Environment-friendly paper fiber cushion packaging material and preparation method thereof

Abstract

The invention discloses an environment-friendly paper fiber cushion packaging material and a preparation method thereof, and belongs to the technical field of biomass conversion materials. According to the material, plant fiber paper pulp, reinforced fibers and an environment-friendly adhesive serve as main raw materials, a papermaking wet-end process and a physical foaming shaping process are deeply fused, pressurized dissolved gas serves as a pore-forming template, blowing is conducted in a fiber network, locking is conducted through synchronous gel of the adhesive, and a three-dimensional porous cavity structure which is communicated with one another is formed. The preparation method takes water as a medium, and the process is green. The obtained material is light in weight, excellent in buffering performance and capable of being completely biodegraded and recycled, perfectly replaces traditional polystyrene foam, can flexibly achieve the functions of hydrophobicity, flame retardance and the like by adding auxiliaries, and is widely applied to the fields of packaging of electronic products and fragile products, cold-chain logistics and the like.

Description

Technical Field

[0001] This invention relates to the field of biomass conversion materials technology, and in particular to cushioning packaging materials made from plant fiber pulp and their preparation methods. Background Technology

[0002] Currently, foamed plastics (such as polystyrene and polyethylene) made from petroleum-based raw materials are widely used in packaging, filling, and cushioning. While these materials are lightweight and have good cushioning properties, they pose serious environmental problems, including being non-degradable, difficult to recycle, producing toxic gases when incinerated, and causing severe white pollution. Developing degradable and recyclable green alternatives is urgently needed.

[0003] Existing technologies also include some pulp molding products, but these are typically formed through vacuum adsorption, resulting in a dense structure, poor softness and resilience, and high energy consumption and long production cycles, making it difficult to compete with traditional polystyrene in terms of cushioning performance and cost. Therefore, the market urgently needs a new material that combines excellent cushioning performance, is completely environmentally friendly, and has controllable costs. Summary of the Invention

[0004] This invention discloses an environmentally friendly paper fiber cushioning packaging material and its preparation method. The material uses plant fiber pulp, reinforcing fibers, and environmentally friendly adhesives as main raw materials. By deeply integrating the wet-end papermaking process with a physical foaming and setting process, it innovatively utilizes pressurized dissolved gas as a pore-forming template to "blow" the material within a fiber network and simultaneously "lock" it in place using the adhesive through gelation, forming an interconnected three-dimensional porous chamber structure. This preparation method uses water as a medium and is environmentally friendly. The resulting material is lightweight, has excellent cushioning performance, is completely biodegradable and recyclable, perfectly replacing traditional polystyrene foam. Furthermore, by adding additives, it can flexibly achieve hydrophobic and flame-retardant functions, making it widely applicable in fields such as electronic products, fragile item packaging, and cold chain logistics. Specific details are as follows: An environmentally friendly paper fiber cushioning packaging material, the raw materials of which include plant fiber pulp, reinforcing fibers and environmentally friendly adhesives, and the material has an internal three-dimensional porous chamber structure formed by physical foaming and fiber cross-linking curing.

[0005] Furthermore, by weight, it includes 50-90 parts plant fiber pulp, 5-30 parts reinforcing fiber, and 5-20 parts environmentally friendly adhesive.

[0006] Furthermore, by weight, it includes 70 parts plant fiber pulp, 18 parts reinforcing fiber, and 13 parts environmentally friendly adhesive.

[0007] Furthermore, the plant fiber pulp is selected from one or more of waste corrugated pulp, sugarcane pulp, and bamboo pulp; the reinforcing fiber is selected from one or more of softwood pulp, hemp fiber, and modified starch fiber; and the environmentally friendly adhesive is selected from one or more of water-based acrylate, starch glue, polyvinyl alcohol, and chitosan.

[0008] Furthermore, the raw material also contains 0.5-5 parts by weight of functional additives, including one or more of hydrophobic agents, flame retardants, and antibacterial agents.

[0009] Furthermore, the raw materials also include polycaprolactone-polylactic acid block copolymer microspheres, castor oil-based waterborne polyurethane dispersions, citric acid crosslinking agents, waterborne acrylate adhesives, glyceryl monostearate, AKD hydrophobic agents, and halogen-free phosphorus-nitrogen flame retardants.

[0010] A method for preparing an environmentally friendly paper fiber cushioning packaging material includes the following steps: S1. The plant fiber pulp is dissolved in water to form primary pulp; S2. Add reinforcing fibers, environmentally friendly adhesives and functional additives to the primary slurry, mix evenly to obtain a homogeneous mixed slurry; S3. Pressurize and shear the homogeneous mixed slurry while introducing gas to form a fiber-gas mixed slurry; S4. Release the fiber-gas mixture slurry into an atmospheric pressure environment, causing the gas in it to expand and simultaneously causing the fibers to cross-link and gel under the action of the adhesive, forming a wet preform with a three-dimensional porous structure. S5. The wet preform is dried to obtain an environmentally friendly paper fiber cushioning packaging material.

[0011] Furthermore, in step S3, the pressurization pressure range is 0.2-0.8 MPa, and the shearing speed is not less than 2000 rpm; the gas is air, carbon dioxide, or nitrogen.

[0012] Furthermore, the drying process described in step S5 is one of hot air drying, microwave drying, or vacuum drying.

[0013] Furthermore, between steps S1 and S2, there is an elastomer pre-activation step for preparing an "activated elastomer premix", and after step S5, there is a hot-press curing step.

[0014] Compared with the prior art, the present invention has at least one of the following technical effects: 1) This invention solves the core environmental problems of petroleum-based expanded polystyrene (EPS) foams in the background technology, namely, their non-degradability, difficulty in recycling, generation of toxic gases upon incineration, and serious white pollution. On the raw material side, this invention uses renewable plant fibers such as waste corrugated paper pulp, sugarcane pulp, and bamboo pulp as the main framework, and environmentally friendly adhesives such as starch glue, chitosan, and water-based acrylates as binding media, achieving a completely biomass-based and renewable raw material. On the product side, the resulting material, after use and disposal, can be completely biodegraded like paper (the 90-day soil degradation rate in Examples 1-4 is all >60%), or can be easily recycled and re-pulped, forming a closed loop of "resource-product-recycled resource," fundamentally breaking away from the petroleum-based system, and is an ideal green solution to replace traditional polystyrene foam.

[0015] 2) This invention overcomes the technical bottleneck of existing pulp molding products, which are characterized by "dense structure, poor softness, and poor resilience," as mentioned in the background section. Through the deep integration of a unique "wet-end papermaking process" and a "physical foaming and setting process," dissolved gas under pressure is used as a "pore-forming template" to "blow" an interconnected three-dimensional porous chamber structure (average porosity >90%) within the fiber network. This structure is similar to the foam structure of EPS, efficiently absorbing and dissipating energy through the bending, deformation, and rupture of the pore walls when impacted. As shown in Example 1, its dynamic buffering coefficient (3.8) and energy absorption efficiency (82%) have fully reached and surpassed the level of ordinary EPS foam, while its density (0.048 g / cm³) is comparable. Therefore, it effectively replaces traditional polystyrene in terms of core buffering performance, solving the problem of insufficient buffering performance of paper-based materials.

[0016] 3) This invention abandons two high-cost approaches in traditional plastic foaming: "thermal decomposition of chemical foaming agents" (requiring high temperatures and leaving residues) and "vacuum dehydration and densification" in pulp molding (high energy consumption and long cycle). In terms of process, water is used as the medium, relying mainly on physical foaming (gas pressurization-release) and room / medium temperature curing of the adhesive. The entire process emits no toxic or harmful substances, and energy consumption is significantly lower than the two traditional processes mentioned above. Regarding raw materials, the core material uses low-cost waste materials such as waste corrugated paper, which are widely available and inexpensive. As shown in Example 3, even using up to 90% waste paper pulp, compliant products can still be produced through process adjustments. This combination of "green process + low-cost raw materials" makes the material of this invention highly competitive in terms of overall cost, laying a solid economic foundation for large-scale replacement of petroleum-based foam.

[0017] 4) This invention, by introducing functional additives during the homogenization mixing stage, easily achieves functional upgrades of materials, overcoming the drawbacks of traditional materials having only one function. For example, adding AKD hydrophobic agent can increase the material's surface contact angle to greater than 110° (reaching 125° in Example 4), meeting the moisture-proof requirements of cold chain logistics packaging; adding halogen-free phosphorus-nitrogen flame retardants can easily achieve UL94 V-0 rating (Examples 2 and 4), meeting the mandatory safety standards for electronic product packaging; adding nano-silver or chitosan can impart antibacterial properties to the material. This design concept of "basic cushioning performance + modular functional addition" allows the same technology platform to generate specialized materials applicable to different fields such as electronic products, fragile items, cold chain logistics, and even building sound and heat insulation, expanding the scope of market applications.

[0018] 5) This invention is not limited to basic replacement; Example 4, a further development, demonstrates a path to performance improvement through material system innovation. By introducing a PCL-PLA / castor oil-based PU bio-based elastomer to construct a "double interpenetrating network" and employing "elastomer pre-activation" and "post-hot pressing curing" processes, significant breakthroughs were achieved in key material properties while retaining the fully biodegradable characteristics: resilience increased to 88%, permanent deformation rate reduced to 6.3% after 100 compressions, and strength retention rate as high as 95% after damp heat aging. These indicators not only surpass the baseline performance of Example 1 but also outperform many traditional petroleum-based foams. This signifies that the material of this invention has been upgraded from an "environmentally friendly alternative" to a "high-performance solution," capable of meeting the requirements of high-end reusable scenarios with high durability and reliability. Detailed Implementation

[0019] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0020] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0021] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0022] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if detected [the described condition or event]" may be interpreted, depending on the context, as meaning "once determined," "in response to determination," "once detected [the described condition or event]," or "in response to detection [the described condition or event]."

[0023] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0024] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0025] This invention relates to the sources of all substances: all key components of this invention are commercially available products with clearly defined molecular chemical formulas and / or CAS identifiers, obtained through commercial sales. The main substances include: waste corrugated paper pulp, bamboo pulp, and softwood pulp, all common natural mixtures, primarily with the molecular formula (C6H). 10 O5) n Cellulose with CAS number 9004-34-6; water-based acrylic adhesives, with the general formula [-(CH2-CH(COOR))-]. n The water-based acrylic adhesive is an acrylic copolymer emulsion, whose common monomers include butyl acrylate (CAS 141-32-2), ethyl acrylate (CAS 140-88-5), methyl methacrylate (CAS 80-62-6), etc.; polycaprolactone-polylactic acid block copolymer microspheres (PCL-PLA) have the molecular formula (C6H 10 O2) x -(C3H4O2) γ CAS No. 9051-89-2; Castor oil-based aqueous polyurethane dispersion (C-PU), CAS No. 9048-90-4; Starch gum / oxidized starch, molecular formula (C6H 10 O5) nCAS No. 65996-63-6; Chitosan / Chitosan Quaternary Ammonium Salt, Molecular Formula is (C6H 11 NO4) n / (C6H 11 NO4·HCl) n CAS No. 9012-76-4 (Chitosan) / CAS No. 70694-72-3 (Chitosan Quaternary Ammonium Salt, HACCP); Citric acid is a common substance; Glyceryl monostearate (GMS), molecular formula C 21 H 42 O4, CAS No. 31566-31-1; AKD hydrophobic agent, molecular formula C 28 H 54 O2, CAS No. 6386-73-8; Halogen-free phosphorus and nitrogen flame retardant, CAS No. 68333-79-9; Nano silver ion antibacterial agent, CAS No. 7440-22-4; Fumed silica, CAS No. 7631-86-9; Phytic acid, molecular formula C6H 18 O 24 P6, CAS No. 83-86-3.

[0026] The concept of this invention is as follows: it mimics the structural formation principle of lightweight porous materials (such as wood and sponge) in nature, but adopts a completely green and low-cost process. Specifically, it abandons the two traditional paths of "chemical foaming agent thermal decomposition" in plastic foaming and "vacuum dehydration and densification" in pulp molding, and innovatively integrates "wet-end papermaking process" and "physical foaming and shaping process". Aquatic plant fiber suspension is used as "construction slurry", gelatable environmentally friendly adhesive is used as "quick-drying cement", and gas released after pressurization and dissolution is used as "pore-forming template". By precisely controlling the dynamics of gas release (foaming) and adhesive gelation (curing), the two processes occur simultaneously, mutually restricting and promoting each other, thereby "blowing" and "locking" a stable three-dimensional porous network structure within the fiber network.

[0027] Example 1

[0028] An environmentally friendly paper fiber cushioning packaging material, by weight, comprises 70 parts waste corrugated pulp, 18 parts softwood pulp, 13 parts water-based acrylic adhesive, 1 part AKD hydrophobic agent, and 2 parts halogen-free phosphorus-nitrogen flame retardant.

[0029] The preparation method of the above-mentioned environmentally friendly paper fiber cushioning packaging material includes the following steps: S1. According to the formula, put the waste corrugated paper pulp into a high-consistency pulper, add enough water, and control the pulp concentration at 2%. Start the machine at 45℃ and run it for 30 minutes until the fiber bundles in the pulp are completely dispersed, forming a uniform suspension mainly composed of single fibers or fine fiber bundles, i.e., "primary pulp".

[0030] The purpose of this step is to dissociate the fibers. Through mechanical shearing force and the lubrication of water, the hydrogen bonds between the fibers in the raw material are broken, allowing them to be fully "dissociated" and exposing a large specific surface area and active groups such as hydroxyl groups. This is the foundation for the fibers to uniformly load air bubbles and effectively bond with the binder. If the fibers are not fully dissociated, it will lead to uneven slurry, unstable foaming, and poor strength of the finished product.

[0031] S2. While the primary pulp obtained in step S1 is still being stirred, add the predetermined weight parts of softwood pulp, water-based acrylic binder, AKD hydrophobic agent and halogen-free phosphorus-nitrogen flame retardant in sequence, and continue mixing in the high-consistency pulper for 40 minutes to ensure that all components are evenly distributed and form a "homogeneous mixed pulp".

[0032] This step achieves the functional compounding of raw materials. Reinforcing fibers (typically longer and stronger) are interwoven with base plant fibers, forming a skeleton to enhance the mechanical properties of the final material. Adhesives are uniformly coated or attached to the fiber surface, and their molecular chains' active groups (such as hydroxyl and carboxyl groups) are prepared to bond with the fibers. Functional additives are then uniformly introduced into the system, imparting additional properties to the material. Uniform mixing is a prerequisite for obtaining a product with stable performance.

[0033] S3. The homogenized slurry is transferred to a pressurized, sealed container (foaming kettle) equipped with a high-speed shear head. After sealing the container, nitrogen gas is first introduced to raise the pressure inside the container to 0.5 MPa. Subsequently, the high-speed shearing device is started, and the slurry is sheared at a speed of 3000 rpm for 5 minutes while maintaining the pressure. At this point, the slurry transforms into a paste-like "fiber-gas mixture" filled with microbubbles.

[0034] Gas Dissolution and Dispersion: Under pressure, more gas is forced to dissolve in the slurry water. High-speed shearing generates strong turbulence and cavitation effects, "tearing" the introduced macroscopic bubbles into microbubbles ranging from tens to hundreds of micrometers in size. Fiber-Loaded Bubbles: The disintegrated fiber surface has a rough microstructure, while the binder in the slurry has a certain viscosity. Under the hydrodynamic action generated by high-speed shearing, these microbubbles are mechanically "captured" and stabilized on the fiber surface or at the intersections of the fiber network, forming a temporary stable system with fibers as the "skeleton" and bubbles as the "filler." Maintaining pressure is to prevent premature bubble expansion at this point.

[0035] S4. Quickly open the valve at the bottom of the foaming reactor or spray the "fiber-gas mixture slurry" onto a molding die at atmospheric pressure through a pipe. The release process must be completed rapidly. After the slurry has been left to stand at atmospheric pressure for 1 minute, you can observe its rapid expansion and solidification, forming a "wet preform" with a fixed shape and a clear porous structure.

[0036] This step is the "magic moment" of structure formation, which includes two core processes that occur simultaneously: 1) Physical foaming (bubble expansion): According to Henry's Law and Boyle's Law, a sudden drop in pressure causes the dissolved gas in the slurry to become supersaturated and precipitate out. At the same time, the existing microbubbles expand rapidly due to the imbalance of internal and external pressure. The force generated by the expansion of the bubbles pushes the surrounding fiber network apart.

[0037] 2) Fiber crosslinking and curing (skeleton fixation): As the bubbles expand, the water in the slurry begins to partially evaporate or migrate, increasing the system concentration. This triggers the curing mechanism of the adhesive: after the water in the waterborne acrylate evaporates or migrates, the polymer latex particles coalesce, forming a continuous polymer film that bonds the fibers together.

[0038] These two processes work synergistically: the expanding bubbles "expand" and "shape" the spatial structure of the porous chambers, while the simultaneously curing adhesive "welds" at the fiber intersections, instantly fixing this expanded three-dimensional network, thus forming an "interconnected three-dimensional porous chamber structure." This interconnectivity stems from the merging of bubbles during expansion and the continuity of the fiber network.

[0039] The porous structure of the material is the result of a dynamic balance between the "bubble expansion force" (physical driving force) and the "adhesive gelation force" (chemical binding force). After the water evaporates, the water-based acrylic latex particles deform and fuse to form a film, which is a physical film-forming process that encapsulates and bonds the fibers.

[0040] At the moment of pressure release, if only air bubbles expand while the adhesive does not cure, the bubbles will merge and escape, eventually collapsing into a dense layer (like traditional foam but without a stable framework). If only the adhesive cures without air bubble expansion, a dense cardboard is obtained. This invention, through the control of formulation (adhesive type, concentration) and process (pressure, shear, pressure release rate), ensures that when the bubbles begin to expand, the adhesive just enters the critical state of rapid gelation, thereby fixing the "blown" fiber network with "glue" to form a permanent porous structure.

[0041] S5. Transfer the wet preform into the drying equipment. Hot air drying can be used, drying in an oven at 120℃ for 6 hours. After drying until the material moisture content is below 10% (by weight), remove it from the mold to obtain the final product.

[0042] The purpose of this step is to remove residual moisture and achieve final shaping. By removing free water and some bound water from the system, the bonding force between the adhesive and the fiber (such as hydrogen bonds) is further strengthened, allowing the porous structure to completely solidify and achieving the final mechanical strength, dimensional stability, and lightweight properties.

[0043] The raw materials for this invention are derived from renewable biomass. The product is biodegradable after use (due to microbial action on fibers and adhesives) or easily recycled and re-pulped, completely eliminating petroleum-based systems and eradicating "white pollution." Under pressure, the porous structure dissipates impact energy through pore wall bending, deformation, and rupture, with a buffering mechanism similar to EPS, thus achieving comparable performance. This differs from the dense, solid structure of traditional pulp molding. It solves the problems of density and poor buffering in traditional pulp molding. The core raw material is waste, with low value. The physical foaming process itself has low energy consumption. The process steps are simple, easy to implement in continuous production, and the overall cost is controllable. Traditional alternatives, on the other hand, are costly and energy-intensive. Additives are uniformly dispersed in the fiber-adhesive system before foaming and finalization, and ultimately fixed on the surface of the porous structure's framework, thus giving the material permanent or durable additional functions, meeting diverse needs such as cold chain (hydrophobicity) and electronic products (flame retardancy). Traditional alternatives have limited functionality.

[0044] A packaging article, made of the environmentally friendly paper fiber cushioning packaging material of this embodiment, includes cushioning pads, corner protectors, filler granules, or molded packaging trays (depending on the mold). This environmentally friendly paper fiber cushioning packaging material can also be used in electronic product packaging, fragile item packaging, cold chain logistics, or building sound and heat insulation.

[0045] Example 2

[0046] An environmentally friendly paper fiber cushioning packaging material, by weight, comprises 50 parts waste corrugated paper pulp, 30 parts softwood pulp, 5 parts water-based acrylic adhesive, 2 parts AKD hydrophobic agent, and 3 parts halogen-free phosphorus-nitrogen flame retardant.

[0047] Formulation characteristics: High softwood pulp content (30 parts), low binder content (5 parts). The formulation tends to build a strong fiber skeleton, but the adhesive network is weak.

[0048] The difference from the preparation method in Example 1 is that: S1 Debonding Step: Due to the high proportion of softwood pulp, its fibers are longer and more difficult to debond. The debonding time needs to be extended to 40 minutes, and the pulping concentration appropriately increased to 2.5% to provide stronger mechanical friction, ensuring sufficient dissociation of long fibers and laying the foundation for a uniform network. Insufficient debonding can lead to fiber agglomeration and uneven structure.

[0049] S3 Foaming and Shearing Steps: Due to the low binder content, the slurry system has a low viscosity and poor bubble stability. The foaming gas pressure needs to be reduced to 0.4 MPa, and the high-speed shearing time extended to 7 minutes. Lower pressure helps generate more uniformly sized bubbles with slightly thicker walls, counteracting the tendency to coalesce due to insufficient adhesion; longer shearing time ensures that the gas is dispersed in a finer, more stable form and effectively captured by the fibers.

[0050] S4 gel setting steps: Less adhesive, slower curing speed, and fewer bond points. The settling time after depressurization needs to be reduced to 2 minutes. A longer setting time allows the water-based acrylic latex particles more time to coalesce into a film, compensating for the insufficient total amount of adhesive and ensuring that the expanded fiber network can be effectively "welded" and fixed, preventing structural collapse.

[0051] S5 Drying Procedure: To avoid cracking of the not-yet-fully-cured adhesive film due to rapid drying, a gentler drying profile is required: first, dry at 100°C for 1 hour for initial setting, then increase to 120°C for complete drying. This helps to form a stronger bond with a smaller amount of adhesive.

[0052] A packaging article, made of the environmentally friendly paper fiber cushioning packaging material of this embodiment, includes cushioning pads, corner protectors, filler granules, or molded packaging trays (depending on the mold). This environmentally friendly paper fiber cushioning packaging material can also be used in electronic product packaging, fragile item packaging, cold chain logistics, or building sound and heat insulation.

[0053] Example 3

[0054] An environmentally friendly paper fiber cushioning packaging material, by weight, comprises 90 parts waste corrugated pulp, 5 parts softwood pulp, 20 parts water-based acrylic adhesive, 0.2 parts AKD hydrophobic agent, and 0.3 parts halogen-free phosphorus-nitrogen flame retardant.

[0055] The formula contains an extremely high amount of waste corrugated paper pulp (90 parts), very little softwood pulp (5 parts), and a high amount of adhesive (20 parts). The fibers are short, there are many impurities, and the skeleton is weak, but the binding material is abundant.

[0056] The difference from the preparation method in Example 1 is that: S1 Beating Step: Waste corrugated paper pulp has a high content, with short fibers and potential impurities. The beating time should be controlled within 25 minutes to avoid over-beating, which would cause excessive fiber breakage and loss of strength. Additionally, a screening or purification step can be added after beating to remove some impurities and ensure pulp cleanliness.

[0057] S2 Mixing Step: Due to the high binder content, in order to avoid premature thickening of the slurry and affecting subsequent foaming, it should be immediately transferred to the next process after being mixed evenly, and should not be left to stand for a long time.

[0058] S3 Foaming and Shearing Steps: Due to the high viscosity of the slurry caused by the large number of short fibers and binders, gas dispersion is difficult. Therefore, the foaming pressure needs to be increased to 0.6 MPa, and the high-speed shearing speed increased to 3500 rpm. Higher pressure and shear force help overcome the resistance of the high-viscosity slurry, forcibly dispersing the gas into tiny bubbles and compelling them into the dense fiber-binder matrix.

[0059] S4 gel setting process: High adhesive content results in significant curing shrinkage stress, which can easily lead to cracking or uneven pore structure. After pressure release, no additional settling is required, or only 30 seconds is needed before quickly proceeding to the drying process. Utilizing the adhesive's rapid film-forming properties, the structure is quickly locked in, reducing the duration of shrinkage stress.

[0060] S5 Drying Steps: High binder content means more moisture needs to be removed, and the drying process is prone to significant shrinkage. A phased gradient drying method is required: first, dry at a low temperature of 80°C with a high air volume for 2 hours to remove most of the free water and initially stabilize the structure; then dry at 100°C to the final stage.

[0061] A packaging article, made of the environmentally friendly paper fiber cushioning packaging material of this embodiment, includes cushioning pads, corner protectors, filler granules, or molded packaging trays (depending on the mold). This environmentally friendly paper fiber cushioning packaging material can also be used in electronic product packaging, fragile item packaging, cold chain logistics, or building sound and heat insulation.

[0062] Example 4

[0063] Based on the original Example 1's "physical foaming + fiber crosslinking," biodegradable biomass-based elastomer microspheres are introduced. Through a "temperature-induced phase separation-expansion curing" process, a second elastic network is constructed within the original porous structure, forming a unique interpenetrating structure of a "rigid cellulose skeleton" and an "elastomer soft network." The first network is a physically crosslinked cellulose network (providing rigid support), and the second network is a chemically crosslinked thermoplastic elastomer network (providing elastic recovery). The elastomer microspheres undergo a phase transition at a specific temperature, expanding and foaming synchronously with the cellulose network but at different mechanisms. The elastomer network preferentially undergoes reversible deformation during compression, protecting the cellulose network from plastic damage. The introduction of the second biomass-based elastomer network further improves the resilience of Example 1.

[0064] An environmentally friendly paper fiber cushioning packaging material, by weight, comprises 70 parts waste corrugated pulp, 18 parts softwood pulp, 5 parts polycaprolactone-polylactic acid block copolymer microspheres (PCL-PLA), 3 parts castor oil-based waterborne polyurethane dispersion (C-PU), 1 part citric acid crosslinking agent, 13 parts waterborne acrylate adhesive, 0.5 parts glyceryl monostearate (GMS), 1 part AKD hydrophobic agent, and 2 parts halogen-free phosphorus-nitrogen flame retardant.

[0065] The preparation method of the above-mentioned environmentally friendly paper fiber cushioning packaging material includes the following steps: S1. According to the formula, put the waste corrugated paper pulp into a high-consistency pulper, add enough water, control the pulp concentration at 2%, start the machine at 45℃ and run for 30 minutes to decompose and form pulp; according to the formula, pre-decompose the softwood pulp separately in another container at a concentration of 1.5% for 15 minutes, combine the two, and continue to stir at low speed for 10 minutes to form "primary pulp".

[0066] This step processes softwood pulp (long fibers) and waste corrugated pulp (short fibers) separately to avoid excessive cutting of long fibers. 45°C warm water softens hemicellulose and residual lignin in the fibers, increasing fiber flexibility. Mechanical shearing force breaks the hydrogen bonds (OH···O) between fibers, increasing the specific surface area from about 1m² / g to 15-20m² / g and exposing more hydroxyl (-OH) active sites. 32°SR ensures that the fibers are properly bristled, which not only ensures that the bubbles can adhere stably during subsequent foaming, but also avoids strength loss due to over-beating.

[0067] S2. Elastomer Pre-activation. In a stirred tank with heating function, add the following components in the following order by weight: 12.5 parts of polycaprolactone-polylactic acid block copolymer microsphere dispersion, 8.57 parts of castor oil-based PU dispersion, 0.5 parts of glyceryl monostearate, 1 part of citric acid, and 20 parts of deionized water. Start stirring (200 rpm) and heat to 65°C. Maintain a constant temperature of 65°C and stir for 30 minutes. Cool down to 40°C for later use to obtain the "activated elastomer premix".

[0068] At 65℃, which is close to the glass transition temperature (Tg≈60℃) of polycaprolactone-polylactic acid block copolymer microspheres (PCL-PLA), the polymer chain mobility on the surface of the microspheres is enhanced, the surface energy is reduced, and they are more easily bound to fibers. GMS, as an amphiphilic molecule, binds to fibers through its hydrophilic end (-OH) and its hydrophobic end (C)... 17 H 35 -) Insertion of elastomer microspheres to form "molecular bridges": GMS mechanism of action: cellulose -OH+HO-CH2-CH(OH)-CH2-O-CO-C 17 H 35 → Hydrogen bonding and; PCL-PLA microspheres + C 17 H 35 - (alkyl chain) → van der Waals forces / hydrophobic interactions.

[0069] Crosslinking agent pre-dispersion: Citric acid is uniformly dispersed in the elastomer system to avoid excessive local acidity that could damage the fibers when added directly to the slurry later. PU and PCL-PLA pre-compatibility: The soft segments (polyester) in castor oil-based PU have good compatibility with PCL-PLA, and pre-mixing can form a more uniform elastic phase.

[0070] The polycaprolactone-polylactic acid block copolymer (PCL-PLA) used in this invention is a bio-based thermoplastic elastomer with a preferred number-average molecular weight (Mn) of 50,000-100,000 g / mol, wherein the mass ratio of PCL to PLA segments is preferably between 70 / 30 and 30 / 70, and the glass transition temperature (Tg) is 55-65°C. The PCL-PLA is available as a commercially available product (e.g., TotalEnergies Corbion's Luminy® PLA-PCL series). By weight percentage, the polycaprolactone-polylactic acid block copolymer microsphere dispersion comprises 40% polycaprolactone-polylactic acid block copolymer (PCL-PLA), which is the active dry matter and the effective ingredient; 58% deionized water as the dispersion medium; 1% surfactant polyoxyethylene sorbitan monooleate, which reduces the interfacial tension between the polymer and water, helping to form and stabilize microspheres; 0.8% sodium dodecyl sulfate, which provides electrostatic stabilization, giving the microsphere surface a negative charge and preventing aggregation through charge repulsion; and 0.2% ammonia, which stabilizes the pH of the system within a weakly alkaline range of 7-9, ensuring the stability of the dispersion during storage. This is a typical "polymer-in-water" emulsion. Through high-speed shearing and the action of the emulsifier, the hydrophobic PCL-PLA polymer is dispersed into micron-sized (1-5 μm) spherical particles. The hydrophilic ends of the surfactant molecules face the aqueous phase, while the hydrophobic ends are anchored on the surface of the polymer microspheres, forming a protective film and imparting a charge. Long-term kinetic stability is achieved through electrostatic repulsion and steric hindrance.

[0071] The castor oil-based aqueous polyurethane dispersion (C-PU) has a solid content of 30-40% and a preferred hydroxyl value of 30-60 mgKOH / g, purchased from BASF's Sovermol® 800 series. By weight, the castor oil-based PU dispersion comprises 35% castor oil-based aqueous polyurethane dispersion (C-PU), which is the active dry matter and effective component; 62% deionized water as the dispersion medium; and 1.5% dimethylolpropionic acid (DMPA, CAS 4767-03-7), the most commonly used internal emulsifier in aqueous PU. During PU polymerization, the carboxyl groups (-COOH) of DMPA are introduced into the polymer backbone. After salt formation (-COO... - N + (CH 2 CH 3 ) 3The DMPA emulsion forms a hydrophilic layer on the surface of PU particles, achieving self-emulsification, which is key to its differentiation from PCL-PLA emulsions (which contain external emulsifiers). Triethylamine, a neutralizing agent, neutralizes the carboxyl groups on DMPA, forming a salt that imparts hydrophilicity to the polymer chains. 1% N-methylpyrrolidone (NMP, CAS872-50-4), a film-forming aid, helps dissolve reactants during polymerization and promotes the aggregation of PU particles into a continuous, dense film during drying. 0.5% polyurethane associative thickener provides shear-thinning rheological properties, facilitating application and storage. Castor oil-based PU dispersion is a self-emulsifying aqueous dispersion. Its stabilization mechanism differs from physically emulsified PCL-PLA. Hydrophilic groups (-COO⁻) are chemically bonded to the PU molecular chains. These hydrophilic groups are oriented at the particle-water interface, allowing the PU polymer itself to be stably dispersed in water, forming nanoscale (typically 50-200 nm) dispersed particles. This structure gives it better storage stability, higher bond strength, and superior water resistance (because the emulsifier is chemically bonded and does not easily migrate).

[0072] S3. Multiphase homogeneous mixing. While maintaining low-speed stirring (50 rpm) on the primary slurry from step S1, slowly add the following in sequence: 13 parts of water-based acrylic adhesive (diluted with 5 parts of water before addition), the activated elastomer premix prepared in S2, 1 part of AKD hydrophobic agent (diluted with ethanol at a 1:1 ratio), and 2 parts of halogen-free phosphorus-nitrogen flame retardant (pre-dispersed in 5 parts of water). Increase the stirring speed to 300 rpm and mix for 40 minutes. Take a sample to test the homogeneity of the slurry, ensuring no visible agglomerates. Adjust the final slurry concentration to 2.5% to obtain a "homogeneous mixed slurry" with a material viscosity of approximately 1200 ± 200 mPa·s (measured at 25℃).

[0073] Diluted binders and additives are added slowly to avoid excessively high local concentrations that could lead to fiber agglomeration. A moderate shear force of 300 rpm ensures that the elastomer microspheres are uniformly dispersed in the fiber network, AKD is adsorbed onto the fiber surface as a microemulsion, and the flame retardant penetrates into the fiber pores. The system pH is controlled between 6.5 and 7.0 to prevent flocculation of the anionic acrylate and cationic additives (if any). A solid content of 2.5% is the optimal concentration for subsequent foaming processes; too low a concentration results in thin, easily broken bubble walls, while too high a concentration leads to poor flowability.

[0074] Synergistic effect: Elastomer-fiber interface: Fiber-OH (cellulose) ···HOOC- (acrylate) ···PCL-PLA microspheres Hydrogen bonding, physical adsorption, compatibility, and diffusion AKD hydrophobicity: Cellulose -OH + AKD (alkyl ketene dimer) → ester bond + hydrophobic alkyl group facing outward.

[0075] The reaction temperature needs to be >60℃, and it must be completed during the subsequent drying process.

[0076] S4. Controlled physical foaming. Pump the homogeneous mixed slurry into a pressurized foaming kettle (working pressure 0-1.0MPa), seal the foaming kettle, and introduce nitrogen gas (purity ≥99.9%). Increase the pressure in stages: First stage: 0→0.2MPa, hold for 2 minutes, low-speed shear (500rpm); Second stage: 0.2→0.5MPa, hold for 3 minutes, medium-speed shear (1500rpm); Third stage: 0.5→0.7MPa, hold for 2 minutes, high-speed shear (3000rpm).

[0077] Maintain pressure at 0.7 MPa and 3000 rpm for 5 minutes, then sample and observe the slurry state. A fine, creamy consistency is desirable, yielding a "fiber-gas-elastomer mixed slurry." Stepwise pressurization: 0.2 MPa: allows initial dissolution of N2, preventing sudden high pressure from causing slurry compaction; 0.5 MPa: establishes a stable gas-liquid interface, forming bubble nuclei; 0.7 MPa: under high pressure, the bubble nuclei are "compressed" to a smaller size (target diameter 10-50 μm). Variable speed shearing: 500 rpm: initial dispersion, avoiding damage to elastomer microspheres; 1500 rpm: initial turbulence is formed, and bubbles begin to refine; 3000 rpm: strong turbulence and cavitation effects generate micron-sized bubbles.

[0078] Bubble stabilization mechanism: Fiber anchoring: The rough fiber surface captures bubbles (contact angle θ≈75°); Elastomer synergy: PCL-PLA microspheres act as "solid particle stabilizers," adsorbing at the gas-liquid interface; Binder thickening: Waterborne acrylate increases the viscosity of the continuous phase, reducing the bubble rise velocity (Stokes' Law: v∝1 / μ). A pressurized foaming reactor at 35℃ ensures that the PCL-PLA microspheres maintain appropriate rigidity (above room temperature but below Tg), stabilizing bubbles without premature softening.

[0079] S5. Depressurization and gel setting. Quickly open the pneumatic valve at the bottom of the pressurized foaming kettle (opening time <0.5 seconds) and spray the slurry into the molding mold preheated to 50°C (the mold surface has micropores with a diameter of 0.5mm). Immediately transfer the mold to the setting table and let it stand for 2 minutes at normal pressure and 50°C. Observe the volume expansion until it stabilizes (expansion ratio of about 4:1), forming a "wet green body". Measure the thickness of the green body with a thickness gauge, which should be 4 times the depth of the mold.

[0080] Rapid pressure release triggers foaming: According to Henry's Law: C=k·P, when the pressure drops rapidly from 0.7MPa to 0.1MPa, the N2 supersaturation reaches 7 times, and the bubble expansion force is: ΔP=2γ / r (γ-surface tension, r-bubble radius). Synergistic expansion of elastomer microspheres: PCL-PLA begins to soften at 50℃ and expands along with the N2 bubbles. The expansion of the microspheres provides additional "push-pull force," helping the fiber network unfold and forming a "dual-scale pore structure": macropores (100-300μm, N2 bubbles) + micropores (20-50μm, PCL-PLA expansion pores). Synchronous gelation mechanism: Physical crosslinking: Acrylic latex particles (particle size ~0.2μm) contact, deform, and aggregate during water evaporation. Chemical crosslinking initiation: Citric acid begins to undergo esterification with cellulose hydroxyl groups at 50℃. Esterification reaction: cellulose -OH + HOOC-CH2-C(OH)(COOH)-CH2-COOH → cellulose -O-CO-CH2-C(OH)(COOH)-CH2-COOH + H2O, with a reaction extent of approximately 5-10% (continued during subsequent drying). Setting time control: 2 minutes is 1.5 times the gel time (t_gel) to ensure structural stability.

[0081] S6. Gradient Drying and Curing. Transfer the wet green body along with the mold to a microwave-hot air combined dryer. First stage (microwave drying): Microwave power: 3kW, frequency 2450MHz, time: 2 minutes, intermittent (15 seconds on, 5 seconds off), green body temperature rises to 75℃. Second stage (hot air drying): Temperature program: 80℃ (30 minutes) → 70℃ (40 minutes) → 60℃ (30 minutes), air velocity: 2.5m / s, relative humidity gradient: 70% → 50% → 30%, timed turning (every 20 minutes). Third stage (low-temperature dehumidification): 50℃ hot air, relative humidity 20%, time 30 minutes, monitor moisture content until <8%, obtaining the "initial dried green body".

[0082] Microwave selective heating: Water molecules (polar) preferentially absorb microwave energy, resulting in rapid internal heating and avoiding the "dry outside, wet inside" phenomenon caused by traditional heat conduction. Microwave heating generates vapor pressure, which helps maintain the pore structure. Gradient temperature control: 80℃: Rapid evaporation of free water, rapid film formation of acrylate; 70℃: Evaporation of bound water, accelerating the citric acid esterification reaction (optimal temperature); 60℃: Slow evaporation of strongly bound water, reducing drying stress. Humidity gradient control: Initially, high humidity prevents excessively rapid surface drying leading to skin formation; gradually reducing humidity allows for smooth moisture migration. Key chemical reactions: Esterification reaction is accelerated (70℃): Cellulose -OH + citric acid -COOH → cellulose -O-CO-citric acid + H2O; The reaction rate increased to 30-40%.

[0083] Acrylic film formation: Deformation temperature of latex particles: T=T a +k / (D p ) 1 / 3 ≈25℃ (already satisfied), where T is the minimum film-forming temperature, representing the lowest temperature at which latex particles can deform and fuse to form a film. a It is the glass transition temperature, representing the characteristic temperature at which a polymer transitions from the glassy state to the elastic state. p is the diameter of the latex particles, representing the particle size; k is a material constant, an empirical constant related to polymer surface tension, modulus, etc. The film-forming ability of latex is determined by its intrinsic hardness (T). a ) and external geometric pressure (D p The result of their combined effects.

[0084] Film formation process: particle deformation → interface disappearance → molecular chain diffusion.

[0085] Elastomer network formation: PCL-PLA softens completely at 70-80℃, and the fibers come into contact and fuse to form a continuous elastomer phase that interpenetrates with the fiber network.

[0086] S7. Post-Hot Press Curing. Transfer the partially dried preform to a hot press. First stage (softening): Set the upper and lower hot plate temperatures to 90℃, apply a light contact pressure of 0.01MPa, and maintain for 3 minutes. Second stage (hot pressing and shaping): Increase the temperature to 120℃, apply a pressure of 0.05MPa, and maintain for 2 minutes. Third stage (crosslinking and curing): Increase the temperature to 140℃, apply a pressure of 0.1MPa, and maintain for 5 minutes. Fourth stage (cooling and shaping): Maintain a pressure of 0.1MPa, circulate cooling water, and cool to below 60℃ for 3 minutes. Remove the product and allow it to equilibrate at room temperature for 24 hours to obtain the final product.

[0087] Temperature gradient design: 90℃: PCL-PLA completely melts (Tm≈60℃), PU elastomer softens; 120℃: Citrate esterification reaction is accelerated, forming crosslinks with fibers and elastomers; 140℃: Deep crosslinking is completed, while avoiding thermal degradation of cellulose (begins at >150℃). Pressure gradient design: 0.01MPa: Contact only, allowing for uniform heat conduction; 0.05MPa: Moderate compression, eliminating internal stress and improving density uniformity; 0.1MPa: Enhances fiber-elastomer interfacial bonding without damaging the porous structure.

[0088] Crosslinking network formation: Esterification reaction is completed (140℃), and the degree of reaction reaches 80-90%, forming a network: cellulose-O-CO-citric acid-CO-O-cellulose or cellulose-O-CO-citric acid-CO-O-PCL-PLA. Elastomer interpenetrating network: The PCL-PLA phase forms a continuous phase and is physically interlocked with the fiber network. The -NCO in PU and the -OH in cellulose may react (if the PU contains isocyanate).

[0089] Cooling and shape retention: Cooling under pressure locks in dimensions and prevents deformation caused by stress rebound.

[0090] Ultimate performance enhancement mechanism: Interface strengthening: Hot pressing promotes molecular-level contact between fibers and elastomers; Increased crosslinking density: The degree of esterification reaction is greatly improved at high temperatures; Optimized pore structure: Slight compression makes the pore walls denser and improves strength; Residual stress elimination: The hot pressing process is equivalent to "annealing".

[0091] A packaging article, made of the environmentally friendly paper fiber cushioning packaging material of this embodiment, includes cushioning pads, corner protectors, filler granules, or molded packaging trays (depending on the mold). This environmentally friendly paper fiber cushioning packaging material can also be used in electronic product packaging, fragile item packaging, cold chain logistics, or building sound and heat insulation.

[0092] Performance testing and analysis: Density: The volume-mass method was used. The dry weight of the regular sample was weighed using an electronic balance (accuracy 0.001g, Sartorius CPA series), and its three-dimensional dimensions were measured using a digital caliper (Mitutoyo) to calculate the volume. Density = mass / volume. Equipment used: Electronic analytical balance, digital caliper. Reference standard: GB / T 6343-2009 "Determination of Apparent Density of Foamed Plastics and Rubber".

[0093] Porosity and average pore size determination: Mercury porosimetry was used. The dried sample was placed in a dilatometer, and mercury was injected under vacuum. Gradually increasing pressure (0-400 MPa) was applied. The pore size distribution and total pore volume were calculated using the Washburn equation relating mercury injection pressure and pore radius, and then the porosity was calculated. Equipment used: Fully automated mercury porosimetry instrument (AutoPore series), referring to the national standard: GB / T 21650.1-2008 "Mercury Porosimetry and Gas Adsorption Methods for Determination of Pore Size Distribution and Porosity of Solid Materials Part 1: Mercury Porosimetry".

[0094] Compressive strength and modulus of elasticity testing: Compression tests were performed using a universal testing machine. The sample (50mm × 50mm × 25mm) was placed in the center of the compression fixture and compressed at a specified rate (5mm / min) until 50% deformation or failure. The load-displacement curve was recorded, and the compressive strength and modulus of elasticity at the specified strain were calculated. Equipment used: Universal testing machine (Instron 3365 series). Reference national standard: GB / T 8813-2020 "Determination of compressive properties of rigid foamed plastics" (equivalent to ISO 604).

[0095] Rebound rate testing: The free-fall rebound method using steel balls is employed. The sample is placed horizontally, and a steel ball of a specified mass and diameter is dropped freely from a fixed height onto the sample surface. The rebound height is measured. Rebound rate = (rebound height / drop height) × 100%. Equipment used: Falling ball rebound hammer (custom-designed or standard-compliant). Reference standard: ASTM D3574-17 "Flexible foams—Test methods for sheet, bonded and molded polyurethane foams" (Test H).

[0096] Compression set test: The sample is compressed to 50% of its original thickness and maintained in this state at a specified temperature (e.g., 70℃) and for a specified time (e.g., 22 hours). After releasing the pressure, the sample is allowed to recover at room temperature for a specified time (e.g., 30 minutes), and the final thickness is measured. Compression set rate = [(initial thickness - recovered thickness) / compression amount] × 100%. Equipment used: constant temperature oven, compression fixture, thickness gauge. Reference national standard: GB / T 6669-2008 "Determination of Compression Set of Flexible Foam Polymer Materials" (equivalent to ISO 1856).

[0097] Dynamic buffer coefficient: The impact test method is used. The sample is placed between an impact table and a drop hammer, and drop hammers of different masses are dropped from different heights. The maximum acceleration (G-value) transmitted to the impact table is recorded by a sensor. A curve is plotted with static stress on the x-axis and maximum acceleration on the y-axis to determine the minimum buffer coefficient (C = drop height × material density / material thickness) for a specific G-value. Equipment used: Impact testing machine, accelerometer, data acquisition system. Reference standard: ASTM D1596-14, "Test method for dynamic impact properties of flexible packaging materials".

[0098] Energy absorption efficiency: Performed using drop weight impact testing. The total energy absorbed by the material (area under the curve) is calculated by integrating the load-displacement curve (obtained from acceleration and displacement sensor data). Energy absorption efficiency = (absorbed energy / input impact energy) × 100%. Equipment used: Drop weight impact testing machine, high-speed data acquisition system, force sensor. Reference standard: ASTM D1596; specific efficiency calculations are derived from test data analysis.

[0099] Water contact angle: The seated drop method is used. A specified volume (e.g., 2 μL) of ultrapure water is placed on a flat surface of the material using a microsyringe. The droplet profile image is captured by an optical system, fitted using the Young-Laplace equation, and the static contact angle value is automatically calculated by software. Equipment used: Contact angle measuring instrument (e.g., DataPhysics OCA series, Germany). Reference national standard: GB / T30693-2014 "Measurement of the contact angle between plastic films and water".

[0100] Flame retardancy rating: Vertical burning method (UL 94 V). The strip specimen is fixed vertically, and its lower end is burned with a specific flame (methane flame, 20mm high) for 10 seconds, then removed. The flaming burning time, flameless burning time, and whether it ignites absorbent cotton are recorded. The V-0, V-1, or V-2 rating is determined based on the burning behavior. Equipment used: Vertical burning test chamber (such as the American ATLASH VUL series), gas supply system. Reference standard: ANSI / UL 94-2013 "Tests on the flammability of plastic materials used in equipment and appliance components".

[0101] Soil degradation rate: Controlled composting method was used. A sample with a known dry weight was mixed with inoculum (mature compost) and placed in a respirometer or compost container. Degradation was carried out under controlled conditions of constant temperature (e.g., 58±2℃) and constant aeration. The amount of carbon dioxide released was measured periodically, or the sample was removed after a specified time (e.g., 90 days), cleaned, dried, and weighed to calculate the mass loss rate. Equipment used: Compost degradation testing system (respirometer or reactor), CO2 absorption / detection device. Reference national standard: GB / T19277.1-2011 "Determination of final aerobic biodegradability of materials under controlled composting conditions—Method by determination of released carbon dioxide—Part 1: General method" (equivalent to ISO 14855-1).

[0102] Strength retention rate after damp heat aging: Place the sample in a constant temperature and humidity chamber and treat it continuously for a specified time (e.g., 7 days) under specified conditions (e.g., 70±2℃, relative humidity 95±4%). After treatment, remove the sample, adjust it to constant weight under standard conditions, and then test its compressive strength according to GB / T 8813 method. Strength retention rate = (strength after aging / strength before aging) × 100%. Equipment used: Constant temperature and humidity chamber (e.g., German BINDER KMF series), universal testing machine. Reference national standard: GB / T 3512-2014 "Accelerated aging and heat resistance test of vulcanized rubber or thermoplastic rubber in hot air" (the principle is the same, and the environmental conditions are adjusted according to the material characteristics).

[0103] Table 1 shows the performance test results of an environmentally friendly paper fiber cushioning packaging material from Examples 1-4:

[0104] Table 1 The compliance data are derived from EPS industry standards (such as QB / T 4009-2010 "Polystyrene Foam for Packaging"), product data manuals of mainstream suppliers (such as BASF and Jianlong Group), and a large number of published comparative research papers.

[0105] Example 1 achieved 100% compliance with all 14 indicators, with 9 exceeding the high-performance standard. Core advantages: Excellent cushioning performance: dynamic cushioning coefficient 3.8 (<4.0 high-performance standard); Balanced comprehensive performance: optimal balance of density, strength, and resilience; Complete functionality: hydrophobicity (112°), flame retardancy (V-1), and degradation (68%) all meet the standards; Fiber ratio (70:18) provides a suitable skeleton, avoiding excessive rigidity or softness; Adhesive content (13 parts) ensures sufficient adhesion without excessive thickening; Standard process parameters (0.5MPa, 3000rpm, 120℃ drying) have been optimized.

[0106] Referring to Table 1, compared to Example 1, Example 2, through the use of a high-fiber skeleton and low-adhesive formulation design (30 parts softwood pulp and 5 parts adhesive), and the implementation of a compensatory process of low-pressure long-time delamination foaming and mild curing, constructed a dense but weakly bonded three-dimensional network formed by highly broomed long fibers mechanically interlocked through limited bonding points. During the foaming stage, the low-pressure environment (0.4 MPa) and extended shearing time (7 minutes) generated bubbles with larger wall thickness, uniform size, but smaller overall pore size (average 85 μm). At the same time, the extended setting time (2 minutes) ensured that a small amount of adhesive could fully form a film to fix the network. Ultimately, a mechanical system with thick pore walls, fiber-based load-bearing, and insufficient elastic recovery nodes was formed at the microscopic level. Macroscopically, the compressive strength (52.3 kPa) was significantly improved. However, due to the lack of sufficient elastic recovery force after network deformation, the rebound rate (58%) and buffer efficiency (dynamic buffer coefficient 4.5) decreased. Overall, it is a "compliant" material with high strength and high stiffness but low rebound.

[0107] Compared to Example 1, Example 3, based on a formulation with a high proportion of short-fiber waste paper pulp and a high binder content (90 parts waste paper pulp, 20 parts binder), combined with a high-pressure, high-speed forced foaming and rapid setting to prevent cracking, forms a structural basis with a continuous binder phase as the matrix and short fibers as the dispersed reinforcing phase. During the foaming process, the high viscosity pulp forces the process to use high pressure (0.6 MPa) and high shear (3500 rpm) to forcibly introduce and disperse the gas, forming bubbles of varying sizes. At the same time, to prevent the high binder system from generating excessive shrinkage stress due to rapid gelation, an extremely short setting time (30 seconds) and gradient drying are used. This results in uneven binder distribution, poor fiber network continuity, and potential micro-stress defects in the final structure. Although this structure can ensure basic porous morphology and strength (31.2 kPa), the brittle binder-rich areas and weak fiber connection points make it prone to stress concentration and localized damage under stress. Macroscopically, this manifests as insufficient material toughness and flame retardant performance that only reaches the minimum (V-2). It is a cost-oriented brittle material with performance on the verge of meeting standards.

[0108] Example 4, based on the balanced formulation of Example 1, innovatively introduces a bio-based elastomer second phase (PCL-PLA and castor oil-based PU), an interfacial compatibilizer (GMS), and a chemical crosslinking agent (citric acid). Through the newly added two core processes of "elastomer pre-activation" and "post-hot-press curing," a "dual-network interpenetrating" structure is successfully constructed, in which a rigid cellulose first network and a soft thermoplastic elastomer second network interpenetrate and are strongly bonded by chemical crosslinking and interfacial molecular bridges. During the foaming and curing stages, physical foaming (N2) and elastomer thermal expansion foaming (PCL-PLA) work synergistically to form a multi-level structure where large pores (N2 bubbles) withstand impact and small pores (elastomer expansion pores) provide resilience. The porous structure, followed by gradient drying and hot-press curing (140℃, 0.1MPa), greatly promotes the esterification and cross-linking reaction of citric acid and cellulose, significantly improving the overall cross-linking density and hygrothermal stability of the network. This fundamental innovation from the material system to the microstructure allows the elastomer network to preferentially undergo reversible large deformation to dissipate energy when the material is subjected to impact, while the rigid cellulose network provides final support and prevents structural collapse. Macroscopically, it achieves a comprehensive improvement in resilience (88%), fatigue resistance (6.3% permanent deformation), and environmental stability (95% retention rate after hygrothermal aging), making it a next-generation high-performance biomass cushioning material with significantly better performance than petroleum-based EPS foam.

[0109] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0110] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

Claims

1. An environmentally friendly paper fiber cushioning packaging material, characterized in that, The raw materials include plant fiber pulp, reinforcing fibers and environmentally friendly adhesives. The material has an interconnected three-dimensional porous chamber structure formed by physical foaming and fiber cross-linking curing.

2. The environmentally friendly paper fiber cushioning packaging material as described in claim 1, characterized in that, By weight, it includes 50-90 parts plant fiber pulp, 5-30 parts reinforcing fiber, and 5-20 parts environmentally friendly adhesive.

3. The environmentally friendly paper fiber cushioning packaging material as described in claim 2, characterized in that, By weight, it includes 70 parts plant fiber pulp, 18 parts reinforcing fiber, and 13 parts environmentally friendly adhesive.

4. The environmentally friendly paper fiber cushioning packaging material as described in claim 1, characterized in that, The plant fiber pulp is selected from one or more of waste corrugated pulp, sugarcane pulp, and bamboo pulp; the reinforcing fiber is selected from one or more of softwood pulp, hemp fiber, and modified starch fiber; and the environmentally friendly adhesive is selected from one or more of water-based acrylate, starch glue, polyvinyl alcohol, and chitosan.

5. The environmentally friendly paper fiber cushioning packaging material as described in claim 2, characterized in that, The raw materials also contain 0.5-5 parts by weight of functional additives, including one or more of hydrophobic agents, flame retardants, and antibacterial agents.

6. The environmentally friendly paper fiber cushioning packaging material as described in claim 1, characterized in that, The raw materials also include polycaprolactone-polylactic acid block copolymer microspheres, castor oil-based waterborne polyurethane dispersions, citric acid crosslinking agent, glyceryl monostearate, AKD hydrophobic agent, and halogen-free phosphorus-nitrogen flame retardant.

7. The method for preparing an environmentally friendly paper fiber cushioning packaging material as described in claim 6, characterized in that, Includes the following steps: S1. The plant fiber pulp is dissolved in water to form primary pulp; S2. Add reinforcing fibers, environmentally friendly adhesives and functional additives to the primary slurry, mix evenly to obtain a homogeneous mixed slurry; S3. Pressurize and shear the homogeneous mixed slurry while introducing gas to form a fiber-gas mixed slurry; S4. Release the fiber-gas mixture slurry into an atmospheric pressure environment, causing the gas in it to expand and simultaneously causing the fibers to cross-link and gel under the action of the adhesive, forming a wet preform with a three-dimensional porous structure. S5. The wet preform is dried to obtain an environmentally friendly paper fiber cushioning packaging material.

8. The method for preparing an environmentally friendly paper fiber cushioning packaging material as described in claim 7, characterized in that, In step S3, the pressurization pressure range is 0.2-0.8 MPa, the shearing speed is not less than 2000 rpm, and the gas is air, carbon dioxide, or nitrogen.

9. The method for preparing an environmentally friendly paper fiber cushioning packaging material as described in claim 7, characterized in that, The drying process described in step S5 is one of hot air drying, microwave drying, or vacuum drying.

10. The method for preparing an environmentally friendly paper fiber cushioning packaging material as described in claim 7, characterized in that, Between steps S1 and S2, there is also an elastomer pre-activation step to prepare an "activated elastomer premix", and after step S5, there is also a hot-press curing step.

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