High-barrier food-grade polypropylene composite material and preparation method thereof
By adding cyclic olefin copolymers and modified nanocellulose to polypropylene materials to form a dense network, the problem of insufficient barrier properties of polypropylene materials in food packaging is solved, achieving highly efficient gas and ultraviolet barrier properties, making it suitable for food packaging.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHENGDU HUAPU PLASTIC CONTAINER CO LTD
- Filing Date
- 2026-04-29
- Publication Date
- 2026-06-02
AI Technical Summary
Existing polypropylene materials have insufficient barrier properties in food packaging, especially low barrier properties against gases such as oxygen and water vapor, which makes food prone to oxidation and spoilage. Existing improvement methods suffer from poor interfacial compatibility, insufficient heat resistance, and decreased mechanical properties.
The high-barrier food-grade polypropylene composite material, comprising polypropylene resin, cyclic olefin copolymer, nano-layered silica and modified nanocellulose, is blended by a twin-screw extruder to form a dense network to improve barrier performance.
It significantly improves the water-blocking, oxygen-blocking, and UV-resistant properties of polypropylene materials, extends the shelf life of food, and has a simple production method and moderate cost.
Abstract
Description
Technical Field
[0001] This invention relates to the field of polymer materials technology, and more specifically to a high-barrier food-grade polypropylene composite material 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, excellent heat resistance, chemical stability, non-toxicity, odorlessness, low density, and significant cost advantages. In plastic packaging, the proportion of barrier plastic packaging is rapidly increasing, especially in industries such as food and pharmaceuticals where strict requirements for the barrier performance of packaging materials are placed. As a general-purpose plastic with good comprehensive properties, polypropylene has wide applications in many fields. A prominent advantage of using polypropylene as a barrier packaging material is its excellent water vapor barrier performance. In addition, polypropylene has low density, high temperature resistance, good microwave adaptability, good chemical and oil resistance, and is easy to process and mold. In particular, it has good hygiene properties, is easy to recycle, and meets current environmental protection requirements. However, due to its structural characteristics, polypropylene has relatively low barrier properties against gases such as oxygen and carbon dioxide (lower than traditional barrier materials), which to some extent limits its application in the packaging field. When applied to barrier packaging, it needs to be combined with other high-barrier materials using a multi-layer co-extrusion method to prepare composite films. However, this method is relatively complex, requires large equipment investment, and is difficult to recycle. Therefore, improving the barrier properties of polypropylene materials has become one of the keys to expanding their application in the packaging field.
[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] CN111040306 A reports a polypropylene material with high barrier properties and its preparation method. It uses a foaming agent to produce microporous foamed polypropylene, primarily for noise reduction in the manufacture of automotive parts. CN107973991A reports a polypropylene composition with high barrier properties and a biaxially oriented film prepared therefrom. The addition of polyethylene enhances water vapor barrier properties, resulting in a stretched film with high water vapor barrier characteristics, but the effect is limited. CN108164908 A reports a high-strength, high-toughness, and high-barrier polypropylene composite material and its preparation method. The addition of EVOH and layered dihydroxyhydroxide further improves the gas permeation barrier properties of polypropylene, but the effect is still not satisfactory.
[0005] Given the above situation, existing technologies generally require the addition of a large number of other substances to improve the barrier properties of polypropylene. However, while the barrier properties of polypropylene used in traditional food packaging are effective, they cannot effectively prevent the penetration of external factors such as oxygen, moisture, and light. This makes it easy for the food inside to come into contact with oxygen, leading to oxidation, spoilage, and contamination, thereby shortening the shelf life of the food.
[0006] Therefore, providing a high-performance polypropylene composite material that can effectively isolate external factors such as oxygen and water vapor is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention
[0007] In view of this, the present invention provides a high-barrier food-grade polypropylene composite material and its preparation method, which solves the problem of low barrier performance in food packaging in the prior art.
[0008] One objective of this invention is to provide a high-barrier food-grade polypropylene composite material, comprising the following raw materials by weight:
[0009] 70-90 parts polypropylene resin, 10-20 parts cyclic olefin copolymer, 5-10 parts nano-layered silica, 5-15 parts modified nanocellulose, and 0.1-0.3 parts compatibilizer.
[0010] The nano-layered silica is prepared from food-grade organic modified vermiculite.
[0011] Preferably, the self-melting index of the polypropylene resin is 0.5-10 g / min.
[0012] Preferably, the polypropylene resin is homopolymer polypropylene or block copolymer polypropylene.
[0013] More preferably, the homopolymer polypropylene has a crystallinity of over 70% and an isotacticity greater than 97.5%; a wide molecular weight distribution (Mw / Mn = 4.0 to 7.0); and the block copolymer polypropylene has ethylene as its comonomer, with a ethylene monomer repeating unit mass content of 5 to 16%.
[0014] Preferably, the cyclic olefin copolymer is an amorphous cyclic olefin copolymer with a molecular weight of 4,000-50,000 and a degree of polymerization of 200-800.
[0015] Furthermore, the method for preparing the nano-layered silica includes the following steps:
[0016] (1) The vermiculite was rapidly expanded at 850℃ for 5 minutes, washed with water to remove impurities, dried to obtain expanded vermiculite, and then crushed for later use.
[0017] (2) Take expanded vermiculite and put it into a hydrothermal reactor. Add citric acid and water, put it into an oven and react at 30°C for 10 hours. Then take it out to obtain a silica mixture.
[0018] The solid-liquid ratio of the expanded vermiculite, citric acid, and water is 0.8 g: 10 g: 50 mL;
[0019] (3) Filter the silica mixture to obtain solid layered silica and filtrate. Dry the solid layered silica at 65°C for 10 hours to obtain nano-layered silica.
[0020] Furthermore, the preparation method of the modified nanocellulose includes the following steps:
[0021] Nanocellulose was added to anhydrous ethanol and ultrasonically dispersed until uniform. Tetrabutyl titanate ethanol solution was then added and ultrasonically dispersed until uniform. After that, an aqueous ethanol solution was added, the mixture was stirred and reacted, and then centrifuged, dried, and ground to obtain modified nanocellulose.
[0022] Preferably, the concentration of tetrabutyl titanate in the tetrabutyl titanate ethanol solution is 20-30 wt%.
[0023] Preferably, the mass ratio of the nanocellulose, anhydrous ethanol, tetrabutyl titanate, and ethanol aqueous solution is 4-5:100-130:30-40:3-4, and the volume ratio of ethanol to water in the ethanol aqueous solution is 8:1.
[0024] Preferably, the stirring reaction is carried out at 50-60°C for 6-8 hours.
[0025] Preferably, the compatibilizer is maleic anhydride-grafted polypropylene.
[0026] The second objective of this invention is to provide a method for preparing a high-barrier food-grade polypropylene composite material. The specific steps include: weighing raw materials according to the specified ratio; placing polypropylene resin, cyclic olefin copolymer, nano-layered silica, modified nanocellulose, and compatibilizer in a high-speed mixer and mixing them to obtain a mixture; feeding the mixture into a twin-screw extruder with a screw speed of 100-500 r / min and a blending temperature of 190-230℃ to obtain the high-barrier food-grade polypropylene composite material.
[0027] The barrier polypropylene composition and its preparation method described in this invention are relatively economical. Only a small amount of other substances need to be added to significantly improve the barrier properties of the polypropylene composition. It is suitable for the packaging industry with barrier and hygiene requirements, such as food packaging.
[0028] As can be seen from the above technical solution, compared with the prior art, the beneficial effects achieved by the present invention include at least the following:
[0029] (1) In this invention, a cyclic olefin copolymer is added to the polypropylene resin base. When the polymer system is extruded from a twin-screw extruder or injection molding machine, the cyclic olefin copolymer can be well mixed with the polypropylene, which can effectively improve the water-blocking performance of the polypropylene composite material. The higher the barrier performance, the lower the water vapor transmission rate.
[0030] (2) Nanolayered silica and nanocellulose are nanoscale particulate materials with high surface area and adsorption capacity, which can enhance the barrier properties of polypropylene composite materials and effectively isolate external oxygen and humidity. Furthermore, this invention uses nanocellulose as a skeleton and utilizes the hydrolysis reaction of tetrabutyl titanate to generate a layer of nano-titanium dioxide in situ on the surface of nanocellulose, which enhances the rigidity and thermal stability of the entire skeleton. In addition, titanium dioxide itself is also an excellent inorganic barrier material and ultraviolet shielding agent. Its introduction forms a synergistic effect of "layer barrier and particulate barrier" with nanocellulose, increases the gas diffusion path, and further improves the barrier properties and UV resistance of polypropylene materials.
[0031] (3) This invention uses high-surface-area nano-layered silica, whose layers form tortuous diffusion paths and dense networks, significantly extending the O2 penetration time and reducing water channels. It can block / regulate water vapor penetration, and the high specific surface area enhances the bonding ability with the substrate interface, effectively reducing interface defects and pinholes. The layered structure of nano-layered silica also has a labyrinth effect, which can effectively preserve aroma and prevent cross-contamination when used in food packaging.
[0032] (4) The polypropylene composition prepared in this invention has good barrier properties against water vapor, oxygen and ultraviolet light. The preparation method is relatively simple, the conditions are easy to control, the applicability is strong, and the production cost is not significantly increased. Detailed Implementation
[0033] The technical solutions 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.
[0034] Unless otherwise specified, all chemical reagents and materials in this invention were purchased from the market or synthesized from raw materials purchased from the market.
[0035] The homopolymer polypropylene resin is a homopolymer polypropylene produced by Sinopec Tianjin Branch, with the trade name PPH-E03 and a melt flow rate of 3g / 10min.
[0036] The block copolymer polypropylene resin is a block copolymer polypropylene produced by Sinopec Tianjin Branch, with the trade name EPS30R and a melt flow rate of 2.5 g / 10 min.
[0037] The cyclic olefin copolymer is TOPAS 8007 manufactured by Leron GmbH, Germany;
[0038] The vermiculite was purchased from the market;
[0039] Maleic anhydride-grafted polypropylene is produced by ExxonMobil Chemicals, under the brand name Exxelor PO 1015.
[0040] In the preparation method of this invention, the screw speed can be 100 r / min, 150 r / min, 200 r / min, 250 r / min, 300 r / min, 350 r / min, 400 r / min, 450 r / min or r / min; the blending temperature of the mixture can be 190℃, 200℃, 210℃, 220℃ or 230℃.
[0041] The present invention will be further described below with reference to specific embodiments, but the scope of the present invention is not limited to these embodiments.
[0042] Example 1
[0043] A high-barrier food-grade polypropylene composite material, comprising the following raw materials by weight:
[0044] 70 parts homopolymer polypropylene, 10 parts cyclic olefin copolymer, 5 parts nanolayered silica, 5 parts modified nanocellulose, and 0.2 parts maleic anhydride grafted polypropylene.
[0045] The preparation method of nano-layered silica includes the following steps:
[0046] (1) The vermiculite was rapidly expanded at 850℃ for 5 minutes, washed with water to remove impurities, dried to obtain expanded vermiculite, and then crushed for later use.
[0047] (2) Take 0.8 g of expanded vermiculite and put it into a hydrothermal reactor. Add 10 g of citric acid and 50 mL of water. Place it in an oven and react at 30 °C for 10 h. Take it out to obtain a silica mixture.
[0048] (3) Filter the silica mixture to obtain solid layered silica and filtrate. Dry the solid layered silica at 65°C for 10 hours to obtain nano-layered silica.
[0049] According to the test results, the specific surface area of vermiculite in this embodiment is 15 m2 / g, and the specific surface area of the final layered silica is 521 m2 / g.
[0050] The preparation method of modified nanocellulose includes the following steps:
[0051] Nanocellulose was added to anhydrous ethanol and ultrasonically dispersed evenly. Tetrabutyl titanate ethanol solution was then added and ultrasonically dispersed evenly. After that, an ethanol-water solution (volume ratio 8:1) was added and reacted at 50-60℃ for 6-8 hours with continuous stirring. After centrifugation, drying, and grinding, modified nanocellulose was obtained.
[0052] The concentration of tetrabutyl titanate in the ethanol solution is 25 wt%.
[0053] The mass ratio of the nanocellulose, anhydrous ethanol, tetrabutyl titanate, and aqueous ethanol solution is 5:100:30:4.
[0054] The preparation method, specifically including the following steps:
[0055] Weigh the raw materials according to the formula, and put the polypropylene resin, cyclic olefin copolymer, nano-layered silica, modified nanocellulose and compatibilizer into a high-speed mixer and stir to obtain a mixture; feed the mixture into a twin-screw extruder, with the screw speed at 100-500 r / min and the blending temperature at 190-230℃, to obtain a high-barrier food-grade polypropylene composite material.
[0056] Example 2
[0057] A high-barrier food-grade polypropylene composite material, comprising the following raw materials by weight:
[0058] 80 parts homopolymer polypropylene, 13 parts cyclic olefin copolymer, 7 parts nanolayered silica, 8 parts modified nanocellulose, and 0.2 parts maleic anhydride grafted polypropylene.
[0059] The preparation method of nano-layered silica includes the following steps:
[0060] (1) The vermiculite was rapidly expanded at 850℃ for 5 minutes, washed with water to remove impurities, dried to obtain expanded vermiculite, and then crushed for later use.
[0061] (2) Take 0.8 g of expanded vermiculite and put it into a hydrothermal reactor. Add 10 g of citric acid and 50 mL of water. Place it in an oven and react at 30 °C for 10 h. Take it out to obtain a silica mixture.
[0062] (3) Filter the silica mixture to obtain solid layered silica and filtrate. Dry the solid layered silica at 65°C for 10 hours to obtain nano-layered silica.
[0063] According to the test results, the specific surface area of vermiculite in this embodiment is 15 m2 / g, and the specific surface area of the final layered silica is 521 m2 / g.
[0064] The preparation method of modified nanocellulose includes the following steps:
[0065] Nanocellulose was added to anhydrous ethanol and ultrasonically dispersed evenly. Tetrabutyl titanate ethanol solution was then added and ultrasonically dispersed evenly. After that, an ethanol-water solution (volume ratio 8:1) was added and reacted at 50-60℃ for 6-8 hours with continuous stirring. After centrifugation, drying, and grinding, modified nanocellulose was obtained.
[0066] The concentration of tetrabutyl titanate in the ethanol solution is 25 wt%.
[0067] The mass ratio of the nanocellulose, anhydrous ethanol, tetrabutyl titanate, and aqueous ethanol solution is 5:100:30:4.
[0068] The preparation method, specifically including the following steps:
[0069] Weigh the raw materials according to the formula, and put the polypropylene resin, cyclic olefin copolymer, nano-layered silica, modified nanocellulose and compatibilizer into a high-speed mixer and stir to obtain a mixture; feed the mixture into a twin-screw extruder, with the screw speed at 100-500 r / min and the blending temperature at 190-230℃, to obtain a high-barrier food-grade polypropylene composite material.
[0070] Example 3
[0071] A high-barrier food-grade polypropylene composite material, comprising the following raw materials by weight:
[0072] 85 parts homopolymer polypropylene, 15 parts cyclic olefin copolymer, 10 parts nanolayered silica, 13 parts modified nanocellulose, and 0.2 parts maleic anhydride grafted polypropylene.
[0073] The preparation method of nano-layered silica includes the following steps:
[0074] (1) The vermiculite was rapidly expanded at 850℃ for 5 minutes, washed with water to remove impurities, dried to obtain expanded vermiculite, and then crushed for later use.
[0075] (2) Take 0.8 g of expanded vermiculite and put it into a hydrothermal reactor. Add 10 g of citric acid and 50 mL of water. Place it in an oven and react at 30 °C for 10 h. Take it out to obtain a silica mixture.
[0076] (3) Filter the silica mixture to obtain solid layered silica and filtrate. Dry the solid layered silica at 65°C for 10 hours to obtain nano-layered silica.
[0077] According to the test results, the specific surface area of vermiculite in this embodiment is 15 m2 / g, and the specific surface area of the final layered silica is 521 m2 / g.
[0078] The preparation method of modified nanocellulose includes the following steps:
[0079] Nanocellulose was added to anhydrous ethanol and ultrasonically dispersed evenly. Tetrabutyl titanate ethanol solution was then added and ultrasonically dispersed evenly. After that, an ethanol-water solution (volume ratio 8:1) was added and reacted at 50-60℃ for 6-8 hours with continuous stirring. After centrifugation, drying, and grinding, modified nanocellulose was obtained.
[0080] The concentration of tetrabutyl titanate in the ethanol solution is 25 wt%.
[0081] The mass ratio of the nanocellulose, anhydrous ethanol, tetrabutyl titanate, and aqueous ethanol solution is 4:120:35:4.
[0082] The preparation method, specifically including the following steps:
[0083] Weigh the raw materials according to the formula, and put the polypropylene resin, cyclic olefin copolymer, nano-layered silica, modified nanocellulose and compatibilizer into a high-speed mixer and stir to obtain a mixture; feed the mixture into a twin-screw extruder, with the screw speed at 100-500 r / min and the blending temperature at 190-230℃, to obtain a high-barrier food-grade polypropylene composite material.
[0084] Example 4
[0085] A high-barrier food-grade polypropylene composite material, comprising the following raw materials by weight:
[0086] 70 parts block copolymer polypropylene, 10 parts cyclic olefin copolymer, 5 parts nanolayered silica, 5 parts modified nanocellulose, and 0.2 parts maleic anhydride grafted polypropylene.
[0087] The preparation method of nano-layered silica includes the following steps:
[0088] (1) The vermiculite was rapidly expanded at 850℃ for 5 minutes, washed with water to remove impurities, dried to obtain expanded vermiculite, and then crushed for later use.
[0089] (2) Take 0.8 g of expanded vermiculite and put it into a hydrothermal reactor. Add 10 g of citric acid and 50 mL of water. Place it in an oven and react at 30 °C for 10 h. Take it out to obtain a silica mixture.
[0090] (3) Filter the silica mixture to obtain solid layered silica and filtrate. Dry the solid layered silica at 65°C for 10 hours to obtain nano-layered silica.
[0091] According to the test results, the specific surface area of vermiculite in this embodiment is 15 m2 / g, and the specific surface area of the final layered silica is 521 m2 / g.
[0092] The preparation method of modified nanocellulose includes the following steps:
[0093] Nanocellulose was added to anhydrous ethanol and ultrasonically dispersed evenly. Tetrabutyl titanate ethanol solution was then added and ultrasonically dispersed evenly. After that, an ethanol-water solution (volume ratio 8:1) was added and reacted at 50-60℃ for 6-8 hours with continuous stirring. After centrifugation, drying, and grinding, modified nanocellulose was obtained.
[0094] The concentration of tetrabutyl titanate in the ethanol solution is 25 wt%.
[0095] The mass ratio of the nanocellulose, anhydrous ethanol, tetrabutyl titanate, and aqueous ethanol solution is 5:100:30:4.
[0096] The preparation method, specifically including the following steps:
[0097] Weigh the raw materials according to the formula, and put the polypropylene resin, cyclic olefin copolymer, nano-layered silica, modified nanocellulose and compatibilizer into a high-speed mixer and stir to obtain a mixture; feed the mixture into a twin-screw extruder, with the screw speed at 100-500 r / min and the blending temperature at 190-230℃, to obtain a high-barrier food-grade polypropylene composite material.
[0098] Example 5
[0099] A high-barrier food-grade polypropylene composite material, comprising the following raw materials by weight:
[0100] 75 parts block copolymer polypropylene, 20 parts cyclic olefin copolymer, 7 parts nanolayered silica, 10 parts modified nanocellulose, and 0.2 parts maleic anhydride grafted polypropylene.
[0101] The preparation method of nano-layered silica includes the following steps:
[0102] (1) The vermiculite was rapidly expanded at 850℃ for 5 minutes, washed with water to remove impurities, dried to obtain expanded vermiculite, and then crushed for later use.
[0103] (2) Take 0.8 g of expanded vermiculite and put it into a hydrothermal reactor. Add 10 g of citric acid and 50 mL of water. Place it in an oven and react at 30 °C for 10 h. Take it out to obtain a silica mixture.
[0104] (3) Filter the silica mixture to obtain solid layered silica and filtrate. Dry the solid layered silica at 65°C for 10 hours to obtain nano-layered silica.
[0105] According to the test results, the specific surface area of vermiculite in this embodiment is 15 m2 / g, and the specific surface area of the final layered silica is 521 m2 / g.
[0106] The preparation method of modified nanocellulose includes the following steps:
[0107] Nanocellulose was added to anhydrous ethanol and ultrasonically dispersed evenly. Tetrabutyl titanate ethanol solution was then added and ultrasonically dispersed evenly. After that, an ethanol-water solution (volume ratio 8:1) was added and reacted at 50-60℃ for 6-8 hours with continuous stirring. After centrifugation, drying, and grinding, modified nanocellulose was obtained.
[0108] The concentration of tetrabutyl titanate in the ethanol solution is 25 wt%.
[0109] The mass ratio of the nanocellulose, anhydrous ethanol, tetrabutyl titanate, and aqueous ethanol solution is 5:130:40:3.
[0110] The preparation method, specifically including the following steps:
[0111] Weigh the raw materials according to the formula, and put the polypropylene resin, cyclic olefin copolymer, nano-layered silica, modified nanocellulose and compatibilizer into a high-speed mixer and stir to obtain a mixture; feed the mixture into a twin-screw extruder, with the screw speed at 100-500 r / min and the blending temperature at 190-230℃, to obtain a high-barrier food-grade polypropylene composite material.
[0112] Comparative Example 1
[0113] The only difference from Example 1 is that a cyclic olefin copolymer is not used.
[0114] By weight, it includes the following ingredients:
[0115] 70 parts homopolymer polypropylene, 5 parts nanolayered silica, 5 parts modified nanocellulose, and 0.2 parts maleic anhydride-grafted polypropylene.
[0116] The preparation method of nano-layered silica includes the following steps:
[0117] (1) The vermiculite was rapidly expanded at 850℃ for 5 minutes, washed with water to remove impurities, dried to obtain expanded vermiculite, and then crushed for later use.
[0118] (2) Take 0.8 g of expanded vermiculite and put it into a hydrothermal reactor. Add 10 g of citric acid and 50 mL of water. Place it in an oven and react at 30 °C for 10 h. Take it out to obtain a silica mixture.
[0119] (3) Filter the silica mixture to obtain solid layered silica and filtrate. Dry the solid layered silica at 65°C for 10 hours to obtain nano-layered silica.
[0120] According to the test results, the specific surface area of vermiculite in this embodiment is 15 m2 / g, and the specific surface area of the final layered silica is 521 m2 / g.
[0121] The preparation method of modified nanocellulose includes the following steps:
[0122] Nanocellulose was added to anhydrous ethanol and ultrasonically dispersed evenly. Tetrabutyl titanate ethanol solution was then added and ultrasonically dispersed evenly. After that, an ethanol-water solution (volume ratio 8:1) was added and reacted at 50-60℃ for 6-8 hours with continuous stirring. After centrifugation, drying, and grinding, modified nanocellulose was obtained.
[0123] The concentration of tetrabutyl titanate in the tetrabutyl titanate ethanol solution is 20-30 wt%.
[0124] The mass ratio of the nanocellulose, anhydrous ethanol, tetrabutyl titanate, and aqueous ethanol solution is 5:100:30:4.
[0125] The preparation method, specifically including the following steps:
[0126] Weigh the raw materials according to the formula, and place the polypropylene resin, nano-layered silica, modified nanocellulose and compatibilizer in a high-speed mixer to mix them to obtain a mixture. Feed the mixture into a twin-screw extruder with a screw speed of 100-500 r / min and a blending temperature of 190-230℃ to obtain a high-barrier food-grade polypropylene composite material.
[0127] Comparative Example 2
[0128] The only difference from Example 1 is that nanolayered silica is not used.
[0129] By weight, it includes the following ingredients:
[0130] 70 parts homopolymer polypropylene, 10 parts cyclic olefin copolymer, 5 parts modified nanocellulose, and 0.2 parts maleic anhydride grafted polypropylene.
[0131] The preparation method of modified nanocellulose includes the following steps:
[0132] Nanocellulose was added to anhydrous ethanol and ultrasonically dispersed evenly. Tetrabutyl titanate ethanol solution was then added and ultrasonically dispersed evenly. After that, an ethanol-water solution (volume ratio 8:1) was added and reacted at 50-60℃ for 6-8 hours with continuous stirring. After centrifugation, drying, and grinding, modified nanocellulose was obtained.
[0133] The concentration of tetrabutyl titanate in the tetrabutyl titanate ethanol solution is 20-30 wt%.
[0134] The mass ratio of the nanocellulose, anhydrous ethanol, tetrabutyl titanate, and aqueous ethanol solution is 5:100:30:4.
[0135] The preparation method, specifically including the following steps:
[0136] Weigh the raw materials according to the formula, and put the polypropylene resin, cyclic olefin copolymer, modified nanocellulose and compatibilizer into a high-speed mixer and stir to obtain a mixture. Feed the mixture into a twin-screw extruder, with the screw speed at 100-500 r / min and the blending temperature at 190-230℃, to obtain a high-barrier food-grade polypropylene composite material.
[0137] Comparative Example 3
[0138] The only difference from Example 1 is that modified nanocellulose is not used.
[0139] By weight, it includes the following ingredients:
[0140] 70 parts homopolymer polypropylene, 10 parts cyclic olefin copolymer, 5 parts nanolayered silica, and 0.2 parts maleic anhydride-grafted polypropylene.
[0141] The preparation method of nano-layered silica includes the following steps:
[0142] (1) The vermiculite was rapidly expanded at 850℃ for 5 minutes, washed with water to remove impurities, dried to obtain expanded vermiculite, and then crushed for later use.
[0143] (2) Take 0.8 g of expanded vermiculite and put it into a hydrothermal reactor. Add 10 g of citric acid and 50 mL of water. Place it in an oven and react at 30 °C for 10 h. Take it out to obtain a silica mixture.
[0144] (3) Filter the silica mixture to obtain solid layered silica and filtrate. Dry the solid layered silica at 65°C for 10 hours to obtain nano-layered silica.
[0145] According to the test results, the specific surface area of vermiculite in this embodiment is 15 m2 / g, and the specific surface area of the final layered silica is 521 m2 / g.
[0146] The preparation method, specifically including the following steps:
[0147] Weigh the raw materials according to the formula, and place the polypropylene resin, cyclic olefin copolymer, nano silica and compatibilizer in a high-speed mixer to mix them to obtain a mixture. Feed the mixture into a twin-screw extruder with a screw speed of 100-500 r / min and a blending temperature of 190-230℃ to obtain a high-barrier food-grade polypropylene composite material.
[0148] Comparative Example 4
[0149] The only difference from Example 1 is that unmodified nanocellulose is used.
[0150] By weight, it includes the following ingredients:
[0151] 70 parts homopolymer polypropylene, 10 parts cyclic olefin copolymer, 5 parts nanolayered silica, 5 parts nanocellulose, and 0.2 parts maleic anhydride grafted polypropylene.
[0152] The preparation method of nano-layered silica includes the following steps:
[0153] (1) The vermiculite was rapidly expanded at 850℃ for 5 minutes, washed with water to remove impurities, dried to obtain expanded vermiculite, and then crushed for later use.
[0154] (2) Take 0.8 g of expanded vermiculite and put it into a hydrothermal reactor. Add 10 g of citric acid and 50 mL of water. Place it in an oven and react at 30 °C for 10 h. Take it out to obtain a silica mixture.
[0155] (3) Filter the silica mixture to obtain solid layered silica and filtrate. Dry the solid layered silica at 65°C for 10 hours to obtain nano-layered silica.
[0156] According to the test results, the specific surface area of vermiculite in this embodiment is 15 m2 / g, and the specific surface area of the final layered silica is 521 m2 / g.
[0157] The preparation method, specifically including the following steps:
[0158] Weigh the raw materials according to the formula, and place the polypropylene resin, cyclic olefin copolymer, nano silica, nano cellulose and compatibilizer in a high-speed mixer to mix them to obtain a mixture; feed the mixture into a twin-screw extruder, with the screw speed at 100-500 r / min and the blending temperature at 190-230℃, to obtain a high-barrier food-grade polypropylene composite material.
[0159] Comparative Example 5
[0160] The only difference from Example 1 is that unmodified nano-silica is used.
[0161] By weight, it includes the following ingredients:
[0162] 70 parts homopolymer polypropylene, 10 parts cyclic olefin copolymer, 5 parts nano silica, 5 parts modified nanocellulose, and 0.2 parts maleic anhydride grafted polypropylene.
[0163] The nano-silica used is commercially available nano-silica.
[0164] The preparation method of modified nanocellulose includes the following steps:
[0165] Nanocellulose was added to anhydrous ethanol and ultrasonically dispersed evenly. Tetrabutyl titanate ethanol solution was then added and ultrasonically dispersed evenly. After that, an ethanol-water solution (volume ratio 8:1) was added and reacted at 50-60℃ for 6-8 hours with continuous stirring. After centrifugation, drying, and grinding, modified nanocellulose was obtained.
[0166] The concentration of tetrabutyl titanate in the ethanol solution is 25 wt%.
[0167] The mass ratio of the nanocellulose, anhydrous ethanol, tetrabutyl titanate, and aqueous ethanol solution is 5:100:30:4.
[0168] The preparation method, specifically including the following steps:
[0169] Weigh the raw materials according to the formula, and put the polypropylene resin, cyclic olefin copolymer, nano silica, modified nano cellulose and compatibilizer into a high-speed mixer and stir to obtain a mixture; feed the mixture into a twin-screw extruder, with the screw speed at 100-500 r / min and the blending temperature at 190-230℃, to obtain a high-barrier food-grade polypropylene composite material.
[0170] The performance of the high-performance polypropylene materials for food packaging prepared in Examples 1-5 and Comparative Examples 1-5 was tested, as follows:
[0171] Each group of materials was injection molded into specimens, and the tensile strength and elongation at break were tested according to the standard GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets";
[0172] The notched impact strength was tested according to GB / T 1843-2008 "Determination of Impact Strength of Plastic Cantilever Beams" standard, using a specimen with dimensions of 80mm×10mm×4mm and a remaining notch thickness of 2mm.
[0173] Each group of materials was made into a film (50μm) by blow molding. The oxygen permeability test was carried out according to GB / T 1038.1-2022 "Test method for gas permeability of plastic products films and sheets - Part 1: pressure difference method", with a test temperature of 23℃, a relative humidity of 1%RH, and a pressure difference of 0.1MPa.
[0174] Water vapor transmission rate test: The test was conducted according to GB / T 26253-2010 "Determination of water vapor transmission rate of plastic films and sheets - Infrared detector method", with a test temperature of 38℃ and a relative humidity of 90%RH.
[0175] The UV aging resistance was tested according to GB / T 16422.3-2022 "Laboratory Light Source Exposure Test Methods for Plastics - Part 3: Fluorescent UV Lamp" standard. The aging conditions were: UV intensity 300W / m2, aging temperature 50℃, aging time 144h, and the tensile strength retention rate of the test sample after aging.
[0176] The test results are shown in Table 1.
[0177] Table 1
[0178] project Tensile strength (MPa) Elongation at break % <![CDATA[Impact strength kJ / m 2 > <![CDATA[Oxygen transmission rate cm 3 / m 2 ·24 h·0.1 MPa]]> <![CDATA[Water vapor transmission rate g / m 2 ·24h]]> Strength retention rate after aging % Example 1 29.3 479 30.5 11.6 0.45 89.8 Example 2 30.8 485 29.8 10.1 0.49 92.1 Example 3 29.8 471 31.0 12.2 0.47 89.7 Example 4 30.1 482 28.7 11.4 0.44 84.0 Example 5 29.6 454 30.8 10.8 0.52 88.7 Comparative Example 1 22.5 287 24.2 52.3 1.53 46.1 Comparative Example 2 23.1 382 25.4 58.1 1.38 53.2 Comparative Example 3 23.7 431 25.7 33.8 0.95 46.7 Comparative Example 4 20.5 395 24.8 41.9 1.32 44.5 Comparative Example 5 25.4 401 27.5 29.0 1.09 73.2
[0179] 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.
[0180] The results of Example 1 and Comparative Example 1 show that adding a small amount of cyclic olefin copolymer to polypropylene can significantly improve its water vapor barrier properties. The results of Example 1, Comparative Example 2, and Comparative Example 3 show that the combined use of nano-layered silica and modified nanocellulose can improve the oxygen and ultraviolet barrier properties of polypropylene. The results of Example 1 and Comparative Example 4 show that modifying nanocellulose with titanate can significantly improve the oxygen and ultraviolet barrier properties of polypropylene. The results of Example 1, Comparative Example 2, and Comparative Example 5 show that the nano-layered silica of the present invention can effectively improve the oxygen, water vapor, and ultraviolet barrier properties of polypropylene.
[0181] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A high-barrier food-grade polypropylene composite material, characterized in that, By weight, it includes the following ingredients: 70-90 parts polypropylene resin, 10-20 parts cyclic olefin copolymer, 5-10 parts nano-layered silica, 5-15 parts modified nanocellulose, and 0.1-0.3 parts compatibilizer; The nano-layered silica is prepared from food-grade organic modified vermiculite.
2. The high-barrier food-grade polypropylene composite material according to claim 1, characterized in that, The self-melting index of the polypropylene resin is 0.5-10 g / min.
3. The high-barrier food-grade polypropylene composite material according to claim 2, characterized in that, The polypropylene resin is homopolymer polypropylene or block copolymer polypropylene.
4. The high-barrier food-grade polypropylene composite material according to claim 1, characterized in that, The cyclic olefin copolymer is an amorphous cyclic olefin copolymer with a molecular weight of 4,000-50,000 and a degree of polymerization of 200-800.
5. The high-barrier food-grade polypropylene composite material according to claim 1, characterized in that, The method for preparing the nano-layered silica includes the following steps: (1) The vermiculite was rapidly expanded at 850℃ for 5 minutes, washed with water to remove impurities, dried to obtain expanded vermiculite, and then crushed for later use. (2) Take expanded vermiculite and put it into a hydrothermal reactor. Add citric acid and water, put it into an oven and react at 30°C for 10 hours. Then take it out to obtain a silica mixture. The solid-liquid ratio of the expanded vermiculite, citric acid, and water is 0.8 g: 10 g: 50 mL; (3) Filter the silica mixture to obtain solid layered silica and filtrate. Dry the solid layered silica at 65°C for 10 hours to obtain nano-layered silica.
6. The high-barrier food-grade polypropylene composite material according to claim 1, characterized in that, The method for preparing the modified nanocellulose includes the following steps: Nanocellulose was added to anhydrous ethanol and ultrasonically dispersed until uniform. Tetrabutyl titanate ethanol solution was then added and ultrasonically dispersed until uniform. After that, an aqueous ethanol solution was added, the mixture was stirred and reacted, and then centrifuged, dried, and ground to obtain modified nanocellulose.
7. The high-barrier food-grade polypropylene composite material according to claim 6, characterized in that, The concentration of tetrabutyl titanate in the tetrabutyl titanate ethanol solution is 20-30 wt%. The mass ratio of the nanocellulose, anhydrous ethanol, tetrabutyl titanate, and ethanol aqueous solution is 4-5:100-130:30-40:3-4, and the volume ratio of ethanol to water in the ethanol aqueous solution is 8:
1.
8. The high-barrier food-grade polypropylene composite material according to claim 6, characterized in that, The stirring reaction is carried out at 50-60℃ for 6-8 hours.
9. The high-barrier food-grade polypropylene composite material according to claim 1, characterized in that, The compatibilizer is maleic anhydride-grafted polypropylene.
10. The method for preparing the high-barrier food-grade polypropylene composite material according to any one of claims 1-9, characterized in that, The specific steps include: weighing the raw materials according to the formula, placing the polypropylene resin, cyclic olefin copolymer, nano-layered silica, modified nanocellulose and compatibilizer in a high-speed mixer and mixing them to obtain a mixture; feeding the mixture into a twin-screw extruder, with the screw speed at 100-500 r / min and the blending temperature at 190-230℃, to obtain a high-barrier food-grade polypropylene composite material.