Preparation method for high-strength, foldable and multifunctional wood paper
Patent Information
- Application Number
- PCT/CN2024/138397
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2024-03-04
- Filing Date
- 2024-12-11
- Publication Date
- 2025-10-02
AI Technical Summary
Existing technologies make it difficult to produce high-strength and high-toughness wood paper with low environmental impact, and traditional modification methods consume high energy and use toxic chemicals, leading to environmental problems.
A swelling and densification treatment method is adopted. Delignified wood is treated with a swelling solution at room temperature, and then air-dried to form a dense cellulose interwoven network, adjusting the crystalline-amorphous two-phase structure, avoiding high-energy intensive processes and hot pressing equipment, and using sodium hydroxide aqueous solution to promote the swelling and dissociation of cellulose microfibrils.
High-strength, foldable wood paper has been achieved, which has super mechanical properties, is both light-transmitting and dyeable, has low environmental impact, and is suitable for fields such as flexible electronics and special decoration.
Smart Images
Figure CN2024138397_02102025_PF_FP_ABST
Abstract
Description
Method for preparing high-strength, foldable, multifunctional wood paper Technical Field
[0001] The invention relates to a method for preparing wood paper. Background Art
[0002] Cellulose paper is one of the most important basic materials in human life and can be used for reading, writing, painting, cleaning, handicrafts, decoration, packaging, etc. Traditionally, cellulose paper made from cellulose fibers is assembled through a complex multi-step bottom-up method. Due to the random distribution of cellulose fibers, the mechanical properties of cellulose paper are poor, which hinders its further commercial application. The mechanical properties of cellulose paper can be effectively improved with the help of various physical, chemical and field-assisted methods. However, all of these processes, including physical hot pressing to increase the hydrogen bond packing density between cellulose fibers, chemical modification to increase the specific surface area and functional groups of cellulose fibers, high-pressure homogenization and ultrasonic methods, as well as methods that use external pressure, magnetic fields and electric fields to orient cellulose, are very energy-consuming, expensive and ineffective.
[0003] Wood is an abundant, sustainable, and renewable natural resource on Earth, with advantages such as wide availability, low thermal conductivity, excellent mechanical properties, good biocompatibility, and low density. In recent years, the use of chemical delignification combined with densification has enabled natural wood to be converted into ultra-strong cellulose film materials, showing great potential in seawater desalination, ion transport, and loudspeakers. In addition, adjusting the surface functional groups and degree of polymerization of cellulose nanofibers while maintaining the wood structure is also an effective method to improve the strength of wood-based membrane materials. However, these modifications usually involve toxic chemicals such as TEMPO and anthraquinone, which greatly increases the environmental problems of the manufacture of high-performance wood films. In addition, the prepared wood films cannot simultaneously take into account both strength and toughness properties.
[0004] In summary, the existing technology is unable to produce high-strength and high-toughness wood paper with low environmental impact. Summary of the Invention
[0005] The present invention aims to solve the problem that the existing technology cannot prepare high-strength and high-toughness wood paper with low environmental impact, and further provides a method for preparing high-strength, foldable, multifunctional wood paper.
[0006] A method for preparing high-strength, foldable, multifunctional wood paper is carried out according to the following steps:
[0007] 1. Swelling treatment:
[0008] Under room temperature, the delignified wood is immersed in a swelling solution for 1 minute to 3 hours to obtain a swelling-treated delignified wood;
[0009] The swelling solution is one of dimethyl sulfoxide solution, water, anhydrous ethanol, phosphoric acid and sodium hydroxide aqueous solution or a mixture of several thereof;
[0010] 2. Densification treatment:
[0011] The delignified wood that has been swelled is air-dried at room temperature to obtain high-strength, foldable, and multifunctional wood paper.
[0012] The beneficial effects of the present invention are:
[0013] The present invention adopts chemical treatment to wood, removes most of the amorphous lignin and hemicellulose in wood, retains crystalline-amorphous cellulose in wood components, thereby reducing the content of amorphous components in wood components, and improving the content of crystalline region components. By using the method of precise regulation of this crystalline region and amorphous region, the two-phase structure of wood cell wall is rationally regulated, and wood can be converted into wood paper without the help of additional hot pressing equipment under atmospheric conditions. This process avoids the preparation process and hot pressing process of high-energy-intensive nanocellulose, and also solves the problem of incompatibility between strength and toughness of traditional paper materials. Taking sodium hydroxide aqueous solution as an example, during the swelling treatment process, hydrated sodium ions rapidly penetrate into the surface of cellulose microfibers and combine with hydroxyl groups, significantly promoting the swelling of cellulose microfibers and causing partial dissociation of cellulose nanofibers. In the subsequent air-drying process, water molecules act as donors and acceptors of hydrogen bonds at the same time. As water molecules evaporate, cellulose nanofibers reassemble to form a denser cellulose interwoven network structure. This method achieves a rational design of a crystalline-amorphous two-phase structure. The increased cellulose crystallinity and enhanced lateral bonding between cellulose fibers provide wood paper with exceptional mechanical properties. Furthermore, the preparation process is simple and amenable to scalable production. In terms of environmental sustainability, a comprehensive comparison of wood paper with commercial printing paper and plastics demonstrated the lowest environmental impact. Furthermore, wood paper's light transmittance, writability, and dyeability demonstrate its potential for applications in flexible electronics, specialty decoration, and other fields.
[0014] Figures in the specification
[0015] FIG1 is a macroscopic photograph of the high-strength, foldable, multifunctional wood paper prepared in Example 1;
[0016] FIG2 is a cross-sectional scanning electron micrograph of the high-strength, foldable, multifunctional wood paper prepared in Example 1;
[0017] FIG3 is a composition analysis diagram, 1-1 is natural balsa wood, 1-2 is the air-dried delignified wood prepared in Comparative Experiment 1, and 1-3 is the high-strength, foldable, multifunctional wood paper prepared in Example 1;
[0018] FIG4 is a tensile stress-strain curve diagram, 1-1 is the high-strength, foldable, multifunctional wood paper prepared in Example 1, and 1-2 is the air-dried delignified wood prepared in Comparative Experiment 1;
[0019] FIG5 is a bar graph of folding times, 1-1 is the high-strength, foldable, multifunctional wood paper prepared in Example 1, and 1-2 is commercial printing paper;
[0020] FIG6 is a photo of the dyed and undyed high-strength, foldable, multifunctional wood paper prepared in Example 1;
[0021] FIG7 is a photograph showing the conductive properties of the high-strength, foldable, multifunctional wood paper prepared in Example 1. DETAILED DESCRIPTION
[0022] Specific embodiment 1: This embodiment is a method for preparing high-strength, foldable, multifunctional wood paper, which is carried out according to the following steps:
[0023] 1. Swelling treatment:
[0024] Under room temperature, the delignified wood is immersed in a swelling solution for 1 minute to 3 hours to obtain a swelling-treated delignified wood;
[0025] The swelling solution is one of dimethyl sulfoxide solution, water, anhydrous ethanol, phosphoric acid and sodium hydroxide aqueous solution or a mixture of several thereof;
[0026] 2. Densification treatment:
[0027] The delignified wood that has been swelled is air-dried at room temperature to obtain high-strength, foldable, and multifunctional wood paper.
[0028] The wood paper of this embodiment can be post-processed, such as dyeing and painting or a combination of both; various colors of wood paper can be prepared by impregnation dyeing with various dyes; various conductive materials or anti-counterfeiting materials can be painted to prepare multifunctional wood paper.
[0029] The beneficial effects of this embodiment are:
[0030] This embodiment uses chemical treatment of wood to remove most of the amorphous lignin and hemicellulose in the wood, retaining the crystalline-amorphous cellulose in the wood components, thereby reducing the content of amorphous components in the wood components and increasing the content of crystalline components. By using this method of precise control of the crystalline and amorphous regions, the two-phase structure of the wood cell wall is rationally adjusted, and the wood can be converted into wood paper under atmospheric conditions without the aid of additional hot pressing equipment. This process avoids the high-energy-intensive preparation process and hot pressing process of nanocellulose, and also solves the problem of incompatibility between the strength and toughness of traditional paper materials. Taking sodium hydroxide aqueous solution as an example, during the swelling treatment process, hydrated sodium ions quickly penetrate into the surface of cellulose microfibers and combine with hydroxyl groups, significantly promoting the swelling of cellulose microfibers and causing partial dissociation of cellulose nanofibers. In the subsequent air-drying process, water molecules act as both donors and acceptors of hydrogen bonds. As the water molecules evaporate, the cellulose nanofibers re-aggregate to form a denser cellulose interwoven network structure. This method achieves a rational design of a crystalline-amorphous two-phase structure. The increased cellulose crystallinity and enhanced lateral bonding between cellulose fibers provide wood paper with exceptional mechanical properties. Furthermore, the preparation process is simple and amenable to scalable production. In terms of environmental sustainability, a comprehensive comparison of wood paper with commercial printing paper and plastics demonstrated the lowest environmental impact. Furthermore, wood paper's light transmittance, writability, and dyeability demonstrate its potential for applications in flexible electronics, specialty decoration, and other fields.
[0031] Specific embodiment 2: This embodiment differs from the specific embodiment 1 in that the delignified wood described in step 1 is prepared according to the following steps:
[0032] ① Soak the wood in distilled water or anhydrous ethanol, and ultrasonically clean it for 10 minutes to 1 hour at a power of 40w to 100w to obtain the cleaned wood;
[0033] ② Immerse the cleaned wood in a delignification solution, heat it in a water bath at a temperature of 60°C to 90°C for 3 to 6 hours, then soak it in deionized water at a temperature of 20°C to 40°C for 1 to 3 hours, and repeat the deionized water soaking process 1 to 5 times to obtain delignified wood. Other steps are the same as those in the first embodiment.
[0034] Specific embodiment 3: This embodiment differs from specific embodiment 1 or 2 in that the wood in step ① is coniferous wood, broadleaf wood or straw. Other aspects are the same as specific embodiment 1 or 2.
[0035] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the thickness of the wood in step ① is 0.1 mm to 1.5 mm. Other aspects are the same as specific embodiments 1 to 3.
[0036] Specific embodiment 5: This embodiment differs from Specific embodiments 1 to 4 in that the solute in the delignification solution in step 2 is one or a combination of sodium sulfite, sodium chlorite, hydrogen peroxide, glacial acetic acid, sodium hydroxide, sodium sulfide, sodium bisulfite, and chlorine dioxide. Otherwise, the same as Specific embodiments 1 to 4.
[0037] Specific embodiment 6: This embodiment differs from Specific embodiments 1 to 5 in that in step 1, when the swelling solution is dimethyl sulfoxide solution, phosphoric acid or sodium hydroxide aqueous solution, the mass percentage of the swelling solution is 0.05% to 15%. Other aspects are the same as Specific embodiments 1 to 5.
[0038] Specific embodiment 7: This embodiment differs from specific embodiments 1 to 6 in that in step 1, when the swelling solution is a sodium hydroxide aqueous solution, the mass fraction of the swelling solution is 0.05% to 1%. Other aspects are the same as specific embodiments 1 to 6.
[0039] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that in step 1, the delignified wood is immersed in a swelling solution at room temperature for 2 to 3 hours to obtain swollen delignified wood. Other aspects are the same as specific embodiments 1 to 7.
[0040] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that in step 1, the delignified wood is immersed in a swelling solution at room temperature for 2 hours to obtain swollen delignified wood. Other aspects are the same as specific embodiments 1 to 8.
[0041] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 9 in that in step 2, the delignified wood subjected to swelling treatment is air-dried at room temperature for 24 to 48 hours. Other aspects are the same as specific embodiments 1 to 9.
[0042] The following examples are used to verify the beneficial effects of the present invention:
[0043] Example 1:
[0044] A method for preparing high-strength, foldable, multifunctional wood paper is carried out according to the following steps:
[0045] 1. Swelling treatment:
[0046] The delignified wood was immersed in the swelling solution for 2 hours at room temperature to obtain the swollen delignified wood.
[0047] The swelling solution is a sodium hydroxide aqueous solution, and the mass percentage of the swelling solution is 1%;
[0048] 2. Densification treatment:
[0049] The delignified wood that had been swollen was air-dried for 24 hours at room temperature (25°C) to obtain high-strength, foldable, multifunctional wood paper with a length, width, and thickness of 10 cm × 10 cm × 0.04 cm.
[0050] The delignified wood described in step 1 is specifically prepared according to the following steps:
[0051] ① Soak the wood in distilled water and ultrasonically clean it for 1 hour at a power of 50W to obtain the cleaned wood;
[0052] ② Immerse the cleaned wood in the delignification solution, heat it in a water bath at 90°C for 4 hours, then soak it in deionized water at 25°C for 1 hour, and repeat the deionized water soaking 3 times to obtain delignified wood.
[0053] The wood described in step ① is balsa wood with a size of 100 mm × 100 mm × 1 mm (thickness).
[0054] The delignification solution described in step ② is a mixture of 500 mL of 5% by mass sodium chlorite solution and 5 mL of acetate buffer with a pH of 4.6.
[0055] Comparative Experiment 1: This comparative experiment differs from Example 1 in that the swelling treatment in step 1 was omitted, and the delignified wood was directly subjected to step 2. The delignified wood was air-dried at room temperature (25°C) for 24 hours to obtain air-dried delignified wood. All other conditions were the same as in Example 1.
[0056] Comparative experiment 1 lacks the regulation of the ratio of crystalline and amorphous phases in wood, the bonding effect between cellulose microfibrils is small, the cellulose network structure is not dense enough, and there are structural defects, so the tensile strength and toughness are very poor.
[0057] Figure 1 is a macroscopic photograph of the high-strength, foldable, multifunctional wood paper prepared in Example 1. As can be seen from the figure, the wood paper is relatively thin and has a certain degree of optical transparency.
[0058] Figure 2 is a cross-sectional SEM image of the high-strength, foldable, multifunctional wood paper prepared in Example 1. As can be seen from the figure, the wood cell walls of the wood paper are highly collapsed, presenting a layered structure.
[0059] Figure 3 shows a compositional analysis chart, with 1-1 representing natural balsa wood, 1-2 representing air-dried delignified wood prepared in Comparative Experiment 1, and 1-3 representing the high-strength, foldable, multifunctional wood paper prepared in Example 1. As can be seen from the chart, the swelling treatment in Example 1 modifies the ratio of crystalline to amorphous regions, increasing the cellulose content (65.1%) and reducing the amorphous hemicellulose (27.8%) and lignin (0.35%) contents.
[0060] Tensile tests were conducted on the air-dried delignified wood prepared in Comparative Experiment 1 and the high-strength, foldable, multifunctional wood paper prepared in Example 1, according to the national standard for tensile testing of metallic materials, GB / T 22.1-2010. Figure 4 shows the tensile stress-strain curves, with Figure 1-1 showing the high-strength, foldable, multifunctional wood paper prepared in Example 1 and Figure 1-2 showing the air-dried delignified wood prepared in Comparative Experiment 1. As can be seen from the figure, the high-strength, foldable, multifunctional wood paper prepared in Example 1 exhibits excellent mechanical strength, reaching a tensile strength of 530 MPa, demonstrating a good reinforcement effect.
[0061] According to the national standard GB / T457-2008, the high-strength, foldable, multifunctional wood paper and commercial printing paper (Deli No. 7362) prepared in Example 1 were subjected to folding endurance tests. Figure 5 is a bar graph of the folding endurance, with 1-1 representing the high-strength, foldable, multifunctional wood paper prepared in Example 1 and 1-2 representing the commercial printing paper. As can be seen from the figure, under different loads, compared to the printing paper, the wood paper exhibits superior toughness due to the dense and strong hydrogen bond network structure of the crystalline-amorphous two-phase structure. Under a load of 2.94N, the wood paper can be folded nearly 4,000 times. Under loads of 4.9N, 9.8N, and 14.7N, the wood paper can be folded 8, 12, and 44 times that of the commercial printing paper, respectively.
[0062] The high-strength, foldable, and multifunctional wood paper prepared in Example 1 was soaked in dyes such as malachite green, crystal violet, methyl orange, methylene blue, and safranin to produce colorful wood paper, as shown in Figure 6 . Figure 6 shows photos of the high-strength, foldable, and multifunctional wood paper prepared in Example 1, both dyed and undyed. As can be seen from the figures, by soaking wood paper in dyes, colorful wood paper can be produced, enriching its application areas.
[0063] Conductive silver paste was applied to the high-strength, foldable, multifunctional wood paper prepared in Example 1, and its conductivity was tested, as shown in Figure 7. Figure 7 shows a photograph of the conductivity of the high-strength, foldable, multifunctional wood paper prepared in Example 1. As shown in the figure, a small light bulb lights up when the wood paper is connected to a circuit at a voltage of 1.5V, indicating that wood paper can be used as a flexible substrate in applications such as flexible electronics.
Claims
1. A method for preparing high-strength, foldable, multifunctional wood paper, characterized in that It is carried out in the following steps:
1. Swelling treatment: Under room temperature, the delignified wood is immersed in a swelling solution for 1 minute to 3 hours to obtain a swelling-treated delignified wood; The swelling solution is one of dimethyl sulfoxide solution, water, anhydrous ethanol, phosphoric acid and sodium hydroxide aqueous solution or a mixture of several thereof; 2. Densification treatment: The delignified wood that has been swelled is air-dried at room temperature to obtain high-strength, foldable, and multifunctional wood paper.
2. The method for preparing a high-strength, foldable, multifunctional wood paper according to claim 1, characterized in that The delignified wood described in step 1 is specifically prepared according to the following steps: ① Soak the wood in distilled water or anhydrous ethanol, and ultrasonically clean it for 10 minutes to 1 hour at a power of 40w to 100w to obtain the cleaned wood; ② Immerse the cleaned wood in a delignification solution, heat it in a water bath at a temperature of 60℃ to 90℃ for 3h to 6h, then soak it in deionized water at a temperature of 20℃ to 40℃ for 1h to 3h, and repeat the deionized water soaking 1 to 5 times to obtain delignified wood.
3. The method for preparing a high-strength, foldable, multifunctional wood paper according to claim 2, characterized in that The wood described in step ① is coniferous wood, broad-leaved wood or straw material.
4. The method for preparing a high-strength, foldable, multifunctional wood paper according to claim 2, characterized in that The thickness of the wood described in step ① is 0.1mm to 1.5mm.
5. The method for preparing high-strength, foldable, multifunctional wood paper according to claim 2, characterized in that The solute in the delignification solution in step ② is one or a combination of sodium sulfite, sodium chlorite, hydrogen peroxide, glacial acetic acid, sodium hydroxide, sodium sulfide, sodium bisulfite and chlorine dioxide.
6. The method for preparing high-strength, foldable, multifunctional wood paper according to claim 1, characterized in that In step 1, when the swelling solution is dimethyl sulfoxide solution, phosphoric acid or sodium hydroxide aqueous solution, the mass percentage of the swelling solution is 0.05% to 15%.
7. The method for preparing high-strength, foldable, multifunctional wood paper according to claim 6, characterized in that In step 1, when the swelling solution is a sodium hydroxide aqueous solution, the mass fraction of the swelling solution is 0.05% to 1%.
8. The method for preparing high-strength, foldable, multifunctional wood paper according to claim 1, characterized in that In step 1, the delignified wood is immersed in a swelling solution for 2 hours to 3 hours at room temperature to obtain swollen delignified wood.
9. The method for preparing high-strength, foldable, multifunctional wood paper according to claim 1, characterized in that In step 1, the delignified wood is immersed in the swelling solution for 2 hours at room temperature to obtain the swollen delignified wood.
10. The method for preparing high-strength, foldable, multifunctional wood paper according to claim 1, characterized in that In step 2, the delignified wood subjected to swelling treatment is air-dried at room temperature for 24 hours to 48 hours.