DE10311865A1 - Production of polyurethane components e.g. diphenylmethane di-isocyanate, involves making intermediates from simple starting materials and then reacting the intermediates, all in a system of micro-technology components - Google Patents

Abstract

A method for the production of polyurethane components, especially isocyanates, involves using a system made up of components used in micro-technology.

Description

Isocyanates are building blocks for polyurethanes (PU). Polyurethanes have the broadest application area of all plastics. The for a production line used to manufacture polyurethanes Isocyanate amounts are usually between 500 kg and 100 t / a. Currently Isocyanates are used almost exclusively in large-scale Plants manufactured with annual capacities of up to 200,000 t / a. From there they are often over transported long distances to the PU manufacturers. The advantage of The production of isocyanates in large plants is particularly important in reducing manufacturing costs by using the economy-of-scale.

Large-scale production of However, isocyanates also have disadvantages. These are in particular in the complex logistics process from the isocyanate manufacturer to the polyurethane manufacturer, continue in that the PU manufacturer handles large amounts of chemicals as well as the fact that the quality of the isocyanate is damaged during the transport process can. Another disadvantage is that in such a large-scale Plant for the production of isocyanates produced only one isocyanate can be.

It would be because of the above Disadvantages in large-scale Production of isocyanates desirable to have a process for producing isocyanates which avoids the disadvantages mentioned. In particular, such a procedure should can be installed decentrally at the PU manufacturer, just-in-time those required for PU production Provide isocyanate quantities with the PU manufacturer and a high elasticity in the Have amount of isocyanate produced.

Surprisingly was found to be possible is to build systems out of building blocks of microtechnology and to operate the production of polyurethane structural components, especially isocyanates and polyols, are suitable and the disadvantages the large-scale Overcome plants.

The invention accordingly relates to Process for the production of polyurethane structural components, in particular Isocyanates and polyols, characterized in that the manufacture takes place in a system that consists of building blocks of microtechnology is constructed.

Because of the "building block" character of micro and mini technology this process is principally for the production of all isocyanates and polyols.

Individual building blocks, hereinafter also referred to as modules, the large-scale technical value chain be replaced by others or left out entirely. Thereby can the type of chemicals used by the manufacturer of the Change polyurethane positively.

The method according to the invention is open to constant inexpensive evolutionary Improvement of the process, such as the replacement of the reactor type or new ones Requirement for the reaction type, because the building blocks of such expanded micro-technical system without much effort, against others replaced or additionally can be installed.

Another advantage of the method according to the invention is that the holdup of chemicals in the plant and the connected logistics units is low.

The means of the inventive method The quantities of end product produced are usually between 1 g / h and 10 kg / h.

The micro and mini technology is meanwhile a mature field and in literature in monographs and Magazines anchored (e.g. Microreactors, W. Ehrfeld, V. Hessel, H. lion, Wiley / VCH 2000). It is due to very small flow channel cross sections (smaller 500 - 1000 μm) and extreme size Surfaces too volume ratios characterized (Sensor Controlled Processes in Chemical Microreactors, H. Möbius, W. Ehrfeld, V. Hessel, Th. Richter, in Transducers, 95 - Eurosensors IX, pp. 775-778; H. Mensinger, Th. Richter, V. Hessel, J. Döpper, W. Ehrfeld, Microreactor with Integrated Static Mixer and Analysis System, Proceeding of the Micro Total Analysis Systems Workshop, eds. A. van Berg, P. Bergveld, Kluwer Acad. Pub., Pp. 237-243 (1995)).

It is known from the literature that for microtechnical Plant individual modules for Basic operations in process engineering, such as reactors, evaporators, Separators and also heat exchangers for multiphase reactors, to disposal stand.

The required microsystems can, for example can be produced inexpensively by lithographic processes.

Due to their small size, the modules have some special features compared to large-scale technical devices:
The thermal and inertia of such systems are low. This enables the system to be started up and shut down quickly, dead spaces are minimized, the product is only subjected to low thermal loads and isothermal conditions can be easily achieved.

The fluid dynamics in the system is mostly through laminar flows, this means Mixing by split and diffusion and not by turbulence.

Typical basic operations are as indicated in the literature, for example reactors for gas phase, liquid phase and also 3-phase reactions, mixers, heat exchangers, evaporators, filter units, Extractors and phase separators are available.

Such a process can, as required, be installed decentrally at the polyurethane manufacturer and provide the quantities of isocyanate required for polyurethane production just in time. The method according to the invention can be new Open up applications in which only small amounts of polyurethane components are required, for example in the electronics industry. Since these systems have little dead space due to their small size, they are easy to clean, quick to start and stop and, depending on the needs of the polyurethane manufacturer, are therefore suitable for campaign-based production of different isocyanates in the same system.

The reaction conditions at the execution the process in microreactors can be easily experimented be found out. The implementation of the same is preferred Conditions carried out as they are common in the corresponding large-scale processes.

Because of the physico-chemical Special features of microtechnology, such as isothermal energy within the Modules, short residence time in the system, low temperature load, good mixing, an isocyanate in the process according to the invention high quality delivered, which mostly exceeds the quality of isocyanates from world-scale plant.

The essence of the invention is to be described below by way of example in the preparation of diphenylmethane diisocyanate (MDI). The prior art for the production of MDI is given, for example, in WO 99/40059 and the literature cited therein. The documents mentioned describe the usual world-scale systems, without the inherent shortcomings associated with this method of production, such as low flexibility in system operation, logistics of large quantities of product over long distances combined with disadvantageous quality requirements of the product during storage and temperature changes, basic limits in the optimization of product quality , since strict isothermal energy cannot be implemented in plant operation, dead spaces and temperature gradients can lead to signs of aging, discoloration and fouling.
The system consisting of micro and mini modules is in the 1 shown.

Feedstocks are common and easily available chemicals such as air, aqueous hydrochloric acid, methanol, Gasoline and urea. In principle, the one shown in Figure 1 System also cut or supplemented at any point and the corresponding intermediate products are fed in there.

aqueous hydrochloric acid serves as a raw material for Hydrogen chloride. By electrolysis or a Deacon process chlorine is produced from it. The Deacon process is preferred worked with ruthenium as an active component. On a micro or mini scale however instead of that in large-scale Attachments usual Fluidized bed preferably an isothermal fixed bed reactor is used, which contains ruthenium as an active component. Methanol serves as the starting material for the Production of synthesis gas, which is a mixture of hydrogen and is carbon monoxide, and formaldehyde. Again, be preferred isothermal microreactors are used. From chlorine and carbon monoxide is preferably phosgene again in an isothermal fixed bed reactor generated. Benzene is separated from petrol and ammonia to aniline implemented. Either ammonia is converted into nitric acid with air, and Nitrobenzene then hydrogenated to aniline or it is preferably a direct amination carried out, again an isothermal fixed bed micro or mini reactor for Commitment comes. Aniline and formaldehyde are treated with acid Catalyst condensed to diphenylmethane diamine (MDA). Doing so preferably an acidic heterogeneous contact is used.

In a mixer or a cascade The intermediates phosgene and MDA are now mixed by mixers and implemented to MDI. A solvent can be used wherein the product itself is advantageously the solvent. The intermediate occurrence solids is controllable in micro / mini reactor technology. After passing through a residence time reactor, preferably with Flow characteristics, the separation of hydrogen chloride and excess phosgene, which occurs with the solvent is returned. For this Separation steps are micro and mini distillation and / or Falling film evaporator used. An MDI will be obtained that in further fractions of isomers and oligomers are separated can. It stands out due to the low thermal load and the isothermal driving style due to its very good quality.

The color values of the MDI produced lie in the lab system (L coordinate: brightness, a coordinate: green-red, b coordinate: blue-yellow) with L values> 93 and B values <40. Total chlorine concentrations are less than 1000 ppm and EHC values (easy hydrolisable chlorine) less than 50 ppm reached.

The pressures and temperatures at the correspond to individual process steps for the production of the MDI those that are common in the corresponding steps in conventional large-scale plants. The MDA is usually manufactured at temperatures in the range between 20 and 70 ° C and normal pressure. The MDA is preferably reacted with phosgene at temperatures in the Range between 90 and 220 ° C and press in the range between normal pressure and 10 bar, preferably between 1 and 10 bar.

The quantities of MDI produced are depending on the size of the facility, between 1 g / h and 10 kg / h.

Despite the exemplary processing for MDI is in principle, the procedure is also valid for the Manufacture of other isocyanates.

The polyol component for the polyurethane can be produced in a microtechnical system. Made from LPG (Liquified Petroleum Gasoli ne) / Propane is produced in heterogeneous catalytic micro / mini reactors propene and propylene oxide. This is converted into polyols. Polyol and isocyanate are combined, if appropriate with catalysts and additives, and thus processed to give the polyurethane.

Claims (6)

Process for the production of polyurethane structural components, in particular isocyanates, characterized in that the production takes place in a plant which is constructed from building blocks of microtechnology. A method according to claim 1, characterized in that the polyurethane structural components isocyanates are. A method according to claim 1, characterized in that the isocyanate is diphenylmethane diisocyanate. The method of claim 3, comprising the steps a) Conversion of hydrogen chloride to chlorine b) implementation of methanol to synthesis gas and formaldehyde, c) implementation of carbon monoxide and chlorine to phosgene, d) reaction of benzene with ammonia to aniline, e) condensation of aniline and formaldehyde with a acid catalyst f) implementation of the implementation products Step c) and e) to MDI. A method according to claim 4, characterized in that steps a) to f) can take place simultaneously. Method according to one of claims 1 to 5, characterized in that that the amount of that manufactured in the microtechnical facility End product is between 1 g / h and 10 kg / h.