A high-barrier and high-temperature retort packaging film made of a single recyclable PP material

Abstract

The present invention relates to the technical field of high-temperature resistant cooking packaging materials, and discloses a high-barrier high-temperature resistant cooking packaging film based on a single recyclable PP material. The preparation method of the packaging film is as follows: vinylated phenyl double-clamped structure cage-type polyhedral oligomeric silsesquioxane is first compounded with graphene oxide through π-π stacking interaction and hydrogen bond interaction, and then loaded onto polypropylene resin through free radical coupling reaction and molecular chain intercalation method. Finally, a high-barrier polypropylene-based composite material with high temperature resistance and puncture resistance is obtained by extrusion using a twin-screw extruder; the high-barrier polypropylene-based composite material with high temperature resistance and puncture resistance is used as the intermediate layer raw material of a five-layer co-extruded film made of a single PP material, and a high-barrier high-temperature resistant cooking packaging film based on a single recyclable PP material is prepared by using a five-layer co-extrusion blow molding process. After being cooked at 140 °C for 30 minutes, the film product has no abnormal phenomena such as deformation and peeling, and has excellent barrier properties and puncture resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature resistant cooking packaging materials, and particularly to a high-barrier high-temperature resistant cooking packaging film based on a single recyclable PP material. Background Art

[0002] High-temperature resistant cooking packaging is a common packaging form for foods such as meat and soy products. Generally, vacuum packaging is used, and after being heated and sterilized at a high temperature (100 - 135 °C), it can be stored at room temperature. The food packaged by high-temperature resistant cooking is convenient to carry, ready to eat after opening the bag, hygienic and convenient, and can well maintain the flavor of the food, which is deeply loved by consumers.

[0003] High-temperature resistant cooking packaging is usually composed of multiple base materials. Common materials include PA, PET, AL, and PP. Common structures include two-layer composite films (such as BOPA / PP, PET / PP), three-layer composite films (such as PA / AL / PP, PET / PA / PP), and four-layer composite films (such as PET / PA / AL / PP). However, it is difficult to classify and recycle multi-material composite packaging after discarding it at the end of the packaging life cycle, which is likely to cause waste of resources and environmental pollution.

[0004] When the packaging film made of a single PP material is recycled, it does not need to be classified and can be recycled repeatedly. However, its puncture resistance is far inferior to that of PA, and it is prone to breakage when pierced by sharp objects. As a high-temperature resistant cooking packaging film, quality problems such as bag breakage and air leakage are likely to occur, affecting the vacuum degree of the commodity packaging, and thus leading to the deterioration of the commodity. In addition, the barrier performance of the packaging film made of a single PP material usually cannot meet the actual use requirements of high-temperature resistant cooking packaging films, which limits its application value. Therefore, it is usually necessary to modify PP.

[0005] The modification methods of polypropylene can be divided into chemical modification and physical modification. Chemical modification mainly changes the molecular chain structure of polypropylene to improve the material properties. Chemical modification mainly includes: copolymerization, grafting, crosslinking, etc. Physical modification is to change the higher-order structure of polypropylene materials to achieve the purpose of improving material properties. Physical modification mainly includes: blending, filling, etc.

[0006] As a derivative of graphene, graphene oxide has a two-dimensional sheet structure similar to that of graphene. When it is added as a filler to the polymer matrix, it can extend the path of water vapor and small gas molecules passing through the composite material, thereby improving the barrier performance of the composite material. Summary of the Invention

[0007] The present invention has developed a high-barrier high-temperature resistant cooking packaging film based on a single recyclable PP material. After being cooked at 140 °C for 30 minutes, the film product has no abnormal phenomena such as deformation, delamination between layers, and delamination at the heat-sealed part, and has excellent barrier performance and puncture resistance.

[0008] A high-barrier and high-temperature resistant retort packaging film based on a single recyclable PP material. The product structure of the film is the following layers arranged in sequence: PP layer / PP-g-MAH layer / functional layer / PP-g-MAH layer / MPP layer;

[0009] PP layer: The raw material formula is 100wt% polypropylene resin, and the dosage is 20 - 35 parts by weight;

[0010] PP-g-MAH layer: The raw material formula is 100wt% maleic anhydride grafted polypropylene resin, and the dosage is 3 - 10 parts by weight;

[0011] MPP layer: The raw material formula is 100wt% metallocene polypropylene resin, and the dosage is 20 - 35 parts by weight;

[0012] Functional layer: The raw material formula is 100wt% high-barrier polypropylene-based composite material that is heat-resistant and puncture-resistant, and the dosage is 20 - 35 parts by weight;

[0013] The high-barrier polypropylene-based composite material that is heat-resistant and puncture-resistant is obtained by first compounding vinylated phenyl double-clamped structure cage-like polyhedral oligomeric silsesquioxane with graphene oxide through π-π stacking and hydrogen bonding interactions, and then loading it onto polypropylene resin through free radical coupling reaction and molecular chain intercalation methods.

[0014] Preferably, the formula of the high-barrier polypropylene-based composite material that is heat-resistant and puncture-resistant is 85 - 90wt% polypropylene resin, 1 - 8wt% vinylated phenyl double-clamped structure cage-like polyhedral oligomeric silsesquioxane, 0.5 - 2wt% peroxide initiator, and 3 - 10wt% graphene oxide.

[0015] Preferably, the preparation method of the vinylated phenyl double-clamped structure cage-like polyhedral oligomeric silsesquioxane is as follows:

[0016] Using phenyltrimethoxysilane as the raw material, adopting the hydrolysis-condensation method, and through the catalytic hydrolysis and polycondensation reaction of phenyltrimethoxysilane by sodium hydroxide, an incompletely condensed double-clamped structure cage-like polyhedral oligomeric silsesquioxane sodium salt is generated;

[0017] Using the incompletely condensed double-clamped structure cage-like polyhedral oligomeric silsesquioxane sodium salt as the raw material, and using 3-isocyanatopropylmethyldichlorosilane as the capping reagent, through the apex-capping method under the catalysis of triethylamine, a terminal isocyanate-functionalized phenyl double-clamped structure cage-like polyhedral oligomeric silsesquioxane is synthesized;

[0018] Utilizing the nucleophilic addition reaction mechanism, under the catalytic action of an organic base catalyst, through the decarboxylation condensation reaction of the isocyanate group of the terminal isocyanate-functionalized phenyl double-clamped structure cage-like polyhedral oligomeric silsesquioxane with the carboxyl functional group of oleic acid, a vinylated phenyl double-clamped structure cage-like polyhedral oligomeric silsesquioxane is generated.

[0019] Preferably, the organic base catalyst is one of triethylamine, triethylenediamine, pyridine, and 4-dimethylaminopyridine.

[0020] Preferably, the method for preparing the high-barrier polypropylene-based composite material with high temperature resistance and puncture resistance is as follows:

[0021] Step 1: Based on π-π stacking interaction and hydrogen bond interaction, vinylated phenyl double-sandwich structure cage-like polyhedral oligomeric silsesquioxane is compounded with graphene oxide to obtain a vinylated phenyl double-sandwich structure cage-like polyhedral oligomeric silsesquioxane / graphene composite material;

[0022] Step 2: Based on the free radical coupling reaction mechanism under the action of a peroxide initiator and the molecular chain intercalation technology, the vinylated phenyl double-sandwich structure cage-like polyhedral oligomeric silsesquioxane / graphene composite material is used to modify polypropylene resin, and extrusion granulation is carried out through a twin-screw extruder to obtain a high-barrier polypropylene-based composite material with high temperature resistance and puncture resistance.

[0023] Preferably, the sheet diameter of the graphene oxide is 3 - 10 μm and the thickness is 8 - 15 nm.

[0024] Preferably, the peroxide initiator is one of dicumyl peroxide, tert-butyl hydroperoxide, benzoyl peroxide, and tert-butyl perbenzoate.

[0025] Preferably, the thickness of the high-barrier high-temperature retort packaging film is 50 - 150 μm.

[0026] Preferably, the high-barrier high-temperature retort packaging film based on a single PP recyclable material is applied under the condition of temperature ≤ 140°C.

[0027] Beneficial effects:

[0028] The present invention designs and synthesizes a vinylated phenyl double-sandwich structure cage-like polyhedral oligomeric silsesquioxane, and therefrom obtains a high-barrier polypropylene-based composite material with high temperature resistance and puncture resistance;

[0029] Taking the high-barrier polypropylene-based composite material with high temperature resistance and puncture resistance as the intermediate layer raw material of a five-layer coextruded film made of a single PP material, and adopting a five-layer coextrusion blow molding process, a high-barrier high-temperature retort packaging film based on a single PP recyclable material is prepared. After being retorted at 140°C for 30 minutes, the film has no abnormal phenomena such as deformation, interlayer peeling, and heat-sealing part peeling, showing excellent high-temperature retort performance;

[0030] The high-barrier high-temperature retort packaging film prepared by the present invention has achieved a significantly improved beneficial technical effect in terms of puncture resistance and barrier performance compared with the conventional polypropylene film prepared by using conventional polypropylene resin.

[0031] The high-barrier and high-temperature resistant retort packaging film prepared by the present invention has excellent comprehensive performance, and its hygienic performance meets the national standard requirements, and it can be used in the packaging of high-temperature resistant retort foods. Brief Description of the Drawings

[0032] Figure 1 is the chemical structural formula of terminal isocyanate-functionalized phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane;

[0033] Figure 2 is the chemical structural formula of alkenylated phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane;

[0034] Figure 3 are the performance test results of the high-barrier and high-temperature resistant retort packaging film based on a single recyclable PP material. Detailed Embodiments

[0035] In the present invention, phenyltrimethoxysilane is first used as a raw material to prepare sodium salt of incompletely condensed double-sandwich structured cage-like polyhedral oligomeric silsesquioxane by hydrolysis-condensation method, and then 3-isocyanatopropylmethyldichlorosilane is used as a capping reagent to prepare terminal isocyanate-functionalized phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane by vertex-capping method. By using the nucleophilic addition reaction of isocyanate-carboxyl group, oleic acid (which is often used as a plasticizer and a surface modifier for improving water and oil barrier properties in the field of packaging film manufacturing) is grafted onto the double-sandwich structured cage-like polyhedral oligomeric silsesquioxane to obtain alkenylated phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane;

[0036] After the alkenylated phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane is compounded with graphene oxide through π-π stacking interaction and hydrogen bond interaction, the modification effect on polypropylene resin is achieved through free radical coupling reaction and molecular chain intercalation method, and finally a high-barrier polypropylene-based composite material with high temperature resistance and puncture resistance is prepared. Example 1:

[0037] A high-barrier and high-temperature resistant retort packaging film I based on a single recyclable PP material, whose product structure is:

[0038] The first layer: a PP layer prepared from 100 wt% polypropylene resin (grade HJ4012), with a dosage of 30 parts by weight;

[0039] The second layer: a PP-g-MAH layer prepared from 100 wt% maleic anhydride grafted polypropylene resin (grade QB510), with a dosage of 5 parts by weight;

[0040] The third layer: a functional layer prepared from 100 wt% high-barrier polypropylene-based composite material with high temperature resistance and puncture resistance, with a dosage of 30 parts by weight;

[0041] Fourth layer: PP-g-MAH layer prepared from 100 wt% maleic anhydride grafted polypropylene resin, with a dosage of 5 parts by weight;

[0042] Fifth layer: MPP layer prepared from 100 wt% metallocene polypropylene resin (grade MR30MC2), with a dosage of 30 parts by weight;

[0043] Among them, the formulation of the high-barrier polypropylene-based composite material with high temperature resistance and puncture resistance is: 90 wt% polypropylene resin, 3 wt% vinylated phenyl double-clamped structure cage-shaped polyhedral oligomeric silsesquioxane, 1 wt% peroxide initiator, and 6 wt% graphene oxide (sheet diameter 3 - 10 μm, thickness 8 - 15 nm);

[0044] The preparation process of vinylated phenyl double-clamped structure cage-shaped polyhedral oligomeric silsesquioxane is as follows:

[0045] First step: Using phenyltrimethoxysilane as the raw material, through hydrolysis-condensation method, sodium hydroxide is used to catalyze the hydrolysis and polycondensation reaction of phenyltrimethoxysilane to generate incompletely condensed double-clamped structure cage-shaped polyhedral oligomeric silsesquioxane sodium salt, and its chemical structural formula is:

[0046] ;

[0047] Second step: Using incompletely condensed double-clamped structure cage-shaped polyhedral oligomeric silsesquioxane sodium salt as the raw material, 3-isocyanatopropylmethyldichlorosilane is used as the capping reagent, and through the vertex-capping method under the catalysis of triethylamine, terminal isocyanate-functionalized phenyl double-clamped structure cage-shaped polyhedral oligomeric silsesquioxane is synthesized, and its chemical structure is as Figure 1 shown;

[0048] Third step: Using the mechanism of nucleophilic addition reaction, under the catalysis of an organic base catalyst, the isocyanate group of the terminal isocyanate-functionalized phenyl double-clamped structure cage-shaped polyhedral oligomeric silsesquioxane reacts with the carboxyl functional group of oleic acid to undergo decarboxylation condensation reaction to generate vinylated phenyl double-clamped structure cage-shaped polyhedral oligomeric silsesquioxane, and its chemical structure is as Figure 2 shown;

[0049] Among them, the organic base catalyst is selected from one of triethylamine, triethylenediamine, pyridine, and 4-dimethylaminopyridine; in this example, 4-dimethylaminopyridine is preferably used;

[0050] The specific experimental steps for preparing vinylated phenyl double-clamped structure cage-shaped polyhedral oligomeric silsesquioxane are as follows:

[0051] Under nitrogen protection, 19.8 g of phenyltrimethoxysilane, 2.7 g of sodium hydroxide, 100 mL of isopropanol and 5 mL of deionized water were added to a three-necked flask, stirred at room temperature until completely dissolved, heated to 90 °C and stirred under reflux for 4 h, cooled to room temperature and then stirred for 15 h, filtered, repeatedly washed with isopropanol, and dried in vacuo to obtain sodium salt of incompletely condensed double-sandwich structure cage-like polyhedral oligomeric silsesquioxane;

[0052] Under nitrogen protection, 5.8 g of sodium salt of incompletely condensed double-sandwich structure cage-like polyhedral oligomeric silsesquioxane, 1.5 mL of triethylamine and 50 mL of anhydrous tetrahydrofuran were added to a three-necked flask, stirred and dissolved in an ice bath for 2 h, then 10 mL of anhydrous tetrahydrofuran solution containing 2.0 g of 3-isocyanatopropylmethyldichlorosilane was slowly added dropwise to the three-necked flask, the ice bath was removed, and the reaction was stirred at room temperature for 24 h. The solvent was removed by rotary evaporation, repeatedly washed with methanol, and dried in vacuo to obtain isocyanate-terminated phenyl double-sandwich structure cage-like polyhedral oligomeric silsesquioxane;

[0053] Under nitrogen protection, 3.3 g of isocyanate-terminated phenyl double-sandwich structure cage-like polyhedral oligomeric silsesquioxane and 50 mL of anhydrous tetrahydrofuran were added to a three-necked flask. Under nitrogen protection and mechanical stirring, 10 mL of anhydrous tetrahydrofuran solution containing 1.4 g of oleic acid and 5 mL of anhydrous tetrahydrofuran solution containing 0.8 g of 4-dimethylaminopyridine were successively added dropwise to the three-necked flask, heated to 90 °C and stirred under reflux for 6 h, cooled to room temperature, the solvent was removed by rotary evaporation, and dried in vacuo to obtain alkenylated phenyl double-sandwich structure cage-like polyhedral oligomeric silsesquioxane;

[0054] The 1H NMR characterization of alkenylated phenyl double-sandwich structure cage-like polyhedral oligomeric silsesquioxane is as follows: 1 H NMR(DMSO-d6, 400 MHz) δ: 0.09(s, 6H), 0.81 - 0.85(t, 6H), 0.91 - 0.94(t, 4H), 1.20 - 1.33(m, 40H), 1.57 - 1.77(m, 16H), 2.14 - 2.17(t, 4H), 3.11 - 3.16(m, 4H), 5.28 - 5.40(m, 4H), 7.33 - 7.54(m, 40H), 7.77 - 7.80(t, 2H). Example 2:

[0055] A preparation process of a high-barrier and high-temperature retort packaging film I based on a single recyclable PP material, comprising the following steps:

[0056] Step 1: Prepare vinyl-phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane / graphene composite material: Based on the π-π stacking interaction (between the benzene ring in the vinyl-phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane and graphene oxide) and hydrogen bond interaction (between the amide group in the vinyl-phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane and the hydroxyl / carboxyl groups on the surface of graphene oxide), the vinyl-phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane is compounded with graphene oxide to obtain the vinyl-phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane / graphene composite material;

[0057] The specific experimental steps for preparing the vinyl-phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane / graphene composite material are as follows: Add 6 g of graphene oxide powder (flake diameter 3 - 10 μm, thickness 8 - 15 nm), 3 g of vinyl-phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane, and 100 mL of anhydrous tetrahydrofuran into a beaker, ultrasonically treat for 30 min, heat up to 60 °C, stir and react for 5 h, centrifuge, repeatedly wash with deionized water by centrifugation, and dry in vacuum to obtain the vinyl-phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane / graphene composite material;

[0058] Step 2: Prepare a high-barrier polypropylene-based composite material with high temperature resistance and puncture resistance: On the one hand, free radicals are generated by polypropylene resin under the action of a peroxide initiator, and the vinyl functional groups contained in the vinyl-phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane / graphene composite material react with the free radicals in the polypropylene resin through a coupling reaction. On the other hand, the alkyl long chains contained in the vinyl-phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane / graphene composite material are intercalated into the molecular chains in the polypropylene resin to achieve the modification treatment of the polypropylene resin, and a high-barrier polypropylene-based composite material with high temperature resistance and puncture resistance is obtained;

[0059] Among them, the peroxide initiator is one of dicumyl peroxide (DCP), tert-butyl hydroperoxide (TBHP), benzoyl peroxide (BPO), and tert-butyl perbenzoate (TBPB); In this example, dicumyl peroxide (DCP) is selected for use;

[0060] The specific experimental steps for preparing the high-barrier polypropylene-based composite material with high temperature resistance and puncture resistance are as follows: First, add 9 g of polypropylene resin, 0.9 g of vinyl-phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane / graphene composite material, and 0.1 g of dicumyl peroxide initiator into a twin-screw extruder from the feeding port, carry out a coupling reaction through high-temperature melt mixing, keep the reaction for 10 min, melt and mix through the twin-screw extruder for 30 min, and extrude and pelletize to obtain the high-barrier polypropylene-based composite material with high temperature resistance and puncture resistance;

[0061] Among them, the process parameters of the twin-screw extruder are set as follows: the preheating temperature is 180 °C, the temperatures of zones 1-6 are 180 °C, 185 °C, 190 °C, 195 °C, 205 °C, and 195 °C respectively, and the rotational speed is 100 r / min;

[0062] Step 2, prepare the high-barrier and high-temperature retort packaging film I based on a single PP recyclable material: According to the formula of the high-barrier and high-temperature retort packaging film I based on a single PP recyclable material, weigh the raw materials for each layer and put them into the hoppers of the five screw extruders of the five-layer coextrusion blown film unit respectively. The molten resins converge at the die head through the diverter, are extruded, blown, and drawn through the die head (the blow-up ratio is controlled at 2.6), cooled, and wound to prepare the high-barrier and high-temperature retort packaging film I with a thickness of 100 μm based on a single PP recyclable material;

[0063] Among them, the process parameters of the screw extruders corresponding to the first layer and the fifth layer are set as follows: the temperatures of zones 1-3 are 120 °C, 150 °C, and 180 °C respectively, the runner temperature is 175 °C, and the rotational speed is 30 r / min;

[0064] The process parameters of the screw extruders corresponding to the second layer and the fourth layer are set as follows: the temperatures of zones 1-3 are 120 °C, 140 °C, and 170 °C respectively, the runner temperature is 165 °C, and the rotational speed is 20 r / min;

[0065] The process parameters of the screw extruder corresponding to the third layer are set as follows: the temperatures of zones 1-3 are 150 °C, 180 °C, and 205 °C respectively, the runner temperature is 195 °C, and the rotational speed is 50 r / min. Example 3:

[0066] A high-barrier and high-temperature retort packaging film II based on a single PP recyclable material, the difference between its product structure and the high-barrier and high-temperature retort packaging film I based on a single PP recyclable material in Example 1 is only that: the formula of the high-temperature and puncture-resistant high-barrier polypropylene-based composite material is: 90 wt% polypropylene resin, 5 wt% vinylated phenyl double-sandwich-structured cage-type polyhedral oligomeric silsesquioxane, 1 wt% peroxide initiator, and 4 wt% graphene oxide;

[0067] The preparation process of the high-barrier and high-temperature retort packaging film II based on a single PP recyclable material is the same as that of the high-barrier and high-temperature retort packaging film I based on a single PP recyclable material in Example 2. Example 4:

[0068] A high-barrier, high-temperature-resistant cooking packaging film III based on a single PP recyclable material, the product structure of which is different from the high-barrier, high-temperature-resistant cooking packaging film I based on a single PP recyclable material in Example 1 only in that: the formula of the high-barrier polypropylene-based composite material that is resistant to high temperature and puncture is: 90wt% polypropylene resin, 1wt% olefinic phenyl double-plywood structure cage-type polysilsesquioxane, 1wt% peroxide initiator and 8wt% graphene oxide;

[0069] The preparation process of the high barrier and high temperature resistant cooking packaging film III based on a single PP recyclable material is the same as the preparation process of the high barrier and high temperature resistant cooking packaging film I based on a single PP recyclable material in Example 2.

[0070] Comparative Example:

[0071] Preparation of conventional polypropylene film: Compared with the high barrier and high temperature resistant cooking packaging film I based on a single PP recyclable material, the only difference is that the raw material of the third layer is polypropylene resin.

[0072] Performance Test:

[0073] (1) High temperature cooking resistance test: The high temperature cooking resistance test of the samples was carried out in accordance with GB / T 10004-2008 "Dry-process lamination and extrusion lamination of plastic composite films and bags for packaging". The specific test steps are as follows: Heat-seal the packaging film sample into a 200mm×120mm packaging bag, fill it with water to two-thirds of its volume, exhaust and seal it, put it in a high pressure sterilizer with a back pressure device, treat it at a temperature of 140℃ for 30 minutes, cool it to room temperature under reduced pressure and take it out, and check whether the packaging bag has obvious deformation, interlayer peeling, peeling of the heat-sealed part and other abnormal phenomena;

[0074] (2) Barrier performance test: The oxygen permeability test and water vapor permeability test of the samples were carried out in accordance with GB / T 1038.1-2022 "Test method for gas permeability of plastic films and sheets - Part 1: Differential pressure method" and GB / T 1037-2021 "Determination of water vapor permeability of plastic films and sheets - Cup weight gain and weight loss method" respectively. The specific test steps are as follows: Place a 30 cm circular sample in a glass desiccator at an ambient temperature of 25°C and anhydrous calcium chloride as a desiccant for 72 hours, and then use a Y110 oxygen permeability tester and a TC-03 water vapor permeability tester to test the barrier properties of the samples;

[0075] (3)Puncture resistance test: The puncture resistance of the sample was tested according to the standard of GB / T 37841-2019 "Test Method for Puncture Resistance of Plastic Films and Sheets". The specific test steps are as follows: Fix a 5 cm × 5 cm film sample on a MCT-02A puncture strength tester. The puncture needle is made of stainless steel, with a diameter of 1.0 mm, the tip of the puncture needle is hemispherical with a radius of 0.5 mm, and the puncture rate is 50 mm / min. Record the puncture strength of the sample;

[0076] (4)Mechanical property test: According to the standard of GB / T 1040.1-2018 "Plastics - Determination of Tensile Properties", fix a 150 mm × 20 mm sample (sampled along the blown film direction) at room temperature on an Instron 5565 universal tensile testing machine, and conduct a tensile test at a tensile rate of 100 mm / min. Record the longitudinal tensile strength of the sample;

[0077] (5)Heat sealing property test: Use an HSG-C type heat sealer to conduct a heat sealing experiment on the sample. The sealing knife area is 15 cm × 1 cm, the heat sealing temperature is 135 °C, the heat sealing pressure is 0.2 MPa, and the heat sealing time is 2.0 s;

[0078] According to QB / T 2358-1998 "Test Method for Heat Seal Strength of Plastic Film Packaging Bags", test the heat sealing property of the heat-sealed sample. The test speed is 300 mm / min, the fixture spacing is 50 mm, and record the heat sealing strength of the sample;

[0079] (6)Hygienic property: According to the standard of GB / T 5009.60-2003 "Analysis Method for Hygienic Standards of Polyethylene, Polystyrene, and Polypropylene Molding Products for Food Packaging", test the hygienic property of the sample. The physical and chemical indexes of the experimental results are based on the standard of GB / T5009.71-2003 "Analysis Method for Hygienic Standards of Polypropylene Resin for Food Packaging";

[0080] The above experimental results are shown in Table 1-3 and Figure 3 。

[0081] Table 1 Performance Experimental Results I of High-Barrier High-Temperature Retort Packaging Film Based on Single PP Recyclable Material

[0082]

[0083] Table 2 Performance Experimental Results II of High-Barrier High-Temperature Retort Packaging Film Based on Single PP Recyclable Material

[0084]

[0085] Table 3 Performance Experimental Results III of High-Barrier High-Temperature Retort Packaging Film Based on Single PP Recyclable Material

[0086]

[0087] Through comprehensive analysis of the above experimental results, the following conclusions can be drawn:

[0088] Conclusion 1: After being cooked at 140°C for 30 minutes, the high-barrier heat-resistant retort packaging film made of a single recyclable PP material prepared by the present invention shows no abnormal phenomena such as deformation, delamination between layers, and delamination at the heat-sealed part, demonstrating excellent heat-resistant retort performance;

[0089] Conclusion 2: The high-barrier heat-resistant retort packaging film prepared by the present invention using a self-developed high-barrier polypropylene-based composite material that is heat-resistant and puncture-resistant has achieved a significantly improved beneficial technical effect in terms of puncture resistance and barrier performance compared to the conventional polypropylene film prepared using conventional polypropylene resin;

[0090] Conclusion 3: The high-barrier heat-resistant retort packaging film prepared by the present invention also has excellent mechanical properties and heat-sealing properties, and its hygienic properties meet the national standard requirements, making it suitable for use in heat-resistant retort food packaging.

Claims

1. A high-barrier and high-temperature retort packaging film made of a single recyclable PP material, characterized in that, The product structure of the film is the following layers arranged in sequence: PP layer / PP-g-MAH layer / functional layer / PP-g-MAH layer / MPP layer; PP layer: The raw material formula is 100wt% polypropylene resin, and the dosage is 20 - 35 parts by weight; PP-g-MAH layer: The raw material formula is 100wt% maleic anhydride grafted polypropylene resin, and the dosage is 3 - 10 parts by weight; MPP layer: The raw material formula is 100wt% metallocene polypropylene resin, and the dosage is 20 - 35 parts by weight; Functional layer: The raw material formula is 100wt% high-barrier polypropylene-based composite material that is heat-resistant and puncture-resistant, and the dosage is 20 - 35 parts by weight; The heat-resistant and puncture-resistant high-barrier polypropylene-based composite material is obtained by first compounding vinylated phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane with graphene oxide through π-π stacking interaction and hydrogen bond interaction, and then loading it onto polypropylene resin through free radical coupling reaction and molecular chain intercalation method; The chemical structural formula of the vinylated phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane is: 。 2. The high-barrier and high-temperature retort packaging film made of a single recyclable PP material according to claim 1, wherein The formula of the heat-resistant and puncture-resistant high-barrier polypropylene-based composite material is 85 - 90wt% polypropylene resin, 1 - 8wt% vinylated phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane, 0.5 - 2wt% peroxide initiator, and 3 - 10wt% graphene oxide.

3. A high-barrier and high-temperature retort packaging film made of a single recyclable PP material according to claim 1, characterized in that, The preparation method of the vinylated phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane is: Using phenyltrimethoxysilane as the raw material, adopting the hydrolysis-condensation method, and catalyzing phenyltrimethoxysilane to undergo hydrolysis and polycondensation reaction by sodium hydroxide to generate incompletely condensed double-sandwich structured cage-like polyhedral oligomeric silsesquioxane sodium salt; Using the incompletely condensed double-sandwich structured cage-like polyhedral oligomeric silsesquioxane sodium salt as the raw material, and using 3-isocyanatopropylmethyldichlorosilane as the capping reagent, synthesizing terminal isocyanate-functionalized phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane by the vertex-capping method under the catalysis of triethylamine; Utilizing the nucleophilic addition reaction mechanism, under the catalytic action of an organic base catalyst, the isocyanate group of the terminal isocyanate-functionalized phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane reacts with the carboxyl functional group of oleic acid to undergo decarboxylation condensation reaction to generate vinylated phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane.

4. A high-barrier heat-resistant retort packaging film based on a single recyclable PP material according to claim 3, characterized in that, The organic base catalyst is one of triethylamine, triethylenediamine, pyridine, and 4-dimethylaminopyridine.

5. A high-barrier heat-resistant retort packaging film based on a single recyclable PP material according to claim 1, characterized in that, The preparation method of the heat-resistant and puncture-resistant high-barrier polypropylene-based composite material is: Step 1: Based on π-π stacking interaction and hydrogen bond interaction, compound vinylated phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane with graphene oxide to obtain a vinylated phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane / graphene composite material; Step 2: Based on the free radical coupling reaction mechanism under the action of a peroxide initiator and molecular chain intercalation technology, use the vinylated phenyl double-sandwich structured cage-like polyhedral oligomeric silsesquioxane / graphene composite material to modify polypropylene resin, and extrude and pelletize it through a twin-screw extruder to obtain a heat-resistant and puncture-resistant high-barrier polypropylene-based composite material.

6. A high-barrier and high-temperature retort packaging film based on a single recyclable PP material according to claim 5, characterized in that, The sheet diameter of the graphene oxide is 3 - 10μm, and the thickness is 8 - 15nm.

7. A high-barrier heat-resistant retort packaging film based on a single recyclable PP material according to claim 5, characterized in that, The peroxide initiator is one of dicumyl peroxide, tert-butyl hydroperoxide, benzoyl peroxide, and tert-butyl peroxybenzoate.

8. A high-barrier and high-temperature retort packaging film based on a single recyclable PP material according to claim 1, characterized in that The thickness of the high-barrier heat-resistant retort packaging film is 50 - 150 μm.

9. A high-barrier heat-resistant retort packaging film made of a single recyclable PP material according to any one of claims 1-8, characterized in that, The high-barrier heat-resistant retort packaging film is applied under the condition that the temperature ≤ 140 °C.

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