DE10027778A1 - Production of an amine-formaldehyde condensate, involves fractionating a mixture of polyoxymethylene glycols, formaldehyde, methylene glycol and water in a column and reacting with an amine in the same column - Google Patents

Abstract

Production of amine-formaldehyde condensate involves fractionating a mixture of polyoxymethylene glycols, formaldehyde, methylene glycol and water in a reaction column and reacting the reactive fraction with a countercurrent of amine in the same column. Production of amine-formaldehyde condensates (I) by reacting: (a) amine(s); with (b) a mixture containing: (i) poly-oxymethylene glycols; (ii) monomeric formaldehyde; (iii) methylene glycol; and (iv) water. The method involves fractionation of mixture the, followed by reaction with the amine in a reaction column. The amine and that part of the fractionated mixture (b) which reacts with (a) move in countercurrent to one another.

Description

The present invention relates to a method for manufacturing of amine-formaldehyde condensation products by reacting at least one amine (a) with a mixture (b), the poly (oxy methylene) glycols (b (i)), monomeric formaldehyde (b (ii)), methylene contains glycol (b (iii)) and water (b (iv)), characterized net that a fractionation of the mixture (b) and an implementation with the amine (a) in a reaction column.

Various processes for the preparation of amine-formaldehyde con Densation products are generally known. The production of methylenedi (phenylamine), hereinafter also referred to as MDA, is one of the most important technical implementations of amines Formaldehyde. This is usually done by continuous or batch reaction of aniline with formaldehyde in Presence of acidic catalysts. In this implementation in addition to the main product to a small extent the undesirable secondary product formed N-methyl-MDA. This by-product works especially with the subsequent implementation of the MDA Phosgene for the production of methylene di (phenyl isocyanate) (MDI) negative because N-methyl-MDA is a precursor for represents chlorinated by-products in MDI. Similar problems with unwanted by-products also occur in other processes for the production of amine-formaldehyde condensation products.

To reduce N-methyl-MDA as a by-product of Various processes are known for producing MDA.

US-A-5,286,760 describes for a continuous MDA manufacturer position a partial neutralization of the reaction mixture between the condensation level of two molecules of aniline and one mole cool formaldehyde and the subsequent rearrangement of the intermediate formed aminobenzylamines to MDA.

EP-A-451 442 and DD-A-238 042 disclose for a continuous Process for MDA production by adding formaldehyde several process stages.

DD-A-295 628 describes for a batch process MDA production the addition of formaldehyde in two steps during the condensation stage, with the Most of the formaldehyde occurs at low temperature and  the second addition of the remaining formaldehyde at the same or higher temperature.

The disadvantage of these methods is that they are insufficient Lowering the content of N-methyl-MDA in the product mixture so that for this technically important amine-formaldehyde condensation product continues to have a need for improvement.

EP-A-934 922 describes a method in which a Mixture is used, the poly (oxymethylene) glycols and optionally monomeric formaldehyde and / or methylene glycol contains. By adding the formaldehyde to the aniline in the form the higher homologs thus have the advantage that very high local concentrations of monomeric formaldehyde in the Mixing with the aniline can be excluded. The Formation of the undesirable by-product N-methyl-MDA is thus suppressed. The above mixture is preferred by a Reaction mixing pump or a nozzle with the aniline or aniline / acid mixed in contact, d. H. in the reactor where the implementation with the aniline should be fed. Around to avoid undesirable parallel reactions to by-products, the mixture containing formaldehyde is added preferably in such a way that it is as quick and complete as possible Mixing with the reaction mixture that is in the reactor takes place. This can be done, for example, by Generation of turbulent flow in the mixing chamber achieved become.

In the process described, the fractionation of the Formaldehyde and the reaction with the amine serially and in different apparatus. Economically advantageous it would be a fractionation of the formaldehyde-containing Mixtures and reaction with the amine in one reaction device without making the selectivity of the to negatively influence the desired reaction.

The object of the invention is therefore a method for the production to provide amine-formaldehyde condensation products, wherein a reaction of an amine or amine mixture with a Mixture comprising formaldehyde and / or formaldehyde derivatives technically and economically advantageous in one reaction device takes place and wherein the formation of the amine-formaldehyde condensates tion products in high selectivity.

This object could be achieved according to the invention in that the production of amine-formaldehyde condensation products Reaction of at least one amine (a) with a mixture (b)  Poly (oxymethylene) glycols, monomeric formaldehyde, methylene glycol and water in a reaction column, wherein in the Reaction column both a fractionation of the mixture (b) as well as a reaction of the amine (a) with a portion of the fractional mixture (b) takes place.

The invention therefore relates to a process for the preparation provision of amine-formaldehyde condensation products Reaction of at least one amine (a) with a mixture (b), the poly (oxymethylene) glycols (b (i)), monomeric formaldehyde (b (ii)), methylene glycol (b (iii)) and water (b (iv)), characterized in that a fractionation of the mixture (b) and reaction with the amine (a) in a reaction column takes place, the amine (a) and the one reacting with the amine (a) Fraction of the fractionated mixture (b) is countercurrent move towards each other.

The at least one amine (a) according to the invention is any primary or secondary amine or a mixture of two or more these amines and is generally referred to in this application as amine (a) designated. Examples of the amine (a) are aniline and dipropylene diamine; N, N'-dimethyldipropylenediamine; N, N'-dimethyl dipropylene diamine; Isophoronediamine; 4-aminomethyl-1,8-octanediamine, MDA (individual isomers, mixture of isomers and / or oligomers from MDA), N-methylethylamine, n-pentylamine, 6-methyl-2-heptanamine, dipentyl amine, diisopentylamine, dihexylamine, cyclopentylamine, N-methyl benzylamine, R, S-1-phenylethylamine, 1-methyl-3-phenylpropylamine, 2,6-xylidine, ethylaminoethylamine, 2-dimethylaminoethylamine, 2-diisopropylaminoethylamine, N, N'-dimethylpropanediamine-1,3, 3-isopropylaminopropylamine, C11-neodiamine, 3,3'-diaminodiphenyl sulfone and N, N-dimethyldipropylenetriamine. Aniline is preferred.

The amine (a) can be liquid or gaseous in the reaction column are introduced. It is advantageous to use the amine (a) at the inlet point with the liquid in as intensely as possible to mix the reaction column. It can still be beneficial be liable to portions of the liquids that are already in the Reaction column are located in this and take them over its own mixing device, preferably a mixing nozzle Mixing pump or a static mixer, with the amine (a) too mix. Alternatively, it is also possible to add the amine before occurs to evaporate and in vapor form in the reaction column feed. In the same way, a mixture (b) with mixing as intensively as possible into the reaction column to be brought.  

In a preferred embodiment, the amine (a) can be introduced into the reaction column together with a solvent or solvent mixture. In principle, all solvents that dissolve amines are suitable. Preferred solvents are selected from water, alcohols, ethers, ketones, aromatic and aliphatic, hydrocarbon-containing solvents which are optionally substituted with halogen atoms. Examples of these include benzene, toluene, monochlorobenzene, dichlorobenzene, dimethylformamide (DMF), tetrahydrofuran (THF) and diethyl isophthalate (DEIP). CFCs and HCFCs as well as inorganic solvents, such as. B. SbCl ₃ , suitable. Water and chlorobenzene are particularly preferred.

If the amine (a) in one of the solvents described above or a mixture thereof used dissolved, is more common the concentration of the amine (a) in the solvent 5 to 90% by weight, preferably 20 to 40% by weight.

In a further preferred embodiment, the amine (a) even serve as a solvent.

The mixture (b) according to the invention comprises poly (oxymethylene) glycols (b (i)), monomeric formaldehyde (b (ii)), methylene glycol (b (iii)) and water (b (iv)). These components are in balance with each other.

HCHO + H ₂ O ↔ CH ₂ (OH) ₂
2CH ₂ (OH) ₂ ↔ HO-CH ₂ O-CH ₂ -OH + H ₂ O
nCH ₂ (OH) ₂ + HO-CH ₂ O-CH ₂ -OH ↔ HO- [CH ₂ O] _n -CH ₂ -O-CH ₂ -OH + nH ₂ O

For the purposes of this invention, the higher homologues of formaldehyde are summarized under the term poly (oxymethylene) glycols (b (i)) and are compounds of the general formula 1

HO- [CH ₂ O] _n -H (1),

in which n is a natural number ≧ 2. Are preferred Poly (oxymethylene) glycols (b (i)), where n is a natural number of 2 to 15, particularly preferably a natural number from 2 to 9 means.

Fractionation of the mixture (b) is part of this Invention to understand that that given in the reaction column Mixture (b), which according to the above equilibrium reactions  Poly (oxymethylene) glycols (b (i)), monomeric formaldehyde (b (ii)), May contain methylene glycol (b (iii)) and water (b (iv)) in the reaction column is separated. In doing so, enrich yourself less volatile poly (oxymethylene) glycols (b (i)) compared to volatile monomeric formaldehyde (b (ii)), methylene glycol (b (iii)) and water (b (iv)) in a deeper part of the Reaction column and monomeric formaldehyde (b (ii)), methylene glycol (b (iii)) and water (b (iv)) accordingly in a higher Part of the reaction column. There can also be a split of the individual poly (oxymethylene) glycols (b (i)). there these accumulate all the more deeply in the reaction column, the higher their molecular weight. With the fractionation of the Mixture (b) is not, however, within the scope of this invention understand that within the reaction column a complete Separation of the mixture (b) must take place, d. H. it can ver at one point or on a bottom of the reaction column different components of the added mixture (b) or ver different poly (oxymethylene) glycols (b (i)). It depends the type of fractionation of the mixture (b) from the combination setting of the mixture used (b), but also of the Reaction conditions, such as temperature curve, pressure, pH value, Water content and concentration ratios in the reaction column from.

The reacting fraction of the fractioned mixture (b) is in Within the scope of this invention a composition with the amine (a) to the desired amine-formaldehyde condensation product can react and by fractionating the in the reaction column introduced mixture (b) arises and predominantly from one or more components of the mixture (b).

In a preferred embodiment, the reactant comprises Fraction of the fractioned mixture (b) predominantly one Mixture of different poly (oxymethylene) glycols (b (i)), the optionally additional small amounts of monomeric formaldehyde (b (ii)) and methylene glycol (b (iii)). In one particularly preferred embodiment comprises the reacting portion of the fractionated mixture (b) predominantly a mixture of Poly (oxymethylene) glycols (b (i)) of the general formula 1, where n is 2 to 9, more preferably 2 to 5.

The mixture (b) can be liquid or gaseous in the reaction column are introduced.  

In a preferred embodiment, a mixture (b) in the Reaction column introduced in the form of an aqueous solution from 1 to 55% by weight, preferably 15 to 50% by weight. there is the molar ratio of poly (oxymethylene) glycols (b (i)) to Sum of monomeric formaldehyde (b (ii)) and methylene glycol (b (iii)) <1: 0.6 and preferably <1: 0.4 to 1: 0. Furthermore are preferably poly (oxymethylene) glycols (b (i)) in the mixture (b) before, for which n is 2 to 10 and particularly preferably for n 2 to 5. These solutions of the mixture (b) can be obtained from a usual formalin solution by known displacement methods balance on the side of the higher homologues be placed, for example in a distillation facility or a thin film evaporator. Because the balance between the higher homologues of formaldehyde and the monomeric Formaldehyde in solution at usual temperatures from 30 to 70 ° C resumes within 0.5 to 15 minutes, d. H. a Enrichment with higher homologues no longer occurs in the solution lies, one brings the solution in a preferred embodiment of the mixture (b) with a high proportion of higher homologues of the form aldehydes within 10 minutes, preferably within not more than 2 minutes after their preparation in the reaction column on.

In a further preferred embodiment, the mixture (b) introduced into the reaction column in gaseous form. There is one Molar ratio of poly (oxymethylene) glycols (b (i)) to the sum of monomeric formaldehyde (b (ii)) and methylene glycol (b (iii)) <1: 5 preferred and particularly preferred of <1:20. Usually is the main component of monomeric formaldehyde (b (ii)). The mixture (b) is usually gaseous at temperatures between 60 and 150 ° C, preferably at 80 to 120 ° C in the Reaction column introduced.

The mixture (b) is introduced into the reaction column in gaseous form brought, preferably poly (oxymethylene) glycols (b (i)) for which n is 2 to 4. Furthermore lies with the gaseous Add the mixture (b) the water content (b (iv)) in the mixture (b) usually less than 50% by weight, preferably less than 5% by weight, more preferably less than 0.5% by weight. Especially mixture (b) water is preferred for the gaseous addition freely admitted.

It is also possible that fractions in the Her provision and purification of formaldehyde in an appropriate Distillation column and the invention Contain mixture (b), removed and into the invention Reaction column can be introduced.  

In a further embodiment, the amine (a) and the mixture (b) is mixed in an external mixing device and then using a suitable device, preferably one Nozzle, are fed into the reaction column.

Reactions in a reaction column, including reactive distillations are generally known to the person skilled in the art. Industrial one They are used for etherifications, such as for example in the production of methyl tertiary butyl ether and Tertiary amyl methyl ether.

An important point in a reactive distillation is the ready setting the dwell time necessary for the course of the reaction. In the Most of the time it is necessary to keep the liquid speed in the reaction column compared to a non-reactive Targeted increase in distillation. This often forces you to be special constructions, for example to column columns with bubble trays and greatly increased level, too long dwell times in the Ab guide shafts from column columns or to separately arranged external retention containers. These reaction columns are heavily dependent on throughput and the part load behavior is problematic. Independence from the residence time can be achieved by the reaction mechanism (e.g. ion reactions in which the reaction occurs spontaneously). In some cases it is necessary to provide the reaction volume additional external containers can be provided. Packing and Packing columns have the disadvantage that in them realized only a relatively short residence time of the liquid can be. The reaction temperature may have to be increased to achieve the required reaction rate, which lead to poorer selectivities of the reaction can.

In the case of homogeneously catalyzed reactive distillations, mostly non-volatile or high-boiling catalysts used, such as e.g. As sulfuric acid, p-toluenesulfonic acid, alkalis or alcoholates. In individual cases, however, homogeneous catalysts can also be used are used whose boiling point is in the range of the reactants, for example nitric acid by the distillation effect predominantly remain in the column.

Heterogeneous catalysts are mostly in the form of solid Catalyst beds within the column or in separate Containers housed outside the reaction column. she can be used as fillings, for example at Ion exchange resins are shaped into packing, for example Ion exchangers pressed into Raschig rings, in filter fabric  introduced and to rolls (so-called "Bales") or columns packs are formed, applied to distillation packs are used or used as a suspension in the column.

The method according to the invention now describes the implementation of an amine (a) with a mixture (b) in a reaction column. Two different reactions take place in the reaction column Reactions. On the one hand, the mixture (b) added is fractional on the other hand, the amine (a) is fractionated Proportion of mixture (b) implemented.

In a preferred embodiment lies in the reaction column a temperature between 10 ° C and 230 ° C, preferred between 25 ° C and 150 ° C. There is also an absolute pressure between 0.1 mbar and 50 bar, preferably between 0.5 mbar and 2 bar before. The temperature profile in the reaction column yourself according to the desired target products and use fabrics. So z. B. the temperature distribution in the Implementation of aniline with a mixture (b) inter alia one Influence on the isomer distribution of the MDA in the product. If 2,2'- and / or 2,4'-MDA should preferably be produced, a high temperature can be beneficial.

In another preferred embodiment, a floor column used as the reaction column, sieve trays, valve floors or bubble-cap trays used commercially become. If necessary, these floors can be separated time containers can be added. The theoretical number of plates The reaction column is generally 5 to 60, preferably 20 to 35.

The residence time of the liquid in the packing, packages or plates of the reaction column is between a few seconds up to an hour, preferably in the range from 2 sec to 2500 sec, each separation level. It does not have to be identical on all floors his. The total residence time of the liquid is usually 5 to 120 minutes, preferably 10 to 30 minutes.

As an alternative to a tray column, a packed and Packing column are used, with appropriate constructive design of the column internals the preferred Separation levels and residence times can be achieved. Especially Special column packs that are suitable in some areas are suitable a fizzy layer with increased fluid content and the same enable a high number of separation stages in good time. These packs make it possible by changing their characteristics Heating output by about 10%, the residence time of the liquid by about  to change the factor 3. This way the dwell time throughput and Selectivity can be optimized. The conventional columns In contrast, internals are liquid dwell time can be influenced only little.

In the figures: 1 reaction column
2 Amin addition point (a)
3 alternative addition points amine (a)
4 Mixing point (b)
5 alternative addition points mixture (b)
6 Tapping point of monomeric formaldehyde (b (ii)), methylene glycol (b (iii)), water (b (iv)) and excess amine (a)
7 Tapping point amine-formaldehyde condensation product.

Fig. 1 illustrates schematically a preferred embodiment of the present invention. Here, a mixture (b) according to the invention is fed into the upper part of the column in the form of an aqueous solution. Mixture (b) can be added at one or more points distributed over one or more trays. The added mixture (b) is then fractionated in the reaction column. Monomeric formaldehyde (b (ii)), methylene glycol (b (iii)) and water (b (iv)) go off over the top of the reaction column or, if the reaction conditions are selected appropriately, become poly again in an equilibrium reaction in the rectifying section of the reaction column (oxymethylene) glycols (b (i)) implemented. Furthermore, excess amine (a), usually in the form of a water-amine (a) azeotrope, can also be removed overhead if appropriate. Poly (oxymethylene) glycols (b (i)) are enriched in the stripping section of the column, where they react with the amine (a) on the trays. The amine (a) can be added at one or more points on one or more trays in the lower part of the reaction column. The reaction product is drawn off at the bottom of the column, optionally in a mixture with water, poly (oxymethylene) glycols (b (i)) and over amine. The reaction conditions are preferably selected so that the reaction product is obtained largely free of water and amine. The mixture of monomeric formaldehyde (b (ii)), methylene glycol (b (iii)) and water (b (iv)) drawn off at the top of the reaction column can alternatively be brought back into equilibrium with the higher homologues in a residence container and then again as a mixture (b) are fed into the reaction column.

If, for example, aniline is selected as amine (a) and the inventive process is carried out as explained above and illustrated in FIG. 1, 4,4'-methylenedi (phenylamine) can be obtained in high selectivity as the main product. The formation of N-methyl-MDA is minimal.

If, for example, MDA is chosen as amine (a) and the inventive process is carried out as explained above and illustrated in FIG. 1, oligomers of MDA can be obtained with high selectivity.

However, if, for example, the formation of N-methyl-MDA is desired, so aniline with a mixture (b) according to the following Aus leadership form implemented.

Fig. 2 illustrates another preferred embodiment. Here, a mixture (b) according to the invention is fed in gaseously at one or more points in the lower part of the reaction column. The mixture (b) is then fractionated in the stripping section of the column, predominantly monomeric formaldehyde (b (ii)) and methylene glycol (b (iii)) reaching the rectifying section of the reaction column, where they react with the amine (a), which is fed at one or more addition points in the upper part of the reaction column. The reaction product can be removed at the bottom of the reaction column.

In one embodiment illustrated in FIG. 2, the reacting fraction of the fractionated mixture (b) preferably comprises a mixture of predominantly monomeric formaldehyde (b (ii)) and methylene glycol (b (iii)), which may also contain small amounts of poly (oxymethylene) glycols (b (i)).

It can be advantageous in the method according to the invention use at least one catalyst. A is preferred acid catalyst used. Is it one homogeneous catalyst, this is preferably mixed with one of the feed streams, particularly preferably with the amine stream, admitted. In particular, hydrochloric acid, Sulfuric acid and phosphoric acid suitable.

If hydrochloric acid is used as the homogeneous catalyst, this can can be used in gaseous or liquid form.

If it is a heterogeneous catalyst, it is located preferably this on the trays of the column. It can ver various forms of accommodation described in the literature of the heterogeneous catalyst can be used in tray columns. As well it is possible to use catalytically active packings or packing to use. The accommodation of the  Catalyst between layers of fabric leading to ordered packings be shaped.

As heterogeneous catalysts, ion exchangers, clays, zeolites, silica-alumina, tungsten or molybdenum oxides on various supports such as TiO ₂ , ZrO ₂ , HfO ₂ , SnO ₂ and Al ₂ O _{3 are} advantageous and acidic ion exchangers are particularly advantageous. The catalysts mentioned can optionally be added to the inventive process in any combination.

Alternatively, it is also possible to use the amine (a) in the form of an acid Bring salt into the inventive method. Prefers the amine (a) is in the form of a hydrochloride, sulfate or phosphate.

The molar ratio of amino groups (a) to catalyst in the In the case of a homogeneous catalyst, the reaction column is usually 1: 0.6 to 1: 0.001, preferably 1: 0.3 to 1: 0.05. in the In the case of a heterogeneous catalyst, this is based on the Amine (a) with 1 to 99 wt .-%, preferably 20 to 60 wt .-% in the Reaction column before.

The molar ver usually present in the reaction column Ratio of formaldehyde used, calculated by theoretical complete degradation of the mixture (b) used to form monomers Formaldehyde (b (ii)), to amino groups (a) used usually 1: 1.7 to 1: 7.5, preferably 1: 1.8 to 1: 5 and especially preferably 1: 1.9 to 1: 3.

Claims (13)

1. Process for the preparation of amine-formaldehyde condensation products by reacting at least one amine (a) with a mixture (b), the poly (oxymethylene) glycols (b (i)), monomeric formaldehyde (b (ii)), Contains methylene glycol (b (iii)) and water (b (iv)), characterized in that the mixture (b) is fractionated and reacted with the amine (a) in a reaction column, the amine (a) and the fraction of the fractionated mixture (b) reacting with the amine (a) move in countercurrent to one another. 2. The method according to claim 1, characterized in that the Reaction column has a theoretical number of plates from 5 to 60 has. 3. The method according to claim 1 or 2, characterized in that in the reaction column a temperature between 10 ° C. and 230 ° C and an absolute pressure between 0.1 mbar and 50 bar is present. 4. The method according to any one of claims 1 to 3, characterized records that the total residence time in the reaction column of the amine (a) and the portion reacting with the amine (a) of the fractionated mixture (b) between 5 and 120 minutes lies. 5. The method according to any one of claims 1 to 4, characterized records that in addition at least one acidic hetero gener catalyst is located in the reaction column. 6. The method according to any one of claims 1 to 5, characterized characterized in that the amine (a) and / or the mixture (b) at least one acidic homogeneous catalyst is added. 7. The method according to any one of claims 1 to 6, characterized records that the mixture (b) in gaseous form and in one mole ratio of poly (oxymethylene) glycols (b (i)) to the sum of monomeric formaldehyde (b (ii)) and methylene glycol (b (iii)) <1: 5 is introduced into the reaction column.   8. The method according to any one of claims 1 to 6, characterized records that the mixture (b) in the form of an aqueous solution from 1 to 55% by weight and in a molar ratio of poly (oxymethylene) glycols (b (i)) to the sum of the monomer form aldehyde (b (ii)) and methylene glycol (b (iii)) <1: 0.6 in the Reaction column is introduced. 9. The method according to any one of claims 1 to 8, characterized characterized in that monomeric formaldehyde (b (ii)), methylene glycol (b (iii)) and water (b (iv)) in the reinforcement part of the Reaction column back into equilibrium with poly (oxy methylene) glycols (b (i)) are brought. 10. The method according to any one of claims 1 to 9, characterized records that the amine (a) from aniline, dipropylenediamine, N, N'-dimethyldipropylenediamine, N, N'-dimethyldipropylene diamine, isophoronediamine, 4-aminomethyl-1,8-octanediamine, MDA or mixtures thereof is selected. 11. The method according to any one of claims 1 to 10, characterized records that as an amine-formaldehyde condensation product Methylenedi (phenylamine) and / or oligomers thereof. 12. The method according to any one of claims 1 to 11, characterized records that the amine (a) at one or more additions place in the lower part of the reaction column and the mixture (b) at one or more addition points in the upper part of the Reaction column is added. 13. The method according to any one of claims 1 to 10, characterized records that the amine (a) at one or more additions place in the upper part of the reaction column and the mixture (b) at one or more addition points in the lower part of the Reaction column is added.