Long-acting antibacterial degradable film material and preparation method thereof

Abstract

The invention relates to the technical field of degradable films, and particularly discloses a long-acting antibacterial degradable film material and a preparation method thereof. The long-acting antibacterial degradable film material is prepared from the following raw materials in parts by weight: 40 to 80 parts of matrix resin, 15 to 35 parts of hydrophobic modified chitosan, 5 to 10 parts of antibacterial agent master batch and 5 to 10 parts of reinforcing agent, the hydrophobic modified chitosan is stearaldehyde grafted chitosan at polylactic acid, and the antibacterial agent master batch is siloxane modified dioctadecyl dimethyl ammonium methyl carbonate at polylactic acid. The material can be well compatible with a hydrophobic polymer matrix, migration and loss of antibacterial components can be inhibited, long-acting stable antibacterial performance is achieved, good mechanical performance and barrier performance are kept, meanwhile, environment degradability of the whole life cycle is ensured, and therefore the urgent requirement of modern green packaging for high-performance, multifunctional and sustainable materials is met.

Description

Technical Field

[0001] This invention relates to the field of biodegradable film technology, and specifically discloses a long-lasting antibacterial biodegradable film material and its preparation method. Background Technology

[0002] With increasing global focus on food safety, environmental protection, and sustainable development, traditional petroleum-based plastic packaging is gradually being replaced by biodegradable materials due to its difficulty in degradation and its tendency to cause "white pollution." Meanwhile, food is susceptible to microbial contamination and spoilage during storage and transportation; therefore, developing novel packaging materials that combine excellent antibacterial properties with environmental friendliness has become a current research hotspot.

[0003] Chitosan, a natural cationic polysaccharide derived from the deacetylation of chitin in the shells of crustaceans, possesses broad-spectrum antibacterial properties, good biocompatibility, and complete biodegradability, making it widely used in food, pharmaceutical, and environmental protection fields. However, the practical application of chitosan in biodegradable packaging materials still faces several technical bottlenecks: First, chitosan molecules contain a large number of hydroxyl and amino groups, and the strong intermolecular and intramolecular hydrogen bonding results in poor thermal stability and a melting temperature close to the decomposition temperature. This makes it difficult to achieve uniform blending with mainstream hydrophobic biodegradable polymers (such as polylactic acid PLA, polybutylene adipate / terephthalate terephthalate PBAT, etc.) through conventional efficient thermal processing methods such as melt extrusion and injection molding, thus limiting its application in industrial continuous production.

[0004] Secondly, chitosan itself has strong hydrophilicity and is prone to absorbing moisture and swelling in high humidity or water-containing food packaging environments, which leads to a significant decrease in the moisture barrier performance of the film material. At the same time, the mechanical strength (such as tensile strength and elongation at break) is greatly reduced, making it difficult to meet actual packaging requirements.

[0005] Furthermore, existing technologies often employ the method of directly physical doping small-molecule antibacterial agents (such as silver ions, organic acids, and plant essential oils) into the polymer matrix to impart antibacterial properties to materials. However, these small molecules are prone to rapid loss during use due to diffusion, migration, or volatilization, which not only shortens the antibacterial efficacy period but may also pose potential food safety risks, failing to achieve stable and long-lasting antibacterial protection.

[0006] Although existing research has attempted to improve the processability and functionality of chitosan through strategies such as chemical modification and nanocompositing, these approaches often suffer from problems such as complex processes, high costs, poor scalability, or sacrifice of material biodegradability, making it difficult to simultaneously achieve multiple objectives such as processing performance, mechanical properties, antibacterial durability, and environmental friendliness. Therefore, there is an urgent need to develop a novel biodegradable antibacterial membrane material and its preparation method to address the shortcomings of existing technologies. Summary of the Invention

[0007] This invention provides a long-lasting antibacterial and biodegradable membrane material. Each component is well compatible with the hydrophobic polymer matrix, which can inhibit the migration and loss of antibacterial components, achieve long-lasting and stable antibacterial effect, and ensure environmental biodegradability throughout the entire life cycle while maintaining good mechanical and barrier properties, thereby meeting the urgent needs of modern green packaging for high-performance, multifunctional, and sustainable materials.

[0008] This invention is achieved through the following technical solution: On one hand, the present invention provides a long-lasting antibacterial and biodegradable membrane material, comprising the following raw materials by weight: 40-80 parts of matrix resin, 15-35 parts of hydrophobically modified chitosan, 5-10 parts of antibacterial agent masterbatch, and 5-10 parts of reinforcing agent; wherein the hydrophobically modified chitosan is stearaldehyde-grafted chitosan@polylactic acid, and the antibacterial agent masterbatch is siloxane-modified dioctadecyl dimethyl methyl carbonate ammonium@polylactic acid.

[0009] Utilizing the principle that the active amino and hydroxyl groups in chitosan can undergo condensation reactions with carboxyl, aldehyde, and epoxy groups, stearaldehyde is grafted onto chitosan molecules through group reactions, introducing hydrophobic molecular chains into chitosan. At the same time, the addition of polylactic acid (PLA) allows the formation of a polymer with PLA as the continuous phase and chitosan grafted with hydrophobic molecular chains as the dispersed phase during the blending process. This further improves the processing performance and hydrophobic properties of chitosan and ensures the compatibility between chitosan and the matrix resin.

[0010] By utilizing siloxane-modified bis(octadecyl)dimethyl methyl carbonate ammonium, the siloxane groups can interact with the end groups of polylactic acid (PLA), thus "locking" the antibacterial agent inside the PLA and effectively preventing its rapid loss during daily use (such as contact with water or friction), achieving long-lasting antibacterial effects. Simultaneously, PLA can improve the compatibility of the siloxane-modified bis(octadecyl)dimethyl methyl carbonate ammonium with the matrix resin, preventing phase separation. Furthermore, during the blending of the antibacterial agent masterbatch with other raw materials, the siloxane groups of the masterbatch can react with the hydroxyl groups on the surface of cellulose nanofibers and chitosan, and also interact with the ester groups or end groups of the matrix resin, forming strong covalent bonds at the interfaces of each component. This strong interfacial bonding effectively prevents the aggregation and phase separation of the hydrophobically modified chitosan, antibacterial agent masterbatch, and reinforcing agent in the polymer matrix, ensuring uniform stress transmission and ultimately resulting in a membrane material exhibiting uniform, stable, and excellent comprehensive performance.

[0011] Chitosan's cationic properties can adsorb and disrupt negatively charged bacterial cell membranes. After hydrophobic modification, its lipophilicity is enhanced, making it even more effective against bacterial lipid membranes. Antimicrobial masterbatches disrupt cell membrane structures through positive charge. The combination of hydrophobically modified chitosan and antimicrobial masterbatches can deliver multiple attacks on bacterial cell membranes, delaying the development of bacterial resistance and synergistically enhancing antimicrobial activity.

[0012] The matrix resin, as a continuous phase, constitutes the macroscopic framework of the material, providing basic strength and toughness. The reinforcing agent, as a reinforcing agent, is dispersed in the matrix to improve the mechanical properties of the material. Polylactic acid and chitosan dominate biodegradation, and polysaccharide and antibacterial agent masterbatch synergistically enhance antibacterial properties, thus providing a long-lasting antibacterial membrane material with good compatibility, long-lasting antibacterial properties, strong hydrophobicity, and complete biodegradability.

[0013] In this invention, the matrix resin includes one or more of polybutylene adipate terephthalate, polyethylene terephthalate-1,4-cyclohexanediol ester, and polylactic acid.

[0014] In this invention, the reinforcing agent comprises one or both of cellulose nanofibers and polyethylene terephthalate (PET). Cellulose nanofibers can form a dense network within the matrix, reducing internal porosity and creating a more compact structure, thus physically blocking microorganisms. Furthermore, strong Si-OC chemical bonds are formed between the cellulose nanofibers and the antibacterial agent masterbatch, thereby improving component compatibility, enhancing interfacial compatibility, preventing phase separation, and ensuring stable performance. Simultaneously, the large specific surface area of ​​cellulose nanofibers also contributes to the uniform loading and dispersion of the antibacterial agent masterbatch, allowing it to more fully contact and act on microorganisms. PET can serve as a robust framework, enhancing the mechanical strength of the membrane material.

[0015] In this invention, the modification method of the hydrophobic modified chitosan is as follows: chitosan, stearaldehyde, KH560, polylactic acid and antioxidant are blended, reacted and extruded in an inert atmosphere at 160-190°C, granulated underwater and dried to obtain the hydrophobic modified chitosan.

[0016] In this invention, the mass ratio of chitosan, stearaldehyde, KH560, polylactic acid and antioxidant is 100:20-30:8-12:15-25:0.3-1.5.

[0017] In this invention, the method for preparing the antibacterial agent masterbatch is as follows: a. Mix bis(octadecylmethyl) tertiary ammonium, KH550 and dimethyl carbonate, and react at 100-130℃ for 6-9 hours to obtain a paste-like siloxane-modified bis(octadecyl) dimethyl carbonate ammonium. After distillation and purification, siloxane-modified bis(octadecyl) methyl carbonate ammonium is obtained. b. Siloxane-modified dioctadecylmethyl methyl carbonate ammonium, polylactic acid and antioxidant are blended, reacted and extruded at 170-180℃, and granulated to obtain halogen-free hydrophobic modified quaternary ammonium salt antibacterial agent masterbatch.

[0018] Utilizing the nucleophilic substitution reaction of tertiary ammonium, dioctadecylmethyl tertiary ammonium and dimethyl carbonate react under high pressure in a reactor with a catalyst. The byproducts are then separated, and the mixture is extruded and granulated with polylactic acid and an antioxidant to obtain a hydrophobically modified quaternary ammonium salt antibacterial agent masterbatch. This quaternary ammonium salt antibacterial agent is halogen-free, exhibits high safety and environmental friendliness, and, due to hydrophobic modification, demonstrates better dispersibility in hydrophobic resins.

[0019] In this invention, in step a, the mass ratio of the dioctadecylmethyl tertiary ammonium, KH550 and dimethyl carbonate is 100:5-15:170-190.

[0020] In this invention, in step b, the mass ratio of the siloxane-modified dioctadecylmethyl methyl carbonate ammonium, polylactic acid, and antioxidant is 25-35:60-80:0.3-1.3.

[0021] In this invention, the antioxidant includes one or two of antioxidant 1010, antioxidant 1076, and antioxidant 168.

[0022] On the other hand, the present invention provides a method for preparing a long-lasting antibacterial biodegradable membrane material, comprising the following steps: melting and blending a matrix resin, hydrophobically modified chitosan, antibacterial agent masterbatch and reinforcing agent, and then extruding and blowing or casting the mixture to obtain the long-lasting antibacterial biodegradable membrane material.

[0023] This invention utilizes a melt chemical modification method to introduce hydrophobic molecular chains into chitosan molecules, preparing hydrophobically modified chitosan. When this modified chitosan is used in combination with antibacterial masterbatch, its hydrophobic structure provides excellent compatibility with the matrix resin, allowing it to be uniformly dispersed in the polymer resin. Through extrusion film formation, a biodegradable membrane material with long-lasting antibacterial function is ultimately obtained, increasing the membrane material's service life. Simultaneously, it possesses good hydrophobicity and mechanical properties, making it suitable for packaging high-moisture foods and fruits and vegetables for long-term preservation.

[0024] The technical solution of the present invention has at least the following advantages and beneficial effects: 1. Excellent compatibility and dispersibility: By hydrophobically modifying chitosan and quaternary ammonium salt antibacterial agents, their compatibility with hydrophobic and biodegradable matrix resins such as PLA and PBAT is fundamentally improved, avoiding the decline in mechanical properties and structural defects of the membrane material caused by phase separation, and ensuring the uniform dispersion of functional components in the matrix.

[0025] 2. Long-lasting antibacterial properties: Modified chitosan itself possesses antibacterial properties, and its synergistic effect with the antibacterial masterbatch broadens the antibacterial spectrum. More importantly, the hydrophobically modified quaternary ammonium salt antibacterial agent is encapsulated by hydrophobic molecular chains, which helps the antibacterial agent to be more stably fixed in the polymer network, slowing down the migration and loss rate of the antibacterial agent, thereby achieving long-lasting antibacterial effects.

[0026] 3. Excellent hydrophobicity and application performance: The introduced hydrophobic segments significantly improve the overall hydrophobicity of the membrane material, making it more suitable for packaging foods and fruits and vegetables with high moisture content, effectively blocking moisture and extending the shelf life.

[0027] 4. Fully biodegradable and environmentally friendly: All components are biodegradable materials, and the final product can degrade into carbon dioxide and water under specific conditions after use and disposal, which meets environmental protection requirements.

[0028] 5. Excellent processing performance: The melt chemical modification and melt extrusion film forming process mainly adopted in this invention is simple, efficient, solvent-free, green and environmentally friendly, and very suitable for large-scale industrial production. Attached Figure Description

[0029] Figure 1 This is a schematic diagram illustrating the preparation of hydrophobically modified chitosan according to an embodiment of the present invention. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0031] Example 1 A method for preparing a long-lasting antibacterial and biodegradable membrane material includes the following steps: Preparation of hydrophobically modified chitosan: Chitosan, stearal, KH560, polylactic acid, and antioxidant 1010 were blended in a mass ratio of 100:25:10:20:0.5, then fed into a twin-screw extruder and reacted and extruded at 180°C in an inert atmosphere. The mixture was then granulated underwater and dried to obtain the final product. (Refer to...) Figure 1 .

[0032] Preparation of antibacterial agent masterbatch: a. Add bis(octadecylmethyl)-tert-ammonium, KH550 and dimethyl carbonate in a mass ratio of 100:10:180 into a high-pressure reactor and react at 110°C for 8 hours to obtain a paste-like siloxane-modified bis(octadecyl)-dimethyl ammonium carbonate. After distillation and purification, siloxane-modified bis(octadecyl)-dimethyl ammonium carbonate is obtained. b. Siloxane-modified dioctadecylmethyl methyl carbonate ammonium, polylactic acid and antioxidant 1076 are blended in a mass ratio of 30:70:0.5, reacted and extruded at 180°C, and granulated to obtain halogen-free hydrophobic modified quaternary ammonium salt antibacterial agent masterbatch.

[0033] Preparation of long-lasting antibacterial biodegradable film material: polylactic acid (PLA), hydrophobically modified chitosan, polyethylene terephthalate (PET) and antibacterial agent masterbatch are added to a high-speed mixer at a ratio of 65:20:10:5 and then mixed. The mixture is then added to an extrusion casting machine to form a film, thereby obtaining a long-lasting antibacterial biodegradable cast film.

[0034] Example 2 A method for preparing a long-lasting antibacterial and biodegradable membrane material includes the following steps: Preparation of hydrophobically modified chitosan: Chitosan, stearaldehyde, KH560, polylactic acid and antioxidant 1076 were mixed in a mass ratio of 100:20:8:15:0.3, then added to a twin-screw extruder and reacted and extruded at 160°C in an inert atmosphere. After underwater granulation and drying, the mixture was obtained.

[0035] Preparation of antibacterial agent masterbatch: a. Add bis(octadecylmethyl)-tert-ammonium, KH550 and dimethyl carbonate in a mass ratio of 100:5:170 into a high-pressure reactor and react at 100°C for 6 hours to obtain a paste-like siloxane-modified bis(octadecyl)-dimethyl ammonium carbonate. After distillation and purification, siloxane-modified bis(octadecyl)-dimethyl ammonium carbonate is obtained. b. Siloxane-modified dioctadecylmethyl methyl carbonate ammonium, polylactic acid and antioxidant 1010 are blended at a mass ratio of 25:60:0.3, reacted and extruded at 170℃, and granulated to obtain halogen-free hydrophobic modified quaternary ammonium salt antibacterial agent masterbatch.

[0036] Preparation of long-lasting antibacterial and biodegradable film material: polyethylene terephthalate-1,4-cyclohexanediethanol ester (PCTG), hydrophobically modified chitosan, polyethylene terephthalate (PET) and antibacterial agent masterbatch are added to a high-speed mixer in a ratio of 45:35:10:10 and then added to an extrusion casting machine to form a film, thereby obtaining a long-lasting antibacterial and biodegradable cast film.

[0037] Example 3 A method for preparing a long-lasting antibacterial and biodegradable membrane material includes the following steps: Preparation of hydrophobically modified chitosan: Chitosan, stearaldehyde, KH560, polylactic acid and antioxidants (antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1) are mixed in a mass ratio of 100:30:12:25:1.5, then fed into a twin-screw extruder and reacted and extruded at 190°C in an inert atmosphere. After underwater granulation and drying, the product is obtained.

[0038] Preparation of antibacterial agent masterbatch: a. Add bis(octadecylmethyl)-tert-ammonium, KH550 and dimethyl carbonate in a mass ratio of 100:15:190 into a high-pressure reactor and react at 130℃ for 9 hours to obtain a paste-like siloxane-modified bis(octadecyl)-dimethyl ammonium carbonate. After distillation and purification, siloxane-modified bis(octadecyl)-dimethyl ammonium carbonate is obtained. b. Siloxane-modified dioctadecylmethyl methyl carbonate ammonium, polylactic acid and antioxidant 1010 are blended in a mass ratio of 35:80:1.3, reacted and extruded at 180°C, and granulated to obtain halogen-free hydrophobic modified quaternary ammonium salt antibacterial agent masterbatch.

[0039] Preparation of long-lasting antibacterial and biodegradable membrane material: Polybutylene adipate terephthalate (PBAT), hydrophobically modified chitosan, cellulose nanofibers and antibacterial agent masterbatch are added to a high-speed mixer in a ratio of 80:15:5:5 and then mixed. The mixture is then added to a blown film unit and undergoes processes such as melt plasticizing, blending, extrusion, cooling and shaping, traction, winding and packaging to obtain a long-lasting antibacterial and biodegradable membrane material.

[0040] Comparative Example 1 The difference between this comparative example and Example 1 is that the hydrophobic modified chitosan is replaced with ordinary chitosan.

[0041] Comparative Example 2 The difference between this comparative example and Example 1 is that the hydrophobically modified chitosan is stearaldehyde-grafted chitosan.

[0042] Comparative Example 3 The difference between this comparative example and Example 1 is that the antibacterial agent masterbatch is dioctadecyl dimethyl methyl carbonate ammonium@polylactic acid.

[0043] Performance Testing The membrane materials prepared in the examples and comparative examples were subjected to performance tests.

[0044] Tensile property test: Refer to GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets".

[0045] Antibacterial performance test: Refer to GB / T 31402-2015 "Test Method for Antibacterial Performance of Plastic Surfaces". The test bacteria are Staphylococcus aureus and Escherichia coli.

[0046] Antimicrobial performance durability test: The membrane materials prepared in the examples and comparative examples were immersed in a solution of simulated food medium (water, 10% (v / v) ethanol, 3% (v / v) acetic acid), left to stand for 30 days, and then removed and subjected to antimicrobial performance test.

[0047] Water vapor permeability: Refer to GB / T 1037-1988 "Test method for water vapor permeability of plastic films and sheets - cup method".

[0048] Contact angle: Refer to GB / T 30447–2013 "Method for measuring contact angle of nanofilms".

[0049] Table 1 Performance test results of membrane materials

[0050] In the tensile strength test conducted at 60℃ for one month, the tensile strength of the membrane material prepared in Comparative Example 1 decreased, while the tensile strength of the membrane materials prepared in Examples 1-3 remained unchanged. This indicates that hydrophobically modified chitosan can improve the mechanical properties of the membrane material. In Comparative Example 2, stearaldehyde-grafted chitosan was used, resulting in a decrease in both the tensile strength and contact angle of the membrane material. This indicates that stearaldehyde-grafted chitosan@polylactic acid can improve compatibility with the matrix resin and enhance the mechanical and hydrophobic properties of the material. In Comparative Example 3, the antibacterial masterbatch was bis(octadecyl dimethyl methyl carbonate)@polylactic acid. The tensile strength and antibacterial rate of the membrane material decreased, while the water vapor permeation increased. This indicates that siloxane-modified bis(octadecyl dimethyl methyl carbonate)@polylactic acid can improve the mechanical properties, barrier properties, and antibacterial rate of the membrane material.

[0051] In summary, the long-lasting antibacterial and biodegradable membrane material provided by this invention has good compatibility with the hydrophobic polymer matrix, which helps to inhibit the migration and loss of antibacterial components, achieving long-lasting and stable antibacterial effects, while maintaining good mechanical and barrier properties, thus meeting the urgent needs of modern green packaging for high-performance, multifunctional, and sustainable materials.

[0052] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A long-lasting antibacterial and biodegradable membrane material, characterized in that, The product comprises the following raw materials by weight: 40-80 parts of matrix resin, 15-35 parts of hydrophobically modified chitosan, 5-10 parts of antibacterial agent masterbatch, and 5-10 parts of reinforcing agent; wherein the hydrophobically modified chitosan is stearaldehyde-grafted chitosan@polylactic acid, and the antibacterial agent masterbatch is siloxane-modified dioctadecyl dimethyl methyl carbonate ammonium@polylactic acid.

2. The long-lasting antibacterial biodegradable membrane material according to claim 1, characterized in that, The matrix resin includes one or more of polybutylene adipate terephthalate, polyethylene terephthalate-1,4-cyclohexanediol ester, and polylactic acid.

3. The long-lasting antibacterial biodegradable membrane material according to claim 1, characterized in that, The reinforcing agent includes one or both of cellulose nanofibers and polyethylene terephthalate.

4. The long-lasting antibacterial biodegradable membrane material according to claim 1, characterized in that, The modification method of the hydrophobic modified chitosan is as follows: chitosan, stearaldehyde, KH560, polylactic acid and antioxidant are mixed, reacted and extruded in an inert atmosphere at 160-190°C, and then granulated and dried underwater to obtain the hydrophobic modified chitosan.

5. The long-lasting antibacterial biodegradable membrane material according to claim 4, characterized in that, The mass ratio of chitosan, stearaldehyde, KH560, polylactic acid and antioxidant is 100:20-30:8-12:15-25:0.3-1.

5.

6. The long-lasting antibacterial biodegradable membrane material according to claim 1, characterized in that, The method for preparing the antibacterial agent masterbatch is as follows: a. Mix bis(octadecylmethyl) tertiary ammonium, KH550 and dimethyl carbonate, and react at 100-130℃ for 6-9 hours to obtain a paste-like siloxane-modified bis(octadecyl) dimethyl carbonate ammonium. After distillation and purification, siloxane-modified bis(octadecyl) methyl carbonate ammonium is obtained. b. Siloxane-modified dioctadecylmethyl methyl carbonate ammonium, polylactic acid and antioxidant are blended, reacted and extruded at 170-180℃, and granulated to obtain halogen-free hydrophobic modified quaternary ammonium salt antibacterial agent masterbatch.

7. The long-lasting antibacterial biodegradable membrane material according to claim 6, characterized in that, In step a, the mass ratio of the dioctadecylmethyl tertiary ammonium, KH550 and dimethyl carbonate is 100:5-15:170-190.

8. The long-lasting antibacterial biodegradable membrane material according to claim 6, characterized in that, In step b, the mass ratio of the siloxane-modified dioctadecylmethyl methyl carbonate ammonium, polylactic acid, and antioxidant is 25-35:60-80:0.3-1.

3.

9. The long-lasting antibacterial biodegradable membrane material according to claim 4 or 6, characterized in that, The antioxidant includes one or two of antioxidant 1010, antioxidant 1076, and antioxidant 168.

10. The method for preparing the long-lasting antibacterial biodegradable membrane material according to any one of claims 1-9, characterized in that, Includes the following steps: The matrix resin, hydrophobically modified chitosan, antibacterial masterbatch and reinforcing agent are melt-blended and then extruded into blown film or cast film to obtain the long-lasting antibacterial biodegradable film material.

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