Online coating high barrier biaxially oriented polyethylene film and preparation method and application thereof

Abstract

The application belongs to the technical field of layered composite film preparation, and provides an online coating high-barrier biaxially stretched polyethylene film and a preparation method and application thereof. First, polyethylene multilayer sheet is co-extruded and longitudinally stretched, and a to-be-coated base film is obtained through corona activation; then, nano clusters are constructed from phytic acid and zirconium salt, and a hybrid dispersion liquid is formed by introducing tannic acid, polyallylamine hydrochloride and epoxy silane; at the same time, sodium-based montmorillonite and colloidal silicon dioxide are compounded under the action of tannic acid and treated by silane to obtain a barrier dispersion liquid; the barrier dispersion liquid, polyvinyl alcohol, polyvinylpyrrolidone and polyhydric alcohol are prepared into an aqueous coating composition, which is coated on the base film online, dried and solidified, and then transversely stretched to obtain a film with stable oxygen and water vapor barrier properties and suitable for packaging applications.

Description

Technical Field

[0001] This invention belongs to the field of layered composite film preparation technology, and relates to an online coated high-barrier biaxially oriented polyethylene film, its preparation method and application. Background Technology

[0002] Polyethylene film is widely used in food and daily chemical packaging, pharmaceutical packaging, and industrial protection due to its wide availability of raw materials, broad processing window, good mechanical properties, and ease of recycling. To meet the packaging requirements for blocking oxygen and water vapor, the industry typically employs multi-layer composite structures or high-barrier coatings on the surface of the polyethylene film to enhance overall barrier performance. Compared to offline coating and multi-stage lamination, wide-width online coating can be integrated with biaxial stretching processes, which is beneficial for improving production efficiency, reducing energy consumption, and minimizing inter-process contamination. It has become an important development direction for high-performance single-material packaging films.

[0003] However, biaxially oriented polyethylene (BOP) films have low surface energy and strong chemical inertness, resulting in insufficient film formation and adhesion stability of water-based high-barrier coatings. This leads to problems such as uneven coating spread, pinhole defects, and interfacial delamination. Furthermore, microcracks and defect propagation are more likely to be induced during subsequent transverse stretching, heat treatment, and winding, causing fluctuations in barrier performance. On the other hand, common hydrophilic barrier resin systems tend to absorb moisture and plasticize in humid and hot environments, leading to decreased coating density and increased diffusion channels, thus degrading barrier performance. To improve coating barrier and moisture resistance, existing technologies have attempted to introduce inorganic lamellar fillers or crosslinking components. However, filler dispersion and orientation control are difficult, easily leading to agglomeration and introducing defects. If the crosslinking system lacks compatibility with the water-based system, it can easily lead to decreased colloidal stability and poor storage stability of the coating solution, thereby affecting the continuity and yield of wide-width high-speed coating. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide an online-coated high-barrier biaxially oriented polyethylene film, its preparation method, and its application. This is achieved by activating the base film surface after longitudinal stretching and constructing a hybrid dispersion system formed by zirconium phytate nanoclusters and tannic acid / polyamine / epoxysilane. Simultaneously, tannic acid-modified montmorillonite / colloidal silica silane bridging barrier dispersion is introduced. This mixture is then formulated into an aqueous coating composition, online-coated, dried, cured, and laterally stretched into a film. This yields a polyethylene film with a dense coating, stable moisture resistance, stable barrier properties, and suitability for packaging, thus meeting the needs of actual production.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a high-barrier biaxially oriented polyethylene film by online coating, the method comprising:

[0007] S1, high-density polyethylene, ethylene-octene copolymer and antioxidant are mixed to obtain core layer mixture, high-density polyethylene, ethylene-octene copolymer and antioxidant are mixed to obtain coating side surface layer mixture, linear low-density polyethylene, ethylene-octene copolymer and low-density polyethylene and antioxidant are mixed to obtain heat-sealing layer mixture, three layers are co-extruded and cast to obtain thick sheet and longitudinally stretched to obtain uniaxial stretched sheet, the uniaxial stretched sheet is subjected to corona treatment to obtain uniaxial stretched polyethylene base film;

[0008] S2, Zirconium acetate solution and phytic acid solution are mixed to obtain phytic acid zirconium nanocluster dispersion, tannic acid and polyallylamine hydrochloride are added to the phytic acid zirconium nanocluster dispersion to obtain tannic acid / polyamine coated phytic acid zirconium nanocluster dispersion, 3-glycidyl etheroxypropyltrimethoxysilane is added to ethanol aqueous solution for pre-hydrolysis and then added to the tannic acid / polyamine coated phytic acid zirconium nanocluster dispersion to obtain epoxy silane hybrid dispersion;

[0009] S3, sodium-based montmorillonite dispersion, tannic acid, and colloidal silica are mixed to obtain tannic acid-modified montmorillonite / colloidal silica mixed dispersion. 3-glycidyl etheroxypropyltrimethoxysilane is pre-hydrolyzed in an aqueous ethanol solution and then added to the tannic acid-modified montmorillonite / colloidal silica mixed dispersion to react and obtain a barrier dispersion. Polyvinyl alcohol solution, polyvinylpyrrolidone aqueous solution, barrier dispersion, epoxy silane hybrid dispersion, glycerol, and sorbitol are mixed to obtain an aqueous coating composition.

[0010] S4, the aqueous coating composition is coated onto the corona-treated surface of the uniaxially stretched polyethylene film, and then dried, cured and stretched laterally to obtain an online coated high-barrier biaxially stretched polyethylene film.

[0011] The preparation method specifically includes:

[0012] S1, high-density polyethylene, ethylene-octene copolymer and antioxidant are added to a mixer and mixed evenly to obtain a core layer mixture. High-density polyethylene, ethylene-octene copolymer and antioxidant are added to a mixer and mixed evenly to obtain a coating side surface layer mixture. Linear low-density polyethylene, ethylene-octene copolymer, low-density polyethylene and antioxidant are added to a mixer and mixed evenly to obtain a heat-sealing layer mixture. The core layer mixture, the coating side surface layer mixture and the heat-sealing layer mixture are respectively added to a three-layer co-extrusion casting equipment for three-layer co-extrusion casting to obtain a thick sheet. The thick sheet is longitudinally stretched to obtain a uniaxially stretched sheet. The coating side surface of the uniaxially stretched sheet is corona treated to obtain a uniaxially stretched polyethylene base film.

[0013] S2, zirconium acetate solution is added dropwise to phytic acid solution, and 1M hydrochloric acid solution is added dropwise to adjust the pH to 2.8-4.2 to obtain zirconium phytate nanocluster dispersion. Tannic acid and polyallylamine hydrochloride are added to the zirconium phytate nanocluster dispersion, and 25wt.% ammonia water is added dropwise to adjust the pH to 7.5-8.5 to obtain tannic acid / polyamine-coated zirconium phytate nanocluster dispersion. 3-glycidyl etheroxypropyltrimethoxysilane is added to an ethanol aqueous solution, the pH is adjusted to 4.0-5.0, pre-hydrolyzed for 20-40 min, and then added to the tannic acid / polyamine-coated zirconium phytate nanocluster dispersion. The reaction is continued at 30-45℃ for 1-3 h to obtain epoxysilane hybrid dispersion.

[0014] S3, sodium-based colloidal silica dispersion, tannic acid, and colloidal silica are mixed and stirred to obtain tannic acid-modified montmorillonite / colloidal silica mixed dispersion. 3-glycidyl etheroxypropyltrimethoxysilane is added to an ethanol aqueous solution, and glacial acetic acid is added dropwise to adjust the pH to 4.0-5.0. After pre-hydrolysis for 20-40 min, it is added to the tannic acid-modified montmorillonite / colloidal silica mixed dispersion. The reaction is carried out at 35-50℃ for 1-3 h, and the mixture is filtered to obtain a barrier dispersion. Polyvinyl alcohol solution, polyvinylpyrrolidone aqueous solution, barrier dispersion, epoxy silane hybrid dispersion, glycerol, and sorbitol are mixed, and the pH is adjusted to 7.2-8.2 with 25 wt.% ammonia water. The mixture is filtered to obtain an aqueous coating composition.

[0015] S4, the aqueous coating composition is coated onto the corona-treated surface of the uniaxially stretched polyethylene film, and then dried, cured and stretched laterally to obtain an online coated high-barrier biaxially stretched polyethylene film.

[0016] Phytic acid exists as a polyphosphate anion under acidic conditions. Zirconium acetate provides a coordinating and exchangeable zirconium center, which coordinates with the phosphate oxygen atom of phytic acid through polydentate coordination, forming an inorganic-organic nanocluster linked by zirconium-phosphate coordination bonds. The surface of this nanocluster retains unsaturated zirconium coordination sites and incompletely coordinated phosphate groups, which can undergo coordination exchange with water molecules and acetate ions in the solution, as well as coordination, ion association, and hydrogen bonding with subsequently introduced polyphenols and polyamines. Tannic acid contains polyphenolic hydroxyl groups, which are partially deprotonated under neutral to slightly alkaline conditions, enabling coordination with the zirconium center as an ortho-polyphenol structure. Simultaneously, it forms an adsorption layer with the residual phosphate ions of phytic acid through hydrogen bonding and electrostatic interactions. Polyallylamine hydrochloride, under neutral to slightly alkaline conditions, exhibits cationic segments that can interact with phosphate groups on the surface of phytic acid nanoclusters via ion-pairing. It also forms a composite coating layer with tannic acid through hydrogen bonding and ion association, giving the nanoclusters an outer layer with polar groups miscible with aqueous polymers and reactive amine sites. Triglycidoxypropyltrimethoxysilane undergoes alkoxy-hydroxyl hydrolysis under weakly acidic conditions to generate silanols. These silanols then condense to form siloxane bonds. Simultaneously, silanols can form hydrogen bonds and condensation adsorption with silanols on the surface of colloidal silica, hydroxyl groups at the edge of montmorillonite, and oxygen-containing groups in the tannic acid / phytic acid system. Its epoxy groups can undergo ring-opening with amine groups in a neutral to slightly alkaline environment to generate β-hydroxyamine structures. These silane segments are covalently grafted onto the polyallylamine coating layer, forming a hybrid particle interface layer that combines a siloxane condensation network and an amine ring-opening grafting network. This restricts the migration of nanoclusters in aqueous systems and immobilizes them in the subsequent film-forming network.

[0017] Sodium-based montmorillonite undergoes interlayer hydration and ion exchange after shear dispersion in an aqueous phase. The interlayer charge is compensated by exchangeable cations, and the sheets peel off under shear conditions to form a high aspect ratio nanosheet dispersion. Tannic acid is adsorbed via hydrogen bonds to the silica-oxygen faces and edge hydroxyl groups on the montmorillonite sheet surface through polyphenolic hydroxyl groups, and can also form coordination associations with exchangeable cations on the sheet surface, thereby altering the solvation state and interfacial energy of the sheet surface, allowing the sheets to remain dispersed in the aqueous system. Colloidal silica, with silanol groups on its surface, can form hydrogen-bonded complexes with tannic acid and participate in the formation of Si-O-Si bridging structures as condensation nuclei during silane hydrolysis and polycondensation. Silica particles provide interstitial filling and support between the montmorillonite sheets, partially fixing the sheet spacing and stacking pattern during drying. After hydrolysis of silane, it is added to the mixed dispersion system. The silanol and silica silanol undergo condensation, and the silanol undergoes condensation or strong adsorption with the edge hydroxyl groups of montmorillonite. It also undergoes hydrogen bonding and condensation coupling with the tannic acid adsorption layer to form an inorganic-organic bridging network that connects the nanosheets, silica and organic adsorption layer. The bridging network continues to condense during the water removal process, reducing the tendency of the inorganic phase to redisperse and reaggregate in the coating.

[0018] After dissolution, polyvinyl alcohol exists as linear segments containing a large number of hydroxyl groups. Polyvinylpyrrolidone segments contain lactam carbonyl groups, which can form hydrogen-bonded complexes with the hydroxyl groups of polyvinyl alcohol, altering the hydrogen bond rearrangement and crystallization process between polyvinyl alcohol segments, resulting in an interpenetrating network dominated by hydrogen bonds during film formation. When the epoxysilane hybrid dispersion enters the polyvinyl alcohol / polyvinylpyrrolidone system, the phosphate and hydroxyl groups on the outer layer of the zirconium phytate nanoclusters can form hydrogen bonds and ion associations with polyvinyl alcohol. The unsaturated coordination sites at the zirconium center can undergo coordination adsorption with the hydroxyl groups of polyvinyl alcohol, and the amino groups of the polyallylamine segments can undergo ring-opening reactions with the epoxy groups and form hydrogen bonds with polyvinyl alcohol. Thus, the nanoclusters are embedded in the polymer network as local crosslinking and confined nodes. After the addition of the barrier dispersion, the montmorillonite nanosheets tend to align along the coating direction during solution shearing and coating shearing. During drying, they further align parallel to the film surface under the shrinkage effect of the polyvinyl alcohol network. The silica interstitial phase and silane bridging network form fixing points between and on the surface of the sheets, maintaining the sheet orientation after dehydration and curing. This orientation structure elongates the diffusion path of gas and water vapor in the normal direction of the film surface. The silica and siloxane condensation network reduces the free volume between the sheets and decreases the connectivity of the interfacial permeable channels.

[0019] Corona treatment oxidizes the surface of uniaxially stretched polyethylene, introducing hydroxyl, carbonyl, carboxyl, and peroxide structures, increasing surface energy and forming an interfacial layer that can interact polarly with the hydrophilic coating system. During the spreading of the aqueous coating composition, polyvinyl alcohol hydroxyl groups form hydrogen bonds and dipole interactions with oxygen-containing functional groups on the surface, while polyvinylpyrrolidone carbonyl groups form dipole interactions with polar groups on the surface. The phosphate groups on the outer layer of zirconium phytate nanoclusters and the tannic acid polyphenol layer enhance interfacial adsorption through hydrogen bonds and charge interactions. Polyallylamine segments can ionically associate with surface carboxyl groups / carboxylates and form hydrogen bonds with oxygen-containing groups on the surface, resulting in a polar-rich adhesion layer at the interface. During the drying and curing process, moisture is gradually removed, and polyvinyl alcohol segments undergo hydrogen bond rearrangement to form local crystalline regions. Polyvinylpyrrolidone and polyols participate in the formation of an amorphous hydrogen bond network. Silane continues to condense to form a Si–O–Si network and couples with the edge sites of silica and montmorillonite. The ring-opening reaction of epoxy and amine groups takes place under neutral to slightly alkaline conditions, fixing part of the inorganic-organic hybrid phase in the polymer network through covalent bonds. Zirconium phytate coordination nodes restrict the mobility of polymer segments under hydration conditions through coordination adsorption and ion association, reducing network relaxation and free volume growth caused by moisture absorption. During transverse stretching, the coating extends in-plane along with the base film in a partially cured state. Oriented montmorillonite nanosheets and silane bridge the inorganic network to bear stress transmission and inhibit local deformation concentration. The phytate-zirconium hybrid nodes and hydrogen bond network undergo reversible dissociation and recombination during stretching, maintaining the continuity of the coating and reducing the formation of penetrating microcracks. During the heat setting stage, the orientation structure of the polyethylene film is fixed, the moisture content in the coating is further reduced, the silane condensation and hydrogen bond network tend to stabilize, and a dense barrier structure is formed, consisting of a nanosheet orientation framework, a silica interstitial phase, a siloxane bridging network, and zirconium phytate.

[0020] As a preferred technical solution of the present invention, in S1, the mass ratio of high-density polyethylene, ethylene-octene copolymer and antioxidant in the core layer mixture is (82-88):(8-14):(0.2-1), for example, it can be (82, 82.6, 83.2, 83.8, 84.4, 85, 85.6, 86.2, 86.8, 87.4 or 88):(8, 8.6, 9.2, 9.8, 10.4, 11, 11.6, 12.2, 12.8, 13.4 or 14):(0.2, 0.28, 0.36, 0.44, 0.52, 0.6, 0.68, 0.76, 0.84, 0.92 or 1.0), but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0021] In some optional embodiments, the high-density polyethylene has a melt mass flow rate of 4.0-8.0 g / 10 min and a density of 0.942-0.948 g / cm³. 3 .

[0022] In some optional embodiments, the ethylene-octene copolymer has a melt flow rate of 5-6 g / 10 min and a density of 0.868-0.875 g / cm³. 3 .

[0023] In some optional embodiments, the mass ratio of high-density polyethylene, ethylene-octene copolymer and antioxidant in the coated side surface mixture is (92-97):(2-6):(0.2-1), for example, it can be (92, 92.5, 93, 93.5, 94, 94.5, 95, 95.5, 96, 96.5 or 97):(2, 2.4, 2.8, 3.2, 3.6, 4, 4.4, 4.8, 5.2, 5.6 or 6):(0.2, 0.28, 0.36, 0.44, 0.52, 0.6, 0.68, 0.76, 0.84, 0.92 or 1.0), but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0024] In some optional embodiments, the mass ratio of linear low-density polyethylene, ethylene-octene copolymer, low-density polyethylene, and antioxidant in the heat-sealing compound is (68-78):(15-25):(4-10):(0.2-1), for example, (68, 69, 70, 71, 72, 73, 74, 75, 76, 77, or 78):(15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25):(4, 4.6, 5.2, 5.8, 6.4, 7, 7.6, 8.2, 8.8, 9.4, or 10):(0.2, 0.28, 0.36, 0.44, 0.52, 0.6, 0.68, 0.76, 0.84, 0.92, or 1.0), but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0025] In some optional embodiments, the linear low-density polyethylene has a melt mass flow rate of 1.7-2.3 g / 10 min and a density of 0.918-0.929 g / cm³. 3 .

[0026] In some optional embodiments, the low-density polyethylene has a melt mass flow rate of 0.25-0.35 g / min and a density of 0.919-0.922 g / cm³. 3 .

[0027] In some optional embodiments, the antioxidant is one or more of antioxidant 1010, antioxidant 1076, and antioxidant 1330.

[0028] In some optional embodiments, the barrel temperature of the three-layer co-extrusion casting equipment is 185-235°C and the die temperature is 220-245°C. For example, the barrel temperature can be (185, 190, 195, 200, 205, 210, 215, 220, 225, 230 or 235)°C and the die temperature can be (220, 222.5, 225, 227.5, 230, 232.5, 235, 237.5, 240, 242.5 or 245)°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] In some optional embodiments, the total thickness of the sheet is 900-1600 μm, and the thickness ratio of the core layer, the coated side surface layer and the heat-sealing layer formed in the sheet is (76-88):(6-12):(6-12). For example, the total thickness could be (900, 970, 1040, 1110, 1180, 1250, 1320, 1390, 1460, 1530 or 1600) μm, and the thickness ratio of the core layer, coated side surface layer and heat-sealing layer formed in the thick sheet could be (76, 77.2, 78.4, 79.6, 80.8, 82, 83.2, 84.4, 85.6, 86.8 or 88): (6, 6.6, 7.2, 7.8, 8.4, 9, 9.6, 10.2, 10.8, 11.4 or 12): (6, 6.6, 7.2, 7.8, 8.4, 9, 9.6, 10.2, 10.8, 11.4 or 12), but it is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0030] In some optional embodiments, the longitudinal stretching is performed at 105-123°C with a stretching ratio of 4.5-6.0 times. For example, it can be performed at (105, 106.8, 108.6, 110.4, 112.2, 114, 115.8, 117.6, 119.4, 121.2, or 123)°C with a stretching ratio of (4.5, 4.65, 4.8, 4.95, 5.1, 5.25, 5.4, 5.55, 5.7, 5.85, or 6.0) times, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0031] In some optional embodiments, the power density of the corona treatment is 10-20 W·min / m³. 2 For example, it could be 10 W·min / m 2 11 W·min / m 2 12W·min / m 2 13W·min / m 2 14 W·min / m2 15W·min / m 2 16 W·min / m 2 17W·min / / m 2 18W·min / m 2 19 W·min / m 2 Or 20 W·min / m 2 However, this does not apply to all values ​​listed; other unlisted values ​​within the same range also apply.

[0032] As a preferred embodiment of the present invention, in S2, the mass ratio of the zirconium acetate solution, phytic acid solution, tannic acid, polyallylamine hydrochloride, 3-glycidyl etheroxypropyltrimethoxysilane, and ethanol aqueous solution is (40-80):(80-120):(1-4):(0.5-2.5):(0.5-2):(15-35), for example, it can be (40, 44, 48, 52, 56, 60, 64, 68, 72, 76 or 80):(80, 84, 88, 92, 96, 100, 104, 108, 112, 116 or 120):(1). 0, 1.3, 1.6, 1.9, 2.2, 2.5, 2.8, 3.1, 3.4, 3.7 or 4.0: (0.5, 0.7, 0.9, 1.1, 1.3, 1.5, 1.7, 1.9, 2.1, 2.3 or 2.5): (0.5, 0.65, 0.8, 0.95, 1.1, 1.25, 1.4, 1.55, 1.7, 1.85 or 2.0): (15, 17, 19, 21, 23, 25, 27, 29, 31, 33 or 35), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0033] In some optional embodiments, the zirconium acetate solution has a mass fraction of 2-10 wt.%, for example, 2%, 2.8%, 3.6%, 4.4%, 5.2%, 6%, 6.8%, 7.6%, 8.4%, 9.2%, or 10%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0034] In some optional embodiments, the phytic acid solution has a mass fraction of 1-4 wt.%, for example, it may be 1.0 wt.%, 1.3 wt.%, 1.6 wt.%, 1.9 wt.%, 2.2 wt.%, 2.5 wt.%, 2.8 wt.%, 3.1 wt.%, 3.4 wt.%, 3.7 wt.%, or 4.0 wt.%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0035] In some optional embodiments, the mass ratio of anhydrous ethanol to deionized water in the aqueous ethanol solution is 3:1.

[0036] As a preferred embodiment of the present invention, in S3, the mass ratio of the sodium-based montmorillonite dispersion, tannic acid, colloidal silica, 3-glycidyl etheroxypropyltrimethoxysilane, and the ethanol aqueous solution is (120-180):(0.2-1):(10-20):(0.2-1):(10-30), for example, (120, 126, 132, 138, 144, 150, 156, 162, 168, 174, or 180):(0.2, 0.28, 0.36, 0.44, 0.52). 0.6, 0.68, 0.76, 0.84, 0.92 or 1.0: (10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20): (0.2, 0.28, 0.36, 0.44, 0.52, 0.6, 0.68, 0.76, 0.84, 0.92 or 1.0): (10, 12, 14, 16, 18, 20, 22, 24, 26, 28 or 30), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0037] In some optional embodiments, the mass fraction of the sodium-based montmorillonite dispersion is 1-4 wt.%, for example, it can be 1.0 wt.%, 1.3 wt.%, 1.6 wt.%, 1.9 wt.%, 2.2 wt.%, 2.5 wt.%, 2.8 wt.%, 3.1 wt.%, 3.4 wt.%, 3.7 wt.%, or 4.0 wt.%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0038] In some optional embodiments, the solid content of the colloidal silica is 25-30 wt.%, for example, it can be 25 wt.%, 25.5 wt.%, 26 wt.%, 26.5 wt.%, 27 wt.%, 27.5 wt.%, 28 wt.%, 28.5 wt.%, 29 wt.%, 29.5 wt.%, or 30 wt.%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0039] In some optional embodiments, the mass ratio of anhydrous ethanol to deionized water in the aqueous ethanol solution is 3:1.

[0040] In some optional embodiments, the mass ratio of the polyvinyl alcohol solution, polyvinylpyrrolidone aqueous solution, barrier dispersion, epoxy silane hybrid dispersion, glycerol, and sorbitol is (120-200):(22-68):(15-60):(2-6):(0.1-1):(0.1-1), for example, it can be (120, 128, 136, 144, 152, 160, 168, 176, 184, 192, or 200):(22, 26.6, 31.2, 35.8, 40.4, 45, 49.6, 54.2, 58.8, 63.4, or 68):(15, 19.5, 24, ...). 28.5, 33, 37.5, 42, 46.5, 51, 55.5 or 60: (2.0, 2.4, 2.8, 3.2, 3.6, 4.0, 4.4, 4.8, 5.2, 5.6 or 6.0): (0.1, 0.19, 0.28, 0.37, 0.46, 0.55, 0.64, 0.73, 0.82, 0.91 or 1.0): (0.1, 0.19, 0.28, 0.37, 0.46, 0.55, 0.64, 0.73, 0.82, 0.91 or 1.0), but not limited to the listed values, other unlisted values ​​within this range also apply.

[0041] In some alternative embodiments, the polyvinyl alcohol solution has a mass fraction of 6-15 wt.%, for example, 6%, 6.9%, 7.8%, 8.7%, 9.6%, 10.5%, 11.4%, 12.3%, 13.2%, 14.1% or 15%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0042] In some optional embodiments, the polyvinyl alcohol has a degree of polymerization of 1700-2400 and a degree of hydrolysis of 98-99 mol%, for example, a degree of polymerization of (1700, 1770, 1840, 1910, 1980, 2050, 2120, 2190, 2260, 2330 or 2400) and a degree of hydrolysis of (98, 98.1, 98.2, 98.3, 98.4, 98.5, 98.6, 98.7, 98.8, 98.9 or 99) mol%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0043] In some optional embodiments, the mass fraction of the polyvinylpyrrolidone aqueous solution is 3-28 wt.%, for example, it can be 3 wt.%, 5.5 wt.%, 8 wt.%, 10.5 wt.%, 13 wt.%, 15.5 wt.%, 18 wt.%, 20.5 wt.%, 23 wt.%, 25.5 wt.%, or 28 wt.%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0044] In a preferred embodiment of the present invention, in step S4, the coating parameters are: a coating width of not less than 2m, a coating line speed of not less than 50m / min, and a wet coating amount of 3-12g / m. 2 For example, it could be: controlling the coating width to be no less than 2m, the coating line speed to be no less than 50m / min, and the wet coating amount to be (3, 3.9, 4.8, 5.7, 6.6, 7.5, 8.4, 9.3, 10.2, 11.1, or 12) g / m 2 However, this does not apply to all values ​​listed; other unlisted values ​​within the same range also apply.

[0045] In some optional embodiments, the drying and curing process is as follows: holding at 60-75℃ for 30-60 seconds, holding at 85-100℃ for 60-120 seconds, and holding at 110-128℃ for 30-90 seconds. For example, it could be: holding at (60, 61.5, 63, 64.5, 66, 67.5, 69, 70.5, 72, 73.5, or 75)℃ for (30, 33, 36, 39, 42, 45, 48, 51, 54, 57, or 60) seconds, and holding at (85, 86.5, 88, 89.5, 91, 92.5, 94, 95.5, 97, 98.5, or 100)℃ for (60, 66, 72, 78, 84, 9...). 0, 96, 102, 108, 114 or 120) s, (110, 111.8, 113.6, 115.4, 117.2, 119, 120.8, 122.6, 124.4, 126.2 or 128) °C for heat preservation (30, 36, 42, 48, 54, 60, 66, 72, 78, 84 or 90) s, but not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0046] In some optional embodiments, the transverse stretching process is as follows: transverse stretching is performed at 118-133°C with a transverse stretching ratio of 6.0-8.0 times, followed by heat setting at 122-138°C for 2-10 seconds. For example, it could be: transverse stretching at (118, 119.5, 121, 122.5, 124, 125.5, 127, 128.5, 130, 131.5 or 133) °C, with a transverse stretching ratio of (6.0, 6.2, 6.4, 6.6, 6.8, 7.0, 7.2, 7.4, 7.6, 7.8 or 8.0) times, followed by heat setting at (122, 123.6, 125.2, 126.8, 128.4, 130, 131.6, 133.2, 134.8, 136.4 or 138) °C for (2, 2.8, 3.6, 4.4, 5.2, 6, 6.8, 7.6, 8.4, 9.2 or 10) s, but not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0047] In a second aspect, the present invention provides an online coated high-barrier biaxially oriented polyethylene film prepared by the preparation method described in the first aspect.

[0048] Thirdly, the present invention provides the application of the online coated high-barrier biaxially oriented polyethylene film described in the second aspect in the preparation of packaging that blocks oxygen and water vapor.

[0049] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention activates the surface of the polyethylene base film after longitudinal stretching and performs wide-width online coating, so that the aqueous coating composition can achieve continuous film formation on the base film surface and maintain compatibility with the subsequent transverse stretching process; the phytic acid zirconium nanoclusters form a stable hybrid dispersion phase after being coated with tannic acid and polyallylamine hydrochloride, and synergistically with the epoxy silane system, so that confined nodes and stable interface bonding structures are formed inside the coating, inhibiting network relaxation and defect channel generation under wet conditions; the tannic acid modified montmorillonite and colloidal silica are bridged with silane to construct a lamellar oriented framework and a dense interstitial structure, which prolongs the diffusion path of gas and water vapor and reduces the connectivity of permeation channels, thereby improving the stability of barrier performance. Furthermore, the high-barrier biaxially oriented polyethylene film provided by this invention can also be laminated online or offline with thermoplastic polyolefin (TPO) waterproof membranes. The polyethylene base film and TPO are both polyolefin materials, with good compatibility at the composite interface and no need for additional adhesives. The water-based barrier coating provides an airtight reinforcing layer for the membrane, further improving the durability of the waterproof system. Detailed Implementation

[0050] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The embodiments described herein are specific implementations of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limiting the implementation of the present invention or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0051] All chemical reagents used in the embodiments and comparative examples of this invention are commercially available products and have not undergone any further purification treatment. Unless otherwise stated, the same polymer used in a single embodiment is of the same specification.

[0052] Unless otherwise stated, the zirconium acetate solution, phytic acid solution, polyvinyl alcohol solution, and polyvinylpyrrolidone aqueous solution in the various embodiments of the present invention all use deionized water as solvent; the sodium montmorillonite dispersion and colloidal silica both use deionized water as dispersion medium, and no additional dispersant is added; the ethanol aqueous solution is obtained by mixing anhydrous ethanol and deionized water; the mass percentage concentration of each solution or dispersion refers to the percentage of the mass of the solute or dispersed phase to the total mass of the corresponding solution or dispersion.

[0053] Example 1

[0054] This embodiment provides an online coating method for high-barrier biaxially oriented polyethylene film and its preparation method. The preparation method specifically includes the following steps:

[0055] S1, high-density polyethylene, ethylene-octene copolymer, and antioxidant are added to a mixer and mixed evenly to obtain a core layer mixture. The mass ratio of high-density polyethylene, ethylene-octene copolymer, and antioxidant in the core layer mixture is 88:8:0.2. High-density polyethylene, ethylene-octene copolymer, and antioxidant are added to a mixer and mixed evenly to obtain a coating side surface layer mixture. The mass ratio of high-density polyethylene, ethylene-octene copolymer, and antioxidant in the coating side surface layer mixture is 92:6:0.2. Linear low-density polyethylene, ethylene-octene copolymer, low-density polyethylene, and antioxidant are added to a mixer and mixed evenly to obtain a heat-sealing layer mixture. The mass ratio of linear low-density polyethylene, ethylene-octene copolymer, low-density polyethylene, and antioxidant in the heat-sealing layer mixture is 92:6:0.2. The oxidant mass ratio is 68:25:4:1, and the antioxidant is antioxidant 1010. The core layer mixture, the coated side surface layer mixture, and the heat-sealing layer mixture are added to a three-layer co-extrusion casting equipment for three-layer co-extrusion casting to obtain a sheet with a total thickness of 900 μm. The thickness ratio of the core layer, the coated side surface layer, and the heat-sealing layer formed in the sheet is 88:6:6. The barrel temperature of the three-layer co-extrusion casting equipment is 185℃, and the die temperature is 220℃. The sheet is longitudinally stretched to obtain a uniaxially stretched sheet. The longitudinal stretching conditions are: longitudinal stretching at 105℃, and a longitudinal stretching ratio of 6.0 times. The coated side surface of the uniaxially stretched sheet is subjected to corona treatment with a power density of 10 W·min / m. 2 , thus obtaining a uniaxially stretched polyethylene-based film;

[0056] S2, a 10 wt.% zirconium acetate solution was added dropwise to a 1 wt.% phytic acid solution, and the pH was adjusted to 2.8 by adding 1M hydrochloric acid solution to obtain a zirconium phytate nanocluster dispersion. Tannic acid and polyallylamine hydrochloride were added to the zirconium phytate nanocluster dispersion, and the pH was adjusted to 8.5 by adding 25 wt.% ammonia water to obtain a tannic acid / polyamine-coated zirconium phytate nanocluster dispersion. 3-glycidyl etheroxypropyltrimethoxysilane was added to an ethanol-water solution, and the zirconium acetate... The mass ratio of the solution, phytic acid solution, tannic acid, polyallylamine hydrochloride, 3-glycidyl etheroxypropyltrimethoxysilane and ethanol aqueous solution is 40:120:1:2.5:0.5:35. The mass ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution is 3:1. The pH is adjusted to 4.0 and pre-hydrolyzed for 40 min. The solution is then added to the tannic acid / polyamine-coated phytic acid zirconium nanoclusters dispersion and reacted at 30 °C for 3 h to obtain an epoxysilane hybrid dispersion.

[0057] S3, 1 wt.% sodium-based montmorillonite dispersion, tannic acid, and 30 wt.% colloidal silica were mixed and stirred to obtain a tannic acid-modified montmorillonite / colloidal silica mixed dispersion. 3-glycidoxypropyltrimethoxysilane was added to an ethanol-water solution. The mass ratio of the sodium-based montmorillonite dispersion, tannic acid, colloidal silica, 3-glycidoxypropyltrimethoxysilane, and the ethanol-water solution was 120:1:10:1:10. Glacial acetic acid was added dropwise to adjust the pH to 4.0. After pre-hydrolyzing for 40 min, the tannic acid-modified montmorillonite / colloidal silica mixed dispersion was added. The mixture was reacted at 50°C for 1 hour in the liquid, and filtered to obtain a barrier dispersion. A 6 wt.% polyvinyl alcohol solution, a 28 wt.% polyvinylpyrrolidone aqueous solution, a barrier dispersion, an epoxy silane hybrid dispersion, glycerol, and sorbitol were mixed. The mass ratio of the polyvinyl alcohol solution, polyvinylpyrrolidone aqueous solution, barrier dispersion, epoxy silane hybrid dispersion, glycerol, and sorbitol was 120:68:15:6:0.1:1. The degree of polymerization of the polyvinyl alcohol was 1700, the degree of alcoholysis was 98 mol%, and the pH was adjusted to 7.2 with 25 wt.% ammonia. The mixture was then filtered to obtain an aqueous coating composition.

[0058] S4, the aqueous coating composition is coated onto the corona-treated surface of the uniaxially stretched polyethylene film. After coating, it is sequentially dried and cured, and then stretched laterally. The coating parameters are: coating width not less than 2m, coating line speed not less than 50m / min, and wet coating amount of 3g / m. 2 The drying and curing process involves holding the film at 60°C for 60 seconds, at 85°C for 120 seconds, and at 110°C for 90 seconds. The transverse stretching process involves stretching the film at 118°C with a stretching ratio of 8.0 times, followed by heat setting at 122°C for 10 seconds to obtain an online coated high-barrier biaxially oriented polyethylene film.

[0059] Example 2

[0060] This embodiment provides an online coating method for high-barrier biaxially oriented polyethylene film and its preparation method. The preparation method specifically includes the following steps:

[0061] S1, high-density polyethylene, ethylene-octene copolymer, and antioxidant are added to a mixer and mixed evenly to obtain a core layer mixture. The mass ratio of high-density polyethylene, ethylene-octene copolymer, and antioxidant in the core layer mixture is 82:14:1. High-density polyethylene, ethylene-octene copolymer, and antioxidant are added to a mixer and mixed evenly to obtain a coating side surface layer mixture. The mass ratio of high-density polyethylene, ethylene-octene copolymer, and antioxidant in the coating side surface layer mixture is 97:2:1. Linear low-density polyethylene, ethylene-octene copolymer, low-density polyethylene, and antioxidant are added to a mixer and mixed evenly to obtain a heat-sealing layer mixture. The mass ratio of linear low-density polyethylene, ethylene-octene copolymer, low-density polyethylene, and antioxidant in the heat-sealing layer mixture is 78:15. The antioxidants are antioxidant 1010 and antioxidant 1076 in a mass ratio of 1:1. The core layer mixture, the coated side surface layer mixture, and the heat-sealing layer mixture are added to a three-layer co-extrusion casting equipment for three-layer co-extrusion casting to obtain a sheet with a total thickness of 1600 μm. The thickness ratio of the core layer, coated side surface layer, and heat-sealing layer formed in the sheet is 76:12:12. The barrel temperature of the three-layer co-extrusion casting equipment is 235℃ and the die temperature is 245℃. The sheet is then longitudinally stretched to obtain a uniaxially stretched sheet. The longitudinal stretching conditions are: longitudinal stretching at 123℃, with a longitudinal stretching ratio of 4.5 times. The coated side surface of the uniaxially stretched sheet is subjected to corona treatment with a power density of 20 W·min / m². 2 , thus obtaining a uniaxially stretched polyethylene-based film;

[0062] S2, a 2 wt.% zirconium acetate solution was added dropwise to a 4 wt.% phytic acid solution, and the pH was adjusted to 4.2 by adding 1 M hydrochloric acid solution to obtain a zirconium phytate nanocluster dispersion. Tannic acid and polyallylamine hydrochloride were added to the zirconium phytate nanocluster dispersion, and the pH was adjusted to 7.5 by adding 25 wt.% ammonia water to obtain a tannic acid / polyamine-coated zirconium phytate nanocluster dispersion. 3-glycidyl etheroxypropyltrimethoxysilane was added to an ethanol aqueous solution, and the acetic acid... The mass ratio of zirconium solution, phytic acid solution, tannic acid, polyallylamine hydrochloride, 3-glycidyl etheroxypropyltrimethoxysilane and aqueous ethanol solution is 80:80:4:0.5:2:15, and the mass ratio of anhydrous ethanol to deionized water in the aqueous ethanol solution is 3:1. The pH is adjusted to 5.0 and pre-hydrolyzed for 20 min, and then added to the tannic acid / polyamine-coated phytic acid zirconium nanoclusters dispersion. The reaction is continued at 45 °C for 1 h to obtain an epoxysilane hybrid dispersion.

[0063] S3, 4 wt.% sodium-based montmorillonite dispersion, tannic acid, and 25 wt.% colloidal silica were mixed and stirred to obtain a tannic acid-modified montmorillonite / colloidal silica mixed dispersion. 3-glycidoxypropyltrimethoxysilane was added to an ethanol-water solution. The mass ratio of the sodium-based montmorillonite dispersion, tannic acid, colloidal silica, 3-glycidoxypropyltrimethoxysilane, and the ethanol-water solution was 180:0.2:20:0.2:30. Glacial acetic acid was added dropwise to adjust the pH to 5.0. After pre-hydrolyzing for 20 min, the tannic acid-modified montmorillonite / colloidal silica mixed dispersion was added. The dispersion was reacted at 35°C for 3 hours, and the mixture was filtered to obtain a barrier dispersion. A 15 wt.% polyvinyl alcohol solution, a 3 wt.% polyvinylpyrrolidone aqueous solution, a barrier dispersion, an epoxy silane hybrid dispersion, glycerol, and sorbitol were mixed. The mass ratio of the polyvinyl alcohol solution, polyvinylpyrrolidone aqueous solution, barrier dispersion, epoxy silane hybrid dispersion, glycerol, and sorbitol was 200:22:60:2:1:0.1. The degree of polymerization of the polyvinyl alcohol was 2400, the degree of alcoholysis was 99 mol%, and the pH was adjusted to 8.2 with 25 wt.% ammonia. The mixture was then filtered to obtain an aqueous coating composition.

[0064] S4, the aqueous coating composition is coated onto the corona-treated surface of the uniaxially stretched polyethylene film. After coating, it is sequentially dried and cured, and then stretched laterally. The coating parameters are: coating width not less than 2m, coating line speed not less than 50m / min, and wet coating amount of 12g / m. 2 The drying and curing process involves holding the film at 75°C for 30 seconds, at 100°C for 60 seconds, and at 128°C for 30 seconds. The transverse stretching process involves stretching the film at 133°C with a stretching ratio of 6.0 times, followed by heat setting at 138°C for 2 seconds to obtain an online coated high-barrier biaxially oriented polyethylene film.

[0065] Example 3

[0066] This embodiment provides an online coating method for high-barrier biaxially oriented polyethylene film and its preparation method. The preparation method specifically includes the following steps:

[0067] S1, high-density polyethylene, ethylene-octene copolymer, and antioxidant are added to a mixer and mixed evenly to obtain a core layer mixture. The mass ratio of high-density polyethylene, ethylene-octene copolymer, and antioxidant in the core layer mixture is 85:11:0.6. High-density polyethylene, ethylene-octene copolymer, and antioxidant are added to a mixer and mixed evenly to obtain a coating side surface layer mixture. The mass ratio of high-density polyethylene, ethylene-octene copolymer, and antioxidant in the coating side surface layer mixture is 95:4:0.6. Linear low-density polyethylene, ethylene-octene copolymer, low-density polyethylene, and antioxidant are added to a mixer and mixed evenly to obtain a heat-sealing layer mixture. The mass ratio of linear low-density polyethylene, ethylene-octene copolymer, low-density polyethylene, and antioxidant in the heat-sealing layer mixture is 95:4:0.6. The mass ratio of the antioxidant is 73:20:7:0.6, and the antioxidant is antioxidant 1330. The core layer mixture, the coated side surface layer mixture, and the heat-sealing layer mixture are added to a three-layer co-extrusion casting equipment for three-layer co-extrusion casting to obtain a sheet with a total thickness of 1200 μm. The thickness ratio of the core layer, the coated side surface layer, and the heat-sealing layer formed in the sheet is 82:9:9. The barrel temperature of the three-layer co-extrusion casting equipment is 210℃, and the die temperature is 230℃. The sheet is then longitudinally stretched to obtain a uniaxially stretched sheet. The longitudinal stretching conditions are: longitudinal stretching at 115℃, and a longitudinal stretching ratio of 5.2 times. The coated side surface of the uniaxially stretched sheet is subjected to corona treatment with a power density of 15 W·min / m. 2 , thus obtaining a uniaxially stretched polyethylene-based film;

[0068] S2, a 6 wt.% zirconium acetate solution was added dropwise to a 2.5 wt.% phytic acid solution, and the pH was adjusted to 3.5 by adding 1M hydrochloric acid solution to obtain a zirconium phytate nanocluster dispersion. Tannic acid and polyallylamine hydrochloride were added to the zirconium phytate nanocluster dispersion, and the pH was adjusted to 8.0 by adding 25 wt.% ammonia water to obtain a tannic acid / polyamine-coated zirconium phytate nanocluster dispersion. 3-glycidyl etheroxypropyltrimethoxysilane was added to an ethanol aqueous solution, and the zirconium acetate... The mass ratio of the solution, phytic acid solution, tannic acid, polyallylamine hydrochloride, 3-glycidyl etheroxypropyltrimethoxysilane and ethanol aqueous solution was 60:100:2.5:1.5:1.2:25. The mass ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution was 3:1. The pH was adjusted to 4.5 and pre-hydrolyzed for 30 min. The solution was then added to the tannic acid / polyamine-coated phytic acid zirconium nanoclusters dispersion and reacted at 38 °C for 2 h to obtain an epoxysilane hybrid dispersion.

[0069] S3, 2.5 wt.% sodium-based montmorillonite dispersion, tannic acid, and 28 wt.% colloidal silica were mixed and stirred to obtain a tannic acid-modified montmorillonite / colloidal silica mixed dispersion. 3-glycidoxypropyltrimethoxysilane was added to an ethanol-water solution. The mass ratio of the sodium-based montmorillonite dispersion, tannic acid, colloidal silica, 3-glycidoxypropyltrimethoxysilane, and the ethanol-water solution was 150:0.6:15:0.6:20. Glacial acetic acid was added dropwise to adjust the pH to 4.5. After pre-hydrolyzing for 30 min, the tannic acid-modified montmorillonite / colloidal silica mixed dispersion was added. The mixture was reacted at 42°C for 2 hours in the liquid, and filtered to obtain a barrier dispersion. A 10 wt.% polyvinyl alcohol solution, a 15 wt.% polyvinylpyrrolidone aqueous solution, a barrier dispersion, an epoxy silane hybrid dispersion, glycerol, and sorbitol were mixed. The mass ratio of the polyvinyl alcohol solution, polyvinylpyrrolidone aqueous solution, barrier dispersion, epoxy silane hybrid dispersion, glycerol, and sorbitol was 160:45:38:4:0.5:0.5. The degree of polymerization of the polyvinyl alcohol was 2000, the degree of alcoholysis was 98.5 mol%, and the pH was adjusted to 7.8 with 25 wt.% ammonia. The mixture was then filtered to obtain an aqueous coating composition.

[0070] S4, the aqueous coating composition is coated onto the corona-treated surface of the uniaxially stretched polyethylene film. After coating, it is sequentially dried and cured, and then stretched laterally. The coating parameters are: coating width not less than 2m, coating line speed not less than 50m / min, and wet coating amount of 8g / m. 2 The drying and curing process involves holding the film at 68°C for 45 seconds, at 92°C for 90 seconds, and at 120°C for 60 seconds. The transverse stretching process involves stretching the film at 125°C with a stretching ratio of 7.0 times, followed by heat setting at 130°C for 6 seconds to obtain an online coated high-barrier biaxially oriented polyethylene film.

[0071] Example 4

[0072] This embodiment provides an online coating method for high-barrier biaxially oriented polyethylene film and its preparation method. The preparation method specifically includes the following steps:

[0073] S1. High-density polyethylene, ethylene-octene copolymer, and antioxidant are added to a mixer and mixed evenly to obtain a core layer mixture. The mass ratio of high-density polyethylene, ethylene-octene copolymer, and antioxidant in the core layer mixture is 86:12:0.8. High-density polyethylene, ethylene-octene copolymer, and antioxidant are added to a mixer and mixed evenly to obtain a coating side surface layer mixture. The mass ratio of high-density polyethylene, ethylene-octene copolymer, and antioxidant in the coating side surface layer mixture is 95:3:0.8. Linear low-density polyethylene, ethylene-octene copolymer, low-density polyethylene, and antioxidant are added to a mixer and mixed evenly to obtain a heat-sealing layer mixture. The mass ratio of linear low-density polyethylene, ethylene-octene copolymer, low-density polyethylene, and antioxidant in the heat-sealing layer mixture is 95:3:0.8. The mass ratio of the agents is 75:18:7:0.8, and the antioxidant is antioxidant 1010. The core layer mixture, the coated side surface layer mixture, and the heat-sealing layer mixture are added to a three-layer co-extrusion casting equipment for three-layer co-extrusion casting to obtain a sheet with a total thickness of 1400 μm. The thickness ratio of the core layer, the coated side surface layer, and the heat-sealing layer formed in the sheet is 80:10:10. The barrel temperature of the three-layer co-extrusion casting equipment is 220℃, and the die temperature is 235℃. The sheet is then longitudinally stretched to obtain a uniaxially stretched sheet. The longitudinal stretching conditions are: longitudinal stretching at 118℃, and a longitudinal stretching ratio of 5.5 times. The coated side surface of the uniaxially stretched sheet is subjected to corona treatment with a power density of 18 W·min / m². 2 , thus obtaining a uniaxially stretched polyethylene-based film;

[0074] S2, 8 wt.% zirconium acetate solution was added dropwise to 3 wt.% phytic acid solution, and 1M hydrochloric acid solution was added dropwise to adjust the pH to 3.8, resulting in a zirconium phytate nanocluster dispersion. Tannic acid and polyallylamine hydrochloride were added to the zirconium phytate nanocluster dispersion, and 25 wt.% ammonia solution was added dropwise to adjust the pH to 8.2, resulting in a tannic acid / polyamine-coated zirconium phytate nanocluster dispersion. 3-glycidyl etheroxypropyltrimethoxysilane was added to an ethanol aqueous solution, and the zirconium acetate... The mass ratio of the solution, phytic acid solution, tannic acid, polyallylamine hydrochloride, 3-glycidyl etheroxypropyltrimethoxysilane and ethanol aqueous solution was 70:90:3:2:1.5:20. The mass ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution was 3:1. The pH was adjusted to 4.8 and pre-hydrolyzed for 25 min. The solution was then added to the tannic acid / polyamine-coated phytic acid zirconium nanoclusters dispersion and reacted at 40 °C for 2.5 h to obtain an epoxysilane hybrid dispersion.

[0075] S3, 3 wt.% sodium-based montmorillonite dispersion, tannic acid, and 26 wt.% colloidal silica were mixed and stirred to obtain a tannic acid-modified montmorillonite / colloidal silica mixed dispersion. 3-glycidoxypropyltrimethoxysilane was added to an ethanol-water solution. The mass ratio of the sodium-based montmorillonite dispersion, tannic acid, colloidal silica, 3-glycidoxypropyltrimethoxysilane, and the ethanol-water solution was 160:0.8:12:0.8:25. Glacial acetic acid was added dropwise to adjust the pH to 4.8. After pre-hydrolyzing for 25 min, the tannic acid-modified montmorillonite / colloidal silica mixed dispersion was added. The mixture was reacted in the liquid at 45°C for 2.5 h, and filtered to obtain a barrier dispersion. A 12 wt.% polyvinyl alcohol solution, a 25 wt.% polyvinylpyrrolidone aqueous solution, a barrier dispersion, an epoxy silane hybrid dispersion, glycerol, and sorbitol were mixed. The mass ratio of the polyvinyl alcohol solution, polyvinylpyrrolidone aqueous solution, barrier dispersion, epoxy silane hybrid dispersion, glycerol, and sorbitol was 180:50:40:5:0.8:0.8. The degree of polymerization of the polyvinyl alcohol was 2200, the degree of alcoholysis was 99 mol%, and the pH was adjusted to 8.0 with 25 wt.% ammonia. The mixture was then filtered to obtain an aqueous coating composition.

[0076] S4, the aqueous coating composition is coated onto the corona-treated surface of the uniaxially stretched polyethylene film. After coating, it is sequentially dried and cured, and then stretched laterally. The coating parameters are: coating width not less than 2m, coating line speed not less than 50m / min, and wet coating amount of 10g / m. 2 The drying and curing process involves holding the film at 70°C for 50 seconds, at 95°C for 100 seconds, and at 125°C for 60 seconds. The transverse stretching process involves stretching the film at 130°C with a stretching ratio of 7.5 times, followed by heat setting at 135°C for 8 seconds to obtain an online coated high-barrier biaxially oriented polyethylene film.

[0077] Comparative Example 1

[0078] This comparative example provides an online coating method for high-barrier biaxially oriented polyethylene film and its preparation method. The difference between this method and Example 1 is that S2 and S3 are not performed when preparing the aqueous coating composition, and the epoxy silane hybrid dispersion is not added. Instead, an equal amount of deionized water is used. Other process parameters and operating conditions are exactly the same as in Example 1.

[0079] Comparative Example 2

[0080] This comparative example provides an online coating method for high-barrier biaxially oriented polyethylene film and its preparation method. The difference between this method and Example 1 is that 3-glycidyl etheroxypropyltrimethoxysilane is not added in S2, and only a dispersion of tannic acid / polyallylamine hydrochloride-coated zirconium phytate nanoclusters is prepared. Other process parameters and operating conditions are exactly the same as in Example 1.

[0081] Comparative Example 3

[0082] This comparative example provides an online coating method for high-barrier biaxially oriented polyethylene film and its preparation method. The difference between this method and Example 1 is that 3-glycidyl etheroxypropyltrimethoxysilane is not added when preparing the barrier dispersion in S3. Instead, the barrier dispersion is obtained by directly filtering the sodium montmorillonite dispersion, tannic acid and colloidal silica after mixing and stirring. Other process parameters and operating conditions are exactly the same as in Example 1.

[0083] Performance testing:

[0084] The Oxygen Transmission Rate (OTR) test method was ASTM D3985; the testing instrument was a MOCONOX-TRAN® 2 / 22(H); the test gas was oxygen (concentration ≥99.5%); the test temperature was 23.0℃; and the test area was 50.00 cm². 2 The test mode was set to Auto, with a test interval of 15 minutes. The test gas humidity was 12.0%RH, and the carrier gas humidity was 0%RH.

[0085] The test method for water vapor transmission rate (WVTR) is GB / T 26253, and the unit is g / (m). 2 •24h).

[0086] The test results are shown in Table 1.

[0087] Table 1. Test results of high-barrier biaxially oriented polyethylene films from Examples 1-4 and Comparative Examples 1-3

[0088]

[0089] As shown in Table 1, compared with Example 1, the oxygen permeability and water vapor permeability of Comparative Example 1 increased; the oxygen permeability and water vapor permeability of Comparative Example 2 increased; and the oxygen permeability and water vapor permeability of Comparative Example 3 increased.

[0090] This is because, in Comparative Example 1, after removing the S2 hybrid dispersion, the coating lacks the coordination confinement nodes provided by the zirconium phytate nanoclusters. The binding between tannic acid / polyallylamine hydrochloride and polyvinyl alcohol and polyvinylpyrrolidone is weakened, making the chain segments more prone to loosening and forming continuous permeation channels under wet conditions, leading to an increase in both OTR and WVTR. In Comparative Example 2, without the introduction of epoxy silane into S2, the outer layer of the zirconium phytate nanoclusters lacks the effect of ring-opening grafting and silicon-oxygen network fixation. The interfacial bonding between the nanoclusters and the organic phase is weakened, resulting in decreased dispersion stability and confinement effect, making local rearrangement and defect propagation more likely under humid and hot conditions. After removing 3-glycidoxypropyltrimethoxysilane from Comparative Example 3, the barrier dispersion lacked the siloxane phase formed by the hydrolysis and condensation of silane and its interface regulation effect. The dispersion stability of montmorillonite sheets and colloidal silica in the aqueous coating composition decreased, and local agglomeration and interfacial voids were more likely to occur during drying and stretching. The inorganic interstitial structure and the continuity of the sheet barrier path in the coating were reduced, resulting in an increase in both OTR and WVTR.

[0091] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a high-barrier biaxially oriented polyethylene film by online coating, characterized in that, The preparation method includes: S1, high-density polyethylene, ethylene-octene copolymer and antioxidant are mixed to obtain core layer mixture, high-density polyethylene, ethylene-octene copolymer and antioxidant are mixed to obtain coating side surface layer mixture, linear low-density polyethylene, ethylene-octene copolymer and low-density polyethylene and antioxidant are mixed to obtain heat-sealing layer mixture, three layers are co-extruded and cast to obtain thick sheet and longitudinally stretched to obtain uniaxial stretched sheet, the uniaxial stretched sheet is subjected to corona treatment to obtain uniaxial stretched polyethylene base film; S2, Zirconium acetate solution and phytic acid solution are mixed to obtain phytic acid zirconium nanocluster dispersion, tannic acid and polyallylamine hydrochloride are added to the phytic acid zirconium nanocluster dispersion to obtain tannic acid / polyamine coated phytic acid zirconium nanocluster dispersion, 3-glycidyl etheroxypropyltrimethoxysilane is added to ethanol aqueous solution for pre-hydrolysis and then added to the tannic acid / polyamine coated phytic acid zirconium nanocluster dispersion to obtain epoxy silane hybrid dispersion; S3, sodium-based montmorillonite dispersion, tannic acid, and colloidal silica are mixed to obtain tannic acid-modified montmorillonite / colloidal silica mixed dispersion. 3-glycidyl etheroxypropyltrimethoxysilane is pre-hydrolyzed in an aqueous ethanol solution and then added to the tannic acid-modified montmorillonite / colloidal silica mixed dispersion to react and obtain a barrier dispersion. Polyvinyl alcohol solution, polyvinylpyrrolidone aqueous solution, barrier dispersion, epoxy silane hybrid dispersion, glycerol, and sorbitol are mixed to obtain an aqueous coating composition. S4, the aqueous coating composition is coated onto the corona-treated surface of the uniaxially stretched polyethylene film, and then dried, cured and stretched laterally to obtain an online coated high-barrier biaxially stretched polyethylene film.

2. The method for preparing a high-barrier biaxially oriented polyethylene film by online coating according to claim 1, characterized in that, In S1: In the core layer mixture, the mass ratio of high-density polyethylene, ethylene-octene copolymer and antioxidant is (82-88):(8-14):(0.2-1).

3. The method for preparing a high-barrier biaxially oriented polyethylene film by online coating according to claim 1, characterized in that, In S1: In the coating side surface mixture, the mass ratio of high-density polyethylene, ethylene-octene copolymer and antioxidant is (92-97):(2-6):(0.2-1).

4. The method for preparing a high-barrier biaxially oriented polyethylene film by online coating according to claim 1, characterized in that, In S1: In the heat-sealing layer mixture, the mass ratio of linear low-density polyethylene, ethylene-octene copolymer, low-density polyethylene and antioxidant is (68-78):(15-25):(4-10):(0.2-1).

5. The method for preparing a high-barrier biaxially oriented polyethylene film by online coating according to claim 1, characterized in that, In S1: The total thickness of the sheet is 900-1600μm, and the thickness ratio of the core layer, the coated side surface layer and the heat-sealing layer formed in the sheet is (76-88):(6-12):(6-12).

6. The method for preparing a high-barrier biaxially oriented polyethylene film by online coating according to claim 1, characterized in that, In S2: The mass ratio of zirconium acetate solution, phytic acid solution, tannic acid, polyallylamine hydrochloride, 3-glycidyl etheroxypropyltrimethoxysilane to ethanol aqueous solution is (40-80):(80-120):(1-4):(0.5-2.5):(0.5-2):(15-35).

7. The method for preparing a high-barrier biaxially oriented polyethylene film by online coating according to claim 1, characterized in that, In S3: The mass ratio of the sodium-based montmorillonite dispersion, tannic acid, colloidal silica, 3-glycidoxypropyltrimethoxysilane, and ethanol aqueous solution is (120-180):(0.2-1):(10-20):(0.2-1):(10-30).

8. The method for preparing a high-barrier biaxially oriented polyethylene film by online coating according to claim 1, characterized in that, In S3: The mass ratio of the polyvinyl alcohol solution, polyvinylpyrrolidone aqueous solution, barrier dispersion, epoxy silane hybrid dispersion, glycerol and sorbitol is (120-200):(22-68):(15-60):(2-6):(0.1-1):(0.1-1).

9. The method for preparing a high-barrier biaxially oriented polyethylene film by online coating according to claim 8, characterized in that, In S3: The degree of polymerization of the polyvinyl alcohol is 1700-2400, and the degree of alcoholysis is 98-99 mol.

10. The method for preparing a high-barrier biaxially oriented polyethylene film by online coating according to claim 1, characterized in that, In S4: The coating parameters are as follows: coating width not less than 2m, coating line speed not less than 50m / min, and wet coating amount of 3-12g / m. 2 .

11. The method for preparing a high-barrier biaxially oriented polyethylene film by online coating according to claim 1, characterized in that, In S4: The drying and curing process is as follows: heat preservation at 60-75℃ for 30-60s, heat preservation at 85-100℃ for 60-120s, and heat preservation at 110-128℃ for 30-90s.

12. An online coated high-barrier biaxially oriented polyethylene film, characterized in that, Obtained by the preparation method according to any one of claims 1-11.

13. The application of the online coated high-barrier biaxially oriented polyethylene film according to claim 12 in the preparation of packaging that blocks oxygen and water vapor.

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