Recyclable paper packaging material and method for its production and use

Abstract

This invention belongs to the field of packaging materials technology, specifically relating to a recyclable paper packaging material, its preparation method, and its application. A method for preparing a recyclable paper packaging material includes the following steps: S1, pre-coating a pre-wetting layer on the surface of a substrate and drying it; S2, preparing the coating; S3, curing and printing the material dried in step S2 to obtain the recyclable paper packaging material; the coating material includes a dispersion, acrylic resin, and an antibacterial agent. This invention's method for preparing recyclable paper packaging material controls the formation process of the paper base and coating interface through specific step sequences, enabling a single paper base to simultaneously achieve recyclability, surface water permeability resistance, mechanical stability, and printability. This effectively solves the problem of existing single-paper packaging materials struggling to balance recyclability, heat-sealing layer continuity, surface water permeability resistance, mechanical stability, and high-precision printing compatibility.

Description

Technical Field

[0001] This invention belongs to the field of packaging materials technology, specifically relating to a recyclable paper packaging material, its preparation method, and its application. Background Technology

[0002] Currently, paper packaging has become an important part of the global packaging industry due to its advantages such as wide availability of raw materials, low cost, and recyclability. However, traditional flexible packaging materials are mostly paper-plastic composites, which, while meeting certain barrier performance requirements, make recycling and reuse difficult due to their complex multi-layered structure. With increasingly stringent environmental policies and rising consumer awareness of environmental protection, the market demand for biodegradable and recyclable environmentally friendly packaging materials is becoming increasingly urgent.

[0003] In terms of coating technology, traditional solvent-based coatings contain volatile organic compounds (VOCs), which pollute the environment and harm human health. While existing water-based coating technologies are more environmentally friendly, they generally suffer from slow film formation, insufficient barrier properties, and weather resistance, affecting the adhesion and stability of products and making it difficult to meet the demands of the high-end packaging market.

[0004] In addition, in terms of printing technology, the existing PS printing process still faces certain challenges in adaptability to single environmentally friendly paper substrates. For example, there are problems such as insufficient ink adhesion stability, limited dot reproduction accuracy under high-line printing conditions, reliance on experience for water-ink balance control, and insufficient registration accuracy and real-time quality monitoring in high-speed production. Therefore, it is difficult to simultaneously meet the comprehensive requirements of green packaging for recyclability, printing fineness, and production stability.

[0005] Therefore, existing technologies lack a preparation process that can simultaneously achieve continuous heat-sealing layer formation, improved surface water penetration resistance, and high-precision printing compatibility on a single repulpable paper substrate. In particular, existing disclosures are still insufficient regarding the synergistic relationship between paper fiber surface wetting, interface construction, and pre-printing surface condition control. Summary of the Invention

[0006] This invention aims to provide a recyclable paper packaging material, its preparation method, and its applications. The preparation method of this invention's recyclable paper packaging material controls the formation process of the paper base and coating interface through a specific operational sequence, enabling a single paper base to simultaneously achieve recyclability, surface water permeability resistance, mechanical stability, and printability. This effectively solves the problem of existing single-paper packaging materials struggling to balance recyclability, heat-sealing layer continuity, surface water permeability resistance, mechanical stability, and high-precision printing compatibility.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing recyclable paper packaging material, comprising the following steps: S1. Pre-coat the substrate surface to form a pre-wetted layer and dry it; S2. Coating preparation: Prepare coating material by applying the coating material in multiple layers to the surface of the pre-wetted layer after drying in step S1, and then drying. S3. The material dried in step S2 is aged and printed to obtain the recyclable paper packaging material. The coating material includes a dispersion, acrylic resin, and an antibacterial agent.

[0008] As one embodiment of the method for preparing recyclable paper packaging material according to the present invention, the substrate in step S1 includes at least one of sugarcane paper, white kraft paper, and yellow kraft paper.

[0009] As one embodiment of the preparation method of the recyclable paper packaging material of the present invention, the raw material selected for the pre-impregnation layer in step S1 includes acrylic resin.

[0010] In one embodiment of the method for preparing the recyclable paper packaging material of the present invention, the thickness of the pre-impregnated layer in step S1 is 2~5μm.

[0011] As one embodiment of the method for preparing recyclable paper packaging material according to the present invention, the drying temperature in step S1 is 40~60℃ and the time is 0.5~2min.

[0012] As one embodiment of the method for preparing the recyclable paper packaging material of the present invention, the dispersion includes a nano-titanium dioxide dispersion and a nano-silica dispersion.

[0013] As one embodiment of the method for preparing the recyclable paper packaging material of the present invention, the antibacterial agent includes at least one of silver ion antibacterial agent and zinc oxide antibacterial agent.

[0014] In one embodiment of the method for preparing the recyclable paper packaging material of the present invention, the amount of antibacterial agent added is 0.1 to 1.0 wt% of the mass of acrylic resin in the coating material.

[0015] In one embodiment of the preparation method of the recyclable paper packaging material of the present invention, the particle size of the nano-silica is 7~50nm. When the particle size of the nano-silica is too low, the specific surface area of ​​the particles is too large, which easily leads to agglomeration, affecting the dispersion stability and film uniformity; when the particle size is too high, the filling ability of the micropores of the coating is weakened, the densification effect decreases, and the surface roughness may increase, which is not conducive to the surface's dynamic water penetration resistance and printability.

[0016] As one embodiment of the preparation method of the recyclable paper packaging material of the present invention, the preparation method of the nano titanium dioxide dispersion includes the following steps: taking nano titanium dioxide particles and dispersing them in anhydrous ethanol to obtain nano titanium dioxide dispersion.

[0017] In one embodiment of the method for preparing the recyclable paper packaging material of the present invention, the amount of anhydrous ethanol added is 5 to 20 times the mass of the nano-titanium dioxide particles.

[0018] In one embodiment of the preparation method of the recyclable paper packaging material of the present invention, the mass of the nano-titanium dioxide particles is 0.1~5wt% of the mass of the acrylic resin contained in the coating material. When the amount of nano-titanium dioxide added is too low, it is difficult to form an effective interface enhancement and surface regulation effect; when the amount added is too high, it is easy to cause unstable dispersion of the system, local aggregation and decreased film continuity, thereby affecting the overall performance of the material.

[0019] As one embodiment of the preparation method of the recyclable paper packaging material of the present invention, the preparation method of the nano silica dispersion includes the following steps: taking nano silica powder, adding it to anhydrous ethanol, and dispersing it by an ultrasonic disperser to obtain a uniform nano silica dispersion.

[0020] In one embodiment of the method for preparing the recyclable paper packaging material of the present invention, the amount of anhydrous ethanol added is 5 to 20 times the mass of the nano-silica particles.

[0021] In one embodiment of the preparation method of the recyclable paper packaging material of the present invention, the mass of the nano-silica is 0.5~5.0 wt% of the mass of the acrylic resin in the coating material. When the amount of nano-silica added is too low, it is difficult to form effective micropore filling and interface enhancement, resulting in limited improvement in surface water resistance and mechanical properties; when the amount added is too high, it is easy to cause increased system viscosity, unstable dispersion and local aggregation, thereby affecting the continuity and overall performance of the film layer.

[0022] As one embodiment of the preparation method of the recyclable paper packaging material of the present invention, in the preparation method of nano-silica, the dispersion time is 10~50min.

[0023] As one embodiment of the preparation method of the recyclable paper packaging material of the present invention, the preparation method of the coating material includes the following steps: adding nano titanium dioxide dispersion to acrylic resin to form a basic dispersion system, then adding an antibacterial agent, and finally adding nano silica dispersion. After mixing and standing to degas, the coating material is obtained.

[0024] In one embodiment of the preparation method of the recyclable paper packaging material of the present invention, the time for static degassing is 10-30 minutes.

[0025] In the preparation method of the present invention, by controlling the raw materials to prepare the coating material in a specific order of addition, it is beneficial to maintain the dispersion stability of the system, reduce the local aggregation and interfacial competition caused by the simultaneous addition of inorganic particles, and significantly improve the stability and other properties of the prepared coating material, so that the final paper packaging material can have better performance.

[0026] As one embodiment of the method for preparing recyclable paper packaging material according to the present invention, the preparation of the coating in step S2 includes the following steps: preparing coating material, applying a first coating to the surface of the pre-wetted layer after drying in step S1, pre-drying, applying a second coating, shaping and drying, and completing the preparation of the coating.

[0027] The preparation method of this invention employs a two-coating process during the coating process. The first coating forms a transition bonding layer on the substrate, while the second coating forms the surface functional layer. Simultaneously, a staged drying method is used. Pre-drying after the first coating effectively promotes surface wetting and coating leveling of the paper base, while shaping and drying after the second coating facilitates the formation of a continuous heat-sealing layer, further improving the surface water resistance and stability properties of the resulting paper packaging material.

[0028] As one embodiment of the preparation method of the recyclable paper packaging material of the present invention, the pre-drying temperature is 50-60℃ and the time is 1-3 min.

[0029] As one embodiment of the preparation method of the recyclable paper packaging material of the present invention, the shaping and drying temperature is 80~100℃ and the time is 1~5min.

[0030] In one embodiment of the method for preparing the recyclable paper packaging material of the present invention, the thickness of the wet film of the first coating is 2~8μm.

[0031] In one embodiment of the method for preparing the recyclable paper packaging material of the present invention, the thickness of the wet film in the second coating is 6~10μm.

[0032] In one embodiment of the method for preparing the recyclable paper packaging material of the present invention, the total wet film thickness of the coating is 12~18μm.

[0033] As one embodiment of the preparation method of the recyclable paper packaging material of the present invention, the curing is: letting the dried material stand at 20~30℃ for 2~12 hours.

[0034] As one embodiment of the method for preparing recyclable paper packaging material according to the present invention, the printing in step S3 adopts a printing device with high-precision ink path control, automatic registration and online quality monitoring functions.

[0035] In a preferred embodiment of the method for preparing the recyclable paper packaging material of the present invention, the printing in step S3 is performed using an intermittent PS printing device.

[0036] In the preparation method of this invention, the combined changes in process parameters such as the particle size and amount of nano-silica, the amount of nano-titanium dioxide added, and the film thickness all affect the surface water resistance and burst resistance of the material. This invention, by selecting appropriate parameters, establishes a balance between the interfaces of the components in the raw material system, thereby ensuring that the final paper packaging material achieves excellent results in terms of water resistance, mechanical properties, and process compatibility.

[0037] The technical effect of this invention stems from the synergistic effect between the steps of pre-impregnation, sequential feeding, multi-coating, graded drying, and pre-printing curing in the preparation method. Specifically, the pre-impregnation layer allows the acrylic resin to preferentially enter the pores of the paper fiber surface and form an initial bonding interface, thereby improving the uneven absorption and roughness of the paper substrate surface; sequential feeding helps improve the dispersion stability of nano-titanium dioxide, antibacterial agents, and nano-silica in the acrylic resin system, reducing surface defects caused by local aggregation of inorganic components; multi-coating allows the paper substrate bonding layer and the surface functional layer to form in stages, reducing the risk of insufficient leveling and internal defects caused by single thick coatings; graded drying avoids excessively rapid skinning of the surface layer and promotes continuous film formation of the functional layers; and pre-printing curing further stabilizes the surface state of the heat-sealing layer, thereby improving the consistency of ink transfer and adhesion during subsequent high-precision printing. This ensures that the final paper packaging material maintains its green and recyclable properties while also considering surface water permeability resistance, mechanical stability, printability, and food safety performance.

[0038] The present invention also claims protection for a recyclable paper packaging material prepared by the aforementioned method.

[0039] The present invention also claims protection for a method of preparation, or for the application of the recyclable paper packaging material in the fields of food, daily necessities, electronic products, and pharmaceuticals.

[0040] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention uses a single paper substrate with repulpable properties and a water-based coating system, avoiding the problem of difficulty in separating different materials in traditional paper-plastic composite structures, thereby improving the recyclability of packaging materials. According to existing test results, the paper packaging material prepared by the method of this invention can achieve a recyclability score of 98 points, demonstrating good environmental applicability.

[0041] (2) The preparation method of the present invention constructs the paper-based coating interface through steps such as pre-impregnation, sequential feeding, multi-coating, and graded drying, which is beneficial to improving the continuity of the heat-sealing layer and the stability of the interface, thereby taking into account both the surface water penetration resistance and mechanical stability. Test results of existing embodiments show that the surface water dynamic penetration resistance and burst resistance of the material both show an improved trend.

[0042] (3) The preparation method of the present invention further stabilizes the surface state of the heat-sealing layer by pre-printing curing, which is beneficial to improving the consistency of image transfer and adhesion stability in the subsequent printing process.

[0043] (4) The paper packaging material prepared by the preparation method of the present invention can maintain the green and recyclable properties of the packaging material while taking into account the surface water permeability resistance, mechanical stability, printability and food safety performance, and is suitable for environmentally friendly packaging applications in the food, daily chemical and other fields. Attached Figure Description

[0044] Figure 1 This is a flowchart illustrating the preparation process of recyclable paper packaging materials in an embodiment of the present invention.

[0045] Figure 2 This is a schematic diagram of a recyclable paper packaging material sample obtained in an embodiment of the present invention. Detailed Implementation

[0046] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0047] Unless otherwise specified, the experimental methods used in the examples and comparative examples are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0048] Example 1 A method for preparing recyclable paper packaging material includes the following steps: S1. Pre-coat the substrate surface to form a pre-wetted layer and dry it; S2. Coating preparation: Prepare coating material, apply the first coating to the surface of the pre-wetted layer after drying in step S1, pre-dry at 55℃ for 1 min, apply the second coating, and set and dry at 85℃ for 2 min to complete the coating preparation. S3. The material dried in step S2 is aged and printed to obtain the recyclable paper packaging material. The coating material includes a dispersion, acrylic resin, and an antibacterial agent.

[0049] in, The substrate selected in step S1 is sugarcane paper with a basis weight of 80 g / m².

[0050] The raw material selected for the pre-impregnated layer in step S1 is acrylic resin, and the thickness of the pre-impregnated layer is 3 μm.

[0051] The drying temperature in step S1 is 50°C and the time is 1 minute.

[0052] The dispersion includes nano-titanium dioxide dispersion and nano-silica dispersion.

[0053] The antibacterial agent is a silver ion antibacterial agent.

[0054] The amount of antibacterial agent added is 0.3 wt% of the mass of acrylic resin in the coating material.

[0055] The mass of the nano-titanium dioxide particles is 2 wt% of the mass of the acrylic resin in the coating material.

[0056] The mass of the nano-silica is 5.0 wt% of the mass of the acrylic resin in the coating material.

[0057] The preparation method of the nano-titanium dioxide dispersion includes the following steps: taking nano-titanium dioxide particles and dispersing them in anhydrous ethanol, wherein the amount of anhydrous ethanol added is 10 times the mass of the nano-titanium dioxide particles, to obtain the nano-titanium dioxide dispersion.

[0058] The preparation method of the nano silica dispersion includes the following steps: take nano silica powder (particle size of 30 nm), add it to anhydrous ethanol, the amount of anhydrous ethanol added is 10 times the mass of the nano silica particles, disperse it in an ultrasonic disperser for 30 min to obtain a uniform nano silica dispersion.

[0059] The preparation method of the coating material includes the following steps: adding nano-titanium dioxide dispersion to acrylic resin, pre-stirring at 1000 rpm for 10 min to form a basic dispersion system, then adding antibacterial agent, stirring for 10 min, finally adding nano-silica dispersion, and stirring at 1500 rpm for 1 h in a high-speed disperser, and allowing to stand for degassing for 15 min to obtain the coating material.

[0060] The thickness of the wet film applied in the first coating is 6 μm.

[0061] The thickness of the wet film after the second coating is 12 μm.

[0062] The total wet film thickness of the coating is 18 μm.

[0063] The curing process involves allowing the dried material to stand at 20-30°C for 4 hours.

[0064] The printing in step S3 is carried out using an intermittent PS printing method with a printing speed of 80m / min and UV drying.

[0065] Example 2 A method for preparing recyclable paper packaging material includes the following steps: S1. Pre-coat the substrate surface to form a pre-wetted layer and dry it; S2. Coating preparation: Prepare coating material, apply the first coating to the surface of the pre-wetted layer after drying in step S1, pre-dry at 55℃ for 1 min, apply the second coating, and set and dry at 85℃ for 2 min to complete the coating preparation. S3. The material dried in step S2 is aged and printed to obtain the recyclable paper packaging material. The coating material includes a dispersion, acrylic resin, and an antibacterial agent.

[0066] in, The substrate selected in step S1 is white kraft paper with a basis weight of 80 g / m².

[0067] The raw material selected for the pre-impregnated layer in step S1 is acrylic resin, and the thickness of the pre-impregnated layer is 2 μm.

[0068] The drying temperature in step S1 is 40°C and the drying time is 2 minutes.

[0069] The dispersion includes nano-titanium dioxide dispersion and nano-silica dispersion.

[0070] The antibacterial agent is a silver ion antibacterial agent.

[0071] The amount of antibacterial agent added is 0.1 wt% of the mass of the acrylic resin in the coating material.

[0072] The mass of the nano-titanium dioxide particles is 0.1 wt% of the mass of the acrylic resin in the coating material.

[0073] The mass of the nano-silica is 0.5 wt% of the mass of the acrylic resin in the coating material.

[0074] The preparation method of the nano-titanium dioxide dispersion includes the following steps: taking nano-titanium dioxide particles and dispersing them in anhydrous ethanol, wherein the amount of anhydrous ethanol added is 5 times the mass of the nano-titanium dioxide particles, to obtain the nano-titanium dioxide dispersion.

[0075] The preparation method of the nano silica dispersion includes the following steps: take nano silica powder (particle size of 7nm), add it to anhydrous ethanol, the amount of anhydrous ethanol added is 5 times the mass of the nano silica particles, disperse it for 10 minutes using an ultrasonic disperser to obtain a uniform nano silica dispersion.

[0076] The preparation method of the coating material includes the following steps: adding nano-titanium dioxide dispersion to acrylic resin, pre-stirring at 1000 rpm for 10 min to form a basic dispersion system, then adding antibacterial agent, stirring for 10 min, finally adding nano-silica dispersion, and stirring at 1500 rpm for 1 h in a high-speed disperser, and allowing to stand for degassing for 15 min to obtain the coating material.

[0077] The thickness of the wet film applied in the first coating is 2 μm.

[0078] The thickness of the wet film after the second coating is 10 μm.

[0079] The total wet film thickness of the coating is 12 μm.

[0080] The curing process involves allowing the dried material to stand at 20-30°C for 3 hours.

[0081] The printing in step S3 is carried out using an intermittent PS printing method with a printing speed of 80m / min and UV drying.

[0082] Example 3 A method for preparing recyclable paper packaging material includes the following steps: S1. Pre-coat the substrate surface to form a pre-wetted layer and dry it; S2. Coating preparation: Prepare coating material, apply the first coating to the surface of the pre-wetted layer after drying in step S1, pre-dry at 55℃ for 1 min, apply the second coating, and set and dry at 85℃ for 2 min to complete the coating preparation. S3. The material dried in step S2 is aged and printed to obtain the recyclable paper packaging material. The coating material includes a dispersion, acrylic resin, and an antibacterial agent.

[0083] in, The substrate selected in step S1 is kraft paper with a basis weight of 80 g / m².

[0084] The raw material selected for the pre-impregnated layer in step S1 is acrylic resin, and the thickness of the pre-impregnated layer is 5 μm.

[0085] The drying temperature in step S1 is 60°C and the drying time is 0.5 min.

[0086] The dispersion includes nano-titanium dioxide dispersion and nano-silica dispersion.

[0087] The antibacterial agent is a zinc oxide antibacterial agent.

[0088] The amount of antibacterial agent added is 1.0 wt% of the mass of the acrylic resin in the coating material.

[0089] The mass of the nano-titanium dioxide particles is 5 wt% of the mass of the acrylic resin in the coating material.

[0090] The mass of the nano-silica is 5.0 wt% of the mass of the acrylic resin in the coating material.

[0091] The preparation method of the nano-titanium dioxide dispersion includes the following steps: taking nano-titanium dioxide particles and dispersing them in anhydrous ethanol, wherein the amount of anhydrous ethanol added is 20 times the mass of the nano-titanium dioxide particles, to obtain the nano-titanium dioxide dispersion.

[0092] The preparation method of the nano silica dispersion includes the following steps: take nano silica powder (particle size of 50 nm), add it to anhydrous ethanol, the amount of anhydrous ethanol added is 20 times the mass of the nano silica particles, disperse it in an ultrasonic disperser for 50 min to obtain a uniform nano silica dispersion.

[0093] The preparation method of the coating material includes the following steps: adding nano-titanium dioxide dispersion to acrylic resin, pre-stirring at 1000 rpm for 10 min to form a basic dispersion system, then adding antibacterial agent, stirring for 10 min, finally adding nano-silica dispersion, and stirring at 1500 rpm for 1 h in a high-speed disperser, and allowing to stand for degassing for 15 min to obtain the coating material.

[0094] The thickness of the wet film applied in the first coating is 8 μm.

[0095] The thickness of the wet film after the second coating is 10 μm.

[0096] The total wet film thickness of the coating is 18 μm.

[0097] The curing process involves allowing the dried material to stand at 20-30°C for 12 hours.

[0098] The printing in step S3 is carried out using an intermittent PS printing method with a printing speed of 80m / min and UV drying.

[0099] Example 4 Compared with Example 1, the only difference in this example is that... The preparation method of the coating material includes the following steps: adding nano-titanium dioxide dispersion and nano-silica dispersion to acrylic resin, pre-stirring at 1000 rpm for 10 min to form a basic dispersion system, then adding antibacterial agent, stirring for 10 min, and stirring at 1500 rpm for 1 h in a high-speed disperser, and letting it stand for 15 min to remove bubbles to obtain the coating material.

[0100] Other preparation methods and parameters are the same as in Example 1.

[0101] Example 5 Compared with Example 1, the only difference in this example is that the preparation method of the coating material includes the following steps: adding nano-silica dispersion to acrylic resin, pre-stirring at 1000 rpm for 10 min to form a basic dispersion system, then adding antibacterial agent, stirring for 10 min, finally adding nano-titanium dioxide dispersion, and stirring at 1500 rpm for 1 h in a high-speed disperser, and allowing to stand for degassing for 15 min to obtain the coating material.

[0102] Other preparation methods and parameters are the same as in Example 1.

[0103] Example 6 Compared with Example 1, the difference in this example is that an equal amount of nano-titanium dioxide dispersion is used instead of nano-silica dispersion in the dispersion.

[0104] The preparation method of the coating material includes the following steps: adding nano-titanium dioxide dispersion to acrylic resin, pre-stirring at 1000 rpm for 10 min to form a basic dispersion system, then adding antibacterial agent, stirring for 10 min, and stirring at 1500 rpm for 1 h in a high-speed disperser, and letting it stand for 15 min to remove bubbles to obtain the coating material.

[0105] Other preparation methods and parameters are the same as in Example 1.

[0106] Example 7 Compared with Example 1, the only difference in this example is that the total wet film thickness of the coating is 8 μm.

[0107] Other preparation methods and parameters are the same as in Example 1.

[0108] Example 8 Compared with Example 1, the only difference in this example is that the total wet film thickness of the coating is 20 μm.

[0109] Other preparation methods and parameters are the same as in Example 1.

[0110] Example 9 Compared with Example 1, the only difference in this example is that the mass of the nano-titanium dioxide particles is 6 wt% of the mass of the acrylic resin in the coating material.

[0111] Other preparation methods and parameters are the same as in Example 1.

[0112] Example 10 Compared with Example 1, the only difference in this example is that the mass of the nano-silica particles is 6 wt% of the mass of the acrylic resin in the coating material.

[0113] Other preparation methods and parameters are the same as in Example 1.

[0114] Comparative Example 1 Compared with Example 1, the only difference in this comparative example is that step S1 is not performed.

[0115] Other preparation process parameters are the same as in Example 1.

[0116] Comparative Example 2 Compared with Example 1, the only difference in this comparative example is that, in S2, the coating preparation is as follows: the coating material is prepared, and the surface of the pre-wetted layer after drying in step S1 is coated once, and then shaped and dried at 85°C for 2 minutes to complete the coating preparation.

[0117] Other preparation process parameters are the same as in Example 1.

[0118] Comparative Example 3 Compared with Example 1, the only difference in this comparative example is that the thickness of the pre-wetting layer is 6 μm.

[0119] Other preparation methods and parameters are the same as in Example 1.

[0120] Comparative Example 4 Compared with Example 1, the only difference in this comparative example is that the thickness of the pre-wetting layer is 1 μm.

[0121] Other preparation methods and parameters are the same as in Example 1.

[0122] Experiment 1: Performance Testing (1) The paper packaging materials prepared in the examples and comparative examples were subjected to surface water resistance dynamic penetration test and burst strength test. The test methods are as follows, and the test results are shown in Tables 1-2.

[0123] Surface water resistance dynamic penetration test: The paper packaging materials prepared in the examples and comparative examples were cut into samples of uniform size and placed under conditions of 23±1℃ and 50±2% relative humidity for at least 24 hours for equilibration. During testing, the samples were fixed on the test platform of a dynamic permeability tester, and distilled water was brought into contact with the sample surface. The dynamic signal changes during the surface wetting and liquid permeation processes were recorded, and the T95 value was calculated. T95 is the time corresponding to the sample reaching 95% of the set wetting / permeation state, expressed in seconds (s). At least three parallel samples were tested for each group of samples, and the average value was taken as the test result. The higher the T95 value, the better the surface water dynamic permeability resistance of the sample.

[0124] Bursting strength test: The paper packaging materials prepared in the examples and comparative examples were cut into samples of uniform size and placed at a temperature of 23±1℃ and a relative humidity of 50±2% for at least 24 hours for equilibration. The samples were tested using a bursting strength tester. The samples were fixed between ring clamps, and hydraulic or pneumatic pressure was applied at a uniform rate until the sample broke. The maximum pressure value at break was recorded in kilopascals (kPa). Four parallel samples were tested for each group, and the average value was taken as the final result. A higher bursting strength value indicates higher mechanical strength of the sample.

[0125] Table 1. Results of surface water resistance dynamic penetration test for each group

[0126] Table 2. Average bursting strength test results for each group

[0127] The experimental results in Tables 1 and 2 show that the recyclable paper packaging material prepared in the embodiments of the present invention can achieve good surface water dynamic penetration resistance and burst resistance.

[0128] In Examples 4 and 5, the order of adding the dispersion during the preparation of the recyclable paper packaging material was inappropriate, resulting in poor surface water resistance and burst resistance of the final recyclable paper packaging material. In Example 6, the dispersion only contained nano-titanium dioxide components, lacking the interaction between the nano-titanium dioxide dispersion and the nano-silica dispersion, resulting in poor surface water resistance and burst resistance of the final material. In Examples 7 and 8, the total wet film thickness of the coating was inappropriate. In Examples 9 and 10, the quality of the added nano-titanium dioxide particles or nano-silica particles was inappropriate, resulting in the final paper packaging material having poorer waterproof and burst resistance than that of Example 1.

[0129] Compared with Example 1, Comparative Example 1 did not perform the pre-impregnation process in step S1, resulting in a significant decrease in the surface water dynamic penetration resistance and burst resistance of the final paper packaging material; Comparative Example 2 used only one coating in the substrate coating preparation process, resulting in a material with significantly worse water resistance and burst resistance than Example 1; Comparative Examples 3 and 4 had unsuitable thickness of the pre-impregnation layer in the preparation process, resulting in a significant decrease in the performance of the final paper packaging material.

[0130] (2) Comprehensive performance test The recyclable paper packaging materials prepared in Examples 1-10 were tested according to the test items and index requirements in Table 3. The test results are shown in Table 3.

[0131] The detection of residual benzene solvent in item 9 and total residual solvent in item 10 of Table 3 was carried out in accordance with the method for determining residual solvent in the current national standard GB / T 10004-2008 "Dry lamination and extrusion lamination of plastic composite films and bags for packaging", and was performed by gas chromatography.

[0132] The detection of isocyanates in item 11 of Table 3 was performed using the following method: a sample of a certain area was taken, cut into small pieces, extracted with a suitable organic solvent, filtered, and the supernatant was taken. After derivatization, the sample was determined by high performance liquid chromatography, and the result was considered as no detection.

[0133] The evaluation of recyclability in item 12 of Table 3 was conducted in accordance with the current national standard GB / T 43588-2023, "Evaluation Methods for Recyclability of Paper, Paperboard and Paper Products".

[0134] Table 3. Test Items and Indicator Requirements for Comprehensive Performance Testing

[0135] The experimental results in Table 3 show that the recyclable paper packaging materials prepared in Examples 1-10 of this invention exhibit good performance in terms of sensory quality, food contact safety, and environmental recyclability. Specifically, the indicators for evaporation residue, heavy metals, solvent residue, and isocyanate all meet the requirements, and the highest recyclability score reaches 98 points, indicating that the recyclable paper packaging materials prepared in these examples can meet packaging safety requirements while also ensuring environmental recyclability.

[0136] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a recyclable paper packaging material, characterized in that, Includes the following steps: S1. Pre-coat the substrate surface to form a pre-wetted layer and dry it; S2. Coating preparation: Prepare coating material by applying the coating material in multiple layers to the surface of the pre-wetted layer after drying in step S1, and then drying; the coating material includes dispersion, acrylic resin, and antibacterial agent; S3. The material dried in step S2 is aged and printed to obtain the recyclable paper packaging material.

2. The method for preparing recyclable paper packaging material as described in claim 1, characterized in that, The substrate mentioned in step S1 includes at least one of sugarcane paper, white kraft paper, and yellow kraft paper; The raw materials used for the pre-impregnated layer in step S1 include acrylic resin; The thickness of the pre-wetting layer in step S1 is 2~5μm; The drying temperature in step S1 is 40~60℃ and the time is 0.5~2min.

3. The method for preparing recyclable paper packaging material as described in claim 1, characterized in that, The dispersion includes a nano-titanium dioxide dispersion and a nano-silica dispersion; The antibacterial agent includes at least one of silver ion antibacterial agent and zinc oxide antibacterial agent; The amount of antibacterial agent added is 0.1 to 1.0 wt% of the mass of acrylic resin in the coating material.

4. The method for preparing recyclable paper packaging material as described in claim 3, characterized in that, The preparation method of the nano-titanium dioxide dispersion includes the following steps: dispersing nano-titanium dioxide particles in anhydrous ethanol to obtain a nano-titanium dioxide dispersion; the mass of the nano-titanium dioxide particles is 0.1~6wt% of the mass of the acrylic resin in the coating material; The preparation method of the nano-silica dispersion includes the following steps: taking nano-silica powder, adding it to anhydrous ethanol, dispersing it to obtain a nano-silica dispersion; the mass of the nano-silica is 0.5~6.0 wt% of the mass of the acrylic resin in the coating material; The particle size of the nano-silica is 7~50nm.

5. The method for preparing recyclable paper packaging material as described in claim 3, characterized in that, The preparation method of the coating material includes the following steps: adding nano-titanium dioxide dispersion to acrylic resin, then adding antibacterial agent, and finally adding nano-silica dispersion. After mixing and allowing to stand to degas, the coating material is obtained.

6. The method for preparing recyclable paper packaging material as described in claim 1, characterized in that, The preparation of the coating in step S2 includes the following steps: preparing coating material, applying a first coating to the surface of the pre-wetted layer after drying in step S1, pre-drying, applying a second coating, drying, and completing the preparation of the coating.

7. The method for preparing recyclable paper packaging material as described in claim 6, characterized in that, The thickness of the wet film applied in the first coating is 2~8μm; The thickness of the wet film applied in the second coating is 6~10μm; The total wet film thickness of the coating is 12~18μm.

8. The method for preparing recyclable paper packaging material as described in claim 1, characterized in that, The curing process involves allowing the dried material to stand at 20-30°C for 2-12 hours. The printing process described in step S3 employs a printing device equipped with high-precision ink path control, automatic registration, and online quality monitoring functions.

9. A recyclable paper packaging material prepared by any one of the preparation methods described in claims 1 to 8.

10. A preparation method as described in any one of claims 1 to 8, or the application of the recyclable paper packaging material as described in claim 9 in the fields of food, daily necessities, electronic products, and pharmaceuticals.

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