Recyclable bamboo fiber foam as well as preparation method and application thereof
Bamboo fiber foam was prepared by partial delignification treatment and atmospheric pressure drying, which solved the problems of high energy consumption and insufficient ecological sustainability in the existing technology. It achieved lightweight bamboo fiber foam with high porosity and low shrinkage, with excellent mechanical properties and recyclability.
Patent Information
- Application Number
- CN202511426072.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-30
- Publication Date
- 2026-01-06
AI Technical Summary
Existing methods for preparing lignocellulose foam/aerogels are characterized by high energy consumption, high cost, and insufficient ecological sustainability. Furthermore, traditional delignification treatment weakens the strength of the cellulose skeleton, making the structure prone to collapse during atmospheric pressure drying.
After crushing and removing thin-walled cells, the bamboo is crushed and then partially deligninized through alkaline solution treatment and heat treatment. Bamboo cell fibers are separated and prepared by atmospheric pressure drying. The bamboo fiber foam is then recycled through mechanical stirring.
The prepared bamboo fiber foam is lightweight, has high porosity, low shrinkage, and excellent mechanical properties. It also has low thermal conductivity, is biodegradable, and recyclable, achieving low energy consumption and ecological sustainability.
Smart Images
Figure CN121271014A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of biomass materials technology, and in particular to a recyclable bamboo fiber foam, its preparation method, and its application. Background Technology
[0002] Lignocellulose is the most abundant natural polymer resource on Earth, possessing renewable and biodegradable properties. It shows broad application prospects in the preparation of lightweight, high-porosity foams / aerogels, and can be used in fields such as thermal insulation, adsorption, and green functional materials.
[0003] Existing preparation processes mainly employ freeze-drying or supercritical drying, which, while maintaining porous structures, suffer from long cycles, expensive equipment, and high energy consumption, making large-scale implementation difficult. To improve the drying process, researchers have attempted to introduce surfactants into the gel to reduce surface tension and capillary forces, thereby maintaining structural stability under room temperature or oven conditions. However, this method carries the risk of chemical reagent residues and lacks ecological sustainability. In contrast, solvent displacement methods can effectively prevent collapse by reducing solvent surface tension and offer the advantage of solvent recycling; however, its complex process and high cost limit its practical application.
[0004] Traditional methods often involve completely deligninizing bamboo and wood raw materials to obtain cellulose. However, the removal of lignin weakens the strength of the cellulose skeleton, making it more prone to shrinkage and collapse during atmospheric pressure drying. To compensate for this deficiency, some studies have introduced polymeric reinforcing agents to construct stable network structures; however, exogenous polymers generally suffer from unsustainability issues.
[0005] Therefore, how to reduce energy consumption and cost while maintaining structural stability and taking into account ecological sustainability has become a key technical problem that urgently needs to be solved in the preparation of lignocellulose foam / aerogel.
[0006] In view of this, the present invention is hereby proposed. Summary of the Invention
[0007] The first objective of this invention is to provide a method for preparing recyclable bamboo fiber foam. This method is simple, and the prepared bamboo fiber foam has lightweight, high porosity, low shrinkage, and excellent mechanical properties. It also has low thermal conductivity, is biodegradable, and can be recycled.
[0008] A second objective of the present invention is to provide a recyclable bamboo fiber foam.
[0009] A third objective of this invention is to provide an application of the above-mentioned recyclable bamboo fiber foam in the preparation of thermal insulation materials.
[0010] To achieve the above objectives, the following technical solution is adopted:
[0011] In a first aspect, the present invention provides a method for preparing recyclable bamboo fiber foam, comprising the following steps:
[0012] a. After crushing the bamboo, disperse it in water, then remove the thin-walled cells on the top layer of the aqueous solution and collect the bamboo powder containing bamboo fiber;
[0013] b. Disperse the bamboo fiber-containing bamboo powder collected in step a in an alkaline solution, and perform partial delignin treatment under heating conditions to obtain partially deligninized bamboo powder;
[0014] c. Disperse the partially lignin-free bamboo powder obtained in step b in water, and separate the bamboo powder into individual bamboo cell fibers to obtain a partially lignin-free bamboo fiber slurry;
[0015] d. Pour the partially deligninized bamboo fiber slurry obtained in step c into a precast mold, and after filtration and drying, prepare recyclable bamboo fiber foam.
[0016] As a further technical solution, in step a, the bamboo is crushed and then the bamboo powder of 5-100 mesh is collected and dispersed in water.
[0017] As a further technical solution, step a, after collecting bamboo fiber and bamboo powder, also includes a step of drying the bamboo fiber and bamboo powder;
[0018] The drying process is carried out in an oven at a temperature of 40–80°C for 12–48 hours.
[0019] As a further technical solution, the alkaline solution includes one or more of sodium hydroxide solution and potassium hydroxide solution;
[0020] The mass concentration of the alkaline solution is 1% to 20%.
[0021] As a further technical solution, the temperature of the partial delignification treatment is 70-100℃ and the time is 5-80 minutes.
[0022] As a further technical solution, step b, after the partial delignification treatment, also includes a water washing step to remove residual alkali.
[0023] As a further technical solution, in step c, the ratio of partially deligninized bamboo powder to water is (1-4 kg): (25-400 L);
[0024] The separation method includes high-speed stirring.
[0025] As a further technical solution, the filtered water is naturally filtered water;
[0026] The drying method is atmospheric pressure drying, with a temperature of 50-105℃ and a time of 4-8 hours.
[0027] Secondly, the present invention provides a recyclable bamboo fiber foam, which is prepared by the above-described preparation method.
[0028] Thirdly, the present invention provides the application of the above-mentioned recyclable bamboo fiber foam in the preparation of thermal insulation materials.
[0029] Compared with the prior art, the present invention has the following beneficial effects:
[0030] (1) The present invention uses bamboo powder containing bamboo fiber obtained after crushing and removing thin-walled cells, which facilitates the subsequent partial delignin removal of fibers. Furthermore, after crushing, bamboo powder with a specific particle size is screened to facilitate the subsequent processing to obtain bamboo cell fiber slurry with intact bamboo cell fiber structure.
[0031] (2) This invention employs a heating and alkaline boiling method to achieve partial deligninization. The preparation process is rapid and energy-efficient, and it controllably produces bamboo powder particles that retain some lignin and hemicellulose. During subsequent separation, the retention of lignin in the bamboo fiber cells maintains the integrity of their structure and rigid fiber skeleton, successfully separating the coarse fibers to prepare bamboo fiber pulp containing individual bamboo cell fibers. Simultaneously, the sodium hydroxide and water used in the production process can be effectively recovered using existing chemical recycling technologies and wastewater treatment processes, technologies frequently used in the pulp and paper industry. This method further reduces resource consumption and improves the overall sustainability of the bamboo fiber foam's lifecycle.
[0032] (3) This invention uses water filtration and atmospheric pressure drying to prepare bamboo fiber foam. Sustainable foam is produced by reassembling partially lignin-free bamboo cell fibers and drying them at atmospheric pressure. The lignin retained in the bamboo cell fibers strengthens the porous bamboo fiber network, effectively preventing structural collapse during drying, thus achieving low shrinkage, low density, and high porosity. Furthermore, after the bamboo fiber foam is used, it can be rapidly redispersed in water by mechanical stirring to form a uniform bamboo cell fiber slurry. This slurry is then reshaped and dried under atmospheric pressure to produce new bamboo fiber foam, forming a closed-loop recycling system. This recycling process is environmentally friendly, requires no toxic reagents or complex procedures, and is highly economically feasible. Attached Figure Description
[0033] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:
[0034] Figure 1Here are SEM images and pore size distribution diagrams of bamboo fiber cells from natural moso bamboo powder in Example 1;
[0035] Figure 2 Here are SEM images and pore size distribution diagrams of the bamboo fiber foam from Example 1;
[0036] Figure 3 SEM images of bamboo fiber foam with unremoved parenchyma cells and bamboo fiber foam without delignification;
[0037] Figure 4 Here are SEM images and pore size distribution diagrams of the bleached bamboo fiber foam from Example 1;
[0038] Figure 5 This is a comparison chart of the cellulose, lignin, and hemicellulose content of natural bamboo, cellulose foam, and bleached bamboo fiber foam in Example 1.
[0039] Figure 6 This is a comparison chart of the normal pressure drying shrinkage rates of bamboo fiber foam and bleached bamboo fiber foam in Example 1.
[0040] Figure 7 This is a density comparison chart of natural bamboo, bamboo fiber foam, and bleached bamboo fiber foam from Example 1.
[0041] Figure 8 The thermal insulation performance diagrams for natural bamboo, bamboo fiber foam, and bleached bamboo fiber foam in Example 1 are shown.
[0042] Figure 9 This is a diagram illustrating the biodegradation of bamboo fiber foam from Example 1.
[0043] Figure 10 This is a diagram illustrating the recyclability of bamboo fiber foam in Example 1. Detailed Implementation
[0044] The embodiments and examples of the present invention will be described in detail below. However, those skilled in the art will understand that the following embodiments and examples are for illustrative purposes only and should not be considered as limiting the scope of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise specified, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.
[0045] In a first aspect, the present invention provides a method for preparing recyclable bamboo fiber foam, comprising the following steps:
[0046] a. After crushing the bamboo, disperse it in water, then remove the thin-walled cells on the top layer of the aqueous solution and collect the bamboo powder containing bamboo fiber;
[0047] b. Disperse the bamboo fiber-containing bamboo powder collected in step a in an alkaline solution, and perform partial delignin treatment under heating conditions to obtain partially deligninized bamboo powder;
[0048] c. Disperse the partially lignin-free bamboo powder obtained in step b in water, and separate the bamboo powder into individual bamboo cell fibers to obtain a partially lignin-free bamboo fiber slurry;
[0049] d. Pour the partially deligninized bamboo fiber slurry obtained in step c into a precast mold, and after filtration and drying, prepare recyclable bamboo fiber foam.
[0050] The preparation method provided by this invention is simple and convenient. It adopts processes such as pretreating bamboo powder under water conditions, partially removing lignin under heating and alkaline boiling conditions, separating bamboo cell fibers and drying fiber foam, etc., which replace the use of organic solvents in bamboo fiber treatment and traditional lignin fiber foam preparation processes. During the preparation process, the lignin retained in the bamboo cell fibers strengthens the porous network, which can reorganize the partially removed bamboo cell fibers under normal pressure drying conditions and prevent structural collapse during the drying process.
[0051] In some optional embodiments, in step a, the bamboo is crushed and then collected into bamboo powder of 5-100 mesh and dispersed in water. In this embodiment, the mesh size of the bamboo powder can be, for example, but not limited to, 5-30 mesh, 20-40 mesh, 40-80 mesh, or 60-100 mesh.
[0052] Screening bamboo powder with a specific particle size helps to obtain a partially lignin-free bamboo cell fiber slurry with intact bamboo cell fiber structure during subsequent processing.
[0053] In some optional embodiments, step a, after collecting the bamboo fiber-containing bamboo powder, further includes a step of drying the bamboo fiber-containing bamboo powder. The drying is performed in an oven at a temperature of 40–80°C for 12–48 hours. In this embodiment, the drying temperature can be, for example, but not limited to, 40°C, 50°C, 60°C, or 80°C, and the drying time can be, for example, but not limited to, 12 hours, 24 hours, 36 hours, or 48 hours.
[0054] In some alternative implementations, step a is as follows:
[0055] First, fresh bamboo is cut into 5-10cm bamboo strips and dried in a forced-air drying oven at 60-105℃ for 6-12 hours. Then, it is pulverized into bamboo chips using a pulverizer and sieved through a mold to obtain bamboo powder of 5-100 mesh. Next, the bamboo powder is dispersed in water at a solid-liquid ratio (kg / L) of 1:8-1:15 and allowed to stand for 5-10 minutes. The upper layer of floating thin-walled cells is removed, and the water is filtered to obtain the lower layer of bamboo fiber-containing bamboo powder particles. These particles are then dried in a forced-air dryer at 40-80℃ for 12-48 hours, and finally dried at room temperature for storage.
[0056] In some optional embodiments, the alkaline solution includes, but is not limited to, one or more of sodium hydroxide solution and potassium hydroxide solution, or other alkaline solutions well known to those skilled in the art;
[0057] In some alternative embodiments, the mass concentration of the alkaline solution may be, for example, but not limited to, 1%, 5%, 10%, or 20%.
[0058] In some alternative embodiments, the temperature of the partial delignification treatment may be, for example, but not limited to, 70°C, 80°C, 90°C, or 100°C, and the time may be, for example, but not limited to, 5 minutes, 20 minutes, 40 minutes, or 80 minutes.
[0059] Heating under alkaline conditions partially removes lignin and hemicellulose from bamboo powder.
[0060] In some optional embodiments, step b, after the partial delignification treatment, further includes a water washing step to remove residual alkali.
[0061] In some alternative implementations, step b is as follows:
[0062] First, 0.8–1.2 kg of bamboo powder particles containing bamboo fiber are stirred and dispersed in 6–25 L of 1–20 wt% NaOH solution, with the solid-liquid ratio of bamboo powder to NaOH solution controlled at 1:5–1:25, and soaked for 5–120 minutes. The mixture is then stirred at 300–600 rpm and heated at 70–100℃ for 5–80 minutes to perform partial delignin treatment. Next, the mixture is washed 4–7 times with deionized water to thoroughly remove residual alkali, ensuring the solution is neutral. After sedimentation and filtration, the solution is stored in a refrigerator (4℃) to obtain partially deligninated bamboo powder.
[0063] In some optional embodiments, in step c, the solid-liquid ratio of partially lignin-de-ligninized bamboo powder and water can be, for example, but not limited to, 1 kg: 25 L, 2 kg: 100 L, 3 kg: 100 L, or 4 kg: 400 L;
[0064] The separation method includes, but is not limited to, high-speed stirring.
[0065] In some alternative implementations, step c is as follows:
[0066] First, soak 1-4 kg of deligated bamboo powder in 25-400 L of water. Place the mixed suspension in a high-speed mixer and stir for 1-4 minutes to separate the coarse bamboo powder particles into individual bamboo cell fibers. Repeat the operation 3-5 times to form a partially deligated bamboo fiber slurry.
[0067] In some optional implementations, in step d, the water filtration method is natural filtration;
[0068] The drying method is atmospheric pressure drying, and the temperature can be, for example, but not limited to, 50°C, 80°C, 90°C or 105°C, and the time can be, for example, but not limited to, 4 hours, 5 hours, 6 hours or 8 hours.
[0069] In some alternative implementations, step d is as follows:
[0070] First, pour 5-20L of partially deligninized bamboo pulp into a pre-made mold with a filter cloth at the bottom. Let it stand for 30 minutes until no water drips from the bottom of the mold. Then, place the mold in an oven at 50-105℃ under normal pressure and dry for 4-8 hours to obtain bamboo fiber foam. After redispersing a piece of bamboo fiber foam with 100-200 parts by volume of water, it can be poured back into the original pre-made mold. After the same filtration and drying under normal pressure, new bamboo fiber foam can still be formed, thus enabling the recycling of bamboo fiber foam.
[0071] In some alternative implementations, the bamboo may be, for example, but not limited to, moso bamboo and cizhu bamboo, and may be sourced from provinces and cities such as Zhejiang, Fujian, Jiangxi, Hunan, Anhui, Sichuan, and Guizhou.
[0072] Secondly, the present invention provides a recyclable bamboo fiber foam, which is prepared by the above-described preparation method.
[0073] The recyclable bamboo fiber foam provided by this invention is lightweight (its density is much lower than that of natural bamboo (more than 14 times) and completely lignin-free foam (more than 1 time)), has high porosity, low shrinkage, and excellent mechanical properties. It also has low thermal conductivity, good insulation, and is biodegradable and recyclable (can be recycled more than 20 times). Its properties are superior to those of traditional commercial plastic foams, and it can be used as an environmentally friendly lightweight thermal insulation foam material.
[0074] Thirdly, the present invention provides the application of the above-mentioned recyclable bamboo fiber foam in the preparation of thermal insulation materials.
[0075] The recyclable bamboo fiber foam provided by this invention is lightweight and has good mechanical and thermal insulation properties, making it suitable for use as a thermal insulation material.
[0076] The present invention will be further illustrated below with specific embodiments and comparative examples. However, it should be understood that these embodiments are merely for the purpose of more detailed illustration and should not be construed as limiting the present invention in any way.
[0077] Example 1
[0078] A recyclable bamboo fiber foam is prepared as follows:
[0079] (1) Pretreatment of bamboo powder: First, fresh bamboo is cut into 6cm bamboo strips and dried in a forced-air drying oven at 80℃ for 10 hours. Then, it is pulverized into bamboo chips using a pulverizer and then screened to obtain bamboo powder of 20-30 mesh using a mold. Then, 1kg of bamboo powder is dispersed in 10L of water at a solid-liquid ratio of 1:10 and allowed to stand for 10 minutes. The upper layer of floating thin-walled cells is removed, and the water is filtered to obtain the lower layer of bamboo powder particles containing bamboo fibers. The particles are dried in a forced-air dryer at 40℃ for 48 hours and then dried at room temperature for storage.
[0080] (2) Preparation of partially delignified bamboo powder: First, 0.8 kg of bamboo fiber-containing bamboo powder particles were stirred and dispersed in 8 L of 5 wt% NaOH solution, with the solid-liquid ratio of bamboo powder to NaOH solution controlled at 1:10, and soaked for 60 minutes. The solution was stirred at 400 rpm and heated at 100℃ for 20 minutes to perform partial delignification treatment. Then, it was washed 5 times with deionized water to thoroughly remove residual NaOH, resulting in a neutral solution. After sedimentation and filtration, the solution was stored in a refrigerator (4℃) to obtain partially delignified bamboo powder.
[0081] (3) Preparation of partially lignin-de-lignin bamboo fiber slurry: First, 2 kg of partially lignin-de-lignin bamboo powder was soaked in 100 L of water. Then, the mixed suspension was placed in a high-speed mixer and stirred for 2 minutes to separate the coarse bamboo powder particles into individual bamboo cell fibers. After repeating the operation 4 times, a partially lignin-de-lignin bamboo fiber slurry was formed.
[0082] (4) Preparation of recyclable bamboo fiber foam: First, pour 10L of partially deligninized bamboo pulp into a pre-made mold with a filter cloth at the bottom. Let it stand for 30 minutes until no water drips from the bottom of the mold, then place the mold in a 50℃ atmospheric pressure oven to dry for 8 hours to obtain bamboo fiber foam. After redispersing a piece of bamboo fiber foam with 100 parts by volume of water, it can be poured back into the original pre-made mold. After the same filtration and atmospheric pressure drying treatment, new bamboo fiber foam can still be formed, thus enabling the recycling of bamboo fiber foam.
[0083] Example 2
[0084] A recyclable bamboo fiber foam is prepared as follows:
[0085] (1) Pretreatment of bamboo powder from Cizhu bamboo: First, fresh Cizhu bamboo is cut into 5cm bamboo pieces and dried in a forced-air drying oven at 60℃ for 12 hours. Then, it is pulverized into bamboo shavings using a pulverizer and then screened into Cizhu bamboo powder with a mesh size of 5-30. Then, 1kg of bamboo powder is dispersed in 15L of water at a solid-liquid ratio of 1:15 and allowed to stand for 10 minutes. The upper layer of floating thin-walled cells is removed, and the water is filtered to obtain the lower layer of bamboo powder particles containing bamboo fibers. The particles are dried in a forced-air dryer at 80℃ for 12 hours and then dried at room temperature for storage.
[0086] (2) Preparation of partially deligninized bamboo powder: First, 1 kg of bamboo powder particles containing bamboo fiber was stirred and dispersed in 20 L of 1 wt% NaOH solution, with the solid-liquid ratio of bamboo powder to NaOH solution controlled at 1:20, and soaked for 30 minutes. The solution was stirred at 500 rpm and heated at 70℃ for 80 minutes to perform partial delignin treatment. Then, it was washed four times with deionized water to thoroughly remove residual NaOH, ensuring the solution was neutral. After sedimentation and filtration, the solution was stored in a refrigerator to obtain partially deligninized bamboo powder.
[0087] (3) Preparation of partially lignin-de-lignin bamboo fiber slurry: First, 1 kg of partially lignin-de-lignin bamboo powder was soaked in 25 L of water. Then, the mixed suspension was placed in a high-speed mixer and stirred for 3 minutes to separate the coarse bamboo powder particles into individual bamboo cell fibers. After repeating the operation 5 times, a partially lignin-de-lignin bamboo fiber slurry was formed.
[0088] (4) Preparation of recyclable bamboo fiber foam: First, pour 5L of partially lignin-de-lignosed bamboo fiber slurry into a pre-made mold with a filter cloth at the bottom. Let it stand for 30 minutes until no water drips from the bottom of the mold, then place the mold in an 80℃ atmospheric pressure oven to dry for 6 hours to obtain bamboo fiber foam. After redispersing a piece of bamboo fiber foam with 200 parts by volume of water, it can be poured back into the original pre-made mold. After the same filtration and atmospheric pressure drying treatment, new bamboo fiber foam can still be formed, thus enabling the recycling of bamboo fiber foam.
[0089] Example 3
[0090] A recyclable bamboo fiber foam is prepared as follows:
[0091] (1) Pretreatment of bamboo powder: First, fresh bamboo is cut into 8cm bamboo strips and dried in a forced-air drying oven at 105℃ for 6 hours. Then, it is pulverized into bamboo chips using a pulverizer and then screened to obtain bamboo powder of 40-80 mesh using a mold. Then, 1kg of bamboo powder is dispersed in 8L of water at a solid-liquid ratio of 1:8 and allowed to stand for 10 minutes. The upper layer of floating thin-walled cells is removed, and the water is filtered to obtain the lower layer of bamboo powder particles containing bamboo fibers. The particles are dried in a forced-air dryer at 60℃ for 24 hours and then dried at room temperature for storage.
[0092] (2) Preparation of partially delignified bamboo powder: First, 1 kg of bamboo powder particles containing bamboo fiber was stirred and dispersed in 25 L of 10 wt% KOH solution, with the solid-liquid ratio of bamboo powder to KOH solution controlled at 1:25, and soaked for 5 minutes. The mixture was then stirred at 300 rpm and heated at 80℃ for 40 minutes to perform partial delignification treatment. Next, it was washed 6 times with deionized water to thoroughly remove residual KOH, ensuring the solution was neutral. After sedimentation and filtration, the solution was stored in a refrigerator (4℃) to obtain partially delignified bamboo powder.
[0093] (3) Preparation of partially lignin-de-lignin bamboo fiber slurry: First, 4 kg of partially lignin-de-lignin bamboo powder was soaked in 400 L of water. Then, the mixed suspension was placed in a high-speed mixer and stirred for 4 minutes to separate the coarse bamboo powder particles into individual bamboo cell fibers. After repeating the operation 3 times, a partially lignin-de-lignin bamboo fiber slurry was formed.
[0094] (4) Preparation of recyclable bamboo fiber foam: First, pour 20L of partially deligninized bamboo pulp into a pre-made mold with a filter cloth at the bottom. Let it stand for 30 minutes until no water drips from the bottom of the mold, then place the mold in a 90℃ atmospheric pressure oven to dry for 5 hours to obtain bamboo fiber foam. After redispersing a piece of bamboo fiber foam with 300 parts by volume of water, it can be poured back into the original pre-made mold. After the same filtration and atmospheric pressure drying treatment, new bamboo fiber foam can still be formed, thus enabling the recycling of bamboo fiber foam.
[0095] Example 4
[0096] A recyclable bamboo fiber foam is prepared as follows:
[0097] (1) Pretreatment of bamboo powder: First, fresh bamboo is cut into 10cm bamboo strips and dried in a forced-air drying oven at 90℃ for 4 hours. Then, it is pulverized into bamboo chips using a pulverizer and then screened to obtain bamboo powder of 60-100 mesh using a mold. Then, 1kg of bamboo powder is dispersed in 12L of water at a solid-liquid ratio of 1:12 and allowed to stand for 5 minutes. The upper layer of floating thin-walled cells is removed, and the water is filtered to obtain the lower layer of bamboo powder particles containing bamboo fibers. The particles are dried in a forced-air dryer at 50℃ for 36 hours and then dried at room temperature for storage.
[0098] (2) Preparation of partially delignified bamboo powder: First, 1.2 kg of bamboo powder particles containing bamboo fiber were stirred and dispersed in 6 L of 20 wt% NaOH solution, with the solid-liquid ratio of bamboo powder to NaOH solution controlled at 1:5, and soaked for 120 minutes. The solution was stirred at 600 rpm and heated at 90℃ for 5 minutes to perform partial delignification treatment. Then, it was washed 7 times with deionized water to thoroughly remove residual NaOH, resulting in a neutral solution. After sedimentation and filtration, the solution was stored in a refrigerator (4℃) to obtain partially delignified bamboo powder.
[0099] (3) Preparation of partially lignin-de-lignin bamboo fiber slurry: First, 2 kg of partially lignin-de-lignin bamboo powder was soaked in 100 L of water. Then, the mixed suspension was placed in a high-speed mixer and stirred for 1 minute to separate the coarse bamboo powder particles into individual bamboo cell fibers. After repeating the operation 5 times, a partially lignin-de-lignin bamboo fiber slurry was formed.
[0100] (4) Preparation of recyclable bamboo fiber foam: First, pour 15L of partially deligninized bamboo pulp into a pre-made mold with a filter cloth at the bottom. Let it stand for 30 minutes until no water drips from the bottom of the mold, then place the mold in a 105℃ atmospheric pressure oven to dry for 4 hours to obtain bamboo fiber foam. After redispersing a piece of bamboo fiber foam with 150 parts by volume of water, it can be poured back into the original pre-made mold. After the same filtration and atmospheric pressure drying treatment, new bamboo fiber foam can still be formed, thus enabling the recycling of bamboo fiber foam.
[0101] Comparative Example 1
[0102] A bamboo fiber foam with intact thin-walled cells is prepared as follows:
[0103] (1) Pretreatment of bamboo powder: First, cut fresh bamboo into 6cm bamboo pieces, dry them in a forced-air drying oven at 80℃ for 10 hours, then crush them into bamboo chips using a pulverizer, and then use a mold to sieve out 20-30 mesh bamboo powder.
[0104] (2) Preparation of partially deligninized bamboo powder: First, 0.8 kg of moso bamboo powder was stirred and dispersed in 8 L of 5 wt% NaOH solution, with the solid-liquid ratio of bamboo powder to NaOH solution controlled at 1:10, and soaked for 60 minutes. The solution was stirred at 400 rpm and heated at 100℃ for 20 minutes to perform partial delignin treatment. Then, it was washed 5 times with deionized water to thoroughly remove residual NaOH, resulting in a neutral solution. After sedimentation and filtration, the solution was stored in a refrigerator (4℃) to obtain partially deligninized bamboo powder.
[0105] (3) Soak 2 kg of partially deligated bamboo powder in 100 L of water. Then, place the mixed suspension in a high-speed mixer and stir for 2 minutes to obtain partially deligated bamboo fiber slurry.
[0106] (4) Finally, pour 10L of partially deligninized bamboo pulp into a pre-made mold with a filter cloth at the bottom. Let it stand for 30 minutes until the bottom of the mold stops dripping water, then place the mold in a 50℃ normal pressure oven to dry for 8 hours to obtain bamboo fiber foam.
[0107] Comparative Example 2
[0108] A method for preparing a non-delionized bamboo fiber foam is as follows:
[0109] (1) Pretreatment of bamboo powder: First, fresh bamboo is cut into 6cm bamboo strips and dried in a forced-air drying oven at 80℃ for 10 hours. Then, it is pulverized into bamboo chips using a pulverizer and then screened to obtain bamboo powder of 20-30 mesh using a mold. Then, 1kg of bamboo powder is dispersed in 1L of water at a solid-liquid ratio of 1:10 and allowed to stand for 10 minutes. The upper layer of floating thin-walled cells is removed, and the water is filtered to obtain the lower layer of bamboo powder particles containing bamboo fibers. The particles are dried in a forced-air dryer at 40℃ for 48 hours and then dried at room temperature for storage.
[0110] (2) First, soak 2 kg of bamboo powder granules in 100 L of water. Then, place the mixed suspension in a high-speed mixer and stir for 2 minutes to obtain bamboo fiber slurry.
[0111] (3) Finally, pour 10L of bamboo fiber slurry into a stainless steel mold with a filter cloth at the bottom. Let it stand for 30 minutes until the bottom of the mold stops dripping water, then place the mold in a 50℃ normal pressure oven to dry for 8 hours to obtain bamboo fiber foam.
[0112] Comparative Example 3
[0113] A bleached bamboo fiber foam is prepared as follows:
[0114] First, 0.8 kg of partially deligated bamboo powder from Example 1 was dispersed in 8 L of 3.5 wt% NaClO2 solution, and acetic acid was added to adjust the pH to approximately 4.6, maintaining a solid-liquid ratio of partially deligated bamboo powder to NaOH solution of 1:10. The mixture was stirred and dispersed at 400 rpm and boiled until the sample turned completely white (approximately 8 hours). It was then washed five times with deionized water until the solution was neutral, yielding bleached bamboo powder.
[0115] Disperse bleached bamboo powder in 100 parts by volume of water and stir for 2 minutes using a high-speed mixer to obtain bleached bamboo fiber slurry.
[0116] Finally, pour 10L of bleached bamboo fiber slurry into a pre-made mold with a filter cloth at the bottom. Let it stand for 30 minutes until no water drips from the bottom of the mold, then place the mold in a 50℃ normal pressure oven to dry for 8 hours to obtain bleached bamboo fiber foam.
[0117] Experimental Example 1
[0118] The recyclable bamboo fiber foam prepared in Example 1 was tested, and the results are as follows:
[0119] Figure 1 SEM images and cell diameter distribution diagrams of fiber cells from natural moso bamboo powder are shown. Figure 1 Image (a) is a SEM image of the fiber cells of natural moso bamboo powder. Figure 1(b) in the figure shows the diameter distribution of fiber cells in natural moso bamboo. It can be seen that the fiber cells of natural moso bamboo have a distinct rigid fiber skeleton, and the fiber cells are arranged in a tight orientation, with the diameter of the fiber cells distributed around 10 μm.
[0120] Figure 2 SEM images and cell diameter distribution diagrams of bamboo fiber foam are shown. Figure 2 Image (a) is a SEM image of bamboo fiber foam. Figure 2 (b) in the figure shows the pore size distribution of bamboo fiber foam. It can be seen that after the delignification treatment, the fiber cells are effectively separated from the bamboo chips, the rigid fiber skeleton is preserved, and the structure of the fiber cells remains basically unchanged during the drying process. At the same time, the average diameter of the fiber cells also remains basically unchanged, with the diameter concentrated around 10 μm.
[0121] Figure 3 SEM images of bamboo fiber foam (without removed parenchyma cells) in Comparative Example 1 and bamboo fiber foam (without delignification) in Comparative Example 2 are shown. Figure 3 (a) is a SEM image of bamboo fiber foam without the removal of thin-walled cells. It can be seen that a large number of thin-walled cells remain in the bamboo fiber foam without the removal of thin-walled cells. At the same time, the structure of thin-walled cells is destroyed during the delignification process and cannot maintain good rigidity like fiber cells. Therefore, the presence of thin-walled cells is not conducive to the formation of the spatial skeleton of the foam. Figure 3 (b) is an SEM image of bamboo fiber foam that has not been deligninated. It can be seen that bamboo powder that has not been deligninated cannot be used to obtain individual bamboo cell fibers by high-speed stirring, and high-speed stirring will significantly damage the surface morphology and structure of bamboo fibers.
[0122] Figure 4 The images show SEM images and pore size distribution diagrams of the bleached bamboo fiber foam from Comparative Example 3. Figure 4 Image (a) is a SEM image of bleached bamboo fiber foam. Figure 4 (b) in the figure shows the pore size distribution of bleached bamboo fiber foam. It can be seen that the bleaching process causes the fiber cell structure to collapse. During the drying process, the fiber cells of bleached bamboo fiber foam cannot resist the capillary force when water evaporates well. The fiber cells are tightly stacked together, and the average cell diameter increases from about 10 μm to 14 μm.
[0123] Figure 5This chart compares the cellulose, lignin, and hemicellulose content of natural bamboo powder, bamboo fiber foam, and bleached bamboo fiber foam. The chart shows that after lignin removal treatment, the lignin and hemicellulose content of bamboo fiber foam is significantly lower than that of natural bamboo powder, while the cellulose content is significantly higher. Meanwhile, the lignin and hemicellulose content of bleached bamboo fiber foam is further reduced, while the cellulose content is increased.
[0124] Table 1 shows the porosity of bamboo fiber foam and bleached bamboo fiber foam. Figure 6 This is a comparison chart of the shrinkage rates of bamboo fiber foam and bleached bamboo fiber foam after atmospheric pressure drying. It can be seen that, compared to bamboo fiber foam, bleached bamboo fiber foam has a significantly reduced porosity and a significantly increased shrinkage rate.
[0125] Table 1
[0126]
[0127] Figure 7 This is a density comparison chart of natural bamboo, bamboo fiber foam, and bleached bamboo fiber foam. The chart shows that the density of natural bamboo is 0.73 ± 0.02 g / cm³. 3 The density of bamboo fiber foam is 0.052 ± 0.001 g / cm³. 3 The density of bleached bamboo fiber foam is 0.085 ± 0.002 g / cm³. 3 The density of bamboo fiber foam is nearly 14 times lower than that of natural bamboo, accounting for only 63% of the density of bleached bamboo fiber foam. These results highlight the crucial role of residual lignin in stabilizing fiber cell structure, preventing structural collapse due to capillary action during drying, and thus maintaining the structural integrity necessary to achieve low shrinkage, lightweight, and high porosity.
[0128] Figure 8 The graph shows the thermal insulation performance of natural bamboo, bamboo fiber foam, and bleached bamboo fiber foam. Bamboo fiber foam exhibits excellent thermal insulation properties. Under conditions of 25℃ and 50% relative humidity, its thermal conductivity is 0.037 W / (m K), which is nearly 7 times lower than that of natural bamboo and only 41% of the thermal conductivity of bleached bamboo fiber foam.
[0129] Figure 9 This is a diagram illustrating the biodegradation of bamboo fiber foam. To assess the biodegradability of bamboo fiber foam, samples were buried 5 cm deep in soil and monitored under conditions of 25°C and 75% relative humidity. It can be seen that the foam surface began to roughen after 15 days of degradation, the surface structure began to collapse by day 30, the foam had broken into multiple small pieces by day 45, and decomposed into small fragments by day 60, achieving complete decomposition within 90 days. Soil microorganisms metabolized the foam into nutrients, allowing it to successfully return to the carbon cycle.
[0130] Figure 10 This diagram illustrates the recyclability of bamboo fiber foam. After use, the foam can be rapidly redispersed in water via mechanical stirring, forming a uniform bamboo cell fiber suspension suitable for reuse. The bamboo cell fiber suspension can be reshaped and dried at room temperature to produce new bamboo fiber foam, making this synthesis method highly economical and enabling closed-loop recycling. Furthermore, the sodium hydroxide and water used in the production process can be effectively recovered using mature chemical recycling technologies and wastewater treatment processes commonly used in the pulp and paper industry. This method further reduces resource consumption and improves the sustainability of bamboo fiber foam throughout its entire lifecycle.
[0131] Furthermore, tests showed that the recyclable bamboo fiber foams prepared in Examples 2, 3, and 4 also have the characteristics of high porosity, low shrinkage, low density, and low thermal conductivity, and can be recycled and reused.
[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing recyclable bamboo fiber foam, characterized by, The method comprises the following steps: a. crushing the bamboo and dispersing the bamboo powder in water, then collecting the bamboo fiber-containing bamboo powder after removing the parenchyma cells on the top layer of the aqueous solution; b. dispersing the bamboo fiber-containing bamboo powder collected in step a in an alkali solution, and obtaining partially delignified bamboo powder after partially delignifying the bamboo powder under heating conditions; c. dispersing the partially delignified bamboo powder obtained in step b in water, and separating the bamboo powder into single bamboo cell fibers to obtain a partially delignified bamboo fiber slurry; d. pouring the partially delignified bamboo fiber slurry obtained in step c into a prefabricated mold, and preparing a recyclable bamboo fiber foam after filtering and drying.
2. The method for preparing recyclable bamboo fiber foam according to claim 1, characterized in that, In step a, the bamboo powder with a particle size of 5-100 μm is collected after crushing the bamboo and dispersing the bamboo powder in water.
3. The method for preparing recyclable bamboo fiber foam according to claim 1, characterized in that, In step a, after collecting the bamboo fiber-containing bamboo powder, the method further comprises a step of drying the bamboo fiber-containing bamboo powder. The drying is performed in an oven at a temperature of 40-80 °C for 12-48 hours.
4. The method for preparing recyclable bamboo fiber foam according to claim 1, characterized in that, The alkali solution comprises one or more of a sodium hydroxide solution and a potassium hydroxide solution. The mass concentration of the alkali solution is 1%-20%.
5. The method for preparing recyclable bamboo fiber foam according to claim 1, characterized in that, The temperature of the partial delignification is 70-100 °C, and the time is 5-80 minutes.
6. The method for preparing recyclable bamboo fiber foam according to claim 1, characterized in that, In step b, after the partial delignification, the method further comprises a step of washing with water to remove residual alkali.
7. The method for preparing recyclable bamboo fiber foam according to claim 1, characterized in that, In step c, the ratio of the partially delignified bamboo powder to water is (1-4 kg):(25-400 L). The separation is performed by high-speed stirring.
8. The method for preparing recyclable bamboo fiber foam according to claim 1, characterized in that, The filtering is natural filtering. The drying is performed under normal pressure at a temperature of 50-105 °C for 4-8 hours.
9. Recyclable bamboo fiber foam, characterized by, The recyclable bamboo fiber foam is prepared by the method according to any one of claims 1-8.
10. Use of the recyclable bamboo fiber foam according to claim 9 in the preparation of thermal insulation materials.