Paper base-PVA film-paper base composite oxygen-blocking waterproof material and preparation method thereof

Abstract

The invention belongs to the technical field of environment-friendly easily-degradable packaging, and relates to a paper-based PVA high-barrier material, in particular to a paper-based PVA film-paper-based composite oxygen-barrier waterproof material and a preparation method thereof. The invention aims to design and prepare a material, and particularly relates to an environment-friendly oxygen-blocking waterproof material which is formed by compounding two layers of paper bases and a middle polyvinyl alcohol (PVA) water-soluble film through a special process. And an original low-temperature stepped pressing process is adopted, so that high-strength and durable combination of a heterogeneous interface is realized on the premise of not damaging the heat-sensitive PVA functional layer. The material has ultrahigh oxygen resistance, water vapor resistance and mechanical strength while keeping the biodegradable characteristic, and is suitable for the high-end packaging fields sensitive to oxygen and water vapor, such as food, medicines and precise electronic components.

Description

Technical Field

[0001] This invention belongs to the field of environmentally friendly and biodegradable packaging technology, and relates to a paper-based PVA high barrier material, specifically a paper-based PVA film-paper-based composite oxygen-barrier and waterproof material and its preparation method. Background Technology

[0002] With increasingly stringent global environmental regulations and rising consumer awareness of environmental protection, the market demand for packaging materials that combine high performance and biodegradability is becoming increasingly urgent. This is particularly true in high-end packaging sectors such as food, pharmaceuticals, and precision electronic components, where stringent requirements are placed on materials' oxygen barrier properties (OTR), moisture barrier properties (WVTR), and mechanical strength. However, existing technologies struggle to achieve an effective balance between environmental friendliness, high performance, and processing feasibility, primarily due to the following technical bottlenecks: 1. Traditional multilayer composite films, such as aluminum foil / polyethylene (AL / PE) and polyethylene terephthalate / aluminum foil / polyethylene (PET / AL / PE), possess excellent barrier properties (OTR can be below 0.05 cm⁻¹). 3 / (m 2 However, its core components, plastic and aluminum foil, are not biodegradable, and their extensive use leads to "white pollution."

[0003] 2. Although pure paper packaging is completely biodegradable, its porous and hydrophilic fiber structure results in extremely poor barrier properties, failing to meet high barrier requirements. While pure polyvinyl alcohol (PVA) film possesses excellent oxygen barrier properties, it has two inherent drawbacks: firstly, it easily swells or even dissolves in water, exhibiting poor water resistance; secondly, pure PVA film is flexible but lacks rigidity, with low mechanical strength (especially tensile strength), making it prone to breakage when used alone as a packaging material.

[0004] 3. However, the "paper-PVA" composite solution has systemic compatibility issues: (1) Weak interfacial bonding and easy delamination: Paper (hydrophilic, porous, cellulose) and PVA (polymer) have significant differences in chemical properties and physical structure, resulting in inherently weak bonding. Existing composite processes (such as those described in patents CN110698959A, etc.) mostly employ conventional coating or hot pressing methods, making it difficult for adhesives to fully penetrate and form a strong interface, or causing internal stress due to curing shrinkage. Under varying temperature and humidity conditions, due to the difference in their coefficients of thermal expansion, the interface is prone to shear stress, leading to delamination and peeling after long-term use, causing packaging failure.

[0005] (2) Although PVA has a high melting point (about 220°C), its glass transition temperature and softening point are low, and it is sensitive to humid and hot environments. If hot pressing is performed at a temperature close to or above its softening point (even if it is far below the melting point), it will cause the PVA film to soften, flow, thin, or even perforate, destroying its continuity and crystalline structure as a barrier layer, and causing a sharp decline in barrier performance.

[0006] (3) Wet coating composite (e.g., WO2019123456A1), which involves directly coating a PVA aqueous solution onto a paper substrate and then drying it, has defects. In the early stages of drying, before the PVA coating layer is fully cured, some of the polymer will undergo "pre-dissolution" due to contact with moisture in the paper substrate or ambient humidity, resulting in discontinuous film formation. After drying, a large number of micron-sized penetrating pinhole defects will form in the film layer. These pinholes become channels for the rapid passage of oxygen and water vapor, resulting in poor overall barrier properties of the composite material (measured OTR is often >5-10 cm). 3 / (m 2 (day), which cannot meet the high barrier requirements.

[0007] Therefore, developing an innovative material structure design and a matching refined preparation process to fundamentally solve the problems of interfacial bonding and performance protection in the paper-based PVA composite process has become a key technology that urgently needs to be broken through in this field. Summary of the Invention

[0008] The purpose of this invention is to design and prepare an environmentally friendly oxygen-barrier and waterproof material, specifically an environmentally friendly material composed of two layers of paper base and an intermediate polyvinyl alcohol (PVA) water-soluble film through a special process. This material maintains its biodegradable properties while possessing ultra-high oxygen barrier properties, water vapor resistance, and mechanical strength, making it suitable for high-end packaging applications sensitive to oxygen and water vapor, such as food, pharmaceuticals, and precision electronic components.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of this invention discloses a method for preparing a paper-based PVA high-barrier material, comprising the following steps: S1. Provides two layers of hydrophobic paper base; S2. Provide a modified polyvinyl alcohol (PVA) film, said modified PVA film being prepared by a casting and drying method using an aqueous PVA solution containing nano-montmorillonite (MMT) and boric acid crosslinking agent; S3. Apply a water-based polyurethane adhesive to the composite surface of the two hydrophobic paper bases and / or to both sides of the modified PVA film; S4. The two hydrophobic paper base layers are laminated with the modified PVA film using a stepped hot-pressing process to form a symmetrical three-layer composite structure of paper base-PVA film-paper base; the stepped hot-pressing process includes: First stage: Pre-compression bonding is carried out at a temperature of 40-50℃ and a pressure of 0.1-0.3 MPa; The second stage: final pressure bonding is carried out at a temperature of 60-70℃ and a pressure of 0.6-1.0 MPa.

[0010] The first stage (40-50℃ / 0.2 MPa) is called "Location and Activation".

[0011] Objective: To enable waterborne polyurethane adhesive to initially wet the paper and PVA surfaces under low energy input, initiating the initial stage of cross-linking and curing ("activation"), and to initially fix the three-layer material to prevent misalignment in subsequent stages.

[0012] Significance: It lays the foundation for high-strength bonding and avoids damage caused by relative slippage between the PVA film and the uncured adhesive due to sudden high temperature and pressure.

[0013] The second stage (60-70℃ / 0.8 MPa) is called "curing and strengthening".

[0014] Objective: To increase energy input while strictly ensuring the temperature remains below the PVA dissolution and significant softening threshold (e.g., 90°C). This temperature is the optimal crosslinking and curing temperature for waterborne polyurethane, allowing for complete reaction. Simultaneously, higher pressure (0.8 MPa) ensures tight contact between layers, eliminates interfacial bubbles, and promotes maximum physical entanglement and chemical bonding between the adhesive molecular chains and the substrate.

[0015] Significance: To maximize interfacial adhesive strength without damaging the PVA functional layer. This temperature window (60-70℃) is a balance point found through extensive experimentation: sufficient for the adhesive to work perfectly while absolutely protecting the PVA film.

[0016] The technical solution of this invention relates to low-temperature gradient pressing. The low temperature avoids PVA deformation and rapid curing of the adhesive; the gradient pressure allows the adhesive sufficient time to flow and penetrate into the pores of the paper fibers and the surface of the PVA film, and cures under mild conditions, thereby forming a strong and durable transition layer and preventing delamination.

[0017] Specifically, this is achieved by controlling its solid content (35%) and coating amount (2.0 g / m²). 2This process, combined with a two-stage temperature-pressure curve, achieves a perfect process from "wetting" to "cross-linking and curing" without dissolving the PVA film. This combination of adhesive application process parameters, tailored to a specific substrate (hydrophobic paper + modified PVA film) and a specific temperature window (<70℃), is not disclosed in existing technologies.

[0018] Preferably, in S1, the water contact angle of the hydrophobic paper base is ≥115°, and its surface is corona-treated, with a surface energy of 42-48 mN / m. Corona treatment of the paper base improves its surface energy and reactivity, creating more sites for adhesive anchoring.

[0019] Preferably, the corona treatment is performed using a corona treatment device with a power of 7 kW and a paper feed speed of 30 m / min.

[0020] Preferably, in S2, the content of nano-montmorillonite (MMT) in the modified PVA film is 1.0%-3.0% of the dry basis mass of the PVA, and the content of boric acid crosslinking agent is 0.1%-0.5%; the thickness of the modified PVA film is 10-20 μm.

[0021] Through systematic experimental data, it was found that when the MMT content is between 1.0% and 3.0%, it produces the best synergistic effect with the adhesive system and the lamination process. If the content is too low, the barrier properties will not be sufficiently improved; if the content is too high (such as 5.0%), the performance will be degraded due to agglomeration and may affect the composite interface.

[0022] Preferably, in S2, the degree of alcoholysis of the PVA is 99% and the degree of polymerization is 1700.

[0023] Preferably, in S2, the interlayer spacing of the nano-montmorillonite MMT is 1.2 nm and the particle size D50 is 50 nm.

[0024] Preferably, in step S3, the solid content of the waterborne polyurethane adhesive is 30%-40%, and the coating amount is 1.5-2.5 g / m². 2 .

[0025] Preferably, in S4, the hot pressing time for the first stage and the second stage is 30-120 seconds each independently.

[0026] The second aspect of this invention discloses a paper-based PVA high-barrier material, which is prepared by the above-described preparation method.

[0027] The third aspect of this invention discloses the application of the above-mentioned paper-based PVA high-barrier material in the packaging field.

[0028] Compared with the prior art, the beneficial effects of this invention are as follows: 1. This invention achieves a balance between environmental friendliness and ultra-high barrier performance. The resulting material, while remaining fully biodegradable (achieving a biodegradability of 94% after 180 days according to ISO 14855-1 standard), exhibits a significant improvement in barrier performance. Specifically, its oxygen permeability (OTR) is less than 0.5 cm. 3 / (m 2 •day), water vapor transmission rate (WVTR) less than 5 g / (m 2 (day). This performance level not only far exceeds that of existing commercially available bio-based membranes, but also provides a truly green and high-performance alternative for the high-end packaging sector.

[0029] 2. By employing an innovative "independent film formation followed by dry lamination" process, pinhole defects were resolved, ensuring the high performance of the barrier layer. The "wet coating and lamination" route, which easily leads to PVA pre-dissolution and discontinuous film formation, was abandoned. Instead, a process was creatively adopted where a dense, defect-free modified PVA film is pre-prepared on a cast steel strip before lamination. This process avoids the formation of micron-level pinholes, ensuring that the core PVA barrier layer has a complete and uniform microstructure.

[0030] 3. Employing a unique "low-temperature stepped pressing" process, a high-strength and durable bond at the heterogeneous interface is achieved without damaging the heat-sensitive PVA functional layer. Addressing the heat and shear sensitivity of PVA films, a two-stage composite process was designed: a pre-press at 40-50℃ / 0.2 MPa and a final press at 60-70℃ / 0.8 MPa. The entire process operates at temperatures far below the softening and melting temperature of PVA (>90℃), perfectly protecting the integrity of the PVA barrier layer. Simultaneously, the stepped heating and pressing strategy provides sufficient wetting, penetration, and cross-linking curing time for the waterborne polyurethane adhesive, enabling it to form a strong transition layer between the paper fibers and the PVA surface. The resulting interfacial bond is extremely strong; after accelerated aging tests, no delamination was observed between layers, and the peel strength retention rate reached 91.1%, solving the problem of easy delamination in existing paper-plastic composites caused by weak interfaces and stress concentration.

[0031] 4. The material exhibits excellent overall performance, possessing superior mechanical strength and durability. The tensile strength of the material described in this invention exceeds 60 MPa, surpassing most commercially available bio-based films and ordinary composite packaging materials, meeting the requirements of high-end packaging for stiffness, burst resistance, and impact resistance. Accelerated aging tests show that its core barrier performance (OTR) retention rate exceeds 83%, and its mechanical strength retention rate exceeds 91%, proving its stable performance under harsh environments, long service life, and high reliability, making it suitable for packaging food, pharmaceuticals, and precision devices requiring long-term storage.

[0032] 5. Through systematic experiments, this invention determined that the optimal addition range of nano-montmorillonite (MMT) in PVA films is 1.0%-3.0% (based on the dry weight of PVA). Within this range, MMT exhibits optimal synergy with the PVA matrix, adhesive system, and lamination process, resulting in improved barrier properties and mechanical strength. Excessive (e.g., 5.0%) or insufficient (e.g., 0.5%) concentrations both lead to performance degradation. Parameter optimization tied to specific structural processes results in a synergistic effect of "1+1+1>3".

[0033] 6. The preparation method described in this invention has clear steps, and the key process parameters (temperature, pressure, MMT content, etc.) are well-defined and controllable, exhibiting good repeatability and a high yield. The main raw materials (paper, PVA, MMT, and water-based adhesive) are all common industrial raw materials with wide availability. Compared to traditional aluminum-plastic composite materials, this invention reduces material costs, providing reliable performance while possessing significant cost competitiveness and feasibility for large-scale industrial production. Detailed Implementation

[0034] The technical solution of the present invention will be described in detail below with reference to embodiments, but this does not limit the present invention to the scope of the embodiments described. Process parameters not specified in the embodiments of this application can be performed according to conventional methods, and all raw materials used can be obtained through commercial channels.

[0035] Example 1 Hydrophobic paper base: 60 g / m² is selected. 2 Bleached kraft paper. During the papermaking process, 2 wt% (relative to oven-dry pulp) of alkyl ketene dimer (AKD) neutral sizing agent was added to give the paper surface strong hydrophobicity, with a measured water contact angle of 118°. The paper base was treated with a corona treatment device (7 kW power, paper feed speed 30 m / min) to increase its surface energy to 45 mN / m.

[0036] Preparation of modified PVA film: PVA resin with a degree of hydrolysis of 99% and a degree of polymerization of 1700 was mixed with 1.0% (by dry weight of PVA) nano-montmorillonite (MMT, interlayer spacing 1.2 nm, particle size D50 = 50 nm) and 0.2% boric acid crosslinking agent. Deionized water was added, and the mixture was stirred at 95℃ until completely dissolved to form a homogeneous PVA aqueous solution. The solution was cast onto a steel belt using a tape drying method and dried in a gradient temperature range of 80-110℃ to prepare a modified PVA film with a uniform thickness of 15 μm. The water solubility temperature of this film was 92℃.

[0037] Adhesive: Environmentally friendly water-based polyurethane adhesive with a solid content of 35% is selected.

[0038] Composite preparation: On the composite surface of two layers of hydrophobic paper substrates treated with corona (the side composited with the modified PVA film), 2.0 g / m 2 The waterborne polyurethane adhesive is evenly coated with the above-mentioned coating amount, and the hydrophobic paper base composite surface is initially bonded to both sides of the modified PVA film.

[0039] A hot press is used for stepped lamination. The first stage involves pre-pressing at 50℃ and 0.2 MPa for 60 seconds to initially activate the adhesive and fix each layer. The second stage immediately follows with final pressing at 65℃ and 0.8 MPa for 90 seconds to fully cross-link and cure the adhesive.

[0040] Performance testing: The oxygen transmission rate (OTR) was tested according to ASTM F1927 at 23°C and 0%RH, and the result was 0.38 cm⁻¹. 3 / (m 2 ·day).

[0041] Water vapor transmission rate (WVTR) was tested according to ASTM E96 standard at 38°C and 90% RH, and the result was 3.2 g / (m²). 2 ·day).

[0042] The tensile strength was tested according to relevant standards and the result was 62.5 MPa.

[0043] The biodegradability (after 180 days) was tested according to ISO 14855-1 standard, and the result was 94%.

[0044] Examples 2-6: Investigating the effect of MMT content on performance To verify the key role and optimal range of nano-montmorillonite (MMT) addition in the system of this invention, keeping the PVA type, boric acid content (0.2%), paper base, adhesive, and stepped lamination process (50℃ / 0.2 MPa→65℃ / 0.8 MPa) constant, only the amount of MMT added to the PVA film (0%, 0.5%, 2.0%, 3.0%, 5.0% based on PVA dry weight) was changed to prepare composite materials and perform performance tests. The results are shown in Table 1: Table 1: Effect of nano-montmorillonite content on the properties of composite materials

[0045] Results analysis: When the MMT content is between 1.0% and 3.0%, the composite material exhibits the best synergistic properties: both OTR and WVTR decrease to extremely low levels (OTR < 0.4, WVTR < 3.5), while the tensile strength reaches its peak. This confirms the feasibility and selectivity of the parameter range (MMT content between 1.0% and 3.0%).

[0046] When the MMT content is 0% (Example 2), the barrier performance is significantly degraded, with an OTR as high as 1.85, proving that MMT modification is indispensable for achieving the target performance of this invention (OTR<0.5).

[0047] When the MMT content is 5.0% (Example 6), both the barrier performance and mechanical strength decrease, indicating that excessive MMT causes defects due to agglomeration. This proves that the preferred range of 1.0%-3.0% in this invention is a non-obvious optimization range determined through a large number of experiments.

[0048] Comparative Example 1: Traditional High-Performance Non-Degradable Materials Sample: PET / aluminum foil / PE (AL / PE) composite film.

[0049] Performance test: OTR < 0.05 cm 3 / (m 2 •day), WVTR<0.5 g / (m 2 •day), tensile strength >80 MPa.

[0050] Comparative analysis: Traditional materials still have advantages in barrier properties and strength, but they are completely non-biodegradable. This invention, while maintaining complete biodegradability (94%, 180 days), improves barrier performance to a level close to that of traditional materials, resolving the core industry contradiction of the incompatibility between environmental protection and high performance.

[0051] Comparative Example 2: Commercially available bio-based membranes Sample: Commercially available NatureFlex™ NVI biodegradable film.

[0052] Performance testing: OTR is approximately 1.2 cm. 3 / (m 2 WVTR is approximately 12 g / (m²) (day). 2 (day), tensile strength approximately 50 MPa.

[0053] Comparative Example 3: Single-layer paper / PVA composite Preparation method: The same hydrophobic paper base as in Example 1 was used. An aqueous solution of the same PVA, MMT (1.0%), and boric acid (0.2%) was directly coated onto the surface of a paper base and dried at 80°C to form a film. Subsequently, a waterborne polyurethane adhesive (2.0 g / m³) was coated onto this PVA coating. 2 It is then pressed together with another layer of paper base at 65°C and 0.8 MPa for 90 seconds in a single press.

[0054] Performance testing: OTR is 5.8 cm 3 / (m 2 (day), in the WVTR test, the PVA layer rapidly dissolved and failed upon exposure to moisture, with a tensile strength of 45.2 MPa. The above results are shown in Table 2: Table 2: Comparison of overall performance with similar products on the market

[0055] While maintaining complete biodegradability, this invention achieves oxygen and moisture barrier properties approaching those of traditional non-degradable aluminum-plastic composites and far exceeding those of existing commercially available bio-based membranes. The symmetrical "paper-PVA-paper" structure (compared to single-layer paper / PVA) gives the material excellent water resistance and mechanical strength, solving the fundamental defects of PVA membranes such as easy solubility and susceptibility.

[0056] Example 7 Stability Test To verify the reliability of the material of the present invention under actual storage conditions, the sample of Example 4 (MMT content 2.0%) was placed in a constant temperature and humidity chamber at 40°C and 75% relative humidity (RH) for a 30-day accelerated aging test. The key performance before and after aging was tested, and the results are shown in Table 3.

[0057] Table 3: Performance Retention Rate After Accelerated Aging

[0058] Conclusion: After accelerated aging in harsh environments, the core barrier properties of the material of this invention remained stable, with only a slight decrease in mechanical strength and interlayer bonding force, and no delamination was observed. This strongly demonstrates that the interfacial bonding formed through corona treatment, water-based polyurethane adhesive, and low-temperature stepped pressing process is strong and durable, completely solving the technical problem of easy delamination of existing paper-plastic composite materials during long-term use, and fully meeting the requirements of high-end packaging for long-term material stability.

[0059] Example 8 Experimental Design of Stepped Composite Process Example 1 of the present invention (gradient temperature composite): adopts a two-stage process of 50℃ / 0.2 MPa pre-composite + 65℃ / 0.8 MPa final composite.

[0060] Comparative Example 4 (single low-temperature composite): only one-time pressing at 60℃ and 0.8 MPa.

[0061] Comparative Example 5 (one-time high-temperature bonding): only one-time pressing at 85℃ and 0.8 MPa.

[0062] To highlight the inventive advantages of the "step-by-step composite" process of this invention, two sets of comparative examples were designed for comparison with the embodiments of this invention under the same conditions. All samples used the same substrate (60 g / m²). 2 AKD hydrophobic paper) and the same modified PVA film (containing 1% nano montmorillonite, 15 μm thick).

[0063] The test results and analysis are shown in Table 4: Table 4: Comparison of the effects of different composite processes on material properties Key findings and mechanism analysis: 1. Comparative Example 4 (one low temperature test) proves that a temperature of 60℃ is insufficient to fully activate and cure the crosslinking reaction of waterborne polyurethane adhesive.

[0064] Result: This resulted in extremely low interfacial bond strength (only 2.1 N / 15 mm), with the adhesive layer in an "unripe" state. In subsequent immersion or damp heat tests, moisture easily penetrated through the weak interface, causing not only delamination but also damage to the PVA barrier layer, leading to a sharp deterioration in OTR. This proves that simply lowering the temperature cannot yield a usable product.

[0065] 2. The failure of Comparative Example 5 (one high-temperature test) demonstrates that the treatment was carried out at a temperature below the water-soluble temperature threshold (90℃) of the modified PVA film. While high-pressure pressing at this temperature facilitates adhesive curing (and the peel strength is acceptable), it leads to thermal damage to the PVA barrier layer.

[0066] result: (1) Microstructure damage: The movement of PVA molecular chain segments intensifies, and uncontrollable softening and deformation occur in some areas (wrinkles are observed). Its crystal morphology is destroyed, resulting in a decrease in intrinsic barrier properties (OTR deteriorates to 0.55, and the water solubility temperature decreases).

[0067] (2) Poor macroscopic reliability: Due to damage to the PVA layer and the internal stress caused by the difference in thermal expansion between the PVA layer and the paper base, the material's performance deteriorates significantly after aging, and the edges are prone to warping and delamination. This proves that even if the conventional "one-step" high-temperature composite approach is adopted, the core functional layer will be damaged, resulting in more harm than good.

[0068] 3. The mechanism of this invention (gradient temperature composite): Division of labor and collaboration: This invention creatively breaks down the composite process into two stages with clearly defined functions and strictly limited temperatures.

[0069] Phase 1 (50℃ / Low Pressure): The core task is "precise positioning and gentle activation". At a temperature that does not damage the PVA layer, the adhesive is initially wetted, spread, and begins to crosslink, initially fixing the three layers of materials and laying a slip-free and stress-free foundation for the strong bonding in Phase 2.

[0070] The second stage (65℃ / high pressure): The core task is to "enhance curing and achieve dense bonding". Within a precise window that is higher than the optimal curing temperature of the adhesive but far below the damage threshold of PVA, higher pressure is applied to promote the complete reaction of the adhesive and achieve maximum close contact between interfacial molecules.

[0071] Final result: This process perfectly resolves the contradiction between "strong adhesion" and "preservation of function." It achieves the highest peel strength (5.4 N / 15mm) while absolutely protecting the integrity and optimal performance of the PVA barrier layer (OTR as low as 0.38), thus giving the final product unparalleled comprehensive reliability and long-term stability.

[0072] This invention is not limited to the above-described embodiments. Any changes in shape or structure are within the scope of protection of this invention. The scope of protection of this invention is defined by the appended claims. Those skilled in the art can make various changes, modifications, substitutions, combinations, and simplifications to these embodiments without departing from the principles and essence of this invention. All such changes and simplifications should be considered equivalent substitutions and fall within the scope of protection of this invention.

Claims

1. A method for preparing a paper-based PVA high-barrier material, characterized in that, Includes the following steps: S1. Provides two layers of hydrophobic paper base; S2. Provide a modified polyvinyl alcohol (PVA) film, said modified PVA film being prepared by a casting and drying method using an aqueous PVA solution containing nano-montmorillonite (MMT) and boric acid crosslinking agent; S3. Apply a water-based polyurethane adhesive to the composite surface of the two hydrophobic paper bases and / or to both sides of the modified PVA film; S4. The two hydrophobic paper base layers are composited with the modified PVA film using a stepped hot-pressing process to form a symmetrical three-layer composite structure of paper base-PVA film-paper base; The stepped hot pressing process includes: First stage: Pre-compression bonding is carried out at a temperature of 40-50℃ and a pressure of 0.1-0.3 MPa; The second stage: final pressure bonding is carried out at a temperature of 60-70℃ and a pressure of 0.6-1.0 MPa.

2. The preparation method according to claim 1, characterized in that, In S1, the water contact angle of the hydrophobic paper base is ≥115°, its surface is corona treated, and its surface energy is 42-48 mN / m.

3. The preparation method according to claim 2, characterized in that, The corona treatment is carried out using a corona treatment device with a power of 7 kW and a paper feed speed of 30 m / min.

4. The preparation method according to claim 1, characterized in that, In S2, the content of nano-montmorillonite (MMT) in the modified PVA film is 1.0%-3.0% of the dry basis mass of the PVA, and the content of boric acid crosslinking agent is 0.1%-0.5%; the thickness of the modified PVA film is 10-20 μm.

5. The preparation method according to claim 1, characterized in that, In S2, the degree of alcoholysis of the PVA is 99%, and the degree of polymerization is 1700.

6. The preparation method according to claim 1, characterized in that, In S2, the interlayer spacing of the nano-montmorillonite (MMT) is 1.2 nm, and the particle size D50 is 50 nm.

7. The preparation method according to claim 1, characterized in that, In S3, the solid content of the waterborne polyurethane adhesive is 30%-40%, and the coating amount is 1.5-2.5 g / m². 2 .

8. The preparation method according to claim 1, characterized in that, In S4, the hot pressing time for the first and second stages is 30-120 seconds each independently.

9. A paper-based PVA high-barrier material, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.

10. The application of the paper-based PVA high-barrier material as described in claim 9 in the packaging field.

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