Anti-aging antibacterial PE film and preparation method thereof

Abstract

The invention discloses an anti-aging antibacterial PE film and a preparation method thereof, and belongs to the technical field of high polymer materials. By adding the specific anti-aging reinforcing agent and the antibacterial agent, the ultraviolet aging resistance and antibacterial property of the PE film can be remarkably improved, and by compounding the specific high-density polyethylene resin and linear low-density polyethylene, the balance of the processability and mechanical property of the PE film can be promoted; the compatibilizer is added, so that the interface bonding of the anti-aging reinforcing agent and the antibacterial agent in a polyethylene matrix can be promoted, and the uniformity and the mechanical property of the PE film can be improved. Besides, the anti-aging reinforcing agent and the antibacterial agent have a synergistic effect, and titanium dioxide also has an antibacterial effect and can have a synergistic effect with the antibacterial agent, so that the long-acting antibacterial effect of the PE film can be improved; and the anti-aging reinforcing agent can effectively form ultraviolet shielding, so that the photodegradation probability of the antibacterial agent is reduced, the durability of the antibacterial effect is further improved, and the comprehensive performance is more excellent.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and more specifically, to an aging-resistant and antibacterial PE film and its preparation method. Background Technology

[0002] Polyethylene (PE) film is widely used in various fields such as agricultural covering, food packaging, medical protection, outdoor advertising, and building waterproofing due to its excellent mechanical properties, good transparency, and low cost. However, with the expansion of application areas and the increase in technical requirements, the performance of traditional PE film in terms of aging resistance and antibacterial properties still needs to be improved.

[0003] In terms of aging resistance, pure PE materials are prone to photo-oxidative degradation under long-term exposure to outdoor ultraviolet radiation, oxygen, heat, humidity, and other environmental factors. This leads to film embrittlement, yellowing, a sharp decline in mechanical properties, and a significantly shortened service life. Currently, common improvement methods involve adding light stabilizers and antioxidants to the PE matrix. However, conventional light stabilizers and antioxidants have limited compatibility with the PE matrix and are prone to physical migration during processing and use, resulting in blooming on the film surface. This not only affects appearance and hygiene but also leads to poor film durability. For example, Chinese patent application CN202311759539.0 discloses a weather-resistant polyvinyl acetal film and its preparation method. The raw materials include polyvinyl acetal resin, plasticizer, modifier, and antioxidant, resulting in a film with excellent optical properties and aging resistance.

[0004] In terms of antibacterial properties, ordinary PE films lack the ability to inhibit or kill microorganisms. In humid, nutrient-rich environments, bacteria and mold easily proliferate, leading to product deterioration and mold growth. Existing antibacterial PE films often employ blending or surface coating methods to add antibacterial agents such as silver ions, quaternary ammonium salts, and nano-titanium dioxide. For example, Chinese patent application CN202510834946.6 discloses a production process for an anti-fog antibacterial PE film, which imparts a certain antibacterial ability to the film by adding a modified zinc oxide-graphene composite antibacterial agent. However, these methods also suffer from the following problems: silver ions are expensive and prone to discoloration; small-molecule quaternary ammonium salts and other organic antibacterial agents exhibit migration, poor antibacterial durability, and may contaminate contact objects; and nano-inorganic particles easily aggregate in the matrix, affecting the mechanical properties of the PE film.

[0005] Simply adding anti-aging and antibacterial functional components to a PE matrix results in multiple small-molecule additives competing with each other in the non-polar PE matrix, leading to accelerated migration rates and even mutual interference, failing to achieve a synergistic effect of 1+1>2. Therefore, there is an urgent need in this field for a PE film and its preparation method that can simultaneously achieve durable and efficient anti-aging properties and broad-spectrum, long-lasting antibacterial activity, fundamentally solving the migration problem of functional additives and ensuring the film's stable performance and safety during long-term use. Summary of the Invention

[0006] In view of this, in order to solve one of the above-mentioned technical problems, the present invention provides an aging-resistant and antibacterial PE film and its preparation method, the specific technical solution of which is as follows: An aging-resistant and antibacterial PE film comprises 85-100 parts of polyethylene resin, 5-10 parts of aging-resistant reinforcing agent, 0.1-5 parts of antibacterial agent, 0.1-0.5 parts of compatibilizer, and 0.01-1 parts of initiator; The preparation method of the anti-aging enhancer is as follows: titanium dioxide is dispersed in anhydrous ethanol, ultrasonically treated to form a suspension, then a silane coupling agent is added, stirred, then a hindered amine light stabilizer, an ultraviolet absorber, tris(2-pyridinemethyl)amine and ethyl 2-bromoisobutyrate are added, and stirred to react to obtain the anti-aging enhancer. The method for preparing the antibacterial agent is as follows: chitosan solution is added to pyridine, and 2-bromopropionyl bromide is added. The reaction is stirred under the first condition, and then 2-(1,3-benzothiazol-2-thioalkyl)-N-(3,4-dichlorophenyl)acetamide and pentamethyldiethylenetriamine are added. Cuprous bromide is added under a nitrogen atmosphere, and the reaction is stirred under the second condition to obtain the antibacterial agent.

[0007] Furthermore, the polyethylene resin is composed of high-density polyethylene resin and linear low-density polyethylene in a weight ratio of (50~70):(30~50), and the melt index of the high-density polyethylene resin at 190°C and 2.16 kg is 1.2 g / 10 min; the melt index of the linear low-density polyethylene at 190°C and 2.16 kg is 1.7 g / 10 min.

[0008] Further, the hindered amine light stabilizer is at least one of 4-acryloyloxy-2,2,6,6-tetramethylpiperidine and 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine.

[0009] Further, the ultraviolet absorber is at least one of 2-hydroxy-4-(methacryloyloxy)benzophenone, 2-hydroxy-4-(2,3-dihydroxypropoxy)benzophenone, and 2-(4-N,N-diethylamino-2-hydroxybenzoyl)benzoic acid hexyl ester.

[0010] Furthermore, by weight, the proportions of titanium dioxide, anhydrous ethanol, silane coupling agent, hindered amine light stabilizer, ultraviolet absorber, tris(2-pyridinemethyl)amine and ethyl 2-bromoisobutyrate are (5~9):(7~15):(3~9):(1~5):(1~5):(1~5):(1~3).

[0011] Further, by weight, the ratio of chitosan solution, pyridine, 2-bromopropionyl bromide, 2-(1,3-benzothiazol-2-thioalkyl)-N-(3,4-dichlorophenyl)acetamide, pentamethyldiethylenetriamine and cuprous bromide is (10~20):(12~25):(5~9):(2~7):(1~3):(1~2).

[0012] Furthermore, the compatibilizer is at least one of maleic anhydride-grafted polyethylene copolymer and ethylene-vinyl acetate copolymer.

[0013] Further, the initiator is at least one selected from dicumyl peroxide, benzoyl peroxide, tert-butyl peroxylaurate, tert-butyl peroxybenzoate, and tert-butyl peroxyacetate.

[0014] In addition, the present invention also provides a method for preparing an aging-resistant and antibacterial PE film, the preparation method comprising the following steps: S1. Polyethylene resin, anti-aging reinforcing agent, antibacterial agent, compatibilizer and initiator are added to a mixer for premixing to obtain mixture A; S2. The mixture A is placed in a twin-screw extruder, melt-extruded, water-cooled and pelletized to obtain mixture B; S3. Place the mixture B in a blow molding machine and prepare an aging-resistant and antibacterial PE film through a blow molding process.

[0015] Further, in step S3, the blown film process is as follows: the temperature of the feeding section is 100~120℃, the temperature of the melting section is 150~170℃, the temperature of the homogenization section is 180~195℃, the temperature of the die head is 160~175℃, the temperature of the die is 160~170℃, the blow-up ratio is (2~3):1, and the stretching ratio is 2~3.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention significantly improves the UV aging resistance and antibacterial properties of PE film by adding specific anti-aging enhancers and antibacterial agents. Furthermore, the compounding of specific high-density polyethylene resin and linear low-density polyethylene helps to improve the balance between the processing performance and mechanical properties of the film. The addition of compatibilizers promotes the dispersion and interfacial bonding of anti-aging enhancers and antibacterial agents in the polyethylene matrix, which helps to improve the uniformity of film performance and mechanical properties, resulting in superior overall performance.

[0017] 2. The aging resistance enhancer of the present invention introduces a silane coupling agent, followed by a hindered amine light stabilizer and an ultraviolet absorber on the surface of titanium dioxide. Under the action of tris(2-pyridinemethyl)amine and ethyl 2-bromoisobutyrate, the reaction crosslinks to form a three-dimensional crosslinked network structure, which can effectively reduce the migration and precipitation of the hindered amine light stabilizer and ultraviolet absorber, overcome the shortcomings of traditional blending addition that is easy to lose and agglomerate, and achieve a significant aging resistance effect.

[0018] 3. The antibacterial agent of the present invention reacts with 2-bromopropionyl bromide on the primary amino and hydroxyl groups on the chitosan molecular chain to form a macromolecular initiator, and then introduces the antibacterial component of 2-(1,3-benzothiazol-2-thioalkyl)-N-(3,4-dichlorophenyl)acetamide to form a chemical covalent bond, which is not easy to migrate and provides a long-lasting antibacterial effect. Moreover, the prepared antibacterial agent has excellent compatibility with the PE matrix, is easy to disperse, does not easily bloom, and can exert a significant antibacterial effect.

[0019] 4. The aging resistance enhancer and antibacterial agent of the present invention have a synergistic effect. Titanium dioxide also has a certain antibacterial effect and can work synergistically with the antibacterial agent to help increase the long-term antibacterial effect of PE film. Moreover, the aging resistance enhancer can effectively form ultraviolet shielding, reduce the probability of photodegradation of antibacterial agent, and further improve the durability of antibacterial effect. Detailed Implementation

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0021] An aging-resistant and antibacterial PE film according to one embodiment of the present invention comprises 85 to 100 parts of polyethylene resin, 5 to 10 parts of aging-resistant reinforcing agent, 0.1 to 5 parts of antibacterial agent, 0.1 to 0.5 parts of compatibilizer, and 0.01 to 1 part of initiator; The preparation method of the anti-aging enhancer is as follows: titanium dioxide is dispersed in anhydrous ethanol, ultrasonically treated to form a suspension, then a silane coupling agent is added, stirred, then a hindered amine light stabilizer, an ultraviolet absorber, tris(2-pyridinemethyl)amine and ethyl 2-bromoisobutyrate are added, and stirred to react to obtain the anti-aging enhancer. The method for preparing the antibacterial agent is as follows: chitosan solution is added to pyridine, and 2-bromopropionyl bromide is added. The reaction is stirred under the first condition, and then 2-(1,3-benzothiazol-2-thioalkyl)-N-(3,4-dichlorophenyl)acetamide and pentamethyldiethylenetriamine are added. Cuprous bromide is added under a nitrogen atmosphere, and the reaction is stirred under the second condition to obtain the antibacterial agent.

[0022] In one embodiment, the polyethylene resin is composed of high-density polyethylene resin and linear low-density polyethylene in a weight ratio of (50~70):(30~50), and the high-density polyethylene resin has a melt index of 1.2 g / 10 min at 190°C and 2.16 kg; the linear low-density polyethylene has a melt index of 1.7 g / 10 min at 190°C and 2.16 kg.

[0023] In one embodiment, the hindered amine light stabilizer is at least one of 4-acryloyloxy-2,2,6,6-tetramethylpiperidine and 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine.

[0024] In one embodiment, the ultraviolet absorber is at least one of 2-hydroxy-4-(methacryloyloxy)benzophenone, 2-hydroxy-4-(2,3-dihydroxypropoxy)benzophenone, and 2-(4-N,N-diethylamino-2-hydroxybenzoyl)benzoic acid hexyl ester.

[0025] In one embodiment, the ratio of titanium dioxide, anhydrous ethanol, silane coupling agent, hindered amine light stabilizer, ultraviolet absorber, tris(2-pyridinemethyl)amine and ethyl 2-bromoisobutyrate by weight is (5~9):(7~15):(3~9):(1~5):(1~5):(1~5):(1~3).

[0026] In one embodiment, the silane coupling agent is at least one of 3-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and γ-aminopropyltriethoxysilane.

[0027] In one embodiment, the conditions for the ultrasonic treatment are: frequency of 20kHz to 25kHz, power of 50W to 100W, and time of 20min to 30min.

[0028] In one embodiment, the stirring conditions in the preparation method of the anti-aging enhancer are: stirring at a speed of 100 r / min to 500 r / min for 10 min to 30 min.

[0029] In one embodiment, the preparation method of the anti-aging enhancer includes the following stirring conditions: a rotation speed of 100 r / min to 500 r / min, a temperature of 60°C to 85°C, and a stirring reaction time of 40 min to 100 min.

[0030] In one embodiment, the chitosan solution, pyridine, 2-bromopropionyl bromide, 2-(1,3-benzothiazol-2-thioalkyl)-N-(3,4-dichlorophenyl)acetamide, pentamethyldiethylenetriamine and cuprous bromide are in the following weight ratios: (10~20):(12~25):(5~9):(2~7):(1~3):(1~2).

[0031] In one embodiment, the chitosan solution is prepared by adding chitosan to an aqueous acetic acid solution with a mass percentage concentration of 1% to 2%, and stirring at 40°C to 65°C for 30 to 60 minutes to obtain the chitosan solution.

[0032] In one embodiment, the ratio of chitosan to aqueous acetic acid solution is (3~9) g / 100 mL.

[0033] In one embodiment, the degree of deacetylation of the chitosan is ≥85%.

[0034] In one embodiment, in the preparation method of the antibacterial agent, the stirring reaction under the first condition is: stirring at a speed of 50 r / min to 200 r / min for 1 h to 3 h.

[0035] In one embodiment, in the preparation method of the antibacterial agent, the stirring reaction under the second condition is: stirring at a speed of 100 r / min to 300 r / min for 1 h to 3 h.

[0036] In one embodiment, the compatibilizer is at least one of maleic anhydride-grafted polyethylene copolymer and ethylene-vinyl acetate copolymer.

[0037] In one embodiment, the initiator is at least one selected from dicumyl peroxide, benzoyl peroxide, tert-butyl peroxylaurate, tert-butyl peroxybenzoate, and tert-butyl peroxyacetate.

[0038] In addition, the present invention also provides a method for preparing an aging-resistant and antibacterial PE film, the preparation method comprising the following steps: S1. Polyethylene resin, anti-aging reinforcing agent, antibacterial agent, compatibilizer and initiator are added to a mixer for premixing to obtain mixture A; S2. The mixture A is placed in a twin-screw extruder, melt-extruded, water-cooled and pelletized to obtain mixture B; S3. Place the mixture B in a blow molding machine and prepare an aging-resistant and antibacterial PE film through a blow molding process.

[0039] In one embodiment, in step S1, the premixing speed is 500 r / min to 1000 r / min, and the time is 10 min to 20 min.

[0040] In one embodiment, in step S2, the temperature of the twin-screw extruder is set to 160°C~210°C, and the screw speed is 100rpm~300rpm.

[0041] In one embodiment, in step S3, the blown film process is as follows: the temperature of the feeding section is 100~120℃, the temperature of the melting section is 150~170℃, the temperature of the homogenization section is 180~195℃, the temperature of the die head is 160~175℃, the temperature of the die is 160~170℃, the blow-up ratio is (2~3):1, and the draw ratio is 2~3.

[0042] The above-mentioned scheme adds specific anti-aging enhancers and antibacterial agents to the preparation of PE films. The anti-aging enhancer constructs a three-dimensional cross-linked network with titanium dioxide as the core and hindered amine light stabilizers and ultraviolet absorbers grafted onto the surface. This achieves efficient shielding of ultraviolet light and free radical capture, allowing the PE film to retain a high tensile strength retention rate even after accelerated aging, fundamentally solving the problems of easy migration and insufficient anti-aging performance of traditional additives. The antibacterial agent is prepared by converting 2-bromopropionyl bromide and chitosan into a macromolecular initiator, and then covalently grafting highly efficient antibacterial monomers. This produces a chemically bonded antibacterial agent, which not only endows the PE film with excellent initial antibacterial properties, but also effectively inhibits the physical migration of antibacterial components through strong chemical bonding, giving it long-lasting antibacterial properties and achieving long-lasting antibacterial effects. Overall, it can achieve significant anti-aging and antibacterial properties. Moreover, the anti-aging enhancer and antibacterial agent can form chemical covalent bonds with the PE matrix molecular chains, making them less prone to migration and resulting in more stable and durable performance.

[0043] The implementation scheme of the present invention will be described in detail below with reference to specific embodiments. The raw materials, reagents, etc. used in the embodiments that are not described in detail are all commercially available. Example 1:

[0044] A method for preparing an aging-resistant and antibacterial PE film includes the following steps: S1. By weight, add 100 parts of polyethylene resin, 7 parts of aging resistance reinforcing agent, 3 parts of antibacterial agent, 0.3 parts of maleic anhydride grafted polyethylene copolymer and 0.05 parts of dicumyl peroxide to a mixer and premix at a speed of 500 r / min for 20 min to obtain mixture A; The polyethylene resin is composed of high-density polyethylene resin and linear low-density polyethylene in a weight ratio of 60:40, and the melt index of the high-density polyethylene resin at 190°C and 2.16 kg is 1.2 g / 10 min; the melt index of the linear low-density polyethylene at 190°C and 2.16 kg is 1.7 g / 10 min. The method for preparing the anti-aging enhancer is as follows: 9 parts by weight of titanium dioxide are dispersed in 10 parts of anhydrous ethanol and ultrasonically treated for 30 minutes at a frequency of 20 kHz and a power of 50 W to form a suspension. Then, 5 parts of 3-aminopropyltriethoxysilane are added and stirred at 300 r / min for 25 minutes. Next, 3 parts of 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, 2 parts of 2-hydroxy-4-(methacryloyloxy)benzophenone, 3 parts of tris(2-pyridinemethyl)amine, and 1 part of ethyl 2-bromoisobutyrate are added and stirred at 200 r / min and a temperature of 65 °C for 60 minutes to obtain the anti-aging enhancer. The antibacterial agent is prepared as follows: 9g of chitosan with a degree of deacetylation of 90% is added to 100mL of acetic acid aqueous solution with a mass percentage concentration of 1%, and stirred at 55℃ for 45min to obtain a chitosan solution; 10 parts of the chitosan solution are added to 12 parts of pyridine by weight ratio, and 5 parts of 2-bromopropionyl bromide are added, and the mixture is stirred at 100r / min for 2h. Then, 3 parts of 2-(1,3-benzothiazol-2-thioalkyl)-N-(3,4-dichlorophenyl)acetamide and 1 part of pentamethyldiethylenetriamine are added. Under a nitrogen atmosphere, 1 part of cuprous bromide is added, and the mixture is stirred at 300r / min for 3h to obtain the antibacterial agent. S2. The mixture A is placed in a twin-screw extruder, melt-extruded, and the temperature of the twin-screw extruder is set to 175°C and the screw speed is 300 rpm. It is then water-cooled and pelletized to obtain mixture B. S3. The mixture B is placed in a blow molding machine and blown film is produced by means of the following process: the temperature of the feeding section is 100°C, the temperature of the melting section is 165°C, the temperature of the homogenization section is 185°C, the temperature of the die head is 165°C, the temperature of the die is 165°C, the blow-up ratio is 2.2:1, and the stretching ratio is 2. An aging-resistant and antibacterial PE film is thus prepared. Example 2:

[0045] A method for preparing an aging-resistant and antibacterial PE film includes the following steps: S1. By weight, add 100 parts of polyethylene resin, 8 parts of aging resistance reinforcing agent, 2 parts of antibacterial agent, 0.4 parts of maleic anhydride grafted polyethylene copolymer and 0.05 parts of dicumyl peroxide to a mixer and premix at a speed of 500 r / min for 20 min to obtain mixture A; The polyethylene resin is composed of high-density polyethylene resin and linear low-density polyethylene in a weight ratio of 60:40, and the melt index of the high-density polyethylene resin at 190°C and 2.16 kg is 1.2 g / 10 min; the melt index of the linear low-density polyethylene at 190°C and 2.16 kg is 1.7 g / 10 min. The preparation method of the anti-aging enhancer is as follows: 9 parts by weight of titanium dioxide are dispersed in 10 parts of anhydrous ethanol and ultrasonically treated for 25 min at a frequency of 25 kHz and a power of 50 W to form a suspension. Then, 7 parts of 3-aminopropyltriethoxysilane are added and stirred at 300 r / min for 30 min. Next, 2 parts of 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, 3 parts of 2-hydroxy-4-(methacryloyloxy)benzophenone, 3 parts of tris(2-pyridinemethyl)amine and 2 parts of ethyl 2-bromoisobutyrate are added and stirred at 200 r / min and a temperature of 65 °C for 60 min to obtain the anti-aging enhancer. The antibacterial agent is prepared as follows: 9g of chitosan with a degree of deacetylation of 90% is added to 100mL of acetic acid aqueous solution with a mass percentage concentration of 1%, and stirred at 60℃ for 45min to obtain a chitosan solution; 10 parts of the chitosan solution are added to 12 parts of pyridine by weight ratio, and 6 parts of 2-bromopropionyl bromide are added, and the mixture is stirred at 200r / min for 2h. Then, 4 parts of 2-(1,3-benzothiazol-2-thioalkyl)-N-(3,4-dichlorophenyl)acetamide and 2 parts of pentamethyldiethylenetriamine are added. Under a nitrogen atmosphere, 1 part of cuprous bromide is added, and the mixture is stirred at 300r / min for 3h to obtain the antibacterial agent. S2. The mixture A is placed in a twin-screw extruder, melt-extruded, and the temperature of the twin-screw extruder is set to 175°C and the screw speed is 300 rpm. It is then water-cooled and pelletized to obtain mixture B. S3. The mixture B is placed in a blow molding machine and blown film is produced by means of the following process: the temperature of the feeding section is 105°C, the temperature of the melting section is 170°C, the temperature of the homogenization section is 190°C, the temperature of the die head is 170°C, the temperature of the die is 170°C, the blow-up ratio is 2.2:1, and the stretching ratio is 2. An aging-resistant and antibacterial PE film is thus prepared. Example 3:

[0046] A method for preparing an aging-resistant and antibacterial PE film includes the following steps: S1. By weight, add 100 parts of polyethylene resin, 7 parts of aging resistance reinforcing agent, 3 parts of antibacterial agent, 0.5 parts of maleic anhydride grafted polyethylene copolymer and 0.02 parts of dicumyl peroxide to a mixer and premix at a speed of 500 r / min for 20 min to obtain mixture A; The polyethylene resin is composed of high-density polyethylene resin and linear low-density polyethylene in a weight ratio of 60:40, and the melt index of the high-density polyethylene resin at 190°C and 2.16 kg is 1.2 g / 10 min; the melt index of the linear low-density polyethylene at 190°C and 2.16 kg is 1.7 g / 10 min. The preparation method of the anti-aging enhancer is as follows: 9 parts by weight of titanium dioxide are dispersed in 10 parts of anhydrous ethanol and ultrasonically treated for 30 min at a frequency of 25 kHz and a power of 50 W to form a suspension. Then, 9 parts of 3-aminopropyltriethoxysilane are added and stirred at 300 r / min for 30 min. Next, 3 parts of 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, 2 parts of 2-hydroxy-4-(methacryloyloxy)benzophenone, 4 parts of tris(2-pyridinemethyl)amine, and 2 parts of ethyl 2-bromoisobutyrate are added and stirred at 200 r / min and a temperature of 70 °C for 65 min to obtain the anti-aging enhancer. The antibacterial agent is prepared as follows: 9g of chitosan with a degree of deacetylation of 90% is added to 100mL of acetic acid aqueous solution with a mass percentage concentration of 1%, and stirred at 65℃ for 50min to obtain a chitosan solution; 10 parts of the chitosan solution are added to 12 parts of pyridine by weight ratio, and 5 parts of 2-bromopropionyl bromide are added, and the mixture is stirred at 200r / min for 2h. Then, 5 parts of 2-(1,3-benzothiazol-2-thioalkyl)-N-(3,4-dichlorophenyl)acetamide and 3 parts of pentamethyldiethylenetriamine are added. Under a nitrogen atmosphere, 2 parts of cuprous bromide are added, and the mixture is stirred at 300r / min for 3h to obtain the antibacterial agent. S2. The mixture A is placed in a twin-screw extruder, melt-extruded, and the temperature of the twin-screw extruder is set to 165°C, the screw speed is 300 rpm, and then water-cooled and pelletized to obtain mixture B; S3. The mixture B is placed in a blow molding machine and blown film is produced by means of the following process: the temperature of the feeding section is 100°C, the temperature of the melting section is 170°C, the temperature of the homogenization section is 185°C, the temperature of the die head is 165°C, the temperature of the die is 165°C, the blow-up ratio is 2.2:1, and the stretching ratio is 2. An aging-resistant and antibacterial PE film is thus prepared.

[0047] Comparative Example 1: The difference between Comparative Example 1 and Example 3 is that Comparative Example 1 uses only a single high-density polyethylene resin, and the melt index of the high-density polyethylene resin at 190°C and 2.16 kg is 2.5 g / 10 min. The rest is the same as Example 3.

[0048] Comparative Example 2: The difference between Comparative Example 2 and Example 3 is that the preparation method of the aging resistance enhancer in Comparative Example 2 is different, while the rest is the same as in Example 3. The preparation method of the anti-aging enhancer in Comparative Example 2 is as follows: 9 parts by weight of titanium dioxide are dispersed in 10 parts of anhydrous ethanol and ultrasonically treated for 30 min at a frequency of 25 kHz and a power of 50 W to form a suspension. Then, 9 parts of 3-aminopropyltriethoxysilane are added and stirred at 300 r / min for 30 min. Next, 5 parts of 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, 4 parts of tris(2-pyridinemethyl)amine, and 2 parts of ethyl 2-bromoisobutyrate are added and stirred at 200 r / min and a temperature of 70 °C for 65 min to obtain the anti-aging enhancer.

[0049] Comparative Example 3: The difference between Comparative Example 3 and Example 3 is that the preparation method of the aging resistance enhancer in Comparative Example 3 is different, while the rest is the same as in Example 3. The preparation method of the anti-aging enhancer in Comparative Example 3 is as follows: 9 parts by weight of titanium dioxide are dispersed in 10 parts of anhydrous ethanol and ultrasonically treated for 30 min at a frequency of 25 kHz and a power of 50 W to form a suspension. Then, 9 parts of 3-aminopropyltriethoxysilane are added and stirred at a speed of 300 r / min for 30 min. Then, 5 parts of 2-hydroxy-4-(methacryloyloxy)benzophenone are added and stirred at a speed of 200 r / min and a temperature of 70 °C for 65 min to obtain the anti-aging enhancer.

[0050] Comparative Example 4: The difference between Comparative Example 4 and Example 3 is that no anti-aging enhancer was added in Comparative Example 4, but otherwise it is the same as Example 3.

[0051] Comparative Example 5: The difference between Comparative Example 5 and Example 3 is that Comparative Example 5 uses conventional chitosan as an antibacterial agent, that is, chitosan is added directly. Otherwise, it is the same as Example 3.

[0052] Comparative Example 6: The difference between Comparative Example 6 and Example 3 is that the preparation method of the antibacterial agent in Comparative Example 6 is different, while the rest is the same as in Example 3; The preparation method of the antibacterial agent in Comparative Example 6 is as follows: 9g of chitosan with a degree of deacetylation of 90% is added to 100mL of acetic acid aqueous solution with a mass percentage concentration of 1%, and stirred at 65℃ for 50min to obtain a chitosan solution; according to the weight ratio, 5 parts of 2-(1,3-benzothiazol-2-thioalkyl)-N-(3,4-dichlorophenyl)acetamide and 3 parts of pentamethyldiethylenetriamine are added to 10 parts of chitosan solution, and 2 parts of cuprous bromide are added under a nitrogen atmosphere, and the mixture is stirred at 300r / min for 3h to obtain the antibacterial agent.

[0053] 1. The PE film samples prepared in Examples 1-3 and Comparative Examples 1-6 were cut into 50mm × 50mm sizes. Tensile properties were tested according to GB1040.3-2006 standard using an intelligent electronic tensile testing machine. Test conditions: temperature 25℃, humidity 50%RH, effective tensile length of PE film: 28mm, width: 5mm, tensile speed: 50mm / min, three samples per group, and the arithmetic mean of the tensile strength results. UV aging resistance: UV light intensity 300W / m². 2 The aging temperature was 60℃, the aging time was 200h, and the tensile strength retention rate % was calculated as (tensile strength after aging / tensile strength before aging) × 100%. The results are shown in Table 1 below.

[0054] Table 1: Performance Test Results

[0055] Analysis of the data in Table 1 shows that the present invention, through component compounding, can effectively inhibit ultraviolet oxidative degradation, slow down the yellowing of PE film and the decline in mechanical properties. Furthermore, the aging resistance enhancer and antibacterial agent have a certain enhancing effect on mechanical properties, resulting in overall superior tensile strength and aging resistance. Compared with Example 3, Comparative Example 1 used a single high-density polyethylene resin, but its tensile strength and aging resistance were inferior to Example 3. This indicates that using two different polyethylene resins for compounding can balance processing fluidity and mechanical strength, promoting overall performance. The aging resistance enhancers in Comparative Examples 2 and 3 were prepared using different methods; Comparative Example 2 did not add an ultraviolet absorber, and Comparative Example 3 did not add a hindered amine light stabilizer, resulting in significantly worse aging resistance than Example 3. Comparative Example 4 did not add an aging resistance enhancer, and its tensile strength and aging resistance were significantly worse than Example 3. This demonstrates that the addition of the anti-aging enhancer in this invention significantly promotes mechanical and anti-aging properties. In Comparative Example 5, chitosan was directly used as an antibacterial agent, resulting in some migration and causing the stability of the PE film to be lower than that of Example 3, leading to a decrease in overall performance. In Comparative Example 6, the antibacterial agent was prepared using a different method and lacked the chemical bonding effect of the antibacterial agent of this invention, resulting in decreased compatibility and dispersibility with the PE matrix and thus lower stability than that of Example 3. This indicates that the addition of the anti-aging enhancer and antibacterial agent in this invention not only exerts their excellent anti-aging and antibacterial properties but also promotes the overall performance of the PE film.

[0056] II. Antibacterial performance test: Referencing GB / T31402-2015, the test bacteria were: *Escherichia coli* ATCC8739 and *Staphylococcus aureus* ATCC6538. The specific steps were as follows: Cut the sample to be tested into 50×50mm pieces. Dilute the bacterial suspension with 1 / 500 nutrient broth. Place 0.4mL of inoculum solution on the sample surface and cover with a 40×40mm film. Then, cover with a petri dish lid and incubate at 35℃ and 90% humidity for 24 hours. Finally, calculate the number of viable bacteria on the sample and the antibacterial rate. Antibacterial durability test: Expose the sample surface to an environment of 25℃ and 50% relative humidity, and store under constant temperature and humidity for 90 days. Then, refer to GB / T31402-2015 standard to test the antibacterial performance against *Escherichia coli* ATCC8739 and *Staphylococcus aureus* ATCC6538. The results are shown in Table 2 below.

[0057] Table 2: Antibacterial Properties

[0058] Analysis of the data in Table 2 shows that the PE film prepared by adding a specific antibacterial agent in this invention exhibits superior antibacterial rate. The antibacterial agent is chemically bonded to the chitosan backbone, reducing migration loss. Furthermore, the antibacterial agent demonstrates excellent compatibility with the PE matrix, resulting in superior and longer-lasting antibacterial properties. Compared to Example 3, Comparative Example 1 uses a single high-density polyethylene resin. The high molecular structure regularity of a single high-density polyethylene resin affects the dispersion and interfacial bonding of the antibacterial agent in the matrix, thereby accelerating the physical migration of the antibacterial agent and resulting in inferior antibacterial performance compared to Example 3. This demonstrates that the compounding of resin systems with different densities in this invention not only helps improve processing fluidity and mechanical properties but also plays a positive role in maintaining the stability of the antibacterial agent. Comparative Example 2's aging resistance enhancer lacks an ultraviolet absorber. Although it contains hindered amine light stabilizers and crosslinking components, the main function of an ultraviolet absorber is to absorb ultraviolet light and convert it into heat energy, reducing the impact of ultraviolet radiation on the material. The degradation of PE, including the reduction of the effect of ultraviolet light on antibacterial agents, indicates that ultraviolet absorbers play a positive role in protecting antibacterial agents from photoaging. Comparative Example 3 lacks a hindered amine light stabilizer. Hindered amine light stabilizers can capture free radicals generated by polymers under ultraviolet light and inhibit chain oxidation reactions. Although ultraviolet absorbers provide some shielding, they cannot completely prevent free radical generation. The absence of hindered amine light stabilizers also affects the degree of photo-oxidation during storage, and the generated free radicals also affect the performance of antibacterial agents, leading to a decrease in antibacterial durability. This indicates a synergistic effect between hindered amine light stabilizers and ultraviolet absorbers, which not only enhances the antibacterial properties of PE but also... The membrane's anti-aging properties promote the stability of the antibacterial agent. Comparative Example 4, without any anti-aging enhancer, showed significantly worse antibacterial performance than Example 3. This indicates that the anti-aging enhancer of the present invention not only improves anti-aging performance, but its three-dimensional cross-linked network structure with titanium dioxide as the core can also physically block the migration of the antibacterial agent and shield ultraviolet light to reduce photodegradation. Comparative Example 5 used unmodified conventional chitosan as the antibacterial agent. Although chitosan itself has antibacterial properties, the amino and hydroxyl groups on its molecular chain are polar groups, resulting in poor compatibility with the non-polar PE matrix and easy phase separation and physical migration. During storage, the chitosan gradually... The migration from the interior of the PE film to the surface and subsequent loss leads to a significant decrease in antibacterial activity. This indicates that the present invention significantly improves the compatibility and immobilization stability with the PE matrix by reacting chitosan with 2-bromopropionyl bromide to form a macromolecular initiator, and then covalently grafting antibacterial components (2-(1,3-benzothiazol-2-thioalkyl)-N-(3,4-dichlorophenyl)acetamide), and can exert excellent synergistic antibacterial effects. The preparation method of the antibacterial agent in Comparative Example 6 is different, resulting in antibacterial performance that is not as good as that in Example 3. This indicates that the antibacterial agent without 2-bromopropionyl bromide initiator treatment has weakened chemical covalent bonding and is prone to migration during long-term storage or use, leading to a decrease in antibacterial activity.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. An aging-resistant and antibacterial PE film, characterized in that, The mixture contains 85 to 100 parts of polyethylene resin, 5 to 10 parts of aging resistance reinforcing agent, 0.1 to 5 parts of antibacterial agent, 0.1 to 0.5 parts of compatibilizer, and 0.01 to 1 part of initiator. The polyethylene resin is composed of high-density polyethylene resin and linear low-density polyethylene in a weight ratio of (50~70):(30~50), and the melt index of the high-density polyethylene resin at 190°C and 2.16 kg is 1.2 g / 10 min; the melt index of the linear low-density polyethylene at 190°C and 2.16 kg is 1.7 g / 10 min. The preparation method of the anti-aging enhancer is as follows: titanium dioxide is dispersed in anhydrous ethanol, ultrasonically treated to form a suspension, then a silane coupling agent is added, stirred and treated, then a hindered amine light stabilizer, an ultraviolet absorber, tris(2-pyridinemethyl)amine and ethyl 2-bromoisobutyrate are added, and stirred and reacted to obtain the anti-aging enhancer. The method for preparing the antibacterial agent is as follows: chitosan solution is added to pyridine, and 2-bromopropionyl bromide is added. The reaction is stirred under the first condition, and then 2-(1,3-benzothiazol-2-thioalkyl)-N-(3,4-dichlorophenyl)acetamide and pentamethyldiethylenetriamine are added. Cuprous bromide is added under a nitrogen atmosphere, and the reaction is stirred under the second condition to obtain the antibacterial agent.

2. The aging-resistant and antibacterial PE film according to claim 1, characterized in that, The hindered amine light stabilizer is at least one of 4-acryloyloxy-2,2,6,6-tetramethylpiperidine and 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine.

3. The aging-resistant and antibacterial PE film according to claim 1, characterized in that, The ultraviolet absorber is at least one of 2-hydroxy-4-(methacryloyloxy)benzophenone, 2-hydroxy-4-(2,3-dihydroxypropoxy)benzophenone, and 2-(4-N,N-diethylamino-2-hydroxybenzoyl)benzoic acid hexyl ester.

4. The aging-resistant and antibacterial PE film according to claim 1, characterized in that, The ratio of titanium dioxide, anhydrous ethanol, silane coupling agent, hindered amine light stabilizer, ultraviolet absorber, tris(2-pyridinemethyl)amine and ethyl 2-bromoisobutyrate by weight is (5~9):(7~15):(3~9):(1~5):(1~5):(1~5):(1~3).

5. The aging-resistant and antibacterial PE film according to claim 1, characterized in that, The ratio of chitosan solution, pyridine, 2-bromopropionyl bromide, 2-(1,3-benzothiazol-2-thioalkyl)-N-(3,4-dichlorophenyl)acetamide, pentamethyldiethylenetriamine and cuprous bromide by weight is (10~20):(12~25):(5~9):(2~7):(1~3):(1~2).

6. The aging-resistant and antibacterial PE film according to claim 1, characterized in that, The compatibilizer is at least one of maleic anhydride-grafted polyethylene copolymer and ethylene-vinyl acetate copolymer.

7. The aging-resistant and antibacterial PE film according to claim 1, characterized in that, The initiator is at least one of dicumyl peroxide, benzoyl peroxide, tert-butyl peroxylaurate, tert-butyl peroxybenzoate, and tert-butyl peroxyacetate.

8. A method for preparing an aging-resistant and antibacterial PE film, characterized in that, The preparation method is used to prepare the aging-resistant and antibacterial PE film as described in any one of claims 1 to 7, and the preparation method includes the following steps: S1. Polyethylene resin, anti-aging reinforcing agent, antibacterial agent, compatibilizer and initiator are added to a mixer for premixing to obtain mixture A; S2. The mixture A is placed in a twin-screw extruder, melt-extruded, water-cooled and pelletized to obtain mixture B; S3. Place the mixture B in a blow molding machine and prepare an aging-resistant and antibacterial PE film through a blow molding process.

9. The preparation method according to claim 8, characterized in that, In step S3, the blown film process is as follows: the temperature of the feeding section is 100~120℃, the temperature of the melting section is 150~170℃, the temperature of the homogenization section is 180~195℃, the temperature of the die head is 160~175℃, the temperature of the die is 160~170℃, the blow-up ratio is (2~3):1, and the stretching ratio is 2~3.

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