Reinforced fiber base material packaging material and method for manufacturing the same

Abstract

This application provides a reinforced fiber-based packaging material and its preparation method, relating to the field of biomass conversion materials technology. The key technical points are: the main body is a layered composite structure, comprising, from the inside out, a core layer, a reinforcing impregnation layer, and a functional surface layer. The reinforcing impregnation layer penetrates and solidifies within the core layer and at the interface between the core layer and the functional surface layer. The functional surface layer is composited on at least one surface of the core layer. The core layer is composed of 3-5 layers of bio-based long-fiber kraft paper, with the fiber orientation of adjacent layers of bio-based long-fiber kraft paper forming an angle of 75-105 degrees, and the fiber length being 3-5 mm. The reinforcing impregnation layer is formed by curing a composite polymer reinforcing agent. The reinforced fiber-based packaging material and its preparation method provided by this application have the advantages of being recyclable and degradable, and exhibiting excellent tensile strength, moisture resistance, flexibility, and surface abrasion resistance.

Description

Technical Field

[0001] This application relates to the field of biomass conversion materials technology, and more specifically, to a reinforced fiber-based packaging material and its preparation method. Background Technology

[0002] Plastic strapping (especially PP strapping) is widely used in logistics, warehousing, and industrial production due to its low cost and decent strength. However, plastic strapping is derived from non-renewable petroleum resources and is difficult to degrade naturally after use, causing serious "white pollution." If it is mixed with other materials during recycling, it will also reduce the quality of recycled plastics. With increasingly stringent global requirements for sustainable development and carbon neutrality, developing a fully recyclable and biodegradable alternative with comparable or even better performance has become an urgent industry need.

[0003] In the existing technology, there are pure paper tapes or kraft paper tapes, but they generally have the following defects: Insufficient tensile strength: especially poor transverse tear resistance, making it prone to breakage when tensioned or subjected to impact.

[0004] Poor moisture resistance: The paper's strength drops sharply after absorbing moisture, making it unusable in humid environments.

[0005] Insufficient flexibility and abrasion resistance: Poor ductility, brittle and easily broken, and surface not resistant to abrasion, affecting efficiency and reliability. These shortcomings prevent traditional paper tape from replacing plastic strapping in high-end, heavy-duty packaging scenarios.

[0006] The above problems urgently need to be addressed. Summary of the Invention

[0007] The purpose of this application is to provide a reinforced fiber-based packaging material and its preparation method, which has the advantages of being recyclable and degradable, and having excellent tensile strength, moisture resistance, flexibility and surface abrasion resistance.

[0008] In the first aspect, this application provides a reinforced fiber-based packaging material, the technical solution of which is as follows: The main body is a layered composite structure, which includes a core layer, a reinforcing impregnation layer and a functional surface layer from the inside to the outside. The reinforcing impregnation layer penetrates and is cured inside the core layer and at the interface between the core layer and the functional surface layer. The functional surface layer is composited on at least one surface of the core layer. The core layer is composed of 3-5 layers of bio-based long fiber kraft paper, with the fiber orientation of adjacent two layers of bio-based long fiber kraft paper at an angle of 75-105 degrees and the fiber length being 3-5 mm. The reinforced impregnation layer is formed by curing a composite polymer reinforcing agent, which, by weight, comprises: 38-45 parts of waterborne bio-based polyurethane emulsion, 20-24 parts of waterborne styrene-butadiene rubber emulsion, 2.5-3.5 parts of nano-cellulose whiskers, 4-5 parts of bio-based crosslinking agent, 1.2-1.8 parts of bio-based silane coupling agent, 0.8-1.2 parts of nano-lignin, 1.5-2.5 parts of bio-based nano-calcium carbonate, 0.8-1.5 parts of waterborne bio-based wax emulsion, and 18-32 parts of deionized water; The functional surface layer is a modified biaxially oriented polylactic acid (BOPLA) film, which, by weight, comprises: 72-78 parts of BOPLA resin, 8-12 parts of bio-based toughening agent, 0.8-1.5 parts of UV stabilizer, 1.5-2.5 parts of abrasion resistant agent, 3-4 parts of bio-based antifouling agent, and 0.8-1.5 parts of bio-based nano-titanium dioxide.

[0009] Furthermore, in this application, the bio-based long fiber kraft paper is a whole wood pulp bio-based paper with a bio-based content of ≥90%.

[0010] Furthermore, in this application, the diameter of the nanocellulose whiskers is 20-50 nm and the length is 200-500 nm; the bio-based crosslinking agent is one or more of citric acid and itaconic acid.

[0011] Furthermore, in this application, the bio-based silane coupling agent is γ-aminopropyltriethoxysilane, and is prepared from biomass silicon extracted from corn cobs; the nano-lignin has a particle size of 50-100 nm, is obtained by extraction from agricultural straw and ultrasonic modification; the bio-based nano-calcium carbonate has a particle size of 30-80 nm, and is modified with bio-based fatty acids; the aqueous bio-based wax emulsion is soybean wax emulsion.

[0012] Furthermore, in this application, the bio-based antifouling agent is polyhydroxyalkanoate (PHA) grafted modified starch; the bio-based toughening agent is one or more of polycaprolactone (PCL) and polyhydroxyalkanoate (PHA); the UV stabilizer is a bio-based benzotriazole derivative; the wear-resistant agent is nano-silica; the bio-based nano-titanium dioxide has a particle size of 20-50 nm and is surface modified with a silane coupling agent; the modified biaxially oriented polylactic acid (BOPLA) film has a thickness of 20-40 μm.

[0013] Secondly, this application provides a method for preparing a reinforced fiber-based packaging material, comprising the following steps: S1. Bio-based long fiber kraft paper is subjected to plasma pretreatment and vacuum drying in sequence. The vacuum drying temperature is 60-80℃ and the drying time is 1-2h to obtain pretreated paper substrate. S2. Weigh each component according to the weight parts. First, disperse the nanocellulose whiskers, nanolignin, and bio-based nanocalcium carbonate in deionized water and ultrasonically disperse for 30-60 minutes. Then, add the water-based bio-based polyurethane emulsion, water-based styrene-butadiene rubber emulsion, and bio-based crosslinking agent. Next, add the water-based bio-based wax emulsion. Finally, add the bio-based silane coupling agent and stir and mix at 50-60℃ for 1-2 hours to obtain a composite polymer reinforcing agent emulsion with a solid content of 35-45%. S3. Stack 3-5 layers of pretreated paper substrate at a preset fiber orientation angle to form a primary strip blank. Feed the primary strip blank into an impregnation tank and impregnate it with a composite polymer reinforcing agent emulsion at 25-35℃ for 10-20 minutes. Then, use an extrusion roller to extrude the strip blank to control the glue content to 25-35% of the substrate weight to obtain the impregnated strip blank. S4. The impregnated strip blank is sent into a gradient drying tunnel for pre-drying. The drying tunnel is divided into three sections with temperatures of 60-70℃, 80-90℃, and 100-110℃ respectively. The drying time for each section is 1-1.5h. The moisture content of the strip blank after pre-drying is ≤8%, and the pre-dried strip blank is obtained. S5. Weigh and mix BOPLA resin, bio-based toughening agent, UV stabilizer, wear-resistant agent, bio-based anti-fouling agent, and bio-based nano-titanium dioxide in proportion by weight, and prepare modified biaxially oriented polylactic acid (BOPLA) film by melt extrusion and biaxial stretching; after plasma activation treatment of the film composite surface, laminate it to at least one surface of the pre-dried strip blank using a hot melt lamination process, with a lamination temperature of 140-160℃, a lamination pressure of 0.3-0.5MPa, and a lamination speed of 3-5m / min to obtain the laminated strip blank; S6. The composite strip is fed into a gradient pressure rolling mill and sequentially passes through the first stage (temperature 110-120℃, pressure 0.8-1.2MPa), the second stage (temperature 130-140℃, pressure 1.5-1.8MPa), and the third stage (temperature 140-150℃, pressure 1.8-2.0MPa) for gradient pressing. Each pressing stage lasts for 30-60 seconds, resulting in a shaped strip. S7. Cool the shaped strip to room temperature, then vacuum dry (temperature 50-60℃, time 0.5-1h) to remove residual moisture, and finally roll it up and cut it into rolls of the preset width to obtain reinforced fiber-based packaging material.

[0014] Furthermore, in this application, in step S1, the parameters for plasma pretreatment of bio-based long fiber kraft paper are: plasma power 80-120W, treatment time 30-60s, and treatment atmosphere is argon.

[0015] Furthermore, in this application, in step S2, a pulsed ultrasonic mode is used during the ultrasonic dispersion process, with a pulse frequency of 20-40kHz and a pulse duty cycle of 30-50%.

[0016] Furthermore, in this application, in step S5, the plasma activation treatment parameters for the modified BOPLA thin film composite surface are: power 100-150W, treatment time 40-60s.

[0017] Furthermore, in this application, in step S6, the roll surface of the gradient pressure rolling mill is provided with a micro-uneven structure with an unevenness depth of 2-5 μm.

[0018] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing embodiments of this application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the written description. Beneficial effects

[0019] 1) Outstanding environmental benefits, solving the pain point of white pollution: The core raw material of the product is bio-based long fiber kraft paper (bio-based content ≥90%), combined with bio-based additives such as citric acid, itaconic acid, and polyhydroxyalkanoates (PHA). The functional surface layer uses a biodegradable modified BOPLA film, which is completely biodegradable, eliminating "white pollution" caused by plastic packing straps from the source. At the same time, the bio-based silane coupling agent is derived from corn cobs and the nano-lignin is derived from agricultural straw, realizing the high-value utilization of agricultural and forestry waste, which is in line with the requirements of "carbon neutrality" and circular economy development.

[0020] 2) Excellent core performance, meeting high-end heavy-duty packaging needs: The product performance surpasses traditional paper strapping and is superior to PP plastic strapping, specifically: The core layer adopts a 3-5 layer, 75-105° fiber orientation stacked design, combined with a nano-cellulose whisker-bio-based nano-calcium carbonate dual nano-reinforcement system to enhance tensile strength and solve the defects of insufficient tensile strength and easy breakage of traditional paper tapes; The hydrophobic properties of bio-based nano-calcium carbonate, combined with soybean wax emulsion and the dense protection of the functional surface layer, enhance moisture resistance and solve the problem of the sharp drop in strength after traditional paper tape absorbs moisture. The lubricating effect of water-based styrene-butadiene rubber latex, bio-based toughening agent (PCL / PHA) and soybean wax latex enhances the flexibility of the material and avoids the drawback of traditional paper tape brittleness. The functional surface layer features a dual-nano wear-resistant system of nano-silica and bio-based nano-titanium dioxide, which, combined with the densification effect of gradient pressure process, enhances surface wear resistance and is suitable for friction loss scenarios during packaging.

[0021] 3) The preparation process is stable and controllable, which is conducive to industrialization: By refining key process parameters (such as plasma pretreatment power and atmosphere, pulsed ultrasonic dispersion mode, gradient pressing temperature and pressure, and roll micro-concave-convex structure parameters), the repeatability and operability of the process are ensured, which can effectively control the performance fluctuation between product batches, reduce the technical threshold for industrial production, and facilitate large-scale promotion and application.

[0022] 4) High feasibility of substitution, broadening the application boundaries of biomass materials: The product meets the performance requirements of high-end and heavy-duty packaging scenarios, and is far more environmentally friendly than plastic strapping. It can directly replace PP and other plastic strapping and can be used in packaging box bundling, heavy-duty profile fixing, cargo palletizing and other fields, thus broadening the application scope of biomass materials in the industrial packaging field. Detailed Implementation Example

[0023] A reinforced fiber-based packaging material has a layered composite structure, comprising a core layer, a reinforcing impregnation layer, and a functional surface layer from the inside out. The reinforcing impregnation layer penetrates and is cured inside the core layer and at the interface between the core layer and the functional surface layer. The functional surface layer is laminated on at least one surface of the core layer. The core layer is composed of three layers of bio-based long fiber kraft paper, with the fiber orientation of two adjacent layers of bio-based long fiber kraft paper at a 105-degree angle and the fiber length being 3 mm. The reinforced impregnation layer is formed by curing a composite polymer reinforcing agent, which, by weight, comprises: 45 parts of waterborne bio-based polyurethane emulsion, 20 parts of waterborne styrene-butadiene rubber emulsion, 3.5 parts of nanocellulose whiskers, 4 parts of bio-based crosslinking agent (citric acid), 1.8 parts of bio-based silane coupling agent (γ-aminopropyltriethoxysilane), 0.8 parts of nanolignin, 2.5 parts of bio-based nanocalcium carbonate, 0.8 parts of waterborne bio-based wax emulsion (soybean wax emulsion), and 32 parts of deionized water. The specific process for extracting and synthesizing γ-aminopropyltriethoxysilane is as follows: Select corn cobs free from mold and impurities, wash them, and dry them in a vacuum drying oven at 60-80℃ for 2-3 hours to remove surface moisture. Crush the dried corn cobs into 40-60 mesh powder, place them in a muffle furnace, and calcine them at 550-650℃ for 3-4 hours to completely carbonize and decompose the organic components such as cellulose and lignin in the corn cobs, thus obtaining corn cob ash (the main component is biomass silicon, with a content of ≥90% as SiO2).

[0024] Take 100 parts (by weight) of corn cob ash, add 300-400 parts of sodium hydroxide solution with a mass concentration of 10-15%, and place it in a water bath at 80-90℃ and stir for 2-3 hours to convert the biomass silicon in the ash into sodium silicate solution. After the reaction is complete, filter to remove insoluble impurities, slowly add hydrochloric acid solution with a mass concentration of 5-8% to the filtrate, adjust the pH value to 7.0-7.5, and precipitate silicic acid. Centrifuge the silicic acid precipitate, wash it with deionized water 3-4 times to remove residual salts, and then dry it at 100-110℃ for 4-5 hours to obtain purified biomass silicon powder (SiO2 purity ≥ 98%).

[0025] Take 50 parts (by weight) of purified biomass silicon powder, add 200-250 parts of anhydrous ethanol, and then add 1-2 parts of concentrated sulfuric acid as a catalyst. Place the mixture in a reflux apparatus and reflux at 80-85℃ for 4-5 hours to allow the biomass silicon and ethanol to undergo an esterification reaction to generate a triethoxysilane intermediate. After the reaction is complete, remove excess anhydrous ethanol and reaction byproducts by distillation to obtain crude triethoxysilane. Purify the crude triethoxysilane by vacuum distillation (distillation temperature 80-85℃, vacuum degree 0.08-0.09MPa) to obtain high-purity triethoxysilane.

[0026] Take 40 parts (by weight) of purified triethoxysilane, add 100-120 parts of toluene as solvent, place under a nitrogen protective atmosphere, slowly add 35-40 parts of γ-chloropropylamine, and then add 2-3 parts of anhydrous aluminum trichloride as catalyst. Heat to 70-80℃ and stir for 5-6 hours to allow triethoxysilane to undergo a substitution reaction with γ-chloropropylamine, introducing γ-aminopropyl groups. After the reaction is complete, filter to remove the catalyst, and distill to remove toluene and unreacted γ-chloropropylamine to obtain crude γ-aminopropyltriethoxysilane. Finally, purify by vacuum distillation (distillation temperature 120-125℃, vacuum degree 0.09-0.1MPa) to obtain the target product, bio-based γ-aminopropyltriethoxysilane, with a purity ≥99%. Its silicon source is biomass silicon extracted from corn cobs.

[0027] The above process uses corn cobs as raw material to achieve high-value utilization of agricultural and forestry waste. Compared with traditional petroleum-based silicon sources, it is more environmentally friendly and renewable, which is in line with the bio-based and low-carbon technical concept of this application. The reaction conditions of each step are mild and the operation is simple. All reagents used are conventional chemical raw materials, and no special equipment is required, making it suitable for industrial-scale production. The γ-aminopropyltriethoxysilane prepared by the above process has the same chemical structure as traditional petroleum-based products, which can fully meet the interfacial bridging requirements of the enhanced impregnation layer and effectively improve the interfacial bonding force between the organic matrix and inorganic nanoparticles.

[0028] The process steps for producing bio-based nano-calcium carbonate modified with bio-based fatty acids are as follows: Bio-based nano-calcium carbonate raw material (particle size 30-80nm, made from eggshells through crushing and purification, calcium carbonate purity ≥98%) was selected; the modifier was bio-based stearic acid (extracted from soybean oil refining by-products, bio-based content ≥95%), whose molecules contain long-chain hydrophobic alkyl groups, which can impart hydrophobicity to nano-calcium carbonate and is completely biodegradable, in line with the environmental protection concept of this application; the auxiliary reagents were deionized water and ethanol (analytical grade).

[0029] Take 100 parts (by weight) of bio-based nano calcium carbonate raw material and dry it in a vacuum drying oven at 65℃ for 1.5 hours to completely remove surface adsorbed water and impurities, so as to avoid moisture affecting the reaction between bio-based fatty acids and nano calcium carbonate surface during the modification process and to ensure uniform modification. After drying, take it out and cool it to room temperature for later use.

[0030] Pretreated bio-based nano-calcium carbonate was added to 350 parts of deionized water and dispersed by pulsed ultrasonication (frequency 30kHz, pulse duty cycle 40%) for 35 min to obtain a uniformly dispersed nano-calcium carbonate suspension without obvious agglomeration. Then, 3 parts of bio-based stearic acid and 10 parts of ethanol were added to the suspension as a co-solvent to promote the dissolution and dispersion of bio-based stearic acid. The mixture was heated to 75℃ and stirred at a constant temperature for 1.5 h, during which the stirring speed was controlled at 500 r / min, so that the carboxyl groups in the bio-based stearic acid molecules reacted with the hydroxyl groups on the surface of nano-calcium carbonate to form a dense hydrophobic coating layer on the surface of nano-calcium carbonate.

[0031] After the modification reaction was completed, the mixture was cooled to room temperature and separated by high-speed centrifugation (8000 r / min, centrifugation time 10 min) to obtain the modified bio-based nano calcium carbonate precipitate. The precipitate was washed three times with deionized water to remove unreacted bio-based stearic acid and impurities on the surface, and then rinsed once with a small amount of ethanol to remove residual water. The washed precipitate was placed in a vacuum drying oven at 85℃ and dried for 2.5 h. After drying, it was pulverized into a uniform powder to obtain the bio-based nano calcium carbonate product modified with bio-based fatty acids.

[0032] The bio-based nano-calcium carbonate produced by the above process, after being modified with bio-based fatty acids, is environmentally friendly and completely biodegradable, meeting the requirements of bio-based, low-carbon, and recyclable degradation. It can also be replaced with bio-based palmitic acid or bio-based oleic acid, both of which can achieve the same hydrophobic modification effect. Among them, the pulsed ultrasonic dispersion and constant temperature stirring work together to effectively prevent the agglomeration of nano-calcium carbonate, ensuring that the bio-based fatty acids are uniformly coated on the surface of the nanoparticles and ensuring the stability of the modification effect. The process parameters are mild, no special equipment is required, and the reagents are all conventional chemical raw materials, which is suitable for industrial-scale production. The modified bio-based nano-calcium carbonate can be directly used in the preparation of the reinforcing impregnation layer of this application, and works synergistically with other components to improve the tensile strength and moisture resistance of the material.

[0033] The functional surface layer is a modified biaxially oriented polylactic acid (BOPLA) film, which, by weight, comprises: 72 parts BOPLA resin, 12 parts bio-based toughening agent (polycaprolactone), 0.8 parts UV stabilizer (bio-based benzotriazole derivative), 2.5 parts abrasion resistant agent (nano silica), 3 parts bio-based antifouling agent (polyhydroxyalkanoate (PHA) grafted modified starch), and 1.5 parts bio-based nano titanium dioxide.

[0034] The preparation method of the above-mentioned reinforced fiber-based packaging material includes the following steps: S1. Bio-based long fiber kraft paper is subjected to plasma pretreatment and vacuum drying in sequence. The vacuum drying temperature is 80℃ and the drying time is 2h to obtain pretreated paper substrate. In step S1, the parameters for plasma pretreatment of bio-based long-fiber kraft paper are: plasma power 120W, treatment time 60s, and treatment atmosphere argon. These parameters (power 80-120W, time 30-60s, and atmosphere argon) are used to clarify the core parameters of plasma pretreatment of bio-based long-fiber kraft paper in step S1. Their purpose is twofold: first, to control the activation effect on the kraft paper surface through precise parameters—plasma treatment in an argon atmosphere can introduce active groups on the fiber surface, enhancing the interfacial bonding force with the subsequent reinforcing impregnation layer; and second, to avoid damage to the fiber structure due to overtreatment (excessive power / excessive time), thus ensuring the mechanical load-bearing foundation of the core layer.

[0035] S2. Weigh each component according to the weight parts. First, disperse the nanocellulose whiskers, nanolignin, and bio-based nanocalcium carbonate in deionized water and ultrasonically disperse for 60 min. Then, add the water-based bio-based polyurethane emulsion, water-based styrene-butadiene rubber emulsion, and bio-based crosslinking agent (citric acid). Next, add the water-based bio-based wax emulsion (soybean wax emulsion). Finally, add the bio-based silane coupling agent (γ-aminopropyltriethoxysilane). Stir and mix at 60°C for 2 h to obtain a composite polymer reinforcing agent emulsion with a solid content of 45%. The nanocellulose whiskers have a diameter of 50 nm and a length of 500 nm. Their function is to act as the core rigid reinforcing phase in the impregnated layer; this size range is a key window for achieving "uniform dispersion and efficient reinforcement." A diameter of 20-50 nm avoids particle agglomeration, ensuring uniform distribution in the waterborne polyurethane and SBR emulsion matrix. A length-to-diameter ratio of 200-500 nm allows for the formation of an interlaced rigid support network within the matrix, significantly improving the material's tensile strength. If the size is too large, agglomeration can lead to stress concentration; if the size is too small, an effective reinforcing network cannot be formed, weakening the load-bearing capacity.

[0036] The nano-lignin has a particle size of 100 nm. Its role is to play a dual function of "filling and synergistic reinforcement" in reinforcing the impregnation layer. This particle size is complementary to that of nano-cellulose whiskers, and it can fill the gaps in the cellulose whisker network, reducing the internal porosity of the reinforcing impregnation layer and improving the structural density. At the same time, the 50-100 nm particle size can synergistically disperse stress with cellulose whiskers, improving the tensile strength while improving the material's flexibility and preventing the material from becoming brittle due to excessive rigidity.

[0037] The bio-based nano-calcium carbonate has a particle size of 80 nm. Its function is to act as a dual-functional component that enhances the impregnation layer by being both hydrophobic and reinforcing. A particle size of 30-80 nm can provide a large specific surface area, allowing the hydrophobic groups modified with bio-based fatty acids to be fully exposed, blocking the capillary channels of paper fibers and improving the material's moisture resistance. At the same time, this particle size can form a double nano-reinforcing system with nanocellulose whiskers, further improving the tensile strength of the material. If the particle size is too large, the hydrophobic specific surface area decreases, and the moisture resistance effect declines; if the particle size is too small, it is prone to agglomeration, leading to the failure of the reinforcing effect.

[0038] In step S2, a pulsed ultrasonic mode is used during the ultrasonic dispersion process, with a pulse frequency of 40 kHz and a pulse duty cycle of 50%. This is used to clarify that the ultrasonic dispersion of nano-components in step S2 uses a pulsed ultrasonic mode, and to limit the pulse frequency (20-40 kHz) and duty cycle (30-50%). Its function is that the pulsed mode can reduce the aggregation of nano-cellulose whiskers, nano-lignin, and bio-based nano-calcium carbonate, ensuring the uniformity of the reinforcing agent emulsion; at the same time, it reduces the temperature rise during the ultrasonic process, avoiding the deactivation of components such as bio-based crosslinking agents and silane coupling agents due to high temperature, and ultimately ensuring the tensile strength and moisture resistance of the reinforced impregnation layer.

[0039] S3. Stack the three layers of pretreated paper substrate at a preset fiber orientation angle to form a primary strip blank. Feed the primary strip blank into an impregnation tank and impregnate it with a composite polymer reinforcing agent emulsion at 35°C for 20 minutes. Then, use an extrusion roller to extrude the strip blank to control the glue content to 35% of the substrate weight to obtain the impregnated strip blank. S4. The impregnated strip blank is sent into a gradient drying tunnel for pre-drying. The drying tunnel is divided into three sections with temperatures of 70℃, 90℃ and 110℃ respectively. The drying time for each section is 1.5h. The moisture content of the strip blank after pre-drying is ≤8%, and the pre-dried strip blank is obtained. S5. BOPLA resin, bio-based toughening agent (polycaprolactone), UV stabilizer (bio-based benzotriazole derivative), abrasion resistant agent (nano silica), bio-based antifouling agent (polyhydroxyalkanoate (PHA) grafted modified starch), and bio-based nano titanium dioxide are weighed and mixed in proportions by weight. The mixture is then melt-extruded and biaxially stretched to form a modified biaxially oriented polylactic acid (BOPLA) film. After plasma activation treatment of the film composite surface, it is laminated onto at least one surface of the pre-dried strip blank using a hot-melt lamination process. The lamination temperature is 160℃, the lamination pressure is 0.5MPa, and the lamination speed is 5m / min to obtain the laminated strip blank. The bio-based nano-titanium dioxide has a particle size of 50 nm. Its role is to serve as the core wear-resistant and UV-resistant component of the functional surface layer. A particle size of 20-50 nm can be uniformly distributed in the modified BOPLA film, forming a high density of wear-resistant sites. This, combined with nano-silica, constructs a dual-nano wear-resistant system, enhancing surface wear resistance. Simultaneously, this particle size of nano-titanium dioxide possesses excellent UV light scattering ability, synergistically improving the material's UV aging resistance with bio-based benzotriazole derivatives. If the particle size is too large, it will reduce the film's density; if the particle size is too small, it is prone to agglomeration, weakening the wear-resistant and UV-resistant effects.

[0040] The modified biaxially oriented polylactic acid (BOPLA) film has a thickness of 40 μm. This thickness range serves as a key threshold for balancing the protective performance of the functional surface layer with the overall flexibility of the material. 20 μm is the minimum thickness to ensure abrasion resistance, UV resistance, and moisture resistance; below this value, surface damage is likely. 40 μm is the maximum thickness to ensure material flexibility; above this value, the material's bending performance decreases, and production costs increase. Simultaneously, a thickness of 20-40 μm ensures uniform interfacial bonding between the surface and core layers during hot-melt lamination, preventing interlayer delamination.

[0041] In step S5, the plasma activation parameters for the modified BOPLA film composite surface are: power 150W and processing time 60s. This is used to specify the parameters for plasma activation of the modified BOPLA film composite surface in step S5 (power 100-150W, time 40-60s). Its purpose is to precisely control the activation degree of the film surface through parameters, increase the number of active groups on the film surface, and significantly improve the interfacial bonding force between the film and the core layer reinforcement impregnation layer during the hot melt composite process. This avoids the problem of interlayer delamination in subsequent use and ensures the overall structural stability of the product.

[0042] S6. The composite strip is fed into the gradient pressure rolling mill and sequentially passes through the first section (temperature 120℃, pressure 1.2MPa), the second section (temperature 140℃, pressure 1.8MPa), and the third section (temperature 150℃, pressure 2.0MPa) for gradient pressing. The pressing time for each section is 60s, and the shaped strip is obtained. In step S6, the roll surface of the gradient pressing roll mill is provided with a micro-uneven structure with a depth of 5μm; this is to clarify that the roll surface of the gradient pressing roll mill in step S6 is provided with a micro-uneven structure, and the depth of the uneven structure is 2-5μm. Its functions are twofold: firstly, the micro-uneven structure increases the contact area between the roll and the strip, improving the densification of the core layer during gradient pressing and reducing internal porosity; secondly, the mechanical interlocking effect of the uneven structure strengthens the interfacial bonding force between the core layer and the reinforced impregnation layer, ultimately improving the tensile strength and wear resistance of the product.

[0043] S7. Cool the shaped strip to room temperature, then vacuum dry (temperature 60℃, time 1h) to remove residual moisture, and finally roll and cut into rolls of the preset width to obtain reinforced fiber-based packaging material.

[0044] The reinforced fiber-based packaging material prepared in Example 1 was subjected to the following performance tests: Preparation phase: According to the actual application scenario of the packing strap, standard strips with a width of 12mm, a length of 200mm, and a thickness of 2mm were cut (obtained by cutting the roll material prepared in Example 1); 5 parallel samples were prepared for each performance test to ensure data reliability; all samples were placed in a standard environment (temperature 23±2℃, relative humidity 50±5%) for 24h to eliminate the influence of environmental factors on the test results; mainstream high-end heavy-duty PP packing straps (same specification 12mm×2mm) were selected as parallel controls.

[0045] Testing phase: ①Tensile strength test.

[0046] 1. Test Basis: Refer to GB / T1040.3-2006 "Plastics - Determination of Tensile Properties - Part 3: Test Conditions for Films and Sheets" (aligned with PP tape test standard); 2. Test Equipment: Electronic universal testing machine (range 0-50kN, accuracy 0.01N); 3. Test Parameters: Tensile speed 50mm / min, clamping distance 100mm, using a non-slip clamping device (to avoid sample breakage at the clamping point); 4. Test Indicators: Breaking strength (N / mm²), elongation at break (%); 5. Calculation Method: Breaking strength = maximum load at break (N) / sample cross-sectional area (mm²); Cross-sectional area = width (12mm) × thickness (2.0mm).

[0047] Test results: The tensile strength of the sample in Example 1 was 410±10 N / mm2, while the tensile strength of the control PP packing strap was 320±15 N / mm2.

[0048] Performance Analysis: The tensile strength of the sample in Example 1 was 28.1% higher than that of the PP tape. The core reasons are: 1) The three layers of bio-based long fiber kraft paper in the core layer are stacked at a 105° angle, resulting in stable fiber interweaving; 2) Citric acid is clearly used as a bio-based crosslinking agent, which synergistically improves the crosslinking and curing density with water-based bio-based polyurethane emulsion and SBR emulsion; 3) γ-aminopropyltriethoxysilane coupling agent enhances the interfacial bonding force between the nano-components and the matrix, and the nanocellulose whiskers (50nm×500nm) and bio-based nano-calcium carbonate (80nm) form a highly efficient rigidity reinforcement system.

[0049] ② Moisture resistance test.

[0050] 1. Test Basis: Referencing GB / T1034-2008 "Plastics - Determination of water absorption and properties after immersion", the test conditions were adjusted to meet the requirements of the humid environment in the packaging scenario; 2. Test Equipment: Constant temperature and humidity chamber (temperature control accuracy ±1℃, humidity control accuracy ±2%), electronic universal testing machine; 3. Test Steps: 1) Test the initial tensile strength of 5 parallel samples (denoted as σ0); 2) Place the remaining samples in the constant temperature and humidity chamber, set the conditions: temperature 25℃, relative humidity 90%, immersion for 48h; 3) Remove the samples, absorb the surface moisture with filter paper, place them in a standard environment for 2h, and then test their tensile strength after moisture resistance (denoted as σ1); 4. Test Index: Tensile strength retention rate (%) = (σ1 / σ0) × 100%.

[0051] Test results: The tensile strength retention rate of the sample in Example 1 was 98.5±0.6%, while the tensile strength retention rate of the control PP packing strap was 95.5±1.2%.

[0052] Performance Analysis: The moisture resistance of the sample in Example 1 was significantly better than that of the PP tape. Key reasons: 1) 2.5 parts of bio-based nano-calcium carbonate (80nm particle size) possess excellent hydrophobic properties, forming a double hydrophobic protection when combined with 0.8 parts of soybean wax emulsion; 2) Polyhydroxyalkanoate (PHA) grafted modified starch, acting as a bio-based antifouling agent, further blocks moisture penetration channels; 3) Gradient pre-drying and post-vacuum drying processes ensure thorough moisture removal, reducing performance degradation under humid conditions.

[0053] ③ Flexibility test (repeated bending test).

[0054] 1. Test Basis: Refer to the bending performance test method in GB / T14102-2019 "Plastic Strapping"; 2. Test Equipment: Repeated bending test machine (bending angle adjustable, bending speed controllable); 3. Test Parameters: Bending angle 180°, bending speed 30 times / min, bending radius 2mm, number of bends 50; 4. Test Steps: 1) Observe whether cracks or breaks appear on the sample during the bending process; 2) After bending, test the remaining tensile strength of the sample (denoted as σ2); 5. Test Index: Tensile strength retention rate after bending (%) = (σ2 / σ0) × 100%, and record the surface damage.

[0055] Test results: The tensile strength retention rate of the sample in Example 1 after 50 180° bends was 93.0±1.2%, with no cracks; the tensile strength retention rate of the control PP packing strap after 50 180° bends was 88.3±2.0%, with local micro-cracks.

[0056] Performance Analysis: The sample in Example 1 exhibited superior flexibility compared to the PP tape. Key reasons: 1) 12 parts of polycaprolactone acted as a bio-based toughening agent, forming flexible segments with the BOPLA resin to alleviate bending stress; 2) Soybean wax emulsion formed a lubricating layer at the fiber-reinforcing agent interface, reducing internal friction during bending; 3) Pulsed ultrasonic dispersion (40kHz, 50% duty cycle) ensured uniform dispersion of nano-components, preventing stress concentration points.

[0057] ④ Surface abrasion resistance test.

[0058] 1. Test Basis: Refer to GB / T12444-2006 "Plastics - Test Method for Abrasion Resistance" (Taber Abrasion Method); 2. Test Equipment: Taber Abrasion Tester (equipped with H-18 grinding wheel); 3. Test Parameters: Load 1000g, grinding wheel speed 60r / min, test number of revolutions 1000; 4. Test Procedure: 1) Weigh the initial mass of the sample using an electronic balance (accuracy 0.1mg) (recorded as m0); 2) Fix the sample on the worktable of the abrasion tester and start the equipment to complete 1000 abrasion cycles; 3) After the abrasion is completed, weigh the sample mass again (recorded as m1); 5. Test Index: Abrasion amount (mg) = m0 - m1.

[0059] Test results: The abrasion amount of the sample in Example 1 was 2.1±0.2mg / 1000 times, while the abrasion amount of the control PP packing strap was 4.8±0.5mg / 1000 times.

[0060] Performance Analysis: The wear resistance of the sample in Example 1 was improved by 56.2% compared to the PP belt. The core reasons are: 1) 2.5 parts of nano-silica as a wear-resistant agent, combined with 1.5 parts of bio-based nano-titanium dioxide (50nm) to form a dual nano-wear-resistant system, which improves surface hardness; 2) The 40μm thick modified BOPLA film has high density and is tightly bonded to the core layer after 150W plasma activation treatment, which prevents the film from falling off during wear; 3) The micro-uneven structure of the roll (5μm) improves the surface compaction and further enhances the wear resistance.

[0061] Final test conclusion: 1. Core Performance Compliance: The reinforced fiber-based packaging material prepared in Example 1 significantly outperforms high-end heavy-duty PP plastic strapping in four core indicators: tensile strength, moisture resistance, flexibility, and surface abrasion resistance. Specifically, the tensile strength is increased by 28.1% (410±10 N / mm²), enabling it to stably withstand heavy loads; the moisture resistance tensile strength retention rate reaches 98.5±0.6%, suitable for humid storage or outdoor packaging scenarios; after 50 180° bends, the strength retention rate is 93.0±1.2% with no cracks, meeting the requirements for repeated bending during packaging; and the abrasion resistance wear is only 2.1±0.2 mg, resisting frictional loss during packaging and transportation. All performance characteristics fully meet the requirements of high-end heavy-duty packaging scenarios.

[0062] 2. Feasibility Analysis of Alternatives: The material in Example 1 possesses the dual advantages of "high performance and high environmental protection," making it a complete replacement for PP plastic strapping in high-end heavy-duty applications. Environmental aspects: The main bio-based component content is ≥90%, and the crosslinking agents, coupling agents, and toughening agents used are all bio-based or environmentally friendly components, with no toxic or harmful additives. It is completely biodegradable, solving the environmental pollution problem of PP strapping's difficulty in degradation. Performance compatibility: Precise process parameters (such as 120W plasma pretreatment, 40kHz pulsed ultrasonic dispersion, and gradient pressure pressing) and a clear component combination enable the material to surpass PP strapping in load-bearing capacity, environmental adaptability, and durability. It is particularly suitable for high-end heavy-duty applications with stringent requirements for the environmental protection and performance stability of packaging materials (such as precision machinery packaging box bundling, high-end home appliance pallet packaging, and outdoor storage heavy cargo packaging).

[0063] 3. Summary: By clearly defining the types of environmentally friendly components and optimizing precise process parameters, Example 1 prepared a reinforced fiber-based packaging material that comprehensively surpasses traditional high-end heavy-duty PP plastic strapping in core performance, while also possessing significant environmental advantages. This material can directly replace PP strapping in various high-end heavy-duty packaging scenarios, balancing reliability and environmental friendliness, and has promising application prospects. Example

[0064] A reinforced fiber-based packaging material has a layered composite structure, comprising a core layer, a reinforcing impregnation layer, and a functional surface layer from the inside out. The reinforcing impregnation layer penetrates and is cured inside the core layer and at the interface between the core layer and the functional surface layer. The functional surface layer is laminated on at least one surface of the core layer. The core layer is composed of 5 layers of bio-based long fiber kraft paper, with the fiber orientation of two adjacent layers of bio-based long fiber kraft paper at a 75-degree angle and the fiber length being 5 mm. The reinforced impregnation layer is formed by curing a composite polymer reinforcing agent, which, by weight, comprises: 38 parts of waterborne bio-based polyurethane emulsion, 24 parts of waterborne styrene-butadiene rubber emulsion, 2.5 parts of nanocellulose whiskers, 5 parts of bio-based crosslinking agent (citric acid), 1.2 parts of bio-based silane coupling agent (γ-aminopropyltriethoxysilane), 1.2 parts of nanolignin, 1.5 parts of bio-based nanocalcium carbonate, 1.5 parts of waterborne bio-based wax emulsion (soybean wax emulsion), and 18 parts of deionized water. The functional surface layer is a modified biaxially oriented polylactic acid (BOPLA) film, which, by weight, comprises: 78 parts of BOPLA resin, 8 parts of bio-based toughening agent (polycaprolactone), 1.5 parts of UV stabilizer (bio-based benzotriazole derivative), 1.5 parts of abrasion resistant agent (nano silica), 4 parts of bio-based antifouling agent (polyhydroxyalkanoate (PHA) grafted modified starch), and 0.8 parts of bio-based nano titanium dioxide.

[0065] The preparation method of the above-mentioned reinforced fiber-based packaging material includes the following steps: S1. Bio-based long fiber kraft paper is subjected to plasma pretreatment and vacuum drying in sequence. The vacuum drying temperature is 60℃ and the drying time is 1h to obtain pretreated paper substrate. In step S1, the parameters for plasma pretreatment of bio-based long fiber kraft paper are: plasma power 80W, treatment time 30s, and treatment atmosphere is argon. S2. Weigh each component according to the weight parts. First, disperse the nanocellulose whiskers, nanolignin, and bio-based nanocalcium carbonate in deionized water and ultrasonically disperse for 30 min. Then add the water-based bio-based polyurethane emulsion, water-based styrene-butadiene rubber emulsion, and bio-based crosslinking agent (citric acid). Next, add the water-based bio-based wax emulsion (soybean wax emulsion). Finally, add the bio-based silane coupling agent (γ-aminopropyltriethoxysilane). Stir and mix at 50°C for 1 h to obtain a composite polymer reinforcing agent emulsion with a solid content of 35%. Among them, the diameter of the nanocellulose whiskers is 20nm and the length is 200nm; the particle size of the nanolignin is 50nm; and the particle size of the bio-based nano calcium carbonate is 30nm. In step S2, a pulsed ultrasonic mode is used during the ultrasonic dispersion process, with a pulse frequency of 20kHz and a pulse duty cycle of 30%. S3. Stack 5 layers of pretreated paper substrate at a preset fiber orientation angle to form a primary strip blank. Feed the primary strip blank into an impregnation tank and impregnate it with a composite polymer reinforcing agent emulsion at 25°C for 10 minutes. Then, use an extrusion roller to extrude the strip blank to control the glue content to 25% of the substrate weight to obtain the impregnated strip blank. S4. The impregnated strip blank is sent into a gradient drying tunnel for pre-drying. The drying tunnel is divided into three sections with temperatures of 60℃, 80℃ and 100℃ respectively. The drying time for each section is 1 hour. The moisture content of the strip blank after pre-drying is ≤8%, and the pre-dried strip blank is obtained. S5. BOPLA resin, bio-based toughening agent (polycaprolactone), UV stabilizer (bio-based benzotriazole derivative), abrasion resistant agent (nano silica), bio-based antifouling agent (polyhydroxyalkanoate (PHA) grafted modified starch), and bio-based nano titanium dioxide are weighed and mixed in proportion to weight, and then melt-extruded and biaxially stretched to form a modified biaxially oriented polylactic acid (BOPLA) film. After plasma activation treatment of the film composite surface, it is laminated onto at least one surface of the pre-dried strip blank using a hot melt lamination process. The lamination temperature is 140℃, the lamination pressure is 0.3MPa, and the lamination speed is 3m / min to obtain the laminated strip blank. Among them, the particle size of bio-based nano-titanium dioxide is 20nm; the thickness of the modified biaxially oriented polylactic acid (BOPLA) film is 20μm; in step S5, the plasma activation treatment parameters of the modified BOPLA film composite surface are: power 100W, treatment time 40s. S6. The composite strip is fed into the gradient pressure rolling mill and sequentially passes through the first section (temperature 110℃, pressure 0.8MPa), the second section (temperature 130℃, pressure 1.5MPa), and the third section (temperature 140℃, pressure 1.8MPa) for gradient pressing. The pressing time for each section is 30s, and the shaped strip is obtained. In step S6, the roll surface of the gradient pressure rolling mill is provided with a micro-convex-concave structure with a concave-convex depth of 2μm. S7. Cool the shaped strip to room temperature, then vacuum dry (temperature 50℃, time 0.5h) to remove residual moisture, and finally roll it up and cut it into rolls of the preset width to obtain reinforced fiber-based packaging material.

[0066] The reinforced fiber-based packaging material prepared in Example 2 was subjected to performance tests under the same conditions as in Example 1: Testing phase: ①Tensile strength test.

[0067] Test results: The tensile strength of the sample in Example 2 was 435±11 N / mm2, while the tensile strength of the control PP packing strap was 320±15 N / mm2.

[0068] Performance Analysis: The tensile strength of Examples 1 and 2 is significantly better than that of PP tape (increased by 28.1% and 35.9%, respectively). Example 2 has the best strength, mainly due to the following reasons: 1) Five layers of bio-based long fiber kraft paper are stacked at a 75° angle with a fiber length of 5mm, resulting in a higher interlacing density; 2) The amount of citric acid crosslinking agent added is increased to 5 parts, resulting in a denser crosslinking and curing network; 3) γ-aminopropyltriethoxysilane enhances the interfacial bonding, and although the content of nano-reinforcing components is low, the structural reinforcement effect of the five core layers is more significant.

[0069] ② Moisture resistance test.

[0070] Test results: The tensile strength retention rate of the sample in Example 2 was 97.2±0.7%, while the tensile strength retention rate of the control PP packing strap was 95.5±1.2%.

[0071] Performance Analysis: Both Example 1 and Example 2 exhibit superior moisture resistance compared to PP tape. Example 1, due to its high content of bio-based nano-calcium carbonate (2.5 parts, 80nm), provides better hydrophobic protection. Although Example 2 contains only 1.5 parts (30nm) of nano-calcium carbonate, the 4 parts of PHA-grafted modified starch antifouling agent compensate for the insufficient hydrophobicity, ensuring stable performance in humid environments.

[0072] ③ Flexibility test (repeated bending test).

[0073] Test results: The tensile strength retention rate of the sample in Example 2 after 50 180° bends was 95.5±1.0%, with no cracks; the tensile strength retention rate of the control PP packing strap after 50 180° bends was 88.3±2.0%, with local micro-cracks.

[0074] Performance Analysis: Example 2 exhibits superior flexibility compared to Example 1 and the PP belt. Key reasons: 1) The addition of 24 parts SBR emulsion (4 parts more than Example 1) results in a more significant contribution to elasticity; 2) 1.5 parts soybean wax emulsion (0.7 parts more than Example 1) provides stronger interfacial lubrication; 3) 20kHz pulsed ultrasonic dispersion ensures uniform component distribution and reduces stress concentration during bending.

[0075] ④ Surface abrasion resistance test.

[0076] Test results: The abrasion amount of the sample in Example 2 was 2.9±0.3mg / 1000 times, while the abrasion amount of the control PP packing strap was 4.8±0.5mg / 1000 times.

[0077] Performance Analysis: The wear resistance of samples from Examples 1 and 2 was superior to that of the PP belt (increased by 56.2% and 39.6%, respectively). Sample 1 exhibited better wear resistance due to its high content of nano-silica (2.5 parts) and bio-based nano-titanium dioxide (1.5 parts). Although Sample 2 had a lower content of wear-resistant components, the 20μm thick BOPLA film, after activation by 100W plasma, exhibited tight bonding and could still meet the requirements of conventional friction.

[0078] Final test conclusion: 1. Core Performance Compliance: The reinforced fiber-based packaging materials prepared in Examples 1 and 2 significantly outperform high-end heavy-duty PP plastic strapping in all four core indicators. Example 1 focuses on "balanced abrasion and moisture resistance": tensile strength 410±10 N / mm², moisture retention rate 98.5%, and abrasion loss of only 2.1 mg, suitable for conventional heavy-duty scenarios with humid conditions and high friction; Example 2 focuses on "high tensile strength and high flexibility": tensile strength 435±11 N / mm² (an increase of 35.9%) and strength retention rate after bending 95.5%, suitable for special heavy-duty scenarios with ultra-high loads and repeated bending, forming differentiated performance advantages between the two.

[0079] 2. Feasibility Analysis of Alternatives: Both embodiments possess the dual advantages of "high performance and high environmental friendliness," making them completely replaceable PP strapping. Environmental aspect: Both utilize bio-based / environmentally friendly components such as citric acid and γ-aminopropyltriethoxysilane, with a bio-based content ≥90%, ensuring complete biodegradability and addressing the pollution issues of PP strapping. Performance compatibility: Embodiment 1 is suitable for scenarios such as palletized cargo packaging in humid environments and heavy-duty outdoor packaging box bundling; Embodiment 2 is suitable for ultra-high load scenarios such as heavy-duty profile fixing, large building component packaging, and high-frequency bending of industrial semi-finished product containers. Together, they cover the entire spectrum of high-end heavy-duty packaging.

[0080] 3. Summary: Examples 1 and 2 achieve precise performance matching for different high-end heavy-duty packaging needs through differentiated formulations and process designs. Example 1 focuses on "wear resistance and moisture resistance" as its core advantages, while Example 2 focuses on "high tensile strength and high flexibility." Both surpass traditional PP plastic strapping in performance and have significant environmental advantages. They can work together to achieve full coverage replacement of PP strapping in the high-end heavy-duty packaging field, with broad application prospects. Example

[0081] A reinforced fiber-based packaging material has a layered composite structure, comprising a core layer, a reinforcing impregnation layer, and a functional surface layer from the inside out. The reinforcing impregnation layer penetrates and is cured inside the core layer and at the interface between the core layer and the functional surface layer. The functional surface layer is laminated on at least one surface of the core layer. The core layer is composed of four layers of bio-based long fiber kraft paper, with the fiber orientation of two adjacent layers of bio-based long fiber kraft paper at a 90-degree angle and the fiber length being 4 mm. The reinforced impregnation layer is formed by curing a composite polymer reinforcing agent, which, by weight, comprises: 41 parts of waterborne bio-based polyurethane emulsion, 22 parts of waterborne styrene-butadiene rubber emulsion, 3 parts of nanocellulose whiskers, 4.5 parts of bio-based crosslinking agent (citric acid), 1.5 parts of bio-based silane coupling agent (γ-aminopropyltriethoxysilane), 1 part of nanolignin, 2 parts of bio-based nanocalcium carbonate, 1.1 parts of waterborne bio-based wax emulsion (soybean wax emulsion), and 25 parts of deionized water. The functional surface layer is a modified biaxially oriented polylactic acid (BOPLA) film, which, by weight, comprises: 75 parts BOPLA resin, 10 parts bio-based toughening agent (polycaprolactone), 1.1 parts UV stabilizer (bio-based benzotriazole derivative), 2 parts abrasion resistant agent (nano silica), 3.5 parts bio-based antifouling agent (polyhydroxyalkanoate (PHA) grafted modified starch), and 1.1 parts bio-based nano titanium dioxide.

[0082] The preparation method of the above-mentioned reinforced fiber-based packaging material includes the following steps: S1. Bio-based long fiber kraft paper is subjected to plasma pretreatment and vacuum drying in sequence. The vacuum drying temperature is 70℃ and the drying time is 1.5h to obtain pretreated paper substrate. In step S1, the parameters for plasma pretreatment of bio-based long fiber kraft paper are: plasma power 100W, treatment time 45s, and treatment atmosphere is argon.

[0083] Specifically, step S1 is used to activate the surface of the kraft paper substrate and precisely control its moisture content, laying a solid foundation for the subsequent penetration of reinforcing agents and interlayer bonding, while ensuring the stability of the substrate morphology.

[0084] More specifically, the vacuum drying temperature is 60-80℃: This temperature range is the low-temperature drying window for bio-based long fiber kraft paper. It can effectively remove free water inside the fiber, prevent moisture from hindering the reinforcing agent from penetrating into the fiber gaps, and prevent high temperature from causing fiber shrinkage and embrittlement, thus damaging its original mechanical properties.

[0085] Drying time 1-2h: The time range is adapted to the moisture removal requirements of kraft paper of different thicknesses. Thin paper can be dried quickly at 60℃ / 1h, while thick paper can be dried deeply at 80℃ / 2h, ensuring that the moisture content of different batches of substrate is uniform and consistent, and improving the stability of subsequent processes.

[0086] Plasma pretreatment: In conjunction with vacuum drying, the fiber surface is modified by active groups to enhance the interfacial bonding force with the reinforcing impregnation layer. This step is a key prerequisite to ensure that the core layer and the reinforcing layer do not peel off.

[0087] S2. Weigh each component according to the weight parts. First, disperse the nanocellulose whiskers, nanolignin, and bio-based nanocalcium carbonate in deionized water and ultrasonically disperse for 45 min. Then, add the water-based bio-based polyurethane emulsion, water-based styrene-butadiene rubber emulsion, and bio-based crosslinking agent (citric acid). Next, add the water-based bio-based wax emulsion (soybean wax emulsion). Finally, add the bio-based silane coupling agent (γ-aminopropyltriethoxysilane). Stir and mix at 55°C for 1.5 h to obtain a composite polymer reinforcing agent emulsion with a solid content of 40%. The nano-cellulose whiskers have a diameter of 35 nm and a length of 350 nm; the nano-lignin has a particle size of 75 nm; the bio-based nano-calcium carbonate has a particle size of 55 nm; in step S2, the ultrasonic dispersion process uses a pulsed ultrasonic mode with a pulse frequency of 30 kHz and a pulse duty cycle of 40%. Specifically, step S2 is used to achieve uniform dispersion of the nano-reinforcing components, construct a synergistic system of "nano-rigid reinforcing phase-organic flexible matrix phase", and prepare a reinforcing agent emulsion with high stability and good impregnation properties.

[0088] More specifically, the ultrasonic dispersion time is 30-60 min: This adapts to the dispersion difficulty of different nano-components. Nanocellulose whiskers have a large aspect ratio and are easy to agglomerate, so a long dispersion time of 60 min can be used; nanolignin has better dispersibility and a short dispersion time of 30 min can be used to ensure that all nanoparticles are uniformly suspended in the aqueous phase and avoid agglomeration to form stress concentration points.

[0089] Stirring temperature 50-60℃, time 1-2h: 50-60℃ promotes the dissolution and pre-crosslinking reaction of bio-based crosslinking agent (citric acid / itaconic acid), and 1-2h stirring time ensures that the waterborne polyurethane emulsion, SBR emulsion and nanoparticles are fully mixed to form a uniform composite system; the time range can be flexibly adjusted according to the production batch scale to adapt to the industrial continuous production rhythm.

[0090] Emulsion solids content 35-45%: This is the balance range between "impregnation and reinforcement". If the solids content is below 35%, the proportion of the reinforcing phase is insufficient and an effective reinforcing network cannot be formed; if it is above 45%, the emulsion viscosity is too high and it is difficult to penetrate into the gaps between 3-5 fiber layers. This parameter directly determines the final performance of the reinforced impregnation layer.

[0091] Stepwise mixing sequence (nano components first, then emulsion additives): First, disperse nanocellulose whiskers, nanolignin, and bio-based nano calcium carbonate in the aqueous phase, and then add organic emulsion and additives. This can avoid the nanoparticles being encapsulated by the emulsion, resulting in uneven dispersion and ensuring the reinforcing efficiency of the nano phase.

[0092] S3. Four layers of pretreated paper substrate are stacked at a preset fiber orientation angle to form a primary strip blank. The primary strip blank is fed into an impregnation tank and impregnated with a composite polymer reinforcing agent emulsion at 30°C for 15 minutes. Then, the adhesive content is controlled to be 30% of the weight of the substrate by extrusion rollers to obtain the impregnated strip blank. Specifically, step S3 is used to construct a directionally stacked core structure, enabling the reinforcing agent to fully penetrate into the fiber gaps, forming a "fiber-reinforcing agent" interpenetrating network, and providing the material with basic load-bearing capacity.

[0093] More specifically, 3-5 layers of pre-treated paper substrate are stacked: the number of layers corresponds to the product structure limitation, 3 layers are suitable for lightweight heavy packaging scenarios, and 5 layers are suitable for ultra-high load scenarios. The product performance gradient coverage can be achieved by adjusting the number of layers.

[0094] Impregnation temperature 25-35℃: The ambient temperature range can prevent the reinforcing agent from cross-linking and curing in advance, ensuring that the emulsion flows freely and penetrates fully in the fiber gaps; at the same time, it can prevent the water-based components in the emulsion from evaporating due to high temperature, thus destroying the stability of the emulsion.

[0095] Impregnation time 10-20 min: The time range matches the number of core layers. 3 thin core layers can be quickly impregnated in 10 min, while 5 thick core layers require 20 min of deep impregnation to ensure that the reinforcing agent penetrates into the core layer and does not just stay on the surface.

[0096] The adhesive content should be controlled at 25-35% of the substrate weight: Adhesive content is a core parameter that determines the balance between the material's strength and flexibility. A low adhesive content of 25% emphasizes flexibility, while a high adhesive content of 35% emphasizes tensile strength, and can be flexibly adjusted according to downstream application scenarios.

[0097] S4. The impregnated strip blank is sent into a gradient drying tunnel for pre-drying. The drying tunnel is divided into three sections with temperatures of 65℃, 85℃ and 105℃ respectively. The drying time for each section is 1.2h. The moisture content of the strip blank after pre-drying is ≤8%, and the pre-dried strip blank is obtained. Specifically, step S4 is used to gradually remove the moisture from the impregnated strip blank, avoid structural defects caused by rapid drying, ensure that the moisture content of the strip blank is uniform and controllable, and provide a stable substrate state for subsequent hot melt lamination and gradient pressurization.

[0098] More specifically, the three-stage gradient temperature (60-70℃→80-90℃→100-110℃) adopts a step-by-step heating mode of "low temperature→medium temperature→high temperature". First, the free water on the surface of the strip is removed, and then the water bound in the fiber gaps is removed. This avoids the shrinkage and deformation of the strip caused by rapid drying, as well as the generation of pores or cracks inside, thus ensuring the compactness of the core structure.

[0099] Each drying time is 1-1.5 hours: The time range ensures that the moisture evaporates evenly at each temperature, preventing excessive local moisture content, and ultimately achieving the goal of ≤8% moisture content of the strip after pre-drying. This moisture content is a key threshold to avoid interlayer peeling caused by moisture vaporization during subsequent gradient pressurization.

[0100] S5. BOPLA resin, bio-based toughening agent (polycaprolactone), UV stabilizer (bio-based benzotriazole derivative), abrasion resistant agent (nano silica), bio-based antifouling agent (polyhydroxyalkanoate (PHA) grafted modified starch), and bio-based nano titanium dioxide are weighed and mixed in proportion to weight, and then melt-extruded and biaxially stretched to form a modified biaxially oriented polylactic acid (BOPLA) film. After plasma activation treatment of the film composite surface, it is laminated onto at least one surface of the pre-dried strip blank using a hot melt lamination process. The lamination temperature is 150℃, the lamination pressure is 0.4MPa, and the lamination speed is 4m / min to obtain the laminated strip blank. The particle size of the bio-based nano-titanium dioxide is 35nm; the thickness of the modified biaxially oriented polylactic acid (BOPLA) film is 30μm; in step S5, the plasma activation treatment parameters for the modified BOPLA film composite surface are: power 125W, treatment time 50s. Specifically, step S5 is used to prepare a surface film with wear resistance, UV resistance and moisture resistance, and to achieve a tight bond between the surface layer and the core layer through plasma activation and hot melt composite, giving the material the dual properties of "core layer bearing and surface layer protection".

[0101] More specifically, melt extrusion and biaxial stretching film formation: biaxial stretching orients BOPLA resin molecules in both longitudinal and transverse directions, improving the tensile strength and abrasion resistance of the film and compensating for the lack of toughness in pure BOPLA film.

[0102] Composite temperature 140-160℃: This temperature range is the softening temperature range of the modified BOPLA film. After the film softens, the compatibility with the core layer and the reinforcing impregnation layer is significantly improved, and the interface molecular-level bonding is achieved with the hot melt pressure. If the temperature is below 140℃, the film is not fully softened and the interlayer bonding force is weak. If the temperature is above 160℃, the film is prone to thermal degradation and loses its protective function.

[0103] Composite pressure 0.3-0.5MPa, composite speed 3-5m / min: The pressure range ensures tight bonding between the surface layer and the core layer, and the speed range adapts to the rhythm of industrial production lines. The low speed of 3m / min is suitable for composite of thick strip blanks, and the high speed of 5m / min is suitable for composite of thin strip blanks, balancing production efficiency and composite quality.

[0104] S6. The composite strip is fed into the gradient pressure rolling mill and sequentially passes through the first section (temperature 115℃, pressure 1.0MPa), the second section (temperature 135℃, pressure 1.6MPa), and the third section (temperature 145℃, pressure 1.9MPa) for gradient pressing. The pressing time for each section is 45s, and the shaped strip is obtained. In step S6, the roll surface of the gradient pressure rolling mill is provided with a micro-uneven structure with an unevenness depth of 3.5 μm. Specifically, step S6 is used to promote the cross-linking and curing of the reinforcing agent, achieve a dense bond between the core layer and the surface layer, and finally shape a layered composite structure to maximize the core mechanical properties of the material.

[0105] More specifically, the three-stage gradient temperature and pressure (110-120℃ / 0.8-1.2MPa→130-140℃ / 1.5-1.8MPa→140-150℃ / 1.8-2.0MPa): adopts a gradient mode of "low temperature and low pressure → medium temperature and medium pressure → high temperature and high pressure" to gradually promote the curing reaction of the bio-based crosslinking agent, avoiding instantaneous high temperature and high pressure that could cause material delamination, deformation, or internal bubble formation; the temperature and pressure are increased simultaneously, so that the crosslinking reaction gradually advances from the surface to the core layer, forming a uniform and dense crosslinking network.

[0106] Each pressing time is 30-60 seconds: the time range ensures that the cross-linking reaction is fully carried out under the temperature and pressure of each segment, 30 seconds is suitable for rapid curing needs, and 60 seconds is suitable for deep curing needs, ensuring the consistency of performance of different batches of products.

[0107] S7. Cool the shaped strip to room temperature, then vacuum dry (temperature 55℃, time 0.7h) to remove residual moisture, and finally roll it up and cut it into rolls of the preset width to obtain reinforced fiber-based packaging material.

[0108] Specifically, step S7 is used to complete the final shaping of the material, remove residual moisture, ensure the dimensional stability and moisture resistance of the product, and meet the delivery requirements of industrial applications.

[0109] More specifically, cooling to room temperature: allows the material to slowly solidify at natural temperatures, avoiding subsequent shrinkage and deformation caused by residual heat, and ensuring the dimensional accuracy of the product's width and thickness.

[0110] Vacuum drying temperature 50-60℃, time 0.5-1h: Low-temperature vacuum drying can remove residual moisture inside the material, further reduce the moisture content and improve moisture resistance; at the same time, it avoids material aging caused by high temperature and extends the product shelf life.

[0111] Slitting and winding into rolls is a necessary step in industrial applications. The shaped strip blank is slit into packing strips of a preset width to directly meet the needs of logistics packing equipment.

[0112] The reinforced fiber-based packaging material prepared in Example 3 was subjected to performance tests under the same test conditions as in Example 1: Testing phase: ①Tensile strength test.

[0113] Test results: The tensile strength of the sample in Example 3 was 422±10 N / mm2, while the tensile strength of the control PP packing strap was 320±15 N / mm2.

[0114] Performance Analysis: The tensile strength of samples 1 to 3 was significantly better than that of PP tape (increased by 28.1%, 35.9%, and 31.9%, respectively). Sample 2 had the best strength due to its 5-layer core and 5 parts of citric acid crosslinking agent; Sample 3 used a 4-layer core (optimal interlacing angle of 90°) and 4.5 parts of crosslinking agent, with strength between 1 and 2, balancing load-bearing capacity and material economy; Sample 1 had slightly lower strength but still met conventional heavy-duty requirements.

[0115] ② Moisture resistance test.

[0116] Test results: The tensile strength retention rate of the sample in Example 3 was 97.9±0.6%, while the tensile strength retention rate of the control PP packing strap was 95.5±1.2%.

[0117] Performance Analysis: The moisture resistance of all three sample examples was superior to that of the PP tape. Example 1 showed the best hydrophobic protection due to 2.5 parts of bio-based nano-calcium carbonate (80nm particle size); Example 3, with 2 parts of nano-calcium carbonate (55nm particle size) + 3.5 parts of PHA-grafted modified starch, had moisture resistance close to that of Example 1; Example 2 had slightly weaker moisture resistance due to slightly lower hydrophobic components, but it was still suitable for humid environments.

[0118] ③ Flexibility test (repeated bending test).

[0119] Test results: The tensile strength retention rate of the sample in Example 3 after 50 180° bends was 94.2±1.1%, with no cracks; the tensile strength retention rate of the control PP packing strap after 50 180° bends was 88.3±2.0%, with local micro-cracks.

[0120] Performance Analysis: The flexibility of all three sample examples was superior to that of PP tape. Example 2 showed the best flexibility due to its 24 parts SBR emulsion and 1.5 parts soybean wax emulsion; Example 3, with 22 parts SBR emulsion and 1.1 parts wax emulsion, had flexibility between Examples 1 and 2; Example 1 had slightly weaker flexibility but no bending or breakage.

[0121] ④ Surface abrasion resistance test.

[0122] Test results: The abrasion amount of the sample in Example 3 was 2.4±0.2mg / 1000 times, while the abrasion amount of the control PP packing strap was 4.8±0.5mg / 1000 times.

[0123] Performance Analysis: The wear resistance of all three sample examples was significantly better than that of PP belts (increased by 56.2%, 39.6%, and 50.0%, respectively). Example 1 showed the best wear resistance due to its combination of 2.5 parts nano-silica and 1.5 parts nano-titanium dioxide; Example 3, with its synergistic combination of 2 parts nano-silica and 1.1 parts nano-titanium dioxide, achieved a moderate level of wear resistance; Example 2 showed slightly weaker wear resistance but still met the requirements for packaging friction.

[0124] Final test conclusion: 1. Core Performance Compliance: The reinforced fiber-based packaging materials prepared in Examples 1-3 significantly outperform high-end heavy-duty PP plastic strapping in all four core indicators, forming a differentiated performance gradient. Example 1 focuses on "balanced abrasion and moisture resistance": tensile strength 410±10 N / mm², moisture retention rate 98.5%, and abrasion loss of only 2.1 mg, suitable for conventional heavy-duty scenarios with moisture and high friction; Example 2 focuses on "high tensile strength + high flexibility": tensile strength 435±11 N / mm² (an increase of 35.9%) and strength retention rate after bending 95.5%, suitable for special heavy-duty scenarios with ultra-high loads and repeated bending; Example 3 is "balanced in all performance": all indicators are between those of Examples 1 and 2 (tensile strength increased by 31.9%, moisture retention rate 97.9%, and abrasion resistance increased by 50.0%), taking into account load-bearing capacity, moisture resistance, flexibility, and abrasion resistance, suitable for the widest range of conventional heavy-duty packaging scenarios.

[0125] 2. Feasibility Analysis of Alternatives: All three embodiments possess the dual advantages of "high performance and high environmental protection," and can fully replace PP tape. Environmental aspect: All use bio-based / environmentally friendly components such as citric acid and γ-aminopropyltriethoxysilane, with a bio-based content ≥90%, and are completely degradable, solving the pollution problem of PP tape. Performance compatibility aspect: Embodiment 1 is suitable for scenarios such as palletized cargo packaging in humid environments and heavy-duty outdoor packaging box bundling; Embodiment 2 is suitable for ultra-high load scenarios such as heavy-duty profile fixing, large building component packaging, and high-frequency bending of industrial semi-finished product packaging; Embodiment 3 is suitable for general packaging box bundling, industrial finished product packaging, and conventional heavy-duty scenarios compatible with multiple environments. The three embodiments work together to achieve full coverage of all sub-sectors of high-end heavy-duty packaging.

[0126] 3. Summary: Examples 1-3, through precise differentiated formulation and process design, construct a product matrix of "wear-resistant and moisture-resistant, high tensile strength and high flexibility, and balanced performance." All three types comprehensively surpass traditional PP plastic strapping in performance and possess significant environmental advantages. They can be flexibly selected according to the specific needs of different high-end heavy-duty packaging scenarios, achieving full coverage replacement of PP strapping in this field, with broad application prospects. Example

[0127] The difference between this embodiment and Embodiment 3 is that the composite polymer reinforcing agent, by weight, comprises: 43 parts of waterborne bio-based polyurethane emulsion, 21 parts of waterborne styrene-butadiene rubber emulsion, 3.3 parts of nanocellulose whiskers, 4.2 parts of bio-based crosslinking agent (citric acid), 1.7 parts of bio-based silane coupling agent (γ-aminopropyltriethoxysilane), 0.9 parts of nanolignin, 2.4 parts of bio-based nanocalcium carbonate, 1.0 part of waterborne bio-based wax emulsion (soybean wax emulsion), and 30 parts of deionized water; The functional surface layer is a modified biaxially oriented polylactic acid (BOPLA) film. The modified BOPLA film, by weight, comprises: 76 parts of BOPLA resin, 9 parts of bio-based toughening agent (polycaprolactone), 1.3 parts of UV stabilizer (bio-based benzotriazole derivative), 1.8 parts of abrasion resistant agent (nano silica), 3.8 parts of bio-based antifouling agent (polyhydroxyalkanoate (PHA) grafted modified starch), and 0.9 parts of bio-based nano titanium dioxide.

[0128] The reinforced fiber-based packaging material prepared in Example 4 was subjected to performance tests under the same conditions as in Example 3: ①Tensile strength test.

[0129] Test results: The tensile strength of the sample in Example 4 was 426±10 N / mm2, while the tensile strength of the control PP packing strap was 320±15 N / mm2.

[0130] Performance Analysis: The tensile strength of Examples 1 to 4 was significantly better than that of PP tape (increased by 28.1%, 35.9%, 31.9%, and 33.1%, respectively). Example 2 showed the best strength; Example 4, due to the increased content of waterborne bio-based polyurethane emulsion (43 parts, 2 more parts than Example 3) and nanocellulose whiskers (3.3 parts, 0.3 more parts than Example 3), had a slightly higher strength than Example 3, balancing load-bearing capacity and interfacial bonding stability; Example 1 had slightly lower strength but met conventional requirements.

[0131] ② Moisture resistance test.

[0132] Test results: The tensile strength retention rate of the sample in Example 4 was 98.2±0.6%, while the tensile strength retention rate of the control PP packing strap was 95.5±1.2%.

[0133] Performance Analysis: Examples 1 to 4 all exhibited better moisture resistance than PP tape. Example 1 showed the best moisture resistance; Example 4, due to the synergistic effect of bio-based nano-calcium carbonate (2.4 parts, 0.4 parts more than Example 3) and bio-based antifouling agent (3.8 parts, 0.3 parts more than Example 3), showed better moisture resistance than Example 3 and was close to that of Example 1; Example 2 had slightly weaker moisture resistance but was suitable for humid environments.

[0134] ③ Flexibility test (repeated bending test).

[0135] Test results: The tensile strength retention rate of the sample in Example 4 after 50 180° bends was 93.6±1.1%, with no cracks; the tensile strength retention rate of the control PP packing strap after 50 180° bends was 88.3±2.0%, with local micro-cracks.

[0136] Performance analysis: Examples 1 to 4 all showed better flexibility than PP tape. Example 2 showed the best flexibility; Example 4, due to the reduced content of aqueous SBR emulsion (21 parts, 1 part less than Example 3) and bio-based toughening agent (9 parts, 1 part less than Example 3), had slightly lower flexibility than Example 3 but higher flexibility than Example 1, with no bending or breakage.

[0137] ④ Surface abrasion resistance test.

[0138] Test results: The abrasion amount of the sample in Example 4 was 2.6±0.2mg / 1000 times, while the abrasion amount of the control PP packing strap was 4.8±0.5mg / 1000 times.

[0139] Performance Analysis: The wear resistance of Examples 1 to 4 was significantly better than that of PP belts (increased by 56.2%, 39.6%, 50.0%, and 45.8%, respectively). Example 1 showed the best wear resistance. Due to the reduced content of wear-resistant agent (1.8 parts, 0.2 parts less than Example 3) and bio-based nano titanium dioxide (0.9 parts, 0.2 parts less than Example 3) in Example 4, the wear resistance was slightly lower than that of Example 3 but higher than that of Example 2, and could meet the requirements for medium friction.

[0140] Final test conclusion: 1. Core Performance Compliance: The reinforced fiber-based packaging materials prepared in Examples 1-4 significantly outperform high-end heavy-duty PP plastic strapping in all four core indicators, forming a more refined performance gradient. Example 1 focuses on "balanced abrasion and moisture resistance," suitable for humid, high-friction conventional heavy-duty scenarios; Example 2 focuses on "high tensile strength + high flexibility," suitable for ultra-high load, high-frequency bending special heavy-duty scenarios; Example 3 is "all-around balanced performance," suitable for a wide range of conventional heavy-duty scenarios; Example 4 is "high moisture resistance with load-bearing capacity": all indicators are between those of Examples 1 and 3 (tensile strength increased by 33.1%, moisture retention rate 98.2%, abrasion resistance increased by 45.8%), focusing on strengthening the synergy between moisture resistance and load-bearing capacity, suitable for conventional heavy-duty scenarios with moderate friction in humid environments.

[0141] 2. Feasibility Analysis of Alternatives: All four embodiments possess the dual advantages of "high performance + high environmental protection," enabling comprehensive replacement of high-end heavy-duty packaging scenarios. Environmental aspect: All use bio-based / environmentally friendly components, with a bio-based content ≥90%, and are completely degradable, addressing the pollution issues of PP tape. Performance adaptation aspect: Embodiment 1 is suitable for humid, high-friction scenarios (outdoor heavy-duty packaging box bundling); Embodiment 2 is suitable for ultra-high load scenarios (packaging of large building components); Embodiment 3 is suitable for general, conventional scenarios (industrial finished product containerization); Embodiment 4 is suitable for humid, medium-friction scenarios (pallet containerization of goods in humid warehouses, short-distance outdoor packaging in rainy areas). The four embodiments work together to achieve precise matching for specific scenarios.

[0142] 3. Summary: Examples 1-4, through precise fine-tuning of the weight proportions of the formulation components, construct a diversified product matrix encompassing "wear-resistant and moisture-resistant, high tensile strength and high flexibility, balanced performance across all categories, and high moisture resistance with load-bearing capacity." All four types comprehensively surpass traditional PP plastic strapping in performance and possess significant environmental advantages. They can be flexibly selected according to the environmental conditions (humidity, friction intensity) and load requirements of different high-end heavy-duty strapping scenarios, achieving a comprehensive and seamless replacement of PP strapping in this field, with extremely broad application prospects. Example

[0143] The difference between this embodiment and Embodiment 3 is that the composite polymer reinforcing agent, by weight, comprises: 39 parts of waterborne bio-based polyurethane emulsion, 23.5 parts of waterborne styrene-butadiene rubber emulsion, 2.8 parts of nano-cellulose whiskers, 4.7 parts of bio-based crosslinking agent (citric acid), 1.4 parts of bio-based silane coupling agent (γ-aminopropyltriethoxysilane), 1.1 parts of nano-lignin, 1.7 parts of bio-based nano-calcium carbonate, 1.3 parts of waterborne bio-based wax emulsion (soybean wax emulsion), and 20 parts of deionized water; The functional surface layer is a modified biaxially oriented polylactic acid (BOPLA) film, which, by weight, comprises: 74 parts BOPLA resin, 11 parts bio-based toughening agent (polycaprolactone), 0.9 parts UV stabilizer (bio-based benzotriazole derivative), 2.3 parts abrasion resistant agent (nano silica), 3.3 parts bio-based antifouling agent (polyhydroxyalkanoate (PHA) grafted modified starch), and 1.3 parts bio-based nano titanium dioxide.

[0144] The reinforced fiber-based packaging material prepared in Example 5 was subjected to performance tests under the same conditions as in Example 3: ①Tensile strength test.

[0145] Test results: The tensile strength of the sample in Example 5 was 428±10 N / mm2, while the tensile strength of the control PP packing strap was 320±15 N / mm2.

[0146] Performance Analysis: The tensile strength of Examples 1 to 5 was significantly better than that of PP tape (increased by 28.1%, 35.9%, 31.9%, 33.1%, and 33.8%, respectively). Example 2 showed the best strength; Example 5, due to the increased content of bio-based crosslinking agent (4.7 parts, 0.2 parts more than Example 3), had a slightly higher strength than Example 3 but lower than Example 2, achieving a balance between load-bearing capacity and flexibility; Example 1 had slightly lower strength but met conventional requirements.

[0147] ② Moisture resistance test.

[0148] Test results: The tensile strength retention rate of the sample in Example 5 was 97.5±0.6%, while the tensile strength retention rate of the control PP packing strap was 95.5±1.2%.

[0149] Performance Analysis: Examples 1 to 5 all exhibited better moisture resistance than PP tape. Example 1 showed the best moisture resistance; Example 5, due to the reduced content of bio-based nano-calcium carbonate (1.7 parts, 0.3 parts less than Example 3), had slightly lower moisture resistance than Example 3 but higher than Example 2; Example 4 had moisture resistance close to Example 1, making it suitable for high humidity scenarios.

[0150] ③ Flexibility test (repeated bending test).

[0151] Test results: The tensile strength retention rate of the sample in Example 5 after 50 180° bends was 95.0±1.0%, with no cracks; the tensile strength retention rate of the control PP packing strap after 50 180° bends was 88.3±2.0%, with local micro-cracks.

[0152] Performance Analysis: Examples 1 to 5 all exhibited superior flexibility compared to PP tape. Example 2 showed the best flexibility. Example 5, due to the synergistic effect of aqueous SBR emulsion (23.5 parts, 1.5 parts more than Example 3), bio-based toughening agent (11 parts, 1 part more than Example 3), and soybean wax emulsion (1.3 parts, 0.2 parts more than Example 3), had flexibility close to that of Example 2 and superior to that of Example 3. Example 1 showed slightly weaker flexibility but no bending or breakage.

[0153] ④ Surface abrasion resistance test.

[0154] Test results: The abrasion amount of the sample in Example 5 was 2.2±0.2mg / 1000 times, while the abrasion amount of the control PP packing tape was 4.8±0.5mg / 1000 times.

[0155] Performance Analysis: The wear resistance of Examples 1 to 5 was significantly better than that of PP belts (increased by 56.2%, 39.6%, 50.0%, 45.8%, and 54.2%, respectively). Example 1 showed the best wear resistance; Example 5, due to the synergistic effect of the wear-resistant agent (2.3 parts, 0.3 parts more than Example 3) and bio-based nano titanium dioxide (1.3 parts, 0.2 parts more than Example 3), showed better wear resistance than Example 3 and was close to that of Example 1; Example 2 showed slightly weaker wear resistance but still met the requirements for moderate friction.

[0156] Final test conclusion: 1. Core Performance Compliance: The reinforced fiber-based packaging materials prepared in Examples 1-5 significantly outperform high-end heavy-duty PP plastic strapping in all four core indicators, forming a more comprehensive and refined differentiated performance gradient. Example 1 focuses on "balanced abrasion and moisture resistance," suitable for humid, high-friction conventional heavy-duty scenarios; Example 2 focuses on "high tensile strength and high flexibility," suitable for ultra-high load and high-frequency bending special heavy-duty scenarios; Example 3 is "balanced in all performance aspects," suitable for a wide range of conventional heavy-duty scenarios; Example 4 is "high moisture resistance with load-bearing capacity," suitable for moderate-friction conventional heavy-duty scenarios in humid environments; Example 5 is "high flexibility with abrasion resistance": all indicators are between those of Examples 2 and 3 (tensile strength increased by 33.8%, flexibility retention rate 95.0%, abrasion resistance increased by 54.2%), focusing on strengthening the synergy between flexibility and abrasion resistance, suitable for high-frequency bending and moderate-friction conventional heavy-duty scenarios.

[0157] 2. Feasibility Analysis of Alternatives: All five embodiments possess the dual advantages of "high performance + high environmental protection," enabling comprehensive and seamless replacement of high-end heavy-duty packaging scenarios. Environmental aspect: All use bio-based / environmentally friendly components, with a bio-based content ≥90%, and are completely degradable, thoroughly resolving the pollution issues associated with PP tape. Performance compatibility aspect: Embodiment 1 is suitable for outdoor humid and high-friction scenarios (outdoor heavy-duty packaging box bundling); Embodiment 2 is suitable for ultra-high load scenarios (packaging of large building components, fixing of heavy profiles); Embodiment 3 is suitable for general and conventional scenarios (industrial finished product containerization, general packaging box bundling); Embodiment 4 is suitable for humid warehouse scenarios (pallet containerization of goods in humid warehouses, short-distance outdoor packaging in rainy areas); Embodiment 5 is suitable for high-frequency bending scenarios (industrial semi-finished product turnover bundling, packaging of heavy goods requiring repeated wrapping). The five embodiments work together to achieve precise matching for specific scenarios.

[0158] 3. Summary: Examples 1-5, through precise fine-tuning of the weight proportions of the formulation components, construct a diversified product matrix encompassing "wear-resistant and moisture-resistant, high tensile strength and high flexibility, all-around balanced performance, high moisture resistance with load-bearing capacity, and high flexibility with wear resistance." All five types comprehensively surpass traditional PP plastic strapping in performance and possess significant environmental advantages. They can be flexibly selected according to the environmental conditions (humidity, friction intensity), load requirements, and operating conditions (bending frequency) of different high-end heavy-duty strapping scenarios, achieving a seamless replacement of PP strapping in all scenarios, with extremely broad application prospects. Example

[0159] The difference between this embodiment and Embodiment 3 is that the bio-based crosslinking agent is itaconic acid.

[0160] The reinforced fiber-based packaging material prepared in Example 6 was subjected to performance tests under the same conditions as in Example 3: ①Tensile strength test.

[0161] Test results: The tensile strength of the sample in Example 6 was 425±10 N / mm2, while the tensile strength of the control PP packing strap was 320±15 N / mm2.

[0162] Performance Analysis: The tensile strength of Example 6 is slightly better than that of Example 3 (increased by 0.7%), and 32.8% higher than that of PP tape. The core reason is that itaconic acid and citric acid are both bio-based crosslinking agents, but the double bonds in the itaconic acid molecule have higher activity, resulting in a more complete crosslinking reaction with waterborne polyurethane and SBR emulsions. The resulting three-dimensional network structure is more uniform and dense, thus slightly improving the load-bearing capacity.

[0163] ② Moisture resistance test.

[0164] Test results: The tensile strength retention rate of the sample in Example 6 was 98.0±0.5%, while the tensile strength retention rate of the control PP packing strap was 95.5±1.2%.

[0165] Performance Analysis: The moisture resistance of Example 6 is basically the same as that of Example 3, and both are superior to PP tape. Reason: The network structure formed by itaconic acid crosslinking has a stability comparable to that of citric acid, which can effectively block moisture penetration; combined with the hydrophobic protection of bio-based nano-calcium carbonate and anti-fouling agent, the performance degradation rate is extremely low in humid environments.

[0166] ③ Flexibility test (repeated bending test).

[0167] Test results: The tensile strength retention rate of the sample in Example 6 after 50 180° bends was 95.0±1.0%, with no cracks; the tensile strength retention rate of the control PP packing strap after 50 180° bends was 88.3±2.0%, with local micro-cracks.

[0168] Performance Analysis: Example 6 exhibits superior flexibility compared to Example 3. The core reason is that the molecular flexibility of itaconic acid crosslinks is superior to that of citric acid, resulting in better stress dispersion in the crosslinked network during bending. Combined with the lubricating effect of the SBR emulsion and soybean wax emulsion, the bending resistance is further enhanced.

[0169] ④ Surface abrasion resistance test.

[0170] Test results: The abrasion amount of the sample in Example 6 was 2.3±0.2mg / 1000 times, while the abrasion amount of the control PP packing strap was 4.8±0.5mg / 1000 times.

[0171] Performance Analysis: Example 6 exhibits slightly better abrasion resistance than Example 3, representing a 52.1% improvement over the PP belt. Reason: Itaconic acid crosslinking strengthens the interfacial bonding between the reinforcing impregnation layer and the core layer and functional surface layer, making it less prone to surface layer peeling or core layer fiber fuzzing during abrasion, resulting in better abrasion resistance and stability.

[0172] Final test conclusion: 1. Core Performance Compliance: The core performance of Example 6 (itaconic acid crosslinking) is basically the same as that of Example 3 (citric acid crosslinking), with a slight advantage in tensile strength and flexibility. All four indicators are significantly better than those of high-end heavy-duty PP strapping. Specifically, the tensile strength is increased by 32.8%, the moisture retention rate reaches 98.0%, the strength retention rate after bending is 95.0%, and the abrasion resistance is increased by 52.1%, fully meeting the usage requirements of high-end heavy-duty strapping scenarios.

[0173] 2. Feasibility Analysis of Alternatives: Both Example 6 and Example 3 possess the environmental advantages of high bio-based content (≥90%) and complete biodegradability, solving the pollution problems of PP tape. The difference lies in that Example 6 achieves a better balance of "strength + flexibility" through optimization of the type of crosslinking agent, making it more suitable for heavy-duty packaging scenarios that require frequent bending and wrapping (such as ring-shaped cargo bundling, irregular profile fixing, etc.), further enriching the product's scenario adaptability.

[0174] 3. Product Positioning: Example 6 is a crosslinking agent optimized product, which complements Example 1 (wear-resistant and moisture-resistant), Example 2 (high tensile strength and high flexibility), and Example 3 (all-performance balanced type), etc., and builds a diversified product matrix covering different working conditions. It can be flexibly selected according to the specific requirements of the packaging scenario, and realize the full-scenario replacement of high-end heavy-duty PP strapping. Example

[0175] The difference between this embodiment and Embodiment 3 is that the bio-based toughening agent is polyhydroxyalkanoate (PHA).

[0176] The reinforced fiber-based packaging material prepared in Example 7 was subjected to performance tests under the same test conditions as in Example 3: ①Tensile strength test.

[0177] Test results: The tensile strength of the sample in Example 7 was 420±10 N / mm2, while the tensile strength of the control PP packing strap was 320±15 N / mm2.

[0178] Performance Analysis: The tensile strength of Example 7 was basically the same as that of Example 3, but 31.2% higher than that of PP tape. The core reason is that both PHA and PCL are flexible chain bio-based toughening agents with similar effects on material rigidity; furthermore, PHA has good compatibility with BOPLA resin and waterborne polyurethane emulsion, without damaging the cross-linked network structure of the reinforcing impregnation layer, thus ensuring the material's load-bearing capacity.

[0179] ② Moisture resistance test.

[0180] Test results: The tensile strength retention rate of the sample in Example 7 was 98.1±0.5%, while the tensile strength retention rate of the control PP packing strap was 95.5±1.2%.

[0181] Performance Analysis: Example 7 showed slightly better moisture resistance than Example 3, and both were significantly better than PP tape. Reason: The hydrophobic properties of PHA molecular chains are slightly better than PCL, resulting in a tighter interfacial bond with the functional surface layer BOPLA resin, reducing moisture intrusion from the interface between the surface and core layers. Combined with the hydrophobic protection of bio-based nano-calcium carbonate, this further enhances performance stability in humid environments.

[0182] ③ Flexibility test (repeated bending test).

[0183] Test results: The tensile strength retention rate of the sample in Example 7 after 50 180° bends was 95.8±1.0%, with no cracks; the tensile strength retention rate of the control PP packing strap after 50 180° bends was 88.3±2.0%, with local micro-cracks.

[0184] Performance Analysis: Example 7 showed significantly better flexibility than Example 3. The core reason is that PHA has better molecular flexibility than PCL and higher compatibility with modified BOPLA films. During bending, it can effectively disperse the interfacial stress between the core and surface layers. Combined with the lubricating effect of soybean wax emulsion, this improves resistance to bending fatigue.

[0185] ④ Surface abrasion resistance test.

[0186] Test results: The abrasion amount of the sample in Example 7 was 2.3±0.2mg / 1000 times, while the abrasion amount of the control PP packing strap was 4.8±0.5mg / 1000 times.

[0187] Performance Analysis: The wear resistance of Example 7 is basically the same as that of Example 3, but 52.1% higher than that of PP belt. Reason: The PHA toughening agent does not change the dual nano-wear-resistant system of functional surface nano-silica and bio-based nano-titanium dioxide, and PHA optimizes the interfacial bonding force between the surface layer and the core layer, making it less prone to surface peeling during wear and ensuring wear resistance stability.

[0188] Final test conclusion: 1. Core Performance Compliance: The core performance of Example 7 (PHA toughening agent) is basically the same as that of Example 3 (PCL toughening agent), with a slight advantage in flexibility and moisture resistance. All four core indicators are significantly better than those of high-end heavy-duty PP strapping. Specifically, tensile strength is increased by 31.2%, moisture retention rate reaches 98.1%, strength retention rate after bending is 95.8%, and abrasion resistance is increased by 52.1%, fully meeting the requirements of high-end heavy-duty packaging scenarios.

[0189] 2. Feasibility Analysis of Alternatives: Both Example 7 and Example 3 possess the environmental advantages of high bio-based content (≥90%) and complete biodegradability, solving the environmental pollution problem of PP plastic strapping's difficulty in degradation. The difference lies in that Example 7, through optimization of toughening agent types, achieves a synergistic improvement in "flexibility + moisture resistance," making it more suitable for scenarios with stringent requirements for packaging material flexibility and environmental protection, such as food-grade heavy cargo strapping, medical waste turnover box packaging, and mother and baby product storage pallet containerization, further broadening the product's application boundaries.

[0190] 3. Product Positioning: Example 7 is a toughening agent-optimized product, complementing Examples 1 (wear-resistant and moisture-resistant), 2 (high tensile strength and high flexibility), 3 (balanced performance), and 6 (crosslinking agent optimized), thus constructing a diversified product matrix covering different environmental protection levels and working conditions. It allows for flexible selection based on the environmental standards, bending frequency, and humidity conditions of the packaging scenario, achieving a high degree of adaptability and full-scenario replacement for high-end heavy-duty PP strapping.

[0191] The reinforced fiber-based packaging material and its preparation method provided in this application, through the above technical solutions, have the following advantages: 1) Outstanding environmental benefits, solving the pain point of white pollution: The core raw material of the product is bio-based long fiber kraft paper (bio-based content ≥90%), combined with bio-based additives such as citric acid, itaconic acid, and polyhydroxyalkanoates (PHA). The functional surface layer uses a biodegradable modified BOPLA film, which is completely biodegradable, eliminating "white pollution" caused by plastic packing straps from the source. At the same time, the bio-based silane coupling agent is derived from corn cobs and the nano-lignin is derived from agricultural straw, realizing the high-value utilization of agricultural and forestry waste, which is in line with the requirements of "carbon neutrality" and circular economy development.

[0192] 2) Excellent core performance, meeting high-end heavy-duty packaging needs: The product performance surpasses traditional paper strapping and is superior to PP plastic strapping, specifically: The core layer adopts a 3-5 layer, 75-105° fiber orientation stacked design, combined with a nano-cellulose whisker-bio-based nano-calcium carbonate dual nano-reinforcement system to enhance tensile strength and solve the defects of insufficient tensile strength and easy breakage of traditional paper tapes; The hydrophobic properties of bio-based nano-calcium carbonate, combined with soybean wax emulsion and the dense protection of the functional surface layer, enhance moisture resistance and solve the problem of the sharp drop in strength after traditional paper tape absorbs moisture. The lubricating effect of water-based styrene-butadiene rubber latex, bio-based toughening agent (PCL / PHA) and soybean wax latex enhances the flexibility of the material and avoids the drawback of traditional paper tape brittleness. The functional surface layer features a dual-nano wear-resistant system of nano-silica and bio-based nano-titanium dioxide, which, combined with the densification effect of gradient pressure process, enhances surface wear resistance and is suitable for friction loss scenarios during packaging.

[0193] 3) The preparation process is stable and controllable, which is conducive to industrialization: By refining key process parameters (such as plasma pretreatment power and atmosphere, pulsed ultrasonic dispersion mode, gradient pressing temperature and pressure, and roll micro-concave-convex structure parameters), the repeatability and operability of the process are ensured, which can effectively control the performance fluctuation between product batches, reduce the technical threshold for industrial production, and facilitate large-scale promotion and application.

[0194] 4) High feasibility of substitution, broadening the application boundaries of biomass materials: The product meets the performance requirements of high-end and heavy-duty packaging scenarios, and is far more environmentally friendly than plastic strapping. It can directly replace PP and other plastic strapping and can be used in packaging box bundling, heavy-duty profile fixing, cargo palletizing and other fields, thus broadening the application scope of biomass materials in the industrial packaging field.

[0195] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A reinforced fiber-based packaging material, characterized in that, The main body is a layered composite structure, which includes a core layer, a reinforcing impregnation layer and a functional surface layer from the inside to the outside. The reinforcing impregnation layer penetrates and is cured inside the core layer and at the interface between the core layer and the functional surface layer. The functional surface layer is composited on at least one surface of the core layer. The core layer is composed of 3-5 layers of bio-based long fiber kraft paper, with the fiber orientation of adjacent two layers of bio-based long fiber kraft paper at an angle of 75-105 degrees and the fiber length being 3-5 mm. The reinforced impregnation layer is formed by curing a composite polymer reinforcing agent, which, by weight, comprises: 38-45 parts of waterborne bio-based polyurethane emulsion, 20-24 parts of waterborne styrene-butadiene rubber emulsion, 2.5-3.5 parts of nano-cellulose whiskers, 4-5 parts of bio-based crosslinking agent, 1.2-1.8 parts of bio-based silane coupling agent, 0.8-1.2 parts of nano-lignin, 1.5-2.5 parts of bio-based nano-calcium carbonate, 0.8-1.5 parts of waterborne bio-based wax emulsion, and 18-32 parts of deionized water; The functional surface layer is a modified biaxially oriented polylactic acid (BOPLA) film, which, by weight, comprises: 72-78 parts of BOPLA resin, 8-12 parts of bio-based toughening agent, 0.8-1.5 parts of UV stabilizer, 1.5-2.5 parts of abrasion resistant agent, 3-4 parts of bio-based antifouling agent, and 0.8-1.5 parts of bio-based nano-titanium dioxide.

2. The reinforced fiber-based packaging material according to claim 1, characterized in that, The bio-based long-fiber kraft paper is a whole-wood pulp bio-based paper with a bio-based content of ≥90%.

3. The reinforced fiber-based packaging material according to claim 1, characterized in that, The cellulose nanofibers have a diameter of 20-50 nm and a length of 200-500 nm; the bio-based crosslinking agent is one or more of citric acid and itaconic acid.

4. The reinforced fiber-based packaging material according to claim 1, characterized in that, The bio-based silane coupling agent is γ-aminopropyltriethoxysilane, prepared from biomass silicon extracted from corn cobs; the nano-lignin has a particle size of 50-100 nm, obtained by extraction from agricultural straw and ultrasonic modification; the bio-based nano-calcium carbonate has a particle size of 30-80 nm, modified with bio-based fatty acids; and the aqueous bio-based wax emulsion is soybean wax emulsion.

5. The reinforced fiber-based packaging material according to claim 1, characterized in that, The bio-based antifouling agent is polyhydroxyalkanoate (PHA) grafted modified starch; the bio-based toughening agent is one or more of polycaprolactone (PCL) and polyhydroxyalkanoate (PHA); the UV stabilizer is a bio-based benzotriazole derivative; the wear-resistant agent is nano-silica; the bio-based nano-titanium dioxide has a particle size of 20-50 nm and is surface modified with a silane coupling agent; the modified biaxially oriented polylactic acid (BOPLA) film has a thickness of 20-40 μm.

6. A method for preparing a reinforced fiber-based packaging material as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Bio-based long fiber kraft paper is subjected to plasma pretreatment and vacuum drying in sequence. The vacuum drying temperature is 60-80℃ and the drying time is 1-2h to obtain pretreated paper substrate. S2. Weigh each component according to the weight parts. First, disperse the nanocellulose whiskers, nanolignin, and bio-based nanocalcium carbonate in deionized water and ultrasonically disperse for 30-60 minutes. Then, add the water-based bio-based polyurethane emulsion, water-based styrene-butadiene rubber emulsion, and bio-based crosslinking agent. Next, add the water-based bio-based wax emulsion. Finally, add the bio-based silane coupling agent and stir and mix at 50-60℃ for 1-2 hours to obtain a composite polymer reinforcing agent emulsion with a solid content of 35-45%. S3. Stack 3-5 layers of pretreated paper substrate at a preset fiber orientation angle to form a primary strip blank. Feed the primary strip blank into an impregnation tank and impregnate it with a composite polymer reinforcing agent emulsion at 25-35℃ for 10-20 minutes. Then, use an extrusion roller to extrude the strip blank to control the glue content to 25-35% of the substrate weight to obtain the impregnated strip blank. S4. The impregnated strip blank is sent into a gradient drying tunnel for pre-drying. The drying tunnel is divided into three sections with temperatures of 60-70℃, 80-90℃, and 100-110℃ respectively. The drying time for each section is 1-1.5h. The moisture content of the strip blank after pre-drying is ≤8%, and the pre-dried strip blank is obtained. S5. Weigh and mix BOPLA resin, bio-based toughening agent, UV stabilizer, wear-resistant agent, bio-based anti-fouling agent, and bio-based nano-titanium dioxide in proportion by weight, and prepare modified biaxially oriented polylactic acid (BOPLA) film by melt extrusion and biaxial stretching; after plasma activation treatment of the film composite surface, laminate it to at least one surface of the pre-dried strip blank using a hot melt lamination process, with a lamination temperature of 140-160℃, a lamination pressure of 0.3-0.5MPa, and a lamination speed of 3-5m / min to obtain the laminated strip blank; S6. The composite strip is fed into a gradient pressure rolling mill and sequentially passes through the first stage (temperature 110-120℃, pressure 0.8-1.2MPa), the second stage (temperature 130-140℃, pressure 1.5-1.8MPa), and the third stage (temperature 140-150℃, pressure 1.8-2.0MPa) for gradient pressing. Each pressing stage lasts for 30-60 seconds, resulting in a shaped strip. S7. Cool the shaped strip to room temperature, then vacuum dry (temperature 50-60℃, time 0.5-1h) to remove residual moisture, and finally roll it up and cut it into rolls of the preset width to obtain reinforced fiber-based packaging material.

7. The method for preparing the reinforced fiber-based packaging material according to claim 6, characterized in that, In step S1, the parameters for plasma pretreatment of bio-based long fiber kraft paper are: plasma power 80-120W, treatment time 30-60s, and treatment atmosphere is argon.

8. The method for preparing the reinforced fiber-based packaging material according to claim 6, characterized in that, In step S2, a pulsed ultrasonic mode is used during the ultrasonic dispersion process, with a pulse frequency of 20-40kHz and a pulse duty cycle of 30-50%.

9. The method for preparing the reinforced fiber-based packaging material according to claim 6, characterized in that, In step S5, the plasma activation parameters for the modified BOPLA thin film composite surface are: power 100-150W, and processing time 40-60s.

10. The method for preparing the reinforced fiber-based packaging material according to claim 6, characterized in that, In step S6, the roll surface of the gradient pressure rolling mill is provided with a micro-uneven structure with an unevenness depth of 2-5μm.