A bio-based high-performance nylon foaming material and its preparation method

Abstract

A bio-based high-performance nylon foaming material and its preparation method. The method includes: mixing 2-methylpentanediamine, tetradecanedioic acid, and benzoic acid in deionized water to prepare a salt, mixing the salt solution with sodium hypophosphite as a polymerization aid, heating to 200-240 °C, and reacting for 1-5 h to obtain a bio-based PA5D14 resin; obtaining blended particles by extruding and granulating high- and low-molecular-weight PA5D14; putting the dried blended particles into a mold, putting the mold into a high-pressure reactor, heating at a preset temperature of 146-154 °C, and using supercritical CO2 for foaming to obtain a bio-based high-performance nylon foaming material. The materials used in the present invention are bio-based nylon, the reaction process is green and solvent-free, and the reaction conditions are mild; the use of supercritical CO2 for foaming is more environmentally friendly and pollution-free compared to chemical foaming; the bio-based nylon itself has multiple melting peaks, and there is no need to add other substances to create a double melting point, and it can be directly used to prepare foaming materials without the problem of poor compatibility.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly relates to a bio-based high-performance nylon foaming material and a preparation method thereof. Background Art

[0002] Nylon, scientifically named polyamide, is a type of polyamide compound of aliphatic or aromatic. Nylon is a polymer material formed by the polycondensation of dibasic acids and diamines or lactams themselves. The repeating units are connected by formed amide bonds, making it have strong hydrogen bonds. Therefore, nylon has excellent wear resistance and self-lubricity, high mechanical strength, excellent chemical resistance, good heat resistance and electrical insulation, and easy processability. Currently, it has been widely used in many fields such as clothing, flooring, automobiles, electrical equipment, food packaging, 5G communication, etc.

[0003] With the global pursuit of a low-carbon economy, green and low-carbon industrialization industries will surely become the key development targets in the future. For nylon foaming materials, the way to achieve green and low-carbon is to choose bio-based nylon materials and supercritical foaming technology. Currently, the supercritical foaming technology has been mature, but bio-based nylon has not been used for foaming.

[0004] For example, Chinese Patent CN112625432A discloses a micro-foamed nylon composite material and its application. Through the compound blending of high-melting-point and low-melting-point nylon resins and the reasonable design of hyperbranched polymers, it avoids the uncontrollable cross-linking and curing means, and realizes the advantages of significant weight reduction effect, little influence on the original performance, high dimensional accuracy, etc., and is not limited to use in specific fields. The materials used in this method are blends of a series of nylons such as PA66, PA56, and PA6. These nylons are all non-bio-based nylons, which do not conform to the concept of green and low-carbon. Moreover, if the compatibility between the blends is not good, it will lead to poor performance of the later products. The average weight reduction of the obtained product is 16%, the foaming ratio is low, and the cell density is relatively low. The traditional chemical foaming is still used in this method. The RA foaming agent used will seriously pollute the environment, and the service life of the product is short, it is easy to age and damage, and there is also the problem of uneven foaming.

[0005] For example, Chinese Patent CN115926260A discloses a degradable high-strength closed-cell polylactic acid foaming material. After grafting acrylic acid onto nano-SiO 2 particles, pulverized PLA resin, and thermoplastic starch are stirred, pre-dispersed and dried in ethanol to obtain a mixed material. After the mixed material is extruded and granulated, supercritical foaming is carried out. This method introduces rigid particles, chain extenders, etc. into PLA to improve the foaming ratio, mechanical properties, etc., but the process is too complicated and it is difficult to achieve large-scale production. Moreover, the cell diameter after foaming is still too large, the cell wall is too thin, and the mechanical properties are still insufficient.

[0006] In summary, most of the foaming of nylon materials at present is by chemical foaming methods, and multiple nylon blends are required to achieve it. It is rarely foamed through a single type of nylon, and the nylon used is non-bio-based and not environmentally friendly. Summary of the Invention

[0007] Based on this, the present invention provides a preparation method of a bio-based high-performance nylon foaming material to solve the problems of uneven foaming, still too large cell diameters after foaming, too thin cell walls, and still insufficient mechanical properties in the existing nylon foaming materials. At the same time, it solves the problems that it is difficult to achieve foaming through a single type of nylon in the existing technology, and the nylon used is non-bio-based and not environmentally friendly.

[0008] To achieve the above object, on the one hand, the present invention provides a preparation method of a bio-based high-performance nylon foaming material, which includes the following steps:

[0009] S1. Mix 2-methylpentanediamine, tetradecanedioic acid, and benzoic acid in deionized water to form a salt, and mix the salt solution with sodium hypophosphite as a polymerization aid, and raise the temperature to 200-240 °C for reaction to obtain a bio-based PA5D14 resin;

[0010] Among them, when the molar ratio of 2-methylpentanediamine, tetradecanedioic acid, and benzoic acid is 10.4:10:0.02, the obtained PA5D14 resin is of high molecular weight; when the molar ratio of 2-methylpentanediamine, tetradecanedioic acid, and benzoic acid is 10.4:10:0.08, the obtained PA5D14 resin is of low molecular weight;

[0011] S2. Using the high-molecular-weight PA5D14 resin as the base resin, add 5-10% by mass of the low-molecular-weight PA5D14 resin, and obtain blended particles by extrusion granulation;

[0012] S3. Put the dried blended particles into a mold, and then put the mold into a high-pressure reaction kettle, heat it at a preset temperature of 146-154 °C. When heated to the set temperature, introduce supercritical CO 2 Discharge all the air in the high-pressure reaction kettle;

[0013] S4. After all the air in the high-pressure reaction kettle is discharged, continue to introduce supercritical CO 2 until the pressure reaches 12 Mpa ± 0.5 MPa, stop introducing gas, and carry out the reaction under closed conditions. During the reaction process, after observing that the pressure gauge shows 16 MPa ± 0.5 MPa and the temperature gauge shows the preset temperature again, open the pressure relief valve of the high-pressure reaction kettle to make CO 2 instantly discharged, so that the inside of the high-pressure reaction kettle is instantly depressurized, and finally open the high-pressure reaction kettle to obtain the bio-based high-performance nylon foaming material.

[0014] As a further preferred technical solution of the present invention, in step S1, for every 10.4 mol of 2-methylpentanediamine used, the amount of sodium hypophosphite used is 0.001 - 0.05 mol.

[0015] As a further preferred technical solution of the present invention, the reaction in step S1 is carried out under a nitrogen atmosphere.

[0016] As a further preferred technical solution of the present invention, in step S1, before heating to 200 - 240 °C, first heat to 100 - 160 °C and discharge a part of the deionized water to reduce the water content in the reaction system to 15 - 20%.

[0017] As a further preferred technical solution of the present invention, the step of heating to 200 - 240 °C for reaction in step S1 specifically includes:

[0018] First, heat to 200 - 220 °C, keep the reaction pressure not higher than 2.5 Mpa, and react for 1 - 2 h; then, relieve the pressure and heat to 230 - 240 °C, and carry out a vacuum reaction for 1 - 2 h to finally obtain a bio-based PA5D14 resin. Among them, the pressure for maintaining the reaction when heating to 200 - 220 °C is preferably 1.5 - 2.2 Mp.

[0019] As a further preferred technical solution of the present invention, before step S3, the blended particles are dried in a vacuum drying oven at 100 - 110 °C.

[0020] As a further preferred technical solution of the present invention, in step S3, the preset temperature is 147 - 150 °C, and more preferably 148 °C.

[0021] According to another aspect of the present invention, the present invention also provides a bio-based high-performance nylon foaming material, which is prepared by the above method.

[0022] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0023] 1. The materials used in the present invention are bio-based nylon, the reaction process is green and solvent-free, and the reaction conditions are mild.

[0024] 2. The supercritical CO 2 foaming used in the present invention is more environmentally friendly and pollution-free compared to chemical foaming.

[0025] 3. The bio-based nylon of the present invention itself has multiple melting peaks, and there is no need to add other substances to create double melting points, and it can be directly used to prepare foaming materials without the problem of poor compatibility.

[0026] 4. Compared with ordinary foaming materials, the falling ball rebound rate, foaming ratio, and foaming density of the foaming materials of the present invention are significantly improved, and the dynamic fatigue performance is significantly enhanced. Description of the Drawings

[0027] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0028] Figure 1 1H NMR spectrum of low molecular weight PA5D14.

[0029] Figure 2 13C NMR spectrum of low molecular weight PA5D14.

[0030] Figure 3 DSC diagrams of high and low molecular weight PA5D14.

[0031] Figure 4 XRD diagram of low molecular weight PA5D14.

[0032] The realization of the object, functional features, and advantages of the present invention will be further described in conjunction with the embodiments with reference to the drawings. Specific Embodiments

[0033] The following further details the specific embodiments of the present invention in conjunction with the drawings. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not used to limit the present invention.

[0034] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which the present invention pertains. The test reagents used in the following embodiments are all conventional biochemical reagents unless otherwise specified; the experimental methods are all conventional methods unless otherwise specified.

[0035] Synthesis methods of PA5D14 resins with different molecular weights:

[0036] 10.4 mol of 2-methylpentanediamine, 10 mol of tetradecanedioic acid, 3 kg of deionized water, 0.01 mol of sodium hypophosphite, and a certain amount of benzoic acid were added to a 10 L high-pressure reaction kettle, and the mixture was reacted for 0.5 h under a nitrogen atmosphere to obtain a PA5D14 salt solution; then the temperature was raised to 150 °C, and a part of the deionized water was discharged to reduce the water content in the reaction system to 20%; the temperature was further raised to 220 °C, and the reaction pressure was maintained not higher than 2.5 Mpa, and the reaction was carried out for 2 hours; finally, the pressure was released and the temperature was raised to 240 °C, and the reaction was carried out under vacuum for 2 h to prepare PA5D14 resin.

[0037] In the above preparation process: when the benzoic acid content is 0.02 mol, a high molecular weight PA5D14 is obtained, which is recorded as 1026; when the benzoic acid content is 0.08 mol, a low molecular weight PA5D14 is obtained, which is recorded as 1030.

[0038] Table 1 is a summary of the GPC results of low molecular weight PA5D14. Compared with high molecular weight PA5D14 (1026), low molecular weight PA5D14 (1030) is 10,000 or less, with a molecular weight reduction of more than 4,000 and a narrower molecular weight distribution. Figure 1 and Figure 2 , we can see that all H and C correspond to the structure of PA5D14, proving that the synthesis was successful.

[0039] Table 1 Molecular weight and molecular weight distribution of high molecular weight and low molecular weight PA5D14

[0040]

[0041] pass Figure 3 It can be clearly seen from the DSC graph that low molecular weight PA5D14 has an obvious double melting point phenomenon. The specific data are shown in Table 2.

[0042] Table 2 DSC data of low molecular weight PA5D14

[0043]

[0044] according to Figure 4 From the XRD diagram, it can be seen that there is a large broad peak at about 21°, and there is a shoulder peak on the broad peak. The broad peak is the γ crystal form, and the shoulder peak may be the α crystal form. This shows that there are two crystal forms with different melting points in low molecular weight nylon. The present invention uses this dual melting point property to further prepare a nylon foam material with a stable and uniform foam structure.

[0045] In order to allow those skilled in the art to further understand the technical solution of the present invention, based on the PA5D14 resins with different molecular weights provided above, the technical solution of the present invention is further described in detail below through specific examples and comparative examples.

[0046] The following formula (5%) is expressed as: low molecular weight PA5D14 mass: high molecular weight PA5D14 mass = 5:95, the mass proportion of low molecular weight PA5D14 is 5%, and the same applies to other formulas.

[0047] Embodiment 1:

[0048] The preparation method of the provided bio-based high-performance nylon foam material specifically comprises:

[0049] 1) Blending and granulation according to the formula (5%)

[0050] Mix high- and low-molecular-weight PA5D14 evenly with a high-speed disperser according to the formula (5%), and then extrude and pelletize through a twin-screw extruder.

[0051] 2) Supercritical foaming at 148°C

[0052] Vacuum-dry the extruded PA5D14 blend granules at 105°C for 6 h. After drying, load them into a mold and place them in a high-pressure reactor. Lock it and put it into a heating device. Set the preset temperature to 148°C. When heated to the preset temperature, introduce supercritical CO for 30 s 2 Discharge all the air in the high-pressure reactor; after exhausting the air, close the pressure relief valve and continue to introduce supercritical CO 2 until the pressure gauge reaches 12 MPa ± 0.5 MPa, and end the air intake; start to maintain the pressure for about 1.5 h. At this time, the material reacts in the reactor, and the pressure rises to 16 MPa ± 0.5 MPa during this reaction process, and the temperature rises back to 148°C at the same time. Immediately open the pressure relief valve to discharge CO 2 instantly, and the internal pressure of the reactor is instantly relieved. After the gas is exhausted, take out the reactor and open it, take out the sample and put it in the refrigerator to prevent the sample from cooling and shrinking, and obtain the test specimen of the nylon foaming material.

[0053] It should be noted here that according to different test requirements, the specifications of the prepared test specimens are different. The specific specifications of the test specimens are as follows (the same for the following examples and comparative examples):

[0054] Tensile specimen: total length 152 mm, end width 25 ± 0.5 mm, parallel part width 13 ± 0.1 mm;

[0055] Permanent compression deformation specimen: length 50 ± 1 mm, width 50 ± 1 mm, thickness 25 ± 1 mm;

[0056] Falling ball rebound specimen: area 100 mm × 100 mm, thickness 50 mm;

[0057] Dynamic fatigue specimen: side length 500 mm, thickness 50 ± 2 mm.

[0058] Test the above test specimens for density, mechanical properties, falling ball rebound rate, dynamic fatigue, etc., and list the test results in Table 3.

[0059] Example 2:

[0060] Prepare various specified test specimens of nylon foaming materials by using basically the same method as in Example 1, except that: high- and low-molecular-weight PA5D14 are evenly mixed according to the formula (7%) and then extruded and pelletized, and the extruded PA5D14 blend granules are subjected to supercritical foaming at 148°C, and other processes remain unchanged.

[0061] The test spline was tested for density, mechanical properties, ball drop rebound rate, dynamic fatigue, etc., and the test results are listed in Table 3.

[0062] Example 3:

[0063] Various specified nylon foamed material test splines were prepared by substantially the same method as in Example 1, except that: PA5D14 with high and low molecular weights were mixed evenly according to the formula (10%) and then extruded into pellets, and the blended pellets of PA5D14 extruded were subjected to supercritical foaming at 148 °C, and other processes remained unchanged.

[0064] The test spline was tested for density, mechanical properties, ball drop rebound rate, dynamic fatigue, etc., and the test results are listed in Table 3.

[0065] Example 4:

[0066] Various specified nylon foamed material test splines were prepared by substantially the same method as in Example 1, except that: only PA5D14 particles with high molecular weight were used for supercritical foaming at 148 °C, and other processes remained unchanged.

[0067] The test spline was tested for density, mechanical properties, ball drop rebound rate, dynamic fatigue, etc., and the test results are listed in Table 3.

[0068] Example 5:

[0069] Various specified nylon foamed material test splines were prepared by substantially the same method as in Example 1, except that: only PA5D14 particles with low molecular weight were used for supercritical foaming at 148 °C, and other processes remained unchanged.

[0070] The test spline was tested for density, mechanical properties, ball drop rebound rate, dynamic fatigue, etc., and the test results are listed in Table 3.

[0071] Comparative Example 1:

[0072] As a comparative experiment of Example 2, various specified nylon foamed material test splines were prepared by substantially the same method as in Example 2, except that: PA5D14 with high and low molecular weights were mixed evenly according to the formula (7%), then extruded into pellets, and the blended pellets of PA5D14 extruded were subjected to supercritical foaming at 140 °C.

[0073] The test spline was tested for density, mechanical properties, ball drop rebound rate, dynamic fatigue, etc., and the test results are listed in Table 4.

[0074] Comparative Example 2:

[0075] As a comparative experiment of Example 2, various specified nylon foamed material test specimens were prepared by using substantially the same method as in Example 2, except that high- and low-molecular-weight PA5D14 were mixed evenly according to the formula (7%), and then extruded and granulated. The blended granules of the extruded PA5D14 were supercritically foamed at 155 °C.

[0076] The test specimens were tested for density, mechanical properties, ball drop rebound rate, dynamic fatigue, etc. The test results are listed in Table 4.

[0077] Comparative Example 3:

[0078] Various specified nylon foamed material test specimens were prepared by using substantially the same method as in Example 2, except that high- and low-molecular-weight PA5D14 were mixed evenly according to the formula (20%), and then extruded and granulated. The blended granules of the extruded PA5D14 were supercritically foamed at 148 °C.

[0079] The test specimens were tested for density, mechanical properties, ball drop rebound, dynamic fatigue, etc. The test results are listed in Table 4.

[0080] Comparative Example 4:

[0081] Based on commercial PP as the base resin, commercial PP and low-molecular-weight PA5D14 were mixed evenly according to the formula (7%), and then extruded and granulated. The blended granules of the extruded materials were supercritically foamed at 170 °C. This foaming process was the same as that of Example 1 except for the temperature. Finally, various specified nylon foamed material test specimens were prepared.

[0082] The test specimens were tested for density, mechanical properties, ball drop rebound rate, dynamic fatigue, etc. The test results are listed in Table 4.

[0083] Comparative Example 5:

[0084] Based on commercial high-molecular-weight PA6 as the base resin, commercial high-molecular-weight PA6 and low-molecular-weight PA6 were mixed evenly according to the formula (7%), and then extruded and granulated. The blended granules of the extruded PA6 were supercritically foamed at 220 °C. This foaming process was the same as that of Example 1 except for the temperature. Finally, various specified nylon foamed material test specimens were prepared.

[0085] The test specimens were tested for density, mechanical properties, ball drop rebound rate, dynamic fatigue, etc. The test results are listed in Table 4.

[0086] Table 3 Test data of Examples 1 - 5

[0087]

[0088] Table 4 Test data of Comparative Examples 1 - 5

[0089]

[0090]

[0091] By comparing the test results of Examples 1-5, it can be seen that as the addition amount of low-molecular-weight PA5D14 increases (≤10%), the difference in the ball-drop rebound rate of the material is not significant, but the density gradually decreases and the material strength also decreases, indicating that the addition of low-molecular-weight PA5D14 can increase the foaming effect of the material, but at the same time will reduce the strength of the material. However, the pure low-molecular-weight PA5D14 itself has low strength. When directly prepared into a foamed material, its own strength is further reduced, making it difficult to have practical application value.

[0092] By comparing Example 2 with Comparative Examples 1 and 2: Foaming was carried out at two temperatures below the melting point of PA5D14 (<146°C). Since the polymer did not melt and the melt strength was too high, the content of supercritical gas that could enter the polymer interior was extremely low, so the foaming effect of the specimen was poor and the ball-drop rebound rate was low. When foaming at two temperatures above the melting point of PA5D14 (>154°C), since the two components of the polymer were completely melted, there was no medium to protect the cell structure, the melt strength was relatively low, and the cells merged with each other to form larger cells, resulting in a reduction in the overall mechanical properties.

[0093] By comparing Examples 1, 2, and 3 with Comparative Example 3, as the addition amount of low-molecular-weight PA5D14 continuously increases, the density of the sample decreases, the ball-drop rebound rate is higher, but the overall strength also decreases accordingly. In the range of 5% - 10% addition amount, the strength of the sample does not decrease significantly; when the addition amount is greater than 10%, such as reaching 20%, due to the excessive formation of cells in the sample and the low strength of low-molecular-weight PA5D14 itself, the strength of the overall material drops significantly, which is not conducive to use in daily life.

[0094] By comparing Example 2 with Comparative Example 4, when the high-molecular-weight PA5D14 base material in the example was replaced with the commercially available PP that is currently used more, since the two are not the same substance, the compatibility is poor. At the same time, the melting points of the two are quite different. At 170°C, PP is partially melted while PA5D14 is completely melted, and it cannot play a role in protecting the cell structure. At this temperature, the melt strength is low and the stability of the cell structure is poor, resulting in the collapse of a large number of cell structures. Therefore, the foaming effect is poor, the density is high, and the ball-drop rebound rate is low.

[0095] By comparing Example 2 with Comparative Example 5, the PA5D14 in the example was replaced with nylon 6 which belongs to the nylon family. Since PA6 itself has only one melting point, when the temperature reaches 220 °C, PA6 has already melted, with low melt strength and no solid components to stabilize the cell structure. Therefore, the cell structure is prone to collapse, resulting in a higher density and lower ball rebound rate of the material.

[0096] The preparation method of the nylon foaming material provided by the present invention utilizes the double melting point property. When the temperature is set between 146 - 154 °C, preferably 148 °C, the low melting point component melts first, and then the gas in the supercritical state is dissolved into the amorphous region at this temperature, while the high melting point component remains solid and can act as a heterogeneous nucleating agent. After the reaction kettle is pressurized to allow more of the supercritical gas to dissolve into it, and then the pressure is instantaneously released, the supersaturation of the supercritical gas becomes the driving force for foaming. At this time, the high melting point part also plays the role of a protective medium to stabilize the formed cells, making the cell distribution uniform and dense. At the same time, low and high molecular weight PA5D14 are essentially the same substance, without the problem of poor compatibility, which can ensure the uniformity of the product.

[0097] As can be seen from Table 3, the double melting point bio - based nylon foaming material prepared by the technology of the present invention not only has a green and simple preparation process, is pollution - free to the environment, but also can obtain a smaller density, a higher ball rebound rate and excellent dynamic fatigue performance. It effectively avoids the pollution of traditional chemical foaming and the use of organic solvents in the synthesis process of raw materials. At the same time, in the preparation process, the double melting point property of the material can be directly utilized to make the foaming uniform, realizing the preparation of high - performance foaming materials.

[0098] In summary, the preparation technology of the nylon foaming material using low - molecular - weight double melting point bio - based PA5D14 has the characteristics of a green and environmentally friendly polymerization process, a simple preparation process, and excellent properties of the obtained material. Using this technology, a nylon foaming material with a high foaming ratio, low density, high ball rebound rate, and high dynamic fatigue degree can be prepared.

[0099] In the above examples and comparative examples, the test methods and standards for each performance parameter are as follows:

[0100] (1) Melting point of PA5D14: Measured using DSC204F1, under a nitrogen atmosphere, with a heating rate of 10 °C / min.

[0101] (2) XRD: Measured using an XRD diffractometer, in the range of 5 - 40°, with a step size of 4° / min.

[0102] (3) Liquid nuclear magnetic: The sample is dissolved using deuterated - trifluoroacetic acid and tested on a 500M nuclear magnetic spectrometer.

[0103] (4) Density: Measured using a solid densitometer by the Archimedes' drainage method.

[0104] (5) Mechanical properties: Refer to GB / T6344-2008 for testing the tensile strength; refer to GB / T6344-2008 for testing the elongation at break; refer to GB / T6669-2008 for testing the permanent compression set.

[0105] (6) Ball rebound rate: Tested using a ball rebound tester in accordance with GB / T6670-2008.

[0106] (7) Dynamic fatigue: Tested using a fatigue testing machine in accordance with GB / T3263-2011.

[0107] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that these are only examples, and various changes or modifications can be made to these embodiments without departing from the principles and essence of the present invention. The protection scope of the present invention is only defined by the appended claims.

Claims

1. A method for preparing a bio-based high-performance nylon foam material, characterized in that: The following steps are involved: S1. 2-methylpentanediamine, tetradecanoic acid and benzoic acid are mixed in deionized water to prepare salt, and the salt solution is mixed with sodium hypophosphite as a polymerization aid, and the temperature is raised to 200-240° C. to react to obtain a bio-based PA5D14 resin; Among them, when the molar ratio of 2-methylpentanediamine, tetradecanoic acid and benzoic acid is 10.4:10:0.02, the obtained PA5D14 resin has a high molecular weight; when the molar ratio of 2-methylpentanediamine, tetradecanoic acid and benzoic acid is 10.4:10:0.08, the obtained PA5D14 resin has a low molecular weight; S2, using high molecular weight PA5D14 resin as the base resin, adding 5-10% by weight of low molecular weight PA5D14 resin, and obtaining blended particles by extrusion granulation; S3, placing the dried blended particles into a mold, and then placing the mold into a high-pressure reactor, heating it at a preset temperature of 146-154° C. When heated to the set temperature, supercritical CO2 is introduced to exhaust all the air in the high-pressure reactor; S4. After all the air in the autoclave is exhausted, continue to introduce supercritical CO2 until the pressure reaches 12MPa±0.5MPa, stop the air intake, and carry out the reaction under closed conditions. During the reaction, observe that the pressure indication of the autoclave reaches 16MPa±0.5MPa and the temperature indication reaches the preset temperature again, then open the pressure relief valve of the autoclave to discharge CO2 instantly and release the pressure inside the autoclave instantly. Finally, open the autoclave to obtain the bio-based high-performance nylon foam material.

2. The method for preparing a bio-based high-performance nylon foam material according to claim 1, characterized in that: In step S1, for every 10.4 mol of 2-methylpentanediamine, the corresponding amount of sodium hypophosphite is 0.001-0.05 mol.

3. The method for preparing a bio-based high-performance nylon foam material according to claim 1, characterized in that: The reaction in step S1 is carried out under a nitrogen atmosphere.

4. The method for preparing a bio-based high-performance nylon foam material according to claim 1, characterized in that: In step S1, before heating to 200-240°C, the temperature is first raised to 100-160°C, and a portion of deionized water is discharged to reduce the water content in the reaction system to 15-20%.

5. The method for preparing a bio-based high-performance nylon foam material according to claim 1, characterized in that: In step S1, the step of heating to 200-240°C for reaction specifically includes: First, the temperature is raised to 200-220°C, the reaction pressure is maintained at no more than 2.5 Mpa, and the reaction is carried out for 1-2 hours; then, the pressure is released and the temperature is raised to 230-240°C, and the vacuum reaction is carried out for 1-2 hours to finally obtain the bio-based PA5D14 resin.

6. The method for preparing a bio-based high-performance nylon foam material according to claim 1, characterized in that: Before step S3, the blended particles are dried in a vacuum drying oven at 100-110°C.

7. The method for preparing a bio-based high-performance nylon foam material according to claim 1, characterized in that: In step S3, the preset temperature is 147-150°C.

8. A bio-based high-performance nylon foam material, characterized in that: The method is prepared by any one of claims 1 to 7.

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