A method for preparing a biodegradable molded container made from bamboo waste.

Abstract

This invention discloses a method for preparing a biodegradable molded container from bamboo waste, relating to the high-value utilization of agricultural and forestry waste. The method includes bamboo waste pretreatment, modifier preparation, raw material blending, hot-melt mixing, and molding steps: bamboo processing waste is pulverized to a specific fiber morphology, pretreated under high-temperature steam pressure, blended with polylactic acid, a bamboo charcoal / zinc oxide composite modifier, and optional composite inorganic additives, and then molded in two steps—hot-melt mixing and hot-pressing-cold pressing—to obtain the finished product. This invention solves the problems of strong hydrophilicity and insufficient mechanical properties in traditional bamboo-plastic composites by controlling the morphology of bamboo waste, optimizing pretreatment, and synergistically combining the composite modification system. The product has a 288h water absorption rate ≤8%, tensile strength ≥4.5MPa, antibacterial rate ≥98%, and is completely biodegradable, meeting environmental protection requirements. This method is simple, low-cost, and achieves high-value utilization of bamboo waste. The product can be widely used in seedling cultivation, food packaging, and daily necessities.

Description

Technical Field

[0001] This invention relates to the field of biodegradable molded container technology, specifically a method for preparing a biodegradable molded container made from bamboo waste. Background Technology

[0002] As the world's largest producer of bamboo resources, my country relies heavily on bamboo forests for its forest ecosystem and modern forestry development. Bamboo forests offer vital ecological services, playing a crucial role in water conservation, soil and water retention, carbon sequestration and oxygen release, noise reduction, and environmental greening. Bamboo possesses advantages such as high strength, hardness, toughness, and wear resistance. It allows for successful afforestation once completed, enabling selective harvesting and sustainable use without damaging the ecological environment – ​​a characteristic unmatched by any other woody plant, making it an ideal alternative to timber. However, the unique structure of bamboo, characterized by its small diameter, thin walls, and hollow interior, makes industrial processing of bamboo more challenging than wood processing, generating substantial amounts of bamboo waste during the dismantling process. Currently, most bamboo processing enterprises in China treat this waste as boiler fuel, but due to the sheer volume, only a portion is utilized, and the added value is low. Therefore, the rational development and utilization of these resources, and the improvement of bamboo processing utilization rate, are of great significance for revitalizing the economy of bamboo-producing areas, expanding the source of raw materials for bamboo products, and promoting the healthy and sustainable development of the bamboo industry. Every year, bamboo processing generates approximately 4 million tons of bamboo waste, most of which is used as fuel or directly discarded, resulting in low resource utilization and environmental pollution. At the same time, the widespread use of traditional plastic containers causes serious "white pollution," which is inconsistent with the concept of green development.

[0003] Currently, the preparation of biodegradable containers faces numerous challenges: some processes require high temperatures (above 180℃) and high doses of adhesives, resulting in high production costs; poor interfacial compatibility between bamboo fiber and biodegradable polymer materials leads to insufficient mechanical properties of the composite material; and it is difficult to simultaneously achieve both water resistance and antibacterial properties in the product. In existing technologies, bamboo waste is mostly used in granular or powder form, failing to fully utilize its reinforcing advantages as a fiber, and there is a lack of targeted composite modification systems to simultaneously improve the material's mechanical properties, water resistance, and antibacterial properties.

[0004] Therefore, developing a simple, low-cost, and high-performance method for preparing biodegradable molded containers from bamboo waste, and realizing the high-value utilization of bamboo waste and the goal of "replacing plastic with bamboo," is of great economic and environmental significance. Summary of the Invention

[0005] This invention provides a method for preparing a biodegradable molded container made from bamboo waste. By optimizing the morphology of bamboo waste, improving the pretreatment process, and constructing a composite modification system, the method solves the problems of poor interfacial bonding between bamboo fiber and polylactic acid and the single performance of the product, thus preparing a biodegradable molded container with excellent mechanical properties, good water resistance, and antibacterial function.

[0006] The purpose of this invention is to provide a method for preparing a biodegradable molded container made from bamboo waste. The specific steps of this method are as follows:

[0007] Step 1: Pretreatment of bamboo waste: Select bamboo processing waste, remove impurities by screening, and then crush it into fiber form. The length of the fiber-shaped bamboo waste is 200-3000μm and the width is 8-300μm, of which 57% of the fibers have a length-to-diameter ratio of 4-10. Place the crushed bamboo waste in a 103℃ oven to dry until the moisture content is less than 3%, and then perform high-temperature steam pressure pretreatment at a temperature of 120-140℃, a pressure of 0.3-0.5MPa, and a time of 30-60min. After cooling, it is ready for use.

[0008] Step 2, Modifier Preparation: Bamboo charcoal and zinc oxide are dispersed separately in anhydrous ethanol at a mass ratio of 1:10, and ultrasonically dispersed for 30-60 min to obtain bamboo charcoal dispersion and zinc oxide dispersion; the bamboo charcoal particle size is 200-400 mesh, and the zinc oxide purity is ≥99%;

[0009] Step 3: Raw material blending: By mass, mix 40-60 parts of pretreated bamboo waste, 40-60 parts of polylactic acid, 0.3-2.0 parts of bamboo charcoal, and 0.3-1.2 parts of zinc oxide, add to a high-speed mixer, and mix at 80-100℃ for 15-20 minutes to obtain a premix; the polylactic acid is grade 4032D, with a density of 1.25 g / cm³ and a melting temperature of 160℃.

[0010] Step 4, Hot melt mixing: Feed the premix into a two-roll mill and mix at 160-180℃ for 8-15 minutes. During the mixing process, control the roll gap to 8mm and the rotation speed to 10rpm to obtain the melt.

[0011] Step 5, Molding: Quickly transfer the molten material into a container-specific mold and use a hot-press-cold-press molding process. The hot pressing temperature is 170-180℃, the pressure is 10-15MPa, and the time is 10-15min. Then, cold press at 10MPa pressure for 5-6min. After demolding, seal and store for 24h to obtain a biodegradable molded container made of bamboo waste.

[0012] Preferably, in step 1, the bamboo waste includes bamboo shavings, bamboo particles, bamboo powder processing residues, which are crushed and then screened through a 60-mesh sieve to remove excessively large impurities.

[0013] Preferably, in step 3, 1-2 parts of a composite inorganic additive may be added. The composite inorganic additive is a mixture of calcium carbonate and KH-550 modified montmorillonite in a mass ratio of 4:1, accounting for 5% of the total raw material mass.

[0014] Preferably, in step 3, the optimal mass ratio of bamboo waste to polylactic acid is 5:5, and the optimal overall performance of the container is achieved when the bamboo charcoal addition is 0.5% and the zinc oxide addition is 0.6%.

[0015] Preferably, in step 5, the mold is designed according to the shape of the container, including specifications such as seedling pots and packaging containers. After molding, the tensile strength of the container is ≥4.5MPa, the water absorption rate is ≤10.8% after 288h, and the antibacterial rate against Escherichia coli and Staphylococcus aureus is ≥98%.

[0016] Preferably, in step 1, the moisture content is less than 3%, which can avoid the formation of air bubble defects during the molding process. The extracts, starch and sugars in the bamboo waste are released through the steam explosion effect, which improves the surface properties, enhances the compatibility with polylactic acid, and improves the anti-mildew properties.

[0017] Preferably, in step 4, the materials need to be turned over periodically during the mixing process to ensure uniform mixing.

[0018] Compared with the prior art, the beneficial effects of the present invention are: the present invention uses fibrous bamboo waste as raw material, and its large aspect ratio characteristics enable the container to form an interwoven network structure, which significantly improves the mechanical properties. The bending strength can reach 87.9MPa and the tensile strength can reach 68.2MPa, which is more than 35% higher than that of containers made from traditional granular bamboo waste.

[0019] Through the synergistic effect of high-temperature steam pressure pretreatment and composite modification with bamboo charcoal and zinc oxide, the interfacial compatibility between bamboo fiber and polylactic acid is improved, and the container is endowed with excellent antibacterial properties. The antibacterial rate against Escherichia coli and Staphylococcus aureus is ≥98%, while the water absorption rate is controlled within 10.8% after 288 hours, and the water resistance is significantly improved.

[0020] The process uses hot-pressing and cold-pressing molding, which does not require high doses of adhesives. The production process is environmentally friendly and pollution-free, and the utilization rate of bamboo waste reaches 100%, realizing the high-value utilization of agricultural and forestry waste. The product is completely biodegradable, which is in line with the concept of "replacing plastic with bamboo" and can replace traditional plastic containers in seedling cultivation, packaging and other fields.

[0021] The raw materials are widely available and inexpensive, and the preparation process is simple and controllable, making it suitable for industrial production. It helps promote the development of a circular economy in the bamboo industry and has significant economic, social and environmental benefits. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the preparation process of the bamboo waste molding container of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0024] Example 1

[0025] Bamboo waste pretreatment: Select bamboo processing waste shavings, screen to remove impurities, and then crush them into fiber form with a length of 200-3000μm and a width of 8-300μm. Dry them at 103℃ for 5 hours until the moisture content is 2.5%. Then, treat them with high-temperature steam pressure at 130℃ and 0.4MPa for 45 minutes and cool them for later use.

[0026] Modifier preparation: 200-400 mesh bamboo charcoal and 99.5% pure zinc oxide were dispersed in anhydrous ethanol at a mass ratio of 1:10 and ultrasonically dispersed for 45 min.

[0027] Raw material blending: Mix 50 parts bamboo fiber, 50 parts polylactic acid, 0.5 parts bamboo charcoal, and 0.6 parts zinc oxide by weight, put them into a high-speed mixer, and mix at 90°C for 18 minutes to obtain a premix;

[0028] Hot melt mixing: The premixed material is fed into a two-roll mill and mixed at 170°C for 12 minutes with a roll gap of 8 mm and a rotation speed of 10 rpm.

[0029] Molding: The molten material is transferred to the seedling pot mold, hot-pressed at 175℃ and 12MPa for 12 minutes, followed by cold-pressed at 10MPa for 5 minutes. After demolding, it is sealed and stored for 24 hours to obtain the seedling pot container.

[0030] The container was tested and found to have a tensile strength of 68.2 MPa, a flexural strength of 87.9 MPa, a water absorption rate of 10.5% over 288 hours, an antibacterial rate of 98.82% against Escherichia coli, and an antibacterial rate of 98.65% against Staphylococcus aureus, meeting the requirements of the LY / T2565-2015 standard.

[0031] Example 2

[0032] Bamboo waste pretreatment: Select bamboo particle processing waste, crush it to fiber morphology, dry it at 103℃ for 6 hours until the moisture content is 2%; treat it with high temperature steam pressure at 140℃ and 0.5MPa for 30 minutes, and then cool it for later use;

[0033] Modifier preparation: 200-400 mesh bamboo charcoal and 99% pure zinc oxide were dispersed in anhydrous ethanol at a mass ratio of 1:10 and ultrasonically dispersed for 60 min.

[0034] Raw material blending: Mix 45 parts bamboo fiber, 55 parts polylactic acid, 1.0 part bamboo charcoal, 0.9 parts zinc oxide, and 1 part composite inorganic additive (calcium carbonate and KH-550 modified montmorillonite in a mass ratio of 4:1) at 100℃ for 15 min.

[0035] Hot melt mixing: The premixed material is fed into a two-roll mill and mixed at 180°C for 10 minutes;

[0036] Compression molding: Transfer the molten material to the packaging container mold, hot press at 180℃ and 15MPa for 10 minutes, then cold press at 10MPa for 6 minutes, and seal and store for 24 hours after demolding.

[0037] The container was tested and found to have a tensile strength of 65.3 MPa, a flexural strength of 82.7 MPa, a 288-hour water absorption rate of 9.8%, and an antibacterial rate of ≥98%, meeting the requirements for packaging containers.

[0038] The preparation method of this invention is simple, highly controllable, and utilizes widely available bamboo waste as raw material, resulting in low production costs and suitability for large-scale industrial production. The prepared biodegradable molded containers exhibit excellent mechanical properties, antibacterial properties, and water resistance, making them widely applicable in seedling cultivation, food packaging, and daily necessities, replacing traditional plastic containers and possessing broad market prospects and promotional value. Simultaneously, this method achieves high-value utilization of bamboo processing waste, contributing to the reduction of "white pollution," promoting the development of a circular economy, and aligning with the national green and low-carbon development policy.

[0039] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a biodegradable molded container made from bamboo waste, characterized in that: The specific steps for preparing this biodegradable molded container from bamboo waste are as follows: Step 1: Pretreatment of bamboo waste: Select bamboo processing waste, remove impurities by screening, and then crush it into fiber form. The length of the fiber-shaped bamboo waste is 200-3000μm and the width is 8-300μm, of which 57% of the fibers have a length-to-diameter ratio of 4-10. Place the crushed bamboo waste in a 103℃ oven to dry until the moisture content is less than 3%, and then perform high-temperature steam pressure pretreatment at a temperature of 120-140℃, a pressure of 0.3-0.5MPa, and a time of 30-60min. After cooling, it is ready for use. Step 2, Modifier Preparation: Bamboo charcoal and zinc oxide are dispersed separately in anhydrous ethanol at a mass ratio of 1:10, and ultrasonically dispersed for 30-60 min to obtain bamboo charcoal dispersion and zinc oxide dispersion; the bamboo charcoal particle size is 200-400 mesh, and the zinc oxide purity is ≥99%; Step 3: Raw material blending: By mass, mix 40-60 parts of pretreated bamboo waste, 40-60 parts of polylactic acid, 0.3-2.0 parts of bamboo charcoal, and 0.3-1.2 parts of zinc oxide, add to a high-speed mixer, and mix at 80-100℃ for 15-20 minutes to obtain a premix; the polylactic acid is grade 4032D, with a density of 1.25 g / cm³ and a melting temperature of 160℃. Step 4, Hot melt mixing: Feed the premix into a two-roll mill and mix at 160-180℃ for 8-15 minutes. During the mixing process, control the roll gap to 8mm and the rotation speed to 10rpm to obtain the melt. Step 5, Molding: Quickly transfer the molten material into a container-specific mold and use a hot-press-cold-press molding process. The hot pressing temperature is 170-180℃, the pressure is 10-15MPa, and the time is 10-15min. Then, cold press at 10MPa pressure for 5-6min. After demolding, seal and store for 24h to obtain a biodegradable molded container made of bamboo waste.

2. The method for preparing a biodegradable molded container from bamboo waste according to claim 1, characterized in that: In step 1, the bamboo waste includes bamboo shavings, bamboo particles, bamboo powder processing residues, which are crushed and then screened through a 60-mesh sieve to remove excessively large impurities.

3. The method for preparing a biodegradable molded container from bamboo waste according to claim 1, characterized in that: In step 3, 1-2 parts of a composite inorganic additive may also be added. The composite inorganic additive is a mixture of calcium carbonate and KH-550 modified montmorillonite in a mass ratio of 4:1, accounting for 5% of the total raw material mass.

4. The method for preparing a biodegradable molded container from bamboo waste according to claim 1, characterized in that: In step 3, the optimal mass ratio of bamboo waste to polylactic acid is 5:5, and the container has the best overall performance when the bamboo charcoal addition is 0.5% and the zinc oxide addition is 0.6%.

5. The method for preparing a biodegradable molded container from bamboo waste according to claim 1, characterized in that: In step 5, the mold is designed according to the shape of the container, including specifications such as seedling pots and packaging containers. After molding, the tensile strength of the container is ≥4.5MPa, the water absorption rate is ≤10.8% after 288h, and the antibacterial rate against Escherichia coli and Staphylococcus aureus is ≥98%.

6. The method for preparing a biodegradable molded container from bamboo waste according to claim 1, characterized in that: In step 1, the moisture content is less than 3%, which can avoid the formation of air bubbles during the molding process. The extracts, starch and sugars in the bamboo waste are released through the steam explosion effect, which improves the surface properties, enhances the compatibility with polylactic acid, and improves the anti-mildew properties.

7. The method for preparing a biodegradable molded container from bamboo waste according to claim 1, characterized in that: In step 4, the materials need to be turned over regularly during the mixing process to ensure uniform mixing.

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