EP3194363A1

EP3194363A1 - Method for producing isocyanates in the gas phase

Info

Publication number: EP3194363A1
Application number: EP15763939.4A
Authority: EP
Inventors: Josef Sanders; Armin SCHYMURA; Martin Ehrig; Manfred Keller-Killewald; Dietmar Wastian
Original assignee: Covestro Deutschland AG
Current assignee: Covestro Intellectual Property GmbH and Co KG
Priority date: 2014-09-19
Filing date: 2015-09-18
Publication date: 2017-07-26
Also published as: WO2016042124A1; CN106715385B; JP2017527596A; US20170305842A1; CN106715385A; KR20170058927A

Abstract

The invention relates to a method for producing isocyanates by reacting the corresponding primary amines with phosgene in the gas phase, wherein the phosgene is injected into the gaseous amine flow in the interior of a flow tube via an outer ring channel and through several radial channels in an angle of ≤ 90° relative to the flow direction of the gaseous amine flow, wherein a static mixer of the Kenics type is provided coaxially in the interior of the flow tube.

Description

Process for the preparation of isocyanates in the gas phase

The invention relates to a process for the preparation of isocyanates by reacting the corresponding primary amines with phosgene in the gas phase.

Isocyanates are produced in large quantities and serve mainly as starting materials for the production of polyurethanes. They are usually prepared by reacting the corresponding amines with phosgene. One possibility for the preparation of isocyanates is the reaction of the amines with the phosgene in the gas phase.

It is known that in gas-phase reactions the good mixing of the starting materials plays an important role in achieving high conversions and selectivities, especially in the reaction of polyfunctional reactants. The methods for realizing short mixing times are known in principle. Suitable mixing units with dynamic or static mixing elements. Preference is given to using static mixers.

Methods in which dynamic mixing means, e.g. Stirrer, are used, for example, in the patent applications GB 1 165 831 AI and EP 2 199 277 Bl described. For the construction of static mixing a number of different implementation options is conceivable, for. As the use of known from the combustion technology nozzles, Glattstrahldüs s or Venturi nozzles.

Above all, continuous processes for the gas-phase phosgenation of amines using tubular reactors are known from the prior art, in which the mixing of the educts takes place according to the jet mixer principle by coaxial nozzles, in particular smooth-jet nozzles (see, for example, Chem.-Ing. Techn. 44, 1979, p. 1051 ff). Such processes are described, for example, in patent applications EP 0 289 840 A1, EP 0 570 799 A1, EP 0 699 657 A1, EP 1 275 639 A1, EP 1 319 655 A2, EP 362 847 A2 and EP 2 199 277 B1.

Furthermore, various patent applications describe variants with which the mixing by means of coaxial nozzles can be further improved. For example, EP 1 449 826 B1 discloses a process in which, for mixing the vaporous educts, multiple nozzles parallel to the

Flow direction can be used.

EP 1 526 1 29 AI discloses a method in which the flow turbulence in the mixing zone by internals, for. B. by spin turning, is increased. EP 1 555 258 A1 discloses a process using a ring-die nozzle in which the gaseous amine, optionally diluted with an inert gas, is fed to the reactor via the annular gap and the phosgene is supplied via the inner nozzle as a central jet and over the remaining Reaktorquers chnitt.

EP 188 247 A1 (WO 2009/027232 A1) and EP 2 188 248 A1 (WO 2009/027234 A1) describe processes in which between the two fluid streams of amine and phosgene in a mixing means, e.g. in a ternary mixing nozzle, an inert medium, e.g. Nitrogen, is dosed. According to the teaching of EP 2 188 248 A1, in addition, the turbulent flow boundary layer of at least one fluid stream before being brought into contact with the other stream is reduced by at least one mechanical baffle.

Although the coaxial mixing of amines with phosgene via nozzles has become established in the art, alternative mixing devices are described in the prior art.

EP 0 928 785 A1 discloses a process in which microstructure mixers are used for rapid mixing of the fluid reactant streams. The disadvantage here, however, is that it is very easy due to the small dimensions of the mixer at the high temperatures to blockages by deposition of solid by-products or decomposition products, which is why this method has not prevailed on an industrial scale.

EP 2 088 139 A1 describes a process in which gaseous amine is injected at 200 ° -600 ° C. at right angles into excess phosgene from an outer annular channel via radial bores and flows in a flow tube. After mixing, the reactant stream is first accelerated by a cross-sectional reduction and then slowed down again by cross-sectional enlargement, before it is then passed into a reactor.

WO 2011/1 15848 A1 discloses a static mixer and its use for the preparation of isocyanates by phosgenation of primary amines, wherein an up to 90% solvent-containing amine stream injected at right angles through an outer annular channel through a plurality of radial holes in the phosgene stream inside a flow tube is where a (very short) Stömungselement in the flow tube at the height of the bores the phosgene stream without changing the flow velocity imposes an annular flow, whereby the mixing with the amine stream is favored. However, no examples of isocyanate production are cited, as well as quantity, pressure and temperature specifications are missing, so that no conclusions about the state of matter of the educts are possible. As the amine, only M DA is mentioned. Although some of the described methods have now been realized on an industrial scale, they still have some disadvantages. Here, above all, the shortening of the running times of the plants (plant life) due to contamination due to the formation of solid by-products should be mentioned. In the processes using mobile mixing devices, z. As stirrers, the mixing is not fast enough despite the high speeds used, resulting in a broad contact time distribution and thus undesirable solids formation. Also, the safety required sealing their drive shafts at the point of entry into the reactor is difficult and requires a high testing and maintenance.

Disadvantages of the methods based on the jet mixer principle are, for. B. high pressure loss or not fast enough mixing. High Druckveriust in the mixing device requires an increased effort in the supply of gaseous reactants and requires higher boiling temperatures to ensure a sufficient form. Especially for educts with reactive functional groups, the increased boiling temperature but thermal damage and thus increased formation of by-products (yield / selectivity losses) result. Not sufficiently rapid mixing or backmixing also lead to increased residence time of a portion of the reactants and products and as a result to undesirable parallel or subsequent reactions. Furthermore, insufficient mixing, especially in the case of strongly exothermic or endothermic reactions, causes an uneven temperature distribution in the reactor. Such "hot spots" or "cold spots" in the reactor lead to an increased thermal decomposition of the products or to undesirably premature condensation of the products. Thermal decomposition products form a solid residue, which deposits on the reactor wall. A sufficiently fast mixing requires high

Flow rates at which the residence times necessary for complete reaction of the amines, especially when using aromatic amines, can only be achieved in very long mixing and reactor tubes. Other disadvantages are the high cost of consuming designed and difficult to manufacture mixing elements and their required precise adjustment in the center of the reactor cross section chnitts. In addition, these mixing devices tend to vibrate or bend during operation, resulting in asymmetry of the flow and hence rapid fouling of the reactor.

The processes described in EP-A 2 088 139 A1 and WO 201 1/1 15848 A1, in which the amine stream is injected via an outer annular channel through a plurality of radial bores at right angles in the phosgene stream in the interior of a flow tube, have a high Druckveriust on the Amine side with the disadvantages described above.

The object of the present invention was therefore to provide a process for the preparation of isocyanates by reacting the corresponding primary amines with phosgene in the gas phase, which avoids the described disadvantages of the known processes and can be achieved with the high yields and, at the same time, long plant service lives , Surprisingly, it has been found that primary amines with phosgene in a tubular reactor above the boiling point of the amine in the gas phase can be advantageously reacted with long plant service lives, if the phosgene via an outer R ingkanal by several radial channels at an angle of <90 ° to the flow direction of gaseous amine troms is injected into the gaseous amine stream in the interior of a flow tube, wherein inside the flow tube is coaxial with a static mixer Kenics type. Such mixers are also referred to in the literature as gas mixer, reversing label or V-E 1 t-M i sc.

The invention relates to a process for preparing diisocyanates or triisocyanates of the general formein (I) or (II)

OCN-R-NCO (I) OCN-R-NCO (Ii),

NGO or mixtures of such di- and / or triisocyanates, wherein

R is a (cyclo) aliphatic, araliphatic or aromatic hydrocarbon radical having up to 15 carbon atoms, with the proviso that at least 2 carbon atoms are arranged between the NCO groups, by phosgenation of the corresponding di- and / or triamines of the general formula ( III) or (IV)

H ₂ N - R - NH ₂ (in) R - NH ₂ (IV)

NH ₂ in which R has the abovementioned meaning, in which the vaporous di- and triamines, optionally diluted with an inert gas or with the vapors of an inert solvent, and phosgene heated separately to temperatures of 200 ° C to 600 ° C, in one Tube reactor are mixed and reacted, characterized in that the phosgene via an outer annular channel through a plurality of radial channels at an angle of <90 ° to the flow direction of the gaseous amine stream in the gaseous amine stream in the interior a flow rotoes is injected, wherein in the interior of the flow tube coaxial with a static mixer Kenics type.

Under steam ammines according to the invention di- and triamines understood that are present in gaseous form and may optionally contain portions of non-vaporized amine droplets (aerosol). However, the vaporous amines preferably contain no droplets of unvaporized amines.

In a first preferred embodiment, the angle is> 60 ° and <90 °, preferably> 75 ° and <90 ° and particularly preferably 90 °. An angle of 90 ° according to the invention is also referred to as rectangular or vertical. According to the invention, channels are understood as meaning openings which are permeable to the educt streams. The openings may have any shape and can be, for example, with

Getting help from a laser or a drill. Preference is given here holes.

In a particularly preferred embodiment, the channels are holes and the angle is 90 °, so that the phosgene is injected via an outer annular channel through a plurality of radial bores at right angles to the gaseous amine stream in the interior of a flow tube.

Typical examples of suitable aliphatic amines are e.g. mentioned in EP 0 289 840 AI. Preference is given to diamines such as the pure isomers or the isomer mixtures of isophorone diamine (IPDA, mixture of isomers), 1,6-hexamethylenediamine (H DA). Bis (p-aminocyclohexyl) methane, 1,3- and 1, 4-bis (aminomethyl) cyclohexane or mixtures thereof, xylylenediamine or isomeric mixtures thereof and particularly preferably 1, 5-pentanediamine used. The preferred triamine is l, 8-diamino-4- (aminomethyl) octane (triaminononane).

Typical examples of suitable aromatic amines are the pure isomers or isomer mixtures of diaminobenzene, diaminotoluene, diaminodimethylbenzene, diaminonaphthaiine and diaminodiphenylmethane. Preference is given to using 2,4- / 2,6-toluylenediamine mixtures of the isomer ratios 80/20 and 65/35 or the pure 2,4-tolylenediamine isomer.

The starting amines of the formula (III) and (IV) are evaporated before carrying out the process according to the invention, optionally with an inert gas such as N 2, He, Ar or with the vapors of an inert solvent, for. B. aromatic hydrocarbons with or without halogen substitution, heated to 200 ° C to 600 ° C, preferably 250 ° C to 450 ° C, and fed to the mixer or reactor. The amount of inert gas optionally used as a diluent or gaseous solvent is not critical. For example, the volume ratio of amine vapor to inert gas or solvent vapor can be between 1: 0.5 and 1: 2.

The phosgene used in the phosgenation is used, based on the amine, in excess. In general, the molar phosgene excess based on an amino group is 30 to 300%, preferably 60 to 200%. Before being fed into the mixer or reactor, the phosgene is heated to a temperature of from 200 ° C to 600 ° C, preferably from 250 ° C to 450 ° C.

In one embodiment, the phosgene can be treated with an inert gas such as N 2, He, Ar, or with the vapors of an inert solvent, e.g. As aromatic hydrocarbons are diluted with or without halogen substitution. Preference is given to the undiluted variant.

The mixing of the two educt streams takes place in a flow tube in which a co-axial static mixer of Ken i es type is, wherein the optionally diluted with an inert gas gaseous amine (gas stream A) is passed coaxially through the flow tube and the mixer and the Phosgene via an outer annular channel through a plurality of radial channels, preferably bores, which are located on a plane on the circumference of the flow tube (introduction level), with an angle of <90 °, preferably> 60 ° and <90 °, more preferably> 75 ° and <90 ° and most preferably 90 ° to the flow direction of the amine stream is introduced. The static mixer begins in the flow direction already above the introduction level of the phosgene and ends downstream significantly below the incipient level of the phosgene, its length depends on the reactivity of the amine used. In a preferred embodiment of the method according to the invention, the number of mixing elements of the static mixer above the introduction level is such that the inert gas possibly added to the amine is mixed homogeneously with it, i.e., in a homogeneous manner. the degree of mixing of amine and inert gas immediately before the introduction level is 50 to 100, preferably 70 to 95%. The ratio of the length of the static mixer before the introduction level to the length behind the introduction level is 0.1 to 1.0, more preferably 0.2 to 0.8. The schematic structure of the mixing device according to the invention is exemplified in Figure 1.

The phosgene stream is introduced into the gas stream A at a rate of 15-90 m / s, more preferably 20-80 m / s. The number of channels and their cross-sectional area result from the phosgene volume flow to be introduced. Preferred is an odd number of channels. The diameter of the mixing tube is dimensioned so that the flow velocity of the gas mixture of all components immediately below (downstream) the introduction level 4-25 m / s, preferably 6-! 5 m / s, more preferably 8-12 m / s. The length of the Kenics type static mixer and the number of its mixing elements are sized so that a sufficient degree of mixing is achieved at the end of the mixer and can be calculated. The design of such mixers is described in detail in the specialist literature, for example in "Mixing and Stirring", ed. Matthias Raume, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2003, pp. 198-220, and in the literature cited therein. The degree of mixing to be achieved depends on the reactivity of the amine used and is generally 50-100%, preferably 80-99%, particularly preferably 95-98%.

Preference is given to using tube reactors without internals and without moving parts in the interior of the reactor in the process according to the invention. The tube reactors are generally made of steel. Glass, alloyed or enamelled steel and are dimensioned to be among the

Process conditions complete conversion of the amine is made possible with the phosgene. The gas streams are introduced via a mixing device described in more detail above at one end of the tubular reactor in this. The temperature in the reactor is 200 ° C to 600 ° C, preferably 250 ° C to 450 ° C, which temperature can optionally be maintained by heating the tubular reactor upright.

In carrying out the process of the invention is generally the pressure in the supply lines to the reaction chamber at 200 - 3.000 mbar abs., Preferably at 800 - 1.500 mbar abs., And at the exit from the reaction chamber at 150 - 2,000 mbar abs., Preferably 750 - 1.440 mbar abs., By maintaining a suitable differential pressure, a flow rate within the reaction space of 3 to 120 m / s, preferably 5 to 75 ms is maintained. Under these conditions, generally turbulent flow conditions prevail within the reaction space.

The refining time is calculated from the time throughput of the educt streams, the reactor dimensioning and the reaction parameters pressure and temperature. Depending on the reactivity of the amine used, the retention time of the reaction mixture in the reactor is 0.05 s to 10 s, preferably 0.08 s to 4 s.

After the phosgenation reaction has taken place in the reaction space, the gaseous mixture leaving the reaction space continuously is freed of the isocyanate formed. This can be done for example by means of an inert solvent whose temperature is chosen so that it is above the decomposition temperature of the isocyanate carbamic acid and on the other hand below the condensation temperature of the isocyanate and preferably also of the optionally used in the vapor form as a diluent solvent, so that Isocyanate and auxiliary solvents condense or the isocyanate dissolves in the auxiliary solvent, while excess phosgene, hydrogen chloride and optionally used as diluent mitverwendetes inert gas through the condensation stage or the solvent in gaseous form. For selective recovery of the auxiliary solvent from the gas leaving the reaction space mixture are particularly suitable at a temperature of 60 to 200 ° C, preferably 90 to 170 ° C, held solvent of the type exemplified above, in particular technical mono- (MCB) and dichlorobenzene (ODB). Preferably MCB. Conceivable methods of selective condensation of the isocyanate formed from the gas mixture leaving the reactor using such solvents are, for example, the passage of the gas mixture through said solvent or the injection of the

Solvent (solvent mist) in the gas stream (quench). The gas mixture passing through the condensation stage to obtain the isocyanate is then freed of excess phosgene in a manner known per se. This can be done by means of a cold trap, absorption in an inert solvent (e.g., MCB or ODB) maintained at a temperature of -10 ° C to 8 ° C, or by adsorption and hydrolysis on activated carbon. The chioreactor gas passing through the phosgene recovery stage can be recycled in a manner known per se for recovery of the chlorine required for phosgene synthesis.

The purification of the isocyanate can be carried out by fractional distillation or by recrystallization or adsorptive removal of impurities, e.g. by treatment with activated charcoal. Diatomaceous earth, silica gel or bleaching earth. If the isocyanate is sufficiently stable in thennish, purification is preferably carried out by the mildest possible distillative workup of the crude isocyanate solution in the solvent used for the isocyanate condensation, the isocyanate fraction optionally being distilled in vacuo.

It is particularly surprising that with the mixing device according to the invention explained in more detail above, very reactive amines, such as e.g. 1, 5-pentanediamine (PDA) can be phosgenated with excellent yields and system lifetime to 1, 5-pentane diisocyanate (PDI). The required flow rates are comparatively low, so that shorter reactors can be used than when using jet mixers. Since the amine, in contrast to the method described in EP 2 088 139 AI and WO 2011/115848 not injected through narrow holes, but is fed through a flow tube with a significantly larger cross-section of the reactor, the pressure drop is very low and thus the United evaporation temp low. As a result, especially sensitive amines such as. Bis (p-aminocyclohexyl) methane or 1, 3 -xylylenediamine be phosgenated with better yields.

The invention relates to a process for the preparation of di- or triisocyanates of the general formulas (I) or (II) OCN-R-NCO OCN-R-NCO

I

NGO or mixtures of such di- and / or triisocyanates, wherein

R is a (cyclo) aliphatic, araliphatic or aromatic hydrocarbon radical having up to 15 carbon atoms, with the proviso that at least 2 carbon atoms are arranged between the NCO groups, by phosgenation of the corresponding di- and / or triamines of the general formula ( III) or

(IV)

H ₂ NR-NH ₂ (in) H ₂ NR-NH ₂ (IV)

NH ₂ in which

R has the abovementioned meaning, in which the vaporous di- and triamines, optionally diluted with an inert gas or with the vapors of an inert solvent, and phosgene separately heated to temperatures of 200 ° C to 600 ° C, mixed in a tubular reactor and Be brought reaction, characterized in that the phosgene is injected via an outer annular channel through a plurality of radial channels at an angle of <90 ° to the flow direction of the gaseous amine stream in the gaseous amine trom inside a flow tube, wherein in the interior of the flow tube coaxial a static one

Kenics-type mixer is located. In a second embodiment of the method, the channels are bores.

In a third embodiment of the method according to one of the embodiments 1 or 2, the angle is> 60 ° and <90 °.

In a fourth embodiment of the method according to one of the embodiments 1 or 2, the angle is> 75 ° and <90 °. In a fifth embodiment of the method according to one of the embodiments 1 or 2, the angle is 90 °. In a sixth embodiment of the method, the method is performed so that the phosgene is injected via an outer annular channel through a plurality of radial bores at right angles in the gaseous amine trom in the interior of a flow tube.

In a seventh embodiment, the method according to any one of embodiments 1 to 6 is performed so that the amine trom heated to 250 ° C to 450 ° C before being fed into the mixer. in an eighth embodiment, the process according to any one of the embodiments 1 to 7 is carried out so that the phosgene stream is heated to 250 ° C to 450 ° C before being fed into the mixer.

In a ninth embodiment, the process according to one of the embodiments 1 to 8 is carried out so that the phosgene is used in excess relative to the amine and the molar phosgene excess based on an amino group is 30 to 300%.

In a tenth embodiment, the process according to one of the embodiments 1 to 8 is carried out so that the phosgene is used in excess relative to the amine and the molar phosgene excess based on an amino group is 60 to 200%.

In an eleventh embodiment, the process according to one of the embodiments 1 to 10 is carried out so that the phosgene stream is introduced at a rate of 15-90 m / s into the gaseous amine gas possibly diluted with an inert gas.

In a twelfth embodiment, the method according to one of Ausfülirungsformen 1 to 10 is performed so that the phosgene stream is introduced at a rate of 20-80 m / s in the optionally diluted with an inert gas gaseous amine trom. In a thirteenth embodiment, the method according to one of embodiments 1 to 12 is performed such that the ratio of the length of the static mixer upstream of the entry level (upstream) to the length downstream of the entry level (downstream) (Figure 1) is 0.1 to 1.0 is.

In a fourteenth embodiment, the method according to one of embodiments 1 to 12 is performed such that the ratio of the length of the static mixer upstream of the entry level (upstream) to the length downstream of the entry level (downstream) (Figure 1) is 0.2 to 0.8 is.

In a fifteenth embodiment, the method according to one of embodiments 1 to 14 is performed so that the diameter of the mixing tube is dimensioned so that the flow velocity of the gas mixture of all components immediately below (downstream) the introduction level (Figure 1) 4-25 m / s is. In a sixteenth embodiment, the method according to one of the embodiments 1 to 14 is performed so that the diameter of the mixing tube is dimensioned such that the Flow rate of the gas mixture of all components immediately below (downstream) of the inlet level (Figure 1) is preferably 6-15 m / s.

In a seventeenth embodiment, the method according to one of the embodiments 1 to 14 is performed so that the diameter of the mixing tube is dimensioned so that the flow velocity of the gas mixture of all components immediately below (downstream) the introduction level (Figure 1) 8-12 m / s is.

In an eighteenth embodiment, the method according to one of the embodiments 1 to

17 so that the length of the Kenics type static mixer and the number of mixing elements are such that a mixing level of 50-100% is achieved at the end of the mixer.

In a nineteenth embodiment, the method according to any one of embodiments 1 to 17 is performed so that the length of the Kenics type static mixer and the number of its mixing elements are such that at the end of the mixer a mixing degree of 80-99% is achieved becomes. In a twentieth embodiment, the method according to one of the embodiments 1 to 17 is performed such that the length of the Kenics type static mixer and the number of its mixing elements are so dimensioned that at the end of the mixer a mixing degree of 95-98% is achieved. is reached.

In a twenty-first embodiment, the process according to any of embodiments 1 to 20 is conducted by adding an inert gas to the amine and by measuring the number of mixing elements of the static mixer above the introduction level (Figure 1) such that the degree of mixing of amine and inert gas immediately before the introduction level (upstream) is 50 to 100%.

In a twenty-second embodiment, the process according to one of the embodiments 1 to 20 is conducted in such a way that an inert gas is added to the amine and the number of mixing elements of the static mixer above the introduction level (Figure 1) is dimensioned so that the degree of mixing of amine and inert gas immediately before the introduction level (upstream) at 70 to 95%. In a twenty-third embodiment, the method according to any one of embodiments 1 to 22 is performed so that the temperature in the reaction space at 200 ° C to 600 ° C. In a twenty-fourth embodiment, the process according to any one of embodiments 1 to 22 is conducted such that the temperature in the reaction space is 250 ° C to 450 ° C.

In a twenty-fifth embodiment, the method according to one of the embodiments 1 to 24 is carried out so that the pressure in the supply lines to the reaction space is 200 to 3,000 mbar abs. and at the exit from the reaction space at 150-2000 mbar abs. lies.

In a s echsundzwanzigsten embodiment, the method according to one of the imple mentation forms 1 to 24 out so that the pressure in the supply lines to the reaction chamber at 800 1500 mbar abs. and at the exit from the reaction space at 750 - 1.440 mbar abs. lies. In a twenty-seventh embodiment, the method according to any one of

Execution forms 1 to 26 performed so that a flow rate within the reaction space of 3 to 120 m / s is maintained.

In a twenty-eighth embodiment, the method according to one of

Embodiments 1 to 26 performed so that a flow rate within the reaction space of 5 to 75 m / s is maintained.

In a twenty-ninth embodiment, the process according to any one of embodiments 1 to 28 is conducted so that the residence time of the reaction mixture in the reactor is 0.05 s to 10 s.

In a thirtieth embodiment, the process according to one of embodiments 1 to 28 is conducted such that the residence time of the reaction mixture in the reactor is from 0.08 s to 4 s.

Examples:

Fig. 1: Schematic structure of a mixing device according to the invention, in which the numbers 1 -3 have the following meaning: 1: amine + inert gas; 2: phosgene; 3: introduction level.

GC method of PDI analysis:

Gas Chromatograph: Agilent (formerly Hewlett PACKARD), 7890, Series A or B

(6890 series A or B are also possible)

Separation column: RXI 17 (Restek), fused silica, length 30 m, inner

Diameter 0.32 mm, film thickness 1, 0 μηι

Temperatures: Injector 250 ° C, Detector (FID) 350 ° C

Oven: start 80 ° C, holding time 0 min.

Hei / rate 10 ° K / min to 140 ° C, Haitezeit 7.5 min.

Heating rate 20 ° K / min to 250 ° C, holding time 5.0 min.

Running time 24 min.

Carrier gas: hydrogen

Gas setting constant flow instead

constant pressure

Column pressure approx. 0.4 bar abs., At start of analysis column flow approx. 100 ml / min at constant flow

Split output flow 100 mV min

Ratio 50: 1

Septum rinsing approx. 3 ml / min.

Comparative example: Phosgenation of 1,5-pentanediamine (PDA) with coaxial nozzle

In a Miniplant for continuous vapor phase phosgenation with a Aminverdampfungsstufe, a tubular reactor (length 720 mm, inner diameter 8 mm) with a arranged on the reactor axis coaxial nozzle (inner diameter 2 mm) and a downstream isocyanate condensation stage were measured at a pressure of 700 mbar abs at the end of the isocyanate condensation step, continuously 250 gh PDA vaporized under introduction of a nitrogen stream of 37 g / h, superheated to 270 ° C and fed via the coaxial nozzle (simple smooth-jet nozzle) to the reactor. At the same time, 1090 g / h of phosgene were heated to 300 ° C. in parallel and likewise continuously fed to the reactor on the annular space released by the nozzle, in which the two educt streams were mixed and reacted. The velocity of the gas stream in the reactor was about 7.1 m / s and the Ges speed ratio of amine / nitrogen to phosgene 5.9. After a mean residence time in the reactor of 0.1 s, the gas stream containing the reaction product 1, 5-pentanediisocyanate (PDI) was cooled by injection cooling with 5 kgh of liquid monochlorobenzene and condensed or dissolved, the temperature of the liquid phase in the quench being approx. 90 ° C was. The MCB and formed PDI-containing vapors were passed to an isocyanate absorption column along with the offgas of the reaction. Isocyanate and MCB were condensed in a downstream condenser and returned to the quench, while the off-gas, consisting essentially of nitrogen, excess phosgene and HCl, was phosgene-killed. The resulting solution of isocyanate in MCB was collected and worked up in portions by distillation.

Of about 50 experiments conducted in which the phosgene excess in the range of 125-175%, the temperature of amine, nitrogen and phosgene in the range of 260-360 ° C and the pressure in the range of 0.7-1.3 bar varies were only 3 experiments with run times of> 4 h could be achieved. The remaining tests had to be prematurely stopped, in some cases already after a few minutes, due to pressure increase due to blockage of nozzle and reactor.

Secondary components in the phosgenation of PDA:

Chloropentyl isocyanate, N-carbamoylpiperidine, N-carbamoyltetrahydropyridine,

CPI "C6-Im" "C6-Az"

The GC analysis of the crude solution obtained showed the following composition (MCB excluded, area% (area%):

Example 1: Phosgenation of 1, 5-pentanediamine (PDA) with static mixer (according to the invention)

In a miniplant for continuous (ias phase hydrogenation with an amine evaporation stage, a tubular reactor (length: 400 mm, internal diameter 8.8 mm) with a mixing tube arranged on the reactor axis (length: 210 mm, internal diameter 8 mm) in which a static mixer of the Kenics type is installed coaxially (length 200 mm, diameter 7.9 mm, 15 mixing elements) and a subsequent isocyanate condensation stage were abs. At a pressure of 700 mbar, measured at the end of I so cy anatkondensations, continuously 210 g / h of PDA with the introduction of a nitrogen stream of 37 g / h evaporated, superheated to 310 ° C and fed through the mixing tube to the reactor At the same time 1090 g / h of phosgene through an outer annular channel through 7 radial holes (diameter 1 mm The average residence time in the mixer was 0.02 sec. The reaction mixture leaving the mixer was metered into the interior of the mixing tube or supplied. The mean velocity of the gas stream in the reactor was about 6 m / s and the speed ratio of amine / nitrogen to phosgene stream was 0.043. After a mean residence time in the reactor of 0.12 s, the gas containing the reaction product PDI was quenched and worked up as described in the comparative example with 5 kg / h of liquid MCB.

With this system configuration, the Miniplant 80 h could be operated without problems. The iC analysis of the crude solution obtained showed the following composition (MCB excluded, Fl .-%):

Example 2: Phosgenation of an isomer mixture of 2,4- and 2,6-toluenediamine with static

Mixer (according to the invention)

In a Miniplant for continuous vapor phase phosgenation with a Aminverdampfungsstufe, a tubular reactor (length: 31 00 mm, inner diameter 16.0 mm) with a arranged on the reactor axis mixing tube (length: 210 mm, Innendurchme ss he 8 mm) in the coaxial one built-in static mixer of Kenics type (length 200 mm, diameter 7.9 mm, 1 5 mixing elements) and a subsequent isocyanate condensation stage are continuously at a pressure of 1000 mbar abs., Measured at the end of the isocyanate condensation step, 210 gh of a technical isomer mixture of 2,4- and 2,6-toluenediamine (TDA) in the ratio 4: 1 evaporated from under the introduction of a nitrogen stream of 40 gh, superheated to 330 ° C and fed via the mixing tube to the reactor. At the same time, 1020 g / h of phosgene are metered into the interior of the mixing tube via an outer annular channel through 7 radial bores (diameter 1 mm) perpendicular to the flow direction of the amine. The mean residence time in the mixer is 0.03 s. The reaction mixture leaving the mixer is fed to the reactor. The average velocity of the gas stream in the reactor is about 1.3 m / s and the rate of flow of amine / nitrogen to phosgene stream is 0.04. After a mean residence time in the reactor of 2.4 s, the gas stream containing the reaction product toluene diisocyanate (TDI) is quenched and worked up analogously to the comparative example with 5 kg / h of liquid o-dichlorobenzene (ODB).

With this system configuration, the Miniplant 80 h could be operated without problems.

The GC analysis of the crude solution obtained shows the following composition (ODB excluded, area%):

Phenylene diisocyanate 0.016

Xylylene diisocyanate 0.007

TDI 99,977

Claims

claims

1. Process / ur Preparation of di- or triisocyanates of the general formulas (I) or (II)

OCN-R-NCO (I) OCN-R-NCO (II)

NGO or mixtures of such di- and / or triisocyanates, wherein

R is a (cyclo) aliphatic, aliphatic or aromatic hydrocarbon radical having up to 1 to 5 carbon atoms, with the proviso that between the NCO groups at least 2 carbon atoms are arranged, by phosgenation of the corresponding di- and / or triamines of the general formula (III) or (IV)

H ₂ NR-NH ₂ (i) H ₂ NR-NH ₂ (IV)

NH, in which

R has the abovementioned meaning, in which the vaporous di- and triamines, optionally diluted with an inert gas or with the vapors of an inert solvent, and phosgene separately heated to temperatures of 200 ° C to 600 ° C, mixed in a tubular reactor and Be brought reaction, characterized in that the phosgene via an outer annular channel through a plurality of radial channels at an angle of <90 ° to the flow direction of the gaseous amine troms in the gaseous amine stream in

Inside a flow tube is injected, wherein inside the flow tube coaxial with a static mixer Kenics type.

2. The method according to claim 1, wherein the channels are bores and / or the angle is> 60 ° and <90 °, preferably> 75 ° and <90 ° and particularly preferably 90 °. 3. The method according to any one of claims 1 or 2, wherein as di- and / or triamines aliphatic amines such as the pure isomers or the isomer mixtures of I sophorondiamins, 1, 6-hexamethylenediamine, bis (p-aminocyclohexyl) methane, 1,

3- or 1,4-bis (aminomethyl) cyclohexane or their isomer mixtures, xylylenediamine or mixtures thereof, 1,5-pentanediamine or l, 8-diamino-4- (aminomethyl) octane, preferably 1,5-pentanediamine, are used.

4. The method according to any one of claims 1 or 2, wherein as diamines aromatic amines such as 2,4- / 2,6-toluenediamine mixtures of the isomer ratios 80/20, 65/35 or the pure 2,4-toluenediamine isomers, or Isomeric mixtures of diaminonaphthalene or

Diaminodiphenylmethans be used.

5. The method according to any one of claims 1 to 4, wherein the amine stream and / or the phosgene stream are heated to 250 ° C to 450 ° C before being fed into the mixer.

6. The method according to any one of claims 1 to 5, wherein the phosgene used in excess relative to the amine and the molar phosgene excess based on an amino group 30 bis

300%, preferably 60 to 200%.

7. The method according to any one of claims 1 to 6, wherein the phosgene stream is introduced at a rate of 15-90 m / s, more preferably 20-80 m / s in the optionally diluted with an inert gas gaseous amine stream. 8. The method according to any one of claims 1 to 7, wherein the ratio of the length of the static mixer before the entry level (upstream) to the length behind the introduction level (downstream), 0.1 to 1.0, preferably 0.2 to 0,

8 is.

9. The method according to any one of claims 1 to 8, wherein the diameter of the mixing tube is dimensioned so that the flow velocity of the gas mixture of all components immediately below (downstream) the introduction level 4-25 m / s, preferably 6-15 m / s, especially preferably 8-12 m / s.

10. The method according to any one of claims 1 to 9, wherein the length of the Kenics-type static mixer and the number of its mixing elements is such that at the end of the mixer, a degree of mixing of 50-100%, preferably 80-99%, particularly preferably at 95-98% is achieved.

11. The method according to any one of claims 1 to 10, wherein an inert gas is added to the amine and the number of mixing elements of the static mixer above the introduction level is such that the degree of mixing of amine and inert gas immediately before the introduction level (upstream) at 50 bis 100%, preferably 70 to 95%.

12. The method according to any one of claims 1 to 11, wherein the temperature in the reaction chamber at 200 ° C to 600 ° C, preferably 250 ° C to 450 ° C.

13. The method according to any one of claims 1 to 12, wherein the pressure in the supply lines to the reaction chamber at 200 - 3000 mbar abs., Preferably at 800 - 1.500 mbar abs., And at the exit from the reaction space at 150 - 2,000 mbar abs., preferably at 750 - 1.440 mbar abs., is located.

14. The method according to any one of claims 1 to 13, wherein a flow rate within the reaction space of 3 to 120 m s, preferably 5 to 75 m / s is maintained.

15. The method according to any one of claims 1 to 14, wherein the residence time of the reaction mixture in the reactor 0.05 s to 10 s, preferably 0.08 s to 4 s.