High-barrier polypropylene film and preparation method thereof

Abstract

The invention discloses a high-barrier polypropylene film and a preparation method of the high-barrier polypropylene film. The modified polypropylene material is prepared from the following raw materials in parts by weight: 80 to 90 parts of polypropylene resin, 0.5 to 2 parts of nano-sheet Mxene, 5 to 10 parts of a composite blocking agent, 1 to 3 parts of a compatilizer, 3 to 5 parts of a coupling agent, 0.1 to 0.5 part of an antioxidant, 0.1 to 0.3 part of a lubricant, 5 to 8 parts of amino-terminated hyperbranched polyamide and 1 to 1.5 parts of N-(4-cyano-3-trifluoromethylphenyl) methacrylamide. The preparation method comprises the steps of melt blending granulation, tape casting shaping, two-way stretching, plasma pretreatment-ultraviolet grafting modification, corona treatment and the like, and all process parameters are controlled in a reasonable range. The film has excellent oxygen / water vapor barrier property, high longitudinal tensile strength and good surface flatness, the synergistic effect of the components is remarkable, the preparation process is stable and controllable, and the requirements of various high-barrier packaging scenes can be met.

Description

Technical Field

[0001] This invention relates to the field of polymer film materials technology, and in particular to a high-barrier polypropylene film and its preparation method. Background Technology

[0002] Polypropylene film is widely used in packaging for food, pharmaceuticals, and electronic products due to its good mechanical properties, chemical stability, processing performance, and relatively low cost. However, traditional polypropylene film has significant limitations in its barrier properties, especially in its ability to block small molecules such as oxygen and water vapor, which is insufficient to meet the packaging requirements for products with high demands for preservation and moisture protection.

[0003] To improve the barrier properties of polypropylene films, various modification schemes have been proposed in existing technologies, mainly including blending modification, coating modification, multilayer composite modification, and inorganic nanoparticle filling modification. However, each of these has significant drawbacks, making it difficult to meet the comprehensive requirements of high-end packaging scenarios for high barrier properties, high mechanical properties, easy processing, and low cost: Blending modification suffers from poor compatibility between different resins, requires the addition of large amounts of high-barrier resin leading to increased costs and the destruction of the inherent advantages of polypropylene; Coating modification suffers from poor adhesion between the coating and the substrate, stringent processing environment requirements, some coatings being environmentally unfriendly, and affecting the flexibility of the film; Multilayer composite modification suffers from complex processing, easy delamination between layers, difficulty in recycling, and decreased flexibility with increasing number of layers; Inorganic nanoparticle filling modification suffers from easy agglomeration of nanoparticles, limited modification effect of single particles, and excessive addition deteriorating processing and molding performance.

[0004] Furthermore, existing modification schemes share common problems: most schemes only focus on improving a single barrier property, failing to achieve synergistic optimization of barrier properties, mechanical properties, and processing performance. Additionally, some schemes involve complex processing techniques and high production costs, making them unsuitable for large-scale industrial production. Currently, no modification scheme has emerged that can simultaneously address all the aforementioned properties and resolve the pain points of existing technologies, severely limiting the application of high-barrier polypropylene films.

[0005] To address the aforementioned issues, patent document CN119463241B discloses a method for preparing a high-barrier polypropylene film, comprising the following raw materials in parts by weight: 80-100 parts polypropylene resin, 18-30 parts ethylene-vinyl alcohol copolymer, 5-15 parts modifier, 0.1-0.3 parts initiator, and 4-6 parts lubricant. Using polypropylene as the matrix, the film possesses excellent water-blocking and mechanical properties. The ethylene-vinyl alcohol copolymer enhances the film's gas barrier properties and is easy to process. The resulting film is a single-layer film, and the preparation process is simple. The modifier significantly enhances the film's antioxidant, antibacterial, and hydrophobic properties, and its performance is long-lasting and stable, preventing detachment. The film prepared by this invention exhibits high mechanical properties, good barrier performance, a simple process, and stable and efficient antioxidant, antibacterial, and hydrophobic properties, possessing significant application value in the field of polypropylene film technology. However, it requires the addition of a high proportion of ethylene-vinyl alcohol copolymer, which not only significantly increases the cost of raw materials, but also makes it difficult to achieve the ultimate synergistic improvement of barrier performance and mechanical properties due to the inherent inadequacy of interfacial compatibility with polypropylene resin. Furthermore, it does not solve the problem of performance degradation during long-term use of the film. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-barrier polypropylene film with excellent barrier properties, mechanical properties and surface smoothness, and a method for preparing the same.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a high-barrier polypropylene film, wherein the raw material composition by weight is as follows: 80-90 parts of polypropylene resin, 0.5-2 parts of nano-sheet Mxene, 5-10 parts of composite barrier agent, 1-3 parts of compatibilizer, 3-5 parts of coupling agent, 0.1-0.5 parts of antioxidant, 0.1-0.3 parts of lubricant, 5-8 parts of amino-terminated hyperbranched polyamide, and 1-1.5 parts of N-(4-cyano-3-trifluoromethylphenyl)methacrylamide.

[0008] Preferably, the polypropylene resin is PPH-T03 resin produced by China Petroleum & Chemical Corporation.

[0009] Preferably, the nanosheet-like Mxene is titanium carbide (Ti3C2T). x MXene nanosheets with a diameter of 1-10µm.

[0010] Preferably, the composite barrier agent is a mixture of graphene quantum dots, organic nano-montmorillonite, and boron nitride nanosheets in a mass ratio of 0.1:(3-5):(0.3-0.5).

[0011] Preferably, the graphene quantum dots have a particle size of 1-4 nm; the organic nano-montmorillonite is Fenghong DK2 polymer-grade organic clay; and the boron nitride nanosheets have a sheet diameter of 1-5 µm and a thickness of <5 nm.

[0012] Preferably, the compatibilizer is PP-g-MAH, model number Jia Yi Rong® CMG9801.

[0013] Preferably, the coupling agent is silane coupling agent KH550, silane coupling agent KH560, or silane coupling agent KH570.

[0014] Preferably, the antioxidant is at least one of antioxidant 1010 and antioxidant 168.

[0015] Preferably, the lubricant is at least one of erucamide and zinc stearate.

[0016] Preferably, the terminal amino hyperbranched polyamide is terminal amino hyperbranched polyamide HyPer N1O3.

[0017] Another object of the present invention is to provide a method for preparing the high-barrier polypropylene film, comprising the following steps: Step S1: Mix polypropylene resin, nano-sheet Mxene, composite barrier agent, compatibilizer, coupling agent, antioxidant, lubricant, and amino-terminated hyperbranched polyamide evenly according to the weight parts, add them to a twin-screw extruder, melt blend at a screw speed of 150-250 r / min, extrude and granulate to obtain premixed granules; Step S2: Add the premixed granules into the casting machine, melt and plasticize them at 190-210℃, and extrude them through a slit die onto a cooling roller for cooling and shaping to obtain a cast base film. Step S3: The cast base film is fed into a biaxial stretching machine for longitudinal and transverse stretching. The longitudinal stretching temperature is 90-110℃ and the stretching ratio is 2.5-4.0 times. The transverse stretching temperature is 100-120℃ and the stretching ratio is 3.0-4.5 times. After stretching, heat setting is performed at a temperature of 120-140℃ for 5-15 seconds to obtain the stretched base film. Step S4: The stretched base film is sent into a low-temperature plasma treatment device, using argon plasma, and pretreated under the conditions of vacuum degree of 10-50 Pa, processing power of 50-150 W, processing temperature of 25-50℃, and processing time of 3-10 min. Then, the pretreated base film is immersed in an N-(4-cyano-3-trifluoromethylphenyl)methacrylamide solution containing a photoinitiator and irradiated with ultraviolet light for 15-35 min. After removal, it is dried with low-temperature hot air to remove residual solvent. The drying temperature is 40-60℃, the air velocity is 1-2 m / s, and the drying time is 5-10 min. Step S5: The thickness of the dried base film is measured by an online thickness gauge to control the finished thickness to be 10-50 μm with a thickness measurement accuracy of ±0.5 μm; then corona treatment is performed, and finally the film is wound up.

[0018] Preferably, the temperatures of each section of the twin-screw extruder in step S1 are as follows: feeding section 165-175℃, plasticizing section 175-190℃, melting section 185-205℃, and die head section 190-200℃.

[0019] Preferably, in step S2, the temperature of the cooling roller is 20-40°C; the temperature of the slit die head is 195-210°C; and the casting speed is 1-3 m / min.

[0020] Preferably, the N-(4-cyano-3-trifluoromethylphenyl)methacrylamide solution containing a photoinitiator in step S4 contains the following components by weight percentage: 3-5% N-(4-cyano-3-trifluoromethylphenyl)methacrylamide, 0.03-0.05% photoinitiator, and the balance being acetone; wherein the photoinitiator is benzoin ether.

[0021] Preferably, the wavelength of the ultraviolet light is 254-365 nm, and the light intensity is 5-15 mW / cm². 2 .

[0022] Preferably, the corona power of the corona treatment in step S5 is 30-50W, and the treatment speed is 1-3m / min.

[0023] Due to the application of the above technical solution, the present invention has the following beneficial effects: (1) The high-barrier polypropylene film and its preparation method disclosed in this invention use a composite barrier agent composed of graphene quantum dots, organic nano-montmorillonite, and boron nitride nanosheets in a specific ratio, and Ti3C2T x MXene nanosheets and amino-terminated hyperbranched polyamide HyPer N103 form a triple synergistic barrier effect. Organic nano-montmorillonite provides the layered barrier basis, boron nitride nanosheets and MXene nanosheets are uniformly dispersed and interwoven through coupling agent KH550, and graphene quantum dots fill the interlayer gaps. Compared with existing single or dual-component barrier modification schemes, this effectively blocks the gas and water vapor permeation channels, while avoiding the barrier failure caused by nanoparticle aggregation. The reduction in oxygen permeability and water vapor permeability far exceeds the superimposed effect of the individual components, achieving a high barrier level that is difficult to achieve with conventional modification.

[0024] (2) The high-barrier polypropylene film and its preparation method disclosed in this invention precisely combine PP-g-MAH compatibilizer and specific silane coupling agent. On the one hand, the anhydride group of the compatibilizer undergoes a covalent reaction with the amino and MXene surface functional groups of the terminal amino hyperbranched polyamide. On the other hand, the coupling agent bridges the inorganic barrier components (composite barrier agent, MXene) and the PP matrix, solving the industry pain points of easy phase separation and weak interfacial bonding in multi-component systems. At the same time, the precise ratio of antioxidant and lubricant avoids the problems of resin degradation and excessive interfacial friction during processing. Compared with the prior art, the finished film not only has significantly improved tensile strength, but also effectively improves the surface roughness defects caused by the addition of multiple nano-components. The surface smoothness meets the standards for high-end packaging films, achieving synergistic optimization of barrier properties, mechanical properties and surface properties, breaking through the bottleneck of the difficulty in achieving all three in the existing modification technology.

[0025] (3) The high-barrier polypropylene film and its preparation method disclosed in this invention limit the specific concentration ratio of N-(4-cyano-3-trifluoromethylphenyl)methacrylamide, and combine it with benzoin ether photoinitiator and precise low-temperature plasma pretreatment parameters to ensure uniform and efficient grafting reaction. Compared with conventional fluorinated monomer grafting process, the grafted layer is more firmly bonded to the matrix and the hydrophobic stability is greatly improved. At the same time, the low-temperature hot air drying process is precisely connected with the grafting step, which not only completely removes acetone solvent, but also avoids high temperature damage to the grafted layer and internal barrier network, so that the film is not prone to hydrophobic failure and barrier performance decay during long-term use. This solves the technical problem of poor hydrophobic durability and susceptibility to solvent residue in existing surface grafting modification.

[0026] (4) The high-barrier polypropylene film and its preparation method disclosed in this invention use PPH-T03 polypropylene resin, Fenghong DK2 organic montmorillonite and other raw materials that are industrial mass-produced products and do not require special customization. Compared with high-end special resin modification schemes, the raw material cost is greatly reduced. At the same time, the optimized melt blending, biaxial stretching and graft drying processes can be directly adapted to existing CPP production lines without the need for additional special equipment. Moreover, the parameters of each step are precisely matched, effectively controlling the film thickness deviation and performance fluctuation during the production process. Compared with the existing complex modification process, the production efficiency is improved and the product qualification rate is significantly improved. It achieves a balance between high performance and large-scale production and has extremely strong industrial application value.

[0027] (5) The high-barrier polypropylene film and its preparation method disclosed in this invention introduce MXene and terminal amino hyperbranched polyamide microfibers in situ to construct a "maze-like" barrier network. The ultra-large specific surface area of ​​MXene nanosheets intertwines with the terminal amino hyperbranched polyamide microfibers, greatly extending the permeation path of gas and water vapor. At the same time, the terminal amino groups of the terminal amino hyperbranched polyamide and the functional groups on the surface of MXene work synergistically to optimize compatibility, avoid agglomeration and phase separation, and synergistically improve the gas and water vapor barrier performance of the material. Detailed Implementation

[0028] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0029] Example 1 A high-barrier polypropylene film, by weight, comprises the following raw materials: 80 parts polypropylene resin, 0.5 parts nano-sheet Mxene, 5 parts composite barrier agent, 1 part compatibilizer, 3 parts coupling agent, 0.1 parts antioxidant, 0.1 parts lubricant, 5 parts amino-terminated hyperbranched polyamide, and 1 part N-(4-cyano-3-trifluoromethylphenyl)methacrylamide.

[0030] The polypropylene resin is PPH-T03 resin produced by China Petroleum & Chemical Corporation; the nano-sheet Mxene is titanium carbide (Ti3C2T). x The composite barrier agent consists of graphene quantum dots, organic nano-montmorillonite, and boron nitride nanosheets in a mass ratio of 0.1:3:0.3; the graphene quantum dots have a particle size of 1-4 nm; the organic nano-montmorillonite is Fenghong DK2 polymer-grade organic clay; the boron nitride nanosheets have a particle size of 1-5 µm and a thickness of <5 nm; the compatibilizer is PP-g-MAH, model Jia Yi Rong® CMG9801; the coupling agent is silane coupling agent KH550; the antioxidant is antioxidant 1010; the lubricant is erucamide; and the terminal amino hyperbranched polyamide is terminal amino hyperbranched polyamide HyPer N103.

[0031] A method for preparing the high-barrier polypropylene film includes the following steps: Step S1: Mix polypropylene resin, nano-sheet Mxene, composite barrier agent, compatibilizer, coupling agent, antioxidant, lubricant, and amino-terminated hyperbranched polyamide evenly according to the weight parts, add them to a twin-screw extruder, melt blend at a screw speed of 150 r / min, extrude and granulate to obtain premixed granules; Step S2: Add the premixed granules into the casting machine, melt and plasticize them at 190°C, and extrude them through a slit die onto a cooling roller for cooling and shaping to obtain a cast base film. Step S3: The cast base film is fed into a biaxial stretching machine for longitudinal and transverse stretching. The longitudinal stretching temperature is 90℃ and the stretching ratio is 2.5 times. The transverse stretching temperature is 100℃ and the stretching ratio is 3.0 times. After stretching, heat setting is performed at a temperature of 120℃ for 5 seconds to obtain the stretched base film. Step S4: The stretched base film is sent into a low-temperature plasma treatment device. Argon plasma is used for plasma pretreatment under the conditions of vacuum degree of 10 Pa, processing power of 50 W, processing temperature of 25℃ and processing time of 3 min. Then, the pretreated base film is immersed in N-(4-cyano-3-trifluoromethylphenyl)methacrylamide solution containing photoinitiator and irradiated with ultraviolet light for 15 min. After removal, it is dried with low-temperature hot air to remove residual solvent. The drying temperature is 40℃, the wind speed is 1 m / s and the drying time is 5 min. Step S5: The thickness of the dried base film is measured by an online thickness gauge to control the finished thickness to 30μm with a thickness measurement accuracy of ±0.5μm; then corona treatment is performed, and finally the film is wound up.

[0032] The temperatures of each section of the twin-screw extruder in step S1 are as follows: feeding section 165℃, plasticizing section 175℃, melting section 185℃, and die head section 190℃; the temperature of the cooling roller in step S2 is 20℃; the temperature of the slit die is 195℃; and the casting speed is 1m / min; the N-(4-cyano-3-trifluoromethylphenyl)methacrylamide solution containing a photoinitiator in step S4 contains the following components by weight percentage: 3% N-(4-cyano-3-trifluoromethylphenyl)methacrylamide, 0.03% photoinitiator, and the balance being acetone; the photoinitiator is benzoin ether; the wavelength of the ultraviolet light is 254nm, and the light intensity is 5mW / cm². 2 The corona power of the corona treatment in step S5 is 30W, and the processing speed is 1m / min.

[0033] Example 2 A high-barrier polypropylene film, by weight, comprises the following raw materials: 83 parts polypropylene resin, 1 part nanosheet Mxene, 6 parts composite barrier agent, 1.5 parts compatibilizer, 3.5 parts coupling agent, 0.2 parts antioxidant, 0.15 parts lubricant, 6 parts amino-terminated hyperbranched polyamide, and 1.2 parts N-(4-cyano-3-trifluoromethylphenyl)methacrylamide.

[0034] The polypropylene resin is PPH-T03 resin produced by China Petroleum & Chemical Corporation; the nano-sheet Mxene is titanium carbide (Ti3C2T). x The composite barrier agent consists of graphene quantum dots, organic nano-montmorillonite, and boron nitride nanosheets in a mass ratio of 0.1:3.5:0.35. The graphene quantum dots have a particle size of 1-4 nm. The organic nano-montmorillonite is Fenghong DK2 polymer-grade organic clay. The boron nitride nanosheets have a particle size of 1-5 µm and a thickness of <5 nm. The compatibilizer is PP-g-MAH, model number Jiayirong® CMG9801. The coupling agent is silane coupling agent KH560. The antioxidant is antioxidant 168. The lubricant is zinc stearate. The terminal amino hyperbranched polyamide is terminal amino hyperbranched polyamide HyPer N103.

[0035] A method for preparing the high-barrier polypropylene film includes the following steps: Step S1: Mix polypropylene resin, nano-sheet Mxene, composite barrier agent, compatibilizer, coupling agent, antioxidant, lubricant, and amino-terminated hyperbranched polyamide evenly according to the weight parts, add them to a twin-screw extruder, melt blend at a screw speed of 180 r / min, extrude and granulate to obtain premixed granules. Step S2: Add the premixed granules into the casting machine, melt and plasticize them at 195°C, and extrude them through a slit die onto a cooling roller for cooling and shaping to obtain a cast base film. Step S3: The cast base film is fed into a biaxial stretching machine for longitudinal and transverse stretching. The longitudinal stretching temperature is 95℃ and the stretching ratio is 3 times. The transverse stretching temperature is 105℃ and the stretching ratio is 3.5 times. After stretching, heat setting is performed at a temperature of 125℃ for 8 seconds to obtain the stretched base film. Step S4: The stretched base film is sent into a low-temperature plasma treatment device. Argon plasma is used for plasma pretreatment under the conditions of vacuum degree of 20 Pa, processing power of 80 W, processing temperature of 35 °C, and processing time of 5 min. Then, the pretreated base film is immersed in N-(4-cyano-3-trifluoromethylphenyl)methacrylamide solution containing photoinitiator and irradiated with ultraviolet light for 20 min. After removal, it is dried with low-temperature hot air to remove residual solvent. The drying temperature is 45 °C, the wind speed is 1.2 m / s, and the drying time is 6 min. Step S5: The thickness of the dried base film is measured by an online thickness gauge to control the finished thickness to 30μm with a thickness measurement accuracy of ±0.5μm; then corona treatment is performed, and finally the film is wound up.

[0036] The temperatures of each section of the twin-screw extruder in step S1 are as follows: feeding section 168℃, plasticizing section 177℃, melting section 190℃, and die head section 193℃; the temperature of the cooling roller in step S2 is 25℃; the temperature of the slit die is 198℃; and the casting speed is 1.5 m / min; the N-(4-cyano-3-trifluoromethylphenyl)methacrylamide solution containing a photoinitiator in step S4 contains the following components by weight percentage: 3.5% N-(4-cyano-3-trifluoromethylphenyl)methacrylamide, 0.035% photoinitiator, and the balance being acetone; the photoinitiator is benzoin ether; the wavelength of the ultraviolet light is 280 nm, and the light intensity is 8 mW / cm². 2 The corona power of the corona treatment in step S5 is 35W, and the processing speed is 1.5m / min.

[0037] Example 3 A high-barrier polypropylene film, by weight, comprises the following raw materials: 85 parts polypropylene resin, 1.3 parts nano-sheet Mxene, 7.5 parts composite barrier agent, 2 parts compatibilizer, 4 parts coupling agent, 0.3 parts antioxidant, 0.2 parts lubricant, 6.5 parts amino-terminated hyperbranched polyamide, and 1.3 parts N-(4-cyano-3-trifluoromethylphenyl)methacrylamide.

[0038] The polypropylene resin is PPH-T03 resin produced by China Petroleum & Chemical Corporation; the nano-sheet Mxene is titanium carbide (Ti3C2T). x The composite barrier agent consists of graphene quantum dots, organic nano-montmorillonite, and boron nitride nanosheets in a mass ratio of 0.1:4:0.4; the graphene quantum dots have a particle size of 1-4 nm; the organic nano-montmorillonite is Fenghong DK2 polymer-grade organic clay; the boron nitride nanosheets have a particle size of 1-5 µm and a thickness of <5 nm; the compatibilizer is PP-g-MAH, model number Jia Yi Rong® CMG9801; the coupling agent is silane coupling agent KH570; the antioxidant is antioxidant 1010; the lubricant is erucamide; and the terminal amino hyperbranched polyamide is terminal amino hyperbranched polyamide HyPer N103.

[0039] A method for preparing the high-barrier polypropylene film includes the following steps: Step S1: Mix polypropylene resin, nano-sheet Mxene, composite barrier agent, compatibilizer, coupling agent, antioxidant, lubricant, and amino-terminated hyperbranched polyamide evenly according to the weight parts, add them to a twin-screw extruder, melt blend at a screw speed of 200 r / min, extrude and granulate to obtain premixed granules; Step S2: Add the premixed granules into the casting machine, melt and plasticize them at 200°C, and extrude them through a slit die onto a cooling roller for cooling and shaping to obtain a cast base film. Step S3: The cast base film is fed into a biaxial stretching machine for longitudinal and transverse stretching. The longitudinal stretching temperature is 100℃ and the stretching ratio is 3.3 times. The transverse stretching temperature is 110℃ and the stretching ratio is 3.8 times. After stretching, heat setting is performed at a temperature of 130℃ for 10 seconds to obtain the stretched base film. Step S4: The stretched base film is sent into a low-temperature plasma treatment device. Argon plasma is used for plasma pretreatment under the conditions of vacuum degree of 30 Pa, processing power of 100 W, processing temperature of 40 °C, and processing time of 6 min. Then, the pretreated base film is immersed in N-(4-cyano-3-trifluoromethylphenyl)methacrylamide solution containing photoinitiator and irradiated with ultraviolet light for 25 min. After removal, it is dried with low-temperature hot air to remove residual solvent. The drying temperature is 50 °C, the wind speed is 1.5 m / s, and the drying time is 8 min. Step S5: The thickness of the dried base film is measured by an online thickness gauge to control the finished thickness to 35μm with a thickness measurement accuracy of ±0.5μm; then corona treatment is performed, and finally the film is wound up.

[0040] The temperatures of each section of the twin-screw extruder in step S1 are as follows: feeding section 170℃, plasticizing section 183℃, melting section 195℃, and die head section 195℃; the temperature of the cooling roller in step S2 is 30℃; the temperature of the slit die is 203℃; and the casting speed is 2m / min; the N-(4-cyano-3-trifluoromethylphenyl)methacrylamide solution containing a photoinitiator in step S4 contains the following components by weight percentage: 4% N-(4-cyano-3-trifluoromethylphenyl)methacrylamide, 0.04% photoinitiator, and the balance being acetone; the photoinitiator is benzoin ether; the wavelength of the ultraviolet light is 350nm, and the light intensity is 13mW / cm². 2 The corona power of the corona treatment in step S5 is 45W, and the processing speed is 2.5m / min.

[0041] Example 4 A high-barrier polypropylene film, by weight, comprises the following raw materials: 88 parts polypropylene resin, 1.8 parts nano-sheet Mxene, 9 parts composite barrier agent, 2.5 parts compatibilizer, 4.5 parts coupling agent, 0.4 parts antioxidant, 0.25 parts lubricant, 7.5 parts amino-terminated hyperbranched polyamide, and 1.4 parts N-(4-cyano-3-trifluoromethylphenyl)methacrylamide.

[0042] The polypropylene resin is PPH-T03 resin produced by China Petroleum & Chemical Corporation; the nano-sheet Mxene is titanium carbide (Ti3C2T). x The composite barrier agent consists of graphene quantum dots, organic nano-montmorillonite, and boron nitride nanosheets in a mass ratio of 0.1:4.5:0.45; the graphene quantum dots have a particle size of 1-4 nm; the organic nano-montmorillonite is Fenghong DK2 polymer-grade organic clay; the boron nitride nanosheets have a particle size of 1-5 µm and a thickness of <5 nm; and the compatibilizer is PP-g-MAH. The model is Jia Yi Rong® CMG9801; the coupling agent is a compound of silane coupling agent KH550, silane coupling agent KH560 and silane coupling agent KH570 in a mass ratio of 1:2:1; the antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 3:5; the lubricant is a compound of erucamide and zinc stearate in a mass ratio of 1:2; the terminal amino hyperbranched polyamide is terminal amino hyperbranched polyamide HyPer N103.

[0043] A method for preparing the high-barrier polypropylene film includes the following steps: Step S1: Mix polypropylene resin, nano-sheet Mxene, composite barrier agent, compatibilizer, coupling agent, antioxidant, lubricant, and amino-terminated hyperbranched polyamide evenly according to the weight parts, add them to a twin-screw extruder, melt blend at a screw speed of 240 r / min, extrude and granulate to obtain premixed granules; Step S2: Add the premixed granules into the casting machine, melt and plasticize them at 205°C, and extrude them through a slit die onto a cooling roller for cooling and shaping to obtain a cast base film. Step S3: The cast base film is fed into a biaxial stretching machine for longitudinal and transverse stretching. The longitudinal stretching temperature is 105℃ and the stretching ratio is 3.8 times. The transverse stretching temperature is 115℃ and the stretching ratio is 4.3 times. After stretching, heat setting is performed at a temperature of 135℃ for 13 seconds to obtain the stretched base film. Step S4: The stretched base film is sent into a low-temperature plasma treatment device. Argon plasma is used for plasma pretreatment under the conditions of vacuum degree of 40 Pa, processing power of 140 W, processing temperature of 45 °C, and processing time of 9 min. Then, the pretreated base film is immersed in N-(4-cyano-3-trifluoromethylphenyl)methacrylamide solution containing photoinitiator and irradiated with ultraviolet light for 33 min. After removal, it is dried with low-temperature hot air to remove residual solvent. The drying temperature is 55 °C, the wind speed is 1.8 m / s, and the drying time is 9 min. Step S5: The thickness of the dried base film is measured by an online thickness gauge to control the finished thickness to 35μm with a thickness measurement accuracy of ±0.5μm; then corona treatment is performed, and finally the film is wound up.

[0044] The temperatures of each section of the twin-screw extruder in step S1 are as follows: feeding section 173℃, plasticizing section 188℃, melting section 203℃, and die head section 198℃; the temperature of the cooling roller in step S2 is 35℃; the temperature of the slit die is 208℃; and the casting speed is 2.5 m / min; the N-(4-cyano-3-trifluoromethylphenyl)methacrylamide solution containing a photoinitiator in step S4 contains the following components by weight percentage: N-(4-cyano-3-trifluoromethylphenyl)methacrylamide 4.5%, photoinitiator 0.045%, and the balance being acetone; the photoinitiator is benzoin ether; the wavelength of the ultraviolet light is 350 nm, and the light intensity is 13 mW / cm². 2 The corona power of the corona treatment in step S5 is 45W, and the processing speed is 2.5m / min.

[0045] Example 5 A high-barrier polypropylene film, by weight, comprises the following raw materials: 90 parts polypropylene resin, 2 parts nano-sheet Mxene, 10 parts composite barrier agent, 3 parts compatibilizer, 5 parts coupling agent, 0.5 parts antioxidant, 0.3 parts lubricant, 8 parts amino-terminated hyperbranched polyamide, and 1.5 parts N-(4-cyano-3-trifluoromethylphenyl)methacrylamide.

[0046] The polypropylene resin is PPH-T03 resin produced by China Petroleum & Chemical Corporation; the nano-sheet Mxene is titanium carbide (Ti3C2T). x The composite barrier agent consists of graphene quantum dots, organic nano-montmorillonite, and boron nitride nanosheets in a mass ratio of 0.1:5:0.5; the graphene quantum dots have a particle size of 1-4 nm; the organic nano-montmorillonite is Fenghong DK2 polymer-grade organic clay; the boron nitride nanosheets have a particle size of 1-5 µm and a thickness of <5 nm; the compatibilizer is PP-g-MAH, model number Jia Yi Rong® CMG9801; the coupling agent is silane coupling agent KH550; the antioxidant is antioxidant 168; the lubricant is erucamide; and the terminal amino hyperbranched polyamide is terminal amino hyperbranched polyamide HyPer N103.

[0047] A method for preparing the high-barrier polypropylene film includes the following steps: Step S1: Mix polypropylene resin, nano-sheet Mxene, composite barrier agent, compatibilizer, coupling agent, antioxidant, lubricant, and amino-terminated hyperbranched polyamide evenly according to the weight parts, add them to a twin-screw extruder, melt blend at a screw speed of 250 r / min, extrude and granulate to obtain premixed granules; Step S2: Add the premixed granules into the casting machine, melt and plasticize them at 210°C, and extrude them through a slit die onto a cooling roller for cooling and shaping to obtain a cast base film. Step S3: The cast base film is fed into a biaxial stretching machine for longitudinal and transverse stretching. The longitudinal stretching temperature is 110℃ and the stretching ratio is 4.0 times. The transverse stretching temperature is 120℃ and the stretching ratio is 4.5 times. After stretching, heat setting is performed at a temperature of 140℃ for 15 seconds to obtain the stretched base film. Step S4: The stretched base film is sent into a low-temperature plasma treatment device. Argon plasma is used for plasma pretreatment under the conditions of vacuum degree of 50 Pa, processing power of 150 W, processing temperature of 50℃, and processing time of 10 min. Then, the pretreated base film is immersed in N-(4-cyano-3-trifluoromethylphenyl)methacrylamide solution containing photoinitiator and irradiated with ultraviolet light for 35 min. After removal, it is dried with low-temperature hot air to remove residual solvent. The drying temperature is 60℃, the wind speed is 2 m / s, and the drying time is 10 min. Step S5: The thickness of the dried base film is measured by an online thickness gauge to control the finished thickness to 35μm with a thickness measurement accuracy of ±0.5μm; then corona treatment is performed, and finally the film is wound up.

[0048] The temperatures of each section of the twin-screw extruder in step S1 are as follows: feeding section 175℃, plasticizing section 190℃, melting section 205℃, and die head section 200℃; the temperature of the cooling roller in step S2 is 40℃; the temperature of the slit die is 210℃; and the casting speed is 3 m / min; the N-(4-cyano-3-trifluoromethylphenyl)methacrylamide solution containing a photoinitiator in step S4 contains the following components by weight percentage: 5% N-(4-cyano-3-trifluoromethylphenyl)methacrylamide, 0.05% photoinitiator, and the balance being acetone; the photoinitiator is benzoin ether; the wavelength of the ultraviolet light is 365 nm, and the light intensity is 15 mW / cm². 2 The corona power of the corona treatment in step S5 is 50W, and the processing speed is 3m / min.

[0049] Comparative Example 1 A high-barrier polypropylene film and its preparation method are basically the same as those in Example 5, except that boron nitride nanosheets are replaced with an equal amount of graphene quantum dots.

[0050] Comparative Example 2 A high-barrier polypropylene film and its preparation method are basically the same as those in Example 5, except that an equal amount of boron nitride nanosheets are used instead of graphene quantum dots.

[0051] Comparative Example 3 A high-barrier polypropylene film and its preparation method are basically the same as those in Example 5, except that an equal amount of boron nitride nanosheets are used instead of organic nano-montmorillonite.

[0052] Comparative Example 4 A high-barrier polypropylene film and its preparation method are basically the same as those in Example 5, except that an equal amount of organic nano-montmorillonite is used instead of boron nitride nanosheets.

[0053] Comparative Example 5 A high-barrier polypropylene film and its preparation method are basically the same as those in Example 5, except that nanosheet MXene is not added.

[0054] Comparative Example 6 A high-barrier polypropylene film and its preparation method are basically the same as those in Example 5, except that no terminal amino hyperbranched polyamide is added.

[0055] Comparative Example 7 A high-barrier polypropylene film and its preparation method are basically the same as those in Example 5, except that step S4 is omitted.

[0056] To further illustrate the beneficial technical effects of the various embodiments of the present invention, relevant performance tests were conducted on the high-barrier polypropylene films prepared in Example 5 and Comparative Examples 1-7. The test results are shown in Table 1, and the test methods are as follows: (1) Oxygen transmission rate test: The test was conducted in accordance with GB / T 1038.1-2022 "Test methods for gas permeability of plastic films and sheets - Part 1: Differential pressure method". The test temperature was 23℃, the relative humidity was 50%RH, the test gas was oxygen, the pressure in the low-pressure chamber was ≤10Pa, and the accuracy of the pressure measuring device was not less than 6Pa. The oxygen transmission rate was calculated (unit: cm). 3 / (m 2 The smaller the value of d (0.1 MPa), the better the barrier performance.

[0057] (2) Water vapor transmission rate test: The test was conducted according to GB / T 1037-2021 "Determination of water vapor transmission performance of plastic films and sheets - cup weight gain and loss method". The test temperature was 38℃ and the relative humidity was 90%RH. After sealing the sample, it was placed in the test cup. The water vapor transmission rate was calculated by weighing the change in mass of the cup before and after the test (unit: g / (m)). 2 The smaller the value of 24h), the better the moisture barrier performance.

[0058] (3) Tensile strength test: Refer to GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets" for testing. Use type 2 strip specimens (width 20mm, length 150mm, gauge length 50mm), tensile speed 50mm / min, test temperature 23℃, relative humidity 50%RH, test 5 specimens per group, and take the average value. The unit of longitudinal tensile strength is MPa.

[0059] (4) Flatness test: The surface roughness Ra of the sample is tested using a surface roughness meter. The unit is μm. The smaller the value, the better the surface flatness. Test conditions: test length 5mm, scanning speed 0.5mm / s.

[0060] Table 1 Performance test results of high-barrier polypropylene film As shown in Table 1, the high-barrier polypropylene film prepared in Example 5 is significantly superior to Comparative Examples 1-7 in all aspects, with an oxygen permeability of only 0.3 cm⁻¹. 3 / (m 2 •d•0.1MPa), water vapor transmission rate is 0.5 g / (m 2 The sample, after 24 hours, exhibited excellent high barrier properties, with a longitudinal tensile strength of 85 MPa, outstanding mechanical properties, a surface roughness Ra of 0.032 μm, and good surface smoothness. Compared to Example 5, the comparative examples showed varying degrees of decrease in barrier properties and longitudinal tensile strength, and worsened surface smoothness, due to the substitution of raw material components or the absence of preparation processes. Among them, Comparative Example 7 (missing step S4) had an oxygen permeability of 7.3 cm⁻¹. 3 / (m 2 ·d·0.1MPa)), water vapor transmission rate (10.2 g / (m 2 The highest tensile strength (24h) and the lowest longitudinal tensile strength (57MPa) further confirm the synergistic effect of nanosheet Mxene, composite barrier agent, and terminal amino hyperbranched polyamide in Example 5, as well as the key role of plasma pretreatment + UV grafting process in improving the overall performance of the film.

[0061] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A high-barrier polypropylene film, characterized in that, The raw material composition by weight is as follows: 80-90 parts polypropylene resin, 0.5-2 parts nano-sheet Mxene, 5-10 parts composite barrier agent, 1-3 parts compatibilizer, 3-5 parts coupling agent, 0.1-0.5 parts antioxidant, 0.1-0.3 parts lubricant, 5-8 parts amino-terminated hyperbranched polyamide, and 1-1.5 parts N-(4-cyano-3-trifluoromethylphenyl)methacrylamide.

2. The high-barrier polypropylene film according to claim 1, characterized in that, The polypropylene resin is PPH-T03 resin produced by China Petroleum & Chemical Corporation; the nano-sheet Mxene is titanium carbide (Ti3C2T). x MXene nanosheets with a diameter of 1-10µm.

3. The high-barrier polypropylene film according to claim 1, characterized in that, The composite barrier agent is composed of graphene quantum dots, organic nano-montmorillonite, and boron nitride nanosheets in a mass ratio of 0.1:(3-5):(0.3-0.5); the particle size of the graphene quantum dots is 1-4 nm; the organic nano-montmorillonite is Fenghong DK2 polymer-grade organic clay; and the boron nitride nanosheets have a diameter of 1-5 µm and a thickness of <5 nm.

4. The high-barrier polypropylene film according to claim 1, characterized in that, The compatibilizer is PP-g-MAH, model number Jia Yi Rong® CMG9801; the coupling agent is silane coupling agent KH550, silane coupling agent KH560, or silane coupling agent KH570.

5. The high-barrier polypropylene film according to claim 1, characterized in that, The antioxidant is at least one of antioxidant 1010 and antioxidant 168; the lubricant is at least one of erucamide and zinc stearate; and the amine-terminated hyperbranched polyamide is amine-terminated hyperbranched polyamide HyPer N103.

6. A method for preparing a high-barrier polypropylene film according to any one of claims 1-5, characterized in that, Includes the following steps: Step S1: Mix polypropylene resin, nano-sheet Mxene, composite barrier agent, compatibilizer, coupling agent, antioxidant, lubricant, and amino-terminated hyperbranched polyamide evenly according to the weight parts, add them to a twin-screw extruder, melt blend at a screw speed of 150-250 r / min, extrude and granulate to obtain premixed granules; Step S2: Add the premixed granules into the casting machine, melt and plasticize them at 190-210℃, and extrude them through a slit die onto a cooling roller for cooling and shaping to obtain a cast base film. Step S3: The cast base film is fed into a biaxial stretching machine for longitudinal and transverse stretching. The longitudinal stretching temperature is 90-110℃ and the stretching ratio is 2.5-4.0 times. The transverse stretching temperature is 100-120℃ and the stretching ratio is 3.0-4.5 times. After stretching, heat setting is performed at a temperature of 120-140℃ for 5-15 seconds to obtain the stretched base film. Step S4: The stretched base film is sent into a low-temperature plasma treatment device, using argon plasma, and pretreated under the conditions of vacuum degree of 10-50 Pa, processing power of 50-150 W, processing temperature of 25-50℃, and processing time of 3-10 min. Then, the pretreated base film is immersed in an N-(4-cyano-3-trifluoromethylphenyl)methacrylamide solution containing a photoinitiator and irradiated with ultraviolet light for 15-35 min. After removal, it is dried with low-temperature hot air to remove residual solvent. The drying temperature is 40-60℃, the air velocity is 1-2 m / s, and the drying time is 5-10 min. Step S5: The thickness of the dried base film is measured by an online thickness gauge to control the finished product thickness to be 10-50 μm, with a thickness measurement accuracy of ±0.5 μm; Then, a corona treatment is performed, followed by winding.

7. The method for preparing a high-barrier polypropylene film according to claim 6, characterized in that, The temperatures of each section of the twin-screw extruder in step S1 are as follows: feeding section 165-175℃, plasticizing section 175-190℃, melting section 185-205℃, and die head section 190-200℃.

8. The method for preparing a high-barrier polypropylene film according to claim 6, characterized in that, In step S2, the temperature of the cooling roller is 20-40℃; the temperature of the slit die head is 195-210℃; and the casting speed is 1-3m / min.

9. The method for preparing a high-barrier polypropylene film according to claim 6, characterized in that, The N-(4-cyano-3-trifluoromethylphenyl)methacrylamide solution containing a photoinitiator in step S4 comprises the following components by weight percentage: 3-5% N-(4-cyano-3-trifluoromethylphenyl)methacrylamide, 0.03-0.05% photoinitiator, and the balance being acetone; the photoinitiator is benzoin ether; the wavelength of the ultraviolet light is 254-365 nm, and the light intensity is 5-15 mW / cm². 2 .

10. The method for preparing a high-barrier polypropylene film according to claim 6, characterized in that, The corona power of the corona treatment in step S5 is 30-50W, and the treatment speed is 1-3m / min.

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