Preparation method of bio-based nylon 56-X copolymer

Abstract

The invention belongs to the technical field of high polymer materials, and particularly discloses a preparation method of a bio-based nylon 56-X copolymer. Replacing the first salt forming kettle and the second salt forming kettle with nitrogen, and maintaining micro-positive pressure in the two salt forming kettles; putting desalted water, diamine and binary acid into a first salt forming kettle for salt forming reaction to obtain a nylon salt solution; adding the obtained nylon salt solution into a second salt forming kettle, and adding a second type of diamine or binary acid for salt forming reaction to obtain a mixed salt solution; filtering the obtained mixed salt solution to remove trace solid impurities, and feeding into a salt storage tank; finally, the mixed salt solution in the salt storage tank is conveyed into a polymerization kettle to be subjected to polymerization reaction, and the bio-based nylon 56-X copolymer is obtained. According to the preparation method, the stability and high efficiency of the copolymerization reaction are ensured by accurately controlling the reaction conditions, particularly by accurately adjusting the pH value and concentration of the mixed salt solution, so that the nylon 56-X copolymer with uniform performance and excellent comprehensive performance is obtained.

Description

1. Technical field:

[0001] The invention relates to the technical field of polymer materials, and in particular to a method for preparing an efficient and economical bio-based nylon 56-X copolymer. 2. Background technology:

[0002] As an important engineering plastic and fiber material, nylon is widely used in automobile manufacturing, electronic and electrical and textile industries due to its excellent mechanical properties, chemical corrosion resistance and thermal stability. However, traditional single nylon materials have many performance bottlenecks in high-end applications, such as insufficient high temperature resistance and difficulty in balancing toughness and strength.

[0003] At present, the material properties can be effectively improved by copolymerizing different nylon monomers. However, the existing method for synthesizing nylon copolymers usually adopts the method of directly mixing two different types of nylon salt solutions and then polymerizing them. This method requires the preparation of two different nylon salt solutions separately, and the concentration and pH value of the mixed salt solution are difficult to accurately control, resulting in large fluctuations in product performance between different batches, which cannot meet the strict requirements of high-performance engineering materials for stability and consistency. 3. Summary of the invention:

[0004] The technical problem to be solved by the present invention is: in view of the technical problems existing in the existing nylon copolymer preparation method, such as the complicated process flow, the inability to accurately control the concentration and pH value of the nylon salt solution entering the polymerization reactor, which leads to large fluctuations in the quality of the salt solution between batches, uneven copolymer performance, and difficulty in meeting the strict requirements of high-performance engineering materials for stability and consistency, the present invention provides a method for preparing a bio-based nylon 56-X copolymer. The preparation method of the present invention is efficient and economical, and the prepared nylon 56-X copolymer has excellent mechanical properties, heat resistance and chemical stability.

[0005] In order to solve the above problems, the technical solution adopted by the present invention is:

[0006] The present invention provides a method for preparing a bio-based nylon 56-X copolymer, the preparation method comprising the following steps:

[0007] 1) Using nitrogen to replace the first salt-forming kettle and the second salt-forming kettle, and maintaining a slight positive pressure in the two salt-forming kettles;

[0008] 2) putting desalted water, diamine and dibasic acid into a first salt-forming kettle and stirring them to fully react with salt to obtain a nylon salt solution having a mass percentage concentration of 40-60%;

[0009] 3) adding the nylon salt solution obtained in step 2) into a second salt-forming kettle, and adding a second type of diamine or dibasic acid to carry out a salt-forming reaction, and obtaining a mixed salt solution with a pH value of 7 to 8.5 after the reaction;

[0010] 4) filtering the mixed salt solution obtained in step 3) to remove trace solid impurities and sending it to a salt storage tank;

[0011] 5) The mixed salt solution in the salt storage tank is transported to a polymerization reactor to carry out a polymerization reaction to obtain a product, a bio-based nylon 56-X copolymer.

[0012] According to the above-mentioned method for preparing bio-based nylon 56-X copolymer, the micro positive pressure in step 1) is 0.01 to 0.03 MPa.

[0013] According to the above-mentioned preparation method of bio-based nylon 56-X copolymer, the diamine in step 2) is pentamethylenediamine or hexamethylenediamine; and the dibasic acid is adipic acid, sebacic acid or dodecanedioic acid.

[0014] According to the above-mentioned preparation method of bio-based nylon 56-X copolymer, expressed in parts by weight, the added amounts of desalted water, diamine and dibasic acid in step 2) are 46 to 71 parts of desalted water, 9 to 28 parts of diamine and 12 to 40 parts of dibasic acid, respectively.

[0015] According to the above-mentioned preparation method of bio-based nylon 56-X copolymer, in the salt-forming reaction process in step 2), the reaction temperature is 40-70° C. and the reaction time is 1-2 h; the pressure in the kettle is controlled to be 0.01-0.03 Mpa.

[0016] According to the above-mentioned preparation method of bio-based nylon 56-X copolymer, the reaction temperature during the salt-forming reaction in step 3) is 40-70° C., and the pressure in the kettle is controlled to be 0.01-0.03 MPa.

[0017] According to the above-mentioned preparation method of bio-based nylon 56-X copolymer, in step 3), the second type of diamine is hexamethylenediamine; and the second type of dibasic acid is sebacic acid or dodecanedioic acid.

[0018] According to the above-mentioned preparation method of bio-based nylon 56-X copolymer, the addition amounts of nylon salt solution and the second diamine or dibasic acid in step 3) are 76-91 parts and 9-24 parts respectively, expressed in parts by weight.

[0019] According to the above-mentioned preparation method of bio-based nylon 56-X copolymer, during the polymerization reaction process described in step 5), the temperature in the kettle is controlled to be 220-280°C and the pressure is controlled to be 1.4-2.1MPa. After the pressure reaches 1.4-2.1MPa, the pressure in the kettle is stabilized, the steam exhaust valve is opened, and water vapor is uniformly released. After the released water vapor is condensed by the condenser, the condensate enters the condensate metering tank. When the condensed water reaches the target value, the exhaust valve is closed, and then the pressure in the kettle is reduced to a slightly positive pressure (0.01-0.04Mpa), and the material is discharged after vacuuming.

[0020] According to the above-mentioned preparation method of bio-based nylon 56-X copolymer, a concentration meter is provided on the circulation pipeline of the first salt kettle to adjust the amount of desalted water added to the first salt kettle, thereby adjusting the salt solution concentration to the target value; a pH meter is provided on the circulation pipeline of the second salt kettle to adjust the amount of the second type of diamine or dibasic acid added to the second salt kettle, thereby adjusting the salt pH value to the target value.

[0021] The chemical reaction equation for preparing nylon 56-66 copolymer of the present invention is:

[0022]

[0023] The technical solution of the present invention is a continuous preparation process, which directly completes the preparation of nylon 56-X salt and significantly optimizes the traditional process flow. The key to the technical solution of the present invention lies in the precise control of reaction conditions, especially by accurately adjusting the pH value and concentration of the mixed salt solution to ensure the stability and efficiency of the copolymerization reaction, thereby obtaining a nylon 56-X copolymer with uniform performance and excellent overall performance.

[0024] The positive beneficial effects of the present invention are:

[0025] 1. The nylon 56-X copolymer prepared by the present invention has excellent mechanical properties, heat resistance and chemical stability, and has a low melting point. It shows good convenience and efficiency during processing and is suitable for various molding processes such as injection molding and extrusion. In addition, the nylon 56-X copolymer prepared by the present invention has excellent transparency and can meet the requirements of high optical properties or visual effects. Its high elongation at break indicates that the material has good toughness and ductility and is not easy to crack, thereby significantly broadening the scope of application.

[0026] 2. The process flow of the present invention is simplified: the traditional process requires the preparation of different nylon salt solutions separately, and then mixed and copolymerized, which is complicated and has multiple process control difficulties. The present invention realizes the continuous preparation of nylon 56-X salt, fundamentally simplifies the process flow, reduces production steps and potential error sources, and improves production efficiency.

[0027] 3. Precise control of reaction conditions in the present invention: The present invention innovatively introduces a precise control method for salt-forming reaction conditions, especially in terms of pH value and salt solution concentration control, and ensures the stability of the copolymerization reaction by optimizing reaction parameters. This precise control effectively reduces the pH fluctuation problem between batches, thereby significantly improving the stability and consistency of copolymer performance.

[0028] 4. Preparation of high-performance copolymers of the present invention: The present invention obtains nylon 56-X copolymers with uniform performance and excellent comprehensive performance by optimizing the salt-forming conditions. Compared with the prior art, the copolymers produced by the present invention perform better in key indicators such as mechanical properties, thermal stability and processing performance, meeting the strict requirements of high-performance engineering materials for high stability and high consistency.

[0029] In summary, the present invention provides an innovative continuous preparation process, which directly completes the preparation of nylon 56-X salt and significantly optimizes the traditional process flow. The key lies in the precise control of reaction conditions, especially by accurately adjusting the pH value and concentration of the salt solution to ensure the stability and efficiency of the copolymerization reaction. And the method is used to prepare nylon 56-X copolymers with uniform properties and excellent overall performance. 4. Description of the drawings:

[0030] Figure 1 Schematic diagram of the production process of nylon 56-X copolymer of the present invention;

[0031] Figure 1 In the figure, 1 is the first salt-forming kettle, 2 is the concentration meter, 3 is the second salt-forming kettle, 4 is the pH meter, 5 is the filter, 6 is the salt storage tank, 7 is the polymerization kettle, and 8 is the pelletizer.

[0032] Figure 2 This is the NMR image of the nylon 56-66 copolymer prepared by the present invention;

[0033] Depend on Figure 2 It can be seen that the signals with a chemical shift in the range of 7.5 to 7.7 belong to the hydrogen atoms of the amino group on the amide bond; the signals with a chemical shift near 3.0 correspond to the hydrogen atoms on the adjacent methylene group connected to the amino group on the amide bond; the signals with a chemical shift near 2 belong to the hydrogen atoms on the adjacent methylene group connected to the carbonyl group on the amide bond; the signals with a chemical shift near 1.3-1.6 belong to the hydrogen atoms on other methylene groups. V. Specific implementation methods:

[0034] The present invention is further described below in conjunction with embodiments, but the protection scope of the technical solution of the present invention is not limited thereto.

[0035] In the following embodiments, a concentration meter is provided on the circulation line of the first salt kettle to adjust the amount of desalted water added to the first salt kettle, thereby effectively adjusting the salt solution concentration to the target value; a pH meter is provided on the circulation line of the second salt kettle to adjust the amount of the second type of diamine or dibasic acid added to the second salt kettle, thereby effectively adjusting the pH value of the salt to the target value.

[0036] Embodiment 1:

[0037] The preparation method of the bio-based nylon 56-66 copolymer of the present invention comprises the following detailed steps:

[0038] 1) Using nitrogen to replace the first salt forming kettle and the second salt forming kettle, and maintaining a slight positive pressure of 0.01-0.03Mpa in the two salt forming kettles;

[0039] 2) 7.65 kg of desalted water, 1.53 kg of pentamethylenediamine and 4.38 kg of adipic acid were sequentially added to the first salt-forming kettle for stirring and mixing, and the temperature was raised to 60° C. for sufficient salt-forming reaction for 2 hours, and the pressure in the kettle was maintained at 0.01-0.03 MPa; after the reaction, a nylon salt solution with a mass percentage concentration of 43.6% was obtained (the concentration of the salt solution was fine-tuned to 43.6% according to the concentration meter on the circulation line of the first salt-forming kettle);

[0040] 3) adding the nylon salt solution obtained in step 2) to a second salt-forming kettle, and adding 1.74 kg of hexamethylenediamine, and carrying out a salt-forming reaction at 60° C. for 2 h, with the pressure in the kettle controlled at 0.01 to 0.03 MPa; obtaining a nylon 56-66 mixed salt solution with a mass percentage concentration of 50% and a pH value of 7.7 (the pH value of the salt solution is fine-tuned to 7.7 according to the pH meter on the circulation line of the second salt-forming kettle);

[0041] 4) filtering the nylon 56-66 mixed salt solution obtained in step 3) to remove trace solid impurities and sending it to a salt storage tank;

[0042] 5) 15 kg of the mixed salt solution in the salt storage tank is transported to the polymerization kettle, and the kettle is filled with nitrogen and evacuated for 3 times to replace the air in the kettle, and then filled with nitrogen; the polymerization reaction is carried out under the conditions of controlling the temperature of the polymerization kettle to 280° C. and the pressure to 1.9 MPa; after the pressure reaches 1.9 MPa, the pressure in the kettle is stabilized, the steam exhaust valve is opened, and water vapor begins to be released evenly. After the released water vapor is condensed by the condenser, the condensate enters the condensate metering tank. When the condensed water reaches the target value (about 6.5 kg), the exhaust valve is closed, and then the pressure in the kettle is reduced to 0.02 MPa, and the kettle is evacuated to -0.09 to -0.1 MPa before discharging to obtain nylon 56-66 copolymer.

[0043] The relevant performance data of the nylon 56-66 copolymer prepared in this example are shown in Table 1.

[0044] Table 1 Performance parameters of nylon 56 / 66 copolymer prepared by the present invention

[0045] Melting point / ℃ Relative viscosity Tensile strength / MPa Bending strength / MPa Nylon 56 / 66 copolymer 236.5 2.4 75.6 80

[0046] Table 1 shows the nylon 56-66 copolymer prepared by the present invention, with a melting point of about 236.5°C, a relative viscosity of 2.4 (sulfuric acid method), a tensile strength of 75.6Mpa, and a flexural strength of 80Mpa. The copolymer has a low melting point, is conducive to secondary processing and molding, and has high tensile strength and flexural strength, maintaining good mechanical properties of the material.

[0047] Embodiment 2:

[0048] The preparation method of the bio-based nylon 56-510 copolymer of the present invention comprises the following detailed steps:

[0049] 1) Using nitrogen to replace the first salt forming kettle and the second salt forming kettle, and maintaining a slight positive pressure of 0.01-0.03Mpa in the two salt forming kettles;

[0050] 2) 12.4 kg of desalted water, 3.06 kg of pentamethylenediamine and 2.19 kg of adipic acid were sequentially added to the first salt-forming kettle for stirring and mixing, and the temperature was raised to 60° C. for sufficient salt-forming reaction for 2 hours, and the pressure in the kettle was maintained at 0.01-0.03 MPa; after the reaction, a nylon salt solution with a mass percentage concentration of 29.7% was obtained (the concentration of the salt solution was fine-tuned to 29.7% according to the concentration meter on the circulation line of the first salt-forming kettle);

[0051] 3) adding the nylon salt solution obtained in step 2) to a second salt-forming kettle, and adding 3.03 kg of sebacic acid, and carrying out a salt-forming reaction at 60° C. for 2 h, with the pressure in the kettle controlled at 0.01 to 0.03 MPa; obtaining a nylon 56-510 mixed salt solution with a mass percentage concentration of 40% and a pH value of 7.6 (the pH value of the salt solution is fine-tuned to 7.6 according to the pH meter on the circulation line of the second salt-forming kettle);

[0052] 4) filtering the nylon 56-510 mixed salt solution obtained in step 3) to remove trace solid impurities and sending it to a salt storage tank;

[0053] 5) 15 kg of the mixed salt solution in the salt storage tank is transported to the polymerization kettle, and the kettle is filled with nitrogen and evacuated for 3 times to replace the air in the kettle, and then filled with nitrogen; the polymerization reaction is carried out under the conditions of controlling the temperature of the polymerization kettle to 280° C. and the pressure to 1.9 MPa; after the pressure reaches 1.9 MPa, the pressure in the kettle is stabilized, the steam exhaust valve is opened, and water vapor begins to be released evenly. After the released water vapor is condensed by the condenser, the condensate enters the condensate metering tank. When the condensed water reaches the target value (about 8.0 kg), the exhaust valve is closed, and then the pressure in the kettle is reduced to 0.02 MPa, and the kettle is evacuated to -0.09 to -0.1 MPa before discharging to obtain nylon 56-510 copolymer.

[0054] Embodiment 3:

[0055] The preparation method of the bio-based nylon 56-512 copolymer of the present invention has the following detailed steps:

[0056] 1) Using nitrogen to replace the first salt forming kettle and the second salt forming kettle, and maintaining a slight positive pressure of 0.01-0.03Mpa in the two salt forming kettles;

[0057] 2) 7.73 kg of desalted water, 4.08 kg of pentamethylenediamine and 2.92 kg of adipic acid were sequentially added to the first salt-forming kettle for stirring and mixing, and the temperature was raised to 60° C. for sufficient salt-forming reaction for 2 hours, and the pressure in the kettle was maintained at 0.01-0.03 MPa; after the reaction, a nylon salt solution with a mass percentage concentration of 47.5% was obtained (the concentration of the salt solution was fine-tuned to 47.5% according to the concentration meter on the circulation line of the first salt-forming kettle);

[0058] 3) adding the nylon salt solution obtained in step 2) to a second salt-forming kettle, and adding 4.6 kg of dodecanedioic acid, and carrying out a salt-forming reaction at 60° C. for 2 h, with the pressure in the kettle controlled at 0.01 to 0.03 MPa; obtaining a nylon 56-512 mixed salt solution with a mass percentage concentration of 60% and a pH value of 7.6 (the pH value of the salt solution is fine-tuned to 7.6 according to the pH meter on the circulation line of the second salt-forming kettle);

[0059] 4) filtering the nylon 56-512 mixed salt solution obtained in step 3) to remove trace solid impurities and sending it to a salt storage tank;

[0060] 5) 15 kg of the mixed salt solution in the salt storage tank is transported to the polymerization kettle, and the kettle is filled with nitrogen and evacuated for 3 times to replace the air in the kettle, and then filled with nitrogen; the polymerization reaction is carried out under the conditions of controlling the temperature of the polymerization kettle to 280° C. and the pressure to 1.9 MPa; after the pressure reaches 1.9 MPa, the pressure in the kettle is stabilized, the steam exhaust valve is opened, and water vapor begins to be released evenly. After the released water vapor is condensed by the condenser, the condensate enters the condensate metering tank. When the condensed water reaches the target value (about 5.0 kg), the exhaust valve is closed, and then the pressure in the kettle is reduced to 0.02 MPa, and the kettle is evacuated to -0.09 to -0.1 MPa before discharging to obtain nylon 56-512 copolymer.

Claims

1. A method for preparing a bio-based nylon 56-X copolymer, characterized in that: The preparation method comprises the following steps: 1) Using nitrogen to replace the first salt-forming kettle and the second salt-forming kettle, and maintaining a slight positive pressure in the two salt-forming kettles; 2) putting desalted water, diamine and dibasic acid into a first salt-forming kettle and stirring them to fully react with salt to obtain a nylon salt solution having a mass percentage concentration of 40-60%; 3) adding the nylon salt solution obtained in step 2) into a second salt-forming kettle, and adding a second type of diamine or dibasic acid to carry out a salt-forming reaction, and obtaining a mixed salt solution with a pH value of 7 to 8.5 after the reaction; 4) filtering the mixed salt solution obtained in step 3) to remove trace solid impurities and sending it to a salt storage tank; 5) The mixed salt solution in the salt storage tank is transported to a polymerization reactor to carry out a polymerization reaction to obtain a product, a bio-based nylon 56-X copolymer.

2. The method for preparing the bio-based nylon 56-X copolymer according to claim 1, characterized in that: The slight positive pressure in step 1) is 0.01-0.03 MPa.

3. The method for preparing the bio-based nylon 56-X copolymer according to claim 1, characterized in that: In step 2), the diamine is pentamethylenediamine or hexamethylenediamine; and the dibasic acid is adipic acid, sebacic acid or dodecanedioic acid.

4. The method for preparing the bio-based nylon 56-X copolymer according to claim 1, characterized in that: In terms of parts by weight, the amounts of desalted water, diamine and dibasic acid added in step 2) are 46-71 parts of desalted water, 9-28 parts of diamine and 12-40 parts of dibasic acid, respectively.

5. The method for preparing the bio-based nylon 56-X copolymer according to claim 1, characterized in that: In the salt-forming reaction process in step 2), the reaction temperature is 40-70° C. and the reaction time is 1-2 h; the pressure in the kettle is controlled to be 0.01-0.03 Mpa.

6. The method for preparing the bio-based nylon 56-X copolymer according to claim 1, characterized in that: In step 3), the reaction temperature during the salt formation reaction is 40-70° C., and the pressure in the kettle is controlled to be 0.01-0.03 MPa.

7. The method for preparing the bio-based nylon 56-X copolymer according to claim 1, characterized in that: In step 3), the second diamine is hexamethylenediamine; and the second dibasic acid is sebacic acid or dodecanedioic acid.

8. The method for preparing the bio-based nylon 56-X copolymer according to claim 1, characterized in that: In terms of parts by weight, the amounts of the nylon salt solution and the second diamine or dibasic acid added in step 3) are 76 to 91 parts and 9 to 24 parts respectively.

9. The method for preparing the bio-based nylon 56-X copolymer according to claim 1, characterized in that: During the polymerization reaction in step 5), the temperature in the kettle is controlled at 220-280° C. and the pressure is controlled at 1.4-2.1 MPa. After the pressure reaches 1.4-2.1 MPa, the pressure in the kettle is stabilized, the steam exhaust valve is opened, and water vapor is released evenly. After the released water vapor is condensed by the condenser, the condensate enters the condensate metering tank. When the condensed water reaches the target value, the exhaust valve is closed, and then the pressure in the kettle is reduced to a slightly positive pressure, and the material is discharged after vacuuming.

10. The method for preparing the bio-based nylon 56-X copolymer according to claim 1, characterized in that: A concentration meter is provided on the circulation pipeline of the first salt kettle to adjust the amount of desalted water added to the first salt kettle, thereby adjusting the salt solution concentration to the target value; a pH meter is provided on the circulation pipeline of the second salt kettle to adjust the amount of the second type of diamine or dibasic acid added to the second salt kettle, thereby adjusting the pH value of the salt to the target value.

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