Epoxy modified starch-based degradable film and preparation method thereof

Abstract

The invention relates to the field of membrane materials, and discloses an epoxy modified starch-based degradable membrane and a preparation method thereof, the epoxy modified starch-based degradable membrane comprises epoxidized starch, modified nanocellulose and a plasticizer; the modified nano cellulose is prepared by mixing a modified composite filler, a nano cellulose dispersion liquid and a zinc acetate dihydrate aqueous solution; the nano-cellulose dispersion liquid is prepared by adhering polytannic acid formed by oxidation and self-polymerization of tannic acid to the surface of nano-cellulose; the modified composite filler is prepared by performing carboxylation modification on nano titanium dioxide coated fumed silica nanoparticles by using succinic anhydride and gamma-aminopropyltriethoxysilane, then reacting with polyethyleneimine to obtain an aminated composite filler, and finally grafting glycidyl dodecyl dimethyl ammonium chloride to the surface of the aminated composite filler. The prepared film material is high in tensile strength, has certain hydrophobicity, and has good heat resistance, antibacterial property and flame retardant property.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane materials, and particularly relates to an epoxy-modified starch-based degradable membrane and a preparation method thereof. Background Art

[0002] The shortage of petroleum resources has led to the gradual replacement of traditional plastics by natural polymers. Among them, starch has been widely used in the food packaging field due to its good film-forming ability, low price, and easy availability. As a natural polymer compound, starch has a granular and microcrystalline structure, is widely present in nature, has abundant reserves, a short regeneration cycle, a low price, and is biodegradable. It is a quite ideal renewable environmental protection resource. However, pure starch-based membrane materials usually have a heterogeneous microstructure, resulting in high brittleness, and unsatisfactory water resistance and mechanical properties. Therefore, inorganic fillers are usually added to the starch matrix to improve the mechanical and barrier properties of the starch-based membrane materials. However, inorganic fillers have the defects of easy agglomeration and poor compatibility with the polymer matrix, and it is difficult to disperse evenly in the starch-based membrane materials, thus affecting the application range of the starch-based membrane materials.

[0003] In addition, existing starch-based membrane materials are generally flammable. Chinese Patent with Application No. CN201410777429.1 discloses a degradable and flame-retardant plastic film and a preparation method thereof. 25-30 parts of a nano flame-retardant composite agent are added to the raw material components, which is mainly composed of silicon hydroxyapatite, red phosphorus, attapulgite, hydrotalcite, montmorillonite, titanium dioxide, calcite, kaolin, etc. However, adding a large amount of nano flame-retardant composite agent will inevitably affect the mechanical properties of the starch-based membrane materials. Moreover, existing starch-based membrane materials have problems such as poor hydrophobicity, lack of antibacterial properties, and insufficient ultraviolet resistance, which severely limit their wide application.

[0004] Existing technologies add nano-titanium dioxide to improve the ultraviolet resistance and antibacterial properties. However, since the antibacterial activity of nano-titanium dioxide mainly depends on the photocatalytic process, the antibacterial effect is very poor under low-light or dark conditions. Natural organic antibacterial materials are derived from nature and have the advantages of strong antibacterial activity, safety, environmental protection, and not easily causing bacteria to develop drug resistance. However, they are prone to migrate and lose in the matrix, resulting in poor antibacterial stability and short antibacterial action time, which greatly limits their development in practical applications. Summary of the Invention

[0005] To solve the deficiencies mentioned in the above background art, the purpose of the present invention is to provide an epoxy-modified starch-based degradable membrane and a preparation method thereof. By adding modified nano-cellulose, the prepared membrane material has high tensile strength, certain hydrophobicity, and good heat resistance, antibacterial properties, and flame retardant properties.

[0006] The purpose of the present invention can be achieved through the following technical solutions: An epoxy-modified starch-based degradable film, comprising the following components in parts by weight: 50-70 parts of epoxidized starch, 5-15 parts of modified nanocellulose, and 15-25 parts of plasticizer; The modified nanocellulose is prepared by mixing a modified composite filler, a nanocellulose dispersion, and an aqueous solution of zinc acetate dihydrate, and carrying out an ion exchange and an acid-base neutralization reaction in an aqueous phase; wherein the nanocellulose dispersion is prepared by using tannic acid to oxidize and self-polymerize to form polytannic acid adhered to the surface of nanocellulose; The modified composite filler is prepared by carboxylating and modifying gas-phase silica nanoparticles coated with titanium dioxide nanoparticles with succinic anhydride and γ-aminopropyltriethoxysilane, then carrying out an amidation reaction with polyethyleneimine to obtain an amino-functionalized composite filler, and finally carrying out a quaternization modification by chemically grafting glycidyl dodecyldimethylammonium chloride onto the surface of the amino-functionalized composite filler through a ring-opening reaction.

[0007] Preferably, the preparation method of the epoxidized starch comprises the following steps: taking dry starch in a reactor, adding ethyl acetate, epichlorohydrin, and pyridine, stirring and reacting at 55-65 °C for 2-3 h, and after the reaction is completed, carrying out suction filtration, washing, and drying to prepare epoxidized starch.

[0008] Preferably, the plasticizer is glycerol; the starch is one or more of corn starch, potato starch, cassava starch, and wheat starch.

[0009] Preferably, the preparation method of the modified nanocellulose comprises the following steps: A. Ultrasonically disperse nanocellulose in deionized water, add Tris buffer solution to adjust the pH value to 7.5-8, and then add tannic acid and stir and react for 10-12 h to prepare a nanocellulose dispersion; B. Ultrasonically disperse the modified composite filler in deionized water, add the nanocellulose dispersion and an aqueous solution of zinc acetate dihydrate, stir and react at 40-50 °C for 4-7 h, and after the reaction is completed, carry out filtration, washing, and drying to prepare modified nanocellulose.

[0010] Preferably, the preparation method of the modified composite filler in step B comprises the following steps: B1. Ultrasonically disperse gas-phase silica in ethanol, then add tetrabutyl titanate, continue to ultrasonically disperse evenly, and then slowly dropwise add deionized water, stir and react for 4-6 h, and after the reaction is completed, carry out suction filtration, washing, and drying, grind the obtained solid product into a uniform powder, and place it in a muffle furnace and heat it to 550-600 °C at a heating rate of 1.5-2 °C / min and calcine for 4-6 h to prepare a composite filler; B2. Ultrasonically disperse the composite filler in N,N-dimethylformamide to obtain a dispersion. After uniformly stirring succinic anhydride, γ-aminopropyltriethoxysilane and N,N-dimethylformamide, add them to the dispersion, and place it at 50-65°C for stirring reaction for 6-8 h. After the reaction is completed, filter, wash, and dry to prepare a carboxylated composite filler; B3. Ultrasonically disperse the carboxylated composite filler in deionized water, add N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide and stir to mix, then add an aqueous solution of polyethyleneimine, ultrasonically disperse uniformly, and continue stirring reaction for 8-12 h. After the reaction is completed, filter, wash, and dry to prepare an aminated composite filler; B4. Place dodecyl dimethyl tertiary amine in a reactor, add epichlorohydrin, and place it at 55-65°C for stirring reaction for 2-3 h. After the reaction is completed, remove the organic solvent by vacuum distillation, recrystallize with acetone, wash with anhydrous ether, and then dry to prepare epichlorohydrin dodecyl dimethyl ammonium chloride; B5. Ultrasonically disperse the aminated composite filler in absolute ethanol, add epichlorohydrin dodecyl dimethyl ammonium chloride, and place it at 55-70°C for stirring reaction for 8-12 h. After the reaction is completed, centrifuge, wash, and dry to prepare a modified composite filler.

[0011] Preferably, the addition ratio of fumed silica, tetrabutyl titanate and deionized water in step B1 is 3-5 g: 5-10 mL: 150-250 mL.

[0012] Preferably, the mass ratio of the composite filler, succinic anhydride and γ-aminopropyltriethoxysilane in step B2 is 1: 5-10: 10-22.

[0013] Preferably, the concentration of the aqueous solution of polyethyleneimine in step B3 is 8-15 mg / mL, and the addition ratio of the carboxylated composite filler and the aqueous solution of polyethyleneimine is 1: 50-100 mL.

[0014] Preferably, the mass ratio of the aminated composite filler and epichlorohydrin dodecyl dimethyl ammonium chloride in step B5 is 1: 2-5.

[0015] A preparation method of an epoxy-modified starch-based degradable film, comprising the following steps: S1. Weigh each raw material by weight, place epoxidized starch and deionized water in a reactor, and place it at 60-70°C for stirring and gelatinization to obtain an epoxidized starch solution with a mass fraction of 8-15%; S2. Ultrasonically disperse the modified nanocellulose in ethanol to obtain a modified nanocellulose dispersion with a mass fraction of 2-5%; S3. Uniformly mix the epoxidized starch solution and the modified nanocellulose dispersion, add a plasticizer, stir and mix evenly, then cast into a film, dry it at 60-70 °C for 2-3 h, and peel off the film after the temperature drops to room temperature to obtain an epoxy-modified starch-based degradable film.

[0016] Advantages of the present invention: In the present invention, alcohol dispersion hydrolysis method is used to uniformly coat titanium dioxide nanoparticles on the surface of fumed silica nanoparticles to obtain a composite filler with a large specific surface area. Then, succinic anhydride and γ-aminopropyltriethoxysilane are used to carboxylate and modify the composite filler, and then an amidation reaction occurs with polyethyleneimine to obtain an amino-functionalized composite filler. At the same time, in the present invention, epoxypropyl dodecyldimethylammonium chloride is prepared by reacting dodecyldimethylamine with epichlorohydrin, and then it is chemically grafted onto the surface of the amino-functionalized composite filler through a ring-opening reaction for quaternization modification to obtain a modified composite filler. In addition, in the present invention, polytannic acid formed by the oxidative self-polymerization of tannic acid adheres to the surface of nanocellulose. Tannic acid is a natural polyphenol with high-density pyrogallol and catechol groups. In addition to having characteristics such as antioxidant and strong adhesion, it also has certain antibacterial and flame-retardant effects. In the present invention, the modified composite filler, nanocellulose dispersion, and zinc acetate dihydrate aqueous solution are mixed, and modified nanocellulose is prepared through ion exchange and acid-base neutralization reactions in the aqueous phase. The tannic acid introduced into the nanocellulose dispersion can form a complex with zinc ions. The polyethyleneimine molecular chain introduced into the modified composite filler contains abundant primary amine, secondary amine, and tertiary amine functional groups, which have a chelating effect on zinc ions and can crosslink with the hydroxyl groups in the nanocellulose dispersion, improving the thermal stability, tensile properties, and flame-retardant properties of the starch-based film material. In addition, the surface of the modified composite filler is chemically bonded with a quaternary ammonium salt with antibacterial effects, zinc ions, and a hydrophobic alkyl long chain, avoiding the problem of long-term migration and loss of antibacterial materials, enhancing the hydrophobicity of the starch-based film material, and facilitating the uniform dispersion of the modified nanocellulose in the starch-based film material. The modified nanocellulose prepared in the present invention combines the advantages of titanium dioxide nanoparticles and organic antibacterial materials, plays a complementary and synergistic antibacterial role, and realizes the advantages of strong antibacterial activity, good antibacterial stability, and long antibacterial action time. In addition, in the present invention, starch is chemically modified with epichlorohydrin to obtain epoxidized starch, making the combination of the modified nanocellulose and the epoxidized starch closer, improving the compatibility between the two, and giving full play to their properties. Specific embodiments

[0017] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0018] Example 1 A method for preparing epoxidized starch comprises the following steps: Take 20 g of dry corn starch in a reactor, add 40 mL of ethyl acetate, 5 g of epichlorohydrin and 2 g of pyridine, place it at 60 °C and stir for reaction for 2 h. After the reaction is completed, carry out suction filtration, washing and drying to prepare epoxidized starch.

[0019] Example 2 A method for preparing a modified composite filler comprises the following steps: B1. Take 3 g of fumed silica and ultrasonically disperse it in 250 mL of ethanol, then add 5 mL of tetrabutyl titanate, continue to ultrasonically disperse evenly, and then slowly dropwise add 150 mL of deionized water, stir and react for 4 h. After the reaction is completed, carry out suction filtration, washing and drying, grind the obtained solid product into a uniform powder, place it in a muffle furnace and heat it to 600 °C at a heating rate of 2 °C / min and calcine for 4 h to prepare a composite filler; B2. Take 1 g of the composite filler and ultrasonically disperse it in 100 mL of N,N-dimethylformamide to obtain a dispersion. Take 5 g of succinic anhydride, 11 g of γ-aminopropyltriethoxysilane and 25 mL of N,N-dimethylformamide, stir evenly and add them to the dispersion, place it at 60 °C and stir and react for 8 h. After the reaction is completed, carry out filtration, washing and drying to prepare a carboxylated composite filler; B3. Take 1 g of the carboxylated composite filler and ultrasonically disperse it in 120 mL of deionized water, add 1.5 g of N-hydroxysuccinimide and 1.8 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide and stir to mix, then add 60 mL of a 10 mg / mL aqueous solution of polyethyleneimine, ultrasonically disperse evenly, continue to stir and react for 10 h. After the reaction is completed, carry out filtration, washing and drying to prepare an amino-functionalized composite filler; B4. Take 10.7 g of dodecyldimethylamine in a reactor, add 23.3 g of epichlorohydrin, place it at 60 °C and stir and react for 2 h. After the reaction is completed, remove the organic solvent by vacuum distillation, carry out recrystallization with acetone, wash with anhydrous ether and then dry to prepare epichlorohydrin dodecyldimethylammonium chloride; B5. Take 1 g of the amino-functionalized composite filler and ultrasonically disperse it in 100 mL of absolute ethanol, add 2.2 g of epichlorohydrin dodecyldimethylammonium chloride, place it at 65 °C and stir and react for 12 h. After the reaction is completed, carry out centrifugation, washing and drying to prepare a modified composite filler.

[0020] Example 3 A method for preparing modified nanocellulose comprises the following steps: A. Take 1 g of nanocellulose and ultrasonically disperse it in 100 mL of deionized water, add 1 mol / L Tris buffer to adjust the pH value to 8, then add 1.3 g of tannic acid and stir for 12 h to prepare a nanocellulose dispersion; B. Take 1.2 g of the modified composite filler prepared in Example 2 and ultrasonically disperse it in 100 mL of deionized water, add 40 mL of nanocellulose dispersion and 20 mL of 0.3 g / mL zinc acetate dihydrate aqueous solution, place it at 50° C. and stir to react for 6 hours. After the reaction is completed, filter, wash and dry to prepare modified nanocellulose.

[0021] Example 4 An epoxy-modified starch-based degradable film comprises the following components in parts by weight: 55 parts of the epoxidized starch prepared in Example 1, 7 parts of the modified nanocellulose prepared in Example 3, and 16 parts of glycerol.

[0022] The method for preparing the epoxy-modified starch-based degradable film comprises the following steps: S1. Weigh the raw materials by weight, put the epoxidized starch and deionized water into a reactor, stir and gelatinize at 70°C to obtain an epoxidized starch solution with a mass fraction of 12%; S2, dispersing the modified nanocellulose in ethanol by ultrasonication to obtain a modified nanocellulose dispersion with a mass fraction of 5%; S3. Evenly mix the epoxidized starch solution and the modified nanocellulose dispersion, add glycerol, stir and mix evenly, then cast into a film, place at 70°C to dry for 2 hours, and remove the film after the temperature drops to room temperature to prepare an epoxy-modified starch-based biodegradable film.

[0023] Example 5 An epoxy-modified starch-based degradable film comprises the following components in parts by weight: 62 parts of the epoxidized starch prepared in Example 1, 10 parts of the modified nanocellulose prepared in Example 3, and 20 parts of glycerol.

[0024] The preparation method of the above-mentioned epoxy-modified starch-based degradable film is as follows: Example 4.

[0025] Example 6 An epoxy-modified starch-based degradable film comprises the following components in parts by weight: 68 parts of the epoxidized starch prepared in Example 1, 13 parts of the modified nanocellulose prepared in Example 3, and 22 parts of glycerol.

[0026] The preparation method of the above-mentioned epoxy-modified starch-based degradable film is as follows: Example 4.

[0027] Comparative Example 1 A method for preparing a modified composite filler comprises the following steps: B1. Take 3 g of fumed silica and ultrasonically disperse it in 250 mL of ethanol. Then add 5 mL of tetrabutyl titanate and continue to ultrasonically disperse evenly. After that, slowly add 150 mL of deionized water and stir for reaction for 4 h. After the reaction is completed, carry out suction filtration, washing, and drying. Grind the obtained solid product into a uniform powder, place it in a muffle furnace, and heat it to 600 °C at a heating rate of 2 °C / min for calcination for 4 h to prepare a composite filler. B2. Take 1 g of the composite filler and ultrasonically disperse it in 100 mL of N,N-dimethylformamide to obtain a dispersion. Take 5 g of succinic anhydride, 11 g of γ-aminopropyltriethoxysilane, and 25 mL of N,N-dimethylformamide, stir evenly, and then add them to the dispersion. Place it at 60 °C and stir for reaction for 8 h. After the reaction is completed, filter, wash, and dry to prepare a carboxylated composite filler. B3. Take 1 g of the carboxylated composite filler and ultrasonically disperse it in 120 mL of deionized water. Add 1.5 g of N-hydroxysuccinimide and 1.8 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide and stir to mix. Then add 60 mL of a 10 mg / mL polyethyleneimine aqueous solution, ultrasonically disperse evenly, and continue to stir for reaction for 10 h. After the reaction is completed, filter, wash, and dry to prepare a modified composite filler.

[0028] Comparative Example 2 A method for preparing modified nanocellulose includes the following steps: A. Take 1 g of nanocellulose and ultrasonically disperse it in 100 mL of deionized water. Add 1 mol / L Tris buffer solution to adjust the pH value to 8, and then add 1.3 g of tannic acid and stir for reaction for 12 h to prepare a nanocellulose dispersion. B. Take 1.2 g of the modified composite filler prepared in Comparative Example 1 and ultrasonically disperse it in 100 mL of deionized water. Add 40 mL of the nanocellulose dispersion and 20 mL of a 0.3 g / mL zinc acetate dihydrate aqueous solution, place it at 50 °C and stir for reaction for 6 h. After the reaction is completed, filter, wash, and dry to prepare modified nanocellulose.

[0029] Comparative Example 3 A method for preparing modified nanocellulose includes the following steps: A. Take 1 g of nanocellulose and ultrasonically disperse it in 100 mL of deionized water. Add 1 mol / L Tris buffer solution to adjust the pH value to 8, and then add 1.3 g of tannic acid and stir for reaction for 12 h to prepare a nanocellulose dispersion. B. Take 1.2 g of the composite filler prepared in Example 2 and ultrasonically disperse it in 100 mL of deionized water. Add 40 mL of the nanocellulose dispersion and 20 mL of a 0.3 g / mL zinc acetate dihydrate aqueous solution, place it at 50 °C and stir for reaction for 6 h. After the reaction is completed, filter, wash, and dry to prepare modified nanocellulose.

[0030] Comparative Example 4 An epoxy-modified starch-based degradable film, comprising the following components in parts by weight: 68 parts of the epoxidized starch prepared in Example 1, 13 parts of the modified nanocellulose prepared in Comparative Example 2, and 22 parts of glycerol.

[0031] The preparation method of the above epoxy-modified starch-based degradable film is the same as that of Example 4.

[0032] Comparative Example 5 An epoxy-modified starch-based degradable film, comprising the following components in parts by weight: 68 parts of the epoxidized starch prepared in Example 1, 13 parts of the modified nanocellulose prepared in Comparative Example 3, and 22 parts of glycerol.

[0033] The preparation method of the above epoxy-modified starch-based degradable film is the same as that of Example 4.

[0034] Comparative Example 6 An epoxy-modified starch-based degradable film, comprising the following components in parts by weight: 68 parts of the epoxidized starch prepared in Example 1, 7 parts of the modified composite filler prepared in Example 2, 6 parts of nanocellulose, and 22 parts of glycerol.

[0035] The preparation method of the above epoxy-modified starch-based degradable film is the same as that of Example 4.

[0036] Performance Testing The epoxy-modified starch-based degradable films prepared in Examples 4-6 and Comparative Examples 4-6 were subjected to performance testing: (1) Tensile property testing: The tensile property was tested using a universal testing machine, with longitudinal stretching at a stretching rate of 2 mm / min, and the data results are shown in Table 1.

[0037] (2) Heat resistance testing: The thermal stability was tested using a thermogravimetric analyzer under a nitrogen atmosphere with a heating rate of 10 °C / min, and the data results are shown in Table 1.

[0038] (3) Water contact angle testing: Under the same environmental conditions, the water contact angle of the film was detected using a contact angle analyzer, and the data results are shown in Table 1.

[0039] (4) Flame retardant property testing: The flame retardant property of the sample was evaluated by the limiting oxygen index, and the data results are shown in Table 1.

[0040] (5) Antibacterial property testing: The antibacterial effects against Escherichia coli and Staphylococcus aureus were detected by the plate counting method. Equal masses of the films were weighed and dispersed in the bacterial suspension. After culturing at 25 °C for 8 h, the bacterial suspension was diluted until the total number of bacterial colonies was 10 6 CFU / mL, and then evenly coated on the agar medium. After culturing at 37 °C for 24 h, the number of colonies corresponding to different samples was observed. The calculation formula for the film antibacterial rate (K) is as follows: K = (N 1 -N2 ) / N 1 , where N 1 is the number of surviving colonies in the blank control group, and N 2 is the number of surviving colonies in the sample group. The data results are shown in Table 1 as follows.

[0041] Table 1 Test Results of Specimen Performance

[0042] It can be seen from the data in Table 1 that the membrane materials prepared in Examples 4-6 of the present invention have high tensile strength, certain hydrophobicity, and good heat resistance, antibacterial property and flame retardancy. Among them, in Comparative Example 4, the modified composite filler introduced in the modified nanocellulose component was not grafted with glycidyl dodecyldimethylammonium chloride, and the measured antibacterial rate and water contact angle were lower than those in Examples 4-6. The reason is that the grafting of glycidyl dodecyldimethylammonium chloride introduced quaternary ammonium salt antibacterial groups and hydrophobic alkyl long chains, which is beneficial to improving the antibacterial property and hydrophobic property of the membrane material. In Comparative Example 5, the composite filler in the added modified nanocellulose component was not modified, and its measured tensile strength, heat resistance, hydrophobicity, antibacterial property and flame retardancy were lower than those in Examples 4-6, indicating that modifying the composite filler is beneficial to improving the comprehensive performance of the membrane material. In Comparative Example 6, the modified composite filler and nanocellulose were simply mixed, and its measured antibacterial rate and limiting oxygen index were lower than those in Examples 4-6, indicating that the introduction of tannic acid and zinc acetate dihydrate is beneficial to improving the antibacterial property and flame retardancy of the membrane material.

[0043] In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0044] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. An epoxy-modified starch-based degradable film, characterized in that: The invention comprises the following components in parts by weight: 50-70 parts of epoxidized starch, 5-15 parts of modified nanocellulose, and 15-25 parts of plasticizer; The modified nanocellulose is prepared by mixing a modified composite filler, a nanocellulose dispersion and a zinc acetate dihydrate aqueous solution, and then undergoing ion exchange and acid-base neutralization reaction in an aqueous phase; wherein the nanocellulose dispersion is prepared by oxidizing tannic acid to form polytannic acid that adheres to the surface of the nanocellulose; The modified composite filler is prepared by carboxylating and modifying nano-titanium dioxide-coated fumed silica nanoparticles using succinic anhydride and γ-aminopropyltriethoxysilane, then reacting with polyethyleneimine to undergo an amidation reaction to obtain an amino composite filler, and finally utilizing a ring-opening reaction to chemically graft epoxypropyl dodecyldimethylammonium chloride onto the surface of the amino composite filler for quaternary ammonium modification.

2. The epoxy-modified starch-based degradable film according to claim 1, characterized in that: The preparation method of epoxidized starch comprises the following steps: taking dry starch into a reactor, adding ethyl acetate, epichlorohydrin and pyridine, stirring and reacting at 55-65° C. for 2-3 hours, and filtering, washing and drying after the reaction is completed to prepare epoxidized starch.

3. The epoxy-modified starch-based degradable film according to claim 1, characterized in that: The plasticizer is glycerol; the starch is a mixture of one or more of corn starch, potato starch, cassava starch and wheat starch.

4. The epoxy-modified starch-based degradable film according to claim 1, characterized in that: The preparation method of the modified nanocellulose comprises the following steps: A. Ultrasonic dispersion of nanocellulose in deionized water, adding Tris buffer to adjust the pH value to 7.5-8, then adding tannic acid and stirring for 10-12 hours to prepare a nanocellulose dispersion; B. Take the modified composite filler and ultrasonically disperse it in deionized water, add nanocellulose dispersion and zinc acetate dihydrate aqueous solution, place it at 40-50°C and stir to react for 4-7 hours. After the reaction is completed, filter, wash and dry to prepare modified nanocellulose.

5. The epoxy-modified starch-based degradable film according to claim 4, characterized in that: The preparation method of the modified composite filler in step B comprises the following steps: B1. Ultrasonic dispersion of fumed silica in ethanol, then adding tetrabutyl titanate, continuing ultrasonic dispersion, then slowly adding deionized water, stirring and reacting for 4-6 hours, filtering, washing and drying after the reaction is completed, grinding the obtained solid product into uniform powder, placing it in a muffle furnace and heating it to 550-600°C at a heating rate of 1.5-2°C / min and calcining it for 4-6 hours to prepare a composite filler; B2, ultrasonically dispersing the composite filler in N,N-dimethylformamide to obtain a dispersion, stirring succinic anhydride, γ-aminopropyltriethoxysilane and N,N-dimethylformamide evenly, adding them to the dispersion, stirring and reacting at 50-65° C. for 6-8 hours, filtering, washing and drying after the reaction is completed to obtain a carboxylated composite filler; B3, ultrasonically disperse the carboxylated composite filler in deionized water, add N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide and stir to mix, then add polyethyleneimine aqueous solution, ultrasonically disperse evenly, continue stirring to react for 8-12 hours, and after the reaction is completed, filter, wash and dry to prepare an amino composite filler; B4, take dodecyl dimethyl tertiary amine in a reactor, add epichlorohydrin, place it at 55-65 ° C, stir and react for 2-3 hours, and after the reaction is completed, remove the organic solvent by distillation under reduced pressure, recrystallize with acetone, wash with anhydrous ether and then dry to prepare glycidyl dodecyl dimethyl ammonium chloride; B5. Ultrasonic dispersion of the amino composite filler in anhydrous ethanol, add glycidyl dodecyl dimethyl ammonium chloride, stir and react at 55-70°C for 8-12 hours. After the reaction is completed, centrifuge, wash and dry to obtain a modified composite filler.

6. The epoxy-modified starch-based degradable film according to claim 5, characterized in that: In the step B1, the addition ratio of fumed silica, tetrabutyl titanate and deionized water is 3-5 g: 5-10 mL: 150-250 mL.

7. The epoxy-modified starch-based degradable film according to claim 5, characterized in that: In the step B2, the mass ratio of the composite filler, succinic anhydride and γ-aminopropyltriethoxysilane is 1:5-10:10-22.

8. The epoxy-modified starch-based degradable film according to claim 5, characterized in that: The concentration of the polyethyleneimine aqueous solution in step B3 is 8-15 mg / mL, and the addition ratio of the carboxylated composite filler to the polyethyleneimine aqueous solution is 1:50-100 mL.

9. The epoxy-modified starch-based degradable film according to claim 5, characterized in that: In the step B5, the mass ratio of the amination composite filler to glycidyl dodecyl dimethyl ammonium chloride is 1:2-5.

10. A method for preparing an epoxy-modified starch-based degradable film according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Weigh the raw materials by weight, put the epoxidized starch and deionized water into a reactor, stir and gelatinize at 60-70° C. to obtain an epoxidized starch solution with a mass fraction of 8-15%; S2, dispersing the modified nanocellulose in ethanol by ultrasonication to obtain a modified nanocellulose dispersion with a mass fraction of 2-5%; S3. Evenly mix the epoxidized starch solution and the modified nanocellulose dispersion, add a plasticizer, stir and mix evenly, then cast into a film, place at 60-70°C to dry for 2-3 hours, and remove the film after the temperature drops to room temperature to prepare an epoxy-modified starch-based biodegradable film.

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