NEW LOW-VISCOSE FUNCTIONAL LIQUIDS

Description

[0001] The present invention describes low-viscosity functional fluids, especially brake fluids based on organic silicon compounds and alkoxy glycols.

[0002] These brake fluids have a high dry and wet boiling point and a low low-temperature viscosity, which makes them particularly suitable for modern brake systems.

[0003] Typical functional fluids contain mixtures of alkoxy glycols and their boric acid esters. These are widely used as brake fluids. Increasing demands on brake fluids require ever higher dry and wet boiling points while simultaneously reducing viscosity.

[0004] The current requirement according to DOT 5.1 demands dry and wet boiling points of more than 260 and 180 °C respectively, as well as a kinematic viscosity at -40 °C of less than 900 mm² / s.

[0005] At least one silicone ester-based brake fluid is freely available on the market, which has a silicon content of 8 wt%, meaning it is essentially a pure reaction product of an organic silicon compound with alkoxy glycols.

[0006] According to the product data sheet, this product has very high dry and wet boiling points of 320 and 270 °C respectively, but a high kinematic viscosity at -40 °C of 1300 mm² / s, which does not meet the requirements of DOT 5.1.

[0007] Such silicone ester-based fluids and their use as hydraulic oils are known from DE-OS 2147853. In the examples, the silicone esters are used either in pure form or in mixtures with boric acid esters and alkoxy glycols. Mixtures of the silicone esters with alkoxy glycols are not described.

[0008] Research Disclosure 694049, published on January 17, 2022, describes compositions of silicone esters and alkoxy glycols. Neither the wet nor dry boiling points of these compositions, nor their viscosity, are specified, so their suitability as brake fluids cannot be assessed.

[0009] The object of the present invention was to develop brake fluids that retain the advantage of high dry and wet boiling points of silicon ester-based compounds and reduce the viscosity at least to the low level required by DOT 5.1, preferably to a kinematic viscosity at -40 °C of no more than 750 cSt (mm² / s) as required in ISO 4925, Class 6.

[0010] This problem was solved by functional fluids with a viscosity at -40 °C according to FMVSS 116 of no more than 750 cSt, containing (A) at least one alkoxyglycol according to formula (I) H3CO-[-CH2-CH2-O-]n-H, wherein n is an integer from 2 to 5 and for at least 30 wt% of all components of formula (I) n = 3; (B) at least one alkoxyglycol according to formula (II) R1<-O-[-CH2-CH2-O-]m-H, wherein R1<C2- to C4-alkyl, m is an integer from 2 to 6 and for at least 65 wt% of all components of formula (II) m = 3; (C) optionally at least one glycol according to formula (III) HO-[-CH2-CH2-O-]k-H, wherein k is an integer of at least 2 and for at least 80 wt% of all components of formula (III) k = 2 or 3; (D) at least one additive selected from the group consisting of corrosion inhibitors. Amines, stabilizers, defoamers and lubricants, (E) at least one silicon organic compound of formula (IV) R 11< x -Si(-[-OC H< 2 -CH 2 -] z -OR 12< ) 4-x wherein x is a positive integer 1, 2 or 3,preferably 2 z is an integer from 2 to 4, R 11 < C 1 to C 4 alkyl, particularly methyl or ethyl, particularly preferably methyl, and R 12 < C 1 to C 4 alkyl, particularly methyl or n-butyl, particularly preferably methyl, wherein the proportion of (E) is 40 to 55 wt%, preferably 43 to 55 wt%, particularly preferably 45 to 53 wt%, most preferably 47 to 52 wt%, (A) 24 to 45 wt%, (B) 5 to 20 wt%, preferably 7 to 15 wt%, (C) 0 to 10 wt%, preferably 0 to 5 wt%, (D) more than 0 to 5 wt%, provided that the sum of all components (A) to (E) always equals 100 wt%, wherein in components (A) to (C) and (E) the sum of all alkoxyglycols or glycols with n, m, k and z = 2 is greater than 0 (zero) and not more than 10 mol%, the sum of all alkoxyglycols or glycols with n, m, k and z = 3 is at least 60 mol%, and the sum of all alkoxyglycols or glycols with n, m,k and z = 4 constitute more than 0 mol% to 20 mol% and the proportion of boric acid esters with alkoxy glycols or glycols does not exceed 3 wt%.

[0011] While silicone ester-based compounds exhibit high dry and wet boiling points but excessively high viscosity, low-molecular-weight glycols or alkoxyglycols show low viscosity but also low boiling points. However, the higher the degree of alkoxylation of the alkoxyglycols, the higher their boiling point rises, but at the same time, the advantage of low viscosity is lost.

[0012] The functional fluids according to the invention exhibit high dry and wet boiling points, yet possess a low viscosity, thus fulfilling the above requirements. These properties are achieved through a balanced and coordinated selection of components exhibiting high dry and wet boiling points and those exhibiting low viscosity. In particular, the degree of alkoxylation of the glycols or alkoxyglycols is selected such that these compounds represent a compromise between a sufficiently high boiling point and a sufficiently low viscosity.

[0013] It has been found that glycols and alkoxyglycols based on triethylene glycol offer this compromise between low viscosity and high dry or wet boiling point; therefore, these species constitute at least 60% of functional fluids.

[0014] Although glycols and alkoxyglycols based on diethylene glycol have a low viscosity, they lower the required boiling point, so their share is no more than 10%.

[0015] Conversely, glycols and alkoxyglycols based on tetraethylene glycol have a high boiling point but also a relatively high viscosity; therefore, their share does not exceed 20%.

[0016] Glycols have a relatively high viscosity due to their two free hydroxyl groups, so their proportion in the functional fluid should not exceed 10 wt%, preferably 5 wt%.

[0017] The percentages refer to the mol% of the respective oligomers mentioned in components (A), (B), (C) and (E), taking into account that the alkoxyglycols in component (E) are incorporated (4-x) times.

[0018] These components are described in detail as follows: Component (A) is at least one alkoxyglycol of formula (I) H 3 CO-[-CH 2 -CH 2 -O-] n -H wherein n is an integer from 2 to 5, preferably 2 to 4 and particularly preferably 3 or 4 and for at least 30 wt% of all components of formula (I) n = 3.

[0019] These can be one to four, preferably one to three, particularly preferably one or two, and most particularly preferably one alkoxyglycol.

[0020] Typical components (A) are diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether and pentaethylene glycol monomethyl ether.

[0021] Among these, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether and tetraethylene glycol monomethyl ether are preferred, triethylene glycol monomethyl ether and tetraethylene glycol monomethyl ether are particularly preferred, and triethylene glycol monomethyl ether is most particularly preferred.

[0022] Typically, component (A) is a mixture consisting mainly of triethylene glycol monomethyl ether and tetraethylene glycol monomethyl ether, in which higher and lower alkylene glycol monomethyl ethers preferably each constitute less than 10 wt%, and particularly preferably together less than 10 wt%. Most preferably, component (A) is mainly triethylene glycol monomethyl ether, in which higher and lower alkylene glycol monomethyl ethers preferably each constitute less than 20 wt%, and particularly preferably together less than 10 wt%.

[0023] The proportion of triethylene glycol monomethyl ether in component (A) is at least 30 wt%, preferably at least 40 wt%, particularly preferably at least 50 wt% and most preferably at least 60 wt%.

[0024] In a preferred embodiment, the proportion of triethylene glycol monomethyl ether in component (A) is at least 75 wt%, particularly preferably at least 85 wt%, most preferably at least 90 wt%, and in particular at least 95 wt%.

[0025] Component (B) is at least one alkoxyglycol of formula (II) R 1< -O-[-CH 2 -CH 2 -O-] m -H wherein R 1< C 2 - to C 4 -alkyl, preferably ethyl, n-propyl, n-butyl, particularly preferably ethyl and n-butyl and most preferably n-butyl, m an integer from 2 to 6, preferably 2 to 5, particularly preferably 2 to 4 and most preferably 3 or 4 and m = 3 applies to at least 65 wt% of all components of formula (II),

[0026] These can be one to five, preferably one to four, particularly preferably one to three, most preferably one or two, and in particular one alkoxyglycol.

[0027] Preferred compounds (B) are the corresponding oligoethylene glycol monoethyl ether, oligoethylene glycol mono n-propyl ether and oligoethylene glycol mono n-butyl ether, particularly preferably oligoethylene glycol monoethyl ether and oligoethylene glycol mono n-butyl ether and most preferably oligoethylene glycol mono n-butyl ether.

[0028] The oligoethylene glycol monoalkyl ethers are preferably diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether, tetraethylene glycol monoalkyl ether and pentaethylene glycol monoalkyl ether, particularly preferably diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether and tetraethylene glycol monoalkyl ether, most preferably triethylene glycol monoalkyl ether and tetraethylene glycol monoalkyl ether and in particular triethylene glycol monoalkyl ether.

[0029] In a preferred embodiment, component (B) is a mixture consisting mainly of triethylene glycol mono n-butyl ether and tetraethylene glycol mono n-butyl ether, wherein higher and lower alkylene glycol monoalkyl ethers preferably each constitute less than 10 wt%, and particularly preferably together less than 10 wt%. Most preferably, component (B) is mainly triethylene glycol mono n-butyl ether, wherein higher and lower alkylene glycol monoalkyl ethers preferably each constitute less than 20 wt%, and particularly preferably together less than 10 wt%.

[0030] The proportion of triethylene glycol monoalkyl ether in component (B) is at least 65 wt%, preferably at least 70, particularly preferably at least 75 and most particularly preferably at least 80 wt%.

[0031] The optional component (C) is at least one glycol, for example one to four, preferably one to three, particularly preferably one or two and most particularly preferably a compound according to formula (III) HO-[-CH 2 -CH 2 -O-] k -H wherein k is an integer of at least 2 and at least 80 wt% of all components of formula (III) k = 2 or 3 holds.

[0032] Examples of such compounds are diethylene glycol, triethylene glycol, tetraethylene glycol and pentaethylene glycol; diethylene glycol, triethylene glycol and tetraethylene glycol are preferred, and diethylene glycol and triethylene glycol are particularly preferred.

[0033] Preferably, at least 80 wt% of all components (C) are diethylene glycol and triethylene glycol, particularly preferably at least 85 wt%, very preferably at least 90 wt%, and particularly preferably at least 95 wt%. In a preferred embodiment, at least 60 wt% of component (C) is diethylene glycol, preferably at least 75 wt%, very preferably at least 85 wt%, and particularly preferably at least 90 wt%.

[0034] Furthermore, the brake fluids according to the invention contain as component (D) at least one additive selected from the group consisting of corrosion inhibitors, amines, stabilizers, defoamers and lubricants.

[0035] Preferably, the components (D) are selected from the group consisting of alkylamine ethoxylates, alkanolamines, fatty acids, esters of phosphonic acid, esters of phosphoric acid, heterocyclic nitrogenous organic compounds, alkylamines, phenothiazines, phenolic compounds, alkoxylates of ricinoleic acid, castor oil or any other ricinoleic acid ester and ethoxylated phenols and C1-C20 alkanols with a degree of ethoxylation of 10 to 100.

[0036] Component (D), which may be present in the functional liquid composition, is an additive package, preferably comprising one or more additives with corrosion-inhibiting properties. Preferably, the at least one additive with corrosion-inhibiting properties is selected from alkylamine ethoxylates and alkanolamines, more preferably selected from the group consisting of alkylamine ethoxylates and trialkanolamines.

[0037] The alkylamine group in the aforementioned alkylamine ethoxylates can be a secondary or, preferably, a primary aliphatic monoamine that can be ethoxylated. Secondary or, preferably, primary aliphatic monoamines are typically used; however, polyamines with at least one secondary and / or primary amino group that can be ethoxylated may also be used. The alkyl groups on the nitrogen atom usually comprise saturated linear or branched alkyl groups; however, unsaturated linear or branched alkyl groups, or saturated or unsaturated cycloalkyl groups, may also be included under the term "alkyl group."

[0038] In a preferred embodiment, the alkylamine ethoxylates comprise at least one linear or branched C3 to C20 alkyl chain, preferably at least one linear or branched C6 to C13 alkyl chain, particularly preferably at least one linear or branched C7 to C12 alkyl chain, most preferably at least one linear or branched C8 to C10 alkyl chain, and most preferably a linear C8 alkyl chain. Preferably, the term "alkyl chain" here means saturated and non-cyclic hydrocarbon residues, and particularly preferably linear unbranched alkyl groups. The alkylamine ethoxylates may also comprise mixtures of such alkyl chains, for example, a mixture of homologous alkyl residues, depending on the specific industrial or natural origin of the alkylamines used.

[0039] Suitable examples of individual alkylamine molecules capable of ethoxylation and also suitable as surfactants for the present invention are n-propylamine, isopropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, n-pentylamine, tert-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, 2-ethylhexylamine, n-nonylamine, n-decylamine, 2-propylheptylamine, n-undecylamine, n-dodecylamine, n-tridecylamine, isotridecylamine, n-tetradecylamine, n-pentadecylamine, n-hexadecylamine, n-heptadecylamine, n-octadecylamine, n-nonadecylamine, and n-eicosylamine. Di-(n-hexyl)amine, di-(n-heptyl)amine, di-(n-octyl)amine, di-(2-ethylhexyl)amine, di-(n-nonyl)amine, di-(n-decyl)amine, di-(2-propylheptyl)amine, di-(n-undecyl)amine, di-(n-dodecyl)amine, Di-(n-tridecyl)amine, di-(isotridecyl)amine, di-(n-tetradecyl)amine, di-(n-pentadecyl)amine, di-(n-hexadecyl)amine, di-(n-heptadecyl)amine, di-(n-octadecyl)amine, di-(n-nonadecyl)amine, Di-(n-eicosyl)amine, n-hexylmethylamine, n-heptylmethylamine,n-Octylmethylamine, (2-Ethylhexyl)methylamine, n-Nonylmethylamine, n-Decylmethylamine, (2-Propylheptyl)methylamine, n-Undecylmethylamine, n-Dodecylmethylamine, n-Tridecylmethylamine, Isotridecylmethylamine, n-Tetradecylmethylamine, n-Pentadecylmethylamine, n-hexadecylmethylamine, n-heptadecylmethylamine, n-octadecylmethylamine, n-nonadecylmethylamine and n-eicosylmethylamine.

[0040] Such alkyl residues can originate entirely from petrochemical production, for example technical C 8 -C 15 alkyl mixtures, 2-ethylhexyl or 2-propylheptyl, or be based wholly or partially on renewable raw materials, for example fatty amines such as stearyl; amines, oleylamines or tallowamines can be used as a basis for the alkylamine ethoxylates.

[0041] The degree of ethoxylation is typically 1 to 35 ethylene oxide ("EO") units per alkylamine molecule, meaning that at least one alkylamine ethoxylate comprises 1 to 35 EO units, preferably 1.5 to 15 EO units, more preferably 1.8 to 9 EO units, and most preferably 2 to 6 EO units. The stated degree of ethoxylation is a statistical value; that is, the alkylamine ethoxylates are normally to be considered as mixtures of species (homologs) with varying numbers of EO units.In a particularly preferred embodiment of the present invention, the at least one alkylamine ethoxylate comprises at least one linear C3 to C20 alkyl chain and 1 to 35 EO units; particularly preferably, the at least one alkylamine ethoxylate comprises at least one linear C6 to C13 alkyl chain and 1.5 to 15 EO units; most preferably, the at least one alkylamine ethoxylate comprises at least one linear C7 to C11 alkyl chain and 1.8 to 9 EO units; in particular, the at least one alkylamine ethoxylate comprises at least one linear C8 to C10 alkyl chain and 2 to 6 EO units.

[0042] Such alkylamine ethoxylates can be primary amines with one oxyethylene chain of the general formula alkyl-NH-(CH₂CH₂O)m-H, or primary amines with two oxyethylene chains of the general formula alkyl-N[(CH₂CH₂O)pH][(CH₂CH₂O)q-H], or secondary amines of the general formula (alkyl)₂N-(CH₂CH₂O)mH, or mixtures of such primary amines with one oxyethylene chain and such primary amines with two oxyethylene chains, or mixtures of such primary and secondary amines, where m and (p + q) are the total degrees of ethoxylation, respectively. "Alkyl" in the above formulas normally means C₃ to C₂₀ alkyl, preferably C₆ to C₁₃ alkyl, more preferably C₇ to C₁₂ alkyl, and most preferably C₈ to C₁₀ alkyl, as defined above. Other alkylamine species may also be present in smaller amounts, especially at low total ethoxylation levels below 2.

[0043] A typical suitable alkylamine ethoxylate is octylamine (caprylamine) with 2 EO units, which is commercially available.

[0044] The aforementioned alkylamine ethoxylates can be prepared by conventional methods, such as the reaction of alkylamine with ethylene oxide catalyzed by alkali metal hydroxides or by double metal cyanides, as are known to those skilled in the art. The alkylamine ethoxylates exhibit, in part, corrosion-inhibiting properties and, in part, solvent properties for the functional fluid composition or brake fluid according to the present invention.

[0045] Component (D) of the present functional liquid composition may, in addition to the alkylamine ethoxylates, comprise at least one further additive with corrosion-inhibiting effect.

[0046] 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; phosphites and phosphates such as ethyl phosphate, dimethyl phosphate, isopropyl phosphate, n-butyl phosphate, triphenyl phosphite, and diisopropyl phosphite; reaction products of phosphorus pentoxide with alkoxy glycols, as described above as components (A) or (B); heterocyclic nitrogenous organic compounds such as benzotriazole, tolutriazole, 1,2,4-triazole, benzoimidazole, purine, adenine, and derivatives of such heterocyclic organic compounds; and alkylamines such as mono- and di-(C4- to C20-alkyl)amines, e.g.n-Butylamine, n-hexylamine, n-octylamine, 2-ethylhexylamine, isononylamine, n-decylamine, n-dodecylamine, oleylamine, di-n-propylamine, diisopropylamine, dini-butylamine, di-n-amylamine, cyclohexylamine and salts of such alkylamines; alkanolamines such as mono-, di- and trimethanolamine, mono-, di- and triethanolamine, mono-, di- and tri-n-propanolamine and mono-, di- and triisopropanolamine. Triethanolamine and triisopropanolamine are preferred, triisopropanolamine is particularly preferred.

[0047] Of course, mixtures of the above-mentioned additives with corrosion-inhibiting effects can also be used.

[0048] In addition to the alkylamine ethoxylates and possibly the additives with corrosion-inhibiting effects, other common additives may be included in the additive package of component (D), for example stabilizers such as pH stabilizers, antioxidants such as phenothiazine and phenolic compounds, e.g. hydroxyanisole and bisphenol A, defoamers and dyes.

[0049] In a preferred embodiment, component (D), as a lubricant, comprises at least one alkoxylate of ricinoleic acid, castor oil, or any other ricinoleic acid ester, preferably ricinoleic acid or castor oil, and most preferably castor oil. This castor oil, as defined in this description, is an at least partially and preferably fully esterified acylglycerol, wherein at least one, preferably at least two, of the acyl groups are ricinoleic acid or isoricinoleic acid, preferably ricinoleic acid.

[0050] For example, the mixture of fatty acids preferably comprises a mixture of two molecules of ricinoleic acid with a fatty acid that does not carry a hydroxyl group, preferably selected from the group consisting of oleic acid, linoleic acid, palmitic acid and stearic acid.

[0051] In a preferred embodiment, the castor oil has an OH number of 160 to 173 mg KOH / g. The alkoxylate of ricinoleic acid, castor oil, or any other ricinoleic acid ester is preferably prepared by reacting a saturated or unsaturated hydroxy-substituted C8 to C22 fatty acid or an ester thereof, in particular by reacting ricinoleic acid, castor oil, or any other ricinoleic acid ester with at least one alkylene oxide. The alkylene oxide can be propylene oxide, butylene oxide, styrene oxide, or preferably ethylene oxide. Mixtures of such alkylene oxides, leading to statistical or block structures of alkylene oxide units, can also be used.

[0052] Specifically, the structure of the alkoxylate preferably comprises a saturated or unsaturated C8 to C22 fatty monocarboxylic acid or at least one saturated or unsaturated C8 to C22 fatty monocarboxylic acid unit in the molecule, which is esterified with one or more oxyalkylenes with the free carboxylic acid function, if such a free carboxylic acid function is present in the molecule and bears a hydroxyl group located on the fatty acid side chain of the alkoxylate, which is etherified by one or more oxyalkylene units. Examples of such saturated or unsaturated hydroxyl-substituted C 8 to C 22 fatty monocarboxylic acids or units thereof, preferably saturated or unsaturated hydroxyl-substituted C 14 to C 20 fatty monocarboxylic acids or units thereof, as a basis for the alkoxylates are 10-hydroxystearic acid, 12-hydroxystearic acid and in particular ricinoleic acid.Such unsaturated hydroxyl-substituted C8 to C22 fatty monocarboxylic acids can be used as free carboxylic acids or as corresponding esters for the preparation of the alkoxylate. In the case of ricinoleic acid, castor oils, as its naturally occurring triglyceride, can advantageously be reacted by transesterification with an alkylene oxide, yielding the desired ricinoleic acid alkoxylate and glycerol. Any other ester of ricinoleic acid can be used as a starting material for the transesterification, e.g., the corresponding di- or monoglyceride or the corresponding methyl, ethyl, propyl, or butyl ester. Depending on the conditions of the alkoxylation reaction with esters of ricinoleic acid, especially with castor oils, the ester can retain its carboxylic acid ester and, in particular, its glycerol triester function, and is alkoxylated solely at the hydroxyl group on the fatty acid side chain, either once or multiple times, by oxyalkylene units.

[0053] The alkoxylate mentioned, in particular the alkoxylate of ricinoleic acid, castor oil, or any other ricinoleic acid ester, typically comprises 2 to 200, preferably 4 to 100, particularly preferably 6 to 80, most preferably 10 to 50, and particularly 20 to 40 alkylene oxide units, which are preferably ethylene oxide units. "Number of alkylene oxide units" means moles of alkylene oxide per mole of saturated or unsaturated hydroxyl-substituted C8 to C22 fatty monocarboxylic acid or units thereof as the basis for the alkoxylate. When using castor oil, which is the triglyceride of ricinoleic acid, the amount of alkylene oxide used for the alkoxylation refers to 3 equivalents of ricinoleic acid or units thereof to be alkoxylated. At higher degrees of alkoxylation, the number of alkylene units is an average value, a statistical number, due to a distribution of alkoxylation homologs in the product.There can be two types of hydroxyl groups in the molecule to be alkoxylated, i.e., one to be esterified (or transesterified) and the other to be etherified; esterification may or may not occur, etherification will always occur.

[0054] Processes for the alkoxylation, in particular ethoxylation, of carboxylic acids or esters thereof, such as castor oil, are known in the prior art and therefore do not need to be described further in this application.

[0055] In a preferred embodiment, the functional liquids according to the invention contain at least one compound selected from the group consisting of benzotriazole, tolutriazole, 1,2,4-triazole and benzoimidazole.

[0056] In a further preferred embodiment, the functional liquids according to the invention additionally or independently, preferably additionally, contain at least one compound selected from the group consisting of alkylamine ethoxylates with a linear C 8 to C 10 alkyl chain and 2 to 6 EO units, mono-, di- and triisopropanolamine.

[0057] In a further preferred embodiment, the functional liquids according to the invention additionally or independently, preferably additionally, contain at least one 10- to 50-fold ethoxylated alkoxylate of ricinoleic acid, castor oil or another ricinoleic acid ester.

[0058] The defoaming agents as component (D) are mostly ethoxylated phenols and C 1 -C 20 -alkanols with a degree of ethoxylation of 10 to 100 ethylene oxide ("EO") units per hydroxy group, preferably 15 to 75 times ethoxylated C 1 -C 20 -alkanols.

[0059] Furthermore, the brake fluid according to the present invention contains at least one organic silicon compound (E) of formula (IV) R 11< x -Si(-[-O-CH 2 -CH 2 -] z -OR 12< ) 4-x wherein x a positive integer 1, 2 or 3, preferably 1 or 2, particularly preferably 2, z an integer from 2 to 4, preferably 3, R 11< C 1 - to C 4 alkyl, particularly methyl or ethyl, particularly preferably methyl and R 12< C 1 - to C 4 alkyl, particularly methyl or n-butyl, particularly preferably methyl.

[0060] As explained above, these organic silicon compounds, especially those with x = 1 and 2, and particularly those with x = 2, exhibit high wet and dry boiling points. The presence of these compounds (E) in the brake fluid therefore increases these boiling points, but also generally increases its viscosity. Therefore, the aim is to select the proportion of component (E) as high as necessary to achieve the desired boiling points, while simultaneously selecting the type and quantity of components (A) to (C), and especially (A) and (B), in such a way that they reduce the high viscosity of component (E) while simultaneously possessing sufficiently high wet and dry boiling points themselves to meet the desired target values.

[0061] For this purpose, the brake fluids according to the invention contain at least one organic silicon compound (E), preferably one to four, more preferably one to three, most preferably one or two and in particular one.

[0062] In compounds (E), the R 11< groups can be C 1 to C 4 alkyl groups, preferably methyl, ethyl or n-butyl, particularly preferably methyl or ethyl, and most preferably methyl. The x R 11< groups can be the same or different independently of one another; preferably they are the same.

[0063] The number x of residues R 11< is from 1 to 3, preferably 1 or 2 and particularly preferably 2.

[0064] The substructures H-[-O-CH₂-CH₂-]z-OR12< are alkylene glycol monoalkyl ethers, as described above for compounds (A) and (B). Preferably, R12< is a C₁- to C₄-alkyl ether, preferably methyl, ethyl, or n-butyl, particularly preferably methyl or n-butyl, and most preferably methyl. The running index z is a positive integer from 2 to 4, preferably 3 or 4, and most preferably 3.

[0065] In a preferred embodiment, the substructures H-[-O-CH 2 -CH 2 -] z -OR 12< are selected from the group consisting of diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monoethyl ether, diethylene glycol mono n-butyl ether, triethylene glycol mono n-butyl ether and tetraethylene glycol mono n-butyl ether, preferably triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, triethylene glycol mono n-butyl ether and tetraethylene glycol mono n-butyl ether, particularly preferably triethylene glycol monomethyl ether and triethylene glycol mono n-butyl ether.

[0066] In a preferred embodiment, the substructures H-[-O-CH 2 -CH 2 -] z -OR 12< are the same alkylene glycol monoalkyl ethers as used as components (A) and / or (B), particularly preferably the same alkylene glycol monoalkyl ethers as used as components (A).

[0067] The composition of the functional fluids according to the invention, preferably the brake fluids according to the invention, is as follows: Component (E) 40 to 55 wt%, preferably 43 to 55 wt%, particularly preferably 45 to 53 wt%, most preferably 47 to 52 wt%, Component (A) 24 to 45 wt%, preferably 24 to 40 wt%, particularly preferably 24 to 35 wt%, most preferably 24 to 30 wt%, (B) 5 to 20 wt%, preferably 7 to 15 wt%, (C) 0 to 10 wt%, preferably 0 to 5 wt%, (D) more than 0 to 5 wt%, preferably 1 to 4 wt%, provided that the sum of all components (A) to (E) always equals 100 wt%.

[0068] It is a preferred embodiment of the present invention that the glycol (C) content in the functional liquids according to the invention does not exceed the glycol content inherent in the manufacturing process of components (A) and (B), i.e., no additional glycol (C) is added to the functional liquid. Particularly preferably, the glycol (C) content in the functional liquids according to the invention is not more than 1% by weight, particularly preferably not more than 0.75% by weight, and most preferably not more than 0.5% by weight.

[0069] In another preferred embodiment of the present invention, at least one glycol (C) is present, particularly preferably in amounts exceeding the manufacturing-related proportion of glycol in components (A) and (B), most preferably in amounts of 1 to 10 wt%, particularly 1 to 5 wt%.

[0070] This embodiment is particularly preferred when the presence of multinucleate organic silicon compounds (see below) is desired.

[0071] The following applies: in components (A) to (C) and (E) The sum of all alkoxyglycols or glycols with n, m, k and z = 2 is greater than 0 (zero) and not more than 10 mol%; the sum of all alkoxyglycols or glycols with n, m, k and z = 3 is at least 60 mol%; and the sum of all alkoxyglycols or glycols with n, m, k and z = 4 is greater than 0 mol% up to 20 mol% turn off.

[0072] Furthermore, the proportion of boric acid esters with alkoxy glycols or glycols is not more than 3 wt%, preferably not more than 2.5, particularly preferably not more than 2, most particularly preferably not more than 1.5, in particular not more than 1 and especially not more than 0.5 wt%.

[0073] Since components (A), (B) and (C) contain reactive groups capable of reacting with the organosilicon compounds (E), the composition of the functional liquids according to the invention can change, for example, upon exposure to temperatures higher than room temperature and / or during storage. Furthermore, such a reaction can be accelerated by the presence of amines as additives (D).

[0074] This change in composition can consist, on the one hand, of the exchange of the substructures H-[-O-CH 2 -CH 2 -] z -OR 12< in component (E) by the alkylene glycol monoalkyl ethers (A) and (B), so that the alkylene glycol monoalkyl ethers (A) and (B) are incorporated into component (E) and free alkylene glycol monoalkyl ether H-[-O-CH 2 -CH 2 -] z -OR 12< is formed in the composition.

[0075] On the other hand, in the presence of difunctional diglycols (C), polynuclear organic silicon compounds can also form, i.e., compounds containing more than one silicon atom. For example, dinuclear or trinuclear silicon compounds can form; higher-nuclear compounds only in small quantities, with dinuclear silicon compounds being the most prevalent.

[0076] The structure of such dinuclear silicon compounds is, for example, as follows: R 11< x -Si(-[-O-CH 2 -CH 2 -] z -OR 12< ) 4-x-1 -(-O-[-CH 2 -CH 2 -O-] k -)-SiR 11< x (-[-O-CH 2 -CH 2 -] z -OR 12< ) 4-x-1 where the variables are defined as above. Here, x must be at least 2.

[0077] The structure of trinuclear silicon compounds is, for example, as follows: R 11< x -Si(-[-O-CH 2 -CH 2 -] z -OR 12< ) 4-x-1 -(-O-[-CH 2 -CH 2 -O-] k -)-Si R 11< x (-[-O-CH 2 -CH 2 -] z -OR 12< ) 4-x-2 -(-O- [-CH 2 -CH 2 -O-] k -)-Si R 11< × (-[-O-CH 2 -CH 2 -] z -OR 12< ) 4-x-1 where the variables are defined as above. Here, x must be at least 2.

[0078] The endpoint of this change is the composition of a mixture of all components (A) to (E), which is established starting from the initial composition in thermodynamic equilibrium.

[0079] Accordingly, a further object of the present invention is a reaction mixture obtainable by reacting components (A) to (E) with one another. If diglycols (C) are present, this reaction mixture can also contain polynuclear silicon compounds, for example dinuclear and trinuclear, preferably dinuclear silicon compounds.

[0080] The composition of the reaction mixture lies between the initial composition and the composition at thermodynamic equilibrium.

[0081] The mixtures according to the invention can be used as functional fluids, for example as hydraulic fluids or, in particular, as brake fluids.

[0082] These brake fluids are particularly advantageous for use in vehicles with hydraulic braking systems, such as passenger cars or commercial vehicles. They are especially suitable for electronic or automatic braking systems with anti-lock braking systems (ABS), which require low-viscosity brake fluids even at low temperatures.

[0083] The following examples demonstrate the scope and benefits of the compositions according to the invention, without reducing them to these examples. Examples

[0084] As an example of a brake fluid, Castrol React SRF Racing with a silicon content of approximately 8.0 wt% ± 0.3 wt% (within the limits of measurement accuracy), determined by ICP-OES, was used. This essentially corresponds to a pure silicon ester with triethylene glycol monoalkyl ether as the incorporated alkoxy glycol (compound (E) with x = 2, z = 3 and R 11< and R 12< are each C 1 to C 4 alkyl). This is referred to here as component 1.

[0085] The following formulations were prepared and their properties determined as follows: Dry boiling point (ERBP) according to ASTM D1120, wet boiling point (WERBP) according to SAE J1703, kinematic viscosity according to ASTM D445 unless otherwise specified at -40 °C Example 1

[0086]

[0087] It can be seen that the pure silicon ester, compared to the pure boric acid ester, has slightly higher values ​​for ERBP and WERBP, but a significantly higher low-temperature viscosity (entries 1 vs. 4).

[0088] When blended with alkyl glycol ethers, the silicone ester-based mixtures retain and even extend their advantage in ERBP and WERBP, with the viscosity being reduced almost to the level of the boric ester-based mixtures (entries 2 vs. 5 and 3 vs. 6). Example 2

[0089] A formulation with the following composition (in wt%) was prepared: Example 1 2 3 V1 V2 V3 V4 V5 V6 V7 Component 1 40 50 55 50 50 50 50 50 50 55 BTG 10 10 10 10 0 10 5 5 15 10 MTG 29,2 24,2 29,2 24,2 34,2 34,2 19,2 0 19,2 23,2 MTeG 15 10 0 2 10 0 20 39,2 10 6 DEG 2 2 2 10 2 2 2 2 2 2 Additive mixture 2 2 2 2 2 2 2 2 2 2 Diisopropanolamin 1 1 1 1 1 1 1 1 1 1 Octyldiethanolamine 0,8 0,8 0,8 0,8 0,8 0,8 0,8 0,8 0,8 0,8 Viscosity at -40 °C [mm² / s] 661 704 746 987 705 674 837 1064 805 810 ERBP [°C] 274 276 278 265 274 273 281 289 280 280 ADVERTISING [°C] 165 177 171 157 159 160 163 165 159 166 BTG: Triethylene glycol mono-n-butyl ether (compound (B), m = 3, R 1 ≤ n-butyl) MTG: Triethylene glycol monomethyl ether (compound (A), n = 3) MTeG: Tetraethylene glycol monomethyl ether (compound (A), n = 4) DEG: Diethylene glycol (compound (C), k = 2) Additive mixture: 2.5% corrosion inhibitor, 2.5% and 10.0% lubricant as described in WO 2015 / 052234, composition FFC4, anionic wetting agent 0.25%, amine antioxidant as heat stabilizer 1.5% dissolved in 83.25% MTG

[0090] Furthermore, Examples 3, 4, 6 and 8, as reported in Research Disclosure 694049, published on January 17, 2022, were replicated and their viscosity at -40 °C [mm² / s], ERBP [°C] and WERBP [°C] was determined as in Example 2:

[0091] The comparative example RD3 has a similar content of component 1 and MTG as the inventive example 2, but contains 24 wt% BTG whereas in the inventive example 2 the content of BTG is only 10 wt%, but it has an MTeG content of also 10 wt%.

[0092] This leads to approximately comparable results for the viscosity at -40 °C and the dry boiling point (ERBP), however, the inventive example 2 has a wet boiling point (WERBP) that is 13 °C higher than the comparative example RD3.

[0093] Thus, MTeG as the component (A) according to the invention with n = 4 shows a more favorable influence on the wet boiling point than an increased content of triethylene glycol mono-n-butyl ether (BTG) while maintaining the good values ​​for viscosity and dry boiling point.

[0094] The comparative example RD8 has a similar content of component 1 and MTG as the inventive example 3, but contains only 2 wt% BTG whereas in the inventive example 2 the content of BTG is 10 wt%.

[0095] This leads to approximately comparable results for the viscosity at -40 °C and the dry boiling point (ERBP), however, the inventive example 3 has a wet boiling point (WERBP) that is 4 °C higher than the comparative example RD8.

[0096] Thus, an increased content of BTG (component (B), m = 3, R 1< = Butyl) shows a favorable influence on the wet boiling point while maintaining the good values ​​for viscosity and dry boiling point.

Claims

1. A functional fluid having a viscosity at -40°C to FMVSS 116 of not more than 750 cSt (mm2 / s), comprising (A) at least one alkoxy glycol of formula (I)         H3C-O-[-CH2-CH2-O-]n-H in which n is an integer from 2 to 5 and n = 3 for at least 30% by weight of all components of the formula (I), (B) at least one alkoxy glycol of formula (II)         R1-O-[-CH2-CH2-O-]m-H in which R1 is C2- to C4-alkyl, m is an integer from 2 to 6 and m = 3 for at least 65% by weight of all components of the formula (II), (C) optionally at least one glycol of formula (III)         H-O-[-CH2-CH2-O-]k-H in which k is an integer of at least 2 and k = 2 or 3 for at least 80% by weight of all components of the formula (III), (D) at least one additive selected from the group consisting of corrosion inhibitors, amines, stabilizers, defoamers and lubricants, (E) at least one organic silicon compound of the formula (IV)         R11x-Si(-[-O-CH2-CH2-]z-O-R12)4-x in which x is a positive integer 1, 2 or 3, preferably 2, z is an integer from 2 to 4, R11 is C1- to C4-alkyl, particularly methyl or ethyl, more preferably methyl, and R12 is C1- to C4-alkyl, particularly methyl or n-butyl, more preferably methyl, in which the proportion of (E) is 40% to 55% by weight, preferably 43% to 55% by weight, more preferably 45% to 53% by weight and most preferably 47% to 52% by weight, (A) is 24% to 45% by weight, (B) is 5% to 20% and preferably 7% to 15% by weight, (C) is 0% to 10% by weight, preferably 0% to 5% by weight, (D) is more than 0% to 5% by weight, with the proviso that the sum total of all components (A) to (E) always adds up to 100% by weight, wherein, in components (A) to (C) and (E), - the sum total of all alkoxy glycols or glycols with n, m, k and z = 2 is more than 0 (zero) and not more than 10 mol%, - the sum total of all alkoxy glycols or glycols with n, m, k and z = 3 is at least 60 mol%, and - the sum total of all alkoxy glycols or glycols with n, m, k and z = 4 is more than 0 mol% to 20 mol%, and - the proportion of boric esters with alkoxy glycols or glycols is not more than 3% by weight.

2. The composition according to claim 1, wherein component (A) consists mainly of triethylene glycol monomethyl ether and tetraethylene glycol monomethyl ether.

3. The composition according to claim 1 or 2, wherein the proportion of triethylene glycol monomethyl ether in component (A) is at least 75% by weight, more preferably at least 85%, even more preferably at least 90% and in particular at least 95% by weight.

4. The composition according to any of the preceding claims, wherein component (B) is selected from the group consisting of triethylene glycol mono-n-butyl ether and tetraethylene glycol mono-n-butyl ether.

5. The composition according to any of the preceding claims, wherein component (C) is selected from the group consisting of diethylene glycol and triethylene glycol.

6. The composition according to any of the preceding claims, wherein component (D) comprises at least one compound selected from the group consisting of alkylamine ethoxylates, alkanolamines, heterocyclic nitrogen-containing organic compounds and alkoxylates of ricinoleic acid, of castor oil or of any other ricinoleic ester.

7. The composition according to any of the preceding claims, wherein x = 2 in component (E).

8. The composition according to any of the preceding claims, wherein R11 is methyl in component (E).

9. The composition according to any of the preceding claims, wherein z = 3 in component (E).

10. The composition according to any of the preceding claims, wherein R12 is methyl in component (E).

11. The composition according to any of the preceding claims, wherein the substructures H-[-O-CH2-CH2-]z-O-R12 in component (E) are the same alkylene glycol monoalkyl ethers as used as components (A) and / or (B), more preferably the same alkylene glycol monoalkyl ethers as used as components (A).

12. A reaction mixture obtainable by interreaction of components (A) to (E) according to any of the preceding claims.

13. The reaction mixture according to claim 12, comprising at least one diglycol (C) and at least one polynuclear silicon compound, for example di- or trinuclear, preferably dinuclear, silicon compound.

14. The reaction mixture according to claim 13, wherein the polynuclear silicon compound is selected from the group consisting of         R11x-Si(-[-O-CH2-CH2-]z-O-R12)4-x-1-(-O-[-CH2-CH2-O-]k-)-Si R11x(-[-O-CH2-CH2-]z-O-R12)4-x-1 and         R11x-Si(-[-O-CH2-CH2-]z-O-R12)4-x-1-(-O-[-CH2-CH2-O-]k-)-Si R11x(-[-O-CH2-CH2-]z-O-R12)4-x-2 = (-O-[-CH2-CH2-O-]k-)-Si R11x (-[-O-CH2-CH2-]z-O-R12)4-x-1, in which the variables are as defined in any of the preceding claims and x is at least 2.

15. The use of the compositions and reaction mixtures according to any of the preceding claims as functional fluid, preferably as hydraulic fluid or brake fluid.