Process for the production of organic silicon compounds

Abstract

The present invention relates to a process for the production of organic silicon compounds and to the use of the compounds obtained in this way.

Description

[0001]Process for the preparation of organic silicon compounds Description The present invention relates to a process for the preparation of organic silicon compounds, as well as the use of the compounds thus obtained. Polysiloxanes are known as components of hydraulic fluids or certain brake fluids that meet the so-called DOT 5 standard of the US Department of Traffic. US 3814691 describes the preparation of such organosilanes by reacting the corresponding alkyl silyl chlorides with the desired alcohols, which can be glycol ethers. A disadvantage of the organosilanes obtained by this reaction, however, is the residual chloride content, which can lead to corrosion in the hydraulic system, which can cause leaks under the high pressures prevailing in the system.EP 557027 A1 describes a multi-stage process in which a polysiloxane is first reacted with an alcohol in the presence of a catalyst, the catalyst is separated, and then reacted with a glycol and glycol ether. A disadvantage of this reaction procedure is that a high proportion of high-molecular residue is formed in the first reaction step, which cannot be used in the reaction with the glycol and glycol ether. US 2015 / 0221986 A1 describes the preparation of organic silicon compounds by reacting various alkoxyalkanols with, for example, hexamethylcyclotrisilazane or alkoxysilanes. A disadvantage of the preparation from hexamethylcyclotrisilazane is its high chlorine content, which is inherent in the production process. These cyclic silazanes and siloxanes are obtained industrially by reacting dimethyldichlorosilane with ammonia to form silazanes or hydrolyzing dimethyldichlorosilane to form siloxanes.In the case of silazanes, 2 mol of ammonium chloride are obtained per mol of dimethyldichlorosilane, and in the case of siloxanes, 2 mol of hydrogen chloride are obtained. When using 1 ton of dimethyldichlorosilane, this corresponds to an inevitable production of approximately 830 kg of ammonium chloride in the production of silazanes compared to approximately 565 kg of hydrogen chloride. The production of by-products is therefore significantly higher in the production of silazanes, so that the use of silazanes should be avoided for waste prevention reasons. International application WO 2023 / 152001 (file number PCT / EP2023 / 052428, filing date February 1, 2023) discloses a process for the production of organic silicon compounds in which acids and bases are used as catalysts. The acids are selected from the group consisting of - inorganic mineral acids, - organic sulfonic acids, preferably alkyl or arylsulfonic acids and - acidic ion exchangers.The bases are selected from the group consisting of - (alkali earth) metal oxides or hydroxides - (alkali earth) metal carbonates or bicarbonates - metal alkoxides and - tertiary amines. Thus, only homogeneous catalysts and organic ion exchangers are disclosed as acids. The disadvantage of liquid acids is that they remain in the reaction mixture and must be separated at great expense and are generally not easily recovered. Organic ion exchangers, on the other hand, are comparatively expensive and only stable up to a maximum temperature of 110 to 120 °C.The objective was to provide a process for the preparation of chlorine-free organic silicon compounds, with which the products can be obtained in high yield and purity and from which the catalyst used can be easily separated, so that the reaction mixtures can be used as soon as possible in their intended applications. This objective was achieved by a process for the preparation of organic silicon compounds of the formula (III) (III) R. 1 xSi(-[-O-CH2-CH2-]nOR 3 )4-x or mixtures thereof, in which at least one alkoxyalkyl silane of the formula (Ia) (Ia) R 1 xSi(OR 2 )4-x and / or for the preparation of compounds (III) with x = 2, a cyclic siloxane of the formula (Ib) (Ib) -(-SiR 1 2-O-) y - with at least one alkoxyalkanol of formula (II) (II) R 3 -O-[-CH2-CH2-O-]nH optionally in a solvent at a temperature of 0 to 200 °C, wherein R1 Phenyl or C1-C4-alkyl, preferably C1-C4-alkyl, particularly preferably methyl, ethyl or n-butyl, very particularly preferably methyl or ethyl, R 2 C1-C4-alkyl, particularly preferably methyl, ethyl or n-butyl, very particularly preferably methyl or ethyl, R 3 C1-C4-alkyl, particularly preferably methyl, ethyl or n-butyl, x is a positive integer 1, 2 or 3, y is a positive integer 3 or 4, preferably 3, and n is a positive integer from 2 to 5, preferably from 2 to 4, particularly preferably 2 or 3 and very particularly preferably 3, in which the reaction is carried out in the presence of at least one inorganic heterogeneous catalyst which is an oxide, hydroxide, carbonate, bicarbonate, phosphate, hydrogen phosphate or dihydrogen phosphate of a metal or semimetal from group 3 to 14 (IUPAC nomenclature) of the Periodic Table of the Elements. In the starting compounds of the formula (Ia) (Ia) R 1 xSi(OR2 )4-x can be monoalkoxytrialkylsilane (x = 3), dialkoxydialkylsilane (x = 2), trialkoxymonoalkylsilane (x = 1) or mixtures thereof. If the radical R is 1 If phenyl, the compounds are the corresponding monoalkoxytriphenyl silanes, dialkoxydiphenyl silanes, or trialkoxymonophenyl silanes. For the sake of simplicity, the compounds of formula (Ia) are referred to in the text as alkoxyalkyl silanes, even if the radical R 1a phenyl group is included. If the compounds of formula (Ia) are used as a mixture, the organic silicon compounds of formula (III) are also obtained as a mixture. The ratio of the compounds of formula (Ia) generally corresponds to the ratio of the proportions of the individual compounds of formula (III) in the mixture. Preferred compounds of the formula (Ia) with x = 1 are methyl trimethoxy silane, methyl triethoxy silane, methyl tri n-butoxy silane, ethyl trimethoxy silane, ethyl triethoxy silane, ethyl tri n-butoxy silane, n-propyl trimethoxy silane, n-propyl triethoxy silane, n-propyl tri n-butoxy silane, n-Butyl trimethoxy silane, n-Butyl triethoxy silane, n-Butyl tri n-butoxy silane, Phenyl trimethoxy silane, Phenyl triethoxy silane and Phenyl tri n-butoxy silane. Particularly preferred are methyl trimethoxy silane, methyl triethoxy silane, ethyl trimethoxy silane, ethyl triethoxy silane, very particularly preferred are methyl trimethoxy silane and ethyl trimethoxy silane.Bevorzugte Verbindungen der Formel (Ia) mit x = 2 sind Dimethyl dimethoxy silan, Dimethyl diethoxy silan, Dimethyl di n-butoxy silan, Diethyl dimethoxy silan, Diethyl diethoxy silan, Diethyl di n-butoxy silan, Di n-propyl dimethoxy silan, Di n-propyl diethoxy silan, Di n-propyl di n-butoxy silan, Di n-butyl dimethoxy silan, Di n-butyl diethoxy silan, Di n-butyl di n-butoxy silan, Diphenyl dimethoxy silan, Diphenyl diethoxy silan und Diphenyl di n-butoxy silan. Besonders bevorzugt sind Dimethyl dimethoxy silan, Dimethyl diethoxy silan, Diethyl dimethoxy silan, Diethyl diethoxy silan, ganz besonders bevorzugt sind Dimethyl dimethoxy silan und Di- methyl diethoxy silan.Preferred compounds of the formula (Ia) with x = 3 are trimethyl monomethoxy silane, trimethyl monoethoxy silane, trimethyl mono n-butoxy silane, triethyl monomethoxy silane, triethyl monoethoxy silane, triethyl mono n-butoxy silane, tri n-propyl monomethoxy silane, tri n-propyl monoethoxy silane, tri n-propyl mono n-butoxy silane, Tri n-butyl monomethoxy silane, Tri n-butyl mono-ethoxy silane, Tri n-butyl mono n-butoxy silane, Tri phenyl monomethoxy silane, Tri phenyl mono-ethoxy silane and Tri phenyl mono n-butoxy silane. Particularly preferred are trimethyl monomethoxy silane, trimethyl monoethoxy silane, triethyl monomethoxy silane, triethyl monoethoxy silane, and very particularly preferred are trimethyl monomethoxy silane and triethyl monomethoxy silane. In a preferred embodiment, in the alkoxyalkyl silanes of the formula (Ia) used, x = 1. In a further, particularly preferred embodiment, in the alkoxyalkyl silanes of the formula (Ia) used, x = 2, iePure dialkoxydialkylsilanes are used as compounds of the formula (Ia). In a further preferred embodiment, mixtures of alkoxyalkylsilanes of the formula (Ia) are used, particularly preferably mixtures of compounds with x = 2 and additionally at least one further compound with x = 1 and / or x = 3, very particularly preferably those mixtures in which the compounds with x = 2 make up at least 50 mol% of the mixture, in particular at least 75 mol%, especially at least 85 mol%. To prepare compounds (III) with x = 2, it may also be possible to use cyclic siloxanes of the formula (Ib) (Ib) -(-SiR) as starting compounds. 1 2-O-) y- with y = 3 or 4, preferably 3. Preference is given to hexamethylcyclotrisiloxane or octamethylcyclotetrasiloxane and mixtures thereof. Conceivable, although less preferred, are hexaethylcyclotrisiloxane and octaethylcyclotetrasiloxane. In the event that the desired product is alkoxyalkyloxysilanes of the formula (III) with x = 2, in particular with R 1= Methyl, are to be obtained, it is a preferred embodiment of the present invention to react cyclic siloxanes of the formula (Ib) with at least one alkoxyalkanol of the formula (II). Mixtures of alkoxyalkylsilanes of the formula (Ia) and cyclic siloxanes of the formula (Ib) are also possible, especially when the desired product is to consist predominantly of compounds where x = 2. In the process according to the invention, the alkoxyalkylsilanes of the formula (Ia) are preferred as starting compounds over the cyclic siloxanes of the formula (Ib). In the at least one alkoxyalkanol of the formula (II) (II) R 3 -O-[-CH2-CH2-O-]nH is R 3C1-C4 alkyl, particularly preferably methyl, ethyl or n-butyl and n is a positive integer from 2 to 5, preferably from 2 to 4, particularly preferably 2 or 3 and most preferably 3.Examples of such alkoxyalkanols, which are also referred to as glycol monoalkyl ethers, are diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol mono-n-butyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether and tetraethylene glycol mono-n-butyl ether. Preferred alkoxyalkanols are diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol monomethyl ether, triethylene glycol mono-ethyl ether and triethylene glycol mono-n-butyl ether. Particularly preferred are diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monomethyl ether and Triethylene glycol monoethyl ether and most preferably triethylene glycol monomethyl ether and triethylene glycol monoethyl ether.The alkoxyalkanols can be used individually or in a mixture; purified individuals of the alkoxyalkanols usually contain minor amounts of higher and lower homologous alkoxyalkanols due to the production process. In a preferred embodiment, the proportion of alkoxyalkanols with n = 3 in the total amount of the incorporated alkoxyalkanols in formula (III) is at least 75% by weight, more preferably at least 85% by weight, very preferably at least 90% by weight, and in particular at least 95% by weight. In a further preferred embodiment, the proportion of alkoxyalkanols with n = 2 in the total amount of the incorporated alkoxyalkanols in formula (III) is not more than 20% by weight, more preferably not more than 10% by weight, and very preferably not more than 5% by weight. In minor amounts, the alkoxyalkanols with n = 2 can also contain alkoxyalkanols with n = 1 due to the production process.However, their content in the alkoxyalkanols with n = 2 is preferably below 7.5% by weight, more preferably below 5% by weight, and most preferably below 2.5% by weight. Such alkoxyalkanols with n = 1 are, for example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and ethylene glycol mono-n-butyl ether. In a further preferred embodiment, the proportion of alkoxyalkanols with n of at least 4, preferably with n = 4, based on the total amount of incorporated alkoxyalkanols in formula (III) is not more than 15% by weight, more preferably not more than 5% by weight, and most preferably not more than 3% by weight. In minor amounts, the alkoxyalkanols with n = 4 may also contain alkoxyalkanols with n > 4, depending on the production process. However, their content in the alkoxyalkanols with n = 4 is preferably below 5% by weight, particularly preferably below 2.5% by weight and very particularly preferably below 1% by weight.The sum of all incorporated alkoxyalkanols with n = 2 to 5 in formula (III) is always 100 wt.%. The reaction of the reactants of formulas (Ia) and / or (Ib) with the alkoxyalkanols of formula (II) leads to the organic silicon compounds of formula (III) (III) R. 1 x Si(-[-O-CH2-CH2-] n -OR 3 ) 4-x where the values ​​for R 1 , R 3, n and x essentially correspond to the values ​​of the starting materials used. Due to incomplete reaction or if a mixture of alkoxyalkanols of formula (II) is used in which the individual components have different reactivity, the incorporation ratios in the product of formula (III) may deviate in individual cases from the ratio of the alkoxyalkanols of formula (II) used in the reaction. The starting compounds of formula (Ia) and / or (Ib) and (II) are mixed together in the desired ratio and reacted with one another. The starting compounds can be completely mixed together and heated together to the desired reaction temperature.In a preferred embodiment, the starting compounds of the formula (Ia) and / or (Ib) are initially charged and the alkoxyalkanol of the formula (II) is added in several, for example two to four, preferably two or three portions, or continuously over the reaction time. After complete addition of the alkoxyalkanol, the reaction mixture is heated further to complete the reaction. In a further preferred embodiment, the alkoxyalkanol of the formula (II) is initially charged and the starting compounds of the formula (Ia) and / or (Ib) are added in several, for example two to four, preferably two or three portions, or continuously over the reaction time. After complete addition of the starting compounds of the formula (Ia) and / or (Ib), the reaction mixture is heated further to complete the reaction.This embodiment is particularly preferred when the starting compounds of formula (Ia) and / or (Ib) exhibit significant volatility under the reaction conditions and therefore escape significantly from the liquid reaction mixture. The at least one alkoxyalkanol of formula (II) is used in various molar ratios depending on the starting material used. Use of (Ia) with x = 1: The alkoxyalkanol (II) is used in a molar ratio of at least 3:1, where the molar ratio refers to the ratio of free hydroxyl groups in compound (II) to silicon atoms in compound (Ia). Preferably in a ratio of at least 3.1:1, particularly preferably at least 3.2:1 to 6:1, very particularly preferably at least 3.3:1 to 5:1, in particular at least 3.5:1 to 4:1.- Use of (Ia) with x = 2 or (Ib): The alkoxyalkanol (II) is used in a molar ratio of at least 2:1, where the molar ratio refers to the ratio of free hydroxyl groups in compound (II) to silicon atoms in compound (Ia) or (Ib). Preferably in a ratio of at least 2.1:1, particularly preferably at least 2.2:1 to 5:1, very particularly preferably at least 2.3:1 to 4:1, in particular at least 2.5:1 to 3:1. - Use of (Ia) with x = 3: The alkoxyalkanol (II) is used in a molar ratio of at least 1:1, where the molar ratio refers to the ratio of free hydroxyl groups in compound (II) to silicon atoms in compound (Ia). Preferably in a ratio of at least 1.1:1, particularly preferably at least 1.2:1 to 4:1, very particularly preferably at least 1.3:1 to 3:1, in particular at least 1.5:1 to 2:1.In general, the alkoxyalkanol (II) is used in a molar ratio of at least 1 : 1 per group to be replaced (R. 2 O-) in the compound of formula (Ia), preferably at least 1.1:1, particularly preferably at least 1.2:1 to 4:1, very particularly preferably at least 1.3:1 to 3:1, in particular at least 1.5:1 to 2:1. If mixtures of compounds (Ia) with different values ​​for x are used, the statistical mean value x' of the alkyl groups R 1which results from the molar proportions of the individual compounds and their respective value for x for the number of alkyl groups in the respective individual. If the mixture also contains at least cyclic siloxane of the formula (Ib), its proportion per silicon atom contained is calculated with x = 2. For example, for a mixture of compounds (Ia) with 30 mol% x = 1, 60 mol% x = 2 and 10 mol% x = 3, a statistical functionality of alkyl groups R 1 of x' = 0.3 * 1 + 0.6 * 2 + 0.1 * 3 = 1.8. This results in a statistical functionality of alkoxy groups (R 2 O-) or Si-O bonds of (4 – x') = 2.2. A mixture of compounds (Ia) with 40 mol% x = 1, 40 mol% x = 2, 10 mol% x = 3 and 10 mol% hexamethylcyclotrisiloxane results in a statistical functionality of alkyl groups R 1of x' = 0.4 * 1 + 0.4 * 2 + 0.1 * 3 + 0.1 * 3 * 2 = 2.1. Accordingly, a statistical functionality of Si-O bonds of 0.4 * 3 + 0.4 * 2 + 0.1 * 1 + 0.1 * 3 * 2 = 2.7 results. The alkoxyalkanol (II) is then used in an at least equimolar ratio based on Si-O bonds, preferably in at least a 1.1-fold excess, particularly preferably in a 1.2 to 4-fold and very particularly preferably in at least a 1.3 to 3-fold excess. It represents a preferred embodiment of the present invention to use the at least one alkoxyalkanol of the formula (II) in an excess and to leave it in the product after completion of the reaction. In this way, mixtures of organic silicon compounds of the formula (III) and at least one alkoxyalkanol of the formula (II) are obtainable.These mixtures are preferably essentially composed as follows: 35 to 70 wt% organic silicon compound of the formula (III): 65 to 30 wt% at least one alkoxyalkanol of the formula (II), particularly preferably 40 to 60: 40 to 60 wt% and very particularly preferably 45 to 55: 55 to 45 wt% of the compounds of the formula (III): compounds of the formula (II). Residual solvent may still be present in minor amounts; these residues are preferably not more than 5 wt%, particularly preferably not more than 3 wt%, very particularly preferably not more than 2 wt% and in particular not more than 1 wt%. In one embodiment, the starting compounds are mixed with one another without further solvents, which has the advantage that no solvent has to be separated from the reaction mixture after the reaction has ended.This is particularly preferred when the viscosity of the starting compounds and the reaction mixture is sufficiently low under the conditions to ensure conveying and mixing of the liquids. In a further preferred embodiment, the reaction is carried out in at least one solvent, preferably precisely one solvent. Preferably, the at least one solvent is selected from the group consisting of - open-chain or cyclic ethers, - alkanols and - hydrocarbons. Examples of open-chain and cyclic ethers are diethyl ether, di-n-butyl ether, tert-butyl methyl ether, tert-butyl ethyl ether, tert-amyl methyl ether, diphenyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol di-n-butyl ether, tetrahydrofuran and dioxane.Examples of alkanols are C1 to C10 alkanols; preferred are methanol, ethanol, isopropanol, n-propanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-hexanol, n-heptanol, 2-ethylhexanol, n-octanol, 2-propylheptanol, and n-decanol. If an alkanol is used as a solvent, a preferred embodiment is the alkanol R. 2OH as a solvent. Alkanols are only preferred as solvents when a metal alkoxide is used as the base. In this case, the alkanol that is also used as the metal alkoxide is preferred as the solvent. Otherwise, the use of alkanols as solvents is less preferred. Preference is given to the use of hydrocarbons as solvents; examples of these are those which predominantly comprise aliphatic, cycloaliphatic, or aromatic C5 to C14 hydrocarbons. Preferred aromatic hydrocarbons are toluene, o-, m-, or p-xylene, trimethylbenzene isomers, tetramethylbenzene isomers, ethylbenzene, cumene, tetrahydronaphthalene, and mixtures containing such. (Cyclo)aliphatic hydrocarbons are, for example, decalin, alkylated decalin and isomer mixtures of straight or branched alkanes and / or cycloalkanes, in particular cyclopentane, cyclohexane, methylcyclohexane and cycloheptane.Preferred alkanes are n-pentane, pentane isomer mixtures, n-hexane, hexane isomer mixtures, n-heptane, heptane isomer mixtures, n-octane, octane isomer mixtures, nonane isomer mixtures, n-decane and decane isomer mixtures. Further examples of solvents are the Solvesso® brands from ExxonMobil Chemical, especially Solvesso® 100 (CAS No. 64742-95-6, predominantly C9 and C10 aromatics, boiling range approximately 154 – 178 °C), 150 (boiling range approximately 182 – 207 °C) and 200 (CAS No. 64742-94-5), as well as the Shellsol® brands from Shell, Caromax® (e.g. Caromax® 18) from Petrochem Carless and Hydrosol from DHC (e.g. as Hydrosol® A 170). Hydrocarbon mixtures of paraffins, cycloparaffins and aromatics are also known under the names crystal oil (e.g. crystal oil 30, boiling range approximately 158 – 198 °C or crystal oil 60: CAS No. 64742-82-1), white spirit (e.g. also CAS No.64742-82-1) or solvent naphtha (light: boiling range about 155 - 180 °C, heavy: boiling range about 225 - 300 °C) are commercially available. The aromatics content of such hydrocarbon mixtures is generally more than 90% by weight, preferably more than 95, more preferably more than 98 and most preferably more than 99% by weight. It may be advantageous to use hydrocarbon mixtures with a particularly reduced naphthalene content. Particular preference is given to using a hydrocarbon which, under the reaction conditions, acts as an entraining agent for water, particularly when using cyclic siloxanes of the formula (Ib), or for the alkanol R. 2OH, particularly when using alkoxyalkylsilanes of formula (Ia). Preferred hydrocarbons are those which form a heteroazeotrope and, after distillative removal from the reaction mixture upon cooling, form two phases, of which the hydrocarbon phase is recycled back into the reaction. Particularly preferably, the at least one solvent is selected from the group consisting of cyclohexane, methylcyclohexane, benzene, toluene, xylene, hexane, and heptane. If a solvent is used, the concentration of the reactants in the solution is generally 10 to 90 wt.%, preferably 20 to 80, particularly preferably 30 to 70, and very particularly preferably 40 to 60 wt.%. By separating the solvent, e.g., by distillation, the concentration increases during the course of the reaction. Although it is possible to carry out the reaction of the starting compounds purely thermally,However, according to the invention, the reaction is preferably carried out in the presence of at least one inorganic heterogeneous catalyst. The inorganic heterogeneous catalyst can be an acidic or basic, preferably acidic, inorganic heterogeneous catalyst. The inorganic heterogeneous catalyst is an oxide, hydroxide, carbonate, bicarbonate, phosphate, hydrogen phosphate, or dihydrogen phosphate of a metal or semimetal from groups 3 to 14 (IUPAC nomenclature) of the Periodic Table of the Elements. The corresponding compounds of groups 1 and 2 (alkali and alkaline earth metals) are generally too soluble in water to be stable in the reaction mixture and are therefore usually unsuitable as a heterogeneous catalyst in the reaction. The metal or semimetal is preferably selected from groups 4 (titanium group), 12 (zinc group),13 (boron group) or 14 (carbon group) according to the IUPAC nomenclature of the Periodic Table of the Elements. The metal or metalloid is preferably selected from the group consisting of titanium, zirconium, zinc, boron, aluminum, and silicon. The heterogeneous catalyst is particularly preferably an oxide or phosphate. Examples of such acidic inorganic heterogeneous catalysts are - Natural clay minerals: kaolinite, bentonite, attapulgite, montmorillonite, clarite, Fuller's earth, zeolites (X, Y, A, H-ZSM, etc.), cation-exchanged zeolites, clays, silica, quartz sand, aluminum oxides, diatomaceous earth - Metal oxides and sulfides: ZnO, CdO, Al2O3, CeO2, ThO2, TiO2, ZrO2, SnO2, PbO, As2O5, Bi2O3, Sb2O5, V2O5, Cr2O3, MoO3, WO3, CdS, ZnS - Metal salts: CuSO4, ZnSO4, CdSO4, Al2(SO4)3, FeSO4, Fe2(SO4)3, CoSO4, NiSO4, Cr2(SO4)3, (NH4)2SO4, Zn(NO3)2, Bi(NO3)3, Fe(NO3)3, BPO4, AlPO4, CrPO4, FePO4, Cu3(PO4)2, Zn3(PO4)2, Ti3(PO4)4, Zr3(PO4)4, Ni3(PO4)2, AgCl, CuCl, AlCl3, TiCl4, SnCl4, AgClO4,- Mixed oxides: SiO2-Al2O3, SiO2-TiO2, SiO2-SnO2, SiO2-ZrO2, SiO2-BeO, SiO2-MgO, SiO2-CaO, SiO2-SrO, SiO2-ZnO, SiO2-Ga2O3, SiO2-Y2O3, SiO2-La2O3, SiO2-MoO3, SiO2-WO3, SiO2-V2O5, SiO2-ThO2, Al2O,-MgO, Al2O3-ZnO, Al2O3-CdO, Al2O3 -B2O3, Al2O3-ThO2, Al2O3-TiO2, Al2O3-ZrO2, Al2O3-V2O5, Al2O3-MoO3, Al2O3-WO3, Al2O3-Cr2O3, Al2O3-Mn2O3, Al2O3-Fe2O3, Al2O3-Co3O4, Al2O3-NiO,TiO2-CuO, TiO2-MgO, TiO2-ZnO, TiO2-CdO, TiO2-ZrO2, TiO2-SnO2, TiO2-Bi2O3, TiO2-Sb2O5, TiO2-V2O5, TiO2-Cr2O3, TiO2-MoO3, TiO2-WO3, TiO2-Mn2O3, TiO2-Fe2O3, TiO2-Co3O4, TiO2-NiO, ZrO2-CdO, ZnO-MgO, ZnO-Fe2O3,MoO3-CoO-Al2O3, MoO3-NiO-Al2O3, TiO2-SiO2-MgO, MoO3-Al2O3-MgO, heteropolyacids. More preferably, the acidic solid catalyst is selected from the group consisting of SiO2, Al2O3, TiO2, ZrO2, B2O3, ZnO2, Nb2O5 or mixtures thereof, in particular selected from the group consisting of SiO2, Al2O3, TiO2, ZrO2,ZnO2 or mixtures thereof. In a preferred embodiment, the acidic solid catalyst is a zeolite, preferably an aluminosilicate or titanosilicate of the lattice type FAU (faujasite type), BEA (beta polymorph A type), MFI (ZSM-5 type), LTA, MOR (mordenite type), MEL, MFI / MEL mixed lattices, CHA (chabazite type) or FER (ferrierite type). The zeolites are particularly preferably aluminosilicates of the type zeolite A, zeolite X, zeolite Y, zeolite L, ZSM 5 and ZSM 11, with zeolite ZSM 5 being very particularly preferred. Aluminosilicates have the general composition M, n+ x / n [(AlO2)- x(SiO2) y] × z H2O where M is an n-valent cation, preferably of an alkali or alkaline earth metal, particularly preferably an alkali metal, very particularly preferably sodium or potassium, in particular sodium, n is the charge of the cation M, preferably 1 or 2, particularly preferably 1, y / x is the molar ratio of SiO2 to AlO2 (modulus), which is a rational number of at least 1, preferably 1 to 10, particularly preferably 1 to 5, very particularly preferably 1 to 3, and z is the number of water molecules absorbed by the crystal. The composition of the unit cells of the zeolites is generally as follows: Zeolite A: Na 12 [(AlO2) 12 (SiO2) 12 ] × 27 H2O Zeolite X: Na 86 [(AlO2) 86 (SiO2) 106 ] × 264 H2O Zeolite Y: Na 56 [(AlO2) 56 (SiO2) 136 ] × 250 H2O Zeolite L: K9[(AlO2)9(SiO2) 27] × 22 H2O ZSM 5: Na0.3H3.8[(AlO2)4.1(SiO2)91.9] and ZSM 11: Na0.1H1.7[(AlO2)1.8(SiO2)94.2]. The acidic solid catalyst is particularly preferably selected from the group consisting of silicates, aluminum oxide, silico-aluminates, and zeolites. In particular, the acidic solid catalyst is a molecular sieve. The average pore diameter of such molecular sieves is 0.1 to 1 nm (1 to 10 Å), preferably 0.1 to 0.6, more preferably 0.2 to 0.5 nm. Such molecular sieves are aluminosilicates having a silicon dioxide to aluminum oxide ratio (SiO2 / Al2O3) of 1:0.1 to 1:5, preferably 1:0.2 to 1:3, and more preferably 1:0.2 to 1:1, in particular 1:0.5.The approximate chemical composition of such aluminosilicates is [(K2O)x (Na2O)y] • Al2O3 • 2 SiO2 • 9 / 2 H2O where x is from 0 to 1, preferably from 0 to 0.7, particularly preferably from 0 to 0.5, most preferably 0, y is from 0 to 1, preferably from 0.3 to 1, particularly preferably from 0.5 to 1, most preferably 1, where x + y = 1. Examples of basic solids are basic aluminum oxides. In a further preferred embodiment, the heterogeneous acidic inorganic solid catalyst is a metal oxide or clay mineral loaded with at least one mineral acid. The mineral acids are preferably selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, sulfurous acid, phosphoric acid and phosphorous acid, among these sulfuric acid and phosphoric acid are preferred, and sulfuric acid is particularly preferred.Suitable metal oxides and clay minerals include the above-mentioned compounds, preferably ZnO, Al2O3, TiO2, ZrO2, and SiO2, particularly preferably Al2O3, TiO2, and SiO2, most preferably Al2O3 and SiO2. The loading level can be from 2 to 25 wt% mineral acid based on the support (metal oxide or clay mineral), preferably from 3 to 20, particularly preferably 4 to 17.5, and most preferably 5 to 15 wt%. The mineral acid can usually be applied to the support by spraying or impregnation. The loaded support is then dried and optionally calcined by known methods. The heterogeneous inorganic catalyst is generally used in amounts of 0.01 to 5 wt% based on the mass of the compounds (Ia), (Ib) and (II) in the reaction mixture, preferably 0.05 to 3 wt%.The use of heterogeneous inorganic catalysts opens up special embodiments for the reactors in which the reaction can be carried out: The reaction is preferably carried out in at least one stirred-tank reactor, preferably a reactor with internal stirring or a pumped-circuit circuit, particularly preferably a pumped-circuit circuit. In a particular embodiment, the heterogeneous inorganic catalyst is located in the pumped-circuit circuit, which results in lower thermal stress on the catalyst and enables a lower reaction temperature. If the heterogeneous inorganic catalyst is not located in the pumped-circuit circuit but in the reactor, the catalyst can be arranged in the reactor as a full-volume reactor or a section reactor (tray reactor). In a tray reactor, the catalyst is divided into several successive beds (trays) in one and the same apparatus, which can be individually thermostatted.It is therefore possible to set the reaction temperature separately for each section; preferably, the reaction temperature increases over the course of the reaction. It is also possible to carry out the reaction in more than one stirred tank reactor, for example in a cascade of at least two stirred tank reactors, preferably 2 to 5, particularly preferably 2 to 3 stirred tank reactors. This has the advantage that the temperature in each reactor in the cascade can be set independently of the other reactors and, if necessary, further reactants can be added to the reaction mixture. A further advantage of conducting the reaction in a stirred tank is the easier separation of the gas phase, since the low-boiling alkanol R. 2OH is formed, the removal of which from the reaction mixture causes a favorable equilibrium shift towards the product. The removal of the gas phase can, for example, take place via rectification columns mounted on the stirred tank (see below) and is easier with a stirred tank than with tubular reactors. In a further embodiment, the reaction is carried out in a tubular reactor; preferably, at least one reactor is used which largely exhibits the residence time characteristics of a plug flow. If plug flow is present in a tubular reactor, the state of the reaction mixture (e.g., temperature, composition, etc.) can vary in the flow direction; however, the state of the reaction mixture is the same for each individual cross-section perpendicular to the flow direction. Thus, all volume elements entering the tube have the same residence time in the reactor.Figuratively speaking, the liquid flows through the tube as if it were a series of plugs sliding easily through the tube. In addition, transverse mixing due to the intensified mass transport perpendicular to the flow direction can compensate for the concentration gradient perpendicular to the flow direction. With laminar flow through equipment, backmixing can be avoided and a narrow residence time distribution similar to that in an ideal flow tube can be achieved. The Bodenstein number is a dimensionless number and describes the ratio of the convection current to the dispersion current (e.g., M. Baerns, H. Hofmann, A. Renken, Chemische Reaktionstechnik, Lehrbuch der Technischen Chemie, Volume 1, 2nd edition, p. 332 ff). It thus characterizes the backmixing within a system. where u is the flow velocity [ms -1 ], L for the length of the reactor [m] and Dax for the axial dispersion coefficient [m2 h -1] A Bodenstein number of zero corresponds to complete backmixing in an ideal continuous stirred tank. An infinitely large Bodenstein number, on the other hand, means absolutely no backmixing, as in the case of continuous flow through an ideal flow tube. In tubular reactors, the desired backmixing behavior can be achieved by adjusting the length-to-diameter ratio depending on the material parameters and the flow state. The underlying calculation rules are known to those skilled in the art (e.g. M. Baerns, H. Hofmann, A. Renken: Chemische Reaktionstechnik, Lehrbuch der Technischen Chemie, Volume 1, 2nd edition, p. 339 ff). If the aim is to achieve behavior with as little backmixing as possible, the Bodenstein number defined above is preferably chosen to be greater than 10, particularly preferably greater than 20, and in particular greater than 50.For a Bodenstein number greater than 100, the tubular reactor then largely has a plug flow character. In one embodiment, the tubular reactor has at least two temperature zones; the reaction temperature is preferably increased during the course of the reaction. To enable the separation of the gas phase forming during the reaction, it is advantageous to arrange apparatus for separating the gas phase between successive tubular reactors, for example flashpots or thin-film evaporators, in which the temperature for the next tubular reactor can also be adjusted. In a further embodiment, several tubular reactors are connected in parallel, for example in the form of a tube bundle reactor. This can have at least 2, preferably at least 3, more preferably at least 5, most preferably at least 10, and in particular at least 20 tubes.An upper limit of up to 500, preferably up to 250, more preferably up to 100, and most preferably up to 50 tubes is conceivable. Here, too, the gas phase formed during the reaction must be separated off in an apparatus for separating the gas phase, for example a separator, flashpot, or thin-film evaporator. As a rule, after a single pass through a tubular reactor or tube bundle reactor, at least one further reaction stage is required to complete the reaction. In a preferred embodiment, the reaction can initially be carried out in at least one or more tubular reactors, which are passed through either serially or in parallel in the form of a tube bundle reactor. The reactor output is then fed into at least one, preferably exactly one, stirred tank reactor, which is preferably equipped with a rectification column for separating off the gas phase.This reactor configuration can be operated with or without a pumped circulation system. In a further preferred embodiment, the reaction can initially be carried out in at least one or more stirred tank reactors, after which the reactor effluent is subsequently fed into a tubular reactor. With this reactor configuration, high conversions up to almost full conversion are possible. The reaction temperature is from 0 (zero) to 200 °C, preferably from 40 to 190 °C, more preferably from 50 to 180 °C, most preferably from 60 to 170 °C and in particular from 70 to 160 °C. In a preferred embodiment, the reaction temperature is increased during the course of the reaction, for example by up to 80 °C, preferably by up to 60 °C and more preferably by up to 50 °C.This is particularly preferred when the minor component of the starting compounds has been converted to at least 50%, preferably to at least 70%, and particularly preferably to at least 80%, so that the conversion is completed by increasing the temperature. It may be useful to carry out the reaction at superatmospheric pressure, for example up to 20, preferably up to 15, and particularly preferably up to 10 bar superatmospheric pressure. This is particularly preferred when at least one of the starting compounds has a boiling point that is about 30°C, preferably 20°C below the reaction temperature. If the boiling points of the starting compounds are sufficiently far from the desired reaction temperature, the reaction is preferably carried out at atmospheric pressure.To remove volatile constituents formed during the reaction and any optionally used solvent, a negative pressure of at least 100 mbar below ambient pressure can preferably be applied, more preferably at least 200 mbar, most preferably at least 500 mbar below ambient pressure. The negative pressure is preferably increased during the reaction and separation of the volatile constituents to a final pressure of 200 mbar, preferably 100, more preferably 50 and most preferably 20 mbar. Separated solvent can then be reused for a subsequent reaction. In a preferred embodiment, volatile constituents formed during the reaction and any optionally used solvent are removed by stripping with an inert gas, preferably by passing it through the reaction mixture.Gases that are inert under the reaction conditions can be, for example, nitrogen, argon, carbon dioxide or oxygen-depleted air with an oxygen content below 10 vol%, preferably below 8, particularly preferably below 5 vol%, preferably nitrogen or argon, particularly preferably nitrogen. The inert gas can be introduced through dip tubes, ring lines, nozzles or frits. When the desired conversion has been reached or almost reached and a solvent has been used, it can be separated from the reaction mixture, preferably by distillation or rectification, optionally assisted by stripping with an inert gas. This can preferably be carried out by raising the temperature of the reaction mixture and / or lowering the pressure, preferably by a combination of these two measures. This increase in temperature generally completes the conversion.A single-stage distillation can take place either from the reactor or by passing it through a suitable unit, such as a rotary evaporator, thin-film evaporator, falling-film evaporator, wiped-blade evaporator, Sambay evaporator, etc. and combinations thereof. Rectification is preferably carried out in distillation columns mounted on top of the reactor, such as tray columns, which can be equipped with internals, valves, side draws, etc. if desired. The distillation column or columns used can be realized in a design known per se (see, for example, Sattler, Thermal Separation Processes, 2nd edition 1995, Weinheim, p. 135 ff; Perry's Chemical Engineers Handbook, 7th edition 1997, New York, Section 13). The distillation columns used can contain separating internals, such as separating trays, e.g. B. perforated trays, bubble cap trays or valve trays, ordered packings, e.g.Sheet metal or fabric packings, or random packings. As a rule, up to 20, preferably up to 10 theoretical plates are sufficient. A particular embodiment of the present invention is to carry out the reaction in the form of a reactive distillation. In this case, the reaction of the starting compounds takes place largely or even entirely on the separating internals of the separation column. Since the alkanol R formed as product. 2Since OH is generally the lowest-boiling component in the reaction system, it is immediately removed from the reaction equilibrium by distillation after formation, allowing the reaction to proceed under relatively mild conditions. The number of theoretical plates is chosen such that the other low-boiling compounds, generally the alkoxyalkylsilane of formula (Ia) and the cyclic siloxane of formula (Ib), remain in the reaction mixture. In one embodiment of reactive distillation, the separating internals are coated with an acid or base to promote the reaction. This has the advantage that no significant reaction takes place unless the reaction mixture is in direct contact with the separating internals. This also suppresses side or subsequent reactions promoted by the presence of acid or base.To increase the contact of the reactants with the separating internals, a portion of the distillation receiver is removed and added to the internals as reflux, optionally supplemented with fresh, unreacted alkoxyalkanol of formula (II). As a rule, the at least one alkoxyalkanol of formula (II) and the product of formula (III) are the highest-boiling components in the reaction mixture, whereas the reactants of formulas (Ia) and / or (Ib) and the resulting alkanol R. 2 OH are lower boiling. During the reaction, the reactants of formulas (Ia) and / or (Ib) should be available for the reaction, i.e. kept in the reaction mixture, whereas the resulting alkanol R 2 OH is preferentially separated from the reaction mixture. Therefore, a preferred embodiment is to select reaction conditions and components such that the alkanol R 2OH is the lowest boiling compound in the system and the boiling points of the reactants of formulas (Ia) and / or (Ib) are between those of R 2 OH and alkoxyalkanol of formula (II) and product of formula (III). In this case, a particularly preferred embodiment is to carry out the reaction in a reactor with a rectification column whose separation efficiency is sufficient to separate the alkanol R 2 OH as low boilers at the top of the column, whereas the higher than R 2 OH-boiling components in the reaction mixture, especially the reactants of the formulas (Ia) and / or (Ib), are recycled as column reflux into the reaction mixture. If the reaction mixture additionally contains a solvent, this can preferably also be recycled as reflux into the reaction mixture or else together with the alkanol R 2OH can be removed as the overhead product. If the solvent and alkanol or water formed form a two-phase mixture after condensation, the solvent phase can be recycled back into the reaction mixture after separation of the phases. This embodiment is particularly preferred when the alkoxyalkylsilane of the formula (Ia) used is dimethoxydimethylsilane (boiling point 81 °C) or dimethoxydiethylsilane. In this case, methanol with a boiling point of 65 °C at atmospheric pressure is released, which can be separated from the dimethoxydimethylsilane by rectification or at least depleted. This embodiment is particularly preferred when the alkoxyalkylsilane of the formula (Ia) used is diethoxydimethylsilane (boiling point 113 - 114 °C) or diethoxydiethylsilane (boiling point approx. 159 °C).In this case, ethanol with a boiling point of 78 °C at atmospheric pressure is released, which can be separated or at least depleted from both diethoxydimethylsilane and diethoxydiethylsilane by rectification. This embodiment is particularly preferred when hexamethylcyclotrisiloxane (boiling point 134 °C) or octamethylcyclotetrasiloxane (boiling point 175-176 °C) is used as the cyclic siloxane of the formula (Ib). In this case, water with a boiling point of 100 °C at atmospheric pressure is released, which can be separated or at least depleted by rectification. After the reaction has ended, unreacted reactants of the formulas (Ia) and / or (Ib) and any solvent present are then removed from the reaction mixture by distillation. After the solvent has been removed, the reaction mixture is purified.Once the desired conversion has been achieved and no solvent has been used, the reaction is generally stopped by cooling, and the reaction mixture is purified. The reaction mixture is left at a temperature at which its viscosity is sufficiently low for purification. Purification removes catalyst debris and any remaining solvent by at least one purification step selected from the group consisting of: filtration, membrane filtration, reverse osmosis, sorption on at least one inorganic metal oxide or activated carbon, and contact with at least one acidic, basic, or mixed ion exchanger. The first three techniques are known per se to those skilled in the art.Sorption can occur on inorganic materials, for example, silica gel, silicates, aluminum oxide, zeolites, diatomaceous earth, mixed aluminum / silicon oxides, and calcium carbonates and oxides, or on activated carbon or charcoal. After purification, the reaction mixture is essentially free of acids, bases, and solvents and can be used as or in functional fluids, preferably hydraulic or brake fluids, as well as for water capture. An advantage of the present invention is that the heterogeneous catalyst is not entrained into the reaction mixture, or is entrained only to a minimal extent, so that the separation of foreign components from the reaction mixture is eliminated or significantly simplified. For the intended use, it may be necessary to add other typical additives to the reaction mixture. Examples include corrosion inhibitors, antifoam agents, pH stabilizers, or antioxidants.An advantage of the process described according to the invention is that the reaction mixtures can be obtained gently. In particular, the reaction mixtures are free from halides, particularly chlorides, so that the reaction mixtures display lower corrosiveness than the corresponding compounds obtained from the corresponding alkylchlorosilanes. The content of halides, particularly chlorides, in the reaction mixtures thus obtained is generally not more than 100 ppm by weight, preferably not more than 75, more preferably not more than 50, very preferably not more than 25, in particular not more than 15 and even not more than 10 ppm by weight. Examples General working procedure (Example 1) In a three-neck flask with Vigreux column, distillation bridge includingTriethylene glycol monomethyl ether (76.7 g, 0.46 mol, 2.0 equiv), diethoxydimethylsilane (35.0 g, 0.23 mol, 1.0 equiv), and the heterogeneous catalyst 2 (0.11 g, 0.1 wt.% based on the total amount) were added to a reflux condenser, thermometer, and nitrogen inlet. The mixture was heated to 135°C for 3.5 hours at atmospheric pressure. The mixture was then stirred for a further 60 minutes at 135°C at a pressure of 100 mbar and for a further 60 minutes at 135°C at a pressure of 10 mbar. In the last two steps, the released ethanol was continuously distilled off as a mixture with diethoxydimethylsilane. After cooling, the catalyst was removed by filtration, and the resulting product was used for testing without further purification. The content of the product was determined using. 1H-NMR spectroscopy. 40.1 g (94.7 wt. %, 43.1% of theory) of the product was obtained as a colorless, clear liquid. The reaction was carried out accordingly with the other heterogeneous catalysts. HRMS expected 402.2518 [M+NH4] + found 402,2514 1 H-NMR (500 MHz, CDCl3): δ = 0.02 (s, 6 H), 3.25 (s, 6 H), 3.42 (m, 4 H), 3.46 (t, J = 5.3 Hz, 4 H), 3.50-3.60 (m, 12 H), 3.71 (t, J = 5.3 Hz, 4 H), 13 C-NMR (125 MHz, CDCl3): δ = -3.5, 55.6, 61.4, 70.1, 70.20, 70.23, 71.5, 72.0, 29 Si-NMR (99 MHz, CDCl3): δ = -1.85 Catalyst wt.% (0.1 wt.%) (NMR) 1 55.7% 2 94.7% 3 90.7% 4 91.8% 5 91.2% 6 89.0% 7 86.7% 8 93.5% Heterogeneous catalysts used: No. 1: Strongly acidic ion exchanger with -SO3H groups (0.8 – 1.3 eq / kg), surface area 75 m 2 / g, average pore diameter 235 Å No. 2: Zeolitic titanium silicalite of the TS-1 type, prepared according to Comparative Example 8 of WO 2023 / 094691, but in the form of 1.5 mm extrudates, BET surface area 300-450 m² / g, pore volume 0.9 ml / g No. 3: Gamma-alumina, BET surface area 230 m² / g, bulk density 650 g / l, 4 mm extrudates No. 4: SiO2 impregnated with phosphoric acid (20 wt% H3PO4, 80 wt% SiO2), BET surface area approx. 50 m² / g, bulk density approx. 550 g / l, 4 mm extrudates No. 5: SiO2 impregnated with sulfuric acid (20 wt% H2SO4, 80 wt% SiO2), BET surface area approx. 150 m² / g, 2.3 mm strands No. 6: Acid clay, BET surface area 240-290 m² / g, bulk density 330-440 g / l, powder No. 7: silica / aluminum oxide mixture (7 wt% Al2O3, 93 wt% SiO2), BET surface area 190 m² / g, bulk density 650 g / l, 3×3 mm tablets No. 8: zirconium dioxide, BET surface area 375 m² / g, bulk density 1400 g / l, 7×3×3 mm rings The BET surface area and the volume of the micropores were determined by nitrogen physisorption at 77 K according to DIN 66131.

Claims

Claims 1. Process for the preparation of organic silicon compounds of the formula (III) (III) R 1 xSi(-[-O-CH2-CH2-]nOR 3 )4-x or mixtures thereof, in which at least one alkoxyalkyl silane of the formula (Ia) (Ia) R 1 xSi(OR 2 )4-x and / or for the preparation of compounds (III) with x = 2, a cyclic siloxane of the formula (Ib) (Ib) -(-SiR 1 2-O-) y - with at least one alkoxyalkanol of formula (II) (II) R 3 -O-[-CH2-CH2-O-] n -H optionally in a solvent at a temperature of 0 to 200 °C, wherein R 1 Phenyl or C1-C4-alkyl, preferably C1-C4-alkyl, particularly preferably methyl, ethyl or n-butyl, very particularly preferably methyl or ethyl, R 2 C1-C4-alkyl, particularly preferably methyl, ethyl or n-butyl, very particularly preferably methyl or ethyl, R 3C1-C4-alkyl, particularly preferably methyl, ethyl or n-butyl, x is a positive integer 1, 2 or 3, y is a positive integer 3 or 4, preferably 3, and n is a positive integer from 2 to 5, preferably from 2 to 4, particularly preferably 2 or 3 and very particularly preferably 3, characterized in that the reaction is carried out in the presence of at least one inorganic heterogeneous catalyst which is an oxide, hydroxide, carbonate, bicarbonate, phosphate, hydrogen phosphate or dihydrogen phosphate of a metal or semimetal from group 3 to 14 (IUPAC nomenclature) of Periodic Table of the Elements.

2. Process according to claim 1, characterized in that the heterogeneous catalyst is an acidic catalyst.

3. Process according to claim 1 or 2, characterized in that the metal or semimetal is selected from group 4, 12, 13 or 14 (IUPAC nomenclature) of the Periodic Table of the Elements.

4. Process according to claim 1 or 2, characterized in that the metal or semimetal is selected from the group titanium, zirconium, zinc, boron, aluminum and silicon.

5. Process according to one of the preceding claims, characterized in that the heterogeneous catalyst is an oxide or phosphate.

6. The process according to claim 1 or 2, characterized in that the heterogeneous catalyst is selected from the group consisting of SiO2, TiO2, Al2O3, ZrO2, B2O3, ZnO2, Nb2O5, zeolites, and mixtures thereof. 7.The process according to any one of the preceding claims, characterized in that the reaction is carried out in at least one stirred-tank reactor, preferably a reactor with internal stirring or a pumped-circulation system, particularly preferably a pumped-circulation system.

8. The process according to any one of the preceding claims, characterized in that the reaction is carried out in a full-volume reactor or a tray reactor (section reactor).

9. The process according to any one of the preceding claims, characterized in that the reaction is carried out in a cascade of at least two stirred-tank reactors, preferably 2 to 5, particularly preferably 2 to 3 stirred-tank reactors.

10. The process according to any one of claims 1 to 6, characterized in that the reaction is carried out in at least one tubular reactor, preferably a tubular reactor with at least two temperature zones or a tube-bundle reactor.

11. The process according to any one of claims 1 to 6, characterized in that the reaction is carried out in at least one or more stirred-tank reactors, after which the reactor effluent is subsequently fed into a tubular reactor.

12. The process according to any one of the preceding claims, characterized in that the alkoxyalkylsilanes of the formula (Ia) used are exclusively compounds where x = 2. 13.Process according to one of the preceding claims, characterized in that the at least one alkoxyalkanol of the formula (II) is used in a molar ratio of at least 1 : 1 per group to be replaced (R. 2O-) in the compound of formula (Ia), preferably at least 1.1:1, particularly preferably at least 1.2:1 to 4:1, very particularly preferably from at least 1.3:1 to 3:1, in particular at least 1.5:1 to 2:

1.

14. The process according to any one of the preceding claims, characterized in that the alkoxyalkylsilane of formula (Ia) is selected from the group consisting of dimethoxydimethylsilane, dimethoxydiethylsilane, diethoxydimethylsilane, and diethoxydiethylsilane.

15. The process according to any one of the preceding claims, characterized in that the reaction temperature is increased during the course of the reaction. 16.Process according to one of the preceding claims, characterized in that the at least one acid or base is separated after completion of the reaction by at least one of the purification steps selected from the group consisting of - filtration, - membrane filtration, - reverse osmosis, - sorption on at least one inorganic metal oxide or activated carbon and. - Contact with at least one acidic, basic, or mixed ion exchanger.

17. The process according to any one of the preceding claims, characterized in that an excess of the at least one alkoxyalkanol of formula (II) is essentially left in the reaction mixture.

18. Use of a reaction mixture obtained according to any one of the preceding claims as or in functional fluids, preferably hydraulic or brake fluids, and for capturing water.

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