Method for producing isocyanates by phosgenation of mixture of (aryl) aliphatic diamines and cycloaliphatic diamines

Abstract

The invention relates to a method for producing isocyanates by gas-phase phosgenation of the corresponding amines, in which an amine mixture formed from at least one first amine and at least one second amine different from the first amine is reacted with phosgene to provide a reaction mixture, the method being characterized in that the first amine is selected from aliphatic and / or araliphatic amines, and the second amine is selected from aliphatic and / or araliphatic amines. The second amine is selected from alicyclic amines. The invention also relates to products obtainable or obtained using such a process and to the use of such products. The invention also relates to the use of an amine mixture formed from at least one first amine and at least one second amine different from the first amine in a method for producing the corresponding isocyanate by gas-phase phosgenation for reducing the acidic chlorine compound content and / or hydrolysable chlorine content of the corresponding isocyanate obtained in the production.

Description

[0001] The present invention relates to a process for producing isocyanates by gas phase phosgenation of corresponding amines, wherein an amine mixture formed from at least one first amine and at least one second amine different from the first amine is reacted with phosgene to provide a reaction mixture. The present invention further relates to products obtainable or obtained by this process and to the use of such products. The present invention also relates to the use of an amine mixture formed from at least one first amine and at least one second amine different from the first amine in a process for producing corresponding isocyanates by gas phase phosgenation for reducing the acidic chlorine compound content and / or the hydrolyzable chlorine content of the corresponding isocyanates obtained in the production.

[0002] Isocyanates, in particular diisocyanates, and in some cases low molecular weight triisocyanates, as well as higher molecular weight polyaddition products with terminal isocyanate groups obtainable from the compounds, are valuable raw materials for the production of polyurethanes. It is technically advantageous to produce isocyanates by phosgenation of the amines on which they are based in a condensed phase (liquid phase phosgenation, also referred to below as FPP) or in a gas phase (gas phase phosgenation, also referred to below as GPP). The latter is only feasible in the case of amines that can be vaporized without decomposition at a selected pressure. In general, it has been found that many isocyanates that cannot be produced by FPP or can only be produced in low yields or with unsatisfactory purity can be better produced by GPP. This is especially true for diisocyanates with sensitive functional groups, such as ether bridges, in their molecular structure (see EP-A 764633 and the sources cited therein).

[0003] DE 2249459 describes the phosgenation of a mixture of two chemically different amines. In this case, an aromatic amine must be used as the "base amine" for the production of aliphatic isocyanates from the corresponding amines in order to avoid having to build expensive separate plants for the aliphatic isocyanates, which are usually in much smaller industrial demand. However, the isocyanates described therein still have a relatively high HC content (0.1% and more). Furthermore, in DE 2249459, gas-phase phosgenation is also not possible due to the different reactivity and boiling behavior / vapor pressure of the aromatic base amines relative to the aliphatic amines.

[0004] In the production of isocyanates from aliphatic and araliphatic amines, it is possible (without being bound by any particular theory) that intramolecular or intermolecular elimination of ammonia occurs, especially at higher temperatures such as those necessary for GPP. This is schematically illustrated in the following examples.

[0005]

[0006] These side reactions give rise to unwanted by-products which contaminate the actual product, reduce the yield and lead to deposits, with the attendant increased clogging of the phosgenation plant, since the ammonia produced in the phosgenation plant also leads to the formation of, for example, NH4Cl. This in turn ultimately not only makes the cleaning of the plant more difficult, but also leads to increased pressure in the plant apparatus during operation of the GPP plant, especially during longer operation times.

[0007] It was therefore an object of the present invention to provide a process for producing aliphatic and / or araliphatic isocyanates by gas-phase phosgenation of the corresponding amines with improved yield and purity, in particular purity in the form of a reduced content of acidic chlorine compounds (AC value) and / or hydrolyzable chlorine content (HC value). A further object of the present invention was to record as little pressure increase in the phosgenation plant as possible.

[0008] This object is achieved by a method having the features of claim 1 .

[0009] The present invention also relates to the use of an amine mixture formed from at least one first amine and at least one second amine different from the first amine in a process according to the invention for producing the corresponding isocyanates by phosgenation for reducing the acidic chlorine compound content and / or the hydrolyzable chlorine content of the corresponding isocyanates obtained in the production.

[0010] The present invention further relates to a product obtainable or obtained by the process of the present invention, preferably a product directly obtainable or obtained by the process of the present invention.

[0011] Furthermore, the invention relates to the use of the products of the invention and / or the isocyanates or isocyanate mixtures obtained or obtainable by the process of the invention as components for the production of polyurethanes, in particular polyurethane foams, polyurethane coatings and polyurethane adhesives, pharmaceuticals, in particular active substances, and auxiliaries, in particular auxiliaries for wet strength finishing of paper and other cellulosic products, emulsifiers and thickeners.

[0012] Surprisingly, it has been found that the yield and purity of isocyanates (hereinafter also referred to as first isocyanates or isocyanate 1) prepared from corresponding aliphatic and / or aromatic aliphatic amines (hereinafter also referred to as first amines or amines 1) can be increased during the phosgenation process when the reaction is carried out in the presence of alicyclic amines (hereinafter also referred to as second amines or amines 2). The reaction of such a mixture is also referred to as cophosgenation, or CoPg for short. The isocyanates 1 obtained are at least comparable in yield and purity (in particular in terms of the content of acidic chlorine compounds (AC value) and / or the content of hydrolyzable chlorine compounds (HC value)) to those obtained by phosgenation of amine 1 alone. In addition, it can be found that fewer impurities are observed with the process of the invention, and the pressure increase remains constant for a longer time, i.e. no significant pressure increase is recorded within a given time. Therefore, an extension of the phosgenation operating time is also observed with the process of the invention, i.e. the phosgenation operation can be carried out in the device for a longer time. Therefore, the process of the invention can also be used to extend the operating time of the phosgenation (extend the working life).

[0013] The measures of purity used in the present invention are in particular the content of acidic chlorine compounds and the content of hydrolyzable chlorine, wherein both the content of acidic chlorine compounds and the content of hydrolyzable chlorine are determined in accordance with standard ISO 15028: 2014. Furthermore, as a measure of the purity and general structural composition of the products of the present invention, it is also possible to use gas chromatography (GC), or high-performance liquid chromatography (HPLC), the latter usually being used after derivatization of the NCO groups, wherein the identity of the products is usually characterized by known methods (see also C. Six, F. Richter, Ullmann's Encyclopedia of Industrial Chemistry, "Isocyanates, Organic", Wiley-VCH, 2003), such as mass spectrometry (GC-MS; HPLC-MS, usually in the so-called "high resolution" mode = HRMS).

[0014] The present invention relates to a process for producing isocyanates by gas phase phosgenation of the corresponding amines, wherein an amine mixture formed from at least one first amine and at least one second amine different from the first amine is reacted with phosgene to provide a reaction mixture. The first amine is selected from aliphatic and / or araliphatic amines, and the second amine is selected from alicyclic amines. Preferably, the first amine and / or the second amine is a diamine.

[0015] Furthermore, it is preferred that the aliphatic amine comprises or consists of a diaminoalkane having 4 to 15 hydrocarbon atoms, wherein preferably the carbon chain from the first amino group to the second amino group of this diaminoalkane has 4 to 6 carbon atoms (i.e. the carbon atoms between the two amino groups). Suitable diaminoalkanes are in particular selected from 1,4-diaminobutane, 1,4-diamino-4-methylpentane, 1,5-diaminopentane, 1,5-diaminohexane, 1,6-diaminohexane, 2,2,4-trimethyl-1,6-diaminohexane, 2,4,4-trimethyl-1,6-diaminohexane or mixtures thereof.

[0016] The aromatic aliphatic amine is preferably selected from xylylene-1,3-diamine, xylylene-1,4-diamine, 1,1'-(1,2-phenylene)bis(ethyl-1-amine), 1,1'-(1,3-phenylene)bis(ethyl-1-amine), 1,1'-(1,4-phenylene)bis(ethyl-1-amine), 2,2'-(1,2-phenylene)bis(propan-2-amine), 2,2'-(1,4-phenylene)bis(propan-2-amine), 2,2'-(1,3-phenylene)bis(propan-2-amine), 3-(aminomethyl)aniline, 4-(aminomethyl)aniline or mixtures thereof.

[0017] Furthermore, the cycloaliphatic amines are preferably selected from 1-amino-3,5,5-trimethyl-5-aminomethylcyclohexane; amino-[(aminocyclohexyl)methyl]cyclohexane, in particular 4,4′-methylenebis(cyclohexane-1-amine), 2-((4-aminocyclohexyl)methyl)cyclohexane-1-amine and 2,2′-methylenebis(cyclohexane-1-amine); 1,3-bis(aminomethyl)cyclohexane; 1,4-bis(aminomethyl)cyclohexane; diaminocyclohexanes, in particular cyclohexane-1,2-diamine, cyclohexane-1,3-diamine and cyclohexane-1,4-diamine. diamines; methyldiaminocyclohexanes, in particular 4-methylcyclohexane-1,3-diamine and 2-methylcyclohexane-1,3-diamine, 4,4'-methylenebis(2-methylcyclohexane-1-amine); or mixtures thereof, preferably 1-amino-3,5,5-trimethyl-5-aminomethylcyclohexane; amino-[(aminocyclohexyl)methyl]cyclohexane, in particular 4,4'-methylenebis(cyclohexane-1-amine), 2-((4-aminocyclohexyl)methyl)cyclohexane-1-amine and 2,2'-methylenebis(cyclohexane-1-amine); or mixtures thereof.

[0018] In a likewise preferred embodiment, the aromatic aliphatic amine comprises xylylene-1,3-diamine and / or xylylene-1,4-diamine, the aromatic aliphatic amine being preferably xylylene-1,3-diamine, and the cycloaliphatic amine comprises 1,3-bis(aminomethyl)cyclohexane and / or 1,4-bis(aminomethyl)cyclohexane, the cycloaliphatic amine being preferably 1,3-bis(aminomethyl)cyclohexane.

[0019] Based on the total weight of the amine mixture, the mass proportion of the first amine is preferably 5.0 to 80.0 wt %, more preferably 10.0 to 60.0 wt %, and the mass proportion of the second amine is preferably 20.0 to 95.0 wt %, more preferably 40.0 to 90.0 wt %.

[0020] The molar ratio of phosgene to the amino groups of the amines in the amine mixture is preferably ≧1:1 to ≦5:1, more preferably >1:1 to ≦3:1.

[0021] Furthermore, inert substances are preferably used in this reaction. Suitable inert substances are selected from

[0022] Inert gases, in particular nitrogen, argon or mixtures thereof;

[0023] - an inert solvent, in particular an aromatic hydrocarbon, preferably chlorobenzene, o-dichlorobenzene, toluene, xylene or a mixture thereof;

[0024] or a mixture of the above inert gases and inert solvents.

[0025] The isocyanate corresponding to the first amine and / or the isocyanate corresponding to the second amine is preferably separated from the reaction mixture, wherein the separation is preferably carried out by distillation, in particular thin-film distillation, extraction, crystallization, recrystallization or a combination thereof, and the respective isocyanates are obtained separately or as an isocyanate mixture.

[0026] Furthermore, it is preferred that the acidic chlorine compound content of the separated one or more isocyanates or isocyanate mixtures is from 1 to 200 ppm, further preferably from 1 to 100 ppm, more preferably from 2 to 80 ppm, most preferably from 5 to 50 ppm, which is determined according to ISO 15028:2014. In particular, it is preferred that the acidic chlorine compound content of the separated one or more isocyanates or isocyanate mixtures is from 1 to 200 ppm when the first amine comprises 1,4-diaminobutane (BDA) or consists of 1,4-diaminobutane (BDA), and for all other amines is from 1 to 100 ppm, further preferably from 2 to 80 ppm, more preferably from 5 to 50 ppm, in each case determined according to ISO 15028:2014. It is also preferred that the hydrolyzable chlorine content of the separated one or more isocyanates or isocyanate mixtures is from 1 to 700 ppm, further preferably from 1 to 500 ppm, more preferably from 5 to 100 ppm, which is determined according to ISO 15028:2014. In particular, the hydrolyzable chlorine content of the separated one or more isocyanates or isocyanate mixtures is from 1 to 700 ppm when the first amine comprises 1,4-diaminobutane (BDA) or consists of 1,4-diaminobutane (BDA), and for all other amines is from 1 to 500 ppm, preferably from 5 to 100 ppm, in each case determined according to ISO 15028:2014. Thus, the use of an amine mixture formed from at least one first amine and at least one second amine different from the first amine in the process for producing the corresponding isocyanates by phosgenation according to the process of the invention can be used to reduce the acidic chlorine compound content and / or the hydrolyzable chlorine content of the corresponding isocyanates obtained in this production.

[0027] The present invention further relates to a product obtainable or obtained by the process of the present invention, preferably a product directly obtainable or obtained.

[0028] The process products of the invention are valuable raw materials for the production of polyurethanes, adhesives, coatings, oligomeric isocyanate-modified products such as polyisocyanates containing uretdione, isocyanurate, iminooxadiazinedione, oxadiazinetriae, carbodiimide, biuret, carbamate and allophanate, auxiliaries such as those for wet strength finishing of paper and other cellulose products (especially as emulsifiers, thickeners), raw materials for the production and / or formulation of active substances, pharmaceuticals. The invention therefore also relates to the use of the products of the invention and / or the isocyanates or isocyanate mixtures of the invention obtained or obtainable by the process of the invention as components for the production of polyurethanes, especially polyurethane foams, polyurethane coatings and polyurethane adhesives, pharmaceuticals, especially active substances, and auxiliaries, especially auxiliaries, emulsifiers and thickeners for wet strength finishing of paper and other cellulose products.

[0029] The main feature of the GPP process of the present invention (i.e., with regard to the equipment configuration, etc.) is that it is carried out by means of prior art methods known per se, for example according to the teachings of EP 0570799 or EP 0676392 and the method variants cited therein. For this purpose, the co-reactants are introduced into a suitable reactor at a temperature close to or above the boiling point of the starting amine (mixture), mixed, and reacted with each other. Depending on the selected pressure, the temperature for this is 100 to 600° C., preferably 150 to 500° C. The method is carried out in a pressure range of 10 mbar to 5 bar, preferably 200 mbar to 3 bar. The reaction components in the gas phase phosgenation can be supplied with or without inert additives such as carrier gases for the phosgenation reaction. Suitable carrier gases include nitrogen, argon or other inert gases, as well as vapors of technically available solvents, such as chlorobenzene, dichlorobenzene, xylene, chloronaphthalene, decalin, etc.

[0030] The isocyanate mixture of the present invention is subsequently obtained by cooling the gas stream to a temperature above the decomposition temperature of the corresponding carbamoyl chloride intermediate. In a preferred embodiment, the isocyanate corresponding to the first amine and / or the isocyanate corresponding to the second amine are then separated from the reaction mixture, wherein the separation is preferably carried out by distillation, in particular thin film distillation, extraction, crystallization, recrystallization or a combination thereof, and the respective isocyanates are obtained separately or as an isocyanate mixture. Particularly preferably, the isocyanate corresponding to the first amine and the isocyanate corresponding to the second amine are separated from the reaction mixture. It is also preferred that recrystallization is optionally carried out after separation by distillation.

[0031] Implementation plan:

[0032] The present invention particularly relates to the following embodiments:

[0033] In a first embodiment, the invention relates to a process for producing isocyanates by gas-phase phosgenation of the corresponding amines, wherein an amine mixture formed from at least one first amine and at least one second amine different from the first amine is reacted with phosgene to provide a reaction mixture, characterized in that

[0034] The first amine is selected from aliphatic and / or araliphatic amines; and

[0035] The second amine is selected from alicyclic amines.

[0036] In a second embodiment, the invention relates to a process according to embodiment 1, characterized in that the first amine and / or the second amine is a diamine.

[0037] In a third embodiment, the invention relates to a process according to embodiment 1 or 2, characterized in that the aliphatic amine comprises or consists of a diaminoalkane having 4 to 15 hydrocarbon atoms, wherein preferably the carbon chain from the first amino group to the second amino group of this diaminoalkane has 4 to 6 carbon atoms and / or this diaminoalkane is selected from 1,4-diaminobutane, 1,4-diamino-4-methylpentane, 1,5-diaminopentane, 1,5-diaminohexane, 1,6-diaminohexane, 2,2,4-trimethyl-1,6-diaminohexane, 2,4,4-trimethyl-1,6-diaminohexane or mixtures thereof.

[0038] In a fourth embodiment, the invention relates to a process according to any of the preceding embodiments, characterized in that the aromatic aliphatic amine is selected from the group consisting of xylylene-1,3-diamine, xylylene-1,4-diamine, 1,1'-(1,2-phenylene)bis(ethyl-1-amine), 1,1'-(1,3-phenylene)bis(ethyl-1-amine), 1,1'-(1,4-phenylene)bis(ethyl-1-amine), 2,2'-(1,2-phenylene)bis(propan-2-amine), 2,2'-(1,4-phenylene)bis(propan-2-amine), 2,2'-(1,3-phenylene)bis(propan-2-amine), 3-(aminomethyl)aniline, 4-(aminomethyl)aniline or mixtures thereof.

[0039] In a fifth embodiment, the invention relates to a process according to any of the preceding embodiments, characterized in that the cycloaliphatic amine is selected from 1-amino-3,5,5-trimethyl-5-aminomethylcyclohexane; amino-[(aminocyclohexyl)methyl]cyclohexane, in particular 4,4'-methylenebis(cyclohexane-1-amine, 2-((4-aminocyclohexyl)methyl)cyclohexane-1-amine and 2,2'-methylenebis(cyclohexane-1-amine); 1,3-bis(aminomethyl)cyclohexane; 1,4-bis(aminomethyl)cyclohexane; diaminocyclohexanes, in particular cyclohexane-1,2-diamine, cyclohexane- 1,3-diamine and cyclohexane-1,4-diamine; methyldiaminocyclohexanes, especially 4-methylcyclohexane-1,3-diamine and 2-methylcyclohexane-1,3-diamine, 4,4'-methylenebis(2-methylcyclohexane-1-amine); or mixtures thereof, preferably 1-amino-3,5,5-trimethyl-5-aminomethylcyclohexane; amino-[(aminocyclohexyl)methyl]cyclohexane, especially 4,4'-methylenebis(cyclohexane-1-amine), 2-((4-aminocyclohexyl)methyl)cyclohexane-1-amine and 2,2'-methylenebis(cyclohexane-1-amine); or mixtures thereof.

[0040] In a sixth embodiment, the invention relates to a method according to any of the preceding embodiments, characterized in that based on the total weight of the amine mixture

[0041] The mass proportion of the first amine is 5.0% to 80.0% by weight, preferably 10.0% to 60.0% by weight, and

[0042] The mass proportion of the second amine is 20.0% to 95.0% by weight, preferably 40.0% to 90.0% by weight.

[0043] In a seventh embodiment, the invention relates to a process according to any of the preceding embodiments, characterized in that the molar ratio of phosgene to the amino groups of the amines in the amine mixture is ≥1:1 ​​to ≤5:1, preferably >1:1 to ≤3:1.

[0044] In an eighth embodiment, the invention relates to a process according to any one of the preceding embodiments, characterized in that an inert substance is used in the reaction, wherein the inert substance is selected from:

[0045] Inert gases, in particular nitrogen, argon or mixtures thereof;

[0046] - an inert solvent, in particular an aromatic hydrocarbon, preferably chlorobenzene, o-dichlorobenzene, toluene, xylene or a mixture thereof;

[0047] or a mixture of the above inert gases and inert solvents.

[0048] In a ninth embodiment, the invention relates to a process according to any of the preceding embodiments, characterized in that the isocyanate corresponding to the first amine and / or the isocyanate corresponding to the second amine is separated from the reaction mixture, wherein the separation is preferably carried out by distillation, in particular thin-film distillation, extraction, crystallization, recrystallization or a combination thereof and the respective isocyanates are obtained separately or as an isocyanate mixture.

[0049] In a tenth embodiment, the present invention relates to a process according to any one of embodiments 1 to 8, characterized in that the isocyanate corresponding to the first amine and / or the isocyanate corresponding to the second amine is separated from the reaction mixture, wherein the separation is preferably carried out by distillation, in particular thin-film distillation, extraction, crystallization, recrystallization or a combination thereof, and the respective isocyanates are obtained as an isocyanate mixture.

[0050] In an eleventh embodiment, the present invention relates to a method according to embodiment 9 or 10, characterized in that the content of acidic chlorine compounds in the separated one or more isocyanates or isocyanate mixtures is from 1 to 200 ppm, preferably from 1 to 100 ppm, further preferably from 2 to 80 ppm, more preferably from 5 to 50 ppm, which is determined according to ISO 15028:2014 standard.

[0051] In a twelfth embodiment, the present invention relates to a process according to embodiments 9 to 11, characterized in that the hydrolyzable chlorine content of the separated one or more isocyanates or isocyanate mixtures is from 1 to 700 ppm, preferably from 1 to 500 ppm, more preferably from 5 to 100 ppm, as determined according to ISO 15028:2014 standard.

[0052] In a thirteenth embodiment, the present invention relates to the use of an amine mixture formed from at least one first amine and at least one second amine different from the first amine in a process for producing the corresponding isocyanates by gas phase phosgenation according to any one of embodiments 1 to 12 for reducing the acidic chlorine compound content and / or the hydrolyzable chlorine content of the corresponding isocyanates obtained in said production.

[0053] In a fourteenth embodiment, the present invention relates to a product obtainable or obtained by a process according to any one of embodiments 1 to 12, preferably according to any one of embodiments 1 to 8 and 10 to 12, preferably directly obtainable or obtained by a process according to any one of embodiments 1 to 12, preferably according to any one of embodiments 1 to 8 and 10 to 12.

[0054] In a fifteenth embodiment, the present invention relates to the use of the product according to embodiment 14 and / or the isocyanate or isocyanate mixture obtained or obtainable by the process according to any one of embodiments 9 to 12 as a component for the production of polyurethanes, in particular polyurethane foams, polyurethane coatings and polyurethane adhesives, pharmaceuticals, in particular active substances, and auxiliaries, in particular auxiliaries for wet strength finishing of paper and other cellulosic products, emulsifiers and thickeners. Example:

[0055] The following examples are intended to describe the process and some of the process products according to the invention in more detail without restricting the invention; unless otherwise stated, all percentage data are based on mass.

[0056] The acidic chlorine compound content and the hydrolyzable chlorine content were determined according to ISO 15028:2014.

[0057] GC-MS was performed using an Agilent GC6890 equipped with a MN 725825.30 Optima-5 MS Accent capillary column (30 m, 0.25 mm inner diameter, 0.5 μm film thickness) and a 5973 mass spectrometer as a detector with helium as a transport gas (flow rate of 2 ml / min). The column temperature was initially 60° C. (2 minutes) and then gradually increased to 360° C. at 8 K / min. GC-MS detection used electron impact ionization with an ionization energy of 70 eV. An injector temperature of 250° C. was selected.

[0058] In some cases, NMR spectroscopy studies were used for further structural elucidation. 1 HNMR) or about 50% ( 13 C NMR) samples were measured in dry C6D6 at 700 MHz ( 1 HNMR) or 176MHz( 13 The measurement is carried out at the measuring frequency of C NMR). The C6D5H contained in the solvent is used as a reference signal for the ppm scale: 1 H-NMR chemical shift 7.15 ppm, 13 C-NMR chemical shift 128.02 ppm.

[0059] All reactions were carried out in glass apparatus previously dried under vacuum at 150-200 °C under nitrogen atmosphere.

[0060] All chemicals used in the examples and comparative examples according to the invention were obtained from Aldrich, D-82018 Taufkirchen. In the following, BDA stands for 1,4-diaminobutane, PDA stands for 1,5-diaminopentane, HDA stands for 1,6-diaminohexane, XDA stands for 1,3-xylylenediamine, and MDA stands for 4,4'-methylenedianiline.

[0061] General operating procedures

[0062] Procedure A—Liquid Phase Phosgenation in the Presence of MDA (FPP) (see DE 2249459):

[0063] In a 4-necked flask cooled to -5°C with a mechanical stirrer, a dropping funnel, an internal thermometer and an inlet tube, 500 ml of monochlorobenzene (MCB) are initially charged, then twice the molar amount of phosgene based on the diamine (mixture) to be reacted is added by condensation, and the solution of the respective amine (mixture) is slowly added dropwise to MCB while further cooling to -10 to a maximum of 0°C. After all the amines (mixture) have been added, 100 ml of MCB are charged to the dropping funnel and added dropwise to the reaction mixture as well. While introducing phosgene (approximately 120 g / h) through the inlet tube, the temperature is then gradually increased until MCB reflux occurs. After reaching the boiling temperature, stirring is continued under reflux while further passing phosgene (approximately 120 g / h) until a clear solution is formed, but for at least 5 hours. In order to remove phosgene, stirring is continued under reflux, but dry nitrogen is passed through the inlet tube instead of phosgene until the absence of phosgene is ensured by means of phosgene test paper. Further post-treatment is described in the individual examples.

[0064] Procedure B – Gas Phase Phosgenation (GPP):

[0065] In a glass apparatus with a heatable mixing tube (reactor temperature = T1) with a diameter of 2.5 mm and a length of 17.5 mm, a downstream condensation stage and a subsequent phosgene adsorption tower equipped with activated carbon, phosgene (temperature = T2) which has been preheated in an upstream heat exchanger is continuously introduced via a nozzle extending into the mixing tube. The same preheated amine mixture (temperature = T3) is introduced simultaneously into the reaction space through the annular gap between the nozzle and the mixing tube at a metering rate optimized according to the amine (mixture), and the amine mixture is optionally diluted with dry nitrogen also preheated to T3 as a diluent. A specific pressure is maintained in the mixing tube by applying a negative pressure at the end of the condensation stage. The hot reaction mixture leaving the reaction space in gaseous form is introduced into the condensation stage by boiling 1,2-dichlorobenzene under reflux. This leads to the selective condensation of the diisocyanate that has been formed. The gas mixture consisting essentially of nitrogen, HCl and excess phosgene through the washing stage is then freed of phosgene in the adsorption tower, and the condensate is freed of residual dissolved phosgene as described in A. Further post-treatment is described in the individual examples.

[0066] Comparative Example 1 - Liquid Phase Phosgenation of Sensitive Aliphatic and Araliphatic Diamines in the Presence of MDA (see DE 2249459)

[0067] According to general procedure A, a mixture of in each case 0.04 mol of amine 1 and 31.8 g of MDA was subjected to liquid phase phosgenation, wherein after distillative workup the diisocyanates based on amine 1 were obtained in the stated purities and yields. The distillation residue (MDI) was not investigated in detail.

[0068] Table 1 Results of Comparative Example 1

[0069]

[0070] 1) [Theoretical % based on amine 1]; 2) By GC, area%, 100% factor-free method

[0071] All diisocyanates are contaminated with chlorine-containing secondary components and cannot be used in typical polyurethane applications.

[0072] Comparative Example 2 - Gas Phase Phosgenation of Sensitive Aliphatic and Araliphatic Diamines

[0073] According to General Procedure B, the amines listed in Table 2 were subjected to gas phase phosgenation under the conditions listed in Table 2.

[0074] Table 2 Results of Comparative Example 2

[0075] Amine <![CDATA[Yield 1) > <![CDATA[Purity 2) > AC [ppm] HC [ppm] BDA 98.4 98.2 768 956 PDA 98.5 98.8 532 622 HDA 98.9 99.1 155 196 XDA 92.4 96.4 856 955

[0076] 1) [Theoretical % based on metered amine]; 2) By GC, area%, 100% factor-free method

[0077] After the metering time per hour, the obtained condensate (1,2-dichlorobenzene, diisocyanate, by-products) was separated, dephosgenated separately, analyzed, and the individual experiments continued under otherwise unchanged conditions. The dephosgenated crude products thus obtained were then combined and post-processed by distillation. Table 2 gives the data on the total yield and purity of the obtained diisocyanates. In all cases, the obtained diisocyanates showed a steady increase in contamination caused by undesirable minor components during the experiment. In the case of XDA / XDI, the experiment had to be terminated after about 2 hours because persistent agglomerates and deposits were formed in the reaction space, which led to a significant increase in pressure.

[0078] Example 3 (according to the invention) - CoPg-GPP by GPP according to General Procedure B, XDA (amine 1) and PACM 20 (amine 2)

[0079] According to general operating procedure B, a mixture of XDA (amine 1) and PACM 20 (amine 2) was phosgenated at a constant temperature of 450° C. (T1=T2=T3). In this case, pure amine 2 was metered in at a molar excess of phosgene of approximately 250% at the start of the experiment (-0.330 mol / h). After an experimental time of 30 minutes, amine 1 was added to meter in an amine mixture consisting of 25 mol % of amine 1 and 75 mol % of amine 2, see Table 3, Example 3a. The concentration of amine 1 was then increased further (Example 3b) to use an amine mixture with 50 mol % of amine 1 / 50 mol % of amine 2. A total of 113.0 g (0.83 mol) of XDA and 383.3 g (1.82 mol) of PACM 20 were processed. The metered amounts, the phosgene excess used and the operating time are given in Table 3. No pressure increase in the plant was recorded.

[0080] Table 3: GPP of XDA and PACM 20

[0081]

[0082]

[0083] pass 1 The dephosgenated crude products were investigated by H-NMR spectroscopy and GC-MS and then combined, as no differences in product purity were found based on XDI.

[0084] The distillation work-up through a 40 cm packed column (inner diameter about 25 mm, packing: #1 Interpack) yielded only 22.4 g of a dark brown, highly viscous distillation residue and 148.2 g of XDI and 463.8 g of H 12 - MDI (in each case a light-colored liquid), which, as demonstrated by combined analytical methods (NMR, GC-MS), consists to an extent of >99% of XDI and H 12 -MDI (isomer mixture) composition (yields, based on the amine used, were 94.9% and 97.2%, respectively). AC / HC content was 35 / 120 ppm (XDI) and 27 / 38 ppm (H 12 -MDI). No discoloration was observed even after storage for several weeks without air.

[0085] Example 4 (according to the invention) - CoPg-GPP of BDA (amine 1) and IPDA (amine 2) by GPP according to general procedure B

[0086] According to general operating procedure B, a mixture consisting of 33.7 g of BDA (amine 1) and 281.4 g of IPDA (amine 2) was phosgenated at a constant temperature of 350° C. (T1=T2=T3) and an apparatus pressure of 500 mbar. No pressure increase in the apparatus was recorded during the experiment. After separation of the residue, of which 10.4 g of a dark brown, highly viscous distillation residue remained, the dephosgenated crude product was distilled over a 40 cm packed column (internal diameter about 25 mm, packing: #1 Interpack). 52.8 g of BDI with a purity of 98.8% (GC) were obtained. The AC / HC content was 117 / 649 ppm. A second fraction of 362.8 g of IPDI with a purity of 99.2% (GC), AC / HC: 122 / 165 ppm was obtained.

[0087] Example 5 (according to the invention) - CoPg-GPP of PDA (amine 1, example 5a) and HDA (amine 1, example 5b) with PACM 20 (amine 2) respectively by GPP according to general procedure B

[0088] According to general operating procedure B, a mixture consisting of 39.1 g of PDA (amine 1) and 348 g of PACM 20 (amine 2) (Example 5a) and of 44.4 g of HDA (amine 1) and 348 g of PACM 20 (amine 2) (Example 5b) was phosgenated at a constant temperature of 450° C. (T1=T2=T3) and a plant pressure of 500 mbar. No pressure increase in the plant was recorded during the experiment. After separation of the residue, of which 3.4 g (Example 5a) and 2.9 g (Example 5b) of dark brown, highly viscous distillation residues remained, the dephosgenated crude product was distilled over a 40 cm packed column (internal diameter about 25 mm, packing: #1 Interpack). This afforded 54.8 g of PDI with a purity of 99.2% (GC) in Example 5a. The AC / HC content was 38 / 87 ppm. In Example 5b, 58.9 g of HDI with a purity of 99.8% (GC) were obtained. The AC / HC content was 22 / 42 ppm. The diisocyanate 2 which remained as a high boiler was not investigated in detail.

[0089] Comparison of the GC-MS results obtained for the diisocyanate 1, PDI and HDI obtained according to the invention with the data obtained for the corresponding compounds from comparative examples 1 and 2 shows that the concentrations of all secondary components in the diisocyanates obtained according to the invention are significantly lower than in the diisocyanates obtained by known prior art processes. In the case of PDI, this relates in particular to chlorine-containing compounds with molecular weights (from HRMS) of 145.03, 147.05, 178.99 and 208.02 (the latter each having an isotopic pattern indicating the presence of at least 2 Cl atoms in the respective molecule), wherein some of these compounds clearly have structural isomers, as evidenced by GC-HRMS signals with retention times very close to one another and very similar fragmentation patterns in the mass spectrum. In the case of HDI, the number of Cl-containing secondary components is significantly lower than in the case of PDI and is essentially limited to compounds known from the literature: tetrahydro-1H-azepine-1-carbonyl chloride (various isomers), azepane-1-carbonyl chloride and (trace amounts) chlorotetrahydro-1H-azepine-1-carbonyl chloride (2 Cl atoms, various isomers).

Claims

1. A process for producing isocyanates by gas-phase phosgenation of the corresponding amines, wherein an amine mixture formed from at least one first amine and at least one second amine different from the first amine is reacted with phosgene to provide a reaction mixture, Features The first amine is selected from aliphatic and / or araliphatic amines; and The second amine is selected from alicyclic amines.

2. The method according to claim 1, characterized in that The first amine and / or the second amine is a diamine.

3. The method according to claim 1 or 2, characterized in that The aliphatic amine comprises or consists of a diaminoalkane having 4 to 15 hydrocarbon atoms, wherein preferably the carbon chain from the first amino group to the second amino group of this diaminoalkane has 4 to 6 carbon atoms and / or this diaminoalkane is selected from 1,4-diaminobutane, 1,4-diamino-4-methylpentane, 1,5-diaminopentane, 1,5-diaminohexane, 1,6-diaminohexane, 2,2,4-trimethyl-1,6-diaminohexane, 2,4,4-trimethyl-1,6-diaminohexane or a mixture thereof.

4. A method according to any one of the preceding claims, characterised in that The aromatic aliphatic amine is selected from the group consisting of xylylene-1,3-diamine, xylylene-1,4-diamine, 1,1'-(1,2-phenylene)bis(ethyl-1-amine), 1,1'-(1,3-phenylene)bis(ethyl-1-amine), 1,1'-(1,4-phenylene)bis(ethyl-1-amine), 2,2'-(1,2-phenylene)bis(propan-2-amine), 2,2'-(1,4-phenylene)bis(propan-2-amine), 2,2'-(1,3-phenylene)bis(propan-2-amine), 3-(aminomethyl)aniline, 4-(aminomethyl)aniline or a mixture thereof.

5. A method according to any one of the preceding claims, characterised in that The cycloaliphatic amine is selected from 1-amino-3,5,5-trimethyl-5-aminomethylcyclohexane; amino-[(aminocyclohexyl)methyl]cyclohexane, especially 4,4'-methylenebis(cyclohexane-1-amine, 2-((4-aminocyclohexyl)methyl)cyclohexane-1-amine and 2,2'-methylenebis(cyclohexane-1-amine); 1,3-bis(aminomethyl)cyclohexane; 1,4-bis(aminomethyl)cyclohexane; diaminocyclohexanes, especially cyclohexane-1,2-diamine, cyclohexane-1,3-diamine and cyclohexane-1,4-diamine ; methyldiaminocyclohexanes, especially 4-methylcyclohexane-1,3-diamine and 2-methylcyclohexane-1,3-diamine, 4,4'-methylenebis(2-methylcyclohexane-1-amine); or mixtures thereof, preferably 1-amino-3,5,5-trimethyl-5-aminomethylcyclohexane; amino-[(aminocyclohexyl)methyl]cyclohexane, especially 4,4'-methylenebis(cyclohexane-1-amine), 2-((4-aminocyclohexyl)methyl)cyclohexane-1-amine and 2,2'-methylenebis(cyclohexane-1-amine); or mixtures thereof.

6. A method according to any one of the preceding claims, characterised in that Based on the total weight of the amine mixture The mass proportion of the first amine is 5.0% to 80.0% by weight, preferably 10.0% to 60.0% by weight, and The mass proportion of the second amine is 20.0% to 95.0% by weight, preferably 40.0% to 90.0% by weight.

7. A method according to any one of the preceding claims, characterised in that The molar ratio of phosgene to the amino groups of the amines in the amine mixture is ≧1:1 to ≦5:1, preferably >1:1 to ≦3:

1.

8. A method according to any one of the preceding claims, characterised in that An inert substance is used in the reaction, wherein the inert substance is selected from: Inert gases, in particular nitrogen, argon or mixtures thereof; - an inert solvent, in particular an aromatic hydrocarbon, preferably chlorobenzene, o-dichlorobenzene, toluene, xylene or a mixture thereof; or a mixture of the above inert gases and inert solvents.

9. A method according to any one of the preceding claims, characterised in that The isocyanate corresponding to the first amine and / or the isocyanate corresponding to the second amine is separated from the reaction mixture, wherein the separation is preferably carried out by distillation, in particular thin-film distillation, extraction, crystallization, recrystallization or a combination thereof, and the respective isocyanates are obtained separately or as an isocyanate mixture.

10. The method according to any one of claims 1 to 8, characterized in that The isocyanate corresponding to the first amine and / or the isocyanate corresponding to the second amine is separated from the reaction mixture, wherein the separation is preferably carried out by distillation, in particular thin-film distillation, extraction, crystallization, recrystallization or a combination thereof, and the respective isocyanates are obtained as an isocyanate mixture.

11. The method according to claim 9 or 10, characterized in that The acidic chlorine compound content in the separated one or more isocyanates or isocyanate mixtures is 1 to 200 ppm, preferably 1 to 100 ppm, further preferably 2 to 80 ppm, more preferably 5 to 50 ppm, which is determined according to ISO 15028:2014 standard.

12. The method according to any one of claims 9 to 11, characterized in that The hydrolyzable chlorine content of the separated one or more isocyanates or isocyanate mixture is 1 to 700 ppm, preferably 1 to 500 ppm, more preferably 5 to 100 ppm, which is determined according to ISO 15028:2014 standard.

13. Use of an amine mixture formed from at least one first amine and at least one second amine different from the first amine in a process for producing the corresponding isocyanates by gas phase phosgenation according to any one of claims 1 to 12 for reducing the acidic chlorine compound content and / or the hydrolyzable chlorine content of the corresponding isocyanates obtained in the production.

14. Product obtainable or obtained by a process as claimed in any one of claims 1 to 12, preferably any one of claims 1 to 8 and 10 to 12, preferably a product directly obtainable or obtained by any one of claims 1 to 12, preferably any one of claims 1 to 8 and 10 to 12.

15. Use of the product according to claim 14 and / or the isocyanate or isocyanate mixture obtained or obtainable by the process according to any one of claims 9 to 12 as a component for the production of polyurethanes, in particular polyurethane foams, polyurethane coatings and polyurethane adhesives, pharmaceuticals, in particular active substances, and auxiliaries, in particular auxiliaries for wet strength finishing of paper and other cellulosic products, emulsifiers and thickeners.

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