Degradable bamboo fiber packaging bag and preparation method and application thereof

Abstract

The present application relates to the technical field of packaging materials, and particularly relates to a degradable bamboo fiber packaging bag and a preparation method and application thereof. The packaging bag comprises the following components in parts by weight: modified bamboo fiber 20-40 parts, polylactic acid 30-50 parts, polybutylene adipate terephthalate 20-35 parts, modified starch 10-20 parts, organic montmorillonite master batch 5-15 parts, epsilon-polylysine 0.5-2 parts, plasticizer 2-5 parts, lubricant 1-3 parts, and antioxidant 0.5-2 parts. The modified bamboo fiber is bamboo fiber modified by silane coupling agent after alkali treatment. The organic montmorillonite master batch comprises organic montmorillonite and polybutylene adipate terephthalate. By using the modified bamboo fiber, modified starch, organic montmorillonite master batch and adding epsilon-polylysine, a degradable bamboo fiber packaging bag with excellent mechanical properties, good barrier properties and antibacterial function is obtained.

Description

Technical Field

[0001] This invention relates to the field of packaging materials technology, and in particular to a biodegradable bamboo fiber packaging bag, its preparation method, and its application. Background Technology

[0002] With the rapid development of e-commerce and the express delivery industry, the use of packaging materials continues to grow. Traditional plastic packaging bags, due to their difficulty in natural degradation, put significant pressure on the environment. Therefore, developing environmentally friendly packaging materials that can decompose in the natural environment has become a key focus of the industry.

[0003] Currently, research on biodegradable packaging materials mainly focuses on biodegradable polyesters such as polylactic acid (PLA) and polybutylene adipate terephthalate (PEG), as well as natural polymers such as starch and bamboo fiber. However, existing technologies still have the following shortcomings: First, while bamboo fiber, as a natural reinforcing material, has the advantages of being widely available and renewable, its surface is rich in hydroxyl groups, resulting in poor compatibility with the hydrophobic polyester matrix. Direct blending easily leads to interfacial defects, significantly reducing the material's mechanical properties. Second, starch is widely available and inexpensive, but thermoplastic starch itself has poor mechanical properties and poor compatibility with the polyester matrix. Third, to improve the barrier properties of packaging materials, existing technologies often add nanofillers such as montmorillonite. However, nanofillers are prone to agglomeration in the polymer matrix, and direct addition makes it difficult to achieve uniform dispersion at the nanoscale, resulting in limited barrier reinforcement effects and even stress concentration due to agglomeration, reducing the material's mechanical properties. Fourth, existing biodegradable packaging materials generally lack antibacterial functions, making it difficult to effectively inhibit microbial growth when packaging fresh food, thus limiting their application scope. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in the prior art by providing a biodegradable bamboo fiber packaging bag, its preparation method, and its application. By subjecting bamboo fiber to alkali treatment and modification with silane coupling agents, modifying starch, using organomontmorillonite masterbatch, and adding ε-polylysine, a biodegradable bamboo fiber packaging bag with excellent mechanical properties, good barrier properties, and antibacterial function is obtained.

[0005] To achieve the above objectives, the present invention provides a biodegradable bamboo fiber packaging bag comprising the following components in parts by weight: Modified bamboo fiber 20-40 parts, polylactic acid 30-50 parts, polybutylene adipate 20-35 parts, modified starch 10-20 parts, organomontmorillonite masterbatch 5-15 parts, ε-polylysine 0.5-2 parts, plasticizer 2-5 parts, lubricant 1-3 parts, antioxidant 0.5-2 parts; The modified bamboo fiber is bamboo fiber that has been treated with alkali and then modified with a silane coupling agent; the organomontmorillonite masterbatch contains organomontmorillonite and polybutylene adipate terephthalate.

[0006] In one optional embodiment, the alkali treatment is performed at a temperature of 60-80°C for 2-4 hours.

[0007] In an optional embodiment, the silane coupling agent is selected from γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560); the silane coupling agent is modified at a pH of 4-5, a temperature of 60-70°C, and a time of 1.5-2.5 h.

[0008] In a more specific embodiment, the method for preparing the modified bamboo fiber includes the following steps: (1) Place bamboo fiber in an alkaline solution and treat it at 60-80℃ for 2-4 hours. After the treatment, filter it, wash it with deionized water until neutral, and finally dry it at 60-80℃ to constant weight to obtain alkaline-treated bamboo fiber. (2) The alkali-treated bamboo fiber is placed in a silane coupling agent solution and stirred at 60-70℃ for 1.5-2.5h. After filtration and washing with anhydrous ethanol 2-4 times, the modified bamboo fiber is finally dried at 85-95℃ for 3.5-4.5h to obtain the modified bamboo fiber.

[0009] In an optional embodiment, in step (1), the alkaline solution is selected from sodium hydroxide solution; the mass fraction of the alkaline solution is 4-8%; and the mass-volume ratio of the bamboo fiber to the alkaline solution is 1g:(10-20)mL.

[0010] In an optional embodiment, step (2) of the preparation method of the silane coupling agent solution includes the following steps: dissolving KH560 in a mixed solvent composed of ethanol and water (the volume ratio of ethanol to water is (8-10):1) to prepare a solution with a mass fraction of 1-3%, and finally adjusting the pH to 4-5 with an acetic acid solution with a mass fraction of 8-12% to obtain the silane coupling agent solution.

[0011] In an optional embodiment, in step (2), the mass-to-volume ratio of the alkali-treated bamboo fiber to the silane coupling agent solution is 1 g: (10-20) mL.

[0012] In one optional embodiment, the polylactic acid (PLA) has a weight-average molecular weight of 80,000-150,000; and the polybutylene adipate terephthalate (PBAT) has a weight-average molecular weight of 60,000-120,000.

[0013] In an optional embodiment, the modified starch is selected from octenyl succinic anhydride starch ester, and its preparation method includes the following steps: mixing corn starch with water, adjusting the pH to 8-9, adding octenyl succinic anhydride, and reacting at 35-45℃ for 2-4 hours to obtain modified starch.

[0014] In a more specific embodiment, the preparation method of the modified starch includes the following steps: mixing corn starch and water at a mass ratio of 1:(2-4), adjusting the pH to 8-9 with a sodium hydroxide solution of concentration 0.3-0.7 mol / L, adding 4-6 wt% octenyl succinic anhydride, and stirring the mixture at 35-45℃ for 2-4 hours. During the reaction, a sodium hydroxide solution of concentration 0.3-0.7 mol / L is added dropwise to maintain the pH at 8-9. After the reaction, the pH is adjusted to neutral with a hydrochloric acid solution of concentration 0.3-0.7 mol / L, filtered, washed 2-4 times with deionized water, washed 2-4 times with anhydrous ethanol, dried at 40-50℃, and pulverized through a 150-250 mesh sieve to obtain the modified starch.

[0015] In an optional embodiment, the mass ratio of the organomontmorillonite to polybutylene terephthalate (PBAT) is 1:(3-10); the organomontmorillonite is sodium-based montmorillonite modified with hexadecyltrimethylammonium bromide.

[0016] In an optional embodiment, the method for preparing the organomontmorillonite includes the following steps: (1) Disperse sodium montmorillonite (cation exchange capacity 80-120 mmol / 100g) in deionized water to prepare a suspension with a mass fraction of 2-5%. Stir and swell at room temperature for 2-4 hours, let stand for 23-25 ​​hours, remove the coarse particles settled at the bottom, and take the upper suspension for later use. (2) Take cetyltrimethylammonium bromide (CTAB) in an amount that is 1.0-1.5 times the molar amount of montmorillonite cation exchange capacity, dissolve it in deionized water to prepare a CTAB solution with a mass fraction of 5-10%, and heat it to 60-80℃ to completely dissolve it. (3) Heat the upper suspension obtained in step (1) to 70-80℃, adjust the stirring speed to 200-400r / min, slowly add the completely dissolved CTAB solution in step (2) to the suspension at a dropping rate of 2-5mL / min, and continue stirring the reaction at 70-80℃ for 2-4h after the addition is complete. (4) After the reaction is complete, cool naturally to room temperature and centrifuge (3000-5000 r / min, 10-15 min). Wash the precipitate with deionized water until no white precipitate is found in the washing solution when tested with 0.1 mol / L silver nitrate solution. (5) The washed precipitate was vacuum dried at 65-75℃ to constant weight, and then ground through a 150-250 mesh sieve to obtain organomontmorillonite.

[0017] In an optional embodiment, the preparation method of the organomontmorillonite masterbatch includes the following steps: adding organomontmorillonite and PBAT at a mass ratio of 1:(3-10) into a high-speed mixer and mixing at 700-900 r / min for 7-9 min. Then, the mixture is added to a twin-screw extruder and melt-blended and extruded at 150-160°C (screw speed 150-250 r / min), and pelletized to obtain organomontmorillonite masterbatch.

[0018] In an optional embodiment, the plasticizer is selected from at least one of tributyl citrate and acetylated tributyl citrate; the lubricant is selected from at least one of calcium stearate and zinc stearate; and the antioxidant is selected from at least one of antioxidant 1010 and antioxidant 168.

[0019] This invention also provides a method for preparing a biodegradable bamboo fiber packaging bag, comprising the following steps: S1. Mix the components, perform melt blending extrusion and granulation in a twin-screw extruder to obtain granules; S2. The granules are blow-molded into films and bags to obtain biodegradable bamboo fiber packaging bags.

[0020] In an optional embodiment, in S1, mixing the components includes: weighing each raw material by weight; adding modified bamboo fiber, modified starch, and ε-polylysine to a high-speed mixer and mixing at 800-1000 r / min for 10-15 min to obtain premix A; adding polylactic acid, polybutylene adipate terephthalate, organomontmorillonite masterbatch, plasticizer, lubricant, and antioxidant to a high-speed mixer and mixing at 1000-1200 r / min for 10-20 min to obtain premix B; mixing premix A and premix B and feeding them into a twin-screw extruder.

[0021] In an optional embodiment, in S1, the screw speed of the twin-screw extruder is 150-250 r / min, and the temperatures of each section of the extruder are set as follows: Zone 1 150-160℃, Zone 2 160-170℃, Zone 3 170-180℃, Zone 4 170-180℃, and the die head temperature is 165-175℃.

[0022] In an optional embodiment, in S2, the blow-up ratio of the blown film is 2.5-3.5, the traction speed is 6-10 m / min, and the film thickness is controlled at 0.02-0.08 mm.

[0023] The present invention also provides the application of the biodegradable bamboo fiber packaging bag described herein or the biodegradable bamboo fiber packaging bag prepared according to the preparation method in food packaging or express packaging.

[0024] The beneficial effects of this invention are as follows: (1) This invention introduces active functional groups onto the surface of bamboo fibers by alkali treatment combined with silane coupling agent modification. These functional groups can react with the terminal carboxyl groups of PLA during melt processing to form chemical bonds, and can also react with the terminal hydroxyl groups of PBAT, thereby forming strong interfacial bonds with the two polyester matrices respectively. This dual chemical bonding significantly enhances the interfacial bonding force between bamboo fibers and the PLA / PBAT blend matrix, effectively solving the problem of poor compatibility between bamboo fibers and hydrophobic polyesters, allowing bamboo fibers to be uniformly dispersed in the matrix and fully exert their reinforcing effect, greatly improving the tensile strength, elongation at break, and puncture resistance of the material.

[0025] (2) This invention uses octenyl succinic anhydride to modify starch, introducing hydrophobic long chains into the starch molecules, thereby improving the compatibility between starch and the polyester matrix. This modification method avoids the use of toxic crosslinking agents such as epichlorohydrin, ensuring the safety and environmental friendliness of the material. The modified starch can be uniformly dispersed in the matrix, forming a good interfacial bond with PLA and PBAT, playing a reinforcing role while maintaining biodegradability.

[0026] (3) This invention solves the problem of easy agglomeration of nano-montmorillonite in polymer matrix by pre-preparing organo-montmorillonite masterbatch. Organo-montmorillonite is melt-blended with PBAT to form masterbatch. The shear force of PBAT melt is used to peel and disperse montmorillonite, which is then added in the form of masterbatch. This ensures that montmorillonite is uniformly dispersed at the nanoscale in the final product, forming effective physical crosslinking points and barrier layers, significantly improving the oxygen barrier and water vapor barrier properties of the material. At the same time, the mechanical properties are further improved by the reinforcing effect of nanofillers.

[0027] (4) In this invention, ε-polylysine is added as a natural antibacterial agent. This substance has broad-spectrum antibacterial properties and is biodegradable. It can be evenly dispersed in the material, giving the packaging bag excellent antibacterial function, effectively inhibiting the reproduction of common pathogenic bacteria such as Staphylococcus aureus and Escherichia coli, extending the shelf life of the contents of the packaging, and will not cause secondary pollution to the environment.

[0028] (5) Through the synergistic effect of modified bamboo fiber, modified starch, organic montmorillonite masterbatch and ε-polylysine, the present invention enables the material to have high strength, high toughness, high barrier and antibacterial functions. At the same time, each component has good biodegradability, thus achieving a comprehensive improvement in the overall performance of the material.

[0029] (6) The preparation process of this invention is simple, the raw materials are widely available, and the cost is low. Both extrusion granulation and blown film forming use conventional equipment, the process parameters are easy to control, and it is suitable for large-scale industrial production. The preparation process does not involve toxic or harmful substances, the product is safe and environmentally friendly, and can be used in the fields of food packaging and express packaging. Attached Figure Description

[0030] Figure 1 This is a comparison chart of the tensile strength and elongation at break of different packaging bags in this invention. Detailed Implementation

[0031] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0032] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0033] In the following examples and comparative examples of the present invention, the weight-average molecular weight of polylactic acid (PLA) is 100,000, the weight-average molecular weight of polybutylene terephthalate adipate (PBAT) is 80,000, and the molecular weight of ε-polylysine is 3,500.

[0034] In the following embodiments and comparative examples of the present invention, the preparation methods of each raw material are as follows: (1) Modified bamboo fiber Bamboo fibers with a length of 3-5 mm were placed in a 6% sodium hydroxide solution at a mass-to-volume ratio of 1 g:15 mL and treated at 70°C for 3 h. After filtration, the fibers were washed with deionized water until neutral and dried at 70°C to constant weight to obtain alkali-treated bamboo fibers.

[0035] KH560 was dissolved in a mixed solvent of ethanol and water (volume ratio of 9:1) to prepare a 2% (w / w) solution. The pH was adjusted to 4.5 with a 10% (w / w) acetic acid solution to obtain a silane coupling agent solution. Alkali-treated bamboo fiber was placed in the silane coupling agent solution at a mass-to-volume ratio of 1 g:15 mL and stirred at 65°C for 2 h. The mixture was then filtered, washed three times with anhydrous ethanol, and finally dried at 90°C for 4 h to obtain modified bamboo fiber.

[0036] (2) Modified starch (octenyl succinate starch ester) Corn starch and water were mixed at a mass ratio of 1:3. The pH was adjusted to 8.5 with 0.5 mol / L sodium hydroxide solution. Octenyl succinic anhydride (5 wt% of starch mass) was added, and the mixture was stirred at 40°C for 3 hours. During the reaction, 0.5 mol / L sodium hydroxide solution was added dropwise to maintain the pH at 8.5. After the reaction, the pH was adjusted to 7.0 with 0.5 mol / L hydrochloric acid solution. The mixture was filtered, washed three times with deionized water, and then washed twice with anhydrous ethanol. It was then vacuum dried at 45°C, pulverized, and passed through a 200-mesh sieve to obtain modified starch.

[0037] (3) Organo-montmorillonite (sodium-based montmorillonite modified with hexadecyltrimethylammonium bromide) Sodium montmorillonite (cation exchange capacity 90 mmol / 100 g) was dispersed in deionized water to prepare a 3% suspension. The suspension was stirred and swollen at room temperature for 2 hours, allowed to stand for 24 hours, and the coarse particles settled at the bottom were removed. The upper suspension was then used for later use.

[0038] Take cetyltrimethylammonium bromide (CTAB) in an amount 1.2 times the molar amount of montmorillonite cation exchange capacity, dissolve it in deionized water to prepare an 8% CTAB solution, and heat it to 70°C to completely dissolve it.

[0039] The upper suspension was heated to 75°C, and the stirring speed was adjusted to 300 r / min. The completely dissolved CTAB solution was slowly added dropwise to the suspension at a dropping rate of 3 mL / min. After the addition was completed, the reaction was continued at 75°C for 3 h.

[0040] After the reaction was complete, the mixture was allowed to cool naturally to room temperature and then centrifuged (4000 r / min, 12 min). The resulting precipitate was washed with deionized water until no white precipitate was found in the washing solution when tested with 0.1 mol / L silver nitrate solution.

[0041] The washed precipitate was vacuum dried at 70°C to constant weight, and then ground through a 200-mesh sieve to obtain organomontmorillonite.

[0042] (4) Organo-montmorillonite masterbatch Organomontmorillonite and PBAT were added to a high-speed mixer at a mass ratio of 1:8 and mixed at 800 r / min for 8 min. The mixture was then fed into a twin-screw extruder and melt-blended and extruded at 155°C (screw speed 200 r / min), and pelletized to obtain organomontmorillonite masterbatch.

[0043] Example 1 This embodiment provides a biodegradable bamboo fiber packaging bag, comprising the following components in parts by weight: 30 parts modified bamboo fiber, 40 parts polylactic acid, 25 parts polybutylene adipate terephthalate, 15 parts modified starch, 10 parts organomontmorillonite masterbatch, 1 part ε-polylysine, 3 parts plasticizer (tributyl citrate), 2 parts lubricant (calcium stearate), and 1 part antioxidant (antioxidant 1010).

[0044] This embodiment also provides a method for preparing the above-mentioned biodegradable bamboo fiber packaging bag, including the following steps: Weigh each raw material according to weight; add modified bamboo fiber, modified starch, and ε-polylysine to a high-speed mixer and mix at 900 r / min for 12 min to obtain premix A; add polylactic acid, polybutylene adipate terephthalate, organomontmorillonite masterbatch, plasticizer, lubricant, and antioxidant to a high-speed mixer and mix at 1100 r / min for 15 min to obtain premix B; mix premix A and premix B, and add to a twin-screw extruder. Set the temperatures of each section of the extruder as follows: Zone 1 155℃, Zone 2 165℃, Zone 3 175℃, Zone 4 175℃, Die head temperature 170℃, and screw speed 200 r / min. Melt-blend extrusion granulation is performed to obtain granules.

[0045] The granules are added to a blown film machine and blown into a film at 176℃ with a blow-up ratio of 3.0, a traction speed of 8m / min, and a film thickness controlled at 0.05mm. Then, the film is made into a bag to obtain a biodegradable bamboo fiber packaging bag.

[0046] Example 2 This embodiment provides a biodegradable bamboo fiber packaging bag, comprising the following components in parts by weight: 25 parts modified bamboo fiber, 45 parts polylactic acid, 20 parts polybutylene adipate terephthalate, 18 parts modified starch, 8 parts organomontmorillonite masterbatch, 1.5 parts ε-polylysine, 4 parts plasticizer (tributyl citrate), 2 parts lubricant (calcium stearate), and 1 part antioxidant (antioxidant 1010).

[0047] This embodiment also provides a method for preparing the above-mentioned biodegradable bamboo fiber packaging bag, which is the same as in Example 1.

[0048] Example 3 This embodiment provides a biodegradable bamboo fiber packaging bag, comprising the following components in parts by weight: 35 parts modified bamboo fiber, 35 parts polylactic acid, 30 parts polybutylene adipate terephthalate, 10 parts modified starch, 12 parts organomontmorillonite masterbatch, 0.8 parts ε-polylysine, 3 parts plasticizer (tributyl citrate), 1.5 parts lubricant (calcium stearate), and 0.8 parts antioxidant (antioxidant 1010).

[0049] This embodiment also provides a method for preparing the above-mentioned biodegradable bamboo fiber packaging bag, which is the same as in Example 1.

[0050] Comparative Example 1 This comparative example provides a biodegradable bamboo fiber packaging bag, which differs from Example 1 in that the modified bamboo fiber is replaced with bamboo fiber (original bamboo fiber without any modification treatment).

[0051] Comparative Example 2 This comparative example provides a biodegradable bamboo fiber packaging bag, which differs from Example 1 in that the addition of organic montmorillonite masterbatch is omitted and replaced with an equal amount of PBAT.

[0052] Comparative Example 3 This comparative example provides a biodegradable bamboo fiber packaging bag, which differs from Example 1 in that the modified starch is replaced with corn starch (raw corn starch that has not undergone any modification treatment).

[0053] Comparative Example 4 This comparative example provides a biodegradable bamboo fiber packaging bag, which differs from Example 1 in that the organic montmorillonite masterbatch is replaced with a single organic montmorillonite (without PBAT).

[0054] Experimental Example 1 The biodegradable bamboo fiber packaging bags prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests, and the test methods are as follows: (1) Tensile strength and elongation at break test The tests were conducted according to GB / T 1040.3-2006, "Determination of tensile properties of plastics – Part 3: Test conditions for films and sheets". The specimen type was Type 2 (dumbbell-shaped), 10 mm wide, with a gauge length of 50 mm and a thickness equal to the actual sample thickness. The test temperature was 23℃±2℃, the relative humidity was 50%±5%, and the tensile speed was 50 mm / min. Five specimens were tested in each group, and the arithmetic mean was taken.

[0055] (2) Puncture resistance test The tests were conducted according to Appendix C of GB / T 10004-2008 "Dry Lamination and Extrusion Lamination of Plastic Composite Films and Bags for Packaging". The test speed was 50 mm / min, the puncture needle diameter was 1.0 mm, and the needle tip radius of curvature was 0.5 mm. Five samples were tested in each group, and the arithmetic mean was taken.

[0056] (3) Degradation rate test The tests were conducted according to GB / T 19277.1-2011, "Determination of the final aerobic biodegradability of materials under controlled composting conditions—Method for determining the release of carbon dioxide—Part 1: General Method". Samples were buried in a simulated controlled composting environment, with the temperature maintained at 58℃±2℃ and humidity controlled at 50%-60%, and regular ventilation and oxygen supply provided. After 60 days of burial, the samples were removed, cleaned, dried, and weighed to calculate the degradation rate. Three samples were tested for each group, and the arithmetic mean was taken. Degradation rate (%) = (W0-W1) / W0×100%, where: W0 refers to the initial mass of the sample, g; W1 refers to the mass of the sample after burial, g.

[0057] (4) Oxygen permeability test The test was conducted according to GB / T 1038-2000 "Gas Permeability Test Method for Plastic Films and Sheets - Differential Pressure Method". The test temperature was 23℃±0.5℃, the relative humidity was 50%±2%, and the test area was 50cm². 2 Three samples were tested in each group, and the arithmetic mean was taken.

[0058] (5) Water vapor transmission rate test The test was conducted according to GB / T 1037-2021 "Determination of Water Vapor Permeability of Plastic Films and Sheets - Cup Method (Gain and Loss Method)". The test temperature was 38℃±0.5℃, the relative humidity was 90%±2%, and the test area was 33cm². 2 Three samples were tested in each group, and the arithmetic mean was taken.

[0059] (6) Antibacterial rate test The test was conducted according to GB / T 31402-2015 "Test Method for Antimicrobial Properties of Plastic Surfaces". Staphylococcus aureus (ATCC 6538) and Escherichia coli (ATCC 8739) were selected as the bacterial strains. The sample size was 50 mm × 50 mm, and the bacterial concentration was 2.5 × 10⁻⁶. 5 CFU / mL, contact time 24h, incubation temperature 37℃±1℃. Three samples were tested in each group, and the arithmetic mean was taken. Antibacterial rate (%) = (BC) / B×100%, where: B refers to the average number of viable bacteria in the blank control sample, CFU; C refers to the average number of viable bacteria in the antibacterial sample (example, comparative sample packaging bag), CFU.

[0060] The performance test results are recorded in Table 1. Simultaneously, a comparison chart of the tensile strength and elongation at break for different packaging bags is plotted, as shown below. Figure 1 As shown.

[0061] Table 1 Performance Test Results

[0062] from Figure 1The test results in Table 1 show that: (1) The packaging bags prepared in Examples 1-3 all showed excellent performance in terms of tensile strength (≥40.2MPa), elongation at break (≥340%), and puncture resistance (≥10.5N), which were significantly higher than those in the comparative examples. This indicates that the present invention endows the material with excellent comprehensive mechanical properties through the synergistic effect of modified bamboo fiber, organomontmorillonite masterbatch, and modified starch.

[0063] (2) The mechanical properties of Comparative Example 1 (unmodified bamboo fiber) decreased significantly, indicating that alkali treatment and silane modification of bamboo fiber are crucial for enhancing the interfacial bonding between the fiber and the matrix. Unmodified bamboo fiber has poor compatibility with the polyester matrix and is prone to forming interfacial defects, resulting in a significant reduction in mechanical properties.

[0064] (3) The oxygen permeability and water vapor permeability of Comparative Example 2 (without organo-montmorillonite masterbatch) were significantly higher than those of Example 2, while the tensile strength and elongation at break were lower than those of Example 2. This demonstrates that the addition of organo-montmorillonite masterbatch not only improved the barrier properties of the material, but also improved the mechanical properties through the reinforcing effect of nanofillers.

[0065] (4) The mechanical properties of Comparative Example 3 (starch unmodified) were all lower than those of the Example, indicating that the octenyl succinate modification improved the compatibility between starch and polyester matrix, enabling starch to be uniformly dispersed in the matrix while maintaining good biodegradability.

[0066] (5) The mechanical and barrier properties of Comparative Example 4 (organo-montmorillonite added directly, without being made into masterbatch) were lower than those of the Example, indicating that the pre-preparation of organo-montmorillonite masterbatch is the key to achieving uniform dispersion of nanofillers. Direct addition easily leads to montmorillonite agglomeration, which not only fails to exert the nano-reinforcement and barrier effects, but may also form stress concentration points due to agglomeration, thus reducing the material properties.

[0067] (6) The degradation rates of Examples 1-3 were between 72.8% and 76.1%, and the degradation rates of Comparative Examples 1-4 were between 68.5% and 73.0%. The overall difference was not significant, indicating that the modification treatment of the present invention did not significantly delay the biodegradation process of the material, and each component still maintained good biodegradability.

[0068] (7) The antibacterial rates of Examples 1-3 all reached over 99.8%, and the antibacterial rates of Comparative Examples 1-4 also reached over 99.5%, indicating that the addition of ε-polylysine endowed the material with excellent antibacterial properties, and the modification of bamboo fiber and starch had no significant negative impact on the antibacterial effect.

[0069] In summary, the biodegradable bamboo fiber packaging bags prepared in Examples 1-3 of this invention exhibit excellent performance in terms of mechanical properties, barrier properties, degradation properties, and antibacterial properties. All performance indicators are superior to those of the comparative examples, and they can meet the application requirements of food packaging and express packaging.

[0070] Finally, it should be noted that the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A biodegradable bamboo fiber packaging bag, characterized in that, It contains the following components in parts by weight: Modified bamboo fiber 20-40 parts, polylactic acid 30-50 parts, polybutylene adipate 20-35 parts, modified starch 10-20 parts, organomontmorillonite masterbatch 5-15 parts, ε-polylysine 0.5-2 parts, plasticizer 2-5 parts, lubricant 1-3 parts, antioxidant 0.5-2 parts; The modified bamboo fiber is bamboo fiber that has been treated with alkali and then modified with a silane coupling agent; the organomontmorillonite masterbatch contains organomontmorillonite and polybutylene adipate terephthalate.

2. The biodegradable bamboo fiber packaging bag according to claim 1, characterized in that, The alkaline treatment is performed at a temperature of 60-80℃ for 2-4 hours.

3. The biodegradable bamboo fiber packaging bag according to claim 1, characterized in that, The silane coupling agent is selected from γ-(2,3-epoxypropoxy)propyltrimethoxysilane; the pH of the silane coupling agent modification is 4-5, the temperature is 60-70℃, and the time is 1.5-2.5h.

4. The biodegradable bamboo fiber packaging bag according to claim 1, characterized in that, The modified starch is selected from octenyl succinic anhydride starch ester, and its preparation method includes the following steps: mixing corn starch with water, adjusting the pH to 8-9, adding octenyl succinic anhydride, and reacting at 35-45℃ for 2-4 hours to obtain modified starch.

5. The biodegradable bamboo fiber packaging bag according to claim 1, characterized in that, The mass ratio of the organomontmorillonite to polybutylene adipate terephthalate is 1:(3-10); the organomontmorillonite is sodium-based montmorillonite modified with hexadecyltrimethylammonium bromide.

6. The biodegradable bamboo fiber packaging bag according to claim 1, characterized in that, The plasticizer is selected from at least one of tributyl citrate and acetylated tributyl citrate; the lubricant is selected from at least one of calcium stearate and zinc stearate; and the antioxidant is selected from at least one of antioxidant 1010 and antioxidant 168.

7. A method for preparing a biodegradable bamboo fiber packaging bag as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Mix the components, perform melt blending extrusion and granulation in a twin-screw extruder to obtain granules; S2. The granules are blow-molded into films and bags to obtain biodegradable bamboo fiber packaging bags.

8. The preparation method according to claim 7, characterized in that, In S1, the screw speed of the twin-screw extruder is 150-250 r / min, and the temperature of each section of the extruder is set as follows: Zone 1 150-160℃, Zone 2 160-170℃, Zone 3 170-180℃, Zone 4 170-180℃, and the die head temperature is 165-175℃.

9. The preparation method according to claim 7, characterized in that, In S2, the blow-up ratio of the blown film is 2.5-3.5, the traction speed is 6-10m / min, and the film thickness is controlled at 0.02-0.08mm.

10. The application of the biodegradable bamboo fiber packaging bag according to any one of claims 1-6 or the biodegradable bamboo fiber packaging bag prepared by the preparation method according to any one of claims 7-9 in food packaging or express packaging.

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