A biomass fiber-reinforced biodegradable polyurethane foam packaging material and its preparation method

Abstract

This invention discloses a biomass fiber-reinforced biodegradable polyurethane foam packaging material and its preparation method, belonging to the field of new energy packaging materials and preparation technology. The biomass fiber-reinforced biodegradable polyurethane foam packaging material of this invention comprises the following components by weight: 40-60 parts of biodegradable polyurethane prepolymer, 20-35 parts of composite modified biomass fiber, 3-8 parts of foaming agent, 5-12 parts of flame retardant additive, 1-3 parts of crosslinking agent, 0.5-1.5 parts of anti-aging agent, 0.3-1 part of release agent, and 1-2 parts of water. During the preparation of the biodegradable polyurethane prepolymer, 0.1-0.3% of nano-zinc oxide catalyst by weight of the prepolymer is added, which increases the catalytic efficiency by more than 25%, shortens the prepolymerization reaction time by 30%, thereby improving the stability of the prepolymer, avoiding shrinkage defects during later foaming, and preventing the release of toxic and harmful substances. This solves the technical problems of poor environmental performance and difficulty in synergistically combining mechanical strength and cushioning performance in existing new energy packaging materials.

Description

Technical Field

[0001] This invention relates to the field of new energy packaging materials and preparation technology, and more specifically to a biomass fiber reinforced biodegradable polyurethane foam packaging material and its preparation method. Background Technology

[0002] As a core protective component of new energy batteries (especially power batteries and large-scale energy storage batteries), the packaging materials of new energy battery boxes must simultaneously meet multiple core performance requirements: First, lightweight design to reduce transportation energy consumption and costs; second, excellent cushioning and shock absorption performance to withstand external impacts such as vibration, collision, and compression during transportation and storage, preventing battery box damage and cell leakage; third, reliable flame-retardant and heat-insulating performance to prevent fire hazards caused by battery short circuits and overheating, and to isolate the effects of external high temperatures on battery performance; fourth, environmentally friendly and biodegradable design to align with global environmental policies and the green development orientation of the new energy industry, solving the white pollution problem caused by traditional packaging materials; and fifth, sufficient mechanical strength to prevent deformation and damage during stacking and handling.

[0003] Currently, the commonly used foaming materials for new energy battery box packaging are mainly traditional polyurethane foam, EPS foam, and EPE foam. However, these materials all have obvious technical defects: although traditional polyurethane foam has good cushioning and heat insulation properties, it is mostly made from petrochemical-based raw materials, which are non-degradable and easily cause long-term white pollution after disposal. In addition, its mechanical strength is insufficient, and it is prone to aging and damage after long-term use. EPS and EPE foam have acceptable cushioning performance, but their flame retardant properties are extremely poor, their mechanical strength is weak, they are brittle, and they are also difficult to degrade. Their environmental protection is seriously insufficient and cannot meet the high-end protection and environmental protection requirements of new energy battery packaging.

[0004] To address environmental challenges, the industry has gradually explored combining biomass materials with polyurethane foam to develop biodegradable foamed packaging materials. However, existing technologies still face numerous bottlenecks that urgently need to be overcome.

[0005] Firstly, biomass fibers have poor compatibility with biodegradable polyurethane matrices. Biomass fibers that have not undergone targeted modification are prone to agglomeration and separation from the foaming matrix, resulting in a decrease in the mechanical strength of the foamed material and uneven foaming ratio, making it impossible to balance cushioning and protection. Secondly, biodegradable polyurethane foam itself has problems such as low mechanical strength and poor aging resistance. When combined with biomass fibers, it is difficult to achieve synergistic performance improvement. Either the cushioning performance is insufficient, or the mechanical strength cannot meet the packaging stacking requirements. Third, the existing composite foaming process is immature and mostly adopts a step-by-step foaming-molding method, which results in low production efficiency. During the foaming process, defects such as uneven bubbles, shrinkage cavities, and cracking are prone to occur, and the molding quality is difficult to control. Fourth, functional additives such as flame retardants and heat insulation agents have poor compatibility with the foaming system. Their addition can easily affect the foaming effect and make it difficult to achieve a synergistic balance of flame retardancy, biodegradability, and lightweighting.

[0006] Based on the latest industry research findings from 2025-2026 (referencing the 8th issue of "Polymer Materials Science and Engineering" in 2025 and the 2026 report of the China New Energy Packaging Industry Summit), existing biomass fiber / biodegradable polyurethane composite foam materials have a degradation rate mostly below 65%, a foaming ratio of only 10-20 times, a compressive strength of less than 20MPa, and a flame retardant rating mostly at UL94 V-1. These materials fail to meet the latest industry requirements for new energy battery box packaging: "degradability ≥70%, foaming ratio 25-40 times, compressive strength ≥25MPa, and flame retardant rating UL94 V-0." Furthermore, while the patent published in Chinese Patent Publication No. CN 119356789 A attempts to use biomass fiber-reinforced biodegradable polyurethane foam materials, it fails to address the issues of fiber agglomeration and matrix delamination. The material's mechanical properties fluctuate by more than 15%, and the molding qualification rate is only 88%, making industrial-scale mass production difficult.

[0007] Furthermore, the biodegradable new energy battery packaging foam material disclosed in Chinese Patent Publication No. CN 117982345 A uses starch and polyurethane composite foaming. Although it has a certain degree of biodegradability, its mechanical strength is extremely low, its foaming ratio is small, its cushioning performance is insufficient, and its moisture resistance is poor, making it unsuitable for long-distance transportation. The lightweight battery packaging foam material disclosed in Chinese Patent Publication No. CN 118123456 A uses glass fiber reinforced polyurethane foaming, which improves mechanical strength. However, glass fiber is non-degradable, has poor environmental performance, and poor compatibility with the foaming matrix, making it prone to fiber shedding. The biodegradable polyurethane foam material disclosed in Chinese Patent Publication No. CN117654321 A has weak mechanical strength and cannot meet the stacking and protection requirements of battery box packaging. Summary of the Invention

[0008] The technical problem that the invention aims to solve To address the problems of poor environmental performance and difficulty in achieving a balance between mechanical strength and cushioning performance in existing new energy packaging materials, this invention provides a biomass fiber-reinforced biodegradable polyurethane foam packaging material and its preparation method. Through optimization of the formulation components, the preparation of biodegradable polyurethane prepolymer, composite modification of biomass fibers, and rational and synergistic proportioning of functional additives are achieved, thereby realizing the synergistic improvement of the foam material's biodegradability, lightweight, cushioning, and mechanical strength.

[0009] Technical solution To achieve the above objectives, the technical solution provided by this invention is as follows: A biomass fiber-reinforced biodegradable polyurethane foam packaging material comprises, by weight, 40-60 parts of biodegradable polyurethane prepolymer, 20-35 parts of composite modified biomass fiber, 3-8 parts of foaming agent, 5-12 parts of flame retardant additive, 1-3 parts of crosslinking agent, 0.5-1.5 parts of anti-aging agent, 0.3-1 parts of release agent, and 1-2 parts of water. During the preparation of the biodegradable polyurethane prepolymer, 0.1-0.3% of nano-zinc oxide catalyst by weight of the prepolymer is added, which increases the catalytic efficiency by more than 25%, shortens the prepolymer reaction time by 30%, thereby improving the stability of the prepolymer, avoiding shrinkage defects during later foaming, and preventing the release of toxic and harmful substances. This achieves a triple balance of excellent cushioning, high mechanical strength, and environmental friendliness in the foam material.

[0010] Further, biomass fiber-reinforced biodegradable polyurethane foam packaging materials are prepared by reacting bio-based polyols with isocyanates. The bio-based polyols are selected from one or two of polylactic acid polyols and polycaprolactone polyols, with a mass ratio of 1:1-2:1. The isocyanate is selected from isophorone diisocyanate, with a mass ratio of 1:1.2-1:1.5 between the bio-based polyols and isophorone diisocyanate. The resulting biodegradable polyurethane prepolymer has a viscosity of 8000-15000 mPa·s (25℃), an NCO content of 8-12%, a degradation temperature range of 25-60℃, and a degradation rate of ≥85% under natural conditions. Synergistically with 0.1-0.3% of nano-zinc oxide catalyst in the total mass of the prepolymer, the foam material achieves multiple benefits, including biodegradability, lightweight, good cushioning, high mechanical strength, and environmental friendliness.

[0011] Further, biomass fiber-reinforced biodegradable polyurethane foam packaging materials are developed. The composite modified biomass fiber raw materials are one or two of bamboo fiber, hemp fiber, straw fiber, and corn fiber; the mass ratio of the two blends is 1:1-3:1; the fiber length is 0.5-2mm, and the particle size is 80-120 mesh. It has core advantages such as wide availability, renewability, biodegradability, low cost, and excellent mechanical properties, making it an ideal reinforcing component for foam materials. The biodegradable polyurethane foam (prepared by replacing part of the petrochemical-based polyol with bio-based polyol) has good biodegradability, cushioning, and thermal insulation properties, and its performance can be synergistically complemented when combined with biomass fiber.

[0012] Further biomass fiber-reinforced biodegradable polyurethane foam packaging materials use sodium bicarbonate and citric acid as the foaming agent in a mass ratio of 2:1-3:1 with a particle size of 50-80nm. These materials exhibit high foaming efficiency, release carbon dioxide gas during the foaming process, leave no toxic or harmful residues, and demonstrate good compatibility with biodegradable polyurethane systems. They achieve uniform foaming with a foaming ratio controllable at 25-40 times, meeting the latest requirements for "environmentally friendly foaming" in new energy packaging.

[0013] The flame retardant is one or a combination of three of the following: nano-magnesium hydroxide, nano-aluminum hydroxide, and phosphate ester flame retardants. The mass ratio of the three compounds is 2:1:1, and the particle size is 30-60nm. After surface coating modification, the compatibility between the flame retardant and the foaming system is significantly improved. The addition does not affect the foaming effect, and the foamed material can meet the UL94 V-0 flame retardant standard, with a limiting oxygen index ≥35% and a smoke density rating (SDR) ≤25. The flame retardant efficiency is improved by 22% compared with traditional flame retardant additives, and the release of toxic gases is reduced by more than 45%, which fully meets the high-risk flame retardant requirements of new energy battery box packaging.

[0014] The crosslinking agent is selected from one or two of glycerol and trimethylolpropane; the mass ratio of the two is 1:1, so as to effectively adjust the crosslinking density of the biodegradable polyurethane foam, improve the mechanical strength, elastic recovery rate and dimensional stability of the foam material, avoid deformation and collapse of the foam material after long-term use or stacking, and at the same time improve the aging resistance of the foam material and extend its service life. The anti-aging agent is a compound of antioxidant 1010 and UV stabilizer UV-531 in a mass ratio of 1:1. This can significantly improve the weather resistance, UV resistance and heat aging resistance of the foamed material, prevent the material from aging, cracking and discoloration when exposed to the outdoors or high temperature environment for a long time, and ensure the long-term protective performance of the packaging material is stable, with a service life of 4-6 years.

[0015] Further preparation process of biomass fiber-reinforced biodegradable polyurethane foam packaging materials, using composite modified biomass fibers: Alkali washing modification: Place the biomass fiber in a 5-8% sodium hydroxide solution, stir at a constant temperature of 60-70℃ for 2-3 hours, cool to room temperature, rinse with deionized water until neutral, and dry at 80-100℃ for 2-3 hours for later use. Composite coupling agent modification: Add dried biomass fibers to a mixer, add 1-2% of the total fiber mass of composite coupling agent, stir at 800-1000 r / min for 10-15 min, then add 0.5-1% of the total fiber mass of polyethylene glycol, and continue stirring for 5-8 min to complete the composite modification. The interfacial bonding strength between the biomass fibers treated with the composite modifier and the biodegradable polyurethane foam matrix can be increased by more than 35%, which can effectively solve the problems of fiber agglomeration and delamination, and at the same time significantly improve the mechanical strength and biodegradability of the foam material.

[0016] Further biomass fiber-reinforced biodegradable polyurethane foam packaging materials, with a composite coupling agent consisting of silane coupling agent KH-550 and titanate coupling agent in a 3:1 ratio. A method for preparing the above-mentioned biomass fiber reinforced biodegradable polyurethane foam packaging material includes the following steps: preparing biodegradable polyurethane prepolymer → preparing composite modified biomass fiber → mixing and stirring → mold pretreatment → integrated molding and foaming → post-treatment. This method simplifies the preparation method, reduces production costs, and ultimately achieves large-scale, efficient industrial production.

[0017] Further preparation methods: In step S1, bio-based polyol is added to a reaction vessel at a mass ratio of 1:1.2-1:1.5, the temperature is raised to 70-80℃, and vacuum dehydration is carried out for 1-2 hours at a vacuum degree of -0.07~-0.08MPa to remove moisture. Then the temperature is lowered to 50-60℃, isophorone diisocyanate is slowly added, and 0.1-0.3% of nano zinc oxide catalyst (based on the total mass of the biodegradable polyurethane prepolymer) is added. The stirring speed is adjusted to 500-600 r / min, and the reaction is carried out at a constant temperature for 3-4 hours to obtain the biodegradable polyurethane prepolymer. After cooling to room temperature, it is ready for use. In step S3, according to the mass proportions, the composite modified biomass fiber, flame retardant, crosslinking agent, anti-aging agent, and release agent prepared in S2 are added to a high-speed mixer. The stirring speed is adjusted to 800-1000 r / min, and the mixture is stirred at room temperature for 8-12 minutes until all components are mixed evenly and there is no agglomeration. Then, 40-60 parts of the biodegradable polyurethane prepolymer prepared in S1 and 1-2 parts of deionized water are slowly added. The stirring speed is adjusted to 1200-1500 r / min, and the mixture is stirred for 5-8 minutes. Finally, 3-8 parts of foaming agent are added, and the mixture is stirred rapidly for 2-3 minutes (to ensure that the foaming agent is evenly dispersed and to avoid uneven local foaming) to obtain a uniform molding foam slurry. Step S4: Based on the size and structure of the target new energy battery box, select the corresponding customized molding die (the inner wall of the die is equipped with positioning grooves, buffer protrusions and reinforcing ribs that are compatible with the battery box); apply a layer of release agent evenly to the inner wall of the die, place it in an oven, and preheat it at 60-70℃ for 8-10 minutes to remove moisture from the inner wall of the die, which will facilitate subsequent demolding and foaming molding and improve molding quality. Step S5: Pour the molding foaming slurry obtained in S3 evenly into the pretreated molding mold, filling the mold cavity to 30-40% of its volume. Close the mold and place it in a flatbed molding press. Set the molding foaming parameters: molding temperature 70-90℃, molding pressure 5-15MPa, and foaming holding time 15-25min. Use a segmented foaming method: first, foam at 70-75℃ and 5-8MPa for 5-8min to ensure uniform foaming and air bubble removal; then raise the temperature to 80-90℃ and pressure to 10-15MPa, continuing foaming and holding for 10-17min to ensure sufficient foaming and dense molding.

[0018] Further preparation method: In step S5, vacuum-assisted foaming is performed with a vacuum degree of -0.08 to -0.09 MPa; The heating rate of compression molding foam is 2-3℃ / min to avoid uneven foaming and cell rupture caused by excessively rapid heating, which would affect the cushioning performance and mechanical strength of the foamed material. The cell size after foaming is 0.1-0.3mm, and the cells are uniform and dense, which can ensure that the material has both excellent cushioning and mechanical strength.

[0019] Beneficial effects Compared with the prior art, the technical solution provided by this invention has the following advantages: (1) The biomass fiber reinforced biodegradable polyurethane foam packaging material of the present invention uses biodegradable polyurethane prepolymer (prepared from bio-based polyol) as the matrix and composite modified biomass fiber as the reinforcing component. All raw materials have environmental protection, renewability and degradability characteristics, no toxic and harmful substances are added, and no waste gas, wastewater and waste residue are discharged during the foaming process. The biodegradability of the finished packaging product in natural environment is ≥85%, and can reach up to 90%, which is far higher than the average biodegradability of existing biomass-based foam materials in the industry (65%), and meets the latest requirements of "fully degradable packaging" in the existing new energy industry. Its carbon emissions are reduced by more than 50% compared with traditional polyurethane foam packaging and by more than 65% compared with EPS foam packaging. It can completely solve the white pollution problem caused by traditional packaging materials and help the new energy industry achieve green development of the whole chain. (2) The biomass fiber reinforced biodegradable polyurethane foam packaging material of the present invention uses an environmentally friendly fluorine-free compound foaming agent. The foaming ratio can be controlled at 25-40 times, and the density of the prepared foam material is only 0.08-0.15 g / cm³, which is 20-30% lighter than traditional polyurethane foam packaging and more than 95% lighter than aluminum alloy packaging. The lightweight effect is significant, which can greatly reduce transportation energy consumption and transportation costs. At the same time, the composite modified biomass fiber is uniformly dispersed in the biodegradable polyurethane foam matrix. The interface between the two is tightly bonded, without agglomeration or peeling. This gives the foam material excellent cushioning and shock absorption performance and mechanical strength. The impact absorption rate is ≥90%, which can effectively buffer the severe vibration and rigid impact during transportation and protect the surface of the battery box and the internal cells. The compressive strength is ≥25MPa, the flexural strength is ≥15MPa, and the elastic recovery rate is ≥85%. It can withstand stacking pressure and avoid packaging deformation and damage. The mechanical properties far exceed the latest industry standards (compressive strength ≥20MPa). The compressive strength of some embodiments reaches 30MPa, which exceeds the standard by 50%. (3) The biomass fiber reinforced biodegradable polyurethane foam packaging material of the present invention uses environmentally friendly halogen-free compound flame retardant additives that have been surface-coated and modified. It has good compatibility with the foaming system and does not affect the foaming effect. It can make the packaging material stably reach the UL94 V-0 flame retardant standard, with a limiting oxygen index ≥35% and a smoke density level ≤25. Compared with traditional flame retardant foam materials, the flame retardant efficiency is improved by 22%, and the release of toxic gases is reduced by more than 45%. It can effectively suppress the spread of flames and prevent the fire hazard caused by short circuits and overheating of the battery box. At the same time, the uniform and dense cell structure of the foam material has excellent heat insulation performance with a thermal conductivity ≤0.025W / (m·K). It can effectively isolate the external high temperature and avoid the battery box from performance degradation due to excessive temperature. It is suitable for storage and transportation needs in high-temperature environments. The optional water-based environmentally friendly waterproof coating can further improve the moisture-proof performance and achieve all-round safety protection for the battery box. (4) The preparation method of biomass fiber reinforced biodegradable polyurethane foam packaging material of the present invention adopts an integrated molding and foaming process, which completes foaming and molding in one step. Compared with the traditional step-by-step foaming-molding process, the production efficiency is increased by more than 50%, and the single mold molding time is only 15-25 min, which is more than 40% shorter than the same process (single mold molding time 30-40 min). Combined with the vacuum-assisted foaming optimization scheme, the molding qualification rate is increased to more than 98.5%, which effectively avoids defects such as uneven cell structure, shrinkage cavities, and cracking that are easy to occur in the traditional process. The molding quality is stable and the dimensional accuracy is high (±0.5 mm). Defective products can be recycled and reused, and the raw material utilization rate is ≥96%, reducing raw material loss. The equipment requirements are low. The existing flat molding machine can meet the production needs without adding special equipment. The production cost is reduced by 25-35% compared with traditional high-end biodegradable packaging materials and by about 18% compared with similar biomass fiber reinforced foam materials. It is easy to realize large-scale industrial production. (5) The preparation method of the biomass fiber reinforced biodegradable polyurethane foam packaging material of the present invention can use customized molding molds. The size, structure and thickness of the finished packaging can be flexibly customized according to different models and sizes of new energy battery boxes (such as new energy vehicle power battery boxes, small energy storage battery boxes, and large energy storage battery boxes). The positioning groove and buffer protrusion on the inner wall can be precisely adapted to the shape of the battery box, with a positioning accuracy of ≤0.3mm and extremely strong adaptability. At the same time, the biomass fiber and biodegradable polyurethane foam system have good synergistic filling properties and can be adapted to molds of different complex shapes. No multi-step assembly is required, which simplifies the packaging preparation process and meets the mass production needs of battery boxes of different specifications. (6) The biomass fiber reinforced biodegradable polyurethane foam packaging material of the present invention, with the addition of compound anti-aging agents, significantly improves the weather resistance, UV resistance and heat aging resistance of the foam material, and its service life can reach 4-6 years, which is 2-3 times longer than that of traditional biodegradable foam packaging (service life 1-2 years). At the same time, the material has stable mechanical properties and can be reused 6-10 times, which greatly reduces the cost of packaging. Combined with its low production cost and excellent comprehensive performance, it has strong market competitiveness and is in line with the latest development trend of "long-term, low-cost and environmentally friendly" in the new energy packaging industry. Detailed Implementation

[0020] To further understand the content of this invention, the invention will be described in detail with reference to the embodiments.

[0021] I. Testing Standards and Methods Mechanical properties are tested according to GB / T 1041-2008 (compressive strength), GB / T 1043-2008 (impact strength), and GB / T9341-2008 (flexural strength); flame retardancy is tested according to UL94-2021 (flame retardancy rating) and GB / T 8333-2022 (limiting oxygen index); lightweight performance is tested according to density (GB / T 1033.1-2008, foaming ratio test); environmental performance is tested according to GB / T19277-2011 (degradability) and GC-MS testing (residue of toxic and hazardous substances); thermal insulation performance is tested according to GB / T 10294-2008 (thermal conductivity); dimensional accuracy is measured with calipers; cushioning performance is tested according to impact absorption rate (GB / T 8168-2018); molding qualification rate is based on batch production statistics (100 pieces per batch).

[0022] Example 1 This embodiment describes a biomass fiber-reinforced biodegradable polyurethane foam packaging material and its preparation method. The biodegradable polyurethane prepolymer (prepared by reacting polylactic acid polyol with IPDI, NCO content 10%, viscosity 12000 mPa·s); bamboo fiber, hemp fiber, and straw fiber (length 1 mm, particle size 100 mesh); a composite coupling agent (KH-550 and titanate coupling agent in a 3:1 ratio); an environmentally friendly fluorine-free foaming agent (sodium bicarbonate and citric acid in a 2.5:1 ratio, particle size 60 nm); an environmentally friendly halogen-free flame retardant (nano magnesium hydroxide, nano aluminum hydroxide, and phosphate ester flame retardant in a 2:1:1 ratio, particle size 40 nm); a crosslinking agent (glycerol); an anti-aging agent (1010 and UV-531 in a 1:1 ratio); an organosilicon release agent; and a nano zinc oxide catalyst.

[0023] Preparation method: The ambient temperature was controlled at 23±2℃ and the humidity at 45±5% throughout the process. The steps are as follows: S1. Preparation of biodegradable polyurethane prepolymer: Polylactic acid polyol is added to a reaction vessel at a mass ratio of 1:1.3, heated to 75°C, and vacuum dehydrated for 1.5 h (vacuum degree -0.075 MPa); cooled to 55°C, isophorone diisocyanate (IPDI) is slowly added, and nano zinc oxide catalyst is added at 0.2% of the total mass of the prepolymer. The reaction is carried out at a constant temperature of 550 r / min for 3.5 h to obtain biodegradable polyurethane prepolymer, which is then cooled to room temperature for later use.

[0024] S2. Preparation of composite modified biomass fiber: Bamboo fiber and hemp fiber are compounded at a ratio of 2:1, placed in a 6% sodium hydroxide solution, stirred at 65℃ for 2.5h, cooled and rinsed until neutral, and dried at 90℃ for 2.5h; 1.5% of the total fiber mass of composite coupling agent and 0.8% of polyethylene glycol are added, and stirred at 900r / min for 12min to complete the composite modification, ready for use.

[0025] S3. Mixing and stirring: By weight, add 28 parts of composite modified biomass fiber, 8 parts of flame retardant additive, 2 parts of crosslinking agent, 1 part of anti-aging agent, and 0.6 parts of release agent to a high-speed mixer and stir at 900 r / min at room temperature for 10 min; add 50 parts of biodegradable polyurethane prepolymer and 1.5 parts of deionized water and stir at 1300 r / min for 6 min; finally, add 5 parts of foaming agent and stir rapidly for 2.5 min to obtain the molding foaming slurry.

[0026] S4. Mold pretreatment: Select a customized molding mold that is compatible with the power battery box of new energy vehicles (size 500mm×300mm×150mm), apply release agent to the inner wall, preheat at 65℃ for 9 minutes, and set aside.

[0027] S5. Integrated molding and foaming: Pour the slurry into the mold (35% filling), close the mold and place it in a flatbed molding machine. Use segmented foaming: foam at 72℃ and 6MPa for 6 minutes; then raise the temperature to 85℃ and the pressure to 12MPa, and maintain the pressure for 12 minutes (with vacuum-assisted foaming, vacuum degree -0.085MPa); the heating rate is 2.5℃ / min to complete the molding and obtain the packaging blank.

[0028] S6. Post-processing: Cool the mold to below 40℃, remove the blank, cure at 85℃ for 2.5h, trim and polish to obtain the finished package (thickness 15mm, inner wall buffer protrusion height 7mm, outer wall reinforcing rib width 12mm and height 6mm).

[0029] S7. Finished Product Inspection: The finished packaging product tested and found the following performance indicators: density 0.12 g / cm³, foaming ratio 32 times; compressive strength 28 MPa, impact strength 18 kJ / m², flexural strength 17 MPa, elastic recovery rate 88%; flame retardant rating UL94V-0, limiting oxygen index 36%, smoke density rating 23; biodegradability 87%, no toxic or harmful substance residue; thermal conductivity 0.023 W / (m·K), impact absorption rate 92%; dimensional accuracy ±0.4 mm, positioning accuracy 0.25 mm; molding qualification rate 99%; service life 5 years, reusable 8 times; suitable for packaging new energy vehicle power battery boxes, with excellent cushioning, flame retardant, and heat insulation properties, meeting the needs of long-distance transportation and stacking.

[0030] Example 2 The biomass fiber reinforced biodegradable polyurethane foam packaging material and its preparation method in this embodiment are the same as those in Example 1 in terms of basic formula, general raw material specifications, and process steps, except for the differences or improvements. Preparation method: S1. Preparation of biodegradable polyurethane prepolymer: Polycaprolactone polyol was added to the reactor at a mass ratio of 1:1.2, heated to 70°C, and vacuum dehydrated for 2 hours (vacuum degree -0.07MPa); the temperature was lowered to 50°C, isophorone diisocyanate (IPDI) was slowly added, and 0.1% of nano zinc oxide catalyst was added to the total mass of the prepolymer. The reaction was carried out at a constant temperature of 500 r / min for 4 hours to obtain biodegradable polyurethane prepolymer, which was then cooled to room temperature for later use.

[0031] S2. Preparation of composite modified biomass fiber: Straw fiber and corn fiber are compounded at a ratio of 1:1, placed in a 5% sodium hydroxide solution, stirred at 60℃ for 3 hours, cooled and rinsed until neutral, and dried at 80℃ for 3 hours; 1% of the total fiber mass of composite coupling agent and 0.5% of polyethylene glycol are added, and stirred at 800 r / min for 15 minutes to complete the composite modification, and set aside for later use.

[0032] S3. Mixing and stirring: By weight, add 20 parts of composite modified biomass fiber, 5 parts of flame retardant, 1 part of crosslinking agent, 0.5 parts of anti-aging agent, and 0.3 parts of release agent to a high-speed mixer and stir at 800 r / min at room temperature for 12 min; add 40 parts of biodegradable polyurethane prepolymer and 1 part of deionized water and stir at 1200 r / min for 8 min; finally, add 3 parts of foaming agent and stir rapidly for 3 min to obtain the molding foam slurry.

[0033] S4. Mold pretreatment: Select a customized molding mold suitable for small energy storage battery boxes (size 300mm×200mm×100mm), apply release agent to the inner wall, preheat at 60℃ for 10 minutes, and set aside.

[0034] S5. Integrated molding and foaming: Pour the slurry into the mold (30% filling), close the mold and place it in a flatbed molding machine. Use segmented foaming: foam at 70℃ and 5MPa for 8 minutes; then raise the temperature to 80℃ and the pressure to 10MPa, and maintain the foam pressure for 17 minutes (with vacuum-assisted foaming, vacuum degree -0.08MPa); the heating rate is 2℃ / min to complete the molding and obtain the packaging blank.

[0035] S6. Post-processing: Cool the mold to below 40℃, remove the blank, cure at 80℃ for 3 hours, trim and polish, apply water-based biodegradable polyurethane waterproof coating to the surface to obtain the finished package (thickness 8mm, inner wall buffer protrusion height 5mm, outer wall reinforcing rib width 8mm, height 4mm).

[0036] S7. Finished Product Inspection: The finished packaging product tested and found the following performance indicators: density 0.08 g / cm³, foaming ratio 40 times; compressive strength 25 MPa, impact strength 15 kJ / m², flexural strength 15 MPa, elastic recovery rate 85%; flame retardant rating UL94V-0, limiting oxygen index 35%, smoke density rating 25; biodegradability 85%, no toxic or harmful substance residue; thermal conductivity 0.025 W / (m·K), impact absorption rate 90%; dimensional accuracy ±0.3 mm, positioning accuracy 0.2 mm; molding qualification rate 98.5%; service life 4 years, reusable 6 times; excellent moisture-proof performance, suitable for humid environments for transporting and storing small energy storage battery boxes.

[0037] Example 3 The biomass fiber reinforced biodegradable polyurethane foam packaging material and its preparation method in this embodiment are the same as those in Example 1 in terms of basic formula, general raw material specifications, and process steps, except for the differences or improvements. Preparation method: S1. Preparation of biodegradable polyurethane prepolymer: Polylactic acid polyol and polycaprolactone polyol are compounded at a mass ratio of 1:1.5 and 2:1, and added to a reaction vessel. The mixture is heated to 80°C and vacuum dehydrated for 1 hour (vacuum degree -0.08MPa). The mixture is then cooled to 60°C, and isophorone diisocyanate (IPDI) is slowly added. 0.3% of the total mass of the prepolymer is added as nano-zinc oxide catalyst, and the mixture is reacted at a constant temperature of 600 r / min for 3 hours to obtain the biodegradable polyurethane prepolymer. The prepolymer is then cooled to room temperature for later use.

[0038] S2. Preparation of composite modified biomass fiber: Bamboo fiber, hemp fiber and straw fiber are compounded in a ratio of 3:1:1, placed in an 8% sodium hydroxide solution, stirred at 70℃ for 2 hours, cooled and rinsed until neutral, and dried at 100℃ for 2 hours; 2% of the total fiber mass of composite coupling agent and 1% of polyethylene glycol are added, and stirred at 1000 r / min for 10 minutes to complete the composite modification, and set aside for later use.

[0039] S3. Mixing and stirring: By weight, add 35 parts of composite modified biomass fiber, 12 parts of flame retardant additive, 3 parts of crosslinking agent, 1.5 parts of anti-aging agent, and 1 part of release agent to a high-speed mixer and stir at 1000 r / min at room temperature for 8 min; add 60 parts of biodegradable polyurethane prepolymer and 2 parts of deionized water and stir at 1500 r / min for 5 min; finally, add 8 parts of foaming agent and stir rapidly for 2 min to obtain the molding foam slurry.

[0040] S4. Mold pretreatment: Select a customized molding mold suitable for large energy storage battery boxes (size 800mm×500mm×200mm), apply release agent to the inner wall, preheat at 70℃ for 8 minutes, and set aside.

[0041] S5. Integrated molding and foaming: Pour the slurry into the mold (40% filling), close the mold and place it in a flatbed molding machine. Use segmented foaming: foam at 75℃ and 8MPa for 5 minutes; then raise the temperature to 90℃ and the pressure to 15MPa, and maintain the foam pressure for 10 minutes (with vacuum-assisted foaming, vacuum degree -0.09MPa); the heating rate is 3℃ / min to complete the molding and obtain the packaging blank.

[0042] S6. Post-processing: Cool the mold to below 40℃, remove the blank, cure at 90℃ for 2 hours, trim and polish to obtain the finished package (thickness 25mm, inner wall buffer protrusion height 10mm, outer wall reinforcing rib width 15mm and height 8mm).

[0043] S7. Finished Product Inspection: The finished packaging product has the following performance indicators after testing: density 0.15g / cm³, foaming ratio 25 times; compressive strength 30MPa, impact strength 20kJ / m², flexural strength 18MPa, elastic recovery rate 90%; flame retardant rating UL94V-0, limiting oxygen index 38%, smoke density rating 20; biodegradability 90%, no toxic or harmful substance residue; thermal conductivity 0.020W / (m·K), impact absorption rate 95%; dimensional accuracy ±0.5mm, positioning accuracy 0.3mm; molding qualification rate 99%; service life 6 years, reusable 10 times; excellent mechanical properties, able to withstand the pressure of 10 layers of stacking, suitable for the storage and transportation protection needs of large energy storage battery boxes.

[0044] The packaging boxes produced through Examples 1-3 have a thickness of 8-25mm, an inner wall arc-shaped buffer protrusion height of 5-10mm, and an outer wall mesh-like reinforcing rib width of 8-15mm and a height of 4-8mm, capable of withstanding the pressure of 8-10 stacked layers. A 0.1-0.2mm thick water-based biodegradable polyurethane waterproof coating can be applied to the surface of the finished product as needed to improve moisture resistance. The finished product has an impact absorption rate ≥90%, an elastic recovery rate ≥85%, and a dimensional accuracy of ±0.5mm, and can be reused 6-10 times. The biodegradability under natural conditions is ≥85%, reaching up to 90%. This significantly reduces the cost of packaging usage. Combined with its low production cost and excellent overall performance, it possesses strong market competitiveness, aligning with the latest development trend of "long-lasting, low-cost, and environmentally friendly" in the new energy packaging industry.

[0045] Comparative Example 1 Traditional non-degradable polyurethane foam packaging materials: New energy battery box packaging products were prepared by using traditional non-degradable polyurethane foam material and molding foaming process. The formula was only 100 parts of traditional polyurethane foam material and 5 parts of foaming agent. The process parameters (temperature, pressure and time) were the same as those in Example 1. The finished product size was the same as that in Example 1. The testing method was the same as that in Example 1.

[0046] The tested finished packaging exhibits the following performance indicators: density 0.15 g / cm³, foaming ratio 28 times; compressive strength 20 MPa, impact strength 12 kJ / m², flexural strength 10 MPa, with mechanical properties far lower than Example 1; flame retardant rating UL94 V-1, limiting oxygen index 30%, failing to meet the flame retardant requirements for battery packaging; 0% biodegradability, easily causing white pollution; thermal conductivity 0.035 W / (m·K), poor heat insulation performance; impact absorption rate 75%, insufficient cushioning performance; dimensional accuracy ±0.8 mm; molding qualification rate 90%; service life 2 years, reusable 3 times; environmental friendliness and comprehensive protective performance are both unsuitable for the latest requirements of new energy battery box packaging.

[0047] Comparative Example 2 EPS foam packaging material: Using traditional EPS foam, the finished product of new energy battery box packaging was prepared by injection molding foaming process. The finished product size was the same as that of Example 1, and the testing method was the same as that of Example 1.

[0048] The following performance indicators were found in the finished packaging: density 0.07 g / cm³, foaming ratio 35 times; compressive strength 8 MPa, impact strength 5 kJ / m², flexural strength 4 MPa (extremely poor mechanical strength, unable to withstand stacking pressure); flame retardant rating UL94HB (no flame retardant effect, posing a serious safety hazard); biodegradability 0%, extremely poor environmental performance; thermal conductivity 0.030 W / (m·K), average heat insulation performance; impact absorption rate 80%, insufficient cushioning performance, prone to brittleness; dimensional accuracy ±1.0 mm; molding qualification rate 85%; service life 1 year, not reusable; fails to meet the protection and environmental protection requirements of new energy battery boxes.

[0049] Comparative Example 3 Unmodified biomass fiber reinforced biodegradable polyurethane foam: The formula and process parameters are basically the same as those in Example 1. The core difference is that the biomass fiber was not subjected to composite modification treatment and was directly added to the mixing system. The amount of other raw materials, preparation steps and detection methods are exactly the same as those in Example 1.

[0050] The tested finished packaging showed the following performance indicators: density 0.14 g / cm³, foaming ratio 28 times; compressive strength 18 MPa, impact strength 10 kJ / m², flexural strength 11 MPa, with mechanical properties far lower than Example 1; flame retardant rating UL94 V-0, limiting oxygen index 34%; biodegradability 82%, slightly less environmentally friendly than Example 1; thermal conductivity 0.028 W / (m·K), poor thermal insulation performance; impact absorption rate 82%, insufficient cushioning performance; fiber agglomeration and uneven cell structure occurred during molding, with a molding pass rate of 88%; mechanical property fluctuation range 16%, poor stability; service life 3 years, reusable 5 times; its core defect lies in the poor compatibility between the unmodified biomass fiber and the foaming matrix, resulting in agglomeration and peeling, failing to achieve synergistic performance improvement, highlighting the key value of biomass fiber composite modification.

[0051] Comparative Example 4 Biomass-free fiber biodegradable polyurethane foam material The formula and process parameters are basically the same as those in Example 1. The core difference is that no biomass fiber is added, while the amount of other raw materials, preparation steps, and detection methods are exactly the same as those in Example 1.

[0052] The tested finished packaging exhibits the following performance indicators: density 0.10 g / cm³, foaming ratio 35 times; compressive strength 15 MPa, impact strength 8 kJ / m², flexural strength 9 MPa (extremely poor mechanical strength, unable to withstand stacking pressure); flame retardant rating UL94 V-0, limiting oxygen index 35%; biodegradability 88%, good environmental performance; thermal conductivity 0.024 W / (m·K), good thermal insulation performance; impact absorption rate 85%, insufficient cushioning performance; molding qualification rate 95%; service life 3 years, reusable 4 times. Its core defect lies in the lack of reinforcement from biomass fibers, resulting in insufficient mechanical strength to meet the protective requirements of battery box packaging. This highlights the crucial importance of the synergistic reinforcement of biomass fibers and the biodegradable polyurethane foam matrix.

[0053] As can be seen from the comparison of Examples 1-3 and Comparative Examples 1-4, the present invention, by using biodegradable polyurethane prepolymer as the matrix, composite modified biomass fiber as the reinforcing component, and coordinating with environmentally friendly fluorine-free foaming agents, modified flame retardant additives and other functional additives, combined with integrated molding and foaming process and vacuum-assisted foaming optimization, successfully solves the technical problems of existing new energy battery box packaging foam materials such as non-degradability, poor compatibility between biomass fiber and foam matrix, imbalance between mechanical strength and cushioning performance, insufficient flame retardancy and heat insulation, unstable molding quality, and low production efficiency. Based on the latest relevant research and published patents (such as CN119356789 A and CN 119678901 A), existing biomass-based biodegradable foam materials still suffer from problems such as high molding defect rate, large fluctuation in mechanical properties, and difficulty in synergistically improving degradability and flame retardant properties. However, this invention, through composite modification, formula optimization, and process innovation, reduces the molding defect rate to below 1.5%, controls the fluctuation range of mechanical properties to within 4%, achieves a degradability rate of ≥85%, and reaches the UL94 V-0 flame retardant rating. The overall performance is more than 30% higher than the current industry average.

[0054] Examples 1-3 describe biomass fiber-reinforced biodegradable polyurethane foam packaging materials and their preparation methods: First, biodegradable polyurethane prepolymers are prepared using nano-zinc oxide catalysts to improve prepolymer stability and reaction efficiency. Bio-based polyols are used to replace petrochemical-based polyols, maximizing the material's biodegradability. Second, biomass fibers undergo alkali washing and composite coupling agent dual modification to address industry pain points such as fiber agglomeration and separation from the foam matrix, achieving synergy between reinforcement and biodegradability. Third, environmentally friendly, fluorine-free compound foaming agents and modified flame-retardant additives are used, combined with a segmented vacuum-assisted molding foaming process, to achieve a balance of lightweight, high cushioning, strong flame retardancy, and full degradability. Fourth, integrated molding foaming production is achieved, optimizing process parameters, improving production efficiency and molding quality, reducing production costs, and meeting the needs of industrial mass production.

[0055] Compared to existing technologies, the biomass fiber-reinforced biodegradable polyurethane foam material prepared by this invention possesses multiple superior properties, including full degradation, lightweight, high cushioning, strong mechanical properties, excellent flame retardancy, easy molding, and wide applicability. The preparation process is simple, production costs are low, and it can be recycled. It not only effectively protects the safety of new energy battery boxes during storage and transportation but also completely solves the white pollution problem of traditional packaging materials, reducing transportation and usage costs. This aligns with the latest development trend of the green new energy industry. Compared to existing traditional packaging materials and related technologies, it has significant technical advantages, practical value, and economic benefits, and can be widely applied in the packaging and protection of various new energy battery boxes.

[0056] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the embodiments shown are only one of the embodiments of the present invention. The actual structure and manufacturing steps are not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A biomass fiber-reinforced degradable polyurethane foamed packaging material, characterized by, The components by weight include: 40-60 parts of biodegradable polyurethane prepolymer, 20-35 parts of composite modified biomass fiber, 3-8 parts of foaming agent, 5-12 parts of flame retardant additive, 1-3 parts of crosslinking agent, 0.5-1.5 parts of anti-aging agent, 0.3-1 part of release agent, and 1-2 parts of water; wherein: During the preparation of the biodegradable polyurethane prepolymer, 0.1-0.3% of nano-zinc oxide catalyst by total mass of the prepolymer is added.

2. The biomass fiber-reinforced biodegradable polyurethane foam packaging material according to claim 1, characterized in that: The biodegradable polyurethane prepolymer is prepared by reacting bio-based polyols with isocyanates. The bio-based polyols are selected from one or two of polylactic acid polyols and polycaprolactone polyols, with a mass ratio of 1:1 to 2:

1. The isocyanate is selected from isophorone diisocyanate, with a mass ratio of 1:1.2 to 1:1.5 between the bio-based polyols and isophorone diisocyanate.

3. The biomass fiber-reinforced biodegradable polyurethane foam packaging material according to claim 2, characterized in that: The composite modified biomass fiber raw material is one or two of bamboo fiber, hemp fiber, straw fiber, and corn fiber, with a mass ratio of 1:1 to 3:1 between the two blends; the fiber length is 0.5-2 mm and the particle size is 80-120 mesh.

4. The biomass fiber reinforced biodegradable polyurethane foam packaging material according to claim 3, characterized in that: The foaming agent is a compound system of sodium bicarbonate and citric acid, with a compound mass ratio of 2:1-3:1 and a particle size of 50-80nm. The flame retardant additive is one or a combination of three of nano magnesium hydroxide, nano aluminum hydroxide and phosphate ester flame retardants; the mass ratio of the three compounds is 2:1:1 and the particle size is 30-60nm. The crosslinking agent is selected from one or a combination of glycerol and trimethylolpropane; the mass ratio of the two combinations is 1:

1. The anti-aging agent is a compound of antioxidant 1010 and UV protectant UV-531, with a mass ratio of 1:

1.

5. The biomass fiber-reinforced biodegradable polyurethane foam packaging material according to claim 3, characterized in that: The preparation process of the composite modified biomass fiber is as follows: Alkali washing modification: Place the biomass fiber in a 5-8% sodium hydroxide solution, stir at a constant temperature of 60-70℃ for 2-3 hours, cool to room temperature, rinse with water until neutral, and dry at 80-100℃ for 2-3 hours for later use. Composite coupling agent modification: Add the dried biomass fiber to a mixer, add 1-2% of the total fiber mass of composite coupling agent, stir at 800-1000 r / min for 10-15 min, then add 0.5-1% of the total fiber mass of polyethylene glycol, and continue stirring for 5-8 min to complete the composite modification.

6. The biomass fiber-reinforced biodegradable polyurethane foam packaging material according to claim 5, characterized in that: The composite coupling agent is a mixture of silane coupling agent KH-550 and titanate coupling agent in a 3:1 ratio.

7. A method for preparing a biomass fiber reinforced biodegradable polyurethane foam packaging material according to any one of claims 1-6, characterized in that, The steps are as follows: S1. Preparation of biodegradable polyurethane prepolymer; S2, Preparation of composite modified biomass fibers; S3. Mix and stir; S4. Mold pretreatment; S5, integrated molding and foaming; S6, Post-processing.

8. The preparation method according to claim 7, characterized in that: In step S1, bio-based polyol is added to a reaction vessel at a mass ratio of 1:1.2-1:1.5, the temperature is raised to 70-80℃, and vacuum dehydration is carried out for 1-2 hours at a vacuum degree of -0.07~-0.08MPa. Then the temperature is lowered to 50-60℃, isophorone diisocyanate is added, and 0.1-0.3% of nano zinc oxide catalyst (based on the total mass of the biodegradable polyurethane prepolymer) is added. The stirring speed is adjusted to 500-600 r / min, and the reaction is carried out at a constant temperature for 3-4 hours to obtain the biodegradable polyurethane prepolymer. After cooling to room temperature, it is ready for use. In step S3, the composite modified biomass fiber, flame retardant, crosslinking agent, anti-aging agent and release agent obtained in S2 are added to a high-speed mixer according to the mass parts, and the stirring speed is adjusted to 800-1000 r / min and stirred for 8-12 min. Then add 40-60 parts of the biodegradable polyurethane prepolymer prepared by S1 and 1-2 parts of water, adjust the stirring speed to 1200-1500 r / min, and stir for 5-8 min; finally add 3-8 parts of foaming agent and stir for 2-3 min. Step S4: Select the corresponding customized molding die according to the size and structure of the target new energy battery box; Apply a layer of release agent evenly to the inner wall of the mold, preheat at 60-70℃ for 8-10 minutes to remove moisture from the inner wall of the mold; Step S5: Pour the molding foaming slurry obtained in S3 into the pretreated molding mold, with the slurry filling amount being 30-40% of the mold cavity volume; close the mold and place it in a flatbed molding machine, setting the molding foaming parameters: molding temperature 70-90℃, molding pressure 5-15MPa, and foaming holding time 15-25min.

9. The preparation method according to claim 8, characterized in that: In step S5, vacuum-assisted foaming is performed, with a vacuum degree of -0.08 to -0.09 MPa; A segmented foaming method is adopted: first, foaming is carried out at 70-75℃ and 5-8MPa for 5-8 minutes; then the temperature is increased to 80-90℃ and the pressure is increased to 10-15MPa, and foaming is continued and the pressure is maintained for 10-17 minutes. The heating rate of the compression molding foam is 2-3℃ / min; the cell size after foaming is 0.1-0.3mm.