Bacteriostatic food packaging bag and preparation method thereof

Abstract

The invention discloses a bacteriostatic food packaging bag and a preparation method thereof, and relates to the technical field of food packaging, the bacteriostatic food packaging bag comprises the following components by weight: 12-22 parts of bamboo fiber; 55 to 80 parts of TPS (Thermoplastic Polystyrene); 15-20 parts of a modified ethylene composite copolymer; 15 to 20 parts of modified chitosan; wherein the modified ethylene composite copolymer is obtained by polymerizing active group-containing ethylene and one of vinyl acetate, butene, hexene or octylene according to a molar ratio of 10: (3-6); the active group is at least one of amino and sulfonic acid group; the modified chitosan is sulfo-grafted chitosan, and the mass grafting rate is greater than 0.1 wt%. The preparation method has the advantages that the compatibility of a composition formula is improved through the modified ethylene composite copolymer and the modified chitosan, a uniform net structure is formed in a cross-linking reaction to serve as a supporting framework, the overall mechanical structure performance is enhanced through the bamboo fibers which are synergistically and uniformly distributed in the composition formula, and the degradable and non-toxic effects are achieved through the cooperation of the bamboo fibers and the TPS.

Description

Technical Field

[0001] This application relates to the field of food packaging technology, and in particular to an antibacterial food packaging bag and its preparation method. Background Technology

[0002] Food packaging bags are a type of packaging design. They were developed to facilitate the preservation and storage of food. Food packaging bags are thin-film containers that come into direct contact with food and are used to hold and protect it.

[0003] Chinese Patent No. CN117799272B discloses a bio-based food packaging bag and its preparation method. The bio-based food packaging bag comprises the following components by weight: an outer layer, a middle layer, and an inner layer; the outer layer comprises the following components by weight: 100 parts PLA, 5-25 parts silicate; the middle layer comprises the following components by weight: 100 parts PLA, 5-25 parts silicate, 2-5 parts 2-methoxycinnamicaldehyde; the inner layer comprises the following components by weight: 100 parts PLA, 5-25 parts silicate, 2-5 parts 2-methoxycinnamicaldehyde.

[0004] This bio-based food packaging bag uses polylactic acid (PLA), a biodegradable material, as its core material, supplemented with silicates to form a barrier structure. It combines outer, middle, and inner layers to improve gas barrier performance. However, it cannot achieve effective antibacterial and anti-mildew effects, affecting the safety of food packaging and needs improvement. Summary of the Invention

[0005] In view of this, the first objective of this application is to provide an antibacterial food packaging bag to achieve effective antibacterial and anti-mold properties. The specific solution is as follows: An antibacterial food packaging bag, comprising the following components by weight: 12-22 parts bamboo fiber; 55-80 TPS; 15-20 parts of modified ethylene composite copolymer; 15-20 parts modified chitosan; The modified ethylene composite copolymer is obtained by polymerizing ethylene containing active groups with one of vinyl acetate, butene, hexene or octene; the active groups are at least one of amino and sulfonic acid groups; the modified chitosan is sulfonic acid-grafted chitosan with a grafting rate greater than 0.1 wt%.

[0006] Preferably, the method for preparing bamboo fiber includes step ① breaking up moso bamboo to obtain disassembled bamboo bodies with a length of less than 2cm and a width of less than 5mm; step ② immersing the disassembled bamboo bodies in a sodium hydroxide solution with a mass concentration of 5wt% and stirring for 4-6 hours to obtain alkali-treated bamboo fiber; and step ③ washing the alkali-treated bamboo fiber with deionized water, drying it, and then grinding it to obtain the finished bamboo fiber.

[0007] Preferably, in step ②, the mass ratio of the disassembled bamboo body to the sodium hydroxide solution is 1:10-100; in step ③, a ball mill is used for grinding.

[0008] Preferably, the modified ethylene composite copolymer is obtained by polymerizing ethylene with one of vinyl acetate, butene, hexene or octene in a molar ratio of 10:3-6.

[0009] Preferably, the content of the active group is 0.5-2 wt%.

[0010] Preferably, the method for preparing the modified chitosan includes step ① mixing sodium hydroxysulfonate and chlorosulfonic acid solution with a concentration of 0.05 mol / L at a mass ratio of 2:48 to obtain an acidic solution; step ② adding chitosan to the acidic solution and stirring to fully dissolve the chitosan in the acidic solution, controlling the reaction and condensation of chitosan and sodium hydroxysulfonate to obtain a modified chitosan solution; step ③ adding 95% ethanol to the modified chitosan solution and precipitating the modified chitosan precipitate, and then obtaining modified chitosan after filtration, washing and vacuum drying.

[0011] Preferably, the sodium hydroxysulfonate is sodium 3-hydroxypropane-1-sulfonate.

[0012] The second objective of this invention is to provide a method for preparing an antibacterial food packaging bag, comprising: step ① preparing bamboo fiber, modified ethylene composite copolymer and modified chitosan; step ② mixing bamboo fiber, TPS, modified ethylene composite copolymer and modified chitosan in parts by weight and feeding them into a screw extruder for extrusion granulation; step ③ melt blow molding the granulated material to obtain a pre-formed antibacterial food packaging bag; and step ④ cutting, trimming and / or printing and finishing the pre-formed antibacterial food packaging bag to obtain the finished antibacterial food packaging bag.

[0013] As can be seen from the above solutions, this application provides an antibacterial food packaging bag and its preparation method, which has the following beneficial effects: 1. By improving the compatibility of the composition formula with modified ethylene composite copolymer and modified chitosan, a uniform network structure is formed in the cross-linking reaction as a supporting skeleton, so as to achieve the overall mechanical structural performance of bamboo fiber that is synergistically and uniformly distributed in the composition, and achieve the effect of degradability and non-toxicity in synergy with TPS. 2. By cross-linking the active groups in the modified ethylene composite copolymer with the modified chitosan to form a uniform network structure as a supporting skeleton, the overall mechanical properties are improved while the compatibility is enhanced. Furthermore, the sulfonic acid groups and chitosan synergistically enhance the antibacterial and antifungal effects. The overall structure is dense and has a strong supporting effect. 3. By using the fiber structure of moso bamboo as a supplementary component to increase strength, while treating it with sodium hydroxide solution, the crystal structure of the moso bamboo fiber structure changes, so as to obtain bamboo fiber that is compatible with and synergistically strengthens the various components. 4. Modified chitosan is obtained by grafting sodium 3-hydroxypropane-1-sulfonate with chitosan, which will further enhance the antibacterial and antifungal effect of chitosan, improve its compatibility with each component, and achieve uniform distribution among the components to achieve cross-linking and improve mechanical properties, so that the antibacterial food packaging bag can effectively achieve the purpose of antibacterial and antifungal. Detailed Implementation

[0014] The technical solutions described below in conjunction with the embodiments of this application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0015] It should be mentioned that the TPS used in this embodiment was purchased from Anhui Jumei Biotechnology Co., Ltd., the bamboo was purchased from the market, and all the equipment used was commercially available, which will not be elaborated here.

[0016] The following will provide a detailed description of the antibacterial food packaging bag of this application.

[0017] An antibacterial food packaging bag comprises 12-22 parts by weight of bamboo fiber, 55-80 parts by weight of TPS, 15-20 parts by weight of modified ethylene composite copolymer and 15-20 parts by weight of modified chitosan.

[0018] The preparation method of the antibacterial food packaging bag includes step ① preparing bamboo fiber, modified ethylene composite copolymer and modified chitosan; step ② mixing bamboo fiber, TPS, modified ethylene composite copolymer and modified chitosan in parts by weight and feeding them into a screw extruder for extrusion granulation; step ③ melting blow molding the granulated material to obtain a pre-formed antibacterial food packaging bag; step ④ cutting, trimming and / or printing and finishing the pre-formed antibacterial food packaging bag to obtain the finished antibacterial food packaging bag.

[0019] The method for preparing bamboo fiber includes step ① breaking up moso bamboo to obtain disassembled bamboo bodies with a length of less than 2cm and a width of less than 5mm; step ② immersing the disassembled bamboo bodies in a sodium hydroxide solution with a mass concentration of 5wt% and stirring for 4-6 hours to obtain alkali-treated bamboo fiber; and step ③ washing the alkali-treated bamboo fiber with deionized water, drying it, and then grinding it to obtain the finished bamboo fiber.

[0020] In step ②, the mass ratio of disassembled bamboo to sodium hydroxide solution is 1:10-100 to ensure sufficient reaction between the sodium hydroxide solution and the disassembled bamboo, and to promote the crystal transformation of the disassembled bamboo. In step ③, a ball mill is used for grinding to obtain thoroughly ground and uniformly sized bamboo fibers.

[0021] It should be noted that the modified ethylene composite copolymer in the embodiments of this application is obtained by polymerizing ethylene containing active groups with one of vinyl acetate, butene, hexene, or octene. The active group is at least one of amino or sulfonic acid groups. The content of the active group is 0.5-2 wt%. Furthermore, the modified ethylene composite copolymer in the embodiments of this application is obtained by polymerizing ethylene with one of vinyl acetate, butene, hexene, or octene in a molar ratio of 10:3-6.

[0022] Meanwhile, the modified chitosan is sulfonic acid-grafted chitosan with a grafting rate greater than 0.1 wt%.

[0023] The method for preparing modified chitosan includes the following steps: Step ① mixing sodium hydroxysulfonate and deionized water at a mass ratio of 2:48 to obtain an acidic solution; Step ② adding chitosan to the acidic solution and stirring to fully dissolve the chitosan in the acidic solution, controlling the reaction and condensation of chitosan and sodium hydroxysulfonate to obtain a modified chitosan solution; Step ③ adding 95% ethanol to the modified chitosan solution and precipitating the modified chitosan precipitate, and then obtaining modified chitosan after filtration, washing and vacuum drying.

[0024] In order to improve the antibacterial and antifungal effects of modified chitosan and the bonding strength of its mixing and curing with modified ethylene composite copolymer, bamboo fiber and TPS, the sodium hydroxysulfonate used in the embodiments of this application is sodium 3-hydroxypropane-1-sulfonate.

[0025] Example 1 An antibacterial food packaging bag comprises 12 parts by weight of bamboo fiber, 55 parts by weight of TPS, 15 parts by weight of modified ethylene composite copolymer and 15 parts by weight of modified chitosan.

[0026] The preparation method of the antibacterial food packaging bag includes step ① preparing bamboo fiber, modified ethylene composite copolymer and modified chitosan; step ② mixing bamboo fiber, TPS, modified ethylene composite copolymer and modified chitosan in parts by weight and feeding them into a screw extruder for extrusion granulation; step ③ melt blow molding the granulated material to obtain a pre-formed antibacterial food packaging bag; step ④ cutting, trimming and printing the pre-formed antibacterial food packaging bag to obtain the finished antibacterial food packaging bag.

[0027] The method for preparing bamboo fiber includes step ① breaking up moso bamboo to obtain disassembled bamboo body with a length of 1.8cm and a width of 4.8mm; step ② immersing the disassembled bamboo body in a sodium hydroxide solution with a mass concentration of 5wt% and stirring for 4h to obtain alkali-treated bamboo fiber; step ③ washing the alkali-treated bamboo fiber with deionized water, drying it, and then grinding it to obtain the finished bamboo fiber.

[0028] In step ②, the mass ratio of disassembled bamboo to sodium hydroxide solution is 1:10 to ensure sufficient reaction between the sodium hydroxide solution and the disassembled bamboo, and to promote the crystal transformation of the disassembled bamboo. In step ③, a ball mill is used for grinding to obtain thoroughly ground and uniformly sized bamboo fibers.

[0029] It should be noted that the modified ethylene composite copolymer in this application embodiment is obtained by polymerizing ethylene containing active groups with vinyl acetate. The active groups are amino groups. The content of the active groups is 0.75 wt%. Furthermore, the ethylene and vinyl acetate in the modified ethylene composite copolymer in this application embodiment are polymerized at a molar ratio of 10:3.

[0030] Meanwhile, the modified chitosan is sulfonic acid-grafted chitosan with a grafting rate of 0.21 wt%.

[0031] The method for preparing modified chitosan includes the following steps: Step ① mixing sodium 3-hydroxypropane-1-sulfonate and deionized water at a mass ratio of 2:48 to obtain an acidic solution; Step ② adding chitosan to the acidic solution and stirring to fully dissolve the chitosan in the acidic solution, controlling the reaction and condensation of chitosan and sodium 3-hydroxypropane-1-sulfonate to obtain a modified chitosan solution; Step ③ adding 95% ethanol to the modified chitosan solution and precipitating the modified chitosan precipitate, followed by filtration, washing, and vacuum drying to obtain modified chitosan.

[0032] Example 2 An antibacterial food packaging bag comprises 15 parts by weight of bamboo fiber, 70 parts by weight of TPS, 17 parts by weight of modified ethylene composite copolymer and 18 parts by weight of modified chitosan.

[0033] The preparation method of the antibacterial food packaging bag includes step ① preparing bamboo fiber, modified ethylene composite copolymer and modified chitosan; step ② mixing bamboo fiber, TPS, modified ethylene composite copolymer and modified chitosan in parts by weight and feeding them into a screw extruder for extrusion granulation; step ③ melt blow molding the granulated material to obtain a pre-formed antibacterial food packaging bag; step ④ cutting, trimming and printing the pre-formed antibacterial food packaging bag to obtain the finished antibacterial food packaging bag.

[0034] The method for preparing bamboo fiber includes step ① breaking up moso bamboo to obtain disassembled bamboo bodies with a length of less than 2cm and a width of less than 5mm; step ② immersing the disassembled bamboo bodies in a sodium hydroxide solution with a mass concentration of 5wt% and stirring for 4-6 hours to obtain alkali-treated bamboo fiber; and step ③ washing the alkali-treated bamboo fiber with deionized water, drying it, and then grinding it to obtain the finished bamboo fiber.

[0035] In step ②, the mass ratio of disassembled bamboo to sodium hydroxide solution is 1:10-100 to ensure sufficient reaction between the sodium hydroxide solution and the disassembled bamboo, and to promote the crystal transformation of the disassembled bamboo. In step ③, a ball mill is used for grinding to obtain thoroughly ground and uniformly sized bamboo fibers.

[0036] It should be noted that the modified ethylene composite copolymer in this application embodiment is obtained by polymerizing ethylene containing active groups with octene. The active groups are sulfonic acid groups. The content of the active groups is 1.5 wt%. Furthermore, the ethylene and octene in the modified ethylene composite copolymer in this application embodiment are polymerized at a molar ratio of 2:1.

[0037] Meanwhile, the modified chitosan is sulfonic acid-grafted chitosan with a grafting rate of 0.75 wt%.

[0038] The method for preparing modified chitosan includes the following steps: Step ① mixing sodium 3-hydroxypropane-1-sulfonate and deionized water at a mass ratio of 2:48 to obtain an acidic solution; Step ② adding chitosan to the acidic solution and stirring to fully dissolve the chitosan in the acidic solution, controlling the reaction and condensation of chitosan and sodium 3-hydroxypropane-1-sulfonate to obtain a modified chitosan solution; Step ③ adding 95% ethanol to the modified chitosan solution and precipitating the modified chitosan precipitate, followed by filtration, washing, and vacuum drying to obtain modified chitosan.

[0039] Example 3 An antibacterial food packaging bag comprises 22 parts by weight of bamboo fiber, 80 parts by weight of TPS, 20 parts by weight of modified ethylene composite copolymer and 20 parts by weight of modified chitosan.

[0040] The preparation method of the antibacterial food packaging bag includes step ① preparing bamboo fiber, modified ethylene composite copolymer and modified chitosan; step ② mixing bamboo fiber, TPS, modified ethylene composite copolymer and modified chitosan in parts by weight and feeding them into a screw extruder for extrusion granulation; step ③ melt blow molding the granulated material to obtain a pre-formed antibacterial food packaging bag; step ④ cutting, trimming and printing the pre-formed antibacterial food packaging bag to obtain the finished antibacterial food packaging bag.

[0041] The method for preparing bamboo fiber includes step ① breaking up moso bamboo to obtain disassembled bamboo body with a length of 1.8cm and a width of 4.8mm; step ② immersing the disassembled bamboo body in a sodium hydroxide solution with a mass concentration of 5wt% and stirring for 6h to obtain alkali-treated bamboo fiber; step ③ washing the alkali-treated bamboo fiber with deionized water, drying it, and then grinding it to obtain the finished bamboo fiber.

[0042] In step ②, the mass ratio of disassembled bamboo to sodium hydroxide solution is 1:100 to ensure sufficient reaction between the sodium hydroxide solution and the disassembled bamboo, and to promote the crystal transformation of the disassembled bamboo. In step ③, a ball mill is used for grinding to obtain thoroughly ground and uniformly sized bamboo fibers.

[0043] It should be noted that the modified ethylene composite copolymer in this application embodiment is obtained by polymerizing ethylene containing active groups with butene. The active groups are sulfonic acid groups. The content of the active groups is 0.81 wt%. Furthermore, the ethylene and butene in the modified ethylene composite copolymer in this application embodiment are polymerized at a molar ratio of 10:4.

[0044] Meanwhile, the modified chitosan is sulfonic acid-grafted chitosan with a grafting rate of 0.35 wt%.

[0045] The method for preparing modified chitosan includes the following steps: Step ① mixing sodium 3-hydroxypropane-1-sulfonate and deionized water at a mass ratio of 2:48 to obtain an acidic solution; Step ② adding chitosan to the acidic solution and stirring to fully dissolve the chitosan in the acidic solution, controlling the reaction and condensation of chitosan and sodium 3-hydroxypropane-1-sulfonate to obtain a modified chitosan solution; Step ③ adding 95% ethanol to the modified chitosan solution and precipitating the modified chitosan precipitate, followed by filtration, washing, and vacuum drying to obtain modified chitosan.

[0046] Comparative Example 1 The difference between Comparative Example 1 and Example 2 is that the chitosan in Comparative Example 1 was not grafted, but only activated by a 2% hydrochloric acid solution.

[0047] Comparative Example 2 The difference between Comparative Example 2 and Example 2 is that in Comparative Example 2, ethylene-vinyl acetate copolymer is used instead of modified ethylene composite copolymer.

[0048] The difference between Comparative Example 3 and Example 2 is that the bamboo fiber in Comparative Example 3 was obtained by mixing and reacting concentrated sulfuric acid at 50°C for 2 hours and then drying.

[0049] Performance testing: 1. Mechanical property testing: Tensile stress testing shall be conducted in accordance with GB / T1040-2006; 2. Antibacterial performance test: The antibacterial ability test shall be conducted in accordance with GB / T31402-2015.

[0050] The test results are shown in Table 1 below.

[0051] Table 1 Performance Test Results

[0052] As shown in Table 1 above, the antibacterial food packaging bag prepared using the bamboo fiber, TPS, modified ethylene composite copolymer, and modified chitosan as a combined formulation in this application has a tensile strength greater than 56 MPa, and achieves an antibacterial effect of 99.99% against Staphylococcus aureus and Escherichia coli in 24 hours. When using ungrafted chitosan, the compatibility of chitosan decreases, affecting its dispersion performance and making it difficult to achieve an effective antibacterial effect. While using ethylene-vinyl acetate copolymer instead of modified ethylene composite copolymer has a smaller impact on the antibacterial effect of the prepared antibacterial food packaging bag, the decreased compatibility leads to a decrease in dispersion, resulting in a decrease in tensile strength. Furthermore, the reduced binding ability with chitosan affects the antibacterial and antifungal effects of chitosan and its grafted groups, causing the 24-hour Staphylococcus aureus inhibition rate to decrease from 99.99% to 99.98%. Meanwhile, when bamboo fiber is obtained by treatment with sodium hydroxide solution as described in the embodiments of this application, the mechanical properties of the prepared antibacterial food packaging bag will be improved to a certain extent. This may be because bamboo fiber, under the corresponding treatment environment, has the effect of combining with modified ethylene composite copolymer and modified chitosan after crystal transformation, and synergistically improving the overall mechanical properties.

[0053] In summary, this application provides an antibacterial food packaging bag. This bag enhances the compatibility of the formulation by using modified ethylene composite copolymer and modified chitosan. During the cross-linking reaction, a uniform network structure is formed as a supporting skeleton, achieving synergistic and uniform distribution of bamboo fiber in the formulation to strengthen the overall mechanical structure. It also synergistically achieves biodegradability and non-toxicity with TPS. Simultaneously, the cross-linking of active groups in the modified ethylene composite copolymer with modified chitosan forms a uniform network structure as a supporting skeleton, thereby improving overall mechanical properties while enhancing compatibility. Furthermore, it synergistically enhances the antibacterial and antifungal effects with sulfonic acid groups and chitosan, resulting in a dense and strongly supportive overall structure. To further improve the structural strength of this antibacterial food packaging bag, the bamboo fiber in this embodiment is a supplementary component using the fiber structure of moso bamboo as a strength-enhancing element. Simultaneously, treatment with sodium hydroxide solution alters the crystal structure of the moso bamboo fiber, resulting in bamboo fiber suitable for compatibility and synergistic reinforcement with the various components. In order to effectively improve the antibacterial and antifungal effect of the antibacterial food packaging bag, 3-hydroxypropane-1-sulfonate sodium is used as hydroxysulfonate to graft with chitosan to obtain modified chitosan. This will further improve the antibacterial and antifungal effect of chitosan, while improving the compatibility between various components, and then achieve uniform distribution among the components to achieve cross-linking and improve mechanical properties, so that the antibacterial food packaging bag can achieve the purpose of effective antibacterial and antifungal effect.

[0054] The terms “first,” “second,” “third,” “fourth,” etc., used in this application (if applicable) are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, or apparatus that includes a series of steps or units is not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, or apparatus.

[0055] It should be noted that the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of those features. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0056] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An antibacterial food packaging bag, characterized in that, The components include the following weights: 12-22 parts bamboo fiber; 55-80 TPS; 15-20 parts of modified ethylene composite copolymer; 15-20 parts modified chitosan; The modified ethylene composite copolymer is obtained by polymerizing ethylene containing active groups with one of vinyl acetate, butene, hexene or octene; the active groups are at least one of amino and sulfonic acid groups; the modified chitosan is sulfonic acid-grafted chitosan with a grafting rate greater than 0.1 wt%.

2. The antibacterial food packaging bag according to claim 1, characterized in that: The method for preparing bamboo fiber includes step ① breaking up moso bamboo to obtain disassembled bamboo bodies with a length of less than 2cm and a width of less than 5mm; step ② immersing the disassembled bamboo bodies in a sodium hydroxide solution with a mass concentration of 5wt% and stirring for 4-6 hours to obtain alkali-treated bamboo fiber; step ③ washing the alkali-treated bamboo fiber with deionized water, drying it, and then grinding it to obtain the finished bamboo fiber.

3. The antibacterial food packaging bag according to claim 2, characterized in that: In step ②, the mass ratio of the disassembled bamboo body to the sodium hydroxide solution is 1:10-100; in step ③, a ball mill is used for grinding.

4. The antibacterial food packaging bag according to claim 1, characterized in that: The modified ethylene composite copolymer is obtained by polymerizing ethylene with one of vinyl acetate, butene, hexene or octene in a molar ratio of 10:3-6.

5. The antibacterial food packaging bag according to claim 1, characterized in that: The content of the active group is 0.5-2 wt%.

6. The antibacterial food packaging bag according to claim 1, characterized in that: The method for preparing the modified chitosan includes the following steps: Step ① mixing sodium hydroxysulfonate and chlorosulfonic acid solution with a concentration of 0.05 mol / L at a mass ratio of 2:48 to obtain an acidic solution; Step ② adding chitosan to the acidic solution and stirring to fully dissolve the chitosan in the acidic solution, controlling the reaction and condensation of chitosan and sodium hydroxysulfonate to obtain a modified chitosan solution; Step ③ adding 95% ethanol to the modified chitosan solution and precipitating the modified chitosan precipitate, followed by filtration, washing and vacuum drying to obtain the modified chitosan.

7. The antibacterial food packaging bag according to claim 6, characterized in that: The sodium hydroxysulfonate is sodium 3-hydroxypropane-1-sulfonate.

8. A method for preparing an antibacterial food packaging bag, used to prepare an antibacterial food packaging bag as described in any one of claims 1-7, characterized in that: The process includes step ① preparing bamboo fiber, modified ethylene composite copolymer and modified chitosan; step ② mixing bamboo fiber, TPS, modified ethylene composite copolymer and modified chitosan in parts by weight and feeding them into a screw extruder for extrusion granulation; step ③ melt blow molding the granulated material to obtain a pre-formed antibacterial food packaging bag; and step ④ cutting, trimming and / or printing and finishing the pre-formed antibacterial food packaging bag to obtain the finished antibacterial food packaging bag.

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