High-performance polypropylene material for food packaging and preparation method thereof

Abstract

The application discloses a kind of high-performance polypropylene materials for food packaging and preparation method thereof, by weight parts, including the following raw materials: polypropylene 80-90 parts, POE 10-15 parts, modified montmorillonite 5-8 parts, compatilizer 4-7 parts, auxiliary 0.3-0.5 parts.The high-performance polypropylene material for food packaging, by introducing the montmorillonite modified by multiple steps in polypropylene matrix, while adding POE elastomer and compatilizer, the prepared composite material is excellent in keeping mechanical toughness and processing performance, its barrier property to oxygen, water vapor and other gases is significantly improved, and the heat resistance, ultraviolet aging resistance of the material are also significantly improved, and the material does not introduce toxic and harmful solvents or auxiliaries, preparation process is stable and controllable, can meet the stringent requirements of long shelf life, high safety and cost control in high-performance food packaging field.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a high-performance polypropylene material for food packaging and its preparation method. Background Technology

[0002] Polypropylene (PP) has become one of the most widely used food packaging materials globally due to its excellent comprehensive properties, such as good mechanical strength, outstanding heat resistance, chemical stability, non-toxicity, odorlessness, low density, and significant cost advantages. From disposable lunch boxes and beverage cups to cling film and retort pouches, polypropylene meets a wide range of market demands with its diverse forms. In particular, after modification with comonomers such as ethylene, the material's impact resistance and low-temperature toughness are significantly improved, further expanding its application in refrigerated and frozen food packaging. Furthermore, polypropylene is easy to process and can be manufactured into packaging containers of various structures through injection molding, extrusion, blow molding, and other methods, providing the food industry with a basic solution that combines functionality and economy.

[0003] However, the inherent molecular structure of polypropylene presents two major challenges for its application in high-performance food packaging. First, as a non-polar crystalline polymer, polypropylene's molecular chains are not tightly packed, exhibiting large amorphous regions, resulting in relatively poor barrier properties against gases such as oxygen and water vapor. This limitation restricts its application in packaging long-shelf-life, oxygen- or moisture-sensitive foods (such as meat products, nuts, and pastries), typically requiring multi-layer composites with high-barrier resins (such as EVOH and PA) to meet requirements, which undoubtedly increases process complexity and recycling difficulty. Second, to improve the barrier properties of polypropylene, existing technologies commonly employ filling it with inorganic nanosheet materials (such as traditional organo-montmorillonite). The technical drawbacks of this approach are: 1) Poor interfacial compatibility: the organic intercalating agents used are mostly short-chain quaternary ammonium salts, which have weak affinity for the non-polar polypropylene matrix, causing the filler to easily aggregate within the matrix and fail to form an effective barrier network. 2) Insufficient heat resistance: These organic intercalating agents are prone to thermal decomposition reactions such as Hoffmann elimination during the high temperatures (>180℃) of polypropylene melt processing, leading to the collapse of the interlayer spacing of montmorillonite. This not only significantly reduces the barrier effect, but the small molecules produced by decomposition can also affect the food contact safety of the material. 3) Sacrifice of mechanical properties: Due to weak interfacial bonding, the aggregated inorganic particles become stress concentration points, significantly reducing the impact strength and elongation at break of the material, causing the material to become brittle and unable to meet the basic requirements for toughness in packaging materials.

[0004] Chinese patent application CN106750990A discloses a food-grade, medical-grade, high-heat-resistant, high-transparency, antibacterial polypropylene material and its preparation method, relating to the field of modified polypropylene plastics. This material is made from the following raw materials in parts by weight: random copolymer polypropylene 30-60%, homopolymer polypropylene 20-50%, transparent nucleating agent 0.2-1%, antibacterial masterbatch 5-15%, compatibilizer 2-5%, lubricating dispersant 0.3-1%, and antioxidant 0.5-1%. This invention, by selecting suitable resin raw materials and the addition ratio of various additives, prepares polypropylene products with good gloss, good heat resistance, high transparency, and excellent antibacterial properties. However, this patented polypropylene material does not have good barrier properties.

[0005] Therefore, how to significantly improve the barrier properties of polypropylene without significantly sacrificing or even improving the mechanical properties of the material is a technical bottleneck that urgently needs to be solved in the field of high-performance food packaging. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a high-performance polypropylene material for food packaging and its preparation method.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A high-performance polypropylene material for food packaging, comprising the following raw materials by weight: 80-90 parts polypropylene, 10-15 parts POE, 5-8 parts modified montmorillonite, 4-7 parts compatibilizer, and 0.3-0.5 parts additives.

[0008] Preferably, a high-performance polypropylene material for food packaging comprises, by weight, the following raw materials: Polypropylene 85-90 parts, POE 10-13 parts, modified montmorillonite 6-7 parts, compatibilizer 5-7 parts, additives 0.3-0.4 parts.

[0009] Preferably, the preparation method of the modified montmorillonite includes the following steps: S1. Add montmorillonite to deionized water and stir vigorously to obtain a suspension; then add zirconium pillaring agent solution to the suspension and stir. After the treatment is completed, filter, wash, dry and calcine to obtain zirconium pillared montmorillonite. S2. Add the zirconium-pillared montmorillonite from step S1 to anhydrous ethanol, disperse it evenly by ultrasonication, then add tetrabutyl titanate ethanol solution, stir evenly, then add ethanol aqueous solution, stir and react, filter, wash and dry after the reaction is complete to obtain composite montmorillonite. S3. Add the composite montmorillonite from step S2 to an aqueous ethanol solution, then add γ-glycidyl etheroxypropyltrimethoxysilane, and heat the reaction. After the reaction is complete, filter, wash, and dry to obtain epoxidized composite montmorillonite. S4. Add the epoxide montmorillonite from step S3 to a mixed solvent of ethyl acetate and isopropanol, then add triethylamine and 1-methylimidazole, stir well, then add 4-octadecylaniline, and carry out a constant temperature reaction. After the reaction is completed, filter, wash, and dry to obtain the product.

[0010] Preferably, in step S1, the mass ratio of montmorillonite, deionized water, and zirconium pillaring agent solution is 40-50:900-1100:200-300; the stirring treatment temperature is 20-30℃ and the time is 12-16h; the calcination temperature is 500-550℃ and the time is 3-4h.

[0011] Preferably, the zirconium pillar support solution is prepared as follows: 20-30g of zirconium tetrachloride is added to 300mL of deionized water, stirred evenly, and then 5% ammonia water is added to adjust the pH to 2-2.5. The solution is then aged at 80-90℃ for 15-20h and cooled to obtain the solution.

[0012] In this invention, zirconium ions (zirconium pillar-supporting agent solution) are introduced between the layers of montmorillonite. After calcination, the zirconium ions are transformed into robust, nano-sized zirconium oxide (ZrO2) particles. These particles permanently expand the montmorillonite layers, forming a stable three-dimensional microporous structure. The zirconium oxide (ZrO2) pillars have extremely high melting points and chemical inertness, and can exist stably at calcination temperatures as high as 500-550°C. Furthermore, they can maintain structural integrity at the melt processing temperature of polypropylene (PP) (usually 200-240°C), ensuring that the montmorillonite layers do not collapse. This not only provides a channel for subsequent modifying reagents to enter the interlayer, but also provides a more tortuous path for blocking gas molecules, giving the polypropylene material a foundation for excellent barrier properties.

[0013] Preferably, in step S2, the mass concentration of tetrabutyl titanate in the tetrabutyl titanate ethanol solution is 20-30%, the mass ratio of zirconium-supported montmorillonite, anhydrous ethanol, tetrabutyl titanate ethanol solution, and ethanol-water solution is 40-50:1000-1300:300-400:30-40, and the volume ratio of ethanol to water in the ethanol-water solution is 8-9:1-2; the stirring reaction temperature is 50-60℃, and the time is 6-8h.

[0014] In this invention, zirconium-pillared montmorillonite is used as a framework. By utilizing the hydrolysis reaction of tetrabutyl titanate, a layer of nano-titanium dioxide is generated in situ on the surface and edges of the montmorillonite sheets and around the zirconium oxide pillars, which enhances the rigidity and thermal stability of the entire inorganic framework. Titanium dioxide itself is also an excellent inorganic barrier material and ultraviolet shielding agent. Its introduction, together with the sheet structure of the zirconium-pillared montmorillonite, forms a synergistic effect of "sheet barrier and particle barrier", which increases the gas diffusion path and further improves the barrier properties and UV resistance of the polypropylene material.

[0015] Preferably, in step S3, the mass ratio of the composite montmorillonite to γ-glycidyl etheroxypropyltrimethoxysilane is 40-50:3-6, and the heating reaction temperature is 60-70℃ for 3-4 hours.

[0016] In this invention, highly active epoxy groups are introduced onto montmorillonite by reacting γ-glycidoxypropyltrimethoxysilane with composite montmorillonite, which is beneficial to the subsequent reaction.

[0017] Preferably, in step S4, the volume ratio of ethyl acetate to isopropanol is 3:1, the mass ratio of montmorillonite epoxide, 4-octadecylaniline, triethylamine, and 1-methylimidazole is 40-50:4-8:0.3-0.4:0.05-0.08, and the isothermal reaction is carried out at a temperature of 80-90°C for 5-7 hours.

[0018] In this invention, 4-octadecylaniline is introduced onto montmorillonite through chemical bonding. Its nonpolar aliphatic hydrocarbon long chain has a chemical structure and physical properties highly similar to those of polypropylene (PP) molecular chains. During melt blending with PP, it physically entangles with the PP molecular chain network. This strong physical entanglement, like countless tiny anchors, produces excellent interfacial compatibility, completely solving the repulsion problem between inorganic fillers and the PP matrix and inhibiting agglomeration. Simultaneously, it allows for efficient stress transfer. When the material is under stress, the stress can be smoothly transferred from the flexible PP matrix to the high-strength montmorillonite sheets, enabling both to work synergistically. This maintains or even enhances toughness while increasing stiffness and strength. Furthermore, the rigid structure of the benzene ring in 4-octadecylaniline acts like a "fence," effectively "pinning" and restricting the local movement of nearby PP chain segments, reducing the "free volume" required for gas permeation, thereby further improving the material's barrier properties.

[0019] In this invention, a green solvent system of "ethyl acetate / isopropanol" is used, and "triethylamine / 1-methylimidazole" is used as a synergistic catalyst. On the one hand, it can replace traditional toxic solvents (such as DMF, toluene, dichloromethane, DMSO, etc.), ensuring the chemical safety of the final material used in food packaging from the source. On the other hand, the composite catalytic system of "triethylamine + 1-methylimidazole" utilizes the synergistic effect of tertiary amine and imidazole to replace traditional highly toxic catalysts. It can drive the reaction efficiently and completely at a milder temperature (80-90℃), which not only saves energy consumption but also minimizes the occurrence of high-temperature side reactions, ensuring the uniformity and integrity of the surface functionalized structure.

[0020] Preferably, the compatibilizer is maleic anhydride-grafted polypropylene, and the additive is composed of an antioxidant and polyethylene wax in a mass ratio of 2-3:1-2.

[0021] This invention also protects a method for preparing a high-performance polypropylene material for food packaging as described above, comprising the following steps: Weigh the raw materials according to the formula, mix half of the polypropylene, modified montmorillonite, and additives evenly, and then add them to a twin-screw extruder for extrusion granulation. After drying, the masterbatch is obtained. Then, add the other half of the polypropylene, masterbatch, POE, and compatibilizer to a high-speed mixer and mix evenly. Then, extrude and granulate again through a twin-screw extruder and dry to obtain the final product.

[0022] Preferably, the high-speed mixer operates at a speed of 1500-2000 r / min for 5-8 min; in the masterbatch granulation, the temperatures of the first to seventh sections of the twin-screw extruder are set to 165-170℃, 175-180℃, 185-190℃, 205-210℃, 210-215℃, 195-200℃, and 185-190℃, with the die head temperature at 190-200℃; in the finished product extrusion granulation step, the temperatures of the first to seventh sections of the twin-screw extruder are set to 160-165℃, 165-170℃, 175-180℃, 190-195℃, 190-195℃, 180-185℃, and 175-180℃, with the die head temperature at 180-185℃.

[0023] In this invention, a mature and efficient "stepwise masterbatch method" is used to prepare high-performance polypropylene materials. This process decomposes the dispersion process of modified montmorillonite into two steps: "high-shear pre-dispersion" and "mild dilution distribution". In the masterbatch preparation stage, the high concentration of fillers interacts under strong shear, which greatly improves the exfoliation efficiency. In the secondary blending stage, the granular and easy-to-handle masterbatch is "diluted" and blended with the remaining polypropylene, POE and compatibilizer. This step can be carried out under milder conditions, ensuring uniform distribution of the masterbatch while minimizing damage to the polymer matrix and POE elastomer molecular chains.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) The high-performance polypropylene material for food packaging provided by the present invention is prepared by introducing montmorillonite modified in multiple steps into a polypropylene matrix, while adding POE elastomer and compatibilizer, and finally using the "masterbatch method" for melt blending. The polypropylene composite material obtained by this method breaks through the technical bottleneck of traditional modified polypropylene in that it is difficult to balance barrier properties and toughness. The prepared composite material maintains excellent mechanical toughness and processing performance, while its barrier properties against gases such as oxygen and water vapor are significantly improved. The heat resistance and UV aging resistance of the material are also significantly improved. Furthermore, the material does not introduce toxic and harmful solvents or additives, and the preparation process is stable and controllable, which can meet the stringent requirements of long shelf life, high safety and cost control in the field of high-performance food packaging.

[0025] (2) The high-performance polypropylene material for food packaging provided by this invention incorporates modified montmorillonite, innovatively employing a two-step method of "zirconium pillar support - in-situ titanium dioxide coating". First, through the zirconium pillar support process, high-temperature resistant zirconium oxide rigid pillars are constructed between the montmorillonite layers, forming a permanent, nano-sized pore structure, fundamentally solving the technical problem that the interlayer spacing of traditional organic intercalated montmorillonite is prone to collapse and the barrier effect fails under the high temperature of polypropylene melting processing; then, by controlling the in-situ hydrolysis of titanate on the surface of zirconium pillar montmorillonite, a nano-titanium dioxide coating layer is formed, which not only physically increases the diffusion path length of gas molecules, further strengthening the barrier effect, but also endows the material with excellent ultraviolet shielding ability, slowing down the oxidative deterioration of food inside the packaging under light conditions; then By grafting an epoxy-based silane coupling agent onto the surface of montmorillonite, and then utilizing this highly reactive epoxy group to conduct a ring-opening reaction with a long-chain hydrophobic molecule (4-octadecylaniline), compared to traditional physical adsorption or short-chain silane modification, the long-chain alkylaniline molecule of this invention exhibits excellent segmental entanglement and physical compatibility with the polypropylene matrix at its octadecyl "tail." Its rigid benzene ring structure provides good interfacial support, and its connection with montmorillonite through stable covalent bonds ensures that the interfacial layer will not detach under molten shear. This long carbon chain, in the molten state, can penetrate deep into the polypropylene matrix like a polymer segment, generating strong physical entanglement and van der Waals forces, acting as a "molecular-level anchor." This is key to achieving uniform dispersion of modified montmorillonite in the matrix without agglomeration and forming a strong bond with the matrix.

[0026] (3) The high-performance polypropylene material for food packaging provided by the present invention adopts the "stepwise masterbatch method" for melt blending. That is, all the modified montmorillonite and part of the polypropylene are first prepared into a high-concentration masterbatch, and then the masterbatch is diluted and blended with other components for a second time. Compared with the traditional one-step blending method, this method can achieve a higher level of peeling and more uniform macroscopic distribution of modified montmorillonite sheets, so that the barrier potential of modified montmorillonite can be maximized, and ultimately the overall barrier performance of the composite material is stabilized and maximized. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Unless otherwise specified, all chemical reagents and materials in this invention are purchased from the market or synthesized from raw materials purchased from the market.

[0029] The polypropylene is food-grade polypropylene, with the grade name Borealis RF365MO; the POE is Dow Chemical POE 8100; and the montmorillonite is food-grade montmorillonite with a mesh size of 325.

[0030] Example 1 A high-performance polypropylene material for food packaging, comprising the following raw materials by weight: 85 parts polypropylene, 13 parts POE, 7 parts modified montmorillonite, 6 parts maleic anhydride grafted polypropylene, and 0.4 parts additives (antioxidant 1098 and polyethylene wax in a mass ratio of 2:2).

[0031] The method for preparing the modified montmorillonite includes the following steps: S1. Add 45g of montmorillonite to 950g of deionized water and stir vigorously at room temperature for 12h to obtain a suspension. Then add 250g of zirconium pillaring agent solution to the suspension and stir at 25℃ for 14h. After treatment, filter, wash, and dry, and calcine at 550℃ in air atmosphere for 3h to obtain zirconium pillared montmorillonite. The zirconium pillaring agent solution is prepared as follows: Add 25g of zirconium tetrachloride to 300mL of deionized water, stir evenly, add 5% ammonia water to adjust the pH to 2.5, age at 85℃ for 18h, and cool to obtain the product. S2. Add 45g of zirconium-supported montmorillonite from step S1 to 1200g of anhydrous ethanol and disperse it evenly by ultrasonication. Then add 350g of tetrabutyl titanate ethanol solution (tetrabutyl titanate mass concentration is 25%), stir evenly, and then add 35g of ethanol aqueous solution (ethanol to water volume ratio is 8.5:1.5). Stir and react at 55℃ for 7h. After the reaction is completed, filter, wash and dry to obtain composite montmorillonite. S3. Add 45g of composite montmorillonite from step S2 to 900mL of ethanol aqueous solution (ethanol mass fraction is 80%), then add 5g of γ-glycidoxypropyltrimethoxysilane, react at 65℃ for 3.5h, filter, wash and dry after the reaction is completed to obtain epoxidized composite montmorillonite. S4. Add 45g of epoxide montmorillonite from step S3 to a mixed solvent of 1L of ethyl acetate and isopropanol (volume ratio of ethyl acetate to isopropanol is 3:1), then add 0.35g of triethylamine and 0.07g of 1-methylimidazole. After stirring evenly, add 7g of 4-octadecylaniline. React at a constant temperature of 85℃ for 6h under a nitrogen atmosphere. After the reaction is complete, filter, wash, and dry to obtain the final product.

[0032] A method for preparing a high-performance polypropylene material for food packaging includes the following steps: Weigh the raw materials according to the formula. Mix half of the polypropylene, modified montmorillonite, and additives evenly, and then add them to a twin-screw extruder for extrusion granulation. The temperature of the first to seventh sections of the twin-screw extruder is set to 170℃, 180℃, 190℃, 210℃, 215℃, 200℃, and 190℃, with the die head temperature at 190℃. After drying, masterbatch is obtained. Then, the other half of the polypropylene, masterbatch, POE, and compatibilizer are added to a high-speed mixer and mixed evenly at a speed of 1500 r / min for 8 min. The mixture is then extruded and granulated again through a twin-screw extruder and dried. The temperature of the first to seventh sections of the twin-screw extruder is set to 160℃, 170℃, 180℃, 195℃, 195℃, 185℃, and 180℃, with the die head temperature at 180℃.

[0033] Example 2 A high-performance polypropylene material for food packaging, comprising the following raw materials by weight: 80 parts polypropylene, 10 parts POE, 5 parts modified montmorillonite, 4 parts maleic anhydride grafted polypropylene, and 0.3 parts additives (antioxidant 1098 and polyethylene wax in a mass ratio of 2:1).

[0034] The method for preparing the modified montmorillonite includes the following steps: S1. Add 40g of montmorillonite to 900g of deionized water and stir vigorously at room temperature for 12h to obtain a suspension; then add 200g of zirconium pillaring agent solution to the suspension and stir at 20℃ for 16h. After treatment, filter, wash, and dry, and calcine at 500℃ in air atmosphere for 4h to obtain zirconium pillared montmorillonite; the zirconium pillaring agent solution is prepared as follows: add 20g of zirconium tetrachloride to 300mL of deionized water, stir evenly, add 5% ammonia water to adjust the pH to 2, age at 80℃ for 20h, and cool to obtain the product; S2. Add 40g of zirconium-supported montmorillonite from step S1 to 1000g of anhydrous ethanol and disperse it evenly by ultrasonication. Then add 300g of tetrabutyl titanate ethanol solution (tetrabutyl titanate mass concentration is 20%), stir evenly, and then add 30g of ethanol aqueous solution (ethanol to water volume ratio is 9:1). Stir and react at 50℃ for 8h. After the reaction is completed, filter, wash and dry to obtain composite montmorillonite. S3. Add 40g of composite montmorillonite from step S2 to 900mL of ethanol aqueous solution (ethanol mass fraction is 80%), then add 3g of γ-glycidoxypropyltrimethoxysilane, react at 60℃ for 4h, filter, wash and dry after the reaction is completed to obtain epoxidized composite montmorillonite. S4. Add 40g of montmorillonite epoxide from step S3 to a mixed solvent of 1L of ethyl acetate and isopropanol (volume ratio of ethyl acetate to isopropanol is 3:1). Then add 0.3g of triethylamine and 0.05g of 1-methylimidazole. After stirring evenly, add 4g of 4-octadecylaniline. React at a constant temperature of 80℃ for 7h under a nitrogen atmosphere. After the reaction is complete, filter, wash, and dry to obtain the final product.

[0035] A method for preparing a high-performance polypropylene material for food packaging includes the following steps: Weigh the raw materials according to the formula. Mix half of the polypropylene, modified montmorillonite, and additives evenly, and then add them to a twin-screw extruder for extrusion granulation. The temperature of the first to seventh sections of the twin-screw extruder is set to 170℃, 180℃, 190℃, 210℃, 215℃, 200℃, and 190℃, with the die head temperature at 190℃. After drying, masterbatch is obtained. Then, the other half of the polypropylene, masterbatch, POE, and compatibilizer are added to a high-speed mixer and mixed evenly at a speed of 1500 r / min for 8 min. The mixture is then extruded and granulated again through a twin-screw extruder and dried. The temperature of the first to seventh sections of the twin-screw extruder is set to 160℃, 170℃, 180℃, 195℃, 195℃, 185℃, and 180℃, with the die head temperature at 180℃.

[0036] Example 3 A high-performance polypropylene material for food packaging, comprising the following raw materials by weight: 90 parts polypropylene, 15 parts POE, 8 parts modified montmorillonite, 7 parts maleic anhydride grafted polypropylene, and 0.5 parts additives (antioxidant 1098 and polyethylene wax in a mass ratio of 3:2).

[0037] The method for preparing the modified montmorillonite includes the following steps: S1. Add 50g of montmorillonite to 1000g of deionized water and stir vigorously at room temperature for 12h to obtain a suspension. Then add 300g of zirconium pillaring agent solution to the suspension and stir at 30℃ for 12h. After treatment, filter, wash, and dry, and calcine at 550℃ in air atmosphere for 3h to obtain zirconium pillared montmorillonite. The zirconium pillaring agent solution is prepared as follows: Add 30g of zirconium tetrachloride to 300mL of deionized water, stir evenly, add 5% ammonia water to adjust the pH to 2.5, age at 90℃ for 15h, and cool to obtain the product. S2. Add 50g of zirconium-supported montmorillonite from step S1 to 300g of anhydrous ethanol and disperse it evenly by ultrasonication. Then add 400g of tetrabutyl titanate ethanol solution (tetrabutyl titanate mass concentration is 30%), stir evenly, and then add 40g of ethanol aqueous solution (ethanol to water volume ratio is 8:2). Stir and react at 60℃ for 6h. After the reaction is completed, filter, wash and dry to obtain composite montmorillonite. S3. Add 50g of composite montmorillonite from step S2 to 900mL of ethanol aqueous solution (ethanol mass fraction is 80%), then add 6g of γ-glycidoxypropyltrimethoxysilane, react at 70℃ for 3h, filter, wash and dry after the reaction is completed to obtain epoxidized composite montmorillonite. S4. Add 50g of montmorillonite epoxide from step S3 to a mixed solvent of 1L of ethyl acetate and isopropanol (volume ratio of ethyl acetate to isopropanol is 3:1). Then add 0.4g of triethylamine and 0.08g of 1-methylimidazole. After stirring evenly, add 8g of 4-octadecylaniline. React at a constant temperature of 90℃ for 5h under a nitrogen atmosphere. After the reaction is complete, filter, wash, and dry to obtain the final product.

[0038] A method for preparing a high-performance polypropylene material for food packaging includes the following steps: Weigh the raw materials according to the formula. Mix half of the polypropylene, modified montmorillonite, and additives evenly, and then add them to a twin-screw extruder for extrusion granulation. The temperature of the first to seventh sections of the twin-screw extruder is set to 170℃, 180℃, 190℃, 210℃, 215℃, 200℃, and 190℃, with the die head temperature at 190℃. After drying, masterbatch is obtained. Then, the other half of the polypropylene, masterbatch, POE, and compatibilizer are added to a high-speed mixer and mixed evenly at a speed of 1500 r / min for 8 min. The mixture is then extruded and granulated again through a twin-screw extruder and dried. The temperature of the first to seventh sections of the twin-screw extruder is set to 160℃, 170℃, 180℃, 195℃, 195℃, 185℃, and 180℃, with the die head temperature at 180℃.

[0039] Comparative Example 1 A high-performance polypropylene material for food packaging, comprising the following raw materials by weight: 85 parts polypropylene, 13 parts POE, 7 parts modified montmorillonite, 6 parts maleic anhydride grafted polypropylene, and 0.4 parts additives (antioxidant 1098 and polyethylene wax in a mass ratio of 2:2).

[0040] The method for preparing the modified montmorillonite includes the following steps: S1. Add 45g of montmorillonite to 950g of deionized water and stir vigorously at room temperature for 12h to obtain a suspension. Then add 250g of zirconium pillaring agent solution to the suspension and stir at 25℃ for 14h. After treatment, filter, wash, and dry, and calcine at 550℃ in air atmosphere for 3h to obtain zirconium pillared montmorillonite. The zirconium pillaring agent solution is prepared as follows: Add 25g of zirconium tetrachloride to 300mL of deionized water, stir evenly, add 5% ammonia water to adjust the pH to 2.5, age at 85℃ for 18h, and cool to obtain the product. S2. Add 45g of zirconium-supported montmorillonite from step S1 to 1200g of anhydrous ethanol and disperse it evenly by ultrasonication. Then add 350g of tetrabutyl titanate ethanol solution (tetrabutyl titanate mass concentration is 25%), stir evenly, and then add 35g of ethanol aqueous solution (ethanol to water volume ratio is 8.5:1.5). Stir and react at 55℃ for 7h. After the reaction is completed, filter, wash and dry to obtain composite montmorillonite. S3. Add 45g of composite montmorillonite from step S2 to 900mL of ethanol aqueous solution (ethanol mass fraction is 80%), then add 5g of γ-glycidoxypropyltrimethoxysilane, react at 65℃ for 3.5h, filter, wash and dry after the reaction is complete to obtain the final product.

[0041] A method for preparing a high-performance polypropylene material for food packaging includes the following steps: Weigh the raw materials according to the formula. Mix half of the polypropylene, modified montmorillonite, and additives evenly, and then add them to a twin-screw extruder for extrusion granulation. The temperature of the first to seventh sections of the twin-screw extruder is set to 170℃, 180℃, 190℃, 210℃, 215℃, 200℃, and 190℃, with the die head temperature at 190℃. After drying, masterbatch is obtained. Then, the other half of the polypropylene, masterbatch, POE, and compatibilizer are added to a high-speed mixer and mixed evenly at a speed of 1500 r / min for 8 min. The mixture is then extruded and granulated again through a twin-screw extruder and dried. The temperature of the first to seventh sections of the twin-screw extruder is set to 160℃, 170℃, 180℃, 195℃, 195℃, 185℃, and 180℃, with the die head temperature at 180℃.

[0042] Compared to Example 1, the modified montmorillonite in this comparative example did not introduce 4-octadecylaniline.

[0043] Comparative Example 2 A high-performance polypropylene material for food packaging, comprising the following raw materials by weight: 85 parts polypropylene, 13 parts POE, 7 parts modified montmorillonite, 6 parts maleic anhydride grafted polypropylene, and 0.4 parts additives (antioxidant 1098 and polyethylene wax in a mass ratio of 2:2).

[0044] The method for preparing the modified montmorillonite includes the following steps: S1. Add 45g of montmorillonite to 1200g of anhydrous ethanol and disperse it evenly by ultrasonication. Then add 350g of tetrabutyl titanate ethanol solution (tetrabutyl titanate mass concentration is 25%), stir evenly, and then add 35g of ethanol aqueous solution (ethanol to water volume ratio is 8.5:1.5). Stir and react at 55℃ for 7h. After the reaction is completed, filter, wash and dry to obtain composite montmorillonite. S2. Add 45g of composite montmorillonite from step S1 to 900mL of ethanol aqueous solution (ethanol mass fraction is 80%), then add 5g of γ-glycidoxypropyltrimethoxysilane, react at 65℃ for 3.5h, filter, wash and dry after the reaction is completed to obtain epoxidized composite montmorillonite. S3. Add 45g of epoxide montmorillonite from step S2 to a mixed solvent of 1L ethyl acetate and isopropanol (volume ratio of ethyl acetate to isopropanol is 3:1), then add 0.35g of triethylamine and 0.07g of 1-methylimidazole. After stirring evenly, add 7g of 4-octadecylaniline. React at a constant temperature of 85℃ for 6h under a nitrogen atmosphere. After the reaction is complete, filter, wash, and dry to obtain the final product.

[0045] A method for preparing a high-performance polypropylene material for food packaging includes the following steps: Weigh the raw materials according to the formula. Mix half of the polypropylene, modified montmorillonite, and additives evenly, and then add them to a twin-screw extruder for extrusion granulation. The temperature of the first to seventh sections of the twin-screw extruder is set to 170℃, 180℃, 190℃, 210℃, 215℃, 200℃, and 190℃, with the die head temperature at 190℃. After drying, masterbatch is obtained. Then, the other half of the polypropylene, masterbatch, POE, and compatibilizer are added to a high-speed mixer and mixed evenly at a speed of 1500 r / min for 8 min. The mixture is then extruded and granulated again through a twin-screw extruder and dried. The temperature of the first to seventh sections of the twin-screw extruder is set to 160℃, 170℃, 180℃, 195℃, 195℃, 185℃, and 180℃, with the die head temperature at 180℃.

[0046] Compared with Example 1, this comparative example did not perform zirconium pillar support on the montmorillonite during the preparation of the modified montmorillonite.

[0047] Comparative Example 3 A high-performance polypropylene material for food packaging, comprising the following raw materials by weight: 85 parts polypropylene, 13 parts POE, 7 parts modified montmorillonite, 6 parts maleic anhydride grafted polypropylene, and 0.4 parts additives (antioxidant 1098 and polyethylene wax in a mass ratio of 2:2).

[0048] The method for preparing the modified montmorillonite includes the following steps: S1. Add 45g of montmorillonite to 950g of deionized water and stir vigorously at room temperature for 12h to obtain a suspension. Then add 250g of zirconium pillaring agent solution to the suspension and stir at 25℃ for 14h. After treatment, filter, wash, and dry, and calcine at 550℃ in air atmosphere for 3h to obtain zirconium pillared montmorillonite. The zirconium pillaring agent solution is prepared as follows: Add 25g of zirconium tetrachloride to 300mL of deionized water, stir evenly, add 5% ammonia water to adjust the pH to 2.5, age at 85℃ for 18h, and cool to obtain the product. S2. Add 45g of zirconium-pillared montmorillonite from step S1 to 900mL of ethanol aqueous solution (ethanol mass fraction is 80%), then add 5g of γ-glycidoxypropyltrimethoxysilane, react at 65℃ for 3.5h, filter, wash and dry after the reaction is completed to obtain epoxidized composite montmorillonite. S3. Add 45g of epoxide montmorillonite from step S2 to a mixed solvent of 1L ethyl acetate and isopropanol (volume ratio of ethyl acetate to isopropanol is 3:1), then add 0.35g of triethylamine and 0.07g of 1-methylimidazole. After stirring evenly, add 7g of 4-octadecylaniline. React at a constant temperature of 85℃ for 6h under a nitrogen atmosphere. After the reaction is complete, filter, wash, and dry to obtain the final product.

[0049] A method for preparing a high-performance polypropylene material for food packaging includes the following steps: Weigh the raw materials according to the formula. Mix half of the polypropylene, modified montmorillonite, and additives evenly, and then add them to a twin-screw extruder for extrusion granulation. The temperature of the first to seventh sections of the twin-screw extruder is set to 170℃, 180℃, 190℃, 210℃, 215℃, 200℃, and 190℃, with the die head temperature at 190℃. After drying, masterbatch is obtained. Then, the other half of the polypropylene, masterbatch, POE, and compatibilizer are added to a high-speed mixer and mixed evenly at a speed of 1500 r / min for 8 min. The mixture is then extruded and granulated again through a twin-screw extruder and dried. The temperature of the first to seventh sections of the twin-screw extruder is set to 160℃, 170℃, 180℃, 195℃, 195℃, 185℃, and 180℃, with the die head temperature at 180℃.

[0050] Compared with Example 1, this comparative example did not introduce titanium dioxide in the preparation of modified montmorillonite.

[0051] Comparative Example 4 A high-performance polypropylene material for food packaging, comprising the following raw materials by weight: 85 parts polypropylene, 13 parts POE, 7 parts modified montmorillonite, 6 parts maleic anhydride grafted polypropylene, and 0.4 parts additives (antioxidant 1098 and polyethylene wax in a mass ratio of 2:2).

[0052] The method for preparing the modified montmorillonite includes the following steps: S1. Add 45g of montmorillonite to 950g of deionized water and stir vigorously at room temperature for 12h to obtain a suspension. Then add 250g of zirconium pillaring agent solution to the suspension and stir at 25℃ for 14h. After treatment, filter, wash, and dry, and calcine at 550℃ in air atmosphere for 3h to obtain zirconium pillared montmorillonite. The zirconium pillaring agent solution is prepared as follows: Add 25g of zirconium tetrachloride to 300mL of deionized water, stir evenly, add 5% ammonia water to adjust the pH to 2.5, age at 85℃ for 18h, and cool to obtain the product. S2. Add 45g of zirconium-supported montmorillonite from step S1 to 1200g of anhydrous ethanol and disperse it evenly by ultrasonication. Then add 350g of tetrabutyl titanate ethanol solution (tetrabutyl titanate mass concentration is 25%), stir evenly, and then add 35g of ethanol aqueous solution (ethanol to water volume ratio is 8.5:1.5). Stir and react at 55℃ for 7h. After the reaction is completed, filter, wash and dry to obtain composite montmorillonite. S3. Mix 45g of composite montmorillonite and 7g of 4-octadecylaniline from step S2 until homogeneous to obtain the final product.

[0053] A method for preparing a high-performance polypropylene material for food packaging includes the following steps: Weigh the raw materials according to the formula. Mix half of the polypropylene, modified montmorillonite, and additives evenly, and then add them to a twin-screw extruder for extrusion granulation. The temperature of the first to seventh sections of the twin-screw extruder is set to 170℃, 180℃, 190℃, 210℃, 215℃, 200℃, and 190℃, with the die head temperature at 190℃. After drying, masterbatch is obtained. Then, the other half of the polypropylene, masterbatch, POE, and compatibilizer are added to a high-speed mixer and mixed evenly at a speed of 1500 r / min for 8 min. The mixture is then extruded and granulated again through a twin-screw extruder and dried. The temperature of the first to seventh sections of the twin-screw extruder is set to 160℃, 170℃, 180℃, 195℃, 195℃, 185℃, and 180℃, with the die head temperature at 180℃.

[0054] Compared with Example 1, the modified montmorillonite in this comparative example was obtained by physically mixing composite montmorillonite with 4-octadecylaniline.

[0055] The performance of the high-performance polypropylene materials for food packaging prepared in Examples 1-3 and Comparative Examples 1-4 was tested as follows: Each group of materials was injection molded into specimens. Tensile strength and elongation at break were tested according to standard GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets". Notched impact strength was tested according to standard GB / T 1843-2008 "Determination of cantilever beam impact strength of plastics", using specimens with dimensions of 80mm × 10mm × 4mm and a remaining notch thickness of 2mm. Each group of materials was blow-molded into films (50μm). Oxygen permeability was tested according to GB / T 1038.1-2022 "Test methods for gas permeability of plastic products films and sheets - Part 1: Pressure difference method", with a test temperature of 23℃, relative humidity of 1%RH, and pressure difference of 0.1MPa. Water vapor permeability was tested according to GB / T... The test was conducted according to GB / T 16422.3-2022 "Determination of Water Vapor Transmission of Plastic Films and Sheets - Infrared Detector Method", with a test temperature of 38℃ and a relative humidity of 90%RH. The UV aging resistance was tested according to GB / T 16422.3-2022 "Laboratory Light Source Exposure Test Methods for Plastics - Part 3: Fluorescent Ultraviolet Lamps", with aging conditions of 300W / m² UV intensity. 2 The aging temperature was 50℃, and the aging time was 144 hours. The tensile strength retention rate of the samples after aging was tested. The test results are shown in Table 1 below: Table 1 As can be seen from Table 1 above, the high-performance polypropylene material for food packaging prepared by this invention maintains excellent mechanical toughness and processing performance, while significantly improving its barrier properties against gases such as oxygen and water vapor, and also significantly improving its resistance to ultraviolet aging, showing good application prospects.

[0056] The above description is a further detailed explanation of the present invention in conjunction with specific implementation examples. It should not be considered that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the protection scope of the present invention.

[0057] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-performance polypropylene material for food packaging, characterized in that, By weight, it includes the following ingredients: Polypropylene 80-90 parts, POE 10-15 parts, modified montmorillonite 5-8 parts, compatibilizer 4-7 parts, additives 0.3-0.5 parts; The preparation method of the modified montmorillonite includes the following steps: S1. Add montmorillonite to deionized water and stir vigorously to obtain a suspension; then add zirconium pillaring agent solution to the suspension and stir. After the treatment is completed, filter, wash, dry and calcine to obtain zirconium pillared montmorillonite. S2. Zirconium-supported montmorillonite was added to anhydrous ethanol and ultrasonically dispersed evenly. Then, tetrabutyl titanate ethanol solution was added and stirred evenly. After stirring, an aqueous ethanol solution was added and stirred to react, thus obtaining composite montmorillonite. S3. Add the composite montmorillonite to an aqueous ethanol solution, then add γ-glycidoxypropyltrimethoxysilane and heat to react, thus obtaining epoxidized composite montmorillonite. S4. Add epoxide montmorillonite to a mixed solvent of ethyl acetate and isopropanol, then add triethylamine and 1-methylimidazole, stir well, then add 4-octadecylaniline, and carry out a constant temperature reaction. After the reaction is completed, filter, wash and dry to obtain the product.

2. The high-performance polypropylene material for food packaging according to claim 1, characterized in that, By weight, it includes the following ingredients: Polypropylene 85-90 parts, POE 10-13 parts, modified montmorillonite 6-7 parts, compatibilizer 5-7 parts, additives 0.3-0.4 parts.

3. The high-performance polypropylene material for food packaging according to claim 1, characterized in that, In step S1, the mass ratio of montmorillonite, deionized water, and zirconium pillaring agent solution is 40-50:900-1100:200-300. The stirring treatment temperature is 20-30℃, and the time is 12-16h. The calcination temperature is 500-550℃, and the time is 3-4h. The zirconium pillaring agent solution is prepared as follows: 20-30g of zirconium tetrachloride is added to 300mL of deionized water, stirred evenly, and then 5% ammonia water is added to adjust the pH to 2-2.

5. The solution is aged at 80-90℃ for 15-20h and then cooled to obtain the final product.

4. The high-performance polypropylene material for food packaging according to claim 1, characterized in that, In step S2, the mass concentration of tetrabutyl titanate in the tetrabutyl titanate ethanol solution is 20-30%, the mass ratio of zirconium-supported montmorillonite, anhydrous ethanol, tetrabutyl titanate ethanol solution, and ethanol-water solution is 40-50:1000-1300:300-400:30-40, and the volume ratio of ethanol to water in the ethanol-water solution is 8-9:1-2; the stirring reaction temperature is 50-60℃, and the time is 6-8h.

5. The high-performance polypropylene material for food packaging according to claim 1, characterized in that, In step S3, the mass ratio of the composite montmorillonite to γ-glycidyl etheroxypropyltrimethoxysilane is 40-50:3-6, and the heating reaction temperature is 60-70℃ for 3-4 hours.

6. The high-performance polypropylene material for food packaging according to claim 1, characterized in that, In step S4, the volume ratio of ethyl acetate to isopropanol is 3:1, the mass ratio of montmorillonite epoxide, 4-octadecylaniline, triethylamine, and 1-methylimidazole is 40-50:4-8:0.3-0.4:0.05-0.08, and the isothermal reaction is carried out at a temperature of 80-90℃ for 5-7 hours.

7. The high-performance polypropylene material for food packaging according to claim 1, characterized in that, The compatibilizer is maleic anhydride-grafted polypropylene, and the additive is composed of an antioxidant and polyethylene wax in a mass ratio of 2-3:1-2.

8. A method for preparing a high-performance polypropylene material for food packaging as described in any one of claims 1-7, characterized in that, Includes the following steps: Weigh the raw materials according to the formula, mix half of the polypropylene, modified montmorillonite, and additives evenly, and then add them to a twin-screw extruder for extrusion granulation. After drying, the masterbatch is obtained. Then, add the other half of the polypropylene, masterbatch, POE, and compatibilizer to a high-speed mixer and mix evenly. Then, extrude and granulate again through a twin-screw extruder and dry to obtain the final product.

9. The preparation method according to claim 8, characterized in that, The high-speed mixer operates at a speed of 1500-2000 r / min for 5-8 min.

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