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MXPA01003484A - Accelerator for the production of polyamides from aminonitriles - Google Patents

Accelerator for the production of polyamides from aminonitriles

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Publication number
MXPA01003484A
MXPA01003484A MXPA/A/2001/003484A MXPA01003484A MXPA01003484A MX PA01003484 A MXPA01003484 A MX PA01003484A MX PA01003484 A MXPA01003484 A MX PA01003484A MX PA01003484 A MXPA01003484 A MX PA01003484A
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Mexico
Prior art keywords
weight
phase
pressure
liquid phase
mixture
Prior art date
Application number
MXPA/A/2001/003484A
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Spanish (es)
Inventor
Ralf Mohrschladt
Volker Hildebrandt
Original Assignee
Basf Ag
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Publication of MXPA01003484A publication Critical patent/MXPA01003484A/en

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Abstract

The invention relates to the utilization of lactams, aminocarboxylic acids or the mixtures thereof as accelerator or co-catalyst in the production of polyamides from aminonitriles and water and to a corresponding production method.

Description

ACCELERATING TO PRODUCE POLYAMIDES FROM INONITRILOS The present invention relates to accelerators and processes for producing polyamides from aminonitriles and water, in particular at elevated temperature and high pressure. US 4,629,776 describes a catalytic process for producing polyamides from β-aminonitriles such as α-aminocapronitrile (ACN). The ACN is reacted with water in the presence of a catalytic amount of an oxidized sulfur compound as a catalyst. Sulfuric acid is an example of the catalyst that is used. US 4,568,736 describes a similar catalytic process for producing polyamides. The catalyst used in this case is a phosphorus compound containing oxygen, phosphoric acid or a phosphonic acid. The complete elimination of the catalyst is practically not possible in any of these processes. The presence of catalyst in the polymer can prevent the accumulation of high molecular weight polymers and compromise subsequent processing operations, for example spinning. In addition, the level of volatiles in the polymers obtained is high, so that it is difficult to process the polyamides.
EP-A-O 479 306 describes the production of polyamides from β-aminonitriles. The α -aminonitriles are reacted with water in the presence of a phosphorus compound containing oxygen as a catalyst. Once a reaction temperature has been obtained from 200 to 260 ° C, the ammonia and water are continuously removed by decompression and at the same time water is added continuously, the pressure being selected within the range from 14 to 24 x 105 Pa ( 14-24 barias). DE-A-43 39 648 relates to a process for producing caprolactam by reacting aminocarbonitriles with water in liquid phase using heterogeneous catalysts. Suitable heterogeneous catalysts include acidic, basic or amphoteric oxides of the elements of major groups 2, 3 and 4 of the Periodic Table. For example, it is possible to use titanium dioxide. The catalyst is used in the form of extrudates, for example. The existing processes provide inadequate space-time yields in some cases and an accumulation of molecular weight that could be improved. In addition, the product is not always obtained in the necessary purity. DE-A-197 09 390 and DE-A-198 04 023, both published on the priority date of the present invention, describe the use of heterogeneous metal oxide catalysts in the reaction of aminonitriles with water to form polyamide. The advantage is that the fixed-bed catalyst that is used can be completely removed from the reaction mixture or the final product and the properties of the product are not adversely affected. However, the use of the fixed-bed catalyst is subject to limitations if pigmented reaction mixtures are used, since the catalyst solids can be covered and therefore lose their catalytic effect. An object of the present invention is to provide an accelerant to produce polyamides from aminonitriles and water and an improved process that leads to products that are not deteriorated by the accelerant. More specifically, the properties of the product and the processing and purity of the final product should not be reduced. We have found that this object is achieved according to the invention by using lactams, aminocarboxylic acids or their mixtures as accelerators or cocatalysts in the production of polyamides from aminonitriles and water. The lactams, aminocarboxylic acids and mixtures thereof are preferably used in an amount from 0.1 to 20% by weight, based on the amount of aminonitrile. These can be used in conjunction with metal oxide fixed bed catalysts as described below.
We have found that this objective is also obtained according to the invention by a process for producing a polyamide by reacting at least one aminonitrile with water, which comprises the following steps: (1) the reaction of at least one aminonitrile with water at a temperature of 90 to 400 ° C and a pressure of 0.1 to 35 x 106 Pa, the reaction of which may be carried out in the presence of a Bronsted acid catalyst selected from a beta-catalyst. zeolite, a lamellar silicate catalyst or a titanium dioxide catalyst consisting of from 70 to 100% by weight of anatase and from 0 to 30% by weight of rutile and in which up to 40% by weight of titanium dioxide can be replaced by tungsten oxide, to obtain a reaction mixture, (2) further the reaction of the reaction mixture at a temperature of 150 to 400 ° C and a pressure that is lower than the pressure in step 1, which reaction can be carried out in the presence of a Brdnsted acid catalyst selected from a catalyst beta-zeolite, a lamellar silicate catalyst or a titanium dioxide catalyst consisting of from 70 to 100% by weight of anatase and from 0 to 30% by weight of rutile, and in which up to 40% by weight of titanium dioxide it can be replaced by tungsten oxide, the temperature and pressure being selected to obtain a first gas phase and a first liquid phase or a first solid phase or a mixture of the first solid phase and the first liquid phase, and the first gas phase is separates from the first liquid phase or the first solid phase or from the mixture of the first liquid phase and the first solid phase, and (3) mixing the first liquid phase or the first solid phase of the mixture of the first liquid phase and the first solid phase with a gaseous or liquid phase containing water at a temperature from 150 to 370 ° C and a pressure from 0.1 to 30 x 106 Pa, optionally in the presence of the above catalyst, to obtain a mixture of products, wherein the reaction is carried out in at least one of steps (1) and (2) in the presence of lactams, aminocarboxylic acids or mixtures of these in an amount from 0.1 to 20% by weight, based on the amount of aminonitrile used.
Preferably, the above process also comprises the following step: (4) the subsequent condensation of the product mixture at a temperature of 200 to 350 ° C and a pressure that is lower than the pressure of step 3, the temperature and pressure being selected to obtain a second gaseous phase containing water and ammonia and a second liquid phase or second solid phase or a mixture of the second liquid phase and the second solid phase, each of which contains the polyamide.
The present invention also provides a continuous process for producing a polyamide by reacting at least one aminonitrile with water, which comprises the following steps: (1) react at least one aminonitrile with water at a temperature of 90 to 400 ° C and a pressure of 0.1 to 35 x 106 Pa, the reaction of which may be carried out in the presence of a "Brónsted acid catalyst selected from a beta catalyst; zeolite, a lamellar silicate catalyst or a titanium dioxide catalyst consisting of from 70 to 100% by weight of anatase and from 0 to 30% by weight of rutile and in which up to 40% by weight of titanium dioxide can be replaced by tungsten oxide, to obtain a reaction mixture, (2) further to react the reaction mixture at a temperature from 150 to 400 ° C and a pressure that is lower than the pressure in step 1, which reaction can be carried out in the presence of a Brónsted acid catalyst selected from a beta-zeolite catalyst, a lamellar silicate catalyst or a titanium dioxide catalyst consisting of from 70 to 100% by weight of anatase and from 0 to 30% by weight of rutile and in which up to 40% by weight of the titanium dioxide can be replaced by tungsten oxide, the temperature and pressure being selected to obtain a first gas phase and a first liquid phase or a first solid phase or a mixture of the first solid phase and the first liquid phase, and the first gas phase is separated from the first liquid phase or the first solid phase or from the mixture of the first liquid phase and the first solid phase, and the subsequent condensation of the first liquid phase or the first solid phase or the mixture of the first liquid phase and the first solid phase at a temperature of 200 to 350 ° C and a pressure that is lower than the pressure of step 3, the temperature and pressure being selected to obtain a second gaseous phase containing water and ammonia, and a second liquid phase or second solid phase or a mixture of the second liquid phase and the second solid phase, each of which contains the polyamide, wherein the reaction is carried out in at least one of steps (1) or (2) in the presence of lactams, aminocarboxylic acids or mixtures thereof in an amount from 0.1 to 20% by weight, based on the amount of the aminonitrile used.
The principle of the process of the invention is described in DE-A-197 09 390, not published on the priority date of the present invention. The aminonitrile in the mixture can be, in principle, any aminonitrile, that is, any compound having at least one amino group and at least one nitrile group. The? -aminonitriles are preferred, especially? -aminoalkyl nitriles having from 4 to 12 carbon atoms, more preferably from 4 to 9 carbon atoms in the alkyl moiety, or an aminoalkylaryl nitrile having from 8 to 13 carbon atoms , preferably aminoalkylaryl nitriles, the aminoalkylaryl nitriles having an alkylene group of at least one carbon atoms between the aromatic unit and the amino and nitrile group. Especially preferred aminoalkylaryl nitriles are those having the amino group and the nitrile group in the 1,4-position relative to one another. The? -aminoalkyl nitrile which is preferably used is a linear? -aminoalkyl nitrile in which the alkylene portion (-CH2-) preferably contains from 4 to 12 carbon atoms, more preferably from 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, in particular β-aminocapronitrile preference. The β-aminocapronitrile is usually obtained by hydrogenation of adiponitrile according to known methods, as described for example in DE-A 836,938, DE-A 648 ', 654 or US-A 5,151,543. Preferably, the lactam used is caprolactam and the aminocarboxylic acid aminocapróics acid. The lactams and / or aminocarboxylic acids are preferably mixed in the feed mixture upstream of the first reaction step. These can also be added in subsequent reaction steps. Preferably, the lactam and the aminocarboxylic acid or its mixture are added as a constituent of an aqueous phase to the reaction mixture. The addition can also take place in highly concentrated form in the solid or liquid state. For this purpose, the lactam and / or the aminocarboxylic acid can be heated, for example, in a tank with stirring above the melting point and pumped to the respective reaction step. The addition of the lactam and / or aminocarboxylic acid to the reaction mixture preferably takes place in the first, second and / or third step, particularly preferably in the first and third steps. The lactams, aminocarboxylic acids or mixtures thereof are used in an amount from 0.01 to 20% by weight, preferably from 0.3 to 105 by weight, particularly preferably from 1.0 to 7.0% by weight, based on the amount of aminonitriles. The addition gives rise to a considerable acceleration of the hydrolytic polymerization. In the process, the reaction product is not changed or contaminated since, if the lactams or aminocarboxylic acids are incorporated in the polymer chain, no new polymeric constituents are included. More specifically, lactam and aminocarboxylic acid must produce the same polymers; that is, aminocapronitrile should be used with caprolactam and / or aminocaproic acid as an accelerant. The use of these compounds gives rise to a considerable acceleration in the reaction of aminonitriles with water. In the following, the different steps are described, the lactams and / or aminocarboxylic acids being added at the points indicated above.
The process can be operated continuously or in batches. According to the invention, the first step (step 1) includes the heating of an aminonitrile with water at a temperature of from 90 to 400 ° C, preferably from 80 to 300 ° C, especially from 220 to 270 ° C, a pressure from 0.1 to approximately 15 x 106 Pa, preferably 1 to 10 x 106 Pa, especially from 4 to 9 x 106 Pa, being established. In this step, the pressure and the temperature can be adjusted one relative to the other in such a way that a liquid phase or a solid phase and a mixture of the liquid phase or the solid phase and a gas phase are obtained. According to the invention, water is used in a molar ratio of aminoalkyl nitrile to water in the range from 1: 1 to 1: 10, particularly preferably in the range from 1: 2 to 1: 8, very particularly preferably within interval from 1: 2 to 1: 6, giving preference to the use of excess water, based on the aminoalkyl nitrile used. In this embodiment, the liquid or solid phase or the mixture of the liquid and solid phase corresponds to the reaction mixture, while the gas phase is separated. As part of this step, the gas phase can be separated from the liquid phase or the solid phase or from the mixture of the solid or liquid phase at the same time, or the synthesis mixture that is formed within this step can be present in Two-phase form: liquid / gaseous, solid / gas or liquid-solid / gas. It will be noted that the pressure and temperature can also be adjusted one relative to the other in such a way that the synthesis mixture is present as a single solid or liquid phase. The elimination of the gas phase can be effected by the use of separation tanks with agitation or without agitation or tank batteries and by the use of evaporator apparatus, for example by means of circulating evaporators or thin film evaporators, such as for example by film extruders, or by means of annular disk reactors, which guarantee an extended phase interface. In certain cases, the recirculation of the synthesis mixture or the use of cyclic reactors may be necessary to increase the phase interface. In addition, the separation of the gas phase can be promoted by the addition of water vapor or inert gas to the liquid phase. Preferably, the pressure is adjusted to a pre-selected temperature so that the pressure is smaller than the equilibrium vapor pressure of the ammonia, but greater than the equilibrium vapor pressure of the other components in the synthesis mixture at the temperature determined. In this way, it is possible to favor especially the separation of ammonia and thereby accelerate the hydrolysis of the acid amide groups. The two-phase process is preferably carried out at a pressure which is above the vapor pressure of the pure water associated with the relative temperature of the reaction mixture, but below the equilibrium vapor pressure of the ammonia. A particularly preferred embodiment of the two-phase process uses a vertical flow tube which operates under upflow and optionally has another orifice above the product outlet for removal of the gas phase. This tubular reactor can be completely or partially packed with granules or catalyst pellets. In a preferred embodiment, the vertical reactor used in the two-stage process is packed to the maximum with catalyst material up to the phase boundary. In another particularly preferred embodiment of the first step, the pressure is selected so that the reaction mixture is present as a single liquid phase, ie, without gas phase present in the reactor. For this single-stage process, the preferred embodiment is a flow tube packed exclusively with catalyst material. According to the invention, the aminonitrile / water mixture is heated with a heat exchanger before being introduced into the first step. It will be appreciated that the aminonitrile and water can also be heated separately from one another and mixed in the first step by the use of mixing elements. Regarding the residence time of the synthesis mixture in the first step there are no restrictions; however, they are generally selected within the range of from about 10 minutes to about 10 hours, preferably within the range of from about 30 minutes to about 6 hours. Although there are no limitations as regards the degree of conversion of the nitrile groups in step 1, economic reasons dictate especially that the conversion of the nitrile groups in step 1 is generally not less than about 70 mol%, preferably not less about 95 mol%, and especially within the range of about 97 to 99 mol%, each based on the moles of aminonitrile used. The conversion of the nitrile group is usually determined by means of IR spectroscopy (vibration of CN elongation at wave numbers 2247), NMR or HPLC, preferably by IR spectroscopy. The invention also does not discharge the reaction in step 1 additionally in the presence of phosphorus compounds containing oxygen, especially phosphoric acid, phosphorous acid and hypophosphorous acid and its salts of alkali metals and alkaline earth metals and ammonium salts such as Na3P04, NaH2P04, Na2HP04, NaH2P03, Na2HP03, K3P04, KH2P04, K2HP04, KH2P03, K2HP03, KH2P02, in which case the molar ratio of α -aminonitrile to phosphorous compounds is selected within the range from 0.01: 1 to 1: 1, preferably within of the interval from 0.01: 1 to 0.1: 1. The reaction in step 1 is preferably carried out in a flow tube containing a Bronsted acid catalyst selected from a beta-zeolite catalyst, a lamellar silicate catalyst or a titanium dioxide catalyst containing from 70 to 100% by weight of anatase and from 0 to 30% by weight of rutile and in which up to 40% by weight of titanium dioxide can be replaced by tungsten oxide. If a very pure aminonitrile is used, the anatase ratio in the titanium dioxide catalyst should be as high as possible. Preferably, a pure anatase catalyst is used. If the aminonitrile used contains impurities, for example 1 to 3% by weight of impurities, preference is given to the use of titanium dioxide catalyst containing a mixture of anatase and rutile. Preferably, the anatase fraction is from 70 to 80% by weight and the rutile fraction from 20 to 30% by weight. In this case, the use of a titanium dioxide catalyst containing about 70% by weight of anatase and about 30% by weight of rutile is particularly preferred. The catalyst preferably has a pore volume from 0.1 to 5 ml / g, particularly preferably from 0.2 to 0.5 ml / g. The average pore diameter is preferably within the range of 0.005 to 0.1 μ, particularly preferably within the range of 0.01 to 0.06 μ. If highly viscous products are used, the average pore diameter should be large. The cutting hardness preferably is greater than 20 N, particularly preferably > 25 N. The BET surface area is preferably greater than 40 m2 / g, particularly preferably greater than 100 m2 / g. If the BET surface area is smaller, the bed volume must be adequately larger to ensure adequate catalyst activity. Particularly preferred catalysts have the following properties: 100% anatase; 0.3 ml / g pore volume; 0.02 μ average pore diameter; 32 N cutting hardness; 116 m2 / g BET surface area or 84% anatase weight; 16% by weight of rutile; 0.3 ml / g pore volume; 0.03 μ average pore diameter; 26 N hardness of the cut; BET surface area 46 m2 / g. The catalysts can be prepared from commercial powders such as those available for example from Degussa, Finnti or Kemira. When tungsten oxide is used, up to 40% by weight, preferably up to 30% by weight, preferably from 15 to 25% by weight, of titanium dioxide is replaced by tungsten oxide. The catalysts can be prepared as described in Ertl, Knózinger, 5 Weitkamp: "Handbook of heterogeneous catalysis", VHC Weinheim, 1997, pages 98ff. The catalyst can be used in any desired convenient way. It is preferable to use it in the form of molded articles, extrudates or pellets, especially in the form of pellets. The pellets are preferably large enough so that they are easily separable from the product mixture and do not impair the flowability of the product during the reaction. The pellet form of the catalyst makes it possible to mechanically remove the catalyst at the point of exit of the first step. For example, filters or mechanical screens are provided at the exit point of the first step. If in addition the catalyst is used in the second and / or third step, it is preferably present in the same way. According to the invention, the reaction mixture obtained in the first step is further reacted in step 2 at a temperature of from about 200 (150) to about 350 (400) ° C, preferably at a temperature in the range from about 210 (200) to about 330 ( 330) ° C, especially inside of the range from about 230 (230) to about 270 (290) ° C, and a pressure that is less than the pressure in step 1. The pressure in the second step is preferably at least about 0.5 x 106 Pa less than the pressure in step 1, generally the pressure will be within the range from about 0.1 to about 45 x 106 Pa, preferably within the range of from about 0.5 to about 15 x 106 Pa, especially within the range from about 2 to about 6 x 106 Pa (values in parentheses: without catalyst). In step 2, the temperature and pressure are chosen to obtain a first gas phase and a first liquid phase or first solid phase or a mixture of the first liquid phase and the first solid phase, and the first gas phase is separated from the first liquid phase or the first solid phase or the mixture of the first liquid phase and the first solid phase. The first gaseous phase, consisting mainly of ammonia and water vapor, is generally continuously separated by means of a distillation apparatus, such as a distillation column. Any of the organic constituents of the distillate separated at the same time in the course of the distillation, mainly unconverted aminonitrile, can be totally or partially recycled to step 1 and / or step 2.
The residence time of the reaction mixture in step 2 is not subject to limitations, but is generally within the range of from about 10 minutes to about 5 hours, preferably within the range of from about 30 minutes to about 3 hours. The product line between the first and second steps optionally contains packing elements, for example Raschig rings or Sulzer mixing elements, which facilitate a controlled extension of the reaction mixture towards the gas phase. This relates in particular to the single-phase process. Preferably, the reactor of the second step in the same way contains the catalyst material of the invention, especially in the form of pellets. It was found that the reactor further provides improvement in the properties of the product compared to a reactor without catalyst, especially at higher temperatures and / or in the presence of a large amount of excess water in the reaction mixture. The temperature and pressure should be selected in such a way that the viscosity of the reaction mixture remains sufficiently low to prevent any shielding of the catalyst surface. According to the invention, the exit point of the second process step is also equipped with screens or filters that guarantee the purity of the reaction mixture and separate the catalyst from the reaction mixture. In step 3, the first liquid phase or the first solid phase or the mixture of the first liquid phase and the first solid phase are mixed with a gaseous or liquid phase containing an aqueous medium, preferably water or water vapor. This is done continuously. The amount of added water (as liquid) is preferably within the range of from about 50 to about 1500 ml, more preferably within the range of from about 100 to about 500 ml, based in each case on 1 kg of the first liquid phase or the first solid phase or the mixture of the first liquid phase and the first solid phase. This addition of water mainly compensates for the water losses incurred in step 2 and promotes the hydrolysis of the acid amide groups in the synthesis mixture. This gives rise to another advantage of this invention, that the mixture of the initial materials as used in step 1 can be used as a small excess of water only. The gaseous or liquid phase containing water is preferably preheated in a heat exchanger before being introduced to step 3 and then mixed with the first liquid phase or the first solid phase or the mixture of the first solid phase and the first liquid phase. The reactor can optionally be adapted with mixing elements that favor the mixing of the components. Step 3 can be operated at a temperature of 150 to 370 ° C and a pressure of 0.1 to 30 x 106 Pa, if a catalyst bed is present, it is possible to use the conditions that apply for step 1. Otherwise, the preferably will be within the range of 180 to 300 ° C, particularly preferably within the range of 220 to 280 ° C. The pressure preferably is within the range from 1 to 10 x 106 Pa, particularly preferably in the range from 2 x 106 Pa to 7 x 106 Pa. The pressure and temperature can be adjusted to each other in such a way that the synthesis mixture is present as a single liquid or solid phase. In another embodiment, the pressure and temperature are selected so as to obtain a liquid phase or a solid phase or a mixture of the solid and liquid phase and also a gas phase. In this embodiment, the liquid or solid phase or the mixture of the liquid and solid phase corresponds to the product mixture, while the gas phase is separated. As part of this step, the gaseous phase can be separated from the liquid or solid phase or the mixture of the solid or liquid phase at the same time, or the synthesis mixture that is formed within this step can be present in the form of two phases: liquid / gaseous, solid / gas or liquid-solid / gas.
The pressure can be adjusted to a pre-selected temperature so that the pressure is smaller than the vapor pressure at the ammonia equilibrium, but greater than the vapor pressure at the equilibrium of the other components in the synthesis mixture at the temperature determined. This form is possible to especially favor the separation of ammonia and thus accelerate further the hydrolysis of the acid amide groups. The apparatus / reactors used in the step can be identical with those of step 1, as already described. The stay time of this step is likewise not subject to restrictions, but for economic reasons a range from 10 minutes to 10 hours is preferred, preferably from 60 minutes to 8 hours, particularly preferably from 60 minutes to 6 hours . The product mixture obtained in step 3 can also be processed as described below. In a preferred embodiment, the mixture of the product from step 3 is subjected to a subsequent condensation in a fourth step at a temperature of from 200 to 350 ° C, preferably at a temperature from 220 to 300 ° C, especially from 240 to 270 ° C. C. Step 4 is carried out at a pressure that is below the pressure of step 3 and preferably is within the range of 5 to 1000 x 103 Pa, more preferably within the range of 10 to 300 x 103 Pa. In the context from this step, the temperature and pressure are selected to obtain a second gas phase and a second liquid or solid phase or a mixture of the second liquid phase and the second solid phase each of which contains the polyamide. The subsequent condensation 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 95% concentration by weight of sulfuric acid) of the Polyamide assumes a value within the range of from 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 mainly on the desired relative viscosity, temperature, pressure and amount of water added in step 3. If step 3 is operated as a single-phase regime , the product line between step 3 and step 4 can optionally contain packaging elements, for example, Raschig rings or Sulzer mixing elements, which allow a controlled expansion of the synthesis mixture in the gas phase.
The fourth step can also be operated using the catalyst. It was found that the use of the catalyst in step 4 improves molecular weight accumulation in particular when the relative viscosity of the third party's effluent or, in the case of the 3-step process, the second step is less than RV = 1.6, and / or the molar content of the nitrile group and the acid amide in the polymer is greater than 1%, each based on the moles of aminonitrile used. In another embodiment of the invention, step 3 can be omitted and the polyamide produced by carrying out steps (1), (2) and (4). This preferred variant is carried out as follows: In step 1, the reaction is carried out as already described. The reaction mixture is treated in step 2 as described above or at a temperature in the range of from about 220 to about 300 ° C and a pressure in the range of from about 1 to about 7 x 106 Pa, the pressure in the second step 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 4 as in step 1 or at a temperature in the range from about 220 to 300 ° C and a pressure in the range from about 10 to about 300 x 10 3 Pa, the second resulting phase containing water and ammonia being separated from the second liquid phase. In this step, the relative viscosity (measured as already described) of the resulting polyamide is adjusted to a desired value within the range of from about 1.6 to about 3.5 by choosing the temperature and the dwell time. The resulting second liquid phase is then traditionally discharged and, if desired, treated. In another preferred embodiment of the present invention, at least one of the gaseous phases obtained in the respective steps can be recycled to at least one of the preceding steps. It is further preferred to select the temperature and pressure in step 1 or step 3 or step 1 and step 3 to obtain a liquid phase or a solid phase or a mixture of the liquid phase and the solid phase and a gas phase and separate the gas phase. Furthermore, in the context of the process of the invention, it is also possible to carry out a chain or branching elongation or a combination of these. For this purpose, branching or chain extender substances of the polymer known to those skilled in the art are added in the individual steps. These substances are preferably added in step 3 or 4. The useful substances are: Amines or trifunctional carboxylic acids as branching or cross-linking agents. Examples of suitable at least trifunctional amines or carboxylic acids are described in EP-A-0 345 648. The at least trifunctional amines have at least three amino groups which are capable of reacting with the carboxylic acid groups. These preferably do not have any carboxylic acid group. The 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 do not contain amino groups 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 acid. The carboxylic acids are preferably defined organic compounds and not polymeric compounds. Examples of the amines having at least three amino groups are nitrilotrialkylamine, especially nitrilotrietanamine, dialkylene triamines, especially diethylene triamine, trialkylene tetraamines and tetraalkylene pentamines, the alkylene portions preferably being ethylene portions. In addition, it is possible to use dendrimers as amines. The dendrimers preferably have the general formula I.
(R2N- (CH2) n) 2N- (CH2) x-N ((CH2) n-NR2) 2 (I) where R is H or - (CH2) n-NR12 / where R1 is H or - (CH2) n-NR22, where R2 is H or - (CH2) n-NR32, where R3 is H or - (CH2) n- NH2, n is an integer from 2 to 6, and x is an integer from 2 to 14. 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 meanings established 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, phthalocyanine, naphthalocyanine. Preference is given to phthalocyanine of 3, 5, 3 '5' -biphenyltetracarboxylic acid, naphthalocyanine, 3,5,5 ', 5'-biphenyltetracarboxylic acid, 1,3,5,7-naphthalenetetracarboxylic acid, 2,4,6-acid pyridintricarboxylic acid, bipyridyltetracarboxylic acid, benzophenonetetracarboxylic acid, 1,3,6,8-acridintetracarboxylic acid, particularly preferably 1,3,5-benzenetricarboxylic acid (trimesic acid) and 1,2,4,5-benzenecarboxylic acid. These compounds are available commercially or can be prepared by the process described in DE-A-43 12 182. If substituted aromatic compounds are used in the ortho position, it is preferred to avoid the formation of the imide through the the choice of convenient reaction temperatures. These substances are at least trifunctional, preferably at least tetrafunctional. The number of functional groups can be from 3 to 16, preferably from 4 to 10, particularly preferably from 4 to 8. The processes of the invention are carried out using at least trifunctional amines or at least trifunctional carboxylic acids, but not mixtures of these 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 from 1 to 50 μmol / g of polyamide, preferably from 1 to 35, particularly preferably from 1 to 20 μmol / g of polyamide. The substances of preference are present in an amount of from 3 to 15, particularly preferably from 5 to 100, especially from 10 to 70 μmol equivalents / g of polyamide. The equivalents are d on the number of amino groups or functional carboxylic acid groups. Diffunctional carboxylic acids or difunctional amines are used as chain extenders. These have two carboxylic acid groups which can react with the amino groups, or two amino groups which can react with the carboxylic acids. The carboxylic acids or difunctional amines, as well as the carboxylic acid groups or amino groups, do not contain any functional group capable of reacting with the amino groups or the carboxylic acid groups. Preferably, these do not contain any additional functional groups. Examples of suitable difunctional amines are those which form salts with difunctional carboxylic acids. These can be linear aliphatics such as alkylene diamine of C? _? , preferably C2-6 alkylene diamine, for example hexylene diamine. These can also be cycloaliphatic. Examples are isophoronediamine, dicyclic, laromine. The aliphatic diamines branched in the same way are usable, an example being Vestamin TMD (trimethylhexamethylenediamine, from Hüls AG). In addition, the diamines can also be aromatic-aliphatic, it being possible to use n-xylylenediamine, for example. The complete amines can each be replaced by C? -? 2 alkyl, preferably alkyl radicals of C? _? on the carbon skeleton. The difunctional carboxylic acids are, for example, those which form salts with difunctional diamines. These may be linear aliphatic dicarboxylic acids, which are preferably C4_2o dicarboxylic acids. Examples are adipic acid, azelaic acid, sebacic acid, suberic acid. These may also be aromatic, examples being isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, as well as dimerized fatty acids. The basic difunctional building blocks (c) are preferably used in quantities from 1 to 55, particularly preferably from 1 to 30, especially from 1 to 15 μm / g of polyamide. According to the invention, the product mixture obtained in step 3, or the second liquid phase or the second solid phase or the mixture of the second liquid phase and the second solid phase (from step 4) each of which contains the polyamide, preferably a polymer melt, is discharged from the reaction vessel in a traditional manner, for example using a pump. Then, the obtained polyamide can be treated according to the traditional methods, as described for example in DE-A 43 21 683 (page 3, line 54 to page 4, line 3) throughout. In a preferred embodiment, the level of the cyclic dimer in the nylon 6 obtained according to the invention can also be reduced by first extracting the polyamide with an aqueous solution of caprolactam and then with water and / or by subjecting it to a gas phase extraction (as it is described in EP-A 0 284 968, for example). The low molecular weight constituents obtained in this subsequent treatment, such as caprolactam, linear caprolactam oligomer and cyclic caprolactam oligomer, can be recycled to the first and / or second and / or third step. The initial mixture and the synthesis mixture can be mixed in all steps with chain regulators such as aliphatic and aromatic carboxylic and dicarboxylic acids and catalysts such as phosphorus compounds containing oxygen in amounts ranging from 0.01 to 5% by weight, preference within the range of 0.2 to 3% by weight, based on the amount of the polyamide-forming monomers and the 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, dyes and stabilizers are generally added to the synthesis mixture before granulation, preferably in the second, third and fourth steps. Particular preference is given to the use of fillers and additives when the synthesis or polymer blend will not encounter fixed bed catalysts in the remainder of the processing. One or more rubbers modified against shock may be present in the compositions as additives in amounts from 0 to 40% by weight, preferably from 1 to 30% by weight, based on the entire composition. It is possible to use, for example, customary shock modifiers which are suitable for polyamides and / or polyarylene ethers. Rubbers that improve the stiffness of polyamides generally have two main characteristics: they have an elastomeric portion that has a glass transition temperature of less than -10 ° C, preferably less than -30 ° C, and contain at least one functional group that It is capable of interaction with polyamide. Suitable functional groups include, for example, carboxylic acid, carboxylic anhydride, carboxylic ester, carboxylic amide, carboxylic imide, amino, hydroxyl, epoxide, urethane and oxazoline groups. Examples of rubbers that improve the rigidity of the blends include, for example: EP and EPDM rubbers grafted with the above functional groups. Suitable graft-forming reagents include, for example, maleic anhydride, itaconic acid, acrylic acid, glycidyl acrylate and glycidyl methacrylate. These monomers can be grafted onto the polymer in the molten state or in solution, in the presence or absence of a free radical initiator such as eumenohydroperoxide. The copolymers of α-olefins described in polymers A, including especially ethylene copolymers, can also be used as rubbers instead of polymers A and mixed as such in the compositions of the invention. Another group of suitable elastomers are grafted core-shell rubbers. These are grafted rubbers that are produced in emulsion and have at least one hard and one soft constituent. A hard component is usually a polymer having a glass transition temperature of at least 25 ° C, while a soft constituent is a polymer having a glass transition temperature not greater than 0 ° C. These products have a structure consisting of a core and at least one cover, the structure being the result of the order in which the monomers are added. The soft constituents generally come from butadiene, isoprene, alkyl acrylates, allyl methacrylates or siloxanes and optionally other comonomers. Suitable siloxane cores can be prepared, for example, starting from cyclic oligomeric octamethyltretasiloxane or tetravinyl tetramethyltretrasiloxane. These can react, for example, with α-mercaptopropylmethyldimethoxysilane in a cationic polymerization with ring opening, preferably in the presence of sulfonic acids, to form the soft siloxane cores. The siloxanes can also be crosslinked, for example, by carrying out the polymerization reaction in the presence of silanes having hydrolysable groups such as halogen or alkoxy groups such as tetraethoxysilane, methyltrimethoxysilane or phenyltrimethoxysilane. Suitable comonomers in this case include, for example, styrene, acrylonitrile and crosslinking or graft-forming monomers having more than one polymerizable double bond such as diallyl phthalate, divinylbenzene, butanediol diacrylate or triallyl (iso) cyanurate. The hard constituents generally come from styrene, α-methylstyrene and copolymers thereof, the preferred comonomers being acrylonitrile, methacrylonitrile and methyl methacrylate. The preferred core-sheathed grafted rubbers have a soft core and a hard shell or a hard core, a soft first shell and at least one other hard shell. The incorporation of the functional groups such as the carbonyl, carboxylic acid, acid anhydride, acid amide, acid imide, carboxylic, amino, hydroxyl, epoxy, oxazoline, urethane, urea, lactam or halobenzyl groups in this case is preferably carried out by means of the addition of functionalized monomers conveniently during the polymerization of the last cover. Suitable functionalized monomers include, for example, maleic acid, maleic anhydride, mono- or diesters of maleic acid, tert-butyl (meth) acrylate, acrylic acid, glycidyl (meth) acrylate and vinyloxazoline. The proportion of the monomers having functional group is generally within the range of 0.1 to 25% by weight, preferably within the range of 0.25 to 15% by weight, based on the total weight of the core-shell inserted rubber. The weight ratio of the soft to hard constituents is generally within the range from 1: 9 to 9: 1, preferably within the range from 3: 7 to 8: 2. Such rubbers, which improve the stiffness of polyamides are known per se and are described in EP-A 0 208 187 for example. Another group of suitable shock modifiers are the thermoplastic polyester elastomers. Polyester elastomers are segmented copolyesters containing long chain segments, generally from poly (alkylene) ether glycols, and short chain segments from diols and dicarboxylic acids of low molecular weight. Such products are known per se and are described in the literature, for example, in US 3,651,014. The corresponding products are also available commercially under the trademarks Hytrel® (Du Pont), Arnitel® (Akzo) and Pelprene® (Toyobo Co. Ltd.). It will be appreciated that it is also possible to use mixtures of different rubbers. Other additives which may be mentioned are, for example, processing aids, stabilizers and oxidation retarders, agents against thermal decomposition and decomposition by ultraviolet light, lubricants and demolding agents, flame retardants, dyes and pigments and plasticizers. The proportion of these is generally up to 40%, preferably up to 15% by weight, based on the total weight of the composition. The pigments and dyes are generally present in amounts of up to 4%, preferably from 0.5 to 3.5% especially from 0.5 to 3% by weight. Pigments of colored thermoplastics are commonly known, see, for example, R. Gachter and H. Müller, Taschenbuch der Kunststoffadditive, Carl Hanser Verlag, 1983 pages 494 to 510. The first preferred group of pigments that can be mentioned are white pigments such as zinc oxide, zinc sulphide, lead white (2) PbC03, Pb (OH) 2), lithopone, white antimony and titanium dioxide. Of the two most common crystalline polymorphs (rutile and anatase) of titanium dioxide, the rutile form is preferred for use as a white pigment for the molding compositions of the invention. The black pigments which can be used according to the invention are black iron oxide (Fe304), spinel black (Cu (Cr, Fe) 204), manganese black (mixture of manganese dioxide, silicon dioxide and iron oxide) ), cobalt black and antimony black and also, particularly preferably, carbon black, which is normally used in the form of oven black or gas (see, for example, G. Benzing, Pigment für Anstrichmittel, Expert-Verlag (1988), p.78ff).
It will be appreciated that according to the invention it is also possible to use inorganic color pigments such as chromium oxide green or organic colored pigments such as azo pigments and phthalocyanines to obtain certain shades. These pigments are generally available commercially. Furthermore, it may be advantageous to use the aforementioned pigments or dyes in a mixture, for example, carbon black with copper phthalocyanines, since this generally facilitates the dispersion of the color in the thermoplastic. Oxidation retarders and thermal stabilizers that can be added to the thermoplastic compositions of the invention include, for example, metal halides of group I of the Periodic Table, for example sodium halides, potassium halides, lithium halides, optionally together with copper (I) halides, for example, chlorides, bromides or iodides. Halides, especially copper, may also contain electron-rich p-ligands. Examples of these copper complexes are copper halide complexes such as triphenylphosphine, for example. It is also possible to use zinc fluoride and zinc chloride. Other possibilities are phenols with spherical hindrance, hydroquinones, substituted representatives of this group, secondary aromatic amines, optionally together with phosphorus-containing acids and salts thereof, and mixtures of these compounds, preferably at a concentration of up to 1% by weight. weight, based on the weight of the mixture. Examples of the UV stabilizers are the different substituted resorcinols, salicylates, benzotriazoles and benzophenones, which are generally used in amounts of up to 2% by weight. The lubricants and mold release agents which are generally included in the thermoplastic material in amounts of up to 1% by weight are stearic acid, stearyl alcohol, alkyl stearates and N-alkyl stearamides and also the esters of pentaerythritol with long chain fatty acids. It is also possible to use calcium, zinc or aluminum salts of stearic acid and also dialkyl ketones, for example, distearyl ketone. The present invention also provides a polyamide that can be produced by one of the processes. The following examples illustrate the invention.
Examples The resolved measurements over time for the production of Examples 1-6 and the products of continuous production of nylon 6 from ACN in a mini-plant (Examples 7-8) show that caprolactam and aminocaproic acid accelerate the reaction of aminocapronitrile.
Comparative example 1: In a 2-liter pressure vessel, equipped with a heating jacket and an anchor stirrer, 1400 g of an aminocapronitrile reaction mixture and water in a molar ratio of 1: 4 were stirred at 250 ° C in a sealed reactor . The autogenous pressure was 48 bar. The hydrolysis of aminocapronitrile (conversion) as a function of the reaction time is reported in Table 1.
Examples 2-4 with caprolactam as a catalytically active additive In a 2 liter pressure vessel, equipped with a heating jacket and an anchor stirrer, 1400 g of an aminocapronitrile reaction mixture and water in a molar ratio of 1: 4 and an addition of 1% by weight, % by weight and 10% by weight of caprolactam (each based on the ACN fraction) were stirred at 250 ° C in a sealed reactor. The autogenous pressure was 48 bar. The hydrolysis of the aminocapronitrile (conversion) as a function of the reaction time is reported in Table 1.
Examples 5-6 with aminocaproic acid as a catalytically active additive In a 2 liter pressure vessel, equipped with a heating jacket and anchor stirrer, 1400 g of an aminocapronitrile reaction mixture and water in a molar ratio of 1: 4 and an addition of 5% by weight and % by weight of aminocaproic acid (each based on the ACN fraction) were stirred at 250 ° C in a sealed reactor. The autogenous pressure was 48 bar. The hydrolysis of the aminocapronitrile (conversion) as a function of the reaction time is reported in Table 1.
Examples 7-8: Continuous production of polyamide from ACN in the presence of caprolactam in a mini-plant Polyamide was continuously produced according to the invention in a multi-step multi-plant. The aminocapronitrile / caprolactam / water reaction mixture contained 50% by weight of aminocapronitrile, 8% by weight of caprolactam and 42% by weight of water. The comparative processes were carried out using a mixture of aminocapronitrile / water containing 50% by weight of ACN and 50% by weight of water. The purity of the aminocapronitrile used was 99.5%. An HPLC pump fed the preheated reaction mixture at a rate of 150 or 600 g / h to a tubular reactor having an empty volume of 1 liter and an internal length of 1000 mm. This was completely packed with catalyst pellets which were 100% Ti02 from Finnti, type S150 in anatase form, and had a strand length in the range from 2 to 14 mm, a strand thickness of approximately 4 mm and an area of specific surface greater than 100 m2 / g. The reaction mixture in the tubular reactor had a temperature of 250 ° C, the pressure in the reactor was 60 bar. The reaction mixture obtained subsequently was transferred to a 2 liter separator vessel and then the reaction at 250 ° C and 4 bar was discharged with the aid of a mechanical pump. The product properties of the polyamides produced and the corresponding residence times are mentioned below in Table II. The purity of the aminocapronitrile used was 99.5%.
Comparative products or examples were prepared by reacting ACN with water without caprolatam under identical process conditions or with the same process parameters. The process parameters and the product properties are tabulated below. The yield is the flow of the mass of the reaction mixture through the first process step.
CL: caprolactam ACS: aminócapróico acid Analysis of the exemplary reactions: Table I: Table II:

Claims (1)

  1. CLAIMS The use of lactams, aminocarboxylic acids or mixtures thereof as accelerator or co-catalyst in the production of polyamides from aminonitriles and water. The use as claimed in claim 1, wherein the lactams, aminocarboxylic acids or mixtures thereof are used in an amount of from 0.3 to 10% by weight, based on the amount of aminonitrile. The use as claimed in claim 1 or 2, whereby the lactams, aminocarboxylic acids or mixtures thereof are used together with metal oxide fixed bed catalysts. A process for producing a polyamide by reacting at least one aminonitrile with water, which comprises the following steps: (1) the reaction of at least one aminonitrile with water at a temperature of 90 to 400 ° C and a pressure of 0.1 up to 35 x 106 Pa, which reaction can be carried out in the presence of a Brónsted acid catalyst selected from a beta-zeolite catalyst, a lamellar silicate catalyst or a titanium dioxide catalyst consisting of from 70 to 100% by weight of anatase and from 0 to 30% by weight of rutile and in which up to 40% by weight of the titanium dioxide can be replaced by tungsten oxide, to obtain a reaction mixture, (2) further the reaction of the reaction mixture at a temperature of 150 to 400 ° C and a pressure that is lower than the pressure in step 1, which reaction can be carried out in the presence of a Bronsted acid catalyst selected from a catalyst beta-zeolite, a lamellar silicate catalyst or a titanium dioxide catalyst consisting of from 70 to 100% by weight of anatase and from 0 to 30% by weight of rutile, and in which up to 40% by weight of titanium dioxide it can be replaced by tungsten oxide, the temperature and pressure being selected to obtain a first gas phase and a first liquid phase or a first solid phase or a mixture of the first solid phase and the first liquid phase, and the first gas phase is separates from the first liquid phase or the first solid phase or from the mixture of the first liquid phase and the first solid phase, and (3) mixing the first liquid phase or the first solid phase of the mixture of the first liquid phase and the first solid phase with a gaseous or liquid phase containing water at a temperature of 150 up to 370 ° C and a pressure from 0.1 to 30 x 106 Pa, optionally in the presence of the above catalyst, to obtain a mixture of products, wherein the reaction is carried out in at least one of steps (1) and (2) in the presence of lactams, aminocarboxylic acids or mixtures thereof in an amount from 0.3 to 10% by weight, based on the amount of aminonitrile used. The process as claimed in claim 4, which further comprises the following step: (4) the subsequent condensation of the product mixture at a temperature of 200 to 350 ° C and a pressure that is less than the pressure of step 3 , the temperature and pressure being selected to obtain a second gaseous phase containing water and ammonia and a second liquid phase or second solid phase or a mixture of the second liquid phase and the second solid phase, each of which contains the polyamide. A process for the production of a polyamide by reaction of at least one aminonitrile with water, which comprises the following steps: (1) reacting at least one aminonitrile with water at a temperature of 90 to 400 ° C and a pressure of 0.1 up to 35 x 106 Pa, which reaction can be carried out in the presence of a Brónsted acid catalyst selected from a beta-zeolite catalyst, a lamellar silicate catalyst or a titanium dioxide catalyst consisting of from 70 to 100% by weight of anatase and from 0 up to 30% by weight of rutile and in which up to 40% by weight of the titanium dioxide can be replaced by tungsten oxide, to obtain a reaction mixture, (2) further react the reaction mixture at a temperature of 150 to 400 ° C and a pressure that is lower than the pressure in step 1, which reaction can be carried out in the presence of a Brónsted acid catalyst selected from a beta catalyst zeolite, a lamellar silicate catalyst or a titanium dioxide catalyst consisting of from 70 to 100% by weight of anatase and from 0 to 30% by weight of rutile and in which up to 40% by weight of titanium dioxide can be substituted by tungsten oxide, the temperature and pressure being selected to obtain a first gaseous phase and a first liquid phase or a first solid phase or a mixture of the first solid phase and the first liquid phase, and the first gaseous phase is separated from the first liquid phase or the first solid phase or the mixture of the first liquid phase and the first solid phase, and (4) the subsequent condensation of the first liquid phase or the first solid phase or the mixture of the first liquid phase and the first solid phase at a temperature of 200 to 350 ° C and a pressure that is lower than the pressure of step 3 , the temperature and pressure being selected to obtain a second gaseous phase containing water and ammonia, and a second liquid phase or second solid phase or a mixture of the second liquid phase and the second solid phase, each of which contains the polyamide , wherein the reaction is carried out in at least one of steps (1) or (2) in the presence of lactams, aminocarboxylic acids or mixtures thereof in an amount from 0.3 to 10% by weight, based on the amount of the aminonitrile used. The process as claimed in any of claims 4 to 6, wherein the temperature and pressure in step 1 or step 3 or in both steps 1 and step 3 is selected to obtain a liquid phase or a solid phase or a mixture of liquid phase and solid phase and a gas phase, and the gas phase is separated. The process as claimed in any of claims 4 to 7, wherein the reaction of step 1 is carried out with a molar ratio of aminonitrile to water from 1: 1 to 1:30. The process as claimed in any of claims 4 to 8, wherein 6-aminocapronitrile and caprolactam, aminocaproic acid or mixtures thereof are used. The process as claimed in any of claims 4 to 6, wherein the lactams, aminocarboxylic acids or mixtures thereof are used in an amount from 1.0 to 7.0% by weight, based on the amount of aminonitrile used.
MXPA/A/2001/003484A 1998-10-06 2001-04-05 Accelerator for the production of polyamides from aminonitriles MXPA01003484A (en)

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