MXPA06008971A - Continuous method for the production of polyamides - Google Patents

Abstract

Disclosed is a continuous method for producing polyamides, the oligomers or mixtures thereof, optionally with other reaction products, by reacting aminonitriles or dinitriles and diamines or mixtures thereof, optionally along with additional polyamide-forming monomers and/or oligomers, with an aqueous medium comprising aqueous monomer extracts or oligomer extracts which are obtained when extracting the polymer with water during the production of polyamides. Said reaction is carried out in a reactor which has a vertical longitudinal axis and is penetrated essentially in the longitudinal direction. According to the inventive method, water and/or the aqueous medium is/are introduced into the reactor at least at two different points located along the vertical longitudinal axis thereof, the aqueous medium being introduced at least at one point.

Description

CONTINUOUS PROCESS FOR THE PRODUCTION OF POLYAMIDES Description The present invention relates to a continuous process for the production of polyamides, their olgómeros, or their mixtures, by the use of an aqueous monomer and the extracts of oligomers obtained from the production of polyamides by the extraction of the polymer with water. The polymers formed in the production of polyamides, by the polymerization of, for example, e-caprolactam, contain low molecular weight fractions, composed of caprolactam and its oligomers. In practice, these low molecular weight fractions are removed by extraction with hot water. The caprolactam fraction can be recovered from this extraction water (aqueous monomer and oligomer extracts), purified and, if appropriate, reintroduced into the polymerization. It is also possible to add siphoning reagents to convert the oligomers of the extraction waters into caprolactam, which can similarly be isolated, purified and reused. The existing processes, for the most part, have the disadvantage that the extraction water has to undergo processing, in multiple stages, in some cases, before all the extract or its constituents, especially caprolactam, can be used for the renewed polymerization . The processes that consider the removal, processing and recycling of caprolactam have the additional disadvantage that the oligomers in the extraction water are not processed, but have to be discarded. Likewise, the aforementioned processes for the recycling of the extraction water,, involve the use of a process step for the hydrolytic polymerization of the extraction water concentrate or of a mixture of the constituents of the extraction water and the caprolactam. WO 00/38907 relates to a process for recycling the extraction water, ie the aqueous monomer and the oligomer extracts, obtained from the production of the polyamide, by extracting the polymer with water, in which the solutions of extracts aqueous can ideally be used in the polymerization of aminonitriles directly, without prior preparation of the concentration or separation steps. The process to recycle the aqueous extracts can be operated in batches. A continuous polymerization process for producing polyamides from aminonitriles is described in WO 00/24808. The reaction in this process is carried out biphasically in a countercurrent (reactive) distillation column. The column, through which the reagent stream flows downwards, has water vapor introduced into it, at multiple points in the lower region. The addition of water to control the temperature in the middle region of the distillation column is similarly possible. WO 99/10408 relates to a process for preparing polyamides from polyamide monomers, which are initially converted to prepolymers. The prepolymer solution is separated in an evaporator and a separator, which follows the evaporator, and the solid prepolymer obtained is crystallized and further converted into a solid state polymerization reactor in a polyamide having a high molecular weight. The existing processes for the production of polyamides of aminonitriles or dinitriles and diamines still have the need for improvements, with respect to the hydrolysis of the starting monomers. It is in many cases desirable, for example, to obtain a prepolymer which has a high content of carboxyl end groups and which can be advantageously converted into a polyamide in subsequent steps.

The object of the present invention is to provide a process for producing polyamides that allow the production of polyamides and their prepolymers, which have a high content of carboxyl end groups and avoid the disadvantages of the existing processes. We have found that this object is achieved, according to the invention, by a continuous process for the production of polyamides, their oligomers or their mixtures, if appropriate, with other reaction products, by means of the reaction of the aminonitriles or dinitriles and diamines or their mixtures, if is suitable, together with other monomers forming polyamides and / or oligomers, with an aqueous medium composed of aqueous monomers and oligomer extracts obtained from the production of polyamides by extraction of the polymer with water, in a reactor, which has an axis vertical longitudinal, and through which there is a flow substantially in the longitudinal direction, in which the water and / or the aqueous medium are introduced into the reactor at two or more different sites, along the vertical longitudinal axis, in which the medium aqueous is introduced in one or more sites. Preferably, the aqueous medium is only conducted into the reactor in at least two different sites.

The inventors have found that by using aqueous extracts of monomers or oligomers from the production of polyamides, by extraction of the polymer with water, instead of water alone, they supply polyamides and especially prepolymers having a high content of carboxyl end groups, when the Aqueous medium comprising aqueous extracts of monomers and oligomers is introduced into the reactor at two or more different sites, along the vertical longitudinal axis. The aqueous medium can be fed in 2 to 4 sites, for example. It is possible to add the aqueous medium in preferably up to 20 and more preferably up to 10 positions. In one embodiment, the aqueous medium can be introduced into the reactor at 2 to 20 or 3 to 0 different sites along the vertical longitudinal axis. The individual addition sites are spaced from one another along the longitudinal direction of the reactor. The loading can take place in the edge region, in the middle or in multiple locations between them, based on the cross-section through the reactor, orthogonally on the longitudinal axis. The addition of the aqueous medium at multiple sites, distributed in the course of the reaction, gives a more hydrolyzed prepolymer, which consequently has a higher content of carboxyl end groups. Also, the temperature profile in the reactor can be smoothed or standardized. This is especially possible when other locations in the continuation of the reactor are fed with the aqueous medium, which has not been heated. This makes it possible to check and equalize the exothermic state of the hydrolysis reaction. As the hydrolysis improves, the polyamides or polyamide prepolymers of the process, according to the present invention, exhibit reduced damage to the product, such as a minimum deficit of amino and carboxyl end groups, for example, since the handling of the reaction, according to the present invention, avoids regions of distinctly higher temperature (i.e., hot zones), which can lead to undesired side reactions. The enter the rector, in contrast, is generally fed with the aqueous medium, which has been preheated. The distributed feed on the reactor, consequently also makes it possible to save energy, since it is not usually necessary to heat the entire amount of water. The position and number of different loads along the continuous flow reactor, can be confirmed the practical requirements, in order to obtain a very homogeneous temperature profile across the length and cross section of the reactor and a very substantial hydrolysis in the course of prepolymer production.

Appropriate positions throughout the reactor can be determined by simple tests. The allocation of the quantity of the aqueous medium to the individual loading locations is similarly calculated so that a very substantial hydrolysis and a very homogeneous temperature profile result. The fraction of the charge of the total aqueous medium to the reactor that is fed into the reactor inlet is typically in the range of 35 to 95% by weight and more preferably in the range of 50 to 75% by weight. The remaining fraction of the aqueous medium is assigned to other individual loading locations. Preferably, the individual locations have added water, so that the differences in the amounts of individual locations is not greater than 50% by weight. The aqueous medium used, according to the present invention, is obtained from the production of polyamide by extraction of the polymer with water. The aqueous monomer and the oligomer extracts are described in WO 99/38907 and DE-A-198 08 442 and can be used for example. The solids content of the aqueous media, according to the present invention, is preferably 2 to 30% by weight, more preferably in the range of 3 to 15% by weight and especially in the range of 4 to 10% by weight . It is possible that the extraction waters obtained are concentrated or diluted with water to achieve the desired level of products that can be extracted. Preferably, at least 50% by weight of the solids in the aqueous medium, based on these solids, are lactams and cyclic oligomeric lactams, having 2 to 6 ring members, which are derived from the aminonitrile used.

The same applies to dinitriles and diamines. More particularly, the aqueous monomer and the oligomer extracts are returned to the polymerization within further processing steps. Thus conveniently there is no need for concentration, separation or purification. The solids content of the aqueous monomer and the oligomer extracts, which come directly from the extraction step, are typically in the range of 30 to 30% by weight, preferably in the range of 4 to 45% in that and especially in the range from 5 to 12% by weight. In the case of N6, the weight ratio in which caprolactam and its cyclic oligomers, having 2 to 5 ring members, are present, is preferably from 0 to 90: 5 to 20: 3 to 12: 2 a 8: 1 to 5, based on caprolactam and, respectively, 2, 3, 4 and 5 rings. For example, the weight ratio may be in the range of 70 to 80: 8 to 12: 3 to 11: 3 to 7: 2 to 4. An example comprises weight ratios of about 79: about 10: about 5: about 4: approximately 2. An extraction water which has been concentrated to approximately 70% by weight of solids content, contains the individual structures in the ratio of 50 to 80: 1 to 5: 0.5 to 2: 0.3 to 2: 0.02 al, for example. Preferred ranges are from 60 to 70: 12 to 4: 0.8 to 1.3: 0.6 to 0.9: 0.1 to 0.7. The feeding of the aqueous extract, described above, continuously throughout the course of the reaction in the first reactor, in different positions, makes it possible to check the exothermic state of the reaction and, for example, adjust the temperature in substantially homogeneous form in too the sector. Consequently, the temperature may be in the preferred range of 220 to 245 ° C, for example. This makes it possible to obtain polyamides and polyamide prepolymers which have a low product damage. The reactor can thus be operated adiabatically and only the aqueous extract and the aminonitrile or dinitrile and the diamine and, if appropriate, other monomers / oligomers that form polyamide at the reactor inlet are generally heated.

Compared to the addition of all water at the entrance to the rector, a more hydrolyzed prepoimer that has less damage to the product is obtained. The energy requirements of the process are reduced and the service life of the hydrolysis performance of any used catalyst is prolonged. One embodiment of the invention comprises conducting the reaction in the first reactor monophasically in the liquid phase. Especially, in this mode of operation, it is important to control the exothermic state of the reaction, since the heat produced is generally difficult to remove from the reactor. The reactor used in the process of the present invention has a vertical longitudinal axis and through which there is a flow substantially in the longitudinal direction. Preferably, the reactor is a flow tube, a TVA reactor (as described, for example, in the Encyclopedia Ullmann's Encylopedia f Industrial Chemistry, 6th edition, 2000 Electronic Edition), a multi-chamber reactor operated concurrently or countercurrent, or a reactive or non-reactive distillation apparatus. In one embodiment, the reactor is a multi-chambered reactor or a flow tube, which is fed with aminonitriles or dinitriles, and diamines or mixtures thereof, if appropriate, with other monomers forming polyamides and / or oligomers, and a first portion of the aqueous medium at one end and with other portions of aqueous media being added in its continuation and from which a reaction mixture comprising a polyamide, its oligomers or mixtures thereof, is discharged at its other end. In a further embodiment, the reactor is a reactive distillation apparatus or the reactor is a flow tube in which a reactive distillation apparatus is attached to the downstream side, in this case, in the reactive distillation apparatus, the reaction product is removed from the bottom and the formed ammonia and any other low molecular weight compound, formed and the water is separated in its upper part. Suitable continuous reactors are known per se. They are described, for example, in publications DE-A-196 35 077, DE-A-198 08 407, EP-A-1 053 275, EP-A-1 054 919, WO 99/038907, WO 00 / 24808. A reactive distillation apparatus may comprise, for example, a tray column, a bubble column, or a partition wall column. The reactors have each been modified so that they allow the introduction of the aqueous medium in two or more different locations along the vertical longitudinal axis. Appropriate modifications of the reactor are known to those skilled in the art.

In one embodiment of the invention, the process takes place in a reactor (1), having a vertically arranged longitudinal axis, in which, in the reactor (1), the reaction product is removed from the bottom and the ammonia formed and any other low molecular weight compound formed and water are removed from the upper part (2), where the reactor (1): comprises at least two chambers (4), arranged one above the other, in the longitudinal direction, in that the cameras (4) are separated from each other by plates (5) liquid-tight bottoms, each chamber (4) is connected by means of an overflow (6) of liquid to the immediately underlying chamber (4) and a stream of liquid product is removed by means of the overflow (7) of liquid above the surface of the liquid, in each chamber (4) that is connected to the chamber ( 4) located immediately above by one or more guide tubes (8) with openings, or which opens in a gas distributor (8), which has openings (11) for the gas outlet below the liquid surface. and it is also provided with at least one guide plate (12), which is arranged vertically around each gas distributor (8) and whose upper end is below the liquid surface and whose lower end is above the plate ( 5) of liquid-tight bottom of the chamber (4) and dividing each chamber (4) in one or more spaces (13) in which the gas flows and one or more spaces (14) in which the gas does not flow .

The gas distributor (9) of the reactor (1) can have a siphon type configuration in the shape of a cap (10) which is closed at the top. The cap of the siphon-type gas distributor (9) may be open at the bottom. The cap (s) (1) of the siphon-type gas distributor or distributors (9) can be formed of two or more interconnected parts, which, in cross-section, are arranged in the shape of a cross and / or stop the or concentrically or radially. The number and size of the openings (11) for the gas outlet and also its distance from the liquid surface in the chamber (4) can be determined such that the pressure drop of the gaseous stream in the distributor (9) of gas is in the range of 0.5 to 50 nabares.

The openings (11) for the gas outlet are each preferably arranged at the same height in the mutated relation. The openings (11) for the gas outlet can be arranged in the lower part of the cap or caps (1) at a distance of 1 to 1.5 cm from the lower end of the cap or caps. The guide plate or plates may each be spaced from the liquid surface and the bottom plate of the chamber (4), so that substantially no throttling of the flow occurs by the guide plate or plates. This at least one guide plate (12), arranged vertically around each gas distributor (9), can be constructed in the form of a thrust tube. The guide plate or plates of the gas distributor or distributors (9) may be arranged so that the cross-sectional area in which no gas flows is in the range of 10 to 80%, preferably in the range of 40 to 60% and more preferably about 50% of the total sum of the cross-sectional areas, in which the gas flows and where the gas does not flow. One or more and preferably all the chambers (4) of the reactor (1) can be equipped with a solid catalyst, especially as a bed of solid particles or in the form of an ordered packing coated with catalyst, for example of a monolith. An ion intercamabon resin can be installed in one or more and preferably in all the chambers (4). The reactor (1) constitutes an apparatus which has no moving parts, by means of an air raising circulation of the liquid, ensures an excellent mixing of the phases in the case of multiple phase reactions and a virtually constant composition of the mixture of reaction on the total volume of camera, that is to say, on its cross section as well as, in particular, on the height of the liquid, with, at the same time, a simple separation of the liquid and gaseous phases, after completing the reaction. The gas outlet from the gas distributor in the liquid space, between the gas distributor and the guide plate or plates arranged vertically around the gas distributor, reduces the hydrostatic pressure in this liquid space, relative to the liquid space , through which the gas does not flow, resulting in a pressure gradient, which is converted into kinetic energy. This pressure gradient drives the circulation of air elevation in the form of a flow, which is directed upwards in the space through which the gas flows, ie in the space between the gas distributor and the plate or plates of guide, arranged around the gas distributor or distributors, is deflected by the guide plate or plates, in the region above the extreme upper end of the guide plate or plates, and below the liquid surface, flows through the liquid space, through which the gas does not flow to the outside of the guide plate or plates, from the top down and above the bm plate to the liquid of the chamber and below the end most to the bm of the chamber. plate or guide plates is once again diverted in a flow directed upwards, thus closing the loop. The reactor is an apparatus having a vertically disposed longitudinal axis, i.e., an upright apparatus supplied with one or more streams of liquid, liquid / solid, gas / liquid or gas / liquid / solid reagents, in its upper region and with a gaseous stream of reactants and / or inert gas, in its lower region, i.e. having a countercurrent region for liquid, liquid / solid and gaseous streams. The reactor (1) is constructed of a plurality of chambers, preferably arranged one above the other.

The number of chambers can, advantageously, be no greater than 200, preferably no greater than 50 and especially or greater than 10. The number of chambers can advantageously be not less than 2 and especially or less than 3. The geometry of the reactor is frequently cylindrical, but other geometries are also possible. The chambers are separated from each other by liquid-tight bottom plates, with each chamber being connected by means of an overflow of liquid to the chamber located immediately below. The overflow of liquid can be configured, for example, in the form of a tube or an arrow and can be located either inside the reactor or outside the reactor. In particular, the liquid overflowing two successive chambers can be located on the opposite sides of the reactor. A stream of liquid product is removed from the chamber further to the bottom by means of the overflow of the liquid. The chamber further to the bottom of the reactor (1), the so-called bottom region, can be subdivided into two or more chambers. These at least two cameras can be arranged side by side or one on top of another or one on top of the other and side by side. In a preferred form, a portion of the product stream is withdrawn from the bottom region of the reactor (1) and fed as a liquid to the heat exchanger.

This heat exchanger converts some or all of the water into the product stream in the gaseous state and the mixture leaving the heat exchanger is fed into the reactor (1). It is preferable that the polyamides, oligomers or their mixtures, which are obtained according to the process of the present invention, can be removed from the reactor (1), especially in the bottom region, as a liquid product. In another preferred embodiment, a portion of all product streams withdrawn from the bottom region of the reactor are fed in liquid form to a heat exchanger, this heat exchanger converts some or all of the water present in the product stream to the gaseous state, the gaseous water is fed to the reactor (1) and the liquid product leaving the heat exchanger is obtained as a valuable product. In another preferred embodiment, the product from at least one of the chambers, in the bottom region of the reactor (1), is fed in liquid form to a heat exchanger, this heat exchanger converts some or all of the water into the stream of product in the gaseous state and the mixture leaving the heat exchanger is fed to the reactor (1). It is preferable that the polyamides, oligomers or their mixtures, which are obtained according to the process of the present invention, can be removed from the reactor (1), especially in the background region, as a liquid product. In another preferred embodiment, the product of at least one of the chambers in the bottom region of the reactor (1) is fed in liquid form to a heat exchanger, this heat exchanger converts all or all of the water into the stream of the product in the gaseous state, the gaseous water is fed to the reactor (1) and the liquid product that leaves The heat exchanger is obtained as a valuable product. The heat exchanger used in these preferred embodiments may be suitable within the reactor (1) or outside the reactor (1), partially inside, partially outside the reactor (1). The heat exchanger may further comprise an apparatus or a plurality of different apparatuses. The gas space above the liquid surface in each chamber is connected to the chamber placed directly above, by one or more guide tubes, which open all or each one within a gas distributor, with openings for the gas outlet below of the liquid surface. There are in principle no restrictions with respect to the number and arrangement of the guide tubes: it is equally possible to provide a simple central guide tube or a plurality of guide tubes distributed over the cross section of the reactor. It is also possible to provide a plurality of separate gas distributors, each supplied with gas, by means of one or more guide tubes for each chamber, instead of a single gas distributor. A gaseous stream is introduced from outside the rector and / or from the bottom region in the gas distributor of the penultimate reactor chamber by means of one or more guide tubes. It is thus also possible to provide a single gas distributor supplied with gas by <; means of one or more guide tubes, or a plurality of gas distributors, which are not interconnected and each supplied with gas by means of one or more guide tubes. There are in principle no restrictions with respect to gas distributors, which may be used for the purposes of the present invention; The important feature is that the gas distributor allows the gas supplied through the tube or guide tubes to exit the gauze space of the chamber located immediately below the liquid surface of the chamber, in which the gas is located. gas distributor. The gas should preferably exit very uniformly. As the gas distributor, it is, in principle, possible to use any commercial gas introduction device, for example, gas distributors in the form of tubes that are equipped with openings for the exit of the gas and can be, for example, arranged horizontally, that is to say in a plane parallel to the bottom plate which is hermetic to the liquid of the chamber. It is also possible to provide gas distributors in the form of a ring. However, the openings for the gas outlet always have to be placed below the liquid surface in the chamber, preferably at a distance from the liquid surface of at least 10% of the total height of the liquid in the chamber, preferably at least 30% and more preferably at least 50%. It has been found that a particularly favorable immersion depth in the part of the openings for the exit of the gauze below the surface of the liquid in the chamber is at least 50 mm. In a preferred variant, the gas distributor or dispensers have a siphon configuration in the shape of a cap, which is closed at the top and has openings for the exit of the gauze at its bottom. However, it is similarly possible that the cap be opened at its bottom. The upper closed end of the cap may be below the surface of the liquid, but may also extend above the surface of the liquid in the gas space. The cap of the siphon-type gas distributor can, in principle, have any geometric configuration; it is possible, for example, that it comprises a plurality of parts, which are connected to each other and in cross-section are preferably arranged in the shape of a cross and / or parallel or concentrically or radially. The number, cross section and distance of the liquid surface in the chamber of the gas outlet openings are preferably such that the pressure drop experienced by the gas stream in the gas distributor is in the range of 0.1 to 50. mbar The openings for the gas distributor are arranged preferably at the same height in relation to each other. They can, in principle, have any geometric configuration, for example circular, triangular or in the form of slits. The center line of the openings is preferably at a distance of about 1 cm to 15 cm, from the lower end of the cap. Alternatively, it is also possible that the lower end of the cap is provided with a zigzag edge instead of openings. In a further alternative, it is possible that the lower end of the cap is in the form of a ring distributor. The arrangement of the openings, at different heights in mutual relation, can be advantageous for an operation using two or more of the loading intervals. The height of the openings for the gas outlet, is chosen as required, depending on the specific reaction to be carried out in the reactor, such as, a sufficient mass transfer area is available for the specific section of the reactor. gas / liquid or gas / liquid / solid and, secondly, sufficient impetus for the circulation of evasion of liquid air is available. Around each gas distributor in the reactor of the present invention at least one vertical guide plate is arrangedwhose upper end is below the liquid surface in the chamber, which is at a distance from the bottom plate of the chamber and which divides each chamber into one or more spaces in which the gas flows and one or more spaces in which the gas does not flow. The guide plate, in a preferred embodiment, can be constructed as a thrust tube having the configuration of a hollow cylinder. However, it is also possible, for example, to have the configuration of a simple flat plate. This at least one guide plate is at a distance from the surface of the liquid and from the bottom plate of the chamber, preferably so as to substantially not strangle the flow of the liquid through the guide plate. The distances of the guide plate or guide plates from the liquid surface and also from the bottom plate of the cylinder are thus preferably determined so that the flow velocity of the liquid is not altered or altered only slightly by the deviation caused by the guide plate. The total height of the guide plate is, in principle, not subject to restrictions. It can be sized appropriately, in particular as a function of the desired residence time per chamber, while, at the same time, ensuring adequate mixing. The process of the present invention can be carried out in one or more stages. The process, according to the present invention, comprises, in one embodiment of the invention, the following steps: 1. react the aminonitriles or dinitriles and diamines or their mixtures, if appropriate, together with other monomers and / or oligomers forming polyamides , with the aqueous medium in the reactor at a temperature of 90 to 400 ° C, preferably 180 to 310 ° C and a pressure of 0.1 to 35 Pa, preferably 1 to 10 x 105 Pa, to obtain a reaction mixture; 2. furthermore reacting the reaction mixture at a temperature of 150 to 400 ° C, preferably 200 to 300 ° C and a pressure which is lower than the pressure of step 1, in which the temperature and the pressure are chosen from so that the first gas phase and a first liquid phase are obtained and the first gas phase is separated from the first liquid phase; and 3. mixing the first liquid phase with a gaseous or liquid phase, comprising water or an aqueous medium at a temperature of 90 to 370 ° C, preferably 200 to 300 ° C and a pressure of 0.1 to 30 x 105 Pa. , to obtain a mix of products. The process may also, or instead of stage 3, comprise the following step: 4. post-condensate the product mixture at a temperature of 300 to 280 ° C and a pressure which is lower than the pressure in step 3. If Step 3 is carried out, in which the temperature and the pressure are selected so that the second gas phase, which comprises water and ammonia, and a second liquid phase, which comprises the polyamide, are obtained. Metal oxide catalysts, in the form of a fixed bed, can be used in the reactor or in stage 1 or stage 3, or not only in the rector or stage 1, but also in stage 3. In In general, the reaction in the reactor can be carried out in the presence of fixed bed catalysts, more preferably Brónsted acid fixed bed catalysts. The aminonitrile in the mixture can be, in principle, any aminonitrile, ie, any compound having both at least one amino group and at least one nitrile group -aminonitriles are preferred, especially the α-aminoalkyl nitriles having 4-amino-nitriles. at 12 carbon atoms and more preferably from 4 to 9 carbon atoms in the alkylene part, or an aminoalkyl nitrile having from 8 to 13 carbon atoms, preferred aminoalkylaryl-nitriles are aminoalkylaryl nitriles having a group of alkylene with at least one carbon atom between the aromatic unit and the amino-nitrile group, Especially preferred aminoalkylaryl-nitriles are those which have the amino group and the nitrile group in the 1,3-position, in mutual relation. The α-aminoalkyl nitrile is preferably a linear α-aminoalkyl nitrile in which the alkylene part (-CH 2 -) preferably contains 4 to 12 carbon atoms, more preferably from 4 to 9 carbon atoms, such as 6. amino-cyanopentane (6-aminocapronitrile), 7-amino-1-cyclohextane, 8-amino-1-cycloheptane, 9-amino-1-cyanooctane, 10-amino-1-cyanononane and more preferably 6-aminocapronitrile. The 6-aminocapronitrile is customarily obtained by hydrogenation of the adiponitrile, according to known processes, described, for example, in DE-A 836 937, DE-A 848,654 or US 4 141 543. Of course, it is also possible to use mixtures of a plurality of aminonitriles or mixtures of an aminonitrile with further comonomers, such as caprolactam or the mixture defined below. In a particular embodiment, especially if the branched or extended chain copolyamides or polyamides are to be prepared. The following mixture is used in place of the pure 6-aminocapronitrile: from 50 to 99.99, preferably from 80 to 90,% by weight, of the 6-aminocapronitrile, from 0.01 to 50, preferably from 1 to 30,% by weight of at least a dicarboxylic acid, selected from the group consisting of aliphatic α, β-C?-dicarboxylic acids, Cs-C? 2 aromatic dicarboxylic acids, C5-C8 cycloalkane-dicarboxylic acids, from 0 to 50, preferably from 0 to 30 Weight% of? -diamine having from 4 to 10 carbon atoms, from 0 to 50, preferably from 0 to 30% by weight of a? -dinitrile, and from 0 to 50, preferably from 0 to 50% by weight of a α, β-C2-C2-amino acid or of the corresponding lactam, from 0 to 10% by weight of at least one inorganic acid or its salts, the individual percentages by weight are added up to 100%.

Suitable dicarboxylic acids include C4_C or aliphatic α, β-dicarboxylic acids, such as succinic acid, glutamic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, particularly preferred adipic acid and dicarboxylic acids Cs-C 2, such as terephthalic acid and also C 5 -C 8 cycloalkanedicarboxylic acids, such as cyclohexanedicarboxylic acid.

Suitable α, β-diamines, having 4 to 10 carbon atoms, include tetramethylene diamine, pentaethylene diamine, hexamethylene diamine, heptamethylene diamine, octamethylene diamine, nonamethylenediamine and decamethylenediamine, preferably hexamethylenediamine. It is also possible to use salts of the aforementioned dicarboxylic acids and diamines, especially adipic acid salt and hexamethylenediamine, which is known as salt 66. The C2-C12 a, β-dinitrile used is preferably an aliphatic dinitrile, such as 1,4-dicyanobutane (adiponitrile), 1,5-dicyanopentane, 1,6-dicyanoxane, 1,7-dicyanoheptane, 1,8-dicyakenoctane, 1,9-dicyanononane, 1,10-dicyanodecane, particularly preferred is the adiponitrile. If desired, it is also possible to use diamines, dinitriles and dinitriles derived from alkylene-arylene or branched alkylarylenes. The C5-α2-amino acid, used may be 5-aminopentanoic acid, 6-aminohexanoic acid, 7-aminoheptanoic acid, 8-aminooctanoic acid, 9-aminononaenoic acid, 10-aminodecanoic acid, 11-aminoiundecanoic acid and acid 12-aminododecanoic, preferably 6-aminohexanoic acid or its internal amides, especially caprolactam.

Starting materials useful for the process of the present invention, further include mixtures with aminocarboxylic acid compounds of the general formula I: R2R3N- (CH2) m-C (0) R1 (I) where R1 is -OH, -OC? _? 2-alkyl or NR2R3, where R2 and R3 are, independently, hydrogen, C1_? 2-alkyl or C3_8-cycloalkyl, and m is 3, 4, 5, 6, 7, 8 , 9, 19, 11 or 12. Particularly preferred aminocarboxylic acid compounds are those in which R1 is OH, -0-C? -alkyl, such as -O-methyl, -O-ethyl, -0-n-propyl, -Oi-propyl, -On-butyl, -O-sec-butyl, -O-tert -butyl and -NR2R3, such as -NH2, NHMe, NHEy, NMe, and NEt2 and m is 5. Particular preference is given to 6-aminocaproic acid, methyl 6-aminocaproate, ethyl 6-aminocaproate, 6-amino- N-methylcaproamide, 6-amino-N, N-dimethylcaproamide, 6-amino-ethylcaproamide, 6-amino-N, N-diethylcaproamide and 6-aminocaproamide. The starting compounds are commercially available or can be prepared, for example, as described in EP-A 0 2234 295 and Ind. Eng. Chem. Process Des. Dev. 17 (1978) 9-16.

It is also possible to use any desired me of the aforementioned compounds, aminocarboxylic acid compounds, lactams, diamines and diacids or their salts. The reaction of the first cap can be carried out without a catalyst or in the presence of a metal oxide catalyst. In the following, the reaction conditions are described without catalyst and with catalyst (in brackets) . According to the invention, the first step (step 1) involves heating an acetonitrile with water, at a temperature of about 100 (90) to about 400 (400) ° C, preferably around 200 (180) to about 350 (310) ° C, especially around 240 (220) to about 290 (270) ° C, where a pressure of about 0.1 to about of 35 (15) x 106 Pa preferably about 1 (1) to about 15 (10) x 106 Pa, especially about 4 (4) to about 11 (9) x 106 Pa is established.

In this step, the pressure and temperature can be adjusted in mutual relationship, such as to obtain a liquid phase and a gas phase. Preferably, the reaction mixture must be present as a single liquid phase. According to the invention, water or an aqueous extract is used in total in a molar ratio of the aminoalkyl nitrile to water within the range of 1: 1 to 1:30 (1:10), particularly preferred within the range of 1. : 2 to 1:10 (1: 8), very particularly preferred within the range of 1: 2 to 1: 8 (1: 6), preference is given to the use of water or an aqueous extract in excess, based on the aminoalkyl amide used. In this embodiment, the liquid phase corresponds to the reaction mixture, while the gas phase separates. As part of this step, the gaseous phase can be separated from the liquid phase at a single time, or the synthesis mixture formed in this step can be present in two phases: liquid / gas. Of course, the pressure and temperature can be adjusted in mutual relation, such that the synthesis mixture is present as a single liquid phase. Removal of the gas phase can be effected by the use of stirred or unstirred separation vessels, or container batteries and by the use of the evaporator apparatus. For example, by means of circulating evaporators or thin film evaporators, such as by film extruders or by means of ring disk reactors, which ensure an enlarged phase interface. In certain cases, the recirculation of the synthesis mixture or the Use of a loop reactor may be necessary to increase the interface of the phase. Also, the removal of the gas phase can be improved by the addition of water vapor or inert gas in the liquid phase. Preferably, the pressure is adjusted to a preselected temperature so that the pressure is less than the equilibrium vapor pressure of the ammonia, but greater than the equilibrium vapor pressure of the other components in the synthesis mixture at a given temperature. In this way it is possible to favor especially the removal of ammonia and thus the acceleration of the hydrolysis of the acid amide groups. In a further embodiment, the reactor of the first stage is provided with packing elements that limit any axial back-mixing of the reagents. As a result, the ammonia gas released into the reactor, predominantly directly after entry into the reactor, reaches the gas phase in the upper part of the reactor by the most direct route. The disruption caused to the flow profile in the further continuation of the reactor by ascending gas bubbles or convection, is, therefore, minimal. With respect to residence time of the synthesis mixture in the first stage, there are no restrictions, however it is generally established within the range of about 10 minutes to about 10 hours, preferably within the range of about 30 minutes to around 6 hours. Although there are no restrictions regarding the degree of conversion of nitrile groups in stage 1, for economic reasons especially state that the conversion of the nitrile groups in step 1 are generally not less than about 70 mol%, preferably at least about 5 mol%, and especially within the range of about 97 to 99% molar, based in each case on the moles of the aminonitrile used. The conversion of the nitrile group is usually determined by means of IR spectroscopy (CN stretch vibration at 2247 nda numbers), NMR or HPLC preferably by IR spectroscopy. In a further preferred embodiment, the aminonitrile / water mixture is continuously heated with the aid of a heat exchanger and the mixture, thus heated, is introduced into a reaction vessel heated to the same temperature, preferably in a tube, which , if desired, may include internal parts, such as Sulzer mixing elements, to avoid backmixing. Of course, aminonitrile and water can also be heated separately.It is not a rule, according to the present invention, to conduct the reaction in step 1 in the presence of oxygen-containing phosphorus compounds, especially phosphoric acid, phosphorous acid and hypophosphorous acid, and their alkali and alkaline earth metal salts and ammonium salts, such as Na2P04, NaH2P0, Na2HP04, Na2HP03, NaH2P02, K3Po4, KH2P04, K2HP04, K2HP04, KH2P03, K2HP03, KH2P02, in this case the molar ratio of α -aminonitrile to the phosphorus compounds is selected within the range from 0.02 to 1: 1, preferably within the range of 0.01: 1 to 0.1: 1 It is another advantage to use oxides of known metals, such as titanium dioxides, zirconium oxide, aluminum oxide, lanthanum oxide, magnesium oxide , etc., preferably a Brónsted acid catalyst, selected from a beta-zeolite catalyst, silicate sheet catalyst or titanium dioxide catalyst, for heterogeneous catalysis in the individual process steps iduals, in order that the conversion, especially of the nitrile groups, can be driven. Catalysts of this type are described, for example, in WO 03/089496 or in the prior art cited therein. Preference is given to titanium diepoxides, especially titanium dioxides comprising from 70 to 100% by weight of anatase and from 0 to 20% by weight of rutile, wherein up to 40% by weight of titanium dioxide can be replaced by other oxides such as tungsten oxide. For pure starting materials (aminonitrile) preference is given to using a titanium dioxide having a high anatase content. The catalyst preferably has a pore volume of 0.05 to 5 ml / g, particularly preferably 0.2 to 0.5 ml / g. The cutting hardness may be in the range of small values, such as 2N to ION, average values, such as greater than ION to 20N, or also high values, such as greater than 20N or more than 25N. The BET surface area is preferably greater than 5 m2 / g and more preferably greater than 15 m2 / g (DIN 66131). The catalysts can be prepared from commercially available Ti02 powders. When the tungsten oxide is used, up to 40% by weight, preferably up to 30% by weight and more preferably from 15 to 25% by weight of the titanium dioxide is replaced by the tungsten oxide. The catalysts can be prepared as described by Ertl, Knóziner, Weitkamp: Manual of heterogeneous catalysis. "VCH Weinheim, 1997, pages 98 et seq .. The metal oxides can be used in any suitable desired form. The shape of pellets, extrudates or other shaped articles Particular preference is given to extrudates of 1 to 6 mm in average diameter and 5 to 30 mm in average length Pellets and extrudates can be used alone or combined with metal packaging, such as Rashig rings A mixture of pellets and shaped articles may be present or a sequence of metal oxide layers and shaped articles may be present.The aforementioned metal oxides are not used in stage 4, but they are they can be used in steps 1 to 3, and preferably 1 and 3, in which case the use in step 1 is particularly preferred In accordance with the invention, the reaction mixture obtained in the first stage it is further reacted in stage 2 at a temperature of about 200 (150) or about 400 (350) ° C, preferably at a temperature in the range of about 210 (200) to about 330 ( 300) ° C, especially within the range of about 230 (200) to about 290 (270) ° C and a pressure the lime is lower than the pressure in step 1. The pressure in the second stage is preferably at least 0.5 x 106 Pa less than the pressure in stage 1, and generally the pressure will be within the range of from about 0.1 to about 45 x 106 Pa, preferably within the range of from about 0.5 to about 15 x 10 * 6 Pa, especially within the range of about 2 to about 6 x 106 Pa.

In step 2, the temperature and pressure are chosen to obtain a first gas phase and a first liquid phase and the first gas phase is separated from the first liquid phase. The first gas phase, which consists essentially of ammonia and water vapor, is usually removed in a continuous manner, by means of a distillation apparatus, such as a distillation column. Any organic constituent of the distillate also removed in the course of this distillation, predominantly unconverted aminonitrile, may be fully or partially recycled in step 1 and / or step 2. The residence time of the reaction mixture in step 2 does not it is subjected to any restriction, but is generally within the range of about 2 minutes to about 5 hours, preferably within the range of about 10 minutes to about 1 hour. The product line between the first and second stages optionally contains packing elements, for example Rashing rings or Sulzer mixing elements, which facilitate a controlled expansion of the reaction mixture in the gas phase.

In step 3, the first liquid is mixed with a gaseous or liquid comprising an aqueous medium, preferably with water or water vapor or extract. This is preferably done continuously. The amount of water or added extract (as liquid) is preferably within the range of from about 10 to about 500 ml, more preferably within the range of from about 20 to about 150 ml, based on 1 g of the first or first phase liquid solid or the mixture of the first liquid and first solid phase. The addition of water or extract primarily compensates for water losses incurred in step 2 and further hydrolysis of the acid amide groups in the synthesis mixture. This results in a further advantage of the invention, that the mixture of the starting materials, as stated in step 1, can be with a small excess of water only. In another embodiment of the invention, step 3 can be carried out using aqueous extracts having a higher content of extractable products of up to 85%. If desired, the highly concentrated aqueous extract may have the caprolactam added thereto, prior to introduction in step 3, to improve the solubility of the caprolactam oligomers and prevent the deposition of oligomers and thus the sealing of the apparatus.

The gaseous or liquid phase comprising water or aqueous extracts, is preferably preheated in a heat exchanger, before being introduced in stage 3 and then mixed with the first liquid phase. The reactor may, optionally, be equipped with mixing elements, which mix the components further. The organic fraction of the phase of gas removed from stage 2, can similarly be recycled within stage 3. This recycling of the organic phase takes place in aqueous form. Stage 3 can be operated at a temperature of 150 to 370 ° C and a pressure of 0.1 to 30 x 106 Pa. If the catalyst bed is present, the conditions applied to stage 3 can be used. The pressure can be adjusted to a preselected temperature so that this pressure is less than the equilibrium vapor pressure of the ammonia, but higher than the equilibrium vapor pressure of the other components in the synthesis mixture at the given temperature. In this way, it is possible to favor especially the removal of ammonia and thus accelerate the hydrolysis of the acid amide groups. The apparatus / rectors that can be used in this stage, can be identical with those of stage 1, discussed above.

In a preferred embodiment, the two-phase process is carried out by subjecting the reactor of the first stage to a downward flow, in which case, this reactor is again preferably equipped with the catalyst and / or packing elements, which limit any axial back-mixing of the reagents. As a result, the ammonia gas released into the reactor, predominantly directly after entry into the reactor, reaches the gas phase in the upper part of the reactor by the most direct route. The interference caused to the flow profile in the further course of the reactor by rising gas bubbles or convection is, therefore, minimal. The residence time of this stage is similarly or subject to any restriction, but economic reasons cite a range of from about 10 minutes to about 10 hours, preferably from about 1 to about 8 hours, particularly preferred from about 1 to 6 hours . The mixture of the product obtained in step 3 can also be processed as described below. In a preferred embodiment, the mixture of the product of step 3 is subjected to a postcondensation in a fourth stage at temperatures of about 200 to about 350 ° C, preferably at temperatures of about 220 to 300 ° C, especially about 250 at 270 ° C. Step 4 is carried out at a pressure that is below the pressure of step 3 and preferably within the range of about 5 to 1000 x 103 Pa, more preferably within the range of about 10 to about 200 Pa. In the context of this step, the temperature and pressure are selected so as to obtain a second phase of gas and a second phase of liquid or solid, or a mixture of second phases of liquid and solid, which each comprise the polyamide. The postcondensation of step 4 is preferably carried out in such a way that the relative viscosity (measured at a temperature of 25 ° C and a concentration of 1 g of the polymer per 100 ml in 96% strength by weight of sulfuric acid) of the polyamide, assumes a value in the range of about 1.6 to about 3.5. In a preferred embodiment, any water present in the liquid phase can be expelled by means of an inert gas, such as nitrogen. The residence time of the reaction mixture, in step 4, depends in particular on the desired relative viscosity, the temperature, the pressure and the amount of water added in step 3.

The product line between stages 3 and stage 4 can optionally contain packing elements, for example Rashig rings or Sulzer mixing elements, which allow a controlled expansion of the synthesis mixture in the gas phase. In a further embodiment of the invention, step 3 can be bypassed and the prepared polyamide is carried out in steps (1), (2) and 839. The variant - with catalyst, is preferably carried out as follows: In the tea 1, at least the aminoalkyl nitrile is heated with an excess of water of extract at a temperature within the range of about 250 to 350 ° C and a pressure of about 4 to 30 x 106 Pa, the pressure and temperature being adjusted to each other so that the synthesis mixture is present as a single liquid phase and the conversion of the nitrile group is not less than 95 mol%, based on the moles of the aminoalkyl nitrile used, to obtain a reaction mixture . The reaction mixture is treated in step 2 at a temperature in the range of about 220 to 300 ° C and a pressure in the range of about 1 to 7 x 106 Pa, the pressure in the second stage being at least 0.5 x 106 Pa less than in step 1. At the same time, the first gas phase resulting is separated from the first liquid phase. The first liquid phase obtained in step 2 is treated in step 3 at a temperature in the approximate range of 220 to 300 ° C and a pressure in the range of about 10 to 300 x 103 Pa, the second resulting phase comprises water and ammonia that includes the gas phase expected from the second liquid phase. Within this step, the relative viscosity (measured as defined above) of the resulting polyamide was adjusted to a desired value within the range of about 1.6 to about 3.5 through the selection of temperature and residence time. The second phase of the resulting liquid is then discharged conventionally and, if desired, processed. The metal oxide catalyst is used, the basic temperatures described above and the pressures can be used. Also, in the context of the process of the invention, it is also possible to carry out a chain or branching extension or combinations thereof. For this purpose, the substances of the polymer branching or chain extension, known to a person skilled in the art, are added in individual steps. These substances are preferably added in steps 3 or 4. Substances that may be used are: trifunctional amines or carboxylic acids as branching or crosslinking agents. Examples of suitable at least trifunctional amines or carboxylic acids are described in EP-A-0 345 648. These at least trifunctional amines have at least three amino groups which are capable of reacting with the carboxylic acid groups. They preferably have any carboxylic acid group. These at least trifunctional carboxylic acids have at least three carboxylic acid groups, which are capable of reacting with the amines and which may also be present, for example, in the form of their derivatives, such as esters. The carboxylic acids preferably or contain any amino group capable of reacting with the carboxylic acid groups. Examples of suitable carboxylic acids are trimesic acid, trimerized fatty acids, prepared, for example, from oleic acid and having from 50 to 60 carbon atoms, naphthalene polycarboxylic acids, such as naphthalene-1, 3, 5, 7- tetracarboxylic. The carboxylic acids are preferably defined organic compounds and not polymeric compounds.

Examples of amines having at least 3 mino groups are the nitrilotrialkylamines, especially the nitrilotrietanamine, dialkylenetriamines, especially diethylenetriamine, trialkylene tetraamines and tetraalkylene pentaamines, the alkylene portions preferably being parts of ethylene. Likewise, dendrimers can be used as amines. The dendrimers preferably have the general formula I: R2N - ((CH2) n) 2 -N- (CH2) X-N ((CH2) n-NR2) 2 (I) where R is H or - (CH ^ n-NR1 ^ in which R1 is H or - (CH2) n-NR22, where R2 is H or - (CH2) n-NR in which R3 is H or - (CH2) n -NH2, n is an integer from 2 to 6, and x is an integer from 2 to 15. Preferably, n is 3 or 4, especially 3, and x is an integer from 2 to 6, preferably from 2 to 4, especially 2. The radicals R can also have the indicated meanings, independently of each other.

Preferably R is a hydrogen atom or a radical - (CH2) n-NH2.

Suitable carboxylic acids are those having from 3 to 10 carboxylic acid groups, preferably 3 or 4 carboxylic acid groups. Preferred carboxylic acids are those having aromatic and / or heterocyclic nuclei. Examples are benzyl, naphthyl, anthracene, biphenyl, triphenyl or heterocyclic radicals, such as pyridine, bipyridine, pyrrole, indole, furan, thiophene, purine, quinoline, phenanthrene, porphyrin, phthaloyania, naphthalocyanine. Preference is given to the phthalocyanine of biphenyltetracarboxylic acid, natalocyanin, 3,5-5'-biphenyltetracarboxylic acid, 1,3,5,7-naphthalenetetracaboxylic acid, 2,4,6-pyridine-tricarboxylic acid, 3, 5, 3 acid ', 5'-bipyridyltetracarboxylic acid, 3, 5, 3', 5'-benzophenone tetracarboxylic acid, 1,2,6,8-acridinotetracarboxylic acid, particularly preferred is 1,3-benzenetricarboxylic acid (trimesic acid) and acid 1 , 2, 4, 5-bencenstraarboxylic. Such compounds are commercially available or can be prepared by the process described in DE-A-43 12 182. If ortho-substituted aromatic compounds are used, the formation of imide is preferably prevented through the selection of suitable reaction temperatures. These substances are at least trifunctional, preferably at least tetrafunctional. The number of functional groups may be from 3 to 16, preferably from 4 to 10, particularly preferred from 4 to 8. The processes of the invention are carried out using at least trifunctional amines or at least trifunctional carboxylic acids, but do not mix of such amines or carboxylic acids. However, small amounts of at least trifunctional amines may be present in the trifunctional carboxylic acids and vice versa. The substances are present in an amount of 1 to 50 μmol / g, of polyamide, preferably 1 to 35, particularly preferably 1 to 20 μmol / g of polyamide. The substances are preferably present in an amount of 3 to 150, particularly preferably 5 to 100, especially 10 to 70, μmol equivalents / g of the polyamide. The equivalents are based on the number of amino functional groups or carboxylic acid groups.

Difunctional carboxylic acids or difunctional amines are used as chain extension agents. They have 2 carboxylic acid groups that can react with amino groups, or 2 mino groups, which can react with the carboxylic acids. The carboxylic acids or difunctional amines, like the carboxylic acid groups or amino groups, do not contain any other functional group capable of the reaction with amino groups or carboxylic acid groups. Preferably they or contain any other functional group. Examples of suitable difunctional amines are those which form salts with difunctional carboxylic acids. They may be linear aliphatics, such as C? _? 4 alkylene diamine, preferably C2_6-alkylene diamine, for example, hexylene diamine. They can also be cycloaliphatic. Examples are isophoronediamine, Laromine, branched aliphatic diamines are similarly usable, an example being Vestamin TMD (trimethylhexamethylenediamine, from Hüls, AG). in addition, diamines can also be aromatic-aliphatic, it being possible to use n-xylylenediamine, for example. The complete amines can each be substituted by C? _? 2 -alkyl preferably C? _? 2 -alkyl radicals in the carbon skeleton.

Diffunctional carboxylic acids are, for example, those that form salts with difunctional diamines. They may be linear, aliphatic, dicarboxylic acids, which are preferably C 2 -dicarboxylic acids. Examples are adipic acid, azelaic acid, sebacic acid, suberic acid. They can also be aromatic. Examples are isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, as well as dimerized fatty acids.

The basic difunctional building blocks are preferably used in amounts of 1 to 55, preferably 1 to 30, especially 1 to 15 μmol / g of polyamide. In a preferred embodiment, the level of the cyclic dimer in nylon-6 obtained according to the invention can also be reduced by extracting the polyamide first with an aqueous solution of caprolactam and lego with water and / or subjecting it to a gas phase extraction (described in EP-A-0 284 968, for example). The low molecular weight constituents obtained after the treatment, such as caprolactam, linear caprolactam oligomer and cyclic caprolactam oligomer, can be recycled in the first and / or second and / or third stages. The starting mixture and the synthesis mixture can be mixtures in all stages with chain regulators, such as aliphatic and aromatic and dicarboxylic carboxylic acids and catalysts, such as phosphorus compounds containing oxygen, in amounts within the range of 0.01 to 5% by weight, preferably within the range of 0.2 to 3% by weight, based on the amount of monomers forming polyamides and aminonitriles used. Suitable chain regulators include, for example, propionic acid, acetic acid, benzoic acid, terephthalic acid and triaceton diamine. Additives and fillers, such as pigments, dye and stabilizers are generally added to the synthesis mixture, prior to the formation of pellets, preferably in the second, third and fourth steps. Particular preference is given to using fillers and additives when the synthesis or mixture of polymers is not found fixed bed catalysts in the rest of the process. One or more modified impact rubbers may be present in the compositions as additives, in amounts of 0 to 40% by weight, preferably 1 to 305 by weight, based on the entire composition.

The following examples illustrate the invention. Example A flow tube of 4.5 m in general length and 10 cm in internal diameter, which is packed with titanium dioxide catalyst, and operated adiabatically at 80 bar, fed continuously from the bottom end, with a stream of input of 20 kg / h of ACN or 14.6 kg / h of water of extract consisting of 91% by weight of water, 8% by weight of caprolactam monomer and 1% by weight of caprolactam dimer. The temperature of the input current is 208 ° C. A continuous flow of 5.3 kg / h of water extract (composition similar to the extract water of the inlet stream) having a temperature of 85 ° C, was introduced at a height of the sector of 1 m. There is a more lateral charge of extract water at a reactor height of 2 m. In this case, the dosing regime is 2.1 kg / h coupled with the same composition and temperature for the extract water as for the first lateral dosing. A N6 prepolymer having a carboxyl end group concentration of 25.3% based on the concentration of amino end groups, was obtained at the end of the flow tube at a rate of 23 g / h, based on the total sum of all organic constituents.

Comparative Example 1 Comparative Example 1 was carried out in the same manner as Example 1, except that there is no lateral dosage of the extract water, that is, the inlet stream comprises just 20 kg / h of ACN and 22 kg / h of extract water consisting of 91% by weight of water, 8% by weight of the caprolactam monomer and 1% by weight of the caprolactam dimer. The temperature of the inlet current is 208 ° C. A N6 prepolymer having an end group concentration of 15.4% based on the concentration of the amino end groups, was obtained at the end of the flow tube at a rate of 23 kg / h, based on the total sum of all the organic constituents.

Comparative Example 2 Comparative Example 1 was carried out in the same manner as Example 1, except that completely ion-free water was used, instead of extract water. Therefore, the input stream comprises 22 kg / h of ACN and 1.3 g / h of water completely free of ions. This completely ion-free water is continuously supplied at a rate of 4.8 kg / h for the first lateral load and at a rate of 1.9 kg / h for the second lateral load. A N6 prepolymer having an end group concentration of 17.2% based on the concentration of the amino end groups, was obtained at the end of the flow tube at a rate of 23 kg / h, based on the total sum of all the organic constituents.

Comparative Example 3 Comparative Example 3 was carried out in the same manner as Example 1, except that completely ion-free water was used instead of extract water. There is no lateral dosage in the flow control. Therefore, the inlet stream comprises 22 kg / h of ACN and 20 kg / h of water completely free of ions. The inlet temperature is again 208 ° C. A N6 prepolymer having a carboxyl end group concentration of 14.5%, based on the concentration of amino end groups, was obtained at the end of the flow tube at a rate of 23 g / h, based on the total sum of all the organic constituents. This example illustrates that the process of the present invention, which is based on the use of water vapor, instead of water completely free of ions, and in its lateral dosage, provides polyamides and polyamide prepolymers having a higher content of groups of carboxyl end, than the processes of the prior art.

Claims (10)

1. CLAIMS 1. A continuous process to produce polyamides, their oligomers or their mixtures and, if appropriate, other reaction products, by means of the reaction of the amino-nitryls or dinitriles and the diamines or their mixtures and, if appropriate, together with other monomer monomers forming polyamides and / or oligomers, with an aqueous medium composed of aqueous monomers, extracts of oligomers, obtained from the production of the polyamide by extraction of the polymer with water, in a reactor, which has a vertical longitudinal axis and through which there is a flow substantially in the longitudinal direction, in which the water and / or the aqueous medium are introduced into the reactor in two or more different locations, along the vertical longitudinal axis, in which the aqueous medium is introduced into the reactor. one or more locations.
2. 2. A process, according to claim 1, in which the aqueous medium is introduced into the reactor in three or more different locations, along the vertical longitudinal axis.
3. 3. A process, according to claim 1 or 2, wherein the reactor is a flow tube, a TVA reactor, a multi-chamber reactor, operated concurrently or countercurrently, or a reactive or non-reactive distillation apparatus.
4. 4. A process, according to claim 3, wherein the reactor is a multi-chambered reactor or a flow tube, which is fed with aminonitriles or dinitriles, and diamines or mixtures thereof, if appropriate, together with other monomers that they form polyamides and / or oligomers and a first portion of the aqueous medium at one end and with other portions of the aqueous medium being added in their continuation and from which a reaction mixture, comprising a polyamide, its oligomers or its mixtures, is discharged at its other end.
5. 5. A process, according to any of claims 1 to 4, comprising the following steps: (1) reacting the aminonitriles or dinitriles and diamines or their mixtures, and, if appropriate, together with other monomers and / or oligomers forming polyamides, with the aqueous medium in the reactor at a temperature of 180 to 310 ° C, and a pressure of 1 to 10 x 105 Pa, to obtain a reaction mixture; (2) further reacting the reaction mixture at a temperature of 200 to 300 ° C, and a pressure which is lower than the pressure of step 1, in which the temperature and the pressure are chosen so that the first phase of gas and a first liquid phase, are obtained and the first gas phase is separated from the first liquid phase; and (3) mixing the first liquid phase with a gaseous or liquid phase, comprising water or an aqueous medium at a temperature of 200 to 300 ° C, and a pressure of 0.1 to 30 x 105 Pa, to obtain a mixture of products.
6. A process, according to claim 5, which, additionally, or in place of step (3) comprises the following step: (4) subsequently condensing the product mixture at a temperature of 300 to 280 ° C and a pressure of which is less than the pressure of step (3), if this step iii) is carried out, in which the temperature and the pressure are selected so that the second gas phase, which comprises water and ammonia, and a second one. Liquid phase, which comprises the polyamide, are obtained.
7. 7. A process, according to any of claims 1 to 6, which utilizes metal oxide catalysts, in the form of a fixed bed in the reactor or in step (1) or in step (3) or not only in the reactor or in stage 1, but also in stage (3)
8. 8. A process, according to claim 3 or claim 4, which uses a reactor having a vertically disposed longitudinal axis, where, in the reactor , the reaction product is removed from the bottom and the ammonia formed and any other low molecular weight compounds formed and the water is ACAN at the top, in which this reactor comprises at least two chambers, arranged one above the other, in the longitudinal direction, where the chambers are separated from each other by liquid-tight bottom plates; each chamber is connected by means of an overflow of liquid to the immediately underlying chamber, and a stream of liquid product is removed by means of the overflow of liquid from the chamber further to the bottom; the space of the gas, above the liquid surface, in each chamber, is connected to the chamber located immediately above, by one or more guide tubes, which are open or which each open inside the gas distributor, which have openings for the exit of the gas below the liquefied surface. And it is also provided with at least one guide plate, which is arranged vertically around each gas distributor, and where the upper end is below the surface of the gas. liquid and whose lower end is above the bottom plate liquid-tight chamber and in which the gas flows and one or more spaces in which the gas does not flow.
9. 9. A process, according to any of claims 1 to 8, wherein the aqueous medium has a solids content in the range of 2 to 30% by weight, and at least 50% by weight of the solids are lactams and lactams cyclic oligomers, having two to six ring members, which are derived from the aminonitrile used.
10. 10. A process, according to any of claims 1 to 9, wherein the aqueous medium is only introduced into the reactor in at least two different locations.