A multilayer high-barrier paper-based composite packaging material and a method for producing the same

Abstract

The present application relates to the technical field of packaging materials, in particular to a kind of multilayer high barrier paper-based composite packaging material and preparation method thereof, from outside to inside, it includes outer protective layer, printing paper base layer, adhesive layer, high barrier function layer, adhesive layer, inner heat-seal layer in sequence;The preparation method of nano barrier filler contained in the high barrier function layer component: step 1, purification of montmorillonite;Step 2, modification of distearyl dimethyl ammonium chloride;Step 3, silane coupling agent grafting;Step 4, graphene oxide composite.The composite packaging film of the present application, through the chemical means of "organicization-coupling-covalent bonding", constructs synergistic barrier network and "filler-toughening agent" interaction network, greatly improves the barrier property, toughness and strength of the material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of packaging materials, in particular to a multi-layer high-barrier paper-based composite packaging material and a preparation method thereof. BACKGROUND

[0002] With the continuous improvement of the demand for preservation, preservation and oxidation prevention in the fields of food, medicine and precision electronics, high-barrier packaging film has become a key material that effectively blocks the penetration of small molecules such as oxygen and water vapor to prolong the shelf life of the contents and ensure the stability of product performance. The main packaging film base materials on the market are mainly polypropylene (PP) and polyethylene (PE). Such polyolefin materials have good processability, low cost, stable mechanical properties and other advantages, but the molecular chain structure is loose, and the barrier ability to oxygen and water vapor is very poor (oxygen transmission rate is usually > 500 cm³ / (m²·24h·0.1MPa), water vapor transmission rate > 10 g / (m²·24h)), which is difficult to meet the needs of high-barrier scenarios. Patent CN117400610A discloses a super-high-barrier multi-layer co-extrusion film for food packaging, which comprises an upper surface layer, a core layer and a lower surface layer arranged in turn from top to bottom. The upper surface layer is composed of ethylene-vinyl alcohol copolymer, nylon 6, modified graphene and additives, the core layer is composed of ethylene-vinyl alcohol copolymer, modified polypropylene, modified graphene and additives, and the lower surface layer is composed of polyvinylidene fluoride, modified polypropylene, modified composite microspheres and additives. The invention improves the compatibility of graphene and composite microspheres by modifying them, and improves the hydrophilicity and air permeability of polypropylene by modifying it with maleic anhydride; but the improvement of the hydrophilicity of modified polypropylene leads to the improvement of the hydrophilicity of the lower surface layer and the core layer, and as the use time of the film layer increases, the ethylene-vinyl alcohol copolymer in the core layer and the upper surface layer will be in a high humidity condition, thereby causing the barrier property of the film layer to decrease.

[0003] To improve the barrier performance, the industry often uses two improvement ideas: one is to introduce high-barrier resins (such as ethylene-vinyl alcohol copolymer, EVOH), which can form a dense hydrogen bond network with strong polar hydroxyl groups and ether bonds in the molecular chain, and the oxygen transmission rate can be as low as 5 cm³ / (m²·24h·0.1MPa) or less, but the compatibility of EVOH with non-polar polyolefins is very poor, and direct blending can easily cause interface delamination, resulting in a sharp decrease in the mechanical properties (such as impact resistance) of the film, and the use of EVOH alone is very costly; the second is to add nano-barrier fillers (such as montmorillonite), which use their lamellar structure to build a "labyrinthine" barrier path to extend the penetration distance of small molecules, but unmodified montmorillonite has a hydrophilic lamellar structure, and the interfacial bonding force with the hydrophobic polyolefin matrix is weak, and it is easy to agglomerate to form defects, not only the barrier effect is not as expected, but also the brittleness of the film increases and it is easy to crack.

[0004] In summary, the prior art is difficult to achieve the synergistic balance of "high barrier property-excellent toughness-good compatibility" at the same time, and it is urgent to develop a composite packaging film technical solution that can coordinate the performance of the three. SUMMARY

[0005] To solve the above problems, the present application provides a multi-layer high-barrier paper-based composite packaging material and a preparation method thereof. The multi-layer high-barrier paper-based composite packaging material of the present application sets up a high-barrier functional layer by combining the chemical means of "organicization-coupling-covalent bonding", realizes the nanoscale dispersion of nanofiller in the matrix, and through multi-step reaction, makes the composite material become an organic whole, realizes the synergy and balance of performance, through the construction of synergistic barrier network and "filler-toughening agent" interaction network, greatly improves the barrier property, toughness and strength of the material.

[0006] The technical scheme adopted by the present application to achieve the above-mentioned purpose is:

[0007] A multi-layer high-barrier paper-based composite packaging material, from outside to inside, includes an outer protective layer, a printed paper base layer, an adhesive layer, a high-barrier functional layer, an adhesive layer, and an inner heat-seal layer; the high-barrier functional layer includes the following components by weight fraction:

[0008] 70-85 parts of base resin polypropylene or polyethylene, 10-15 parts of nanometer barrier filler, 8-15 parts of ethylene-vinyl alcohol copolymer, 4-8 parts of compatibilizer, 5-10 parts of composite toughening agent, 0.3-0.8 parts of antioxidant, and 0.5-1.5 parts of lubricant;

[0009] The preparation method of the nanometer barrier filler includes the following steps:

[0010] Step 1, take montmorillonite and add it to deionized water, stir and disperse at 800-1000 rpm for 3-4 h at 70-80℃, then stand for 18-24 h, form a suspension with upper, middle and lower three layers, extract the middle layer suspension, centrifuge at 10000-12000 rpm, collect the precipitate and dry to obtain product 1;

[0011] Step 2, disperse product 1 in deionized water to obtain a suspension, add dioctadecyl dimethyl ammonium chloride into ethanol, and add the ethanol solution of dioctadecyl dimethyl ammonium chloride to the suspension of product 1 under stirring, react at 80-85℃ for 5-6 h, then purify to obtain product 2;

[0012] Step 3, mix product 2 with toluene, ultrasonically disperse at 400-500 W power for 40-50 min, then add silane coupling agent KH-550, heat to 112-118℃, reflux under nitrogen protection for 12-14 h, purify to obtain product 3;

[0013] Step 4, the product 3 is dispersed in N,N-dimethylformamide solvent to obtain a suspension of product 3, and the suspension is ultrasonically treated for 25-35 min. The graphene oxide is dispersed in N,N-dimethylformamide and ultrasonically peeled at a power of 350-450 W for 1-2 h to obtain a uniform graphene oxide dispersion. The graphene oxide dispersion is added to the suspension of product 3 under stirring, and the reaction is carried out at 60-70℃ for 10-12 h. After the reaction is completed, purification is performed to obtain the product.

[0014] Preferably, in step 1, the weight ratio of the montmorillonite to deionized water is 100:600-800, and in step 2, the weight ratio of product 1 to deionized water is 100:500-600, and the weight ratio of product 1, dioctadecyl dimethyl ammonium chloride and ethanol is 100:25-30:80-100.

[0015] Preferably, in step 3, the weight ratio of product 2 to toluene and silane coupling agent KH-550 is 100:350-450:10-15.

[0016] Preferably, in step 4, the weight ratio of product 3 to N,N-dimethylformamide and graphene oxide is 100:350-450:3-8, and the weight ratio of graphene oxide to N,N-dimethylformamide in the graphene oxide dispersion is 3-8:200.

[0017] Preferably, the preparation method of the composite toughening agent comprises the following steps:

[0018] Step a, the polyolefin elastomer particles are dissolved by heating to 100-105℃ with xylene, then maleic anhydride and dicumyl peroxide are added, and the reaction is carried out at 108-115℃ for 6-7 h to obtain a maleic anhydride grafted polyolefin mixture. The fumed silica is dispersed in a mixed solvent of ethanol and water, ultrasonically dispersed, and then the silane coupling agent KH-550 is added, and the pH value is adjusted to 4-5. The mixture is stirred at 70-75℃ for 5-6 h to obtain an activated nano-silica dispersion. The maleic anhydride grafted polyolefin mixture and the activated nano-silica dispersion are mixed and stirred at 80-85℃ for 3-4 h, and then purified to obtain a core-shell structured composite powder.

[0019] Step b, the composite powder obtained in step a is subjected to melt reaction extrusion with dibenzoyl peroxide and glycidyl methacrylate, and the temperature is: zone 1 160-170℃, zone 2 175-185℃, zone 3 180-190℃, and the die head 185-195℃, and the screw rotation speed is 260-300 rpm.

[0020] Preferably, in step a, the weight ratio of polyolefin elastomer particles, xylene, maleic anhydride, dicumyl peroxide, silicon dioxide, mixed solvent of ethanol and water, and mixed solvent of ethanol and water is 100:400-500:4-5:1.5-2.0:40-50:300-400, and the volume ratio of ethanol and water in the mixed solvent of ethanol and water is 9:1.

[0021] Preferably, in step b, the weight ratio of the composite powder, dibenzoyl peroxide and glycidyl methacrylate is 100:2.5-3.5:8-10.

[0022] Preferably, the base resin is linear low-density polyethylene, the compatibilizer is maleic anhydride grafted polypropylene, the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1-2, and the lubricant is ethylene bis-stearamide.

[0023] The preparation method of the multi-layer high-barrier paper-based composite packaging material is as follows: the outer protective layer, the printed paper-based layer, the adhesive layer, the high-barrier functional layer and the inner heat-seal layer are compounded, and the multi-layer high-barrier paper-based composite packaging material is obtained.

[0024] The application has the following beneficial effects:

[0025] The multilayer high-barrier paper-based composite packaging material of the present application, by adding nano-barrier filler, composite toughening agent, ethylene-vinyl alcohol copolymer, compatibilizer and other components in the base polypropylene or polyethylene in the preparation of the high-barrier functional layer, through the chemical means of "organicization-coupling-covalent bonding", the nano-scale dispersion of the nano-filler in the base is realized, and through multi-step reaction, the covalent bond or strong ionic bond is introduced at the interfaces of filler-base, filler-filler, base-EVOH and other interfaces, so that the composite material becomes an organic whole, realizes the synergy and balance of performance, and through the construction of synergistic barrier network and "filler-toughening agent" interaction network, the barrier property, toughness and strength of the material are greatly improved. Among them, in the preparation process of the nano-barrier filler, step 1 removes inert impurities to obtain high-purity montmorillonite, which not only avoids the interference of impurities on the subsequent reaction, but more importantly provides a pure and efficient "reaction matrix" for the subsequent chemical modification, ensuring that the modifier only acts on the target montmorillonite layer. In step 2, the quaternary ammonium salt group of didodecyldimethylammonium chloride (cationic surfactant) is combined with the negative charge on the surface of the montmorillonite layer through electrostatic attraction, and the long-chain alkyl (C18) is arranged in the interlayer of the montmorillonite, which not only makes the montmorillonite change from hydrophilic to hydrophobic, and the compatibility with the polyolefin matrix is significantly improved, but also the steric hindrance of the long-chain alkyl can expand the interlayer spacing of the montmorillonite, leaving space for the subsequent coupling agent to access and graphene oxide composite, avoiding the barrier path breakage caused by the aggregation of the layers. In step 3, silane coupling agent KH-550 (aminopropyl triethoxysilane) undergoes hydrolysis to generate silanol (-Si-OH), which reacts with the silicon hydroxyl on the surface of the montmorillonite to form a firm Si-O-Si covalent bond. At the same time, the other end of KH-550 introduces an active amine group (-NH2). It not only increases the "molecular bridge" between the filler and the polymer, greatly enhancing the interfacial adhesion, but more importantly, it provides a chemical anchoring point (-NH2) for the fourth step reaction. In step 4, the carboxyl group (-COOH) on the surface of graphene oxide (GO) reacts with the amine group (-NH2) on the surface of the modified montmorillonite in the previous step to form an amide, and the GO nanosheet is chemically bonded to the montmorillonite through a firm covalent bond. This not only realizes the uniform dispersion of GO itself, but also constructs a "interleaved and stacked" multi-level network structure on a nanometer scale, forming a more tortuous and dense synergistic barrier network far beyond a single filler, greatly extending the diffusion path of gas and small molecules, thereby making the film exhibit extremely high oxygen and water vapor barrier properties. The nano-barrier filler realizes "purification-organicization-coupling-complexing" hierarchical optimization through four-step modification, constructs a dense and "multi-level interleaved" barrier network, and significantly improves the small molecule barrier capability.

[0026] The polyolefin segment of the compatilizer molecule is compatible with the base resin, while its anhydride group (-CO-O-CO-) can react with the hydroxyl group (-OH) of EVOH, thus acting as a "ambassador" to strongly bind the two together, preventing macroscopic phase separation and ensuring uniform material structure. The synergistic effect of the composite toughening agent and the filler also forms a chemical bridge between the toughening agent and the filler, allowing the toughening agent to not only disperse in the matrix but also be connected to the entire reinforcing network through chemical bonds. In this way, when subjected to external force impact, energy can be effectively dissipated through this powerful network, achieving both toughening and reinforcement, while also having good barrier properties.

[0027] Further, the synergistic effect of the nano-barrier filler and the composite toughening agent coordinates the "barrier-toughness-compatibility", achieving the improvement of comprehensive performance. Structural complementarity: the lamellar structure of the nano-barrier filler constructs a "lateral dense barrier layer" in the matrix, while the core-shell structure of the composite toughening agent is distributed in the interstices of the barrier layer in the form of "vertical elastic support points". On the one hand, the elastic particles of the core-shell structure can absorb the internal stress generated by the agglomeration of the nano-filler, avoiding the increase of brittleness of the film due to the addition of the nano-filler; on the other hand, the lamellar barrier layer can fill the small gaps between the core-shell structures, preventing the permeation channels that may be introduced by the toughening agent, so that the barrier property and toughness form a "defect-free superposition". Interface synergy: the KH-550 amino group (-NH2) on the surface of the nano-barrier filler can undergo ring-opening reaction with the GMA epoxy group (-C-O-C-) of the shell layer of the composite toughening agent, and at the same time, undergo amide reaction with the anhydride group (-CO-O-CO-) grafted by POE, so that the nano-filler and the toughening agent are connected through chemical bonds to form a continuous interface phase of "barrier layer-core-shell particle-matrix". This interface phase can eliminate the interface defects among the three, not only improving the overall mechanical properties of the film, but also further extending the small molecule permeation path, so that the barrier property is further improved compared to when the nano-filler is added alone. The synergistic effect of the "multi-level staggered barrier network" of the nano-barrier filler and the "core-shell-epoxy grafting structure" of the composite toughening agent solves the brittleness problem of the nano-filler through elastic deformation and interface strengthening, and the nano-filler makes up for the permeation defects of the toughening agent through the dense barrier network, so that the film finally has high barrier property, excellent toughness and mechanical property, fully meeting the high barrier packaging requirements of food, medicine and other products.

[0028] The preparation method of the application has controllable process, high production efficiency and is suitable for industrial production. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0030] The raw materials used below are all ordinary commercially available.

[0031] Linear low density polyethylene, brand DFDA-7042, Suzhou Deyi Plastic Co., Ltd.; Ethylene-vinyl alcohol copolymer, Dongguan Xingshengli Plastic New Material Science and Technology Co., Ltd.; Maleic anhydride grafted polypropylene, Shanghai Xianshun Plastic Co., Ltd.; Antioxidant 1010, hindered phenolic, volatile content ≤0.5%, Jiangsu Xinluda Polymer Material Co., Ltd.; Antioxidant 168, volatile content ≤0.5%, Jiangsu Xinluda Polymer Material Co., Ltd.; Ethylene bis-stearamide, 110-30-5, Wuhan Shur Biological Technology Co., Ltd.; Montmorillonite is sodium-based montmorillonite, specification 325 mesh, Lingshou County Shunlei Mineral Product Processing Factory; Polyolefin elastomer, brand: USA Dow; Organic nano-montmorillonite, DK10, dry powder particle size (D98) / um: ≤20, Zhejiang Fenghong New Material Co., Ltd.;

[0032] Example 1

[0033] A multi-layer high-barrier paper-based composite packaging material, from outside to inside, includes an outer protective layer, a printed paper-based layer, an adhesive layer, a high-barrier functional layer, an adhesive layer, and an inner heat-seal layer; the high-barrier functional layer includes the following components by weight fraction:

[0034] The base resin polyethylene is 80 parts, the nano-barrier filler is 12 parts, the ethylene-vinyl alcohol copolymer is 12 parts, the compatibilizer is 6 parts, the composite toughening agent is 8 parts, the antioxidant is 0.5 parts, and the lubricant is 1 part; the base resin is linear low density polyethylene, the compatibilizer is maleic anhydride grafted polypropylene, the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1.5, and the lubricant is ethylene bis-stearamide;

[0035] The preparation method of the nano-barrier filler includes the following steps:

[0036] Step 1, take montmorillonite and add it to deionized water, stir at a speed of 900 rmp for 3.5 h at 75°C, then stand for 21 h, form a suspension with upper, middle and lower three layers, extract the middle layer suspension, centrifuge at a speed of 11000 rmp, collect the precipitate and vacuum dry at 85°C to constant weight, obtain product 1; in step 1, the weight ratio of montmorillonite to deionized water is 100:700;

[0037] Step 2, the product 1 is dispersed in deionized water to obtain a product 1 suspension, and the dioctadecyl dimethyl ammonium chloride is placed in a round-bottom flask with a reflux condenser, ethanol is added and heated to 65 DEG C, and dissolved by stirring, the ethanol solution of the dioctadecyl dimethyl ammonium chloride is added dropwise to the product 1 suspension at 1100 rpm under stirring at a rate of 4 mL / min, and reacted at 82 DEG C for 5.5 h, then filtered, washed with hot water at 65 DEG C for 3 times, and washed with anhydrous ethanol for 2 times until no white precipitate is generated in the filtrate by using 0.1 mol / L silver nitrate solution, and dried at 85 DEG C under vacuum to constant weight to obtain the product 2; in step 2, the weight ratio of the product 1 to deionized water is 100:500, and the weight ratio of the product 1, the dioctadecyl dimethyl ammonium chloride and ethanol is 100:27:90;

[0038] Step 3, the product 2 is mixed with toluene, and dispersed by ultrasonic at a power of 450 W for 45 min, then the silane coupling agent KH-550 is added, heated to 115 DEG C, and reacted under reflux for 13 h under nitrogen protection, then filtered after cooling, washed with toluene for 2 times, and dried at 82 DEG C for 7 h to obtain the product 3; in step 3, the weight ratio of the product 2, toluene and the silane coupling agent KH-550 is 100:400:12;

[0039] Step 4, the product 3 is dispersed in N,N-dimethylformamide solvent and treated by ultrasonic for 30 min, the graphene oxide is dispersed in N,N-dimethylformamide and peeled off by ultrasonic at a power of 400 W for 1.5 h to obtain a uniform graphene oxide dispersion liquid, the graphene oxide dispersion liquid is added dropwise to the montmorillonite N,N-dimethylformamide suspension at a rate of 2 mL / min under stirring, and reacted at 65 DEG C for 11 h, then filtered after the reaction, washed with N,N-dimethylformamide and anhydrous ethanol for 3 times in sequence, and finally dried at 80 DEG C under vacuum for 24 h, and ground through an 800 mesh screen to obtain the product. In step 4, the weight ratio of the product 3, N,N-dimethylformamide and graphene oxide is 100:400:5, and the weight ratio of graphene oxide to N,N-dimethylformamide in the graphene oxide dispersion liquid is 5:200.

[0040] The preparation method of the composite toughening agent comprises the following steps:

[0041] Step a, take 100 parts of polyolefin elastomer particles, together with 450 parts of xylene into the reaction kettle, nitrogen protection for 20 min, heating to 102℃ to make polyolefin elastomer particles completely dissolved, then add 4.5 parts of maleic anhydride and 1.8 parts of dicumyl peroxide, reaction at 110℃ for 6.5h, to obtain maleic anhydride grafted polyolefin mixture; 45 parts of fumed silica is dispersed in 350 parts of mixed solvent of ethanol and water (volume ratio 9:1), ultrasonic dispersion for 40 min, add 6 parts of silane coupling agent KH-550, adjust pH value to 4-5 with acetic acid, stirring at 72℃ for 5.5h, to obtain activated nano-silica dispersion; mix the maleic anhydride grafted polyolefin mixture and the activated nano-silica dispersion, stirring at 80-85℃ for 3.5h, to make the anhydride group fully react with the amine group, then pour the mixture into excess acetone to precipitate, filter, wash with acetone for 3 times, vacuum drying at 70℃ for 12h, to obtain the core-shell structured composite powder;

[0042] Step b, melt reaction extrusion of 100 parts of the composite powder obtained in step a with 3 parts of dibenzoyl peroxide and 9 parts of glycidyl methacrylate, in a twin-screw extruder, the temperature is set as: zone 1 165℃, zone 2 180℃, zone 3 185℃, die head 190℃, screw speed 280rmp, to make the glycidyl methacrylate monomer grafted onto the molecular chain of the polyolefin elastomer particle shell layer.

[0043] The preparation method of the high barrier functional layer is:

[0044] (1) Raw material pretreatment:

[0045] The ethylene-vinyl alcohol copolymer is dried in a vacuum oven at 85℃ for 11h, the nano-barrier filler is vacuum dried at 90℃ for 5h, and the composite toughening agent is vacuum dried at 60℃ for 4h;

[0046] (2) Premixing:

[0047] According to the above weight parts, the base resin polyethylene, the compatibilizer, the antioxidant, the lubricant, the nano-barrier filler after drying in step (1), the ethylene-vinyl alcohol copolymer, and the composite toughening agent are put into a high-speed mixer, mixed at a speed of 1100rmp for 13min, to obtain a uniform premix;

[0048] (3) Melt blending extrusion and casting film formation:

[0049] The premix obtained in step (2) is fed into the feeding hopper of a twin-screw extruder, and after melting plasticization, mixing and devolatilization, the molten sheet is extruded through a T-shaped die, and the processing temperature of the twin-screw extruder is set from the feeding port to the die as follows: 175℃ for the first zone, 185℃ for the second zone, 195℃ for the third zone, 205℃ for the fourth zone, 210℃ for the fifth zone, and 215℃ for the head; the screw rotation speed is 300rmp;

[0050] (4) Cooling, shaping and winding:

[0051] The molten sheet extruded from the T-shaped die is immediately attached to a mirror surface cooling roller with a surface temperature controlled at 20-25℃ for rapid cooling and shaping, and is wound into a film, thereby obtaining a high-barrier functional layer with a thickness of 30-50μm.

[0052] The preparation method of the above-mentioned multilayer high-barrier paper-based composite packaging material is as follows:

[0053] In the first step, the molten low-density polyethylene is directly coated onto the outer surface of the paper base treated by corona discharge (single-side film coating), and is extruded and cooled by a cooling steel roller and a rubber pressure roller, thereby forming a continuous and dense outer protective layer with a thickness of 20μm; the extrusion temperature is 180℃, the air gap distance is 130mm, and the cooling roller temperature is 18℃.

[0054] In the second step, the inner side (the side without the outer protective layer) of the paper base is coated with polyurethane adhesive using a ceramic anilox roller, and the coating amount is 3g / m²; the paper base coated with the adhesive is attached to one side of the high-barrier functional layer by pressing with a compounding roller, and the pressure is 0.5MPa; the other side of the high-barrier functional layer is coated with polyurethane adhesive, and the coating amount is 2g / m², and then is attached to the heat-seal layer film by pressing with a compounding roller, and the pressure is 0.3MPa; then it is sent to a curing chamber for heat preservation at 45℃ for 32 hours, so that the adhesive is fully crosslinked, thereby obtaining the product.

[0055] Example 2

[0056] A multilayer high-barrier paper-based composite packaging material comprises, from outside to inside, an outer protective layer, a printed paper base layer, an adhesive layer, a high-barrier functional layer, an adhesive layer, and an inner heat-seal layer; the high-barrier functional layer comprises the following components by weight fraction:

[0057] The base resin is linear low-density polyethylene, the compatibilizer is maleic anhydride grafted polypropylene, the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:2, and the lubricant is ethylene bis-stearamide;

[0058] The preparation method of the nano-barrier filler comprises the following steps:

[0059] Step 1, take the montmorillonite into deionized water, high speed stirring at 1000rmp for 3h at 70℃, then stand for 18h, form a suspension with upper, middle and lower three layers, extract the middle layer suspension, centrifugal separation at 10000rmp, collect the precipitate and vacuum dry at 85℃ to constant weight, get product 1; in step 1, the weight ratio of montmorillonite and deionized water is 100:600;

[0060] Step 2, disperse product 1 in deionized water to get product 1 suspension, put dioctadecyl dimethyl ammonium chloride in a round bottom flask with reflux condenser, add ethanol and heat to 70℃, stir to dissolve, add the ethanol solution of dioctadecyl dimethyl ammonium chloride to the product 1 suspension at 3mL / min with 1000rmp stirring, react at 80℃ for 6h, then filter, wash with hot water at 60℃ for 3 times, then wash with anhydrous ethanol for 2 times, until no white precipitate is produced in the filtrate detected by 0.1mol / L silver nitrate solution, vacuum dry at 85℃ to constant weight, get product 2; in step 2, the weight ratio of product 1 and deionized water is 100:550, the weight ratio of product 1, dioctadecyl dimethyl ammonium chloride and ethanol is 100:25:100;

[0061] Step 3, mix product 2 with toluene, ultrasonic dispersion for 40min at 500W power, then add silane coupling agent KH-550, heat to 112℃, reflux under nitrogen protection for 12h, cool, filter, wash with toluene for 2 times, dry at 85℃ for 6h, get product 3; in step 3, the weight ratio of product 2, toluene and silane coupling agent KH-550 is 100:350:15;

[0062] In step 4, the weight ratio of product 3, N,N-dimethylformamide and graphene oxide is 100:450:3, in the graphene oxide dispersion, the weight ratio of graphene oxide and N,N-dimethylformamide is 3:200, the rest is the same as example 1.

[0063] In the preparation method of the composite toughening agent, in step a, the weight ratio of polyolefin elastomer particles, xylene, maleic anhydride, dicumyl peroxide, silicon dioxide, ethanol and water mixed solvent is 100:500:4:1.5:40:400, the volume ratio of ethanol and water in the mixed solvent of ethanol and water is 9:1; in step b, the weight ratio of the composite powder, dibenzoyl peroxide and glycidyl methacrylate is 100:2.5:10, the rest is the same as example 1.

[0064] The preparation method of the above high barrier functional layer and multi-layer high barrier paper-based composite packaging material is the same as example 1.

[0065] Example 3

[0066] A multi-layer high-barrier paper-based composite packaging material comprises, from outside to inside, an outer protective layer, a printed paper-based layer, an adhesive layer, a high-barrier functional layer, an adhesive layer, and an inner heat-seal layer; the high-barrier functional layer comprises the following components by weight fraction:

[0067] 85 parts of base resin polyethylene, 10 parts of nano-barrier filler, 8 parts of ethylene-vinyl alcohol copolymer, 4 parts of compatibilizer, 10 parts of composite toughening agent, 0.8 parts of antioxidant, and 1.5 parts of lubricant; the base resin is linear low-density polyethylene, the compatibilizer is maleic anhydride grafted polypropylene, the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1, and the lubricant is ethylene bis-stearamide;

[0068] The preparation method of the nano-barrier filler comprises the following steps:

[0069] Step 1: Take montmorillonite and add it to deionized water, stir and disperse at 800 rpm for 4 h at 80℃, then stand for 24 h to form a suspension with upper, middle and lower layers, extract the middle layer suspension, centrifuge at 12000 rpm, collect the precipitate and vacuum dry at 85℃ until constant weight to obtain product 1; in step 1, the weight ratio of montmorillonite to deionized water is 100:800;

[0070] Step 2: Disperse product 1 in deionized water to obtain a suspension of product 1, place dioctadecyl dimethyl ammonium chloride in a round-bottom flask with a reflux condenser, add ethanol and heat to 60℃, stir and dissolve, add the ethanol solution of dioctadecyl dimethyl ammonium chloride to the suspension of product 1 at a rate of 5 mL / min with stirring at 1200 rpm, react at 85℃ for 5 h, then filter, wash with hot water at 70℃ for 3 times, and then wash with anhydrous ethanol for 2 times until no white precipitate is generated in the filtrate when tested with 0.1 mol / L silver nitrate solution, and vacuum dry at 85℃ until constant weight to obtain product 2; in step 2, the weight ratio of product 1 to deionized water is 100:600, and the weight ratio of product 1, dioctadecyl dimethyl ammonium chloride and ethanol is 100:30:80;

[0071] Step 3: Mix product 2 with toluene, ultrasonically disperse for 50 min at a power of 400 W, then add silane coupling agent KH-550, heat to 118℃, and reflux under nitrogen protection for 14 h, cool, filter, wash with toluene for 2 times, and dry at 80℃ for 8 h to obtain product 3; in step 3, the weight ratio of product 2, toluene and silane coupling agent KH-550 is 100:450:10;

[0072] In step 4, the product 3 is mixed with N,N-dimethylformamide and graphene oxide in a weight ratio of 100:350:8, and the weight ratio of graphene oxide to N,N-dimethylformamide in the graphene oxide dispersion is 8:200, and the rest is the same as in Example 1.

[0073] In the preparation method of the composite toughening agent, in step a, the weight ratio of polyolefin elastomer particles, xylene, maleic anhydride, dicumyl peroxide, silicon dioxide, and the mixed solvent of ethanol and water is 100:400:5:2.0:50:300, and the volume ratio of ethanol to water in the mixed solvent of ethanol and water is 9:1; in step b, the weight ratio of the composite powder, dibenzoyl peroxide and glycidyl methacrylate is 100:3.5:8, and the rest is the same as in Example 1.

[0074] The preparation method of the high-barrier functional layer and the multilayer high-barrier paper-based composite packaging material described above is the same as in Example 1.

[0075] Comparative Example 1

[0076] A high-barrier functional layer, wherein the nano-barrier filler is replaced by ordinary commercially available organic nano-montmorillonite, and the rest is the same as in Example 1.

[0077] Comparative Example 2

[0078] A high-barrier functional layer, wherein the composite toughening agent is replaced by ordinary commercially available polyolefin elastomer, and the rest is the same as in Example 1.

[0079] Comparative Example 3

[0080] A high-barrier functional layer, wherein the nano-barrier filler is replaced by ordinary commercially available organic nano-montmorillonite, and the composite toughening agent is replaced by ordinary commercially available polyolefin elastomer, and the rest is the same as in Example 1.

[0081] Comparative Example 4

[0082] A multilayer high-barrier paper-based composite packaging material, wherein the high-barrier functional layer of Comparative Example 1 is used, and the rest is the same as in Example 1.

[0083] Comparative Example 5

[0084] A multilayer high-barrier paper-based composite packaging material, wherein the high-barrier functional layer of Comparative Example 2 is used, and the rest is the same as in Example 1.

[0085] Comparative Example 6

[0086] A multilayer high-barrier paper-based composite packaging material, wherein the high-barrier functional layer of Comparative Example 3 is used, and the rest is the same as in Example 1.

[0087] Performance test:

[0088] The oxygen transmission rate of the high-barrier functional layer prepared in Examples 1-3 and Comparative Examples 1-3 was tested according to GB / T1038.1-2022, so as to characterize the oxygen barrier property of the high-barrier functional layer;

[0089] The water vapor transmission rate of the high-barrier functional layer prepared in Examples 1-3 and Comparative Examples 1-3 was tested according to GB / T1037-2021, so as to characterize the water vapor barrier property of the high-barrier functional layer;

[0090] The elongation at break and tensile strength of the high-barrier functional layer prepared in Examples and Comparative Examples were tested according to GB / T1040.1-2012 “Determination of tensile properties of plastics”, so as to characterize the toughness of the high-barrier functional layer. The results are shown in Table 1.

[0091] The oxygen barrier property and water vapor barrier property of the composite packaging material obtained in Examples 1-3 and Comparative Examples 4-6 were tested according to GB / T1038.1-2022 and GB / T1037-2021, and the results are shown in Table 2.

[0092] Table 1, performance test results

[0093]

[0094] Table 2

[0095]

[0096] As can be seen from Table 1 and Table 2, the barrier properties of the high-barrier functional layer and the composite packaging material of Examples 1-3 are significantly better than those of Comparative Examples. This proves that the nano-barrier filler of the present application forms a more complex and tortuous penetration path in the high-barrier functional layer film through the “montmorillonite-graphene oxide” hybrid nano filler, greatly delaying the passage of gas and water vapor. At the same time, it cooperates with the composite toughening agent, while maintaining good tensile properties and having high tensile strength.

[0097] It should be noted that, in this document, relational terms such as first and second and the like can only be used to distinguish one entity or action from another entity or action, without necessarily requiring or implying that there is any such actual relationship or order between these entities or actions. Moreover, the terms “comprises”, “comprising”, or any other variations thereof are intended to cover a non-exclusive inclusion, so that a process, method, article, or apparatus that comprises a list of elements does not include only those elements, but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0098] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary and that changes can be made in detail without departing from the principles and spirit of the application. The scope of the application is therefore defined by the appended claims and their equivalents.

Claims

1. A multi-layer high-barrier paper-based composite packaging material, characterized in that, From the outside in, it comprises, in sequence, an outer protective layer, a printed paper base layer, an adhesive layer, a high-barrier functional layer, an adhesive layer, and an inner heat-sealing layer; the high-barrier functional layer comprises the following components by weight: The base resin is polypropylene or polyethylene, which contains 70-85 parts; nano-barrier filler, which contains 10-15 parts; ethylene-vinyl alcohol copolymer, which contains 8-15 parts; compatibilizer, which contains 4-8 parts; composite toughening agent, which contains 5-10 parts; antioxidant, which contains 0.3-0.8 parts; and lubricant, which contains 0.5-1.5 parts. The preparation method of the nano-barrier filler includes the following steps: Step 1: Add montmorillonite to deionized water and disperse it at 70-80℃ with high-speed stirring at 800-1000 rpm for 3-4 hours. Then let it stand for 18-24 hours to form a suspension with three layers: upper, middle and lower. Extract the middle layer suspension and centrifuge it at 10000-12000 rpm. Collect the precipitate and dry it to obtain product 1. Step 2: Disperse product 1 in deionized water to obtain a suspension. Add bis(octadecyldimethylammonium chloride) to ethanol, and add the ethanol solution of bis(octadecyldimethylammonium chloride) to the suspension of product 1 under stirring. React at 80-85℃ for 5-6 hours, and then purify to obtain product 2. Step 3: Mix product 2 with toluene and ultrasonically disperse at 400-500W for 40-50 min. Then add silane coupling agent KH-550, heat to 112-118℃, and reflux under nitrogen protection for 12-14 h to obtain product 3. Step 4: Disperse product 3 in N,N-dimethylformamide solvent to obtain a suspension of product 3. Sonicate the suspension for 25-35 min. Disperse graphene oxide in N,N-dimethylformamide and ultrasonically exfoliate it at 350-450W power for 1-2 h to obtain a uniform graphene oxide dispersion. Add the graphene oxide dispersion to the suspension of product 3 with stirring. Stir and react at 60-70℃ for 10-12 h. After the reaction is completed, purify the product to obtain the final product. The preparation method of the composite toughening agent includes the following steps: Step a: Take polyolefin elastomer particles and heat them with xylene to 100-105℃ to dissolve the polyolefin elastomer particles. Then add maleic anhydride and dicumyl peroxide and react at 108-115℃ for 6-7 hours to obtain a maleic anhydride-grafted polyolefin mixture. Disperse fumed silica in a mixed solvent of ethanol and water, sonicate, add silane coupling agent KH-550, adjust the pH to 4-5, and stir at 70-75℃ for 5-6 hours to obtain an activated nano silica dispersion. Mix the maleic anhydride-grafted polyolefin mixture with the activated nano silica dispersion and stir at 80-85℃ for 3-4 hours to obtain a core-shell structured composite powder. Step b: The composite powder obtained in step a is melt-extruded with benzoyl peroxide and glycidyl methacrylate at the following temperatures: Zone 1 160-170℃, Zone 2 175-185℃, Zone 3 180-190℃, die head 185-195℃, and screw speed 260-300 rpm.

2. The multi-layer high-barrier paper-based composite packaging material according to claim 1, characterized in that, In step 1, the weight ratio of montmorillonite to deionized water is 100:600-800. In step 2, the weight ratio of product 1 to deionized water is 100:500-600. The weight ratio of product 1, dioctadecyldimethylammonium chloride, and ethanol is 100:25-30:80-100.

3. The multi-layer high-barrier paper-based composite packaging material according to claim 1, characterized in that, In step 3, the weight ratio of product 2 to toluene and silane coupling agent KH-550 is 100:350-450:10-15.

4. The multi-layer high-barrier paper-based composite packaging material according to claim 1, characterized in that, In step 4, the weight ratio of product 3 to N,N-dimethylformamide and graphene oxide is 100:350-450:3-8, and the weight ratio of graphene oxide to N,N-dimethylformamide in the graphene oxide dispersion is 3-8:

200.

5. The multi-layer high-barrier paper-based composite packaging material according to claim 1, characterized in that, In step a, the weight ratio of the polyolefin elastomer particles to the mixed solvent of xylene, maleic anhydride, dicumyl peroxide, silica, ethanol and water is 100:400-500:4-5:1.5-2.0:40-50:300-400, and the volume ratio of ethanol to water in the mixed solvent of ethanol and water is 9:

1.

6. The multi-layer high-barrier paper-based composite packaging material according to claim 1, characterized in that, In step b, the weight ratio of the composite powder, benzoyl peroxide, and glycidyl methacrylate is 100:2.5-3.5:8-10.

7. The multi-layer high-barrier paper-based composite packaging material according to claim 1, characterized in that, The base resin is linear low-density polyethylene, the compatibilizer is maleic anhydride-grafted polypropylene, the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1-2, and the lubricant is ethylene bis-stearamide.

8. The method for preparing the multilayer high-barrier paper-based composite packaging material according to any one of claims 1-7, characterized in that, Specifically, the outer protective layer, the printed paper base layer, the adhesive layer, the high-barrier functional layer, and the inner heat-sealing layer are combined to obtain the final product.

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