Method for producing hydrosiloxanes

Abstract

The present invention relates to a process for preparing unbranched hydrosiloxanes bearing dimethylhydrosiloxy groups comprising providing a siloxane mixture comprising at least two different siloxanes and reacting the siloxane mixture in an equilibrium reaction in the presence of a sulfonic acid ion exchange resin to form a reaction mixture, wherein the siloxanes used collectively have dimethylhydrosiloxy groups, methylhydrosiloxy groups, dimethylsiloxy groups and preferably trimethylsiloxy groups, and wherein the reaction mixture is monitored by ultrasonic measurements in order to determine the appropriate time at which the equilibrium reaction is ended, the equilibrium reaction being ended once the determined time has been reached.

Description

Technical Field

[0001] This invention belongs to the field of silicone chemistry, and specifically relates to a method for preparing hydrosiloxanes using ultrasonic measurement. Background Technology

[0002] Hydrosiloxanes, i.e. siloxanes with SiH groups, are balancers and play an important role as precursors, for example, in further processing to obtain polyether siloxanes, silicone acrylates, silicone quaternary ammonium salts, silicone waxes and many other derivatives.

[0003] In addition to the oldest equilibrium method using homogeneous catalysis, heterogeneous catalysis methods have been increasingly used in industrial silicone production using solid-phase catalysts in recent years.

[0004] One example of the significant advantages of acidic solid-phase catalysts in the production of hydrosiloxanes is that the liquid siloxane phase can be separated from the acidic solid-phase catalyst without complex post-treatment, and in particular without the need to neutralize the homogeneous acid, which would otherwise typically be used and the resulting salts removed by filtration.

[0005] Macroporous sulfonated polystyrene resins are of significant importance in solid-phase catalysts used for hydrosiloxane equilibration. They have been found to be particularly suitable for equilibrating siloxane systems with siloxane components containing methylhydrosiloxy groups.

[0006] To achieve this objective, the teachings of WO 2010 / 031654 A1 specifically relate to the equilibration of poly(methylhydro)polydimethylsiloxane copolymers on sulfonic acid cation exchange resins, wherein an organosiloxane or a mixture of organosiloxanes used as a starting material is contacted with a macroporous crosslinked cation exchange resin containing sulfonic acid groups at a temperature of 10°C to 120°C, and the resulting equilibrated organosiloxane is separated. The cation exchange resin used according to the teachings of WO 2010 / 031654 A1 is characterized in that the product of its specific surface area and its average pore size, P, is P ≥ 2.2 × 10⁻⁶. -3 m 3 / kg and specific surface area A is ≥35m² 2 / g, and its water content is 8 to 25% by weight, depending on the mass of the cation exchanger used.

[0007] WO 2010 / 074831 A1 describes a process for the preparation of siloxanes comprising the conversion of at least two siloxanes in the presence of an ion exchange resin catalyst comprising 6 to 19 wt.-% of water, wherein preferably at least one of the siloxanes comprises at least one silicon-bonded hydrogen atom, and wherein preferably at least one of the siloxanes is a poly(hydro)methylsiloxane or a cyclic siloxane. In particular, it describes the reaction of at least two siloxanes on an aqueous ion exchange resin catalyst, wherein at least one of the siloxanes comprises silicon-bonded hydrogen atoms, and wherein after the reaction the ion exchange resin catalyst is recovered and the water loading of 6 to 19 wt.-%, based on the dry weight of the ion exchange resin catalyst, is established by adding water to the ion exchange resin catalyst, and then the at least two siloxanes are reacted again in the presence of this ion exchange resin catalyst. The reactants selected in the examples of WO 2010 / 074831 A1 are octamethylcyclotetrasiloxane and tetramethyldisiloxane, and the content of octamethylcyclotetrasiloxane (D4) in the siloxane matrix at the end of the reaction determined via gas chromatography is considered to be an indicator of the establishment of equilibrium. Furthermore, the SiH content is determined only at the beginning of the reaction with reference to the reaction mixture. However, WO 2010 / 074831 A1 does not give any data on the SiH content of the reaction mixture at the end of each reaction. However, the SiH content of the reaction product is even more important in addition to the D4 content determined via gas chromatography, since this reference parameter is required for all further reactions of the building blocks (such as hydrosilylation or dehydrogenation reactions) to determine the respective stoichiometry.

[0008] Likewise, DE 102014211680 A1 discloses teachings on the production of siloxanes with the simple example of an a,w-dihydro polydimethylsiloxane, wherein the ion exchange resin can be used further without regeneration, the process is based on the use of at least one OH-functional siloxane, the reaction of at least two siloxanes on a sulfonic acid cation exchange resin. In the examples of DE 102014211680 A1 a,w-dihydro polydimethylsiloxane and decamethylcyclopentasiloxane are used. In the context of the disclosure of DE 102014211680 A1 it is found that many sulfonic acid cation exchange resins are suitable for the equilibration of a,w-dihydro polydimethylsiloxanes which undergo SiOSi rearrangements. However, DE 102014211680 A1 does not show how to obtain an equilibrated (i.e. highly homogeneously distributed) SiH siloxane with both chain end and pendant SiH functionalities.

[0009] The following prior art documents relating to the production of different structural hydrosiloxanes on sulfonic acid cation exchange resins are also cited here: WO 2010 / 031654 A1, DE 102005001039 A1, EP 1 439200 A1, EP 2 628 763 A1 and published specification DE 21 52 270 A.

[0010] The equilibration of siloxanes which simultaneously carry dimethylhydrosiloxy and methylhydrosiloxy units in the equilibration matrix is a great challenge to date, so superacids such as perfluoroalkanesulfonic acids, in particular triflic acid and perfluorobutanesulfonic acid, are still the preferred homogeneous equilibration catalysts for these particular hydrosiloxanes.

[0011] In the coming years, it will become increasingly difficult to overcome this challenge, preferably in relation to hydrosiloxanes of the following general structural type

[0012]

[0013] This is particularly because of the planned measures in Europe to restrict perfluorinated and polyfluorinated alkyl substances (PFAS) within the EU, which will also affect the homogeneously tested equilibration catalysts, for example triflic acid.

[0014] In the equilibration of these unbranched hydrosiloxanes which carry dimethylhydrosiloxy groups and also methylhydrosiloxy and dimethylsiloxy groups, the particular technical challenge is to achieve a highly statistically uniform distribution of the SiH functionality along the oligomer chain without too much of the sensitive dimethylhydrosiloxy groups being lost as a result of the dehydrogenation process.

[0015] In comparison with perfluorinated superacids, the effective acidity of sulfonic acid ion exchange resins in a siloxane matrix containing SiH groups is significantly lower, so it is very important to find suitable reaction parameters for the respective equilibration system when using sulfonic acid ion exchange resins.

[0016] Here, the required acidity is determined in particular by the equilibration task to be achieved, i.e. by the structure of the desired hydrosiloxane. The acidity, i.e. the ability to provide protons, which the catalyst has to exert for the synthesis of a, co-dihydro-polydimethylsiloxane requires a minimum. If, for example, a mixture consisting of octamethylcyclotetrasiloxane and tetramethyldisiloxane is converted into a, co-dihydro-polydimethylsiloxane under acidic catalysis, then, in theory, only one proton is required to open the octamethylcyclotetrasiloxane molecule, which is initiated by the protonation of the oxygen atom in the SiOSi bond present therein. The same applies to the SiOSi bond present in the tetramethyldisiloxane molecule, in theory, only one proton is required to open it. The adjustment of the oligomer chain distribution additionally requires a relatively low proton activity.

[0017] However, this is completely different for copolymersiloxanes containing methylhydrogensiloxy units (D H units) and dimethylsiloxy units (D units) in addition to trimethylsiloxy units (M units) and prepared, for example, from poly(methylhydro)siloxane, octamethylcyclotetrasiloxane and hexamethyldisiloxane under acidic catalysis. Theoretically, only one proton is needed to open the octamethylcyclotetrasiloxane molecule after protonation of one of the oxygen atoms in one of the four SiOSi bonds present therein. The same is true for the hexamethyldisiloxane molecule, where theoretically only one proton is needed to initiate the opening of the SiOSi bond present therein. Theoretically, the molecular cleavage of poly(methylhydro)siloxane also requires only one proton per siloxanyl bond (SiOSi bond). However, to achieve a statistical distribution of methylhydrogensiloxy units along the oligomer chains of the desired poly(methylhydro)siloxane-polydimethylsiloxane copolymer within the time window of the reaction, more protons per unit volume of the reaction mixture are needed, because only the almost simultaneous cleavage and reformation of multiple SiOSi bonds can lead to copolymers without any accumulation of methylhydrogensiloxy units within the siloxane oligomer chains. This purely statistical theoretical consideration of the acidity required to equilibrate such siloxane copolymers is supported by the experiments in the publication G. Sauvet, M. Moreau, G. Hélary, E. Daudet, P. Cancouet, “Functional polysiloxanes. I. Microstructure of poly(hydrogenmethylsiloxane-co-dimethylsiloxane)s obtained by cationic copolymerization” in J. Polymer Science, Part A: Polymer Chemistry Vol. 38, 826-36 (2000), where the authors (p. 833, ibid.) come to the clear conclusion that the reactivity of the siloxane bond (SiOSi) between two D H units is lower than the reactivity of the siloxane bond between two D units, which directly influences the partial reactions involved in the acid equilibrium, such as backbiting, crosslinking and acidolysis.

[0018] It is best to avoid accumulation of methylhydrogensiloxy groups in the sense of a juxtaposition as far as possible, since the hydrosiloxane equilibrates in the hydrosilylation reaction, in particular in those reactions in which, for example, polyether mixtures are used to obtain polyether siloxanes for high-demand surfactant applications, the subsequent use of which (for example as stabilizers in polyurethane foams) is directly related to the structural feature of the copolymer with polyether-containing Si atoms which are distributed as randomly as possible on the oligomer chain, i.e. as far as possible isolated from one another, since they are separated from one another by D units.

[0019] Sauvet et al. (page 835, right column, supra) conclude that knowledge of the distribution of D and D H units in the chain is key to understanding the properties of (SiH) copolymers themselves and many other properties of functionalized derivatives derived therefrom, and mention that the distribution of D and D H units in the chain has a direct influence on the reaction speed of the hydrosilylation reaction.

[0020] In this context, P. Cancouet, S. Pernin, G. Hélary and G. Sauvet in their article "Functional polysiloxanes. II. Neighboring effect in the hydrosilylation of poly(hydrogen methylsiloxane-co-dimethylsiloxane)s by allyl glycidyl ether" in J. Polymer Science, Part A: Polymer Chemistry, Vol. 38, 837-45 (2000) investigated the neighboring group effect of the hydrosilylation of allyl glycidyl ether onto poly(hydrogen methylsiloxane)-polydimethylsiloxane copolymers and demonstrated that the presence of methylhydrogensiloxy dyads (D H D H ) leads to an acceleration of the hydrosilylation, whereas isolated D H units surrounded by D units (DD H D) exhibit a slower reaction kinetics. Against this background it will be apparent to the person skilled in the art that the microstructure of the hydrosiloxane, in particular in the case of the addition of polyether mixtures with their respective reactivity ranges, has a crucial influence on the later target structure of the polyether siloxane copolymer.

[0021] Methods for determining the molecular fine structure of hydrosiloxanes are known. For example, in J. Polymer Science, Part A: Polymer Chemistry, Vol. 38, 826-36 (2000), G. Sauvet et al. in particular use high-resolution 29 Si NMR spectroscopy to detect diads, triads, pentads, etc. in poly(methylhydrosiloxane)-polydimethylsiloxane copolymers, i.e. the accumulation in the sense of direct juxtaposition of methylhydrosiloxy groups.

[0022] However, to date, NMR technology has not found a place in the industrial production of polyorganohydrosiloxanes as an in-process analysis method, in particular as a real-time method, due to factors including the cost of the equipment to be installed and, in particular, the fundamental problem of housing sources of extremely strong electromagnetic radiation such as NMR magnets and measuring heads in an operationally safe manner in explosion-protected production plants.

[0023] The teaching of WO 2022 / 132446 A1 attempts to solve the problem of in-process analysis by using vibrational spectroscopy such as infrared spectroscopy and Raman spectroscopy, in particular supported by the example of poly(methylhydrosiloxane)-polydimethylsiloxane copolymers, in order to determine the degree of direct correlation of the methylhydrosiloxy units (D H ) and the methylhydrosiloxy units isolated by dimethylsiloxy units (DD H D H ) in the acid-catalyzed equilibrium of siloxanes acting as D source and siloxanes acting as D H D source, in order to assess the degree of distribution achieved. Focusing on the rate of curing in siloxane elastomers, a direct relationship is observed between the concentration of isolated, i.e. statistically distributed, methylhydrosiloxy units determined by vibrational spectroscopy and the curing kinetics when using the respective SiH copolymers. For example (ibid., p. 18, Table 3), the SiH copolymer from batch 1, after an equilibration time of 3 hours and a decoupled SiH IR intensity of 2.08, requires 144.3 seconds to fully cure when introduced into the elastomer system, while the SiH copolymer from batch 7, after an equilibration time of 16 hours and a decoupled SiH IR intensity of 3.32, already leads to curing of the elastomer system after only 61.4 seconds.

[0024] The process presented in WO 2022 / 132446 A1 aims at facilitating the minimization of the batch time while achieving a higher statistical homogeneity of the SiH copolymer equilibrates, in particular targeting various different cured systems (condensation-cured products and / or hydrosilazation-cured products) as target products. However, WO 2022 / 132446 A1 does not teach which approach should be taken to achieve a highly statistically homogeneous hydrosiloxane equilibrates, which especially also contains dimethylhydrosiloxy groups.

[0025] The propagation of ultrasound in a liquid medium is known to be useful, inter alia, for determining concentrations and densities. For example, A. Zips in his article “Prozesskontrolle mittels Ultraschall” [Process Control by means of Ultrasound] in Technisches Messen 67 (2000), 201-207, and B. Henning in his article “Die akustische Impedanz als Messparameter zur Charakterisierung flüssiger Stoffsysteme” [Acoustic Impedance as Measurement Parameter for Characterization of Liquid Systems of Matter] in Technisches Messen 71 (2004), 492-500, focus on the theory and basic applications of ultrasound for measuring liquid concentrations. SUMMARY

[0026] Preferably, for silicone polyether copolymers used in very sensitive applications, such as in the case of rigid polyurethane foam stabilizers, the present invention relates to a process for achieving a high statistical homogeneity of the SiH functionality in hydrosiloxanes having pendant SiH groups in the form of methylhydrosiloxy and dimethylhydrosiloxy groups and dimethylsiloxy groups and preferably a certain proportion of trimethylsiloxy groups.

[0027] It is an object of the present invention to provide a process for equilibrating hydrosiloxanes which preferably allows for an evaluation of the equilibrates quality at the production site. The equilibration process is particularly suitable for those hydrosiloxanes having pendant SiH groups in the form of methylhydrosiloxy and dimethylhydrosiloxy groups and dimethylsiloxy groups and preferably a certain proportion of trimethylsiloxy groups.

[0028] ​The present inventors have now surprisingly found that the production of a hydrosiloxane equilibrant can be successfully carried out using a sulfonic acid ion exchange resin, wherein the reaction mixture is monitored by ultrasonic measurements in order to be able to determine the appropriate point in time at which the reaction is to be ended. The ultrasonic measurements are here preferably used to detect the speed of sound in the reaction mixture.

[0029] The above objects are achieved by the subject matter of the present invention. The present invention provides a process for the preparation of unbranched hydrosiloxanes with dimethylhydrosiloxy groups, which comprises:

[0030] providing a siloxane mixture comprising at least two different siloxanes and allowing the siloxane mixture to react in an equilibration reaction in the presence of a sulfonic acid ion exchange resin to form a reaction mixture,

[0031] wherein the siloxanes used collectively have dimethylhydrosiloxy groups, methylhydrosiloxy groups, dimethylsiloxy groups and preferably trimethylsiloxy groups,

[0032] and wherein

[0033] (a) monitoring the reaction mixture by ultrasonic measurements in order to determine the point in time at which the equilibration reaction is to be ended,

[0034] (b) ending the equilibration reaction as soon as the point in time determined in (a) is reached.

[0035] The ultrasonic measurements are here used to detect the speed of sound in the reaction mixture. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figures 1 to 4 BRIEF DESCRIPTION

[0037] Figure 1 shows exemplary shift regions of the triad signals containing methylhydrosiloxy groups and the accompanying integrals I, which were obtained from the Si NMR spectrum in the context of Example 1. 29 Si NMR spectrum in the context of Example 1.

[0038] Figure 2 shows exemplary evolution of the percentage I(DD H D) of isolated methylhydrosiloxy groups (= DD H D) based on the sum of all methylhydrosiloxy groups in the hydrosiloxane equilibrant (= I(D H total) as a function of the equilibration time t, wherein the percentage of isolated methylhydrosiloxy groups is determined by dividing the signal integral I(DD 29 D) assignable to DD H D groups in the Si NMR spectrum by the sum of all integrals I(D H D) assignable to D 29 groups in the Si NMR spectrum. H H ​Calculated in total.

[0039] Figure 3 This demonstrates, in the context of Example 1, the application of hydrosiloxanes at T... 反应 An exemplary graph showing the evolution of the temperature-corrected velocity of sound v (corrected) as a function of reaction time t at 40°C, as determined experimentally, and, in the context of Example 1, for hydrosiloxanes at T 反应 An exemplary graph showing the evolution of the derivative of the temperature-corrected speed of sound with respect to time at 40°C (expressed as the intensity change of the difference quotient Δv(correction) / Δt) as a function of reaction time.

[0040] Figure 4 This shows, in the context of Example 1, the hydrosiloxane balance based on the sum of all methylhydrosiloxy groups, through 29 Isolated methylhydrosiloxy groups (=DD) identified by Si NMR analysis H The percentage of D) I(DD) H D) / I(D H An exemplary graph showing the evolution of the total sound velocity v (corrected) with equilibrium time t, and an exemplary graph showing the evolution of the temperature-corrected sound velocity v (corrected) with equilibrium time t for the hydrosiloxane produced in Example 1 of the present invention.

[0041] Figures 1 to 4 This is only used to further illustrate the present invention, particularly Example 1 in the experimental examples section, and does not constitute any kind of limitation on the present invention. Invention Details

[0043] In the context of this invention, "ultrasonic measurement" means measuring and detecting the velocity of sound in a reaction mixture by means of sound waves in the ultrasonic frequency range.

[0044] The present invention preferably preserves SiH to produce acid-free hydrosiloxanes, which have methylhydrosiloxy groups, and also have dimethylhydrosiloxy and dimethylsiloxy groups, preferably also having a certain proportion of trimethylsiloxy groups, and the SiH functional groups therein have a highly statistically uniform distribution on the oligomer chain.

[0045] Ultrasound itself is known. This means that the frequency of sound is in the range of 20 kHz to 1 GHz.

[0046] In the context of this invention, instruments or measurement techniques suitable for ultrasonic measurements are commercially available. For example, those from SensoTech GmbH (Magdeburg-Barleben, Germany) can be used. Such a device, or for example, the one from Mat Mess- und Analysentechnik Dr. Frank Dinger / (Hofgeismar, Germany), is capable of reliably detecting and recording the speed of sound and its derivative with respect to time.

[0047] The preferred moment for ending the equilibrium reaction is when chemical equilibrium is reached, preferably when, for example, the ternary distribution along the siloxane oligomer chain shows no significant change, meaning that within a certain timeframe, the equilibrium can be achieved. 29 Within the accuracy range for Si NMR analysis visualization, this distribution preferably remains constant over time. This required consistency is preferably determined by the quotient Q = I(DD). H D) / I(D H The total value is used to define this. If the change in Q is preferably less than 0.02 / hour, it is considered, for example, that a statistically uniform distribution has been achieved. This is also associated with the fact that the concentration of siloxane cyclic compounds (D4+D5+D6), which can be detected by gas chromatography, is preferably kept constant.

[0048] Ultrasonic measurement can monitor the equilibrium reaction throughout the entire reaction process and makes it possible to determine the optimal moment for the equilibrium reaction to end in a simple manner, preferably without relying on the above-mentioned methods. 29 Si NMR analysis. However, preferably, the above can be used in addition to this. 29 Si NMR analysis.

[0049] Preferably, ultrasonic measurement is used to detect the velocity of sound in the reaction mixture and / or the derivative of the velocity of sound in the reaction mixture with time.

[0050] The speed of sound (formula v) is defined as ds / dt, which is the derivative of the distance (s) traveled by sound with respect to time (t). It is reported in m / s.

[0051] The derivative of the speed of sound with respect to time is defined as dv / dt, in m / s. 2 .

[0052] The present invention can determine the appropriate time to end the equilibrium reaction by, for example, by considering the change in the speed of sound in the reaction mixture, or by, for example, by considering the derivative of the speed of sound with respect to time, whether a preferred desired equilibrium target has been reached.

[0053] Preferably, the appropriate time to end the equilibrium reaction is determined by the change in the speed of sound in the reaction mixture.

[0054] Preferably, the velocity of sound in the reaction mixture before the equilibrium reaction begins is compared with the velocity of sound as the equilibrium reaction proceeds. This comparison allows for simple monitoring of the reaction.

[0055] Preferably, the influence of the measuring temperature on the sound velocity is first determined in the respective medium in question, preferably in the unbranched hydrosiloxane in question with dimethylhydrosiloxy groups, in order to determine a correction function, so that the measured sound velocity can be converted into a temperature-corrected sound velocity.

[0056] By "respective medium in question" is meant the starting mixture of siloxane reactants for equilibration, the hydrosiloxane derived therefrom which has not yet been completely equilibrated, more preferably the equilibrated unbranched hydrosiloxane with dimethylhydrosiloxy groups according to the application.

[0057] In the context of the present application, by "correction function" is meant a simple mathematical function which describes the influence of the temperature on the sound velocity in the respective medium in question, preferably the respective hydrosiloxane.

[0058] Thus, in the context of the present application, by "temperature-corrected sound velocity" is meant the sound velocity which depends only on the composition of the respective medium in question.

[0059] In order to determine the correction function which describes the influence of the temperature on the sound velocity in the medium in question, preferably in the hydrosiloxane in question, the sound velocity can preferably be measured in the temperature range between T min and T max , of course, the subsequent measuring temperature should be within this temperature range, and the values obtained are connected to one another by a straight line by fitting. min represents 20°C, and T max represents 50°C.

[0060] The slope of this straight line then gives the change in sound velocity per degree Celsius as a derivative at the respective reference temperature T (reference). By "reference temperature T (reference) " is meant the desired conversion temperature.

[0061] For the respective medium in question, preferably the hydrosiloxane, the numerical value of the slope of the straight line in (m / s) / °C can thus be determined, so that the measured sound velocity v (measured) can be converted into a temperature-corrected sound velocity v (corrected) :

[0062] v (corrected) = v (measured) - slope value (m / s) / °C * (T (reference) - T (measured) ).

[0063] When the change in sound velocity is less than 0.25% / 15 minutes, preferably less than 0.15% / 15 minutes, a very particularly suitable point in time for ending the equilibration reaction is preferably reached.

[0064] The inventors have also found that, optionally with concomitant performance of a high-resolution 29Si NMR spectroscopy can preferably relate the measurement data from the ultrasonic measurement to conclusions about the microstructure of the resulting equilibration which can be obtained from NMR spectroscopy and preferably compare this data such that a way can be determined by which the triad distribution of methylhydrogensiloxy groups in the siloxane oligomer chain can be unambiguously determined by the ultrasonic index for further ultrasonic measurements.

[0065] The term "microstructure" means the way in which methylhydrogensiloxy groups are distributed along the siloxane chain.

[0066] The term "triad" means in each case three Si units which are bonded via two siloxane groups, for example DD H D vs. DD H D H vs. D H D H D H vs. MD H D vs. MD H D H vs. M H D H D vs. M H D H D H In the context of the present application, the following triads are considered in particular: DD H D vs. DD H D H vs. D H D H D H .

[0067] The term "triad distribution" thus means in the context of the present application the population of these triads DD H D vs. DD H D H vs. D H D H D H which can be determined by means of 29 Si NMR spectroscopy.

[0068] Preferably, a sample is removed from the reaction mixture during the equilibration process and is analyzed, preferably by means of 29 Si NMR spectroscopy,

[0069] wherein the evaluation preferably involves considering all integrals in the range of -34.0 to -40.0 ppm shift which are related to methylhydrogensiloxy triads, as well as integrals which represent isolated methylhydrogensiloxy groups (DD H D or MD Hthe integral of the triad of D) occurring in the shift range of -36.8 to -38.2 ppm. In brief, in the context of the present teachings, hereinafter only DD H D triad, although it is clear that also the MD H The NMR signal of the D triad will also be present in the spectrum at a similar chemical shift.

[0070] Preferably, for each sample taken, the integral value determined for DD H The quotient Q is determined from the integral value determined for DD

[0071] in order to detect the evolution of the percentage of isolated methylhydrogensiloxy units (DD H D) in the reaction mixture based on the sum of all methylhydrogensiloxy units as a function of the equilibration time.

[0072] Herein, it is preferred to use 29 the integral signal strength of the Si NMR spectrum in the shift range of about -35 ppm for the analysis of the respective triad distribution (DD H D vs. DD H D H vs. D H D H D H ).

[0073] Under isothermal reaction conditions, which can be achieved by using a reaction calorimeter, for example, the reaction progress can preferably be monitored in a simple manner using the evolution of the sound velocity as a function of the reaction time.

[0074] However, under practical operating conditions, ideal temperature control as in a reaction calorimeter is hardly achievable. It is known that the sound velocity in a particular medium also depends on the temperature. In view of this influence, it is therefore particularly preferred in accordance with the present application to determine a correction function for a non-isothermal reaction system, which correction function describes the dependence of the sound velocity on the temperature change in the respective equilibration. For the purpose of subsequent evaluation of the measurement data, the recorded sound velocities can then preferably be converted to a defined reference temperature by means of the determined correction function.

[0075] In connection with the purpose of recognizing the end of the equilibration (or determining the appropriate moment of time at which the equilibration reaction is completed), it is particularly preferred to select the respective final equilibration as the reference medium and to determine the dependence of the sound velocity on the temperature therein. Preferably, a linear correlation can be started from within the temperature range (T min = 20°C, T max = 50°C) and the respective linear equation can be derived from a small number of values pairs.

[0076] Assuming identical reaction conditions, the individual sound velocities and the corresponding specific triplet distribution can thus preferably be attributed to any individual hydrosiloxane structure at any reaction time.

[0077] Once these characteristic parameters of the hydrosiloxane of a specific structure type have been determined in this way, the method can be applied in a simple and reliable manner, for example for monitoring and evaluating any equilibration under different catalysis.

[0078] In this context, it is preferably possible to make a statement about the statistical homogeneity reached by the equilibrated hydrosiloxane, or preferably also to answer the question of whether the equilibrant has reached the desired distribution of methylhydrogensiloxy groups after a specific reaction time.

[0079] If the experimentally determined and preferably temperature-corrected sound velocity difference (sound velocity in the equilibrant minus sound velocity in the equilibration mixture) is normalized to 100%, it is found that the desired statistical homogeneity of the SiH siloxane is reached when the change in the sound velocity is preferably less than 0.25% / 15 minutes, preferably less than 0.15% / 15 minutes.

[0080] Statistical homogeneity of the SiH siloxane means a highly statistical distribution of the methylhydrogensiloxy units along the siloxane chain.

[0081] By high-resolution 29 The preferred correlation or preferably normalization of the sound velocity by means of Si NMR spectroscopy can preferably enable an immediate and direct quality assessment in production (online) by means of the ultrasonic measurement method, whereas in other cases this can only be obtained via complex sampling and analysis at a distance from production.

[0082] The application thus preferably not only enables reliable end-point recognition in the acid-catalyzed equilibration of hydrosiloxanes, which is important for optimizing the space-time yield and batch cycle time, but preferably also enables reproducible control of the target setting of hydrosiloxanes having a specific microstructure, which is crucial for the quality of the active surfactants (polyether siloxanes) produced therefrom.

[0083] The method according to the application preferably also enables any activity decline occurring in the heterogeneous catalyst (e.g. sulfonic acid resin) in different production cycles to be countered.

[0084] Focusing on the principle of quality, it is preferably possible to target hydrosiloxanes having a specific microstructure. A spent solid-phase catalyst will manifest itself in the need for longer reaction times to reach this equilibration target. With the aid of the method according to the application, the reaction time can then preferably be lengthened accordingly. The preferred indicator of the achievement of the equilibration target and thus of the formation of the preferred microstructure in the hydrosiloxane copolymer is the sound velocity in the equilibrant, more preferably the derivative of the sound velocity with respect to time, i.e. the change in the sound velocity.

[0085] The process according to the application is used for the production of unbranched hydrocarbons with dimethylhydrogensiloxy groups. Preferred unbranched hydrocarbons with dimethylhydrogensiloxy groups are equilibrated hydrocarbons which satisfy the following average formula:

[0086]

[0087] wherein

[0088] 3 < x < 100, preferably 30 < x < 80,

[0089] 1 < y < 30, preferably 2 < y < 10,

[0090] a + b = 1

[0091] 0.4 < a < 1.0, preferably 0.6 < a < 0.95,

[0092] 0 < b < 0.6, preferably 0.05 < b < 0.4,

[0093] More preferably x + y + 2 > 13.

[0094] In the process according to the application a sulfonic acid ion exchange resin is used. Such sulfonic acid ion exchange resins are known per se.

[0095] Preferably a macrocrosslinked aqueous cation exchange resin containing sulfonic acid groups is used, wherein the product of its specific surface area and average pore diameter P is P > 2.2 x 10 -3 m 3 / g and the specific surface area A is > 35 m 2 / g, and the water content based on the weight of the cation exchange resin is 6 to 16% by weight, preferably the water content is 8 to 12% by weight. Such preferred cation exchange resins are likewise known per se.

[0096] The equilibration reaction according to the application is preferably carried out at a temperature of 20°C to 50°C, preferably 35°C to 45°C, within a period of preferably 4 to 10 hours, preferably within a period of 5 to 8 hours.

[0097] The process according to the application, in particular preferably the equilibration reaction, is preferably carried out at a pressure of preferably 800 mbar to 1200 mbar, more preferably 950 mbar to 1100 mbar.

[0098] It can be preferred to add water to the reactant system according to the application comprising at least two different siloxanes as described in claim 1 in order to, for example, counteract any possible water consumption in the sulfonic acid cation exchange resin.

[0099] This can preferably be achieved by, for example, placing a sulfonic acid cation exchange resin in a container equipped with a suitable sieve plate and / or a rectangular sieve, and then, for example by means of a conveying unit, preferably a pump, conveying the equilibrium mixture to the cation exchange resin thus fixed, and connecting the arrangement of the container and the pump to, for example, a stirred reactor containing a measuring probe, such that the preferred interconnection as a whole results in a reaction loop.

[0100] Such local liquid-solid separation can also be preferably achieved by suspending the cation exchange resin directly in an equilibrium mixture in a stirred reactor, and then immersing an ultrasonic measuring probe, for example protected by a screen structure, into the suspension, such that only liquid volume elements can pass through the screen and thus through the measuring probe because the screen size is adapted to the particle size of the cation exchange resin.

[0101] The following examples are for further illustration of the present invention and do not constitute any limitation on the present invention. Detailed Implementation

[0102] Example:

[0103] In the context of this invention, measurements were recorded at a frequency of 79.506 MHz using a Bruker Avance Neo 400 spectrometer. 29 Si NMR spectroscopy was performed using a spectrometer equipped with a Z179883 sample head with a 10 mm gap width, dissolved in CDCl3 at 22 °C, with tetramethylsilane (TMS) as an external standard [d( 29 Si) = 0.0 ppm.

[0104] Example 1

[0105] Equipped with products from SensoTech GmbH Ultrasonic measuring probe (connected to from) In the RC1 reactive calorimeter (from Mettler-Toledo) of Lab's signal sensor, an initial feed of 119 g of poly(methylhydrosiloxane) (SiH value = 15.60 mol / kg), 377 g of α,ω-dihydropolydimethylsiloxane (SiH value = 2.88 mol / kg), and 1304 g of decamethylcyclopentasiloxane was heated to 40°C with stirring. The reactive calorimeter was connected via a bottom outlet to a lower opening in the form of a pipe fitting to a vertical cylindrical double-layered glass frit (porosity P1) consisting of a shell and an inner core, the glass frit containing 108 g of sulfonic acid cation exchange resin (…). The initial feed of the cation exchange resin of the sulfonic acid K2621) has been previously dried to a water content of 10%. The upper opening of the double glass frit is likewise in the form of a pipe joint, which on the suction side is connected by means of a hose to a dosing diaphragm pump (type: ProMinent Gamma / L), which on the pressure side is connected via a hose to the filling tube which is immersed in the reaction calorimeter.

[0106] Overall, the interconnection of the apparatus components described here thus constitutes a closed loop (feedback circuit).

[0107] The diaphragm pump is adjusted to a volume flow of 11 1 / hour and the reaction mixture is circulated through the cation exchange resin feed in the double glass frit, while continuously stirring in the reaction calorimeter and pumping the circulation for 6 hours.

[0108] By means of a syringe provided with a long cannula, 5 ml samples are taken from the reaction calorimeter at times t = 0, t = 30 minutes, t = 60 minutes, t = 90 minutes, t = 120 minutes, t = 180 minutes, t = 240 minutes, t = 300 minutes and t = 360 minutes through the diaphragm lid and then analyzed by means of 29 Si NMR spectroscopy.

[0109] In the evaluation of the recorded 29 Si NMR spectra, all integrals in the shift range of -34.0 to -40.0 ppm, which are associated with the methyl hydrogen siloxy triad signal, are considered, in particular the integrals of the triad signals which represent isolated methyl hydrogen siloxy groups (DD H D) which occur in the shift range of -36.8 to -38.2 ppm (see Figure 1 ).

[0110] For each real-time reaction sample taken, the integral value determined as DD H D triad signal is divided by the integral sum of all signals containing methyl hydrogen siloxy units (= I(D H D) and normalized to 100% (see Table 1).

[0111] On the basis of these values thus determined, an evolution can be shown which shows the percentage of isolated methyl hydrogen siloxy groups (= DD H D) in the hydrosiloxane equilibrium based on the sum of all methyl hydrogen siloxy groups as a function of the equilibration time (see Figure 2 ).

[0112] At a reaction temperature of 40°C, the sound velocity and the derivative of the sound velocity with respect to time are detected. The sound velocity as well as the change in sound velocity per minute is detected over the entire reaction time.

[0113] Figure 3The temperature-corrected sound velocity progression versus the reaction time and the change in temperature-corrected sound velocity per minute at a reaction temperature of 40°C is shown. The temperature-corrected sound velocity is calculated as described further below.

[0114] In the derivative plot of the temperature-corrected sound velocity versus time, small deviations from the ideal curve progression can be explained by sampling at the respective time.

[0115] The equilibrium according to the application is intended to result in the following average hydrosiloxane structure:

[0116]

[0117] where x = 36.85, y = 3.15, a = 0.92, and b = 0.08.

[0118] Concomitantly 29 The Si NMR spectroscopy confirms that a hydrosiloxane equilibrium of such a structure is obtained.

[0119] In order not to be bound to the isothermal operating mode, a correction function is determined which describes the influence of the temperature on the sound velocity in such a hydrosiloxane equilibrium. For this purpose, the sound velocity is measured in the temperature range between 25°C and 55°C and the resulting values are correlated to one another by means of a calibration line.

[0120] The slope of the straight line gives the change in sound velocity per degree Celsius as a derivative at the respective reference temperature T(ref).

[0121] For the hydrosiloxane equilibrium specified above, the slope is -2.697 (m / s) / °C, so that the measured sound velocity v(measured) can be converted into the temperature-corrected sound velocity v(corrected):

[0122] v(corrected) = v(measured) - 2.697 (m / s) / °C * (T(ref) - T(measured)).

[0123] If the triad distribution determined beforehand by means of Si NMR analysis for the hydrosiloxane according to the application is combined with these temperature-corrected sound velocities determined experimentally for the special hydrosiloxane, this results in 29 the plot shown. Figure 4

[0124] For each time in the reaction, the sound velocity is associated with a single microstructure in the hydrosiloxane process which is achieved in equilibrium. The curve describing the difference in temperature-corrected sound velocity (see Figure 4 ) exhibits an asymptotic progression.

[0125] ​It has been found that a particularly preferred statistical homogeneity of the hydrogen siloxane is achieved when the change in the sound velocity is less than 0.25% / 15 minutes, preferably less than 0.15% / 15 minutes.

[0126] Table 1: 29 Evaluation of Si NMR spectra, DD H D triad ratio determination.

[0127]

[0128] I(D H Total) = sum of integrals in the range of -34.0 to -40.0 ppm shift

[0129] I(DD H D) = integral from -36.8 to -38.2 ppm

Claims

1. A method for preparing unbranched hydrosiloxanes bearing a dimethylhydrosiloxy group, comprising: A mixture of siloxanes comprising at least two different siloxanes is provided, and the mixture is reacted in an equilibrium reaction in the presence of a sulfonic acid ion exchange resin to form a reaction mixture, wherein the siloxanes used collectively have dimethylhydrosiloxy, methylhydrosiloxy, dimethylsiloxy, and preferably trimethylsiloxy, characterized in that... (a) The reaction mixture is monitored by ultrasonic measurement to determine the appropriate time to end the equilibrium reaction. (b) Once the time specified in (a) is reached, the equilibrium reaction is terminated.

2. The method according to claim 1, characterized in that, The ultrasonic measurement detects the velocity of sound in the reaction mixture and / or the time derivative of the velocity of sound in the reaction mixture.

3. The method according to claim 1 or 2, characterized in that, The appropriate moment to end the equilibrium reaction is determined by the change in the speed of sound in the reaction mixture.

4. The method according to claim 3, characterized in that, The velocity of sound in the reaction mixture before the equilibrium reaction begins is compared with the velocity of sound as the equilibrium reaction proceeds.

5. The method according to any one of claims 1 to 4, characterized in that, When the change in sound velocity is less than 0.25% / 15 minutes, preferably less than 0.15% / 15 minutes, the appropriate time to end the equilibrium reaction is reached.

6. The method according to any one of claims 1 to 5, characterized in that, First, the effect of the measurement temperature on the speed of sound is determined in the relevant medium under discussion, preferably in the unbranched hydrosiloxane with dimethylhydrosiloxy group under discussion, in order to determine the correction function so that the measured speed of sound can be converted into the temperature-corrected speed of sound.

7. The method according to any one of claims 1 to 6, characterized in that, During the equilibrium reaction, a sample is taken from the reaction mixture and, by means of... 29 SiNMR spectroscopy analysis is preferably performed by considering all integrals in the shift range of -34.0 to -40.0 ppm associated with the methylhydrosiloxy ternary group, and the ternary group (DD) representing the isolated methylhydrosiloxy group. H The integral of D) occurs in the displacement range of -36.8 to -38.2 ppm. Furthermore, for each sample taken out, it is preferable to use the DD... H The integral value determined by the D triplet and the cumulative integral value of all methylhydrosiloxy units form the quotient Q. In order to detect isolated methylhydrosiloxy groups (DDs) in the reaction mixture based on the sum of all methylhydrosiloxy groups. H The evolution of the percentage of D) over equilibrium time.

8. The method according to any one of claims 1 to 7, characterized in that, The balanced hydrosiloxanes satisfy the following average equation: in: 3≤x≤100, preferably 30≤x≤80. 1≤y≤30, preferably 2≤y≤10. a+b=1, 0.4≤a≤1.0, preferably 0.6≤a≤0.

95. 0≤b≤0.6, preferably 0.05≤b≤0.

4. More preferably, x+y+2≥13.

9. The method according to any one of claims 1 to 8, characterized in that, The sulfonic acid ion exchange resin used is a macroporous cross-linked aqueous cation exchange resin containing sulfonic acid groups, wherein the product of its specific surface area and average pore size, P, is preferably P ≥ 2.2 × 10⁻⁶. -3 m 3 / kg and the specific surface area A is preferably ≥35m² 2 / g, and based on the weight of the cation exchange resin, its water content is preferably 6 to 16% by weight, more preferably 8 to 12% by weight.

10. The method according to any one of claims 1 to 9, characterized in that, The equilibrium reaction is carried out at a temperature of 20°C to 50°C, preferably 35°C to 45°C, for a period of preferably 4 to 10 hours, preferably 5 to 8 hours.

11. The method according to any one of claims 1 to 10, characterized in that, Ultrasonic measurements are performed using an ultrasonic measuring probe, wherein the ultrasonic measuring probe is preferably arranged such that only liquid components can flow through the measuring probe and be detected.

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