Process and apparatus for continous hydrosilylation reactions

The invention relates to a continuous process for the preparation of organomodified polysiloxanes by the transition metal-catalyzed addition of SiH group-containing polysiloxanes to CC multiple bonds containing substances. Furthermore, a suitable technical device for carrying out the method according to the invention is described.

Among the processes for the construction and modification of organosiloxanes, the transition metal-catalyzed hydrosilylation is of particular importance, since it enables SiC linkages in a variety of ways. However, regardless of the breadth of application of this reaction, its technical implementation is often accompanied by considerable difficulties. At the center of these problems is the time-varying catalyst activity, which is subject to many interferences. Against the background of the released in hydrosilylation energy (exothermic) often leads fluctuating catalyst activity in batch processes to critical operating conditions, because in the meantime Reaktandmengen accumulate and thus can build a potential danger. The batch process represents the usual state of the art for technical hydrosilylations, not least because experience has shown that a preforming phase for forming the catalytically active species from the inactive starting material is mandatory. The fluctuating reaction processes of technical hydrosilylation reactions require a high presence of qualified employees.

A particular danger potential arises from the material systems in hydrosilylation processes which have a high hydride hydrogen density. In addition to the monomeric silanes, the derivatives of poly (methylhydrogen) siloxane are to be mentioned here in particular.

Along with the moment of danger, the critical systems also deliver unwanted by-products, ie the selectivity of the target reaction suffers.

therefore Notably, the known chemical process for preparing organo-poly (methyl hydrogen) siloxanes then seek to minimize the steady-state concentration of active SiH groups in the SiC-linking step.

For example, WO 98/05700 describes a (semi) continuous process for the manufacture of multifunctional polyorganosiloxanes having Si-Si alkyl and alkoxy groups in a multi-stage reaction apparatus consisting of a combination of a Dehydrokondensationsreaktors with a hydrosilylation. The dehydrocondensation reactor is reacted with an SiH-containing polyorganosiloxane and - referred to in the sub-section - with an alcohol or Charged thioalcohol in the presence of a platinum catalyst, wherein H₂Release a mixed alkoxy-hydrogen siloxane or Thioalkoxy-hydrogen siloxane is formed, which is then immediately subjected to SiC-linking alkylation with an olefin in a downstream hydrosilylation reactor. On page 2, line 29 to page 3, line 3 of this document is focused on the hazards in dealing with SiH-containing compounds - even those with partially alkoxy or thioalkoxy-functionalized chains. Consciously, the actual hydrosilylation is therefore carried out only after the partial defusing reaction (dehydrocondensation), although the operation of this process is accompanied by the technical problem of ensuring complete separation of alcohol / thiol and hydrogen gas prior to hydrosilylation. Apparatus technology therefore requires a complex and costly solution.

Continuous hydrosilylation processes, which are already known per se, are also aimed at lowering the in-situ concentration of active SiH groups. DE 196 32 157 A teaches a process for the continuous preparation of organosilicon compounds of the 3-halogen-propyl-organosilane type of the general structure R._bH_3-abX_aYourself₂CH₂CH₂Y by the reaction of an allyl halide with a bearing at least one H atom silane, which is given in excess. Unwanted by-products are unprofitable propylorganosilanes. The essential feature of this method is that by setting a partial conversion of the reactants of 10-80% based on the deficiency component suppresses the by-product formation.

Another method for the continuous implementation of hydrosilylation reactions is disclosed in DE 196 19 138 A. Described is a process for the preparation of vinylated organosilicon compounds, which is characterized in that one brings at least one SiH group-containing silicon-organic compound with acetylene in excess in a substantially inert liquid phase in the presence of a catalyst for reaction. To ensure intensive mixing of the reaction matrix, a jet nozzle loop reactor is used.

As continuous gas phase processes in a flow-through reactor, both the addition of acetylene to methyldichlorosilane to a chrysotile-asbestos-anchored Wilkinson catalyst (Appl. Organomet Chem (1987), 1 (5), 459-63) and those with limited selectivity proceeding hydrosilylation of acetylene with trichlorosilane on SiO 2₂-fixed Rh and Ru phosphine complexes (Appl. Organomet Chem. (1987), 1 (3), 267-73).

The prior art thus documents three methods for diluting active SiH groups:<ul id="ul0001" list-style="none" compact="compact"><li>the partial sales procedure,</li><li>the use of an inert liquid phase and</li><li>the reaction in the gas space.</li></ul>

Against this background, the problem of the invention to provide a method and a device that allow an economical and reproducible implementation of the hydrosilylation unys reaction in difficult material systems while avoiding known hazard potentials and also dispense with complicated and expensive apparatus technology. In addition, the process should ensure a consistently high product quality with economical use of high-priced precious metal catalysts. In addition, the process should be applicable at almost complete conversion, waiving an inert auxiliary phase and also for non-decomposable-volatilizable, higher molecular weight reactants.

The above object is achieved in a first embodiment of the invention by a process for the continuous hydrosilylation of C-C multiple bonds-containing substances, characterized, if appropriate, in a loop-shaped, the reactants in the presence of a homogeneous or heterogeneous catalyst, introduces a heatable reaction cycle, having a static mixing element and / or a dynamic mixing element, to mix reactants and formed product, leaving the reaction mixture in the reaction circuit up to a predetermined degree of conversion, then transferred the reaction mixture still containing starting materials to complete the reaction in a tubular reactor and removed via a template.

A general representation of the principle underlying the invention is shown in FIG. The material flow is emphasized by a wider line than the temperature control (cooling or heating) to the variable system parameters serving oil circuit. The educts present in the batches B1 and B2, optionally charged with catalyst, are fed into the loop reactor with the aid of the metering pumps P1 and P2. The continuous circulation of the reactant mixture within the loop is ensured by the pump P3. To support intensive mixing of the reaction matrix, static mixing elements (SM) are integrated into the loop. After a predetermined residence time, the reaction mixture passes into the tubular reactor. When the post-reaction in the tube reactor is complete, the product is collected in the original B3.

Surprisingly, it has been found that the required requirements are met by a reactor system in which metered reactant streams are passed in the presence of a heterogeneous or homogeneous noble metal catalyst through a temperature-controlled loop reactor (loop reactor) in combination with a temperature-controlled tubular reactor. The loop reactor takes on the function of making the critical initial phase of the onset of hydrosilylation controllable. The accumulation of critical quantities of starting materials is counteracted in the loop reactor by rapid and intensive mixing, which is ensured both by the incorporation of static mixing elements and by a high circulation capacity of the integrated delivery pump. Optionally, the static mixing elements can also be replaced by flow-operated dynamic mixer, for example, according to the rotor / stator principle, or used in combination with these (Fig. 2). These measures individually and / or in combination bring about a timely, rapid reaction of SiH group-carrying and CC multiple bond-containing substance. The tube reactor connected to the loop reactor through an overflow serves for the less exothermic after-reaction of the reaction mixture.

A further embodiment of the present invention thus consists of a device for the continuous hydrosilylation of substances containing at least one C-C multiple bond, comprising a template (B1) for receiving the substance which may be charged with a catalyst, a template (B2) for receiving the hydrosilylation component, Conveying device (P1, P2) for introducing a reactant stream into a loop-shaped, temperature-controlled reaction cycle, containing a stationary mixing element or a dynamic mixing element (SM) for mixing the educts and the product formed, Means for dissipating the heat of reaction, a tube reactor to complete the reaction and means to capture the product (B3).

A stirred tank equipped with a static mixing element (as shown in Figure 4) or a dynamic flow mixer (as shown in Figure 3) can be integrated into the loop reactor loop. An alternative reaction system suitable for the process according to the invention is also a stirred tank cascade consisting of at least two or more stirred kettles flowed through one after the other (FIG. 5), which can optionally be used for postcatalysis.

The observation that, compared to the conventional batch technique, significantly lower amounts of noble metal catalyst must be used to achieve quantitative conversions is astonishing to those skilled in the art. The lower precious metal consumption is not only of interest in terms of cost reduction, but also directly affects the product quality achieved, as certain undesirable discolorations are directly attributable to the presence of transition metal compounds. Furthermore, the separation of the catalyst from the reaction mixture is facilitated.

The achievable with the invention claimed reaction system space-time yields significantly exceed the productivity of conventional stirred tank technology.

This makes it possible to build small and compact production plants that convince in a limited space by their efficiency.

As a further favorable aspect, the chemoselectivity of the hydrosilylation reaction is directly linked to the high space-time yields of the process presented. In particular, ambident or multifunctional reactants (eg OH-functional allyl polyethers) can be converted into the target products with good yields.

In a particular embodiment of the present invention, a supported noble metal contact is integrated into the reaction loop, so that the catalyst in heterogeneous form promotes the SiC coupling reaction in the inflowing fluid. In this case, the product adhesion is minimized with transition metal compounds, so that time-consuming filtration steps to remove the catalyst omitted.

The process according to the invention ensures a consistently high product quality and moreover makes it possible to achieve a high degree of automation in the production of organomodified siloxanes. By determining the dosing of the conveying elements in the educt feed directly the residence time in the reactor system and thus to be reached at a certain temperature to be reached turnover. Coupled to a conventional measuring control and regulation system, the method according to the invention or the device according to the invention then permit, for example when using integrated near-infrared probes, an on-line adaptation of the process parameters to the current operating state. As a result, subjective human errors in the reaction can be eliminated. In addition, the accumulation of unreacted educts is prevented by the defined dosage of the reactants in a reaction loop, the initial exothermic safely dissipated and ensures safe process control.

As an alternative to the variable system parameters, a number of predefined products can be produced easily and reproducibly even with fixed system parameters without measuring control technology.

embodiments

:

Example 1:

In vessel B1, 1379 g of heptamethyltrisiloxane (4.99 equivalents SiH / kg) and in vessel B2 4491 g of a hydroxy-functional allyl polyether (M about 522 g / mol, structure:<chemistry id="chem0001" num="0001"><img file="EP1013701A2_D0001.tif" /></chemistry> JZ: 48.6 gJ / 100 g) in which 18.1 mg of cis-diamino-platinum (II) dichloride (2 ppm Pt) are uniformly suspended. With pumping capacities of 280 ml / h and 720 ml / h, the metering pumps P1 and P2 conveyed the reactants into the previously heated to 130 ° C loop reactor (<maths id="math0001" num=""><math display="inline"><mrow><msub><mrow><mtext>V</mtext></mrow><mrow><mtext>loop</mtext></mrow></msub><mtext> = 1 l</mtext></mrow></math><img file="EP1013701A2_D0002.tif" /></maths>). Pump P3 recirculated the reaction mixture at 800-1000 l / h. In the reaction system, a pressure of 4 bar established. After a mean residence time of 2 hours, the product left the downstream tubular reactor (<maths id="math0002" num=""><math display="inline"><mrow><msub><mrow><mtext>V</mtext></mrow><mrow><mtext>R</mtext></mrow></msub><mtext> = 1 l</mtext></mrow></math><img file="EP1013701A2_D0003.tif" /></maths>) and was isolated in template B3.

The gasvolumetric SiH determination (decomposition with Na-butoxide) showed a final conversion of ≥ 99%. accompanying²⁹Si NMR spectroscopy showed that the signal position characteristic of the SiH group completely disappeared at δ -36.5 ppm.

Example 2:

In analogy to Example 1, 1637 g of a polydimethylsiloxane having pendant SiH functions (structure: MD_20.5D<maths id="math0003" num=""><math display="inline"><mrow><mfrac><mrow><mtext>H</mtext></mrow><mrow><mtext>5</mtext></mrow></mfrac></mrow></math><img file="EP1013701A2_D0004.tif" /></maths> M, SiH value: 2.5 eq / kg) in vessel B1 and 4564 g of a hydroxy-functional allyl polyether (M approx. 838 g / mol,<chemistry id="chem0002" num="0002"><img file="EP1013701A2_D0005.tif" /></chemistry> , JZ: 30.3 gJ / 100 g) in which 19.1 mg of cis-diamino-platinum (II) dichloride (2 ppm Pt) were suspended, presented in vessel B2. The metering pumps P1 and P2 promoted the reactants in the stoichiometric ratio of 1.3 equivalents of polyether / 1 Val of SiH-siloxane in the previously heated to 130 ° C Reaktionsloop. After an average residence time of 2 hours, an adduct was collected in B3, which had 98% SiH conversion.²⁹Si NMR spectroscopy ensured the structural identity of the product with the target.

Comparative Example 1

In a 2000 ml four-necked flask equipped with KPG stirrer, dropping funnel and reflux condenser, 1140 g of a hydroxy-functional allyl polyether (M ca. 522 g / mol<chemistry id="chem0003" num="0003"><img file="EP1013701A2_D0006.tif" /></chemistry> JZ: 48.6 gJ / 100 g), together with 22.9 mg of cis-diamino-platinum (II) dichloride (≡ 10 ppm) and 35 g of heptamethyltrisiloxane (4.99 equivalents SiH / kg) are introduced with vigorous tube and brisk heated to 100 ° C. The onset of exothermic reaction led to a temperature rise to 125 ° C. At this temperature, a further 315 g of heptamethyltrisiloxane were added dropwise so that on the one hand neither the temperature of the reaction mixture fell nor that the evolution of gas became too strong. After completion of the addition (1 hour), the SiH conversion was determined gas volumetrically (90.7%). The reaction mixture was kept at 130 ° C for a further 7 hours and the conversion determined hourly. After 7 hours, a final conversion of 96.4% was achieved.

Comparative Example 2:

In a 2000 ml four-necked flask with KPG stirrer, dropping funnel and reflux condenser, 1254 g of a hydroxy-functional allyl polyether (M ca. 838 g / mol,<chemistry id="chem0004" num="0004"><img file="EP1013701A2_D0007.tif" /></chemistry> JZ: 30.3 gJ / 100 g) together with 26.2 mg (≡ 10 ppm) of cis-diaminoplatinum (II) dichloride and 45 g of a polydimethylsiloxane having pendant SiH functions (structure: MD_20.5D<maths id="math0004" num=""><math display="inline"><mrow><mfrac><mrow><mtext>H</mtext></mrow><mrow><mtext>5</mtext></mrow></mfrac></mrow></math><img file="EP1013701A2_D0008.tif" /></maths> M, SiH value: 2.5 Val / kg) with vigorous stirring and heated rapidly to 80 ° C. The exotherm of the onset of the reaction raised the temperature of the reaction to 112 ° C. After the pre-reaction had subsided, the reaction mixture was heated to 130 ° C and then added dropwise to 405 g of the hydrogen siloxane so that little gas evolution was observed and the temperature of the reaction mixture did not drop below 125 ° C. After completion of the addition (approx. 2 Hours), the gas volumetric SiH conversion was 89% and reached in a post-reaction phase of a further two hours 97%.