Methods for preparing isocyanates

Abstract

This invention relates to a method for preparing isocyanates by reacting a corresponding amine with phosgene in a liquid phase. The method comprises: (a) mixing a feed stream containing an amine, a feed stream containing phosgene, and optionally an inert solvent; (b) reacting the amine with phosgene in a first reaction zone to obtain an intermediate reaction mixture containing isocyanate, carbamoyl chloride, amine hydrochloride, and unreacted phosgene; (c) cleaving the carbamoyl chloride in a second reaction zone and removing phosgene from the intermediate reaction mixture to obtain a crude product containing isocyanate; and (d) optionally post-processing the crude product. wherein reaction (b) is carried out such that the intermediate reaction mixture contains 1.7 to 5 mol% of solid amine hydrochloride, based on the molar amount of the amine fed into the method.

Description

[0001] The present invention relates to a method for preparing isocyanates by reacting a corresponding amine with phosgene in a liquid phase, by mixing a feed stream containing an amine, a feed stream containing phosgene and optionally an inert medium, and reacting the amine with phosgene in a reaction zone to form a reaction mixture containing isocyanates.

[0002] In principle, the preparation of isocyanates via the phosgenation of corresponding amines can be carried out through either liquid-phase phosgenation or gas-phase phosgenation. Particularly for high-boiling-point amines, phosgenation occurs in the liquid phase. For liquid-phase phosgenation, a feed stream containing amines is mixed with a feed stream containing phosgene, and then the amine reacts with the phosgene to form isocyanates.

[0003] A feed stream containing amines may contain amines dissolved in a solvent. Furthermore, it is known that an amine is reacted with hydrogen chloride in a pre-stage to form an amine hydrochloride, and the amine hydrochloride is then suspended in a solvent, resulting in a suspension containing amines.

[0004] The method of preparing isocyanates by reacting the corresponding amine with phosgene in the liquid phase is well known to those skilled in the art and is described, for example, in Isocyanates, Organic, Ullmann's Encyclopedia of Industrial Chemistry, 7th edition, vol. 20, 2012, pp. 63-82.

[0005] Specifically, for the preparation of poly(phenylmethylene diisocyanate) (PMDI) or toluene diisocyanate (TDI), a liquid feed stream containing phosgene is mixed with a liquid feed stream containing amine. Upon mixing, the reaction begins immediately, producing isocyanate carbamoyl chloride and decomposing hydrogen chloride. The hydrogen chloride thus formed reacts with the amine to form amine hydrochloride, which can precipitate as solid particles.

[0006] It is well known that unreacted solid amine hydrochloride at the end of the reaction zone leads to yield loss through the formation of ureas and subsequent products with isocyanates. Therefore, the primary goal of optimization is to minimize solid amine hydrochloride. This can be achieved by reducing the quantity and size of solids through appropriate mixing. This allows for complete conversion within a reasonable residence time in the reaction zone.

[0007] Methods for preparing PMDI in the liquid phase are described, for example, in WO-A99 / 54289. To improve the yield of isocyanates, the amount of chlorination byproducts is reduced.

[0008] WO-A 2004 / 056756 discloses a method for preparing polyisocyanates, wherein in a first reaction stage, an amine is converted to amine hydrochloride and carbamoyl chloride, in a second reaction stage, the amine hydrochloride is converted to carbamoyl chloride, and in a third reaction stage, the carbamoyl chloride is decomposed into isocyanate and hydrogen chloride. The examples in WO-A 2004 / 056756 specifically relate to the formation of TDI and MDI (methylene di(phenyl isocyanate)).

[0009] For example, WO-A 2010 / 015667 discloses a mixing apparatus for mixing a feed stream containing amines and a feed stream containing phosgene, which allows the feed streams to be rapidly mixed in liquid-phase phosgenation.

[0010] Surprisingly, it has been shown that minimizing the concentration of amine hydrochloride in the reaction mixture can have an adverse effect on the overall yield of isocyanates in this method.

[0011] Therefore, the object of the present invention is to further optimize the yield of isocyanates in the method for preparing isocyanates by reacting the corresponding amines with phosgene in the liquid phase.

[0012] This objective is achieved by a method for preparing isocyanates by reacting the corresponding amine with phosgene in a liquid phase, the method comprising:

[0013] (a) Mixing a feed stream containing an amine, a feed stream containing phosgene, and optionally an inert solvent;

[0014] (b) In the first reaction zone, the amine is reacted with phosgene to obtain an intermediate reaction mixture comprising isocyanate, carbamoyl chloride, amine hydrochloride and unreacted phosgene;

[0015] (c) Crack carbamoyl chloride in the second reaction zone and remove phosgene from the intermediate reaction mixture to obtain a crude product containing isocyanate.

[0016] (d) Optional post-processing of the crude product;

[0017] Reaction (b) is carried out such that the intermediate reaction mixture contains 1.7 to 5 mol% of solid amine hydrochloride, based on the molar amount of amine fed into the method.

[0018] The reaction is carried out in such a manner that the amount of solid amine hydrochloride in the intermediate reaction mixture taken from the first reaction zone is 1.7 to 5 mol%, preferably 1.7 to 3.5 mol%, more preferably 2.0 to 3.2 mol%, and particularly 2.2 to 3.0 mol%, to maximize the yield of isocyanate. The yield of isocyanate prepared by this method decreases at both lower and higher concentrations of amine hydrochloride.

[0019] To prepare isocyanates in the liquid phase, a feed stream containing an amine and a feed stream containing phosgene, along with an optional inert medium, are mixed and then reacted to form isocyanates. This mixing and reaction can be carried out in any suitable mixing and reaction apparatus known to those skilled in the art and used in known methods for preparing isocyanates in the liquid phase.

[0020] Within the scope of this invention, the first reaction zone operates in a device in which no fluid flows backflow during operation. The second reaction zone begins at the inlet of the first countercurrent device. The countercurrent device can be any device in which a portion of the contents flows in one direction while another portion flows backflow in the opposite direction to the first portion. Such a countercurrent device can be, for example, a tower in which vapor flows upward and liquid flows downward, such as a reaction tower or distillation tower.

[0021] Preferably, the first reaction zone comprises two stages. If the first reaction zone is carried out in at least two stages, the pressure is reduced in each stage. The first stage includes a mixer for mixing a feed stream containing amine and a feed stream containing phosgene. The mixer is preferably a static mixer and, in particular, a nozzle. The upstream pressure of the nozzle is preferably 3 to 70 bar, particularly 15 to 45 bar. The pressure differential across the nozzle is at least 0.5 bar. The temperature of the first stage is preferably 80 to 190°C, particularly 90 to 150°C. The second stage includes one or more residence apparatuses, preferably one residence apparatus, operating at a pressure of 2.5 to 35 bar, preferably 15 to 35 bar. Downstream of the nozzle, the reaction mixture is depressurized to the pressure of the residence apparatus in the second stage via a regulating valve or some other means suitable for this purpose. However, the natural pressure drop of the nozzle can also be used for depressurization.

[0022] The first-stage reactor in the first reaction zone can also be incorporated into the second-stage reactor in the first reaction zone. In particular, the mixing nozzle can be immersed in the gas phase or preferably the liquid phase of the second reactor, that is, it can be completely or partially located therein. The output of the nozzle can also be delivered to the gas phase of the second-stage reactor, preferably to the liquid phase, via pipes, immersion pipes, or insertion pipes.

[0023] The temperature of the second stage is 80 to 190°C, preferably 90 to 150°C. Possible reactor types for the second stage in the first reaction zone include tubular reactors, stirred vessels, non-stirred residence devices, phase separation devices, and other equipment. The reactor can also be equipped with a pump loop, which in turn can have a heat exchanger for setting the reaction temperature. In the case of stirred vessels, non-stirred residence devices, or possibly phase separation devices, the liquid phase is preferably depressurized under level control, and the gas phase is depressurized under pressure control before entering the reactor in the second reaction zone. However, the gas phase, mainly consisting of phosgene, hydrogen chloride, and possibly solvents, can also directly enter post-treatment, such as fractionation into phosgene, hydrogen chloride, and solvents or mixtures thereof. Depending on the required residence time and equipment capacity, the residence reactor for the second stage in the first reaction zone can have a relatively large size and volume, which can be considered a disadvantage from a cost or safety perspective, such as the retention of phosgene under high pressure. In this case, the reactor for the second stage in the first reaction zone can be implemented with two or more similar but different reactors and reactor types, which can be connected in parallel or in series if suitable for influencing the residence time spectrum.

[0024] The reactor in the second reaction zone is preferably operated at a pressure of 2 to 20 bar, more preferably 3.5 to 16 bar. Downstream of the residence reactor in the second stage of the first reaction zone, the reaction mixture is depressurized to the pressure of the reactor in the second reaction zone via a regulating valve or some other device suitable for this purpose. Natural pressure drop can also be utilized.

[0025] In any case, as mentioned above, choose the next stage of pressure to make it lower than the previous stage.

[0026] The temperature of the second reaction zone is 80 to 190°C. The reactor used for the second reaction zone is a column, particularly a reaction column as described, for example, in WO 99 / 54289. The bottom temperature is 80 to 190°C, and the top temperature is 50 to 120°C. The column used as the reactor for the second reaction zone can also be used to remove excess phosgene from the reaction mixture. Similar to the reactor for the second stage of the first reaction zone, the reactor for the second reaction zone may disadvantageously be large. In this case, the second reaction zone can also be implemented as two or more similar or different columns connected in series. The crude product is taken from the bottom of the last reaction column and preferably post-treated by conventional methods to remove any remaining phosgene and separate the solvent. In the case of preparing TDI, the crude TDI is then purified by removing high-boiling-point substances and by distillation. Phosgene, hydrogen chloride, and possibly the solvent can be separated from the vapor leaving the reaction column of the second reaction zone in a known manner, and the residence reactor of the second stage of the first reaction zone can be recycled if appropriate.

[0027] The inert solvent is preferably selected from chlorinated aromatic hydrocarbons, such as dichlorobenzene, chlorobenzene, trichlorobenzene or mixtures thereof; aromatic or aliphatic hydrocarbons, such as toluene, xylene, benzene, pentane, hexane, heptane, octane, cyclohexane, biphenyl; ketones, such as 2-butanone, methyl isobutyl ketone; esters, such as diethyl isophthalate, ethyl acetate, butyl acetate; nitriles, such as acetonitrile and sulfonyl sulfone.

[0028] The feed stream containing the amine can be a liquid form of the amine or preferably a solution containing the amine dissolved in an inert solvent. If the amine is dissolved in an inert solvent, the concentration of the amine in the inert solvent depends on the amine and the solvent used. In the case of diphenylmethane diamine (MDA) and / or polyphenylene-polymethylene polyamine (PMDA) or a mixture of the two, the concentration can be 5 to 50% by weight, preferably 25 to 40% by weight; in the case of toluene diamine (TDA) or hexamethylene diamine (HDA), the concentration can be 5 to 50% by weight, preferably 15 to 30% by weight; and in the case of isophorone diamine (IPDA), the concentration can also be 5 to 50% by weight and preferably 15 to 30% by weight.

[0029] The feed stream containing phosgene can be pure phosgene or phosgene dissolved in an inert solvent. If pure phosgene is used, it is in liquid form and is mixed as a liquid in the feed stream containing liquid amine in (a). However, preferably, the phosgene is dissolved in an inert solvent, and the concentration in the inert solvent can be from 10 to 98% by weight, preferably from 50 to 95% by weight. The inert solvent used in the feed stream containing phosgene is preferably the same as the inert solvent used in the feed stream containing amine.

[0030] If the first reaction proceeds in two stages, physical separation of the first and second stages is not absolutely necessary.

[0031] The reactions in all stages of the first and second reaction zones can be carried out at elevated temperatures, or isothermally if necessary.

[0032] If the reaction proceeds such that the first reaction zone comprises only one stage, then in the first reaction zone, the feed stream containing amine and the feed stream containing phosgene are mixed to initiate the reaction and form an intermediate reaction mixture, and the intermediate reaction mixture obtained therefrom is fed into a residence reactor in the second reaction zone, particularly the reaction tower described in WO-A 99 / 54289.

[0033] The temperature and pressure used depend to some extent on the amine used. Similarly, the excess phosgene and residence time used in each device depend on the amine used. In the case of methylene di(phenyl)isocyanate (MDI) and / or polymeric methylene di(phenyl)isocyanate (PMDI) or a mixture of the two, the excess phosgene should be at least 100% stoichiometric, while in the case of toluene diisocyanate (TDI), it should be at least 300% stoichiometric, and similarly, in the case of hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), it should also be at least 300% stoichiometric. The residence time in the first reaction stage in the first reaction zone (static mixer) is typically very short and is limited by the device design. The average residence time in the second stage of the first reaction zone can range from 1 second to 60 minutes. The average residence time is preferably 30 seconds to 30 minutes, particularly 2 to 15 minutes. The average residence time in the second reaction zone (reaction tower) depends on the theoretical number of plates, weir height, liquid volume, throughput, and other process parameters. The preferred stay time is no more than 1 hour.

[0034] According to the invention, the reaction is carried out in such a manner that the intermediate reaction mixture taken from the second reaction stage of the first reaction zone contains 1.7 to 5 mol% amine hydrochloride, preferably 1.7 to 3.5 mol%, more preferably 2.0 to 3.5 mol%, and especially 2.2 to 3.0 mol%. The amine hydrochloride is typically a solid and is formed during the reaction. The amount of amine hydrochloride in the intermediate reaction mixture can be set by changing process conditions such as temperature, pressure, phosgene excess, solvent, amount of hydrogen chloride in the feed stream containing phosgene, and / or mixing rate.

[0035] To control the amount of solid amine hydrochloride in the intermediate reaction mixture, it is preferable to determine the amount of solid amine hydrochloride in the intermediate reaction mixture, and if the amount is too low or too high, the process conditions are changed.

[0036] The amount of solid amine hydrochloride can be determined by any method known to those skilled in the art. For continuous determination of the amount of solid amine hydrochloride, a portion of the intermediate reaction mixture can be taken out and the amount of solids in that portion can be determined, for example. To determine the amount of solid particles, the portion can be diluted with a solvent, and the amount and size of the solid particles can be determined by photographic methods and automated image evaluation. In addition to this method, every suitable known particle counter can be used. The solvent used to dilute the portion is particularly the same solvent used as an inert solvent in the method for preparing isocyanates.

[0037] To adjust the amount of solid amine hydrochloride in the intermediate reaction mixture, for example, to control the excess of phosgene fed into the reaction. If the amount of solid amine hydrochloride is lower than a preset value, the excess of phosgene is reduced; if the amount of amine hydrochloride is higher than a preset value, the excess of phosgene is increased.

[0038] Alternatively, the amount of solid amine hydrochloride in the intermediate reaction mixture can be adjusted by controlling the amount of inert solvent. In this case, if the amount of solid amine hydrochloride is lower than a preset value, the amount of inert solvent is reduced; if the amount of solid hydrochloride is higher than a preset value, the amount of inert solvent is increased.

[0039] Furthermore, the amount of solid amine hydrochloride in the intermediate reaction mixture can also be adjusted by selecting an inert solvent. If the amount of amine hydrochloride is too low due to the reaction in the first reaction zone, an inert solvent with a lower solubility for amines than the solvent used when the amount of amine hydrochloride is below a preset value is selected. Besides selecting an inert solvent with lower solubility for amines, the mixing rate of amine and phosgene can also be reduced if the amount of amine hydrochloride in the crude product is too low. Conversely, if the amount of solid amine hydrochloride is higher than a preset value, a solvent with higher solubility for amines can be selected, or the mixing rate can be increased. The mixing rate can typically be adjusted, for example, by the type of mixing nozzle or by the speed of the feed stream containing amine and the feed stream containing phosgene. To adjust the mixing rate, a dynamic mixer that allows setting the mixing time can be used. Alternatively, a mixing nozzle with an adjustable nozzle opening (which allows adjustment of the mixing rate) can be used.

[0040] Since changing the solvent or the mixing nozzle is difficult or even impossible in this method if a mixing nozzle without an adjustable nozzle opening is used, these measures can be taken if it is necessary to adjust an already running operation.

[0041] In addition to the measures described above for adjusting the amount of solid amine hydrochloride in the intermediate reaction mixture, or in addition to these measures, the amount of solid amine hydrochloride in the intermediate reaction mixture can also be adjusted by controlling the temperature and / or by controlling the pressure. If the amount of solid amine hydrochloride is adjusted by controlling the temperature, the temperature is decreased when the amount of solid amine hydrochloride is below a preset value, and the temperature is increased when the amount of solid amine hydrochloride is above a preset value. If the amount of solid amine hydrochloride is adjusted by controlling the pressure, the pressure is increased when the amount of solid amine hydrochloride is below a preset value, and the pressure is decreased when the amount of solid amine hydrochloride is above a preset value.

[0042] Another possibility for adjusting the amount of solid amine hydrochloride in the intermediate reaction mixture is to control the amount of hydrogen chloride in the phosgene-containing feed stream. The hydrogen chloride content in the phosgene-containing feed stream specifically comes from the recycled phosgene separated from the intermediate reaction products. The gas stream containing phosgene and hydrogen chloride separated from the intermediate reaction products is further post-treated to separate phosgene and hydrogen chloride. The phosgene-containing stream is then mixed with fresh phosgene and fed into the first reaction zone as a phosgene-containing feed stream. Since it is impossible to separate phosgene without hydrogen chloride residue, hydrogen chloride is also fed into the reaction along with the phosgene-containing feed stream. The amount of hydrogen chloride in the phosgene-containing feed stream can be adjusted by regulating the separation conditions of the gas stream separated from the intermediate reaction products. To reduce the amount of solid amine hydrochloride in the intermediate reaction products, the amount of hydrogen chloride in the phosgene-containing feed stream is increased.

[0043] Regardless of the type of adjustment of the amount of solid amine hydrochloride in the intermediate reaction mixture, the preset value is 1.7 to 5 mol%, preferably 1.7 to 3.5 mol%, more preferably 2.0 to 3.2 mol%, and particularly 2.2 to 3.0 mol%. Therefore, only one preset value or a first lower preset value and a second higher preset value can be given, wherein the amount of solid amine hydrochloride is adjusted in such a way that it is maintained between the first lower preset value and the second higher preset value.

[0044] Each of the measures for adjusting the amount of solid amine hydrochloride can be performed individually. Alternatively, at least two of the measures can be used to adjust the amount of solid amine hydrochloride in the intermediate reaction mixture. However, for ease of implementation, it is preferable to use only one of the measures. Example

[0045] Example 1

[0046] In the apparatus for preparing TDI described in WO-A 2004056756, the apparatus has a tubular reactor as a residence time reactor as described in Example 1 of that international application, in which a 19.5% TDA solution in chlorobenzene is mixed with a 90% phosgene solution in chlorobenzene in a mixing device as described in WO-A 2010 / 015667, with a phosgene excess molar amount of 500%. The amount and size of solid particles in the intermediate reaction mixture taken from the end of the reaction tube are determined by photographic methods and subsequent image evaluation. For this purpose, a portion of the intermediate reaction mixture is taken out and diluted with chlorobenzene. The resulting mixture is then fed through an absorption cell for taking transmitted light photographs.

[0047] The particle concentration in the intermediate reaction mixture determined by this method was 0.23% by volume, corresponding to a molar concentration of 2.7 mol%, based on the amount of TDA fed into the method. The yield loss, determined by the amount of TDI prepared throughout the method and the amount of TDA fed into the method, was 3.01%.

[0048] Comparative Example 1

[0049] TDI was prepared in the same manner as described in Example 1. However, by using an improved mixing nozzle, the amount of amine hydrochloride in the intermediate reaction mixture could be reduced to 0.04 vol%, corresponding to 0.47 mol%, based on the amount of TDA fed into the method. Despite the reduction in the amount of solid amine hydrochloride, the yield loss increased to 3.26%.

[0050] Example 2

[0051] MDI was prepared in a two-step process via the phosgenation of MDA according to WO-A 99 / 54289 (EP 1073628?). Therefore, 50 kg / h of MDA was mixed with solvent chlorobenzene at a mass ratio of chlorobenzene:MDA of 1.4. In a reaction mixing nozzle, a feed containing phosgene (65% phosgene, 32% chlorobenzene, 3% HCl) was mixed with a feed containing an amine. The reaction product was fed into a series of stirred vessels serving as residence time reactors, and operated at 100 °C and 5.5 bar, 4.5 bar, 2.8 bar, and 2.5 bar, respectively. The gas phase separated in each reactor and the liquid phase from the last reactor were fed into a distillation column operated at a tank temperature of approximately 1.2 bar and 172 °C to obtain an MDI-solvent mixture at the bottom. A portion of the liquid feed stream from the column was removed, mixed with chlorobenzene, and the particle size distribution and amount of solid particles were determined using a particle counter from Markus Klotz GmbH. The solvent is removed from the tank product during distillation to obtain crude MDI product.

[0052] By carrying out the method in this manner, the amount of solid particles, particularly the amount of amine hydrochloride, is 0.55 vol%, corresponding to 2.27 mol%, based on the amount of MDA fed into the method. The overall yield is determined by the NCO value of crude MDI, which is 32.1 g NCO / 100 g.

[0053] Example 3

[0054] MDI was prepared according to the method of Example 2, but the temperature of the second stirred tank reactor was set to 110°C. The solids concentration decreased by 0.35% by volume, corresponding to 1.7% by mol%, based on the amount of MDA fed into the method. The NCO value was 31.75 g / 100 g.

[0055] Comparative Example 2

[0056] MDI was prepared according to the method of Example 2, but the temperature of the second stirred tank reactor was set to 120°C. The solids concentration decreased by 0.2% by volume, which corresponds to 1.0 mol%, based on the amount of MDA fed into the method. The NCO value was 31.6 g / 100 g.

[0057] Example 4

[0058] MDI was prepared according to the method of Example 2, but the temperature of the second stirred tank reactor was set to 90°C. The solids concentration increased by 0.7% by volume, which corresponds to 3.5 mol%, based on the amount of MDA fed into the method. The NCO value was 31.74 g / 100 g.

[0059] Comparative Example 3

[0060] MDI was prepared according to the method of Example 2, but the amount of solvent was reduced to obtain a chlorobenzene to MDA mass flow rate ratio of 1.0. The solids concentration increased by 1.05 vol%, which corresponds to 5.1 mol%, based on the amount of MDA fed into the method. The NCO value was 31.54 g / 100 g.

Claims

1. A method for preparing isocyanates, comprising reacting a corresponding amine with phosgene in a liquid phase, the method comprising: (a) Mixing a feed stream containing an amine, a feed stream containing phosgene, and optionally an inert solvent; (b) In the first reaction zone, the amine is reacted with phosgene to obtain an intermediate reaction mixture comprising isocyanate, carbamoyl chloride, amine hydrochloride and unreacted phosgene; (c) Crack carbamoyl chloride in the second reaction zone and remove phosgene from the intermediate reaction mixture to obtain a crude product containing isocyanate. (d) Optional post-processing of the crude product; Reaction (b) is carried out such that the intermediate reaction mixture contains 1.7 to 5 mol% of solid amine hydrochloride, based on the molar amount of amine fed into the method.

2. The method according to claim 1, wherein the amount of amine hydrochloride in the intermediate reaction mixture is adjusted by controlling the excess of phosgene fed into the reaction.

3. The method according to claim 1 or 2, wherein the amount of amine hydrochloride in the intermediate reaction mixture is adjusted by controlling the amount of inert solvent.

4. The method according to claim 1 or 2, wherein the inert solvent is selected such that the solubility of the amine decreases if the amount of solid amine hydrochloride is below a predetermined value, and the solubility of the amine increases if the amount of solid amine hydrochloride exceeds a predetermined value.

5. The method according to claim 1 or 2, wherein the amount of amine hydrochloride in the intermediate reaction mixture is adjusted by controlling the temperature of the feed stream entering the first reaction zone and / or the reaction in the first reaction zone.

6. The method according to claim 1 or 2, wherein the amount of amine hydrochloride in the intermediate reaction mixture is adjusted by controlling the amount of hydrogen chloride in the feed stream containing phosgene.

7. The method according to claim 1 or 2, wherein the amount of amine hydrochloride in the intermediate reaction mixture is adjusted by controlling the mixing rate of the feed stream.

8. The method according to claim 1 or 2, wherein the amount of amine hydrochloride in the intermediate reaction mixture is adjusted by controlling the pressure during reaction (b).

9. The method according to claim 1 or 2, wherein the amount of solid amine hydrochloride in the intermediate reaction mixture is determined by diluting a portion of the intermediate reaction mixture with a solvent and counting the particles in the diluted portion of the reaction mixture.

10. The method according to claim 1 or 2, wherein the amine is diphenylmethane diamine (MDA), polyphenylene-polymethylene polyamine (PMDA), toluene diamine (TDA), hexamethylene diamine (HDA), or isophorone diamine (IPDA).

11. The method according to claim 1 or 2, wherein the first reaction zone is operated in a residence time reactor.