Multifunctional wood-based thermal insulation film and preparation method thereof

Abstract

The application discloses a multifunctional wood-based heat insulation film and a preparation method thereof. The preparation method comprises the following steps: firstly, obtaining a micro-nano level oxidized cellulose water dispersion by performing multi-step solvent encapsulation treatment on industrial pulp; and secondly, using a chitosan and sodium lignosulfonate aqueous solution to prepare sodium lignosulfonate nanoparticles as a functional filler. The synthesis method is simple, raw materials are widely sourced, the comprehensive performance of cellulose and lignin is combined, the preparation cost is low, the obtained wood-based film has stable mechanical performance and heat insulation performance, and the wood-based film is expected to become a substitute for traditional heat insulation building materials.

Description

Technical Field

[0001] This invention belongs to the field of functional materials technology, and relates to heat insulation materials, specifically to a multifunctional wood-based heat insulation film and its preparation method. Background Technology

[0002] Heating and cooling account for a significant portion of societal energy consumption. Due to the diffusivity of heat, insulation is crucial for energy management to reduce waste and improve efficiency. Today, smartphones, laptops, and other electronic devices play an increasingly important role in our work and lives, and we are becoming more discerning about their usability. Overheating can cause component malfunctions; in extreme cases, it can even lead to lithium battery explosions. Engineers go to great lengths to prevent overheating in electronic devices. They typically use glass, plastic, or multi-layered air as insulation materials to prevent heat generated by microprocessors and other heat-generating components from damaging other components or causing user dissatisfaction. The trend towards miniaturization of electronic devices presents significant challenges for engineers in designing insulation materials and entire insulation systems. Furthermore, in the construction sector, the development of lightweight, high-strength insulation materials holds promise, as buildings currently consume approximately 40% of the world's energy to maintain comfortable indoor conditions. One effective solution is to develop next-generation energy-intensive manufacturing processes to reduce energy consumption. Currently, several thermal insulation materials for the building industry are available on the market, such as reflective thermal insulation paint. This is a type of coating, and because it's a coating, it's very easy to apply. Simply spraying one coat onto the roof or wall provides effective insulation. It has low production costs and is a popular material, although its lifespan is somewhat short. Extruded polystyrene (XPS) boards are rigid boards made from polystyrene resin through a continuous extrusion foaming process. They have a closed-cell structure and are a thermal insulation material with excellent properties such as high compressive strength, water resistance, air tightness, lightweight, long service life, and low thermal conductivity. However, they are not very flexible, are relatively thick, and are not suitable for complex terrain. Rock wool insulation materials are mainly used for fireproofing and soundproofing building partitions and curtain walls, roof and enclosure insulation, geothermal system insulation, and insulation and fireproofing of industrial furnaces, ovens, large-diameter storage tanks, and ships. However, it has high hygroscopicity, so special attention must be paid to rain protection, especially avoiding construction in rainy weather. The above-mentioned building thermal insulation materials generally have some limitations in use, therefore, developing an environmentally friendly thermal insulation material is of research value. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a multifunctional wood-based thermal insulation film and its preparation method, which produces a multifunctional wood-based thermal insulation film with excellent mechanical stability, water stability, high wear resistance, good flexibility and thermal insulation performance, and is also environmentally friendly.

[0004] To achieve the above objectives, the present invention employs the following technical solution:

[0005] A method for preparing a multifunctional wood-based heat-insulating film includes the following steps:

[0006] Step 1: Add HCl solution to industrial pulp with a water content of 90-92% until the concentration of HCl in the pulp is 1 mol / L, and continue stirring for 1-2 hours. Then filter and wash with water to obtain solid substance I.

[0007] Step 2: Disperse the solid substance I prepared in Step 1 in water to prepare an aqueous dispersion with a mass fraction of 8-10 wt%, and adjust the pH to 10 with NaOH. According to the volume ratio of the aqueous dispersion, the mass of TEMPO, the mass of NaBr, and the volume of NaClO solution, 100 mL : (0.03-0.05) g : (0.3-0.5) g : (20-30) mL, add TEMPO, NaBr, and 1 mol / L NaClO solution to the mixture, let it stand for 15-30 min, then stir rapidly for 15 min. Then adjust the pH of the dispersion to 10 again with NaOH, and continue stirring for 15 min. After homogenization, filter and wash with water to obtain solid substance II.

[0008] Step 3: Grind the solid substance II obtained in Step 2, disperse it in water to prepare an aqueous dispersion slurry with a mass fraction of 8-10 wt%, and then crush it.

[0009] Step 4: Add acetic acid to the dispersion slurry that has been crushed in Step 3 to adjust the pH to 5-6. Then add 1 mol / L disodium phosphate solution, 1 mol / L sodium phosphate solution and TEMPO and stir rapidly for 15-30 min. Then add NaClO2 and continue stirring for 20 min. Transfer the mixture to a 60℃ constant temperature water bath and stir for 48 hours. After the reaction is complete, filter and wash with water to obtain solid substance III.

[0010] The mass ratio of the dispersion slurry, the disodium phosphate solution, the sodium phosphate solution, the mass of TEMPO, and the mass of NaClO2 is 100 mL: (20–30) mL: (20–30) mL: (0.03–0.05) g: (0.3–0.5) g.

[0011] Step 5: Disperse the solid substance III prepared in Step 4 in water to prepare an aqueous dispersion slurry with a mass fraction of 8-10 wt%, and then crush it to obtain the nano-oxidized cellulose aqueous dispersion slurry.

[0012] Step 6: Disperse chitosan solid in water to prepare a solution with a concentration of 0.1 wt%, and disperse sodium lignosulfonate in water to prepare a solution with a concentration of 1.0 wt%. Adjust the pH of both solutions to 4-5 using acetic acid.

[0013] Step 7: Place the sodium lignosulfonate solution on a magnetic stirrer and stir. Add the chitosan solution dropwise at a volume ratio of 1:1. After the addition is complete, homogenize the solution, then filter, wash with water, and dry to obtain a solid powder.

[0014] Step 8: Add the solid powder obtained in Step 8 to the nano-oxidized cellulose aqueous dispersion slurry prepared in Step 5 at a mass-to-volume ratio of 1g:(100-150)mL and homogenize it. Then, vacuum filter the mixed slurry into a thin film and dry it at room temperature.

[0015] The present invention also has the following technical features:

[0016] Preferably, the water washing described in steps one, two, four and seven involves washing with distilled water 3 to 5 times.

[0017] Preferably, the dispersion in step two involves treating the dispersion with a homogenizer for 60–120 minutes.

[0018] Preferably, the grinding in step three is mechanical grinding for 30 to 60 minutes.

[0019] Preferably, the disruption process described in steps three and five involves treating the slurry with a cell disruptor for 30–60 minutes.

[0020] Preferably, the drying process described in step seven is freeze-drying at -60°C for 48 hours.

[0021] Preferably, the homogenization process described in steps seven and eight is performed using a homogenizer for 30 to 60 minutes.

[0022] The present invention also protects a multifunctional wood-based heat-insulating film prepared by the method described above.

[0023] Compared with the prior art, the present invention has the following technical effects:

[0024] This invention first obtains a micro-nano-scale oxidized cellulose aqueous dispersion through a multi-step solvent encapsulation process. Multiple homogenization processes open the cellulose aggregate structure, selectively converting its surface groups into carboxyl functional groups. Secondly, sodium lignin sulfonate nanoparticles are prepared as functional fillers using chitosan and sodium lignin sulfonate aqueous solutions. The numerous hydrogen bonds generated during the stacking of nano-sized oxidized cellulose exhibit excellent mechanical durability, tensile strength, and flexibility. The presence of sodium lignin sulfonate nanoparticles, with their hydrophobic surface groups interacting with the carboxyl groups on the nanocellulose surface, enhances the mechanical strength of the composite film. The hydrophobic lignin backbone effectively isolates water molecules, imparting water resistance to the film. The uniform distribution of nanoparticles between film layers also contributes to the film's excellent wear resistance under external friction.

[0025] Sodium lignosulfonate is an excellent ultraviolet absorber that can effectively block ultraviolet rays emitted in the natural environment. Both nano-sized oxidized cellulose and sodium lignosulfonate particles are derivatives of wood materials. Nano-sized oxidized cellulose with a large number of carboxyl groups on its surface stacks together to form a dense layered structure and constructs a multi-level transition layer, while sodium lignosulfonate nanoparticles are distributed between the layers. The synergistic effect of the two effectively blocks the spread of heat and gives it good thermal insulation properties.

[0026] In summary, the wood-based composite material prepared by the present invention is characterized by the fact that the prepared wood-based film exhibits excellent mechanical stability, high wear resistance, excellent water stability, good flexibility, thermal insulation performance and recyclability.

[0027] The synthesis method of this invention is simple, the raw materials are widely available, and it combines the comprehensive properties of cellulose and lignin. Moreover, the preparation cost is low, and the obtained wood-based film has stable mechanical and thermal insulation properties. It is expected to become a substitute for traditional thermal insulation building materials and has the advantages of green and sustainable development. Attached Figure Description

[0028] Figure 1 This is a stress-strain curve of the wood-based thermal insulation film prepared in Example 1;

[0029] Figure 2 This is a surface morphology diagram of the wood-based heat-insulating film prepared in Example 1;

[0030] Figure 3 This is a cross-sectional morphology diagram of the wood-based heat insulation film prepared in Example 2;

[0031] Figure 4 This is a test graph showing the flexibility of the wood-based heat insulation film prepared in Example 2;

[0032] Figure 5This is a test chart of the abrasion resistance of the wood-based heat insulation film prepared in Example 3;

[0033] Figure 6 These are test results for the weather resistance of the wood-based thermal insulation film prepared in Example 3;

[0034] Figure 7 This is a test diagram of the water resistance of the wood-based heat insulation film prepared in Example 4;

[0035] Figure 8 This is a test diagram of the thermal insulation performance of the wood-based thermal insulation film prepared in Example 4. Detailed Implementation

[0036] The specific content of the present invention will be further explained in detail below with reference to the embodiments.

[0037] In the following examples, the HCl solution had a mass fraction of 36%;

[0038] Industrial pulp is a pulp produced through papermaking processes using various raw materials rich in lignocellulose.

[0039] TEMPO is a 2,2,6,6-tetramethylpiperidine-N-oxy radical.

[0040] Example 1

[0041] Step 1: Add HCl solution to industrial pulp with a water content of 90% until the concentration of HCl in the pulp is 1 mol / L, and continue stirring for 1 hour. Then filter and wash with water 3 times to obtain solid substance I.

[0042] Step 2: Disperse the solid substance I prepared in Step 1 in water to prepare an aqueous dispersion with a mass fraction of 8 wt%, and adjust the pH to 10 with NaOH. Add TEMPO, NaBr and 1 mol / L NaClO solution to the mixture according to the volume ratio of the aqueous dispersion, the mass of TEMPO, the mass of NaBr and the volume of NaClO solution of 100 mL : 0.03 g : 0.3 g : 20 mL. Let it stand for 15 min, then stir rapidly for 15 min. Then adjust the pH of the dispersion to 10 again with NaOH and continue stirring for 15 min. Treat the dispersion with a homogenizer for 60 min, filter and wash with water 3 times to obtain solid substance II.

[0043] Step 3: Mechanically grind the solid substance II obtained in Step 2 for 30 minutes, then disperse it in water to prepare an aqueous dispersion slurry with a mass fraction of 8 wt%, and process the slurry with a cell disruptor for 30 minutes.

[0044] Step 4: Add acetic acid to the dispersion slurry that has been crushed in Step 3 to adjust the pH to 5. Then add 1 mol / L disodium phosphate solution, 1 mol / L sodium phosphate solution and TEMPO and stir rapidly for 15 min. Then add NaClO2 and continue stirring for 20 min. Transfer the mixture to a 60℃ constant temperature water bath and stir for 48 hours. After the reaction is complete, filter and wash with water 3 times to obtain solid substance III.

[0045] The volume ratio of the dispersion slurry, the disodium phosphate solution, the sodium phosphate solution, the mass of TEMPO, and the mass of NaClO2 is 100mL:20mL:20mL:0.03g:0.3g.

[0046] Step 5: Disperse the solid substance III prepared in Step 4 in water to prepare an aqueous dispersion slurry with a mass fraction of 8 wt%. Treat the slurry with a cell disruptor for 30 min to obtain the nano-oxidized cellulose aqueous dispersion slurry.

[0047] Step 6: Disperse chitosan solid in water to prepare a solution with a concentration of 0.1 wt%, disperse sodium lignosulfonate in water to prepare a solution with a concentration of 1.0 wt%, and adjust the pH of both solutions to 4 using acetic acid.

[0048] Step 7: Place the sodium lignosulfonate solution on a magnetic stirrer and stir. Add the chitosan solution dropwise at a volume ratio of 1:1. After the addition is complete, use a homogenizer for 30 minutes, then filter and wash with water 3 times, and dry to obtain a solid powder.

[0049] Step 8: Add the solid powder obtained in Step 8 to the nano-oxidized cellulose aqueous dispersion slurry prepared in Step 5 at a mass-to-volume ratio of 1g:100mL and treat it with a homogenizer for 30min. Then, vacuum filter the mixed slurry into a thin film and dry it at room temperature.

[0050] Please refer to Figure 1 The figure shows the stress-strain curve of the wood-based thermal insulation film prepared in Example 1. The maximum tensile strength of the wood-based thermal insulation film reached 135.4 MPa, which is 123% higher than that of the pure nanocellulose film (60.8 MPa). This indicates that the pure biomass film prepared in this invention has excellent mechanical strength due to the large number of hydrogen bond interactions generated during the stacking of nano-sized oxidized cellulose.

[0051] Please refer to Figure 2The image shows the surface morphology of the wood-based thermal insulation film prepared in Example 1. The filtration process enabled the wood-based thermal insulation film to achieve spontaneous self-assembly. Sodium lignosulfonate nanoparticles were uniformly distributed on the film surface, creating numerous uneven structures. These structures promote diffuse reflection of direct sunlight, thereby dispersing most of the energy and insulating against heat generated by direct sunlight. Furthermore, these deposited particles form a good wear-resistant transition layer, effectively improving the film's wear resistance, which is one of the important indicators for improving commonly used thermal insulation materials.

[0052] Example 2

[0053] Step 1: Add HCl solution to industrial pulp with a water content of 91% until the concentration of HCl in the pulp is 1 mol / L, and continue stirring for 2 hours. Then filter and wash with water 4 times to obtain solid substance I.

[0054] Step 2: Disperse the solid substance I prepared in Step 1 in water to prepare an aqueous dispersion with a mass fraction of 9 wt%, and adjust the pH to 10 with NaOH. Add TEMPO, NaBr and 1 mol / L NaClO solution to the mixture according to the volume ratio of the aqueous dispersion, the mass of TEMPO, the mass of NaBr and the volume of NaClO solution of 100 mL : 0.04 g : 0.4 g : 25 mL. Let it stand for 20 min, then stir rapidly for 15 min. Then adjust the pH of the dispersion to 10 again with NaOH and continue stirring for 15 min. Treat the dispersion with a homogenizer for 100 min, filter and wash with water 4 times to obtain solid substance II.

[0055] Step 3: Mechanically grind the solid substance II obtained in Step 2 for 40 minutes, then disperse it in water to prepare an aqueous dispersion slurry with a mass fraction of 9 wt%. Treat the slurry with a cell disruptor for 50 minutes.

[0056] Step 4: Add acetic acid to the dispersion slurry that has been crushed in Step 3 to adjust the pH to 6. Then add 1 mol / L disodium phosphate solution, 1 mol / L sodium phosphate solution and TEMPO and stir rapidly for 20 min. Then add NaClO2 and continue stirring for 20 min. Transfer the mixture to a 60℃ constant temperature water bath and stir for 48 hours. After the reaction is complete, filter and wash with water 4 times to obtain solid substance III.

[0057] The volume ratio of the dispersion slurry, the disodium phosphate solution, the sodium phosphate solution, the mass of TEMPO, and the mass of NaClO2 is 100mL:30mL:30mL:0.05g:0.5g.

[0058] Step 5: Disperse the solid substance III prepared in Step 4 in water to prepare an aqueous dispersion slurry with a mass fraction of 9 wt%. Treat the slurry with a cell disruptor for 40 min to obtain the nano-oxidized cellulose aqueous dispersion slurry.

[0059] Step 6: Disperse chitosan solid in water to prepare a solution with a concentration of 0.1 wt%, and disperse sodium lignosulfonate in water to prepare a solution with a concentration of 1.0 wt%. Adjust the pH of both solutions to 5 using acetic acid.

[0060] Step 7: Place the sodium lignosulfonate solution on a magnetic stirrer and stir. Add the chitosan solution dropwise at a volume ratio of 1:1. After the addition is complete, use a homogenizer for 60 minutes, then filter and wash with water 4 times, and dry to obtain solid powder.

[0061] Step 8: Add the solid powder obtained in Step 8 to the nano-oxidized cellulose aqueous dispersion slurry prepared in Step 5 at a mass-to-volume ratio of 1g:150mL and treat it with a homogenizer for 60min. Then, vacuum filter the mixed slurry into a thin film and dry it at room temperature.

[0062] Please refer to Figure 3 The image shown is a cross-sectional morphology diagram of the wood-based thermal insulation film prepared in Example 2. It can be observed that nano-sized oxidized cellulose gradually stacks together under vacuum filtration conditions, forming a dense film with a compacted layered structure. Based on the numerous hydrogen bond interactions generated during the stacking process of the nano-sized oxidized cellulose, it exhibits excellent mechanical stability. Furthermore, due to the presence of sodium lignosulfonate nanoparticles, the hydrophobic groups on their surface interact with the carboxyl groups on the surface of the nano-cellulose, ensuring a tight bond between the stacked layers and further enhancing the mechanical strength of the composite film.

[0063] Please refer to Figure 4 The figure shows the flexibility test results of the wood-based thermal insulation film prepared in Example 2. Compared with the pure oxidized cellulose nanoparticle film, the wood-based thermal insulation film has higher fracture toughness. This is because the surface negative charge associated with the carboxyl group prevents the aggregation of cellulose nanoparticles. Under protonation induction under acidic conditions, these cellulose nanoparticles are linked together through hydrogen bonds between carboxyl groups, enhancing the fracture toughness of the film. At the same time, the phenolic hydroxyl groups on the sodium lignosulfonate nanoparticles are further linked to the carboxyl groups on the cellulose surface through hydrogen bonding, enhancing the mechanical stability of the film.

[0064] Example 3

[0065] Step 1: Add HCl solution to industrial pulp with a water content of 92% until the concentration of HCl in the pulp is 1 mol / L, and stir continuously for 1.5 hours. Then filter and wash with water 5 times to obtain solid substance I.

[0066] Step 2: Disperse the solid substance I prepared in Step 1 in water to prepare an aqueous dispersion with a mass fraction of 10 wt%, and adjust the pH to 10 with NaOH. Add TEMPO, NaBr and 1 mol / L NaClO solution to the mixture according to the volume ratio of the aqueous dispersion, the mass of TEMPO, the mass of NaBr and the volume of NaClO solution of 100 mL: 0.05 g: 0.5 g: 30 mL. Let it stand for 30 min, then stir rapidly for 15 min. Then adjust the pH of the dispersion to 10 again with NaOH and continue stirring for 15 min. Treat the dispersion with a homogenizer for 120 min, filter and wash with water 5 times to obtain solid substance II.

[0067] Step 3: Mechanically grind the solid substance II obtained in Step 2 for 60 minutes, then disperse it in water to prepare an aqueous dispersion slurry with a mass fraction of 10 wt%. Use a cell disruptor to process the slurry for 60 minutes.

[0068] Step 4: Add acetic acid to the dispersion slurry that has been crushed in Step 3 to adjust the pH to 5.5. Then add 1 mol / L disodium phosphate solution, 1 mol / L sodium phosphate solution and TEMPO and stir rapidly for 30 min. Then add NaClO2 and continue stirring for 20 min. Transfer the mixture to a 60℃ constant temperature water bath and stir for 48 hours. After the reaction is complete, filter and wash with water 5 times to obtain solid substance III.

[0069] The volume ratio of the dispersion slurry, the disodium phosphate solution, the sodium phosphate solution, the mass of TEMPO, and the mass of NaClO2 is 100mL:25mL:25mL:0.04g:0.4g.

[0070] Step 5: Disperse the solid substance III prepared in Step 4 in water to prepare an aqueous dispersion slurry with a mass fraction of 10 wt%. Treat the slurry with a cell disruptor for 60 min to obtain the nano-oxidized cellulose aqueous dispersion slurry.

[0071] Step 6: Disperse chitosan solid in water to prepare a solution with a concentration of 0.1 wt%, and disperse sodium lignosulfonate in water to prepare a solution with a concentration of 1.0 wt%. Adjust the pH of both solutions to 5 using acetic acid.

[0072] Step 7: Place the sodium lignosulfonate solution on a magnetic stirrer and stir. Add the chitosan solution dropwise at a volume ratio of 1:1. After the addition is complete, use a homogenizer for 40 minutes, then filter and wash with water 5 times, and dry to obtain a solid powder.

[0073] Step 8: Add the solid powder obtained in Step 8 to the nano-oxidized cellulose aqueous dispersion slurry prepared in Step 5 at a mass-to-volume ratio of 1g:120mL and treat it with a homogenizer for 50min. Then, vacuum filter the mixed slurry into a thin film and dry it at room temperature.

[0074] Please refer to Figure 5 The figure shows the abrasion resistance test results of the wood-based thermal insulation film prepared in Example 3. After testing the abrasion resistance of the film surface using a ball-disc friction and wear tester, it was found that the coefficient of friction changed very little during long-term friction, exhibiting long-term frictional stability. The surface wear marks showed a smooth morphology. The 3D morphology image also showed that the surface roughness of the wear marks was basically the same as that of the surrounding morphology, indicating that the film exhibited a low wear rate. This is due to the uniform distribution of nanoparticles between the film layers. When subjected to external frictional force, these nanospheres can endow the film with excellent abrasion resistance.

[0075] Please refer to Figure 6 The figure shows the weather resistance test results of the wood-based thermal insulation film prepared in Example 3. We used a xenon lamp to simulate sunlight irradiation on the film surface, with a light power density of 100 mW / cm³, approximately the intensity of sunlight. Under continuous sunlight irradiation for 4 hours, the film surface temperature reached a maximum of 38.3°C, with a maximum mass loss of less than 0.09%. This is attributed to the absorption and shielding properties of polyphenolic entities in its structure for ultraviolet-visible light, while the multilayered cellulose structure effectively reflects most visible-infrared light, ensuring its excellent weather resistance.

[0076] Example 4

[0077] Step 1: Add HCl solution to industrial pulp with a water content of 92% until the concentration of HCl in the pulp is 1 mol / L, and continue stirring for 2 hours. Then filter and wash with water 5 times to obtain solid substance I.

[0078] Step 2: Disperse the solid substance I prepared in Step 1 in water to prepare an aqueous dispersion with a mass fraction of 10 wt%, and adjust the pH to 10 with NaOH. Add TEMPO, NaBr and 1 mol / L NaClO solution to the mixture according to the volume ratio of the aqueous dispersion, the mass of TEMPO, the mass of NaBr and the volume of NaClO solution of 100 mL: 0.05 g: 0.3 g: 20 mL. Let it stand for 25 min, then stir rapidly for 15 min. Then adjust the pH of the dispersion to 10 again with NaOH and continue stirring for 15 min. Treat the dispersion with a homogenizer for 800 min, filter and wash with water 4 times to obtain solid substance II.

[0079] Step 3: Mechanically grind the solid substance II obtained in Step 2 for 50 minutes, then disperse it in water to prepare an aqueous dispersion slurry with a mass fraction of 9 wt%. Treat the slurry with a cell disruptor for 40 minutes.

[0080] Step 4: Add acetic acid to the dispersion slurry that has been crushed in Step 3 to adjust the pH to 6. Then add 1 mol / L disodium phosphate solution, 1 mol / L sodium phosphate solution and TEMPO and stir rapidly for 25 min. Then add NaClO2 and continue stirring for 20 min. Transfer the mixture to a 60℃ constant temperature water bath and stir for 48 hours. After the reaction is complete, filter and wash with water 3 times to obtain solid substance III.

[0081] The volume ratio of the dispersion slurry, the disodium phosphate solution, the sodium phosphate solution, the mass of TEMPO, and the mass of NaClO2 is 100mL: 22mL: 25mL: 0.05g: 0.3g.

[0082] Step 5: Disperse the solid substance III prepared in step 4 in water to prepare an aqueous dispersion slurry with a mass fraction of 8 wt%. Treat the slurry with a cell disruptor for 50 min to obtain the nano-oxidized cellulose aqueous dispersion slurry.

[0083] Step 6: Disperse chitosan solid in water to prepare a solution with a concentration of 0.1 wt%, disperse sodium lignosulfonate in water to prepare a solution with a concentration of 1.0 wt%, and adjust the pH of both solutions to 4.5 using acetic acid;

[0084] Step 7: Place the sodium lignosulfonate solution on a magnetic stirrer and stir. Add the chitosan solution dropwise at a volume ratio of 1:1. After the addition is complete, use a homogenizer for 60 minutes, then filter and wash with water 3 times, and dry to obtain solid powder.

[0085] Step 8: Add the solid powder obtained in Step 8 to the nano-oxidized cellulose aqueous dispersion slurry prepared in Step 5 at a mass-volume ratio of 1g:130mL and process it with a homogenizer for 40min. Then, vacuum filter the mixed slurry into a thin film and dry it at room temperature.

[0086] Please refer to Figure 7 The figure shows the water resistance test results of the wood-based thermal insulation film prepared in Example 4. During the same time period, the wood-based thermal insulation film has a lower water absorption rate than the nanocellulose film, indicating its excellent water stability. This is because of the presence of sodium lignosulfonate nanoparticles, whose hydrophobic groups interact with the carboxyl groups on the surface of nanocellulose, enhancing the mechanical strength of the composite film. The hydrophobic backbone of lignin can effectively isolate the attack of water molecules, giving the film water resistance.

[0087] Please refer to Figure 8 The figure shows the thermal insulation performance test diagram of the wood-based thermal insulation film prepared in Example 4. Compared with the pure oxidized cellulose film, the wood-based thermal insulation film prepared in this invention has a lower surface temperature on the heating plate at 50°C, indicating its good thermal insulation performance. This is because both the nano-sized oxidized cellulose and sodium lignosulfonate particles are derivatives of wood materials. The nano-sized oxidized cellulose with a large number of carboxyl groups on the surface is stacked together to form a dense layered structure and construct a multi-level transition layer, while the sodium lignosulfonate nanoparticles are distributed between the layers. The synergistic effect of the two effectively blocks the spread of heat.

[0088] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description should not be considered as a limitation of the present invention.

Claims

1. A method for preparing a multifunctional wood-based heat-insulating film, characterized in that, Includes the following steps: Step 1: Add HCl solution to industrial pulp with a water content of 90-92% until the concentration of HCl in the pulp is 1 mol / L, and continue stirring for 1-2 hours. Then filter and wash with water to obtain solid substance I. Step 2: Disperse the solid substance I prepared in Step 1 in water to prepare an aqueous dispersion with a mass fraction of 8-10 wt%, and adjust the pH to 10 with NaOH. According to the volume ratio of the aqueous dispersion, the mass of TEMPO, the mass of NaBr, and the volume of NaClO solution, 100 mL : (0.03-0.05) g : (0.3-0.5) g : (20-30) mL, add TEMPO, NaBr, and 1 mol / L NaClO solution to the mixture, let it stand for 15-30 min, then stir rapidly for 15 min. Then adjust the pH of the dispersion to 10 again with NaOH, and continue stirring for 15 min. After homogenization, filter and wash with water to obtain solid substance II. Step 3: Grind the solid substance II obtained in Step 2, disperse it in water to prepare an aqueous dispersion slurry with a mass fraction of 8-10 wt%, and then crush it. Step 4: Add acetic acid to the dispersion slurry that has been crushed in Step 3 to adjust the pH to 5-6. Then add 1 mol / L disodium phosphate solution, 1 mol / L sodium phosphate solution and TEMPO and stir rapidly for 15-30 min. Then add NaClO2 and continue stirring for 20 min. Transfer the mixture to a 60℃ constant temperature water bath and stir for 48 hours. After the reaction is complete, filter and wash with water to obtain solid substance III. The volume ratio of the dispersion slurry, the disodium phosphate solution, the sodium phosphate solution, the mass of TEMPO, and the mass of NaClO2 is 100 mL : (20~30) mL : (20~30) mL : (0.03~0.05) g : (0.3~0.5) g; Step 5: Disperse the solid substance III prepared in Step 4 in water to prepare an aqueous dispersion slurry with a mass fraction of 8-10 wt%, and then crush it to obtain the nano-oxidized cellulose aqueous dispersion slurry. Step 6: Disperse chitosan solid in water to prepare a solution with a concentration of 0.1 wt%, disperse sodium lignosulfonate in water to prepare a solution with a concentration of 1.0 wt%, and adjust the pH of both solutions to 4-5 using acetic acid. Step 7: Place the sodium lignosulfonate solution on a magnetic stirrer and stir. Add the chitosan solution dropwise at a volume ratio of 1:

1. After the addition is complete, homogenize the solution, then filter, wash with water, and dry to obtain nano-sized sodium lignosulfonate-chitosan composite filler solid powder. Step 8: Add the solid powder obtained in Step 7 to the nano-oxidized cellulose aqueous dispersion slurry prepared in Step 5 at a mass-to-volume ratio of 1g:(100~150)mL and homogenize it. Then, vacuum filter the mixed slurry into a thin film and dry it at room temperature.

2. The method for preparing the multifunctional wood-based heat-insulating film as described in claim 1, characterized in that, The water washing mentioned in steps one, two, four and seven refers to washing with distilled water 3 to 5 times.

3. The method for preparing the multifunctional wood-based heat-insulating film as described in claim 1, characterized in that, The dispersion described in step two involves treating the dispersion with a homogenizer for 60-120 minutes.

4. The method for preparing the multifunctional wood-based heat-insulating film as described in claim 1, characterized in that, The grinding described in step three is mechanical grinding for 30-60 minutes.

5. The method for preparing the multifunctional wood-based heat-insulating film as described in claim 1, characterized in that, The disruption process described in steps three and five involves treating the slurry with a cell disruptor for 30-60 minutes.

6. The method for preparing the multifunctional wood-based heat-insulating film as described in claim 1, characterized in that, The drying process described in step seven involves freeze-drying at -60°C for 48 hours.

7. The method for preparing the multifunctional wood-based heat-insulating film as described in claim 1, characterized in that, The homogenization process described in steps seven and eight involves using a homogenizer for 30-60 minutes.

8. A multifunctional wood-based heat-insulating film prepared by the method described in any one of claims 1 to 7.

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