High-barrier antibacterial PE film and preparation method thereof

Abstract

The invention relates to a high-barrier antibacterial PE film and a preparation method thereof, preparation raw materials comprise antibacterial biochar and PE particles, the antibacterial biochar is biochar loaded with the antibacterial particles, and the micropore volume of the biochar accounts for 90-96% of the total pore volume. On one hand, the antibacterial biochar distributed on the surface of the PE film can play a better antibacterial role because antibacterial particles are distributed in mesopores and macropores in the surface of the biochar, and the pores allow moisture on the surface of the PE film to enter and contact with the antibacterial particles in the pores, so that the antibacterial role is played; on the other hand, the combination of the biochar material and the antibacterial particles can form a more complex pore structure to prevent gas / moisture from diffusing in the PE film, and even if the moisture on the surface of the PE film enters mesopores and macropores of the biochar, the moisture is difficult to further diffuse into the PE film through the biochar material. The PE film material provided by the scheme not only has good antibacterial performance, but also has better barrier performance, and has the characteristic of'surface wetting but not penetrating '.

Description

Technical Field

[0001] This application relates to the technical field of PE films, and particularly relates to a high-barrier antibacterial PE film and a preparation method thereof. Background Art

[0002] PE (Polyethylene, PE) is a thermoplastic resin polymerized from polyethylene monomers, with the chemical formula (C2H4) n , and it is one of the most produced general plastics. PE materials are widely used to manufacture films, packaging materials, containers, pipes, and insulating materials, etc. When PE films are applied in the field of food packaging, they are required to have certain antibacterial properties, that is, they can effectively inhibit or kill bacteria attached to their surfaces, thereby extending the shelf life of food. Traditional PE film materials achieve antibacterial effects by directly blending antibacterial particles such as nano-zinc oxide or nano-silver with PE particles. However, these materials are generally hydrophilic materials, and adding them to PE films will affect the water barrier performance of PE films; some researchers add hydrophobic materials such as silica particles to PE films, which can provide the water barrier performance of PE films. However, if antibacterial particles and hydrophobic materials are added simultaneously, the hydrophobic materials will have a shielding effect on the antibacterial particles. Antibacterial particles such as nano-zinc oxide need to contact with water to release Zn2+ or generate reactive oxygen species (ROS) to exert antibacterial effects. In this way, water cannot contact the nano-zinc oxide on the surface of the PE film material to produce antibacterial effects, resulting in a reduction in the antibacterial effect of the PE film. Therefore, it is difficult for the prior art to balance the antibacterial performance and high-barrier performance of PE film materials.

[0003] Based on this, it is necessary to provide a high-barrier antibacterial PE film and a preparation method thereof. Summary of the Invention

[0004] In order to solve the problem that it is difficult to balance the antibacterial performance and high-barrier performance of PE film materials, it is necessary to provide a high-barrier antibacterial PE film and a preparation method thereof.

[0005] In the first aspect of this application, a high-barrier antibacterial PE film is provided. The raw materials for preparation include antibacterial biochar and PE particles. The antibacterial biochar is biochar loaded with antibacterial particles, and the micropore volume of the biochar accounts for 90-96% of the total pore volume.

[0006] This solution uses biochar loaded with antibacterial particles as antibacterial biochar. The micropore (pore diameter < 2nm) volume of the biochar accounts for 90 - 96% of the total pore volume, that is, the volume ratio of mesopores (pore diameter 2 - 50nm) and macropores is 4 - 10%. The particle size of the antibacterial particles is generally 10 - 50nm, so that the antibacterial particles can be embedded in the mesopores and macropores of the biochar. On the one hand, the antibacterial biochar distributed on the surface of the PE film can play a better antibacterial role because its antibacterial particles are distributed in the mesopores and macropores on the surface of the biochar, and these pores allow the moisture on the surface of the PE film to enter and contact with the antibacterial particles inside to play an antibacterial role; on the other hand, the combination of the biochar material and the antibacterial particles can form a more complex pore structure that can prevent the diffusion of gas / moisture in the PE film, and it is difficult for the moisture on the surface of the PE film to further diffuse into the PE film even if it enters the mesopores and macropores of the biochar. Therefore, the PE film material of this solution not only has good antibacterial performance, but also has better barrier performance, with the characteristic of "surface wetting without penetration".

[0007] Furthermore, the biochar is coconut shell biochar. Coconut shell biochar has a natural hierarchical pore structure. Compared with other biochars, it has a higher proportion of micropore structure and better gas barrier effect; at the same time, its surface has abundant hydroxyl groups that can enhance the anchoring effect of antibacterial particles to reduce the dissolution rate of antibacterial particles.

[0008] Furthermore, by mass, the preparation raw materials include 100 parts of PE particles and 2 - 5 parts of antibacterial biochar. If the addition amount is too low, it is difficult to obtain better barrier and antibacterial effects; if the addition amount is too high, the particles are prone to agglomeration, resulting in a decrease in the barrier and antibacterial effects.

[0009] Furthermore, the antibacterial particles are nano - zinc oxide, and the preparation method of the antibacterial biochar is as follows: Biochar with a particle size of 80 - 100 mesh is placed in a zinc nitrate solution and mixed evenly, and sodium hydroxide solution is added dropwise until the pH = 10 - 11, and then stirred at a constant temperature of 60 - 70°C for 4 - 8 hours. The precipitate is collected by centrifugation, and the precipitate is washed with deionized water until it is neutral to obtain the antibacterial biochar. Compared with the impregnation method, this solution can reduce the risk of particle shedding of antibacterial particles.

[0010] Furthermore, the micropore volume of the biochar accounts for 96% of the total pore volume. Using the above - mentioned biochar can obtain the best effect.

[0011] Furthermore, the antibacterial particles contain at least one of nano - zinc oxide and nano - silver oxide. Both nano - zinc oxide and nano - silver oxide need to contact with moisture to play an antibacterial role and are suitable for this solution.

[0012] Furthermore, the antibacterial biochar is prepared by a physical mixing method, and the average particle size of the antibacterial particles is 10 - 50 nm. By the physical mixing method, the antibacterial particles can also be distributed in the mesopores and macropores of the biochar. At this time, the average particle size of the antibacterial particles matches the particle size of the mesopores of the biochar.

[0013] Furthermore, the surface of the antibacterial biochar is modified by maleic anhydride grafted polyethylene. Maleic anhydride grafted polyethylene can improve the compatibility between the antibacterial biochar and the PE film, so as to promote the uniform distribution of the antibacterial biochar and obtain better barrier properties and antibacterial properties.

[0014] The second aspect of the present invention provides a method for preparing the above-mentioned PE film, which includes the following steps: mixing PE particles and biochar particles and then extruding and granulating, and then blow molding to obtain the PE film.

[0015] The PE film obtained by the above preparation method has high barrier and strong antibacterial properties. Specific Embodiments

[0016] To facilitate the understanding of the present application, the present application will be described more comprehensively below. The present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0017] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In the description of the present application, the meaning of "several" is at least one, such as one, two, etc., unless otherwise clearly and specifically defined.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the description of the present application in this specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0019] In the present application, among the technical features described in an open-ended manner, there are included closed technical solutions composed of the listed features, as well as open technical solutions including the listed features.

[0020] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as every value between such minimum and maximum values. Further, when the range refers to integers, it includes every integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0021] In this application, the percentage content involved, unless otherwise specified, refers to the mass percentage for solid-liquid mixtures and solid-solid mixtures, and refers to the volume percentage for liquid-liquid mixtures.

[0022] In this application, the percentage concentration involved, unless otherwise specified, refers to the final concentration. The final concentration refers to the proportion of the added component in the system after adding the component.

[0023] In this application, the temperature parameter, unless otherwise specified, allows for both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument.

[0024] The "particles" mentioned in this application, or substances with a defined particle size distribution, do not necessarily have a spherical shape and may be irregular. They can be primary particles or secondary particles. The particle size of irregular particles is calculated as the average of their maximum diameter and minimum diameter.

[0025] Example 1: This example provides a highly barrier antibacterial PE film.

[0026] Preparation of antibacterial biochar: Immerse bamboo biochar (determined by BET nitrogen adsorption method, and the determination methods for other biochars are the same. Calculated by total pore volume, the micropore proportion is 91%, the mesopore proportion is 8%, the macropore proportion is 1%, and the particle size is 100 mesh) into a 0.5 mol / L zinc nitrate solution, and ultrasonically disperse for 30 minutes. The solid-liquid ratio is 1:10 (g / mL). Gradually add 3 mol / L sodium hydroxide solution until the pH equals 10, and stir at a constant temperature of 70 °C for 6 hours to form nanoparticles in the macropores and mesopores of coconut shell biochar. Centrifuge and collect the precipitate, wash it with deionized water until neutral, and vacuum dry at 80 °C for 12 hours to obtain antibacterial biochar particles loaded with zinc oxide.

[0027] Surface modification: Mix antibacterial biochar and maleic anhydride grafted polyethylene (mass ratio 1:0.2) in a mixer at 180 °C for 15 minutes.

[0028] Mixing and extrusion molding: The antibacterial biochar prepared by the above method and high-density polyethylene particles (the materials of high-density polyethylene particles in other examples and comparative examples are the same) are added to a twin-screw extruder at a mass ratio of 4:100 (and 0.5% by mass fraction of antioxidant 1010 is added) for mixing and extrusion granulation, and the extrusion temperature is 200 °C. The mixed particles are added to a blown film machine to obtain a high-barrier antibacterial PE film with a thickness of 30 μm.

[0029] Example 2: This example provides a high-barrier antibacterial PE film.

[0030] Preparation of antibacterial biochar: Immerse coconut shell biochar (with a micropore ratio of 96%, a mesopore ratio of 3.5%, and a macropore ratio of 0.5% based on the total pore volume) in a 0.5 mol / L zinc nitrate solution, ultrasonically disperse for 30 minutes, and the solid-liquid ratio is 1:10 (g / mL). Gradually add 3 mol / L sodium hydroxide solution until the pH equals 10, and stir at a constant temperature of 70 °C for 6 hours to form nanoparticles in the macropores and mesopores of the coconut shell biochar. Centrifuge and collect the precipitate, wash it with deionized water until neutral, and vacuum dry at 80 °C for 12 hours to obtain antibacterial biochar particles loaded with zinc oxide.

[0031] Surface modification: Mix the antibacterial biochar and maleic anhydride-grafted polyethylene (mass ratio 1:0.2) in a mixer at 180 °C for 15 minutes.

[0032] Mixing and extrusion molding: The antibacterial biochar prepared by the above method and high-density polyethylene particles are added to a twin-screw extruder at a mass ratio of 4:100 (and 0.5% by mass fraction of antioxidant 1010 is added) for mixing and extrusion granulation, and the extrusion temperature is 200 °C. The mixed particles are added to a blown film machine to obtain a high-barrier antibacterial PE film with a thickness of 30 μm.

[0033] Example 3: This example provides a high-barrier antibacterial PE film.

[0034] Preparation of antibacterial biochar: Immerse bamboo biochar (with a micropore ratio of 91%, a mesopore ratio of 8%, and a macropore ratio of 1%, particle size of 100 mesh) in a 0.5 mol / L zinc nitrate solution, ultrasonically disperse for 30 minutes, and the solid-liquid ratio is 1:10 (g / mL). Gradually add 3 mol / L sodium hydroxide solution until the pH equals 10, and stir at a constant temperature of 70 °C for 6 hours to form nanoparticles in the macropores and mesopores of the coconut shell biochar. Centrifuge and collect the precipitate, wash it with deionized water until neutral, and vacuum dry at 80 °C for 12 hours to obtain antibacterial biochar particles loaded with zinc oxide.

[0035] Surface modification: Mix the antibacterial biochar and maleic anhydride-grafted polyethylene (mass ratio 1:0.2) in a mixer at 180 °C for 15 minutes.

[0036] Hybrid extrusion molding: The antibacterial biochar prepared by the above method and high-density polyethylene particles are added to a twin-screw extruder at a mass ratio of 2:100 (and 0.5% by mass of antioxidant 1010 is added) for hybrid extrusion granulation, and the extrusion temperature is 200 °C. The mixed particles are added to a blown film machine to obtain a high-barrier antibacterial PE film with a thickness of 30 μm.

[0037] Example 4: This example provides a high-barrier antibacterial PE film.

[0038] Preparation of antibacterial biochar: Bamboo biochar (with a micropore ratio of 91%, a mesopore ratio of 8%, a macropore ratio of 1%, and a particle size of 100 mesh based on the total pore volume) is immersed in a 0.5 mol / L zinc nitrate solution, ultrasonically dispersed for 30 minutes, and the solid-liquid ratio is 1:10 (g / mL). 3 mol / L sodium hydroxide solution is added dropwise until the pH equals 11, and the mixture is stirred at a constant temperature of 60 °C for 4 hours to form nanoparticles in the macropores and mesopores of coconut shell biochar. The precipitate is centrifuged and collected, washed with deionized water until neutral, and vacuum dried at 80 °C for 12 hours to obtain antibacterial biochar particles loaded with zinc oxide.

[0039] Surface modification: The antibacterial biochar and maleic anhydride-grafted polyethylene (mass ratio 1:0.2) are mixed in a mixer at 180 °C for 15 minutes.

[0040] Hybrid extrusion molding: The antibacterial biochar prepared by the above method and high-density polyethylene particles are added to a twin-screw extruder at a mass ratio of 4:100 (and 0.5% by mass of antioxidant 1010 is added) for hybrid extrusion granulation, and the extrusion temperature is 200 °C. The mixed particles are added to a blown film machine to obtain a high-barrier antibacterial PE film with a thickness of 30 μm.

[0041] Example 5: This example provides a high-barrier antibacterial PE film.

[0042] Preparation of antibacterial biochar: Bamboo biochar (with a micropore ratio of 91%, a mesopore ratio of 8%, a macropore ratio of 1%, and a particle size of 100 mesh based on the total pore volume) is immersed in a 0.5 mol / L zinc nitrate solution, ultrasonically dispersed for 30 minutes, and the solid-liquid ratio is 1:10 (g / mL). 3 mol / L sodium hydroxide solution is added dropwise until the pH equals 10, and the mixture is stirred at a constant temperature of 70 °C for 6 hours to form nanoparticles in the macropores and mesopores of coconut shell biochar. The precipitate is centrifuged and collected, washed with deionized water until neutral, and vacuum dried at 80 °C for 12 hours to obtain antibacterial biochar particles loaded with zinc oxide.

[0043] Mixing and extrusion molding: The antibacterial biochar prepared by the above method and high-density polyethylene particles are added to a twin-screw extruder at a mass ratio of 4:100 (and 0.5% by mass of antioxidant 1010 is added) for mixing and extrusion granulation, and the extrusion temperature is 200 °C. The mixed particles are added to a blown film machine to obtain a high-barrier antibacterial PE film with a thickness of 30 μm.

[0044] Example 6: This example provides a high-barrier antibacterial PE film.

[0045] Preparation of antibacterial biochar: Silver oxide nanoparticles (particle size 30 nm) and bamboo biochar (with a micropore ratio of 91%, a mesopore ratio of 8%, and a macropore ratio of 1% in terms of total pore volume, and a particle size of 100 mesh) are mixed at a mass ratio of 5:100 so that the silver oxide nanoparticles fill the mesopores and macropores of the biochar to obtain the antibacterial biochar.

[0046] Surface modification: The antibacterial biochar and maleic anhydride-grafted polyethylene (mass ratio 1:0.2) are mixed in a mixer at 180 °C for 15 minutes.

[0047] Mixing and extrusion molding: The antibacterial biochar prepared by the above method and high-density polyethylene particles are added to a twin-screw extruder at a mass ratio of 4:100 (and 0.5% by mass of antioxidant 1010 is added) for mixing and extrusion granulation, and the extrusion temperature is 200 °C. The mixed particles are added to a blown film machine to obtain a high-barrier antibacterial PE film with a thickness of 30 μm.

[0048] Comparative Example 1: This comparative example provides a PE film.

[0049] High-density polyethylene particles are added to a blown film machine to obtain a PE film with a thickness of 30 μm.

[0050] Comparative Example 2: This comparative example provides a PE film.

[0051] Preparation of antibacterial biochar: Bamboo biochar (with a micropore ratio of 91%, a mesopore ratio of 8%, and a macropore ratio of 1% in terms of total pore volume, and a particle size of 100 mesh) Mixing and extrusion molding: Bamboo biochar (with a micropore ratio of 91%, a mesopore ratio of 8%, and a macropore ratio of 1% in terms of total pore volume, and a particle size of 100 mesh) and high-density polyethylene particles are added to a twin-screw extruder at a mass ratio of 4:100 (and 0.5% by mass of antioxidant 1010 is added) for mixing and extrusion granulation, and the extrusion temperature is 200 °C. The mixed particles are added to a blown film machine to obtain a PE film with a thickness of 30 μm.

[0052] Comparative Example 3: This comparative example provides a PE film.

[0053] Preparation of antibacterial biochar: Immerse the straw biochar (with a micropore ratio of 61%, a mesopore ratio of 28%, a macropore ratio of 11% in terms of total pore volume and a particle size of 100 mesh) into a 0.5 mol / L zinc nitrate solution, and ultrasonically disperse for 30 minutes with a solid-liquid ratio of 1:10 (g / mL). Dropwise add 3 mol / L sodium hydroxide solution until the pH equals 10, and stir at a constant temperature of 70 °C for 6 hours to form nanoparticles in the macropores and mesopores of the coconut shell biochar. Centrifuge and collect the precipitate, wash it with deionized water until neutral, and vacuum dry at 80 °C for 12 hours to obtain antibacterial biochar particles loaded with zinc oxide.

[0054] Surface modification: Mix the antibacterial biochar and maleic anhydride-grafted polyethylene (mass ratio 1:0.2) in a mixer at 180 °C for 15 minutes.

[0055] Mixing and extrusion molding: Add the antibacterial biochar prepared in the above manner and high-density polyethylene particles into a twin-screw extruder at a mass ratio of 4:100 (and add 0.5% by mass of antioxidant 1010) for mixing and extrusion granulation, and the extrusion temperature is 200 °C. Add the mixed particles into a blown film machine to prepare an antibacterial PE film with a thickness of 30 μm.

[0056] Test the barrier properties and antibacterial properties of the PE films in the above examples and comparative examples. Among them, the gas permeability is detected according to GB / T 1038-2000, the water permeability is detected according to GB / T 1037-1988, and the antibacterial property is detected according to QB / T 2591-2003 Table 1 Test results of the barrier properties and antibacterial properties of the examples and comparative examples.

[0057]

[0058] The data of Examples 1-6 are significantly better than those of Comparative Examples 1-3. This is because in this solution, biochar loaded with antibacterial particles is used as antibacterial biochar, and the volume of micropores (pore diameter < 2 nm) in the biochar accounts for 90-96% of the total pore volume, that is, the volume ratio of mesopores (pore diameter 2-50 nm) and macropores is 4-10%. The particle size of the antibacterial particles is generally 10-50 nm, so the antibacterial particles can be embedded in the mesopores and macropores of the biochar. On the one hand, the antibacterial biochar distributed on the surface of the PE film can play a better antibacterial role because its antibacterial particles are distributed in the mesopores and macropores on the surface of the biochar, and these pores allow the moisture on the surface of the PE film to enter and contact the antibacterial particles inside to play an antibacterial role; on the other hand, the combination of the biochar material and the antibacterial particles can form a more complex pore structure that can prevent the diffusion of gas / moisture in the PE film. Even if the moisture on the surface of the PE film enters the mesopores and macropores of the biochar, it is difficult to further diffuse through the biochar material into the interior of the PE film. Therefore, the PE film material of this solution not only has good antibacterial performance but also has better barrier performance, with the characteristic of "surface wetting without penetration". In Comparative Example 2, no antibacterial particles are loaded, its barrier performance is reduced and it has no antibacterial effect. In Comparative Example 3, straw biochar is used. The content of mesopores in this biochar is too high, and it is difficult for the antibacterial particles and the biochar to form a complex channel to play a barrier role. Moreover, due to the introduction of antibacterial particles, the water barrier performance of this PE film is relatively low.

[0059] Example 2 uses coconut shell biochar with a micropore ratio of 96%, and its barrier performance is better, and it can achieve a strong antibacterial effect; in Example 5, maleic anhydride grafted polyethylene is not used for surface modification, and the barrier performance is relatively poor, but it still has an antibacterial effect.

[0060] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A high-barrier antibacterial PE film, characterized in that, The preparation raw materials include antibacterial biochar and PE particles. The antibacterial biochar is biochar loaded with antibacterial particles, and the micropore volume of the biochar accounts for 90 - 96% of the total pore volume.

2. The PE film according to claim 1, wherein The biochar is coconut shell biochar.

3. The PE film according to claim 1, wherein By mass, the preparation raw materials include 100 parts of PE particles and 2 - 5 parts of antibacterial biochar.

4. The PE film according to claim 1, wherein The antibacterial particles include at least one of nano zinc oxide and nano silver oxide.

5. The PE film according to claim 1, wherein The antibacterial particles are nano zinc oxide. The preparation method of the antibacterial biochar is as follows: Place biochar with a particle size of 80 - 100 mesh in a zinc nitrate solution and mix evenly. Dropwise add sodium hydroxide solution until the pH = 10 - 11, stir at a constant temperature of 60 - 70 °C for 4 - 8 hours, centrifuge to collect the precipitate, and wash the precipitate with deionized water until it is neutral to obtain the antibacterial biochar.

6. The PE film according to claim 1, wherein The micropore volume of the biochar accounts for 96% of the total pore volume.

7. The PE film according to claim 1, wherein The antibacterial biochar is prepared by a physical mixing method, and the average particle size of the antibacterial particles is 10 - 50 nm.

8. The PE film according to claim 1, wherein The preparation raw materials also include an antioxidant.

9. The PE film according to claim 1, wherein, The surface of the antibacterial biochar is modified by maleic anhydride grafted polyethylene.

10. The preparation method of the PE film according to any one of claims 1-9, characterized in that, It includes the following steps: Mix PE particles and biochar particles and then extrude and granulate, and then blow mold to obtain a PE film.

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