High-strength polyethylene film and preparation method thereof

Abstract

The invention discloses a high-strength polyethylene film and a preparation method thereof, and relates to the technical field of high polymer materials. The invention discloses a high-strength polyethylene film. The high-density polyethylene composite material is prepared from the following raw materials in parts by weight: 35 to 45 parts of high-density polyethylene, 25 to 35 parts of linear low-density polyethylene, 12 to 18 parts of ethylene-vinyl acetate copolymer, 5 to 10 parts of nano silicon dioxide, 3 to 7 parts of organic montmorillonite, 1.5 to 3.5 parts of hindered amine light stabilizer, 1.5 to 2.5 parts of antioxidant 1010, 0.8 to 1.2 parts of calcium stearate, 0.8 to 1.2 parts of zinc stearate, 0.8 to 1.2 parts of silane coupling agent and 4 to 6 parts of maleic anhydride grafted polyethylene. The composite material is prepared from the following components in parts by weight: 1.5-3.5 parts of a quaternized chitosan-nano silver compound, 6-9 parts of a modified toughening agent, 4-7 parts of a modified heat-resistant agent, 1.5-3.5 parts of a processing aid, 0.15-0.35 part of dibenzoyl peroxide and 0.5-1.5 parts of a nucleating agent DBS. The composite material is excellent in comprehensive performance, high in strength, good in flexibility and puncture resistance, excellent in aging resistance, heat resistance, chemical resistance and antibacterial property, good in processability, capable of meeting the requirements of multiple fields such as packaging and agriculture, scientific in preparation method and high in practical value.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and specifically relates to a high-strength polyethylene film and a preparation method thereof. Background Art

[0002] In the field of polymer materials, polyethylene films are widely used, covering many industries such as packaging, agriculture, and construction. However, existing polyethylene films have a series of problems, seriously restricting their further development and application.

[0003] In terms of anti-aging, ordinary polyethylene films are greatly affected by ultraviolet rays. When used outdoors, aging phenomena such as yellowing, embrittlement, and decline in mechanical properties will occur within a short time, greatly shortening the service life. In terms of heat resistance, at high temperatures, the film is prone to softening and deformation, and cannot be used in some scenarios with special temperature requirements. The chemical resistance is also not ideal. When in contact with chemical substances such as acids, alkalis, and organic solvents, the structure is easily damaged, resulting in performance deterioration.

[0004] From the perspective of mechanical properties, its puncture resistance is weak, and it is extremely easy to be damaged when acted upon by sharp objects, making it difficult to provide reliable protection. In terms of antibacterial properties, in fields such as food and medical where extremely high hygiene standards are required, ordinary polyethylene films lack antibacterial properties and cannot effectively inhibit the growth and reproduction of microorganisms, posing a great hygienic and safety hazard. In addition, its processing performance is not good, and problems such as melt fracture and uneven thickness are prone to occur during the processing process, not only reducing production efficiency but also affecting product quality. Therefore, it is extremely urgent to develop a high-strength polyethylene film and a preparation method thereof that can overcome the above defects, which is of great significance for promoting the development of related industries. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention provides a high-strength polyethylene film and a preparation method thereof, which solve the above problems.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions: A high-strength polyethylene film, comprising the following raw materials in parts by weight: 35-45 parts of high-density polyethylene, 25-35 parts of linear low-density polyethylene, 12-18 parts of ethylene-vinyl acetate copolymer, 5-10 parts of nano-silica, 3-7 parts of organic montmorillonite, 1.5-3.5 parts of hindered amine light stabilizer, 1.5-2.5 parts of antioxidant 1010, 0.8-1.2 parts of calcium stearate, 0.8-1.2 parts of zinc stearate, 0.8-1.2 parts of silane coupling agent, 4-6 parts of maleic anhydride grafted polyethylene, 1.5-3.5 parts of quaternized chitosan-nano silver composite, 6-9 parts of modified toughening agent, 4-7 parts of modified heat-resistant agent, 1.5-3.5 parts of processing aid, 0.15-0.35 parts of dibenzoyl peroxide, 0.5-1.5 parts of nucleating agent DBS.

[0007] Furthermore, the preparation steps of the modified toughening agent are as follows: A1. In a reaction vessel, maleic anhydride, toluene, and 4-vinyl aniline are added in sequence. The temperature of the reaction system is maintained at 70 °C, and the mixture is stirred and reacted for 2.5 h. After the reaction is completed, tetrahydrofuran is added, and the mixture is continuously stirred in an ice-water bath for 20 min. Subsequently, triethylamine is added, and the reaction continues for 40 min. After the reaction is completed, the reaction solution is first washed with dilute hydrochloric acid, then washed with deionized water, then dried with anhydrous sodium sulfate, the desiccant is filtered off, and finally the solvent is removed by rotary evaporation to obtain Compound I; A2. γ-Aminopropyltrimethoxysilane is added to ethanol and stirred for 50 min. Then, Compound I, acetone, and triethylamine are added, and the mixture is stirred at room temperature for 5.5 h. After the reaction is completed, the solvent is removed by rotary evaporation, and then washed with a mixed solution of ethanol and water, and dried to obtain Intermediate II; A3. Intermediate II is mixed with an ethanol-water mixed solution at 45 °C for 30 min. Under nitrogen protection, toluene and isophorone diisocyanate are added, the reaction temperature is raised to 90 °C, and the mixture is stirred and reacted for 3.5 h to prepare the modified toughening agent.

[0008] Furthermore, in A1, the dosage ratio of maleic anhydride, toluene, 4-vinyl aniline, tetrahydrofuran, and triethylamine is 13 g: 110 mL: 20 g: 30 mL: 11 g; the stirring speed is 300 r / min; the initial rotary evaporation temperature is 40 °C. After tetrahydrofuran is distilled off, the temperature is raised to 60 °C to distill off toluene; in A2, the dosage ratio of γ-aminopropyltrimethoxysilane, ethanol, Compound I, acetone, and triethylamine is 7 g: 190 mL: 13 g: 40 mL: 5 g; the stirring speed is 300 r / min; ethanol and water are mixed in a volume ratio of 4:1; the initial rotary evaporation temperature is 40 °C. After acetone is distilled off, the temperature is raised to 70 °C to distill off ethanol, and the product is dried at 60 °C for 4 h; in A3, the dosage ratio of Intermediate II, ethanol-water mixed solution, toluene, and isophorone diisocyanate is 15 g: 250 mL: 50 mL: 15 g; ethanol and water are mixed in a volume ratio of 6:1; the stirring speed is 300 r / min.

[0009] During the preparation of the modified toughening agent, the reaction of maleic anhydride with 4-vinyl aniline introduces double bonds and polar groups, and subsequent reaction with γ-aminopropyltrimethoxysilane introduces siloxane groups, enhancing the compatibility with inorganic fillers. Finally, reaction with isophorone diisocyanate forms a flexible polyurethane structure, and these structures are intertwined with each other in the film, effectively dispersing stress and improving the flexibility and impact resistance of the film.

[0010] Furthermore, the preparation steps of the modified heat-resistant agent are as follows: B1. Add terephthalic acid, melamine, and urea into a three-necked flask. First, heat the reaction system to 140 °C and stir for 2.5 h. Then, raise the temperature to 190 °C and keep the temperature for 12 h. After the reaction, perform vacuum pumping for 1.5 h. After cooling, add acetone, wash, filter by suction, and dry in vacuum to obtain Compound III. B2. Add 3-methacryloxypropyltrimethoxysilane into ethanol, stir at 90 °C for 14 h, then add Compound III and continue stirring for 18 h. After cooling to room temperature, filter and wash to obtain Precursor IV. B3. Mix Precursor IV with an ethanol-water mixed solution at 45 °C for 30 min, then add benzoxazine monomer and bismaleimide, and react at 120 °C for 7 h. Then, adjust the temperature to 35 °C, dropwise add Mixed Solution A composed of triethylamine, toluene, and phenylphosphonic dichloride. After the addition, slowly raise the temperature to 110 °C, keep the temperature for 5 h, cool and dry to obtain the modified heat-resistant agent.

[0011] Further, in B1, the dosage ratio of terephthalic acid, melamine, urea, and acetone is 16 g: 13 g: 6 g: 110 mL; the stirring speed is 300 r / min; the vacuum degree during vacuum pumping is -0.1 MPa and the temperature is 190 °C; the product is washed with acetone and dried at -0.1 MPa and 60 °C for 5 h; in B2, the dosage ratio of 3-methacryloxypropyltrimethoxysilane, ethanol, and Compound III is 8 g: 250 mL: 11 g; the stirring speed is 300 r / min; the product is washed with ethanol; in B3, the dosage ratio of Precursor IV, ethanol-water mixed solution, benzoxazine monomer, bismaleimide, and Mixed Solution A is 40 g: 250 mL: 7 g: 5 g: 102 g; the Mixed Solution A is composed of 7 g of triethylamine, 80 g of toluene, and 15 g of phenylphosphonic dichloride; ethanol and water are mixed at a volume ratio of 6:1, and the product is dried at 60 °C for 5 h.

[0012] When preparing the modified heat-resistant agent, terephthalic acid, melamine, and urea react to form a nitrogen-containing heterocyclic heat-resistant compound, and 3-methacryloxypropyltrimethoxysilane introduces crosslinkable groups and siloxane groups. Benzoxazine monomer and bismaleimide participate in the reaction to construct a highly crosslinked network, and phenylphosphonic dichloride enhances the heat resistance, thereby improving the overall thermal stability of the film.

[0013] Further, the preparation method of the quaternized chitosan-nanosilver composite is as follows: Dissolve quaternized chitosan in deionized water, add silver nitrate, stir evenly, and dropwise add a 1% sodium borohydride solution until the color of the solution no longer changes. Continue stirring for 2.5 h, then centrifuge, wash, and dry to obtain the quaternized chitosan-nanosilver composite.

[0014] In the quaternized chitosan-silver nanocomposite, the quaternary ammonium groups of quaternized chitosan carry positive charges, which can disrupt the bacterial cell membrane and cause the leakage of cell contents; silver nanoparticles have broad-spectrum antibacterial properties and can bind to proteins in bacteria to inhibit their growth and reproduction. The two work synergistically to exert antibacterial effects.

[0015] Furthermore, for the quaternized chitosan-silver nanocomposite, the dosage ratio of the raw materials quaternized chitosan, deionized water, and silver nitrate is 6 g: 120 mL: 0.2 g; the centrifugation speed is 5000 r / min, and each centrifugation lasts for 10 min; the product is washed with deionized water and dried at 60 °C for 6 h.

[0016] Furthermore, the processing aid is a mixture obtained by compounding glycerol monostearate and ethylene bisstearamide in a mass ratio of 1:1.

[0017] A method for preparing a high-strength polyethylene film specifically comprises the following steps: S1. Add the dried high-density polyethylene and linear low-density polyethylene into a high-speed mixer and stir at a low speed for 5 min; then add ethylene-vinyl acetate copolymer and maleic anhydride-grafted polyethylene and stir at 90 °C for 10 min; then sequentially add nano-silica, organic montmorillonite, and silane coupling agent, raise the temperature to 100 °C and continue stirring for 15 min; finally, add calcium stearate, zinc stearate, processing aid, dibenzoyl peroxide, and nucleating agent DBS, and maintain the temperature at 110 °C and stir for 20 min; S2. Add the substance obtained in S1 above into a twin-screw extruder, melt and extrude at 170 - 190 °C, and simultaneously add a hindered amine light stabilizer, antioxidant 1010, modified toughening agent, modified heat-resistant agent, and quaternized chitosan-silver nanocomposite through a side feeding device. The extrusion temperature is controlled at 190 - 210 °C, and extrusion granulation is carried out to obtain modified polyethylene particles; S3. Add the modified polyethylene particles into a blow molding machine and blow mold into a film at 210 - 230 °C, and control the blow-up ratio and draw speed to obtain a high-strength polyethylene film.

[0018] Furthermore, in S1, the stirring speed for adding high-density polyethylene and linear low-density polyethylene is 200 r / min, and the stirring speed for adding the subsequent materials is 400 r / min; in S2, the screw speed is 350 - 450 r / min; in S3, the blow-up ratio is controlled at 3.5 - 4.5, and the draw speed is 18 - 22 m / min.

[0019] The present invention provides a high-strength polyethylene film and a method for preparing the same, having the following beneficial effects: 1. Improvement in mechanical properties: In the high-strength polyethylene film of the present invention, the combined action of nano-silica, organic montmorillonite and modified toughening agent significantly improves the mechanical properties of the film. Nano-silica has an extremely small particle size and a large specific surface area. After being uniformly dispersed in the polyethylene matrix, it is like a closely arranged tiny reinforcing column, constructing a stable microscopic reinforcing framework for the film and effectively bearing the externally applied stress. Organic montmorillonite, with its unique lamellar structure, forms an ordered dispersed phase in polyethylene. When the film is subjected to external forces such as stretching and tearing, these lamellae can hinder the propagation of cracks and consume a large amount of energy. The modified toughening agent plays a key role by virtue of its complex molecular structure. It introduces flexible chain segments and special functional groups through multi-step reactions. When the film is subjected to external impact, these flexible chain segments can undergo elastic deformation, effectively dispersing the stress and avoiding film rupture caused by stress concentration. For example, when packaging sharp objects, the film can rely on these strengthening mechanisms to resist the puncture of the objects, greatly reducing the risk of damage. When used in the agricultural and construction fields, it can also better withstand various external tensile forces and extend the service life.

[0020] 2. Enhancement of anti-aging and heat resistance: The synergistic effect of hindered amine light stabilizer and antioxidant 1010 provides a strong guarantee for the anti-aging performance of the film. The hindered amine light stabilizer can capture the free radicals generated in the film under ultraviolet irradiation and convert them into stable substances, thus blocking the chain process of photo-oxidation reaction. Antioxidant 1010 mainly inhibits the oxidative degradation of the film under the action of heat and oxygen. It can react with the peroxides generated during the oxidation process and prevent them from further decomposing to produce harmful free radicals. The two cooperate with each other, greatly extending the service life of the film in the outdoor environment and reducing the cost increase caused by frequent film replacement due to aging. The modified heat-resistant agent significantly improves the thermal stability of the film by constructing a highly cross-linked network structure. In a high-temperature environment, this cross-linked network can limit the thermal movement of polyethylene molecular chains, prevent the slippage and rearrangement between molecular chains, so that the film can maintain a stable size and good mechanical properties. For example, in the packaging of high-temperature industrial products or in building waterproof projects that need to withstand a certain temperature, the film can continuously play a protective role at high temperatures and will not lose its due function due to softening and deformation, broadening the application temperature range of the polyethylene film.

[0021] 3. Excellent antibacterial performance: The quaternized chitosan-silver nanocomposite endows the film with excellent antibacterial performance. The quaternary ammonium groups in the quaternized chitosan molecule carry positive charges, while the bacterial surface usually carries negative charges. The electrostatic attraction between the two enables the quaternized chitosan to tightly adsorb on the bacterial surface, thereby destroying the bacterial cell membrane, resulting in the leakage of cell contents, and ultimately causing the death of bacteria. Silver nanoparticles have broad-spectrum antibacterial properties. They can bind to biological macromolecules such as proteins and nucleic acids in bacteria, interfere with the normal physiological metabolism of bacteria, and inhibit their growth and reproduction. In the field of food packaging, this antibacterial performance can effectively inhibit the growth of microorganisms on the food surface, extend the shelf life of food, and ensure the freshness and safety of food. In the medical field, when used for packaging medical supplies, it can prevent microbial contamination, reduce the risk of infection, provide reliable sanitation for the medical environment, and meet the strict requirements of these fields with extremely high hygiene standards.

[0022] 4. Optimized processing performance: The processing aid composed of glycerol monostearate and ethylene bisstearamide compounded in a specific ratio plays a key role in optimizing the processing performance of the film. Glycerol monostearate has good lubricity, which can reduce the friction between the polyethylene melt and the processing equipment, reduce energy consumption, and improve the fluidity of the melt. Ethylene bisstearamide forms a microscopic lubricating network structure in the melt, further improving the flow uniformity of the melt and effectively preventing the phenomenon of too fast or too slow local flow rate of the melt during the processing. During the film blowing process, this compounded processing aid greatly reduces the probability of melt fracture. Melt fracture will cause defects such as cracks and holes on the film surface, seriously affecting the product quality. After using this processing aid, the melt can flow evenly in the mold, ensuring the smooth progress of the film blowing process. At the same time, due to the improvement of the melt fluidity, the production efficiency during the processing is also greatly improved, and more high-quality film products can be produced in a shorter time, reducing the production cost and enhancing the competitiveness of the product in the market. Detailed implementation method

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0024] Example 1, preparation of high-strength polyethylene film, the specific preparation steps are as follows: S1. Add 35 parts of high-density polyethylene and 25 parts of linear low-density polyethylene that have been dried to a high-speed mixer, and stir at a low speed of 200 r / min for 5 min. Then add 12 parts of ethylene-vinyl acetate copolymer and 4 parts of maleic anhydride grafted polyethylene, and stir at a speed of 400 r / min at 90 °C for 10 min. Then add 5 parts of nano-silica, 3 parts of organic montmorillonite, and 0.8 part of silane coupling agent in sequence, raise the temperature to 100 °C and continue to stir at a speed of 400 r / min for 15 min. Finally, add 0.8 part of calcium stearate, 0.8 part of zinc stearate, 1.5 parts of processing aid, 0.15 part of dibenzoyl peroxide, and 0.5 part of nucleating agent DBS, and maintain the temperature at 110 °C and stir at a speed of 400 r / min for 20 min; S2. Add the substance obtained in S1 above to a twin-screw extruder, melt and extrude at 170 °C, and at the same time add 1.5 parts of hindered amine light stabilizer, 1.5 parts of antioxidant 1010, 6 parts of modified toughening agent, 4 parts of modified heat-resistant agent, and 1.5 parts of quaternized chitosan-nano silver composite through a side feeding device. The extrusion temperature is controlled at 190 °C, the screw speed is 350 r / min, and extrude and pelletize to obtain modified polyethylene particles; S3. Add the modified polyethylene particles to a blow molding machine, blow mold into a film at 210 °C, control the blow-up ratio at 3.5, and the traction speed is 18 m / min to obtain a high-strength polyethylene film.

[0025] Example 2. To prepare a high-strength polyethylene film, the specific preparation steps are as follows: S1. Add 45 parts of high-density polyethylene and 35 parts of linear low-density polyethylene that have been dried to a high-speed mixer, and stir at a low speed of 200 r / min for 5 min. Then add 18 parts of ethylene-vinyl acetate copolymer and 6 parts of maleic anhydride grafted polyethylene, and stir at a speed of 400 r / min at 90 °C for 10 min. Then add 10 parts of nano-silica, 7 parts of organic montmorillonite, and 1.2 parts of silane coupling agent in sequence, raise the temperature to 100 °C and continue to stir at a speed of 400 r / min for 15 min. Finally, add 1.2 parts of calcium stearate, 1.2 parts of zinc stearate, 3.5 parts of processing aid, 0.35 part of dibenzoyl peroxide, and 1.5 part of nucleating agent DBS, and maintain the temperature at 110 °C and stir at a speed of 400 r / min for 20 min; S2. Add the substance obtained in S1 above to a twin-screw extruder, melt and extrude at 190 °C, and at the same time add 3.5 parts of hindered amine light stabilizer, 2.5 parts of antioxidant 1010, 9 parts of modified toughening agent, 7 parts of modified heat-resistant agent, and 3.5 parts of quaternized chitosan-nano silver composite through a side feeding device. The extrusion temperature is controlled at 210 °C, the screw speed is 450 r / min, and extrude and pelletize to obtain modified polyethylene particles; S3. Add the modified polyethylene particles into a blow molding machine and blow them into a film at 230 °C. Control the blow-up ratio at 4.5 and the drawing speed at 22 m / min to obtain a high-strength polyethylene film.

[0026] Example 3. Preparation of a high-strength polyethylene film. The specific preparation steps are as follows: S1. Add 40 parts of high-density polyethylene and 30 parts of linear low-density polyethylene that have been dried into a high-speed mixer and stir at a low speed of 200 r / min for 5 min. Then add 15 parts of ethylene-vinyl acetate copolymer and 5 parts of maleic anhydride-grafted polyethylene, and stir at a speed of 400 r / min at 90 °C for 10 min. Then successively add 7 parts of nano-silica, 5 parts of organic montmorillonite, and 1 part of silane coupling agent, raise the temperature to 100 °C and continue to stir at a speed of 400 r / min for 15 min. Finally, add 1 part of calcium stearate, 1 part of zinc stearate, 2 parts of processing aid, 0.25 part of dibenzoyl peroxide, and 1 part of nucleating agent DBS, and maintain the temperature at 110 °C and stir at a speed of 400 r / min for 20 min. S2. Add the substance obtained in S1 above into a twin-screw extruder and melt-extrude at 180 °C. At the same time, add 2 parts of hindered amine light stabilizer, 2 parts of antioxidant 1010, 7 parts of modified toughening agent, 5 parts of modified heat-resistant agent, and 2 parts of quaternized chitosan-nano silver composite through a side feeding device. Control the extrusion temperature at 200 °C, the screw speed at 400 r / min, and extrude and pelletize to obtain modified polyethylene particles. S3. Add the modified polyethylene particles into a blow molding machine and blow them into a film at 220 °C. Control the blow-up ratio at 4 and the drawing speed at 20 m / min to obtain a high-strength polyethylene film.

[0027] Example 4. Preparation of a modified toughening agent. The specific preparation steps are as follows: A1. In a reaction vessel, successively add 13 g of maleic anhydride, 110 mL of toluene, and 20 g of 4-vinyl aniline. Maintain the temperature of the reaction system at 70 °C and stir and react at 300 r / min for 2.5 h. After the reaction is completed, add 30 mL of tetrahydrofuran, place it in an ice-water bath and continuously stir for 20 min, then add 11 g of triethylamine and continue to react for 40 min. After the reaction is completed, first wash the reaction solution with dilute hydrochloric acid, then wash it with deionized water, then add anhydrous sodium sulfate for drying, filter to remove the desiccant, and finally perform rotary evaporation. The initial temperature is 40 °C. After the tetrahydrofuran is distilled out, raise the temperature to 60 °C to distill out toluene to obtain Compound I. A2. Add 7 g of γ-aminopropyltrimethoxysilane to 190 mL of ethanol, stir for 50 min, then add 13 g of Compound I, 40 mL of acetone and 5 g of triethylamine, and stir at 300 r / min at room temperature for 5.5 h; after the reaction is completed, remove the solvent by rotary evaporation. The initial rotary evaporation temperature is 40 °C. After the acetone is distilled off, raise the temperature to 70 °C to distill off the ethanol, then wash with a mixed solution of ethanol-water with a volume ratio of 4:1, and then dry at 60 °C for 4 h to obtain Intermediate Product II; A3. Mix 15 g of Intermediate Product II with 250 mL of a mixed solution of ethanol-water with a volume ratio of 6:1 at 45 °C for 30 min. Under nitrogen protection, add 50 mL of toluene and 15 g of isophorone diisocyanate, raise the reaction temperature to 90 °C, and stir and react at a speed of 300 r / min for 3.5 h to prepare a modified toughening agent.

[0028] Example 5. Preparation of a modified heat-resistant agent. The specific preparation steps are as follows: B1. Add 16 g of terephthalic acid, 13 g of melamine and 6 g of urea to a three-necked flask. First, heat the reaction system to 140 °C and stir and react at a speed of 300 r / min for 2.5 h, then raise the temperature to 190 °C and keep the temperature for 12 h; after the reaction is completed, carry out vacuum operation at a vacuum degree of -0.1 MPa and a temperature of 190 °C for 1.5 h. After cooling, add 110 mL of acetone, wash with acetone, filter by suction, and dry at -0.1 MPa and a temperature of 60 °C for 5 h to obtain Compound III; B2. Add 8 g of 3-methacryloxypropyltrimethoxysilane to 250 mL of ethanol, stir at 90 °C at 300 r / min for 14 h, then add 11 g of Compound III, continue to stir for 18 h, cool to room temperature, filter and wash with ethanol to obtain Precursor IV; B3. Mix 40 g of Precursor IV with 250 mL of a mixed solution of ethanol-water with a volume ratio of 6:1 at 45 °C for 30 min, then add 7 g of benzoxazine monomer and 5 g of bismaleimide, and react at 120 °C for 7 h; then adjust the temperature to 35 °C, and dropwise add a mixed solution A composed of 7 g of triethylamine, 80 g of toluene and 15 g of phenylphosphonic dichloride. After the dropwise addition is completed, slowly raise the temperature to 110 °C, keep the temperature for 5 h, cool, and dry at 60 °C for 5 h to prepare a modified heat-resistant agent.

[0029] Example 6. Preparation of quaternized chitosan-silver nanocomposite. The specific preparation method is as follows: Dissolve 6 g of quaternized chitosan in 120 mL of deionized water, add 0.2 g of silver nitrate, stir evenly, and gradually add a 1% sodium borohydride solution dropwise until the color of the solution no longer changes. Continue stirring for 2.5 h, then centrifuge at a rotational speed of 5000 r / min for 10 min each time. Wash the precipitate with deionized water and dry it at 60 °C for 6 h to obtain a quaternized chitosan-silver nanocomposite.

[0030] Comparative Example 1: Prepare a high-strength polyethylene film. The specific preparation steps are as follows: Keep the remaining steps unchanged, and only replace the modified toughening agent in Example 2 with linear low-density polyethylene without any treatment to prepare a high-strength polyethylene film.

[0031] Comparative Example 2: Prepare a high-strength polyethylene film. The specific preparation steps are as follows: Keep the remaining steps unchanged, and only replace the modified heat-resistant agent in Example 2 with talc without any treatment to prepare a high-strength polyethylene film.

[0032] Comparative Example 3: Prepare a high-strength polyethylene film. The specific preparation steps are as follows: Keep the remaining steps unchanged, and only replace the quaternized chitosan-silver nanocomposite in Example 2 with chitosan without any treatment to prepare a high-strength polyethylene film.

[0033] Performance testing Test Items Test Methods Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Tensile Strength (MPa) According to the GB / T1040.3-2006 standard, using a universal material testing machine, dumbbell-shaped specimens were made from the film and tested at a tensile speed of 50 mm / min 45 52 48 32 40 45 Elongation at Break (%) According to the GB / T1040.3-2006 standard, the tensile strength of dumbbell-shaped film specimens was tested using a universal material testing machine, and the elongation at the moment of specimen fracture was recorded 480 520 500 350 420 450 Puncture Resistance (g) Using the falling dart impact test, the film specimen was placed horizontally, and darts of different masses were freely dropped to impact the film, and the minimum dart mass that caused the film to be punctured and damaged was recorded 450 520 480 300 400 430 Aging Resistance The film specimen was exposed in a xenon lamp aging test chamber and tested according to the GB / T16422.2-2014 standard. After 1000 h of aging, the appearance of the film was observed and the tensile strength retention rate was tested Appearance slightly yellowed, tensile strength retention rate 85% Appearance slightly discolored, tensile strength retention rate 90% Appearance slightly changed, tensile strength retention rate 88% Appearance severely yellowed and brittle, tensile strength retention rate 60% Appearance significantly discolored, tensile strength retention rate 70% Appearance slightly discolored, tensile strength retention rate 80% Heat Resistance The film specimen was placed in a heat aging test chamber and maintained at 120 °C for 24 h. Whether the film softened and deformed was observed, and the change rate of its tensile strength was tested No obvious deformation, tensile strength change rate 5% No obvious change, tensile strength change rate 3% No obvious change, tensile strength change rate 4% Significantly softened and deformed, tensile strength change rate 20% Slightly deformed, tensile strength change rate 12% No obvious change, tensile strength change rate 6% Antibacterial Performance Using the film sticking method, the film specimen was stuck on a culture medium containing Escherichia coli and Staphylococcus aureus. After culturing at 37 °C for 24 h, the size of the antibacterial zone on the film surface was observed Antibacterial zone diameter against Escherichia coli 18 mm, antibacterial zone diameter against Staphylococcus aureus 16 mm Antibacterial zone diameter against Escherichia coli 20 mm, antibacterial zone diameter against Staphylococcus aureus 18 mm Antibacterial zone diameter against Escherichia coli 19 mm, antibacterial zone diameter against Staphylococcus aureus 17 mm Antibacterial zone diameter against Escherichia coli 10 mm, antibacterial zone diameter against Staphylococcus aureus 8 mm Antibacterial zone diameter against Escherichia coli 6 mm, antibacterial zone diameter against Staphylococcus aureus 6 mm Antibacterial zone diameter against Escherichia coli 5 mm, antibacterial zone diameter against Staphylococcus aureus 4 mm Processing Performance Observe the fluidity of the melt during the blown film forming process, whether there is melt fracture phenomenon, and the thickness uniformity of the film Good melt fluidity, no melt fracture, film thickness uniformity deviation ±0.005 mm Smooth melt flow, no melt fracture, film thickness uniformity deviation ±0.004 mm Normal melt flow, no melt fracture, film thickness uniformity deviation ±0.005 mm Poor melt fluidity, a small amount of melt fracture occurred, film thickness uniformity deviation ±0.01 mm General melt fluidity, slight melt fracture, film thickness uniformity deviation ±0.008 mm The melt has good fluidity, no melt fracture, and the uniform deviation of the film thickness is ±0.006 mm Perform performance tests on the examples and comparative examples of the high-strength polyethylene film. The results show that: the examples are superior to the comparative examples in terms of tensile strength, elongation at break, puncture resistance, aging resistance, heat resistance, antibacterial performance, and processing performance. For example, the tensile strength of the examples is 45 - 52 MPa, the diameter of the antibacterial zone is 16 - 20 mm, and there is no melt fracture; while the tensile strength of the comparative examples is as low as 32 MPa, the diameter of the antibacterial zone is only 4 - 10 mm, and some melts have fractures, demonstrating the advantages of the comprehensive performance of the film of the present invention.

[0034] The above content is only an example and explanation of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar methods to replace them. As long as they do not deviate from the invention or exceed the scope defined by this claim book, they should fall within the protection scope of the present invention.

Claims

1. A high-strength polyethylene film, characterized in that: It contains the following raw materials in parts by weight: 35-45 parts of high-density polyethylene, 25-35 parts of linear low-density polyethylene, 12-18 parts of ethylene-vinyl acetate copolymer, 5-10 parts of nano-silica, 3-7 parts of organic montmorillonite, 1.5-3.5 parts of hindered amine light stabilizer, 1.5-2.5 parts of antioxidant 1010, 0.8-1.2 parts of calcium stearate, 0.8-1.2 parts of zinc stearate, 0.8-1.2 parts of silane coupling agent, 4-6 parts of maleic anhydride grafted polyethylene, 1.5-3.5 parts of quaternized chitosan-nano silver composite, 6-9 parts of modified toughening agent, 4-7 parts of modified heat-resistant agent, 1.5-3.5 parts of processing aid, 0.15-0.35 parts of dibenzoyl peroxide, 0.5-1.5 parts of nucleating agent DBS.

2. The high-strength polyethylene film according to claim 1, wherein: The specific preparation steps of the modified toughening agent are as follows: A1. In a reaction vessel, maleic anhydride, toluene and 4-vinyl aniline are added in sequence. The temperature of the reaction system is maintained at 70 °C, and the reaction is stirred for 2.5 h. After the reaction is completed, tetrahydrofuran is added, and the mixture is continuously stirred in an ice-water bath for 20 min. Then triethylamine is added, and the reaction continues for 40 min. After the reaction is completed, the reaction solution is washed with dilute hydrochloric acid first, then with deionized water, then dried with anhydrous sodium sulfate, the desiccant is filtered off, and finally the solvent is removed by rotary evaporation to obtain Compound I; A2. γ-aminopropyltrimethoxysilane is added to ethanol and stirred for 50 min. Then Compound I, acetone and triethylamine are added, and the mixture is stirred at room temperature for 5.5 h. After the reaction is completed, the solvent is removed by rotary evaporation, and then washed with a mixed solution of ethanol and water, and dried to obtain Intermediate II; A3. Intermediate II is mixed with an ethanol-water mixed solution at 45 °C for 30 min. Under nitrogen protection, toluene and isophorone diisocyanate are added, and the reaction temperature is raised to 90 °C, and the reaction is stirred for 3.5 h to obtain the modified toughening agent.

3. The high-strength polyethylene film according to claim 2, characterized in that: In A1, the dosage ratio of maleic anhydride, toluene, 4-vinyl aniline, tetrahydrofuran, and triethylamine is 13 g: 110 mL: 20 g: 30 mL: 11 g; the stirring speed is 300 r / min; the initial rotary evaporation temperature is 40 °C. After tetrahydrofuran is distilled off, the temperature is raised to 60 °C to distill off toluene; in A2, the dosage ratio of γ-aminopropyltrimethoxysilane, ethanol, Compound I, acetone, and triethylamine is 7 g: 190 mL: 13 g: 40 mL: 5 g; the stirring speed is 300 r / min; ethanol and water are mixed in a volume ratio of 4:1; the initial rotary evaporation temperature is 40 °C. After acetone is distilled off, the temperature is raised to 70 °C to distill off ethanol, and the product is dried at 60 °C for 4 h; in A3, the dosage ratio of Intermediate II, ethanol-water mixed solution, toluene, and isophorone diisocyanate is 15 g: 250 mL: 50 mL: 15 g; ethanol and water are mixed in a volume ratio of 6:1; the stirring speed is 300 r / min.

4. The high-strength polyethylene film according to claim 1, wherein: The specific preparation steps of the modified heat-resistant agent are as follows: B1. Add terephthalic acid, melamine and urea into a three-necked flask. First, heat the reaction system to 140 °C and stir for 2.5 h, then raise the temperature to 190 °C and keep the temperature for 12 h. After the reaction is completed, perform vacuum pumping for 1.5 h. After cooling, add acetone, wash, filter by suction, and dry in vacuum to obtain Compound III. B2. Add 3-methacryloxypropyltrimethoxysilane into ethanol, stir at 90 °C for 14 h, then add Compound III and continue to stir for 18 h. After cooling to room temperature, filter and wash to obtain Precursor IV. B3. Mix Precursor IV with an ethanol-water mixed solution at 45 °C for 30 min, then add benzoxazine monomer and bismaleimide, and react at 120 °C for 7 h. Then adjust the temperature to 35 °C, dropwise add Mixed Solution A composed of triethylamine, toluene and phenylphosphonic dichloride. After the dropping is completed, slowly raise the temperature to 110 °C and keep the temperature for 5 h. Cool and dry to obtain the modified heat-resistant agent.

5. The high-strength polyethylene film according to claim 4, wherein: In B1, the dosage ratio of terephthalic acid, melamine, urea and acetone is 16 g: 13 g: 6 g: 110 mL; the stirring speed is 300 r / min; the vacuum degree during vacuum pumping is -0.1 MPa and the temperature is 190 °C; the product is washed with acetone and dried at -0.1 MPa and 60 °C for 5 h. In B2, the dosage ratio of 3-methacryloxypropyltrimethoxysilane, ethanol and Compound III is 8 g: 250 mL: 11 g; the stirring speed is 300 r / min; the product is washed with ethanol. In B3, the dosage ratio of Precursor IV, ethanol-water mixed solution, benzoxazine monomer, bismaleimide and Mixed Solution A is 40 g: 250 mL: 7 g: 5 g: 102 g; the Mixed Solution A is composed of 7 g of triethylamine, 80 g of toluene and 15 g of phenylphosphonic dichloride; ethanol and water are mixed at a volume ratio of 6:1, and the product is dried at 60 °C for 5 h.

6. The high-strength polyethylene film according to claim 1, wherein: The preparation method of the quaternized chitosan-nanosilver composite is as follows: Dissolve quaternized chitosan in deionized water, add silver nitrate, stir evenly, and dropwise add a 1% sodium borohydride solution until the color of the solution no longer changes. Continue to stir for 2.5 h, then centrifuge, wash, and dry to obtain the quaternized chitosan-nanosilver composite.

7. The high-strength polyethylene film according to claim 6, characterized in that: For the quaternized chitosan-nanosilver composite, the dosage ratio of the raw materials quaternized chitosan, deionized water and silver nitrate is 6 g: 120 mL: 0.2 g; the centrifugation speed is 5000 r / min and each centrifugation is for 10 min; the product is washed with deionized water and dried at 60 °C for 6 h.

8. A high-strength polyethylene film according to claim 1, wherein: The processing aid is a mixture of glycerol monostearate and ethylene bisstearamide compounded at a mass ratio of 1:

1.

9. A method for preparing a high-strength polyethylene film, characterized in that: Specifically, it includes the following steps: S1. Add the dried high-density polyethylene and linear low-density polyethylene into a high-speed mixer, and stir at a low speed for 5 min. Then add ethylene-vinyl acetate copolymer and maleic anhydride grafted polyethylene, and stir at 90 °C for 10 min. Then successively add nano-silica, organic montmorillonite and silane coupling agent, raise the temperature to 100 °C and continue to stir for 15 min. Finally, add calcium stearate, zinc stearate, processing aid, dibenzoyl peroxide and nucleating agent DBS, and maintain the temperature at 110 °C and stir for 20 min; S2. Add the substance obtained in S1 above into a twin-screw extruder, melt and extrude at 170 - 190 °C. At the same time, add hindered amine light stabilizer, antioxidant 1010, modified toughening agent, modified heat-resistant agent and quaternized chitosan-nano silver composite through a side feeding device. Control the extrusion temperature at 190 - 210 °C, extrude and pelletize to obtain modified polyethylene particles; S3. Add the modified polyethylene particles into a blow molding machine, blow mold into a film at 210 - 230 °C, control the blow-up ratio and draw speed, and prepare a high-strength polyethylene film.

10. The preparation method of a high-strength polyethylene film according to claim 9, characterized in that: In S1, the stirring speed for adding high-density polyethylene and linear low-density polyethylene is 200 r / min, and the stirring speed for adding subsequent materials is 400 r / min; in S2, the screw speed is 350 - 450 r / min; in S3, the blow-up ratio is controlled at 3.5 - 4.5, and the draw speed is 18 - 22 m / min.