Preparation method of a fully bio-based polyamide elastomer

Abstract

The present invention provides a preparation method of a fully bio-based polyamide elastomer, belonging to the technical field of material preparation. A bio-based dibasic acid, a bio-based diamine, and water are melt-mixed and then reacted to obtain a carboxyl-terminated polyamide hard segment; a bio-based diol, a bio-based dibasic acid, and a catalyst are melt-mixed and then reacted to obtain a hydroxyl-terminated polyester diol soft segment; the carboxyl-terminated polyamide hard segment, the hydroxyl-terminated polyester diol soft segment, and a catalyst are melt-mixed and then reacted, and the reactants are mixed with a second catalyst and then reacted to obtain a fully bio-based polyamide elastomer. Since the content of polar groups in the chemical structure of the obtained polyamide elastomer material has been increased to a certain extent, it also exhibits excellent mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of material preparation, and particularly to a preparation method of a fully bio-based polyamide elastomer. Background Art

[0002] Polyamide elastomers, also known as nylon elastomers, are a new type of linear alternating block copolymer composed of polyamide hard segments and polyether (or polyester) soft segments. Due to their excellent combination of the good properties of polyamide hard segments and polyether (or polyester) soft segments, they exhibit extremely excellent resilience, good heat resistance, excellent low-temperature performance, etc. Moreover, the properties of polyamide elastomers can be regulated by changing the relative content between the soft segments and the hard segments, which further expands the application fields of polyamide elastomers. Up to now, polyamide elastomers have been widely used in many fields such as the automotive industry, sports equipment, medical and health, thin films and pipes, etc. They are high-value-added high-end elastomer materials with great development potential.

[0003] However, the monomer raw materials used in current polyamide elastomer materials basically come from non-renewable fossil resources. Therefore, the rapid development of polyamide elastomers is bound to lead to a large consumption of fossil resources and increasingly serious ecological and environmental problems. In order to reduce the consumption of fossil resources and improve the ecological environment, the development of renewable bio-based polymer materials using biomass raw materials has attracted extensive attention in the academic and industrial fields. Compared with traditional polyamide elastomer materials derived from fossil resources, bio-based polyamide elastomer materials have outstanding advantages such as wide and sustainable raw material sources, low carbon emissions, low global warming potential, and environmental friendliness. Summary of the Invention

[0004] To solve the above problems, the present invention provides a preparation method of a fully bio-based polyamide elastomer. The present invention uses a variety of bio-based monomers as raw materials. First, a carboxyl-terminated polyamide hard segment and a hydroxyl-terminated polyester diol soft segment are respectively prepared through molecular structure design, and then the above hard segment and soft segment are subjected to a polymerization reaction through an optimized catalyst system, and finally a fully bio-based polyamide elastomer material is successfully prepared. Moreover, due to a certain degree of increase in the content of polar groups in the chemical structure of the obtained polyamide elastomer material, it also exhibits excellent mechanical properties.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a preparation method of a fully bio-based polyamide elastomer, comprising the following steps:

[0007] 1) Melting and mixing a bio-based dicarboxylic acid with a bio-based diamine and water, and then reacting to obtain a carboxyl-terminated polyamide hard segment;

[0008] 2) The bio-based diol is melt-mixed with the bio-based diacid and the first catalyst and then reacted to obtain a hydroxyl-terminated polyester diol soft segment;

[0009] 3) The carboxyl-terminated polyamide hard segment obtained in step 1) is melt-mixed with the hydroxyl-terminated polyester diol soft segment obtained in step 2) and the first catalyst and then reacted to obtain a reaction product. The reaction product is mixed with the second catalyst and then reacted to obtain a fully bio-based polyamide elastomer;

[0010] The first catalyst is nano-titanium dioxide;

[0011] The second catalyst is tetrabutyl titanate or tetrabutyl zirconate.

[0012] Preferably, the bio-based diacid includes glutaric acid, azelaic acid or sebacic acid;

[0013] The bio-based diamine includes pentamethylenediamine, nonamethylenediamine or decamethylenediamine;

[0014] The bio-based diol includes pentanediol, nonamethylenediamine alcohol and decanediol.

[0015] Preferably, the mass ratio of the bio-based diacid to the bio-based diamine in step 1) is 100:40 to 75.

[0016] Preferably, the conditions for the melt mixing in step 1) include: temperature is 135-140 °C, stirring for 30 min;

[0017] The conditions for the reaction include: temperature is 190-200 °C, time is 2 h.

[0018] Preferably, the mass ratio of the bio-based diol to the bio-based diacid and the first catalyst in step 2) is 100:64 to 171:0.33 to 0.54.

[0019] Preferably, the conditions for the melt mixing in step 2) include: temperature is 135-140 °C, stirring for 30 min;

[0020] The conditions for the reaction include: temperature is 210-220 °C, time is 3 h.

[0021] Preferably, the mass ratio of the carboxyl-terminated polyamide hard segment to the hydroxyl-terminated polyester diol soft segment and the first catalyst in step 3) is 100:20 to 471:0.24 to 1.1.

[0022] Preferably, the conditions for the melt mixing in step 3) include: temperature is 170-185 °C, stirring for 30 min;

[0023] The conditions of the reaction include: temperature of 220 - 230 °C and time of 3 h.

[0024] Preferably, the dosage of the second catalyst in step 3) is 2 - 5‰ of the total mass of the reactants.

[0025] Preferably, the conditions for mixing the reactants with the second catalyst in step 3) include: temperature of 250 °C and time of 30 min;

[0026] The conditions of the reaction include: temperature of 250 °C and time of 4 h.

[0027] In the present invention, the first catalyst in step 3) is nano - titanium dioxide. Relatively more water is generated in the early stage of polymerization, and it is a solid catalyst, which can effectively prevent hydrolysis and thus has a long - term catalytic effect; the second catalyst is tetrabutyl titanate or tetrabutyl zirconate. Although these two catalysts have higher catalytic activity, they are prone to hydrolysis, and relatively less water is generated in the later stage of the polymerization reaction. Therefore, this composite catalyst system can achieve an efficient catalytic effect under such conditions, and thus obtain a polymer material with excellent performance.

[0028] In view of the current situation that polyamide elastomers are basically synthesized from monomers derived from fossil resources and belong to non - renewable polymers, the present invention selects a variety of bio - based monomers as raw materials. Through molecular structure design, on the basis of separately preparing a carboxyl - terminated polyamide hard segment and a hydroxyl - terminated polyester diol soft segment derived from bio - based raw materials, the two are further subjected to a polymerization reaction, and finally a fully bio - based polyamide elastomer material is successfully prepared. The fully bio - based polyamide elastomer material proposed by the present invention has excellent comprehensive properties and is a high - end elastomer material with great development potential and broad application prospects.

[0029] The beneficial effects of the present invention are as follows:

[0030] (1) A fully bio - based long - carbon - chain polyamide elastomer is synthesized, which is more conducive to reducing the use of fossil resources, and helps to reduce carbon emissions and promote sustainable development;

[0031] (2) By using the method of controlling the chemical structure and molecular weight of the hard and soft segments, the synthesis of the fully bio - based long - carbon - chain polyamide elastomer is carried out controllably. The content of polar groups in the obtained material has been increased to a certain extent, showing excellent mechanical properties;

[0032] (3) In step 3, namely the polymerization process of the fully bio - based long - carbon - chain polyamide elastomer, an optimized catalyst usage method (a composite usage method of solid catalyst + liquid catalyst) is adopted, which enables the polymerization reaction to proceed better, with a higher reaction degree, and the properties of the obtained product are also more excellent. Description of the Drawings

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings required for use in the embodiments will be briefly introduced below.

[0034] Figure 1 It is the synthesis reaction equation of a fully bio-based polyamide elastomer, where X is 3, 7 or 8, p is the repeating unit of the bio-based polyamide hard segment capped with carboxyl groups, and is 1 to 7; q is the number of repeating units of the hydroxyl-terminated polyester diol soft segment, and is 1 to 7; n is 5 - 20. Detailed implementation manners

[0035] The present invention provides a preparation method of a fully bio-based polyamide elastomer, including the following steps:

[0036] 1) Melting and mixing a bio-based dicarboxylic acid, a bio-based diamine and water, and then reacting to obtain a carboxyl-terminated polyamide hard segment;

[0037] 2) Melting and mixing a bio-based diol, a bio-based dicarboxylic acid and a first catalyst, and then reacting to obtain a hydroxyl-terminated polyester diol soft segment;

[0038] 3) Melting and mixing the carboxyl-terminated polyamide hard segment obtained in step 1) with the hydroxyl-terminated polyester diol soft segment obtained in step 2) and a first catalyst, and then reacting to obtain a reaction product. Mixing the reaction product with a second catalyst and then reacting to obtain a fully bio-based polyamide elastomer;

[0039] The first catalyst is nano-titanium dioxide;

[0040] The second catalyst is tetrabutyl titanate or tetrabutyl zirconate.

[0041] The present invention melts and mixes a bio-based dicarboxylic acid, a bio-based diamine and water, and then reacts to obtain a carboxyl-terminated polyamide hard segment.

[0042] In the present invention, the water is preferably deionized water. The addition of the deionized water is for two purposes. One is to make the materials mix better and add them into the reaction kettle; the other is to provide a certain pressure for the system in the early stage of the reaction.

[0043] In the present invention, the bio-based dicarboxylic acid preferably includes glutaric acid, azelaic acid or sebacic acid. In the present invention, the bio-based diamine preferably includes pentamethylenediamine, nonamethylenediamine or decamethylenediamine. In the present invention, the mass ratio of the bio-based dicarboxylic acid to the bio-based diamine is preferably 100:40 to 75, more preferably 100:43 to 68. In the present invention, the conditions for melt mixing preferably include: a temperature of 135 to 140 °C and stirring for 30 min. In the present invention, the conditions for the reaction preferably include: a temperature of 190 to 200 °C and a time of 2 h. In the present invention, the melt mixing and the reaction are preferably carried out under a nitrogen atmosphere.

[0044] In the present invention, a bio-based diol is melt mixed with a bio-based dicarboxylic acid and a first catalyst and then reacted to obtain a hydroxyl-terminated polyester diol soft segment. In the present invention, the bio-based diol preferably includes pentanediol, nonanediol or decanediol. In the present invention, the mass ratio of the bio-based diol to the bio-based dicarboxylic acid and the first catalyst is preferably 100:64 to 171:0.33 to 0.54, more preferably 100:98 to 107:0.4 to 0.41. In the present invention, the conditions for melt mixing preferably include: a temperature of 135 to 140 °C and stirring for 30 min. In the present invention, the conditions for the reaction preferably include: a temperature of 210 to 220 °C and a time of 3 h. In the present invention, the reaction temperature is more preferably 215 °C.

[0045] In the present invention, the obtained carboxyl-terminated polyamide hard segment is melt mixed with the obtained hydroxyl-terminated polyester diol soft segment and a first catalyst and then reacted to obtain a reaction product, and the reaction product is mixed with a second catalyst and then reacted to obtain a fully bio-based polyamide elastomer; the first catalyst is nano titanium dioxide; the second catalyst is tetrabutyl titanate or zirconium tetrabutylate.

[0046] In the present invention, the mass ratio of the carboxyl-terminated polyamide hard segment to the hydroxyl-terminated polyester diol soft segment and the first catalyst is preferably 100:20 to 471:0.24 to 1.1, more preferably 100:93 to 98:0.39 to 0.4. In the present invention, the conditions for melt mixing preferably include: a temperature of 170 to 185 °C and stirring for 30 min, and the temperature is more preferably 180 °C. In the present invention, the conditions for the reaction preferably include: a temperature of 220 to 230 °C and a time of 3 h, and the temperature is more preferably 225 °C. In the present invention, the dosage of the second catalyst is preferably 2 to 5‰ of the total mass of the reaction product. In the present invention, the conditions for mixing the reaction product with the second catalyst preferably include: a temperature of 250 °C and a time of 30 min. In the present invention, the conditions for the reaction preferably include: a temperature of 250 °C and a time of 4 h.

[0047] To further illustrate the present invention, the present invention will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0048] Example 1

[0049] A preparation method of a fully bio-based polyamide elastomer, the steps are as follows:

[0050] (1) Add 100 parts by weight of sebacic acid, 43 parts by weight of decanediamine and 14.3 parts by weight of deionized water into a reaction kettle, displace the air in the kettle with nitrogen, then heat up to 135 °C, and keep stirring at a constant temperature for 30 min to fully melt and mix the materials. Subsequently, heat up to 190 °C and keep reacting at a constant temperature for 2 h, then stop the reaction to obtain a carboxyl-terminated polyamide hard segment.

[0051] (2) Add 100 parts by weight of sebacic acid, 98 parts by weight of decanediol and 0.4 parts by weight of nano-titanium dioxide into a reaction kettle, displace the air in the kettle with nitrogen, then heat up to 135 °C, and keep stirring at a constant temperature for 30 min to fully melt and mix the materials. Subsequently, heat up to 210 °C and keep reacting at a constant temperature for 3 h, then stop the reaction to obtain a hydroxyl-terminated polyester diol soft segment.

[0052] (3) Add 100 parts by weight of carboxyl-terminated polyamide hard segment, 471 parts by weight of hydroxyl-terminated polyester diol soft segment and 1.1 parts by weight of nano-titanium dioxide into a reaction kettle, displace the air in the kettle with nitrogen, then heat up to 170 °C, and keep stirring at a constant temperature for 30 min to fully melt and mix the materials. Subsequently, heat up to 220 °C and keep reacting at a constant temperature for 3 h. Then release the system to atmospheric pressure, add 1.1 parts by weight of tetrabutyl titanate, and at the same time heat up the system to 250 °C, then perform a vacuum pumping operation, reduce the system pressure to below 100 Pa within 30 min, and keep reacting at a constant temperature for 4 h. Finally, stop the reaction, restore the system to atmospheric pressure, and obtain a fully bio-based polyamide elastomer.

[0053] Example 2

[0054] A preparation method of a fully bio-based polyamide elastomer, the steps are as follows:

[0055] (1) Add 100 parts by weight of sebacic acid, 75 parts by weight of decanediamine and 17.5 parts by weight of deionized water into a reaction kettle, displace the air in the kettle with nitrogen, then heat up to 140 °C, and keep stirring at a constant temperature for 30 min to fully melt and mix the materials. Subsequently, heat up to 200 °C and keep reacting at a constant temperature for 2 h, then stop the reaction to obtain a carboxyl-terminated polyamide hard segment.

[0056] (2) Add 100 parts by weight of sebacic acid, 171 parts by weight of decanediol, and 0.54 part by weight of nano-titanium dioxide into a reaction kettle, displace the air in the kettle with nitrogen, then heat up to 140 °C, and keep stirring at a constant temperature for 30 min to fully melt and mix the materials. Subsequently, heat up to 220 °C and keep reacting at a constant temperature for 3 h, then stop the reaction to obtain a hydroxyl-terminated polyester diol soft segment.

[0057] (3) Add 100 parts by weight of a carboxyl-terminated polyamide hard segment, 20 parts by weight of a hydroxyl-terminated polyester diol soft segment, and 0.24 part by weight of nano-titanium dioxide into a reaction kettle, displace the air in the kettle with nitrogen, then heat up to 180 °C, and keep stirring at a constant temperature for 30 min to fully melt and mix the materials. Subsequently, heat up to 230 °C and keep reacting at a constant temperature for 3 h. Then release the pressure of the system to atmospheric pressure, add 0.24 part by weight of tetrabutyl zirconate, simultaneously heat up the system to 250 °C, then perform a vacuum pumping operation, reduce the pressure of the system to below 100 Pa within 30 min, and keep reacting at a constant temperature for 4 h. Finally, stop the reaction, restore the system to atmospheric pressure to obtain a fully bio-based polyamide elastomer.

[0058] Example 3

[0059] A preparation method of a fully bio-based polyamide elastomer, the steps are as follows:

[0060] (1) Add 100 parts by weight of sebacic acid, 68 parts by weight of decanediamine, and 16.8 parts by weight of deionized water into a reaction kettle, displace the air in the kettle with nitrogen, then heat up to 135 °C, and keep stirring at a constant temperature for 30 min to fully melt and mix the materials. Subsequently, heat up to 195 °C and keep reacting at a constant temperature for 2 h, then stop the reaction to obtain a carboxyl-terminated polyamide hard segment.

[0061] (2) Add 100 parts by weight of sebacic acid, 107 parts by weight of decanediol, and 0.41 part by weight of nano-titanium dioxide into a reaction kettle, displace the air in the kettle with nitrogen, then heat up to 135 °C, and keep stirring at a constant temperature for 30 min to fully melt and mix the materials. Subsequently, heat up to 215 °C and keep reacting at a constant temperature for 3 h, then stop the reaction to obtain a hydroxyl-terminated polyester diol soft segment.

[0062] (3) Add 100 parts by weight of carboxyl - terminated polyamide hard segments, 98 parts by weight of hydroxyl - terminated polyester diol soft segments, and 0.40 part by weight of nano - titanium dioxide into a reaction kettle. Replace the air in the kettle with nitrogen, then heat up to 185 °C and keep stirring at a constant temperature for 30 min to fully melt - mix the materials. Subsequently, heat up to 225 °C and react at a constant temperature for 3 h. Then release the pressure of the system to atmospheric pressure, add 0.40 part by weight of tetrabutyl titanate, simultaneously heat up the system to 250 °C, then perform a vacuum - pumping operation, reduce the pressure of the system below 100 Pa within 30 min, and react at a constant temperature for 4 h. Finally, stop the reaction and restore the system to atmospheric pressure to obtain a fully bio - based polyamide elastomer.

[0063] Example 4

[0064] A preparation method of a fully bio - based polyamide elastomer, the steps are as follows:

[0065] (1) Add 100 parts by weight of sebacic acid, 40 parts by weight of pentamethylenediamine, and 21 parts by weight of deionized water into a reaction kettle. Replace the air in the kettle with nitrogen, then heat up to 135 °C and keep stirring at a constant temperature for 30 min to fully melt - mix the materials. Subsequently, heat up to 190 °C and react at a constant temperature for 2 h, then stop the reaction to obtain carboxyl - terminated polyamide hard segments.

[0066] (2) Add 100 parts by weight of sebacic acid, 64 parts by weight of pentanediol, and 0.33 part by weight of nano - titanium dioxide into a reaction kettle. Replace the air in the kettle with nitrogen, then heat up to 135 °C and keep stirring at a constant temperature for 30 min to fully melt - mix the materials. Subsequently, heat up to 210 °C and react at a constant temperature for 3 h, then stop the reaction to obtain hydroxyl - terminated polyester diol soft segments.

[0067] (3) Add 100 parts by weight of carboxyl - terminated polyamide hard segments, 93 parts by weight of hydroxyl - terminated polyester diol soft segments, and 0.39 part by weight of nano - titanium dioxide into a reaction kettle. Replace the air in the kettle with nitrogen, then heat up to 170 °C and keep stirring at a constant temperature for 30 min to fully melt - mix the materials. Subsequently, heat up to 220 °C and react at a constant temperature for 3 h. Then release the pressure of the system to atmospheric pressure, add 0.39 part by weight of tetrabutyl titanate, simultaneously heat up the system to 250 °C, then perform a vacuum - pumping operation, reduce the pressure of the system below 100 Pa within 30 min, and react at a constant temperature for 4 h. Finally, stop the reaction and restore the system to atmospheric pressure,

[0068] to obtain a fully bio - based polyamide elastomer.

[0069] Comparative Example 1

[0070] A preparation method of a fully bio - based polyamide elastomer, the steps are as follows:

[0071] (1) Add 100 parts by weight of sebacic acid, 68 parts by weight of decanediamine, and 16.8 parts by weight of deionized water into a reaction kettle. Replace the air in the kettle with nitrogen, then heat up to 135 °C and keep stirring at a constant temperature for 30 min to fully melt and mix the materials. Subsequently, heat up to 195 °C and keep reacting at a constant temperature for 2 h, then stop the reaction to obtain a carboxyl-terminated polyamide hard segment.

[0072] (2) Add 100 parts by weight of sebacic acid, 107 parts by weight of decanediol, and 0.41 part by weight of tetrabutyl titanate into a reaction kettle. Replace the air in the kettle with nitrogen, then heat up to 135 °C and keep stirring at a constant temperature for 30 min to fully melt and mix the materials. Subsequently, heat up to 215 °C and keep reacting at a constant temperature for 3 h, then stop the reaction to obtain a hydroxyl-terminated polyester diol soft segment.

[0073] (3) Add 100 parts by weight of the carboxyl-terminated polyamide hard segment, 98 parts by weight of the hydroxyl-terminated polyester diol soft segment, and 0.40 tetrabutyl titanate into a reaction kettle. Replace the air in the kettle with nitrogen, then heat up to 185 °C and keep stirring at a constant temperature for 30 min to fully melt and mix the materials. Subsequently, heat up to 225 °C and keep reacting at a constant temperature for 3 h. Then release the pressure of the system to atmospheric pressure, add 0.40 part by weight of tetrabutyl titanate, and at the same time heat up the system to 250 °C. Subsequently, perform a vacuum pumping operation, reduce the pressure of the system to below 100 Pa within 30 min, and keep reacting at a constant temperature for 4 h. Finally, stop the reaction and restore the system to atmospheric pressure to obtain a fully bio-based polyamide elastomer.

[0074] Comparative Example 1 corresponds to Example 3 (only the catalyst used in Step (2) and the early stage of Step (3) is changed from nano-titanium dioxide to tetrabutyl titanate): From the results of mechanical properties, it can be found that under the same hard segment content, the product obtained in Example 3 has better mechanical properties, while the mechanical properties of the product obtained in Comparative Example 1 have decreased to a large extent. This is because the catalyst (i.e., tetrabutyl titanate) used in Step (2) and the early stage of Step (3) in Comparative Example 1 is very easy to hydrolyze, and a large amount of water is generated in the above two processes, which leads to a significant reduction in its catalytic efficiency, thereby resulting in a reduction in the reaction degree and a decrease in the product performance. The results are shown in Table 1.

[0075] The test standards for tensile strength and elongation at break are ISO527–1:2012;

[0076] Table 1 Performance Results

[0077] Example Hard segment content (%) Tensile strength (MPa) Elongation at break (%) Example 1 17.5 12 720 Example 2 83.4 48 310 Example 3 50.4 36 520 Example 4 52.0 39 440 Comparative Example 1 50.4 22 320

[0078] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments based on this embodiment without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A preparation method of a fully bio - based polyamide elastomer, characterized in that, it comprises the following steps: 1) Melting and mixing a bio - based dicarboxylic acid, a bio - based diamine and water, and then reacting to obtain a carboxyl - terminated polyamide hard segment; 2) Melting and mixing a bio - based diol, a bio - based dicarboxylic acid and a first catalyst, and then reacting to obtain a hydroxyl - terminated polyester diol soft segment; 3) Melting and mixing the carboxyl - terminated polyamide hard segment obtained in step 1) with the hydroxyl - terminated polyester diol soft segment obtained in step 2) and a first catalyst, and then reacting to obtain a reaction product. Mixing the reaction product with a second catalyst and then reacting to obtain a fully bio - based polyamide elastomer; The first catalyst is nano - titanium dioxide; The second catalyst is tetrabutyl titanate or tetrabutyl zirconate.

2. The preparation method according to claim 1, characterized in that, the bio - based dicarboxylic acid includes glutaric acid, azelaic acid or sebacic acid; the bio - based diamine includes pentamethylenediamine, nonanediamine or decanediamine; the bio - based diol includes pentanediol, nonanediol or decanediol.

3. The preparation method according to claim 1, characterized in that, the mass ratio of the bio - based dicarboxylic acid to the bio - based diamine in step 1) is 100:40 - 75.

4. The preparation method according to claim 1, characterized in that, the conditions for melting and mixing in step 1) include: temperature is 135 - 140 °C, stirring for 30 min; the conditions for the reaction include: temperature is 190 - 200 °C, time is 2 h.

5. The preparation method according to claim 1, characterized in that, the mass ratio of the bio - based diol to the bio - based dicarboxylic acid and the first catalyst in step 2) is 100:64 - 171:0.33 - 0.

54.

6. The preparation method according to claim 1, characterized in that, the conditions for melting and mixing in step 2) include: temperature is 135 - 140 °C, stirring for 30 min; the conditions for the reaction include: temperature is 210 - 220 °C, time is 3 h.

7. The preparation method according to claim 1, characterized in that, the mass ratio of the carboxyl - terminated polyamide hard segment to the hydroxyl - terminated polyester diol soft segment and the first catalyst in step 3) is 100:20 - 471:0.24 - 1.

1.

8. The preparation method according to claim 1, characterized in that, the conditions for melting and mixing in step 3) include: temperature is 170 - 185 °C, stirring for 30 min; the conditions for the reaction include: temperature is 220 - 230 °C, time is 3 h.

9. The preparation method according to claim 1, characterized in that, the dosage of the second catalyst in step 3) is 2 - 5‰ of the total mass of the reaction product.

10. The preparation method according to claim 1, characterized in that, the conditions for mixing the reaction product with the second catalyst in step 3) include: temperature is 250 °C, time is 30 min; the conditions for the reaction include: temperature is 250 °C, time is 4 h.

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