Bio-based flame-retardant TPU (thermoplastic polyurethane) material for new energy vehicles and preparation method thereof

Abstract

The invention relates to the technical field of production of polyurethane elastomers, in particular to a bio-based flame-retardant TPU material for a new energy automobile and a preparation method of the bio-based flame-retardant TPU material. The bio-based flame-retardant TPU material for the new energy automobile is prepared from the following components in parts by mass: 40 to 67 parts of bio-based dihydric alcohol; 27 to 45 parts of isocyanate; 6 to 15 parts of a chain extender; 1-3 parts of a bio-based flame retardant; 0.2 to 0.5 part of an antioxidant; 0.1 to 0.4 part of a hydrolysis resistant agent; 0.05 to 0.15 part of a catalyst; and 0.2 to 0.4 part of an ultraviolet absorbent. Phosphorus-modified gallic acid is taken as a flame retardant and reacts in TPU production, so that the problems that the flame retardant and a polymer matrix are poor in dispersion compatibility and easy to separate out are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of polyurethane elastomer production, and specifically to a bio-based flame-retardant TPU material for new energy vehicles and a preparation method thereof. Background Art

[0002] The production and sales volume of new energy vehicles has been growing at a high speed. As an important supporting facility for new energy vehicles, the charging pile cable has higher requirements for its use environment and safety, and also puts forward higher requirements for the coating material of the charging pile cable.

[0003] Thermoplastic polyurethane elastomer (TPU), as a new type of elastomer material, has a wide range of hardness compared with other materials and has good comprehensive properties in terms of wear resistance, elasticity and mechanical properties, etc., and is an excellent base material for use as a cable sheath. However, TPU itself belongs to a flammable material. In order to achieve a sufficient flame-retardant effect, a large amount of flame retardant needs to be added. Although such flame retardants can inhibit combustion or slow down the flame spread rate, when added in large amounts, they will have a great impact on the mechanical properties of the material, etc., and the compatibility between the filler and the polymer is generally poor, resulting in easy precipitation of the liquid flame retardant. In addition, the heat resistance and mechanical properties of the TPU material also need to be further improved. Therefore, it is necessary to develop a new flame-retardant TPU material to solve the above problems.

[0004] Nowadays, flame retardants and flame-retardant materials are developing towards the direction of low smoke and low toxicity. The common sources of flame retardants are non-renewable resources such as petroleum-based. Along with the requirements of environmental protection and sustainable development, the development of green and efficient bio-based flame-retardant materials has become a new focus. Compared with petroleum-based flame retardants, bio-based reactive flame retardants have the advantages of being cheap and easily available, low toxicity, renewable and biodegradable. Most bio-based compounds, as a natural carbon source, can generate a carbon layer during the thermal decomposition process, have good char-forming properties, and achieve a better flame-retardant effect.

[0005] Chinese Patent Application CN117362764A, with a publication date of January 9, 2024, discloses a bio-based flame retardant, a preparation method thereof and a bio-based flame-retardant TPU material. The flame retardant is a multi-layer self-assembled structure flame retardant with a chitosan microsphere as the core and a layer of ammonium polyphosphate and a layer of chitosan coated layer by layer, which can inhibit the heat transfer process and the generation of combustible gases and smoke, but has a relatively large addition amount and a risk of precipitation. Summary of the Invention

[0006] In view of the above deficiencies in the prior art, the purpose of the present invention is to provide a bio-based flame-retardant TPU material for new energy vehicles, which has good flame-retardant effect, improves the thermal stability and mechanical properties of the TPU material, and has a high bio-based content in the product.

[0007] Another object of the present invention is to provide a preparation method of a bio-based flame retardant TPU material for new energy vehicles. Using phosphorus-modified gallic acid as a flame retardant and reacting it into TPU production, it solves the problems of poor dispersion compatibility and easy precipitation between the flame retardant and the polymer matrix.

[0008] The present invention is realized by adopting the following technical solutions: The bio-based flame retardant TPU material for new energy vehicles described above comprises the following components in parts by mass: Bio-based diol: 40 - 67 parts; Isocyanate: 27 - 45 parts; Chain extender: 6 - 15 parts; Bio-based flame retardant: 1 - 3 parts; Antioxidant: 0.2 - 0.5 part; Hydrolysis resistant agent: 0.1 - 0.4 part; Catalyst: 0.05 - 0.15 part; Ultraviolet absorber: 0.2 - 0.4 part.

[0009] The number average molecular weight of the bio-based diol (PES) is 1000 - 3500. The bio-based diol is prepared by using small molecule diol and dicarboxylic acid as raw materials, carrying out an esterification reaction under the protection of nitrogen at 200 - 240 °C, and carrying out a transesterification reaction under a vacuum degree of -0.09 - -0.11 MPa and a temperature of 235 - 240 °C.

[0010] The small molecule diol is one of bio-based 1,3-propanediol and bio-based 1,4-butanediol. The dicarboxylic acid is one of bio-based sebacic acid and bio-based succinic acid. The mass ratio of the small molecule diol to the dicarboxylic acid is (0.44 - 1):1.

[0011] The isocyanate is diphenylmethane diisocyanate.

[0012] The chain extender is at least one of bio-based 1,4-butanediol (BDO) and bio-based 1,3-propanediol.

[0013] The antioxidant is a phosphite antioxidant, further preferably one of tris(2,4-di-tert-butylphenyl) phosphite (antioxidant 168), poly(dipropylene glycol) phenyl phosphite (PDP), and diphenylisodecyl phosphite (DPDP); the hydrolysis resistant agent is carbodiimide; the catalyst is one of stannous octoate or bismuth octoate.

[0014] The ultraviolet absorber is one of 2,4-dihydroxybenzophenone (UV-0), N-(ethoxycarbonylphenyl)-N'-methyl-N'-phenylformamidine (UV-1), N-(ethoxycarbonylphenyl)-N'-ethyl-N'-phenylformamidine (UV-2), 2-hydroxy-4-methoxybenzophenone (UV-9), 2-(2'-hydroxy-5'-methylphenyl)benzotriazole (UV-P), or 2-hydroxy-4-n-octyloxybenzophenone (UV-531).

[0015] The bio-based flame retardant is phosphorus-modified gallic acid, and its structural formula is: .

[0017] The preparation method of the phosphorus-modified gallic acid includes the following steps: (1) Add gallic acid, propionic anhydride, and sulfuric acid in a molar ratio of 2:10:0.05 to a 5L single-necked round-bottom flask, stir at 25 - 30 °C for 15 - 20 min until the gallic acid is completely dissolved to obtain sample solution Y1; reflux sample solution Y1 at 70 - 75 °C for 2 - 3 h to obtain sample solution Y2; after the reaction is completed and cooled to room temperature, add 2L of deionized water, and continuously stir at 25 - 30 °C for 4 - 6 h until the solid product completely precipitates to obtain a solid-liquid mixed sample Y3, and after suction filtration and washing with water, obtain a white filter residue; dry the white filter residue at 65 - 70 °C for 15 - 20 h to obtain a white powdery product, acylated protected gallic acid Y4; (2) Add acylated protected gallic acid Y4, tetrahydrofuran, and tripropylamine in a molar ratio of 1:1.5:1 to a 5L single-necked round-bottom flask, cool to -6~-8 °C, and continuously stir until acylated protected gallic acid Y4 is completely dissolved to obtain sample solution Y5; gradually add a 400mL tetrahydrofuran solution containing 1 mmol of phosphorus oxychloride to sample solution Y5, and continuously stir and react at -6~-8 °C for 30 - 36 h to obtain sample solution Y6; sample solution Y6 is suction filtered, washed with water, and separated to remove the generated tripropylamine hydrochloride, and then the tetrahydrofuran is removed by rotary evaporation at 45 - 50 °C; dry at 65 - 70 °C for 15 - 20 h to obtain sample Y7; (3) Add 0.3 kg of sample Y7 and 1.5L of deionized water to a 5L single-necked round-bottom flask, stir at 25 - 30 °C to obtain sample solution Y8; dissolve 0.03 kg of potassium carbonate in 1.5L of deionized water, transfer it to sample solution Y8, heat up to 80 - 85 °C, and stir and react for 4 - 6 h to obtain sample solution Y9; extract and separate through methyl acrylate to obtain the organic layer, remove methyl acrylate by rotary evaporation at 50 - 55 °C, and dry at 70 - 75 °C for 15 - 20 h to obtain phosphorus-modified gallic acid.

[0018] The reaction process is: .

[0019] The preparation method of the bio-based flame-retardant TPU material for new energy vehicles includes the following steps: adding a bio-based flame retardant, an antioxidant, a hydrolysis-resistant agent, and an ultraviolet absorber into bio-based diol. After stirring evenly in a large kettle, adding them together with isocyanate, a chain extender, and a catalyst into the first zone of a twin-screw extruder for continuous polymerization reaction. After underwater pelletizing and aging and drying, a bio-based flame-retardant TPU material is obtained.

[0020] One of the devices for synthesizing TPU is the large kettle for storing bio-based diol, which is used to store diol and dissolve additives in the bio-based diol for subsequent reactions. The temperature of the large kettle is 100 - 110 °C. The twin-screw extruder has a total of 14 temperature zones. Generally, when feeding materials into the twin-screw extruder, it is fed in the first zone, and the twin-screw pushes the materials forward for reaction.

[0021] The twin-screw extruder is divided into fourteen temperature zones. The temperatures from the first zone to the fourteenth zone are 150 - 175 °C, 195 - 220 °C, 195 - 220 °C, 195 - 220 °C, 195 - 215 °C, 195 - 215 °C, 185 - 210 °C, 180 - 200 °C, 165 - 195 °C, 155 - 185 °C, 155 - 180 °C, 155 - 180 °C, 155 - 180 °C, 155 - 180 °C; the die head outlet temperature is 205 - 230 °C; the main machine speed is 190 - 220 r / min.

[0022] Compared with the prior art, the beneficial effects of the present invention are: The present invention synthesizes a new bio-based flame retardant. Phosphorus-modified gallic acid has characteristics such as thermal stability and non-flammability. The flame retardant mechanism is as follows: when burning, the flame retardant absorbs heat and decomposes, the O=P-O- bond breaks, generating phosphorus-containing free radicals to capture active free radicals (H••, OH•), interrupting the combustion chain reaction; in the condensed phase, phosphoric acid is generated and further condensed into polyphosphoric acid compounds, which can promote the dehydration and carbonization of the material, forming a heat-insulating protective carbon layer, reducing the release of gas and molten dripping at high temperatures. Through multi-phase flame retardancy, the flame retardant performance of TPU is greatly increased.

[0023] The multi-functional group structure of gallic acid makes it have good reactivity. It contains phenolic hydroxyl groups in its structure, which are incorporated into TPU, increasing its compatibility with TPU and solving the problems of poor dispersion compatibility and easy precipitation between the flame retardant and the polymer matrix. A small addition amount can achieve a V-0 flame retardant effect, improving the flame retardant performance of the TPU material. At the same time, the phenolic hydroxyl group structure can form multiple hydrogen bonds with polymer molecules to generate a more compact spatial structure (network macromolecule), which can form a crosslinked network during the combustion process, promote carbonization, and ultimately form a dense carbon layer to protect the matrix, avoiding further combustion and decomposition, and improving the mechanical properties and thermal stability of the TPU material. Detailed implementation mode

[0024] In order to make the purpose and technical solution of the present invention clearer and more understandable, the present invention will be further described in detail below.

[0025] The raw materials used in the embodiments of the present invention are all commercially available conventional raw materials unless otherwise specified; the process methods used in the embodiments are all conventional methods in the art unless otherwise specified.

[0026] Bio-based sebacic acid: Wilmar Oils Technology Co., Ltd.; Bio-based succinic acid: Shandong Landian Biotechnology Co., Ltd.; Bio-based 1,3-propanediol: DuPont; Bio-based 1,4-butanediol: Yuanli Chemical Group Co., Ltd.

[0027] Example 1 The bio-based flame-retardant TPU material for new energy vehicles in this embodiment comprises the following components in parts by mass: PES: 40 parts; MDI: 45 parts; Bio-based BDO: 15 parts; Bio-based flame retardant: 1 part; Antioxidant 168: 0.2 part; Carbodiimide: 0.1 part; Stannous octoate: 0.05 part; UV-0: 0.2 part.

[0028] Among them, the number-average molecular weight of PES is 1000.

[0029] Among them, the bio-based flame retardant is phosphorus-modified gallic acid, and its preparation method is as follows: Gallic acid, propionic anhydride, and sulfuric acid are added to a 5L single-neck round-bottom flask according to a molar ratio of 2:10:0.05, and stirred at 30°C for 20 min until the gallic acid is completely dissolved to obtain sample solution Y1. Sample solution Y1 is refluxed at 75°C for 3 h to obtain sample solution Y2. After the reaction is completed and cooled to room temperature, 2 L of deionized water is added, and stirring is continued at 25°C for 6 h until the solid product is completely precipitated to obtain a solid-liquid mixed sample Y3, which is filtered by suction and washed with water to obtain a white filter residue. The white filter residue is dried at 65°C for 15 h to obtain a white powdery product, acylated protected gallic acid Y4.

[0030] The acylated protected gallic acid Y4, tetrahydrofuran, and tripropylamine were added to a 5 L single-necked round-bottom flask at a molar ratio of 1:1.5:1, cooled to -6 °C, and continuously stirred until the acylated protected gallic acid Y4 was completely dissolved to obtain sample solution Y5. A 400 mL tetrahydrofuran solution containing 1 mmol of phosphorus oxychloride was gradually added dropwise to sample solution Y5, and the mixture was continuously stirred and reacted at -6 °C for 30 h to obtain sample solution Y6. Sample solution Y6 was filtered by suction, washed with water, and separated to remove the generated tripropylamine hydrochloride, and then tetrahydrofuran was removed by rotary evaporation at 45 °C. Drying was carried out at 65 °C for 15 h to obtain sample Y7.

[0031] 0.3 kg of sample Y7 and 1.5 L of deionized water were added to a 5 L single-necked round-bottom flask, and stirred at 25 °C to obtain sample solution Y8. 0.03 kg of potassium carbonate was dissolved in 1.5 L of deionized water, transferred to sample solution Y8, heated to 80 °C, and stirred and reacted for 4 h to obtain sample solution Y9. The organic layer was obtained by extraction and separation with methyl acrylate, and methyl acrylate was removed by rotary evaporation at 50 °C, and drying was carried out at 70 °C for 20 h to obtain phosphorus-modified gallic acid.

[0032] The preparation method of the bio-based flame-retardant TPU material for new energy vehicles in this example is as follows: First, the bio-based flame retardant, antioxidant 168, carbodiimide, and UV-0 were added to PES, stirred evenly, and then poured into the first zone of a twin-screw extruder together with MDI, BDO, and continuous polymerization reaction was carried out. Stannous octoate was added in the first zone of the twin-screw extruder with a perfusion machine (Wuyi Henghui Polyurethane Equipment Factory, model TPU-MS); after underwater pelletizing and curing and drying, the bio-based flame-retardant TPU material for new energy vehicles was obtained.

[0033] The twin-screw extruder has fourteen temperature zones, and the temperatures from the first zone to the fourteenth zone are 160 °C, 210 °C, 210 °C, 215 °C, 205 °C, 205 °C, 200 °C, 185 °C, 180 °C, 160 °C, 160 °C, 160 °C, 160 °C, 160 °C in sequence; the die head outlet temperature is 225 °C; the main machine speed is 200 r / min.

[0034] The bio-based diol is prepared by carrying out an esterification reaction on a small molecule diol and a dicarboxylic acid as raw materials under the protection of nitrogen and at 200 °C, and carrying out a transesterification reaction under a vacuum degree of -0.09 MPa and a temperature of 235 °C. The small molecule diol is bio-based 1,3-propanediol. The dicarboxylic acid is bio-based sebacic acid. The mass ratio of the small molecule diol to the dicarboxylic acid is 0.44:1.

[0035] Example 2 The bio-based flame-retardant TPU material for new energy vehicles in this example includes the following components in parts by mass: PES: 67 parts; MDI: 27 parts; Bio - based BDO: 6 parts; Bio - based flame retardant: 1.4 parts; PDP: 0.25 parts; Carbodiimide: 0.15 parts; Stannous octoate: 0.07 parts; UV - 1: 0.24 parts.

[0036] Among them, the number - average molecular weight of PES is 1500.

[0037] Among them, the bio - based flame retardant is phosphorus - modified gallic acid, and its preparation method is the same as that of Example 1.

[0038] The preparation method of the bio - based flame - retardant TPU material for new energy vehicles in this example is as follows: First, add the bio - based flame retardant, PDP, carbodiimide and UV - 1 into PES, stir evenly, and then pour it into the first zone of a twin - screw extruder together with MDI, BDO through a casting machine, and carry out continuous polymerization reaction. Stannous octoate is added in the first zone of the twin - screw extruder with a perfusion machine (Wuyi Henghui Polyurethane Equipment Factory, model TPU - MS); after underwater pelletizing and aging and drying, the bio - based flame - retardant TPU material for new energy vehicles is obtained.

[0039] The twin - screw extruder is divided into fourteen temperature zones, and the temperatures from the first zone to the fourteenth zone are 165 °C, 205 °C, 205 °C, 205 °C, 200 °C, 200 °C, 200 °C, 185 °C, 180 °C, 165 °C, 165 °C, 165 °C, 165 °C, 165 °C in sequence; the die head outlet temperature is 210 °C; the main machine speed is 195 r / min.

[0040] The bio - based diol is prepared by carrying out an esterification reaction with small - molecule diol and dicarboxylic acid as raw materials under the protection of nitrogen and at 240 °C, and carrying out a transesterification reaction under the conditions of a vacuum degree of - 0.11 MPa and a temperature of 240 °C. The small - molecule diol is bio - based 1,4 - butanediol. The dicarboxylic acid is bio - based succinic acid. The mass ratio of the small - molecule diol to the dicarboxylic acid is 1:1.

[0041] Example 3 The bio - based flame - retardant TPU material for new energy vehicles in this example comprises the following components in parts by mass: PES: 46 parts; MDI: 41 parts; Bio - based BDO: 13 parts; Bio - based flame retardant: 1.8 parts; DPDP: 0.3 parts; Carbodiimide: 0.2 parts; Stannous octoate: 0.09 parts; UV-2: 0.28 parts.

[0042] Among them, the number-average molecular weight of PES is 2000.

[0043] Among them, the bio-based flame retardant is phosphorus-modified gallic acid, and its preparation method is the same as that of Example 1.

[0044] The preparation method of the bio-based flame-retardant TPU material for new energy vehicles in this example is as follows: First, add the bio-based flame retardant, DPDP, carbodiimide and UV-2 to PES, stir evenly, and then pour them into the first zone of a twin-screw extruder together with MDI, BDO through a casting machine for continuous polymerization reaction. Stannous octoate is added in the first zone of the twin-screw extruder using a perfusion machine (Wuyi Henghui Polyurethane Equipment Factory, model TPU-MS); after underwater pelletizing and curing and drying, the bio-based flame-retardant TPU material for new energy vehicles is obtained.

[0045] The twin-screw extruder is divided into fourteen temperature zones, and the temperatures from the first zone to the fourteenth zone are 170 °C, 215 °C, 215 °C, 215 °C, 210 °C, 210 °C, 205 °C, 190 °C, 185 °C, 170 °C, 170 °C, 170 °C, 170 °C, 170 °C in sequence; the die head outlet temperature is 220 °C; the main machine speed is 205 r / min.

[0046] The bio-based diol is prepared by carrying out an esterification reaction on small molecule diol and dicarboxylic acid under the protection of nitrogen at 210 °C and carrying out a transesterification reaction under the conditions of a vacuum degree of -0.1 MPa and a temperature of 236 °C. The small molecule diol is bio-based 1,3-propanediol. The dicarboxylic acid is bio-based succinic acid. The mass ratio of the small molecule diol to the dicarboxylic acid is 0.6:1.

[0047] Example 4 The bio-based flame-retardant TPU material for new energy vehicles in this example includes the following components in parts by mass: PES: 53 parts; MDI: 36 parts; Bio-based BDO: 11 parts; Bio-based flame retardant: 2.2 parts; Antioxidant 168: 0.35 parts; Carbodiimide: 0.25 parts; Bismuth octanoate: 0.11 parts; UV-9: 0.32 parts.

[0048] Among them, the number-average molecular weight of PES is 2500.

[0049] Among them, the bio-based flame retardant is phosphorus-modified gallic acid, and its preparation method is the same as that of Example 1.

[0050] The preparation method of the bio-based flame-retardant TPU material for new energy vehicles in this example is as follows: First, add the bio-based flame retardant, antioxidant 168, carbodiimide, and UV-9 to PES. After stirring evenly, pour it into the first zone of a twin-screw extruder together with MDI, BDO through a casting machine, and carry out continuous polymerization reaction. Bismuth octanoate is added in the first zone of the twin-screw extruder using a perfusion machine (Wuyi Henghui Polyurethane Equipment Factory, model TPU-MS); after underwater pelletizing and aging and drying, the bio-based flame-retardant TPU material for new energy vehicles is obtained.

[0051] The twin-screw extruder is divided into fourteen temperature zones, and the temperatures from the first zone to the fourteenth zone are 155°C, 200°C, 200°C, 200°C, 200°C, 200°C, 195°C, 190°C, 185°C, 180°C, 175°C, 175°C, 175°C, 175°C in sequence; the die head outlet temperature is 215°C; the main machine speed is 210 r / min.

[0052] The bio-based diol is prepared by carrying out an esterification reaction on small molecule diol and dicarboxylic acid under the protection of nitrogen and at 220°C, and carrying out a transesterification reaction under the conditions of a vacuum degree of -0.09 MPa and a temperature of 237°C. The small molecule diol is bio-based 1,4-butanediol. The dicarboxylic acid is bio-based sebacic acid. The mass ratio of the small molecule diol to the dicarboxylic acid is 0.75:1.

[0053] Example 5 The bio-based flame-retardant TPU material for new energy vehicles in this example includes the following components in parts by mass: PES: 59 parts; MDI: 31 parts; Bio-based BDO: 10 parts; Bio-based flame retardant: 2.6 parts; PDP: 0.4 parts; Carbodiimide: 0.3 parts; Bismuth octanoate: 0.13 parts; UV-P: 0.36 parts.

[0054] Among them, the number-average molecular weight of PES is 3000.

[0055] Among them, the bio-based flame retardant is phosphorus-modified gallic acid, and its preparation method is the same as that of Example 1.

[0056] The preparation method of the bio-based flame-retardant TPU material for new energy vehicles in this embodiment is as follows: First, add the bio-based flame retardant, PDP, carbodiimide, and UV-P to PES. After stirring evenly, pour it into the first zone of a twin-screw extruder together with MDI, BDO, and carry out continuous polymerization reaction. Bismuth octanoate is added in the first zone of the twin-screw extruder using a perfusion machine (Wuyi Henghui Polyurethane Equipment Factory, model TPU-MS); after underwater pelletizing and aging and drying, the bio-based flame-retardant TPU material for new energy vehicles is obtained.

[0057] The twin-screw extruder is divided into fourteen temperature zones, and the temperatures from the first zone to the fourteenth zone are 175 °C, 220 °C, 220 °C, 220 °C, 215 °C, 215 °C, 210 °C, 200 °C, 195 °C, 185 °C, 180 °C, 180 °C, 180 °C, 180 °C in sequence; the die head outlet temperature is 230 °C; the main machine speed is 220 r / min.

[0058] The bio-based diol is prepared by carrying out an esterification reaction on small molecule diol and dicarboxylic acid as raw materials under the protection of nitrogen and at 230 °C, and carrying out a transesterification reaction under the conditions of a vacuum degree of -0.11 MPa and a temperature of 238 °C. The small molecule diol is bio-based 1,3-propanediol. The dicarboxylic acid is bio-based sebacic acid. The mass ratio of the small molecule diol to the dicarboxylic acid is 0.85:1.

[0059] Example 6 The bio-based flame-retardant TPU material for new energy vehicles in this embodiment includes the following components in parts by mass: PES: 63 parts; MDI: 29 parts; Bio-based BDO: 8 parts; Bio-based flame retardant: 3.0 parts; DPDP: 0.5 parts; Carbodiimide: 0.4 parts; Bismuth octanoate: 0.15 parts; UV-531: 0.4 parts.

[0060] Among them, the number-average molecular weight of PES is 3500.

[0061] Among them, the bio-based flame retardant is phosphorus-modified gallic acid, and its preparation method is the same as that in Example 1.

[0062] The preparation method of the bio-based flame-retardant TPU material for new energy vehicles in this embodiment is as follows: First, add the bio-based flame retardant, DPDP, carbodiimide, and UV-531 to PES. After stirring evenly, pour it into the first zone of a twin-screw extruder together with MDI, BDO through a casting machine, and carry out continuous polymerization reaction. Bismuth octoate is added in the first zone of the twin-screw extruder using a perfusion machine (Wuyi Henghui Polyurethane Equipment Factory, model TPU-MS); after underwater pelletizing and aging and drying, the bio-based flame-retardant TPU material for new energy vehicles is obtained.

[0063] The twin-screw extruder is divided into fourteen temperature zones, and the temperatures from the first zone to the fourteenth zone are 150 °C, 195 °C, 195 °C, 195 °C, 195 °C, 195 °C, 195 °C, 185 °C, 180 °C, 155 °C, 155 °C, 155 °C, 155 °C, 155 °C in sequence; the die head outlet temperature is 205 °C; the main machine speed is 190 r / min.

[0064] The bio-based diol is prepared by carrying out an esterification reaction with small molecule diol and dicarboxylic acid as raw materials under the protection of nitrogen and at 215 °C, and carrying out a transesterification reaction under the conditions of a vacuum degree of -0.1 MPa and a temperature of 239 °C. The small molecule diol is bio-based 1,4-butanediol. The dicarboxylic acid is bio-based succinic acid. The mass ratio of the small molecule diol to the dicarboxylic acid is 0.5:1.

[0065] Comparative Example 1 The difference from Example 1 is that an equal amount of the flame retardant resorcinol bis(diphenyl phosphate) (RDP) is used to replace the bio-based flame retardant.

[0066] Comparative Example 2 The difference from Example 1 is that an equal amount of commercially available conventional gallic acid is used to replace the bio-based flame retardant.

[0067] Comparative Example 3 The difference from Example 1 is that the flame retardant tolyl diphenyl phosphate (CDP) is used to replace the bio-based flame retardant, and the mass fraction is 20 parts.

[0068] Comparative Example 4 The difference from Example 1 is that the mass fraction of the bio-based flame retardant is 5 parts.

[0069] Perform performance tests on the TPU materials prepared in Examples 1-6 and Comparative Examples 1-4, among which: The tensile strength, elongation at break, and 100% modulus are tested with reference to the standard "ASTM-D412 Standard Test Method for Rubber and Thermoplastic Elastomers Tensile"; The tear strength was tested according to the reference standard "ASTM-D624 Standard Test Method for Tear Strength of Conventional Vulcanized Rubber and Thermoplastic Elastomers". The flame retardant grade was tested according to the UL94 vertical burning test method. The flame retardant grades from high to low are V-0, V-1, and V-2 in sequence. The test conditions for the precipitation situation were as follows: The specimen was placed at 80 °C for 168 h, taken out and left standing at room temperature for 4 h. Observe and record the precipitation situation on the surface of the specimen, and classify it into three levels: no precipitation, slight precipitation, and obvious precipitation according to the precipitation amount. The bio-based content was tested according to Method B (AMS) of "ASTM D6866-22 Standard Test Method for Determining the Bio-based Content of Solid, Liquid, and Gas Samples by Radiocarbon Analysis".

[0070] The test conditions for high-temperature aging resistance were as follows: The specimen was placed at 100 °C for 168 h, taken out and left standing at room temperature for 3 h, and test the change rates of its tensile strength and elongation at break.

[0071] The performance test results are shown in Table 1: Table 1 Performance test results of TPU materials prepared in Examples 1-6 and Comparative Examples 1-4

[0072] As can be seen from Table 1, the phosphorus-modified gallic acid in Examples 1-6 is a bio-based flame retardant. Reacted into TPU, the prepared TPU materials have high flame retardant grades, good mechanical properties, good heat resistance and no precipitation. Compared with Example 1, in Comparative Example 1, an equal amount of the flame retardant resorcinol bis(diphenyl phosphate) (RDP) was used to replace the bio-based flame retardant, and the flame retardant grade of the prepared TPU material decreased and there was precipitation, and the high-temperature aging resistance performance became worse. In Comparative Example 2, commercially available conventional gallic acid was used to replace the phosphorus-modified gallic acid, and the flame retardant grade of the prepared TPU material decreased, and the mechanical properties decreased (the reason is that the phosphorus-modified gallic acid mostly has hydroxyl groups and polybenzene ring structures, has more hydrogen bond action sites, forms a parallel linear structure, increases the toughness of TPU and improves the elongation at break. At the same time, the increase in the action sites increases the crosslinking density of TPU and increases the tensile strength of TPU). In Comparative Example 3, the flame retardant cresyl diphenyl phosphate (CDP) was used to replace the bio-based flame retardant. To achieve the same flame retardant effect, the addition amount of the flame retardant needs to be much more, but adding too much will lead to a decrease in the mechanical properties of the TPU material and obvious precipitation. In Comparative Example 4, beyond the supercritical value of the bio-based flame retardant, the flame retardant grade of the prepared TPU material remained unchanged, but the mechanical properties decreased. This is because the bio-based flame retardant is a compound with a functionality greater than 2, and excessive crosslinking in the reaction weakens the force between molecular chains, thus leading to a decrease in the mechanical properties of the TPU material.

Claims

1. A bio-based flame-retardant TPU material for new energy vehicles, characterized in that, Comprising the following components in parts by mass: Bio-based diol: 40 - 67 parts; Isocyanate: 27 - 45 parts; Chain extender: 6 - 15 parts; Bio-based flame retardant: 1 - 3 parts; Antioxidant: 0.2 - 0.5 part; Hydrolysis resistant agent: 0.1 - 0.4 part; Catalyst: 0.05 - 0.15 part; UV absorber: 0.2 - 0.4 part.

2. The bio-based flame-retardant TPU material for new energy vehicles according to claim 1, wherein The number average molecular weight of the bio-based diol is 1000 - 3500. The bio-based diol is prepared by using small molecule diol and dicarboxylic acid as raw materials, carrying out an esterification reaction under the protection of nitrogen and at 200 - 240 °C, and carrying out a transesterification reaction under a vacuum of -0.09 to -0.11 MPa and at 235 - 240 °C.

3. The bio-based flame-retardant TPU material for new energy vehicles according to claim 1, characterized in that, The isocyanate is diphenylmethane diisocyanate.

4. The bio-based flame-retardant TPU material for new energy vehicles according to claim 1, wherein, The chain extender is at least one of bio-based 1,4-butanediol and bio-based 1,3-propanediol.

5. The bio-based flame-retardant TPU material for new energy vehicles according to claim 1, wherein The antioxidant is a phosphite antioxidant; the hydrolysis resistant agent is carbodiimide; the catalyst is one of stannous octoate or bismuth octoate.

6. The bio-based flame-retardant TPU material for new energy vehicles according to claim 1, characterized in that, The UV absorber is one of 2,4-dihydroxybenzophenone, N-(ethoxycarbonylphenyl)-N'-methyl-N'-phenylformamidine, N-(ethoxycarbonylphenyl)-N'-ethyl-N'-phenylformamidine, 2-hydroxy-4-methoxybenzophenone, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole or 2-hydroxy-4-n-octyloxybenzophenone.

7. The bio-based flame-retardant TPU material for new energy vehicles according to claim 1, wherein, The bio-based flame retardant is phosphorus-modified gallic acid.

8. The bio-based flame-retardant TPU material for new energy vehicles according to claim 7, wherein, The preparation method of the phosphorus-modified gallic acid comprises the following steps: (1) Add gallic acid, propionic anhydride, and sulfuric acid in a molar ratio of 2:10:0.05 to a 5L single-necked round-bottom flask, stir at 25 - 30 °C for 15 - 20 min until the gallic acid is completely dissolved to obtain sample solution Y1; reflux sample solution Y1 at 70 - 75 °C for 2 - 3 h to obtain sample solution Y2; after the reaction, cool to room temperature, add 2L of deionized water, and continuously stir at 25 - 30 °C for 4 - 6 h to obtain a solid-liquid mixed sample Y3. After filtration and washing with water, obtain a filter residue; dry the filter residue at 65 - 70 °C for 15 - 20 h to obtain the product acyl-protected gallic acid Y4; (2) Add acyl-protected gallic acid Y4, tetrahydrofuran, and tripropylamine in a molar ratio of 1:1.5:1 to a 5L single-necked round-bottom flask, cool to -6 to -8 °C, and continuously stir until the acyl-protected gallic acid Y4 is completely dissolved to obtain sample solution Y5; gradually add a 400 mL tetrahydrofuran solution containing 1 mmol of phosphorus oxychloride to sample solution Y5, and continuously stir and react at -6 to -8 °C for 30 - 36 h to obtain sample solution Y6; sample solution Y6 is filtered, washed with water, and separated to remove the generated tripropylamine hydrochloride, and then the tetrahydrofuran is removed by rotary evaporation at 45 - 50 °C; dry at 65 - 70 °C for 15 - 20 h to obtain sample Y7; (3) Add 0.3 kg of sample Y7 and 1.5 L of deionized water into a 5 L single-necked round-bottom flask, and stir to obtain sample solution Y8 at 25 - 30 °C; dissolve 0.03 kg of potassium carbonate in 1.5 L of deionized water, transfer it to sample solution Y8, heat up to 80 - 85 °C, and stir and react for 4 - 6 h to obtain sample solution Y9; extract and separate with methyl acrylate to obtain the organic layer, remove methyl acrylate by rotary evaporation at 50 - 55 °C, and dry at 70 - 75 °C for 15 - 20 h to obtain phosphorus-modified gallic acid.

9. A method for preparing the bio-based flame-retardant TPU material for new energy vehicles according to any one of claims 1-8, characterized in that, It includes the following steps: Add a bio-based flame retardant, an antioxidant, a hydrolysis-resistant agent, and an ultraviolet absorber into a bio-based diol, stir evenly, and then add them together with an isocyanate, a chain extender, and a catalyst into the first zone of a twin-screw extruder for continuous polymerization reaction. After underwater pelletizing and curing and drying, a bio-based flame-retardant TPU material is obtained.

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