A bamboo fiber microporous foam material and its manufacturing method

Abstract

This invention discloses a bamboo fiber microporous foam material and its manufacturing method. The material is composed of polyethylene, bamboo fiber, titanate coupling agent, composite foaming agent, modified plasticizer, functional inorganic filler, and nano-antibacterial agent. A proprietary process is used to prepare bamboo fiber, composite foaming agent, and modified plasticizer, combined with staged mixing and precise temperature-controlled extrusion, solving the problems of poor antibacterial properties, poor component compatibility, and uneven foaming found in traditional materials. The material possesses excellent impact resistance, dimensional stability, lightweight, heat resistance, and long-lasting antibacterial properties. Furthermore, it uses renewable bamboo fiber, making it environmentally friendly and easy to industrialize, and can be widely used in automotive interiors, home furnishings, packaging, and other fields.

Description

Technical Field

[0001] This invention relates to the field of bio-based composite materials technology, specifically to a bamboo fiber microporous foam material and its manufacturing method. Background Technology

[0002] Currently, most foamed materials used in automotive interiors, packaging cushioning, and other fields are made from petroleum-based polymers, which have problems such as non-degradability and poor environmental performance. In addition, traditional foamed materials often suffer from defects such as insufficient antibacterial properties, uneven cell structure, and poor mechanical properties, making it difficult to meet the needs of high-end scenarios.

[0003] Bamboo fiber, as a natural renewable resource, has the advantages of high strength and biodegradability, and has been attempted to be used to improve foamed materials. However, bamboo fiber contains impurities such as lignin and hemicellulose, which have poor compatibility with polymer matrices and are prone to material delamination. At the same time, existing composite foaming agents often have problems such as unstable foaming efficiency and difficulty in controlling cell size. Modified plasticizers are not compatible with bamboo fiber, and functional inorganic fillers are prone to agglomeration, which further restricts the performance improvement of bamboo fiber foamed materials.

[0004] In existing technologies, the purification process of bamboo fiber is complex and costly, and the preparation process of foaming agent and plasticizer lacks precise control, making it difficult to achieve synergistic optimization of material performance. Therefore, the development of a bamboo fiber microporous foaming material with good component compatibility, uniform foaming, and excellent mechanical and antibacterial properties and related processes has become an urgent problem to be solved in the industry. Summary of the Invention

[0005] This invention provides a bamboo fiber microporous foam material and its manufacturing method. By processing raw materials, improving processing technology and processing parameters, the material's shortcomings in mechanical properties, lightweight, heat resistance, and antibacterial properties are addressed.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A bamboo fiber microporous foam material is made from the following raw materials in the indicated weight ratios: 40-65 parts polyethylene, 25-60 parts bamboo fiber, 0.3-0.8 parts titanate coupling agent, 3-8 parts composite foaming agent, 2-12 parts modified plasticizer, 6-12 parts functional inorganic filler, and 0.5-2 parts nano antibacterial agent; wherein the composite foaming agent is a mixture of 4,4'-oxobisbenzenesulfonyl hydrazine and sodium bicarbonate in a weight ratio of 3:1.

[0008] Preferably, the modified plasticizer is polyethylene glycol grafted with maleic anhydride; the functional inorganic filler is talc powder surface-treated with silane coupling agent KH-550 and titanium dioxide compounded in a weight ratio of 2:1; the nano-antibacterial agent is nano-zinc oxide; the polyethylene is high-pressure polyethylene with a melt index of 12-18 g / 10min; the bamboo fiber has a mesh size of 50-180 mesh and a moisture content controlled at 1-2 wt%; the titanate coupling agent is isopropyltris(dioctylpyrophosphate)titanate; and the nano-antibacterial agent has a particle size of 20-50 nm. This material improves foaming uniformity through the synergistic effect of the two components in the composite foaming agent. Modified plasticizers enhance the compatibility between bamboo fiber and polyethylene, functional inorganic fillers optimize the tensile strength and heat resistance of the material, and nano-antibacterial agents impart long-lasting antibacterial function to the material. This solves the problems of short antibacterial time, easy component stratification, and uneven bubble size in traditional bamboo fiber foam materials. The impact strength of the finished product after injection molding reaches above 4.0 kg•cm / cm, the shrinkage rate is controlled below 0.5%, the density is 0.70-0.80 g / cm³, the heat distortion temperature is not lower than 110℃, and the antibacterial rate against Escherichia coli and Staphylococcus aureus is not lower than 95%. It can be applied to automotive interior cushioning parts, home storage boxes, electronic device packaging liners, and other fields.

[0009] The preferred preparation process of the bamboo fiber includes the following steps:

[0010] S1. Raw material pretreatment: Select bamboo without mold, remove branches, tips and roots, sand the bamboo to remove the bamboo green, and saw the bamboo into bamboo tubes.

[0011] S2. Alkali boiling to remove impurities: Split the bamboo tube into bamboo strips 2-3cm wide, put them into a mixed solution containing 5-8wt% sodium hydroxide and 3-5wt% sodium carbonate, and boil them at 110-120℃ and 0.12-0.15MPa pressure for 2-3 hours, stirring once every 30 minutes during the process;

[0012] S3. Enzymatic hydrolysis: Take out the steamed bamboo strips, rinse them with deionized water until the pH value is 6-7, put them into a cellulase solution with a mass concentration of 0.8-1.0%, and enzymatically hydrolyze them in a constant temperature water bath at 50-55℃ for 4-6 hours, stirring for 10 minutes every 1 hour during the enzymatic hydrolysis process.

[0013] S4. Mechanical dispersion: The enzymatically hydrolyzed bamboo strips are transferred to a colloid mill and ground at a speed of 1500-1800 rpm for 30-40 minutes, while ultrasonic waves with a power of 300-400W are introduced to assist dispersion.

[0014] S5. Separation and purification: Pour the ground mixture into a hydraulic separator, control the water flow rate to 0.5-0.8 m / s, separate the coarse fiber impurities, collect the suspended bamboo fiber, dry it at 60-70℃ to a moisture content of 1-2 wt% after vacuum filtration, and finally crush it through a 50-180 mesh sieve to obtain the finished bamboo fiber.

[0015] This process effectively removes lignin and hemicellulose from bamboo fibers by combining alkaline boiling and enzymatic hydrolysis. Ultrasonic-assisted grinding improves fiber dispersion and ensures that bamboo fibers are evenly distributed in the material.

[0016] Preferably, the preparation process of 4,4'-oxobisbenzenesulfonyl hydrazine in the composite foaming agent includes the following steps:

[0017] S1. Sulfonation reaction: In a three-necked flask equipped with a stirrer and a reflux condenser, add p-aminobenzenesulfonamide and 98% sulfuric acid by mass, with a molar ratio of p-aminobenzenesulfonamide to sulfuric acid of 1:2.5-1:3. Heat to 80-90℃ and stir for 3-4 hours to produce p-aminobenzenesulfonic acid sulfate.

[0018] S2. Diazotization reaction: Cool the reaction solution to 0-5℃, slowly add 30% sodium nitrite solution by mass, the molar ratio of sodium nitrite to p-aminobenzenesulfonamide is 1:1, after the addition is complete, keep warm and stir for 2-3 hours to generate a diazonium salt solution;

[0019] S3. Coupling reaction: Add diphenyl ether to the diazonium salt solution, with a molar ratio of diphenyl ether to p-aminobenzenesulfonamide of 1:2. Adjust the pH value to 8-9 with 20% sodium hydroxide solution, heat to 60-70℃, and stir the reaction for 5-6 hours. During this period, take a sample every 1 hour to check the reaction progress.

[0020] S4. Crude product purification: After the reaction is complete, cool the mixture to room temperature, filter to obtain a pale yellow solid, wash with deionized water 3-4 times until the pH of the washing solution is 7;

[0021] S5. Refining and drying: Add the washed solid to ethanol, heat to 70-75℃ to dissolve the solid, filter while hot to remove insoluble impurities, cool the filtrate to room temperature to crystallize, filter to obtain crystals, and dry at 40-50℃ and -0.09MPa vacuum for 3-4 hours to obtain high-purity 4,4'-oxobis(benzenesulfonyl)hydrazine.

[0022] This process improves the purity of 4,4'-oxobisbenzenesulfonyl hydrazine to over 98% by precisely controlling the reaction temperature and pH value, ensuring stable foaming efficiency of the composite foaming agent.

[0023] The preferred preparation process of the modified plasticizer grafted with maleic anhydride in polyethylene glycol includes the following steps:

[0024] S1. Raw material preparation: Vacuum dry polyethylene glycol 4000 at 80-90℃ for 2-3 hours to remove moisture, and set aside for later use;

[0025] S2. Reaction system setup: In a four-necked flask equipped with a stirrer, thermometer and reflux condenser, add dried polyethylene glycol and toluene. The mass ratio of polyethylene glycol to toluene is 1:3-1:4. Stir until the polyethylene glycol is completely dissolved.

[0026] S3. Grafting reaction: Heat to 110-120℃, add maleic anhydride and initiator benzoyl peroxide, the molar ratio of maleic anhydride to polyethylene glycol is 1:1.2-1:1.5, the amount of benzoyl peroxide is 0.5-1.0% of the mass of polyethylene glycol, stir and react for 4-6 hours under nitrogen protection;

[0027] S4. Product purification: After the reaction is completed, toluene is removed by vacuum distillation (distillation temperature is 80-90℃, vacuum degree is -0.08MPa) to obtain a viscous product;

[0028] S5. Washing and drying: Pour the viscous product into acetone, the amount of acetone being 5-8 times the mass of the product. After stirring, let it stand for 2-3 hours to precipitate the solid. Filter and collect the solid. Wash it repeatedly with acetone 3-4 times. Finally, vacuum dry it at 50-60℃ for 2-3 hours to obtain polyethylene glycol grafted with maleic anhydride.

[0029] This process uses nitrogen protection to prevent oxidation during the reaction, and multiple acetone washes remove ungrafted maleic anhydride, improving the compatibility between the plasticizer and bamboo fiber.

[0030] The preferred preparation process of the functional inorganic filler includes the following steps:

[0031] S1. Raw material mixing: Weigh talc powder and titanium dioxide at a weight ratio of 2:1, put them into a high-speed mixer, and premix them for 10-15 minutes at a speed of 500-600 rpm;

[0032] S2. Coupling agent preparation: Mix silane coupling agent KH-550 with ethanol at a volume ratio of 1:10 and stir until homogeneous to obtain a coupling agent solution;

[0033] S3. Surface treatment: Slowly drip the coupling agent solution into the premixed filler, keeping the speed of the high-speed mixer at 600-700 rpm during the dripping process. The amount of coupling agent is 1.5-2.0% of the total mass of the filler. After the dripping is completed, continue stirring for 20-25 minutes.

[0034] S4. Drying and removing alcohol: Transfer the treated packing material into a forced-air drying oven and dry it at 80-90℃ for 1.5-2 hours to remove ethanol;

[0035] S5. Crushing and sieving: The dried filler is crushed in a crusher and sieved through a 200-mesh sieve to remove agglomerated particles, thus obtaining functional inorganic filler.

[0036] This process enhances the bonding force between the filler and the polyethylene matrix through surface modification with silane coupling agents, preventing the filler from settling and stratifying in the material.

[0037] Furthermore, the raw material also includes 0.2-0.6 parts of an antioxidant, wherein the antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0038] Adding this antioxidant can inhibit the thermal oxidative degradation of the material during the twin-screw extrusion process, prevent yellowing and embrittlement after long-term use, and extend the service life of the material. When the material is used in outdoor storage cabinets and other scenarios, it can increase the aging resistance of the material to more than 3 years, while not affecting the antibacterial properties and foaming effect of the material.

[0039] Furthermore, the weight ratio of 4,4'-oxobisbenzenesulfonyl hydrazine to sodium bicarbonate in the composite foaming agent can be adjusted to 4:1.

[0040] The adjusted material has a 15-20% increase in foaming ratio and a decrease in density to 0.65-0.75 g / cm³, while maintaining the cell diameter within the range of 50-100 μm. This makes it suitable for applications with higher lightweight requirements, such as drone fuselage cushioning components and portable folding chair frame filling materials. At the same time, the material's impact strength remains above 3.8 kg•cm / cm, meeting the strength requirements for use.

[0041] A method for manufacturing a bamboo fiber microporous foam material includes the following steps:

[0042] S1. Raw material weighing and pretreatment: Weigh polyethylene, bamboo fiber, titanate coupling agent, modified plasticizer, functional inorganic filler, and nano antibacterial agent according to the weight ratio. Place the bamboo fiber in a vacuum drying oven and dry it at 80-90℃ and -0.08 to -0.09MPa vacuum for 3-4 hours, ensuring that the moisture content is controlled at 1-2wt%.

[0043] S2. Premixing: Add the dried bamboo fiber, polyethylene, titanate coupling agent, modified plasticizer, functional inorganic filler, and nano antibacterial agent into a high-speed mixer. First, stir at 600 rpm for 3 minutes, then stir at 900 rpm for 4-6 minutes to obtain a uniform premixed material.

[0044] S3. Melt Blending: The premixed material is added to the main feeder of the twin-screw extruder, and the composite foaming agent is added to the side feeder. The twin-screw extruder barrel is divided into three sections along the material conveying direction: the first section temperature is 175℃, the second section temperature is 180℃, and the third section temperature is 185℃. The extrusion die temperature is 180℃, and the screw speed is 220-280 rpm. The main feeder is started first, and the side feeder is started after the die discharge is stable. The main feeder speed is 30-40 rpm, and the side feeder speed is 10-15 rpm. After melt blending, the material is extruded from the die.

[0045] S4. Granulation and Cooling: The extruded material is granulated by a pelletizer with a cutter speed of 800-1000 rpm and a distance of 0.1-0.2 mm between the cutter and the die head to obtain particles with a diameter of 2-3 mm. The particles are then placed in a cold water bath at 15-20℃ to cool for 5-8 minutes.

[0046] S5. Post-processing: After cooling, the granules are taken out and placed in a ventilated and dry place with a relative humidity of 40-50% for 12-24 hours to balance the internal moisture of the granules and obtain the finished granular bamboo fiber microporous foam material.

[0047] This method ensures uniform mixing of raw materials by controlling the mixing speed in stages, adds foaming agent by side feeding to prevent premature decomposition of foaming agent, and improves the stability of material performance by segmented temperature control and precise control of feeding speed.

[0048] Furthermore, the pellets after pelleting in step S4 need to be screened using a double-layer screen of 2mm and 3mm to remove small particles smaller than 2mm and large particles larger than 3mm.

[0049] The qualified rate of the screened particles is controlled at over 95% to ensure consistent material flow during subsequent injection molding, avoid local density differences in the finished product due to uneven particle size, and reduce mold blockage during injection molding.

[0050] Furthermore, in step S5, an air circulation device needs to be installed in the ventilated and drying area, with an air circulation speed of 0.3-0.5 m / s.

[0051] Ensure that the granules are heated evenly during the placement process to avoid localized moisture absorption. After drying, the moisture content of the granules is controlled at 1.5-2.5wt%. No further drying is required before subsequent injection molding, and they can be used directly. Moreover, the shrinkage rate of the injection-molded products fluctuates within a range of less than 0.1%, resulting in higher dimensional accuracy.

[0052] The beneficial effects of this invention are:

[0053] 1. In terms of mechanical and molding properties, the innovative bamboo fiber preparation process effectively removes impurities from the fiber and improves dispersion uniformity. At the same time, the modified plasticizer enhances the compatibility between bamboo fiber and polymer matrix, avoids component stratification, and gives the material better impact resistance, enabling it to better cope with external forces during use and reduce the risk of breakage. Moreover, the material has better dimensional stability after molding, which can accurately meet the dimensional requirements of various products and reduce the scrap rate caused by molding shrinkage. It is especially suitable for applications with high dimensional accuracy requirements.

[0054] 2. Regarding lightweight and heat resistance, relying on the precise preparation process of high-purity composite foaming agent, the material's cell structure can be effectively controlled. While ensuring mechanical properties, the overall density of the material is significantly reduced, meeting the requirements of lightweight applications. The weight of the product is reduced without affecting its strength. At the same time, the synergistic effect of functional inorganic fillers and other components greatly improves the material's heat resistance, enabling it to maintain structural stability at higher temperatures and expanding the material's application range in high-temperature scenarios.

[0055] 3. In terms of antibacterial performance, the optimized bamboo fiber purification process provides a more uniform dispersion environment for nano-antibacterial agents, avoiding local aggregation or uneven distribution of antibacterial agents due to fiber impurities. This ensures that all parts of the material can exert antibacterial effects, giving the material a long-lasting and stable antibacterial effect, effectively inhibiting the growth of microorganisms, reducing odor and mold problems, and improving the hygiene and safety of products during use. It is especially suitable for packaging, home furnishings, and other scenarios where items come into contact with the human body or need to be stored for a long time.

[0056] 4. In addition, the selection of material components and process design take into account both environmental protection and practicality. As a natural and renewable resource, bamboo fiber reduces dependence on petroleum-based raw materials, which is in line with the trend of green development. At the same time, the overall process flow is highly controllable, which is conducive to industrial production and provides the industry with foaming material solutions with better performance and wider application range. Detailed Implementation

[0057] The technical solutions in the embodiments of the present invention have been clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] Example 1

[0059] Raw materials were weighed according to the following parts by weight: 40 parts of polyethylene (melt index 12g / 10min), 60 parts of bamboo fiber (prepared by process, mesh size 50, water content 1wt%), 0.3 parts of titanate coupling agent, 3 parts of composite foaming agent (4,4'-oxobisbenzenesulfonyl hydrazine and sodium bicarbonate 3:1, 4,4'-oxobisbenzenesulfonyl hydrazine prepared by process), 2 parts of modified plasticizer (prepared by process), 6 parts of functional inorganic filler (prepared by process), and 0.5 parts of nano antibacterial agent (particle size 20nm).

[0060] The material was manufactured using a method for producing bamboo fiber microporous foam: S1 Vacuum drying of bamboo fiber (80℃, -0.08MPa, 3h); S2 High-speed mixing (600 rpm for 3min, 900 rpm for 4min); S3 Twin-screw extrusion (barrel three-stage temperature control 175 / 180 / 185℃, die 180℃, screw 220 rpm, main feed 30 rpm, side feed 10 rpm); S4 Granulation (cutter 800 rpm, spacing 0.1mm), cold water bath (15℃, 5min); S5 Ventilation drying (40% humidity, 12h). Finished product properties: impact strength 4.0 kg•cm / cm, shrinkage 0.5%, density 0.80 g / cm³, heat distortion temperature 110℃, antibacterial rate 95%.

[0061] Example 2

[0062] Raw materials were weighed according to the following parts by weight: 52 parts polyethylene (melt index 15g / 10min), 42 parts bamboo fiber (prepared by process, mesh size 110, water content 1.5wt%), 0.5 parts titanate coupling agent, 5 parts composite foaming agent (4,4'-oxobisbenzenesulfonyl hydrazine and sodium bicarbonate 3:1, prepared by process), 7 parts modified plasticizer (prepared by process), 9 parts functional inorganic filler (prepared by process), 1.2 parts nano antibacterial agent (particle size 35nm), and 0.4 parts antioxidant.

[0063] The material was manufactured using a method for producing bamboo fiber microporous foam: S1 Vacuum drying (85℃, -0.085MPa, 3.5h); S2 High-speed mixing (600 rpm for 3min, 900 rpm for 5min); S3 Twin-screw extrusion (barrel temperature 175 / 180 / 185℃, die temperature 180℃, screw 250 rpm, main feed 35 rpm, side feed 12 rpm); S4 Granulation (cutter 900 rpm, spacing 0.15mm), cold water bath (17℃, 6.5min); S5 Ventilation drying (45% humidity, 18h). Finished product properties: impact strength 4.3 kg•cm / cm, shrinkage 0.4%, density 0.75 g / cm³, heat distortion temperature 113℃, antibacterial rate 97%.

[0064] Example 3

[0065] Raw materials were weighed according to the following parts by weight: 65 parts polyethylene (melt index 18 g / 10 min), 25 parts bamboo fiber (prepared by process, mesh size 180 mesh, water content 2 wt%), 0.8 parts titanate coupling agent, 8 parts composite foaming agent (4,4'-oxobisbenzenesulfonyl hydrazine and sodium bicarbonate 4:1, prepared by process), 12 parts modified plasticizer (prepared by process), 12 parts functional inorganic filler (prepared by process), 2 parts nano antibacterial agent (particle size 50 nm), and 0.6 parts antioxidant.

[0066] The material was manufactured using a method for producing bamboo fiber microporous foam: S1 Vacuum drying (90℃, -0.09MPa, 4h); S2 High-speed mixing (600 rpm for 3min, 900 rpm for 6min); S3 Twin-screw extrusion (barrel temperature 175 / 180 / 185℃, die temperature 180℃, screw 280 rpm, main feed 40 rpm, side feed 15 rpm); S4 Granulation (cutter 1000 rpm, spacing 0.2mm), cold water bath (20℃, 8min); S5 Ventilation drying (50% humidity, 24h), followed by particle screening. The finished product exhibits the following properties: impact strength 4.5 kg•cm / cm, shrinkage 0.3%, density 0.65 g / cm³, heat distortion temperature 115℃, and antibacterial rate 98%.

[0067] Comparative Example 1

[0068] The bamboo fiber preparation process of this invention was not used. The raw materials were the same as in Example 2, but the bamboo fiber was prepared using a conventional alkali boiling process (only boiling at 100℃ for 1 hour, without enzymatic hydrolysis and ultrasonic dispersion). The manufacturing method was the same as in Example 2. Finished product properties: impact strength 3.2 kg•cm / cm (due to high fiber impurities and poor dispersion), shrinkage rate 0.7%, density 0.82 g / cm³, heat distortion temperature 102℃, antibacterial rate 90% (fiber impurities affected antibacterial agent dispersion).

[0069] Comparative Example 2

[0070] The composite foaming agent preparation process of this invention was not used. The raw materials were the same as in Example 2, but 4,4'-oxobisbenzenesulfonyl hydrazine was a commercially available conventional product (90% purity). The manufacturing method was the same as in Example 2. Finished product properties: impact strength 3.5 kg•cm / cm (uneven cell structure), shrinkage 0.6%, density 0.80 g / cm³, heat distortion temperature 105℃, antibacterial rate 95% (low purity of the foaming agent affects the material structure).

[0071] Comparative Example 3

[0072] The modified plasticizer preparation process of this invention was not used. The raw materials were the same as in Example 2, but the modified plasticizer was ordinary polyethylene glycol without maleic anhydride grafting. The manufacturing method was the same as in Example 2. Finished product properties: impact strength 3.3 kg•cm / cm (poor compatibility, component delamination), shrinkage rate 0.8%, density 0.83 g / cm³, heat distortion temperature 100℃, antibacterial rate 92% (poor compatibility affects the antibacterial agent's effectiveness).

[0073] Table of test results for bamboo fiber microporous foam materials (examples and comparative examples):

[0074]

[0075] Note: 1. Impact strength is tested according to GB / T1043.1-2008 standard; 2. Shrinkage rate is tested according to GB / T 17037.4-2003 standard; 3. Density is tested according to GB / T1033.1-2008 standard; 4. Heat distortion temperature is tested according to GB / T1634.1-2025 standard; 5. Antibacterial rate is tested according to GB / T31402-2023 standard (average antibacterial rate against Escherichia coli and Staphylococcus aureus).

[0076] The test results clearly show that the bamboo fiber microporous foam material of this invention is significantly superior to the comparative example in key performance indicators. Specifically, its advantages are reflected in the following three aspects: First, superior mechanical and molding properties. The impact strength of Examples 1-3 is all above 4.0 kg·cm / cm, reaching a maximum of 4.5 kg·cm / cm, with a minimum shrinkage rate of only 0.3%. In contrast, Comparative Example 1, due to the bamboo fiber not using the purification process of this invention, has an impact strength of only 3.2 kg·cm / cm and a shrinkage rate of 0.7%. Comparative Example 3, due to the lack of plasticizer grafting modification, has an impact strength of 3.3 kg·cm / cm and a shrinkage rate of 0.8%. This fully demonstrates that the bamboo fiber preparation process and modified plasticizer of this invention can effectively improve material compatibility and structural stability, and improve mechanical properties and molding precision. Second, superior lightweight and heat resistance. Example 3, by adjusting the ratio of the composite foaming agent (4:1), reduced the density to 0.65 g / cm³ and achieved a heat distortion temperature of 115°C. Comparative Example 2 used a commercially available low-purity foaming agent (90% purity), resulting in a density of 0.80 g / cm³ and a heat distortion temperature of 105°C. This demonstrates that the composite foaming agent preparation process of this invention (purity ≥98%) can precisely control the cell structure, improving heat resistance while achieving lightweighting, thus meeting the needs of high-temperature applications. Finally, the antibacterial performance is more stable. The antibacterial rates of Examples 1-3 are all ≥95%, with Example 3 reaching 98%. Comparative Example 1, due to the high impurity content in bamboo fiber affecting the dispersion of the antibacterial agent, had an antibacterial rate of only 90%. This indicates that this invention, through optimizing the bamboo fiber purification process (alkali boiling + enzymatic hydrolysis + ultrasonic dispersion), can ensure uniform distribution of the antibacterial agent, giving the material a long-lasting and stable antibacterial effect, suitable for packaging and home furnishing applications with high hygiene requirements. Overall, this invention achieves a comprehensive improvement in the mechanical, lightweight, heat-resistant, and antibacterial properties of materials through a proprietary preparation process for bamboo fiber, composite foaming agent, and modified plasticizer, as well as synergistic optimization of raw material ratio and manufacturing process. It solves the performance shortcomings of traditional bamboo fiber foam materials and has stronger practical value and market competitiveness.

[0077] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A bamboo fiber microcellular foamed material, characterized in that, The bamboo fiber is prepared by the following steps: S1. raw material pretreatment: select mildew-free moso bamboo, remove branches, tips and roots, polish with sandpaper to remove green bamboo, and saw the bamboo into bamboo tubes; S2. alkali cooking and impurity removal: split the bamboo tubes into bamboo pieces with a width of 2-3 cm, put them into a mixed solution containing 5-8 wt% sodium hydroxide and 3-5 wt% sodium carbonate, cook at 110-120℃ under a pressure of 0.12-0.15 MPa for 2-3 hours, and stir every 30 minutes during the cooking process; S3. enzymatic hydrolysis: take out the cooked bamboo pieces, rinse with deionized water until the pH value is 6-7, put them into a cellulase solution with a mass concentration of 0.8-1.0%, and hydrolyze in a constant temperature water bath at 50-55℃ for 4-6 hours, stirring for 10 minutes every hour during the hydrolysis process; S4. mechanical dispersion: put the hydrolyzed bamboo pieces into a colloid mill, grind at a speed of 1500-1800 rpm for 30-40 minutes, and simultaneously input ultrasonic waves with a power of 300-400 W for auxiliary dispersion; S5. separation and purification: pour the ground mixture into a hydraulic separator, control the water flow rate to be 0.5-0.8 m / s, separate the coarse fiber impurities, collect the suspended bamboo fibers, vacuum filter, dry at 60-70℃ until the water content is 1-2 wt%, and finally crush through a 50-180 mesh sieve to obtain the finished bamboo fiber. The preparation process of the 4,4'-oxybisbenzenesulfonyl hydrazide in the composite foaming agent is as follows: S1. sulfonation reaction: in a three-necked flask equipped with a stirrer and a reflux condenser, add p-aminobenzenesulfonamide and 98% sulfuric acid, the molar ratio of p-aminobenzenesulfonamide to sulfuric acid is 1:2.5-1:3, heat to 80-90℃, and stir for 3-4 hours to generate p-aminobenzenesulfonic acid sulfate; S2. diazotization reaction: cool the reaction solution to 0-5℃, slowly add 30% sodium nitrite solution, the molar ratio of sodium nitrite to p-aminobenzenesulfonamide is 1:1, after the addition is completed, keep stirring for 2-3 hours to generate a diazonium salt solution; S3. coupling reaction: cool the diazonium salt solution to 0-5℃, slowly add 2,2'-diphenyl ether, the molar ratio of 2,2'-diphenyl ether to p-aminobenzenesulfonic acid sulfate is 1:1, and keep stirring for 2-3 hours to generate the 4,4'-oxybisbenzenesulfonyl hydrazide.

2. The bamboo fiber microcellular foamed material according to claim 1, characterized in that, ​ ​ ​ S3. Coupling reaction: add diphenyl ether to the diazonium salt solution, the molar ratio of diphenyl ether to p-aminobenzenesulfonamide is 1:2, adjust the pH value to 8-9 with 20% sodium hydroxide solution, heat to 60-70℃, stir for 5-6 hours, take sample every 1 hour to detect the reaction progress; S4. Purification of crude product: after the reaction is completed, cool the mixture to room temperature, filter to obtain a light yellow solid, wash with deionized water for 3-4 times until the pH value of the washing liquid is 7; S5. Drying: add the washed solid to ethanol, heat to 70-75℃ to dissolve the solid, filter to remove insoluble impurities while hot, cool the filtrate to room temperature to crystallize, filter to obtain crystals, dry at 40-50℃ under vacuum condition of -0.09 MPa for 3-4 hours to obtain high-purity 4,4'-oxobisbenzenesulfonyl hydrazide.

3. The bamboo fiber microcellular foamed material according to claim 1, wherein, The preparation process steps of the modified plasticizer grafted polyethylene glycol maleic anhydride are as follows: S1. Raw material preparation: vacuum dry polyethylene glycol 4000 at 80-90℃ for 2-3 hours to remove water; S2. Reaction system setup: add the dried polyethylene glycol and toluene to a four-necked flask equipped with a stirrer, thermometer and reflux condenser, the mass ratio of polyethylene glycol to toluene is 1:3-1:4, stir until the polyethylene glycol is completely dissolved; S3. Grafting reaction: heat to 110-120℃, add maleic anhydride and initiator dibenzoyl peroxide, the molar ratio of maleic anhydride to polyethylene glycol is 1:1.2-1:1.5, the amount of dibenzoyl peroxide is 0.5-1.0% of the mass of polyethylene glycol, stir for 4-6 hours under nitrogen protection; S4. Product purification: after the reaction is completed, remove toluene by vacuum distillation to obtain a viscous product; S5. Washing and drying: pour the viscous product into acetone, the amount of acetone is 5-8 times the mass of the product, stir and stand for 2-3 hours, the solid is precipitated, filter to collect the solid, repeat washing with acetone for 3-4 times, finally dry at 50-60℃ under vacuum for 2-3 hours to obtain polyethylene glycol grafted with maleic anhydride.

4. The bamboo fiber microcellular foamed material according to claim 1, wherein, The preparation process steps of the functional inorganic filler are as follows: S1. Raw material mixing: weigh talc and titanium dioxide according to the weight ratio of 2:1, put them into a high-speed mixer, pre-mix for 10-15 minutes at a speed of 500-600 rpm; S2. Coupling agent preparation: mix silane coupling agent KH-550 and ethanol according to the volume ratio of 1:10, stir uniformly to obtain a coupling agent solution; S3. Surface treatment: slowly drop the coupling agent solution into the pre-mixed filler, keep the high-speed mixer at a speed of 600-700 rpm during the dropping process, the amount of coupling agent is 1.5-2.0% of the total mass of the filler, continue stirring for 20-25 minutes after the dropping is completed; S4. Alcohol removal by drying: transfer the treated filler into a forced air drying oven, dry at 80-90℃ for 1.5-2 hours to remove ethanol; S5. Crushing and sieving: put the dried filler into a crusher, crush and sieve through a 200 mesh sieve to remove agglomerated particles, obtain the functional inorganic filler.

5. The bamboo fiber microcellular foamed material according to claim 1, wherein, The raw materials also include 0.2-0.6 parts of an antioxidant, which is tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]pentaerythritol ester.

6. The bamboo fiber microcellular foamed material according to claim 1, wherein, The weight ratio of 4,4'-oxybisbenzenesulfonylhydrazide to sodium bicarbonate in the composite foaming agent can be adjusted to 4:

1.

7. A method for manufacturing a bamboo fiber microcellular foamed material, for manufacturing the bamboo fiber microcellular foamed material according to any one of claims 1 to 6, characterized by, The method comprises the following steps: S1. Raw material weighing and pretreatment: the polyethylene, bamboo fiber, titanate coupling agent, modified plasticizer, functional inorganic filler, and nano-antibacterial agent are weighed according to the weight ratio, the dried bamboo fiber is placed in a vacuum drying oven, dried at 80-90 DEG C and a vacuum degree of-0.08 to-0.09 MPa for 3-4 hours, and the water content is controlled to be 1-2 wt%; S2. Premixing: the dried bamboo fiber, polyethylene, titanate coupling agent, modified plasticizer, functional inorganic filler, and nano-antibacterial agent are added into a high-speed mixer, stirred at a speed of 600 rpm for 3 minutes, and then stirred at a speed of 900 rpm for 4-6 minutes to obtain a uniform premixed material; S3. Melt blending: the premixed material is added into a main feeder of a twin-screw extruder, the composite foaming agent is added into a side feeder, the barrel of the twin-screw extruder is divided into three sections along the material conveying direction, the temperature of the first section is 175 DEG C, the temperature of the second section is 180 DEG C, the temperature of the third section is 185 DEG C, the temperature of the extrusion die is 180 DEG C, the screw rotation speed is 220-280 rpm, the main feeder is started first, the side feeder is started after the material is stably discharged from the die, the rotation speed of the main feeder is 30-40 rpm, the rotation speed of the side feeder is 10-15 rpm, and the material is extruded from the die after melt blending; S4. Granulation and cooling: the extruded material is granulated by a granulator, the cutter rotation speed of the granulator is 800-1000 rpm, the distance between the cutter and the die is 0.1-0.2 mm, 2-3 mm granules are obtained, and the granules are cooled in a 15-20 DEG C cold water bath for 5-8 minutes; S5. Post-treatment: the cooled granules are taken out and placed in a ventilated and dried place with a relative humidity of 40-50% for 12-24 hours to balance the internal moisture of the granules, and finally the granular bamboo fiber microporous foaming material is obtained.

8. The method of claim 7, wherein the bamboo fiber microcellular foamed material is characterized by, The granules after granulation in step S4 need to be screened using a double-layer screen with a mesh size of 2 mm and 3 mm to remove the granules with a particle size less than 2 mm and the coarse granules with a particle size greater than 3 mm.

9. The method of claim 7, wherein the bamboo fiber microcellular foamed material is characterized by, In step S5, an air circulation device needs to be arranged in the ventilated and dried place, and the air circulation speed is 0.3-0.5 m / s.

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