A preparation method of nylon MXD6 salt and nylon MXD6 prepared therefrom

Abstract

The invention relates to the technical field of preparation of nylon MXD6 salt, and specifically discloses a preparation method of nylon MXD6 salt and nylon MXD6 prepared therefrom. The method comprises: dissolving adipic acid and meta-xylylenediamine in water respectively to obtain adipic acid solution and meta-xylylenediamine solution; taking a certain amount of meta-xylylenediamine solution, dropping it into adipic acid solution under stirring in a water bath at 70-90°C to obtain a carboxyl-terminated intermediate solution; taking a certain amount of adipic acid solution, dropping it into meta-xylylenediamine solution under stirring in a water bath at 40-60°C to obtain an amine-terminated intermediate solution; dropping the amine-terminated intermediate solution into the carboxyl-terminated intermediate solution under stirring at 60-80°C, reacting completely, and obtaining a nylon MXD6 salt crude solution; during which an inert gas is introduced; and refining. The oxidation of meta-xylylenediamine can be effectively inhibited by the forward and reverse feeding method. The prepared nylon MXD6 salt has high purity and low UV index, which is conducive to the synthesis of nylon MXD6 by polycondensation reaction. The synthesized nylon MXD6 has high relative viscosity and excellent performance.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of nylon MXD6 salt, and particularly relates to a preparation method of nylon MXD6 salt and nylon MXD6 prepared therefrom. Background Art

[0002] Nylon MXD6 (meta-xylylene adipamide), scientific name poly(m-xylylene adipamide), is a crystalline, semi-aromatic special nylon material formed by condensation polymerization of adipic acid and m-xylylene diamine. Toyobo Co., Ltd. and Mitsubishi Gas Chemical Co., Ltd. of Japan first successfully synthesized semi-aromatic nylon MXD6 in 1972. Aliphatic nylon is easy to process and shape, but it has strong water absorption and low glass transition temperature; although fully aromatic nylon has largely solved the shortcomings of aliphatic products, the processing difficulty has doubled. Nylon MXD6 resin not only overcomes the shortcomings of aliphatic nylon and fully aromatic nylon to a large extent, but also has some advantages of fully aromatic nylon. Semi-aromatic nylon MXD6 has the characteristics of high heat resistance, low moisture absorption, high gas barrier, excellent processing compatibility and dimensional stability. It can be used as an engineering structural material to replace metal materials to achieve lightweighting of automobiles and machinery, such as power tools, magnetic materials, automobile shells, chassis, beams, engine accessories, etc. In addition, as a molding material, nylon MXD6 is also used to produce monofilaments and special fibers, plastic modification, and is also used in large quantities as packaging materials. In the global market, its demand continues to grow rapidly.

[0003] There are two main preparation processes for nylon MXD6: the salt-forming method and the melting method, represented by the process of Toyobo Co., Ltd. and the process of Mitsubishi Gas Chemical Co., Ltd., respectively. The salt-forming method is to make a nylon MXD6 salt solution from adipic acid and m-phenylenediamine, and then condense and polymerize the target product through purification, heating and pressurization. However, in the salt-forming process, because amines are unstable in the air, they are prone to side reactions when exposed to heat or oxygen, resulting in the deterioration of the quality of nylon salt and yellowing of the color, which in turn has a fatal effect on the condensation polymerization of nylon, seriously affecting the quality of nylon MXD6. Therefore, in order to obtain high-quality nylon MXD6, it is necessary to ensure that the polymerized monomer nylon MXD6 salt has few impurities and high purity. In addition, the salt-forming process is mostly produced by intermittent processes, which is difficult to stabilize batch production. Mitsubishi Gas Chemical Co., Ltd. has developed a continuous melting process, which can achieve continuous production, but due to the slow polycondensation reaction, the viscosity of the reaction system increases significantly, and the process equipment requirements are high, and the purity of the raw materials is also more stringent.

[0004] In the salt-forming process, in order to obtain high-quality nylon MXD6, it is necessary to ensure the high purity of the polymerized monomer nylon MXD6 salt. Based on this, it is urgent to find a preparation process for nylon MXD6 salt with less impurities and high purity. Summary of the invention

[0005] In view of the above problems existing in the existing preparation process of nylon MXD6 salt, the present invention provides a preparation method of nylon MXD6 salt and nylon MXD6 prepared therefrom. The nylon MXD6 salt prepared by the preparation method has few impurities and high purity, and the nylon MXD6, a condensation product of the nylon MXD6 salt, has a large relative viscosity and excellent performance.

[0006] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0007] A method for preparing nylon MXD6 salt comprises the following steps:

[0008] (1) dissolving adipic acid in water to obtain an adipic acid solution; dissolving meta-xylylenediamine in water to obtain a meta-xylylenediamine solution;

[0009] (2) taking a certain amount of the m-phenylenediamine solution, and adding it dropwise to a certain amount of the adipic acid solution under the protection of an inert gas and stirring in a water bath at 70° C. to 90° C. to obtain a carboxyl-terminated intermediate solution;

[0010] (3) taking a certain amount of the adipic acid solution, and adding it dropwise to a certain amount of the m-xylylenediamine solution under the protection of an inert gas and stirring in a water bath at 40° C. to 60° C. to obtain an amine-terminated intermediate solution;

[0011] (4) under the protection of inert gas, at 60° C. to 80° C., adding the amino-terminated intermediate solution dropwise to the carboxyl-terminated intermediate solution, and reacting completely to obtain a crude solution of nylon MXD6 salt;

[0012] (5) The crude nylon MXD6 salt solution is purified to obtain a nylon MXD6 salt solid.

[0013] In the preparation process of nylon MXD6 salt, in step (2), the m-phenylenediamine solution is added dropwise to an equimolar amount or excess amount of adipic acid solution with m-phenylenediamine to obtain a carboxyl-terminated intermediate solution. During this period, the reaction temperature needs to be strictly controlled at 70°C to 90°C. Too high a temperature causes oxidation of m-phenylenediamine, affecting the quality of the generated nylon MXD6 salt, while too low a temperature causes a slow reaction rate, thereby affecting the reaction. In addition, the amount of m-phenylenediamine used in this step is relatively small, and the temperature can be appropriately raised within the range of 70°C to 90°C, which can not only ensure that m-phenylenediamine is not oxidized, but also appropriately increase the reaction rate. The reaction of this step is as follows:

[0014]

[0015] In step (3), the adipic acid solution is added dropwise to a solution of m-xylenediamine in an equimolar amount or in excess with adipic acid to obtain an amine-terminated intermediate solution. Similarly, this step also requires strict control of the reaction temperature. In this step, the amount of m-xylenediamine used is large. Compared with step (2), the temperature needs to be controlled in a lower range of 40°C to 60°C to ensure that m-xylenediamine is not easily oxidized. The reaction in this step is as follows:

[0016]

[0017] Step (4) Add the amine-terminated intermediate solution dropwise to the carboxyl-terminated intermediate solution to obtain a crude solution of nylon MXD6 salt. This step also requires controlling the temperature within the range of 60°C to 80°C to ensure product quality. The reaction of this step is as follows:

[0018]

[0019] Compared with the prior art, the preparation method of nylon MXD6 salt of the present invention has at least the following beneficial effects:

[0020] 1. In the preparation method of the present invention, first, a m-phenylenediamine solution is added dropwise to an adipic acid solution in an equimolar amount or excess amount to m-phenylenediamine to obtain a carboxyl-terminated intermediate solution; an adipic acid solution is added dropwise to a m-phenylenediamine solution in an equimolar amount or excess amount to adipic acid to obtain an amine-terminated intermediate solution, and then the amine-terminated intermediate solution is added dropwise to the carboxyl-terminated intermediate solution to obtain a nylon MXD6 salt crude solution. The oxidation of m-phenylenediamine can be effectively inhibited by the forward and reverse feeding method, and side reactions are few. Without purification, the purity of the prepared nylon MXD6 salt is guaranteed, which helps to improve the conversion rate of the polycondensation reaction and the yield of nylon MXD6 is high; in addition, during the preparation process, the temperature and pH are easy to control, simplifying the process flow.

[0021] 2. The nylon MXD6 salt prepared by the method of the present invention has less impurities, high purity and low UV index, which is conducive to the polycondensation reaction to synthesize nylon MXD6, and it is easier to obtain high-quality nylon MXD6.

[0022] In one embodiment, in step (1), the concentration of the adipic acid solution is 20-50 wt %, and the concentration of the m-xylylenediamine solution is 60-90 wt %.

[0023] Preferably, in step (1), the concentration of the adipic acid solution is 30-40 wt %, and the concentration of the m-xylylenediamine solution is 70-80 wt %.

[0024] In one embodiment, in step (2), the m-xylylenediamine solution and the adipic acid solution are weighed in a stoichiometric ratio of m-xylylenediamine to adipic acid of 1:(1-5).

[0025] Preferably, in step (2), the m-xylylenediamine solution and the adipic acid solution are weighed in a stoichiometric ratio of m-xylylenediamine to adipic acid of 1:2.

[0026] In one embodiment, in step (3), the m-xylylenediamine solution and the adipic acid solution are weighed in a stoichiometric ratio of m-xylylenediamine to adipic acid of (1-5):1.

[0027] Preferably, in step (3), the m-xylylenediamine solution and the adipic acid solution are weighed in a stoichiometric ratio of m-xylylenediamine to adipic acid of 2:1.

[0028] In step (2), the amount of meta-phenylenediamine and adipic acid or an excess of adipic acid can be used to obtain a carboxyl-terminated intermediate; in step (3), the amount of meta-phenylenediamine and adipic acid or an excess of meta-phenylenediamine can be used to obtain an amine-terminated intermediate. Compared with the traditional preparation process, the embodiment of the present invention obtains a carboxyl-terminated intermediate and an amine-terminated intermediate by forward and reverse feeding, respectively, and then reacts the two intermediates, which can reduce the oxidation of meta-phenylenediamine, have few by-products, and are conducive to obtaining high-quality nylon MXD6 salt. Based on this, in step (2), the molar ratio of meta-phenylenediamine to adipic acid can be set to 1: (1 to 5) to ensure the yield of the carboxyl-terminated intermediate. Furthermore, the molar ratio of meta-phenylenediamine to adipic acid is set to 1: 2, which can use the least amount of adipic acid while ensuring the yield, reducing the amount of raw materials and excess impurities. In step (3), the molar ratio of m-phenylenediamine to adipic acid can be set to (1-5):1 to ensure the yield of the amino-terminated intermediate. Further, the molar ratio of m-phenylenediamine to adipic acid is set to 1:2, which can use the minimum amount of xylenediamine while ensuring the yield, thereby reducing the amount of raw materials and excess impurities.

[0029] In one embodiment, in step (4), the pH of the reaction solution is adjusted with the m-xylylenediamine to a pH of 7.0 to 7.5.

[0030] Using m-phenylenediamine to adjust the pH of the reaction solution can maintain the appropriate acidity and alkalinity of the reaction system without introducing additional impurities.

[0031] In one embodiment, the specific process of step (5) includes: cooling and crystallizing the crude nylon MXD6 salt solution, filtering the cooled solution, and vacuum drying the filtered solid to obtain the nylon MXD6 salt solid.

[0032] By refining the crude nylon MXD6 salt solution, and sequentially performing cooling crystallization, filtering, and drying processes, a dry, pure nylon MXD6 salt solid can be obtained, which provides high-quality polymerization monomers for the subsequent nylon MXD6 salt polycondensation reaction to synthesize nylon MXD6 polymers, thereby ensuring the quality of the prepared nylon MXD6 polymers. In addition, the cooling crystallization process in the refining process of the present invention can effectively avoid the problem of oxidation of the nylon MXD6 salt due to excessively high temperature during the concentration and crystallization process, further improve the purity of the MXD6 salt, and thus facilitate the polycondensation reaction.

[0033] Specifically, the vacuum drying temperature is 70° C. to 90° C., and the drying time is 12 h to 24 h.

[0034] It can be understood that the inert gas is not specifically limited and can be a common inert gas, such as nitrogen, argon, helium, neon, etc.

[0035] The present invention also provides a method for preparing nylon MXD6 from nylon MXD6 salt prepared by the above-mentioned method for preparing nylon MXD6 salt, comprising the following steps:

[0036] A: dissolving the nylon MXD6 salt solid in water to obtain a nylon MXD6 salt solution; placing the nylon MXD6 salt solution into a reaction kettle, evacuating the reactor, and introducing N2;

[0037] B: Turn on the stirring device to increase the temperature in the reactor to carry out a prepolymerization reaction;

[0038] C: Continue to increase the temperature in the reactor and release the pressure in the reactor to normal pressure to carry out polycondensation reaction;

[0039] D: Vacuum and react for a certain period of time to obtain nylon MXD6.

[0040] In one embodiment, in step A, the concentration of the nylon MXD6 salt solution is 50-80 wt %.

[0041] Preferably, in step A, the concentration of the nylon MXD6 salt solution is 70-80 wt %.

[0042] In one of the embodiments, in step B, the temperature in the reactor is 180° C. to 230° C., the pressure in the reactor is 1.2 MPa to 2.0 MPa, and the prepolymerization reaction time is 0.5 h to 5 h.

[0043] Preferably, in step B, the temperature in the reactor is 200° C. to 220° C., the pressure in the reactor is 1.7 MPa to 1.8 MPa, and the prepolymerization reaction time is 1 h to 2 h.

[0044] In one embodiment, in step C, the temperature in the reactor is 250° C. to 270° C., and the polycondensation reaction time is 0.5 h to 5 h.

[0045] Preferably, in step C, the temperature in the reactor is 260° C. to 270° C., and the polycondensation reaction time is 1 h to 2 h.

[0046] In one embodiment, in step D, the reaction time after vacuuming is 0.5h to 2h.

[0047] Preferably, in step D, the reaction time after vacuuming is 1 h to 2 h.

[0048] The nylon MXD6 product obtained by the nylon MXD6 preparation method of the present invention has high relative viscosity, high melting point, high glass transition temperature and excellent mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 : Infrared spectrum analysis of nylon MXD6 salt obtained in Example 1.

[0050] Figure 2 : TG analysis of nylon MXD6 salt obtained in Example 1.

[0051] Figure 3 : DSC analysis of nylon MXD6 salt obtained in Example 1.

[0052] Figure 4 : Infrared spectrum analysis of nylon MXD6 obtained in Example 1.

[0053] Figure 5 : TG analysis of nylon MXD6 obtained in Example 1.

[0054] Figure 6 : DSC analysis of nylon MXD6 obtained in Example 1.

[0055] Figure 7 : XRD analysis of nylon MXD6 obtained in Example 1. DETAILED DESCRIPTION

[0056] The present invention is further described below in conjunction with specific embodiments. It should be noted that the following embodiments are only used to illustrate the present invention rather than to limit the technical solutions described in the present invention, and all technical solutions and improvements that do not depart from the present invention should be included in the scope of the claims of the present invention.

[0057] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the invention, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In the description of the present invention, the meaning of "several" is at least one, such as one, two, etc., unless otherwise clearly and specifically defined.

[0058] The words "preferably", "more preferably", etc. in the present invention refer to embodiments of the present invention that may provide certain beneficial effects in certain circumstances. However, other embodiments may also be preferred under the same circumstances or other circumstances. In addition, the description of one or more preferred embodiments does not imply that other embodiments are not applicable, nor is it intended to exclude other embodiments from the scope of the present invention.

[0059] When a numerical range is disclosed herein, the above range is considered to be continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0060] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0061] The following are specific examples. Unless otherwise specified, the raw materials used in the examples are all commercially available products.

[0062] Example 1

[0063] The preparation method of nylon MXD6 salt specifically comprises the following steps:

[0064] (1) Weigh 219.3 g (1.50 mol) of adipic acid and dissolve it in water to prepare a 20% adipic acid solution; weigh 204.3 g (1.50 mol) of m-xylylenediamine and dissolve it in water to prepare a 60% m-xylylenediamine solution;

[0065] (2) 115.2 g of m-phenylenediamine solution was added dropwise to 730.7 g of adipic acid solution under stirring in a water bath at 70° C., with inert gas protection, to obtain a carboxyl-terminated intermediate solution;

[0066] (3) 365.35 g of adipic acid solution was added dropwise to 230.4 g of m-xylylenediamine solution under stirring in a water bath at 40° C., with inert gas protection, to obtain an amine-terminated intermediate solution;

[0067] (4) adding the amine-terminated intermediate solution to the carboxyl-terminated intermediate solution under stirring at 60° C. to complete the reaction and obtain a crude nylon MXD6 salt solution. During the process, the reaction temperature is controlled, an inert gas is introduced for protection, and the pH value of the solution is tested. Finally, a trace amount of m-xylylenediamine is added to adjust the pH value to 7.0-7.5;

[0068] (5) The crude nylon MXD6 salt solution was cooled and crystallized, the cooled solution was filtered, and the filtered solid was dried in a vacuum drying oven at 70° C. for 12 h to obtain a dry nylon MXD6 salt solid.

[0069] The method for preparing nylon MXD6 from the above-mentioned nylon MXD6 salt solid comprises the following steps:

[0070] A: Dissolve nylon MXD6 salt solid in water to prepare a 50wt% nylon MXD6 salt solution; put it into a reactor, evacuate and check the air tightness of the reactor, and introduce N2, repeating three times;

[0071] B: Turn on the stirring device, raise the temperature in the reactor to 180°C, react for 0.5h, and perform prepolymerization;

[0072] C: Continue to raise the temperature in the reactor to 250°C, while slowly releasing the pressure in the reactor to normal pressure, and keep the temperature at normal pressure for 5 hours;

[0073] D: Vacuum the reaction for 2 hours to obtain nylon MXD6, and then open the kettle to unload.

[0074] Example 2

[0075] The preparation method of nylon MXD6 salt specifically comprises the following steps:

[0076] (1) Weigh 219.3 g (1.50 mol) of adipic acid and dissolve it in water to prepare a 30% adipic acid solution; weigh 204.3 g (1.50 mol) of m-xylylenediamine and dissolve it in water to prepare a 70% m-xylylenediamine solution;

[0077] (2) taking 72.9 g of m-phenylenediamine solution, adding it dropwise to 548.25 g of adipic acid solution under stirring in a water bath at 80° C., during which an inert gas was introduced for protection, to obtain a carboxyl-terminated intermediate solution;

[0078] (3) 182.75 g of adipic acid solution was added dropwise to 219.0 g of m-xylylenediamine solution under stirring in a 50° C. water bath, with inert gas protection, to obtain an amine-terminated intermediate solution;

[0079] (4) adding the amine-terminated intermediate solution dropwise to the carboxyl-terminated intermediate solution under stirring at 70° C., and reacting completely to obtain a crude solution of nylon MXD6 salt. During this process, the reaction temperature is controlled, an inert gas is introduced for protection, and the pH value of the solution is tested. Finally, a trace amount of m-xylylenediamine is added to adjust the pH value to 7.0-7.5;

[0080] (5) The crude nylon MXD6 salt solution was cooled and crystallized, the cooled solution was filtered, and the filtered solid was dried in a vacuum drying oven at 80° C. for 18 h to obtain a dry nylon MXD6 salt solid.

[0081] The method for preparing nylon MXD6 from the above-mentioned nylon MXD6 salt solid comprises the following steps:

[0082] A: Dissolve nylon MXD6 salt solid in water to prepare a 70wt% nylon MXD6 salt solution; put it into a reactor, evacuate and check the air tightness of the reactor, and introduce N2, repeating three times;

[0083] B: Turn on the stirring device, raise the temperature in the reactor to 200°C, react for 1 hour, and perform prepolymerization;

[0084] C: Continue to raise the temperature in the reactor to 260°C, while slowly releasing the pressure in the reactor to normal pressure, and keep the temperature at normal pressure for 2 hours;

[0085] D: Vacuum the reaction for 2 hours to obtain nylon MXD6, and then open the kettle to unload.

[0086] Example 3

[0087] The preparation method of nylon MXD6 salt specifically comprises the following steps:

[0088] (1) Weigh 219.3 g (1.50 mol) of adipic acid and dissolve it in water to prepare a 50% adipic acid solution; weigh 204.3 g (1.50 mol) of m-xylylenediamine and dissolve it in water to prepare a 80% m-xylylenediamine solution;

[0089] (2) 51.08 g of m-phenylenediamine solution was added dropwise to 350.88 g of adipic acid solution under stirring in a water bath at 90° C., with inert gas protection, to obtain a carboxyl-terminated intermediate solution;

[0090] (3) 87.72 g of adipic acid solution was added dropwise to 204.33 g of m-xylylenediamine solution under stirring in a water bath at 60° C., with inert gas protection, to obtain an amine-terminated intermediate solution;

[0091] (4) adding the amine-terminated intermediate solution dropwise to the carboxyl-terminated intermediate solution under stirring at 80° C., and reacting completely to obtain a crude solution of nylon MXD6 salt. During this process, the reaction temperature is controlled, an inert gas is introduced for protection, and the pH value of the solution is tested. Finally, a trace amount of m-xylylenediamine is added to adjust the pH value to 7.0-7.5;

[0092] (5) The crude nylon MXD6 salt solution was cooled and crystallized, the cooled solution was filtered, and the filtered solid was dried in a vacuum drying oven at 90° C. for 24 h to obtain a dry nylon MXD6 salt solid.

[0093] The method for preparing nylon MXD6 from the above-mentioned nylon MXD6 salt solid comprises the following steps:

[0094] A: Dissolve nylon MXD6 salt solid in water to prepare 80wt% nylon MXD6 salt solution; put it into a reactor, evacuate and check the air tightness of the reactor, introduce N2, and repeat three times;

[0095] B: Turn on the stirring device, raise the temperature in the reactor to 210°C, react for 5 hours, and perform prepolymerization;

[0096] C: Continue to raise the temperature in the reactor to 270°C, while slowly releasing the pressure in the reactor to normal pressure, and keep the temperature at normal pressure for 0.5h;

[0097] D: Vacuum the reaction for 0.5h to obtain nylon MXD6, and then open the kettle to unload.

[0098] Example 4

[0099] The preparation method of nylon MXD6 salt specifically comprises the following steps:

[0100] (1) Weigh 219.3 g (1.50 mol) of adipic acid and dissolve it in water to prepare a 40% adipic acid solution; weigh 204.3 g (1.50 mol) of m-xylylenediamine and dissolve it in water to prepare a 70% m-xylylenediamine solution;

[0101] (2) taking 97.3 g of m-phenylenediamine solution, adding it dropwise to 365.5 g of adipic acid solution under stirring in a water bath at 80° C., during which an inert gas was introduced for protection, to obtain a carboxyl-terminated intermediate solution;

[0102] (3) 182.75 g of adipic acid solution was added dropwise to 194.6 g of m-xylylenediamine solution under stirring in a 50° C. water bath, with inert gas protection, to obtain an amine-terminated intermediate solution;

[0103] (4) adding the amine-terminated intermediate solution dropwise to the carboxyl-terminated intermediate solution under stirring at 80° C., and reacting completely to obtain a crude solution of nylon MXD6 salt. During this process, the reaction temperature is controlled, an inert gas is introduced for protection, and the pH value of the solution is tested. Finally, a trace amount of m-xylylenediamine is added to adjust the pH value to 7.0-7.5;

[0104] (5) The crude nylon MXD6 salt solution was cooled and crystallized, the cooled solution was filtered, and the filtered solid was dried in a vacuum drying oven at 70° C. for 24 h to obtain a dry nylon MXD6 salt solid.

[0105] The method for preparing nylon MXD6 from the above-mentioned nylon MXD6 salt solid comprises the following steps:

[0106] A: Dissolve nylon MXD6 salt solid in water to prepare 80wt% nylon MXD6 salt solution; put it into a reactor, evacuate and check the air tightness of the reactor, introduce N2, and repeat three times;

[0107] B: Turn on the stirring device, raise the temperature in the reactor to 220°C, react for 2 hours, and perform prepolymerization;

[0108] C: Continue to raise the temperature in the reactor to 260°C, while slowly releasing the pressure in the reactor to normal pressure, and keep the temperature at normal pressure for 5 hours;

[0109] D: Vacuum the reaction for 1 hour to obtain nylon MXD6, and then open the kettle to unload.

[0110] Example 5

[0111] The preparation method of nylon MXD6 salt specifically comprises the following steps:

[0112] (1) Weigh 219.3 g (1.50 mol) of adipic acid and dissolve it in water to prepare a 30% adipic acid solution; weigh 204.3 g (1.50 mol) of m-xylylenediamine and dissolve it in water to prepare a 70% m-xylylenediamine solution;

[0113] (2) taking 72.9 g of m-phenylenediamine solution, adding it dropwise to 411.25 g of adipic acid solution under stirring in a water bath at 80° C., during which an inert gas was introduced for protection, to obtain a carboxyl-terminated intermediate solution;

[0114] (3) 137.0 g of adipic acid solution was added dropwise to 219.0 g of m-xylylenediamine solution under stirring in a 50° C. water bath, with inert gas protection, to obtain an amine-terminated intermediate solution;

[0115] (4) adding the amine-terminated intermediate solution dropwise to the carboxyl-terminated intermediate solution under stirring at 80° C., and reacting completely to obtain a crude solution of nylon MXD6 salt. During this process, the reaction temperature is controlled, an inert gas is introduced for protection, and the pH value of the solution is tested. Finally, a trace amount of m-xylylenediamine is added to adjust the pH value to 7.0-7.5;

[0116] (5) The crude nylon MXD6 salt solution was cooled and crystallized, the cooled solution was filtered, and the filtered solid was dried in a vacuum drying oven at 70° C. for 24 h to obtain a dry nylon MXD6 salt solid.

[0117] The method for preparing nylon MXD6 from the above-mentioned nylon MXD6 salt solid comprises the following steps:

[0118] A: Dissolve nylon MXD6 salt solid in water to prepare 80wt% nylon MXD6 salt solution; put it into a reactor, evacuate and check the air tightness of the reactor, introduce N2, and repeat three times;

[0119] B: Turn on the stirring device, raise the temperature in the reactor to 230°C, react for 2 hours, and perform prepolymerization;

[0120] C: Continue to raise the temperature in the reactor to 260°C, while slowly releasing the pressure in the reactor to normal pressure, and keep the temperature at normal pressure for 1 hour;

[0121] D: Vacuum the reaction for 1 hour to obtain nylon MXD6, and then open the kettle to unload.

[0122] Example 6

[0123] The preparation method of nylon MXD6 salt specifically comprises the following steps:

[0124] (1) Weigh 219.3 g (1.50 mol) of adipic acid and dissolve it in water to prepare a 40% adipic acid solution; weigh 204.3 g (1.50 mol) of m-xylylenediamine and dissolve it in water to prepare a 70% m-xylylenediamine solution;

[0125] (2) 58.38 g of m-phenylenediamine solution was added dropwise to 438.6 g of adipic acid solution under stirring in a water bath at 80° C., with inert gas protection, to obtain a carboxyl-terminated intermediate solution;

[0126] (3) 109.65 g of adipic acid solution was added dropwise to 233.52 g of m-xylylenediamine solution under stirring in a 50° C. water bath, with inert gas protection, to obtain an amine-terminated intermediate solution;

[0127] (4) adding the amine-terminated intermediate solution dropwise to the carboxyl-terminated intermediate solution under stirring at 80° C., and reacting completely to obtain a crude solution of nylon MXD6 salt. During this process, the reaction temperature is controlled, an inert gas is introduced for protection, and the pH value of the solution is tested. Finally, a trace amount of m-xylylenediamine is added to adjust the pH value to 7.0-7.5;

[0128] (5) The crude nylon MXD6 salt solution was cooled and crystallized, the cooled solution was filtered, and the filtered solid was dried in a vacuum drying oven at 70° C. for 24 h to obtain a dry nylon MXD6 salt solid.

[0129] The method for preparing nylon MXD6 from the above-mentioned nylon MXD6 salt solid comprises the following steps:

[0130] A: Dissolve nylon MXD6 salt solid in water to prepare 80wt% nylon MXD6 salt solution; put it into a reactor, evacuate and check the air tightness of the reactor, introduce N2, and repeat three times;

[0131] B: Turn on the stirring device, raise the temperature in the reactor to 210°C, react for 2 hours, and perform prepolymerization;

[0132] C: Continue to raise the temperature in the reactor to 260°C, while slowly releasing the pressure in the reactor to normal pressure, and keep the temperature at normal pressure for 1 hour;

[0133] D: Vacuum the reaction for 1 hour to obtain nylon MXD6, and then open the kettle to unload.

[0134] Comparative Example 1

[0135] The preparation method of nylon MXD6 salt specifically comprises the following steps:

[0136] (1) Weigh 219.3 g (1.50 mol) of adipic acid and dissolve it in water to prepare a 30% adipic acid solution; weigh 204.3 g (1.50 mol) of m-xylylenediamine;

[0137] (2) heating the adipic acid solution to 80° C., stirring at a constant rate and maintaining nitrogen purge, slowly adding m-xylenediamine dropwise, maintaining the system temperature at 80-85° C., and using a precision acidity meter and a thermometer to monitor the pH and temperature changes of the reaction system during the addition process. Before each pH test, stop adding m-xylenediamine dropwise, wait until the system is stable, test the pH value again, and then continue adding dropwise, and repeat this process until pH = 7.1, which is the end point of the reaction, to obtain a crude solution of nylon MXD6 salt;

[0138] (3) cooling and crystallizing the crude nylon MXD6 salt solution, and filtering the cooled solution;

[0139] (4) Dry the filtered solid in a vacuum drying oven at 70° C. for 24 h to obtain a dry nylon MXD6 salt solid.

[0140] The method for preparing nylon MXD6 from the above-mentioned nylon MXD6 salt solid comprises the following steps:

[0141] A: Dissolve nylon MXD6 salt solid in water to prepare 80wt% nylon MXD6 salt solution; put it into a reactor, evacuate and check the air tightness of the reactor, introduce N2, and repeat three times;

[0142] B: Turn on the stirring device, raise the temperature in the reactor to 210°C, react for 2 hours, and perform prepolymerization;

[0143] C: Continue to raise the temperature in the reactor to 260°C, while slowly releasing the pressure in the reactor to normal pressure, and keep the temperature at normal pressure for 1 hour;

[0144] D: Vacuum the reaction for 1 hour to obtain nylon MXD6 salt, and then open the kettle to unload.

[0145] Comparative Example 2

[0146] The preparation method of nylon MXD6 salt specifically comprises the following steps:

[0147] (1) Weigh 219.3 g (1.50 mol) of adipic acid and dissolve it in water to prepare a 40% adipic acid solution; weigh 204.3 g (1.50 mol) of m-phenylenediamine;

[0148] (2) heating the adipic acid solution to 80° C., stirring at a constant rate and maintaining nitrogen purge, slowly adding m-xylenediamine dropwise, maintaining the system temperature at 80-85° C., and using a precision acidity meter and a thermometer to monitor the pH and temperature changes of the reaction system during the addition process. Before each pH test, stop adding m-xylenediamine dropwise, wait until the system is stable, test the pH value again, and then continue adding dropwise, and repeat this process until pH = 7.1, which is the end point of the reaction, to obtain a crude solution of nylon MXD6 salt;

[0149] (3) cooling and crystallizing the crude nylon MXD6 salt solution, and filtering the cooled solution;

[0150] (4) Dry the filtered solid in a vacuum drying oven at 70° C. for 24 h to obtain a dry nylon MXD6 salt solid.

[0151] The method for preparing nylon MXD6 from the above-mentioned nylon MXD6 salt solid comprises the following steps:

[0152] A: Dissolve nylon MXD6 salt solid in water to prepare 80wt% nylon MXD6 salt solution; put it into a reactor, evacuate and check the air tightness of the reactor, introduce N2, and repeat three times;

[0153] B: Turn on the stirring device, raise the temperature in the reactor to 210°C, react for 2 hours, and perform prepolymerization;

[0154] C: Continue to raise the temperature in the reactor to 260°C, while slowly releasing the pressure in the reactor to normal pressure, and keep the temperature at normal pressure for 1 hour;

[0155] D: Vacuum the reaction for 1 hour to obtain nylon MXD6 salt, and then open the kettle to unload.

[0156] Test example

[0157] The reaction yields of Examples 1 to 6 and Comparative Examples 1 to 2, as well as the prepared nylon MXD6 salt and nylon MXD6 were tested for performance indicators. The specific test indicators and methods are as follows:

[0158] 1. Yield of nylon MXD6 salt

[0159]

[0160] 2. UV index detection of nylon MXD6 salt

[0161] The UV index is measured according to the test method specified in standard SH / T 1498.7-1997. The UV index refers to the absorbance A at a wavelength of 279nm when the concentration of nylon MXD6 salt solution is 0.1% (m / V) and the thickness of the absorption cell is 1cm. UV index = A×10 -3 .

[0162] 3. Relative viscosity test of nylon MXD6

[0163] The test is carried out according to the test method specified in standard GB / T 12006.1-2009.

[0164] Table 1 Performance index measurement results of nylon MXD6 salt and nylon MXD6 in the embodiments and comparative examples

[0165]

[0166] From Table 1, it can be seen from the performance index data of Examples 1 to 6 and Comparative Examples 1 to 2 that the yield of nylon MXD6 in Examples 1 to 6 is significantly higher than that in Comparative Examples 1 to 2. The UV index of nylon MXD6 salt in Examples 1 to 6 is significantly lower than that in Comparative Examples 1 to 2, indicating that the nylon MXD6 salt obtained by the preparation method of nylon MXD6 salt of the present application has less impurities and high purity, and the yield of nylon MXD6 prepared therefrom is high, and the relative viscosity of nylon MXD6 prepared in Examples 1 to 6 of the present invention is significantly higher than that in Comparative Examples 1 to 2, and the performance is excellent.

[0167] The infrared spectrum of the nylon MXD6 salt prepared in Example 1 is as follows Figure 1 As shown, 1394cm -1 The peak at 1529 cm is the deformation vibration peak of methylene CH. -1 The peak at 698 cm is the asymmetric stretching vibration peak of C=C on the benzene ring. -1 and 784cm -1 The peak at 1394cm is the deformation vibration peak of CH on the benzene ring; -1 -NH3 +- The characteristic absorption peak at COO- proves that adipic acid reacts with m-phenylenediamine to form ammonium carboxylate salt, namely nylon MXD6 salt.

[0168] Thermogravimetric analysis (TG) of nylon MXD6 salt prepared in Example 1 is shown in FIG. Figure 2 As shown, it can be seen from the figure that the maximum decomposition rate temperature of nylon MXD6 salt is 211°C.

[0169] The differential scanning calorimetry curve (DSC curve) of the nylon MXD6 salt prepared in Example 1 is as follows: Figure 3 As shown, it can be seen that the melting point of nylon MXD6 salt is 200°C.

[0170] The infrared spectrum of nylon MXD6 prepared in Example 1 is as follows Figure 4 As shown, 3280cm -1 The peak at 3073 cm is the stretching vibration peak of the NH bond in the amide group. -1 The peak at 2927 cm is the CH stretching vibration peak of the benzene ring. -1 、2853cm -1 It is the methylene vibration absorption peak; 1632cm -1 The characteristic absorption peak of carbonyl in amide group belongs to amide band I; 1539cm -1 The absorption peak at 1264cm is formed by the superposition of CN stretching vibration and -CO-NH- deformation vibration in the amide group, which belongs to amide band II. -1 、1032cm -1is the absorption peak of the CH in-plane bending vibration of the benzene ring; compared to Figure 1 , nylon MXD6 salt 1394cm -1 -NH3 +- The COO-characteristic absorption peak disappeared, indicating that nylon MXD6 salt underwent a condensation polymerization reaction to generate an amide bond, and the product nylon MXD6 was obtained.

[0171] The TG graph of nylon MXD6 prepared in Example 1 is as follows: Figure 5 As shown, it can be seen from the figure that the maximum decomposition rate of nylon MXD6 is at 407℃.

[0172] The DSC curve of nylon MXD6 prepared in Example 1 is as follows: Figure 6 As shown, there is only one endothermic peak (exothermic peak) in both the heating curve and the cooling curve. Through analysis, it can be obtained that the melting point of nylon MXD6 is 237°C and the crystallization temperature is 149°C.

[0173] The X-ray diffraction (XRD) of nylon MXD6 prepared in Example 1 is as follows: Figure 7 As shown, it is consistent with the XRD spectrum characteristics of nylon MXD6.

[0174] The nylon MXD6 salt and nylon MXD6 prepared in Examples 2-6 can achieve technical effects substantially equivalent to those in Example 1.

[0175] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0176] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing nylon MXD6 salt, characterized in that: The following steps are involved: (1) dissolving adipic acid in water to prepare an adipic acid solution; Dissolving m-xylylenediamine in water to prepare a m-xylylenediamine solution; (2) taking a certain amount of the m-phenylenediamine solution, and adding it dropwise to a certain amount of the adipic acid solution under the protection of an inert gas and stirring in a water bath at 70° C. to 90° C. to obtain a carboxyl-terminated intermediate solution; (3) taking a certain amount of the adipic acid solution, and adding it dropwise to a certain amount of the m-xylylenediamine solution under inert gas protection and stirring in a water bath at 40° C. to 60° C. to obtain an amine-terminated intermediate solution; (4) under the protection of inert gas, under stirring at 60° C. to 80° C., the amino-terminated intermediate solution is added dropwise to the carboxyl-terminated intermediate solution, and the reaction is completed to obtain a crude solution of nylon MXD6 salt; The pH of the reaction solution is adjusted with the m-xylylenediamine to a pH of 7.0 to 7.5; (5) The crude nylon MXD6 salt solution is purified to obtain a nylon MXD6 salt solid.

2. The method for preparing nylon MXD6 salt according to claim 1, characterized in that: In step (1), the concentration of the adipic acid solution is 20-50 wt %, and the concentration of the m-xylylenediamine solution is 60-90 wt %.

3. The method for preparing nylon MXD6 salt according to claim 2, characterized in that: In step (1), the concentration of the adipic acid solution is 30-40 wt %, and the concentration of the m-xylylenediamine solution is 70-80 wt %.

4. The method for preparing nylon MXD6 salt according to claim 1, characterized in that: In step (2), the m-xylylenediamine solution and the adipic acid solution are weighed in a stoichiometric ratio of m-xylylenediamine to adipic acid of 1:(1-5); and / or In step (3), the m-xylylenediamine solution and the adipic acid solution are weighed in a stoichiometric ratio of m-xylylenediamine to adipic acid of (1-5):

1.

5. The method for preparing nylon MXD6 salt according to claim 4, characterized in that: In step (2), the m-xylylenediamine solution and the adipic acid solution are weighed in a stoichiometric ratio of m-xylylenediamine to adipic acid of 1:2; and / or In step (3), the m-xylylenediamine solution and the adipic acid solution are weighed in a stoichiometric ratio of m-xylylenediamine to adipic acid of 2:

1.

6. The method for preparing nylon MXD6 salt according to claim 1, characterized in that: The specific process of step (5) includes: cooling and crystallizing the crude nylon MXD6 salt solution, filtering the cooled solution, and vacuum drying the filtered solid to obtain the nylon MXD6 salt solid.

7. The method for preparing nylon MXD6 salt according to claim 6, characterized in that: The vacuum drying temperature is 70° C. to 90° C., and the drying time is 12 h to 24 h.

8. A method for preparing nylon MXD6 from nylon MXD6 salt prepared by the method for preparing nylon MXD6 salt according to any one of claims 1 to 7, characterized in that: The following steps are involved: A: dissolving the nylon MXD6 salt solid in water to prepare a nylon MXD6 salt solution; The nylon MXD6 salt solution is put into a reaction kettle, evacuated, and introduced with N2; B: Turn on the stirring device to increase the temperature in the reactor to carry out a prepolymerization reaction; C: Continue to increase the temperature in the reactor and release the pressure in the reactor to normal pressure to carry out polycondensation reaction; D: Vacuum and react for a certain period of time to obtain nylon MXD6.

9. The method for preparing nylon MXD6 as claimed in claim 8, characterized in that: In step A, the concentration of the nylon MXD6 salt solution is 50-80wt%; and / or In step B, the temperature in the reactor is 180° C. to 230° C., the pressure in the reactor is 1.2 MPa to 2.0 MPa, and the prepolymerization time is 0.5 h to 5 h; and / or In step C, the temperature in the reactor is 250°C to 270°C, and the polycondensation reaction time is 0.5h to 5h; and / or In step D, the reaction time after vacuuming is 0.5 h to 2 h.

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