DE10313682A1 - Process for the production of polyamides - Google Patents

Abstract

Process for the preparation of polyamides, their oligomers or mixtures thereof, optionally with further reaction products, by reacting aminonitriles or dinitriles and diamines or a mixture comprising aminonitrile, dinitrile and diamine, and optionally further polyamide-forming monomers and / or oligomers with water in a reactor (1), characterized in that the reactor (1) DOLLAR A - a boiler cascade with DOLLAR A - at least two boilers (4) connected in series, DOLLAR A - each boiler (4) with a liquid overflow (6) each the immediately following boiler (4) is connected and a liquid product stream is withdrawn via the liquid overflow (6) of the last boiler (4), DOLLAR A - ammonia formed in the tank (4) above the liquid level in each boiler (4) and possibly further low-molecular compounds and water are removed (2).

Description

The present invention relates to a process for the preparation of polyamides, their oligomers or Mixtures thereof, optionally with further reaction products, by reacting aminonitriles or dinitriles and diamines or a mixture containing aminonitrile, dintiril and diamine and optionally further polyamide-forming monomers and / or oligomers with water.

Process for the preparation of polyamides, their Oligomers or mixtures thereof, optionally with further reaction products, by reacting aminonitriles or dinitriles and diamines or a mixture containing aminonitrile, dinitrile and diamine and optionally further polyamide-forming monomers and / or oligomers with water, especially such continuous processes known.

So WO 99/43732 describes the implementation of such in particular continuous processes in a reactive distillation device, heat being introduced into the lower part of the reactive distillation device becomes. The reaction products are the reactive distillation device in the sump, ammonia formed during the reaction, optionally further emerging low molecular weight compounds and water overhead taken. As possible Reactive distillation columns become tray columns, bubble columns or called dividing wall columns.

US 6,201,096 describes the implementation of such in particular continuous processes in a reactive distillation device, water vapor being introduced into the lower part of the reactive distillation device. The high molecular weight compounds obtained as a product are removed from the bottom of the reactive distillation device. Tray columns, such as those with perforated plate trays, are mentioned as possible reactive distillation columns. According to US 6,437,089 can in the in US 6,201,096 described methods, a mixture of 6-aminocapronitrile and caprolactam can be used as the starting monomer.

To equalize the temperature should according to US 6,201,096 and US 6,437,089 all or most of the trays of the column may be equipped with aids for independently controlling the temperature of the trays, such as heating elements.

According to WO 99/43732 is in the mentioned method the phase mixing due to the low liquid hold-up on the Soils limited. To improve the phase mixing, the liquid hold-up on the floors could be increased. this leads to however to a higher one gas-side pressure loss over the floors. This creates a greater temperature spread across the Floors with the consequence of very different reaction rates. This can cause decomposition of the product in the lower part of the reactor to lead, while in the upper part of the reactor the reaction due to too low temperature asleep.

In addition, the aim of the above-mentioned processes is to: Separation of the mixture of water and ammonia and the polymer Make products by rectification in the top and bottom product. This requires a temperature gradient over the height of the apparatus to the desired To achieve separation effect.

According to WO 00/24808 in the upper part of the described "multistage" reactor the temperature, and above the water content can be adjusted so that on the one hand a sufficient hydrolysis guaranteed is; on the other hand, however, degassing of low molecular weight reaction products is to be avoided become.

The polymerization in the “multistage” reactor mentioned brings the disadvantage with it that to restrict the degassing of low molecular weight organic compounds required in the upper part of the apparatus Temperatures an optimal hydrolysis of the nitrile groups and amide groups not allowed in a reasonable dwell time. In the lower part of the "multistage" reactor is included high temperatures such a low water content that the viscosity of the product melt is increased so that high gas-side flow losses arise. Furthermore the product is damaged at high temperatures.

Desirable is a further equalization of the temperature profile over the Reaction path and an improvement in the mixing of the reaction components, which lead to a reduction in the average reaction time and so the implementation a process for the production of polyamides on technically simple and economical way while avoiding the disadvantages mentioned enable.

Accordingly, a process for the preparation of polyamides, their oligomers or mixtures thereof, optionally with further reaction products, by reacting aminonitriles or dintriles and diamines or a mixture containing aminonitrile, dinitrile and diamine, and optionally further polyamide-forming monomers and / or oligomers with water in a reactor ( 1 ), characterized in that the reactor ( 1 )
represents a cascade with
at least two boilers connected in series ( 4 ) in which
each boiler ( 4 ) each with a liquid overflow ( 6 ) with the immediately following boiler ( 4 ) is connected and via the liquid overflow ( 6 ) of the last boiler ( 4 ) a liquid product stream is withdrawn,
over the gas space ( 7 ) above the liquid level in each boiler ( 4 ) ammonia formed and any further low molecular compounds and water which may be formed are drawn off ( 2 )
found.

The process can preferably be continuous carried out become.

The process can be carried out via reactor ( 1 ), preferably via the boiler ( 4 ) below that in the respective boiler ( 4 ) existing own pressure can be carried out. It is an advantage of the present method that devices known per se, such as pressure control valves or pumps, can be used in individual or all boilers ( 4 ) the pressure can be set independently of the temperature.

To carry out the method according to the invention, the boiler ( 4 ) known boilers are used, as described for example in: Ullmann's Encyclopedia of Industrial Chemistry, Vol. B4, 5th edition, VCH Verlagsgesellschaft mbH, Weinheim, 1992, pages 87-120 and pages 167-180. If desired, one or more boilers known per se, such as those mentioned in the description of the boilers, can have internals, such as baffles.

In a preferred embodiment, the guide plate can as a cylindrical jacket Insert tube be formed.

That is at least one baffle from the liquid level and advantageously spaced from the bottom of the boiler, preferably in such a way that in essentially no throttling of the liquid flow through the baffle is done. The distances the baffle or the baffles to the liquid surface and The bottom of the boiler should therefore preferably be fixed in such a way that itself the flow rate the liquid not or only slightly changed when deflected by the guide plate.

Regarding the total height of the baffle it basically no restrictions. This can depend in particular of the desired Dwell time per boiler, while taking sufficient time into account Mixing can be dimensioned accordingly.

At least one, like some or all, of the boiler ( 4 ) can be mixed mechanically. Suitable devices are described, for example, in: Ullmann's Encyclopedia of Industrial Chemistry, Vol. B2, 5th edition, VCH Verlagsgesellschaft mbH, Weinheim, 1988, sections 25 and 26.

In an advantageous embodiment, at least one, like some or all, of the boiler ( 4 ) are mixed by introducing a gas, a liquid or a gas / liquid mixture into the vessel in question above, preferably below, the liquid level in such a way that it causes the vessel to mix. For this purpose, conventional devices can be used in a manner known per se. This is preferably done via the gas space ( 7 ) of a boiler ( 4 ) withdrawn electricity ( 2 ) into the boiler ( 4 ) in which it was removed or another boiler, such as the first one ( 4 ) from reactor ( 1 ) or the extraction boiler ( 4 ) upstream boiler ( 4 ).

The initiation of a stream ( 2 ) in a cauldron ( 4 ) can also be done in such a way that there is no mixing of the respective boiler ( 4 ) causes. This is preferably done via the gas space ( 7 ) of a boiler ( 4 ) withdrawn electricity ( 2 ) into the boiler ( 4 ) in which it was removed or another boiler, such as the first one ( 4 ) from reactor ( 1 ) or the extraction boiler ( 4 ) upstream boiler ( 4 ).

The feed of one or more liquid, liquid / solid, gaseous / liquid or gaseous / liquid / solid educt streams can be fed into one or more boilers ( 4 ) in the front area of the reactor ( 1 ) as in the first cauldron ( 4 ), by directing this stream towards one or more boilers in the rear area of the reactor ( 1 ), like the last cauldron ( 4 ), and a gaseous stream - starting material and / or inert gas - from one or more boilers in the rear area of the reactor ( 1 ), like the last cauldron ( 4 ), to one or more kettles ( 4 ) in the front area of the reactor ( 1 ), like the first cauldron ( 4 ), i.e. with countercurrent flow of the liquid or liquid / solid and the gaseous flow.

In addition, one or more of the boilers in the middle or rear area of the reactor ( 1 ) supply one or more liquid, liquid / solid, gaseous / liquid or gaseous / liquid / solid streams - starting material, intermediate product, product or inert gas or mixtures of several or all such substances. Advantageously, such a feed into the middle or rear area of the reactor ( 1 ) Compounds which do not have any nitrile groups, preferably diamines, in particular in the preparation of polyamides from dinitriles and diamines or a mixture comprising aminonitrile, dinitrile and diamine.

The reactor ( 1 ) is made up of several boilers.

The number of boilers can be advantageous at the most 10, preferably at most 7, in particular at most 5.

The number of boilers can be advantageous be at least 2, in particular at least 3.

The geometry of the boiler ( 4 ) is often cylindrical, but other geometries are also possible.

From the cauldrons ( 4 ) a liquid stream ( 8th ) via a liquid overflow ( 6 ) can be removed. For the purposes of the present invention, a liquid overflow means a removal above or below the liquid level of the boiler in question.

According to the invention, the liquid overflow ( 6 ) of the last boiler ( 4 ) a liquid product stream is withdrawn. This boiler can do this be divided into at least two chambers. These at least two chambers can be arranged side by side or one above the other or one above the other and side by side.

In a preferred embodiment, a part of the last boiler of the reactor ( 1 ) Take the product stream taken in liquid form to a heat exchanger, use this heat exchanger to partially or completely convert the water contained in the product stream to the gaseous state and the mixture leaving the heat exchanger to the reactor ( 1 ) respectively. The reactor ( 1 ) polyamides, oligomers or their mixtures obtained according to the process as a liquid product, in particular the last vessel of the reactor ( 1 ), remove.

In another preferred embodiment, part or all of the last boiler of the reactor ( 1 ) supply the product stream taken in liquid form to a heat exchanger, with the help of this heat exchanger convert the water contained in the product stream partially or completely into the gaseous state, the gaseous water to the reactor ( 1 ) and receive the liquid product leaving the heat exchanger as a valuable product.

In a further preferred embodiment, at least one of the (in the last vessel of the reactor ( 1 ) supply the product in liquid form to a heat exchanger, use this heat exchanger to partially or completely convert the water contained in the product stream to the gaseous state and the mixture leaving the heat exchanger to the reactor ( 1 ) respectively. The reactor ( 1 ) polyamides, oligomers or mixtures thereof obtained according to the process as a liquid product, in particular in the last vessel of the reactor ( 1 ), remove.

In a further preferred embodiment, at least one of the (in the last vessel of the reactor ( 1 ) supply the product in liquid form to a heat exchanger, use this heat exchanger to convert some or all of the water contained in the product stream to the gaseous state, the gaseous water to the reactor ( 1 ) and receive the liquid product leaving the heat exchanger as a valuable product.

The heat exchanger used in these preferred embodiments can be in the reactor ( 1 ) or outside the reactor ( 1 ) or partly inside, partly outside the reactor ( 1 ) are located. Furthermore, the heat exchanger can comprise one device or a plurality of separate devices.

In a preferred embodiment can in one or more, preferably in all vessels of the reactor a solid catalyst can be introduced, in particular as a solid bed or in the form of ordered packings coated with catalyst, for example monoliths.

More preferably, one or more than one, preferably in all boilers, an ion exchange resin is introduced his.

The reactor therefore has the advantage that he for gas / liquid or gas / liquid / solid reactions a very good phase mixing and thus a high degree of turnover as well after thorough mixing and reaction, an extensive separation of gaseous and more fluid Phase guaranteed.

In one possible mode of operation, for example, aminonitrile or dinitrile and diamine or a mixture comprising aminonitrile, dinitrile and diamine, and water are fed into one or more of the front boilers, such as the first boiler, from reactor ( 1 ) fed. The low-boiling ammonia and water formed during the reaction can then be passed in the top of one or more boilers of the reactor ( 1 ) are enriched and discharged, while the product of value from oligomers and polyamide as a liquid product stream (<rn> 8 </rn>) in one or more of the last kettles, such as the last kettle, from reactor ( 1 ), arises.

In a further possible procedure, for example, compounds containing nitrile groups, in particular aminonitrile or dinitrile or a mixture comprising aminonitrile and dinitrile, and water are fed into one or more of the front boilers, such as the first boiler, from reactor ( 1 ) fed and nitrile group-free compounds, in particular diamines, into one or more of the middle or rear boilers of the reactor ( 1 ) fed. The low-boiling ammonia and water formed during the reaction can then be passed in the top of one or more boilers of the reactor ( 1 ) are enriched and discharged, while the product of value from oligomers and polyamide as a liquid product stream (<rn> 8 </rn>) in one or more of the last kettles, such as the last kettle, from reactor ( 1 ), arises.

Through this integrated process control with continuous Product separation becomes an ideal, parallel heat and material exchange with high exergetic efficiency, which is also achieved through a rapid heating of the starting materials and their uniform mixing characterized is.

For the present reaction system, the countercurrent flow of prepolymer and the reaction product ammonia, combined with the continuous ammonia separation via the boiler of the reactor ( 1 ), very low ammonia contents in the parts of the apparatus, which largely contain aminonitrile converted into valuable products.

It was found that by the inventive method higher revenues to the product of value than without continuous ammonia removal via the Boilers can be reached, which shortens the response time and the formation of undesirable Minor components is reduced.

Any catalysts which accelerate the hydrolysis and / or condensation can be used to support the reaction. Preferred catalysts are those which can either be introduced in solid form and consequently easily separated from the product of value or else as a coating on reactor parts, such as a wall coating of one or more or all of the vessels ( 4 ).

The invention relates to a preferably continuous, process for hydrolytic conversion aminonitriles or dinitriles and diamines or a mixture, containing aminonitrile, dinitrile and diamine, to polyamide and / or Its pre-products and any other polyamide-forming products Mono- and oligomers to polyamide.

Aminonitrile or dinitrile and diamine or a mixture containing aminonitrile, dinitrile and diamine is preferably introduced into one or more of the front vessels, in particular the first vessel, from reactor ( 1 ) dosed. Aminonitrile or dinitrile and diamine or a mixture containing aminonitrile, dinitrile and diamine are then moved backwards through the apparatus and thereby react continuously with water. The resulting ammonia rises continuously due to its volatility in the respective boiler and can be removed overhead.

In a further preferred embodiment, for example, compounds containing nitrile groups, in particular aminonitrile or dinitrile or a mixture comprising aminonitrile and dinitrile, can be introduced into one or more of the front vessels, in particular the first vessel, of reactor ( 1 ) dose and nitrile group-free compounds, especially diamines, into one or more of the middle or rear vessels of the reactor ( 1 ) feed. The nitrile group-containing compounds are then moved backward in the apparatus. Due to its volatility, the ammonia formed rises continuously in the respective boiler and can be removed overhead.

If desired, the Educts preheated become.

It was found that that too Introducing catalyst pellets into the apparatus to even out the Gas and liquid flow in leads the cauldrons.

The ammonia reduction in the melt can by stripping with inert gases (such as nitrogen) or water vapor additionally supports become.

In principle, all aminonitriles, this means Compounds that have both at least one amino and at least one have a nitrile group, are used. Among them are ω-aminonitriles preferred, with the latter in particular ω-aminoalkyl nitriles with 4 to 12 carbon atoms, more preferably 4 to 9 carbon atoms in the alkylene radical, or an aminoalkylaryl nitrile with 8 to 13 carbon atoms can be used, preference is given to those between the aromatic Unit and the amino and nitrile group an alkyl spacer with at least have a carbon atom. Among the aminoalkylaryl nitriles are in particular preferred those that the amino and Have nitrile group in the 1,4 position to each other.

Linear ω-aminoalkyl nitriles are more preferably used as the ω-aminoalkyl nitrile, the alkylene radical (-CH ₂ -) preferably containing 4 to 12 carbon atoms, more preferably 4 to 9 carbon atoms, such as 6-amino-1-cyanopentane (6-aminocapronitrile), 7-amino-1-cyanohexane, 8-amino-1-cyanoheptane, 9-amino-1-cyanooctane, 10-amino-1-cyanononane, particularly preferably 6-aminocapronitrile.

6-aminocapronitrile is usually obtained by hydrogenating adiponitrile by known processes, for example described in DE-A 836, 938 . DE-A 848, 654 or US 5,151,543 ,

Of course, mixtures of several can Aminonitriles or mixtures of an aminonitrile with other comonomers, for example caprolactam or the mixture defined in more detail below become.

In principle, all dinitriles, this means Compounds which have at least two nitrile groups are used become. Among them are α, ω-dinitriles preferred, with the latter in particular α, ω-dinitriles having 4 to 12 carbon atoms, more preferably 4 to 9 carbon atoms in the alkylene radical, or a cyanoalkylaryl nitrile with 7 to 12 carbon atoms are used, where there are preferred those between the aromatic unit and the two nitrile groups an alkyl spacer have at least one carbon atom. Among the cyanoalkylaryl nitriles those which have the two nitrile groups are particularly preferred have in the 1,4 position to each other.

The α, ω-alkylenedinitrile used is more preferably linear α, ω-alkylenedinitrile, the alkylene radical (-CH ₂ -) preferably containing 3 to 11 carbon atoms, more preferably 3 to 8 carbon atoms, such as 1.4 -Dicyanbutane (adipodinitrile), 1,5-dicyanopentane, 1,6-dicyanhexane, 1,7-dicyanheptane, 1,8-dicyanooctane, 1,9-dicyannonane, 1,10-dicyandecane, particularly preferably adipodinitrile.

In principle, all diamines, that is called Compounds that have at least two amino group used become. Among them are α, ω-diamines preferred, with the latter in particular α, ω-diamines having 4 to 14 C atoms, further preferably 4 to 10 carbon atoms in the alkylene radical, or an aminoalkylarylamine can be used with 7 to 12 carbon atoms, preference being given to those there be that between the aromatic unit and the two nitrile group have an alkyl spacer with at least one carbon atom. Under the aminoalkylarylamines are particularly preferred those which have two amino groups in the 1,4-position to each other.

As α, ω-alkylenediamine one continues to be preferably linear α, ω-alkylenediamines, the alkylene radical (-CH ₂ -) preferably containing 3 to 12 C atoms, more preferably 3 to 8 C atoms, such as 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane (hexamethylenediamine), 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, particularly preferably hexamethylenediamine.

If you want, you can also Diamines, dinitriles and aminonitriles, which are branched alkylene or derived from arylene or alkylarylenes, such as 2-methylglutarodinitrile or 2-methyl-1,5-diaminopentane.

Is used in the production according to the invention of polyamides containing dinitriles and diamines or a mixture Dinitrile, diamine and aminonitrile, so has a molar ratio of Nitrile groups present in the feedstocks capable of forming polyamides to the amino groups present in the feedstocks capable of forming polyamides in the range of 0.9 to 1.1, preferably 0.95 to 1.05, in particular 0.99 to 1.01, particularly preferably of 1, has proven to be advantageous.

Other polyamide-forming monomers which can be used are, for example, dicarboxylic acids, such as alkanedicarboxylic acids having 6 to 12 carbon atoms, in particular 6 to 10 carbon atoms, such as adipic acid, pimelic acid, suberic acid, azelaic acid or sebacic acid and terephthalic acid, isophthalic acid and cyclohexanedicarboxylic acid, or amino acids, such as alkane-amino acids with 5 to 12 amino acids Use 12 carbon atoms, especially α, ω-C ₅ -C ₁₂ amino acids.

As α, ω-C ₅ -C ₁₂ amino acid there can be 5-aminopentanoic acid, 6-aminohexanoic acid, 7-aminoheptanoic acid, 8-aminooctanoic acid, 9-aminononanoic acid, 10-aminodecanoic acid, 11-aminoundecanoic acid and 12-aminododecanoic acid, preferably 6-aminohexanoic acid , or their internal amides, so-called lactams, in particular caprolactam.

Mixtures with aminocarboxylic acid compounds of the general formula I are also suitable as starting materials in the process according to the invention R ² R ³ N- (CH ₂ ) _m -C (O) R ¹ (I)

In the R ¹ for -OH, -OC _1-12 alkyl or -NR ² R ³ independently of one another hydrogen, C _{1 12} alkyl and C ₅ _ ₈ cycloalkyl, and m for 3, 4, 5, 6, 7 , 8, 9, 10, 11 or 12.

Particularly preferred aminocarboxylic acid compounds are those in which R ¹ OH, -OC _1-4 alkyl such as -O-methyl, -O-ethyl, -On-propyl, -Oi-propyl, -On-butyl, -O-sec.- Butyl, -O-ter.-butyl and -NR ² R ³ as -NH ₂ , -NHMe, -NHEt, -NMe ₂ and -NEt ₂ mean, and m is 5.

6-Aminocaproic acid, 6-aminocaproic acid methyl ester, 6-aminocaproic acid ethyl ester are very particularly preferred, 6-Aminocapronsäuremethylamid, 6-aminocaproic acid dimethylamide, 6-aminocaproic acid ethyl amide, 6-Aminocapronsäurediethylamid and 6-aminocaproic acid amide.

The starting compounds are commercially available or, for example, according to EP-A 0 234 295 and Ind. Eng. Chem. Process Des. Dev. 17 (1978) 9-16.

Any mixes can also be used of the compounds mentioned, aminocarboxylic acid compounds, lactams, diamines and diacids or their salts are used.

Are preferred as polyamide-forming monomers Containing amino nitriles or dinitriles and diamines or mixtures Aminonitrile, dinitrile and diamine, together with water, especially preferably in a molar ratio used in the range of 1: 1 to 1 20, based on the overall process. Especially aminocapronitrile is preferred, with a molar ACN: water ratio in Overall process of 1: 1 to 1:10. A mixture is furthermore particularly preferred from adiponitrile and hexamethylenediamine, at a molar ratio of Sum of adiponitrile and hexamethylenediamine: water in the overall process of 1 : 1 to 1: 10. Furthermore, a mixture of is particularly preferred Adiponitrile, hexamethylenediamine and aminocapronitrile, in one molar ratio the sum of adiponitrile, hexamethylenediamine and aminocapronitrile : Water in the overall process of 1: 1 to 1:10.

Mixtures of polyamide-forming can also be used Monomers and oligomers are used.

Are preferred as polyamide-forming monomers in addition to aminocapronitrile, if desired, caprolactam and / or hexamethylene diammonium adipate ("AH salt") is used.

Are preferred as polyamide-forming monomers in addition to adiponitrile and hexamethylenediamine, if desired, caprolactam and / or Hexamethylene diammonium adipate ("AH salt") is used.

In addition to acid catalysts such as phosphoric acid, etc., which are often described in the literature, particularly heterogeneous catalysts are suitable as catalysts. Bronsted acid catalysts are preferably used, selected from a beta-zeolite, layered silicate or a fixed bed catalyst which essentially consists of TiO ₂ with 70 to 100% anatase and 0 to 30% rutile, in which up to 40% of the TiO _{2 can be} replaced by tungsten oxide.

For example, corresponding TiO ₂ modifications, such as FINNTi S150 (Kemira Pigments Oy, Finland), can be used.

The heterogeneous catalysts can be introduced into the apparatus, for example, as a suspension, sintered onto packing or as an optionally coated catalyst packing or bed or internals. They can also be present as wall coverings or fillings in the apparatus, so that the reaction mixture can be separated off easily he follows.

The water concentration in the majority of the reactor boilers ( 1 ), which lie behind the feed point of the aminonitriles or dinitriles and diamines or the mixture containing dinitrile, diamine and aminonitrile, reaches very high concentrations (molar ratio heavy boiler: water about 1: 4 to 1:50, preferably 1:10 to 1: 40) so that even if the components are metered stoichiometrically into the apparatus, water can be present in the apparatus itself in excess of stoichiometry, which can shift the reaction equilibrium to the product side and increase the rate of equilibrium.

The temperature for the reaction should be in the boilers of the reactor ( 1 ), that is, behind the educt feed, depending on the water concentration, the residence time, the use of catalysts and the feed composition or concentration, are about 180 ° C to 300 ° C, preferably 200 to 280 ° C and particularly preferably 220 to 270 ° C. The temperatures in the boilers ( 4 ) from reactor ( 1 ) should advantageously be within a narrow range, preferably within 15 ° C, preferably within 10 ° C, in particular within 8 ° C.

The two-phase driving style allowed a lowering of the pressure level required for the reaction, since gaseous components not how with a single-phase driving style - must be kept in the liquid phase. It only the intrinsic pressure of the system preferably sets in dependence from the temperature. This is about 10 to 60 bar. The Equipment expenditure is due to the integration of process engineering Operations such as thermal and mass transfer in one and the same apparatus is reduced.

With increasing number of boilers ( 4 ) the flow profile of the liquid phase in the reactor approaches an ideal plug flow, which leads to a very even residence time spectrum in the apparatus.

The product of value obtained has, depending on the residence time in the reactor ( 1 ) the process temperatures, the pressure conditions and other process parameters, a different molecular weight which can be set within wide limits and different properties. If desired, the product can be further processed after the reaction to set desired product properties.

The product can be used to advantage Increase of Molecular weight to be subjected to polycondensation. A Such polycondensation can in itself be used for the production and after-treatment processes known from polyamides, such as in a fully continuous process Flow pipe ("VK pipe") are carried out.

You can the resulting polyamide z. B. according to known methods, such as in the DE-A 43 21 683 (P. 3, line 54 to p. 4, line 3) are described in detail.

In a preferred embodiment, the content of cyclic dimer in the polyamide-6 obtained according to the invention can be further reduced by first extracting the polyamide with an aqueous solution of caprolactam and then with water and / or gas phase extraction (described for example in US Pat EP-A 0 284 968 ) subjects. The low-molecular constituents obtained in this aftertreatment, such as caprolactam and linear and cyclic oligomers, can be returned to the process according to the invention or to the upstream reactor.

The one obtained after the extraction In general, polyamide can then be prepared in a manner known per se dry.

This can be advantageous when using Inert gases, such as nitrogen or superheated Water vapor, for example as a heat transfer medium take place in countercurrent. The desired viscosity can be determined in 1% by weight solution in 96% sulfuric acid at 25 ° C, by tempering at elevated Temperature, preferably in the range of 150 ° C to 190 ° C, are set.

The method according to the invention stands out through continuous reaction management, reduced energy and raw material costs and, because standard equipment can be used a comparatively low expenditure on equipment.

The method can therefore be compared to known ones Process cheaper work and a higher quality Deliver product.

The invention is illustrated below of examples closer explains:

example 1

In a reactor ( 1 ) According to the characterizing claims with 5 stages, a continuous stream of caprolactam (9.7% by weight) and water (4.6% by weight), the rest nylon 6 prepolymer as in Example 1 of US 6,437,089 inserted into the first vessel of the reactor added.

This input stream has a throughput of 20.4 kg / h and a temperature of 250 ° C.

In the lower area of the last boiler 14.5 kg / h of water vapor are fed in at a temperature of 250 ° C.

The pressure in the reactor is regulated and amounts to 18.25 bar overpressure. The liquid phase of a boiler flows to the next boiler, the gas phase from one boiler is in the liquid phase of the upstream boiler.

The temperature curve in the reactor develops adiabatically, with the mathematical model following Temperature curve calculated: first boiler 257.5 ° C, second boiler 257.3 ° C, third Boiler 257.0 ° C, fourth boiler 256.3 ° C and fifth Boiler 254 ° C.

The total residence time in the reactor is 1.6 H.

The calculation results provide a gas flow from the top of the first boiler of the reactor with a throughput of 14.5 kg / h. The gas stream contains 1.8% by weight of NH ₃ , 0.0015% by weight of ACN, 1.2% by weight of caprolactam and approximately 97% by weight of water.

The mathematical model yields one Nylon 6 product flow of 20.4 kg / h with 6.7 wt .-% water. The end groups result as follows: 245 mmol / kg amino, 236 mmol / kg carboxyl, 3 mmol / kg amide and 6 mmol / kg nitrile end groups. In the product is the average number of monomer units per molecule 23.9.

This creates a valuable product of comparable quality as in Example 1 of US 6,437,089 obtained in a technically simpler and more economical way.

Example 2

From a mixture of 6-aminocapronitrile and Water is at a pressure of 80 bar and a temperature of 250 ° C in a prepolymer in a tubular reactor manufactured. The residence time is selected so that the prepolymer 975 mmol / kg amino, 547 mmol / kg carboxyl, 423 mmol / kg amide and 5 mmol / kg nitrile end groups included.

In a reactor ( 1 ) according to the characteristic claims with 5 kettles, a continuous stream of caprolactam (12.3% by weight), water (22.4% by weight) and NH ₃ (0.53% by weight), the rest of the above-described nylon 6 prepolymer in the first Kettle of the reactor added.

This input stream has a throughput of 37.7 kg / h and a temperature of 235 ° C.

The pressure in the reactor is regulated and amounts to 28 bar overpressure.

The liquid phase of a boiler flows to the next one Boiler, the gas phase from a boiler turns into the liquid phase of the upstream boiler.

The temperature in the last boiler is regulated and amounts 275 ° C.

The temperature curve in the reactor develops adiabatically, with the mathematical model following Temperature curve calculated: first boiler 238.2 ° C, second boiler 239.9 ° C, third Boiler 240.7 ° C and fourth boiler 241.5 ° C.

The total residence time in the reactor is 1.53 H.

The calculation results provide a gas flow from the top of the reactor with a throughput of 6.3 kg / h. The gas stream contains 7.5% by weight of NH ₃ , 0.000086% by weight of ACN, 0.077% by weight of caprolactam and approx. 92.4% by weight of water.

The mathematical model yields one Nylon 6 product flow of 31.4 kg / h with 8.9% water by weight. The end groups result as follows: 317.8 mmol / kg amino, 311.7 mmol / kg carboxyl, 5.6 mmol / kg amide and 0.5 mmol / kg nitrile end groups. In the product is the average number of monomer units per molecule 23.3.

Claims (33)

Process for the preparation of polyamides, their oligomers or mixtures thereof, optionally with further reaction products, by reacting aminonitriles or dintriles and diamines or a mixture comprising aminonitrile, dinitrile and diamine, and optionally further polyamide-forming monomers and / or oligomers with water in a reactor ( 1 ), characterized in that the reactor ( 1 ) - represents a boiler cascade with - at least two boilers connected in series ( 4 ) where - each boiler ( 4 ) each with a liquid overflow ( 6 ) with the immediately following boiler ( 4 ) is connected and via the liquid overflow ( 6 ) of the last boiler ( 4 ) a liquid product stream is withdrawn, - via the gas space ( 7 ) above the liquid level in each boiler ( 4 ) ammonia formed and any further low molecular compounds and water which may be formed are drawn off ( 2 ). The method of claim 1, wherein the in a boiler ( 4 ) over the gas space ( 7 ) withdrawn electricity ( 2 ) in this cauldron ( 4 ) upstream boiler is returned. The method of claim 1 or 2, wherein the in a boiler ( 4 ) over the gas space ( 7 ) withdrawn electricity ( 2 ) is returned to another boiler in the stirred tank cascade. A method according to claim 2 or 3, wherein the withdrawn stream ( 2 ) is returned to the respective boiler below the liquid level. The method of claim 4, wherein the recycle stream ( 2 ) causes the liquid to mix in the respective boiler. Method according to one of claims 1 to 5, wherein the withdrawn current ( 2 ) is returned to the respective boiler above the liquid level. Method according to one of claims 1 to 6, wherein at least one of the boilers ( 4 ) the boiler cascade is mixed mechanically. Method according to one of claims 1 to 7, wherein the number the boiler in the boiler cascade is 2 to 10. Method according to one of claims 1 to 8, wherein in one, more or all of the boilers ( 4 ) of the reactor ( 1 ) a solid catalyst is introduced, in particular as a solid bed or in the form of an ordered packing coated with catalyst, for example a monolith, or as a coating of reactor parts. Method according to one of claims 1 to 9, characterized in that in one or more, preferably in all boilers ( 4 ) an ion exchange resin is introduced. Method according to one of claims 1 to 10, wherein the method in the presence of Bronsted acids Catalysts carried out becomes. The method of claim 11, wherein Bronsted acid Heterogeneous catalysts are used. Method according to one of claims 1 to 12, wherein the reaction carried out under autogenous pressure becomes. Method according to one of claims 1 to 12, wherein in one or more or all of the boilers ( 4 ) of the reactor ( 1 ) the pressure is set regardless of the temperature. Method according to one of claims 1 to 14, wherein as polyamide-forming Monomeric aminonitriles and water in a molar ratio on the overall process, be used in a range from 1: 1 to 1:20. A method according to any one of claims 1 to 15, wherein water of steam is used. Method according to one of claims 1 to 16, wherein in the Reaction in addition is stripped with an inert gas. Process according to one of claims 1 to 17, wherein the reactor ( 1 ) upstream of another reactor. The method of claim 18, wherein the further upstream Single-phase reactor is operated. The method of claim 18, wherein the further upstream Reactor is operated in two phases. Method according to one of claims 18 to 20, wherein between the further upstream reactor and reactor ( 1 ) there is a device for separating reaction products via the gas phase. Process according to one of claims 1 to 21, wherein the reactor ( 1 ) downstream of another reactor. The method of claim 22, wherein the further downstream Single-phase reactor is operated. The method of claim 22, wherein the further downstream Reactor is operated in two phases. Method according to one of claims 1 to 24, wherein at least one of the boilers ( 4 ) has a heat exchanger. Method according to one of claims 1 to 25, wherein in at least one of the boilers ( 4 ) Feeds water in liquid or gaseous form. Method according to one of claims 1 to 26, wherein the last boiler ( 4 ) from reactor ( 1 ) is divided into at least two chambers. The method of claim 27, wherein the chambers are side by side are arranged. The method of claim 27 or 28, wherein the chambers are one above the other are arranged. Method according to one of claims 1 to 29, wherein a part of the last boiler ( 4 ) from reactor ( 1 ) takes the product stream taken in liquid form to a heat exchanger, with the aid of this heat exchanger the water contained in the product stream is partially or completely converted into the gaseous state and the mixture leaving the heat exchanger is passed to the reactor ( 1 ) feeds. Method according to one of claims 1 to 29, wherein part or all of the last boiler ( 4 ) from reactor ( 1 ) takes the product stream taken in liquid form to a heat exchanger, with the help of this heat exchanger the water contained in the product stream is partially or completely converted into the gaseous state, the gaseous water to the reactor ( 1 ) and receives the liquid product leaving the heat exchanger as a valuable product. Method according to one of claims 27 to 29, wherein at least one of the in the last boiler ( 4 ) from reactor ( 1 ) located product chambers in liquid form to a heat exchanger, with the help of this heat exchanger the water contained in the product stream is partially or completely converted into the gaseous state and the mixture leaving the heat exchanger to the reactor ( 1 ) feeds. Method according to one of claims 27 to 29, wherein at least one of the in the last boiler ( 4 ) from reactor ( 1 ) located product chambers in liquid form feeds a heat exchanger, with the help of this heat exchanger the water contained in the product stream is partially or completely converted into the gaseous state, the gaseous water to the reactor ( 1 ) and receives the liquid product leaving the heat exchanger as a valuable product.