Bio-based modified high polymer material and preparation method thereof

Abstract

The invention discloses a bio-based modified high polymer material and a preparation method thereof, and relates to the technical field of high polymer materials. When the bio-based modified high polymer material is prepared, firstly, lignin reacts with terephthalaldehyde to prepare formylated lignin; carrying out multi-component reaction on the aldehyde lignin to obtain modified lignin; the preparation method comprises the following steps: reacting 4-mercaptophenylboronic acid with 1-mercaptoglycerol to prepare a dimercaptoborate cross-linking agent; the preparation method comprises the following steps: reacting isophorone diisocyanate with polytetrahydrofuran ether glycol, and then reacting with a flame-retardant chain extender, 1, 2-propylene glycol and hydroxyethyl methylacrylate to prepare modified polyurethane; and mixing the modified polyurethane, the modified lignin and a dimercaptoborate cross-linking agent, casting and curing to obtain the bio-based modified high polymer material. The bio-based modified high polymer material prepared by the invention has the advantages of flame retardance, antibacterial property, aging resistance, self-repairing property, repeatable processing and high mechanical strength.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high molecular materials, in particular to a bio-based modified high molecular material and a preparation method thereof. BACKGROUND

[0002] Once entering the natural environment, the high molecular material waste is easily affected by the weathering process to be broken into microplastics and nanoplastics. Considering the harmful effects of non-biodegradable high molecular materials on the ecological environment, people pay more and more attention to bio-based high molecular materials as a substitute to alleviate the pollution problem of high molecular materials. Lignin has good water resistance, ultraviolet resistance, mechanical enhancement and other characteristics, and is a sustainable substitute. And the preparation of high molecular materials often needs to consume non-renewable fossil resources, in the face of the reduction of fossil resources and the pollution problems caused thereby, the use of renewable biomass resources to prepare high molecular materials becomes an effective solution. SUMMARY

[0003] The present application aims to provide a bio-based modified high molecular material and a preparation method thereof to solve the problems in the prior art.

[0004] In order to solve the above technical problems, the present application provides the following technical scheme: A bio-based modified high molecular material, which is prepared by mixing and casting a modified polyurethane, a modified lignin and a dimercapto borate crosslinking agent, and then curing to obtain the bio-based modified high molecular material. The modified polyurethane is prepared by reacting isophorone diisocyanate with polytetrahydrofuran ether glycol, and then reacting with a flame-retardant chain extender, 1,2-propanediol and hydroxyethyl methacrylate; the flame-retardant chain extender is prepared by reacting cinnamaldehyde-based Schiff base with DOPO; the cinnamaldehyde-based Schiff base is prepared by reacting 2,4-dihydroxy cinnamaldehyde with 2-(5-amino-2-benzotriazolyl) phenol; The modified lignin is prepared by reacting aldehyde-based lignin with sulfonamide dimethyl isoxazole, ethyl isocyanacetate and 6-heptenoic acid; the aldehyde-based lignin is prepared by reacting lignin with p-phenylenedimethylene; The dimercapto borate crosslinking agent is prepared by reacting 4-mercapto phenyl boronic acid with 1-mercapto glycerol.

[0005] A preparation method of a bio-based modified high molecular material, comprising the following preparation steps: (1) according to the mass fraction, 5~6 parts of lignin, 7~8 parts of p-phenylenediamine, 25~30 parts of dioxane are mixed uniformly, stirred at room temperature at 200~300 r / min until dissolved, 0.8~0.9 parts of 12 mol / L hydrochloric acid solution is added, stirred at 80~90℃, 200~300 r / min reflux reaction for 3~4 h, naturally cooled to room temperature, 50~70 parts of pure water is added to precipitate for 20~30 min, suction filtration, washed with pure water, vacuum dried at 60~70℃ for 10~12 h, to obtain aldehyde lignin; (2) according to the mass fraction, 2~3 parts of aldehyde lignin, 0.8~1.2 parts of sulfonamide dimethyl isoxazole, 15~20 parts of methanol are mixed uniformly, stirred at room temperature at 200~300 r / min for 50~60 min, 0.34~0.51 parts of ethyl isocyanate, 0.38~0.57 parts of 6-heptene acid are added, stirred at room temperature at 200~300 r / min for 24~26 h, suction filtration, washed with anhydrous ethanol and pure water alternately, vacuum dried at 50~60℃ for 10~12 h to obtain modified lignin; (3) according to the mass fraction, 3~4 parts of 4-mercapto phenylboronic acid, 2.21~2.95 parts of 1-mercapto glycerol, 70~80 parts of tetrahydrofuran, 0.05~0.1 parts of pure water are mixed uniformly, 6~10 parts of magnesium sulfate is added, stirred at room temperature at 200~300 r / min for 24~26 h, suction filtration, the filtrate is rotary evaporated, dried, washed with n-heptane, dried again to obtain a dithiol borate ester crosslinking agent; (4) according to the mass fraction, 2~3 parts of 2,4-dihydroxy cinnamaldehyde, 2.76~4.14 parts of 2-(5-amino-2-benzotriazolyl) phenol, 30~40 parts of methanol are mixed uniformly, under nitrogen atmosphere, refluxed at 60~65℃, 200~300 r / min for 7~8 h, rotary evaporation to remove methanol, 10~15 parts of anhydrous ethanol at 0~5℃ is added, ultrasonic for 3~4 min, stand at 0~5℃ for 50~60 min, filter, washed with anhydrous ethanol at 0~5℃, vacuum dried at 50~60℃ for 7~8 h to obtain cinnamaldehyde Schiff base; (5) according to the mass fraction, 2~3 parts of cinnamaldehyde Schiff base, 30~40 parts of anhydrous ethanol are mixed uniformly under nitrogen atmosphere, stirred at 60~70℃, 200~300 r / min until dissolved, 1.16~1.74 parts of DOPO is added, refluxed at 75~80℃, 200~300 r / min for 8~10 h, naturally cooled to room temperature, suction filtration, washed with acetone, vacuum dried at 50~60℃ for 10~12 h to obtain a flame-retardant chain extender; (6) under the atmosphere of nitrogen, 60~70℃, 200~300r / min, the polytetrahydrofuran ether glycol and isophorone diisocyanate are mixed uniformly according to the molar ratio of hydroxyl group to isocyanate group of 1:(1.6~2), 0.4~0.5 times of the mass of isophorone diisocyanate is added with N,N-dimethylformamide, 0.004~0.006 times of the mass of isophorone diisocyanate is added with dibutyltin dilaurate, stirring at 60~70℃, 200~300r / min for 2~2.5h, 1:(0.5~0.6) of the molar ratio of the remaining isocyanate group to hydroxyl group is added with flame-retardant chain extender, stirring at 70~80℃, 200~300r / min for 2~2.5h, 1:(0.7~0.8) of the molar ratio of the remaining isocyanate group to hydroxyl group is added with 1,2-propanediol, stirring at 60~70℃, 200~300r / min for 1.5~2h, 1:(1.02~1.05) of the molar ratio of the remaining isocyanate group to hydroxyl group is added with hydroxyethyl methacrylate, 0.0002~0.0003 times of the mass of hydroxyethyl methacrylate is added with hydroquinone, stirring at 40~50℃, 200~300r / min for 1.5~2h, natural cooling to room temperature, to obtain the modified polyurethane; (7) 8~9 parts of the modified polyurethane, 2~3 parts of the modified lignin, 0.7~0.8 parts of the dimercapto borate ester crosslinking agent, 4~5 parts of N,N-dimethylformamide, 0.014~0.016 parts of azobisisobutyronitrile are mixed uniformly, stirring at room temperature, 300~400r / min for 50~60min, poured into a polytetrafluoroethylene mold for casting and forming, dried and cured to obtain the bio-based modified polymer material.

[0006] As an optimization, the lignin in step (1) is alkali lignin.

[0007] As an optimization, the reaction process of the aldehyde-based lignin in step (1) is as follows: .

[0008] As an optimization, the reaction process of the modified lignin in step (2) is as follows: .

[0009] As an optimization, the reaction process of the dimercapto borate ester crosslinking agent in step (3) is as follows: .

[0010] As an optimization, the reaction process of the cinnamaldehyde-based Schiff base in step (4) is as follows: .

[0011] As an optimization, the reaction process of the flame retardant chain extender in step (5) is as follows: .

[0012] As an optimization, the weight-average molecular weight of the polytetrahydrofuran ether diol in step (6) is 2000.

[0013] As an optimization, the drying and curing in step (7) is to first dry in a constant temperature drying oven at 80~90℃ for 12~14h, then dry in a vacuum drying oven at 80~90℃ for 24~26h, and then cure at 120~130℃ for 10~12h.

[0014] Compared with the prior art, the beneficial effects achieved by the present invention are: In preparing bio-based modified polymer materials, this invention first reacts lignin with terephthalaldehyde to obtain aldehyde-modified lignin; then reacts the aldehyde-modified lignin with sulfadiazine, ethyl isocyanate, and 6-heptenoic acid to obtain modified lignin; reacts 4-mercaptophenylboronic acid with 1-mercaptoglycerol to obtain a dimercaptoboronic ester crosslinking agent; reacts 2,4-dihydroxycinnamaldehyde with 2-(5-amino-2-benzotriazolyl)phenol to obtain a cinnamaldehyde Schiff base; reacts the cinnamaldehyde Schiff base with DOPO to obtain a flame-retardant chain extender; reacts isophorone diisocyanate with polytetrahydrofuran ether diol, and then reacts with the flame-retardant chain extender, 1,2-propanediol, and hydroxyethyl methacrylate to obtain modified polyurethane; finally, the modified polyurethane, modified lignin, and dimercaptoboronic ester crosslinking agent are mixed, cast, and cured to obtain the bio-based modified polymer material.

[0015] First, lignin is reacted with terephthalaldehyde. The hydroxyl groups on the lignin undergo aldol condensation with the aldehyde groups, thus introducing aldehyde reactive groups onto the lignin. These aldehyde groups can then participate in subsequent Ugi multicomponent reactions, reacting with sulfadiazine, ethyl isocyanate, and 6-heptenoic acid to form an α-acylaminoamide structure. Sulfamethazole possesses excellent antibacterial properties; its introduction into lignin through the Ugi multicomponent reaction imparts these properties. 6-heptenoic acid contains reactive double bonds that can participate in subsequent cross-linking reactions. Lignin itself, due to its abundant benzene rings and phenolic hydroxyl groups, also exhibits excellent ultraviolet absorption capabilities, effectively... The crosslinking agent improves the performance against UV aging. 4-Mercaptophenylboronic acid reacts with 1-mercaptoglycerol to prepare dimercaptoboronic ester crosslinking agent. The obtained crosslinking agent contains two active thiol groups and dynamic boronic ester bonds. Boronic ester groups have good reversibility. Introducing them into the polymer matrix can endow it with excellent self-healing properties and reprocessing ability. After combustion, boronic ester groups form a glassy protective layer, thereby synergistically improving the flame retardant effect with phosphorus and nitrogen flame retardant elements. Thiol groups can undergo click-catalyzed reactions with double bonds, thereby forming a crosslinking network in the polymer matrix. At the same time, the thioether structure formed after the reaction of thiol groups with double bonds also has the ability to assist in anti-aging. It can synergistically improve the anti-aging performance with other anti-aging structures.

[0016] Secondly, 2,4-dihydroxycinnamaldehyde reacts with 2-(5-amino-2-benzotriazolyl)phenol to prepare a cinnamaldehyde Schiff base. The aldehyde group on 2,4-dihydroxycinnamaldehyde reacts with the amino group on 2-(5-amino-2-benzotriazolyl)phenol to form an imine bond, which then reacts with the phosphorus hydrogen on DOPO to obtain a flame retardant chain extender. The flame retardant chain extender contains two reactive hydroxyl groups, which can participate in the chain extension reaction of polyurethane. Although the UV absorption performance of the cinnamaldehyde group is reduced after the aldehyde group participates in the reaction, it can still synergize with the benzotriazole structure to provide a higher UV absorption effect and improve the material's resistance to UV aging. Furthermore, the benzotriazole group contains a large amount of nitrogen, while DOPO contains the flame retardant element phosphorus. The large amount of nitrogen can effectively synergize with phosphorus, thereby effectively improving the flame retardant performance, reducing the risk of combustion, and reducing losses caused by fire.

[0017] Finally, isophorone diisocyanate was reacted with polytetrahydrofuran ether diol, and then reacted with a flame retardant chain extender, 1,2-propanediol, and hydroxyethyl methacrylate to prepare modified polyurethane. The introduction of the flame retardant chain extender into the polyurethane main chain introduced a large number of flame retardant elements, effectively improving the flame retardant properties of the polyurethane. Finally, hydroxyethyl methacrylate was used for end-capping, thereby sealing the polyurethane chain segments with double bonds, allowing them to participate in subsequent crosslinking. The modified polyurethane, modified lignin, and dimercaptoborate crosslinking agent were then mixed and cast. After curing, a bio-based modified polymer material is obtained. The double bonds introduced on the modified polyurethane and modified lignin through the modification reaction undergo a click reaction with the thiol groups on the dithiol borate ester crosslinking agent, thereby forming a crosslinked network structure. At the same time, due to the introduction of dynamic covalent bonds in the borate ester, the mechanical strength in normal application environment is improved, and it is also endowed with self-healing and reprocessing properties, which greatly extends its service life. Meanwhile, the introduction of lignin in the bio-based material also improves its biodegradability and reduces its environmental impact. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] The raw material information used in all the following examples and comparative examples is as follows: Lignin: Alkali lignin, model number JYS1545, purchased from Wuhan Jiyesheng Chemical Co., Ltd.; Polytetrahydrofuran ether diol: weight average molecular weight 2000, model FAS PTMG2000, purchased from Longnan Haoyu New Material Technology Co., Ltd.

[0020] Example 1: A method for preparing a bio-based modified polymer material, the method comprising the following preparation steps: (1) By mass fraction, 5 parts of lignin, 7 parts of terephthalaldehyde and 25 parts of dioxane were mixed evenly and stirred at 200 r / min at room temperature until dissolved. 0.8 parts of 12 mol / L hydrochloric acid solution were added and the mixture was stirred and refluxed at 200 r / min at 80℃ for 4 h. After naturally cooling to room temperature, 50 parts of pure water were added to precipitate for 20 min. The mixture was then filtered, washed with pure water, and dried under vacuum at 60℃ for 12 h to obtain aldehyde-modified lignin. (2) By mass fraction, 2 parts of aldehyde-modified lignin, 0.8 parts of sulfadiazine and 15 parts of methanol were mixed evenly and stirred at 200 r / min for 60 min at room temperature. 0.34 parts of ethyl isocyanate and 0.38 parts of 6-heptenic acid were added and stirred at 200 r / min for 26 h at room temperature. The mixture was filtered, washed alternately with anhydrous ethanol and pure water, and dried under vacuum at 50 °C for 12 h to obtain modified lignin. (3) According to the mass fraction, 3 parts of 4-mercaptophenylboronic acid, 2.21 parts of 1-mercaptoglycerol, 70 parts of tetrahydrofuran, and 0.05 parts of pure water are mixed evenly, 6 parts of magnesium sulfate are added, and the mixture is stirred at 200 r / min for 26 h at room temperature. The mixture is then filtered, the filtrate is evaporated by rotary evaporation, dried, washed with n-heptane, and dried again to obtain the dimercaptoboronic ester crosslinking agent. (4) By mass fraction, 2 parts of 2,4-dihydroxycinnamaldehyde, 2.76 parts of 2-(5-amino-2-benzotriazolyl)phenol and 30 parts of methanol were mixed evenly and refluxed at 60°C and 200 r / min for 8 h under a nitrogen atmosphere. The methanol was removed by rotary evaporation, 10 parts of anhydrous ethanol at 0°C were added, the mixture was sonicated for 3 min, and allowed to stand at 0°C for 50 min. The mixture was then filtered, washed with anhydrous ethanol at 0°C, and dried under vacuum at 50°C for 8 h to obtain cinnamaldehyde Schiff base. (5) By mass, in a nitrogen atmosphere, 2 parts of cinnamaldehyde Schiff base and 30 parts of anhydrous ethanol are mixed evenly, stirred at 60°C and 200 r / min until dissolved, 1.16 parts of DOPO are added, and the mixture is refluxed at 75°C and 200 r / min for 10 h. After naturally cooling to room temperature, the mixture is filtered, washed with acetone, and dried under vacuum at 50°C for 12 h to obtain the flame retardant chain extender. (6) Under a nitrogen atmosphere, at 60°C and 200 r / min, with a molar ratio of hydroxyl to isocyanate groups of 1:1.6, polytetrahydrofuran ether diol and isophorone diisocyanate were mixed evenly. 0.4 times the mass of isophorone diisocyanate N,N-dimethylformamide and 0.004 times the mass of isophorone diisocyanate dibutyltin dilaurate were added. The mixture was stirred at 60°C and 200 r / min for 2.5 h. Flame retardant was then added with a molar ratio of the remaining isocyanate groups to hydroxyl groups of 1:0.5. Chain extender was added, and the mixture was stirred at 70℃ and 200 r / min for 2.5 h. 1,2-propanediol was added at a molar ratio of 1:0.7 of the remaining isocyanate groups to hydroxyl groups. The mixture was stirred at 60℃ and 200 r / min for 2 h. Hydroxyethyl methacrylate was added at a molar ratio of 1:1.02 of the remaining isocyanate groups to hydroxyl groups. Hydroquinone was added at 0.0002 times the mass of hydroxyethyl methacrylate. The mixture was stirred at 40℃ and 200 r / min for 2 h. The mixture was then allowed to cool naturally to room temperature to obtain the modified polyurethane. (7) By mass, 8 parts of modified polyurethane, 2 parts of modified lignin, 0.7 parts of dimercaptoborate crosslinking agent, 4 parts of N,N-dimethylformamide, and 0.014 parts of azobisisobutyronitrile are mixed evenly and stirred at 300 r / min for 60 min at room temperature. The mixture is then poured into a polytetrafluoroethylene mold for casting and molding. The mixture is first dried in a constant temperature drying oven at 80℃ for 14 h, then dried in a vacuum drying oven at 80℃ for 26 h, and finally cured at 120℃ for 12 h to obtain a bio-based modified polymer material.

[0021] Example 2: A method for preparing a bio-based modified polymer material, the method comprising the following preparation steps: (1) By mass fraction, 5.5 parts of lignin, 7.5 parts of terephthalaldehyde and 28 parts of dioxane were mixed evenly and stirred at 250 r / min at room temperature until dissolved. 0.85 parts of 12 mol / L hydrochloric acid solution were added and the mixture was stirred and refluxed at 250 r / min at 85℃ for 3.5 h. After naturally cooling to room temperature, 60 parts of pure water were added to precipitate for 25 min. The mixture was filtered, washed with pure water, and dried under vacuum at 65℃ for 11 h to obtain aldehyde-modified lignin. (2) By mass, 2.5 parts of aldehyde-modified lignin, 1 part of sulfadiazine and 18 parts of methanol were mixed evenly and stirred at 250 r / min for 55 min at room temperature. 0.42 parts of ethyl isocyanate and 0.48 parts of 6-heptenic acid were added and stirred at 250 r / min for 25 h at room temperature. The mixture was filtered and washed alternately with anhydrous ethanol and pure water. The modified lignin was obtained by vacuum drying at 55 °C for 11 h. (3) By mass, 3.5 parts of 4-mercaptophenylboronic acid, 2.58 parts of 1-mercaptoglycerol, 75 parts of tetrahydrofuran, and 0.075 parts of pure water were mixed evenly, and 8 parts of magnesium sulfate were added. The mixture was stirred at 250 r / min for 25 h at room temperature, filtered, the filtrate was evaporated by rotary evaporation, dried, washed with n-heptane, and dried again to obtain the dimercaptoboronic ester crosslinking agent. (4) By mass fraction, 2.5 parts of 2,4-dihydroxycinnamaldehyde, 3.45 parts of 2-(5-amino-2-benzotriazolyl)phenol and 35 parts of methanol were mixed evenly and refluxed at 60°C and 250 r / min for 7.5 h under a nitrogen atmosphere. The methanol was removed by rotary evaporation, and 12 parts of anhydrous ethanol at 0°C were added. The mixture was sonicated for 4 min, allowed to stand at 0°C for 55 min, filtered, washed with anhydrous ethanol at 0°C, and vacuum dried at 55°C for 7.5 h to obtain cinnamaldehyde Schiff base. (5) By mass, 2.5 parts of cinnamaldehyde Schiff base and 35 parts of anhydrous ethanol were mixed evenly in a nitrogen atmosphere, stirred at 65°C and 250 r / min until dissolved, 1.45 parts of DOPO were added, and the mixture was refluxed at 75°C and 250 r / min for 9 h. After naturally cooling to room temperature, the mixture was filtered, washed with acetone, and dried under vacuum at 55°C for 11 h to obtain the flame retardant chain extender. (6) Under a nitrogen atmosphere, at 65°C and 250 r / min, with a molar ratio of hydroxyl to isocyanate groups of 1:1.8, polytetrahydrofuran ether diol and isophorone diisocyanate were mixed evenly. 0.45 times the mass of N,N-dimethylformamide and 0.005 times the mass of dibutyltin dilaurate were added. The mixture was stirred at 65°C and 250 r / min for 2 h. A flame retardant chain extender was then added with a molar ratio of the remaining isocyanate groups to hydroxyl groups of 1:0.55. The reaction was stirred at 75℃ and 250 r / min for 2.5 h. 1,2-Propanediol was added at a molar ratio of 1:0.75 of the remaining isocyanate groups to hydroxyl groups. The reaction was stirred at 65℃ and 250 r / min for 1.5 h. Hydroxyethyl methacrylate was added at a molar ratio of 1:1.035 of the remaining isocyanate groups to hydroxyl groups. Hydroquinone was added at 0.00025 times the mass of hydroxyethyl methacrylate. The reaction was stirred at 45℃ and 250 r / min for 1.5 h. The mixture was then allowed to cool naturally to room temperature to obtain the modified polyurethane. (7) By mass, 8.5 parts of modified polyurethane, 2.5 parts of modified lignin, 0.75 parts of dimercaptoboronic acid crosslinking agent, 4.5 parts of N,N-dimethylformamide, and 0.015 parts of azobisisobutyronitrile are mixed evenly and stirred at 350 r / min for 55 min at room temperature. The mixture is then poured into a polytetrafluoroethylene mold for casting. The mixture is first dried in a constant temperature drying oven at 85℃ for 13 h, then dried in a vacuum drying oven at 85℃ for 25 h, and finally cured at 125℃ for 11 h to obtain a bio-based modified polymer material.

[0022] Example 3: A method for preparing a bio-based modified polymer material, the method comprising the following preparation steps: (1) By mass fraction, 6 parts of lignin, 8 parts of terephthalaldehyde and 30 parts of dioxane were mixed evenly and stirred at 300 r / min at room temperature until dissolved. 0.9 parts of 12 mol / L hydrochloric acid solution were added and the mixture was stirred and refluxed at 300 r / min at 90℃ for 3 h. After naturally cooling to room temperature, 70 parts of pure water were added to precipitate for 30 min. The mixture was then filtered, washed with pure water, and vacuum dried at 70℃ for 10 h to obtain aldehyde-modified lignin. (2) By mass fraction, 3 parts of aldehyde-modified lignin, 1.2 parts of sulfadiazine and 20 parts of methanol were mixed evenly and stirred at 300 r / min for 50 min at room temperature. 0.51 parts of ethyl isocyanate and 0.57 parts of 6-heptenic acid were added and stirred at 300 r / min for 24 h at room temperature. The mixture was filtered, washed alternately with anhydrous ethanol and pure water, and dried under vacuum at 60℃ for 10 h to obtain modified lignin. (3) By mass, 4 parts of 4-mercaptophenylboronic acid, 2.95 parts of 1-mercaptoglycerol, 80 parts of tetrahydrofuran, and 0.1 parts of pure water are mixed evenly, 10 parts of magnesium sulfate are added, and the mixture is stirred at 300 r / min for 24 h at room temperature. The mixture is then filtered, the filtrate is evaporated by rotary evaporation, dried, washed with n-heptane, and dried again to obtain the dimercaptoboronic ester crosslinking agent. (4) By mass fraction, 3 parts of 2,4-dihydroxycinnamaldehyde, 4.14 parts of 2-(5-amino-2-benzotriazolyl)phenol and 40 parts of methanol were mixed evenly and refluxed at 65°C and 300 r / min for 7 h under a nitrogen atmosphere. The methanol was removed by rotary evaporation, 15 parts of anhydrous ethanol at 5°C were added, the mixture was sonicated for 4 min, and allowed to stand at 5°C for 60 min. The mixture was then filtered, washed with anhydrous ethanol at 5°C, and dried under vacuum at 60°C for 7 h to obtain cinnamaldehyde Schiff base. (5) By mass, in a nitrogen atmosphere, 3 parts of cinnamaldehyde Schiff base and 40 parts of anhydrous ethanol are mixed evenly, stirred at 70°C and 300 r / min until dissolved, 1.74 parts of DOPO are added, and the mixture is refluxed at 80°C and 300 r / min for 8 h. After cooling naturally to room temperature, the mixture is filtered, washed with acetone, and dried under vacuum at 60°C for 10 h to obtain the flame retardant chain extender. (6) Under a nitrogen atmosphere, at 70°C and 300 r / min, with a molar ratio of hydroxyl to isocyanate groups of 1:2, polytetrahydrofuran ether diol and isophorone diisocyanate were mixed evenly. Then, 0.5 times the mass of N,N-dimethylformamide and 0.006 times the mass of dibutyltin dilaurate were added. The mixture was stirred at 70°C and 300 r / min for 2 h. Finally, a flame retardant chain extender was added with a molar ratio of the remaining isocyanate groups to hydroxyl groups of 1:0.6. The mixture was stirred at 80℃ and 300 r / min for 2 h. 1,2-Propanediol was added at a molar ratio of 1:0.8 of the remaining isocyanate groups to hydroxyl groups. The mixture was stirred at 70℃ and 300 r / min for 1.5 h. Hydroxyethyl methacrylate was added at a molar ratio of 1:1.05 of the remaining isocyanate groups to hydroxyl groups. Hydroquinone was added at 0.0003 times the mass of hydroxyethyl methacrylate. The mixture was stirred at 50℃ and 300 r / min for 1.5 h. The mixture was then allowed to cool naturally to room temperature to obtain the modified polyurethane. (7) According to the mass fraction, 9 parts of modified polyurethane, 3 parts of modified lignin, 0.8 parts of dimercaptoboronic acid crosslinking agent, 5 parts of N,N-dimethylformamide, and 0.016 parts of azobisisobutyronitrile are mixed evenly and stirred at 400 r / min for 50 min at room temperature. The mixture is then poured into a polytetrafluoroethylene mold for casting and molding. The mixture is first dried in a constant temperature drying oven at 90℃ for 12 h, then dried in a vacuum drying oven at 90℃ for 24 h, and finally cured at 130℃ for 10 h to obtain a bio-based modified polymer material.

[0023] Comparative Example 1: The difference between the preparation method of the bio-based modified polymer material in Comparative Example 1 and Example 2 lies in step (2). Step (2) is modified as follows: 2.5 parts by mass of aldehyde-modified lignin, 1 part of sulfadiazine, and 18 parts of methanol are mixed evenly and stirred at 250 r / min for 55 min at room temperature. Then, 0.42 parts of ethyl isocyanate and 0.49 parts of heptanoic acid are added and stirred at 250 r / min for 25 h at room temperature. The mixture is then filtered, washed alternately with anhydrous ethanol and pure water, and dried under vacuum at 55°C for 11 h to obtain modified lignin. The remaining steps are the same as in Example 2.

[0024] Comparative Example 2: The difference between the preparation method of the bio-based modified polymer material in Comparative Example 2 and Example 2 lies in step (2). Step (2) is modified as follows: 2.5 parts by mass of aldehyde-modified lignin, 0.35 parts by mass of aniline, and 18 parts by mass of methanol are mixed evenly and stirred at 250 r / min for 55 min at room temperature. Then, 0.42 parts by mass of ethyl isocyanate and 0.48 parts by mass of 6-heptenic acid are added, and the mixture is stirred at 250 r / min for 25 h at room temperature. The mixture is then filtered, washed alternately with anhydrous ethanol and pure water, and dried under vacuum at 55 °C for 11 h to obtain modified lignin. The remaining steps are the same as in Example 2.

[0025] Comparative Example 3: The preparation method of the bio-based modified polymer material in Comparative Example 3 differs from that in Example 2 in that step (2) is omitted, and step (7) is modified as follows: 8.5 parts by mass of modified polyurethane, 2.5 parts by aldehyde-modified lignin, 0.75 parts by mass of dimercaptoboronic acid ester crosslinking agent, 4.5 parts by mass of N,N-dimethylformamide, and 0.015 parts by mass of azobisisobutyronitrile are mixed evenly, stirred at 350 r / min for 55 min at room temperature, poured into a polytetrafluoroethylene mold for casting, dried in a constant temperature drying oven at 85℃ for 13 h, then dried in a vacuum drying oven at 85℃ for 25 h, and cured at 125℃ for 11 h to obtain the bio-based modified polymer material. The remaining steps are the same as in Example 2.

[0026] Comparative Example 4: The preparation method of the bio-based modified polymer material in Comparative Example 4 differs from that in Example 2 in that step (1) is omitted, and step (2) is modified as follows: 2 parts by mass of lignin, 0.8 parts by mass of sulfadiazine, and 15 parts by mass of methanol are mixed evenly and stirred at 200 r / min for 60 min at room temperature. Then, 0.34 parts by mass of ethyl isocyanate and 0.38 parts by mass of 6-heptenic acid are added, and the mixture is stirred at 200 r / min for 26 h at room temperature. The mixture is then filtered, washed alternately with anhydrous ethanol and pure water, and dried under vacuum at 50 °C for 12 h to obtain the modified lignin. The remaining steps are the same as in Example 2.

[0027] Comparative Example 5: The preparation method of the bio-based modified polymer material in Comparative Example 5 differs from that in Example 2 in that steps (1) and (2) are omitted, and step (7) is modified as follows: 8 parts by mass of modified polyurethane, 0.7 parts by mass of dimercaptoboronic acid ester crosslinking agent, 4 parts by mass of N,N-dimethylformamide, and 0.014 parts by mass of azobisisobutyronitrile are mixed evenly, stirred at 300 r / min for 60 min at room temperature, poured into a polytetrafluoroethylene mold for casting, dried in an 80℃ constant temperature drying oven for 14 h, then dried in an 80℃ vacuum drying oven for 26 h, and cured at 120℃ for 12 h to obtain the bio-based modified polymer material. The remaining steps are the same as in Example 2.

[0028] Comparative Example 6: The preparation method of the bio-based modified polymer material in Comparative Example 6 differs from that in Example 2 in that step (3) is omitted, and step (7) is modified as follows: 8.5 parts by mass of modified polyurethane, 2.5 parts by mass of modified lignin, 0.5 parts by mass of 1,6-hexanedithiol, 4.5 parts by mass of N,N-dimethylformamide, and 0.015 parts by mass of azobisisobutyronitrile are mixed evenly, stirred at 350 r / min for 55 min at room temperature, poured into a polytetrafluoroethylene mold for casting, dried in a constant temperature drying oven at 85℃ for 13 h, then dried in a vacuum drying oven at 85℃ for 25 h, and cured at 125℃ for 11 h to obtain the bio-based modified polymer material. The remaining steps are the same as in Example 2.

[0029] Comparative Example 7: The preparation method of the bio-based modified polymer material in Comparative Example 7 differs from that in Example 2 in that step (3) is omitted, and step (7) is modified as follows: 8.5 parts by mass of modified polyurethane, 2.5 parts by mass of modified lignin, 4.5 parts by mass of N,N-dimethylformamide, and 0.015 parts by mass of azobisisobutyronitrile are mixed evenly, stirred at 350 r / min for 55 min at room temperature, poured into a polytetrafluoroethylene mold for casting, dried in a constant temperature drying oven at 85℃ for 13 h, then dried in a vacuum drying oven at 85℃ for 25 h, and cured at 125℃ for 11 h to obtain the bio-based modified polymer material. The remaining steps are the same as in Example 2.

[0030] Comparative Example 8: The difference between the preparation method of the bio-based modified polymer material in Comparative Example 8 and Example 2 lies in step (4). Step (4) is modified as follows: 2.5 parts by mass of 2,4-dihydroxycinnamaldehyde, 1.42 parts by mass of aniline, and 35 parts by mass of methanol are mixed evenly and refluxed at 60°C and 250 r / min for 7.5 h under a nitrogen atmosphere. The methanol is removed by rotary evaporation, and 12 parts by mass of anhydrous ethanol at 0°C are added. The mixture is sonicated for 4 min, allowed to stand at 0°C for 55 min, filtered, washed with anhydrous ethanol at 0°C, and vacuum dried at 55°C for 7.5 h to obtain the cinnamaldehyde Schiff base. The remaining steps are the same as in Example 2.

[0031] Comparative Example 9: The preparation method of the bio-based modified polymer material in Comparative Example 9 differs from that in Example 2 in that step (5) is omitted, and step (6) is modified as follows: Under a nitrogen atmosphere, at 65°C and 250 r / min, polytetrahydrofuran ether diol and isophorone diisocyanate are mixed evenly according to a molar ratio of hydroxyl to isocyanate groups of 1:1.8. Then, 0.45 times the mass of N,N-dimethylformamide and 0.005 times the mass of dibutyltin dilaurate are added. The mixture is stirred at 65°C and 250 r / min for 2 h. The remaining isocyanate groups are then added. Cinnamaldehyde Schiff base was added at a molar ratio of 1:0.55 to hydroxyl groups, and the mixture was stirred at 75°C and 250 rpm for 2.5 h. Then, 1,2-propanediol was added at a molar ratio of 1:0.75 to the remaining isocyanate groups, and the mixture was stirred at 65°C and 250 rpm for 1.5 h. Hydroxyethyl methacrylate was added at a molar ratio of 1:1.035 to the remaining isocyanate groups, followed by hydroquinone at a mass of 0.00025 times that of hydroxyethyl methacrylate. The mixture was stirred at 45°C and 250 rpm for 1.5 h, and then allowed to cool naturally to room temperature to obtain the modified polyurethane. The remaining steps were the same as in Example 2.

[0032] Comparative Example 10: The difference between the preparation method of the bio-based modified polymer material in Comparative Example 10 and Example 2 lies in step (6). Step (6) is modified as follows: under a nitrogen atmosphere, at 65°C and 250 r / min, polytetrahydrofuran ether diol and isophorone diisocyanate are mixed evenly according to a molar ratio of hydroxyl to isocyanate groups of 1:1.8. Then, N,N-dimethylformamide (0.45 times the mass of isophorone diisocyanate) and dibutyltin dilaurate (0.005 times the mass of isophorone diisocyanate) are added. The mixture was stirred at 250 rpm for 2 hours at 65°C. 1,2-Propanediol was added at a molar ratio of 1:0.9 of the remaining isocyanate groups to hydroxyl groups. The mixture was then stirred at 250 rpm for 1.5 hours at 65°C. Hydroxyethyl methacrylate was added at a molar ratio of 1:1.035 of the remaining isocyanate groups to hydroxyl groups. Hydroquinone was added at 0.00025 times the mass of hydroxyethyl methacrylate. The mixture was stirred at 250 rpm for 1.5 hours at 45°C. The mixture was then allowed to cool naturally to room temperature to obtain the modified polyurethane. The remaining steps were the same as in Example 2.

[0033] Comparative Example 11: The difference between the preparation method of the bio-based modified polymer material in Comparative Example 11 and Example 2 lies in step (6). Step (6) is modified as follows: Under a nitrogen atmosphere, at 65°C and 250 r / min, polytetrahydrofuran ether diol and isophorone diisocyanate are mixed evenly according to a molar ratio of hydroxyl to isocyanate groups of 1:1.8. Then, 0.45 times the mass of N,N-dimethylformamide and 0.005 times the mass of dibutyltin dilaurate are added. The mixture is then heated at 65°C and 250 r / min. The mixture was stirred for 2 hours. A flame retardant chain extender was added at a molar ratio of 1:0.55 of the remaining isocyanate groups to hydroxyl groups. The mixture was stirred at 75°C and 250 rpm for 2.5 hours. 1,2-propanediol was added at a molar ratio of 1:0.75 of the remaining isocyanate groups to hydroxyl groups. The mixture was stirred at 65°C and 250 rpm for 1.5 hours. Ethanol was added at a molar ratio of 1:1.035 of the remaining isocyanate groups to hydroxyl groups. The mixture was stirred at 45°C and 250 rpm for 1.5 hours. The mixture was then allowed to cool naturally to room temperature to obtain the modified polyurethane. The remaining steps were the same as in Example 2.

[0034] Test Example 1: Mechanical properties, anti-aging properties, self-healing properties, and reprocessing properties were tested: The tensile strength, strength retention rate after UV aging, strength recovery rate after self-healing, and strength recovery rate after reprocessing of the prepared bio-based modified polymer materials were tested to evaluate their mechanical properties, anti-aging properties, self-healing properties, and reprocessing properties. The test methods are as follows: Mechanical property testing: The tensile strength of the prepared bio-based modified polymer material was tested according to GB / T 1040.3-2006. The specimen shape was type 5, the test speed was 50 mm / min, and each group of specimens was tested in parallel 5 times. The average value was taken and the data was recorded.

[0035] Anti-aging performance test: The prepared bio-based modified polymer material was made into samples according to the tensile strength test method. In accordance with the standard GB / T 16422.3-2022, the samples were artificially accelerated aged for 10 days using an FR-1205-QUV ultraviolet aging tester. The tensile strength was tested again, and the strength retention rate was calculated. Each group of samples was tested 5 times, and the average value was recorded.

[0036] Self-healing performance test: The prepared bio-based modified polymer material was made into tensile strength specimens. A scalpel was used to cut a scratch on the surface of the middle section of the specimen. The length of the scratch was the width of the specimen at that part, and the depth was about 1 mm. The specimen with the scratch was kept at 120℃ for 4 hours to repair. The tensile strength of the repaired specimen was tested again, and the strength recovery rate was calculated. Each group of specimens was tested 5 times, and the average value was recorded.

[0037] Reprocessing performance test: The prepared bio-based modified polymer material was cut into fragments smaller than 2cm×2cm and placed in a mold. It was held under pressure of 10MPa at 120℃ for 10min to make tensile strength specimens. The tensile strength was tested and the strength recovery rate after reprocessing was calculated. Each group of specimens was tested 5 times and the average value was recorded.

[0038] The results are shown in Table 1: A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-11 in Table 1 reveals that the bio-based modified polymer materials prepared in this invention possess excellent mechanical strength, self-healing properties, anti-aging properties, and secondary processing properties.

[0039] By comparing the data in the table, the data in Comparative Example 1 shows that the introduction of 6-heptenic acid successfully introduced reactive double bonds into the modified lignin. These bonds can undergo click reactions with the thiol groups on the crosslinking agent, thereby connecting with the polyurethane backbone to form a crosslinking network, thus improving the tensile strength.

[0040] By comparing the data in the table, the data in Comparative Example 3 shows that the aldehyde-modified lignin was successfully introduced with various functional groups through a multi-component reaction. Among them, 6-heptenoic acid introduced a reactive double bond, thereby improving the tensile strength.

[0041] By comparing the data in the table, the data in Comparative Example 4 shows that aldehyde modification of lignin increases the aldehyde carbonyl content on lignin. When this modification is not performed, the carbonyl content on lignin is low, and the multi-component reaction modification cannot be fully carried out, which in turn leads to a decrease in tensile strength.

[0042] By comparing the data in the table, the data in Comparative Example 5 shows that the addition of modified lignin successfully improved the mechanical properties of bio-based modified polymer materials. At the same time, modified lignin itself also has good UV absorption capacity, which can synergistically improve the anti-UV aging performance.

[0043] By comparing the data in the table, the data in Comparative Example 6 shows that the synthesized dithioboronic acid ester crosslinking agent contains dynamic borate bonds, which can complete the repair of the matrix through dynamic exchange capacity at the repair temperature. When a crosslinking agent without borate ester is used, the self-repair relies only on the weak capacity of urethane, resulting in a decrease in self-repair ability and reprocessing performance.

[0044] By comparing the data in the table, the data in Comparative Example 7 shows that the addition of the dithiol borate crosslinking agent successfully formed a crosslinking network in the bio-based modified polymer material, thereby significantly improving the mechanical properties. At the same time, the thioether group formed after the click reaction between the thiol group and the double bond also has a certain anti-aging ability, which can synergistically improve the anti-aging performance.

[0045] By comparing the data in the table, the data in Comparative Example 8 shows that the introduction of 2-(5-amino-2-benzotriazolyl)phenol into the flame retardant chain extender effectively improves the ultraviolet absorption capacity, thereby improving the anti-ultraviolet aging performance.

[0046] By comparing the data in the table, the data in Comparative Example 10 shows that the introduction of the flame retardant chain extender provides a large number of rigid benzene rings, which improves tensile strength. The benzotriazole structure and cinnamaldehyde structure on it have good ultraviolet absorption properties, which can effectively improve anti-aging performance.

[0047] By comparing the data in the table, the data in Comparative Example 11 shows that the use of hydroxyethyl methacrylate for end-capping in the preparation of modified polyurethane successfully introduced double bonds into the modified polyurethane. This allows double bonds to undergo click-catalyzed reactions with the thiol groups on the crosslinking agent to form a crosslinking network, thereby improving tensile strength. Furthermore, the dynamic borate ester bonds are connected between the polyurethane backbone and the modified lignin, providing excellent self-healing and reprocessing properties.

[0048] Test Example 2: Flame retardant performance testing: The limiting oxygen index and UL 94 flammability rating of the prepared bio-based modified polymer materials were tested to evaluate their flame retardant effect. The specific test methods are as follows: Limiting oxygen index test: The limiting oxygen index of the bio-based modified polymer materials prepared in the examples and comparative examples was tested using an oxygen index instrument according to GB / T 2406.1-2008. The sample size was 150mm×10mm×3mm. Five samples were tested in each group and the average value was recorded. Vertical combustion test: The test was conducted using a vertical-horizontal combustion tester according to ASTM D3801-2010. Five samples were tested in each group, and the average value was recorded.

[0049] The results are shown in Table 2: A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-11 in Table 2 reveals that the bio-based modified polymer materials prepared in this invention exhibit good flame retardant properties.

[0050] By comparing the data in the table, the data in Comparative Example 5 shows that the modified lignin contains a large number of rigid benzene rings, which can promote the formation of carbon layers and thus synergistically improve flame retardant properties.

[0051] By comparing the data in the table, the data in Comparative Example 6 shows that the introduction of borate esters synergistically improves the flame retardant performance. The borate ester bonds can form a protective layer after combustion, thereby synergistically improving the flame retardant performance.

[0052] By comparing the data in the table, the data in Comparative Example 7 shows that in addition to introducing borate groups, the dimercaptoboronic ester crosslinking agent also introduces the flame-retardant element sulfur, which can work together to improve flame-retardant performance.

[0053] By comparing the data in the table, the data in Comparative Example 8 shows that the introduction of 2-(5-amino-2-benzotriazolyl)phenol into the flame retardant chain extender brings a large amount of flame retardant element nitrogen, which in turn significantly improves the flame retardant performance in conjunction with the flame retardant element phosphorus.

[0054] By comparing the data in the table, the data in Comparative Example 9 shows that the addition of DOPO in the flame retardant chain extender is the main source of flame retardant performance. It can work together with flame retardant elements nitrogen, sulfur and boron ester bonds to improve flame retardant performance, thereby reducing the risk of combustion.

[0055] The data comparison in the table shows that the flame retardant chain extender contains a large amount of flame retardant elements phosphorus and nitrogen, and its introduction into polyurethane effectively improves the flame retardant ability.

[0056] Test Example 3: Antibacterial performance test: The shaking method in GB / T 20944.3-2008 was adopted. The prepared bio-based modified polymer material was mixed with bacterial solution at a sample size of 0.75±0.05g and shaken for 5min. The shaken bacterial solution was then cultured in agar medium. The inhibition rate of water treatment filter material against Escherichia coli and Staphylococcus aureus was determined by the number of colonies. Each group of samples was tested 5 times and the average value was recorded.

[0057] The results are shown in Table 3: A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-11 in Table 3 reveals that the bio-based modified polymer materials prepared in this invention exhibit good antibacterial properties.

[0058] By comparing the data in the table, the data in Comparative Example 2 shows that the antibacterial agent sulfadiazine successfully introduced modified lignin through a multi-component reaction, thereby endowing it with good antibacterial properties and effectively improving its antibacterial performance.

[0059] By comparing the data in the table, the data in Comparative Example 3 shows that the modification of aldehyde-modified lignin through a multi-component reaction successfully introduced sulfadiazine with antibacterial properties, thereby effectively improving the antibacterial properties.

[0060] By comparing the data in the table, the data in Comparative Example 4 shows that the aldehyde modification of lignin effectively increases the aldehyde carbonyl content on lignin, provides more reaction sites, and thus allows for the grafting of more sulfadiazine with antibacterial effects, thereby improving antibacterial performance.

[0061] By comparing the data in the table, the data in Comparative Example 5 shows that the addition of modified lignin effectively improves the antibacterial properties. In addition to sulfadiazine, which has excellent antibacterial effects, lignin itself also has some intrinsic antibacterial properties and can have a certain antibacterial effect against Staphylococcus aureus.

[0062] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A bio-based modified polymer material, characterized in that, The bio-based modified polymer material is prepared by mixing modified polyurethane, modified lignin, and dimercaptoborate crosslinking agent, casting, and curing. The modified polyurethane is prepared by reacting isophorone diisocyanate with polytetrahydrofuran ether diol, followed by reaction with a flame retardant chain extender, 1,2-propanediol, and hydroxyethyl methacrylate; the flame retardant chain extender is prepared by reacting cinnamaldehyde Schiff base with DOPO; the cinnamaldehyde Schiff base is prepared by reacting 2,4-dihydroxycinnamaldehyde with 2-(5-amino-2-benzotriazolyl)phenol. The modified lignin is prepared by reacting aldehyde-modified lignin with sulfadiazine, ethyl isocyanate, and 6-heptenoic acid; the aldehyde-modified lignin is prepared by reacting lignin with terephthalaldehyde. The dimercaptoboronic acid ester crosslinking agent is prepared by reacting 4-mercaptophenylboronic acid with 1-mercaptoglycerol.

2. The bio-based modified polymer material according to claim 1, characterized in that, The preparation method of the modified polyurethane includes the following steps: (1) Mix 2,4-dihydroxycinnamaldehyde, 2-(5-amino-2-benzotriazolyl)phenol and methanol evenly, reflux under nitrogen atmosphere, rotary evaporate, add anhydrous ethanol, sonicate, stand, filter, wash and dry to obtain cinnamaldehyde Schiff base. (2) In a nitrogen atmosphere, cinnamaldehyde Schiff base and anhydrous ethanol are mixed evenly and stirred until dissolved. DOPO is added, the mixture is refluxed, cooled, filtered, washed, and dried to obtain a flame retardant chain extender. (3) Under a nitrogen atmosphere, polytetrahydrofuran ether diol and isophorone diisocyanate were mixed evenly, N,N-dimethylformamide and dibutyltin dilaurate were added, and the mixture was stirred and reacted. Flame retardant chain extender was added and stirred and reacted. 1,2-propanediol was added and stirred and reacted. Hydroxyethyl methacrylate was added and hydroquinone was added and stirred and reacted. The mixture was cooled to obtain modified polyurethane.

3. The bio-based modified polymer material according to claim 2, characterized in that, The modified polyurethane was prepared under a nitrogen atmosphere at 60-70°C, with a molar ratio of hydroxyl to isocyanate groups of 1:(1.6-2). Polytetrahydrofuran ether diol and isophorone diisocyanate were mixed uniformly, and then 0.4-0.5 times the mass of isophorone diisocyanate N,N-dimethylformamide and 0.004-0.006 times the mass of isophorone diisocyanate dibutyltin dilaurate were added. The mixture was stirred at 60-70°C for 2-2.5 hours, and the remaining isocyanate groups were mixed with hydroxyl groups at a molar ratio of 1:(0.5-0.6). 6) Add flame retardant chain extender, stir and react at 70~80℃ for 2~2.5h, add 1,2-propanediol at a molar ratio of 1:(0.7~0.8) of the remaining isocyanate groups to hydroxyl groups, stir and react at 60~70℃ for 1.5~2h, add hydroxyethyl methacrylate at a molar ratio of 1:(1.02~1.05) of the remaining isocyanate groups to hydroxyl groups, add hydroquinone at 0.0002~0.0003 times the mass of hydroxyethyl methacrylate, stir and react at 40~50℃ for 1.5~2h, and cool to obtain the final product.

4. The bio-based modified polymer material according to claim 3, characterized in that, The flame retardant chain extender is prepared by mixing 2-3 parts of cinnamaldehyde Schiff base and 30-40 parts of anhydrous ethanol in a nitrogen atmosphere, stirring at 60-70°C until dissolved, adding 1.16-1.74 parts of DOPO, stirring and refluxing at 75-80°C for 8-10 hours, naturally cooling to room temperature, filtering, washing, and vacuum drying.

5. The bio-based modified polymer material according to claim 4, characterized in that, The cinnamaldehyde Schiff base is prepared by mixing 2-3 parts of 2,4-dihydroxycinnamaldehyde, 2.76-4.14 parts of 2-(5-amino-2-benzotriazolyl)phenol, and 30-40 parts of methanol by mass, stirring and refluxing at 60-65°C for 7-8 hours under a nitrogen atmosphere, removing methanol by rotary evaporation, adding 10-15 parts of anhydrous ethanol at 0-5°C, sonicating, standing at 0-5°C for 50-60 minutes, filtering, washing, and vacuum drying.

6. The bio-based modified polymer material according to claim 1, characterized in that, The method for preparing the modified lignin includes the following steps: by mass, 2-3 parts of aldehyde-modified lignin, 0.8-1.2 parts of sulfadiazine, and 15-20 parts of methanol are mixed evenly and stirred at room temperature for 50-60 min. Then, 0.34-0.51 parts of ethyl isocyanate and 0.38-0.57 parts of 6-heptenic acid are added and stirred at room temperature for 24-26 h. The mixture is then filtered, washed, and vacuum dried to obtain the modified lignin.

7. The bio-based modified polymer material according to claim 6, characterized in that, The aldehyde-modified lignin is prepared by mixing 5-6 parts lignin, 7-8 parts terephthalaldehyde, and 25-30 parts dioxane by mass, stirring until dissolved at room temperature, adding 0.8-0.9 parts 12mol / L hydrochloric acid solution, stirring and refluxing at 80-90℃ for 3-4 hours, cooling, adding 50-70 parts pure water to precipitate for 20-30 minutes, filtering, washing, and vacuum drying.

8. The bio-based modified polymer material according to claim 1, characterized in that, The preparation method of the dimercaptoboronic ester crosslinking agent includes the following steps: by mass, 3-4 parts of 4-mercaptophenylboronic acid, 2.21-2.95 parts of 1-mercaptoglycerol, 70-80 parts of tetrahydrofuran, and 0.05-0.1 parts of pure water are mixed evenly, 6-10 parts of magnesium sulfate are added, the mixture is stirred at room temperature for 24-26 hours, filtered, the filtrate is evaporated by rotary evaporation, dried, washed, and dried again to obtain the dimercaptoboronic ester crosslinking agent.

9. A method for preparing a bio-based modified polymer material, characterized in that, The preparation steps include the following: By mass, 8-9 parts of modified polyurethane, 2-3 parts of modified lignin, 0.7-0.8 parts of dimercaptoboronic acid ester crosslinking agent, 4-5 parts of N,N-dimethylformamide, and 0.014-0.016 parts of azobisisobutyronitrile are mixed evenly, stirred at room temperature for 50-60 minutes, poured into a polytetrafluoroethylene mold for casting, and dried and cured to obtain a bio-based modified polymer material.

10. The method for preparing a bio-based modified polymer material according to claim 9, characterized in that, The drying and curing process involves first drying in a constant temperature drying oven at 80-90℃ for 12-14 hours, then drying in a vacuum drying oven at 80-90℃ for 24-26 hours, and finally curing at 120-130℃ for 10-12 hours.

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