Functional fluid

Abstract

The invention relates to a functional fluid composition comprising (A) 74 - 94 wt.% of an alkoxyglycol borate ester of the formula (I) [R1-O-(CH2CH2-O)n]3B (I) wherein R1 represents a C1- to C4-alkyl group or a mixture of such alkyl groups, and n has a value of 2 to 6, (B) from 3 to 23 wt.% of an alkoxyglycol ether of the formula (II) R2-O-(CH2CH2O)mH (II) wherein R2 represents H, a C1- to C4-alkyl radical or a mixture of such alkyl radicals, and m is a number from 2 to 6, (C) from 2 to 5 wt.% of a cycloalkylamine alkoxylate of the formula (III) wherein R3 represents a cycloalkyl radical having 5 to 7 carbon atoms, R is a methyl group or H, and p and q independently of one another represent a number between 1 and 15, (D) at least one additive selected from the group consisting of corrosion inhibitors, alkalinity agents, stabilizers, defoamers, dyes and lubricants.

Description

[0001] The present invention describes a functional fluid, in particular brake fluid, based on glycol ethers and their borate esters and an additive package containing cycloalkylamine alkoxylates. The functional fluid is characterized by a kinematic low-temperature viscosity of less than 1500 centistokes, determined at -40 °C, an equilibrium reflux boiling point (ERBP) of at least 270 °C, and a wet equilibrium reflux boiling point (WERBP) of at least 190 °C according to FMVSS No. 116. Furthermore, the functional fluid exhibits a low tendency for the borate components to precipitate and good noise behavior.

[0002] Functional fluid compositions based on glycols and their borate esters are well known to those skilled in the art. For example, to meet the requirements of DOT 4 or DOT 5.1 brake fluids, these borate ester-based compositions must meet numerous physical properties and performance requirements, particularly with regard to the highest possible dry equilibrium reflux boiling point ("ERBP") and the highest possible wet equilibrium reflux boiling point ("WERBP"), as well as maximum low-temperature kinematic viscosity (e.g., at -40 °C), good corrosion resistance, stability, and compliance with other physical requirements such as pH, reserve alkalinity, and rubber swell.

[0003] While a high weight percent of borate ester in brake fluid compositions is beneficial to meet DOT 4 and DOT 5.1 criteria according to Federal Motor Vehicle Safety Standards (FMVSS) No. 116, specifically a very high wet boiling point (WERBP). Federal Motor Vehicle Safety Standards (FMVSS) No. 116 references 49 CFR § 571.116 in the 10-1-2016 edition and is referred to as FMVSS in this specification, despite the beneficial properties, the content of boron or borate ester in brake fluids is associated with a certain risk of gel formation or precipitation due to the salt formation of the inorganic nature of boron salts, especially as the brake fluids age. As a result, particulate matter may appear in the brake fluid and limit its performance in critical situations.

[0004] US-5750407 teaches a method for testing hydraulic fluids. A water content of 3 to 20 wt.%, based on the hydraulic fluid, is established. The water-containing fluid is then mixed with at least 1 part by volume of tetrahydrofuran or monoethylene glycol dimethyl ether per part by volume of water-containing fluid, after which the formation or non-formation of a precipitate is determined. The examples in US-5750407 show that the combination of low-molecular-weight secondary amines and a high proportion of borate ester exhibits a tendency to precipitate. Fatty amine ethoxylates, such as caprylamine + 2 EO, on the other hand, demonstrate sufficient stability in this precipitation test, even with a high weight proportion of borate ester.

[0005] EP-0617116A1 describes a hydraulic fluid composition with a high boiling point, in particular a high equilibrium reflux boiling point (ERBP) of over 300 °C and a viscosity of maximum 1400 cSt at -40 °C. The composition contains as an additive at least one etheramine with a molecular weight between 120 and 300 of the formula where R3 is a linear or branched radical with at least one ether linkage and does not contain a free OH group, R is a methyl radical or a hydrogen atom, p is an integer from 1 to 3 and q is an integer from 0 to 2.

[0006] EP-2850163 describes a low-viscosity functional fluid composition or brake fluid having a dry equilibrium reflux boiling point (ERBP) of at least 260 °C and / or a wet equilibrium reflux boiling point (WERBP) of at least 180 °C, comprising (A) from 15 to 90% of alkoxyglycol borate ester [R1-O-(CH2CH2-O)n]3B, wherein R1 is a C1 to C8 alkyl radical and n has a value of 2 to 6,10 (B) from 5 to 80% of alkoxyglycol components R2-O-(CH2CH2-O)mH, wherein R2 is a C1 to C8 alkyl radical and m has a value of 2 to 6, (C) from 0.1 to 10% of an additive package comprising additives with a corrosion-inhibiting effect, wherein at least one of the additives contained in the additive package is selected from alkylamine ethoxylates.

[0007] EP-3055391 taught a functional fluid composition useful as a brake fluid, consisting of 0 to 94.99 wt% alkoxyglycols of borate esters, from 5 to 99.99 wt% alkoxyglycols, from 0.01 to 5 wt% alkoxylates of saturated or unsaturated hydroxy-substituted fatty acids such as ricinoleic acid or its esters, wherein the hydroxyl group located on the fatty acid side chain is etherified by at least one oxyalkylene unit, and from 0 to 10 wt% of an additive package containing additives having a corrosion-inhibiting effect.

[0008] US2019 / 0161700 teaches the addition of 0.05 to 5.0 wt. % of a polyetheramine with a molecular weight of 600 to 2000 g / mol as a noise suppression additive in brake fluids. The polyetheramine is used in addition to conventional alkanolamines, alkylamines, or cycloalkylamines.

[0009] EP-3358336 describes a method for evaluating the noise behavior of a fluid, wherein a counter-body is moved relative to a base body while the fluid is located between the counter-body and the base body, during the movement a frictional force (RK) and / or a friction coefficient (RW) between the counter-body and the base body is recorded as a function of a positioning of the counter-body relative to the base body; a friction force fluctuation (RKS) and / or a friction coefficient fluctuation (RWS) is determined from the friction force (RK) and / or a friction coefficient fluctuation (RWS) is determined from the friction force fluctuation (RKS) and / or from the friction coefficient fluctuation (RWS). The invention also relates to a device for evaluating the noise behavior of a fluid.

[0010] A high wet boiling point in brake fluids requires the use of larger amounts of boric acid ester (borate ester). However, at a high weight fraction of borate ester, borate precipitation can occur during the application phase, as described in US-5750407. While suitable formulations are known to avoid the risk of borate salt precipitation, primarily through the use of linear alkylamine ethoxylates, other parameters such as lubrication properties and noise behavior are negatively affected. There is currently no technical solution to achieve a superior wet boiling point (greater than 190 °C) with high weight percent borate ester and superior lubrication.

[0011] According to the present invention, a functional fluid composition has been found that has a wet boiling point (WERBP) above 190°C while simultaneously offering good noise characteristics and a low risk of borate salt precipitation. The functional fluid according to the invention also has a high dry boiling point (ERBP), excellent corrosion resistance, high stability, and meets other physical property requirements such as pH, reserve alkalinity, and rubber swelling.

[0012] The present invention relates to functional fluid compositions containing (A) 74 - 94 wt.% of an alkoxyglycol borate ester of the formula (I) [R 1< -O-(CH 2 CH 2 -O) n ] 3 B (I) wherein R 1< represents a C 1 - to C 4 -alkyl group or a mixture of such alkyl groups, and n has a value of 2 to 6, (B) from 3 to 23 wt.% of an alkoxyglycol ether of the formula (II) R 2 -O-(CH 2 CH 2 O) m -H (II) wherein R 2 is H, a C 1 - to C 4 -alkyl radical or a mixture of such alkyl radicals, and m is a number from 2 to 6, (C) from 2 to 5 wt.% of a cycloalkylamine alkoxylate of the formula (III) wherein R 3 is a cycloalkyl radical having 5 to 7 carbon atoms, a pure methyl group or H, and p and q independently of one another represent a number between 1 and 15, (D) at least one additive selected from the group consisting of corrosion inhibitors, alkalinity agents, stabilizers, defoamers, dyes and lubricants.

[0013] The functional fluid composition according to the invention is also referred to below as functional fluid.

[0014] The present invention comprises, in a second aspect, the use of the functional fluid of the first aspect as brake fluid in brake systems.

[0015] In a third aspect, the present invention comprises a method for hydraulic brake force transmission within an automotive hydraulic brake system by filling the automotive hydraulic brake system with the functional fluid from the first aspect.

[0016] Component (A) of the functional fluid according to the invention according to formula (I) comprises species with a degree of ethoxylation of n = 2 to n = 6, preferably of n = 2 to n = 4, more preferably of n = 3 to n = 4 and very preferably n = 3. The radical R 1< is a C 1 - to C 4 -alkyl radical. R 1< is preferably methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, particularly preferably n-butyl or methyl and in particular methyl. With regard to the degree of ethoxylation and / or the radical R 1<, component (A) can be a single species or a mixture of different species.

[0017] Component (A) is a boric acid ester. Boric acid esters and their preparation processes are widely known. Boric acid esters as a component of the functional fluid of the present invention can be prepared by reacting boric acid with suitable ethoxyglycols. The ethoxyglycol can be a single compound or a mixture of different ethoxyglycols. This ethoxyglycol is preferably identical to component (B).

[0018] Typically, such ethoxyglycols are mixtures of different species that differ in the degree of ethoxylation and / or in the radical R 1<. Preferably, the ethoxyglycols differ in their average degree of ethoxylation, which leads to a distribution of the number m. If the ethoxyglycol is identical to component (B), this also applies to n.

[0019] Examples of suitable boric acid esters include those containing methyl triethylene glycol boric acid ester, which is also known as tris-[2-[2-(2-methoxyethoxy)ethoxy]ethyl)orthoborate.

[0020] Other suitable boric acid esters include those containing methyltetraethylene glycol boric acid ester, methyldiethylene glycol boric acid ester, ethyltetraethylene glycol boric acid ester, ethyldiethylene glycol boric acid ester, n-butyltetraethylene glycol boric acid ester, n-butyldiethylene glycol boric acid ester and mixtures thereof.

[0021] In a preferred embodiment, component (A) comprises at least one alkoxyglycol borate ester of the general formula (I), wherein the degree of ethoxylation has a value of n = 3 and R 1< is a methyl radical.

[0022] Component (B) of the functional fluid according to the invention comprises species having a degree of ethoxylation of m = 2 to m = 6, preferably of m = 2 to m = 4, more preferably of m = 3 to m = 4 and particularly preferably m = 3.

[0023] The radical R 2 is a C 1 - to C 4 -alkyl radical. R 2 is preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, particularly preferably n-butyl or methyl, and in particular methyl.

[0024] Component (B) may be a single species or a mixture of different species with regard to the degree of ethoxylation and / or the radical R 2.

[0025] Examples of suitable alkoxyglycol ethers for component (B) of the present invention include diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, methyl diglycol, methyl triglycol, methyl tetraglycol, methyl pentaglycol, methyl hexaglycol, ethyl diglycol, ethyl triglycol, ethyl tetraglycol, ethyl pentaglycol, ethyl hexaglycol, n-propyl diglycol, n-propyl triglycol, n-propyl tetraglycol, n-propyl pentaglycol, n-propyl hexaglycol, n-butyl diglycol, n-butyl triglycol, n-butyl tetraglycol, n-butyl pentaglycol, n-butyl hexaglycol, and mixtures thereof. The glycol group is an ethylene glycol group.

[0026] In a preferred embodiment, component (B) comprises a mixture of glycol ethers of the general formula (II) which exclusively or predominantly comprises species with m = 3 and / or 4. Predominantly means that at least 60% by weight, preferably at least 75% by weight of component (B) comprises species with m = 3 and / or 4. A particularly preferred mixture of such glycol ethers which form component (B) is a mixture which consists exclusively or predominantly of diethylene glycol, methyl triglycol and n-butyl triglycol.

[0027] Component (C) of the functional fluid composition comprises one or more species of cycloalkylamine alkoxylates, wherein R 3 is a cycloalkyl radical having 5 to 7 carbon atoms and R is a methyl group or H. p and q are each a number between 1 and 15.

[0028] The cycloalkylamine alkoxylate is preferably a primary, saturated cyclohexylamine that has been alkoxylated with ethylene oxide and / or propylene oxide. The cyclohexylamine alkoxylate as a component of component (D) of the functional fluid composition can be a single species or a mixture of different species with respect to the degree of alkoxylation, the type of alkylene oxide, and the ring size of R3.

[0029] The cyclohexylamine alkoxylate is preferably present with two oxyalkylene chains, i.e., as a tertiary amine that is doubly alkoxylated at the amine nitrogen. Primary and secondary cycloalkylamine derivatives with one or no oxyalkylene chains are preferably present in amounts of less than 10 wt.%, particularly less than 3 wt.%. The percentage refers to the total weight of all cycloalkylamine derivatives with no, one, and two oxyalkylene chains.

[0030] The degree of alkoxylation is generally 2 to 15 alkylene oxide units per cycloalkylamine. The stated degree of alkoxylation is a statistical value, meaning that the alkylamine ethoxylates are normally considered to be mixtures of species (homologues) with different numbers of alkoxy units. Preferred alkylene oxides are ethylene oxide and propylene oxide. The alkylene oxide groups p and q can bear identical or different R radicals (ethylene oxide and propylene oxide). They can be randomly distributed or present as defined blocks.

[0031] The preparation of cycloalkylamine alkoxylates is known from the literature. Preferably, 2 equivalents of alkylene oxide per amine are first reacted at elevated temperature, so that almost entirely tertiary amines are formed and no random product distribution is present. In a further step, these cycloalkylamine derivatives with 2 alkylene oxide units are reacted with further alkylene oxide using alkaline catalysts (e.g., NaOH, NaOMe, KOH, KOMe) and methods known from the literature to form a product with a random homolog distribution of different chain lengths. The catalysts used can remain in component (C) or be removed by methods known from the literature. Preference is given to using species of component (C) in which the catalyst has been removed, so that the weight fraction of alkali metal, based on component (C), is less than 0.1 wt. %.

[0032] Preferred cycloalkylamine alkoxylates are cyclohexylamine with 2 EO units, cyclohexylamine with 5 EO units, and cyclohexylamine with 2 EO and 3 PO units, as well as mixtures thereof, where the number of alkoxylene oxide units is the sum of p and q. It is preferred that the cycloalkylamine alkoxylates be present as tertiary amines.

[0033] Component (D) is an additive required to impart certain properties to the functional fluid to meet specifications that must be met for brake fluids according to the current norms and standards FMVSS, SAE J 1703 and ISO 4925. The total amount of all components (D) in the fluid depends on the properties to be achieved and is, for example, 0.1 to 5 wt.%, specifically 0.2 to 3 wt.%.

[0034] Component (D) comprises one or more additives selected from the group consisting of corrosion inhibitors, amines as reserve alkalinity agents, stabilizing antioxidants, defoamers, lubricants and dyes.

[0035] Component (D) may, in addition to component (C), comprise an amine or mixtures of amines as alkalinity agents. These amines differ in chemical composition from component (C). Examples of useful amines are aliphatic amines, especially alkylamines, alkanolamines, alkylamine ethoxylates, and mixtures thereof. Preferred alkylamines are mono- and di-(C4- to C20-alkyl)amines. Examples of suitable alkylamines are n-butylamine, n-hexylamine, n-octylamine, 2-ethylhexylamine, isononylamine, n-decylamine, n-dodecylamine, oleylamine, dn-propylamine, di-isopropylamine, di-n-butylamine, tri-n-butylamine, dinamylamine, and salts of such amines. Examples of suitable alkanolamines are mono-, di- and trimethanolamine, mono-, di- and triethanolamine, mono-, di- and tri-n-propanolamine and mono-, di- and triisopropanolamine.Examples of suitable alkylamine ethoxylates are those linear or branched alkylamine ethoxylates which carry 1.5 to 5 EO units and an alkyl chain with 4 to 18 carbon atoms.

[0036] Component (D) of the functional fluid according to the invention can comprise, in addition to an amine component, at least one additive with corrosion-inhibiting action, although the amines and amine alkoxylates themselves have corrosion protection properties. Common additives with corrosion-inhibiting properties include fatty acids such as lauric, palmitic, stearic, or oleic acid; esters of phosphonic or phosphoric acid with aliphatic alcohols or aliphatic alcohol ethoxylates, such as ethyl phosphate, dimethyl phosphate, isopropyl phosphate, n-butyl phosphate, 2-ethylhexyl phosphate, triphenyl phosphite, and diisopropyl phosphite; alkenyl succinic acid derivatives, heterocyclic nitrogen-containing organic compounds such as benzotriazole, tolyltriazole, 1,2,4-triazole, benzoimidazole, purine, adenine, and derivatives of such heterocyclic organic compounds. Of course, mixtures of the above-mentioned additives with corrosion-inhibiting action can be used.

[0037] Defoamers can be selected from groups of oil-based defoamers such as natural oils, glycerides, waxes, powdered silicon dioxide, alkoxylates such as EO / PO block copolymers, silicone-based defoamers, preferably modified polyether or silicone derivatives and mixtures thereof.

[0038] The fluid may contain one or more lubricants. Suitable lubricants include, for example, alkylene oxide-containing polymers optionally substituted with a C1 to C4 alkyl group, triglycerides, castor oil, ricinoleic acid, and ethoxylates of castor oil or ricinoleic acid, and mixtures thereof. In a preferred embodiment, the lubricants are homopolymers of propylene oxide, copolymers of propylene oxide with ethylene oxide and / or butylene oxide, mono-C1 to C4 alkyl-substituted homopolymers of propylene oxide, mono-C1 to C4 alkyl-substituted copolymers of propylene oxide with ethylene oxide and / or butylene oxide, triglycerides, castor oil, ricinoleic acid, and ethoxylates of castor oil or ricinoleic acid, and mixtures thereof. For such ethoxylates, 1 to 50 ethoxy units are preferred.In a further preferred embodiment, the alkylene oxide-containing polymers, which are optionally substituted with a C 1 to C 4 alkyl group, have a number-average molecular weight in the range from 150 to 3000 g / mol.

[0039] Suitable anti-aging agents or antioxidants include phenolic stabilizers such as bisphenols (e.g., bisphenol A or bisphenol M), butylhydroxytoluene, methoxyphenols, butylated hydroxyanisole, hydroquinone derivatives; sterically hindered amines such as benzylated, alkylated, or styrenated diphenylamine, styrenated phenylamine, substituted piperidine derivatives, phenothiazine derivatives, or quinoline derivatives, and mixtures thereof. In general, all glycol stabilizers known from the literature can be used.

[0040] The functional fluid of the present invention exhibits superior ERBP and WERBP performance. It has an ERBP of at least 275°C, preferably at least 280°C, and a WERBP of at least 190°C, preferably at least 195°C.

[0041] The functional fluid shows superior stability in the THF precipitation test (US-5750407) with excellent low-noise behavior, tested according to the method described in EP-3358336 and a pH value in the range of 7 to 10.

[0042] The functional fluid composition of the present invention further exhibits a low-temperature kinematic viscosity of less than 1500 centistokes ("cSt") (= mm 2 / s), preferably less than 1400 cSt, determined at a temperature of -40 °C. The analytical methods for ERBP, WERBP, and low-temperature viscosity are described in FMVSS 116, to which reference is made.

[0043] In addition to the superior behavior with regard to ERBP and WERBP, the functional fluid composition according to the invention has good corrosion protection, good water compatibility, a pH value between 7 and 10, good stability to low and high temperatures, good oxidation stability, good chemical stability, good behavior towards rubber and elastomers and low foaming. Description of the THF test

[0044] To determine the precipitation tendency of the functional fluids, samples of the fluids to be tested are mixed with 8 and 12 wt% water. 10 mL of these solutions are placed in a 100 mL test tube, each with 40 mL of THF, and, after inserting rubber stoppers, mixed by repeated inversion. The test tubes are stored vertically in a rack, and their appearance is evaluated after three days of storage at room temperature. A distinction is made between a positive evaluation (clear solution) and a negative evaluation (formation of turbidity, precipitate, or sediment, NS). Assessment of noise behavior

[0045] The noise behavior is assessed according to the method described in EP-3358336, whereby the base body is a stainless steel surface and the counter body is a section of EPDM cord with a hardness of 70 IRDH. The combination of steel and EPDM represents a relevant material combination in hydraulic components, for example when an EPDM sealing material is moved across a steel surface. The EPDM is moved across the counter body at a frequency of 0.5 to 2 Hz, and the normal force varies between 15 and 25 N. During the movement, the noise behavior is recorded via a microphone, and the background signal of the environment is subtracted. The noise intensity is given in dB (decibels) above the background noise and is therefore not to be understood as absolute noise intensity.The noise impression is also differentiated qualitatively: quiet = no additional noise is perceived in addition to the background, slightly noticeable = a small but perceptible noise occurs, noticeable = clearly perceptible noises occur.

[0046] The state of the art teaches various amine alkoxylates as suitable additives for brake fluids.

[0047] Linear alkylamine ethoxylates can reduce the risk of borate precipitation analogous to the test procedure in US-5750407 (the so-called THF test). However, the use of linear alkylamine ethoxylates leads to negative lubrication properties between EPDM and steel and thus to noise development. Linear alkylamine propoxylates also exhibit adverse noise behavior in this test. In addition, the reaction products of alkylamines with PO exhibit lower alkalinity, so that the pH value of the functional fluids remains below 7 even at a use rate of 4 wt.% – resulting in a reduced corrosion protection effect.

[0048] Low molecular weight amines such as diisopropanolamine and dibutylethanolamine show an increased tendency to precipitate in the THF test. Examples

[0049] Table 1 shows functional fluids and their properties. The figures are given in wt.% unless otherwise stated.

[0050] Vgl-1 meets the pH requirements, viscosity at -40 °C, and exhibits low noise. However, a precipitate forms in the precipitation test with water and THF, which is due to the tendency of diisopropanolamine and a high weight fraction of borate ester to precipitate, as previously described in US-5750407.

[0051] The tendency to precipitation is avoided, as also described in US-5750407, by the use of octylamine + 2 EO (cf.-2), but this combination is noticeable in the noise behavior.

[0052] The combination of both amines, diisopropanolamine and octylamine + 2 EO (Cf.-3), also shows precipitate formation in the THF precipitation test as soon as sufficient amounts of amine are used to achieve a pH value greater than 7 (see examples Cf.-3, Cf.-4, and Cf.-5). In addition, the combined use of diisopropanolamine and octylamine + 2 EO shows noticeable noise behavior, which is only slightly improved by the addition of lubricants such as castor oil ethoxylate.

[0053] The addition of "noise reducers" known from the literature in the form of polyether monoamines (see also US2019 / 0161700, Vgl-6) leads to a significant improvement in noise behavior, but at a high weight fraction of borate esters they are characterized by a pH value that is too low and do not produce clear, homogeneous fluids at low temperatures.

[0054] Other alkylamine alkoxylate derivatives with longer carbon chains or propylene oxide units instead of ethylene oxide also show noticeable noise behavior (see Figs. 7 and 8) and partly insufficient pH value or turbidity at - 40 °C.

[0055] The inventive examples can meet all requirements for functional fluids through the use of cycloalkylamine alkoxylates. The use of sufficient amounts to achieve a pH value greater than 7 despite the high borate ester content shows no precipitation in the THF precipitation test and results in clear fluids with the desired viscosity at -40 °C. At the same time, the noise behavior is unobtrusive. The inventive examples (Ex-1, Ex-2, Ex-3, and Ex-4) also exhibit a high boiling point (ERBP) of above 280 °C and a wet boiling point (WERBP) of above 200 °C.

Claims

1. Functional fluid compositions containing (A) 74 - 94 wt.% of an alkoxyglycol borate ester of the formula (I) [R 1 -O-(CH2CH2-O) n ]3B (I) where R 1 represents a C1- to C4-alkyl group or a mixture of such alkyl groups, and n has a value of 2 to 6, (B)from 3 to 23 wt.% of an alkoxyglycol ether according to formula (II) R2-O-(CH2CH2O) m -H (II) wherein R2 is H, a C1- to C4-alkyl radical or a mixture of such alkyl radicals, and m is a number from 2 to 6, (C) from 2 to 5% by weight of a cycloalkylamine alkoxylate according to formula (III) wherein R3 is a cycloalkyl radical having 5 to 7 carbon atoms, R is a methyl group or H, and p and q independently of one another represent a number between 1 and 15, (D) at least one additive selected from the group consisting of corrosion inhibitors, alkalinity agents, stabilizers, defoamers, dyes and lubricants.

2. The functional fluid composition of claim 1, wherein the cycloalkylamine alkoxylate in component (C) comprises two ethylene oxide units.

3. Functional fluid composition according to claim 2, wherein the cycloalkylamine alkoxylate in component (C) additionally comprises a further 3 EO or PO units.

4. Functional fluid composition according to claims 1 to 3, wherein the cycloalkylamine alkoxylate in component (C) is a mixture of at least two components comprising a) cyclohexylamine ethoxylated with two ethylene oxide units and, as a further component b) at least one from the group consisting of b1) cyclohexylamine alkoxylated with two ethylene oxide units and three propylene oxide units and b2) cyclohexylamine alkoxylated with five ethylene oxide units.

4. Functional fluid composition according to claims 1 to 3 having a dry equilibrium reflux boiling point (ERBP) of at least 270 °C and / or a wet equilibrium reflux boiling point (WERBP) of at least 190 °C.

5. Functional fluid composition according to claims 1 to 4, having a kinematic low-temperature viscosity of less than 1500 mm 2 / s (centistokes), determined at a temperature of -40°C.

6. Functional fluid composition according to claims 1 to 5, wherein n is 2, 3 or 4, preferably 3 or 4 and in particular 3.

7. Functional fluid composition according to claims 1 to 6, wherein R 1 represents methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, preferably n-butyl or methyl and in particular methyl.

8. Functional fluid composition according to claims 1 to 7, wherein m is 2, 3 or 4, preferably 3 or 4 and in particular 3.

9. Functional fluid composition according to claims 1 to 8, wherein R2 is methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, preferably n-butyl or methyl and in particular methyl.

10. Functional fluid composition according to claims 1 to 9, wherein component (B) is a mixture of glycol ethers of the general formula (II) which comprises at least 60% by weight, preferably at least 75% by weight, based on the weight of component (B), of species with m = 3 and / or 4.

11. Use of the functional fluid according to claims 1 to 10 as brake fluid.

12. A method for hydraulic brake force transmission within an automotive hydraulic brake system, wherein the automotive hydraulic brake system is filled with the functional fluid according to one or more of claims 1-10.

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