Coolant with improved temperature stability

Abstract

The present invention describes a novel water-based coolant with improved temperature stability, its preparation and use.

Description

[Technical Field]

[0001] This invention describes a novel aqueous coolant having improved temperature stability, its preparation, and its use. [Background technology]

[0002] Modern internal combustion engines achieve higher combustion temperatures than conventional engines. Consequently, in terms of thermal management, not only is the amount of heat that needs to be dissipated greater, but the temperature difference between the combustion chamber walls and the cooling water passages in the cooling system also greater.

[0003] As a result, the aqueous coolant is exposed to higher temperatures, and the components present are subjected to a higher thermal load, thus imposing higher demands on the coolant in terms of thermal load.

[0004] Currently, certain stabilizers (hard water stabilizers) added to aqueous coolants to complexize alkaline earth metal ions in the water used have relatively high thermal stability, and have been found to reduce or prevent the precipitation of alkaline earth metal compounds. As a result of the thermal decomposition of polymer chains, the walls of the cooling water channels become hot, and as a result, conventional poly(meth)acrylates, which are often used as hard water stabilizers, decompose. Therefore, the alkaline earth metal ions present in the aqueous coolant can no longer remain in solution, and deposits of alkaline earth metal compounds are formed on the walls of the cooling water channels. Consequently, this worsens the heat transfer through the walls between the combustion space and the cooling water channels and the corresponding heat transfer coefficient. [Overview of the project] [Problems that the invention aims to solve]

[0005] The object of the present invention was to provide an aqueous coolant that can reduce or prevent the formation of deposits on the cooling water channel wall, particularly as a result of the precipitation of alkaline earth metal compounds, even when the wall temperature is high. [Means for solving the problem]

[0006] The purpose is an aqueous coolant, (A) Water, (B) at least one alkylene glycol, alkylene glycol monoalkyl ether or glycerol, (C) at least one phosphate, carbonate and / or sulfate, which is in the form of the free acid or salt thereof, particularly an alkali metal salt thereof, particularly preferably a sodium or potassium salt thereof, (D) at least one hard water stabilizer, Optionally, further inhibitors and typical coolant components. The hard water stabilizer (D) is an aqueous coolant comprising at least one homo or copolymer containing acrylic acid and / or methacrylic acid and / or maleic acid and / or itaconic acid in polymerized form, having a weight-average molecular weight Mw determined by GPC of at least 3000 g / mol, preferably at least 3500, particularly preferably at least 4000, and very particularly preferably at least 4500 g / mol, and having a mass loss of 10% by weight or less, preferably 8% by weight or less, particularly preferably 7% by weight or less, very particularly preferably 5% by weight or less, specifically 3% by weight or less, and particularly 2% by weight or less in the temperature range of 200°C to 300°C.

[0007] In this specification, mass loss is measured by thermogravimetric analysis in an argon atmosphere at a flow rate of 40 ml / min and a heating rate of 5 K / min over a temperature range of 30°C to 800°C. The mass loss in the temperature range of 200°C to 300°C is used for compound (D) usable according to the present invention, the mass present at 200°C is taken as the baseline, and the reduction due to further heating up to 300°C is taken as the mass loss.

[0008] The use of these specific hard water stabilizers (D) makes it possible to reduce or prevent the precipitation of alkaline earth metal compounds in the coolant, thereby reducing or eliminating deposition formation on the walls of the cooling water channels. These alkaline earth metal compound precipitates can form not only on the walls of the cooling water channels, but also elsewhere in the cooling system, such as in the circulation pump (coolant pump), temperature measurement (thermal switches, temperature probes), or the cooling water channels of the heat exchanger (cooler), and may have an effect there. [Brief explanation of the drawing]

[0009] [Figure 1] This shows the MHTA designed as a circulating device. [Modes for carrying out the invention]

[0010] The individual components of the coolant according to the present invention are as follows:

[0011] Water (A) The water used in connection with the present invention should be neutral with a pH of about 7. This may be, but is not necessarily, demineralized water or distilled water. To allow the use of hard water as well, the compositions of the present invention include at least one hard water stabilizer (D).

[0012] The water used may contain alkaline earth metal ions, such as magnesium, calcium, strontium, or barium ions, the latter usually present in trace amounts at most. Preferably, essentially only magnesium and / or calcium ions are present as hardness-forming agents.

[0013] The water used is preferably soft water with a water hardness of 8.4°dH or less, particularly preferably 10°dH or less, and very preferably 12°dH or less.

[0014] An advantage of the present invention is that it is possible to use water with a hardness of 14°dH or less, preferably 17°dH or less, particularly preferably 20°dH or less, and even more preferably 25°dH or less.

[0015] For the hardness-forming agent, the water used in the coolant is a common source of carbonates and / or sulfates present in the coolant as component (C).

[0016] An advantage of the coolant according to the present invention is that it is not necessary to use demineralized water or distilled water to reduce or prevent precipitates of alkaline earth metal compounds.

[0017] Therefore, the present invention provides a method for reducing or preventing precipitates of alkaline earth metal compounds from an aqueous coolant containing phosphates, carbonates and / or sulfates by adding at least one hard water stabilizer (D) having the criteria according to the present invention to the aqueous coolant. <000009l> Alkylene glycol, alkylene glycol monoalkyl ether or glycerol (B) Component (B) has a major freezing point depression effect in the coolant. The component is monomeric to tetrameric 1,2-ethylene glycol, 1,2-propylene glycol or less commonly 1,3-propylene glycol, preferably monomeric to trimeric 1,2-ethylene glycol or 1,2-propylene glycol, particularly preferably monomeric or dimeric 1,2-ethylene glycol, very particularly preferably monomeric 1,2-ethylene glycol and in any case mixtures thereof.

[0019] The alkylene glycol monoalkyl ether is a mono C1-C4 alkyl ether of the above alkylene glycol, preferably monomethyl, -ethyl or -n-butyl ether, particularly preferably monomethyl or -n-butyl ether, very particularly preferably monomethyl ether.

[0020] Furthermore, glycerol or an oligomer of glycerol is also a possible component (B).

[0021] Preferred alkylene glycol components or derivatives include, in particular, monoethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol and mixtures thereof, as well as monopropylene glycol, dipropylene glycol and mixtures thereof, polyglycols, glycol ethers, such as 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, which can be used individually or as mixtures thereof.

[0022] Particularly preferred is monoethylene glycol alone or a mixture mainly composed of monoethylene glycol, i.e., a mixture containing more than 50% by weight, specifically more than 80% by weight, and especially more than 95% by weight, and also containing other alkylene glycols or alkylene glycol derivatives.

[0023] Phosphates, carbonates and / or sulfates (C) Anion (C) is a compound that, under the concentration present in the coolant and the conditions of the cooling system, can form precipitates with alkaline earth metal ions, particularly calcium or magnesium cations.

[0024] Phosphates are used as hydrogen phosphate, dihydrogen phosphate, or free acids (H3PO4) as phosphates, particularly alkali metal salts, especially sodium or potassium salts. Acidic protons in phosphates can be partially or completely substituted by alkali metal salts.

[0025] While it is also conceivable to use the corresponding diphosphate, triphosphate, or oligophosphate in mixtures with monophosphate, it is preferable to use them as monomeric phosphates.

[0026] It is preferable to use it as a free acid (H3PO4), disodium hydrogen phosphate, or trisodium phosphate.

[0027] The same applies to carbonates that may exist as alkali metal salts of carbonates or bicarbonates, preferably sodium or potassium salts.

[0028] The same applies to sulfates that may exist as alkali metal salts of sulfates or hydrogen sulfates, preferably sodium or potassium salts.

[0029] Carbonates and / or sulfates are generally not added to coolants or coolant concentrates, but are present in the water (A) used for dilution.

[0030] Among the compounds (C), carbonates and / or phosphates are preferred, and phosphates are particularly preferred.

[0031] Hard water stabilizer (D) The hard water stabilizer (D) comprises, preferably comprises, at least one homo or copolymer containing acrylic acid and / or methacrylic acid and / or maleic acid and / or itaconic acid in polymerized form, and has a weight-average molecular weight Mw determined by GPC of at least 3000 g / mol, preferably at least 3500, particularly preferably at least 4000, and very particularly preferably at least 4500 g / mol, and additionally has a mass loss of 10% by weight or less, preferably 8% by weight or less, particularly preferably 7% by weight or less, very particularly preferably 5% by weight or less, specifically 3% by weight or less, and particularly particularly 2% by weight or less in the range of 200°C to 300°C.

[0032] The hard water stabilizer (D) is preferably a homopolymer or copolymer containing acrylic acid and / or methacrylic acid and / or maleic acid in polymerized form, particularly preferably a homopolymer or copolymer containing acrylic acid and / or maleic acid in polymerized form, and very preferably a homopolymer or copolymer containing acrylic acid in polymerized form.

[0033] To prepare these homopolymers or copolymers, monoethylene unsaturated C3-C5 carboxylic acids are polymerized under the conditions specified below.

[0034] Both monocarboxylic acids and dicarboxylic acids are preferred, such as acrylic acid, methacrylic acid, crotonic acid, vinyl lactic acid, maleic acid, fumaric acid, aconitic acid, itaconic acid, mesaconic acid, citraconic acid, and methylenemalonic acid. Homopolymers of acrylic acid, methacrylic acid, maleic acid, or itaconic acid, or copolymers of acrylic acid and methacrylic acid, acrylic acid and maleic acid, acrylic acid and itaconic acid, methacrylic acid and maleic acid, and methacrylic acid and itaconic acid are preferred. The carboxylic acids mentioned can be copolymerized with each other in desired ratios. Naturally, instead of the two carboxylic acids mentioned, it is possible to copolymerize three or four different carboxylic acids with each other.

[0035] The carboxylic acids mentioned can be optionally polymerized with copolymerizable ethylenically unsaturated monomers that do not contain a carboxyl group. Depending on the solubility of the copolymer formed, suitable comonomers used in polymerization include amides, nitriles, or esters of ethylenically unsaturated C3-C5 carboxylic acids, such as acrylamide, methacrylamide, methyl acrylate, methyl (meth)acrylate, ethyl acrylate, ethyl (meth)acrylate, hydroxyethyl acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl acrylate, hydroxypropyl (meth)acrylate, butane-1,4-diol monoacrylate, butane-1,4-diol mono(meth)acrylate, dimethylaminoethyl acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl acrylate, diethylaminoethyl (meth)acrylate, and vinyl esters, such as vinyl acetate, vinyl propionate, and vinyl butyrate, as well as 2-acrylamido-2-methylpropanesulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, vinyl glycol, allyl alcohol, ethylene, propylene, styrene, methylstyrene, and butadiene.

[0036] Among the monomers mentioned, vinyl acetate, diethylaminoethyl acrylate, dimethylaminoethyl acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and methyl acrylate are preferred.

[0037] Basic acrylates, such as dimethylaminoethyl acrylate, are used either in the form of a salt or in the form of a quaternized compound, such as one quaternized with benzyl chloride or methyl chloride. This group of comonomers plays a role in modifying carboxyl group-containing polymers and accounts for 0% to 40% by weight of the copolymer structure.

[0038] The monomers are polymerized in aqueous solution using polymerization initiators, preferably water-soluble initiators, such as sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide, azobis(2-aminopropane) hydrochloride, 2,2'-azobis(N,N'-dimethylene isobutylamidine) dihydrochloride, and 2,2'-azobis(4-cyanopentanoic acid).

[0039] Initiators are used either alone or in mixtures, such as a mixture of hydrogen peroxide and sodium persulfate. In addition to water-soluble initiators, organic peroxides, hydroperoxides, and azo compounds that are only sparingly soluble in water may be used. Examples include the following compounds: tert-butylperpivalate, 2,2'-azobis(valeronitrile), tert-butylper-2-ethylhexanoate, 2,2'-azobis(isobutyronitrile), tert-butylperbenzoate, tert-butylhydroperoxide, and p-menthanehydroperoxide.

[0040] Monomers can also be polymerized using redox catalysts. For this purpose, reducing agents used include, for example, ascorbic acid, benzoin, dimethylaniline, and optionally additionally, soluble complexes and heavy metal salts. As is already known, this allows polymerization to be carried out at relatively low temperatures.

[0041] The polymerization temperature is 60°C to 160°C, preferably 80°C to 130°C. At temperatures above 100°C, polymerization must, of course, be carried out under pressure. The monomer concentration in the aqueous solution is 20% to 70% by weight, preferably 35% to 60% by weight.

[0042] The molecular weight Mw of compound (D) can be up to 100,000 g / mol, preferably up to 75,000 g / mol, particularly preferably up to 50,000 g / mol, very particularly preferably up to 25,000 g / mol, and especially up to 10,000 g / mol.

[0043] A further characteristic of compound (D) is its mass loss of 10% by weight or less, preferably 8% by weight or less, particularly preferably 7% by weight or less, very particularly preferably 5% by weight or less, specifically 3% by weight or less, and especially 2% by weight or less, measured by thermogravimetric analysis in the temperature range of 30°C to 800°C at a flow rate of 40 ml / min and a heating rate of 5 K / min in an argon atmosphere, compared to compound (D) in the temperature range of 200°C to 300°C.

[0044] In the temperature range below 200°C, the behavior of a compound in thermogravimetric analysis is determined by the evaporation of water present in the resulting homopolymer or copolymer.

[0045] At temperatures exceeding 300°C, particularly above 325°C, and specifically above 350°C, homopolymers or copolymers are likely to undergo thermal decomposition under the thermogravimetric conditions described.

[0046] Conversely, temperatures between 200°C and 300°C show a good correlation with precipitate formation. Please refer to the examples below.

[0047] Particularly preferred as compound (D) is a homo or copolymer containing acrylic acid in polymerization form, having a weight-average molecular weight Mw of at least 3500 g / mol to 25000 g / mol and a mass loss of 3% by weight or less, as determined by GPC, and very preferably having a weight-average molecular weight of at least 4000 g / mol to 10000 g / mol and a mass loss of 2% by weight or less.

[0048] While not bound by any particular theory, homopolymers and copolymers with the minimum molecular weight described are considered to have a sufficient number of carboxyl groups that can be initially complexed with alkaline earth metal ions and subsequently retained in solution in an aqueous medium, serving as an indicator of the degree of polymerization. Low mass loss by thermogravimetric analysis is an indicator of the temperature stability of the hard water stabilizer within the critical temperature range in the cooling system when the coolant is exposed to rising wall temperatures. The hard water stabilizer (D) used according to the present invention does not significantly decompose at the high wall temperatures of modern internal combustion engines, and is therefore capable of complexing with alkaline earth metal ions and keeping them in solution, thereby reducing or preventing the precipitation of sparingly soluble alkaline earth metal compounds.

[0049] Further optional inhibitors and typical coolant components Further inhibitors and typical coolant components are each independently and arbitrarily selected from the following group: (E) Azole compounds, (F) Inorganic compounds other than (C) selected from the group consisting of silicates, borates, nitrates, and molybdates. (G) Organic carboxylic acids, (H) Defoaming agents, dyes and bitter substances, and (I) Inorganic base.

[0050] Azole compound (E) In relation to this specification, azole derivative (E) is understood to mean a five-membered heterocyclic compound that may have two or three heteroatoms derived from nitrogen and sulfur groups, and which may contain no sulfur atoms incorporated into the ring or at most one sulfur atom, and which may optionally have aromatic or saturated six-membered fusions.

[0051] These five-membered heterocyclic compounds (azole derivatives) typically contain two nitrogen atoms as heteroatoms and no sulfur atoms, or three nitrogen atoms and no sulfur atoms, or one nitrogen atom and one sulfur atom.

[0052] The preferred group of the azole derivative mentioned is the following general formula [ka] These are fusion imidazoles and fusion 1,2,3-triazoles, in which, The variable R is either hydrogen or C1~C 10 Alkyl radicals, specifically methyl or ethyl, The variable X is either a nitrogen atom or a CH moiety.

[0053] Typical and preferred examples of azole derivatives of general formula (III) are benzimidazole (X=CH, R=H), benzotriazole (X=N, R=H), and tolyltriazole (X=N, R=CH3). A typical example of an azole derivative of general formula (IV) is hydrogenated 1,2,3-tolyltriazole (X=N, R=CH3).

[0054] A further preferred group of azole derivatives mentioned is the general formula (V) [ka] It is a benzothiazole, and in the formula, The variable R has the above definition, The variable R' represents hydrogen, C1~C 10 The alkyl radical is specifically a methyl or ethyl group, or specifically a mercapto group (-SH). Although not very desirable, R' is probably of formula -(C m H 2m It can also be a carboxyalkyl radical of the form )-COOR'', where m is a number from 1 to 4, and R'' is hydrogen or C1 to C 10 Alkyl, specifically methyl or ethyl or C6-C 12These are aryl compounds. Examples include (2-benzothiadylthio)acetic acid, (2-benzothiadylthio)acetic acid ester, 3-(2-benzothiadylthio)propionic acid, or 3-(2-benzothiadylthio)propionic acid ester. When these compounds are used in acidic form, they are not among the carboxylic acids excluded according to the present invention. A typical example of an azole derivative of general formula (V) is 2-mercaptobenzothiazole.

[0055] Furthermore, General Formula (VI) [ka] Non-condensed azole derivatives are also preferred, where the variables X and Y are either two nitrogen atoms or a nitrogen atom and a CH moiety, for example, 1H-1,2,4-triazole (X=Y=N) or preferably imidazole (X=N, Y=CH).

[0056] The most particularly preferred azole derivatives of the present invention are benzimidazole, benzotriazole, toltriazole, hydrogenated toltriazole, or mixtures thereof, specifically benzotriazole or toltriazole, and especially toltriazole.

[0057] The azole derivatives mentioned are either commercially available or can be produced by common methods. Hydrogenated benzotriazoles, such as hydrogenated toltriazole, are also available in accordance with German Patent Application Publication No. 1948794 and are commercially available.

[0058] The azole is preferably selected from the group consisting of benzotriazole, toltriazole, (2-benzothiadylthio)acetic acid, 3-(2-benzothiadylthio)propionic acid, and 2-mercaptobenzothiazole.

[0059] Inorganic compounds (F) other than compound (C), selected from the group consisting of silicates, borates, nitrates, and molybdates. The inorganic inhibitor (F) is a silicate, borate, nitrate or molybdate or a mixture thereof, in the form of its free acid or its salts, especially its alkali metal salts, particularly preferably its sodium or potassium salts, of silicate, borate, nitrate or molybdate or a mixture thereof. The form in which these are used in the composition, superconcentrate, concentrate or coolant (protonated or salt form) depends on the corresponding pK of the compound or composition a and on the corresponding pH of the medium established by the amount of base (D).

[0060] Inorganic silicates act mainly as corrosion inhibitors for aluminum and are usually used as alkali metal salts or, more rarely, as magnesium, calcium or aluminum salts, preferably sodium or potassium salts.

[0061] Silicates are preferably selected from the group consisting of orthosilicates (SiO4 4- ), metasilicates (SiO3 2- ) and pyrosilicates (Si2O7 6- ), particularly preferably metasilicates (SiO3 2- ), very particularly preferably sodium metasilicate (Na2SiO3) or potassium metasilicate (K2SiO3), especially sodium metasilicate (Na2SiO3).

[0062] Instead of or in addition to the inorganic silicates described, the coolant may also contain organic orthosilicic esters of the general formula Si(OR)4, in which each R is independently a C1-C4 alkyl, preferably methyl, ethyl or n-butyl, particularly preferably methyl or ethyl or a mixture of methyl and ethyl.

[0063] When the composition of the invention contains at least one silicate, in a preferred embodiment at least one silicophosphate is added in addition to the silicate as described in the unpublished European patent application publication No. 20213979.6 filed on December 15, 2020.

[0064] Silicophosphonates are preferably of the following general formula [ka] It is a compound of the formula, in which, R 5 This is a divalent organic radical, preferably a 1,ω-alkylene group having 1 to 6, preferably 1 to 4 carbon atoms, particularly preferably methylene, 1,2-ethylene, 1,2-propylene, 1,3-propylene or 1,4-butylene, very particularly preferably 1,2-ethylene or 1,3-propylene and especially 1,2-ethylene. R 6 These are independently hydrogen, C1-C4 alkyl or hydroxy-C2-C4 alkyl, preferably hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl, 2-hydroxyethyl or 2-hydroxypropyl, particularly preferably hydrogen, methyl, ethyl or propyl. R 7 The C1-C4 alkyl group is preferably methyl, ethyl, n-propyl, or n-butyl, most preferably methyl, ethyl, or n-butyl, and most preferably methyl, ethyl, and especially methyl.

[0065] Silicophosphonates can be used as free acids or alkali metal salts, preferably sodium salts or potassium salts, and particularly preferably sodium salts.

[0066] The borate is preferably used as sodium tetraborate (borax) or potassium tetraborate, and particularly preferably as sodium tetraborate.

[0067] The nitrate used is an alkali metal or alkaline earth metal nitrate, preferably sodium nitrate, potassium nitrate, or magnesium nitrate, preferably sodium nitrate or potassium nitrate, and particularly preferably sodium nitrate.

[0068] Component (F) is preferably at least one compound selected from the group consisting of silicates, borates, or nitrates, and particularly preferably at least one compound selected from the group consisting of silicates or nitrates.

[0069] Organic carboxylic acids (G) The organic carboxylic acid may be an organic monocarboxylic acid (G1) or a dicarboxylic acid (G2), preferably a monocarboxylic acid having 2 to 18 carbon atoms and an organic dicarboxylic acid having 4 to 20 carbon atoms.

[0070] (G1) Monocarboxylic acid having 2 to 18 carbon atoms A suitable monocarboxylic acid (G1) may be a linear or branched aliphatic, alicyclic, or aromatic monocarboxylic acid having 2 to 18 carbon atoms, preferably 5 to 16, particularly preferably 5 to 15, very particularly preferably 6 to 12, and especially preferably 8 to 10 carbon atoms.

[0071] Branched-chain aliphatic monocarboxylic acids are preferred over their corresponding linear monocarboxylic acids.

[0072] Suitable examples of linear or branched aliphatic monocarboxylic acids (G1) include propionic acid, pentanoic acid, 2,2-dimethylpropanoic acid, hexanoic acid, 2,2-dimethylbutanoic acid, cyclohexylacetic acid, octanoic acid, 2-ethylhexanoic acid, nonanoic acid, isononanoic acid, decanoic acid, undecanoic acid, and dodecanoic acid.

[0073] One particularly preferred aromatic monocarboxylic acid (G1) is benzoic acid, and also C1-C8 alkylbenzoic acid, such as o-,m-,p-methylbenzoic acid or p-tert-butylbenzoic acid, as well as hydroxyl group-containing aromatic monocarboxylic acids, such as o-,m-,p-hydroxybenzoic acid, o-,m-,p-(hydroxymethyl)benzoic acid, or halobenzoic acid, such as o-,m-,p-fluorobenzoic acid.

[0074] Particularly preferred monocarboxylic acids are 2-ethylhexanoic acid and isononanoic acid.

[0075] In relation to this specification, isononanoic acid describes one or more branched-chain aliphatic monocarboxylic acids having nine carbon atoms. Of particular importance are isomers such as 7-methyloctanoic acid (e.g., CAS numbers 693-19-6 and 26896-18-4), 6,6-dimethylheptanoic acid (e.g., CAS number 15898-92-7), 3,5,5-trimethylhexanoic acid (e.g., CAS number 3302-10-1), 3,4,5-trimethylhexanoic acid, 2,5,5-trimethylhexanoic acid, 2,2,4,4-tetramethylpentanoic acid (e.g., CAS number 3302-12-3), and mixtures containing these isomers or mixtures thereof. In preferred embodiments, the isononanoic acid isomer mixture comprises, as a main component, 7-methyloctanoic acid, 6,6-dimethylheptanoic acid, 3,5,5-trimethylhexanoic acid, 3,4,5-trimethylhexanoic acid, 2,5,5-trimethylhexanoic acid, and 2,2,4,4-tetramethylpentanoic acid in amounts exceeding 90% by weight. The remainder is formed by other isomers of monocarboxylic acids having nine carbon atoms and trace amounts of impurities. In even more preferred embodiments, the isononanoic acid comprises, in particular, 3,5,5-trimethylhexanoic acid in amounts exceeding 90% by weight, and especially preferably at least 95% by weight.

[0076] (G2) Organic dicarboxylic acids having 4 to 20 carbon atoms The organic dicarboxylic acid having 4 to 20 carbon atoms is a linear or branched alkanedicarboxylic acid, preferably a linear alkane or alkenedicarboxylic acid, particularly preferably an alkanedicarboxylic acid, particularly preferably having 5 to 14 carbon atoms, and very particularly preferably having 6 to 12 carbon atoms.

[0077] The dicarboxylic acid (G2) is preferably succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, pimelic acid (heptanediic acid), azelaic acid (nonanediic acid), sebacic acid (decanediic acid), undecanediic acid, dodecanediic acid, as well as alkyl and alkenyl succinic acid, and glutaric acid, such as 2-methylbutanediic acid, 2-ethyl-3-methylbutanediic acid, 2-ethylpentanediic acid, 2-dodecylbutanediic acid, 2- The following are selected from the group consisting of dodecenylbutanediic acid, 2-phenylbutanediic acid, 2-(p-methylphenyl)butanediic acid, 2,2-dimethylbutanediic acid, 2,3,4-trimethylpentanediic acid, 2,2,3-trimethylpentanediic acid, glutaconic acid (penta-2-enedioic acid), itaconic acid, hexa-2-enedioic acid, hexa-3-enedioic acid, 5-methylhexa-2-enedioic acid, and 2,3-dimethylpenta-2-enedioic acid.

[0078] Dicarboxylic acids having 6 to 12 carbon atoms are particularly preferred, alkanedicarboxylic acids having 6 to 12 carbon atoms are especially preferred, and linear alkanedicarboxylic acids having 6 to 12 carbon atoms are very preferred.

[0079] Particularly preferred dicarboxylic acids (G2) are adipic acid, sebacic acid, azelaic acid, and dodecanedicarboxylic acid.

[0080] Defoaming agents, dyes and / or bittering substances (H) As further conventional auxiliary agents, the compositions of the present invention may conventionally include small amounts of defoaming agents (generally in amounts of 0.003% to 0.008% by weight in the diluted coolant) and, for reasons of hygiene and safety in case of ingestion, bitter substances (e.g., of the type of denatonium benzoate) and dyes.

[0081] Inorganic base (I) The pH of the finished coolant is typically in the range of 4 to 11.5, preferably 5 to 10, and particularly 6 to 9.

[0082] Therefore, the coolant optionally contains a certain amount of an inorganic base that, when properly diluted, establishes this desired pH in the coolant. For this reason, the composition of the present invention preferably comprises an alkali metal hydroxide, particularly preferably solid lithium hydroxide, sodium hydroxide, or potassium hydroxide, which may optionally be in the form of an aqueous solution of lithium hydroxide, sodium hydroxide, or potassium hydroxide.

[0083] Lithium, sodium, or potassium carbonates or bicarbonates are not very desirable.

[0084] Preferred alkali metals are sodium and potassium.

[0085] Typically, coolants are: - At least 40% by weight of water (A), - At least 30% by weight of alkylene glycol, alkylene glycol monoalkyl ether and glycerol (B), - 0.01% to 5% by weight, preferably 0.02% to 2% by weight, particularly preferably 0.03% to 1% by weight of at least one phosphate, carbonate and / or sulfate (C), - At least one hard water stabilizer (D) in an amount of 0.1% to 2% by weight, - At least one azole(E) in an amount of 0% to 2% by weight, preferably 0.05% to 1% by weight, and particularly preferably 0.1% to 0.5% by weight, - At least one inorganic compound (F) selected from the group consisting of silicates, borates, nitrates, and molybdates, in an amount of 0% to 5% by weight, preferably 0.01% to 2% by weight, and particularly preferably 0.02% to 1% by weight. - At least one organic carboxylic acid (G) in an amount of 0% to 6% by weight, preferably 1% to 5% by weight, and particularly preferably 2% to 4% by weight. - At least one compound selected from the group consisting of defoaming agents, dyes, and bittering substances, in an amount of 0% to 0.2% by weight, preferably 0.001% to 0.15% by weight, and - At least one inorganic base in an amount of 0% to 10% by weight, preferably 0.5% to 8% by weight, and particularly preferably 1% to 7% by weight. It is structured as follows, however, - The sum of all components must always be 100% by weight.

[0086] To reduce the volume to be transported, concentrates with omitted or significantly reduced water content are usually sold. The coolant is prepared by the end user by adding water (A) to the concentrate, preferably half to twice the amount of water, and especially preferably the same amount of water.

[0087] Therefore, the present invention typically includes the following: - Water (A) in an amount of 15% by weight or less, preferably 10% by weight or less, and more preferably 5% by weight or less. - At least 60% by weight of alkylene glycol, alkylene glycol monoalkyl ether and glycerol (B), - 0.02% to 10% by weight, preferably 0.04% to 4% by weight, particularly preferably 0.06% to 2% by weight of at least one phosphate, carbonate and / or sulfate (C), - At least one hard water stabilizer (D) in an amount of 0.2% to 4% by weight, - At least one azole (E) in an amount of 0% to 4% by weight, preferably 0.1% to 2% by weight, and particularly preferably 0.2% to 1% by weight, - At least one inorganic compound (F) selected from the group consisting of silicates, borates, nitrates, and molybdates, in an amount of 0% to 10% by weight, preferably 0.02% to 4% by weight, and particularly preferably 0.04% to 2% by weight. - At least one organic carboxylic acid (G) in an amount of 0% to 12% by weight, preferably 2% to 10% by weight, and particularly preferably 4% to 8% by weight. - At least one compound selected from the group consisting of defoaming agents, dyes, and bittering substances, in an amount of 0% to 0.4% by weight, preferably 0.002% to 0.3% by weight, and - At least one inorganic base in an amount of 0% to 20% by weight, preferably 1% to 16% by weight, and particularly preferably 2% to 14% by weight. It is structured as follows, however, - Further provides coolant concentrates, provided that the sum of all components is always 100% by weight.

[0088] To further reduce the volume to be transported, ultra-concentrates, which have not only reduced or eliminated water content but also significantly reduced glycol content, are often produced intensively. Subsequently, these ultra-concentrates are used only locally by compounders to create concentrates by blending them with glycol.

[0089] The superconcentrate differs from the concentrate in that it completely or partially lacks component (B), so that other components are present at correspondingly higher concentrations. A concentrate of the above concentrations is therefore obtained from such a superconcentrate by mixing in component (B).

[0090] The compositions described are used as coolants to remove heat in an internal combustion engine or a hybrid of an internal combustion engine and / or a fuel cell and / or battery, and the cooling system for cooling the internal combustion engine includes the coolant according to the present invention.

[0091] As a result of the described composition, which has higher thermal stability than conventional coolants containing hard water stabilizers, the present invention relates to a method for cooling an internal combustion engine, wherein relatively high-temperature heat from a heat source is transferred to a coolant via at least one first heat exchanger, the coolant is passed to at least one second heat exchanger in a cooling circuit, and in the second heat exchanger, the heat is removed from the coolant at a relatively low temperature. - The above composition is used as a cooling agent. - Relatively high temperatures are 60°C to 300°C, preferably 70°C to 280°C, and particularly preferably 80°C to 250°C. - Relatively low temperatures are -50°C to 100°C, preferably -40°C to 90°C, and particularly preferably -30°C to 80°C. - A relatively low temperature is at least 50°C lower than a relatively high temperature, which further provides a method.

[0092] In this specification, a relatively high temperature is preferably, for example, the wall temperature of an internal combustion engine in a vehicle that operates solely on an internal combustion engine or in a hybrid vehicle consisting of a fuel cell and / or a battery and an internal combustion engine.

[0093] The present invention further provides a vehicle having an internal combustion engine or a hybrid of a fuel cell and / or a battery, wherein the cooling system for cooling the internal combustion engine includes a coolant according to the present invention.

[0094] In this specification, a relatively low temperature is preferably the ambient temperature at which the heated coolant is in contact with the second heat exchanger.

[0095] All components of a heat exchanger may be known to those skilled in the art for these purposes.

[0096] The present invention further provides a general method for increasing heat transfer on a surface with a high wall temperature and cooled with an aqueous coolant containing a phosphate, carbonate and / or sulfate, wherein the aqueous coolant containing a phosphate, carbonate and / or sulfate is at least one homo or copolymer comprising acrylic acid and / or methacrylic acid and / or maleic acid and / or itaconic acid in polymerized form, and having a weight-average molecular weight Mw determined by GPC of at least 3000 g / mol, preferably at least 3500, particularly preferably at least 4000, and very particularly preferably at least 4500 g / mol, and comprising a hard water stabilizer (D) having a mass loss of 10% by weight or less, preferably 8% by weight or less, particularly preferably 7% by weight or less, very particularly preferably 5% by weight or less, specifically 3% by weight or less, and particularly 2% by weight or less in the temperature range of 200°C to 300°C.

[0097] The present invention further provides the use of a hard water stabilizer (D) in aqueous coolants, particularly coolants containing phosphates, carbonates and / or sulfates (C), which is a homo or copolymer containing acrylic acid and / or methacrylic acid and / or maleic acid and / or itaconic acid in polymerized form, having a weight-average molecular weight Mw determined by GPC of at least 3000 g / mol, preferably at least 3500, particularly preferably at least 4000, and very particularly preferably at least 4500 g / mol, and having a mass loss of 10% by weight or less, preferably 8% by weight or less, particularly preferably 7% by weight or less, very particularly preferably 5% by weight or less, specifically 3% by weight or less, and particularly particularly 2% by weight or less in the temperature range of 200°C to 300°C.

[0098] In this specification, quantities reported in units of percent, ppm, or parts refer to weight percent, weight ppm, or weight parts, unless otherwise specified. [Examples]

[0099] thermogravimetry The weight change of approximately 20 mg of a sample of compound (D) in the form of a 50 wt% aqueous solution was determined in an open crucible at a flow rate of 40 ml / min, in an argon atmosphere, at a heating rate of 5 K / min, and within a temperature range of 30°C to 800°C.

[0100] The table below shows the mass loss in the range of 200°C to 300°C as Δm in weight percent, with the mass present at 200°C being used as the reference.

[0101] MHTA test following the FVV [German Research Association for Combustion Engines] test method, as per Booklet R 530 / 2005. A modular thermal testing apparatus (MHTA) was developed at the Institute for Materials Science of TU Darmstadt.

[0102] A modular thermal testing apparatus (MHTA) is used to evaluate the performance of coolant additives under operating conditions, in accordance with the FVV test method booklet R 530 / 2005 (Testing the suitability of coolant additives for coolants of internal combustion engines. Booklet R 530 / 2005 of the FVV, Frankfurt am Main, 2005).

[0103] In the deviation from the Corrosion tests with heat transfer (hot test) at point 8 of the FVV booklet R530 / 2005, the test specimen used was not the one described in 8.2.1, but a specimen with a central cooling water channel of approximately 3.4 mm in diameter. These specimens are commercially available from TheSys GmbH, located in Kirchentellinsfurt.

[0104] Designed as a circulating system, the MHTA (see Figure 1) consists of several modular test modules that enable practical load conditions and cycle simulations.

[0105] This modular structure allows for differentiated testing of the mechanism and effectiveness of coolant preparations under various operating conditions. Essentially, the heat flow density or volumetric flow rate of a coolant can differ independently of each other when different coolants are used.

[0106] Unlike actual internal combustion engines, MHTA enables the achievement of consistently high heat flow density and simultaneously low coolant flow temperature at the heated surface by controlling the coolant flow temperature across the cooling zone (Christina Berger, Torsten Trossmann, Markus Kaiser, MTZ 2008, 02, volume 69, page 148).

[0107] Therefore, it is possible to test different heat flow densities in MHTA for various coolants with different coolant volume flow rates, corrosion behavior, and heat removal characteristics.

[0108] The measurement accuracy of this method is approximately + / - 2°C.

[0109] The composition of the coolant used (units are in weight % or weight ppm)

[0110] [Table 1]

[0111] Next, an aqueous coolant was prepared by diluting it with the same amount of water having the hardness shown in Table 2, and then an additional 0.3% by weight of the hard water stabilizer shown in Table 2 in the form of a 50% aqueous solution was added to the aqueous coolant.

[0112] Water hardness stabilizers (HWS) used The hard water stabilizers used are commercially available polyacrylic acid or polycarboxylate copolymers, and their molecular weights and Δm results from thermogravimetric analysis are shown in Table 1.

[0113] [Table 2]

[0114] Results of the MHTA trial

[0115] [Table 3]

[0116] Example 1 is Ca 2+ and Mg 2+ To determine the effect of thermal load on the coolant in the absence of cations, distilled water was used.

[0117] In the case of a test plate without deposits, thermal equilibrium is found to be established at a temperature of 210°C 5 hours after the start of the test. During the 30-hour test, the initial temperature rises by +4°C, which may be due to a decrease in heat transfer due to deposition not based on alkaline earth metal compounds, such as the formation of an anti-corrosion layer as a result of corrosion inhibitors.

[0118] In Example 3, a coolant containing alkaline earth metal ion-containing water was tested in the absence of a hard water stabilizer. Deposits formed on the test plate, which reduced heat transfer to such an extent that the temperature of the test plate rose to 316°C, resulting in the power of the test apparatus being turned off.

[0119] Chemical analysis of the deposit revealed that it consists of a mixture of calcium phosphate and magnesium phosphate.

[0120] In Examples 4 and 5, coolants containing alkaline earth metal ion-containing water were tested in the presence of a hard water stabilizer (HWS3) that does not have the molecular weight required in the present invention, or a hard water stabilizer (HWS2) that does not meet the thermogravimetric standards.

[0121] The initial temperature of the test plate was found to be significantly higher than the zero-value starting temperature in Example 1, which suggests undesirable heat transfer.

[0122] In Example 4, the temperature rise over the test period was only +2°C, but the heat transfer remained unfavorable.

[0123] In Examples 2 and 6, the hard water stabilizers HWS1 and HWS4 of the present invention, which meet both criteria (molecular weight and thermogravimetric analysis), are used.

[0124] The starting temperature corresponds to that of Example 1 within the measurement accuracy range, and rises by only +10°C or +2°C during the test process, respectively.

[0125] This indicates that the heat transfer, which was already good at the start, is essentially maintained even when a thermal load is applied to the coolant. Even under thermal load, the hard water stabilizer used was able to complex the alkaline earth metal ions in the water, keeping them in solution, and as a result, no significant deposition of alkaline earth metal compounds was formed during the test process. The observed temperature increase did not exceed (Example 6) or hardly exceed (Example 2) that of the zero sample (Example 1). Several embodiments are shown below. Item 1 A water-based coolant, (A) Water, (B) at least one alkylene glycol, alkylene glycol monoalkyl ether or glycerol, (C) at least one phosphate, carbonate and / or sulfate, which is in the form of the free acid or salt thereof, particularly an alkali metal salt thereof, particularly preferably a sodium or potassium salt thereof, (D) at least one hard water stabilizer, Optionally, further inhibitors and typical coolant components. The hard water stabilizer (D) comprises at least one homo or copolymer comprising acrylic acid and / or methacrylic acid and / or maleic acid and / or itaconic acid in polymerized form, having a weight-average molecular weight Mw determined by GPC of at least 3000 g / mol, preferably at least 3500, particularly preferably at least 4000, and very particularly preferably at least 4500 g / mol, and having a mass loss of 10% by weight or less, preferably 8% by weight or less, particularly preferably 7% by weight or less, very particularly preferably 5% by weight or less, specifically 3% by weight or less, and particularly 2% by weight or less in the temperature range of 200°C to 300°C. The mass loss is measured by thermogravimetric analysis in an argon atmosphere at a flow rate of 40 ml / min and a heating rate of 5 K / min over a temperature range of 30°C to 800°C, with the mass present at 200°C taken as the baseline value, and the decrease due to further heating up to 300°C taken as the mass loss, in an aqueous coolant. Section 2 The aqueous coolant according to item 1, wherein the water (A) is water containing alkaline earth metal ions. Section 3 Component (B) is monomer to tetramer 1,2-ethylene glycol, 1,2-propylene glycol, or 1,3-propylene glycol, or its mono-C 1 ~C 4 - An aqueous coolant selected from the group consisting of alkyl ethers and glycerol, as described in item 1 or 2. Section 4 The aqueous coolant according to item 1 or 2, wherein component (B) is 1,2-ethylene glycol. Section 5 The aqueous coolant according to any one of claims 1 to 4, wherein component (C) is selected from the group consisting of monophosphates, diphosphates, triphosphates and oligophosphates, carbonates, bicarbonates, sulfates and bisulfates as free acids or alkali metal salts. Section 6 The aqueous coolant according to any one of claims 1 to 5, preferably further comprising at least one azole derivative (E) selected from the group consisting of benzimidazole, benzotriazole, toltriazole, 2-mercaptobenzothiazole, (2-benzothiadylthio)acetic acid and 3-(2-benzothiadylthio)propionic acid. Section 7 An aqueous coolant according to any one of claims 1 to 6, further comprising silicates, borates, nitrates, molybdates and mixtures thereof, wherein the coolant additionally comprises at least one inorganic inhibitor (F) selected from the group consisting of silicates, borates, nitrates, molybdates and mixtures thereof in the form of their free acids or salts. Section 8 An aqueous coolant according to any one of claims 1 to 7, further comprising at least one monocarboxylic acid (G1) having 2 to 18 carbon atoms and / or at least one organic dicarboxylic acid (G2) having 4 to 20 carbon atoms. Section 9 Propionic acid, pentanoic acid, 2,2-dimethylpropanoic acid, hexanoic acid, 2,2-dimethylbutanoic acid, cyclohexylacetic acid, octanoic acid, 2-ethylhexanoic acid, nonanoic acid, isononanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, pimelic acid (heptanedioic acid), azelaic acid (nonanedioic acid), sebacic acid (decanediic acid), undecanediic acid, dodecanediic acid, as well as alkyl and alkenyl succinic acids, and glutaric acid, such as 2-methylbutanediic acid, 2-ethyl-3-methylbutanediic acid, 2-ethyl methylbutanediic acid. An aqueous coolant according to any one of claims 1 to 7, further comprising at least one organic carboxylic acid (G) selected from the group consisting of pentanediic acid, 2-dodecylbutanediic acid, 2-dodecenylbutanediic acid, 2-phenylbutanediic acid, 2-(p-methylphenyl)butanediic acid, 2,2-dimethylbutanediic acid, 2,3,4-trimethylpentanediic acid, 2,2,3-trimethylpentanediic acid, glutaconic acid (penta-2-enediic acid), itaconic acid, hexa-2-enediic acid, hexa-3-enediic acid, 5-methylhexa-2-enediic acid, and 2,3-dimethylpenta-2-enediic acid. Section 10 An aqueous coolant according to any one of claims 1 to 9, having a pH of 4 to 11.5 established with lithium hydroxide, sodium hydroxide, or potassium hydroxide. Section 11 - At least 40% by weight of water (A), - At least 30% by weight of alkylene glycol, alkylene glycol monoalkyl ether and glycerol (B), - 0.01% to 5% by weight, preferably 0.02% to 2% by weight, particularly preferably 0.03% to 1% by weight of at least one phosphate, carbonate and / or sulfate (C), - At least one hard water stabilizer (D) in an amount of 0.1% to 2% by weight, - At least one azole(E) in an amount of 0% to 2% by weight, preferably 0.05% to 1% by weight, and particularly preferably 0.1% to 0.5% by weight, - At least one inorganic compound (F) selected from the group consisting of silicates, borates, nitrates, and molybdates, in an amount of 0% to 5% by weight, preferably 0.01% to 2% by weight, and particularly preferably 0.02% to 1% by weight. - At least one organic carboxylic acid (G) in an amount of 0% to 6% by weight, preferably 1% to 5% by weight, and particularly preferably 2% to 4% by weight. - At least one compound selected from the group consisting of defoaming agents, dyes, and bittering substances, in an amount of 0% to 0.2% by weight, preferably 0.001% to 0.15% by weight, and - At least one inorganic base in an amount of 0% to 10% by weight, preferably 0.5% to 8% by weight, and particularly preferably 1% to 7% by weight. This includes, however, - A coolant according to any one of items 1 to 10, provided that the sum of all components is always 100% by weight. Section 12 A coolant concentrate for preparing a coolant described in any one of items 1 to 11, - Water (A) in an amount of 15% by weight or less, preferably 10% by weight or less, and particularly preferably 5% by weight or less. - At least 60% by weight of alkylene glycol, alkylene glycol monoalkyl ether and glycerol (B), - 0.02% to 10% by weight, preferably 0.04% to 4% by weight, particularly preferably 0.06% to 2% by weight of at least one phosphate, carbonate and / or sulfate (C), - At least one hard water stabilizer (D) in an amount of 0.2% to 4% by weight, - At least one azole (E) in an amount of 0% to 4% by weight, preferably 0.1% to 2% by weight, and particularly preferably 0.2% to 1% by weight, - At least one inorganic compound (F) selected from the group consisting of silicates, borates, nitrates, and molybdates, in an amount of 0% to 10% by weight, preferably 0.02% to 4% by weight, and particularly preferably 0.04% to 2% by weight. - At least one organic carboxylic acid (G) in an amount of 0% to 12% by weight, preferably 2% to 10% by weight, and particularly preferably 4% to 8% by weight. - At least one compound selected from the group consisting of defoaming agents, dyes, and bittering substances, in an amount of 0% to 0.4% by weight, preferably 0.002% to 0.3% by weight, and - At least one inorganic base in an amount of 0% to 20% by weight, preferably 1% to 16% by weight, and particularly preferably 2% to 14% by weight. This includes, however, - A coolant concentrate, provided that the sum of all components is always 100% by weight. Item 13 A method for cooling an internal combustion engine, wherein relatively high-temperature heat from a heat source is transferred to a coolant via at least one first heat exchanger, the coolant is passed to at least one second heat exchanger in a cooling circuit, and in the second heat exchanger, heat is removed from the coolant at a relatively low temperature. - The composition described in any one of items 1 to 11 is used as a coolant. - The aforementioned relatively high temperature is 60°C to 300°C, preferably 70°C to 280°C, and particularly preferably 80°C to 250°C. - The relatively low temperature is -50°C to 100°C, preferably -40°C to 90°C, and particularly preferably -30°C to 80°C, and - A method wherein the relatively low temperature is at least 50°C lower than the relatively high temperature. Item 14 A method for increasing heat transfer on a surface with a high wall temperature and cooled with a phosphate-containing aqueous coolant, wherein the phosphate-containing aqueous coolant is at least one homo or copolymer comprising acrylic acid and / or methacrylic acid and / or maleic acid and / or itaconic acid in polymerized form, and comprises a hard water stabilizer (D) having a weight-average molecular weight Mw determined by GPC of at least 3000 g / mol, preferably at least 3500, particularly preferably at least 4000, and very particularly preferably at least 4500 g / mol, and having a mass loss of 10% by weight or less, preferably 8% by weight or less, particularly preferably 7% by weight or less, very particularly preferably 5% by weight or less, specifically 3% by weight or less, and particularly 2% by weight or less in the temperature range of 200°C to 300°C. Section 15 A method for reducing or preventing the precipitation of alkaline earth metal compounds from a phosphate-containing aqueous coolant, wherein the aqueous coolant is supplemented with at least one hard water stabilizer (D), which is a homo or copolymer comprising acrylic acid and / or methacrylic acid and / or maleic acid and / or itaconic acid in polymerized form, having a weight-average molecular weight Mw determined by GPC in an amount of at least 3000 g / mol, preferably at least 3500, particularly preferably at least 4000, and very particularly preferably at least 4500 g / mol, and having a mass loss of 10% by weight or less, preferably 8% by weight or less, particularly preferably 7% by weight or less, very particularly preferably 5% by weight or less, specifically 3% by weight or less, and particularly 2% by weight or less in the temperature range of 200°C to 300°C. Section 16 Use of a coolant according to any one of paragraphs 1 to 11 for removing heat in an internal combustion engine or a hybrid of a fuel cell and / or a battery, wherein the cooling system for cooling the internal combustion engine includes the coolant according to the present invention. Section 17 The use of a hard water stabilizer (D) in an aqueous coolant, particularly a coolant containing a phosphate (C), which is a homo or copolymer containing acrylic acid and / or methacrylic acid and / or maleic acid and / or itaconic acid in polymerized form, having a weight-average molecular weight Mw determined by GPC of at least 3000 g / mol, preferably at least 3500, particularly preferably at least 4000, and very particularly preferably at least 4500 g / mol, and having a mass loss of 10% by weight or less, preferably 8% by weight or less, particularly preferably 7% by weight or less, very particularly preferably 5% by weight or less, specifically 3% by weight or less, and particularly 2% by weight or less. Section 18 A vehicle having an internal combustion engine or a hybrid of a fuel cell and / or a battery, wherein the cooling system for cooling the internal combustion engine includes a coolant according to the present invention.

Claims

1. It is an aqueous coolant, (A) Water, (B) at least one alkylene glycol, alkylene glycol monoalkyl ether or glycerol, (C) at least one phosphate, carbonate and / or sulfate, which is in the form of the free acid or salt thereof, (D) at least one hard water stabilizer, The hard water stabilizer (D) comprises at least one homo or copolymer containing acrylic acid in a polymerized form, having a weight-average molecular weight Mw determined by GPC of at least 3500 to 25000 g / mol, and having a mass loss of 10% by weight or less in the temperature range of 200°C to 300°C. The mass loss is measured by thermogravimetric analysis in an argon atmosphere at a flow rate of 40 ml / min and a heating rate of 5 K / min over a temperature range of 30°C to 800°C, with the mass present at 200°C taken as the reference value, and the decrease due to further heating up to 300°C taken as the mass loss, in an aqueous coolant.

2. The aqueous coolant according to claim 1, wherein the water (A) is water containing alkaline earth metal ions.

3. Component (B) is monomer to tetramer 1,2-ethylene glycol, 1,2-propylene glycol, or 1,3-propylene glycol, or its mono-C １ ~C ４ - An aqueous coolant according to claim 1 or 2, selected from the group consisting of alkyl ethers and glycerol.

4. The aqueous coolant according to claim 1 or 2, wherein component (B) is 1,2-ethylene glycol.

5. The aqueous coolant according to any one of claims 1 to 4, wherein component (C) is selected from the group consisting of monophosphates, diphosphates, triphosphates and oligophosphates, carbonates, bicarbonates, sulfates and bisulfates as free acids or alkali metal salts.

6. The aqueous coolant according to any one of claims 1 to 5, further comprising at least one azole derivative (E).

7. An aqueous coolant according to any one of claims 1 to 6, further comprising silicates, borates, nitrates, molybdates, and mixtures thereof, wherein it further comprises at least one inorganic inhibitor (F) selected from the group consisting of silicates, borates, nitrates, molybdates, and mixtures thereof in the form of their free acids or salts.

8. An aqueous coolant according to any one of claims 1 to 7, further comprising at least one monocarboxylic acid (G1) having 2 to 18 carbon atoms and / or at least one organic dicarboxylic acid (G2) having 4 to 20 carbon atoms.

9. Propionic acid, pentanoic acid, 2,2-dimethylpropanoic acid, hexanoic acid, 2,2-dimethylbutanoic acid, cyclohexylacetic acid, octanoic acid, 2-ethylhexanoic acid, nonanoic acid, isononanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, pimelic acid (heptanedioic acid), azelaic acid (nonanedioic acid), sebacic acid (decandioic acid), undecandioic acid, dodecandioic acid, 2-methylbutanediic acid, 2-ethyl-3-methylbutanediic acid, 2-ethylpentanedioic acid, 2-dodecylbutanediic acid The aqueous coolant according to any one of claims 1 to 7, further comprising at least one organic carboxylic acid (G) selected from the group consisting of 2-dodecenylbutanediic acid, 2-phenylbutanediic acid, 2-(p-methylphenyl)butanediic acid, 2,2-dimethylbutanediic acid, 2,3,4-trimethylpentanediic acid, 2,2,3-trimethylpentanediic acid, glutaconic acid (penta-2-enediic acid), itaconic acid, hexa-2-enediic acid, hexa-3-enediic acid, 5-methylhexa-2-enediic acid, and 2,3-dimethylpenta-2-enediic acid.

10. An aqueous coolant according to any one of claims 1 to 9, having a pH of 4 to 11.

5.

11. The aqueous coolant according to any one of claims 1 to 10, wherein the hard water stabilizer (D) has a weight-average molecular weight Mw of at least 4,000 to 10,000 g / mol.

12. The aqueous coolant according to any one of claims 1 to 10, wherein the hard water stabilizer (D) has a weight-average molecular weight Mw of at least 4500 g / mol.

13. The aqueous coolant according to any one of claims 1 to 10, wherein the hard water stabilizer (D) has a mass loss of 5% by weight or less in a temperature range of 200°C to 300°C.

14. The aqueous coolant according to any one of claims 1 to 10, wherein the hard water stabilizer (D) has a mass loss of 2% by weight or less in a temperature range of 200°C to 300°C.

15. - At least 40% by weight of water (A), - At least 30% by weight of alkylene glycol, alkylene glycol monoalkyl ether and glycerol (B), - 0.01% to 5% by weight of at least one phosphate, carbonate and / or sulfate (C), - At least one hard water stabilizer (D) in an amount of 0.1% to 2% by weight, - At least one azole (E) in an amount of 0% to 2% by weight, - 0% to 5% by weight of at least one inorganic compound (F) selected from the group consisting of silicates, borates, nitrates, and molybdates. - At least one organic carboxylic acid (G) in an amount of 0% to 6% by weight, - At least one compound selected from the group consisting of compounds of the type denatonium benzoate as a defoaming agent, dye, and bittering agent, in an amount of 0% to 0.2% by weight, and - At least one inorganic base in an amount of 0% to 10% by weight This includes, however, - The coolant according to any one of claims 1 to 14, provided that the total amount of all components is always 100% by weight.

16. A coolant concentrate for preparing the coolant described in any one of claims 1 to 15, - Water (A) at a weight of 15% or less, - At least 60% by weight of alkylene glycol, alkylene glycol monoalkyl ether and glycerol (B), - 0.02% to 10% by weight of at least one phosphate, carbonate and / or sulfate (C), - At least one hard water stabilizer (D) in an amount of 0.2% to 4% by weight, - At least one azole (E) in an amount of 0% to 4% by weight, - 0% to 10% by weight of at least one inorganic compound (F) selected from the group consisting of silicates, borates, nitrates, and molybdates. - At least one organic carboxylic acid (G) in an amount of 0% to 12% by weight, - At least one compound selected from the group consisting of compounds of the type denatonium benzoate as a defoaming agent, dye, and bittering agent, in an amount of 0% to 0.4% by weight, and - At least one inorganic base in an amount of 0% to 20% by weight This includes, however, - A coolant concentrate, provided that the sum of all components is always 100% by weight.

17. A method for cooling an internal combustion engine, wherein relatively high-temperature heat from a heat source is transferred to a coolant via at least one first heat exchanger, the coolant is passed to at least one second heat exchanger in a cooling circuit, and in the second heat exchanger, heat is removed from the coolant at a relatively low temperature. - The composition according to any one of claims 1 to 14 is used as a coolant. - The aforementioned relatively high temperature ranges from 60°C to 300°C. - The aforementioned relatively low temperature is -50°C to 100°C, and - A method wherein the relatively low temperature is at least 50°C lower than the relatively high temperature.

18. A method for increasing heat transfer on a surface with a high wall temperature and cooled with a phosphate-containing aqueous coolant, wherein the phosphate-containing aqueous coolant comprises a hard water stabilizer (D) which is at least one homo or copolymer containing acrylic acid in a polymerized form, has a weight-average molecular weight Mw determined by GPC at least 3500 to 25000 g / mol, and has a mass loss of 10% by weight or less in a temperature range of 200°C to 300°C. The mass loss is measured by thermogravimetric analysis in a temperature range of 30°C to 800°C in an argon atmosphere at a flow rate of 40 ml / min and a heating rate of 5 K / min, with the mass present at 200°C taken as the reference value, and the decrease due to further heating up to 300°C taken as the mass loss.

19. A method for reducing or preventing the deposition of alkaline earth metal compounds from a phosphate-containing aqueous coolant, wherein at least one hard water stabilizer (D) is added to the aqueous coolant, which is at least one homo or copolymer containing acrylic acid in a polymerized form, has a weight-average molecular weight Mw determined by GPC at least 3,500 to 25,000 g / mol, and has a mass loss of 10% by weight or less in the temperature range of 200°C to 300°C, wherein the mass loss is measured by thermogravimetric analysis in the temperature range of 30°C to 800°C at a flow rate of 40 ml / min and a heating rate of 5 K / min in an argon atmosphere, the mass present at 200°C is taken as a reference value, and the decrease due to further heating up to 300°C is taken as the mass loss.

20. Use of a coolant according to any one of claims 1 to 14 for removing heat from an internal combustion engine or a hybrid of a fuel cell and / or a battery, wherein the cooling system for cooling the internal combustion engine includes the coolant according to any one of claims 1 to 14.

21. The use of a hard water stabilizer (D) in an aqueous coolant, which is a homo or copolymer containing acrylic acid in a polymerized form, having a weight-average molecular weight Mw determined by GPC in an amount of at least 3500 to 25000 g / mol, and having a mass loss of 10% by weight or less in a temperature range of 200°C to 300°C, wherein the mass loss is measured by thermogravimetric analysis in a temperature range of 30°C to 800°C at a flow rate of 40 ml / min and a heating rate of 5 K / min in an argon atmosphere, the mass present at 200°C is taken as a reference value, and the decrease due to further heating up to 300°C is taken as the mass loss.

22. A vehicle having an internal combustion engine or a hybrid of a fuel cell and / or a battery, wherein the cooling system for cooling the internal combustion engine includes the coolant described in any one of claims 1 to 14.

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