transfer fluid comprises a corrosion inhibitor and optionally a dye.

9. The method according to claim 8, wherein the corrosion inhibitor is selected from the group consisting of triazoles, thiazoles, triazines, diazoles and combinations thereof.

10. The method according to claim 8 or 9, wherein the dye is selected from compounds comprising a chromophore selected from the group consisting of xanthene, anthraquinone, triphenylmethane, diphenylmethane, azo-containing compounds, disazo-containing compounds, trisazo-containing compounds, diazo containing compounds, and combinations thereof.

11. The method according to any one of claims 8 to 10, wherein the binding affinity of the zwitterionic compound to the ion-exchange resin is greater than the binding affinity of the corrosion inhibitor to the ion-exchange resin and/or wherein the binding affinity of the zwitterionic compound to the ion-exchange resin is greater than the binding affinity of the dye to the ion-exchange resin.

12. A heat-transfer fluid comprising a base fluid and a zwitterionic compound; 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 pS/cm, preferably less than 50 pS/cm, more preferably less than 25 pS/cm, more preferably less than 10 pS/cm, most preferably less than 5 pS/cm; and

-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 .

13. A composition comprising: a heat-transfer fluid comprising a base fluid and a zwitterionic compound; and an 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 is less than 100 pS/cm, preferably less than 50 pS/cm, more preferably less than 25 pS/cm, more preferably less than 10 pS/cm, most preferably less than 5 pS/cm; and wherein

14. The use of a heat-transfer fluid comprising a base fluid and a zwitterionic compound as a heattransfer 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 heattransfer fluid is less than 100 pS/cm, preferably less than 50 pS/cm, more preferably less than 25 pS/cm, more preferably less than 10 pS/cm, most preferably less than 5 pS/cm.

15. The use of a zwitterionic compound:

• for prolonging the coloration or reducing the fading of colour of a heat-transfer fluid comprising a dye when contacting an ion-exchange resin, preferably when used as a heattransfer fluid in a cooling system comprising an ion-exchange resin in contact with the heattransfer 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.