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CN-121590108-B - Multifunctional high-barrier multilayer packaging film and preparation method thereof

CN121590108BCN 121590108 BCN121590108 BCN 121590108BCN-121590108-B

Abstract

The invention belongs to the field of packaging materials, and provides a multifunctional high-barrier multilayer packaging film and a preparation method thereof. The invention adopts a five-layer structural design, and sequentially comprises a polypropylene layer, a first bonding layer, an ethylene-vinyl alcohol copolymer layer, a second bonding layer and a polyethylene layer from outside to inside, wherein the bonding layer comprises master batches formed by covalently compounding maleic anhydride grafted polyethylene and aminopropyl silane modified montmorillonite through an amide bond and an imide bond, so that the strong interface combination of a barrier layer and a polyolefin layer and the synergistic enhancement of an inorganic sheet layer are realized. The film has the oxygen transmittance of not more than 1.0 cm < 3 >/(m2.24 24 h.0.1: 0.1 MPa), the water vapor transmittance of not more than 1.0 g/(m2.24 24 h), and no delamination at the interlayer interface under the condition of 121 ℃ heat treatment, solves the problems of attenuation of barrier performance, interlayer stripping and insufficient toughness of the existing multilayer barrier film under the damp-heat environment, and has application value in the fields of high-temperature digestion packaging, aseptic packaging, medical packaging and the like.

Inventors

  • LEI HUI

Assignees

  • 环球新材料(南通)股份有限公司

Dates

Publication Date
20260505
Application Date
20260129

Claims (6)

  1. 1. The multifunctional high-barrier multilayer packaging film is characterized by comprising an outer layer, a first bonding layer, a barrier layer, a second bonding layer and an inner layer from outside to inside in sequence; Wherein the outer layer is a polypropylene layer, the inner layer is a polyethylene layer, and the barrier layer is an ethylene-vinyl alcohol copolymer layer; At least one layer of the first bonding layer and the second bonding layer comprises covalent bonding composite master batch, the total thickness of the multifunctional high-barrier multilayer packaging film is 40-200 mu m, the oxygen transmittance measured according to GB/T19789-2021 under the conditions of 23+/-0.5 ℃ and relative humidity of 0% -5% is not more than 1.0 cm < 3 >/(m2.24 24 h.0.1: 0.1 MPa), and the water vapor transmittance measured according to GB/T1037-2021 at 38 ℃ by adopting a weight increasing method is not more than 1.0 g/(m2.24 h); The covalent bonding composite master batch I comprises, by mass, 60-95 parts of maleic anhydride grafted polyethylene and 5-40 parts of aminopropyl silane modified montmorillonite, wherein the total of the maleic anhydride grafted polyethylene and the aminopropyl silane modified montmorillonite is 100 parts; In the covalent bonding composite master batch, covalent bonds between montmorillonite and the maleic anhydride grafted polyethylene in the covalent bonding composite master batch I comprise amic acid structures formed by the reaction of maleic anhydride groups and amino groups, and the amic acid structures comprise amide bonds, and imide bonds formed by further dehydration cyclization; The thickness of the outer layer is 10-60 mu m, and the thickness of the inner layer is 15-100 mu m; the thickness of the barrier layer is 2-30 mu m; the thickness of the first bonding layer and the second bonding layer is 2-20 mu m independently; The mole fraction of ethylene in the ethylene-vinyl alcohol copolymer is 20-45 mol%; the first bonding layer and the second bonding layer both comprise the covalent bonding composite master batch, and the addition amount of the covalent bonding composite master batch in the corresponding bonding layer is 1-30 wt% by the total mass of the corresponding bonding layer; The multifunctional high-barrier multilayer packaging film has the sequence of a polypropylene layer/a first bonding layer/an ethylene-vinyl alcohol copolymer layer/a second bonding layer/a polyethylene layer, and the polymer continuous phases of the first bonding layer and the second bonding layer are maleic anhydride grafted polyethylene.
  2. 2. The multifunctional high-barrier multilayer packaging film according to claim 1, wherein the preparation method of the aminopropyl silane modified montmorillonite comprises the following sub-steps: a1, adding montmorillonite into a dispersion medium consisting of ethanol and water with the volume ratio of 6:4 to 9:1 based on 100 parts by mass of montmorillonite, wherein the addition amount of the dispersion medium is 5-20 mL/g based on the mass of montmorillonite, and stirring and dispersing for 10-60 min at the temperature of 25-40 ℃ and normal pressure by adopting mechanical stirring at the speed of 300-800 r/min; A2, adding 2-10 parts by mass of total aminopropyl silane and continuously stirring for 30-120 min, wherein the aminopropyl silane is selected from one or two of 3-aminopropyl triethoxy silane and 3-aminopropyl trimethoxy silane; A3, titrating and adjusting the pH value of the system to 4.0-5.5 by adopting an acetic acid aqueous solution with the mass fraction of 1% -10% under stirring; a4, continuously stirring and reacting at 40-60 ℃ and normal pressure for 1-6 h; a5, filtering after the reaction is finished, and washing the filtrate with ethanol and water in sequence until the pH value of the filtrate obtained in the last water washing is 6.5-7.5; A6, drying 6-12 h under vacuum condition with absolute pressure of 0.01-0.03 MPa at 60-90 ℃ to obtain the aminopropyl silane modified montmorillonite, wherein the aminopropyl silane modified montmorillonite satisfies the water content of not higher than 1.0 wt% and the nitrogen content of 0.2-1.5 wt%.
  3. 3. The multifunctional high-barrier multilayer packaging film according to claim 1, wherein the preparation method of the maleic anhydride grafted polyethylene comprises the following sub-steps: B1, premixing 100 parts by mass of polyethylene, 0.3-2.0 parts by mass of maleic anhydride and 0.03-0.20 parts by mass of dicumyl peroxide; B2, carrying out twin-screw reactive extrusion under the protection of nitrogen, wherein the temperature of each temperature zone in the reactive extrusion process is 170-220 ℃, the screw rotating speed is 200-500 r/min, and the total material residence time is 30-180 s; B3, controlling the absolute pressure to be 0.02-0.06 MPa in a vacuum exhaust section to remove free maleic anhydride; B4, granulating the extruded strips after water cooling, and drying 4-8 h under the vacuum condition of 80-100 ℃ and absolute pressure of 0.01-0.03 MPa to obtain the maleic anhydride grafted polyethylene, wherein the maleic anhydride grafted polyethylene satisfies that the maleic anhydride group content is 0.05-2.0 wt percent and the free maleic anhydride content is not higher than 0.05 wt percent.
  4. 4. The multifunctional high-barrier multilayer packaging film according to claim 1, wherein the preparation method of the covalently bonded composite master batch comprises the following sub-steps: C1, mixing the aminopropyl silane modified montmorillonite with the maleic anhydride grafted polyethylene according to parts by mass, wherein the aminopropyl silane modified montmorillonite is 5-40 parts by mass, and the maleic anhydride grafted polyethylene is 60-95 parts by mass; Carrying out interfacial reaction and dispersion by a double screw extruder under the condition of nitrogen protection and normal pressure, wherein the temperature of an extrusion temperature zone is 170-220 ℃, the screw rotating speed is 250-600 r/min, and the residence time is 30-150 s; And C3, extruding the strips, carrying out water-cooling and granulating to obtain the covalent bonding composite master batch, wherein the water content of the covalent bonding composite master batch is not higher than 1.0 wt%.
  5. 5. The multifunctional high-barrier multilayer packaging film according to claim 1, wherein the multifunctional high-barrier multilayer packaging film is suitable for packaging with 10-60 min of saturated steam heat treatment at 121 ℃ and no visible delamination of the adhesive layer interface on both sides of the barrier layer.
  6. 6. A method of making the multifunctional high-barrier multilayer packaging film of any one of claims 1-5, comprising the steps of: S1, preparing aminopropyl silane modified montmorillonite, preparing maleic anhydride grafted polyethylene and preparing covalent bonding composite master batch; S2, respectively melting raw materials of polypropylene, ethylene-vinyl alcohol copolymer, polyethylene and a bonding layer formed by maleic anhydride grafted polyethylene and covalent bonding composite master batch in respective extruders, and performing coextrusion to form a film according to the layer sequence of an outer layer/a first bonding layer/a barrier layer/a second bonding layer/an inner layer through a coextrusion die head, wherein the melt temperature of the polypropylene is 190-240 ℃, the melt temperature of the polyethylene is 170-220 ℃, and the melt temperature of the ethylene-vinyl alcohol copolymer is 170-210 ℃; and S3, cooling and shaping the co-extrusion melt, and then rolling to obtain the multifunctional high-barrier multilayer packaging film.

Description

Multifunctional high-barrier multilayer packaging film and preparation method thereof Technical Field The invention relates to the field of packaging materials, in particular to a multifunctional high-barrier multilayer packaging film and a preparation method thereof. Background In the modern packaging industry, the multilayer composite barrier film is used as a core material for guaranteeing the quality of contents and prolonging the shelf life, and is widely applied to packaging of oxygen and water vapor sensitive products such as foods, medicines, medical appliances and the like. With the development of consumer upgrading and cold chain logistics, the market has higher requirements on the barrier performance of packaging films, namely, the packaging films need to realize extremely low oxygen transmittance to inhibit grease oxidation and microorganism propagation in the food field, have water vapor barrier property to protect the stability of hygroscopic drugs in medical packaging, and need to resist the treatment of saturated steam at 121 ℃ without performance degradation in the scene of high-temperature steaming packaging. The application scenes require that the barrier film not only has excellent barrier property under the condition of normal temperature drying, but also maintains barrier stability and interlayer bonding reliability under severe environments such as high temperature, high humidity and the like, and simultaneously combines heat sealing performance, mechanical strength and processing suitability so as to meet the high-speed continuous operation requirement of an automatic packaging production line. Therefore, the development of the multilayer barrier film which can maintain the lasting barrier property under the damp and hot condition, has no delamination of interfaces and good processability has important significance for improving the packaging safety, expanding the application field and pushing the packaging industry to develop towards the high performance. At present, the multi-layer barrier film generally adopts an ethylene-vinyl alcohol copolymer as a core barrier layer, and is combined with polyolefin layers such as polyethylene, polypropylene and the like through a coextrusion compounding process to form a multi-layer structure. However, the prior art has a plurality of defects that firstly, the ethylene-vinyl alcohol copolymer absorbs moisture and swells under a high-humidity environment due to the hydrophilicity of hydroxyl groups, a hydrogen bond network is destroyed by water molecules to cause water plasticization, so that the oxygen transmittance is rapidly increased, the barrier performance is greatly attenuated, for example, china patent with publication number CN104149446A discloses a high barrier film and a preparation method thereof, but the barrier stability is insufficient under the high-humidity condition, secondly, the polarity difference between the ethylene-vinyl alcohol copolymer and polyolefin is large to cause weak interfacial bonding force, interlayer thermal stress is generated due to mismatch of thermal expansion coefficients in the heat treatment process, and water molecule permeation is used for inducing interfacial swelling stress, interfacial delamination or microcrack channels are easily generated under the coupling effect of the two, barrier failure is caused in severe cases, for example, china patent with publication number CN219338880U discloses a multilayer barrier film structure for food packaging, but the reliability of interfacial bonding is insufficient, thirdly, maleic anhydride grafted polyolefin is often introduced as a bonding layer for improving the interfacial bonding, but melt rheological property of a graft is not matched with a matrix to cause narrowing a coextrusion processing window, and the rheological property and the stability between a reactive compatilizer and an inorganic composite is difficult to guarantee the consistency of processing batch. Disclosure of Invention The invention aims to provide a multifunctional high-barrier multilayer packaging film and a preparation method thereof, which solve the coupling contradiction that when the aim of extremely low oxygen transmission rate and low water vapor transmission rate is achieved by the existing multilayer structure, the barrier durability is attenuated and the interface delamination risk is caused by EVOH moisture sensitive water plasticization and interlayer thermal humidity stress mismatch, melt rheological fluctuation and coextrusion processing window narrowing and batch-to-batch consistency deficiency are caused after reaction compatibility and inorganic sheet reinforcement are introduced, and the coupling contradiction that the barrier and interface strengthening requirements are improved by high modulus densification and the brittle fracture resistance and microcrack resistance channel formation are difficult to be compatible after heat treatment. The invention realizes