Dynamic imine covalent modified polymer and hot working forming method thereof

Abstract

The invention relates to the field of functional plastics, in particular to a dynamic imine covalent modified polymer and a hot working forming method thereof. The hot processing forming method of the dynamic imine covalent modified polymer comprises the following steps: firstly, modifying a hydroxyl-containing polymer by using p-toluenesulfonyl chloride, and then preparing the dynamic imine covalent modified polymer through amination and Schiff base reaction, the mechanical properties of the dynamic imine covalent modified polymer can be effectively regulated and controlled by changing the crosslinking density of the imine network, so that the dynamic imine covalent modified polymer shows good thermal stability, water resistance, tensile strength and physicochemical stability. In addition, the composite material also has excellent biodegradability, and can be completely degraded in the natural environment through a soil burying method. The dynamic imine covalent modified polymer disclosed by the invention has good hot workability, degradability and self-adaptability, and can be applied to the field of application of bio-based degradable plastic substitute materials.

Description

Technical Field

[0001] This application relates to the field of functional plastics, and in particular to a dynamic imine covalently modified polymer and its thermoforming method. Background Technology

[0002] Bio-based plastics are becoming a future trend, replacing traditional petroleum-based plastics. However, bio-based plastics such as polylactic acid (PLA) and thermoplastic starch are difficult to compete with petroleum-based plastics due to their poor mechanical properties and thermal stability, as well as the potential impact of raw materials competing with human food production. Starch, vegetable oils, cellulose, and polyvinyl alcohol, as the most abundant polymers in industry, have advantages such as low cost and biodegradability, but their high-density hydrogen bond network and crystalline structure make them difficult to thermoform.

[0003] Currently, the primary method for achieving thermal processing of cellulose bioplastics is through extensive chemical modification of their internal hydroxyl groups. However, these methods still require the addition of large amounts of carcinogenic aromatic substances as plasticizers, severely weakening the performance, lifespan, and sustainability of the molded materials. Therefore, there is an urgent need to develop new, sustainable, and effective thermal processing methods for materials to develop cellulose bioplastics with excellent overall performance. Summary of the Invention

[0004] In order to develop a simple, heat-processable bio-based plastic, this application provides a dynamically imine covalently modified polymer and a method for preparing the same.

[0005] The present invention provides a dynamically imine covalently modified polymer, which is achieved through the following technical solution:

[0006] A dynamic imine covalently modified polymer is made from a polymer containing hydroxyl groups, a polar solvent, a benzoyl chloride, a catalyst, a diamine compound, and a diformaldehyde compound.

[0007] The dynamic imine covalently modified polymer of this invention is first modified by p-toluenesulfonyl chloride to modify a polymer containing hydroxyl groups, then modified by amination, and finally prepared by Schiff base reaction.

[0008] Preferably, the hydroxyl-containing polymer includes any one or a combination of vegetable oil, lignin, polyvinyl alcohol, starch, and cellulose.

[0009] More preferably, the macromolecular polymer is cellulose, which is widely available.

[0010] Preferably, the benzoyl chloride is any one of p-toluyl chloride, p-toluenesulfonyl chloride, benzenesulfonyl chloride, and p-fluorobenzenesulfonyl chloride.

[0011] Preferably, the polar solvent is any one of water, acetone, dimethyl sulfoxide, dimethylformamide, and tetrahydrofuran.

[0012] Preferably, the diamine compound has the structural formula H2N-R-NH2, where R is any one of alkane, alkene, ester, or benzene ring.

[0013] More preferably, the diamine compound is one or more combinations of 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,8-octanediamine, p-toluenediamine, and 1,11-diaminoundecane.

[0014] Preferably, the diformaldehyde compound has the structural formula HOC-R-CHO, where R is any one of alkane, alkene, ester, or benzene ring.

[0015] More preferably, the diformaldehyde compound is one or more combinations of 1,4-butanedialdehyde, 1,5-pentanedialdehyde, 1,6-hexanedialdehyde, 1,8-octanedialdehyde, p-toluenedialdehyde, and 1,11-dialdehyde undecane.

[0016] The present invention provides a method for preparing a dynamically imine covalently modified polymer, which is achieved through the following technical solution:

[0017] A method for preparing a dynamically imine covalently modified polymer includes the following steps:

[0018] Step 1: The polymer containing hydroxyl groups is dissolved in polar solvent A, and benzoyl chloride is added to carry out an acylation reaction under the action of a catalyst to obtain intermediate product A; Step 2: The intermediate product is dissolved in polar solvent B, and a diamine compound is added to carry out a dehydration condensation reaction to obtain intermediate product B; Step 3: Intermediate product B is dissolved in polar solvent C, and a formaldehyde compound is added to carry out a Schiff base reaction to obtain a dynamically imine covalently modified polymer.

[0019] Preferably, the reaction process of the dynamically imine covalently modified polymer is as follows:

[0020] .

[0021] Preferably, in step one, the hydroxyl-containing polymer is dissolved in a polar solvent A, which is any one of water, acetone, dimethyl sulfoxide, dimethylformamide, and tetrahydrofuran. Anhydrous lithium chloride is added and mixed evenly to obtain a transparent viscous solution. A catalytic amount of triethylamine and benzoyl chloride are added, and an acylation reaction is carried out under the action of the catalyst to obtain a dark gel-like product. After precipitation with excess ice water, the product is washed three times with ultrapure water and ethanol, respectively. The product is then vacuum filtered and vacuum dried to obtain intermediate product A.

[0022] Preferably, in step two, the intermediate product is dissolved in a polar solvent B, which is any one of acetone, dimethyl sulfoxide, dimethylformamide, and tetrahydrofuran. A diamine compound is added, with a molar ratio of the diamine compound to benzoyl chloride of (12-14):1. The reaction is carried out at 90-100°C with stirring for 2-4 hours for dehydration condensation. After the reaction is completed, the mixture is cooled to room temperature, and the product is separated by precipitation with excess isopropanol. The product is then washed with pure water and ethanol, vacuum filtered, and vacuum dried to obtain intermediate product B.

[0023] Preferably, in step three, intermediate product B is dissolved in polar solvent C, which is any one of acetone, dimethyl sulfoxide, dimethylformamide, and tetrahydrofuran. The pH of the system is adjusted to 4.8-5.2. Under stirring conditions at 90-100°C, a formaldehyde compound is added dropwise to carry out a Schiff base reaction. The molar ratio of the formaldehyde compound to the diamine compound is 10:(5-15). After the reaction is completed, the mixture is cooled to room temperature to obtain a dark gel-like product. After precipitation and separation with acetone, the product is washed multiple times with isopropanol and vacuum filtered to obtain a dark solid product. Subsequently, the product is vacuum dried to obtain a dynamically modified imine covalent polymer.

[0024] Preferably, the dynamic imine covalently modified polymer is obtained by hot processing injection molding, blow molding, or extrusion molding to obtain dynamic imine covalently modified polymer products; the dynamic imine covalently modified polymer products can be any form among films, sheets, plates, and irregular shapes.

[0025] In summary, this application has the following advantages:

[0026] 1. The dynamic imine covalently modified polymer of the present invention can be thermally processed to obtain a bio-based biodegradable film. The resulting bio-based biodegradable film has a hydrostatic pressure ≥1500mmH2O, Young's modulus ≥2.60GPa, elongation at break ≥45%, tensile strength ≥38.0MPa and self-healing efficiency ≥90%, and has excellent comprehensive performance.

[0027] 2. The dynamic imine network in the dynamic imine covalently modified polymer of this invention endows bio-based biodegradable plastics with good thermally driven adaptive properties, enabling self-repair and reprocessing.

[0028] 3. The glass transition temperature (Tg) of the dynamic imine covalently modified polymer in this invention is ≥240℃, which has a wider application temperature range compared with thermoplastics.

[0029] 4. The dynamically imine covalently modified polymer of this invention can be thermally processed to obtain a bio-based biodegradable film that exhibits good water resistance, chemical stability and degradation performance. It can achieve efficient chemical degradation and biodegradation, and is an ideal substitute for traditional petroleum-based plastics and biodegradable plastics. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the synthesis reaction process of the dynamic imine covalently modified polymer in this invention.

[0031] Figure 2 This is the TGA curve of the dynamically imine covalently modified polymer film of Example 8.

[0032] Figure 3 This is the DTG curve of the dynamically imine covalently modified polymer film of Example 8.

[0033] Figure 4 This is a graph showing the weight loss of the dynamically imine covalently modified polymer film and sugar-coated paper of Example 8 over 50 days. Detailed Implementation

[0034] To further understand the inventiveness and technical advancements of this invention, the preferred embodiments of this invention will be discussed in detail below with reference to examples and comparative examples.

[0035] Example

[0036] A dynamic imine covalently modified polymer is made from a polymer containing hydroxyl groups, a polar solvent, a benzoyl chloride, a catalyst, a diamine compound, and a diformaldehyde compound.

[0037] The hydroxyl-containing polymer includes any one or a combination of vegetable oils, lignin, polyvinyl alcohol, starch, and cellulose. Preferably, the hydroxyl-containing polymer is cellulose.

[0038] The benzoyl chloride is any one of p-toluyl chloride, p-toluenesulfonyl chloride, benzenesulfonyl chloride, and p-fluorobenzenesulfonyl chloride. Preferably, the benzoyl chloride is p-toluenesulfonyl chloride.

[0039] The polar solvent is any one of water, acetone, dimethyl sulfoxide, dimethylformamide, or tetrahydrofuran. The polar solvent is either dimethylformamide (DMF) or dimethyl sulfoxide (DMSO).

[0040] The structural formula of the diamine compound is H2N-R-NH2, where R is any one of alkane, alkene, ester, or benzene ring. Preferably, the diamine compound is one or more combinations of 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,8-octanediamine, p-toluenediamine, and 1,11-diaminoundecane.

[0041] The structural formula of diformaldehyde compounds is HOC-R-CHO, where R is any one of alkane, alkene, ester, or benzene ring. Preferably, the diformaldehyde compounds are one or more combinations of 1,4-butanedialdehyde, 1,5-pentanedialdehyde, 1,6-hexanedialdehyde, 1,8-octanedialdehyde, p-toluenedialdehyde, and 1,11-dialdehyde undecane.

[0042] For the covalent modification reaction process of the dynamic imine covalently modified polymer powder, please refer to [link / reference]. Figure 1 The dynamic imine covalently modified polymer of this invention is first modified by p-toluenesulfonyl chloride to modify a polymer containing hydroxyl groups, then modified by amination, and finally prepared by Schiff base reaction.

[0043] A method for preparing a dynamically imine covalently modified polymer includes the following steps:

[0044] Step 1: Weigh a certain amount of cellulose into a 500mL round-bottom flask, add sufficient water or organic solvent, and stir magnetically at 90-120℃ for 2-4 hours. Then add anhydrous lithium chloride (LiCl) as a catalyst and continue stirring until a transparent viscous solution is obtained. Finally, add triethylamine (Et3N) and p-toluenesulfonyl chloride (TsCl) as catalysts and continue the reaction for 12-24 hours until a dark gel-like product is obtained. Precipitate the gel product with excess ice water and wash it three times with ultrapure water and ethanol, respectively. Obtain the solid product by vacuum filtration. Place the solid product in a fume hood overnight to evaporate the residual solvent. Finally, vacuum dry for 12 hours to obtain intermediate product A.

[0045] Preferably, the specific preparation method of intermediate product A in step one is as follows: 10g of cellulose is added to 200mL of dimethylformamide (DMF) solution, and magnetically stirred at 90-120℃ for 2-4 hours. Then, 2g of anhydrous lithium chloride is added, and stirring is continued until a transparent viscous solution is obtained. Finally, 3g of triethylamine and 18g of p-toluenesulfonyl chloride are added, and the reaction is continued for 12-24 hours until a dark gel-like product is obtained. The gel product is precipitated with excess ice water and washed three times with ultrapure water and ethanol, respectively. The solid product is obtained by vacuum filtration. The powder sample is placed in a fume hood overnight to evaporate residual solvent, and finally vacuum dried for 12 hours to obtain intermediate product A.

[0046] Step 2: Weigh intermediate product A from step 1 into dimethyl sulfoxide (DMSO), add a diamine compound at a molar ratio of p-toluenesulfonic acid group to amino group of 1:25, and magnetically stir at 90-100℃ for 2-4 hours. After the reaction is complete, cool to room temperature, precipitate and separate the product with excess isopropanol, wash five times with pure water and ethanol, and obtain a dark solid product by vacuum filtration. Place the dark solid product in a fume hood overnight to evaporate the residual solvent, and vacuum dry for 12 hours to obtain intermediate product B.

[0047] Preferably, the specific preparation method of intermediate product B in step two is as follows: Weigh 10g of the modified product in step one into 100mL of dimethyl sulfoxide (DMSO), add 100g of 1,6-hexanediamine at a molar ratio of p-toluenesulfonic acid group to amino group of 1:25, and magnetically stir at 90-100℃ for 2-4 hours. After the reaction is completed, cool to room temperature, precipitate and separate the product with excess isopropanol, wash five times with pure water and ethanol, and obtain a dark solid product by vacuum filtration. Place the dark solid product in a fume hood overnight to evaporate the residual solvent, and vacuum dry for 12 hours to obtain intermediate product B.

[0048] Step 3: The intermediate product B from Step 2 is reacted with a formaldehyde compound using a Schiff base reaction to prepare a dynamic imine covalently modified polymer with an aldehyde to amino group ratio of 1:(0.5-1.5). Specifically: Sufficient amount of intermediate product B is weighed and dispersed in dimethyl sulfoxide (DMSO) and stirred and dissolved at 90-100℃. The formaldehyde compound is dissolved in a small amount of DMSO to prepare a solution. After adjusting the pH of the reaction system to 4.8-5.2 by adding dilute hydrochloric acid, the formaldehyde compound solution is slowly added and reacted for 4-6 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a dark gel-like product. This product is first separated by precipitation with acetone, then washed 5 times with isopropanol, and the dark solid product is obtained by vacuum filtration. The dark solid product is placed in a fume hood overnight to evaporate residual solvent, and then vacuum dried for 12 hours to obtain the final product - dynamic imine covalently modified polymer powder.

[0049] The obtained dynamic imine covalently modified polymer powder was further pulverized using a grinder and then sieved through a 60-80 mesh sieve to obtain 60-80 mesh dynamic imine covalently modified polymer powder. The 60-80 mesh dynamic imine covalently modified polymer powder was spread evenly on a PEI film in a size of 3cm×5cm and covered with another PEI film. The plastic film was obtained by hot pressing on a flat plate at 90-100℃ and 30MPa for 15-30 minutes.

[0050] Preferably, the specific preparation method of the dynamic imine covalently modified polymer powder in step three is as follows: The amino-modified product from step two is subjected to a Schiff base reaction to prepare the dynamic imine covalently modified polymer with an aldehyde to amino group ratio of 1:(0.5-1.5): 5g of intermediate product B is weighed and dispersed in 100mL of dimethyl sulfoxide (DMSO), and dissolved by stirring at 90-100℃; 1g of terephthalaldehyde is dissolved in 10mL of... A terephthalaldehyde solution was prepared in dimethyl sulfoxide (DMSO). After adjusting the pH of the reaction system to 4.8-5.2 by adding dilute hydrochloric acid, the terephthalaldehyde solution was slowly added and the reaction was carried out for 4-6 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain a dark gel-like product. The product was first separated by precipitation with acetone, then washed 5 times with isopropanol, and the dark solid product was obtained by vacuum filtration. The dark solid product was placed in a fume hood overnight to evaporate the residual solvent, and then vacuum dried for 12 hours to obtain the final product. The final product was obtained by grinding and sieving to obtain a 60-80 mesh dynamic imine covalently modified polymer powder.

[0051] Table 1: Information on raw materials for the synthesis of dynamic imine covalently modified polymers

[0052] synthetic raw materials CAS number source Cellulose 9004-34-6 McLean Chemical Reagents Company Anhydrous lithium chloride (LiCl) 7447-41-8 McLean Chemical Reagents Company Triethylamine Et3N 121-44-8 McLean Chemical Reagents Company p-Toluenesulfonyl chloride TsCl 98-59-9 McLean Chemical Reagents Company Dimethylformamide (DMF) 68-12-2 McLean Chemical Reagents Company Dimethyl sulfoxide (DMSO) 67-68-5 McLean Chemical Reagents Company ethylenediamine 6780-13-8 McLean Chemical Reagents Company 1,4-Butanediamine 110-60-1 McLean Chemical Reagents Company 1,6-Hexamethylenediamine 124-09-4 McLean Chemical Reagents Company terephthalaldehyde 623-27-8 McLean Chemical Reagents Company 1,6-Hexadialdehyde 1072-21-5 McLean Chemical Reagents Company 1,4-Butanedialdehyde 638-37-9 McLean Chemical Reagents Company

[0053] Example 1: A method for preparing a dynamically imine covalently modified polymer, comprising the following steps:

[0054] Step 1: Add 10g of cellulose to 200mL of dimethyl sulfoxide (DMF) solution and dissolve it completely for 3 hours at 105℃ with magnetic stirring at 200rpm. Then add 2g of anhydrous lithium chloride and continue stirring until a transparent viscous solution is obtained. Finally, add 3g of triethylamine and 18g of p-toluenesulfonyl chloride and continue the reaction for 24 hours at 105℃ with magnetic stirring at 200rpm until a dark gel-like product is obtained. Precipitate the gel product with excess ice water and wash it three times with ultrapure water and ethanol, respectively. Obtain the solid product by vacuum filtration. Place the solid product in a fume hood overnight to evaporate the residual solvent. Finally, vacuum dry for 12 hours to obtain intermediate product A.

[0055] Step 2: Weigh 10g of intermediate product A from Step 1 into 100mL of dimethyl sulfoxide (DMSO), add 100g of ethylenediamine at a molar ratio of p-toluenesulfonic acid group to amino group of 1:25, and magnetically stir at 200rpm for 4 hours at 90℃. After the reaction is completed, cool to room temperature, precipitate and separate the product with excess isopropanol, wash five times with pure water and ethanol, and obtain a dark solid product by vacuum filtration. Place the dark solid product in a fume hood overnight to evaporate the residual solvent, and vacuum dry for 12 hours to obtain intermediate product B.

[0056] Step 3: Weigh 5g of intermediate product B and disperse it in 100mL of dimethyl sulfoxide (DMSO). Dissolve it at 90℃ with magnetic stirring at 200rpm to obtain mixture A. Dissolve 1g of 1,4-butanedialdehyde in 10mL of DMSO to prepare mixture B. Adjust the pH of the reaction system to 5.0 by adding dilute hydrochloric acid. Slowly add mixture B to mixture A at 1g / min and maintain the reaction at 90℃ for 6 hours. After the reaction is completed, cool to room temperature to obtain a dark gel-like product. Separate the product by precipitation with acetone, wash it 5 times with isopropanol, and obtain a dark solid product by vacuum filtration. Place the dark solid product in a fume hood overnight to evaporate the residual solvent. Vacuum dry for 12 hours to obtain the final product. Grind and sieve to obtain 60-80 mesh dynamic imine covalently modified polymer powder.

[0057] The method for preparing a film using 60-80 mesh dynamic imine covalently modified polymer powder is as follows: 60-80 mesh dynamic imine covalently modified polymer powder is spread evenly on PEI film A, the size of which is 3cm×5cm. Another PEI film B is then placed over the dynamic imine covalently modified polymer powder layer laid on PEI film A. The film is then hot-pressed on a flat plate at 95℃ and 30MPa for 30 minutes, and then naturally cooled to room temperature to obtain a dynamic imine modified plastic film.

[0058] The difference between Example 2 and Example 1 is as follows: In step two of the preparation method of the dynamic imine covalently modified polymer, 10g of intermediate product A from step one is weighed into 100mL of dimethyl sulfoxide (DMSO), and 146.7g of 1,4-butanediamine is added at a molar ratio of p-toluenesulfonic acid group to amino group of 1:25. The mixture is magnetically stirred at 200rpm for 4 hours at 90°C. After the reaction is completed, the mixture is cooled to room temperature, and the product is separated by precipitation with excess isopropanol. The product is then washed five times with pure water and ethanol. The product is obtained by vacuum filtration and placed in a fume hood overnight to evaporate the residual solvent. The product is then vacuum dried for 12 hours to obtain intermediate product B. The remaining steps are the same.

[0059] The difference between Example 3 and Example 1 is as follows: In step two of the preparation method of the dynamic imine covalently modified polymer, 10g of intermediate product A from step one is weighed into 100mL of dimethyl sulfoxide (DMSO), and 193.4g of 1,6-hexanediamine is added at a molar ratio of p-toluenesulfonic acid group to amino group of 1:25. The mixture is magnetically stirred at 200rpm for 4 hours at 90°C. After the reaction is completed, the mixture is cooled to room temperature, and the product is separated by precipitation with excess isopropanol. The product is then washed five times with pure water and ethanol. The product is obtained by vacuum filtration and placed in a fume hood overnight to evaporate the residual solvent. The product is then vacuum dried for 12 hours to obtain intermediate product B. The remaining steps are the same.

[0060] The difference between Example 4 and Example 1 is as follows: In step three of the preparation method of the dynamic imine covalently modified polymer, 5g of intermediate product B is weighed and dispersed in 100mL of dimethyl sulfoxide (DMSO). The mixture is dissolved at 90°C with magnetic stirring at 200rpm to obtain mixture A. 1g of 1,6-hexanedialdehyde is dissolved in 10mL of DMSO to prepare mixture B. After adjusting the pH of the reaction system to 5 by adding dilute hydrochloric acid, mixture B is slowly added to mixture A at 1g / min to maintain the reaction at 90°C for 6 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a dark gel-like product. The product is first separated by precipitation with acetone, then washed 5 times with isopropanol, and a dark solid product is obtained by vacuum filtration. The dark solid product is placed in a fume hood overnight to evaporate the residual solvent, and then vacuum dried for 12 hours to obtain the final product. The final product is obtained by grinding and sieving to obtain 60-80 mesh dynamic imine covalently modified polymer powder. The remaining steps are the same.

[0061] The difference between Example 5 and Example 2 is as follows: In step three of the preparation method of the dynamic imine covalently modified polymer, 5g of intermediate product B is weighed and dispersed in 100mL of dimethyl sulfoxide (DMSO). The mixture is dissolved at 90°C with magnetic stirring at 200rpm to obtain mixture A. 1g of 1,6-hexanedialdehyde is dissolved in 10mL of DMSO to prepare mixture B. After adjusting the pH of the reaction system to 5 by adding dilute hydrochloric acid, mixture B is slowly added to mixture A at 1g / min to maintain the reaction at 90°C for 6 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a dark gel-like product. The product is first separated by precipitation with acetone, then washed 5 times with isopropanol, and a dark solid product is obtained by vacuum filtration. The dark solid product is placed in a fume hood overnight to evaporate the residual solvent, and then vacuum dried for 12 hours to obtain the final product. The final product is obtained by grinding and sieving to obtain 60-80 mesh dynamic imine covalently modified polymer powder. The remaining steps are the same.

[0062] The difference between Example 6 and Example 3 is as follows: In step three of the preparation method of the dynamic imine covalently modified polymer, 5g of intermediate product B is weighed and dispersed in 100mL of dimethyl sulfoxide (DMSO). The mixture is dissolved at 90°C with magnetic stirring at 200rpm to obtain mixture A. 1g of 1,6-hexanedialdehyde is dissolved in 10mL of DMSO to prepare mixture B. After adjusting the pH of the reaction system to 5 by adding dilute hydrochloric acid, mixture B is slowly added to mixture A at 1g / min to maintain the reaction at 90°C for 6 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a dark gel-like product. The product is first separated by precipitation with acetone, then washed 5 times with isopropanol, and a dark solid product is obtained by vacuum filtration. The dark solid product is placed in a fume hood overnight to evaporate the residual solvent, and then vacuum dried for 12 hours to obtain the final product. The final product is obtained by grinding and sieving to obtain 60-80 mesh dynamic imine covalently modified polymer powder. The remaining steps are the same.

[0063] The difference between Example 7 and Example 1 is as follows: In step three of the preparation method of the dynamic imine covalently modified polymer, 5g of intermediate product B is weighed and dispersed in 100mL of dimethyl sulfoxide (DMSO). The mixture is dissolved at 90°C with magnetic stirring at 200rpm to obtain mixture A. 1g of terephthalaldehyde is dissolved in 10mL of DMSO to prepare mixture B. After adjusting the pH of the reaction system to 5 by adding dilute hydrochloric acid, mixture B is slowly added to mixture A at 1g / min to maintain the reaction at 90°C for 6 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a dark gel-like product. The product is first separated by precipitation with acetone, then washed 5 times with isopropanol, and a dark solid product is obtained by vacuum filtration. The dark solid product is placed in a fume hood overnight to evaporate the residual solvent, and then vacuum dried for 12 hours to obtain the final product. The final product is obtained by grinding and sieving to obtain 60-80 mesh dynamic imine covalently modified polymer powder. The remaining steps are the same.

[0064] The difference between Example 8 and Example 2 is as follows: In step three of the preparation method of the dynamic imine covalently modified polymer, 5g of intermediate product B is weighed and dispersed in 100mL of dimethyl sulfoxide (DMSO). The mixture is dissolved at 90°C with magnetic stirring at 200rpm to obtain mixture A. 1g of terephthalaldehyde is dissolved in 10mL of DMSO to prepare mixture B. After adjusting the pH of the reaction system to 5 by adding dilute hydrochloric acid, mixture B is slowly added to mixture A at 1g / min to maintain the reaction at 90°C for 6 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a dark gel-like product. The product is first separated by precipitation with acetone, then washed 5 times with isopropanol, and a dark solid product is obtained by vacuum filtration. The dark solid product is placed in a fume hood overnight to evaporate the residual solvent, and then vacuum dried for 12 hours to obtain the final product. The final product is obtained by grinding and sieving to obtain 60-80 mesh dynamic imine covalently modified polymer powder. The remaining steps are the same.

[0065] The difference between Example 9 and Example 3 is as follows: In step three of the preparation method of the dynamic imine covalently modified polymer, 5g of intermediate product B is weighed and dispersed in 100mL of dimethyl sulfoxide (DMSO). The mixture is dissolved at 90°C with magnetic stirring at 200rpm to obtain mixture A. 1g of terephthalaldehyde is dissolved in 10mL of DMSO to prepare mixture B. After adjusting the pH of the reaction system to 5 by adding dilute hydrochloric acid, mixture B is slowly added to mixture A at 1g / min to maintain the reaction at 90°C for 6 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a dark gel-like product. The product is first separated by precipitation with acetone, then washed 5 times with isopropanol, and a dark solid product is obtained by vacuum filtration. The dark solid product is placed in a fume hood overnight to evaporate the residual solvent, and then vacuum dried for 12 hours to obtain the final product. The final product is obtained by grinding and sieving to obtain 60-80 mesh dynamic imine covalently modified polymer powder. The remaining steps are the same.

[0066] Performance testing:

[0067] 1. Mechanical property characterization: The tensile properties of the plastic film were tested using an Instron 5565 universal testing machine from the United States. The sample size was 50mm × 5mm, and the test length and tensile rate were 30mm and 2mm / min, respectively. All samples were tested in triplicate, and the average value was taken.

[0068] 2. Characterization of self-healing performance: A crack was cut on the surface of the plastic film with a scalpel, and the damaged film was repaired in a flat plate hot press at 100℃ and 30MPa for 15 minutes to investigate the scratch self-healing performance of the plastic film. A self-healing rate greater than 90% was recorded as OK, otherwise it was recorded as NG.

[0069] 3. Thermal stability characterization: The thermogravimetric curves of the plastic film were tested using a Netzsch TG209F1 thermometer under nitrogen protection. The test temperature range and heating rate were 30-600℃ and 20℃ / min, respectively.

[0070] 4. Degradability test: Place a 5mm×30mm plastic film in a 20mL brown glass bottle and add 10mL of 5%wt acetic acid solution or alkaline amine solution. Stir magnetically at room temperature for 24 hours to achieve acid or alkali degradation. Complete degradation in acid or alkali is marked as OK, otherwise it is marked as NG.

[0071] 5. Test method for hydrostatic pressure: Measured according to GB / T 19082-2023. A hydrostatic pressure ≥1500mmH2O is recorded as Pass, otherwise it is recorded as NG.

[0072] Table 1: Test parameters of physicochemical properties of common materials and thin films in Examples 1-9

[0073] Material Young's modulus (GPa) Tensile strength (MPa) Self-healing performance (NG / OK) Biodegradability (NG / OK) <![CDATA[Hydrostatic pressure (mmH20)]]> LDPE 1.06 18.1 NG NG Pass HDPE 1.01 26.8 NG NG Pass PS 1.80 20.0 NG NG Pass PP 1.00 27.0 NG NG Pass PU 5.60 24.6 NG NG Pass PVC 0.03 33.8 NG NG Pass PMMA 1.60 35.0 NG NG Pass PC 2.00 65.0 NG NG Pass PET 2.76 48.3 NG NG Pass PLA 2.48 57.0 OK OK Pass pH value B 1.00 26.0 NG NG Pass Example 1 2.60 38.1 OK OK Pass Example 2 2.84 52.1 OK OK Pass Example 3 2.69 49.9 OK OK Pass Example 4 2.77 51.3 OK OK Pass Example 5 2.83 52.7 OK OK Pass Example 6 2.92 53.1 OK OK Pass Example 7 3.01 55.2 OK OK Pass Example 8 3.20 58.0 OK OK Pass Example 9 3.19 61.9 OK OK Pass

[0074] As can be seen from Examples 1-9 and Table 1, the Young's modulus of the bio-based biodegradable film of this invention is generally higher than that of the petroleum-based plastics compared, while its tensile strength is significantly superior. It is not only significantly higher than general-purpose plastics such as low-density polyethylene (LDPE), high-density polyethylene (HDPE), polystyrene (PS), polypropylene (PP), polyurethane (PU), and polyvinyl chloride (PVC), but also slightly higher than engineering plastics such as polymethyl methacrylate (PMMA), polycarbonate (PC), and polyethylene terephthalate (PET). Furthermore, compared with commercially available bioplastics such as polylactic acid (PLA) and poly(β-hydroxybutyric acid) (pH B), the bio-based biodegradable film also exhibits higher tensile strength and Young's modulus.

[0075] In Example 8, the thermal stability of bio-based biodegradable films was evaluated by thermogravimetric analysis.

[0076] Figure 2 and Figure 3 The TGA and DTG curves of cellulose-based dynamically imine covalently modified polymer films are shown.

[0077] Depend on Figure 2 It is known that cellulose has excellent thermal stability, starting to degrade around 300℃ and reaching its maximum degradation rate at around 350℃. For bio-based biodegradable films, significant mass loss was observed in the TGA curves of the films in the temperature ranges of room temperature to 100℃, 100 to 250℃, 250 to 380℃, and 380 to 500℃. These four stages correspond to the evaporation of water, the removal of residual DMSO solvent, the thermal decomposition of cellulose macromolecular chains, and the thermal decomposition of dynamic imine networks, respectively.

[0078] from Figure 3 The DTG curves show that the initial decomposition temperature of the bio-based biodegradable film is around 300℃, indicating that it has good thermal stability.

[0079] The biodegradability of bio-based biodegradable films was evaluated using a simple soil burial method.

[0080] Figure 4 This study demonstrates the morphological changes of candy-coated paper and bio-based biodegradable film over time after burying them in soil. After being buried 2 cm deep in natural soil, significant changes in the appearance of both the candy-coated paper and the bio-based biodegradable film were observed. Firstly, due to the abundance of microorganisms in the soil capable of attacking and digesting cellulose molecular chains, both the candy-coated paper and the bio-based biodegradable film underwent expansion and fragmentation within one month, and were completely degraded after 40 and 50 days, respectively.

[0081] In summary, the dynamic imine covalently modified polymer of this invention can be thermally processed to obtain a bio-based biodegradable film. The resulting bio-based biodegradable film has a hydrostatic pressure ≥1500mmH2O, Young's modulus ≥2.60GPa, elongation at break ≥45%, tensile strength ≥38.0MPa, and self-healing efficiency ≥90%, exhibiting excellent overall performance.

[0082] It should be noted that this specific embodiment is merely an explanation of the technical solution of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A dynamically imine covalently modified polymer, characterized in that: The dynamic imine covalently modified polymer is made from a polymer containing hydroxyl groups, a polar solvent, a benzoyl chloride, a catalyst, a diamine compound, or a diformaldehyde compound; the polymer containing hydroxyl groups includes any one or more combinations of vegetable oil, lignin, polyvinyl alcohol, starch, and cellulose.

2. The dynamically imine covalently modified polymer according to claim 1, characterized in that: The benzoyl chloride is any one of p-toluyl chloride, p-toluenesulfonyl chloride, benzenesulfonyl chloride, and p-fluorobenzenesulfonyl chloride.

3. The dynamically imine covalently modified polymer according to claim 1, characterized in that: The polar solvent is any one of water, acetone, dimethyl sulfoxide, dimethylformamide, and tetrahydrofuran.

4. The dynamically imine covalently modified polymer according to claim 1, characterized in that: The diamine compound is one or more combinations of 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,8-octanediamine, p-toluenediamine, and 1,11-diaminoundecane.

5. The dynamically imine covalently modified polymer according to claim 4, characterized in that: The diformaldehyde compounds are one or more combinations of 1,4-butanedialdehyde, 1,5-pentanedialdehyde, 1,6-hexanedialdehyde, 1,8-octanedialdehyde, p-toluenedialdehyde, and 1,11-dialdehyde undecane.

6. A method for preparing a dynamically imine covalently modified polymer according to any one of claims 1-5, characterized in that: The process includes the following steps: Step 1, the polymer containing hydroxyl groups is dissolved in polar solvent A, and benzoyl chloride is added to carry out an acylation reaction under the action of a catalyst to obtain intermediate product A; Step 2, the intermediate product is dissolved in polar solvent B, and a diamine compound is added to carry out a dehydration condensation reaction to obtain intermediate product B; Step 3, intermediate product B is dissolved in polar solvent C, and a formaldehyde compound is added to carry out a Schiff base reaction to obtain a dynamically imine covalently modified polymer.

7. The method for preparing a dynamically imine covalently modified polymer according to claim 6, characterized in that: In step one, the hydroxyl-containing polymer is dissolved in polar solvent A, which is any one of water, acetone, dimethyl sulfoxide, dimethylformamide, and tetrahydrofuran. Anhydrous lithium chloride is added and mixed evenly to obtain a transparent viscous solution. A catalytic amount of triethylamine and benzoyl chloride are added, and an acylation reaction is carried out under the action of the catalyst to obtain a dark gel-like product. After precipitation with excess ice water, the product is washed three times with ultrapure water and ethanol, respectively. The product is then vacuum filtered and vacuum dried to obtain intermediate product A.

8. The method for preparing a dynamically imine covalently modified polymer according to claim 6, characterized in that: In step two, the intermediate product is dissolved in polar solvent B, which is any one of acetone, dimethyl sulfoxide, dimethylformamide, and tetrahydrofuran. A diamine compound is added, with a molar ratio of the diamine compound to benzoyl chloride of (12-14):

1. The reaction is carried out at 90-100°C with stirring for 2-4 hours for dehydration condensation. After the reaction is completed, the mixture is cooled to room temperature, and the product is separated by precipitation with excess isopropanol. The product is then washed with pure water and ethanol, vacuum filtered, and vacuum dried to obtain intermediate product B.

9. The method for preparing a dynamically imine covalently modified polymer according to claim 6, characterized in that: In step three, intermediate product B is dissolved in polar solvent C, which is any one of acetone, dimethyl sulfoxide, dimethylformamide, and tetrahydrofuran. The pH of the system is adjusted to 4.8-5.

2. Under stirring conditions at 90-100℃, a formaldehyde compound is added dropwise to carry out a Schiff base reaction. The molar ratio of the formaldehyde compound to the diamine compound is 10:(5-15). After the reaction is completed, the mixture is cooled to room temperature to obtain a dark gel-like product. After precipitation and separation with acetone, the product is washed multiple times with isopropanol and vacuum filtered to obtain a dark solid product. Subsequently, the product is vacuum dried to obtain a dynamically modified imine covalent polymer.

10. The method for preparing a dynamically imine covalently modified polymer according to claim 6, characterized in that: The dynamic imine covalently modified polymer is obtained by hot processing injection molding, blow molding or extrusion molding to obtain dynamic imine covalently modified polymer products; the dynamic imine covalently modified polymer products can be any form among films, sheets, plates or irregular shapes.

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