Bamboo fiber microcellular foam material and manufacturing method thereof

Abstract

The invention discloses a bamboo fiber microcellular foam material and a manufacturing method thereof. The bamboo fiber microcellular foam material is prepared from polyethylene, bamboo fibers, a titanate coupling agent, a composite foaming agent, a modified plasticizer, functional inorganic filler, a nano antibacterial agent and the like. The bamboo fiber, the composite foaming agent and the modified plasticizer are prepared through an exclusive process, and the manufacturing steps of staged mixing, precise temperature control extrusion and the like are combined, so that the problems that a traditional material is poor in antibacterial property, poor in component compatibility and uneven in foaming are solved. The material has excellent impact resistance, dimensional stability, light weight, heat resistance and long-acting antibacterial property, is prepared from renewable bamboo fibers, is environment-friendly and easy for industrial production, and can be widely applied to the fields of automotive trim, home furnishing, packaging and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bio-based composite materials, and particularly relates to a bamboo fiber microporous foaming material and a manufacturing method thereof. BACKGROUND

[0002] At present, the foaming materials widely used in the fields of automobile interiors, packaging cushioning and the like are mostly made of petroleum-based polymers, and have the problems of non-degradability and poor environmental protection, and the traditional foaming materials often have defects such as insufficient antibacterial property, uneven cells, and poor mechanical properties, and are difficult to meet the needs of high-end scenarios.

[0003] Bamboo fiber, as a natural renewable resource, has the advantages of high strength and degradability, and is tried to be used to improve the foaming material, but the bamboo fiber contains impurities such as lignin and hemicellulose, and has poor compatibility with the polymer matrix, which easily leads to material delamination; at the same time, the existing composite foaming agents have the problems of unstable foaming efficiency and difficult cell control, the adaptability of the modified plasticizer to the bamboo fiber is insufficient, and the functional inorganic fillers are prone to agglomeration, which further restricts the performance improvement of the bamboo fiber foaming material.

[0004] In the prior art, the purification process of the bamboo fiber is complex and has high cost, and the preparation process of the foaming agent and the plasticizer lacks precise control, and it is difficult to realize the synergistic optimization of the material performance, therefore, it becomes an urgent problem to be solved in the industry to develop a bamboo fiber microporous foaming material with good component compatibility, uniform foaming, excellent mechanical and antibacterial properties and related process. SUMMARY

[0005] The present application provides a bamboo fiber microporous foaming material and a manufacturing method thereof, which realizes the deficiencies of the material in material mechanics, lightweight, heat resistance and antibacterial performance by raw material treatment, improved treatment process and processing process parameters.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: A bamboo fiber microporous foaming material is made of the following raw materials in a weight ratio: polyethylene 40-65 parts, bamboo fiber 25-60 parts, titanate coupling agent 0.3-0.8 parts, composite foaming agent 3-8 parts, modified plasticizer 2-12 parts, functional inorganic filler 6-12 parts, and nano-antibacterial agent 0.5-2 parts; the composite foaming agent is made by mixing 4,4'-oxobisbenzenesulfonyl hydrazide and sodium bicarbonate in a weight ratio of 3:1.

[0007] Preferably, the modified plasticizer is grafted maleic anhydride polyethylene glycol, the functional inorganic filler is talc powder surface treated by silane coupling agent KH-550 compounded with titanium dioxide at 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 / 10 min, the bamboo fiber has a mesh number of 50-180 and a water content controlled at 1-2 wt%, the titanate coupling agent is isopropyl tri(dioctyl pyrophosphoric acyloxy) titanate, and the particle size of the nano antibacterial agent is 20-50 nm. The material improves the uniformity of foaming through the synergistic effect of the two components in the composite foaming agent, the modified plasticizer enhances the compatibility of bamboo fiber and polyethylene, the functional inorganic filler optimizes the tensile strength and heat resistance of the material, and the nano antibacterial agent gives the material long-acting antibacterial function, solving the problems of short antibacterial time, easy stratification of components, and uneven foaming pore size of traditional bamboo fiber foaming materials. The impact strength of the finished product after injection molding is 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 less than 110℃, and the antibacterial rates of Escherichia coli and Staphylococcus aureus are not less than 95%, which can be applied in the fields of automobile interior cushioning parts, household storage boxes, and electronic device packaging liners.

[0008] Preferably, the preparation process of the bamboo fiber comprises the following steps: S1. Raw material pretreatment: select mildew-free moso bamboo, remove branches, tips and roots, polish with sandpaper to remove bamboo green, and saw the bamboo into bamboo cylinders; S2. Alkali cooking and impurity removal: split the bamboo cylinders 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℃ and 0.12-0.15 MPa pressure for 2-3 hours, and stir every 30 minutes during the 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 1 hour during the 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 hydrodynamic separator, control the water flow rate at 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%, finally crush through a 50-180 mesh sieve, and obtain the finished bamboo fiber.

[0009] The process effectively removes lignin and hemicellulose in bamboo fiber by combining alkali cooking and enzymatic hydrolysis, and ultrasonic-assisted grinding improves fiber dispersion to ensure uniform distribution of bamboo fiber in the material.

[0010] Preferably, the preparation process of 4,4'-oxybisbenzenesulfonylhydrazide in the composite foaming agent comprises the following steps: S1. Sulfonation reaction: In a three-necked flask equipped with a stirrer and a reflux condenser, p-aminobenzenesulfonamide and 98% sulfuric acid are added, the molar ratio of p-aminobenzenesulfonamide to sulfuric acid is 1:2.5-1:3, the temperature is raised to 80-90℃, and the reaction is stirred 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, the solution is stirred for 2-3 hours to generate a diazonium salt solution; 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, raise the temperature to 60-70℃, and stir for 5-6 hours, during which the reaction progress is detected every 1 hour; S4. Purification of crude product: After the reaction is completed, cool the mixture to room temperature, and 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. Refining and 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, and dry at 40-50℃ under vacuum condition of -0.09MPa for 3-4 hours to obtain high-purity 4,4'-oxybisbenzenesulfonylhydrazide.

[0011] The process precisely controls the reaction temperature and pH value to improve the purity of 4,4'-oxybisbenzenesulfonylhydrazide to more than 98%, ensuring the stable foaming efficiency of the composite foaming agent.

[0012] Preferably, the preparation process of modified plasticizer grafted polyethylene glycol maleic anhydride comprises the following steps: S1. Raw material preparation: Vacuum dry polyethylene glycol 4000 at 80-90℃ for 2-3 hours to remove water; S2. Reaction system setup: In a four-necked flask equipped with a stirrer, a thermometer and a reflux condenser, add dried polyethylene glycol and toluene, the mass ratio of polyethylene glycol to toluene is 1:3-1:4, and stir until the polyethylene glycol is completely dissolved; S3. Grafting reaction: temperature is raised to 110-120℃, maleic anhydride and initiator dibenzoyl peroxide are added, 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, stirring under nitrogen protection for 4-6 hours; S4. Product purification: after the reaction is completed, remove toluene by distillation under reduced pressure (distillation temperature is 80-90℃, vacuum degree is -0.08MPa), obtain 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, precipitate solid, collect the solid by filtration, repeat washing with acetone for 3-4 times, finally dry at 50-60℃ under vacuum for 2-3 hours, obtain polyethylene glycol grafted with maleic anhydride.

[0013] This process avoids oxidation during the reaction process by nitrogen protection, removes ungrafted maleic anhydride by multiple acetone washing, and improves the compatibility of the plasticizer and the bamboo fiber.

[0014] Preferably, the preparation process of the functional inorganic filler comprises the following steps: S1. Raw material mixing: take talcum powder and titanium dioxide according to a weight ratio of 2:1, put them into a high-speed mixer, and pre-mix for 10-15 minutes at a speed of 500-600 revolutions per minute; S2. Coupling agent preparation: mix silane coupling agent KH-550 and ethanol according to a 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 speed of the high-speed mixer at 600-700 revolutions per minute during the dropping process, the amount of the 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: put 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 pass through a 200-mesh sieve to remove agglomerated particles, obtain the functional inorganic filler.

[0015] This process enhances the bonding force between the filler and the polyethylene matrix through surface modification by silane coupling agent, and avoids the settlement and stratification of the filler in the material.

[0016] Further, the raw material further includes an antioxidant 0.2-0.6 parts, and the antioxidant is tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]pentaerythritol ester.

[0017] The addition of the antioxidant can inhibit the thermal oxidative degradation of the material during the twin-screw extrusion process, prevent the material from yellowing and embrittlement after long-term use, and prolong the service life of the material. When the material is applied to outdoor storage cabinets and other scenarios, the material's aging resistance time can be improved to more than 3 years, without affecting the material's antibacterial performance and foaming effect.

[0018] Further, the weight ratio of 4,4'-oxybisbenzenesulfonylhydrazide to sodium bicarbonate in the composite foaming agent can be adjusted to 4:1.

[0019] After adjustment, the foaming ratio of the material is increased by 15-20%, the density is reduced to 0.65-0.75 g / cm³, and the cell diameter is still controlled within the range of 50-100 μm, which is suitable for scenarios with higher lightweight requirements, such as unmanned aerial vehicle body cushion components, portable folding chair frame fillers, etc. At the same time, the impact strength of the material remains above 3.8 kg•cm / cm, meeting the strength requirements.

[0020] A manufacturing method of a bamboo fiber microcellular foaming material, comprising the following steps: S1. Raw material weighing and pretreatment: weigh and mix polyethylene, bamboo fiber, titanate coupling agent, modified plasticizer, functional inorganic filler, and nano-antibacterial agent according to the weight ratio. Dry the bamboo fiber in a vacuum drying oven at 80-90°C and a vacuum degree of -0.08 to -0.09 MPa for 3-4 hours to ensure the water content is controlled within 1-2 wt%. S2. Pre-mixing: 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 a speed of 600 rpm for 3 minutes, then stir at a speed of 900 rpm for 4-6 minutes to obtain a uniform pre-mixture. S3. Melt blending: add the pre-mixture to the main feeder of a twin-screw extruder, and add the composite foaming agent to the side feeder. The barrel of the twin-screw extruder is divided into three sections along the material conveying direction, with the first section temperature being 175°C, the second section temperature being 180°C, and the third section temperature being 185°C. The extrusion die temperature is 180°C, and the screw rotation speed is 220-280 rpm. First start the main feeder, then start the side feeder after the die output stabilizes. The main feeder rotation speed is 30-40 rpm, and the side feeder rotation speed is 10-15 rpm. The material is extruded from the die after melt blending. S4. Granulation and cooling: granulate the extruded material using a granulator. The cutter rotation speed of the granulator is 800-1000 rpm, and the distance between the cutter and the die is 0.1-0.2 mm. The obtained granules have a particle size of 2-3 mm. Place the granules in a cold water bath at 15-20°C for 5-8 minutes. S5. Post-processing: After cooling, the particles are fished out and placed in a ventilated drying place with relative humidity of 40-50% for 12-24 hours to balance the internal moisture of the particles, and the finished granular bamboo fiber microporous foaming material is obtained.

[0021] The method ensures uniform mixing of raw materials by controlling the mixing speed in stages, avoids premature decomposition of the foaming agent by adding the foaming agent through side feeding, and improves the stability of the material performance by controlling the temperature in stages and precisely controlling the feeding speed.

[0022] Further, the granules after cutting in step S4 also need to be screened, using a double-layer screen with a mesh size of 2mm and 3mm, to remove granules with a particle size less than 2mm and coarse granules with a particle size greater than 3mm.

[0023] The qualified rate of the screened granules is controlled to be more than 95%, ensuring the consistency of the material flow during subsequent injection molding, avoiding local density differences in the finished product due to uneven particle size, and reducing the mold blocking phenomenon during injection molding.

[0024] Further, the air circulation device needs to be provided in the ventilated drying place in step S5, and the air circulation speed is 0.3-0.5m / s.

[0025] Ensure uniform heating of the particles during placement, avoid local moisture, and control the moisture content of the dried particles to 1.5-2.5wt%, so that the particles can be used directly without the need for further drying during subsequent injection molding, and the shrinkage rate of the injection molded product fluctuates less than 0.1%, with higher dimensional accuracy.

[0026] Advantages of the present application: 1. In terms of mechanics and forming performance, the impurities in the bamboo fiber are effectively removed and the dispersion uniformity is improved through the innovative bamboo fiber preparation process, and the compatibility of the bamboo fiber and the polymer matrix is enhanced with the help of the modified plasticizer, avoiding component delamination, making the material have better impact resistance, better responding to external forces during use, and reducing the risk of damage; and the dimensional stability of the material after forming is better, which can accurately meet the size requirements of various products, reduce the product scrap rate caused by shrinkage during forming, and is especially suitable for application scenarios with high dimensional accuracy requirements. 2. In terms of lightweight and heat resistance, the precise preparation process of high-purity composite foaming agent is relied on to effectively control the pore structure of the material, significantly reducing the overall density of the material while ensuring mechanical properties, meeting the lightweight application requirements, reducing the weight of the product while not affecting the use strength; at the same time, the synergistic effect of functional inorganic fillers and other components greatly improves the heat resistance of the material, enabling it to maintain structural stability at higher temperatures, expanding the application range of the material in high-temperature scenarios.

[0027] 3. In terms of antibacterial performance, the optimized purification process of bamboo fiber provides a more uniform dispersion environment for nano-antibacterial agents, avoiding the local aggregation or uneven distribution of antibacterial agents due to the obstruction of fiber impurities, ensuring that each part of the material can exert antibacterial effect, giving the material long-term and stable antibacterial effect, effectively inhibiting the growth of microorganisms, reducing odor and mold problems, and improving the hygiene safety during product use, especially suitable for packaging, home and other scenarios that contact with human body or need to store goods for a long time. 4. In addition, the selection of each component of the material and the design of the process consider environmental protection and practicality. Bamboo fiber, as a natural renewable resource, reduces the dependence on petroleum-based raw materials, conforms to the green development trend, and the overall process is controllable, facilitating industrial production, and providing a foaming material solution with better performance and wider application range for the industry. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application are described clearly and completely. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0029] Embodiment 1 The raw materials are weighed by weight parts: polyethylene 40 parts (melt index 12 g / 10 min), bamboo fiber 60 parts (prepared by process, mesh number 50 mesh, water content 1 wt%), titanate coupling agent 0.3 parts, composite foaming agent 3 parts (4,4'-oxobisbenzenesulfonyl hydrazide and sodium bicarbonate 3:1, 4,4'-oxobisbenzenesulfonyl hydrazide prepared by process), modified plasticizer 2 parts (prepared by process), functional inorganic filler 6 parts (prepared by process), nano-antibacterial agent 0.5 parts (particle size 20 nm).

[0030] A kind of bamboo fiber microporous foaming material is manufactured according to the manufacturing method: S1 vacuum drying bamboo fiber (80℃, -0.08MPa, 3h); S2 high-speed mixing (600r / min 3min, 900r / min 4min); S3 double screw extrusion (cylinder three section temperature 175 / 180 / 185℃, die head 180℃, screw 220r / min, main feeding 30r / min, side feeding 10r / min); S4 granulation (cutter 800r / min, interval 0.1mm), cold water bath (15℃, 5min); S5 ventilation drying (humidity 40%, 12h). The performance of finished product: impact strength 4.0kg•cm / cm, shrinkage 0.5%, density 0.80g / cm³, heat distortion temperature 110℃, antibacterial rate 95%.

[0031] Embodiment 2 The raw materials were weighed by parts by weight: polyethylene 52 parts (melt index 15 g / 10 min), bamboo fiber 42 parts (prepared by process, mesh 110 mesh, water content 1.5 wt%), titanate coupling agent 0.5 parts, composite foaming agent 5 parts (4,4'-oxobisbenzenesulfonyl hydrazide and sodium bicarbonate 3:1, prepared by process), modified plasticizer 7 parts (prepared by process), functional inorganic filler 9 parts (prepared by process), nano-antibacterial agent 1.2 parts (particle size 35 nm), antioxidant 0.4 parts.

[0032] A bamboo fiber microcellular foam material was manufactured according to the manufacturing method: S1 vacuum drying (85°C, -0.085MPa, 3.5h); S2 high-speed mixing (600rpm for 3min, 900rpm for 5min); S3 double screw extrusion (cylinder temperature 175 / 180 / 185°C, die temperature 180°C, screw speed 250rpm, main feeding speed 35rpm, side feeding speed 12rpm); S4 granulation (cutter speed 900rpm, distance 0.15mm), cold water bath (17°C, 6.5min); S5 ventilation drying (humidity 45%, 18h). The finished product performance: impact strength 4.3kg•cm / cm, shrinkage rate 0.4%, density 0.75g / cm³, heat distortion temperature 113°C, antibacterial rate 97%.

[0033] Example 3 The raw materials were weighed by parts by weight: polyethylene 65 parts (melt index 18 g / 10 min), bamboo fiber 25 parts (prepared by process, mesh 180 mesh, water content 2 wt%), titanate coupling agent 0.8 parts, composite foaming agent 8 parts (4,4'-oxobisbenzenesulfonyl hydrazide and sodium bicarbonate 4:1, prepared by process), modified plasticizer 12 parts (prepared by process), functional inorganic filler 12 parts (prepared by process), nano-antibacterial agent 2 parts (particle size 50 nm), antioxidant 0.6 parts.

[0034] A bamboo fiber microcellular foam material was manufactured according to the manufacturing method: S1 vacuum drying (90°C, -0.09MPa, 4h); S2 high-speed mixing (600rpm for 3min, 900rpm for 6min); S3 double screw extrusion (cylinder temperature 175 / 180 / 185°C, die temperature 180°C, screw speed 280rpm, main feeding speed 40rpm, side feeding speed 15rpm); S4 granulation (cutter speed 1000rpm, distance 0.2mm), cold water bath (20°C, 8min); S5 ventilation drying (humidity 50%, 24h), and screening of granules. The finished product performance: impact strength 4.5kg•cm / cm, shrinkage rate 0.3%, density 0.65g / cm³, heat distortion temperature 115°C, antibacterial rate 98%.

[0035] Comparative Example 1 Example 2 was not prepared by the bamboo fiber preparation process of the present application, and the raw materials were the same as those of Example 2, but the bamboo fiber was prepared by a conventional alkali boiling process (only 100°C alkali boiling for 1h, without enzymatic hydrolysis and ultrasonic dispersion). The manufacturing method was the same as that of Example 2. The finished product performance: impact strength 3.2 kg•cm / cm (due to many impurities and poor dispersion of the fiber), shrinkage rate 0.7%, density 0.82 g / cm³, heat distortion temperature 102°C, antibacterial rate 90% (fiber impurities affect the dispersion of the antibacterial agent).

[0036] Comparative Example 2 Example 2 was not prepared by the bamboo fiber preparation process of the present application, and the raw materials were the same as those of Example 2, but 4,4'-oxybisbenzenesulfonylhydrazide was a commercially available conventional product (purity 90%). The manufacturing method was the same as that of Example 2. The finished product performance: impact strength 3.5 kg•cm / cm (cell uniformity), shrinkage rate 0.6%, density 0.80 g / cm³, heat distortion temperature 105°C, antibacterial rate 95% (low purity of foaming agent affects the material structure).

[0037] Comparative Example 3 Example 2 was not prepared by the bamboo fiber preparation process of the present application, and the raw materials were the same as those of Example 2, but the modified plasticizer was ordinary polyethylene glycol without grafted maleic anhydride. The manufacturing method was the same as that of Example 2. The finished product performance: impact strength 3.3 kg•cm / cm (poor compatibility, component layering), shrinkage rate 0.8%, density 0.83 g / cm³, heat distortion temperature 100°C, antibacterial rate 92% (poor compatibility affects the effect of the antibacterial agent).

[0038] Test results of bamboo fiber microporous foaming material examples and comparative examples: Note: 1. Impact strength was tested according to GB / T1043.1-2008 standard; 2. Shrinkage rate was tested according to GB / T 17037.4-2003 standard; 3. Density was tested according to GB / T1033.1-2008 standard; 4. Heat distortion temperature was tested according to GB / T1634.1-2025 standard; 5. Antibacterial rate was tested according to GB / T31402-2023 standard (average antibacterial rate against Escherichia coli and Staphylococcus aureus).

[0039] From the table detection result can be clearly seen, the bamboo fiber microporous foaming material of the application is significantly better than the comparative example in key performance indicators, the specific advantages are reflected in the following three aspects: first, the mechanical and forming properties are better. The impact strength of examples 1-3 is above 4.0 kg·cm / cm, the highest is 4.5 kg·cm / cm, and the shrinkage rate is only 0.3%; while the impact strength of comparative example 1 is only 3.2 kg·cm / cm due to the use of the purification process of the application, and the shrinkage rate rises to 0.7%, and the impact strength of comparative example 3 is 3.3 kg·cm / cm and the shrinkage rate is 0.8% due to the non-graft modification of the plasticizer, which fully shows that the bamboo fiber preparation process and modified plasticizer of the application can effectively improve the material compatibility and structural stability, and improve the mechanical properties and forming precision. Secondly, the lightweight and heat resistance are more prominent. The density of example 3 is reduced to 0.65 g / cm3 by adjusting the ratio of composite foaming agent (4:1), and the heat distortion temperature is 115℃; the density of comparative example 2 is 0.80 g / cm3 and the heat distortion temperature is 105℃ by using the commercially available low-purity foaming agent (purity 90%), which proves that the preparation process of the composite foaming agent (purity ≥98%) of the application can precisely control the pore structure, and improve the heat resistance while achieving lightweight, and meet the use requirements in high temperature scene. Finally, the antibacterial performance is more stable. The antibacterial rate of examples 1-3 is ≥95%, and the antibacterial rate of example 3 is 98%; the antibacterial rate of comparative example 1 is only 90% due to the influence of impurities in bamboo fiber on the dispersion of antibacterial agent, which shows that the purification process (alkali cooking + enzymatic hydrolysis + ultrasonic dispersion) of bamboo fiber of the application can ensure the uniform distribution of antibacterial agent, and give the material long-term stable antibacterial effect, which is suitable for packaging and home field with high hygiene requirements. Overall, the application realizes the comprehensive improvement of the mechanical properties, lightweight, heat resistance and antibacterial performance of the material through the exclusive preparation process of bamboo fiber, composite foaming agent and modified plasticizer, and the synergistic optimization of raw material ratio and manufacturing process, solves the performance short board of traditional bamboo fiber foaming material, and has stronger practical value and market competitiveness.

[0040] Although embodiments of the application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the application, the scope of the application being defined by the appended claims and their equivalents.

Claims

1. A bamboo fiber microcellular foamed material, characterized in that, The bamboo fiber is prepared from the following raw materials in the following weight ratio: 40-65 parts of polyethylene, 25-60 parts of bamboo fiber, 0.3-0.8 parts of titanate coupling agent, 3-8 parts of composite foaming agent, 2-12 parts of modified plasticizer, 6-12 parts of functional inorganic filler, and 0.5-2 parts of nano antibacterial agent.

2. The bamboo fiber microcellular foamed material according to claim 1, wherein, The preparation process of the bamboo fiber comprises the following steps: S1. Raw material pretreatment: select mold-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℃ and 0.12-0.15 MPa for 2-3 hours, and stir every 30 minutes during the cooking; 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, and stir every 1 hour during the hydrolysis; 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 hydrodynamic separator, control the water flow speed to be 0.5-0.8 m / s, separate the coarse fiber impurities, collect the suspended bamboo fiber, 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.

3. The bamboo fiber microcellular foamed material according to claim 1, wherein, The preparation process of 4,4'-oxybisbenzenesulfonylhydrazide in the composite foaming agent comprises the following steps: 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: 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℃, and stir for 5-6 hours, during which the reaction progress is detected every 1 hour; S4. Purification of crude product: after the reaction is completed, cool the mixture to room temperature, filter to obtain a light yellow solid, and wash with deionized water for 3-4 times until the pH value of the washing liquid is 7; S5. Refining and drying: add the washed solid into 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 of-0.09MPa for 3-4 hours to obtain high-purity 4,4'-oxobisbenzenesulfonylhydrazide.

4. The bamboo fiber microcellular foamed material according to claim 1, wherein, The preparation process of the modified plasticizer grafted polyethylene glycol maleic anhydride includes the following steps: 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 into 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 under nitrogen protection for 4-6 hours; 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, precipitate the solid, filter and collect the solid, repeat the 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.

5. The bamboo fiber microcellular foamed material according to claim 1, wherein, The preparation process of the functional inorganic filler includes the following steps: S1. Raw material mixing: weigh talc and titanium dioxide according to a weight ratio of 2:1, put them into a high-speed mixer, and pre-mix at a speed of 500-600 rpm for 10-15 minutes; S2. Coupling agent preparation: mix silane coupling agent KH-550 and ethanol according to a volume ratio of 1:10, and 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, and obtain the functional inorganic filler.

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

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

1.

8. 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 7, characterized by, The preparation process includes 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 bamboo fiber is placed in a vacuum drying oven and dried at 80-90°C and a vacuum degree of-0.08 to-0.09 MPa for 3-4 hours to ensure that the water content is controlled at 1-2wt%; S2. Premixing: The dried bamboo fiber, polyethylene, titanate coupling agent, modified plasticizer, functional inorganic filler, and nano-antibacterial agent are added to a high-speed mixer. First, they are stirred at a speed of 600 rpm for 3 minutes, and then at a speed of 900 rpm for 4-6 minutes to obtain a uniform premixed material; S3. Melt blending: The premixed material is added to the main feeder of a twin-screw extruder, and the composite foaming agent is added to the side feeder. The barrel of the twin-screw extruder is divided into three sections along the material conveying direction, with the first section at 175°C, the second section at 180°C, and the third section at 185°C. The extrusion die temperature is 180°C, the screw speed is 220-280 rpm, the main feeder is started first, and then the side feeder is started after the die discharge stabilizes. The main feeder speed is 30-40 rpm, the side feeder speed 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 with a cutter speed of 800-1000 rpm and a cutter-to-die distance of 0.1-0.2 mm to obtain granules with a particle size of 2-3 mm. The granules are cooled in a 15-20°C cold water bath for 5-8 minutes; S5. Post-treatment: The cooled granules are removed and placed in a well-ventilated drying area with a relative humidity of 40-50% for 12-24 hours to balance the internal moisture of the granules, obtaining finished granular bamboo fiber microporous foaming material.

9. The method of claim 8, 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 2mm and 3mm mesh sizes to remove granules smaller than 2mm and larger than 3mm.

10. The method for manufacturing bamboo fiber microporous foamed material according to claim 8, characterized in that, In step S5, the well-ventilated drying area needs to be equipped with an air circulation device with an air circulation speed of 0.3-0.5 m / s.

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