Bamboo fiber film biodegradable material

Abstract

The invention discloses a bamboo fiber film biodegradable material, and belongs to the technical field of biodegradable high polymer materials. The material is prepared by taking acetylated-tannic acid modified bamboo fibers as a reinforcing phase, matching with a poly (butylene succinate) / polyhydroxyalkanoate composite matrix, assisting with epoxy linseed oil, polyethylene glycol, bacterial cellulose nanowhiskers and carnauba wax, and performing solid-phase pre-crosslinking, twin-screw melt blending and two-way stretching film forming. The material disclosed by the invention is excellent in interfacial compatibility, has high strength, high toughness and full biodegradation characteristics, is good in processing stability, and can be widely applied to the fields of food packaging, agricultural mulching films and the like.

Description

Technical Field

[0001] This invention belongs to the field of biodegradable polymer materials technology, specifically relating to a bamboo fiber film biodegradable material. Background Technology

[0002] With the widespread use of plastic products, traditional petroleum-based plastics are difficult to degrade naturally, causing serious white pollution and posing long-term harm to soil, water bodies, and the ecological environment. Developing environmentally friendly, fully biodegradable materials has become a core direction for solving the plastic pollution problem. Bamboo fiber, as a widely available natural biomass material, is renewable, inexpensive, fully biodegradable, and has good mechanical reinforcement properties, making it an ideal reinforcing filler for preparing biodegradable composite materials.

[0003] Bamboo fiber molecules are rich in hydroxyl groups, exhibiting strong hydrophilicity, while commonly used biodegradable polyester matrices are hydrophobic. The significant difference in polarity between the two leads to weak interfacial bonding, bamboo fiber agglomeration, and severe phase separation when directly blended, resulting in a substantial decrease in the mechanical properties, processing performance, and dimensional stability of the composite material. Current technologies often employ alkali treatment, silane coupling agent grafting, dopamine modification, and ionic liquid treatment to modify bamboo fiber. However, these modification processes suffer from drawbacks such as high chemical toxicity, significant environmental pollution, and complex modification procedures. Some modification methods can even damage the natural structure of bamboo fiber, reducing its biodegradability and reinforcing effect. Furthermore, existing bamboo fiber biodegradable films often use poly(butylene adipate / terephthalate) or polylactic acid as matrices, relying on petroleum-based compatibilizers and plasticizers. These methods suffer from slow degradation rates, insufficient environmental friendliness, and difficulty in simultaneously achieving both mechanical and biodegradable properties, resulting in a narrow processing window and failing to meet the demands of continuous industrial production. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies, such as poor compatibility between bamboo fiber and biodegradable polyester matrix, difficulty in balancing the mechanical and degradation properties of composite materials, reliance on petroleum-based additives, and poor processability, and to provide a bamboo fiber film biodegradable material and its preparation method.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A biodegradable bamboo fiber film material is prepared from the following raw materials in parts by weight: 25-45 parts of acetylated-tannic acid modified bamboo fiber, 30-50 parts of polybutylene succinate, 15-25 parts of polyhydroxyalkanoate, 3-8 parts of epoxidized linseed oil, 2-5 parts of polyethylene glycol, 0.5-3 parts of bacterial cellulose nanofibers, and 0.5-2 parts of carnauba wax.

[0006] Furthermore, the preparation steps of the acetylated-tannic acid modified bamboo fiber are as follows: S1. Bamboo fiber pretreatment: Crush bamboo fiber to 100-200 mesh and dry it in an oven at 60-80℃ for 4-6 hours to obtain dried bamboo fiber; S2. Acetylation treatment: Dry bamboo fiber is added to a mixture of glacial acetic acid and acetic anhydride, with a volume ratio of glacial acetic acid to acetic anhydride of 2:1 and a solid-liquid ratio of bamboo fiber to the mixture of 1g:10mL. 0.5% concentrated sulfuric acid by mass of the mixture is added as a catalyst, and the mixture is reacted at 40-50℃ for 2-4h. After the reaction is completed, the mixture is filtered, washed with ethanol until the filtrate is neutral, and dried at 60℃ to obtain acetylated bamboo fiber. S3. Tannic acid crosslinking treatment: Add acetylated bamboo fiber to a tannic acid aqueous solution with a mass concentration of 2-4% at a solid-liquid ratio of 1g:15mL, stir and react at 30-40℃ for 3-5h, filter, wash 3 times with deionized water, and vacuum dry at 60-70℃ for 8-12h to obtain acetylated-tannic acid modified bamboo fiber.

[0007] Furthermore, the number average molecular weight of the polyethylene glycol is 2000-4000.

[0008] Furthermore, the bacterial cellulose nanocrystals have a diameter of 20-50 nm and a length of 100-500 nm.

[0009] A method for preparing a bamboo fiber film biodegradable material includes the following steps: S1. Solid-phase pre-crosslinking: Acetylated tannic acid modified bamboo fiber, polybutylene succinate, polyhydroxyalkanoate, epoxidized linseed oil, polyethylene glycol, bacterial cellulose nanofibers, and carnauba wax are added to a high-speed mixer in parts by weight and mixed at 80-90℃ and 800-1200 r / min for 10-15 min to obtain a premix; the premix is ​​then placed in an internal mixer and internally mixed at 110-120℃ and 60-80 r / min for 15-20 min to obtain a pre-crosslinked material; S2. Twin-screw melt blending: The pre-crosslinked material is added to a twin-screw extruder. The temperatures of each section of the extruder are set as follows: feeding section 120-130℃, melting section 135-145℃, homogenization section 140-150℃, die head 135-145℃, screw speed 200-300r / min. The material is extruded into strands, water-cooled, and pelletized to obtain composite masterbatch. S3. Biaxial stretching film formation: The composite masterbatch is vacuum dried at 60-70℃ for 6-8 hours, then added to a casting machine and cast at 135-145℃ to form a sheet with a thickness of 0.3-0.5 mm. The sheet is then fed into a biaxial stretching machine with a longitudinal stretching ratio of 2.5-3.5 times and a transverse stretching ratio of 3-4 times at a stretching temperature of 100-110℃. After stretching, the sheet is heat-set at 120-130℃ for 5-10 seconds, cooled, and then wound up to obtain a bamboo fiber film biodegradable material.

[0010] The beneficial effects of this invention are: This invention employs an acetylation-tannic acid composite modification process to treat bamboo fiber. First, acetylation is used to block some hydroxyl groups on the surface of bamboo fiber, reducing its hydrophilicity and surface energy, decreasing intermolecular hydrogen bonding, and preventing fiber agglomeration. Then, through the polyphenolic hydroxyl structure of tannic acid, active binding sites are constructed on the surface of bamboo fiber, forming stable hydrogen and ester bonds with the polyester matrix molecular chains. This significantly enhances the interfacial bonding force between bamboo fiber and the hydrophobic polyester matrix, while fully preserving the natural skeletal structure and biodegradability of bamboo fiber, achieving a balance between reinforcement and degradation performance.

[0011] This invention employs a composite matrix system constructed from polybutylene succinate and polyhydroxyalkanoates. Polybutylene succinate provides excellent processing fluidity, fracture toughness, and hydrolysis resistance, while polyhydroxyalkanoates enhance the tensile rigidity and biodegradation rate of the material. The synergistic combination of these two components solves the problems of difficulty in achieving both rigidity and toughness, and uncontrollable degradation rate, inherent in single polyester matrices. Furthermore, it utilizes fully bio-based epoxy linseed oil as a compatibilizer, polyethylene glycol as a plasticizer, bacterial cellulose nanofibers as a reinforcing agent, and carnauba wax as a lubricant. With no petroleum-based additives, the material is completely biodegradable after use, leaving no environmental residue and exhibiting excellent environmental friendliness.

[0012] This invention employs a preparation process of solid-phase pre-crosslinking-twin-screw melt blending-biaxial stretching film formation. The solid-phase pre-crosslinking step, conducted below the polyester melting temperature, allows the modified bamboo fiber and matrix components to form a stable interfacial bond in advance, avoiding the phase separation and uneven component dispersion problems that occur during high-temperature melt blending. The biaxial stretching process aligns the molecular chains and fibers within the material, forming a uniform network structure, which significantly improves the tensile strength, tear strength, dimensional stability, and barrier properties of the film. At the same time, it broadens the processing and forming window of the material, resulting in high process stability and enabling continuous industrial production.

[0013] The bamboo fiber film biodegradable material prepared by this invention has a tensile strength of not less than 25 MPa, an elongation at break of not less than 220%, a right-angle tear strength of not less than 60 kN / m, and a biodegradation rate of not less than 92% after 180 days under controlled composting conditions. It also has good water vapor barrier properties and can be widely used in food packaging, agricultural mulch film, disposable daily necessities and other fields, with significant economic and environmental benefits. Detailed Implementation

[0014] The technical solutions in the embodiments of the present invention have been clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] The specifications of the raw materials used in the embodiments and comparative examples of this invention are as follows: Bamboo fiber: 100-200 mesh length, moisture content ≤8%; Polybutylene succinate: weight-average molecular weight 1×10^5, melt index 5g / 10min (190℃, 2.16kg). Polyhydroxy fatty acid ester: weight average molecular weight 8×10^4, melt index 4g / 10min (190℃, 2.16kg). Epoxy linseed oil: Epoxy value ≥ 6.0%; Polyethylene glycol: number average molecular weight 2000, 3000, 4000; Bacterial cellulose nanocrystals: diameter 20-50nm, length 100-500nm; Brazilian carnauba wax: melting point 80-85℃; Glacial acetic acid, acetic anhydride, concentrated sulfuric acid, tannic acid, and ethanol were all of analytical grade.

[0016] The performance testing in the embodiments and comparative examples of this invention was performed in accordance with the following current national standards: Tensile properties: GB / T 1040.3-2006; Right-angle tear resistance: GB / T 16578.1-2008; Biodegradability: GB / T 19277.1-2011; Water vapor permeability coefficient: GB / T 1037-2021. Example 1

[0017] This embodiment provides a bamboo fiber film biodegradable material, which is prepared from the following raw materials in parts by weight: 35 parts of acetylated-tannic acid modified bamboo fiber, 40 parts of polybutylene succinate, 20 parts of polyhydroxyalkanoate, 5 parts of epoxidized linseed oil, 3 parts of polyethylene glycol, 1.5 parts of bacterial cellulose nanofibers, and 0.5 parts of carnauba wax; wherein the number average molecular weight of polyethylene glycol is 3000.

[0018] The preparation steps of the acetylated-tannic acid modified bamboo fiber are as follows: S1. Bamboo fiber pretreatment: The bamboo fiber is crushed to 150 mesh and dried in a 70℃ oven for 5 hours to obtain dried bamboo fiber; S2. Acetylation treatment: Dry bamboo fiber was added to a mixture of glacial acetic acid and acetic anhydride, with a volume ratio of glacial acetic acid to acetic anhydride of 2:1 and a solid-liquid ratio of bamboo fiber to the mixture of 1g:10mL. 0.5% concentrated sulfuric acid by mass of the mixture was added as a catalyst, and the mixture was reacted at 45℃ for 3h. After the reaction was completed, the mixture was filtered, washed with ethanol until the filtrate was neutral, and dried at 60℃ to obtain acetylated bamboo fiber. S3. Tannic acid crosslinking treatment: Acetylated bamboo fiber was added to a 3% (w / w) tannic acid aqueous solution with a solid-liquid ratio of 1g:15mL. The mixture was stirred and reacted at 35℃ for 4h. After filtration, the mixture was washed three times with deionized water and dried under vacuum at 65℃ for 10h to obtain acetylated-tannic acid modified bamboo fiber.

[0019] The preparation method of the bamboo fiber film biodegradable material includes the following steps: S1. Solid-phase pre-crosslinking: Acetylated-tannic acid modified bamboo fiber, polybutylene succinate, polyhydroxyalkanoate, epoxidized linseed oil, polyethylene glycol, bacterial cellulose nanofibers, and carnauba wax are added to a high-speed mixer in parts by weight and mixed at 85°C and 1000 r / min for 12 min to obtain a premix; the premix is ​​then placed in an internal mixer and internally mixed at 115°C and 70 r / min for 18 min to obtain a pre-crosslinked material; S2. Twin-screw melt blending: The pre-crosslinked material is added to a twin-screw extruder. The temperatures of each section of the extruder are set as follows: feeding section 125℃, melting section 140℃, homogenization section 145℃, die head 140℃, screw speed 250r / min. The material is extruded into strands, water-cooled, and pelletized to obtain composite masterbatch. S3. Biaxial stretching film formation: The composite masterbatch is vacuum dried at 65℃ for 7 hours, added to a casting machine, and cast into a sheet with a thickness of 0.4 mm at 140℃; the sheet is fed into a biaxial stretching machine, with a longitudinal stretching ratio of 3 times and a transverse stretching ratio of 3.5 times, a stretching temperature of 105℃, and after stretching, it is heat-set at 125℃ for 8 seconds, cooled and wound up to obtain a bamboo fiber film biodegradable material with a thickness of 0.05 mm. Example 2

[0020] This embodiment provides a bamboo fiber film biodegradable material, which is prepared from the following raw materials in parts by weight: 25 parts of acetylated-tannic acid modified bamboo fiber, 50 parts of polybutylene succinate, 15 parts of polyhydroxyalkanoate, 3 parts of epoxidized linseed oil, 2 parts of polyethylene glycol, 0.5 parts of bacterial cellulose nanofibers, and 1 part of carnauba wax; wherein the number average molecular weight of polyethylene glycol is 2000.

[0021] The preparation steps of the acetylated-tannic acid modified bamboo fiber are as follows: S1. Bamboo fiber pretreatment: Bamboo fiber is crushed to 100 mesh and dried in an oven at 60℃ for 6 hours to obtain dried bamboo fiber; S2. Acetylation treatment: Dry bamboo fiber is added to a mixture of glacial acetic acid and acetic anhydride, with a volume ratio of glacial acetic acid to acetic anhydride of 2:1 and a solid-liquid ratio of bamboo fiber to the mixture of 1g:10mL. 0.5% concentrated sulfuric acid by mass of the mixture is added as a catalyst, and the mixture is reacted at 40℃ for 4h. After the reaction is completed, the mixture is filtered, washed with ethanol until the filtrate is neutral, and dried at 60℃ to obtain acetylated bamboo fiber. S3. Tannic acid crosslinking treatment: Acetylated bamboo fiber was added to a 2% (w / w) tannic acid aqueous solution at a solid-liquid ratio of 1g:15mL. The mixture was stirred and reacted at 30℃ for 5h. After filtration, the mixture was washed three times with deionized water and dried under vacuum at 60℃ for 12h to obtain acetylated-tannic acid modified bamboo fiber.

[0022] The preparation method of the bamboo fiber film biodegradable material includes the following steps: S1. Solid-phase pre-crosslinking: Acetylated tannic acid modified bamboo fiber, polybutylene succinate, polyhydroxyalkanoate, epoxidized linseed oil, polyethylene glycol, bacterial cellulose nanofibers, and carnauba wax are added to a high-speed mixer in parts by weight and mixed at 80°C and 800 r / min for 15 min to obtain a premix; the premix is ​​then placed in an internal mixer and internally mixed at 110°C and 60 r / min for 20 min to obtain a pre-crosslinked material; S2. Twin-screw melt blending: The pre-crosslinked material is added to a twin-screw extruder. The temperature of each section of the extruder is set as follows: feeding section 120℃, melting section 135℃, homogenization section 140℃, die head 135℃, screw speed 200r / min. The material is extruded into strands, water-cooled, and pelletized to obtain composite masterbatch. S3. Biaxial stretching film formation: The composite masterbatch is vacuum dried at 60℃ for 8 hours, added to a casting machine, and cast into a sheet with a thickness of 0.3 mm at 135℃; the sheet is fed into a biaxial stretching machine with a longitudinal stretching ratio of 2.5 times and a transverse stretching ratio of 3 times at a stretching temperature of 100℃. After stretching, it is heat-set at 120℃ for 10 seconds, cooled and wound up to obtain a bamboo fiber film biodegradable material with a thickness of 0.05 mm. Example 3

[0023] This embodiment provides a bamboo fiber film biodegradable material, which is prepared from the following raw materials in parts by weight: 45 parts of acetylated-tannic acid modified bamboo fiber, 30 parts of polybutylene succinate, 25 parts of polyhydroxyalkanoate, 8 parts of epoxidized linseed oil, 5 parts of polyethylene glycol, 3 parts of bacterial cellulose nanofibers, and 2 parts of carnauba wax; wherein the number average molecular weight of polyethylene glycol is 4000.

[0024] The preparation steps of the acetylated-tannic acid modified bamboo fiber are as follows: S1. Bamboo fiber pretreatment: Bamboo fiber is crushed to 200 mesh and dried in an 80℃ oven for 4 hours to obtain dried bamboo fiber; S2. Acetylation treatment: Dry bamboo fiber is added to a mixture of glacial acetic acid and acetic anhydride, with a volume ratio of glacial acetic acid to acetic anhydride of 2:1 and a solid-liquid ratio of bamboo fiber to the mixture of 1g:10mL. 0.5% concentrated sulfuric acid by mass of the mixture is added as a catalyst, and the mixture is reacted at 50℃ for 2h. After the reaction is completed, the mixture is filtered, washed with ethanol until the filtrate is neutral, and dried at 60℃ to obtain acetylated bamboo fiber. S3. Tannic acid crosslinking treatment: Acetylated bamboo fiber was added to a 4% (w / w) tannic acid aqueous solution at a solid-liquid ratio of 1g:15mL. The mixture was stirred and reacted at 40℃ for 3h. After filtration, the mixture was washed three times with deionized water and dried under vacuum at 70℃ for 8h to obtain acetylated-tannic acid modified bamboo fiber.

[0025] The preparation method of the bamboo fiber film biodegradable material includes the following steps: S1. Solid-phase pre-crosslinking: Acetylated-tannic acid modified bamboo fiber, polybutylene succinate, polyhydroxyalkanoate, epoxidized linseed oil, polyethylene glycol, bacterial cellulose nanofibers, and carnauba wax are added to a high-speed mixer in parts by weight and mixed at 90°C and 1200 r / min for 10 min to obtain a premix; the premix is ​​then placed in an internal mixer and internally mixed at 120°C and 80 r / min for 15 min to obtain a pre-crosslinked material; S2. Twin-screw melt blending: The pre-crosslinked material is added to a twin-screw extruder. The temperatures of each section of the extruder are set as follows: feeding section 130℃, melting section 145℃, homogenization section 150℃, die head 145℃, screw speed 300r / min. The material is extruded into strands, water-cooled, and pelletized to obtain composite masterbatch. S3. Biaxial stretching film formation: The composite masterbatch is vacuum dried at 70℃ for 6 hours, added to a casting machine, and cast into a sheet with a thickness of 0.5 mm at 145℃; the sheet is fed into a biaxial stretching machine with a longitudinal stretching ratio of 3.5 times and a transverse stretching ratio of 4 times at a stretching temperature of 110℃. After stretching, it is heat-set at 130℃ for 5 seconds, cooled and wound up to obtain a bamboo fiber film biodegradable material with a thickness of 0.05 mm.

[0026] Comparative Example 1 This comparative example provides a bamboo fiber film biodegradable material. The difference from Example 1 is that unmodified bamboo fiber is used to replace acetylated-tannic acid modified bamboo fiber. The other raw materials, dosages and preparation methods are exactly the same as in Example 1.

[0027] Comparative Example 2 This comparative example provides a bamboo fiber film biodegradable material. The difference between this example and Example 1 is that only acetylated bamboo fiber is used to replace acetylated-tannic acid modified bamboo fiber, and there is no tannic acid crosslinking treatment step. The other raw materials, dosages and preparation methods are exactly the same as in Example 1.

[0028] Comparative Example 3 This comparative example provides a bamboo fiber film biodegradable material. The difference between this example and Example 1 is that the matrix uses 32 parts of polybutylene adipate / terephthalate and 8 parts of polylactic acid, replacing 40 parts of polybutylene succinate and 20 parts of polyhydroxyalkanoate. The remaining raw materials, dosages, and preparation methods are exactly the same as in Example 1.

[0029] Comparative Example 4 This comparative example provides a bamboo fiber film biodegradable material. The difference from Example 1 is that there is no solid-phase pre-crosslinking step. All raw materials are directly mixed and added to a twin-screw extruder. The remaining raw materials, dosages, and preparation methods are exactly the same as in Example 1.

[0030] Comparative Example 5 This comparative example provides a bamboo fiber film biodegradable material. The difference from Example 1 is that there is no biaxial stretching film-forming step. The composite masterbatch is dried and then directly extruded and blown into film using a single screw at a blowing temperature of 140°C to obtain a film with a thickness of 0.05 mm. The remaining raw materials and amounts are exactly the same as in Example 1.

[0031] Performance testing The thin film materials prepared in Examples 1-3 and Comparative Examples 1-5 were subjected to performance testing, and the test results are shown in Table 1.

[0032] Table 1 Performance test results of bamboo fiber film biodegradable materials Sample number Tensile strength (MPa) Elongation at break (%) Right-angle tear strength (kN / m) Water vapor transmission coefficient (g·mm / (m²·24h·kPa)) 180-day compost biodegradation rate (%) Example 1 32.6 385 78.2 3.25 95.8 Example 2 28.4 420 72.5 3.68 94.2 Example 3 35.1 240 85.3 2.87 97.1 Comparative Example 1 12.3 85 26.7 8.92 92.5 Comparative Example 2 18.7 160 39.4 6.35 93.7 Comparative Example 3 22.5 210 52.1 5.74 82.3 Comparative Example 4 20.1 195 45.8 5.12 95.1 Comparative Example 5 17.8 180 41.3 6.89 95.5 The test results in Table 1 show that: The bamboo fiber film biodegradable materials prepared in Examples 1-3 all possess excellent mechanical properties, barrier properties, and biodegradability. The maximum tensile strength can reach 35.1 MPa, the maximum elongation at break can reach 420%, the maximum right-angle tear strength can reach 85.3 kN / m, and the biodegradability rate after 180 days of composting is higher than 94%, achieving a synergistic improvement in mechanical properties and degradation performance.

[0033] Comparative Example 1 uses unmodified bamboo fiber, and the mechanical properties and barrier properties of the material are significantly reduced. This is because unmodified bamboo fiber has strong hydrophilicity and poor compatibility with the polyester matrix, and it is easy to agglomerate and form stress concentration points, which makes the material prone to breakage when under stress.

[0034] Comparative Example 2 uses only acetylated modified bamboo fiber, and the material properties are improved compared to Comparative Example 1, but are far lower than those of Example 1. The reason is that single acetylation modification can only reduce the hydrophilicity of bamboo fiber and cannot build a strong interfacial bond with the matrix. Insufficient interfacial force leads to limited reinforcement effect.

[0035] Comparative Example 3 uses a PBAT / PLA composite matrix, and the biodegradability of the material is significantly reduced. At the same time, the mechanical properties and barrier properties are lower than those of Example 1, which proves that the PBS / PHA composite matrix system of the present invention has a significant advantage in balancing degradation performance and mechanical properties.

[0036] In Comparative Example 4, the mechanical and barrier properties of the material decreased due to the absence of a solid-phase pre-crosslinking step. This was because the lack of a pre-crosslinking step made the raw materials prone to phase separation during high-temperature melting, resulting in uneven component dispersion and structural defects within the material.

[0037] In Comparative Example 5, without the biaxial stretching step, the mechanical strength and barrier properties of the material were significantly reduced. This is because without stretching and orientation, the molecular chains inside the material were randomly arranged and could not form a dense network structure, resulting in a decrease in mechanical and barrier properties.

[0038] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A bamboo fiber film biodegradable material, characterized in that, It is prepared from the following raw materials in parts by weight: 25-45 parts of acetylated-tannic acid modified bamboo fiber, 30-50 parts of polybutylene succinate, 15-25 parts of polyhydroxyalkanoate, 3-8 parts of epoxidized linseed oil, 2-5 parts of polyethylene glycol, 0.5-3 parts of bacterial cellulose nanofibers, and 0.5-2 parts of carnauba wax. The acetylated-tannic acid modified bamboo fiber is prepared by acetylation of 100-200 mesh bamboo fiber with a mixture of glacial acetic acid and acetic anhydride in a volume ratio of 2:1, and crosslinking with a 2-4% tannic acid aqueous solution.

2. The bamboo fiber film biodegradable material according to claim 1, characterized in that, The preparation steps of the acetylated-tannic acid modified bamboo fiber are as follows: S1. Bamboo fiber pretreatment: Crush bamboo fiber to 100-200 mesh and dry it in an oven at 60-80℃ for 4-6 hours to obtain dried bamboo fiber; S2. Acetylation treatment: Dry bamboo fiber is added to a mixture of glacial acetic acid and acetic anhydride, with a volume ratio of glacial acetic acid to acetic anhydride of 2:1 and a solid-liquid ratio of bamboo fiber to the mixture of 1g:10mL. 0.5% concentrated sulfuric acid by mass of the mixture is added as a catalyst, and the mixture is reacted at 40-50℃ for 2-4h. After the reaction is completed, the mixture is filtered, washed with ethanol until the filtrate is neutral, and dried at 60℃ to obtain acetylated bamboo fiber. S3. Tannic acid crosslinking treatment: Add acetylated bamboo fiber to a tannic acid aqueous solution with a mass concentration of 2-4% at a solid-liquid ratio of 1g:15mL, stir and react at 30-40℃ for 3-5h, filter, wash 3 times with deionized water, and vacuum dry at 60-70℃ for 8-12h to obtain acetylated-tannic acid modified bamboo fiber.

3. The bamboo fiber film biodegradable material according to claim 1, characterized in that, The number average molecular weight of the polyethylene glycol is 2000-4000.

4. The bamboo fiber film biodegradable material according to claim 1, characterized in that, The bacterial cellulose nanocrystals have a diameter of 20-50 nm and a length of 100-500 nm.

5. The bamboo fiber film biodegradable material according to claim 1, characterized in that, Includes the following steps: S1. Solid-phase pre-crosslinking: Acetylated tannic acid modified bamboo fiber, polybutylene succinate, polyhydroxyalkanoate, epoxidized linseed oil, polyethylene glycol, bacterial cellulose nanofibers, and carnauba wax are added to a high-speed mixer in parts by weight and mixed at 80-90℃ and 800-1200 r / min for 10-15 min to obtain a premix; the premix is ​​then placed in an internal mixer and internally mixed at 110-120℃ and 60-80 r / min for 15-20 min to obtain a pre-crosslinked material; S2. Twin-screw melt blending: The pre-crosslinked material is added to a twin-screw extruder. The temperatures of each section of the extruder are set as follows: feeding section 120-130℃, melting section 135-145℃, homogenization section 140-150℃, die head 135-145℃, screw speed 200-300r / min. The material is extruded into strands, water-cooled, and pelletized to obtain composite masterbatch. S3. Biaxial stretching film formation: The composite masterbatch is vacuum dried at 60-70℃ for 6-8 hours, then added to a casting machine and cast at 135-145℃ to form a sheet with a thickness of 0.3-0.5 mm. The sheet is then fed into a biaxial stretching machine with a longitudinal stretching ratio of 2.5-3.5 times and a transverse stretching ratio of 3-4 times at a stretching temperature of 100-110℃. After stretching, the sheet is heat-set at 120-130℃ for 5-10 seconds, cooled, and then wound up to obtain a bamboo fiber film biodegradable material.