A plant polyphenol and maleic anhydride copolymer modified polyester and a method for preparing the same

Abstract

The application discloses a kind of plant polyphenol and maleic anhydride copolymer modified polyester and its preparation method, the modified polyester includes polyester, plant polyphenol and maleic anhydride copolymer.The preparation method includes that the plant polyphenol and maleic anhydride copolymer are dissolved in organic solvent, catalyst is added and mixed uniformly, and reaction liquid is obtained;The reaction liquid is heated to 25-80 DEG C, and is reacted under the condition of stirring for 4-16h, is cooled to room temperature, then is added in petroleum ether or ethyl acetate, and solid precipitate is separated out;Solid precipitate is filtered out and is washed with ethanol, and is dried, and antibacterial and antioxidant functional modified material is obtained;Antibacterial and antioxidant functional modified material is mixed with the polyester and is placed in high mixer, and is extruded again, and the modified polyester is obtained.The modified polyester material has the characteristics of good antibacterial and antioxidant performance, good processing performance, good tensile strength and toughness.

Description

Technical Field

[0001] This invention relates to a polyester and its preparation method, particularly a polyester modified with a copolymer of plant polyphenols and maleic anhydride and its preparation method. Background Technology

[0002] Fresh fruits and vegetables have a very short shelf life and are prone to mold and rot during transportation and storage, rendering them inedible, causing food waste and food safety issues. Therefore, extending the shelf life of fruits and vegetables through effective methods is crucial. Among the many methods available, plastic wrap is considered an economical and effective solution.

[0003] Biodegradable polyester materials offer significant advantages over traditional non-degradable materials like polypropylene and polyethylene in reducing environmental pollution due to their biodegradability. However, pure polyester films inherently lack antibacterial properties and exhibit low tensile strength and poor barrier properties, limiting their application in food packaging. Therefore, modifying biodegradable polyester materials to impart antibacterial and antioxidant capabilities, and improving their mechanical properties to meet the application requirements of fruit and vegetable preservation films, is an important pathway for the green development of the food preservation packaging sector in the future.

[0004] To produce multifunctional biodegradable polyester food preservation films with antioxidant, antibacterial, and barrier properties, researchers have added essential oils, chitosan, polyphenolic flavonoids, and metal nanoparticles to the films. For example, adding ZnO and ZnO-Ag nanoparticles to a PBAT matrix produces an antibacterial composite film. However, packaging with these metal or metal oxide nanoparticles is harmful to the environment and human health after disposal, and is also expensive and poses a migration risk. To reduce the negative impacts of chemical additives and nanoparticles on humans, films based on natural antibacterial and antioxidant agents, such as curcumin, tea polyphenols, essential oils, and their complexes, are currently a sought-after alternative, as the phenolic hydroxyl groups endow them with powerful antioxidant and antibacterial properties.

[0005] Plant polyphenols are a class of natural active substances widely found in plants. They possess a polyphenolic structure, strong reducing properties, and scavenging activity against free radicals, while also protecting against free radical-induced damage to biomolecules. They exhibit excellent antioxidant, anti-aging, antibacterial, antiviral, anti-inflammatory, and preservative functions. Plant polyphenols are currently widely used in food preservation, pharmaceuticals, and cosmetics. They are now widely applied in the storage and preservation of vegetables, fruits, meat and poultry products, and aquatic products, effectively improving preservation and extending shelf life.

[0006] However, due to the large number of hydrophilic phenolic hydroxyl groups in natural plant phenols, their compatibility with hydrophobic polymer materials is poor. When added alone, they cannot be uniformly dispersed in the polymer matrix. In addition, plant polyphenols themselves contain a large number of benzene ring structures, which are highly rigid. Direct physical blending with polyester materials does not enhance their properties but may even further degrade them. Furthermore, polyester materials such as PET have slow crystallization rates and are difficult to process, while PLA and PGA have poor toughness and poor processability, making them impossible to process directly without modification. Therefore, there are few reports on the use of plant polyphenols for polyester material modification through blending, and even those that exist suffer from poor compatibility and difficult processing.

[0007] In other words, the application of the antioxidant and antibacterial activities of plant polyphenols to polyester food contact materials without damaging or further reducing the processing difficulty of polyester materials and improving their mechanical properties is in line with current policy guidance and market demand from both practical application needs and environmental protection requirements, and has great market prospects. Summary of the Invention

[0008] The purpose of this invention is to provide a polyester modified with plant polyphenols and maleic anhydride copolymer and its preparation method. On the one hand, it improves the tensile and impact strength of polyester products, enhances processing rheology, and improves surface finish. On the other hand, it provides additional antibacterial, antioxidant, and gas barrier properties to the polyester material, offering unique properties not found in existing polyester materials. These unique properties will endow it with broad application prospects.

[0009] The technical solution of the present invention is a polyester modified by a copolymer of plant polyphenols and maleic anhydride, comprising polyester, plant polyphenols and maleic anhydride copolymer.

[0010] Preferably, the aforementioned polyester modified with plant polyphenols and maleic anhydride copolymer has the following mixing ratio: by weight, it contains 80-99.9 parts polyester and 0.1-20 parts plant polyphenols and maleic anhydride copolymer; wherein the molar ratio of hydroxyl groups in the plant polyphenols to anhydride groups in the maleic anhydride copolymer is 1:0.01-1:50.

[0011] Preferably, the aforementioned plant polyphenol and maleic anhydride copolymer modified polyester is a petroleum-based polyester and / or a bio-based polyester.

[0012] Preferably, the aforementioned plant polyphenol and maleic anhydride copolymer-modified polyester, wherein the petroleum-based polyester is one or any combination of polyethylene terephthalate, polyethylene terephthalate-1,4-cyclohexanediol, polyethylene terephthalate-1,4-cyclohexanediol, polyethylene naphthalate, polybutylene succinate, polycyclohexamethylene terephthalate, polypropylene terephthalate, or polycarbonate; and the bio-based polyester is one or any combination of polylactic acid, polyhydroxyalkanoate, polybutylene succinate, 2,5-furandicarboxylate-based polyester, polycaprolactone, or polybutylene adipate-butylene terephthalate.

[0013] Preferably, the aforementioned polyester modified with plant polyphenols and maleic anhydride copolymers, wherein the plant polyphenols are one or any combination of caffeic acid, curcumin, chlorogenic acid, anthocyanins, catechins, gallic acid, ellagic acid, arbutin, quercetin, resveratrol, kaempferol, baicalin, luteolin, apigenin, or robinin.

[0014] Preferably, the polyester modified with the aforementioned plant polyphenols and maleic anhydride copolymer has the following general structural formula:

[0015]

[0016] in, It can be any of the following structures:

[0017]

[0018] x and y are independent integers from 5 to 10, and n is an integer from 5 to 20.

[0019] A method for preparing the aforementioned plant polyphenol and maleic anhydride copolymer-modified polyester includes the following steps:

[0020] (1) Dissolve the plant polyphenols and maleic anhydride copolymer in an organic solvent, add a catalyst and mix well to obtain a reaction solution;

[0021] (2) Heat the reaction solution to 25-80℃ and react for 4-16 hours under stirring. Cool to room temperature and then add petroleum ether or ethyl acetate to precipitate a solid precipitate.

[0022] (3) The solid precipitate obtained in step (2) is filtered out, washed with ethanol and water, and dried to obtain antibacterial and antioxidant modified material;

[0023] (4) The antibacterial and antioxidant modified material is mixed with the polyester in a high-speed mixer and then melt-extruded to obtain the modified polyester.

[0024] Preferably, in the aforementioned method for preparing polyester modified with plant polyphenols and maleic anhydride copolymer, the organic solvent is one or any combination of acetonitrile, ethanol, 1,4-dioxane, dimethyl sulfoxide, or tetrahydrofuran.

[0025] Preferably, in the aforementioned method for preparing polyester modified with plant polyphenols and maleic anhydride copolymer, the catalyst is triethylamine, dimethylisopropylamine, N,N-diisopropylethylamine, 1-methylpyrrolidine, N-methylmorpholine, N-methylimidazolium, 1,4-diazabicyclo[2.2.2]octane, 1,5-diazabicyclo[4.3.0]non-5-ene, 4-dimethylaminopyridine, p-toluenesulfonic acid, pyridine, 1,8-diazabicycloundec-7-ene, 4-dimethylaminopyridine, 4-pyrrolylpyridine, zinc chloride, or 2,6-di-tert-butyl-4-methylphenol magnesium.

[0026] Preferably, in the aforementioned method for preparing polyester modified with plant polyphenols and maleic anhydride copolymer, in step (1), the molar ratio of plant polyphenols to maleic anhydride copolymer in the reaction solution is 5:1-5:10, and the molar ratio of plant polyphenols to catalyst is 100:0.5-100:1; in step (2), when the reaction solution is added to petroleum ether or ethyl acetate, the volume ratio of the reaction solution to petroleum ether or ethyl acetate is 1:1-1:10.

[0027] Beneficial effects of the present invention

[0028] This invention incorporates plant polyphenols with strong antibacterial and antioxidant functions into polyester materials, giving the polyester materials strong antibacterial and antioxidant properties, and making them promising for use in packaging materials for vegetables and fruits, livestock and poultry meat and their products, aquatic products, or pharmaceuticals.

[0029] The method of the present invention improves the compatibility of polyester and plant polyphenols. At the same time, through graft modification of maleic anhydride copolymer, the processing and molding performance of polyester material is improved, the molding difficulty is reduced, the tensile strength and toughness are improved, and the gas barrier properties are improved.

[0030] The principle of this invention is as follows: Maleic anhydride copolymer is grafted onto natural plant polyphenols with antibacterial and antioxidant activities via a catalytic reaction to prepare a functional modifier for polyester materials with antibacterial and antioxidant properties. By controlling the molar ratio of plant polyphenols to maleic anhydride copolymers during the reaction, the functional modifier can simultaneously retain the anhydride functional groups of the maleic anhydride copolymer and the phenolic hydroxyl groups of the plant polyphenols. The anhydride functional groups in the modifier can undergo chain extension reactions with the terminal hydroxyl or carboxyl groups of the polyester material, improving the performance of the polyester itself. Simultaneously, because the maleic anhydride copolymer itself has excellent compatibility with polyester materials, this process naturally also improves the compatibility between plant polyphenols and polyester materials, resulting in better dispersion of plant polyphenols in the polyester and improved mechanical properties of the polyester material.

[0031] On the other hand, the phenolic hydroxyl groups in the modifier can donate hydrogen atoms, giving the polyester composite material antibacterial and antioxidant properties. By increasing the reaction with peroxy free radicals, stable phenoxy free radicals are generated, so that the unpaired single electrons on the oxygen atom can interact with the electron cloud on the benzene ring, producing a conjugation effect, thereby reducing the energy of the free radical and interrupting the chain reaction of lipid peroxidation.

[0032] In other words, this invention enables polyester composite materials to simultaneously possess antibacterial and antioxidant properties, while improving the mechanical and processing properties of polyester. Furthermore, since plant polyphenols are derived from plants, animals, or microorganisms in nature, they are renewable, environmentally friendly, and will not harm the human body, making them more suitable for polyester packaging that comes into direct contact with food or pharmaceuticals, and polyester fibers that come into direct contact with human skin. Moreover, even with extremely low addition levels, the invention enables functional modification of polyester materials, further expanding the application areas of polyester materials and enhancing product competitiveness. Attached Figure Description

[0033] Appendix Figure 1 The invention includes blow molding process diagrams of embodiments and comparative examples; where a is Example 1 and b is Comparative Example 2.

[0034] Appendix Figure 2 The image shows an infrared comparison of SMA, quercetin, and quercetin-SMA in Example 1.

[0035] Appendix Figure 3 The image shows an infrared comparison of SMA, curcumin, and curcumin-SMA in Example 2.

[0036] Appendix Figure 4 Comparison of the hydrogen NMR spectra of SMA, quercetin, and quercetin-SMA in Example 1.

[0037] Appendix Figure 5 Comparison of the hydrogen NMR spectra of SMA, curcumin, and curcumin-SMA in Example 2.

[0038] Appendix Figure 6 This is a comparison chart of the antibacterial properties of the polyesters obtained in the embodiments and comparative examples of the present invention. Detailed Implementation

[0039] The present invention will be further described below with reference to embodiments, but these embodiments are not intended to limit the scope of the invention.

[0040] Embodiments of the present invention

[0041] Example 1

[0042]

[0043] Step 1: Add 20g of styrene-maleic anhydride copolymer (SMA) and 200mL of acetonitrile to a 500mL round-bottom flask. Dissolve the SMA by stirring at 60℃. After complete dissolution, add 0.0658mol of 20g of quercetin and stir until homogeneous. Add 0.4g (0.0033mol) of 4-dimethylaminopyridine to the reaction solution as a catalyst. Then, react the solution at 60℃ for 4 hours. After the reaction is complete, cool the reaction solution to room temperature and pour it into petroleum ether. A solid precipitates, which is filtered and dried in an oven at 60℃ to constant weight to obtain a powdered solid product, i.e., quercetin-SMA. Infrared comparison of raw materials and products is shown below. Figure 2 As shown in the figure. 3030cm -1 700cm -1 The two peaks are the CH stretching vibration peak and the bending vibration peak on the SMA benzene ring, respectively, at 1770 cm⁻¹. -1 The peak at 1560 cm⁻¹ represents the stretching vibration of the carbonyl group on the SMA anhydride ring. -1 The peak at this point represents the stretching vibration of the carbonyl group on the carboxylic acid ester formed after the reaction, which indicates that SMA has been successfully grafted onto quercetin.

[0044] SMA, quercetin-SMA, and quercetin 1H NMR spectra, for example... Figure 4 As shown, the solvent used for quercetin-SMA and quercetin was deuterated methanol, with solvent peaks at 3.31 and water peaks at 4.87, respectively. The solvent used for SMA was deuterated chloroform, with a solvent peak at 7.26. The peak at 3.66 represents the hydrogen on the methylene group after the anhydride ring opens. Comparing this with the hydrogen peaks on the benzene ring from 6.0 to 7.8 confirms that SMA has been successfully grafted onto quercetin.

[0045] Step 2: By weight, mix 1 part of the modifier (quercetin-SMA) prepared in Step 1 with 99 parts of polybutylene adipate-butylene terephthalate (PBAT) in a high-speed mixer at 80°C for 10 minutes. Extrude and granulate in a twin-screw extruder at a melt extrusion temperature of 110-130°C and a screw speed of 200 rpm. After extrusion, granulate the resulting granules and put them into a blown film machine at a screw speed of 450 rpm. Blow-mold the film at a blown film temperature of 130°C to obtain PBAT / quercetin-SMA.

[0046] Example 2

[0047]

[0048] Step 1: Add 20g of styrene-maleic anhydride copolymer (SMA) and 200mL of acetonitrile to a 500mL round-bottom flask. Dissolve the SMA by stirring at 60℃. After complete dissolution, add 0.1mol of 36.87g of curcumin and stir until homogeneous. Add 0.8g (0.0067mol) of 4-dimethylaminopyridine to the reaction solution as a catalyst. Then, react the solution at 60℃ for 4 hours. After the reaction is complete, cool the reaction solution to room temperature and pour it into petroleum ether. A solid precipitates, which is filtered. The precipitate is then dried in an oven at 60℃ to constant weight to obtain a powdered solid product, namely curcumin-SMA. Infrared comparison of raw materials and product is shown below. Figure 3 As shown in the figure. 700cm -1 The peak at 1770 cm⁻¹ represents the bending vibration on the benzene ring of the SMA. -1 The peak at 1563 cm⁻¹ represents the stretching vibration of the carbonyl group on the SMA anhydride ring. -1 The peak at this point represents the stretching vibration of the carbonyl group on the carboxylic acid ester formed after the reaction, which indicates that SMA has been successfully grafted onto quercetin.

[0049] SMA, curcumin, curcumin-SMA 1H NMR spectrum for example Figure 5 As shown, curcumin-SMA was used with deuterated methanol as the solvent, with solvent peaks at 3.31 and water peaks at 4.87, respectively. SMA and curcumin were used with deuterated chloroform as the solvent, with a solvent peak at 7.26. The peak at 3.66 represents the hydrogen on the methylene group after the anhydride ring opens. Comparison with the hydrogen peaks on the benzene ring from 6.0 to 7.8 confirms that SMA has been successfully grafted onto curcumin.

[0050] Step 2: By weight, 1 part of the modifier (curcumin-SMA) prepared in Step 1 and 99 parts of polybutylene adipate-butylene terephthalate (PBAT) are mixed in a high-speed mixer at 80°C for 10 minutes. The mixture is then extruded and granulated in a twin-screw extruder at a melt extrusion temperature of 110-130°C and a screw speed of 200 rpm. After extrusion, the granules are placed in a blown film extruder at a screw speed of 450 rpm and blown at a blown film temperature of 130°C to obtain PBAT / curcumin-SMA.

[0051] Example 3

[0052]

[0053] Step 1: Take 15.6g of methyl vinyl ether-maleic anhydride copolymer (PVA-MA) into a round-bottom flask, add 200mL of 1,4-dioxane as solvent, stir thoroughly until completely dissolved, then add 0.1mol ellagic acid (30.2g) and 1.5mL of N,N-diisopropylethylamine. After reacting for 4h, stop the reaction and let it cool to room temperature. Add 200mL of petroleum ether to the reaction solution, and a viscous product will precipitate. After discarding the solvent, put the solid product into an oven at 60℃ and dry it to constant weight. Grind it to obtain a solid powder, wash it with ethanol and dry it to obtain the product, i.e., ellagic acid-PVM / MA.

[0054] Step 2: By weight, 5 parts of the modifier (ellagic acid-PVM / MA) prepared in Step 1 and 95 parts of polybutylene adipate-butylene terephthalate (PBAT) are mixed in a high-speed mixer at 80°C for 10 minutes. The mixture is then extruded and granulated in a twin-screw extruder at a melt extrusion temperature of 110-130°C and a screw speed of 200 rpm. After extrusion, the granules are placed in a blown film extruder at a screw speed of 450 rpm and blown at a blown film temperature of 130°C to obtain PBAT / ellagic acid-PVM / MA.

[0055] Example 4

[0056]

[0057] Step 1: Take 15.4g of poly(isobutylene-maleic anhydride) (PIB / MA) in a round-bottom flask, use 200mL of 1,4-dioxane as solvent, stir thoroughly until completely dissolved, add 0.1mol of kaempferol (28.6g), 1,8-diazabicycloundec-7-ene (1.5mL), and 13.8g of potassium carbonate. After reacting for 4 hours, stop the reaction. After cooling to room temperature, add 200mL of petroleum ether to the reaction solution, and a viscous product will precipitate. After discarding the solvent, put the solid product into an oven at 60℃ and dry it to constant weight. Grind it to obtain a solid powder, wash it with ethanol and dry it to obtain the product, namely kaempferol-PIB / MA.

[0058] Step 2: By weight, 5 parts of the modifier (kaempferol-PIB / MA) prepared in Step 1 are mixed with 95 parts of polybutylene adipate-butylene terephthalate (PBAT) in a high-speed mixer at 80°C for 10 minutes. The mixture is then extruded and granulated in a twin-screw extruder at a melt extrusion temperature of 110-130°C and a screw speed of 200 rpm. After extrusion, the granules are placed in a blown film extruder at a screw speed of 450 rpm and blown at a blown film temperature of 130°C to obtain PBAT / kaempferol-PIB / MA.

[0059] Comparative Example 1

[0060] By weight, 100 parts of polybutylene adipate-butylene terephthalate (PBAT) were dried in a vacuum drying oven at 80°C for 24 hours, and then extruded in a twin-screw extruder at a melt extrusion temperature of 110-130°C and a screw speed of 200 rpm. After extrusion, the material was granulated, and the resulting granules were fed into a blown film machine at a screw speed of 450 rpm and blown into a film at a blown film temperature of 130°C.

[0061] Comparative Example 2

[0062] By weight, 1 part quercetin and 99 parts polybutylene adipate-butylene terephthalate (PBAT) were dried in a vacuum drying oven at 80°C for 24 hours, and then extruded in a twin-screw extruder at a melt extrusion temperature of 110-130°C and a screw speed of 200 rpm. After extrusion, the mixture was granulated, and the resulting granules were fed into a blown film machine at a screw speed of 450 rpm and blown into a film at a blown film temperature of 130°C.

[0063] Comparative Example 3

[0064] By weight, 1 part SMA and 99 parts polybutylene adipate-butylene terephthalate (PBAT) were dried in a vacuum drying oven at 80°C for 24 hours, and then extruded in a twin-screw extruder at a melt extrusion temperature of 110-130°C and a screw speed of 200 rpm. After extrusion, the material was granulated, and the resulting granules were fed into a blown film machine at a screw speed of 450 rpm and blown into a film at a blown film temperature of 130°C.

[0065] Comparative Example 4

[0066] By weight, 1 part curcumin and 99 parts polybutylene adipate-butylene terephthalate (PBAT) were dried in a vacuum drying oven at 80°C for 24 hours, and then extruded in a twin-screw extruder at a melt extrusion temperature of 110-130°C and a screw speed of 200 rpm. After extrusion, the mixture was granulated, and the resulting granules were fed into a blown film machine at a screw speed of 450 rpm and blown into a film at a blown film temperature of 130°C.

[0067] Comparative Example 5

[0068] By weight, 5 parts ellagic acid and 95 parts polybutylene adipate-butylene terephthalate (PBAT) were dried in a vacuum drying oven at 80°C for 24 hours, and then extruded in a twin-screw extruder at a melt extrusion temperature of 110-130°C and a screw speed of 200 rpm. After extrusion, the mixture was granulated, and the resulting granules were fed into a blown film machine at a screw speed of 450 rpm and blown into a film at a blown film temperature of 130°C.

[0069] Comparative Example 6

[0070] By weight, 5 parts of kaempferol and 95 parts of polybutylene adipate-butylene terephthalate (PBAT) were dried in a vacuum drying oven at 80°C for 24 hours, and then extruded in a twin-screw extruder at a melt extrusion temperature of 110-130°C and a screw speed of 200 rpm. After extrusion, the mixture was granulated, and the resulting granules were fed into a blown film machine at a screw speed of 450 rpm and blown into a film at a blown film temperature of 130°C.

[0071] Mechanical property testing

[0072] The mechanical property test results of Examples 1-4 and Comparative Examples 1-6 are shown in Table 1. The test standards are as follows: tensile strength is tested according to GB / T1040.1-2006; crystallization performance is tested by differential scanning calorimetry.

[0073] Table 1

[0074]

[0075]

[0076] The experimental data in the table show that, as can be seen from Comparative Examples 1 and 2, 4, 5, and 6, the strength and elongation at break of PBAT decreased significantly after the direct addition of plant polyphenols. This indicates that plant polyphenols and PBAT have poor compatibility, and their direct addition leads to a reduction in the performance of the composite material, as well as poor processing and molding (see attached table). Figure 1 (As shown in b), it is difficult to apply. Comparative Examples 1 and 3 show that PBAT and SMA have good compatibility; the performance of PBAT slightly decreases after SMA is added. Comparing Examples 1, 2, 3, and 4, the addition of maleic anhydride copolymer-modified plant polyphenols enhances the tensile strength of the PBAT composite material, increases the crystallization temperature, and decreases the elongation at break. This is because the maleic anhydride copolymer-modified plant polyphenols are well dispersed in PBAT and, being carboxylates, act as nucleating agents, improving the tensile strength of the composite material. Although the elongation at break shows a certain degree of decrease, it is not severe.

[0077] Antibacterial performance test

[0078] The inhibition zone method was used to conduct antibacterial tests on the embodiments and comparative examples of the present invention. A 10 mg / ml dispersion sample was diluted 10-fold and inoculated with *Escherichia coli* and *Staphylococcus aureus* on agar medium to form a suspension of 10⁸ CFU / ml. The suspension was incubated at 37°C for 24 hours. The antibacterial effect was evaluated by observing whether an inhibition zone was formed. The results are as follows: Figure 6 As shown.

[0079] The inhibition zone experiment shows that Examples 1-4 of this invention all possess good antibacterial properties. Under chemical reaction conditions, plant polyphenols and maleic anhydride copolymers are bonded through chemical bonds, maximizing the release of antibacterial activity from the plant polyphenols. A comparison of Comparative Examples 1 and 3 shows that pure PBAT and PBAT with added maleic anhydride copolymer alone do not possess antibacterial activity. While adding the same amount of plant polyphenols to PBAT alone does produce some antibacterial activity, the dispersion problem results in weak antibacterial activity and poor processing performance, preventing the effective formation of an antibacterial and antioxidant active material and limiting the application of polyester materials.

[0080] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A polyester modified with a copolymer of plant polyphenols and maleic anhydride, characterized in that: The mixing ratio of the polyester, plant polyphenols and maleic anhydride copolymer is as follows: by weight, it contains 80-99.9 parts of polyester and 0.1-20 parts of plant polyphenols and maleic anhydride copolymer; wherein, the molar ratio of hydroxyl groups in the plant polyphenols to anhydride groups in the maleic anhydride copolymer is 1:0.01-1:

50. The general structural formula of the maleic anhydride copolymer is as follows: ； in, It can be any of the following structures: , , , , , or x and y are independent integers from 5 to 10, and n is an integer from 5 to 20. The polyester is PBAT; The plant polyphenol is curcumin.

2. A method for preparing the polyester modified with plant polyphenols and maleic anhydride copolymer as described in claim 1, characterized in that, Includes the following steps: (1) Dissolve the plant polyphenols and maleic anhydride copolymer in an organic solvent, add a catalyst and mix well to obtain a reaction solution; (2) Heat the reaction solution to 25-80℃ and react for 4-16 hours under stirring. Cool to room temperature and then add petroleum ether or ethyl acetate to precipitate a solid precipitate. (3) The solid precipitate obtained in step (2) is filtered out, washed with ethanol and water, and dried to obtain antibacterial and antioxidant modified material; (4) The antibacterial and antioxidant modified material is mixed with the polyester in a high-speed mixer and then melt-extruded to obtain the modified polyester.

3. The method for preparing polyester modified with plant polyphenols and maleic anhydride copolymer according to claim 2, characterized in that: The organic solvent is one or any combination of acetonitrile, ethanol, 1,4-dioxane, dimethyl sulfoxide, or tetrahydrofuran.

4. The method for preparing polyester modified with plant polyphenols and maleic anhydride copolymer according to claim 2, characterized in that: The catalyst is triethylamine, dimethylisopropylamine, N,N-diisopropylethylamine, 1-methylpyrrolidine, N-methylmorpholine, N-methylimidazolium, 1,4-diazabicyclo[2.2.2]octane, 1,5-diazabicyclo[4.3.0]non-5-ene, 4-dimethylaminopyridine, p-toluenesulfonic acid, pyridine, 1,8-diazabicycloundec-7-ene, 4-dimethylaminopyridine, 4-pyrrolylpyridine, zinc chloride, or 2,6-di-tert-butyl-4-methylphenol magnesium.

5. The method for preparing polyester modified with plant polyphenols and maleic anhydride copolymer according to claim 2, characterized in that: In step (1), the molar ratio of plant polyphenols to maleic anhydride copolymer in the reaction solution is 5:1-5:10, and the molar ratio of plant polyphenols to catalyst is 100:0.5-100:1; in step (2), when the reaction solution is added to petroleum ether or ethyl acetate, the volume ratio of the reaction solution to petroleum ether or ethyl acetate is 1:1-1:10.

Images