Method for producing isocyantes via phosgenation of a mixture of (AR)aliphatic diamines and cycloaliphatic diamines
Patent Information
- Application Number
- EP2023733766
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-01-05
- Filing Date
- 2023-06-20
- Publication Date
- 2025-04-30
AI Technical Summary
The production of isocyanates through gas-phase phosgenation of aliphatic and araliphatic amines often results in low yields and impurities, including acidic chlorine compounds, leading to system clogging and pressure increases due to ammonia side reactions, making it difficult to maintain purity and extend phosgenation cycle times.
A process involving a mixture of aliphatic or araliphatic amines with cycloaliphatic amines in gas-phase phosgenation, known as co-phosgenation, which reduces the content of acidic and hydrolyzable chlorine compounds, maintaining yield and purity, and preventing pressure increases, thereby extending the phosgenation cycle.
This method enhances the yield and purity of isocyanates, reduces impurities, and maintains stable pressure, allowing for longer phosgenation cycles and improved system operation, with the isocyanates being suitable for polyurethane production and other applications.
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Abstract
Description
[0001] Process for the preparation of isocyanates by phosgenation of a mixture of (ar)aliphatic
[0002] Diamines and cycloaliphatic diamines
[0003] The invention relates to a process for producing isocyanates by gas-phase phosgenation of the corresponding amines, wherein an amine mixture comprising at least one first amine and at least one second amine different from the first amine is reacted with phosgene to form a reaction mixture. Furthermore, the invention relates to a product obtainable or obtained by this process and the use of such a product. The invention also relates to the use of an amine mixture comprising 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 to reduce the content of acidic chlorine compounds and / or the content of hydrolyzable chlorine in the corresponding isocyanates obtained during production.
[0004] Isocyanates, especially diisocyanates, and occasionally low-molecular triisocyanates, as well as the higher-molecular polyaddition products with terminal isocyanate groups accessible from the above-mentioned compounds, are valuable raw materials for the production of polyurethanes. Isocyanates are produced technically advantageously by phosgenating the underlying amines, both in the condensed phase (liquid phosgenation, hereinafter also referred to as FPP) and in the gas phase (gas phase phosgenation, hereinafter also referred to as GPP). The latter is only feasible for amines that can be evaporated without decomposition under the selected pressure. In general, it has been shown that many isocyanates that cannot be produced using FPP, or can only be produced in poor yields or with unsatisfactory purity, can be produced more effectively using GPP. This applies in particular to diisocyanates that contain sensitive functional groups, such asEther bridges, in the molecular structure (cf. EP-A 764633 and sources cited therein).
[0005] DE 2249459 describes the phosgenation of a mixture of two chemically different amines. It is essential to use an aromatic amine as the “base amine” for the production of aliphatic isocyanates from the corresponding amines in order to avoid the need to build an expensive separate plant for the aliphatic isocyanates, which are generally required on a much smaller scale. However, the isocyanates described therein still have relatively high HC contents (0.1% and above). Furthermore, gas-phase phosgenation is not an option in DE 2249459 due to the different reactivities and boiling behavior / vapor pressures of the aromatic base amines compared to the aliphatic amines. In the production of isocyanates from aliphatic and araliphatic amines, it can (without being bound to any theory) occur with higher temperatures, such as those used, for example, at elevated temperatures.Intra- or intermolecular ammonia release can occur in the reaction conditions necessary for GPP. This is shown schematically in the following examples.
[0006] H
[0007] N
[0008] H2NJ LNH2- - < n = 4 - 6 n n - NH3 ^n-2
[0009] These side reactions lead to undesirable byproducts that contaminate the actual products, reduce yield, and cause deposits and the associated increasing clogging of the phosgenation plant, as the resulting ammonia can also lead to the formation of NH4Cl, for example. This, in turn, not only ultimately complicates the cleaning of the plant but can also lead to an increase in pressure in the plant's equipment during operation under GPP, especially during extended periods.
[0010] The object of the present invention was therefore to provide a process for producing aliphatic and / or araliphatic isocyanates by gas-phase phosgenation of the corresponding amines, which process exhibits improved yield and purity, in particular purity in the form of a reduction in the content of acidic chlorine compounds (AC value) and / or hydrolyzable chlorine (HC value). Furthermore, a further object of the present invention was to minimize any increase in pressure in the phosgenation plant.
[0011] This object is achieved by a method having the features of claim 1.
[0012] Furthermore, the invention relates to the use of an amine mixture of at least one first amine and at least one second amine different from the first amine in a process for preparing the corresponding isocyanates by phosgenation according to the process according to the invention for reducing the content of acidic chlorine compounds and / or the content of hydrolyzable chlorine of the corresponding isocyanates obtained in the preparation.
[0013] Furthermore, the invention relates to a product obtainable or obtained by the process according to the invention, preferably directly obtainable or obtained by the process according to the invention. Furthermore, the invention relates to the use of the product according to the invention and / or the isocyanate or isocyanate mixture obtained or obtainable by the process according to the invention as a component for the production of polyurethanes, in particular polyurethane foams, polyurethane coatings and polyurethane adhesives, of pharmaceutical products, in particular active ingredients, and of auxiliaries, in particular auxiliaries for the wet strength finishing of paper and other cellulose products, emulsifiers and thickeners.
[0014] Surprisingly, it was found that the yield and purity of the isocyanates (hereinafter also referred to as first isocyanate or isocyanate 1) from the corresponding aliphatic and / or araliphatic amines (hereinafter also referred to as first amine or amine 1) during phosgenation can be increased if the reaction is carried out in the presence of cycloaliphatic amines (hereinafter also referred to as second amine or amine 2). The reaction of such a mixture is also referred to below as co-phosgenation, or CoPg for short. The isocyanates 1 obtained in this way are at least equivalent in terms of yield and purity (in particular the content of acidic chlorine compounds (AC value) and / or hydrolyzable chlorine compounds (HC value)) to those resulting from phosgenation of the amines 1 alone.Furthermore, it was found that the process according to the invention resulted in fewer impurities and that pressure increases remained constant for a longer period of time, meaning that no significant pressure increases were observed over a given period of time. Accordingly, the process according to the invention also extended the phosgenation runtime, meaning that one phosgenation run could be carried out in the plant for a longer period of time. Consequently, the process according to the invention can also be used to extend the runtime (increase the service life) of the phosgenation.
[0015] Within the scope of the invention, the content of acidic chlorine compounds and the content of hydrolyzable chlorine are used in particular as a measure of purity, with both the content of acidic chlorine compounds and the content of hydrolyzable chlorine being determined in accordance with the ISO 15028:2014 standard. Furthermore, gas chromatography (GC) or, optionally, high-performance liquid chromatography (HPLC), the latter generally after derivatization of the NCO groups, can also serve as a measure of the purity and, more generally, the structural composition of the products according to the invention, with the identity of the products usually being characterized by known methods (cf. also C. Six, F. Richter, Ullmann's Encyclopedia of Industrial Chemistry, "Isocyanates, Organic", Wiley-VCH, 2003), such as mass spectrometry (GC-MS; HPLC-MS, generally in the so-called "high resolution" version = HRMS).
[0016] The invention relates to a process for preparing isocyanates by gas-phase phosgenation of the corresponding amines, wherein an amine mixture comprising at least one first amine and at least one second amine different from the first amine is reacted with phosgene to form a reaction mixture. The first amine is selected from the group comprising or consisting of aliphatic and / or araliphatic amines, whereas the second amine is selected from the group comprising or consisting of cycloaliphatic amines. Preferably, the first amine and / or the second amine is a diamine.
[0017] Furthermore, it is preferred that the aliphatic amine comprises or consists of a diaminoalkane having 4 to 15 hydrocarbon atoms, wherein the carbon chain from the first to the second amino group of this diaminoalkane preferably has 4 to 6 carbon atoms (i.e., the carbon atoms between the two amino groups). Suitable diaminoalkanes are selected in particular from the group comprising or consisting of 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.
[0018] The araliphatic amine is preferably selected from the group comprising or consisting of 1,3-xylylenediamine, 1,4-xylylenediamine, 1,1'-(1,2-phenylene)bis(ethane-1-amine), 1,1'-(1,3-phenylene)bis(ethane-1-amine), l,l'-(l,4-phenylene)bis(ethane-l-amine), 2,2'-(l,2-phenylene)bis(propan-2-amine), 2,2'-(l,4-phenylene)bis(propan-2-amine), 2,2'-(l,3-phenylene)bis(propan-2-amine), 3-(aminomethyl)aniline, 4-(aminomethyl)aniline or mixtures thereof.
[0019] Furthermore, the cycloaliphatic amine is preferably selected from the group comprising or consisting of l-amino-3,5,5-trimethyl-5-aminomethylcyclohexane; amino-[(aminocyclohexyl)methyl]cyclohexane, in particular 4,4'-methylenebis(cyclohexane-l-amine), 2-((4-aminocyclohexyl)methyl)cyclohexane-l-amine and 2,2'-methylenebis(cyclohexane-l-amine); 1,3-bis(aminomethyl)cyclohexane; 1,4-bis(aminomethyl)cyclohexane; diaminocyclohexane, in particular cyclohexane-1,2-diamine, cyclohexane-1,3-diamine and cyclohexane-1,4-diamine; Methyldiaminocyclohexane, 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.
[0020] In a likewise preferred embodiment, the araliphatic amine comprises 1,3-xylylenediamine and / or 1,4-xylylenediamine; preferably, the araliphatic amine is 1,3-xylylenediamine; and the cycloaliphatic amine comprises 1,3-bis(aminomethyl)cyclohexane and / or 1,4-bis(aminomethyl)cyclohexane; preferably, the cycloaliphatic amine is 1,3-bis(aminomethyl)cyclohexane. The mass fraction of the first amine is preferably 5.0 to 80.0 wt.%, more preferably 10.0 to 60.0 wt.%, and that of the second amine is preferably 20.0 to 95.0 wt.%, more preferably 40.0 to 90.0 wt.%, based on the total weight of the amine mixture.
[0021] The molar ratio of phosgene to the amino groups of the amines of the amine mixture is preferably > 1 : 1 to < 5 : 1, more preferably > 1 : 1 to < 3 : 1.
[0022] In addition, an inert substance is preferably used in the reaction. Suitable inert substances are selected from the group comprising or consisting of
[0023] • Intergases, in particular nitrogen, argon or mixtures of these;
[0024] • inert solvents, in particular aromatic hydrocarbons, preferably chlorobenzene, o-dichlorobenzene, toluene, xylene or mixtures of these;
[0025] • or mixtures of the aforementioned inert gases and inert solvents.
[0026] 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 means of distillation, in particular thin-film distillation, extraction, crystallization, recrystallization or a combination of these, and the respective isocyanates are obtained separately or as an isocyanate mixture.
[0027] Furthermore, it is preferred that the content of acidic chlorine compounds in the separated isocyanate(s) or the isocyanate mixture is from 1 to 200 ppm, more preferably from 1 to 100 ppm, particularly preferably from 2 to 80 ppm, most preferably from 5 to 50 ppm, determined according to the standard ISO 15028:2014. In particular, the content of acidic chlorine compounds in the separated isocyanate(s) or the isocyanate mixture is preferably from 1 to 200 ppm if the first amine contains or consists of 1,4-diaminobutane (BDA), and from 1 to 100 ppm, more preferably from 2 to 80 ppm, particularly preferably from 5 to 50 ppm, for all other amines, in each case determined according to the standard ISO 15028:2014. Furthermore, it is preferred that the content of hydrolyzable chlorine in the separated isocyanate(s) or the isocyanate mixture is from 1 to 700 ppm, more preferably from 1 to 500 ppm, particularly preferably from 5 to 100 ppm, determined according to the standard ISO 15028:2014.In particular, the content of hydrolyzable chlorine in the separated isocyanate(s) or the isocyanate mixture is from 1 to 700 ppm when the first amine contains or consists of 1,4-diaminobutane (BDA), and from 1 to 500 ppm, preferably from 5 to 100 ppm, for all other amines, in each case determined according to the standard ISO 15028:2014. The use of an amine mixture comprising at least one first amine and at least one second amine different from the first amine in a process for preparing the corresponding isocyanates by phosgenation according to the process according to the invention can therefore be used to reduce the content of acidic chlorine compounds and / or the content of hydrolyzable chlorine in the corresponding isocyanates obtained during the preparation.
[0028] Furthermore, the invention relates to a product obtainable or obtained, preferably directly obtainable or obtained, by the process according to the invention.
[0029] The process products according to the invention are valuable raw materials for the production of polyurethanes, adhesives, coating materials, oligomeric isocyanate modification products such as uretdione, isocyanurate, iminooxadiazinedione, oxadiazinetrione, carbodiimide, biuret, urethane and allophanate-containing polyisocyanates, auxiliaries such as those used for the wet strength finishing of paper and other cellulose products, as emulsifiers, thickeners, etc., as raw materials for the production and / or formulation of active ingredients, pharmaceuticals, etc.Therefore, the invention also relates to the use of the product according to the invention and / or the isocyanate or isocyanate mixture according to the invention obtained or obtainable by the process according to the invention as a component for the production of polyurethanes, in particular polyurethane foams, polyurethane coatings and polyurethane adhesives, of pharmaceutical products, in particular active ingredients, and of auxiliaries, in particular auxiliaries for the wet strength finishing of paper and other cellulose products, emulsifiers and thickeners.
[0030] The basic features of the GPP process according to the invention (i.e., with regard to the plant design, etc.) are carried out using a method known per se from the prior art, e.g., according to the teachings of EP 0 570 799 or EP 0 676 392 and process variants cited therein. For this purpose, the reactants are introduced into suitable reactors near or above the boiling point of the starting amine (mixture), mixed, and reacted with one another. The temperatures for this are, depending on the selected pressure, between 100 and 600 °C, preferably between 150 and 500 °C. The process is carried out in a pressure range between 10 mbar and 5 bar, preferably 200 mbar and 3 bar. The reaction components can be introduced during the gas-phase phosgenation with or without the use of additives that are inert with respect to the phosgenation reaction, such as carrier gases.Suitable carrier gases include nitrogen, argon or other inert gases as well as vapors of technically available solvents such as chlorobenzene, dichlorobenzenes, xylenes, chlorophthalenes, decahydronaphthalene, etc.
[0031] The isocyanate mixtures according to the invention are then obtained by cooling the gas stream to a temperature above the decomposition temperature of the corresponding intermediate carbamic acid chlorides. In a preferred embodiment, the isocyanate corresponding to the first amine and / or the isocyanate corresponding to the second amine is then separated from the reaction mixture, wherein the separation is preferably carried out by means of 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. Particular preference is given to separating the isocyanate corresponding to the first amine and the isocyanate corresponding to the second amine from the reaction mixture. It is further preferred that the separation is carried out by means of distillation, optionally followed by recrystallization.
[0032] Embodiments:
[0033] The present invention particularly relates to the following embodiments:
[0034] According to a first embodiment, the invention relates to a process for the preparation of isocyanates by a gas phase phosgenation of the corresponding amines, wherein an amine mixture of at least one first amine and at least one second amine different from the first amine is reacted with phosgene to form a reaction mixture, characterized in that
[0035] • the first amine is selected from the group comprising or consisting of aliphatic and / or araliphatic amines; and
[0036] • the second amine is selected from the group comprising or consisting of cycloaliphatic amines.
[0037] According to 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.
[0038] According to 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 of the first to the second amino group of this diaminoalkane has 4 to 6 carbon atoms and / or this diaminoalkane is selected from the group comprising or consisting of 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.
[0039] According to a fourth embodiment, the invention relates to a process according to one of the preceding embodiments, characterized in that the araliphatic amine is selected from the group comprising or consisting of 1,3-xylylenediamine, 1,4-xylylenediamine, 1,1'-(1,2-phenylene)bis(ethane-1-amine), 1,1'-(1,3-phenylene)bis(ethane-1-amine), 1,1'-(1,4-phenylene)bis(ethane-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 of them.
[0040] According to a fifth embodiment, the invention relates to a process according to one of the preceding embodiments, characterized in that the cycloaliphatic amine is selected from the group comprising or consisting of l-amino-3,5,5-trimethyl-5-aminomethylcyclohexane; amino-[(aminocyclohexyl)methyl]cyclohexane, in particular 4,4'-methylenebis(cyclohexane-l-amine), 2-((4-aminocyclohexyl)methyl)cyclohexane-l-amine and 2,2'-methylenebis(cyclohexane-l-amine); 1,3-bis(aminomethyl)cyclohexane; 1,4-bis(aminomethyl)cyclohexane; diaminocyclohexane, in particular cyclohexane-1,2-diamine, cyclohexane-1,3-diamine and cyclohexane-1,4-diamine; Methyldiaminocyclohexane, 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(cyclohexan-l-amine), 2-((4-aminocyclohexyl)methyl)cyclohexan-l-amine and 2,2'-methylenebis(cyclohexan-l-amine); or mixtures thereof.;
[0041] According to a sixth embodiment, the invention relates to a method according to one of the preceding embodiments, characterized in that the mass fraction
[0042] • of the first amine 5.0 to 80.0 wt.%, preferably 10.0 to 60.0 wt.% and
[0043] • the second amine is 20.0 to 95.0 wt.%, preferably 40.0 to 90.0 wt.%, based on the total weight of the amine mixture.
[0044] According to a seventh embodiment, the invention relates to a process according to one of the preceding embodiments, characterized in that the molar ratio of phosgene to the amino groups of the amines of the amine mixture is > 1 : 1 to < 5 : 1, preferably > 1 : 1 to < 3 : 1.
[0045] According to an eighth embodiment, the invention relates to a process according to one of the preceding embodiments, characterized in that an inert substance is used in the reaction, wherein the inert substance is selected from the group comprising or consisting of
[0046] • Intergases, in particular nitrogen, argon or mixtures of these;
[0047] • inert solvents, in particular aromatic hydrocarbons, preferably chlorobenzene, o-dichlorobenzene, toluene, xylene or mixtures of these;
[0048] • or mixtures of the aforementioned inert gases and inert solvents.
[0049] According to a ninth embodiment, the invention relates to a process according to one 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 means of distillation, in particular thin-film distillation, extraction, crystallization, recrystallization or a combination of these, and the respective isocyanates are obtained separately or as an isocyanate mixture.
[0050] According to a tenth embodiment, the invention relates to a process according to 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 means of distillation, in particular thin-film distillation, extraction, crystallization, recrystallization or a combination of these, and the respective isocyanates are obtained as an isocyanate mixture.
[0051] According to an eleventh embodiment, the invention relates to a process according to embodiment 9 or 10, characterized in that the content of acidic chlorine compounds in the separated isocyanate(s) or the isocyanate mixture is from 1 to 200 ppm, preferably from 1 to 100 ppm, more preferably from 2 to 80 ppm, particularly preferably from 5 to 50 ppm, determined according to the standard ISO 15028:2014.
[0052] According to a twelfth embodiment, the invention relates to a process according to embodiments 9 to 11, characterized in that the content of hydrolyzable chlorine in the separated isocyanate(s) or the isocyanate mixture is from 1 to 700 ppm, preferably from 1 to 500 ppm, more preferably from 5 to 100 ppm, determined according to the standard ISO 15028:2014.
[0053] According to a thirteenth embodiment, the invention relates to the use of an amine mixture of at least one first amine and at least one second amine different from the first amine in a process for preparing the corresponding isocyanates by gas phase phosgenation according to a process according to one of embodiments 1 to 12 for reducing the content of acidic chlorine compounds and / or the content of hydrolyzable chlorine of the corresponding isocyanates obtained in the preparation.
[0054] According to a fourteenth embodiment, the 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.
[0055] According to a fifteenth embodiment, the invention relates to the use of the product according to embodiment 14 and / or the isocyanate or isocyanate mixture obtained or obtainable by a process according to one of embodiments 9 to 12 as a component for the production of polyurethanes, in particular polyurethane foams, polyurethane coatings and polyurethane adhesives, of pharmaceutical products, in particular active ingredients, and of auxiliaries, in particular auxiliaries for the wet strength treatment of paper and other cellulose products, emulsifiers and thickeners. Examples:
[0056] The examples described below are intended to describe the process and some of the process products according to the invention in more detail without limiting the invention; all percentages refer to the mass unless otherwise stated.
[0057] The content of acidic chlorine compounds and the content of hydrolyzable chlorine were determined according to ISO 15028:2014.
[0058] 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 pm film thickness) and a 5973 mass spectrometer as the detector, using helium as the transport gas (flow rate 2 mL / min). The column temperature was initially 60 °C (2 min) and subsequently increased gradually at 8 K / min to 360 °C. Electron impact ionization with an ionization energy of 70 eV was used for GC-MS detection. The injector temperature was 250 °C.
[0059] NMR spectroscopic investigations were also carried out for further structural elucidation. The measurements were carried out on a Bruker DRX 700 instrument on samples with a concentration of approximately 1% (' H-NMR) or approximately 50% ( 13 C-NMR) samples in dry C6D6 at 700 MHz ('H-NMR) or 176 MHz ( 13C-NMR) measurement frequency. The ppm scale was used as a reference to the signal of the CeDsH contained in the solvent: 7.15 ppm 'H-NMR-chcm. Shift, 128.02 ppm 13 C-NMR chemical shift.
[0060] All reactions were carried out under a nitrogen atmosphere in glass apparatus previously dried in vacuum at 150 - 200°C.
[0061] All chemicals used in the inventive and comparative examples were purchased from Aldrich, D-82018 Taufkirchen. Hereinafter, BDA stands for 1,4-diaminobutane, PDA for 1,5-diaminopentane, HDA for 1,6-diaminohexane, XDA for 1,3-xylylenediamine, and MDA for 4,4'-methylenedianiline.
[0062] General working regulations
[0063] Procedure A - Liquid-phase phosgenation (FPP) in the presence of MDA (comparison to DE 2249459):
[0064] 500 ml of monochlorobenzene (MCB) were placed in a 4-neck flask cooled to -5 °C, equipped with a mechanical stirrer, dropping funnel, internal thermometer, and gas inlet tube. The mixture was condensed into a double molar amount of phosgene, based on the diamine (mixture) to be reacted, and a solution of the respective amine (mixture) in MCB was slowly added dropwise while cooling further to -10 to a maximum of 0 °C. After the amine (mixture) had been completely added, 100 ml of MCB was charged to the dropping funnel, and this was also added dropwise to the reaction mixture. While phosgene was passed through the gas inlet tube (approx. 120 g / h), the temperature was then gradually increased until MCB reflux occurred. After boiling point was reached, stirring was continued under reflux while phosgene was passed through (approx. 120 g / h) until a clear solution was formed, but for at least 5 hours.For dephosgenation, stirring was continued at reflux, and dry nitrogen was passed through the gas inlet tube instead of phosgene until phosgene-free status was confirmed using phosgene indicator paper. Further workup is described in the respective examples.
[0065] Procedure B - Gas-phase phosgenation (GPP):
[0066] In a glass system with a heatable mixing tube (reactor temperature = T 1) measuring 2.5 mm in diameter and 17.5 mm in length, with a downstream condensation stage and subsequent activated carbon-filled phosgene adsorption tower, phosgene was continuously introduced through a nozzle extending into the mixing tube. The phosgene was preheated in an upstream heat exchanger (temperature = T 2). A preheated amine mixture (temperature = T 3), optionally diluted with dry nitrogen as a diluent, also preheated to T 3, was simultaneously introduced into the reaction chamber through the annular gap between the nozzle and the mixing tube at a metering rate optimized for the specific amine (mixture). A defined pressure was maintained in the mixing tube by applying a vacuum at the end of the condensation stage. The hot reaction mixture leaving the reaction chamber in gaseous form was passed through refluxing 1,2-dichlorobenzene in a condensation stage.This involved selective condensation of the resulting diisocyanates. The gas mixture passing through the scrubbing stage, consisting essentially of nitrogen, HCl, and excess phosgene, was then freed of phosgene in the adsorption tower, and the condensate was freed of residual dissolved phosgene as described under A. Further processing is described in the respective examples.
[0067] Comparative Examples 1 - Phosgenation of sensitive aliphatic and araliphatic diamines in the liquid phase in the presence of MDA (Comparison with DE 2249459)
[0068] According to general procedure A, a mixture of 0.04 mol of amine 1 and 31.8 g of MDA was subjected to phosgenation in the liquid phase. After distillation, the diisocyanates underlying amine 1 were obtained in the stated purity and yield. The distillation residue (MDI) was not further investigated. Table 1: Results of Comparative Examples 1
[0069] All diisocyanates are contaminated with chlorine-containing by-components and are unsuitable for use in typical polyurethane applications.
[0070] Comparative Examples 2 - Gas-phase phosgenation of sensitive aliphatic and araliphatic diamines
[0071] According to general procedure B, the amines listed in Table 2 were subjected to gas phase phosgenation under the conditions listed in Table 2.
[0072] Table 2 Results of Comparative Examples 2
[0073] After each one-hour dosing time, the resulting condensate (1,2-dichlorobenzene, diisocyanate, by-products) was isolated, dephosgenated separately, analyzed, and the respective experiment continued under otherwise unchanged conditions. The dephosgenated raw materials thus obtained were then combined and processed by distillation. Table 2 shows the total yield and purity of the resulting diisocyanates. In all cases, a successively increasing contamination of the resulting diisocyanates with undesirable by-components was observed over the course of the experiment. In the case of XDA / XDI, the experiment had to be discontinued after only approximately 2 hours because stubborn deposits and coatings had formed in the reaction chamber, leading to a significant increase in pressure. Example 3 (according to the invention) - CoPg-GPP of XDA (amine 1) and PACM 20 (amine 2) by GPP according to general procedure B
[0074] According to general procedure B, mixtures of XDA (amine 1) and PACM 20 (amine 2) were phosgenated at a uniform temperature of 450 °C (T1=T2=T3). At the start of the experiment, pure amine 2 (approximately 0.330 mol / h) with a molar phosgene excess of approximately 250% was added. After 30 minutes of the experiment, amine 1 was added to obtain an amine mixture consisting of 25 mol% amine 1 and 75 mol% amine 2 (see Table 3, Example 3a). Subsequently, the concentration of amine 1 was further increased (Example 3b), resulting in an amine mixture containing 50 mol% amine 1 / 50 mol% 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 quantities, excess phosgene used, and run times are listed in Table 3. No pressure increase was observed in the plant.
[0075] Table 3: GPP of XDA and PACM 20
[0076] The dephosgenated raw materials were analyzed by 'H-NMR spectroscopy and GC-MS and then combined, since no differences in product purity relative to XDI were observed.
[0077] Distillation through a 40 cm packed column (inner diameter approx. 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 H12MDI, each as light-colored liquids, which, according to combined analytical methods (NMR, GC-MS), consisted of >99% XDI and H12MDI (isomer mixture) (94.9% and 97.2% yield based on the amines used). The AC / HC content was 35 / 120 ppm (XDI) and 27 / 38 ppm (H12MDI), respectively. No discoloration was observed even after weeks of storage under airtight conditions.
[0078] Example 4 (according to the invention) - CoPg-GPP of BDA (amine 1) and IPDA (amine 2) by GPP according to general procedure B
[0079] According to general 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 uniform temperature of 350 °C (T1=T2=T3) and a plant pressure of 500 mbar. No pressure increase in the plant was observed during the experiment. After residue separation, the dephosgenated crude product, which left 10.4 g of a dark brown, highly viscous distillation residue, was distilled through a 40 cm packed column (internal diameter approx. 25 mm, packing: #1 Interpack). This yielded 52.8 g of BDI with a purity of 98.8% (GC). The AC / HC content was 117 / 649 ppm. As the second fraction, 362.8 g of IPDI with 99.2% purity (GC), AC / HC: 122 / 165 ppm, were obtained.
[0080] Example 5 (according to the invention) - CoPg-GPP of PDA (Amine 1, Example 5a) or HDA (Amine 1, Example 5b) with PACM 20 (Amine 2) by GPP according to general procedure B
[0081] According to general procedure B, a mixture consisting of Example 5a) 39.1 g PDA (amine
[0082] 1) and 348 g PACM 20 (Amin 2) or in Example 5b) 44.4 g HDA (Amin 1) and 348 g PACM 20 (Amin
[0083] 2) phosgenated at a uniform temperature of 450 °C (T1=T2=T3) and a system pressure of 500 mbar. No pressure increase in the system was observed during the test. After residue separation, the dephosgenated raw materials were distilled through a 40 cm packed column (internal diameter approx. 25 mm, packing: #1 Interpack) after residue separation, leaving 3.4 g in Example 5a and 2.9 g in Example 5b of a dark brown, highly viscous distillation residue. This resulted in 54.8 g of PDI with 99.2% purity (GC) in Example 5a. The AC / HC content was 38 / 87 ppm, and in Example 5b, 58.9 g of HDI with 99.8% purity (GC). The AC / HC content was 22 / 42 ppm. Diisocyanate 2, which remained as a high boiler, was not investigated further.
[0084] A comparison of the GC-MS results obtained for the diisocyanates 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 concentration of all secondary components in the diisocyanates obtained according to the invention is significantly lower than in the diisocyanates obtained by known prior art methods. In particular, in the case of PDI, this applies to chlorine-containing compounds with molecular weights (from HRMS) of 145.03, 147.05, 178.99, and 208.02 (the latter each with isotopic patterns indicating the presence of at least two Cl atoms in the respective molecules). Structural isomers of some of these compounds appear to exist, recognizable by GC-HRMS signals with very close retention times and very similar fragmentation patterns in the mass spectra.In HDI, the number of Cl-containing secondary components is significantly lower than in PDI and is essentially limited to the compounds known from the literature: tetrahydro-IH-azepine-l-carbonyl chloride (several isomers), azepan-l-carbonyl chloride and (in traces) chloro-tetrahydro-lH-azepine-l-carbonyl chloride (2 CI atoms, several isomers).
Claims
A process for the production of isocyanates by gas-phase phosgenation of the corresponding amines, wherein an amine mixture of at least one first amine and at least one second amine different from the first amine is reacted with phosgene to form a reaction mixture, characterized in that • the first amine selected is from the group comprising or consisting of aliphatic and / or araliphatic amines; and • the second amine is selected from the group comprising or consisting of cycloaliphatic amines.
2. Method according to claim 1, characterized in that the first amine and / or the second amine is a diamine.
3. A 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 of the first to the second amino group of this diaminoalkane has 4 to 6 carbon atoms and / or this diaminoalkane is selected from the group comprising or consisting of 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.
4. A method according to any one of the preceding claims, characterized in that the araliphatic amine is selected from the group comprising or consisting of 1,3-xylylenediamine, 1,4-xylylenediamine, 1,1'-(1,2-phenylene)bis(ethan-1-amine), 1,1'-(1,3-phenylene)bis(ethan-1-amine), 1,1'-(1,4-phenylene)bis(ethan-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.
5. A method according to any one of the preceding claims, characterized in that the cycloaliphatic amine is selected from the group comprising or consisting of 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; diaminocyclohexane, in particular cyclohexane-1,2-diamine, cyclohexane-1,3-diamine and cyclohexane-1,4-diamine; methyldiaminocyclohexane, 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. A process according to any one of the preceding claims, characterized in that the mass fraction • of the first amine 5.0 to 80.0 wt.%, preferably 10.0 to 60.0 wt.% and • of the second amine, 20.0 to 95.0 wt.%, preferably 40.0 to 90.0 wt.%, based on the total weight of the amine mixture. A process according to any one of the preceding claims, characterized in that the molar ratio of phosgene to the amino groups of the amines of the amine mixture is > 1 : 1 to < 5 : 1, preferably > 1 : 1 to < 3 :
1. A process according to any one of the preceding claims, characterized in that an inert substance is used in the reaction, wherein the inert substance is selected from the group comprising or consisting of • Intergases, especially nitrogen, argon or mixtures thereof; • inert solvents, especially aromatic hydrocarbons, preferably chlorobenzene, o-dichlorobenzene, toluene, xylene or mixtures thereof; • or mixtures of the aforementioned inert gases and inert solvents. A process according to any one of the preceding claims, 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. A process 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.A process according to claim 9 or 10, characterized in that the content of acidic chlorine compounds in the separated isocyanate(s) or the isocyanate mixture is 1 to 200 ppm, preferably 1 to 100 ppm, more preferably 2 to 80 ppm, and particularly preferably 5 to 50 ppm, determined according to ISO 15028:2014. A process according to any one of claims 9 to 11, characterized in that the content of hydrolyzable chlorine in the separated isocyanate(s) or the isocyanate mixture is 1 to 700 ppm, preferably 1 to 500 ppm, and more preferably 5 to 100 ppm, determined according to ISO 15028:2014.Use of an amine mixture comprising at least one first amine and at least one second amine different from the first amine in a process for the preparation of the corresponding isocyanates by gas-phase phosgenation according to a process according to any one of claims 1 to 12 for reducing the content of acidic chlorine compounds and / or the content of hydrolyzable chlorine of the corresponding isocyanates obtained in the preparation. Product obtainable or obtained by a process according to any one of claims 1 to 12. 12, preferably according to one of claims 1 to 8 and 10 to 12, preferably directly obtainable or obtained by any one of claims 1 to 12, preferably by any one of claims 1 to 8 and 10 to 12. Use of the product according to claim 14 and / or of the isocyanate or isocyanate mixture obtained or obtainable by a 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, pharmaceutical products, in particular active ingredients, and excipients, in particular excipients for the wet-strength treatment of paper and other cellulose products, emulsifiers and thickeners.