Preparation method of a high-performance bamboo fiber hydrophobic heat-insulating lightweight porous material

Abstract

The present invention provides a method for preparing a high-performance hydrophobic and heat-insulating lightweight porous bamboo fiber material. The method is as follows: First, bamboo waste is dissociated to prepare parenchyma cells and bamboo fibers. A part of the parenchyma cells is prepared into nanocellulose by mechanical enzymolysis, and a part of the parenchyma cells is prepared into smaller-sized parenchyma cell fragments by pulverization. Then, a mixed solution of silica aerogel / ethanol / distilled water is prepared, and the nanocellulose and parenchyma cell fragments, together with partially de-chemically-composed bamboo fibers, are poured into the mixed solution, and vacuum impregnation is carried out. Finally, the material is poured into a mold to fix its shape. After the ethanol volatilizes, high-temperature rapid thermoforming is carried out to produce the hydrophobic and heat-insulating lightweight porous bamboo fiber material. The present invention prepares a bamboo fiber porous material with high strength, good heat-insulating performance, low humidity sensitivity, environmental friendliness and low cost through innovative technologies, which is of great significance for promoting the application of green packaging, building materials and the development of the bamboo industry.

Description

Technical Field

[0001] The present invention belongs to the technical field of bamboo processing, and particularly relates to a preparation method of a high-performance bamboo fiber hydrophobic heat-insulating lightweight porous material. Background Art

[0002] At present, energy-saving thermal insulation materials for buildings and thermal insulation packaging materials in cold chain transportation usually mainly use organic thermal insulation materials, namely petroleum-based plastic foam materials. For example, polystyrene foam plastic, because of its low price and good thermal insulation and waterproof performance, is commonly used in places such as inside buildings; it is usually divided into two categories, expanded type and extruded type. The extruded foam material is more expensive than the expanded type, and its surface needs to be treated during construction, so its usage rate in green buildings is gradually decreasing. Since the organic thermal insulation material is petroleum-based foam plastic, its use temperature is relatively low (<70 °C), and it is flammable when heated. Its durability is poor under the influence of ultraviolet radiation and meteorological conditions outdoors. And the organic thermal insulation material composed of organic substances such as polymers is relatively complex in structure, difficult to be effectively separated and treated by traditional recycling methods, and also difficult to be degraded by the natural environment. At present, there are also bio-based foam materials to replace traditional petroleum-based plastic foam materials. For example, nanocellulose-based aerogels have the advantages of light weight, heat insulation, and environmental friendliness, but their preparation cost is high and freeze-drying cannot be used for industrial production. Inorganic thermal insulation materials such as rock wool, expanded perlite, and foam glass are applied to the enclosure structures of current buildings because of their strong fire resistance, sound absorption, and resistance to insect damage. However, they have problems such as high moisture sensitivity, high density, and high brittleness. Their thermal insulation performance decreases and they are prone to cracking after absorbing water, and their usage scenarios and geographical environments are restricted. For example, they cannot be used in humid environments (basements). During on-site construction, they need to be waterproofed again before being applied to buildings. New inorganic thermal insulation materials, such as foam glass, have better fire resistance, thermal insulation, waterproof, and sound insulation properties, but they are relatively fragile during processing and cutting, the construction difficulty is large, and the preparation cost is high and it is difficult to recycle.

[0003] As a dominant forest resource in China, bamboo provides a rich resource base for the processing and utilization of bamboo products. However, due to its hollow interior, thin walls, non-uniformity, and small diameter, bamboo is difficult to process and standardize in large batches, resulting in a very low utilization rate of only about 30%. During industrial processing, bamboo waste such as small-diameter bamboo poles at the tip, bamboo materials with more bamboo knots at the base, bamboo branches, and various processing residues of bamboo units are often generated. Currently, these bamboo wastes are often discarded in landfills, used as fertilizers, fuels, or added to resins to prepare semi-green composite materials. However, these simple and crude treatment methods do not fully increase the added value of bamboo. Approximately 20-60% of parenchyma cells, 40-60% of bamboo fibers, and 10% of vessel tissues are present in natural bamboo. The arrangement and shape of parenchyma cells in bamboo endow bamboo with high strength, rigidity, and excellent bending resistance. However, in some current high-value utilization scenarios of bamboo, parenchyma cells are often removed. For example, when preparing bamboo fibers, parenchyma cells need to be completely removed, which greatly wastes bamboo resources. The density of parenchyma cells is much lower than that of bamboo fibers, and compared with bamboo fibers, the crystallinity of cellulose in parenchyma cells is lower. The relatively loose arrangement of cellulose chains in parenchyma cells allows chemical reagents to penetrate more easily into the crystalline cellulose of parenchyma cells. Therefore, compared with using bamboo fibers to prepare nanocellulose, using parenchyma cells can prepare nanocellulose with fewer reagents and lower energy consumption. The high-value utilization of bamboo waste is an effective way to improve the utilization rate of bamboo. Therefore, there is an urgent need to develop a method for the high-value reuse of bamboo waste to prepare bamboo fiber porous materials with low humidity sensitivity, high strength, environmental friendliness, and low cost. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a high-performance hydrophobic and heat-insulating lightweight porous bamboo fiber material in view of the above-mentioned deficiencies of the prior art. In this preparation method, bamboo waste is first dissociated to prepare parenchyma cells and bamboo fibers. A part of the parenchyma cells is prepared into nanocellulose by mechanical enzymolysis, and a part of the parenchyma cells is prepared into smaller parenchyma cell fragments by crushing. Then, a mixed solution of silica aerogel / ethanol / distilled water is prepared, and the parenchyma cell fragments and partially de-chemically-composed bamboo fibers are poured into the mixed solution, and vacuum impregnation is carried out. Finally, the material is poured into a mold to fix its shape. After the ethanol volatilizes, high-temperature rapid thermoforming is carried out to produce a hydrophobic and heat-insulating lightweight porous bamboo fiber material.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a high-performance hydrophobic and heat-insulating lightweight porous bamboo fiber material, the preparation method comprising the following steps:

[0006] S1, bamboo waste dissociation: crushing bamboo waste into bamboo chips, preparing a solution with hydrogen peroxide and glacial acetic acid, soaking the bamboo chips in the solution at a certain temperature, and stirring; washing the soaked bamboo chips with water until neutral, stirring the soaked bamboo chips in water, and sieving thin-walled cells and bamboo fibers respectively with a sieve;

[0007] crushing a portion of the thin-walled cells to obtain thin-walled cell fragments, and then subjecting another portion of the thin-walled cells to mechanical enzymatic hydrolysis to prepare nanocellulose;

[0008] S2. preparing a mixed solution: placing the silica aerogel powder in a mixed solution of ethanol and distilled water, and stirring evenly at room temperature to obtain a mixed solution;

[0009] S3, bamboo material mixing: the nanocellulose obtained in S1 and the thin-walled cell fragments obtained in S1 are placed in the mixed solution obtained in S2 and stirred, and then the bamboo fibers screened in S1 are added and stirred at a certain temperature, and then impregnated under vacuum pressure after stirring to obtain an impregnated bamboo mixture;

[0010] S4, placing the impregnated bamboo mixture obtained in S3 in a shaping mold, placing it in a ventilated place for a certain period of time, and then performing a thermoforming process to obtain a high-performance bamboo fiber hydrophobic heat-insulating lightweight porous material.

[0011] Preferably, the length of the bamboo scraps in S1 is 40-50 mm; the volume ratio of hydrogen peroxide to glacial acetic acid in the solution is 1:1, and the mass fraction of the hydrogen peroxide is 30%.

[0012] Preferably, in S1, the mixture is immersed at a temperature of 60 to 70° C. for 12 to 18 hours; thin-walled cells are obtained by sieving with a sieve having a particle size of 180 to 200 meshes, and bamboo fibers are obtained by sieving with a sieve having a particle size of 120 to 160 meshes.

[0013] Preferably, the size of the thin-walled cell fragments in S1 is 1 to 20 μm.

[0014] Preferably, the diameter of the silica aerogel powder in S2 is 40nm~20μm; the mass of the silica aerogel powder is 0.05%~0.1% of the mixed solution of ethanol and distilled water, and the volume ratio of ethanol to distilled water in the mixed solution of ethanol and distilled water is (2~4):1.

[0015] Preferably, the stirring rate in S2 is 40 to 80 r / min, and the time is 10 to 30 min.

[0016] Preferably, the mass ratio of the total mass of the bamboo fiber, parenchyma cell fragments, and nanocellulose in S3 to the mass of the mixed solution is 1:(8 - 12); the absolute dry mass ratio of the bamboo fiber, parenchyma cell fragments, and nanocellulose is (85 - 95):(2.5 - 7.5):(2.5 - 7.5).

[0017] Preferably, in S3, it is stirred for 10 - 30 min under the condition that the temperature is 25 - 30 °C, the stirring rate is 40 - 80 r / min, and after stirring, it is impregnated for 3 - 5 h under the condition that the vacuum pressure is 0.08 - 0.09 MPa.

[0018] Preferably, the time for placing in a ventilated place in S4 is 30 - 40 min; the temperature of the thermoforming process is 160 - 200 °C, and the time of the thermoforming process is 5 - 10 min / mm.

[0019] The present invention has the following advantages compared with the prior art:

[0020] 1. There are approximately 20 - 60% parenchyma cells, 40 - 60% bamboo fibers, and 10% vessel tissues in natural bamboo. As the main components of bamboo, the cell wall hardness of bamboo fibers is uniform, and the average elastic modulus is 22.5 GPa; while the cell wall structure of parenchyma cells alternates between hard and soft, the average elastic modulus is 17.3 GPa, and the cell wall density is about 1.4 g / cm 3 , so parenchyma cells are more prone to fragmentation compared to bamboo fibers. Bamboo fibers have thick cell walls and small cavities, and the size of individual fiber cells is small, with a specific surface area of about 0.63 m 2 / g. While parenchyma cells have thin cell walls and large cavities, the size of individual parenchyma cells is much larger than that of bamboo fibers, with a specific surface area of about 0.96 m 2 / g, and there are more pits in the cell wall of parenchyma cells, so parenchyma cells are more likely to carry micro-nano modified particles (such as silica aerogel powder). The hemicellulose, cellulose, and lignin in bamboo fibers are approximately 17.2%, 38.5%, and 25.5%; the hemicellulose, cellulose, and lignin in parenchyma cells are approximately 20.4%, 35.8%, and 26.6%. Hemicellulose has more hydroxyl groups than cellulose and lignin. Therefore, fragmented parenchyma cells are beneficial for filling the interface between nanocellulose and bamboo fibers, further strengthening the interfacial bonding between parenchyma cells and bamboo fibers, reducing pore collapse, and improving mechanical properties.

[0021] The cell wall density of bamboo fibers is about 1.5 g / cm 3 , and the cell wall porosity is about 2.9%; while the cell wall density of parenchyma cells is about 1.4 g / cm 3, the porosity of the cell wall is about 5.1%, which provides a way for the reagent to fully penetrate into the interior. The cellulose crystallinity of bamboo fiber is 55.1%, and that of the parenchyma cells is about 41.6%. Therefore, compared with the bamboo fiber, the relatively loosely arranged cellulose chains in the parenchyma cells make it easier for the reagent to penetrate into the crystalline cellulose of the parenchyma cells, and thus it is easier to prepare nanocellulose. The main structure of nanocellulose is composed of β-d-glucose monomers connected by 1,4-β-glycosidic bonds. It not only has the morphological structure and properties of cellulose fibers, but also has excellent properties of nanomaterials such as high surface area, high adsorption capacity, and easy surface functionalization. At the same time, nanocellulose enhances the strength and biodegradability of bamboo fiber. Therefore, the nanocellulose prepared by mechanical enzymatic hydrolysis of parenchyma cells is selected as the adhesive between bamboo fiber and bamboo fiber, and between bamboo fiber and silica aerogel.

[0022] The main chemical components of bamboo fiber are lignin, cellulose and hemicellulose. Among them, cellulose and hemicellulose are hydrophilic, have a relatively high heat conduction rate, and poor dimensional stability. Silica aerogel has an ultra-low density and a unique porous structure, with strong hydrophobic and heat insulation properties. When combined with bamboo fiber, it can effectively solve the disadvantages of bamboo fiber such as hydrophilicity, poor heat insulation performance, and low surface hardness. Because silica aerogel is light, porous, and has strong polarity and hydrophobic properties, ethanol is used as the medium to make silica aerogel suspend in the mixed solution. Adding a small amount of distilled water can make the aerogel solid suspend more evenly in the mixed solution, and the silica aerogel powder with a smaller diameter is easier to disperse in the solution and also easier to adhere to the surface of bamboo materials.

[0023] By mixing bamboo materials and using high-temperature rapid thermoforming technology, bamboo fiber hydrophobic thermal insulation lightweight porous materials can be rapidly prepared, which have low cost, high efficiency, and are easy to achieve batch production. And through one-time high-temperature rapid thermoforming, the lightweight porous material can achieve better compressive strength, hydrophobic performance and heat resistance.

[0024] 2. The present invention uses bamboo waste as raw material, dissociates bamboo waste through chemical pretreatment to prepare parenchyma cells and bamboo fibers. Some parenchyma cells are used to prepare nanocellulose through mechanical enzymolysis, and some parenchyma cells are used to prepare smaller-sized parenchyma cell fragments through pulverization. After mixing bamboo fibers, parenchyma cell fragments, nanocellulose, and silica aerogel powder with ethanol / distilled water and then using high-temperature rapid thermoforming, a hydrophobic heat-insulating lightweight porous bamboo fiber material is prepared. This method uses bamboo fibers as the framework, nanocellulose as the binder, parenchyma cell fragments and silica aerogel as the interface filling materials to prepare a hydrophobic heat-insulating lightweight porous bamboo fiber material with a modifier. Since its interface is effectively filled, on the one hand, it can reduce pore collapse and improve its strength, and on the other hand, it can also effectively reduce the moisture entry path and thus reduce its moisture sensitivity. When mixing bamboo materials, water and ethanol are used as the medium, which improves the dispersion degree of silica aerogel in the mixture, reduces the adverse effects brought by polarity between silica aerogel and bamboo fibers and parenchyma cell fragments at the same time, and improves the bonding degree between bamboo fibers, parenchyma cell fragments and silica aerogel to achieve the purpose of hydrophobicity. Thermoforming under high-temperature and short-time environment enables the material to be used in high-temperature environments to achieve the purpose of strong fire resistance. And because the raw materials used are all bamboo waste, the preparation process is simple and convenient, so the cost is low. And the prepared lightweight porous material is completely green, environmentally friendly, degradable, recyclable, and has no VOCs release, truly realizing the high-value utilization of bamboo waste and the low-carbon footprint preparation of green packaging and building materials.

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0026] Figure 1 Among them, (a) and (c) are the electron micrograph and model diagram of the hydrophobic heat-insulating lightweight porous bamboo fiber material prepared in Example 1 of the present invention, and (b) and (d) are the electron micrograph and model diagram of the hydrophobic heat-insulating lightweight porous bamboo fiber material prepared in Comparative Example 1.

[0027] Figure 2 is the structural diagram of parenchyma cells and bamboo fibers in the present invention.

[0028] Figure 3 is the electron micrograph of a single parenchyma cell isolated in the present invention.

[0029] Figure 4 is the electron micrograph of a single bamboo fiber isolated in the present invention.

[0030] Figure 5 is the filling diagram of silica aerogel and parenchyma cell fragments between the interfaces of bamboo fibers and nanocellulose in the present invention.

[0031] Figure 6It is a performance test diagram of the bamboo fiber hydrophobic heat-insulating lightweight porous material prepared in Embodiments 1 and 2 of the present invention and the bamboo fiber hydrophobic heat-insulating lightweight porous material prepared in Comparative Examples 1 and 2. (a) is the compression force-strain curve, (b) is the impact toughness, (c) is the compressive strength test diagram of the bamboo fiber hydrophobic heat-insulating lightweight porous material prepared in Comparative Example 1, and (d) is the compressive strength test diagram of the bamboo fiber hydrophobic heat-insulating lightweight porous material prepared in Embodiment 1. Detailed implementation manners

[0032] Embodiment 1

[0033] The preparation method of the high-performance bamboo fiber hydrophobic heat-insulating lightweight porous material in this embodiment includes the following steps:

[0034] S1. Dissociation of bamboo waste: The bamboo waste is crushed into bamboo chips with a length of 40-50 mm, and then a solution is prepared by mixing hydrogen peroxide with a mass fraction of 30% and glacial acetic acid in a volume ratio of 1:1. The bamboo chips are placed in the solution and soaked at a temperature of 60°C for 18 h with stirring; the soaked bamboo chips are washed with water until neutral, and the soaked bamboo chips are stirred in water at the same time. The parenchyma cells are obtained by sieving with a sieve with a particle size of 180-200 mesh, and the bamboo fibers are obtained by sieving with a sieve with a particle size of 120-160 mesh;

[0035] A part of the parenchyma cells is crushed to obtain parenchyma cell fragments with a size of 1-20 μm, and another part of the parenchyma cells is used to prepare nanocellulose by mechanical enzymolysis; the specific operation process of the mechanical enzymolysis method can be seen in the published Chinese invention patent CN 116375891 A;

[0036] S2. Preparation of the mixed solution: The silica aerogel powder with a diameter of 40 nm is placed in a mixed solution of ethanol and distilled water, and stirred evenly at room temperature (25°C) at a stirring rate of 60 r / min for 10 min until there is no obvious precipitate to obtain the mixed solution;

[0037] The mass of the silica aerogel powder is 0.05% of the mixed solution of ethanol and distilled water, and the volume ratio of ethanol to distilled water in the mixed solution of ethanol and distilled water is 4:1;

[0038] S3. Mixing of bamboo materials: The nanocellulose obtained in S1 and the parenchyma cell fragments obtained in S1 are placed in the mixed solution obtained in S2 and stirred, and then the bamboo fibers sieved in S1 are added and stirred at a temperature of 27°C for 30 min at a stirring rate of 60 r / min. After stirring, it is impregnated in a vacuum impregnation tank with a vacuum pressure of 0.08 MPa for 3 h to obtain the impregnated bamboo mixture;

[0039] The mass ratio of the total mass of the bamboo fiber, parenchyma cell fragments, and nanocellulose to the mass of the mixed solution is 1:8; the absolute dry mass ratio of the bamboo fiber, parenchyma cell fragments, and nanocellulose is 95:2.5:2.5;

[0040] S4. Place the impregnated bamboo mixture obtained in S3 in a semi-sealed mold. The radial cross-section of the mold is square. Place it in a ventilated place for 40 min to allow the ethanol to volatilize, and then perform a thermoforming process at a temperature of 200 °C and a time of 5 min / mm to obtain a high-performance hydrophobic and heat-insulating lightweight porous bamboo fiber material.

[0041] The high-performance hydrophobic and heat-insulating lightweight porous bamboo fiber material prepared in this embodiment can be used for cold storage insulation wall panels;

[0042] Detect the high-performance hydrophobic and heat-insulating lightweight porous bamboo fiber material prepared in this embodiment: Density: 0.15 g / cm 3 ; Thermal conductivity: 0.042 W / m·K; Water absorption rate: 0; Contact angle: 139°; Degradation rate: 94.5%; Compressive strength: 2.58 MPa; Impact toughness: 170 KJ / m 3 .

[0043] Figure 2 In (a) is the SEM image of the bamboo cross-section, (b) is the SEM image of the parenchyma cell wall cross-section, and (c) is the SEM image of the bamboo fiber cross-section. It can be seen that the parenchyma cell wall is a multi-layer structure, the bamboo fiber cell wall is a multi-layer structure with alternating thick and thin layers, the parenchyma cell structure is loose and easy to be damaged, and the fiber structure is dense and has high strength. Utilizing the different morphologies and structures of bamboo fibers and parenchyma cells, bamboo fibers are slender and parenchyma cells are short and thick, and the two are separated by the pore size of the sieve mesh. The parenchyma cell wall is thin and has weak mechanical properties, and it is very easy to be broken into fragments and decomposed into nanocellulose.

[0044] Figure 3 is the SEM image of a single separated parenchyma cell, Figure 4 is the SEM image of a single separated bamboo fiber. It can be seen that the aspect ratio of bamboo fibers is much larger than that of parenchyma cells, indicating that bamboo fibers are suitable as the reinforcing phase to enhance the mechanical properties of the material, and parenchyma cells are suitable for filling large pores to further provide mechanical support.

[0045] With bamboo fibers as the skeleton, nanocellulose as the binder, and parenchyma cell fragments and silica aerogel as the interface filling materials, since their interfaces are effectively filled, on the one hand, it can reduce pore collapse and improve its strength, and on the other hand, it can also effectively reduce the moisture entry path and thus reduce its humidity sensitivity; Figure 5As shown, silica aerogel fills between the fibers and the interface of nanocellulose and parenchyma cell fragments (the red color in the lower right corner represents the distribution of silicon elements, and at the same time indicates the distribution of silica aerogel).

[0046] Comparative Example 1

[0047] For the preparation method of the high-performance bamboo fiber hydrophobic and heat-insulating lightweight porous material in this comparative example, nanocellulose and parenchyma cells are not prepared in S1, and nanocellulose and parenchyma cell fragments are not added in S3. The rest of the preparation method is exactly the same as that in Example 1.

[0048] The high-performance bamboo fiber hydrophobic and heat-insulating lightweight porous material prepared in this comparative example was tested: Density: 0.13 g / cm 3 ; Thermal conductivity: 0.095 W / m·K; Water absorption rate: 473.1%; Contact angle: 0°; Degradation rate: 93.3%; Compressive strength: 0.12 MPa; Impact toughness: 8.81 KJ / m 3 .

[0049] Figure 1 In (a) and (c) are the high-performance bamboo fiber hydrophobic and heat-insulating lightweight porous materials prepared in Example 1. In (a), the parenchyma cells are within the red frame. Figure 1 In (b) and (d) are the porous materials prepared in this comparative example. It can be seen that there are more large pores in the figure, which is not conducive to mechanical properties. Therefore, the compressive strength of the porous material prepared in this comparative example is much lower than that of the high-performance bamboo fiber hydrophobic and heat-insulating lightweight porous material prepared in Example 1.

[0050] Comparative Example 2

[0051] For the preparation method of the high-performance bamboo fiber hydrophobic and heat-insulating lightweight porous material in this comparative example, the soaking time of bamboo scraps in the solution prepared with hydrogen peroxide and glacial acetic acid in S1 is 12 h. The rest of the preparation method is exactly the same as that in Comparative Example 1.

[0052] Figure 6A and B are the bamboo fiber hydrophobic thermal insulation lightweight porous materials prepared in Examples 1 and 2, C and D are the bamboo fiber hydrophobic thermal insulation lightweight porous materials prepared in Comparative Examples 1 and 2. The chemical component contents of C and D are different, and the lignin content of D is higher. The longer the bamboo chips are soaked in the solution prepared with hydrogen peroxide and glacial acetic acid, the less the lignin content. (a) is the compressive stress-strain curve. It can be seen that the compressive stress-strain curves of the bamboo fiber hydrophobic thermal insulation lightweight porous materials prepared in Examples 1 and 2 are better than those of the bamboo fiber hydrophobic thermal insulation lightweight porous materials prepared in Comparative Examples 1 and 2; (b) is the impact toughness. It can be seen that the impact toughness of the bamboo fiber hydrophobic thermal insulation lightweight porous materials prepared in Examples 1 and 2 is stronger than that of the bamboo fiber hydrophobic thermal insulation lightweight porous materials prepared in Comparative Examples 1 and 2; and (c) is the bamboo fiber hydrophobic thermal insulation lightweight porous material prepared in Comparative Example 1, without adding parenchyma cell fragments and nanocellulose materials, (d) is the bamboo fiber hydrophobic thermal insulation lightweight porous material prepared in Example 1, proving that the compressive strength of the bamboo fiber hydrophobic thermal insulation lightweight porous material prepared in Comparative Example 1 is better than that of the bamboo fiber hydrophobic thermal insulation lightweight porous material prepared in Comparative Example 1.

[0053] Comparative Example 3

[0054] For the preparation method of the high-performance bamboo fiber hydrophobic thermal insulation lightweight porous material in this comparative example, the preparation of the mixed solution in S2 is not carried out, and the rest of the preparation method is exactly the same as that in Example 1.

[0055] The high-performance bamboo fiber hydrophobic thermal insulation lightweight porous material prepared in this comparative example is tested: Density: 0.14 g / cm 3 ; Thermal conductivity: 0.049 W / m·K; Water absorption rate: 251.7%; Contact angle: 0°; Degradation rate 95.3%: Compressive strength 2.14 MPa; Impact toughness 150 KJ / m 3 .

[0056] Comparative Example 4

[0057] For the preparation method of the high-performance bamboo fiber hydrophobic thermal insulation lightweight porous material in this comparative example, parenchyma cells are not prepared in S1, and parenchyma cell fragments are not added in S3. The rest of the preparation method is exactly the same as that in Example 1.

[0058] The high-performance bamboo fiber hydrophobic thermal insulation lightweight porous material prepared in this comparative example is tested: Density: 0.16 g / cm 3 ; Thermal conductivity: 0.041 W / m·K; Water absorption rate: 0; Contact angle: 140°; Degradation rate 95.5%: Compressive strength 1.5 MPa; Impact toughness 120 KJ / m 3 .

[0059] In this comparative example, no parenchyma cell fragments were added, and the compressive strength and impact toughness of the prepared bamboo fiber hydrophobic thermal insulation lightweight porous material were lower than those of the bamboo fiber hydrophobic thermal insulation lightweight porous material in Example 1.

[0060] Example 2

[0061] S1. Bamboo waste dissociation: The bamboo waste was crushed into bamboo chips with a length of 40 - 50 mm, and then a solution was prepared by mixing hydrogen peroxide with a mass fraction of 30% and glacial acetic acid in a volume ratio of 1:1. The bamboo chips were placed in the solution and soaked at a temperature of 65°C for 15 h with stirring; the soaked bamboo chips were washed with water until neutral, and while stirring the soaked bamboo chips in water, parenchyma cells were obtained by screening with a sieve with a particle size of 180 - 200 mesh, and bamboo fibers were obtained by screening with a sieve with a particle size of 120 - 160 mesh;

[0062] A part of the parenchyma cells was crushed to obtain parenchyma cell fragments with a size of 1 - 10 μm, and another part of the parenchyma cells was used to prepare nanocellulose by a mechanical enzyme method; the specific operation process of the mechanical enzyme method can be seen in the published Chinese invention patent CN 116375891 A;

[0063] S2. Preparation of a mixed solution: Silica aerogel powder with a diameter of 40 nm was placed in a mixed solution of ethanol and distilled water, and stirred evenly at room temperature (28°C) with a stirring rate of 80 r / min for 20 min until there was no obvious precipitate, obtaining a mixed solution;

[0064] The mass of the silica aerogel powder was 0.07% of the mass of the mixed solution of ethanol and distilled water, and the volume ratio of ethanol to distilled water in the mixed solution of ethanol and distilled water was 4:1;

[0065] S3. Bamboo material mixing: The nanocellulose obtained in S1 and the parenchyma cell fragments obtained in S1 were placed in the mixed solution obtained in S2 and stirred, and then the bamboo fibers screened in S1 were added and stirred at a temperature of 25°C for 20 min with a stirring rate of 40 r / min. After stirring, impregnation was carried out in a vacuum impregnation tank with a vacuum pressure of 0.085 MPa for 4 h to obtain an impregnated bamboo mixture;

[0066] The mass ratio of the total mass of the bamboo fibers, parenchyma cell fragments and nanocellulose to the mass of the mixed solution was 1:12; the absolute dry mass ratio of the bamboo fibers, parenchyma cell fragments and nanocellulose was 95:5:5;

[0067] S4. Place the impregnated bamboo mixture obtained in S3 in a semi-sealed mold. The radial cross-section of the semi-sealed mold is square. Place it in a ventilated place for 35 minutes to allow the ethanol to volatilize, and then perform a thermoforming process at a temperature of 190 °C and a time of 8 min / mm to obtain a high-performance bamboo fiber hydrophobic and heat-insulating lightweight porous material.

[0068] The high-performance bamboo fiber hydrophobic and heat-insulating lightweight porous material prepared in this example can be used for moisture-proof and heat-insulating boards for basements;

[0069] Test the high-performance bamboo fiber hydrophobic and heat-insulating lightweight porous material prepared in this example: Density: 0.12 g / cm 3 ; Thermal conductivity: 0.048 W / m·K; Water absorption rate: 0; Contact angle: 145°; Degradation rate: 95.7%; Compressive strength: 2.75 MPa; Impact toughness: 150 KJ / m 3 .

[0070] Example 3

[0071] S1. Bamboo waste dissociation: Crush the bamboo waste into bamboo chips with a length of 40 - 50 mm, and then prepare a solution by mixing hydrogen peroxide with a mass fraction of 30% and glacial acetic acid in a volume ratio of 1:1. Place the bamboo chips in the solution and soak them at a temperature of 70 °C for 12 h with stirring; Wash the soaked bamboo chips with water until neutral, and stir the soaked bamboo chips in water at the same time. Screen them with a sieve with a particle size of 180 - 200 mesh to obtain parenchyma cells, and screen them with a sieve with a particle size of 120 - 160 mesh to obtain bamboo fibers;

[0072] Crush a part of the parenchyma cells to obtain parenchyma cell fragments with a size of 1 - 10 μm, and prepare nanocellulose from another part of the parenchyma cells by mechanical enzymolysis; The specific operation process of the mechanical enzymolysis method can be found in the published Chinese invention patent CN 116375891 A;

[0073] S2. Prepare a mixed solution: Place silica aerogel powder with a diameter of 40 nm in a mixed solution of ethanol and distilled water, stir evenly at room temperature (30 °C), with a stirring rate of 40 r / min and a stirring time of 30 min until there is no obvious precipitate to obtain a mixed solution;

[0074] The mass of the silica aerogel powder is 0.1% of the mixed solution of ethanol and distilled water, and the volume ratio of ethanol to distilled water in the mixed solution of ethanol and distilled water is 2:1;

[0075] S3. Bamboo material mixing: Place the nanocellulose obtained in S1 and the parenchyma cell fragments obtained in S1 into the mixed solution obtained in S2 and stir. Then add the bamboo fibers screened out in S1 and stir at a temperature of 30°C for 10 min at a stirring rate of 80 r / min. After stirring, impregnate in a vacuum impregnation tank with a vacuum pressure of 0.09 MPa for 5 h to obtain an impregnated bamboo mixture.

[0076] The mass ratio of the total mass of the bamboo fibers, parenchyma cell fragments and nanocellulose to the mass of the mixed solution is 1:10; the absolute dry mass ratio of the bamboo fibers, parenchyma cell fragments and nanocellulose is 85:7.5:7.5.

[0077] S4. Place the impregnated bamboo mixture obtained in S3 into a semi-sealed mold. The radial cross-section of the semi-sealed mold is square. Place it in a ventilated place for 30 min to allow the ethanol to volatilize. Then perform a thermoforming process at a temperature of 160°C and a time of 10 min / mm to obtain a high-performance bamboo fiber hydrophobic and heat-insulating lightweight porous material.

[0078] The high-performance bamboo fiber hydrophobic and heat-insulating lightweight porous material prepared in this example can be used for indoor thermal insulation wall panels for high-rise buildings.

[0079] Detect the high-performance bamboo fiber hydrophobic and heat-insulating lightweight porous material prepared in this example: Density: 0.09 g / cm 3 ; Thermal conductivity: 0.035 W / m·K; Water absorption rate: 0; Contact angle: 153°; Degradation rate: 96.3%; Compressive strength: 3.06 MPa; Impact toughness: 170 KJ / m 3 .

[0080] In this embodiment S1, thin-walled cells can be obtained by sieving with a sieve having a particle size of 180 mesh, 190 mesh, and 200 mesh, and bamboo fibers can be obtained by sieving with a sieve having a particle size of 120 mesh, 130 mesh, 140 mesh, 150 mesh, and 160 mesh; in S2, the diameter of the silica aerogel powder can also be 50 nm, 100 nm, 500 nm, 1 μm, 2 μm, 3 μm, 4 μm..... or 20 μm; the volume ratio of ethanol to distilled water in the mixed solution of ethanol and distilled water is 2.5:1, 3:1, or 3.5:1; in S3, the stirring temperature can also be 26 °C, 27 °C, 28 °C, or 29 °C, and the stirring time can also be 12 min, 15 min, 18 min, 23 min, 25 min, 27 min, 28 min, or 29 min; the mass ratio of the total mass of the bamboo fibers, thin-walled cell fragments, and nanocellulose to the mass of the mixed solution can also be 1:8.5, 1:9, 1:9.5, 1:9.8, 1:10.5, 1:11, or 1:11.5; in S4, the temperature of the thermoforming process can also be 170 °C, 175 °C, 180 °C, 185 °C, 190 °C, 195 °C, or 199 °C, and the time can also be 6 min / mm, 6.5 min / mm, 7 min / mm, 7.5 min / mm, 8 min / mm, 8.5 min / mm, 9 min / mm, or 9.5 min / mm.

[0081] The bamboo fiber hydrophobic heat-insulating lightweight porous material prepared by the preparation method of the high-performance bamboo fiber hydrophobic heat-insulating lightweight porous material of the present invention can select different shaping molds according to different uses, and the shaping molds can also be selected from open molds, special-shaped molds (such as gourd-shaped, apple-shaped, etc.).

[0082] The above is only a preferred embodiment of the present invention and does not impose any limitation on the present invention. Any simple modification, change, and equivalent change made to the above embodiments according to the technical essence of the invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A preparation method of a high-performance bamboo fiber hydrophobic heat-insulating lightweight porous material, characterized in that The preparation method includes the following steps: S1. Bamboo waste dissociation: Crush the bamboo waste into bamboo chips, prepare a solution with hydrogen peroxide and glacial acetic acid, place the bamboo chips in the solution, soak at a certain temperature, and stir; wash the soaked bamboo chips with water until neutral, and stir the soaked bamboo chips in water at the same time, and separately screen out parenchyma cells and bamboo fibers with a sieve; Crush a part of the parenchyma cells to obtain parenchyma cell fragments, and prepare nanocellulose from another part of the parenchyma cells by mechanical enzymolysis method; S2. Prepare a mixed solution: Place the silica aerogel powder in a mixed solution of ethanol and distilled water, and stir evenly at room temperature to obtain a mixed solution; S3. Bamboo material mixing: Place the nanocellulose obtained in S1 and the parenchyma cell fragments obtained in S1 in the mixed solution obtained in S2 and stir, then add the bamboo fibers screened out in S1 and stir at a certain temperature, and perform impregnation under vacuum pressure after stirring to obtain an impregnated bamboo mixture; S4. Place the impregnated bamboo mixture obtained in S3 in a shaping mold, place it in a ventilated place for a certain time, and then perform a thermoforming process to obtain a high-performance hydrophobic and heat-insulating lightweight porous bamboo fiber material.

2. The preparation method of a high-performance bamboo fiber hydrophobic heat-insulating lightweight porous material according to claim 1, characterized in that, In S1, the length of the bamboo chips is 40-50 mm; the volume ratio of hydrogen peroxide to glacial acetic acid in the solution is 1:1, and the mass fraction of hydrogen peroxide is 30%.

3. The preparation method of a high-performance bamboo fiber hydrophobic and heat-insulating lightweight porous material according to claim 2, characterized in that, In S1, soak at a temperature of 60-70 °C for 12-18 h; screen out parenchyma cells with a sieve with a particle size of 180-200 mesh, and screen out bamboo fibers with a sieve with a particle size of 120-160 mesh.

4. The preparation method of a high-performance bamboo fiber hydrophobic heat-insulating lightweight porous material according to claim 3, characterized in that, In S1, the size of the parenchyma cell fragments is 1-20 μm.

5. The preparation method of a high-performance bamboo fiber hydrophobic and heat-insulating lightweight porous material according to claim 1, characterized in that, In S2, the diameter of the silica aerogel powder is 40 nm-20 μm; the mass of the silica aerogel powder is 0.05%-0.1% of the mixed solution of ethanol and distilled water, and the volume ratio of ethanol to distilled water in the mixed solution of ethanol and distilled water is (2-4):

1.

6. The preparation method of a high-performance bamboo fiber hydrophobic and heat-insulating lightweight porous material according to claim 5, characterized in that, In S2, the stirring rate is 40-80 r / min and the time is 10-30 min.

7. The preparation method of a high-performance bamboo fiber hydrophobic heat-insulating lightweight porous material according to claim 1, characterized in that, In S3, the mass ratio of the total mass of bamboo fibers, parenchyma cell fragments and nanocellulose to the mass of the mixed solution is 1:(8-12); the absolute dry mass ratio of bamboo fibers, parenchyma cell fragments and nanocellulose is (85-95):(2.5-7.5):(2.5-7.5).

8. The preparation method of a high-performance bamboo fiber hydrophobic heat-insulating lightweight porous material according to claim 7, characterized in that, In S3, stir at a temperature of 25-30 °C for 10-30 min, the stirring rate is 40-80 r / min, and perform impregnation for 3-5 h under a vacuum pressure of 0.08-0.09 MPa after stirring.

9. The preparation method of a high-performance bamboo fiber hydrophobic heat-insulating lightweight porous material according to claim 1, characterized in that, In S4, the time for placing in a ventilated place is 30-40 min; the temperature of the thermoforming process is 160-200 °C, and the time of the thermoforming process is 5-10 min / mm.

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