A fully biomass-based multifunctional transparent wood and its adhesive-free self-adhesive synthesis and molding preparation method

Abstract

The present invention provides a fully biomass-based multifunctional transparent wood and a method for its adhesive-free self-bonding synthesis and molding. Using wood chips or wood processing waste as raw materials, through de-matrix treatment combined with surface oxidation technology, a multi-level self-crosslinking network structure is established between fibers, and an adhesive-free transparent material with multi-scale self-bonding characteristics within and between layers is prepared without using any adhesives. Further introducing natural gelatin and combining it with tannic acid, through the synergistic effect of chemical grafting and physical crosslinking between oxidized cellulose and gelatin, a fully biomass-based degradable multifunctional transparent material with excellent mechanical, optical, water resistance, heat insulation and ultraviolet light shielding functions is prepared. As a potential substitute for petroleum-based transparent plastics and glass, it has important applications in the fields of intelligent anti-counterfeiting, optoelectronic devices, energy-saving buildings, lightweight automobiles, food preservation, etc., and is of great significance for the high-value utilization of wood processing waste.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, and specifically to a fully biomass-based multifunctional transparent wood and a method for its adhesive-free self-adhesive synthesis and molding preparation. Background Art

[0002] Common transparent materials mainly include plastics and glass. As a material commonly seen in daily life, plastics are widely used in fields such as construction, transportation, electronics, and packaging due to their high flexibility, excellent optical properties, and water resistance. However, most plastics synthesized from petroleum are non-biodegradable, and the harm they cause to the environment and human health is obvious to all. Glass has high mechanical strength and light transmittance and is often used as building windows, but its manufacturing process is complex and its heat dissipation is high, resulting in the energy dissipated by buildings through glass windows accounting for about 30% of the building's energy consumption. Therefore, developing a transparent material with high strength, optical transparency, water resistance, heat insulation, and biodegradability is of great significance for protecting the environment, reducing building energy consumption, and promoting the realization of the dual-carbon strategic goal.

[0003] In recent years, wood has attracted much attention in the field of biomass biodegradable transparent materials due to its unique hierarchical structure, low density, high strength, and degradability. Cellulose can be decomposed from trees, cotton, flax, or bacterial cellulose by mechanical, chemical, or biological methods, and cellulose nanofibers can be assembled through nanotechnology to prepare thin films or bulk materials (such as aerogels and hydrogels) with a three-dimensional nanonetwork structure. On this basis, introducing a transparent resin into its nanofibered network structure can prepare a transparent nanocellulose film. However, producing cellulose fibers at the nanoscale by this method requires a relatively complex treatment process and consumes a large amount of energy, chemicals, water, and time, which limits its further large-scale development.

[0004] During the wood processing process, a lot of waste will also be generated, especially the amount of wood waste in urban areas is increasing continuously, such as waste from furniture, branches, sawdust, wood chips, and rotten wood. Incinerating these wastes will result in high operating costs and energy consumption in flue gas treatment, while the landfill method is prone to the risks of land occupation and secondary pollution. Therefore, there are still huge challenges in how to better improve resource utilization efficiency and reduce environmental impact, convert residual or waste wood into high-performance structural materials, and realize the high-value application of waste wood. Summary of the Invention

[0005] The object of the present invention is to provide a fully biomass-based multifunctional transparent wood and a method for its adhesive-free self-adhesive synthesis and molding. This method uses natural wood or wood processing waste as raw materials, and under the condition of not adding any chemical adhesives or petroleum-based transparent polymers, through de-matrix treatment combined with surface oxidation and densification processes, a fully wood-based multifunctional transparent wood with excellent optical, mechanical, water resistance, ultraviolet shielding and heat insulation properties, or transparent water-resistant paper is prepared; on this basis, by introducing a natural and degradable gelatin component, a fully biomass-based transparent wood film with excellent ultraviolet light shielding and antioxidant functions can be further prepared.

[0006] To achieve the above object, the present invention proposes the following technical solution: A fully biomass-based multifunctional transparent wood and a method for its adhesive-free self-adhesive synthesis and molding, comprising the following steps:

[0007] In the first step a1, using natural wood as the raw material, slicing it along the axial direction, and using acidic sodium chlorite and sodium hydroxide solutions, and ultrasonic treatment to respectively remove lignin and hemicellulose, and then thoroughly washing the sample with deionized water to obtain a complete wood skeleton (WF); Conventional low-concentration alkali treatment to remove hemicellulose in wood can only be carried out under the condition of "standing still" because the wood skeleton is already very loose, and the application of external mechanical force will cause the wood skeleton to disintegrate and also make it difficult to fully remove hemicellulose. The alkali treatment used in the present invention improves the hydrogen bond density between fibers through the swelling effect of sodium ions in the cellulose crystalline region, thereby improving the structural stability of the wood skeleton; enabling it to fully remove hemicellulose while maintaining structural stability under the action of external mechanical force.

[0008] The first step may also be b1, using wood processing waste as the raw material, and using acidic sodium chlorite and sodium hydroxide solutions, and ultrasonic treatment to respectively carry out lignin removal and hemicellulose treatment, and then thoroughly washing the sample with deionized water to obtain lignocellulose fibers (CF);

[0009] In the second step a21, putting the wood skeleton obtained in the first step a1 into a sodium periodate solution for stepwise oxidation treatment, inducing the cleavage of the C2-C3 bond of the cellulose glucose ring, and oxidizing the adjacent secondary hydroxyl groups into aldehyde groups to obtain an oxidized modified wood skeleton (OWF);

[0010] The second step may also be a22, placing the wood skeleton obtained in the first step a1 between two glass plates, placing it in room temperature air for 12 hours to remove unbound water, and then transferring it to an oven at 60-80 °C for drying for 12-24 hours to obtain a de-matrix wood film (WFM).

[0011] The second step may be b2. The lignocellulose fibers obtained in the first step b1 are formed into a film by vacuum filtration and then placed in a sodium periodate solution for stepwise oxidation treatment to induce the cleavage of the C2-C3 bond in the cellulose glucose ring and oxidize the adjacent secondary hydroxyl groups into aldehyde groups, obtaining an oxidized modified lignin fiber film (OCF).

[0012] The third step a31: The oxidized modified wood framework (OWF) obtained in the second step a21 is placed between two glass plates and left in room-temperature air for 12 hours, and then transferred to an oven at 60-80 °C for drying for 12-24 hours to obtain an oxidized modified transparent wood film (OWFM).

[0013] The third step may also be a32. The oxidized modified wood framework (OWF) obtained in the second step a21 is subjected to staggered laminating and then hot-pressed and dried or dried at normal pressure to obtain a non-glue self-adhesive multi-layer transparent wood (M-OWFM) without using any interlayer adhesives.

[0014] The third step may also be a33. The oxidized modified wood framework (OWF) obtained in the second step a21 is immersed in a gelatin solution for several hours, taken out and placed between two glass plates, and dried in an oven at 60-80 °C for 12-24 hours to obtain a gelatin / oxidized modified transparent wood film (G / OWFM).

[0015] The third step may also be b3. The oxidized modified lignin fiber film (OCF) obtained in the second step b2 is subjected to multiple hot-pressing treatments in a mechanical hot press to obtain an oxidized modified lignin fiber transparent film (OCFM).

[0016] The fourth step a4: The gelatin / oxidized modified transparent wood film (G / OWFM) obtained in the third step a33 is immersed in a tannic acid solution for several hours, then thoroughly rinsed to remove free radicals, and then hot-pressed and dried or dried at normal pressure to prepare an ultraviolet-shielding transparent wood film (TA / G / OWFM) with ultraviolet-blocking and antioxidant functions.

[0017] Furthermore, in the present invention, it also includes a fifth step a51. A luminescent layer ink is printed onto the surface of the wood-based transparent material using an anti-counterfeiting inkjet printer. The wood-based transparent material includes a de-matrix wood film (WFM), an oxidized modified lignin fiber film (OCF), an oxidized modified transparent wood film (OWFM), a multi-layer transparent wood (M-OWFM), a gelatin / oxidized modified transparent wood film (G / OWFM), an oxidized modified lignin fiber transparent film (OCFM), and an ultraviolet-shielding transparent wood film (TA / G / OWFM). After printing, the film is placed on a hot stage at 80 °C for annealing for 15 minutes to obtain a luminescent anti-counterfeiting film.

[0018] The fifth step may be a52. The above-mentioned wood-based transparent material is used as transparent glass for building windows or food packaging.

[0019] Further, in the present invention, the specific operation of the first step a1 is as follows: Select natural wood as the raw material, where the natural wood includes balsa wood, poplar wood, and basswood. After natural drying, slice the wood along the fiber growth direction to prepare a wood thin slice sample with a thickness of 0.5 - 10 mm. Prepare a sodium chlorite solution with a concentration of 2 - 3 wt%, and adjust the pH to 4 - 5 with glacial acetic acid. Immerse the above thin slice sample in this solution and heat it at 100°C for 2 - 4 hours. After removing lignin, rinse the sample with deionized water until neutral. Then immerse it in NaOH with a concentration of 15 - 18 wt% and heat it at 25 - 40°C for 2 - 4 hours, and assist with ultrasonic treatment to fully remove hemicellulose. Subsequently, wash the sample with deionized water until neutral to obtain a complete wood skeleton.

[0020] Further, in the present invention, the specific operation of the first step b1 is as follows: Select wood waste as the raw material, where the wood waste includes balsa wood, poplar wood, and basswood, with a particle size of 2 - 5 mm. Prepare a sodium chlorite solution with a concentration of 2 - 3 wt%, and adjust the pH to 4 - 5 with glacial acetic acid. Immerse the above wood chips in this solution and heat it at 100°C for 2 - 4 hours. After removing lignin, rinse the sample with deionized water until neutral. Then immerse it in NaOH with a concentration of 15 - 18 wt% and heat it at 25 - 40°C for 2 - 4 hours, and assist with ultrasonic treatment to fully remove hemicellulose. Subsequently, wash the sample with deionized water until neutral to obtain lignocellulose fibers.

[0021] Further, in the present invention, the specific operation of obtaining a wood fiber membrane by vacuum filtration in the second step b2 is as follows: Put the extracted lignocellulose fibers into a blender and stir for 5 - 20 min to make the cellulose undergo fibrillation under external force and increase the specific surface area. Subsequently, add deionized water for dilution, pour it into a funnel for vacuum filtration to obtain a lignocellulose fiber membrane.

[0022] Further, in the present invention, the specific operation of obtaining an oxidized modified wood sample by sodium periodate oxidation in the second step a21 and the second step b2 is as follows: Immerse the wood skeleton or lignocellulose fiber membrane in a NaIO4 solution with a concentration of 0.5 - 2 wt% and perform step - by - step oxidation treatment at a temperature of 25 - 50°C for 1 - 4 hours. Subsequently, thoroughly wash the sample with a large amount of deionized water to obtain an oxidized modified wood skeleton or an oxidized modified lignocellulose fiber membrane.

[0023] Further, in the present invention, the specific operation of the third step b3 is as follows: Using a steel mesh, a polytetrafluoroethylene membrane, a filter paper, a non-stick paper, etc. as diaphragms respectively, covering the upper and lower layers of the oxidized modified wood fiber membrane, then placing a filter paper and a steel plate in sequence, putting them into a mechanical hot press, setting the temperature at 80 - 100 °C, the pressure at 0.2 - 0.8 MPa, hot pressing for 20 - 40 min, and after replacing the filter paper, performing secondary hot pressing according to the same steps to obtain an oxidized modified wood fiber transparent membrane (OCFM).

[0024] It can be known through experiments that the oxidized modified wood fiber transparent membrane (OCFM) prepared by using a polytetrafluoroethylene membrane and a non-stick paper as diaphragms respectively has a denser structure than the sample prepared by using a conventional steel mesh diaphragm. Compared with the prior art, in this experiment, through low-pressure mechanical hot press drying, during the process of removing water molecules, the fibers are fully induced to achieve high-density crosslinking through physical and covalent bonding methods, greatly improving the densification degree of the material, thereby improving the mechanical strength of the sample.

[0025] Further, in the present invention, the specific process of the third step a32 (atmospheric drying) is as follows: Orthogonally laying the oxidized modified wood skeleton and performing humidity control treatment, with a relative humidity of 30% - 60%, then placing it between two glass plates, covering the upper and lower layers of the sample with a non-stick paper and a filter paper respectively; placing it in room temperature air for 12 hours, and then drying it at 60 - 80 °C for 12 - 24 hours to obtain a multi-layer transparent wood (M-OWFM) with self-adhesive and self-compacting properties without glue under atmospheric pressure conditions;

[0026] The specific process of the third step a32 (hot press drying) is as follows: Orthogonally laying the oxidized modified wood skeleton and performing humidity control treatment, with a relative humidity of 30% - 60%, using a steel mesh, a polytetrafluoroethylene membrane, a filter paper, a non-stick paper, etc. as diaphragms respectively, covering the upper and lower layers of the wood sample obtained after the oxidation modification treatment, then placing a filter paper and a steel plate in sequence, putting them into a mechanical hot press, setting the temperature at 80 - 100 °C, the pressure at 0.2 - 0.8 MPa, hot pressing for 20 - 40 min, and after replacing the filter paper, performing secondary hot pressing according to the same steps to obtain a multi-layer transparent wood under pressure conditions.

[0027] Further, in the present invention, when operating in the third step a33, when grafting oxidized modified wood skeleton with gelatin, the mass fraction of the configured gelatin is 0.1 - 0.5 wt%, the reaction process is carried out at 55 - 65 °C, and the reaction time is 4 - 6 hours;

[0028] When operating in the fourth step a4, when crosslinking with tannic acid, the impregnation treatment is carried out at room temperature of 20 - 35 °C, the impregnation time is 24 - 48 hours, and the concentration of tannic acid is 10 - 20 mg·mL -1 。

[0029] Further, in the present invention, during the operation of step a51, a mixed solvent of TCTA:26DCzPPy:Ir(ppy)2(acac) (45 wt%:45 wt%:10 wt%) solute and CB:CN (70 vol.%:30 vol.%) with a concentration of 20 mg / mL is used. Stir at room temperature for 4 hours until the solute is completely dissolved, and then use an inkjet printer to print the luminescent layer ink on the surface of the ultraviolet-shielding transparent wood film to obtain a luminescent anti-counterfeiting film.

[0030] Advantages. The technical solution of this application has the following technical effects:

[0031] 1. The present invention makes full use of natural wood and wood processing waste. By removing matrix components such as lignin and hemicellulose, retaining the wood skeleton or directly using wood chip waste derivatives to prepare wood fiber membranes, and then combining methods such as sodium periodate surface oxidation, gelatin grafting, and tannic acid crosslinking or orthogonal lamination, a functionalized wood-based transparent material with excellent optical transparency, mechanical strength, water resistance, ultraviolet shielding, heat insulation, and antioxidant properties is prepared. It is expected to be an important alternative product to glass and petroleum-based transparent plastics and has potential application value in the fields of intelligent anti-counterfeiting, optoelectronic devices, energy-saving buildings, automotive sunroofs, transparent interiors, fresh-keeping packaging, etc. It also provides a high-value and sustainable development path for low-value wood processing waste.

[0032] 2. Without adding any chemical adhesives or petroleum-based transparent polymers, a fully wood-based transparent wood glass or transparent water-resistant paper with excellent optical, mechanical, water resistance, ultraviolet shielding, and heat insulation properties is prepared through matrix removal treatment combined with surface oxidation and densification processes, solving the technical problem of poor water resistance due to the large number of hydrophilic hydroxyl groups on the cellulose surface; on this basis, introducing a natural degradable gelatin component can further prepare a fully biomass-based transparent wood film with excellent ultraviolet light shielding and antioxidant functions.

[0033] 3. Without introducing complex nanotechnology and difficult-to-degrade chemical adhesives, a high-performance glue-free self-adhesive wood-based transparent material can be prepared, effectively solving the problems of a large consumption of energy, chemicals, water, and time caused by common cellulose nanonation methods, as well as the problem of difficult degradation caused by introducing chemical adhesives or petroleum-based transparent polymers; at the same time, it further expands the high-value utilization of a large amount of waste wood in the wood processing industry (such as wood processing surplus shavings, wood chips, wood powder, etc.) and promotes the diversified application of wood in research fields such as intelligent packaging, optoelectronic device substrates, energy-saving buildings, lightweight automobiles, and food preservation.

[0034] 4. The wet strength of the specimen prepared from natural wood or waste wood chips in the present invention can reach 114 MPa, which is 3-5 times that of common petroleum-based transparent plastics. At the same time, it has the functions of antioxidant and ultraviolet blocking, can isolate 100% of the light in the UVB and UVC regions, and can be used for food preservation, anti-counterfeiting packaging, etc. And it can be completely degraded under natural conditions. It has low thermal conductivity, and the thermal conductivity of the obtained transparent wood is only 1 / 5 of that of ordinary glass, making it an ideal energy-saving and heat-insulating material. It has printing adaptability and ink fixation effect, and can print luminescent layer ink for intelligent luminescent anti-counterfeiting films. It has good self-cleaning property, can be used under water conditions such as rainy days, and remains clean during daily use, becoming a candidate material for new energy-saving buildings.

[0035] 5. Based on the above performance advantages, the present invention is expected to be an important alternative product to petroleum-based transparent plastics and glass, and can be applied to intelligent luminescent anti-counterfeiting labels, substrates for optoelectronic devices, ultraviolet-shielding transparent films, lightweight automotive windows, transparent interiors, food preservation packaging, and intelligent building energy-saving windows, etc.

[0036] It should be understood that all combinations of the foregoing concepts and additional concepts described in greater detail below can be regarded as part of the inventive subject matter of the present disclosure as long as such concepts do not contradict each other.

[0037] The foregoing and other aspects, embodiments, and features of the teachings of the present invention can be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the present invention, such as the features and / or beneficial effects of exemplary embodiments, will be apparent in the following description or will be learned through practice of the specific embodiments according to the teachings of the present invention. Brief Description of the Drawings

[0038] The drawings are not intended to be drawn to scale. In the drawings, each identical or approximately identical component shown in each figure may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Now, embodiments of various aspects of the present invention will be described by way of example and with reference to the drawings, wherein:

[0039] Figure 1 The surface and cross-section scanning electron microscope images of the ultraviolet-shielding transparent wood film (TA / G / OWFM) prepared in Example 3 of the present invention at a magnification of 1000 times are shown. Figure 1 a in it is the surface. Figure 1 b in it is the cross-section, the cross-section is dense and continuous, the surface is smooth, and there is no obvious phase separation after the addition of gelatin and tannic acid, and they have good compatibility with each other.

[0040] Figure 2 The flexibility of the ultraviolet-shielding transparent wood film (TA / G / OWFM) prepared in Example 3 of the present invention is shown.

[0041] Figure 3 Shows a photo of the luminescent film formed by inkjet printing of the ultraviolet-shielding transparent wood film (TA / G / OWFM) prepared in Example 3 of the present invention ( Figure 3 in a)) and a photo of laser printing ( Figure 3 in b)).

[0042] Figure 4 Shows the physical comparison diagrams of the samples of the wood fiber film prepared in Examples 5-7 of the present invention and Comparative Example 2 before and after hot pressing, Figure 4 where a is the sample morphology before hot pressing (from left to right are Comparative Example 2, Examples 5 / 6 / 7), Figure 4 and b is the sample morphology after hot pressing (from left to right are Comparative Example 2, Examples 5 / 6 / 7).

[0043] Figure 5 Shows the scanning electron microscope images of the wood fiber transparent film prepared in Example 6 of the present invention at different magnifications, Figure 5 where a is 100 times, Figure 5 and b is 1000 times. As the concentration of sodium periodate increases, the cellulose on the surface of the wood fiber film is intertwined more tightly, the pores are significantly reduced, a dense fiber network is formed, and macroscopically, the mechanical, optical and other properties are increased.

[0044] In the figure, 6 is a physical diagram, where a is the physical diagram of Comparative Example 1 (WFM), b is the physical diagram of Comparative Example 2 (CFM), c is the physical diagram of Example 1 (OWFM), d is the physical diagram of Example 3 (TA / G / OWFM), e is the physical diagram of Example 4 (M-OWFM), f is the physical diagram of Example 5 (wood fiber transparent film - 0.5), g is the physical diagram of Example 6 (wood fiber transparent film - 1), and h is the physical diagram of Example 7 (wood fiber transparent film - 2). Detailed Embodiments

[0045] In order to better understand the technical content of the present invention, specific embodiments are hereby given and described in conjunction with the accompanying drawings as follows. In the present disclosure, aspects of the present invention are described with reference to the accompanying drawings, and many illustrative embodiments are shown in the drawings. The embodiments of the present disclosure do not necessarily define all aspects of the present invention. It should be understood that the various concepts and embodiments introduced above, as well as those concepts and embodiments described in more detail below, can be implemented in any of many ways, because the concepts and embodiments disclosed in the present invention are not limited to any embodiment. Additionally, some aspects of the present invention can be used alone, or in any suitable combination with other aspects of the present invention that are disclosed.

[0046] The following are the specific steps of the environmentally friendly all-biomass-based high-strength, ultraviolet-proof, heat-insulating transparent wood glass and its glue-free self-adhesive synthetic molding preparation method of the present invention:

[0047] 1. Dematrix treatment

[0048] 1.1 Dematrix treatment of wood chips

[0049] (1) Place 5 - 10 pieces of longitudinal-section wood chips of natural wood (including balsa wood, poplar wood, basswood, etc.) with a thickness of 0.5 - 10 mm into 500 - 1000 ml of 2 - 3 wt% sodium chlorite solution, adjust the pH to 4 - 5 with glacial acetic acid, and heat at 100 °C for 2 - 3 hours to conduct delignification treatment on the wood chips. Then rinse with a large amount of deionized water and thoroughly rinse the obtained delignified wood until it is neutral.

[0050] (2) Immerse the delignified wood in 500 - 1000 ml of 15 - 18 wt% sodium hydroxide solution, heat at 40 °C for 2 - 4 hours, and assist with ultrasonic treatment to fully remove hemicellulose. Wash the sample with deionized water until it is neutral to obtain a complete wood skeleton. Conventional low-concentration alkali treatment for removing hemicellulose from wood can only be carried out under the condition of "static state" because the wood skeleton is already very loose, and external mechanical force will cause the wood skeleton to disintegrate, also making it difficult to fully remove hemicellulose. The alkali treatment used in the present invention, through the swelling effect of sodium ions in the cellulose crystalline region, increases the hydrogen bond density between fibers, thereby improving the structural stability of the wood skeleton; enabling it to fully remove hemicellulose while maintaining structural stability under the action of external mechanical force.

[0051] 1.2 Dematrix treatment of wood waste

[0052] (1) Place wood chips with a particle size of 2 - 5 mm into 500 - 1000 ml of 2 - 3 wt% sodium chlorite solution, adjust the pH to 4 - 5 with glacial acetic acid, and heat at 100 °C for 2 - 3 hours to conduct delignification treatment on the wood chips. Then perform vacuum filtration with a Buchner funnel until the sample is washed to neutral.

[0053] (2) Immerse the delignified wood chips in 500 - 1000 ml of 15 - 18 wt% sodium hydroxide solution, heat at 40 °C for 2 - 4 hours, and assist with ultrasonic treatment for 10 - 20 min to remove hemicellulose; then perform vacuum filtration with a Buchner funnel until the sample is washed to neutral, and repeat step 3 to fully remove lignin to obtain lignocellulose fibers.

[0054] 2. Surface oxidation treatment

[0055] 2.1 Oxidation modification of wood skeleton

[0056] Prepare a 0.5 - 2.0 wt% NaIO4 solution and perform a step - by - step oxidation treatment on the wood skeleton at a temperature of 25 - 50 °C for 1 - 4 hours. During the oxidation process, wrap the beaker with aluminum foil to prevent photo - induced decomposition of periodate and adverse reactions. After the oxidation treatment, thoroughly wash the sample with a large amount of deionized water to obtain the oxidized - modified wood skeleton.

[0057] 2.2 Oxidized - modified wood fiber membrane

[0058] (1) Put the extracted lignocellulose fibers into a food - grade mechanical blender and stir for 5 - 20 min to cause fibrillation of the cellulose under external forces, increasing its specific surface area and the binding force between fibers. Add H2O for ultrasonic comminution to make the solution more uniform, and then pour it into a funnel for vacuum filtration to obtain the lignocellulose fiber membrane.

[0059] (2) Prepare a 0.5 - 2.0 wt% NaIO4 solution and perform a step - by - step oxidation treatment on the wood fiber membrane at a temperature of 25 - 50 °C for 1 - 4 hours. During the oxidation process, wrap the beaker with aluminum foil to prevent photo - induced decomposition of periodate and adverse reactions. After the oxidation treatment, thoroughly wash the sample with a large amount of deionized water to obtain the oxidized - modified wood fiber membrane.

[0060] 3. Densification treatment

[0061] 3.1 Multi - layer transparent wood

[0062] (1) Atmospheric drying: Orthogonally lay up the oxidized - modified wood skeleton obtained in step 2.1 and perform humidity control treatment (relative humidity: 30 - 60%). Then place it between two glass plates, with anti - sticking paper and filter paper covering the upper and lower layers of the sample respectively; place it in room - temperature air for 12 hours, and then dry it at 60 - 80 °C for 12 - 24 hours to obtain multi - layer transparent wood (M - OWFM).

[0063] (2) Hot - press drying: Orthogonally lay up the oxidized - modified wood skeleton and perform humidity control treatment (relative humidity: 30 - 60%). Use steel mesh, polytetrafluoroethylene film, filter paper, and anti - sticking paper as diaphragms respectively, covering the upper and lower layers of the wood sample obtained after the oxidized - modified treatment. Then place filter paper and a steel plate on it in turn, place it in a mechanical hot - press, set the temperature at 80 - 100 °C, the pressure at 0.2 - 0.8 MPa, and hot - press for 20 - 40 min. After replacing the filter paper, perform secondary hot - pressing according to the same steps to obtain multi - layer transparent wood under pressure conditions; through the above densification process, without adding any polymers and adhesives, the inter - layer self - adhesion can be realized by using the self - cross - linked structure between fibers to prepare high - strength multi - layer transparent wood.

[0064] 3.2 Wood fiber transparent membrane

[0065] Using a steel mesh, a polytetrafluoroethylene membrane, a filter paper, a non-stick paper, etc. as diaphragms respectively, covering the upper and lower layers of the oxidized modified wood fiber membrane, then placing a filter paper and a steel plate in sequence, putting them into a mechanical hot press, setting the temperature at 80 - 100 °C, the pressure at 0.2 - 0.8 MPa, hot pressing for 20 - 40 min, and performing secondary hot pressing according to the same steps after replacing the filter paper, an oxidized modified wood fiber transparent membrane can be obtained.

[0066] 4. Gelatin functionalization composite treatment

[0067] (1) Prepare a 0.1 - 0.5 wt% gelatin solution for grafting onto the oxidized modified wood skeleton prepared in step 2.1, stir at 55 - 65 °C until the gelatin dissolves, keep the solution temperature at 55 - 65 °C, put the oxidized modified wood skeleton into the solution, soak for several hours, and then take it out.

[0068] (2) After the impregnation, place the gelatin-grafted oxidized modified wood skeleton between two glass plates, and fix the glass plates with clips to prevent the wood from curling. Place it in an oven at 60 - 80 °C and dry for 12 - 24 hours to obtain a gelatin / oxidized modified transparent wood film.

[0069] (3) Immerse the dried gelatin / oxidized modified transparent wood film into a 10 - 20 mg·mL -1 tannic acid solution at room temperature of 20 - 35 °C. After impregnating for several hours, then rinse to remove free radicals, and then obtain an ultraviolet-shielding transparent wood film according to the atmospheric pressure drying in step 3.1.

[0070] 5. Preparation of luminescent anti-counterfeiting film

[0071] Use a mixed solvent of TCTA:26DCzPPy:Ir(ppy)2(acac) (45 wt%:45 wt%:10 wt%) solute and CB:CN (70 vol%:30 vol%), with a concentration of 20 mg / mL, stir at room temperature for 4 hours until the solute is completely dissolved. Use an inkjet printer (Dimatix Fujifilm, DMP - 2850, Japan) to print the luminescent layer ink onto the surface of the wood film, and the effect is as Figure 3 . After printing, place the film on a hot stage and anneal at 80 °C for 15 min.

[0072] 6. Performance testing

[0073] Characterize and analyze the microscopic morphology, mechanical properties, optical properties, water resistance, etc. of the above transparent wood film by using a scanning electron microscope, a universal mechanical testing machine, an ultraviolet-visible near-infrared spectrophotometer, a contact angle measuring instrument, etc.

[0074] Comparative example 1: Dematrix wood film (WFM)

[0075] 1. Ten longitudinal balsa wood chips with a size of 50 mm × 50 mm (length × width) (density: 0.15 - 0.2 g / cm 3 , thickness: 2 mm) were placed in 600 ml of a 2 wt% sodium chlorite solution, and the pH was adjusted to 4.5 with glacial acetic acid. They were heated at 100 °C for 2 hours to perform delignification treatment on the balsa wood chips. Then, they were rinsed with a large amount of deionized water, and the obtained delignified wood was thoroughly rinsed until neutral.

[0076] 2. The delignified wood was soaked in 600 ml of a 15 wt% sodium hydroxide solution, heated at 40 °C for 2 hours, and assisted with ultrasonic treatment for 15 min to remove hemicellulose. The sample was washed with deionized water until neutral to obtain a complete wood skeleton.

[0077] 3. The wood skeleton was placed in air at room temperature for 12 hours, and then placed between two glass plates. Anti-sticking paper and filter paper were respectively covered on the upper and lower layers of the sample, and the glass plates were fixed with clips to prevent the wood from curling. It was dried in an oven at 60 °C for 24 hours to obtain a de-matrix wood film.

[0078] 4. The microscopic morphology, mechanical properties, optical properties, water resistance, etc. of the above transparent wood film were characterized and analyzed by using a scanning electron microscope, a universal mechanical testing machine, an ultraviolet-visible-near-infrared spectrophotometer, a contact angle measuring instrument, etc. The test results showed that the surface of the WFM was rough and obvious buckling occurred in the cell wall. Due to the shrinkage and densification treatment of the fiber skeleton after the removal of matrix such as lignin and hemicellulose, the thickness of the WFM decreased and the density increased to about 1.27 g / cm 3 . However, although the cell wall collapsed, small holes and cracks could still be observed, indicating that it was not fully densified. The breaking tensile strength and elastic modulus of the sample were 128.94 ± 5.38 MPa and 5.93 ± 0.05 GPa respectively. The light transmittance of the sample was 22.3%. The initial contact angle of the WFM was 66.51°, which rapidly decreased to 22.16° after 3 s, and the water droplet was completely absorbed after 20 s; the wet tensile strength was 3.55 ± 1.38 MPa.

[0079] Comparative Example 2: Wood fiber membrane (CFM)

[0080] 1. Poplar wood waste chips with a particle size of 2 - 5 mm were placed in 600 ml of a 2 wt% sodium chlorite solution, and the pH was adjusted to 4.5 with glacial acetic acid. They were heated at 100 °C for 2 hours to perform delignification treatment on the wood chips. Then, vacuum filtration was carried out with a Buchner funnel until the sample was washed to neutral.

[0081] 2. Immerse the delignified wood chips in 600 ml of 15 wt% sodium hydroxide solution, heat at 40 °C for 2 hours, and assist with ultrasonic treatment for 15 min to remove hemicellulose; then perform vacuum filtration using a Buchner funnel until the sample is washed to neutral, and repeat step 1 to fully remove lignin to obtain lignocellulose fibers.

[0082] 3. Put the extracted lignocellulose fibers into a blender and stir for 20 min to fibrillate the cellulose under external forces; then add deionized water for dilution, pour into a funnel for vacuum filtration to obtain a lignin fiber membrane.

[0083] 4. Use a steel mesh as a diaphragm to cover the upper and lower layers of the lignocellulose fiber membrane, then place filter paper and a steel plate in sequence, put them in a mechanical hot press, set the temperature at 100 °C, the pressure at 0.2 MPa, and hot press for 40 min. After replacing the filter paper, perform secondary hot pressing according to the same steps to obtain an oxidized modified lignin fiber transparent membrane.

[0084] 5. Use a scanning electron microscope, a universal mechanical testing machine, an ultraviolet-visible-near-infrared spectrophotometer, a contact angle measuring instrument, etc. to characterize and analyze the microscopic morphology, mechanical properties, optical properties, and water resistance of the above transparent wood membrane. The test results show that there are obvious pores on the surface of the CFM, and the binding force between cellulose is low. The tensile strength at break of the sample is 18.84 MPa, and the light transmittance is 23.5%. The initial contact angle of the CFM is 38.48°, which rapidly drops to 16.34° after 2 s, and the water droplet is completely absorbed after 3 s; the wet tensile strength is only 0.74 MPa.

[0085] Example 1: Oxidized modified transparent wood membrane (OWFM)

[0086] 1. Place 10 pieces of balsa wood chips with a longitudinal section of 50 mm × 50 mm (length × width) (density: 0.15 - 0.2 g / cm 3 , thickness: 2 mm) in 600 ml of 2 wt% sodium chlorite solution, adjust the pH to 4.5 with glacial acetic acid, and heat at 100 °C for 2 hours to delignify the balsa wood chips. Then rinse with a large amount of deionized water and wash the obtained delignified wood thoroughly to neutral.

[0087] 2. Immerse the delignified wood in 600 ml of 15 wt% sodium hydroxide solution, heat at 40 °C for 2 hours, and assist with ultrasonic treatment for 15 min to remove hemicellulose, and wash the sample with deionized water to neutral to obtain a complete wood skeleton.

[0088] 3. Adjust the electronic balance, weigh 2 g of NaIO4 with weighing paper and pour it into a beaker. Then weigh 198 g of H2O to prepare a 1 wt% NaIO4 solution, and perform a stepwise oxidation treatment at 50 °C for 4 hours. During the oxidation process, wrap the beaker with aluminum foil to prevent the photoinduced decomposition of periodate and adverse reactions. After the oxidation treatment, thoroughly wash the sample with a large amount of deionized water to obtain the oxidized and modified wood skeleton.

[0089] 4. Place the oxidized and modified wood skeleton between two glass plates, cover the upper and lower layers of the sample with non-stick paper and filter paper respectively, and fix the glass plates with clips to prevent the wood from curling. Place it in an oven at 60 °C and dry for 24 hours.

[0090] 5. Use a scanning electron microscope, universal mechanical testing machine, ultraviolet-visible-near-infrared spectrophotometer, contact angle measuring instrument, etc. to characterize and analyze the microscopic morphology, mechanical properties, optical properties, and water resistance of the above transparent wood film. The test results show that the surface of OWFM is relatively smooth, the cross-section has a dense layered structure, and no pores are shown at the micron scale, and its density is further increased. The fracture tensile strength and elastic modulus of the sample are 126.41 ± 2.19 MPa and 12.29 ± 0.11 GPa respectively. The light transmittance and haze of the sample are 89.1% and 18.76% respectively; the initial contact angle of OWFM is 83.17°, and after 600 s, it still remains 81.16°; the wet tensile strength reaches 114 ± 3.14 MPa.

[0091] Example 2: Gelatin / oxidized modified transparent wood film (G / OWFM)

[0092] 1. Place 10 longitudinal balsa wood slices with a size of 50 mm × 50 mm (length × width) (density: 0.15 - 0.2 g / cm 3 , thickness: 2 mm) in 600 ml of 2 wt% sodium chlorite solution, and adjust the pH to 4.5 with glacial acetic acid. Heat at 100 °C for 2 hours to perform delignification treatment on the balsa wood slices. Then rinse with a large amount of deionized water and thoroughly rinse the obtained delignified wood until it is neutral.

[0093] 2. Immerse the delignified wood in 600 ml of 15 wt% sodium hydroxide solution, heat at 40 °C for 2 hours, and assist with ultrasonic treatment for 20 min to remove hemicellulose. Wash the sample with deionized water until it is neutral to obtain a complete wood skeleton.

[0094] 3. Adjust the electronic balance, weigh 2 g of NaIO4 with weighing paper and pour it into a beaker. Then weigh 198 g of H2O to prepare a 1 wt% NaIO4 solution, and conduct a stepwise oxidation treatment at 50 °C for 4 hours. During the oxidation process, wrap the beaker with aluminum foil to prevent the photoinduced decomposition of periodate and adverse reactions. After the oxidation treatment, thoroughly wash the sample with a large amount of deionized water to obtain the oxidized and modified wood skeleton.

[0095] 4. Prepare a 0.1 wt% gelatin solution for grafting onto the oxidized and modified wood skeleton. Stir it at 65 °C until the gelatin dissolves, keep the solution temperature at 65 °C, put the oxidized and modified wood skeleton into the solution, soak it for 4 hours, and then take it out.

[0096] 5. After the impregnation, place the gelatin-grafted oxidized and modified wood skeleton between two glass plates, and use clips to fix the glass plates to prevent the wood from curling. Place it in an oven at 60 °C and dry for 24 hours.

[0097] 6. Use a scanning electron microscope, a universal mechanical testing machine, an ultraviolet-visible-near-infrared spectrophotometer, a contact angle measuring instrument, etc. to characterize and analyze the microscopic morphology, mechanical properties, optical properties, and water resistance of the above transparent wood film. The test results show that the tensile strength at break and the elongation at break of the sample are 122.41 ± 2.28 MPa and 3.28 ± 0.13% respectively; the light transmittance of the sample is 90.3%; the initial contact angle of G / OWFM is 83.56°, and after 600 s, it still remains 81.28°; the wet tensile strength is 112 ± 3.13 MPa.

[0098] Example 3: Ultraviolet-shielding transparent wood film (TA / G / OWFM)

[0099] 1. Place 10 longitudinal-section balsa wood pieces with a size of 50 mm × 50 mm (length × width) (density: 0.15 - 0.2 g / cm 3 , thickness: 2 mm) into 600 ml of 2 wt% sodium chlorite solution, adjust the pH to 4.5 with glacial acetic acid, and heat at 100 °C for 2 hours to conduct a delignification treatment on the balsa wood pieces. Then rinse with a large amount of deionized water and thoroughly rinse the obtained delignified wood until it is neutral.

[0100] 2. Immerse the delignified wood in 600 ml of 15 wt% sodium hydroxide solution, heat at 40 °C for 2 hours, and assist with ultrasonic treatment for 15 min to remove hemicellulose. Wash the sample with deionized water until it is neutral to obtain a complete wood skeleton.

[0101] 3. Adjust the electronic balance, weigh 2 g of NaIO4 with weighing paper and pour it into a beaker. Then weigh 198 g of H2O to prepare a 1 wt% NaIO4 solution, and carry out oxidation treatment at 50 °C for 4 hours. During the oxidation process, wrap the beaker with aluminum foil to prevent photoinduced decomposition of periodate and adverse reactions. After the oxidation treatment, thoroughly wash the sample with a large amount of deionized water to obtain the oxidized and modified wood skeleton.

[0102] 7. Prepare a 0.1 wt% gelatin solution for grafting onto the oxidized and modified wood skeleton, stir it at 65 °C until the gelatin dissolves, keep the solution temperature at 65 °C, put the oxidized and modified wood skeleton into the solution, soak it for 4 hours, and then take it out.

[0103] 4. After impregnation, place the gelatin-grafted oxidized and modified wood skeleton between two glass plates and fix the glass plates with clips to prevent the wood from curling. Place it in an oven at 60 °C and dry for 24 hours.

[0104] 5. Immerse the dried film in a 10 mg·mL -1 tannin solution, soak it at room temperature for 48 hours to scavenge the added free radicals, effectively absorb light in the ultraviolet range, endow the film with ultraviolet resistance, prevent solar radiation, then rinse it with a large amount of deionized water, and then dry it according to step 4 to obtain TA / G / OWFM;

[0105] 6. Use a scanning electron microscope, a universal mechanical testing machine, an ultraviolet-visible-near-infrared spectrophotometer, a contact angle measuring instrument, etc. to characterize and analyze the microscopic morphology, mechanical properties, optical properties, and water resistance of the above transparent wood film. The test results show that the cross-section of TA / G / OWFM is dense and continuous, the surface is smooth, and there is no obvious phase separation after the addition of gelatin and tannic acid, indicating good compatibility between the two. The tensile strength at break of the sample is 152.41 ± 2.28 MPa. The light transmittance of the sample is 86%, and it can completely absorb all UVB (275–320 nm), UVC (200–275 nm), and most of UVA (320–400 nm). The initial contact angle of TA / G / OWFM is 84.18°, and after 600 s, it still remains 82.33°; the wet tensile strength is as high as 132 ± 3.13 MPa.

[0106] 7. Since the tannin system is rich in phenolic groups, it can effectively scavenge the added free radicals, effectively absorb light in the ultraviolet range, endow the film with ultraviolet resistance, prevent solar radiation, and has certain antioxidant properties; TA / G / OWFM cracks and fragments after being buried in the soil for 2 months and is completely biodegradable after being buried for 5 months.

[0107] Example 4: Multilayer transparent wood (M-OWFM)

[0108] 1. Ten longitudinal balsa wood pieces with a size of 50 mm × 50 mm (length × width) (density: 0.15 - 0.2 g / cm 3 , thickness: 1.5 mm) were placed in 600 ml of a 2 wt% sodium chlorite solution, and the pH was adjusted to 4.5 with glacial acetic acid. The wood pieces were heated at 100 °C for 2 hours for delignification treatment. Then, they were rinsed with a large amount of deionized water, and the obtained delignified wood was thoroughly rinsed until neutral.

[0109] 2. The delignified wood was soaked in 600 ml of a 15 wt% sodium hydroxide solution, heated at 40 °C for 2 hours, and assisted by ultrasonic treatment for 15 min to remove hemicellulose. The sample was washed with deionized water until neutral to obtain a complete wood skeleton.

[0110] 3. The electronic balance was adjusted. 2 g of NaIO4 was weighed with weighing paper and poured into a beaker, and then 198 g of H2O was weighed to prepare a 1.5 wt% NaIO4 solution. Stepwise oxidation treatment was carried out at 50 °C for 4 hours. During the oxidation process, the beaker was wrapped with aluminum foil to prevent photoinduced decomposition of periodate and adverse reactions. After the oxidation treatment was completed, the sample was thoroughly washed with a large amount of deionized water to obtain an oxidized and modified wood skeleton.

[0111] 4. The oxidized and modified wood skeleton was orthogonally laminated (5 layers), and humidity control treatment (relative humidity: 50%) was carried out. Subsequently, it was placed between two glass plates, and the upper and lower layers of the sample were covered with anti-sticking paper and filter paper respectively; it was placed in room temperature air for 12 hours and then dried at 60 °C for 24 hours to obtain multi-layer transparent wood (M-OWFM).

[0112] 5. The microstructure, mechanical properties, optical properties, water resistance, etc. of the above transparent wood film were characterized and analyzed by using a scanning electron microscope, a universal mechanical testing machine, an ultraviolet-visible-near-infrared spectrophotometer, a contact angle measuring instrument, etc. The test results showed that there were no obvious voids and defects between each layer in the cross-section of M-OWFM, and the density of M-OWFM was further increased. The sample showed approximately isotropic mechanical strength (162.37 ± 8.03 MPa in the L direction; 143.21 ± 5.73 MPa in the R direction). The light transmittance and haze of the sample were 86% and 20% respectively, and it showed approximately isotropic optical properties. The initial contact angle of M-OWFM was 82.31°, and it still remained 80.97° even after 600 seconds, indicating good water resistance. More importantly, the wet tensile strength in the L direction was 133.44 ± 7.03 MPa, and the wet tensile strength in the R direction was 116.48 ± 5.74 MPa, showing almost isotropic high tensile strength.

[0113] 6. After being buried in the soil for 2 months, M-OWFM cracked and fragmented, and was completely biodegradable after 5 months of burial, showing degradability. The analysis through simulated house tests showed that the thermal conductivity of M-OWFM was as low as 0.2 W·m -1 ·K -1 , almost one-fifth of that of glass, having good heat insulation, being able to more effectively reduce heat loss and dissipation, save energy, and can be applied to building house windows, car sunroofs, transparent interiors, etc.

[0114] Example 5: Wood fiber transparent film - 0.5 (0.5 wt% sodium periodate)

[0115] 1. Sawdust (poplar, basswood) with a particle size of 2 - 5 mm was placed in 600 ml of 2 wt% sodium chlorite solution, and the pH was adjusted to 4.5 with glacial acetic acid. It was heated at 100 °C for 2 hours to carry out delignification treatment on the sawdust, and then vacuum filtration was carried out with a Buchner funnel until the sample was washed to neutral.

[0116] 2. The delignified sawdust was soaked in 600 ml of 15 wt% sodium hydroxide solution, heated at 40 °C for 2 hours, and assisted by ultrasonic treatment for 10 min to remove hemicellulose. Vacuum filtration was carried out with a Buchner funnel until the sample was washed to neutral, and step 1 was repeated to fully remove lignin to obtain wood cellulose fibers.

[0117] 3. The extracted wood cellulose fibers were put into a blender and stirred for 20 min to make the cellulose fibrillate under external forces; then deionized water was added for dilution, and it was poured into a funnel for vacuum filtration to obtain a wood fiber membrane.

[0118] 4. The electronic balance was adjusted, 1 g of NaIO4 was weighed with weighing paper and poured into a beaker, and then 199 g of H2O was weighed to prepare a 0.5 wt% NaIO4 solution. The wood cellulose skeleton or wood fiber membrane was oxidized at 50 °C for 4 hours. During the oxidation process, the beaker was wrapped with aluminum foil to prevent photoinduced periodate decomposition and adverse reactions. After the oxidation treatment, the sample was thoroughly washed with a large amount of deionized water to obtain wood fiber transparent film - 0.5.

[0119] 5. A steel mesh, filter paper, and steel plate were successively covered on both sides of the wood fiber transparent film - 0.5 for flattening, and it was put into a mechanical hot press. The temperature was set at 100 °C, the pressure was 0.8 MPa, and it was hot-pressed for 20 min. After replacing the filter paper, secondary hot pressing was carried out to obtain a dry wood fiber transparent film - 0.5.

[0120] 6. The microscopic morphology, mechanical properties, optical properties, water resistance, etc. of the above-mentioned lignocellulose membrane were characterized and analyzed using a scanning electron microscope, universal mechanical testing machine, ultraviolet-visible near-infrared spectrophotometer, contact angle measuring instrument, etc. The test results showed that the surface of the 0.5 wt% sodium periodate oxidized lignocellulose membrane was slightly flat, the breaking tensile strength of the sample was 22.14 MPa, the light transmittance was 46.4%, the initial contact angle was 76.80°, and it remained at 75.42° after 60 s, and the wet tensile strength was 12.27 MPa.

[0121] Example 6: Lignocellulose Transparent Membrane-1 (1 wt% Sodium Periodate)

[0122] 1. Wood chips (poplar and basswood) with a particle size of 2 - 5 mm were placed in 600 ml of 2 wt% sodium chlorite solution, and the pH was adjusted to 4.5 with glacial acetic acid. They were heated at 100 °C for 2 hours for delignification treatment of the wood chips, and then vacuum filtered with a Buchner funnel until the sample was washed to neutral.

[0123] 2. The delignified wood chips were soaked in 600 ml of 15 wt% sodium hydroxide solution, heated at 40 °C for 2 hours, and assisted with ultrasonic treatment for 10 min to remove hemicellulose. They were vacuum filtered with a Buchner funnel until the sample was washed to neutral, and step 1 was repeated to fully remove lignin to obtain lignocellulose fibers.

[0124] 3. The extracted lignocellulose fibers were put into a blender and stirred for 20 min to cause fibrillation of the cellulose under external forces; then deionized water was added for dilution, and it was poured into a funnel for vacuum filtration to obtain a lignocellulose membrane.

[0125] 4. The electronic balance was adjusted, 2 g of NaIO4 was weighed with weighing paper and poured into a beaker, and then 198 g of H2O was weighed to prepare a 1.0 wt% NaIO4 solution. The lignocellulose membrane was subjected to stepwise oxidation treatment at 50 °C for 4 hours. During the oxidation process, the beaker was wrapped with aluminum foil to prevent photoinduced decomposition of periodate and adverse reactions. After the oxidation treatment was completed, the sample was thoroughly washed with a large amount of deionized water to obtain lignocellulose transparent membrane-1.

[0126] 5. Steel mesh, filter paper, and steel plate were successively covered on both sides of the lignocellulose transparent membrane-1 for flattening, and it was placed in a mechanical hot press. The temperature was set at 100 °C, the pressure was 0.8 MPa, and it was hot pressed for 20 min. After replacing the filter paper, it was hot pressed for the second time to obtain a dry lignocellulose transparent membrane-1.

[0127] 6. The microscopic morphology, mechanical properties, optical properties, water resistance, etc. of the above-mentioned lignocellulose membranes were characterized and analyzed using a scanning electron microscope, universal mechanical testing machine, ultraviolet-visible near-infrared spectrophotometer, contact angle measuring instrument, etc. The test results showed that the surface of the 1.0 wt% sodium periodate oxidized lignocellulose membrane was flat, the surface fibers were more intertwined, the pores were significantly reduced, and a dense fiber network was formed. The breaking tensile strength of the sample was 43.15 MPa, the light transmittance was 82.6%, the initial contact angle was 102.38°, and it decreased to 101.75° and stabilized after 600 s, and the wet tensile strength could reach 32.34 MPa.

[0128] 7. The lignocellulose transparent film-1 cracked and fragmented after being buried in the soil for 2 months, and was completely biodegradable after 4 months of burial, showing biodegradability;

[0129] Example 7: Lignocellulose transparent film-2 (2 wt% sodium periodate)

[0130] 1. Wood chips (poplar, basswood) with a particle size of 2 - 5 mm were placed in 600 ml of 2 wt% sodium chlorite solution, and the pH was adjusted to 4.5 with glacial acetic acid. They were heated at 100 °C for 2 hours for delignification treatment of the wood chips, and then vacuum filtered with a Buchner funnel until the sample was washed to neutral.

[0131] 2. The delignified wood chips were soaked in 600 ml of 15 wt% sodium hydroxide solution, heated at 40 °C for 2 hours, and assisted with ultrasonic treatment for 10 min to remove hemicellulose. They were vacuum filtered with a Buchner funnel until the sample was washed to neutral, and step 3 was repeated to fully remove lignin to obtain lignocellulose fibers.

[0132] 3. The extracted lignocellulose fibers were put into a blender and stirred for 20 min to cause fibrillation of the cellulose under external forces; then deionized water was added for dilution, and it was poured into a funnel for vacuum filtration to obtain a lignocellulose membrane.

[0133] 4. The electronic balance was adjusted, and 4 g of NaIO4 was weighed with weighing paper and poured into a beaker. Then 196 g of H2O was weighed to prepare a 2.0 wt% NaIO4 solution. The wood cellulose skeleton or lignocellulose membrane was subjected to stepwise oxidation treatment at 50 °C for 4 hours. During the oxidation process, the beaker was wrapped with aluminum foil to prevent photoinduced decomposition of periodate and adverse reactions. After the oxidation treatment was completed, the sample was thoroughly washed with a large amount of deionized water to obtain lignocellulose transparent film-2.

[0134] 5. Cover the two sides of the wood fiber transparent film-2 with a steel mesh, filter paper and steel plate in turn to flatten it, put it into a mechanical hot press, set the temperature to 100°C, the pressure to 0.8MPa, and hot press for 20 minutes. After replacing the filter paper, perform a second hot press to obtain a dry wood fiber transparent film-2.

[0135] 6. The microscopic morphology, mechanical properties, optical properties and water resistance of the above-mentioned wood fiber membrane were characterized and analyzed using a scanning electron microscope, a universal mechanical testing machine, a UV-visible near-infrared spectrophotometer, a contact angle meter, etc. The test results show that the surface of the 2.0wt% sodium periodate oxidized wood fiber membrane is smooth and has no obvious texture. The tensile strength at break of the sample is 35.76MPa. The light transmittance of the sample is 84.3%. The initial contact angle of the sample is 115.25°, and it almost remains at 100.22° after 40s; the wet tensile strength is 18.44Mpa.

[0136] The process parameters and performance data of each embodiment and comparative example are shown in the following table:

[0137]

[0138] The actual pictures of various embodiments and comparative examples are shown in Figure 6.

[0139] By comparing Comparative Example 1 with Example 1, it can be seen that the high iodine oxidation treatment of the present invention acts on the wood skeleton, increases the density of the sample, makes the structure more compact, cross-links occur between fibers, further reduces the pores, and thus makes the refractive index more uniform. It can also significantly inhibit the scattering of light in the film, thereby improving its clarity (from 22.3% to 89.1%) and reducing its haze. In addition, the sodium periodate oxidation treatment also improves the water resistance of the wood film (the wet strength is increased from 3.55MPa to 114), which is 3-5 times that of common petroleum-based transparent plastics.

[0140] Furthermore, it can be seen from the comparison between Example 1 and Example 3 that the present invention uses gelatin grafted oxidatively modified wood and forms an insoluble complex through physical crosslinking of tannin, which further improves the mechanical properties (tensile strength at break increased from 126.41 MPa to 152.41 MPa, and wet strength increased from 114 MPa to 132 MPa) on the basis of maintaining the excellent optical properties and water resistance of OWFM. Figure 1 a is the surface, Figure 1Among them, b is the cross-section, which is dense and continuous, with a smooth surface. After adding gelatin and tannic acid, there is no obvious phase separation, indicating good compatibility between the two. At the same time, due to the rich phenolic groups in the tannin system, it can effectively scavenge the added free radicals and has good antioxidant properties; it can also effectively absorb light in the UV-B / UV-C range, thereby endowing the film with UV protection properties and can be used in fields such as food preservation and intelligent anti-counterfeiting.

[0141] Furthermore, by comparing Example 1 and Example 4, it can be seen that when the oxidized modified wood film is orthogonally laminated, the thickness is increased by nearly 5 times, but its light transmittance can still reach more than 86%, showing relatively excellent optical properties. Compared with the traditional method for preparing transparent wood film, the present invention realizes interlayer self-bonding by using the self-crosslinking bonds between fibers without adding any polymers and adhesives, which is environmentally friendly. More importantly, on the premise of ensuring the light transmittance of the film, the isotropy of the optical properties and mechanical properties is enhanced. The tensile strength of M-OWFM in the R direction increases significantly from 29.46 MPa (single-layer OWFM) to 143.21 MPa (five-layer M-OWFM), and at the same time, the wet strength increases from 26.19 MPa to 116.48 MPa. Compared with traditional glass, the thermal conductivity of M-OWFM is as low as 0.2 W m -1 K -1 , almost 1 / 5 of that of glass, indicating that M-OWFM can more effectively reduce heat loss and dissipation than glass materials, thereby reducing building energy consumption and becoming a candidate material for new sustainable energy-saving buildings.

[0142] By comparing Examples 5-7 with Comparative Example 2, it can be seen that during the process of treating the de-matrix combined with sodium periodate oxidation, as the oxidation concentration increases, the density of the wood fiber membrane increases and the structure becomes more dense, which is beneficial to reducing phenomena such as light refraction and scattering. Compared with the light transmittance (46.4%) of the 0.5 wt% oxidized wood fiber membrane, the light transmittance of the oxidized sample is greatly improved, up to 84.3%, and it shows a low haze (14.21%). Oxidation treatment can improve the water resistance of the material, and through the water absorption test and contact angle test, it can be observed that as the concentration increases, the fiber cross-linking binding force gradually increases and the wet strength improves. Based on the above advantages, this material is expected to be used as a substrate in fields such as wearable, anti-counterfeiting packaging, electronic tags, and barrier packaging.

[0143] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Those with ordinary knowledge in the technical field to which the present invention pertains can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the scope defined in the claims.

Claims

1. A method for preparing a glue-free self-adhesive synthetically formed all-biomass-based multifunctional transparent wood, characterized in that, It includes the following steps: a1. Using natural wood as raw material, slice it along the axial direction. Utilize sodium chlorite and sodium hydroxide solutions, under ultrasonic treatment, to fully remove lignin and hemicellulose. Then, thoroughly wash the sample with deionized water to obtain a complete wood skeleton; b1. Using wood processing waste as raw material, utilize sodium chlorite and sodium hydroxide solutions, under ultrasonic treatment, to separately conduct lignin and hemicellulose removal treatments. Then, thoroughly wash the sample with deionized water to obtain lignocellulose fibers; a21. Place the wood skeleton obtained in a1 into a sodium periodate solution for stepwise oxidation treatment, inducing the cleavage of the C2-C3 bond in the cellulose glucose ring and oxidizing the adjacent secondary hydroxyl groups into aldehyde groups to obtain an oxidized modified wood skeleton; a22. Place the wood skeleton obtained in a1 between two glass plates, leave it in air at room temperature for 12 hours, and then transfer it to an oven at 60-80 °C for drying for 12-24 hours to obtain a matrix-removed wood film; b2. Filter the lignocellulose fibers obtained in b1 into a film by vacuum filtration, and then place it into a sodium periodate solution for stepwise oxidation treatment, inducing the cleavage of the C2-C3 bond in the cellulose glucose ring and oxidizing the adjacent secondary hydroxyl groups into aldehyde groups to obtain an oxidized modified lignocellulose fiber film; a31. Place the oxidized modified wood skeleton obtained in a21 between two glass plates, leave it in air at room temperature for 12 hours to remove unbound water, and then transfer it to an oven at 60-80 °C for drying for 12-24 hours to obtain an oxidized modified transparent wood film; a32. Stack the oxidized modified wood skeletons obtained in a21 in an alternating pattern, and then conduct hot pressing drying or atmospheric drying to achieve densification, and obtain multi-layer transparent wood without using any adhesives; a33. Immerse the oxidized modified wood skeleton obtained in a21 in a gelatin solution for several hours, take it out, remove the excess gelatin solution on the surface, place it between two glass plates, and dry it in an oven at 60-80 °C for 12-24 hours to obtain a gelatin / oxidized modified transparent wood film; b3. Place the oxidized modified lignocellulose fiber film obtained in b2 in air at room temperature for 12 hours to remove unbound water, and then conduct multiple stepwise hot pressing treatments using a mechanical hot press to obtain an oxidized modified lignocellulose fiber transparent film; a4. Immerse the gelatin / oxidized modified transparent wood film obtained in a33 in a tannic acid solution for several hours, then thoroughly rinse it to remove free radicals, and then conduct hot pressing drying or atmospheric drying to achieve densification, and prepare an ultraviolet shielding transparent wood film with ultraviolet blocking and antioxidant functions; It also includes a51. Use a security inkjet printer to print a luminescent layer ink on the surface of the wood-based transparent material to obtain a luminescent anti-counterfeiting film. The wood-based transparent material includes a matrix-removed wood film, an oxidized modified lignocellulose fiber film, an oxidized modified transparent wood film, multi-layer transparent wood, a gelatin / oxidized modified transparent wood film, an oxidized modified lignocellulose fiber transparent film, and an ultraviolet shielding transparent wood film. After printing, place the luminescent anti-counterfeiting film on a hot stage and anneal it at 80 °C for 15 min.

2. The non-glue self-adhesive synthetic forming preparation method of a fully biomass-based multifunctional transparent wood according to claim 1, characterized in that: The specific method for a1 is as follows: Select natural wood as the raw material. The natural wood includes balsa wood, poplar wood, and basswood. After natural drying, cut the wood along the fiber growth direction to prepare a wood thin slice specimen with a thickness of 0.5 - 10 mm. Prepare a sodium chlorite solution with a concentration of 2 - 3 wt%, and adjust the pH to 4 - 5 with glacial acetic acid. Immerse the above wood thin slice specimen in this solution and heat it at 100 °C for 2 - 4 hours. After removing lignin, rinse the specimen with deionized water until neutral. Then immerse it in NaOH with a concentration of 15 - 18 wt% and heat it at 25 - 40 °C for 2 - 4 hours, and use ultrasonic treatment to fully remove hemicellulose. Subsequently, wash the sample with deionized water until neutral to obtain a complete wood skeleton.

3. The non-glue self-adhesive synthetic molding preparation method of a fully biomass-based multifunctional transparent wood according to claim 1, characterized in that: The specific method for b1 is as follows: Select wood waste as the raw material. The wood waste includes balsa wood, poplar wood, and basswood, with a particle size of 2 - 5 mm. Prepare a sodium chlorite solution with a concentration of 2 - 3 wt%, and adjust the pH to 4 - 5 with glacial acetic acid. Immerse the above wood waste in this solution and heat it at 100 °C for 2 - 4 hours. After removing lignin, rinse the specimen with deionized water until neutral. Then immerse it in NaOH with a concentration of 15 - 18 wt% and heat it at 25 - 40 °C for 2 - 4 hours, and use ultrasonic treatment to fully remove hemicellulose. Subsequently, wash the sample with deionized water until neutral to obtain lignocellulose fibers.

4. The non-glue self-adhesive synthetic molding preparation method of a fully biomass-based multifunctional transparent wood according to claim 1, characterized in that: The specific method for obtaining a lignin fiber membrane by vacuum filtration in b2 is as follows: Put the extracted lignocellulose fibers into a food - grade blender and stir for 5 - 20 min to make the cellulose fibrillate under external force and increase the specific surface area. Subsequently, add deionized water for dilution, pour it into a funnel for vacuum filtration to obtain a lignocellulose fiber membrane.

5. A method for preparing a self-adhesive synthetic molding of a fully biomass-based multifunctional transparent wood according to claim 1, characterized in that: The specific method for obtaining an oxidized modified wood specimen by sodium periodate oxidation in a21 and b2 is as follows: Immerse the wood skeleton or lignocellulose fiber membrane in a 0.5 - 2 wt% NaIO4 solution and perform step - by - step oxidation treatment at 25 - 50 °C for 1 - 4 hours. Subsequently, thoroughly wash the sample with a large amount of deionized water to obtain an oxidized modified wood skeleton or an oxidized modified lignocellulose fiber membrane.

6. The non-glue self-adhesive synthetic molding preparation method of a fully biomass-based multifunctional transparent wood according to claim 1, characterized in that: The specific method for b3 is as follows: Use a steel mesh, a polytetrafluoroethylene membrane, filter paper, and anti - sticking paper as diaphragms respectively, cover the upper and lower layers of the oxidized modified lignocellulose fiber membrane, then place filter paper and a steel plate in sequence, put them in a mechanical hot press, set the temperature at 80 - 100 °C, the pressure at 0.2 - 0.8 MPa, and hot - press for 20 - 40 min. After changing the filter paper, perform secondary hot - pressing according to the same steps to obtain an oxidized modified lignocellulose transparent membrane.

7. The non-glue self-adhesive synthetic molding preparation method of a fully biomass-based multifunctional transparent wood according to claim 1, characterized in that: The specific process for a32 is as follows: Atmospheric drying. Orthogonally lay the oxidized modified wood skeleton and perform humidity control treatment with a relative humidity of 30% - 60%. Subsequently, place it between two glass plates, and cover the upper and lower layers of the sample with anti - sticking paper and filter paper respectively. Place it in room - temperature air for 12 hours, then dry it at 60 - 80 °C for 12 - 24 hours to obtain multilayer transparent wood under atmospheric pressure. The specific process of a32 is as follows: hot press drying. The oxidized and modified wood skeleton is orthogonally laminated, and humidity control treatment is carried out with a relative humidity of 30% - 60%. Steel mesh, polytetrafluoroethylene film, filter paper, and anti-sticking paper are used as diaphragms respectively, covering the upper and lower layers of the wood specimen obtained after the oxidation modification treatment. Then, filter paper and steel plates are placed in sequence, and it is placed in a mechanical hot press. The temperature is set at 80 - 100 °C, the pressure is 0.2 - 0.8 MPa, and hot pressing is carried out for 20 - 40 min. After replacing the filter paper, secondary hot pressing is carried out according to the same steps, and multi-layer transparent wood is obtained under the pressure condition.

8. A method for preparing a self-adhesive and synthetically formed all-biomass-based multifunctional transparent wood according to claim 1, characterized in that: During the operation of a33, when using gelatin to graft the oxidized and modified wood skeleton, the mass fraction of the configured gelatin is 0.1 - 0.5 wt%, the reaction process is carried out at 55 - 65 °C, and the reaction time is 4 - 6 hours; When performing the a4 operation and crosslinking with tannic acid, the impregnation treatment is carried out at room temperature of 20 - 35 °C, the impregnation time is 24 - 48 hours, and the concentration of tannic acid is 10 - 20 mg·mL -1 .

9. The wood-based transparent material prepared by the method for preparing a glue-free self-adhesive synthetic type of a fully biomass-based multifunctional transparent wood according to claim 1 is used as transparent glass in building windows, automotive sunroofs, transparent interiors, or food fresh-keeping packaging.

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