A bio-based transparent nylon and preparation method thereof

Abstract

The invention discloses a bio-based transparent nylon and a preparation method thereof. The bio-based transparent nylon is synthesized from 1,5-pentanediamine as a diamine, and a dibasic acid containing a benzene ring structure and a long carbon chain dibasic acid as a dibasic acid. The dibasic acid containing a benzene ring structure is selected from terephthalic acid and isophthalic acid, and the long carbon chain dibasic acid is selected from sebacic acid, dodecanedioic acid and tetradecanedioic acid.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a bio-based transparent nylon and a preparation method thereof. Background Art

[0002] With the rapid development of the consumer electronics industry, the research on lightweight transparent materials with high light transmittance, excellent solvent resistance and strong mechanical properties has become a major development direction for plastic products. Such products can be widely used in smart watches, virtual reality VR headsets, plastic frame lenses, medical goggles and other fields.

[0003] As a special new nylon material, transparent nylon has large side groups, alicyclic or aromatic ring structures in its molecular chain structure, which greatly reduces its crystallinity and even makes it an amorphous material, thus achieving its high light transmittance.

[0004] In addition to its high light transmittance (light transmittance reaches over 90%), transparent nylon material also retains the wear resistance, solvent resistance, fatigue resistance and stress cracking resistance of traditional nylon materials. It effectively avoids the problems of traditional plexiglass (polymethyl methacrylate) materials such as insufficient heat resistance and solvent resistance and poor stress cracking resistance of polycarbonate (PC), and has quickly become the preferred material option for consumer electronic products.

[0005] For example, Chinese patent CN101050303A discloses a transparent nylon prepared by polycondensation of bis(3-methyl-4-aminocyclohexyl)methane (MACM) as a diamine and a long carbon chain dibasic acid (with a carbon number of 10 to 20). This type of transparent nylon has the characteristics of low density, good toughness, resistance to bending fatigue, and resistance to stress cracking, and is particularly suitable for application fields such as sports glasses, protective masks, and display screen protective films. Another example is Chinese patent CN1312192C discloses a method for preparing a copolymer transparent nylon with MACM and PACM (4,4-diaminodicyclohexylmethane) as a mixed diamine and dodecanedioic acid as a dibasic acid unit. This copolymer transparent nylon has a high glass transition temperature, excellent fatigue resistance and high transparency, and has a very high mechanical property retention rate after solvent treatment. For example, Plastics Industry (2020, 48(12)) reported that transparent nylon 6T / 6I (T is terephthalic acid and I is isophthalic acid) still has good light transmittance and mechanical properties after multiple melt extrusion under the action of an antioxidant system. This transparent nylon 6T / 6I has very excellent solvent resistance and high strength.

[0006] In summary, currently common transparent nylons mostly use large sterically hindered meta-benzene ring structures or alicyclic structures introduced into the nylon molecular structure in order to reduce or even eliminate the crystallinity of nylon materials to obtain highly transparent optical properties. And there is not much consideration on increasing the bio-based monomer content of the material to achieve the green, low-carbon and environmentally friendly nature of the material. Summary of the invention

[0007] In view of this, the inventors selected appropriate bio-based dibasic acids and bio-based diamines, and when they were mixed in appropriate amounts, the obtained bio-based nylon had good transparency, thereby completing the present invention.

[0008] The object of the present invention is to provide a bio-based transparent nylon, which is synthesized from 1,5-pentanediamine as a diamine, and a dibasic acid containing a benzene ring structure and a long carbon chain dibasic acid as a dibasic acid.

[0009] Another object of the present invention is to provide a method for preparing bio-based transparent nylon, which is polymerized in an aqueous environment by using 1,5-pentanediamine as a diamine and a dibasic acid with a benzene ring structure and a long carbon chain dibasic acid as a dibasic acid.

[0010] The bio-based transparent nylon and the preparation method thereof provided by the present invention have the following advantages:

[0011] (1) Two of the three copolymers of bio-based transparent nylon are bio-based monomers, so the material has excellent low-carbon and environmentally friendly performance;

[0012] (2) Bio-based transparent nylon has a microcrystalline aggregate structure and long carbon chain molecular chain structural units. On the one hand, it has the excellent bending and fatigue resistance of traditional long carbon chain transparent nylon, and on the other hand, it has very excellent solvent resistance;

[0013] (3) Bio-based transparent nylon has good melt fluidity and good processing and molding properties, and can be adapted to the molding of thin-walled complex transparent products;

[0014] (4) Bio-based transparent nylon has good transparency and is widely used;

[0015] (5) The preparation method of bio-based transparent nylon has simple process, mild conditions and is easy to operate. DETAILED DESCRIPTION

[0016] The present invention is further described in detail below through preferred embodiments. Through these descriptions, the characteristics and advantages of the present invention will become clearer and more specific.

[0017] The inventors obtain transparent nylon with high bio-based content by designing a novel molecular structure, selecting appropriate diamines and dibasic acids, and adopting in-situ polymerization to obtain nylon with excellent transparency, solvent resistance, bending fatigue resistance and heat resistance.

[0018] In the present invention, 1,5-pentanediamine is used as the diamine, and a combination of a dibasic acid containing a benzene ring structure and a long carbon chain dibasic acid is used as the dibasic acid.

[0019] Among them, as the dibasic acid containing a benzene ring structure, it is preferably selected from terephthalic acid and isophthalic acid;

[0020] As the long carbon chain dibasic acid, it is preferably selected from sebacic acid, dodecanedioic acid and tetradecanedioic acid.

[0021] The present inventors have found that when the above diamine and dibasic acid are used for synthesis, transparent bio-based nylon can be obtained.

[0022] In a preferred embodiment, the molar ratio of the dibasic acid to 1,5-pentanediamine is preferably 1:1 to 1:1.05. When the usage is within this range, a transparent bio-based nylon with excellent performance can be obtained.

[0023] In a further preferred embodiment, in the dibasic acid, the ratio of the long carbon chain dibasic acid to the dibasic acid containing a benzene ring structure is 8:2-7:3, more preferably 8:2 or 7:3.

[0024] In a preferred embodiment, the high bio-based content transparent nylon of the present invention is synthesized by diamine and dibasic acid in the presence of a functional additive, wherein the functional additive is a metal stearate, more preferably iron stearate or magnesium stearate, and the added amount is 0.05% to 0.5% of the total mass of the dibasic acid monomer, more preferably 0.2%.

[0025] The inventors have found through research that the above functional additives promote the in-situ polymerization of diamine and dibasic acid, thereby forming transparent nylon with excellent performance.

[0026] The present invention also provides a method for preparing bio-based transparent nylon, which comprises the following steps:

[0027] Step (1): 1,5-pentanediamine, a dibasic acid containing a benzene ring structure, a long carbon chain dibasic acid and deionized water are salified to obtain a nylon mixed salt solution;

[0028] Step (2): the nylon mixed salt solution prepared in step (1) is put into a high-pressure polymerization reactor together with an antioxidant system, a capping agent, a catalyst and a functional additive. The temperature is first raised to 180° C. in a closed environment and under the protection of nitrogen, and the reaction is carried out for 0.5-1h. The temperature is then raised to 220° C., the reaction pressure is controlled to be ≤2Mpa, and the reaction is carried out for 1-1.5h. Finally, the pressure is released and the temperature is raised to 250° C., and a vacuum reaction is carried out for 1-1.5h to obtain bio-based transparent nylon.

[0029] Preferably, in step (1), the amount of deionized water added is 100% to 200% of the total mass of the dibasic acid and diamine monomers.

[0030] In a preferred embodiment, in step (1), the pH value of the salt-forming reaction at the end point of the reaction is 7.5-8.

[0031] In step (2), the antioxidant system is antioxidant 1098 and antioxidant 168, more preferably a combination of antioxidant 1098 and antioxidant 168 (mass ratio is 1:1), and the added amount is 0.1% to 0.5% of the total mass of the dibasic acid monomer.

[0032] In step (2), the end-capping agent is selected from one or more of benzoic acid, terephthalic acid, 2-naphthalenecarboxylic acid or phthalic anhydride, and the added amount is 0.1% to 1% of the total mass of the dibasic acid monomer.

[0033] In step (2), the catalyst is selected from one or more of sodium hypophosphite, phosphoric acid, phosphorous acid, and metaphosphoric acid, and the added amount is 0.05% to 0.2% of the total mass of the dibasic acid monomer.

[0034] In step (2), the functional auxiliary agent is a metal stearate, more preferably iron stearate or magnesium stearate, and the added amount is 0.05% to 0.5% of the total mass of the dibasic acid monomer.

[0035] Example

[0036] Example 1 Preparation of bio-based transparent nylon resin

[0037] (1) Salt-forming reaction: 7 mol of sebacic acid and 3 mol of terephthalic acid were dissolved in 4 kg of deionized water. Under continuous stirring at 60°C, about 10.3 mol of 1,5-pentanediamine was slowly added dropwise to the above mixed system solution for about 30 minutes. The pH value of the system reaction endpoint was strictly controlled in the range of 7.5 to 8 to obtain a nylon mixed salt solution.

[0038] (2) Polymerization reaction. The mass of the nylon mixed salt obtained in step (1) is recorded as 100 parts, and the nylon mixed salt solution, 0.2 parts of the antioxidant system (1098:168=1:1), 0.2 parts of benzoic acid, 0.1 parts of sodium hypophosphite and 0.2 parts of magnesium stearate are put into a 10L high-pressure polymerization reactor, and high-purity nitrogen is introduced and vacuumed. This is repeated more than three times to fully replace the air in the reactor. Stirring is started and the stirring rate is controlled at 60-120rpm. The temperature in the reactor is raised to 200℃ and the reaction is carried out for 0.5h; the temperature is raised to 220℃ again, and the reaction pressure is controlled to ≤2Mpa by appropriate pressure relief. The pre-condensation reaction is carried out by maintaining the pressure for 1 hour; the temperature in the reactor is raised to 260℃, and the pressure relief valve is slowly opened during the heating process. The steam in the reactor is gradually released within 90 minutes to reduce the pressure in the reactor to normal pressure. Vacuum to -0.06~-0.08MPa, react for 1 hour, and complete the condensation reaction. Finally, high-purity nitrogen was filled until the pressure in the reactor was positive. After standing for a period of time, the discharge valve at the bottom of the reactor was opened to allow the material to pass through the cooling water tank. After wire drawing and pelletizing and vacuum drying, bio-based transparent nylon 510 / 5T resin was obtained.

[0039] The melting point, viscosity, mechanical properties, light transmittance, melt fluidity and other properties of the bio-based transparent nylon resin were tested, and the test results of various properties are listed in Table 1.

[0040] Example 2

[0041] The component ratio and preparation method of the bio-based nylon resin in this embodiment are basically the same as those in Example 1, except that the dibasic acid monomers in this embodiment are sebacic acid and isophthalic acid, wherein the amount of sebacic acid is 8 mol and the amount of isophthalic acid is 2 mol, and the prepared product is a bio-based transparent nylon 510 / 5I resin.

[0042] The test results of various properties of the bio-based nylon resin in this example are listed in Table 1

[0043] Example 3

[0044] The component ratio and preparation method of the bio-based nylon resin in this embodiment are basically the same as those in Example 1, except that the dibasic acid monomers in this embodiment are dodecanedioic acid and terephthalic acid, wherein the amount of dodecanedioic acid is 8 mol, the amount of terephthalic acid is 2 mol, and the functional additive is iron stearate, which is added in an amount of 0.2 parts, and the prepared product is a bio-based transparent nylon 512 / 5T resin.

[0045] The test results of various properties of the bio-based nylon resin in this example are listed in Table 1.

[0046] Example 4

[0047] The component ratio and preparation method of the bio-based nylon resin in this embodiment are basically the same as those in Example 1, except that the dibasic acid monomers in this embodiment are dodecanedioic acid and isophthalic acid, wherein the amount of dodecanedioic acid is 7 mol, the amount of isophthalic acid is 3 mol, and the functional additive is iron stearate, which is added in an amount of 0.2 parts, and the prepared product is a bio-based transparent nylon 512 / 5I resin.

[0048] The test results of various properties of the bio-based nylon resin in this example are listed in Table 1.

[0049] Example 5

[0050] The component ratio and preparation method of the bio-based nylon resin in this embodiment are basically the same as those in Example 1, except that the dibasic acid monomers in this embodiment are tetradecanedioic acid and terephthalic acid, wherein the amount of tetradecanedioic acid is 8 mol, the amount of terephthalic acid is 2 mol, and the functional additive is iron stearate, which is added in an amount of 0.2 parts, and the prepared bio-based transparent nylon 514 / 5T resin is obtained.

[0051] The test results of various properties of the bio-based nylon resin in this example are listed in Table 1.

[0052] Example 6

[0053] The component ratio and preparation method of the bio-based nylon resin in this embodiment are basically the same as those in Example 1, except that the dibasic acid monomers in this embodiment are tetradecanedioic acid and isophthalic acid, wherein the amount of tetradecanedioic acid is 8 mol, the amount of isophthalic acid is 2 mol, and the functional additive is iron stearate, which is added in an amount of 0.2 parts, and the prepared product is a bio-based transparent nylon 514 / 5I resin.

[0054] The test results of various properties of the bio-based nylon resin in this example are listed in Table 1.

[0055] Comparative Example 1

[0056] The bio-based nylon resin was prepared by a process substantially the same as that in Example 1, except that the amounts of dibasic acid monomers were different, wherein the amount of sebacic acid was 9 mol and the amount of terephthalic acid was 1 mol, and the obtained bio-based PA 510 / 5T resin was obtained.

[0057] The test results of various properties of the bio-based nylon resin in this comparative example are listed in Table 2.

[0058] Comparative Example 2

[0059] The bio-based nylon resin was prepared by the same process as in Example 1, except that the amount of sebacic acid used was 4 mol, the amount of terephthalic acid used was 6 mol, and the obtained bio-based PA 510 / 5T resin was obtained.

[0060] The test results of various properties of the bio-based nylon resin in this comparative example are listed in Table 2.

[0061] Comparative Example 3

[0062] The bio-based nylon resin was prepared in substantially the same process as in Example 1, except that magnesium stearate was not added.

[0063] The test results of various properties of the bio-based nylon resin in this comparative example are listed in Table 2.

[0064] Comparative Example 4

[0065] The bio-based nylon resin was prepared by substantially the same process as in Example 1, except that nano-silicon dioxide was used instead of magnesium stearate.

[0066] The test results of various properties of the bio-based nylon resin in this comparative example are listed in Table 2.

[0067] Comparative Example 5

[0068] The bio-based nylon resin was prepared by a process substantially the same as that in Example 1, except that the dibasic acid monomers and their amounts were different, wherein adipic acid was used instead of sebacic acid, the amount of adipic acid was 8 mol, and the amount of terephthalic acid was 2 mol, and the obtained bio-based PA 56 / 5T resin was obtained.

[0069] The test results of various properties of the bio-based nylon resin in this comparative example are listed in Table 2.

[0070] Comparative Example 6

[0071] The bio-based nylon resin was prepared by a process substantially the same as that in Example 1, except that the dibasic acid monomers and their amounts were different, wherein adipic acid was used instead of sebacic acid, the amount of adipic acid was 7 mol, and the amount of terephthalic acid was 3 mol, and the obtained bio-based PA 56 / 5T resin was obtained.

[0072] The test results of various properties of the bio-based nylon resin in this comparative example are listed in Table 2.

[0073] Comparative Example 7

[0074] The bio-based nylon resin was prepared by a process substantially the same as that in Example 1, except that the dibasic acid monomers and their amounts were different, wherein adipic acid was used instead of sebacic acid, the amount of adipic acid was 6 mol, and the amount of terephthalic acid was 4 mol, and the obtained bio-based PA 56 / 5T resin was obtained.

[0075] The test results of various properties of the bio-based nylon resin in this comparative example are listed in Table 2.

[0076] Comparative Example 8

[0077] The bio-based nylon resin was prepared by a process substantially the same as that in Example 1, except that the dibasic acid monomers and their amounts were different, wherein adipic acid was used instead of sebacic acid, the amount of adipic acid was 5 mol, and the amount of terephthalic acid was 5 mol, and the obtained bio-based PA 56 / 5T resin was obtained.

[0078] The test results of various properties of the bio-based nylon resin in this comparative example are listed in Table 2.

[0079] Comparative Example 9: Preparation of nylon 6I / 6T resin

[0080] (1) Salt-forming reaction: 7 mol of isophthalic acid and 3 mol of terephthalic acid are dissolved in 4 kg of deionized water. Under continuous stirring at 60°C, about 10.3 mol of hexamethylenediamine is slowly added dropwise to the mixed system solution. The system addition time is controlled to be about 30 minutes. The process strictly controls the pH value of the system reaction end point to be in the range of 7.5 to 7.8, and finally a nylon mixed salt solution is obtained.

[0081] (2) Polymerization reaction: The mass of the nylon mixed salt obtained in step (1) is recorded as 100 parts, and the nylon mixed salt solution, 0.2 parts of antioxidant system (1098:168=1:1), 0.2 parts of benzoic acid, and 0.1 parts of sodium hypophosphite are put into a 10L high-pressure polymerization reactor, and high-purity nitrogen is introduced and vacuumed. This is repeated more than three times to fully replace the air in the reactor. Stirring is started and the stirring rate is controlled at 60-120rpm. The temperature in the reactor is raised to 200°C and the reaction is carried out for 0.5h; the temperature is raised to 220°C again, and the reaction pressure is controlled to ≤2Mpa by appropriate pressure relief, and the pressure is maintained for 1 hour for pre-condensation reaction; the temperature in the reactor is raised to 280-290°C, and the pressure relief valve is slowly opened during the heating process. The steam in the reactor is gradually released within 90 minutes to reduce the pressure in the reactor to normal pressure. Vacuum to -0.06--0.08MPa, react for 1 hour, and complete the polycondensation reaction. Finally, high-purity nitrogen is filled until the pressure in the reactor is positive. After standing for a period of time, the discharge valve at the bottom of the reactor is opened to allow the material to pass through the cooling water tank, and then the material is drawn, pelletized and vacuum dried to obtain transparent nylon 6I / 6T resin.

[0082] The test results of various properties of the nylon resin in this comparative example are listed in Table 2.

[0083] Comparative Example 10: Preparation of nylon PACM12 resin

[0084] (1) Salt-forming reaction: 10 mol of dodecanedioic acid was dissolved in 4 kg of deionized water. Under continuous stirring at 60°C, about 10.3 mol of pentamethylenediamine was slowly added dropwise to the mixed system solution. The system addition time was controlled to be about 30 min. The pH value of the system reaction endpoint was strictly controlled to be in the range of 7.5 to 7.8. Finally, a nylon salt solution was obtained.

[0085] (2) Polymerization reaction: The mass of the nylon salt obtained in step (1) is recorded as 100 parts, and the nylon mixed salt solution, 0.2 parts of the antioxidant system (1098:168=1:1), 0.2 parts of benzoic acid, and 0.1 parts of sodium hypophosphite are put into a 10L high-pressure polymerization reactor, and high-purity nitrogen is introduced and vacuumed. This is repeated more than three times to fully replace the air in the reactor. Stirring is started and the stirring rate is controlled at 60-120rpm. The temperature in the reactor is raised to 200°C and the reaction is carried out for 0.5h; the temperature is raised to 220°C again, and the reaction pressure is controlled to ≤2Mpa by appropriate pressure relief, and the pressure is maintained for 1 hour for pre-condensation reaction; the temperature in the reactor is raised to 250-270°C, and the pressure relief valve is slowly opened during the heating process. The steam in the reactor is gradually released within 90 minutes to reduce the pressure in the reactor to normal pressure. Vacuum to -0.06--0.08MPa, react for 1 hour, and complete the polycondensation reaction. Finally, high-purity nitrogen was filled until the pressure in the reactor was positive. After standing for a period of time, the discharge valve at the bottom of the reactor was opened to allow the material to pass through the cooling water tank. After wire drawing, pelletizing and vacuum drying, the bio-based transparent nylon PACM12 resin was obtained.

[0086] The test results of various properties of the nylon resin in this comparative example are listed in Table 2.

[0087] In the above embodiments and comparative examples, the test methods and standards of various performance parameters are as follows:

[0088] (1) Melting point: measured using a DSC tester in a nitrogen atmosphere at a heating rate of 10°C / min.

[0089] (2) Relative viscosity: The relative viscosity of the product at a concentration of 0.5 g / dL was measured in a 98% concentrated sulfuric acid solution at (25±0.01)°C using an Ubbelohde viscometer.

[0090] (3) Mechanical properties: The tensile strength was tested according to ISO 527-1 / -2, the flexural strength and flexural modulus were tested according to ISO 178, and the simply supported beam impact strength was tested according to ISO 179 / 1eA.

[0091] (4) Transmittance test: Place the sheet sample in a UV spectrophotometer and perform a transmittance test.

[0092] (5) Water absorption test: According to ISO 62 standard, the sheet sample was placed in 25°C water for 24 hours, and the weight change before and after water absorption was tested.

[0093] (6) Heat deformation temperature: The heat deformation temperature is measured under a load of 0.45 MPa according to standard ISO 75-1 / -2.

[0094] (7) Wohler fatigue test: According to ISO 178 standard, the sample fracture cycle test was carried out on the CIMTronic 2000 device of Dyna Mess.

[0095] (8) Alcohol resistance test: Place a 55mm*65mm*3mm sheet sample in 98% alcohol and soak it for 1 hour. Take it out and observe the surface condition of the sample. Score according to the surface condition. Evaluation criteria: 1: The surface is transparent and there is no stress whitening. 2: The surface is transparent and there is a small amount of stress whitening. 3: The surface is transparent and there is obvious stress whitening. 4: The surface is opaque and there is a large amount of stress whitening.

[0096] Table 1 Performance test results of bio-based nylon resin in Example

[0097]

[0098] Table 2 Performance test results of comparative bio-based nylon resin

[0099]

[0100] From the test results in Table 1 and Table 2, it can be seen that for nylon 510 / 5T, only when the molar ratio of 510:5T is between 8:2 and 7:3, nylon 510 / 5T will show the performance characteristics of transparent nylon (more than 90% transmittance). When it is in other copolymer monomer ratios, nylon 510 / 5T is not a transparent nylon material.

[0101] Moreover, the addition of the functionalized auxiliary agent metal stearate can simultaneously improve the material's light transmittance (the material's light transmittance is increased from 86.5% to 90.5%), heat resistance (the material's heat deformation temperature is increased from 124°C to 135°C), and solvent resistance (the material's alcohol resistance test results change from the original stress whitening phenomenon to transparent stress-free whitening phenomenon). This may be due to the presence of the functionalized auxiliary agent metal stearate, which further optimizes the construction of the aggregated state of the microcrystalline structure.

[0102] This phenomenon also applies to the material systems of PA512 / 5T, PA512 / 5I, PA514 / 5T, and PA514 / 5I, but not to the PA5T / 56 system. When the molar ratio of 56:5T is between 5:5 and 8:2, the materials do not show excellent transparency. This shows that the patented technology of the present invention is only applicable in a specific copolymer nylon system.

[0103] In addition, compared with typical transparent nylon 6I / 6T and PACM12, the bio-based transparent nylon of the present invention retains the high toughness and fatigue resistance characteristics of the long carbon chain transparent nylon PACM12, while also possessing the excellent solvent resistance characteristics of transparent nylon 6I / 6T materials.

[0104] In summary, the preparation of the bio-based transparent nylon of the present invention promotes the formation of a special aggregation structure of the microcrystalline structure through molecular structure design and in-situ polymerization of special functional additives, thereby giving the bio-based transparent nylon excellent transparency, solvent resistance, bending fatigue resistance, low density and heat resistance.

[0105] The present invention has been described in detail above in conjunction with preferred embodiments and exemplary examples. However, it should be noted that these specific embodiments and examples are only illustrative explanations of the present invention and do not constitute any limitation on the protection scope of the present invention. Without exceeding the spirit and protection scope of the present invention, various improvements, equivalent substitutions or modifications may be made to the technical content of the present invention and its implementation methods, all of which fall within the protection scope of the present invention. The protection scope of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing bio-based transparent nylon, which is synthesized from 1,5-pentanediamine as a diamine, and a dibasic acid containing a benzene ring structure and a long carbon chain dibasic acid as a dibasic acid in the presence of a functional additive. The dibasic acid containing a benzene ring structure is isophthalic acid, The long carbon chain dibasic acid is selected from sebacic acid, dodecanedioic acid and tetradecanedioic acid; The molar ratio of the long carbon chain dibasic acid to the dibasic acid containing a benzene ring structure is 8:2 to 7:3; The molar ratio of the total amount of dibasic acid to that of 1,5-pentanediamine is 1:1 to 1:1.05; The functional auxiliary agent is a metal stearate. in, The amount of metal stearate added is 0.05% to 0.5% of the total mass of the dibasic acid monomer. Wherein, the metal stearate is magnesium stearate or iron stearate, The method comprises the following steps: Step (1): 1,5-pentanediamine as a diamine, a dibasic acid containing a benzene ring structure, a long carbon chain dibasic acid and deionized water are salted to obtain a nylon mixed salt solution, wherein the amount of deionized water added is 100% to 200% of the total mass of the dibasic acid and the diamine monomers, and the pH value of the reaction end point system of the salt-forming reaction is 7.5 to 8. Step (2): putting the nylon mixed salt solution prepared in step (1) into a high-pressure polymerization reactor with an antioxidant system, a capping agent, a catalyst and a functional additive, first heating to 180° C. in a closed environment and under the protection of nitrogen, reacting for 0.5-1h, then heating to 220° C., controlling the reaction pressure to ≤2Mpa, reacting for 1-1.5h; finally, releasing the pressure and heating to 250° C., vacuumizing and reacting for 1-1.5h to obtain bio-based transparent nylon; In step (2), The antioxidant system is antioxidant 1098 and antioxidant 168, and the addition amount is 0.1% to 0.5% of the total mass of the dibasic acid monomer; The end-capping agent is selected from one or more of benzoic acid, terephthalic acid, 2-naphthalenecarboxylic acid or phthalic anhydride, and the added amount is 0.1% to 1% of the total mass of the dibasic acid monomer; The catalyst is selected from one or more of sodium hypophosphite, phosphoric acid, phosphorous acid and metaphosphoric acid, and the added amount is 0.05% to 0.2% of the total mass of the dibasic acid monomer.

2. The method according to claim 1, wherein: The molar ratio of the long carbon chain dibasic acid to the dibasic acid containing a benzene ring structure is 8:2 or 7:

3.

3. The method according to claim 1, wherein: The amount of metal stearate added is 0.2% of the total mass of the dibasic acid monomer.

4. The method according to claim 1, wherein: In step (2), The antioxidant system is a combination of antioxidant 1098 and antioxidant 168 in a mass ratio of 1:1.

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