The present invention relates to coolants for cooling systems in electric vehicles having fuel cells and/or batteries, preferably in motor vehicles, particularly preferably in passenger cars and commercial vehicles (known as light and heavy duty vehicles), based on alkylene glycols or derivatives thereof, which contain additional corrosion inhibitors in addition to specific azole derivatives for improved corrosion protection.

Fuel cells and/or batteries for mobile use, in particular in motor vehicles, have to be able to be operated even at low exterior temperatures of down to about −40° C. A freezing-protected coolant circuit is therefore indispensable.

The use of conventional cooler protection compositions used in internal combustion engines would not be possible in the case of fuel cells and/or batteries without complete electric insulation of the cooling channels, since these compositions have an undesirably high electrical conductivity because of the salts and ionizable compounds comprised therein as corrosion inhibitors, which would adversely affect the function of the fuel cell or battery.

DE-A 198 02 490 (1) describes fuel cells having a freezing-protected cooling circuit in which a paraffinic isomer mixture having a pour point of less than −40° C. is used as coolant. However, the combustibility of such a coolant is disadvantageous.

EP-A 1 009 050 (2) discloses a fuel cell system for automobiles, in which air is used as cooling medium. However, this has the disadvantage that air is, as is known, a poorer heat conductor than a liquid cooling medium.

WO 00/17951 (3) describes a cooling system for fuel cells, in which a pure monoethylene glycol/water mixture in a ratio of 1:1 without additives is used as coolant. Since no corrosion protection at all would be present in respect of the materials present in the cooling system because of a lack of corrosion inhibitors, the cooling circuit comprises an ion-exchange unit in order to maintain the purity of the coolant and ensure a low specific conductivity over a prolonged period of time, as a result of which short circuits and corrosion are prevented. As suitable ion exchangers, mention is made of anionic resins such as those of the strongly alkaline hydroxyl type and cationic resins such as those based on sulfonic acid groups and also other filtration units such as activated carbon filters.

The structure and the function of a fuel cell for automobiles, in particular a fuel cell having an electron-conducting electrolyte membrane (“PEM fuel cell”, “polymer electrolyte membrane fuel cell”) is described by way of example in (3), with aluminum being preferred as preferred metal component in the cooling circuit (cooler).

WO 02/101848 A2 describes antifreeze compositions for cooling systems in fuel cell drives and concentrates thereof which comprise particular azole derivatives.

The antifreeze compositions display good corrosion protection on aluminum samples, but no longer satisfy modern requirements in respect of corrosion of iron and nonferrous metals.

DE-A 100 63 951 (4) describes coolants for cooling systems in fuel cell drives, which comprise ortho-silicic esters as corrosion inhibitors.

US 2012/0064426 A1 discloses coolants for fuel cells which comprise an ion exchanger, which coolants comprise ethylene glycol or propylene glycol as antifreeze component and inhibitors, for example, inter alia, azoles, against aluminum corrosion and also polyoxyethylene alkyl ethers or polyoxyethylene fatty acid esters as surface-active agents.

Apart from aluminum corrosion, no further corrosion is examined and the polyoxyethylene alkyl ethers or polyoxyethylene fatty acid esters used are employed exclusively as surface-active agents.

A main problem in cooling systems in fuel cell drives is, compared to conventional coolants, maintenance of a low electrical conductivity of the coolant in order to ensure safe and malfunction-free function of the fuel cell and batteries connected thereto and to prevent short circuits and corrosion in the long term.

U.S. Pat. No. 3,931,029 discloses antifreeze compositions which comprise ethylene glycol or diethylene glycol as antifreeze component and alkoxylated higher fatty acids or fatty amines as antifoams and also inorganic compounds as further inhibitors.

These inorganic compounds in these compositions are preferably used as alkali metal salts or ammonium salts, so that the compositions comprise a significant proportion of ionic constituents, so that these compositions are not suitable for use in fuel cells because of their inherent conductivity.

WO 2014 029654 A1 discloses corrosion protection formulations which can contain further additives in addition to glycols and polyalkylene glycols as antifreeze components and alkylamine ethoxylates as surfactant component. When choosing such additives, no attention is paid to the conductivity and anionic and cationic surfactants are also disclosed, with borax for adjusting the pH and carboxylic acids in the form of their salts.

These compositions, too, thus comprise a significant proportion of ionic constituents and are not suitable for use in fuel cells because of their inherent conductivity.

The same applies to U.S. Pat. No. 4,704,220, in which compositions which comprise at least one emulsifier and at least one organic hydrophobicizing agent and can be used as concentrates after dilution with water as coolant are described. The organic hydrophobicizing agent bears salt-forming groups and the emulsifier can also be anionic or cationic compounds. Inorganic compounds are added in a targeted manner to the water with which the compositions are admixed in the examples.

These compositions, too, thus comprise a significant proportion of ionic constituents and are not suitable for use in fuel cells because of their inherent conductivity.

It was an object of the present invention to make the antifreeze compositions known from WO 02/101848 A2 more corrosion-stable relative to metals other than aluminum.

It has now been found that the duration of a low electrical conductivity in a cooling system based on alkylene glycol/water can be significantly lengthened by addition of small amounts of azole derivatives even and particularly when it comprises, as per (3), an integrated ion exchanger. The good protection of aluminum and aluminum-comprising alloys against corrosion described in WO 02/101848 A2 is also offered for other metals, in particular iron materials, iron-comprising alloys and nonferrous metals, among these copper and brass in particular, by the use according to the invention of the compounds (V), (VI) and/or (VII). This covers in practice the advantage that the time intervals between two coolant changes for fuel cells can be extended further, which is of particular interest in the automobile sector.

Accordingly, we have found antifreeze concentrates for cooling systems in fuel cells and/or batteries, from which ready-to-use aqueous coolant compositions having a conductivity of not more than 50 μS/cm result, based on alkylene glycols or derivatives thereof which comprise one or more five-membered heterocyclic compounds (azole derivatives) having 2 or 3 heteroatoms from the group consisting of nitrogen and sulfur and comprise no or at most one sulfur atom and can bear an aromatic or saturated six-membered fused-on ring, and additionally comprise at least one of the compounds (V), (VI) and/or (VII). Preference is here given to antifreeze concentrates which comprise a total of from 0.05 to 5% by weight, in particular from 0.075 to 2.5% by weight, especially from 0.1 to 1% by weight, of the azole derivatives mentioned. Preference is given here to antifreeze compositions which comprise a total of from 0.05 to 5% by weight, in particular from 0.1 to 1% by weight, especially from 0.2 to 0.5% by weight, of at least one of the compounds (V), (VI) and/or (VII).

These five-membered heterocyclic compounds (azole derivatives) usually contain two N atoms and no S atom, 3 N atoms and no S atom or one N atom and one S atom as heteroatoms.

Preferred groups of the specified azole derivatives are annellated imidazoles and annellated 1,2,3-triazoles of the general formula


where
the variable R is hydrogen or a C1-C10-alkyl radical, in particular methyl or ethyl, and the variable X is a nitrogen atom or the C—H group.

Typical and preferred examples of azole derivatives of the general formula (I) are benzimidazole (X=C—H, R=H), benzotriazoles (X=N, R=H) and tolutriazole (tolyltriazole) (X=N, R=CH3). A typical example of an azole derivative of the general formula (II) is hydrogenated 1,2,3-tolutriazole (tolyltriazole) (X=N, R=CH3).

A further preferred group of the specified azole derivatives is benzothiazoles of the general formula (III)


where
the variable R is as defined above and
the variable R′ is hydrogen, a C1-C10-alkyl radical, in particular methyl or ethyl, or in particular a mercapto group (—SH). A typical example of an azole derivative of the general formula (III) is 2-mercaptobenzothiazole.

Further suitable azole derivatives are non-annellated azole derivatives of the general formula (IV)


where
the variables X and Y together are two nitrogen atoms or
one nitrogen atom and a C—H group,
for example 1H-1,2,4-triazole (X=Y=N) or preferably imidazole (X=N, Y=C—H).

For the purposes of the present invention, benzimidazole, benzotriazole, tolutriazole, hydrogenated tolutriazole or mixtures thereof, in particular benzotriazole or tolutriazole, are very particularly preferred as azole derivatives.

The azole derivatives mentioned are commercially available or can be prepared by conventional methods. Hydrogenated benzotriazoles such as hydrogenated tolutriazole are likewise obtainable as described in DE-A 1 948 794 (5) and are also commercially available.

Apart from the azole derivatives mentioned, the antifreeze concentrates of the invention preferably additionally comprise ortho-silicic esters as are described in (4). Typical examples of such ortho-silicic esters are tetraalkoxysilanes, preferably tetramethoxysilane and tetraethoxysilane, and alkoxyalkylsilanes, preferably triethoxymethylsilane, diethoxydimethylsilane, ethoxytrimethylsilane, trimethoxymethylsilane, dimethoxydimethylsilane and methoxytrimethylsilane. Preference is given to tetraalkoxysilanes, particularly preferably tetramethoxysilane and tetraethoxysilane, with very particular preference being given to tetraethoxysilane. Preference is given here to antifreeze concentrates, in particular those having a total content of from 0.05 to 5% by weight of the azole derivative mentioned, from which ready-to-use aqueous coolant compositions having a silicon content of from 2 to 2000 ppm by weight of silicon, in particular from 25 to 500 ppm by weight of silicon, result.

According to the invention, the antifreeze compositions and antifreeze concentrates of the present invention comprise at least one compound selected from the group consisting of compounds of the formula (V), compounds of the formula (VI), compounds of the formula (VII) and mixtures thereof.

These are compounds of the general formula (V)


where
R1is an organic radical having from 7 to 21 carbon atoms, in particular an alkyl or alkenyl radical having from 7 to 21 carbon atoms, preferably from 9 to 19, particularly preferably from 11 to 19, very particularly preferably from 13 to 19, in particular from 15 to 19 and especially 17, carbon atoms,
R2is an organic radical having from 8 to 22 carbon atoms, in particular an alkyl or alkenyl radical having from 8 to 22 carbon atoms, preferably from 10 to 20, particularly preferably from 12 to 20, very particularly preferably from 14 to 20, in particular from 16 to 20 and especially 18, carbon atoms,
R3is an organic radical having from 6 to 10 carbon atoms, in particular an alkyl or alkenyl radical having from 6 to 10 carbon atoms, preferably from 7 to 9 and particularly preferably 8 carbon atoms,
n is a positive integer from 10 to 60, preferably from 12 to 50, particularly preferably from 15 to 40, very particularly preferably from 18 to 30 and in particular from 20 to 25,
p and q are each, independently of one another, a positive integer from 1 to 40, preferably from 1 to 30, particularly preferably from 2 to 25, very particularly preferably from 3 to 20 and in particular from 5 to 15,
and
each Xifor i=1 to n, 1 to p and 1 to q is selected independently from the group consisting of —CH2—CH2—O—, —CH2—CH(CH3)—O—, —CH(CH3)—CH2—O—, —CH2—C(CH3)2—O—, —C(CH3)2—CH2—O—, —CH2—CH(C2H5)—O—, —CH(C2H5)—CH2—O—, —CH(CH3)—CH(CH3)—O—, —CH2—CH2—CH2—O— and —CH2—CH2—CH2—CH2—O—, preferably selected from the group consisting of —CH2—CH2—O—, —CH2—CH(CH3)—O— and —CH(CH3)—CH2—O—, with particular preference being given to —CH2—CH2—O—.

It should be noted that the compounds of the formulae (V), (VI) and (VII) are usually reaction mixtures having a distribution of the product composition which depends on the reaction conditions. Thus, the length of the chain —[—Xi—]— is subject to a distribution about a statistical average, so that the values for n, p and q can be distributed about a statistical average. Thus, the value for n, p and q for each individual compound of the formula (V), (VI) or (VII) is a positive integer, but for the reaction mixture can on statistical average also have nonintegral values.

Among these, compounds of the formulae (V) and (VII) are preferred, and compounds of the formula (VII) are particularly preferred.

In a preferred embodiment of the present invention, the structural element R1—COO— in formula (V) is derived from fatty acids or mixtures thereof, preferably from 2-ethylhexanoic acid, octanoic acid (caprylic acid), pelargonic acid (nonanoic acid), 2-propylheptanoic acid, decanoic acid (capric acid), undecanoic acid, dodecanoic acid (lauric acid), tridecanoic acid, tetradecanoic acid (myristic acid), pentadecanoic acid, palmitic acid (hexadecanoic acid), palmitoleic acid [(9Z)-hexadec-9-enoic acid], margaric acid (heptadecanoic acid), stearic acid (octadecanoic acid), oleic acid [(9Z)-octadec-9-enoic acid], elaidic acid [(9E)-octadec-9-enoic acid], linoleic acid [(9Z,12Z)-octadeca-9,12-dienoic acid], linolenic acid [(9Z,12Z,15Z)-octadeca-9,12,15-trienoic acid], eleostearic acid [(9Z,11E,13E)-octadeca-9,11,13-trienoic acid], ricinoleic acid ((R)-12-hydroxy-(Z)-octadec-9-enoic acid), isoricinoleic acid [(5)-9-hydroxy-(Z)-octadec-12-enoic acid], nonadecanoic acid, arachidic acid (eicosanoic acid), behenic acid (docosanoic acid) and erucic acid [(13Z)-docos-13-enoic acid].

Among these, the structural element R1—COO— in formula (V) is preferably derived from decanoic acid (capric acid), dodecanoic acid (lauric acid), tetradecanoic acid (myristic acid), palmitic acid (hexadecanoic acid), palmitoleic acid [(9Z)-hexadec-9-enoic acid], stearic acid (octadecanoic acid), oleic acid [(9Z)-octadec-9-enoic acid] or arachidic acid (eicosanoic acid), particularly preferably from tetradecanoic acid (myristic acid), palmitic acid (hexadecanoic acid), palmitoleic acid [(9Z)-hexadec-9-enoic acid], stearic acid (octadecanoic acid), oleic acid [(9Z)-octadec-9-enoic acid], ricinoleic acid ((R)-12-hydroxy-(Z)-octadec-9-enoic acid), isoricinoleic acid [(5)-9-hydroxy-(Z)-octadec-12-enoic acid] or arachidic acid (eicosanoic acid), very particularly preferably from palmitic acid (hexadecanoic acid), palmitoleic acid [(9Z)-hexadec-9-enoic acid], stearic acid (octadecanoic acid), oleic acid [(9Z)-octadec-9-enoic acid] or arachidic acid (eicosanoic acid) and in particular from stearic acid (octadecanoic acid).

Particular mention may be made of the twenty-fold, forty-fold and sixty-fold ethoxylated alkoxylates thereof.

In a further preferred embodiment, it is possible to employ fatty acid mixtures which are obtainable industrially from the work-up of natural, vegetable or animal fats and oils, particularly preferably from linseed oil, coconut oil, palm kernel oil, palm oil, soy oil, peanut oil, cocoa butter, shea butter, cottonseed oil, maize oil, sunflower oil, rapeseed oil or castor oil, very particularly preferably from linseed oil, palm oil, soy oil, peanut oil, cocoa butter, shea butter, cottonseed oil, maize oil, sunflower oil, rapeseed oil or castor oil.

Mixtures of saturated and unsaturated fatty acids can also be employed.

The compounds (V) are, for example, obtainable by reaction of the respective acids or esters, preferably the C1-C4-alkyl esters or glycerides, having the structural element R1—COO— in formula (V) with the respective alcohol HO—[—Xi—]n—H in an esterification or transesterification under known conditions.

The respective acids R1—COOH or salts thereof are preferably, however, reacted with alkylene oxides to the desired average statistical degree of alkoxylation, preferably under basic conditions. This is particularly preferred when the structural unit Xiis derived from ethylene oxide or propylene oxide, preferably from ethylene oxide.

According to the invention, the compounds (V) reduce corrosion, in particular nonferrous metal corrosion, but can also perform other tasks in the coolant compositions of the invention, for example reducing foam formation (antifoams, defoamers). Among the compounds (V), preference is given to those which reduce both foam formation and corrosion, in particular nonferrous metal corrosion, with particular preference being given to those which do not significantly influence foam formation but reduce corrosion, in particular nonferrous metal corrosion.

In the compounds of the formula (VI), the structural element R2—O— is preferably derived from fatty alcohols which are preferably obtainable by hydrogenation of fatty acids and esters, particularly preferably by hydrogenation of the abovementioned fatty acids. In a particular embodiment, the radical R2is thus a R1—CH2— radical. What has been said above with regard to the fatty acids also applies analogously to the fatty alcohols.

In a preferred embodiment, the fatty alcohols are octyl alcohol (capryl alcohol), nonyl alcohol (pelargonyl alcohol), decyl alcohol (capric alcohol), undecyl alcohol, dodecyl alcohol (lauryl alcohol), tridecyl alcohol, tetradecyl alcohol (myristyl alcohol), pentadecyl alcohol, hexadecyl alcohol (cetyl alcohol, palmityl alcohol), heptadecyl alcohol, octadecyl alcohol (stearyl alcohol), oleyl alcohol, elaidyl alcohol, linoleyl alcohol, linolenoyl alcohol, nonadecyl alcohol, eicosyl alcohol (arachyl alcohol) or mixtures thereof.

In a preferred embodiment, the compounds of the formula (VI) are alkoxylated castor oils, particularly preferably hydrogenated alkoxylated castor oils, very particularly preferably ethoxylated, propoxylated and/or butoxylated castor oils, in particular ethoxylated castor oils.

Further examples of alcohols having the structural element R2—O— are n-octanol, 2-ethylhexanol, 2-propylheptanol, tridecanol isomer mixtures and heptadecanol isomer mixtures.

Particular mention may be made of the twenty-fold and forty-fold ethoxylated alkoxylates thereof.

A tridecanol isomer mixture as parent alcohol R2—OH is a mixture of alcohols having 13 carbon atoms, particularly preferably a mixture obtainable by hydroformylation from a C12-olefin mixture which is in turn obtainable by oligomerization of an olefin mixture comprising predominantly hydrocarbons having four carbon atoms.

On statistical average, this olefin mixture has from 11 to 13 carbon atoms, preferably from 11.1 to 12.9, particularly preferably from 11.2 to 12.8, very particularly preferably from 11.5 to 12.5 and in particular from 11.8 to 12.2.

In a very particularly preferred embodiment, this alcohol R1—OH has an average degree of branching, measured as ISO index, of from 2.8 to 3.7.

In particular, this alcohol R2—OH is obtained by a process as described in WO 00/02978 or WO 00/50543.

A heptadecanol isomer mixture as parent alcohol R2—OH is a mixture of alcohols having 17 carbon atoms, particularly preferably a mixture which is obtainable by hydroformylation of a C16-olefin mixture which in turn is obtainable by oligomerization of an olefin mixture which predominantly comprises hydrocarbons having four carbon atoms.

On statistical average, this olefin mixture has from 15 to 17 carbon atoms, preferably from 15.1 to 16.9, particularly preferably from 15.2 to 16.8, very particularly preferably from 15.5 to 16.5 and in particular from 15.8 to 16.2.

In a very particularly preferred embodiment, this alcohol R1—OH has an average degree of branching, measured as ISO index, of from 2.8 to 3.7.

In particular, this alcohol R1—OH is obtained by a process as described in WO 2009/124979 A1, there in particular page 5, line 4 to page 16, line 29, and also the examples of page 19, line 19 to page 21, line 25, which is hereby incorporated by reference into the present disclosure.

A C17-alcohol mixture having particularly advantageous use properties can be prepared by this preferred process as product of the transition metal-catalyzed oligomerization of olefins having from 2 to 6 carbon atoms. Here, a C16-olefin mixture is firstly isolated by distillation from the product of the olefin oligomerization and only subsequently is this C16-olefin mixture subjected to hydroformylation. This makes it possible to provide a more highly branched C17-alcohol mixture having particularly advantageous use properties.

The compounds (VI) are preferably obtainable by reacting the corresponding alcohols R2—OH with alkylene oxides to the desired average statistical degree of alkoxylation, preferably under basic conditions. This is particularly preferred when the structural unit Xiis derived from ethylene oxide or propylene oxide, preferably from ethylene oxide.

According to the invention, the compounds (VI) reduce corrosion, in particular nonferrous metal corrosion, but can also perform other tasks in the coolant compositions of the invention, for example reducing foam formation (antifoams, defoamers). Among the compounds (V), preference is given to those which reduce both foam formation and also corrosion, in particular nonferrous metal corrosion, with particular preference being given to those which do not significantly influence foam formation but reduce corrosion, in particular nonferrous metal corrosion.

In the compounds of the formula (VII), the structural element R3—N< is preferably derived from fatty amines which are preferably obtainable by hydrogenation and amination of fatty acids and esters, particularly preferably by hydrogenation and amination of the abovementioned fatty acids or amination of the abovementioned fatty alcohols. What has been said with regard to the fatty alcohols also applies analogously to the fatty amines.

As radicals R3, preference is given to alkyl radicals over alkenyl radicals.

In a preferred embodiment, the fatty amines are n-hexylamine, 2-methylpentylamine, n-heptylamine, 2-heptylamine, isoheptylamine, 1-methylhexylamine, n-octylamine, 2-ethylhexylamine, 2-aminooctane, 6-methyl-2-heptylamine, n-nonylamine, isononylamine, n-decylamine and 2-propylheptylamine or mixtures thereof.

Particular preference is given to n-hexylamine, n-octylamine, 2-ethylhexylamine and n-decylamine, with n-octylamine and 2-ethylhexylamine, in particular n-octylamine, being particularly preferred.

Particular mention may be made of two-fold, eight-fold, twenty-fold and forty-fold ethoxylated n-octylamine and also eight-fold, twenty-fold and forty-fold ethoxylated n-hexylamine.

In the alkoxylated amines of the general formula (VII), the degree of alkoxylation refers to the sum (p+q), i.e. to the average total number of alkoxylation units per molecule of amine.

The compounds (VII) are preferably obtainable by reacting the corresponding amines R3—NH2with alkylene oxides to the desired average statistical degree of alkoxylation, preferably under basic conditions. This is particularly preferred when the structural unit Xiis derived from ethylene oxide or propylene oxide, preferably from ethylene oxide.

The compounds of the formulae (V) to (VII), preferably the compounds of the formulae (V) and (VII), particularly preferably the compounds of the formula (VII), are particularly suitable for reducing nonferrous metal corrosion in the use of coolant compositions in fuel cells and are accordingly added to the coolant compositions in a method according to the invention.

Ready-to-use aqueous coolant compositions which have a conductivity of not more than 50 μS/cm, preferably up to 40 μS/cm, particularly preferably up to 30 and in particular up to 20 μS/cm, and consist essentially of

(a) from 10 to 90% by weight of alkylene glycols or derivatives thereof,

(b) from 90 to 10% by weight of water,

(c) from 0.005 to 5% by weight, in particular from 0.0075 to 2.5% by weight, especially from 0.01 to 1% by weight, of the azole derivatives mentioned, and

(d) optionally at least one ortho-silicic ester and also

(e) from 0.05 to 5% by weight, in particular from 0.1 to 1% by weight, especially from 0.2 to 0.5% by weight, of at least one of the compounds (V), (VI) and/or (VII) can be produced from the antifreeze concentrates of the invention by dilution with ion-free water. The sum of all components here is 100% by weight.

The present invention therefore also provides ready-to-use aqueous coolant compositions for cooling systems in fuel cells and/or batteries, which consist essentially of

(a) from 10 to 90% by weight of alkylene glycols or derivatives thereof,

(b) from 90 to 10% by weight of water,

(c) from 0.005 to 5% by weight, in particular from 0.0075 to 2.5% by weight, especially from 0.01 to 1% by weight, of the azole derivatives mentioned, and

(d) optionally at least one ortho-silicic ester and also

(e) from 0.05 to 5% by weight, in particular from 0.1 to 1% by weight, especially from 0.2 to 0.5% by weight, of at least one of the compounds (V), (VI) and/or (VII) and are obtainable by dilution of the specified antifreeze concentrates with ion-free water. The sum of all components here is 100% by weight.

The ready-to-use aqueous coolant compositions of the invention have an initial electrical conductivity of not more than 50 μS/cm, in particular 25 μS/cm, preferably 10 μS/cm, especially 5 μS/cm. The conductivity is maintained at this low level over a long period of time during long-term operation of the fuel cell, in particular when a cooling system having an integrated ion exchanger is used in the fuel cell.

The pH of the ready-to-use aqueous coolant compositions of the invention decreases significantly more slowly over the period of operation than in the case of cooling liquids to which the azole derivatives mentioned have not been added. The pH is usually in the range from 4.5 to 7 in the case of fresh coolant compositions according to the invention and in long-term operation usually decreases to 3.5. The ion-free water used for dilution can be pure distilled or twice-distilled water or water which has been deionized, for example by ion exchange.

The preferred mixing ratio by weight of alkylene glycol or derivatives thereof to water in the ready-to-use aqueous coolant compositions is from 20:80 to 80:20, in particular from 25:75 to 75:25, preferably from 65:35 to 35:65, especially from 60:40 to 40:60. As alkylene glycol component or derivative thereof, it is possible to use, in particular, monoethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol and mixtures thereof, but also monopropylene glycol, dipropylene glycol and mixtures thereof, polyglycols, glycol ethers, for example monoethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, monoethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monoethyl ether, monoethylene glycol mono-n-butyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol mono-n-butyl ether and tetraethylene glycol mono-n-butyl ether, or glycerol, in each case either alone or as mixtures thereof. Particular preference is given to monoethylene glycol alone or mixtures of monoethylene glycol as main component, i.e. having a content in the mixture of more than 50% by weight, in particular more than 80% by weight, especially more than 95% by weight, with other alkylene glycols or derivatives of alkylene glycols.

The antifreeze concentrates of the invention themselves, from which the above-described ready-to-use aqueous coolant compositions result, can be produced by dissolving the azole derivatives mentioned in alkylene glycols or derivatives thereof, which can be used in water-free form or with a small content of water (up to about 10% by weight, in particular up to 5% by weight).

The present invention also provides for the use of at least one of the compounds (V), (VI) and/or (VII) for producing antifreeze concentrates for cooling systems in fuel cells and/or batteries, in particular in motor vehicles, particularly preferably in passenger cars and commercial vehicles, based on alkylene glycols or derivatives thereof.

The present invention further provides for the use of these antifreeze concentrates for producing ready-to-use aqueous coolant compositions having a conductivity of not more than 50 μS/cm for cooling systems in fuel cells and/or batteries, in particular in motor vehicles, particularly preferably in passenger cars and commercial vehicles.

The coolant compositions of the invention can also be used in a fuel cell apparatus as described in DE-A 101 04 771 (6), in which the cooling medium is additionally electrochemically deionized in order to prevent corrosion.

