Preparation method of formaldehyde-free low-carbon wood composite material

Abstract

The application discloses a preparation method of formaldehyde-free low-carbon wood composite material, which comprises the following steps: preparing an impregnation solution, removing lignin on wood by using an alkaline solution to obtain a wood matrix; pretreating the obtained wood matrix by using a gas phase treatment process to control and adjust the pores on the wood matrix; cyclically freezing and impregnating the wood matrix by using the impregnation solution; heating the wood matrix after the S3 treatment; and ultraviolet curing, so that the voids on the wood after the lignin is removed are more uniform, the impregnation of the impregnation solution in the later impregnation process is easier, the situation that all areas cannot be filled is avoided, the uniformity of the pores is greatly improved, the impregnation degree and impregnation efficiency in the later impregnation process are improved, and the physical performance and stability of the wood are improved.

Description

Technical Field

[0001] This invention relates to the field of wood composite material preparation, and more particularly to a method for preparing a formaldehyde-free, low-carbon wood composite material. Background Technology

[0002] Wood-based composite materials, as a new type of environmentally friendly material, have been widely used in various fields in recent years. Based on wood, they optimize and enhance wood properties through compounding with other materials, meeting the modern society's demand for high-performance, environmentally friendly materials. However, with the expansion of the application scope of wood-based composite materials, some problems have gradually emerged, such as formaldehyde release and uneven curing during the freeze-impregnation process.

[0003] Wood-based composite materials, with their unique performance advantages, are widely used in industries such as automotive, construction, interior and exterior decoration, home appliances, and transportation. In the automotive sector, wood-based composite materials are used to manufacture body parts and interior trim, not only reducing the overall weight of the vehicle and improving fuel efficiency, but also adding design elements to the interior. In the construction sector, wood-based composite materials are widely used in the manufacture of doors, windows, wall components, and other parts due to their excellent thermal insulation and environmentally friendly properties. Furthermore, in the interior and exterior decoration and home appliance industries, wood-based composite materials are also widely welcomed for their aesthetic appeal and durability.

[0004] However, with the widespread use of wood-based composite materials, formaldehyde release has gradually attracted attention. Formaldehyde is a common indoor air pollutant, and long-term exposure to high concentrations of formaldehyde can harm human health. In the manufacturing process of wood-based composite materials, the use of adhesives is the main source of formaldehyde release. Although some low-formaldehyde or formaldehyde-free adhesives have been developed, their application is not widespread due to limitations in cost and technology. Therefore, how to reduce the formaldehyde content in wood-based composite materials and reduce formaldehyde release is an urgent problem to be solved.

[0005] Besides formaldehyde issues, uneven curing is another problem in wood-based composite materials during freeze-impregnation. Freeze-impregnation is a common method for modifying wood-based composites, using low-temperature impregnation to further enhance material properties. However, in practice, due to the complex pore structure of wood, the penetration and diffusion of the impregnating solution within the wood are often uneven, leading to differences in the properties of the cured material. This uneven curing not only affects the overall performance of the wood-based composite material but may also cause problems such as cracking and deformation during use. Summary of the Invention

[0006] This invention overcomes the shortcomings of the prior art and provides a method for preparing formaldehyde-free, low-carbon wood composite materials.

[0007] To achieve the above objectives, the technical solution adopted by this invention is: a method for preparing a formaldehyde-free, low-carbon wood-based composite material, comprising the following steps:

[0008] S1: Prepare an impregnation solution and use an alkaline solution to remove lignin from the wood to obtain a wood matrix;

[0009] S2: The wood matrix obtained in S1 is pretreated by a gas phase treatment process to control and adjust the porosity of the wood matrix.

[0010] S3: The wood matrix is ​​subjected to cyclic freeze impregnation treatment using an impregnation solution. After the wood matrix is ​​treated with S3, it is then heated and cured with ultraviolet light to obtain a wood composite.

[0011] In a preferred embodiment of the present invention, in S1, the impregnation solution is composed of a polymer monomer, an initiator and a crosslinking agent; the alkaline solution is a solution formed by mixing alkaline substances such as sodium hydroxide, sodium carbonate, and ammonia with water, with a concentration of 2%-4% and a treatment time of 15-20 hours.

[0012] In a preferred embodiment of the present invention, the polymer monomer is one of methyl methacrylate (MMA), ethyl acrylate (EA), and butyl acrylate (BA); the initiator is one of acetyl peroxide (PA), benzoyl peroxide (BPO), and propionyl peroxide (PPA); and the crosslinking agent is one of melamine-formaldehyde resin (MF) or glyceryl triacrylate (GTA).

[0013] In a preferred embodiment of the present invention, the impregnation liquid contains 60%-80% by mass of polymer monomers, 1%-5% by mass of initiator, and 10%-30% by mass of crosslinking agent. The impregnation liquid is formed by mixing polymer monomers, initiator, and crosslinking agent.

[0014] In a preferred embodiment of the present invention, in S2, the gas phase treatment method is as follows: the lignin-removed wood matrix is ​​placed in a vacuum furnace, and an inert gas is introduced into the vacuum furnace to control the uniformity of the pores of the wood matrix.

[0015] In a preferred embodiment of the present invention, in S2, the inert gas is one or two of water vapor, argon, nitrogen, or argon, and the gas phase treatment parameters are: temperature 100℃-200℃, carried out in a vacuum furnace, time 5-15h.

[0016] In a preferred embodiment of the present invention, in S3, the cyclic freeze impregnation process specifically involves placing the gas-treated wood matrix in an impregnation tank with a circulation system and a freezing function, and continuously circulating the impregnation liquid within the impregnation tank.

[0017] In a preferred embodiment of the present invention, in S3, the parameters for the cyclic freeze impregnation treatment are: temperature -15℃ to 25℃, impregnation time 20-30h, and circulation speed 5L / min to 15L / min.

[0018] In a preferred embodiment of the present invention, in S3, the parameters for ultraviolet curing are: ultraviolet wavelength of 200-400nm and irradiation time of 20-50min.

[0019] In a preferred embodiment of the present invention, in step S3, the heating treatment parameters are: temperature 65-80°C and time 2-4 hours.

[0020] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0021] (1) This invention provides a method for preparing a formaldehyde-free, low-carbon wood composite material. The method involves first removing lignin from the wood using an alkaline solution, then combining gas-phase treatment with cyclic freeze impregnation to completely impregnate the wood with the impregnation solution, and finally curing it. This avoids the use of adhesives, curing agents, and other materials to complete the wood composite material. Compared with the prior art, the method avoids the use of formaldehyde-containing materials in the entire preparation process, while removing lignin and reducing the volatilization of formaldehyde from the wood itself, thereby improving the safety of this wood composite material.

[0022] (2) This invention provides a method for preparing formaldehyde-free low-carbon wood composite material. By combining gas phase treatment and cyclic freeze impregnation treatment, the voids on the wood after lignin removal are made more uniform through gas phase treatment, which makes it easier for the impregnation liquid to impregnate during the subsequent impregnation process, avoiding the situation that the impregnation liquid cannot fill all areas, greatly improving the uniformity of the pores. While improving the impregnation degree and impregnation efficiency during the subsequent impregnation process, it also improves the physical properties and stability of the wood.

[0023] (3) This invention provides a method for preparing formaldehyde-free, low-carbon wood composite materials. By combining gas-phase treatment and cyclic freeze-impregnation, the temperature gradient difference between the inside and outside of the wood during the cyclic freeze-impregnation process allows for step-by-step impregnation, effectively preventing uneven curing in the later stages. Furthermore, the homogenization of the wood's pores in the early stages allows the impregnating liquid to penetrate the wood more smoothly during impregnation. The homogenization of pores through gas-phase treatment also regulates the wood's ability to absorb and release moisture, helping to reduce dimensional changes caused by humidity variations. This stability ensures that the impregnating liquid is better fixed in the wood during subsequent impregnation processes, preventing loss due to environmental changes. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a three-dimensional structural diagram of a preferred embodiment of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0028] As shown in the figure, a method for preparing a formaldehyde-free, low-carbon wood-based composite material includes the following steps:

[0029] S1: Prepare an impregnation solution and use an alkaline solution to remove lignin from the wood to obtain a wood matrix;

[0030] S2: The wood matrix obtained in S1 is pretreated by a gas phase treatment process to control and adjust the porosity of the wood matrix.

[0031] S3: The wood matrix is ​​subjected to cyclic freeze impregnation treatment using an impregnation solution. After the wood matrix is ​​treated with S3, it is then heated and cured with ultraviolet light to obtain a wood composite.

[0032] It should be noted that by using an alkaline solution to remove lignin from the wood, the formaldehyde production of the wood itself is reduced, resulting in a wood matrix. Subsequently, the pores on the wood matrix are homogenized through gas phase treatment, and then the wood matrix is ​​subjected to cyclic freeze impregnation, so that the impregnation solution is uniformly and completely impregnated into the pores of the wood matrix. After the impregnation is completed, the wood matrix is ​​taken out and heated. As the temperature rises, the polymerization and cross-linking chemical reactions are activated, ultimately forming a three-dimensional network structure, thereby improving the performance of the wood composite. Finally, the wood composite is further cured using ultraviolet light to improve its stability.

[0033] An impregnation solution was prepared, and an alkaline solution was used to remove lignin from the wood to obtain a wood matrix.

[0034] In a preferred embodiment of the present invention, in S1, the impregnation solution is composed of a polymer monomer, an initiator and a crosslinking agent; the alkaline solution is a solution formed by mixing alkaline substances such as sodium hydroxide, sodium carbonate, and ammonia with water, with a concentration of 2%-4% and a treatment time of 15-20 hours.

[0035] In a preferred embodiment of the present invention, the polymer monomer is one of methyl methacrylate (MMA), ethyl acrylate (EA), and butyl acrylate (BA); the initiator is one of acetyl peroxide (PA), benzoyl peroxide (BPO), and propionyl peroxide (PPA); and the crosslinking agent is one of melamine-formaldehyde resin (MF) or glyceryl triacrylate (GTA).

[0036] It should be noted that the impregnation solution is prepared as follows: 60%-80% of the MMA monomer is poured into a clean reaction vessel. Then, according to the calculated ratio, 1%-5% of the BPO initiator is gradually added to the MMA while stirring thoroughly to ensure that the initiator is evenly dispersed in the monomer. During stirring, the temperature is controlled within 20-25℃ and the stirring speed is 25-50 min / r to avoid triggering unnecessary polymerization reactions. Continue stirring thoroughly, then add 10%-30% of MF and 1%-3% of solvent, and stir for 30-60 min. Finally, use a 0.45μm filter membrane to remove insoluble matter and impurities to obtain the impregnation solution.

[0037] In a preferred embodiment of the present invention, the impregnation liquid contains 60%-80% by mass of polymer monomers, 1%-5% by mass of initiator, and 10%-30% by mass of crosslinking agent. The impregnation liquid is formed by mixing polymer monomers, initiator, and crosslinking agent.

[0038] It should be noted that the specific steps for removing lignin from wood using an alkaline solution are as follows: Prepare one or two of sodium hydroxide, sodium carbonate, or ammonia water, mix them with water to prepare an alkaline solution with a concentration of 2%-4%. Soak the wood in the alkaline solution for 15-20 hours to remove lignin and reduce the production of aldehydes. After removal, place the wood in a well-ventilated environment at room temperature to dry, obtaining the wood matrix.

[0039] The wood matrix obtained in S1 is pretreated by a gas phase treatment process to control and adjust the porosity of the wood matrix.

[0040] In a preferred embodiment of the present invention, in S2, the gas phase treatment method is as follows: the lignin-removed wood matrix is ​​placed in a vacuum furnace, and an inert gas is introduced into the vacuum furnace to control the uniformity of the pores of the wood matrix.

[0041] It should be noted that gas-phase treatment introduces inert gases, which interact with the surface and interior of the wood matrix. These gas molecules can penetrate the porous structure of the wood, undergoing adsorption, diffusion, and possible chemical reactions with active sites within the wood. During this process, gas molecules fill the tiny pores in the wood, altering their morphology and structure through physical and chemical actions. Simultaneously, the inert gases react with functional groups in the wood, leading to a rearrangement of the internal chemical structure, resulting in more homogeneous porosity. Furthermore, gas treatment can remove residual moisture, impurities, or other volatile substances from the wood, further promoting porosity.

[0042] When the gas is ammonia, it reacts with the carboxyl groups (R-COOH) in the wood:

[0043] R-COOH + NH3 → R-COONH4 + H2O

[0044] Reaction with hydroxyl groups (R-OH) in wood:

[0045] R-OH + NH3 → R-NH2 + H2O

[0046] When the gas is water vapor, it reacts with the hydroxyl groups in the wood (hydrolysis):

[0047] R-OH + H2O → RO- + H2O+

[0048] Here, RO- represents oxygen anions in the wood, while H3O+ is hydrated hydrogen ions, which actually convert rapidly into H+ and H2O in aqueous solution.

[0049] In a preferred embodiment of the present invention, in S2, the inert gas is one or two of water vapor, argon, nitrogen, or argon, and the gas phase treatment parameters are: temperature 100℃-200℃, pressure 95-105kPa, carried out in a vacuum furnace, for 5-15 hours.

[0050] It should be noted that the specific operation during gas phase treatment is as follows: the wood matrix is ​​placed in a vacuum furnace, inert gas is introduced into the vacuum furnace, and the interior is controlled at normal pressure, temperature 100℃-200℃, time 5-15h. This ensures that the gas is fully distributed in the wood, penetrates into the deep pores of the wood, and reacts with the wood, resulting in a rearrangement of the internal structure of the wood, making the pore distribution more uniform.

[0051] When inert gases are used for gas-phase treatment of wood, they gradually penetrate from the surface layer into the deep pores. This process is achieved through the diffusion of gas molecules, where gas molecules move from areas of high concentration to areas of low concentration under the influence of a concentration gradient.

[0052] During the infiltration process, inert gas molecules come into contact with the pore walls of the wood. Due to the physical properties of the gas, it diffuses freely within the pores of the wood, filling the existing voids. As the treatment time increases, more and more gas molecules penetrate deeper into the wood, allowing the internal pore structure of the wood to rearrange.

[0053] Simultaneously, inert gas treatment induces physical changes within the wood. The presence of gas alters the moisture distribution within the wood, reducing its hygroscopicity and further promoting the homogenization of the pore structure. Furthermore, the penetration and diffusion of the gas exert pressure on the fiber and cellular structures within the wood, leading to a degree of rearrangement of the wood's internal microstructure. Inert gas treatment itself does not chemically react with the wood; rather, it alters the pore structure through physical processes. Therefore, the chemical composition of the wood remains essentially unchanged during the treatment process.

[0054] In a preferred embodiment of the present invention, in S3, the cyclic freeze impregnation process specifically involves placing the gas-treated wood matrix in an impregnation tank with a circulation system and a freezing function, and continuously circulating the impregnation liquid within the impregnation tank.

[0055] In a preferred embodiment of the present invention, in S3, the parameters for the cyclic freeze impregnation treatment are: temperature -15℃ to 25℃, impregnation time 20-30h, and circulation speed 5L / min to 15L / min.

[0056] It should be noted that the specific operation during the cyclic freeze-impregnation process is as follows:

[0057] Prepare the impregnation solution: First, prepare an appropriate amount of impregnation solution.

[0058] Place the wood substrate into the impregnation tank: Place the wood substrate to be impregnated into the impregnation tank, ensuring that the wood substrate is completely immersed in the impregnation solution.

[0059] Start the circulation system: Starting the circulation system usually involves pumping the impregnation solution out of the tank and then transporting it back into the tank through pipelines to form a circulation flow.

[0060] Impregnation process control: During the cyclic impregnation process, monitor the temperature of the impregnation solution to be -15℃ to -25℃, the impregnation time to be 20-30h, and the circulation speed to be 5L / min to 15L / min to ensure that the impregnation effect meets the requirements.

[0061] Stop the circulation and remove the wood substrate: Once the required impregnation time has been reached, stop the circulation system, remove the impregnated wood substrate, and proceed with subsequent processing or curing.

[0062] By circulating the impregnation process, the impregnation solution is evenly distributed within the wood matrix, improving impregnation efficiency and uniformity, thereby enhancing the performance and quality of the wood material. The circulation system ensures the impregnation solution flows throughout the wood matrix, allowing for a more even distribution of heat. This reduces localized overheating or underheating, minimizing temperature gradients. The circulating impregnation solution also promotes thorough contact and mixing with the wood matrix, resulting in more uniform heat transfer. Compared to static impregnation, circulation accelerates heat transfer and reduces temperature gradients. Furthermore, cyclic freeze-impregnation, by increasing the circulation speed, allows impregnation at lower freezing temperatures, eliminating concerns about the impregnation solution freezing and preventing further impregnation. Lower temperatures also reduce motion-induced uneven distribution, and the reduced freezing temperature helps to more thoroughly freeze the wood's pore structure, resulting in a more uniform distribution of the polymer monomer solution and initiator within the wood.

[0063] In a preferred embodiment of the present invention, in step S3, the heating treatment parameters are: temperature 65-80°C and time 2-4 hours.

[0064] It should be noted that the gas-phase treated wood matrix is ​​placed in an impregnation tank equipped with a circulation system and a freezing function. The temperature, circulation speed, and circulation time are set to impregnate the wood matrix. After impregnation, the wood matrix is ​​removed and placed in a heated environment for heat treatment. Temperature activates the polymerization and crosslinking reactions. The free radical polymerization reaction involves three stages: chain initiation, chain propagation, and chain termination. Taking methyl methacrylate (MMA) and benzoyl peroxide (BPO) as an example, the reaction is as follows: Chain initiation: BPO decomposes under heating conditions, generating free radicals:

[0065] BPO-2C6H5COO

[0066] These free radicals then supply MMA molecules, initiating a polymerization reaction:

[0067] C6H5COO+CH2=C(CH3)COOCH3-C6H5COOCH2C(CH3)COOCH3

[0068] Chain growth: The generated polymer radicals continue to react with monomers, causing chain growth.

[0069] C6H5COOCH2C(CH3)COOCH3+CH2=C(CH3)COOCH3-C6H5COOCH2C(CH3)COOCH3CH2C(CH3)C

[0070] OOCH3

[0071] This process is repeated continuously;

[0072] Chain termination: Coupling or disproportionation reactions between free radicals lead to chain termination.

[0073] C6H5COOCH2C(CH3)COOCH3+C6H5COOCH2C(CH3)COOCH3- polymer

[0074] For the crosslinking reaction, melamine-formaldehyde resin (MF) is used as the crosslinking agent. The reaction involves the reaction with functional groups (such as hydroxyl or carboxyl groups) on the polymer chain to form crosslinking points.

[0075] Simplified representation: -OH+-CHO--O-CH2-

[0076] The actual MF structure is far more complex than this, containing multiple amino, methylene, and formaldehyde groups. These groups can react with different functional groups on the polymer chain to form various types of crosslinking sites. Therefore, in practice, the crosslinking reaction involves multiple steps and different types of reactions.

[0077] In a preferred embodiment of the present invention, in S3, the parameters for ultraviolet curing are: ultraviolet wavelength of 200-400nm and irradiation time of 20-50min.

[0078] It should be noted that UV curing involves irradiating the wood composite with a UV light source of 200-400nm. When UV light shines on the surface of the impregnated wood, the photoinitiator can quickly absorb the UV energy and convert it into chemical energy, thereby initiating a polymerization reaction. This reaction can be completed in a relatively short time under UV irradiation, achieving rapid curing.

[0079] Example 1:

[0080] A 3% alkaline solution was prepared by uniformly mixing sodium hydroxide, ammonia, and water. The wood was then soaked in this solution for 18 hours to remove lignin. The wood was then removed and dried in a well-ventilated area at room temperature to obtain a wood matrix. An impregnation solution was prepared, consisting of a mixture of methyl methacrylate (MMA), benzoyl peroxide (BPO), and melamine-formaldehyde resin (MF). The MMA had a purity of 99%, the BPO a purity of 98%, and the MF a solid content of 60%. The mass percentages were MMA: 70%, BPO: 3%, and MF: 27%. 2% ethanol was used as the solvent for MMA and MF, which did not negatively affect subsequent polymerization and crosslinking reactions. Preparation was carried out at ℃, with a stirring speed of 25-50 min / r for 50 min. The mixture was then filtered through a 0.45 μm filter membrane to obtain the impregnation solution. Simultaneously, the wood matrix was homogenized using nitrogen gas. The gas phase treatment parameters were: pressure 101.3 kPa, temperature 150℃, and time 9 h. The gas-phase treated wood matrix was then placed in an impregnation tank with a circulation system and a freezing function. The impregnation was carried out using the impregnation solution. The impregnation treatment parameters were: temperature -20℃, impregnation time 25 h, and circulation speed 10 L / min. After impregnation, the impregnation solution was fully incorporated into the pores of the wood matrix. Then, a heat treatment was carried out at 70℃ for 3 h to activate the reaction between the impregnation solutions and form a stable three-dimensional network structure. Finally, the wood composite material was cured again by irradiation with an ultraviolet lamp at a wavelength of 320 nm for 40 min.

[0081] Experiment 1:

[0082] Based on the preparation method of Example 1, the process parameters of gas phase treatment and cyclic freeze impregnation were changed to prepare several wood composites as experimental groups. Similarly, the wood composites prepared in Example 1 were used as reference groups. The experimental and reference groups were cut into thin slices, and the slices were placed on a stage. The focus and light source were adjusted to make the image clearly visible. The pore structure of the wood and the distribution of polymer monomers in the pores were observed to see if there were obvious aggregations or blank areas. See Table 1 and Table 2 for details.

[0083] Table 1

[0084]

[0085] Table 1 shows the parameters related to the vapor phase treatment. According to Table 1, during the vapor phase treatment of the wood matrix, when the temperature is below 100℃ or above 200℃, the diffusion rate of inert gas molecules in the wood slows down, resulting in incomplete treatment of the wood's pores. If the temperature is too high, it may cause thermal damage to the wood. High temperatures cause rapid evaporation of moisture in the wood, leading to surface cracking or damage to the internal structure, resulting in over-treatment of the wood matrix and subsequent damage. When the pressure is below 95 kPa or above 105 kPa, the diffusion ability of inert gas molecules in the wood weakens, similarly leading to incomplete treatment or low treatment efficiency. If the pressure is too high, it may exert excessive physical pressure on the wood. Under high pressure, the impact force of gas molecules on the wood surface increases, which may lead to damage or deformation of the wood surface. According to the data in Table 1, when the temperature is below 100℃ or above 200℃, or the pressure is below 95kPa or above 105kPa, incomplete gas phase treatment will result in blanks due to incomplete penetration. Therefore, according to Table 1, the preferred parameters for gas phase treatment are a temperature of 100℃-200℃ and a pressure of 95-105kPa, among which the most suitable gas phase treatment parameters are 150℃ and 101.3kPa.

[0086] Table 2

[0087]

[0088]

[0089] Table 2 shows the parameters related to cyclic freeze impregnation after using the most suitable parameters in Table 1. According to Table 1, when the freezing temperature, impregnation time, and circulation speed are adjusted respectively, the impregnation can completely penetrate the pores of the wood matrix when the freezing temperature is within -15℃ to -25℃, the impregnation time is within 20 to 30 hours, and the circulation speed is 5 to 15 L / min. When any one of the data is outside the range, there will be blank areas where the impregnation is not complete, resulting in incomplete freeze impregnation cycle treatment.

[0090] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing a formaldehyde-free, low-carbon wood-based composite material, characterized in that, Includes the following steps: S1: Prepare an impregnation solution and use an alkaline solution to remove lignin from the wood to obtain a wood matrix; S2: The wood matrix obtained in S1 is pretreated by a gas phase treatment process to control and adjust the porosity of the wood matrix. S3: The wood matrix is ​​subjected to cyclic freeze impregnation treatment using an impregnation solution. The wood matrix after S3 treatment is then subjected to heat treatment and ultraviolet curing to obtain a wood composite. In S1, the impregnation solution is composed of a polymer monomer, an initiator, and a crosslinking agent; In S2, the gas phase treatment method is as follows: the lignin-removed wood matrix is ​​placed in a vacuum furnace, and an inert gas is introduced into the vacuum furnace to control the uniformity of the pores of the wood matrix. The inert gas is one or two of water vapor, argon, and nitrogen. The gas phase treatment parameters are: temperature 100℃-200℃, vacuum furnace, pressure 95-105 kPa, and time 5-15 h. In S3, the circulating freeze impregnation process specifically involves placing the gas-treated wood matrix into an impregnation tank with a circulation system and a freezing function, and continuously circulating the impregnation solution within the impregnation tank. The parameters for the cyclic freeze impregnation treatment are: temperature -15℃ to 25℃, impregnation time 20-30h, and circulation rate 5L / min-15L / min. The heat treatment parameters are: temperature 65-80℃, time 2-4h.

2. The method for preparing a formaldehyde-free, low-carbon wood-based composite material according to claim 1, characterized in that: In S1, the alkaline solution is a solution formed by mixing sodium hydroxide, sodium carbonate, or ammonia with water, with a concentration of 2%-4%, and a treatment time of 15-20 hours.

3. The method for preparing a formaldehyde-free, low-carbon wood-based composite material according to claim 1, characterized in that: The polymer monomer is one of methyl methacrylate, ethyl acrylate, and butyl acrylate; the initiator is one of acetyl peroxide, benzoyl peroxide, and propionyl peroxide; and the crosslinking agent is one of melamine-formaldehyde resin or glyceryl triacrylate.

4. The method for preparing a formaldehyde-free, low-carbon wood-based composite material according to claim 1, characterized in that: The impregnation solution contains 60%-80% polymer monomers, 1%-5% initiator, and 10%-30% crosslinking agent by mass. The impregnation solution is formed by mixing polymer monomers, initiator, and crosslinking agent.

5. The method for preparing a formaldehyde-free, low-carbon wood-based composite material according to claim 1, characterized in that: In S3, the ultraviolet curing parameters are: ultraviolet wavelength of 200-400nm and irradiation time of 20-50min.

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