A kind of nylon 46 and its preparation method and application

Abstract

The invention provides nylon 46 and a preparation method and application thereof, which relate to the technical field of polymer materials. The method comprises the following steps: adding butanediamine to a dicarboxylic acid solution to form a salt once, then adding butanediamine to form a salt twice, and then sequentially performing prepolymerization and solid phase polycondensation; wherein the solvent of the dicarboxylic acid solution comprises alcohol and water; the solid phase polycondensation is reacted in a gradient heating mode, the method is simple to operate, salt is prepared in a one-pot process under low temperature and high pressure, reasonable polymerization process parameters and flow are set, the time of solid phase polycondensation is controlled, and the temperature is increased in a gradient manner to obtain high-temperature nylon 46 which is white in color and has a high molecular weight, thereby solving the problems of high production cost, low molecular weight and poor color value of nylon 46 at present.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to nylon 46 and a preparation method and application thereof. Background Art

[0002] Nylon 46 is a new type of engineering plastic with excellent comprehensive performance. Its melting point is as high as 295℃ and it has excellent heat resistance. It is not only light in weight and high in strength, but also has many excellent properties such as wear resistance, radiation resistance, fatigue resistance, flame resistance, aging resistance, dimensional stability, excellent dielectric properties and chemical resistance.

[0003] However, the synthesis of nylon 46 is relatively difficult. When the reaction conditions deviate, it is easy to cause the degree of polymerization and molecular weight of the prepolymer to be low, which makes it difficult to increase the molecular weight of the final product.

[0004] Chinese invention patent application with publication number CN115850692A discloses a high temperature resistant nylon and its preparation method and application. It adopts a "one pot method" to prepare the high temperature resistant nylon, but the viscosity of the final product is not high, only about 2.

[0005] The Chinese invention patent application with publication number CN115819755A discloses a method for producing high-temperature nylon based on butanediamine, which uses butanediamine and an organic dibasic acid as raw materials, and sequentially undergoes steps such as salt formation, pre-condensation and solid phase post-condensation to obtain high-temperature nylon based on butanediamine, but the viscosity of the final product is not high, with the highest being only 3.35. The viscosity of the obtained product is not high, and the mechanical properties are not very good. In this invention, the nylon salt solution has a high moisture content (50%), and huge energy is required to remove the moisture in the later polymerization process, thereby promoting the smooth progress of the pre-polymerization reaction and increasing the investment cost.

[0006] The solid phase polycondensation process is very important for the molecular weight of nylon 46. At present, a large part of the solid phase polycondensation is carried out under a nitrogen atmosphere, and the temperature is directly raised to a higher temperature, which can easily cause the color of nylon 46 to change to brown. This limits the development of nylon 46 in products with higher color requirements.

[0007] In view of this, the present invention is proposed. Summary of the invention

[0008] One of the purposes of the present invention is to provide a method for preparing nylon 46, so as to at least solve one of the technical problems existing in the prior art. The method for preparing nylon 46 provided by the present invention is simple to operate, and adopts a solid phase polycondensation process of two salt formations, prepolymerization and gradient temperature increase to prepare nylon 46 with high molecular weight and good color value.

[0009] A second object of the present invention is to provide nylon 46 prepared by a nylon 46 preparation method.

[0010] The third object of the present invention is to provide a method for preparing nylon 46 or to use nylon 46 in preparing industrial products.

[0011] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0012] In a first aspect, the present invention provides a method for preparing nylon 46, comprising the following steps:

[0013] Adding butanediamine to the dicarboxylic acid solution to form a salt once, then adding butanediamine to form a salt twice, and then sequentially performing prepolymerization and solid phase polycondensation;

[0014] Wherein, the solvent of the dicarboxylic acid solution includes alcohol and water;

[0015] The solid phase polycondensation is carried out in a gradient temperature increase manner.

[0016] Furthermore, the preparation process of the dicarboxylic acid solution includes: mixing dicarboxylic acid, deionized water and alcohol to obtain the dicarboxylic acid solution;

[0017] Preferably, the mass ratio of the deionized water to the alcohol is 0.5 to 120, preferably 0.8 to 110;

[0018] Preferably, the temperature of the desalted water is 5°C to 20°C, preferably 5°C to 18°C;

[0019] Preferably, the alcohol includes at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol and isobutanol.

[0020] Furthermore, the primary salt formation comprises: adding diamine dropwise to the dicarboxylic acid solution, and then performing primary salt formation at a first pressure and a first temperature;

[0021] Preferably, the first pressure is 5MPa-10MPa, preferably 6MPa-9MPa, and the first temperature is 15°C-30°C, preferably 15°C-28°C;

[0022] Preferably, in the primary salt formation, the molar ratio of diaminobutane to dicarboxylic acid is 1.01 to 1.15, preferably 1.01 to 1.10;

[0023] Preferably, in the primary salt formation, the addition rate of diaminobutane is 1 to 3 wt% / min, preferably 1 to 2.5 wt% / min;

[0024] Preferably, the mass fraction of the nylon salt solution obtained after the primary salt formation is 10% to 50%, preferably 10% to 30%.

[0025] Furthermore, the secondary salt formation comprises: adding dibutyleneamine to the salt solution after the primary salt formation at normal pressure, and then performing secondary salt formation at a second pressure and a second temperature;

[0026] Preferably, the second pressure is 0.3 MPa to 0.8 MPa, preferably 0.5 to 0.7 MPa, and the second temperature is 50° C. to 100° C., preferably 50° C. to 70° C.;

[0027] Preferably, the amount of the additional butanediamine is 0.05 to 2 mol % of the amount of the dicarboxylic acid used, preferably 0.08 to 1.5 mol %.

[0028] Further, the prepolymerization includes: performing a precondensation reaction at a third pressure and a third temperature, followed by degassing and discharging in sequence to obtain a prepolymer material;

[0029] Preferably, the reaction temperature of the prepolymerization is 180°C to 220°C, preferably 190°C to 210°C, and the reaction pressure is 0.8MPa to 1.3MPa, preferably 1.0MPa to 1.2MPa;

[0030] Preferably, the reaction time of the prepolymerization is 10 min to 200 min, preferably 30-90 min.

[0031] Furthermore, the solid phase polycondensation comprises: sequentially performing polycondensation in a first temperature section, polycondensation in a second temperature section, and polycondensation in a third temperature section under a nitrogen and water vapor atmosphere;

[0032] Preferably, the polycondensation temperature in the first temperature section is 200-230°C;

[0033] Preferably, the polycondensation temperature in the second temperature section is 240-260°C;

[0034] Preferably, the polycondensation temperature in the third temperature section is 270-280°C;

[0035] Preferably, the total reaction time of the solid phase polycondensation is 4.0 to 17.0 h;

[0036] Preferably, when the temperature reaches 150°C to 200°C, water vapor is introduced, and the temperature is preferably 160°C to 180°C.

[0037] Further, the dicarboxylic acid includes at least one of an aliphatic dibasic acid and an aromatic dibasic acid containing 4 to 20 carbon atoms;

[0038] Preferably, the aliphatic dibasic acid containing 4 to 20 carbon atoms includes at least one of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, hexadecanedioic acid and octadecanedioic acid;

[0039] Preferably, the aromatic dibasic acid includes at least one of terephthalic acid and isophthalic acid.

[0040] Furthermore, after the secondary salt formation and before the prepolymerization, the temperature is adjusted to 120° C. to 150° C., preferably 130° C. to 140° C., to remove methanol and part of the water.

[0041] In a second aspect, the present invention provides nylon 46 prepared by the nylon 46 preparation method.

[0042] In a third aspect, the present invention provides a method for preparing nylon 46 or use of nylon 46 prepared by the method in preparing industrial products.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The nylon 46 preparation method provided by the invention adopts two salt-forming, prepolymerization and solid phase polycondensation processes. The solid phase polycondensation is carried out in a gradient temperature rising manner, which can improve the color of the product and obtain white nylon 46. Meanwhile, water and alcohol are used as composite solvents. The compounding of water and alcohol can adjust the polarity and dielectric constant of the solvent, thereby optimizing the solubility of the reactants, improving the stability of the amine salt and improving the product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0046] Figure 1 The figure is a schematic diagram of the process flow of nylon 46 and its preparation method described in Example 1 of the present invention. DETAILED DESCRIPTION

[0047] Unless otherwise defined herein, scientific and technical terms used in conjunction with the present invention shall have the meanings commonly understood by those of ordinary skill in the art. The meaning and scope of the terms should be clear, however, in the case of any potential ambiguity, the definitions provided herein take precedence over any dictionary or external definitions. In this application, unless otherwise stated, the use of "or" means "and / or". In addition, the use of the term "including" and other forms is non-limiting.

[0048] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] The first aspect of the present invention provides a method for preparing nylon 46, comprising the following steps:

[0050] Adding butanediamine to a dicarboxylic acid solution to form a salt once, then adding more butanediamine to form a salt twice, followed by sequential prepolymerization and solid phase polycondensation; wherein the solvent of the dicarboxylic acid solution includes alcohol and water; and the solid phase polycondensation is carried out by a gradient temperature increase method.

[0051] In the present invention, two salt-forming, prepolymerization and solid-phase polycondensation processes are adopted, and the solid-phase polycondensation is carried out in a gradient temperature increase mode, which can improve the color of the product and obtain white nylon 46. At the same time, water and alcohol are used as composite solvents, and the compounding of water and alcohol can adjust the polarity and dielectric constant of the solvent, thereby optimizing the solubility of the reactants, improving the stability of the amine salt, and improving the product quality.

[0052] Furthermore, the preparation method of nylon 46 of the present invention simplifies the preparation process of nylon salt and reduces investment cost and equipment maintenance cost. The present invention prepares salt by a one-pot method under low temperature and high pressure, and obtains nylon 46 with high molecular weight and good color value by optimizing the process parameters of prepolymerization and solid phase polycondensation.

[0053] In some preferred embodiments, the preparation process of the dicarboxylic acid solution comprises: mixing dicarboxylic acid, deionized water and alcohol to obtain the dicarboxylic acid solution;

[0054] In the present invention, the preparation process of the dicarboxylic acid solution is preferably: dissolving the dicarboxylic acid in deionized water, and then adding alcohol. Since methanol has good solubility in water, it helps to ensure that the two solvents are fully mixed. Therefore, according to the order of adding the above solvents, the operation is more convenient.

[0055] Preferably, the mass ratio of the deionized water to the alcohol is 0.5 to 120, for example, 0.6, 10, 30, 60, 90, 120, etc.; preferably 0.8 to 110, for example, 0.8, 90, 100, 110, etc.;

[0056] Preferably, the alcohol includes at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol and isobutanol.

[0057] In the present invention, water and methanol are preferably used as solvents. The compounding of water and methanol can adjust the polarity and dielectric constant of the solvent at a certain ratio, thereby optimizing the solubility of the reactants and improving the stability of the amine salt.

[0058] Preferably, the temperature of the desalted water is 5°C to 20°C, for example, 5°C, 10°C, 15°C, 20°C, etc.; preferably, it is 5°C to 18°C, for example, 5°C, 10°C, 15, 18°C.

[0059] In some preferred embodiments, the primary salt formation comprises: adding dibutylene diamine dropwise to a dicarboxylic acid solution, and then performing a primary salt formation at a first pressure and a first temperature;

[0060] Preferably, the first pressure is 5MPa-10MPa, for example, it can be 5MPa, 6MPa, 7MPa, 8MPa, 9MPa, 10MPa, etc., and it is preferred to use nitrogen to control the pressure at 6MPa-9MPa, for example, it can be 6MPa, 6.5MPa, 7MPa, 7.5MPa, 8MPa, 8.5MPa, 9MPa, etc. The first temperature is 15℃~30℃, for example, it can be 15℃, 20℃, 25℃, 30℃, etc.; preferably, the temperature in the reactor is controlled at 15℃~28℃, for example, it can be 15℃, 16℃, 17℃, 18℃, 19℃, 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 28℃, etc.

[0061] In the present invention, low temperature and high pressure salt preparation is adopted in the preparation of nylon salt solution. Under low temperature, the volatilization and cyclization of diaminodiamine are greatly reduced, and under high pressure, the molecular collision frequency is increased to promote the reaction.

[0062] Preferably, in the primary salt formation, the molar ratio of diaminobutane to dicarboxylic acid is 1.01 to 1.15, for example, 1.01, 1.05, 1.10, 1.15, etc.; preferably 1.01 to 1.10, for example, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, etc.;

[0063] Preferably, in the primary salt formation, the addition rate of diaminobutane is 1-3 wt% / min, for example, 1 wt% / min, 1.5 wt% / min, 2 wt% / min, 2.5 wt% / min, 3 wt% / min, etc., preferably 1-2.5 wt% / min, for example, 1 wt% / min, 1.5 wt% / min, 2 wt% / min, 2.5 wt% / min, etc.;

[0064] In the present invention, dibutylene diamine needs to be added slowly. If dibutylene diamine is added to the dicarboxylic acid solution at one time, heat will be released violently and the solution will easily splash out.

[0065] Preferably, the mass fraction of the nylon salt solution obtained after the primary salt formation is 10% to 50%, for example, it can be 10%, 20%, 30%, 40%, 50%, etc.; preferably, it is 10% to 30%, for example, it can be 10%, 15%, 20%, 25%, 30%, etc.

[0066] In some preferred embodiments, the secondary salt formation comprises: adding dibutyleneamine to the salt solution after the primary salt formation at normal pressure, and then performing secondary salt formation at a second pressure and a second temperature;

[0067] Preferably, the second pressure is 0.3MPa-0.8MPa, for example, 0.3MPa, 0.4MPa, 0.5MPa, 0.6MPa, 0.7MPa, 0.8MPa, etc.; preferably 0.5-0.7MPa, for example, 0.5MPa, 0.6MPa, 0.7MPa, etc.; the second temperature is 50℃-100℃, for example, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, etc.; preferably 50℃-70℃, for example, 50℃, 55℃, 60℃, 65℃, 70℃, etc.;

[0068] Preferably, the amount of the added butanediamine is 0.05-2 mol.% of the amount of dicarboxylic acid used, for example, it can be 0.05 mol.%, 0.1 mol.%, 1 mol.%, 2 mol.%, etc.; the excess ratio of the added butanediamine is preferably 0.08-1.5 mol.%, for example, it can be 0.08 mol.%, 0.1 mol.%, 0.2 mol.%, 0.3 mol.%, 0.4 mol.%, 0.5 mol.%, 0.6 mol.%, 0.7 mol.%, 0.9 mol.%, 1.0 mol.%, 1.1 mol.%, 1.2 mol.%, 1.3 mol.%, 1.4 mol.%, 1.5 mol.%, etc.

[0069] It should be noted that mol.% is a commonly used unit in the art, which represents molar percentage. For example, the amount of butanediamine added is 0.1 mol.%, which means that 0.1 mol of butanediamine needs to be additionally added for every 100 mol of dicarboxylic acid.

[0070] In the present invention, the water content of the salt solution is relatively low, and under the low temperature and high pressure conditions in the primary salt formation, the volatilization and cyclization of diethylenediamine are greatly reduced, while the reaction is promoted. The secondary salt formation reaction is combined to ensure that the nylon salt and the added diethylenediamine are fully dissolved in water. Therefore, the amount of diethylenediamine that needs to be added in the secondary salt formation stage before the prepolymerization stage is very small, thereby greatly reducing the production cost.

[0071] In some preferred embodiments, the prepolymerization includes: performing a precondensation reaction at a third pressure and a third temperature, followed by degassing and discharging in sequence to obtain a prepolymer material;

[0072] In the present invention, the discharging method can be pelletizing to obtain prepolymer pellets or spraying, and preferably a nozzle spraying method is used to obtain prepolymer powder.

[0073] Preferably, the reaction temperature of the prepolymerization is 180°C to 220°C, for example, 180°C, 200°C, 220°C, etc.; preferably 190°C to 210°C, for example, 190°C, 200°C, 205°C, 210°C, etc.; the reaction pressure is 0.8MPa to 1.3MPa, for example, 0.8MPa, 1.0MPa, 1.3MPa, etc.; preferably 1.0MPa to 1.2MPa, for example, 1.0MPa, 1.1MPa, 1.2MPa, etc.;

[0074] Preferably, the reaction time of the prepolymerization is 10 min to 200 min, for example, 10 min, 50 min, 100 min, 150 min, 200 min, etc., preferably 30-90 min, for example, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, etc.

[0075] In the present invention, the reactor is vented to remove excess water, so that the prepolymerization reaction proceeds in a positive direction and oligomers are gradually formed.

[0076] In some preferred embodiments, the solid phase polycondensation comprises: sequentially performing polycondensation in a first temperature section, polycondensation in a second temperature section, and polycondensation in a third temperature section under a nitrogen and water vapor atmosphere;

[0077] In the present invention, a three-stage solid phase polycondensation is adopted, which are respectively a first temperature stage polycondensation (low temperature stage polycondensation), a second temperature stage polycondensation (medium temperature stage polycondensation) and a third temperature stage polycondensation (high temperature stage polycondensation). In a nitrogen-water vapor atmosphere, the temperature is increased gradually and the time is controlled to obtain high-temperature nylon 46 with white color and high molecular weight.

[0078] Furthermore, the viscosity, chromaticity and other indicators of high molecular weight nylon 46 prepared by the method of the present invention are significantly improved, and the viscosity can be controlled and the molecular weight can be very high. The method can improve reaction efficiency and product quality and reduce environmental pollution.

[0079] Preferably, the polycondensation temperature in the first temperature section is 200-230°C, for example, 200°C, 210°C, 220°C, 230°C, etc.;

[0080] Preferably, the polycondensation temperature in the second temperature section is 240-260°C, for example, 240°C, 250°C, 260°C, etc.;

[0081] Preferably, the polycondensation temperature in the third temperature section is 270-280°C, for example, 270°C, 275°C, 280°C, etc.;

[0082] Preferably, the total reaction time of the solid phase polycondensation is 4.0 to 17.0 h, for example, 4.0 h, 5.0 h, 6.0 h, 7.0 h, 8.0 h, 9.0 h, 10.0 h, 11.0 h, 12.0 h, 13.0 h, 14.0 h, 15.0 h, 16.0 h, 17.0 h, etc.;

[0083] Preferably, when the temperature reaches 150°C to 200°C, such as 150°C, 180°C, 200°C, etc., water vapor is introduced and the temperature is preferably 160°C to 180°C, such as 160°C, 170°C, 180°C, etc.

[0084] In the present invention, by controlling the amine-acid ratio of the raw materials during salt formation, the prepolymerization reaction temperature, pressure and specific solid phase polycondensation, the residence time can be significantly reduced and the polymerization efficiency can be improved.

[0085] In some preferred embodiments, the dicarboxylic acid comprises at least one of an aliphatic dibasic acid and an aromatic dibasic acid containing 4 to 20 carbon atoms;

[0086] Preferably, the aliphatic dibasic acid containing 4 to 20 carbon atoms includes at least one of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, hexadecanedioic acid and octadecanedioic acid;

[0087] Preferably, the aromatic dibasic acid includes at least one of terephthalic acid and isophthalic acid.

[0088] In some preferred embodiments, after the secondary salt formation and before the prepolymerization, the temperature is adjusted to 120°C to 150°C, for example, 120°C, 130°C, 140°C, 150°C, etc., preferably 130°C to 140°C, for example, 130°C, 135°C, 140°C, etc., to remove methanol and part of the water.

[0089] The method for preparing nylon 46 provided by the present invention preferably comprises the following steps:

[0090] A1. Preparation of nylon salt: The molar ratio of diaminobutane to dicarboxylic acid is 1.01 to 1.15. The dicarboxylic acid powder is dissolved in low-temperature deionized water (5°C to 20°C), and then alcohol is added. The mass ratio of water to alcohol is 0.5 to 120. Then, liquid diaminobutane is slowly added dropwise at a rate of 1 to 3 wt% / min. Nitrogen is pressurized and the pressure is controlled at 5 MPa to 10 MPa. The temperature in the reactor is controlled at 15°C to 30°C. A salt-forming reaction is carried out and stabilized for a period of time to form a salt solution with a mass fraction of 10% to 50%.

[0091] A2. Prepolymerization: Slowly release the pressure to normal pressure, and the excess ratio of the added diaminodiamine is 0.05-2 mol.% (relative to the content of dicarboxylic acid added in step A1). At a temperature of 50°C to 100°C, pressurize with nitrogen, and stabilize the pressure at 0.3MPa to 0.8MPa for a period of time. Then gradually increase the temperature to 120°C to 150°C, open the vent valve, and stabilize for a period of time to remove excess methanol and a small amount of water. Then heat up for pre-condensation reaction, and the final temperature is controlled at 180°C to 220°C, and the pressure is controlled at 0.8MPa to 1.3MPa. While removing water, the reaction proceeds forward and gradually forms oligomers. The reaction time (i.e., the degassing time) is 10min to 200min. After cooling and pelletizing, prepolymer powder or pellets are obtained, or prepolymer powder is obtained by spraying with a nozzle.

[0092] A3. Solid phase polycondensation: Put the prepolymer material into a vacuum drum, in a nitrogen-water vapor atmosphere, introduce water vapor when the temperature rises to 150℃~200℃, and turn on the vacuum pump. Perform three-stage solid phase polycondensation to finally obtain a high molecular weight nylon product.

[0093] The preparation method of nylon 46 provided by the invention is a preparation method of nylon 46 with high molecular weight. The operation is simple. By adopting the method of the invention, salt is prepared by a one-pot method under low temperature and high pressure, reasonable polymerization process parameters and processes are set, the time of solid phase polycondensation is controlled, and the temperature is increased gradually to obtain high-temperature nylon 46 with white color and high molecular weight, thereby solving the problems of high production cost, low molecular weight and poor color value of nylon 46 at the current stage.

[0094] The second aspect of the present invention provides nylon 46 prepared by the nylon 46 preparation method.

[0095] The third aspect of the present invention provides a method for preparing nylon 46 or the use of nylon 46 prepared by the method in preparing industrial products.

[0096] The preparation method of nylon 46 of the present invention is simple to operate, high in efficiency, low in pollution, energy-saving, high in yield, and conducive to industrial production. The product has broad application prospects in the fields of machinery, automobiles, electrical appliances, and the like. For example, in the machinery industry, gears, bearings, seals, and gaskets can be made; in the automobile industry, engine parts, oil pump housings, and intake manifolds can be made; in the electrical field, switches, sockets, and motor insulation materials can be made.

[0097] The present invention is further described below by way of examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or directly purchased from the market.

[0098] Example 1

[0099] like Figure 1 As shown, this embodiment provides a method for preparing nylon 46, comprising the following steps:

[0100] A1. Preparation of nylon salt: 10 mol of adipic acid powder was added into a reactor, followed by 15°C low-temperature deionized water, followed by methanol, with the mass ratio of water to methanol being 1, and then 10.2 mol of liquid diaminobutane was slowly added dropwise at a rate of 2 wt% / min, and then nitrogen was added to pressurize the reactor at 8 MPa, and the temperature in the reactor was controlled at 25°C and stabilized for 90 min to form a salt solution with a mass fraction of 20%.

[0101] A2. Prepolymerization: Slowly reduce the pressure to normal pressure, then add 0.1 mol.% of diaminodiamine (relative to the content of dicarboxylic acid added in step A1). At 55°C, pressurize with nitrogen and perform secondary salt-forming reaction at 0.7 MPa. Then gradually increase the temperature to 135°C, open the vent valve, stabilize for 15 minutes, then gradually increase the temperature to perform pre-condensation reaction, and finally control the temperature at 200°C, the pressure at 1.1 MPa, the venting time (i.e., the reaction time) at 80 minutes, and use a nozzle spraying method to obtain prepolymer powder.

[0102] A3. Solid phase polycondensation: Put the prepolymer powder into a vacuum drum, introduce nitrogen, and control the flow rate at 4L / min. Then turn on the vacuum pump, and introduce water vapor when the temperature reaches 170°C, and control the flow rate at 1L / min. The reaction temperature is controlled at 225°C, and the residence time is controlled at 1.0-1.5h under stirring at 50rpm. Subsequently, the reaction temperature is controlled at 255°C, and the residence time is controlled at 1.0-1.5h. Finally, the reaction temperature is controlled at 275°C, and the residence time is controlled at 2h. After the reaction is completed, stop the introduction of water, wait until the temperature drops to room temperature, turn off the instrument, and discharge the material.

[0103] Example 2

[0104] This embodiment provides a method for preparing nylon 46, comprising the following steps:

[0105] A1. Preparation of nylon salt: 10 mol of adipic acid powder was added into a reactor, followed by 18°C ​​low-temperature deionized water, followed by methanol, with the mass ratio of water to methanol being 0.8, and then 10.15 mol of liquid diaminobutane was slowly added dropwise at a rate of 2.5 wt% / min, and then nitrogen was added to pressurize the reactor at 6 MPa, and the temperature in the reactor was controlled at 28°C, and stabilized for 90 minutes to form a salt solution with a mass fraction of 15%.

[0106] A2. Prepolymerization: Slowly reduce the pressure to normal pressure, then add 1.5 mol.% of diaminodiamine (relative to the content of dicarboxylic acid added in step A1). At 53°C, pressurize with nitrogen and perform secondary salt-forming reaction at 0.7 MPa. Then gradually increase the temperature to 130°C, open the vent valve, stabilize for 15 minutes, then gradually increase the temperature to perform pre-condensation reaction, and finally control the temperature at 190°C, the pressure at 1.2 MPa, the venting time at 30 minutes, and use a nozzle spraying method to obtain prepolymer powder.

[0107] A3. Solid phase polycondensation: Put the prepolymer powder into a vacuum drum, introduce nitrogen, and control the flow rate at 4L / min. Then turn on the vacuum pump, and introduce water vapor when the temperature reaches 180°C, and control the flow rate at 1L / min. The reaction temperature is controlled at 200°C, and the residence time is controlled at 1.0-1.5h under stirring at 50rpm. Subsequently, the reaction temperature is controlled at 260°C, and the residence time is controlled at 1.0-1.5h. Finally, the reaction temperature is controlled at 270°C, and the residence time is controlled at 2h. After the reaction is completed, stop the introduction of water, wait for the temperature to drop to room temperature, turn off the instrument, and discharge the material.

[0108] Example 3

[0109] This embodiment provides a method for preparing nylon 46, comprising the following steps:

[0110] A1. Preparation of nylon salt: 10 mol of adipic acid powder was added into a reactor, followed by 10°C low-temperature deionized water, followed by methanol, with the mass ratio of water to methanol being 1:10, and then 11 mol of liquid diaminobutane was slowly added dropwise at a rate of 1.5 wt% / min, followed by nitrogen pressurization at 9 MPa, and the temperature in the reactor was controlled at 20°C, and stabilized for 90 min to form a salt solution with a mass fraction of 30%.

[0111] A2. Prepolymerization: Slowly reduce the pressure to normal pressure, then add 0.08 mol.% of diaminodiamine (relative to the content of dicarboxylic acid added in step A1). At 70°C, pressurize with nitrogen and perform secondary salt-forming reaction at 0.5 MPa. Then gradually increase the temperature to 140°C, open the vent valve, stabilize for 15 minutes, then gradually increase the temperature to perform pre-condensation reaction, and finally control the temperature at 210°C, the pressure at 1.0 MPa, the venting time at 90 minutes, and use a nozzle spraying method to obtain prepolymer powder.

[0112] A3. Solid phase polycondensation: Put the prepolymer powder into a vacuum drum, introduce nitrogen, and control the flow rate at 4L / min. Then turn on the vacuum pump, and introduce water vapor when the temperature reaches 160°C, and control the flow rate at 1L / min. The reaction temperature is controlled at 230°C, and the residence time is controlled at 1.0-1.5h under stirring at 50rpm. Subsequently, the reaction temperature is controlled at 240°C, and the residence time is controlled at 1.0-1.5h. Finally, the reaction temperature is controlled at 280°C, and the residence time is controlled at 2h. After the reaction is completed, stop the introduction of water, wait for the temperature to drop to room temperature, turn off the instrument, and discharge the material.

[0113] Example 4

[0114] This embodiment provides a method for preparing nylon 46, comprising the following steps:

[0115] A1. Preparation of nylon salt: 10 mol of adipic acid powder was added into a reactor, followed by 20°C low-temperature deionized water, followed by methanol, with the mass ratio of water to methanol being 0.5, and then 10.1 mol of liquid butanediamine was slowly added dropwise at a rate of 3 wt% / min, and then nitrogen was added to pressurize the reactor at 5 MPa, and the temperature in the reactor was controlled at 30°C and stabilized for 90 minutes to form a salt solution with a mass fraction of 10%.

[0116] A2. Prepolymerization: Slowly reduce the pressure to normal pressure, then add 2 mol.% of diaminodiamine (relative to the content of dicarboxylic acid added in step A1). At 50°C, pressurize with nitrogen and perform secondary salt-forming reaction at 0.8 MPa. Then gradually increase the temperature to 120°C, open the vent valve, stabilize for 15 minutes, then gradually increase the temperature to perform pre-condensation reaction, and finally control the temperature at 220°C, the pressure at 0.8 MPa, the venting time at 200 minutes, and use a nozzle spraying method to obtain prepolymer powder.

[0117] A3. Solid phase polycondensation: Put the prepolymer powder into a vacuum drum, introduce nitrogen, and control the flow rate at 4L / min. Then turn on the vacuum pump, and introduce water vapor when the temperature reaches 150℃, and control the flow rate at 1L / min. The reaction temperature is controlled at 230℃, and the residence time is controlled at 1.0-1.5h under stirring at 50rpm. Subsequently, the reaction temperature is controlled at 240℃, and the residence time is controlled at 1.0-1.5h. Finally, the reaction temperature is controlled at 280℃, and the residence time is controlled at 2h. After the reaction is completed, stop the introduction of water, wait for the temperature to drop to room temperature, turn off the instrument, and discharge the material.

[0118] Example 5

[0119] This embodiment provides a method for preparing nylon 46, comprising the following steps:

[0120] A1. Preparation of nylon salt: 10 mol of adipic acid powder was added into a reactor, followed by 5°C low-temperature deionized water, followed by methanol, with the mass ratio of water to methanol being 120, and then 11.5 mol of liquid diaminobutane was slowly added dropwise at a rate of 1 wt% / min, followed by nitrogen pressurization at 10 MPa, and the temperature in the reactor was controlled at 15°C, and stabilized for 90 min to form a salt solution with a mass fraction of 50%.

[0121] A2. Prepolymerization: Slowly reduce the pressure to normal pressure, then add 0.05 mol.% of diaminodiamine (relative to the content of dicarboxylic acid added in step A1). At 100°C, pressurize with nitrogen and perform secondary salt-forming reaction at 0.3 MPa. Then gradually increase the temperature to 150°C, open the vent valve, stabilize for 15 minutes, then gradually increase the temperature to perform pre-condensation reaction, and finally control the temperature at 180°C, the pressure at 1.3 MPa, the venting time at 10 minutes, and use a nozzle spraying method to obtain prepolymer powder.

[0122] A3. Solid phase polycondensation: Put the prepolymer powder into a vacuum drum, introduce nitrogen, and control the flow rate at 4L / min. Then turn on the vacuum pump, and introduce water vapor when the temperature reaches 200℃, and control the flow rate at 1L / min. The reaction temperature is controlled at 200℃, and the residence time is controlled at 1.0-1.5h under stirring at 50rpm. Subsequently, the reaction temperature is controlled at 260℃, and the residence time is controlled at 1.0-1.5h. Finally, the reaction temperature is controlled at 270℃, and the residence time is controlled at 2h. After the reaction is completed, stop the introduction of water, wait for the temperature to drop to room temperature, turn off the instrument, and discharge the material.

[0123] Example 6

[0124] This embodiment provides a method for preparing nylon 46, which is different from Embodiment 1 in that:

[0125] In step A1, 11.6 mol of liquid butanediamine was added dropwise, and the remaining steps were the same as those in Example 1.

[0126] Example 7

[0127] This embodiment provides a method for preparing nylon 46, which is different from Embodiment 1 in that:

[0128] In step A3, the reaction temperature is controlled at 225°C at the beginning, and the residence time is controlled at 1.0 to 1.5 hours under stirring at 50 rpm. Finally, the reaction temperature is controlled at 275°C, and the residence time is controlled at 3 to 4 hours. After the reaction is completed, the water is stopped, the temperature is lowered to room temperature, the instrument is turned off, and the material is discharged; the remaining steps are the same as those in Example 1.

[0129] Example 8

[0130] This embodiment provides a method for preparing nylon 46, which is different from Embodiment 1 in that:

[0131] In step A3, the reaction temperature is controlled at 225°C at the beginning, and the residence time is controlled at 1.0 to 1.5 h under stirring at 50 rpm. Subsequently, the reaction temperature is controlled at 255°C, and the residence time is controlled at 1.0 to 1.5 h. Finally, the reaction temperature is controlled at 275°C, and the residence time is controlled at 4 h. After the reaction is completed, the water is stopped, the temperature drops to room temperature, the instrument is turned off, and the material is discharged; the remaining steps are consistent with Example 1.

[0132] Example 9

[0133] This embodiment provides a method for preparing nylon 46, which is different from Embodiment 1 in that:

[0134] In step A3, the reaction temperature is controlled at 225°C at the beginning, and the residence time is controlled at 1.0 to 1.5 h under stirring at 50 rpm. Subsequently, the reaction temperature is controlled at 255°C, and the residence time is controlled at 1.0 to 1.5 h. Finally, the reaction temperature is controlled at 275°C, and the residence time is controlled at 6 h. After the reaction is completed, the water is stopped, the temperature drops to room temperature, the instrument is turned off, and the material is discharged; the remaining steps are consistent with Example 1.

[0135] Example 10

[0136] This embodiment provides a method for preparing nylon 46, which is different from Embodiment 1 in that:

[0137] In step A2, the excess ratio of the added butanediamine is 2.5 mol% (relative to the content of the dicarboxylic acid added in step A1); the remaining steps are consistent with Example 1.

[0138] Embodiment 11

[0139] This embodiment provides a method for preparing nylon 46, which is different from Embodiment 1 in that:

[0140] In step A1, the reaction pressure is controlled at 4.5 MPa; the remaining steps are consistent with Example 1.

[0141] Example 12

[0142] This embodiment provides a method for preparing nylon 46, which is different from Embodiment 1 in that:

[0143] In step A1, the temperature in the reactor was controlled at 14° C.; the remaining steps were the same as those in Example 1.

[0144] Embodiment 13

[0145] This embodiment provides a method for preparing nylon 46, which is different from Embodiment 1 in that:

[0146] In step A1, the mass ratio of water to methanol is 0.4; the remaining steps are consistent with Example 1.

[0147] Embodiment 14

[0148] This embodiment provides a method for preparing nylon 46, which is different from Embodiment 1 in that:

[0149] In step A1, the mass ratio of water to methanol is 130; the remaining steps are consistent with Example 1.

[0150] Embodiment 15

[0151] This embodiment provides a method for preparing nylon 46, which is different from Embodiment 1 in that:

[0152] In step A1, the raw material dicarboxylic acid is terephthalic acid, and the solvent is n-butanol and deionized water;

[0153] The remaining steps are consistent with Example 1.

[0154] Example 16

[0155] This embodiment provides a method for preparing nylon 46, which is different from that of embodiment 1 in that: in step A3, water vapor is not introduced;

[0156] The remaining steps are consistent with Example 1.

[0157] Comparative Example 1

[0158] This comparative example provides a method for preparing nylon 46, which differs from Example 1 in that:

[0159] In step A1, the temperature in the reactor is controlled at 75° C. under normal pressure;

[0160] In step A2, the pressure is slowly reduced to normal pressure, and then 0.1 mol.% of diaminobutane is added without secondary salt formation, and then a prepolymerization reaction is carried out;

[0161] The remaining steps are consistent with Example 1.

[0162] Comparative Example 2

[0163] This comparative example provides a method for preparing nylon 46, which differs from Example 1 in that:

[0164] In step A2, the pressure is slowly reduced to normal pressure, and then 0.1 mol% of diaminobutane is added without secondary salt formation, and the temperature is directly raised to carry out prepolymerization reaction; the remaining steps are consistent with Example 1.

[0165] Comparative Example 3

[0166] This comparative example provides a method for preparing nylon 46, which differs from Example 1 in that:

[0167] In step A3, the reaction temperature is controlled at 275°C at the beginning, and the residence time is controlled at 4 to 5 hours under stirring at 50 rpm. After the reaction is completed, the water is stopped, the temperature is lowered to room temperature, the instrument is turned off, and the material is discharged; the remaining steps are the same as those in Example 1.

[0168] Comparative Example 4

[0169] This comparative example provides a method for preparing nylon 46, which differs from Example 1 in that:

[0170] In step A3, the reaction temperature is controlled at 255°C, and the residence time is controlled at 4 to 5 hours under stirring at 50 rpm. After the reaction is completed, the water is stopped, the temperature is lowered to room temperature, the instrument is turned off, and the material is discharged; the remaining steps are the same as in Example 1.

[0171] Comparative Example 5

[0172] This comparative example provides a method for preparing nylon 46, which differs from Example 1 in that:

[0173] In step A3, the reaction temperature is controlled at 275°C, and the residence time is controlled at 16.0-17.0 hours under stirring at 50 rpm. After the reaction is completed, the water is stopped, the temperature is lowered to room temperature, the instrument is turned off, and the material is discharged; the remaining steps are the same as in Example 1.

[0174] Comparative Example 6

[0175] This comparative example provides a method for preparing nylon 46, which differs from Example 1 in that:

[0176] In step A1, a single solvent (deionized water) is used; the remaining steps are consistent with Example 1.

[0177] Comparative Example 7

[0178] This comparative example provides a method for preparing nylon 46, which differs from Example 1 in that:

[0179] In step A1, a single solvent (methanol) is used;

[0180] In order to remove methanol later, additional steps must be added: In the prepolymerization stage: gradually increase the temperature to 135°C, open the vent valve, and stabilize for 60 minutes.

[0181] The remaining steps are consistent with Example 1.

[0182] Test samples: Nylon 46 prepared in Examples 1-16 and Nylon 46 prepared in Comparative Examples 1-7 were used as samples for testing.

[0183] Test method: The nylon 46 prepared in Examples 1-16 and the nylon 46 prepared in Comparative Examples 1-7 were used as samples, and infrared and nuclear magnetic resonance tests proved that they were all nylon 46. The relative viscosity test method is the sulfuric acid method: 0.125g of the sample is dissolved in 25mL of 96% concentrated sulfuric acid, and the flow-through time t of the sample is measured by an Ubbelohde viscometer in a constant temperature water bath at 25°C. The flow-through time of the pure solvent is t0, and the ratio of t to t0 is the relative viscosity η.

[0184] Table 1 shows the relevant process parameters of Examples 1-16 and Comparative Examples 1-7.

[0185] Table 1

[0186]

[0187]

[0188] It can be seen from the data results in Table 1 that the embodiment of the present invention can produce high-temperature nylon 46 with white color and high molecular weight by preparing salt through a one-pot process at low temperature and high pressure and setting reasonable polymerization process parameters and processes.

[0189] It can be seen from the data of Example 1 and Example 6 that when the polymerization conditions are the same, the amount of diaminobutane used during salt formation has a greater influence on the polymer viscosity. When the amount of diaminobutane added is too much, the amino acid molar ratio is high, resulting in too much amine end-capping in the polymer, resulting in a low molecular weight of the product after solid phase polycondensation.

[0190] It can be seen from the data of Examples 1 and 7 that when the solid phase polycondensation time is the same, if there is no medium temperature polycondensation stage, it will hinder the increase of polymer molecular weight; it may be that the gradient temperature increase is more conducive to the contact and discharge of water vapor and materials.

[0191] It can be seen from the data of Example 1, Example 7, Example 8 and Example 9 that the gradient temperature increase process will have a positive effect on the viscosity of the product. At the same time, by comparing Example 1, Example 8 and Example 9, it can be seen that when the solid phase polycondensation time is prolonged, the polymer molecular weight will increase, so the polymer molecular weight can be adjusted by controlling the solid phase polycondensation time; although the products of Examples 1 and 9 are products that meet the standard requirements, compared with Example 9, the viscosity of the product of Example 1 is better, because if the solid phase polycondensation time is too long, the molecular weight of PA46 will be too large, which is not conducive to the processing of nylon.

[0192] It can be seen from the data of Examples 1 and 10 that when an excessive amount of butanediamine is added, the viscosity is affected. Since too much butanediamine is added, most of the butanediamine will not participate in the reaction, and the excess butanediamine will undergo side reactions such as cyclodeamination, resulting in a low molecular weight and affecting the viscosity of the product.

[0193] The preparation conditions of Example 1 and Example 16 are the same, except that no water vapor is introduced. It is found that the color of the nylon turns yellow significantly, indicating that water vapor can effectively control the side reactions during the solid phase polycondensation reaction.

[0194] It can be seen from Examples 11-14 that by selecting a specific parameter range, high-temperature nylon 46 with a high molecular weight can be obtained by a one-pot salt production process at low temperature and high pressure.

[0195] It can be seen from the data of Example 1 and Comparative Example 1 that the present invention is different from the conventional nylon 46 polymerization method. When the amount of dibutylene oxide added is small, dibutylene oxide volatilizes more during the salt formation of conventional nylon 46 at 75° C., resulting in a low amine-acid molar ratio in the system, and ultimately a low molecular weight of the polymer. This proves that the low-temperature and high-pressure preparation of nylon salt in the present invention effectively alleviates the volatilization of dibutylene oxide and ensures the amine-acid ratio in the system.

[0196] It can be seen from the data of Example 1 and Comparative Example 2 that when the salt-forming conditions are the same, if the secondary salt-forming reaction is not carried out at 55° C. and 0.7 MPa in the prepolymerization stage, butanediamine is directly cyclized and the amine-acid molar ratio deviates.

[0197] It can be seen from the data of Example 1 and Comparative Example 3 that if the temperature is not increased gradually and the solid phase polycondensation time is the same, the reaction is directly carried out at a higher temperature, which will hinder the increase of the polymer viscosity; high temperature will lead to the decomposition of dibutylene diamine, which escapes too quickly at high temperature and does not fully participate in the reaction. At high temperature, the water vapor is drawn away before it completely contacts the material and has no effect. Instead, it will take away some heat, which will hinder the increase of the polymer viscosity.

[0198] It can be seen from the data of Example 1 and Comparative Example 4 that without setting a gradient temperature increase, when the solid-phase polycondensation time is the same, reacting at a lower temperature will greatly hinder the increase in the molecular weight of the polymer; in the present invention, water vapor is introduced during solid-phase polycondensation and reacts at a lower temperature. This part of the water vapor is not removed in time and will fully contact with the material, which will eventually cause the material to become moist, greatly hindering the increase in the molecular weight of the polymer.

[0199] It can be seen from the data of Example 1 and Comparative Example 5 that directly reacting at a higher temperature will hinder the increase of polymer viscosity. The color of nylon 46 in Comparative Example 5 is dark yellow, indicating that high temperature for a long time will cause the color value of the final product to deteriorate, while gradient heating will greatly improve the color of the final product. Among them, the color of nylon 46 prepared in Examples 1-16 is all white.

[0200] It can be seen from the data of Example 1, Comparative Example 6 and Comparative Example 7 that, during the salt formation process, if there is no methanol and water in the system to form a mixed solution, the relative viscosity of the final product will decrease, indicating that water and methanol as solvents can optimize the solubility of the reactants and the stability of the ammonium salt; and when single methanol is used as a solvent, it must be gradually heated to 135°C in the prepolymerization stage, the vent valve is opened, and stabilized for 60 minutes. Using a process with an extended venting time to remove methanol has the disadvantage of increasing energy consumption and cost.

[0201] In summary, by controlling the amino acid molar ratio, salt is prepared at low temperature and high pressure, methanol and water are used as mixed solvents, and diaminodiamine is added in the prepolymerization stage to perform salt formation reaction again at 55°C and 0.7MPa. In the nitrogen-water vapor atmosphere, solid phase polycondensation is carried out by three-stage solid phase polycondensation, and nylon 46 products with high molecular weight, high viscosity and good color value can be obtained in a relatively short time.

[0202] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing nylon 46, characterized in that: The following steps are involved: Adding butanediamine to the dicarboxylic acid solution to form a salt once, then adding butanediamine to form a salt twice, and then sequentially performing prepolymerization and solid phase polycondensation; Wherein, the solvent of the dicarboxylic acid solution includes alcohol and water; The solid phase polycondensation is carried out in a gradient temperature increase manner.

2. The method for preparing nylon 46 according to claim 1, characterized in that: The preparation process of the dicarboxylic acid solution comprises: mixing dicarboxylic acid, deionized water and alcohol to obtain the dicarboxylic acid solution; Preferably, the mass ratio of the deionized water to the alcohol is 0.5 to 120, preferably 0.8 to 110; Preferably, the temperature of the desalted water is 5°C to 20°C, preferably 5°C to 18°C; Preferably, the alcohol comprises at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol and isobutanol.

3. The method for preparing nylon 46 according to claim 1, characterized in that: The primary salt formation comprises: adding dibutylene diamine dropwise to a dicarboxylic acid solution, and then performing a primary salt formation at a first pressure and a first temperature; Preferably, the first pressure is 5MPa-10MPa, preferably 6MPa-9MPa, and the first temperature is 15°C-30°C, preferably 15°C-28°C; Preferably, in the primary salt formation, the molar ratio of diaminobutane to dicarboxylic acid is 1.01 to 1.15, preferably 1.01 to 1.10; Preferably, in the primary salt formation, the addition rate of diaminobutane is 1 to 3 wt% / min, preferably 1 to 2.5 wt% / min; Preferably, the mass fraction of the nylon salt solution obtained after the primary salt formation is 10% to 50%, preferably 10% to 30%.

4. The method for preparing nylon 46 according to claim 1, characterized in that: The secondary salt formation comprises: adding dibutylene diamine to the salt solution after the primary salt formation at normal pressure, and then performing secondary salt formation at a second pressure and a second temperature; Preferably, the second pressure is 0.3 MPa to 0.8 MPa, preferably 0.5 to 0.7 MPa, and the second temperature is 50° C. to 100° C., preferably 50° C. to 70° C.; Preferably, the amount of the additional butanediamine is 0.05 to 2 mol % of the amount of the dicarboxylic acid used, preferably 0.08 to 1.5 mol %.

5. The method for preparing nylon 46 according to claim 1, characterized in that: The prepolymerization comprises: performing a precondensation reaction at a third pressure and a third temperature, followed by degassing and discharging in sequence to obtain a prepolymer material; Preferably, the reaction temperature of the prepolymerization is 180°C to 220°C, preferably 190°C to 210°C, and the reaction pressure is 0.8MPa to 1.3MPa, preferably 1.0MPa to 1.2MPa; Preferably, the reaction time of the prepolymerization is 10 min to 200 min, preferably 30-90 min.

6. The method for preparing nylon 46 according to claim 1, characterized in that: The solid phase polycondensation comprises: sequentially carrying out polycondensation in a first temperature section, polycondensation in a second temperature section and polycondensation in a third temperature section under a nitrogen and water vapor atmosphere; Preferably, the polycondensation temperature in the first temperature section is 200-230°C; Preferably, the polycondensation temperature in the second temperature section is 240-260°C; Preferably, the polycondensation temperature in the third temperature section is 270-280°C; Preferably, the total reaction time of the solid phase polycondensation is 4.0 to 17.0 h; Preferably, when the temperature reaches 150°C to 200°C, water vapor is introduced, and the temperature is preferably 160°C to 180°C.

7. The method for preparing nylon 46 according to claim 1, characterized in that: The dicarboxylic acid includes at least one of an aliphatic dibasic acid and an aromatic dibasic acid containing 4 to 20 carbon atoms; Preferably, the aliphatic dibasic acid containing 4 to 20 carbon atoms includes at least one of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, hexadecanedioic acid and octadecanedioic acid; Preferably, the aromatic dibasic acid includes at least one of terephthalic acid and isophthalic acid.

8. The method for preparing nylon 46 according to claim 1, characterized in that: After the secondary salt formation and before the prepolymerization, the temperature is adjusted to 120° C. to 150° C., preferably 130° C. to 140° C., to remove methanol and part of the water.

9. Nylon 46 prepared by the method for preparing nylon 46 according to any one of claims 1 to 8.

10. The method for preparing nylon 46 according to any one of claims 1 to 8 or use of nylon 46 according to claim 9 in preparing industrial products.

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