High-toughness wood-plastic composite material based on carboxyl functionalized ionic liquid modified lignin and preparation method of high-toughness wood-plastic composite material

Abstract

The invention relates to the field of polymer composite materials, and particularly discloses a high-toughness wood-plastic composite material based on carboxyl functionalized ionic liquid modified lignin and a preparation method of the high-toughness wood-plastic composite material. Chemical bonding is formed through covalent grafting of the carboxyl functionalized ionic liquid and lignin phenolic hydroxyl groups, meanwhile, physical entanglement is formed on the interface of the wood-plastic composite material through a long-chain structure, and the interface bonding strength is improved through the dual effects, so that the tensile property and the bending property are remarkably improved; and the impact strength can be effectively recovered and even improved by improving microwave-assisted homogeneous reaction parameters, and the difficulty of'enhancing embrittlement 'is overcome.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials, specifically to a method for modifying lignin with microwave-assisted carboxyl functionalized ionic liquid, enhancing the interfacial properties of wood-plastic composite materials, and the high-strength and high-toughness wood-plastic composite materials prepared thereby. Background Technology

[0002] Wood-plastic composites (WPCs) are widely used in construction and packaging due to their combination of the renewability of wood fibers and the processability of plastics. However, natural biomass materials generally have strong hydrophilicity, making it difficult to integrate with hydrophobic thermoplastics, resulting in poor compatibility and mechanical properties between wood flour and the plastic matrix. Modifying the components of WPCs by adding coupling agents can improve the polarity between components to some extent, thereby enhancing compatibility and improving the performance of WPCs. Lignin is an amphiphilic polymer with two polar components in its structure: polar (hydrophilic) and non-polar (hydrophobic). Studies have shown that lignin can be used as a coupling agent in wood-polymer composites. Compared with chemical coupling agents, lignin cannot fully meet the requirements for preparing modern composite materials. Therefore, to develop lignin as a bio-coupling agent, its structure must be modified. Traditional lignin modification methods (such as silane and maleic anhydride grafted polyethylene) rely on physical adsorption or simple esterification, resulting in weak interfacial bonding. In addition, they suffer from problems such as long reaction time, high energy consumption, and the need to use toxic solvents (Younesi-Kordkheili H, Pizzi A. Ionic liquid-modified lignin as a bio-coupling agent for natural fiber-recycled polypropylene composites[J]. Composites Part B: Engineering, 2020, 181:107587.DOI: [10.1016 / j.compositesb.2019.107587]). Therefore, it is necessary to find a green, efficient, and more feasible method to improve the performance of lignin in this regard. Summary of the Invention

[0003] Purpose of the invention: The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a high-strength and tough wood-plastic composite material based on lignin modified by carboxyl functionalized ionic liquid and its preparation method.

[0004] To solve the above-mentioned technical problems, the present invention discloses the following technical solution: In a first aspect, the present invention discloses a carboxyl-functionalized ionic liquid-modified lignin.

[0005] The carboxyl groups of the carboxyl-functionalized ionic liquid are grafted onto the surface of lignin by forming covalent ester bonds through interaction with the phenolic hydroxyl groups of lignin.

[0006] The carboxylic acid functionalized ionic liquids include 1-carboxymethyl-3-methylimidazolium chloride, 1-carboxymethyl-3-methylimidazolium bromide, 1-carboxymethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-carboxymethyl-3-methylimidazolium trifluoromethanesulfonate, 1-carboxymethyl-3-methylimidazolium hydrogen sulfate, 1-carboxyethyl-3-methylimidazolium chloride, 1-carboxyethyl-3-methylimidazolium bromide, 1-carboxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and 1-carboxyethyl-3-methylimidazolium chloride. Ionic liquids containing carboxyl groups, such as trifluoromethane sulfonates, are preferably any one or a combination of several of the following: 1-carboxyethyl-3-methylimidazolium chloride, 1-carboxymethyl-3-methylimidazolium chloride, 1-carboxymethyl-3-methylimidazolium bromide, 1-carboxymethyl-3-methylimidazolium trifluoromethane sulfonate, 1-carboxymethyl-3-methylimidazolium hydrogen sulfate, 1-carboxyethyl-3-methylimidazolium bromide, 1-carboxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, and 1-carboxyethyl-3-methylimidazolium trifluoromethane sulfonate.

[0007] Secondly, the present invention discloses a method for preparing the modified lignin described in the first aspect above.

[0008] The method involves covalently grafting a carboxyl-functionalized ionic liquid with lignin in a microwave reactor. In some embodiments, water is added to dilute the carboxyl-functionalized ionic liquid to ensure homogeneous dispersion of the ionic liquid and lignin. In some embodiments, the method specifically includes: (1) mixing lignin with water to obtain a first mixture, and adding the carboxyl-functionalized ionic liquid to the first mixture to obtain a second mixture; (2) premixing the obtained second mixture in an ultrasonic disperser; (3) covalently grafting the premixed mixture in a microwave reactor; after the reaction is completed, centrifuging and drying are performed to obtain modified lignin.

[0009] The mass ratio of lignin to water is 1:(4-10), preferably 1:(6-8).

[0010] The mass of the carboxyl-functionalized ionic liquid is 0.03%-1% of the lignin content, preferably 0.45%-0.55%, or 0.5%-0.6%.

[0011] The ultrasonic disperser has an ultrasonic power of 300-500W and an ultrasonic frequency of 23-33KHz.

[0012] The premixing time is 3-5 minutes.

[0013] The power of the microwave reactor is 200-800W, preferably 240-400W.

[0014] The temperature of the covalent grafting reaction is 60-140℃, preferably 90-135℃.

[0015] The covalent grafting reaction takes 3-15 minutes, preferably 6-12 minutes.

[0016] Thirdly, this invention discloses a high-strength and tough wood-plastic composite material.

[0017] The wood-plastic composite material is made from the modified lignin described in the first aspect and the modified lignin prepared by the method described in the second aspect, together with a plastic matrix, biomass powder and auxiliary materials.

[0018] The plastic matrix includes polypropylene (PP), polyethylene (PE), etc.

[0019] The biomass powder includes bamboo powder, wood powder, etc.

[0020] The modified lignin is 0.5%-20% of the total mass of the modified lignin, plastic matrix, biomass powder and auxiliary materials, such as 1%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, etc.

[0021] The auxiliary materials include antioxidants; the mass ratio of modified lignin to antioxidant is (1-5):(0.5-1), preferably 3:(0.5-0.8).

[0022] The mass ratio of the plastic matrix to the biomass powder is 4:(5-6).

[0023] The wood-plastic composite material is made by the following method: a mixture containing modified lignin, plastic matrix, biomass powder and auxiliary materials is melt-blended, plasticized and granulated in a twin-screw extruder, and the resulting particles are hot-pressed to form a wood-plastic composite material.

[0024] The twin-screw extruder has a heating zone temperature of 165-180℃, a die head temperature of 165-175℃, and a screw speed of 50-70 rpm. In some embodiments, the twin-screw extruder is configured with heating zones of 165, 170, 175, 180, 180, and 175℃, a die head temperature of 170℃, a screw speed of 60 rpm, and a feeding speed of 3 rpm for extrusion and pelletizing.

[0025] The hot pressing temperature is 170-210℃, such as 180℃, 190℃, or 200℃.

[0026] The hot pressing time is 5-50 min.

[0027] The biomass powder mentioned in this invention is biomass powder that has passed through a 60, 80, 100 or 120 mesh sieve.

[0028] The high-strength and tough wood-plastic composite material provided by this invention breaks the dilemma of "reinforcement inevitably leads to embrittlement". Compared with wood-plastic composite materials made of unmodified lignin, the lignin modified by the carboxylic acid functionalized ionic liquid provided by this invention can further improve the mechanical properties of wood-plastic composite materials, especially the impact strength can be greatly restored or even improved.

[0029] In some embodiments, when PE is used as the plastic matrix, the tensile strength of the high-strength and tough wood-plastic composite material of the present invention is 25-32.66 MPa, such as 26.5 MPa and 27.66 MPa. Compared with wood-plastic composite materials without added lignin, the tensile properties of the high-strength and tough wood-plastic composite material of the present invention are improved by 21%-58%, such as 28%, 29%, 30%, 31%, 32%, 33%, 35%, 38%, 40%, 45%, and 50%. Compared with wood-plastic composite materials without added lignin, the tensile strength of wood-plastic composite materials using unmodified lignin can only be improved by 12%. It is evident that the improvement in tensile strength of the high-strength and tough wood-plastic composite material of the present invention is far greater than that of wood-plastic composite materials using unmodified lignin compared to those without added lignin.

[0030] In some embodiments, when PE is used as the plastic matrix, the tensile modulus of the high-strength and tough wood-plastic composite material is 445-500 MPa, such as 451.3 MPa and 492.5 MPa. Compared to wood-plastic composite materials without added lignin, the tensile modulus of the high-strength and tough wood-plastic composite material produced by this invention is increased by 8%-21%, such as 9%, 10%, 13%, 15%, 17%, and 19%. Compared to wood-plastic composite materials without added lignin, the tensile modulus of wood-plastic composite materials using unmodified lignin can only be increased by 2%. Therefore, compared to wood-plastic composite materials without added lignin, the increase in tensile modulus of the high-strength and tough wood-plastic composite material of this invention is much greater than the increase in tensile modulus of wood-plastic composite materials using unmodified lignin.

[0031] In some embodiments, when PE is used as the plastic matrix, the flexural strength of the high-strength and tough wood-plastic composite material is 37-43.48 MPa, such as 37.41 MPa and 40.48 MPa. Compared with wood-plastic composite materials without added lignin, the flexural strength of the high-strength and tough wood-plastic composite material prepared by the present invention is increased by 6%-24%, such as 7%, 9%, 11%, 13%, 15%, 17%, and 19%. Compared with wood-plastic composite materials without added lignin, the flexural strength of wood-plastic composite materials using unmodified lignin can only be increased by 2%. Therefore, compared with wood-plastic composite materials without added lignin, the increase in flexural strength of the high-strength and tough wood-plastic composite material of the present invention is much greater than the increase in flexural strength of wood-plastic composite materials using unmodified lignin.

[0032] In some embodiments, when PE is used as the plastic matrix, the flexural modulus of the high-strength and tough wood-plastic composite material is 2400-2700 MPa, such as 2435.2 MPa and 2685.4 MPa. Compared with wood-plastic composite materials without added lignin, the flexural modulus of the high-strength and tough wood-plastic composite material produced by the present invention is increased by 30%-46%, such as 32%, 34%, 36%, 38%, and 40%. Compared with wood-plastic composite materials without added lignin, the flexural modulus of wood-plastic composite materials using unmodified lignin can only be increased by 13%. It is evident that the increase in flexural modulus of the high-strength and tough wood-plastic composite material of the present invention is far greater than that of wood-plastic composite materials using unmodified lignin compared to those without added lignin.

[0033] In some embodiments, when PE is used as the plastic matrix, the impact strength of wood-plastic composites made with unmodified lignin decreases. However, the high-strength and tough wood-plastic composites of the present invention, using the modified lignin of the present invention, can improve the impact strength, achieving an impact strength of 13-15 KJ·m. 2 For example, 13.5 kJ·m 2 14 kJ·m 2 14.5 kJ·m 2 15 kJ·m 2 .

[0034] Beneficial effects:

[0035] 1. This invention forms a chemical bond by covalently grafting functionalized ionic liquids with lignin phenolic hydroxyl groups. At the same time, its long-chain structure forms a physical entanglement at the interface of wood-plastic composite materials. The dual effect enhances the interfacial bonding strength, and the tensile and bending properties are significantly improved. By improving the microwave-assisted homogeneous reaction parameters, the impact strength can be restored or even improved, thus breaking the dilemma of "reinforcement inevitably leads to embrittlement".

[0036] 2. This invention utilizes microwave-assisted homogeneous reaction and the high-efficiency heating characteristics of microwaves to accelerate the reaction of ionic liquids with the functional groups of lignin, achieving rapid grafting within 5-12 minutes (traditional methods require several hours) to obtain a lignin-based bio-coupler. This aims to improve the interfacial bonding strength between wood flour and polyolefins, avoid the large-scale agglomeration that occurs during the blending of wood flour and polyolefins, and obtain a simple and high-performance method for preparing modified lignin-reinforced wood-plastic composite materials.

[0037] 3. This invention uses water as the diluent for the ionic liquid and employs a low-toxicity solvent system. The microwave reaction consumes little energy. After lignin modification, only centrifugation is needed to recover the solvent before drying, eliminating the problems of repeated washing and large-scale wastewater discharge. The process is simple and convenient to operate, saves production time, improves modification efficiency, and meets environmental protection requirements. Attached Figure Description

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0039] Figure 1 Infrared spectra of unmodified lignin and modified lignin.

[0040] Figure 2 This is an electron microscope image of wood-plastic composite material. Detailed Implementation

[0041] The present invention can be better understood from the following embodiments. However, those skilled in the art will readily understand that the descriptions in the embodiments are for illustrative purposes only and should not, and will not, limit the invention as detailed in the claims.

[0042] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0043] In the following examples, both the bamboo powder and wood powder are powders that have passed through a 100-mesh sieve.

[0044] The method for testing various mechanical properties in this invention is as follows: The material is melt-extruded and granulated using a twin-screw extruder at a temperature range of 160-180℃, and then injection-molded into dumbbell-shaped standard test specimens at 210℃ and 40MPa using an injection molding machine. Tensile strength, tensile modulus, flexural strength, and flexural modulus are tested using an electronic universal testing machine, and impact strength is tested using a cantilever beam impact tester. Test conditions: tensile strength and tensile modulus are tested according to standard GB / T 1040.1; flexural strength and flexural modulus are tested according to standard GB / T 9341-2008; and impact strength is tested according to standard GB / T 1843-2008.

[0045] Unless otherwise specified, all parts mentioned in this invention refer to parts by weight.

[0046] Example 1: Preparation of modified lignin (1) Mix lignin and deionized water at a mass ratio of 1:7 to obtain the first mixture. Take 0.5% of the lignin mass of the functionalized ionic liquid and dissolve it in the first mixture to dilute it and obtain the second mixture. Place the second mixture in an ultrasonic disperser and premix it for 3-5 minutes with a certain ultrasonic power (400W) and ultrasonic frequency (28KHz).

[0047] (2) In a microwave reactor, control the microwave power to 240-400W and react at 90-132.5℃ for 6-12 minutes to allow the carboxyl active functional groups in the ionic liquid to undergo a covalent grafting reaction with the phenolic hydroxyl groups of lignin.

[0048] (3) After the reaction is complete, centrifuge and dry to obtain modified lignin 1-7.

[0049] Table 1 shows the ionic liquid used in Example 1 and the reaction conditions in step (2).

[0050] Comparison of infrared spectra of unmodified lignin and lignin modified with carboxyl-functionalized ionic liquid ( Figure 1 It can be seen that after modification, the height is 1735 cm. -1 A new and significant absorption peak appears, attributed to the stretching vibration of the ester carbonyl group (C=O), proving that the carboxyl group in the ionic liquid undergoes an esterification reaction with the lignin phenolic hydroxyl group to form a covalent ester bond, successfully achieving grafting. Furthermore, the characteristic peak of the aromatic ring (1600 cm⁻¹) is also observed. -1 and 1510 cm -1 The lignin was retained after modification, indicating that the lignin framework was not damaged. FTIR results fully confirmed that the carboxyl-functionalized ionic liquid was efficiently grafted onto the lignin surface via a microwave-assisted method.

[0051] Example 2: Preparation of wood-plastic composite materials (1) Place unmodified lignin or modified lignin, wood flour, plastic matrix PE and antioxidant (BASF antioxidant 1010) in a high-speed mixer and premix for 8 minutes at a certain speed (800 rpm / min) to obtain a uniformly dispersed blend.

[0052] (2) The obtained blend is melt-blended and plasticized into granules by entering a twin-screw extruder; the twin-screw extruder is set with heating zones of 165, 170, 175, 180, 180, and 175°C, a die head temperature of 170°C, a screw speed of 60 rpm, and a feeding speed of 3 rpm for extrusion and pelletizing.

[0053] (3) The prepared sample was placed in an oven at 102℃ and dried for 2 hours for later use; finally, it was hot-pressed at 190℃ (pre-pressed for 10 minutes in a vulcanizing machine, and then hot-pressed for 30 minutes) to prepare the composite material.

[0054] Table 2. Conditions for preparing wood-plastic composites with no lignin, no modified lignin, and lignin modified with different ionic liquids.

[0055]

[0056] Electron micrographs of the prepared composite material are shown below. Figure 2 As shown.

[0057] PE0 (lignin-free): Obvious gaps or voids should be visible between the wood flour and the plastic matrix, indicating poor interfacial bonding. A smooth surface of the wood flour, not fully coated by the plastic, suggests poor compatibility.

[0058] PE 未改性 The addition of unmodified lignin improved the interface of the composite material, but localized peeling or gaps still existed, indicating that physical mixing had some effect but was limited. The lignin may exist in particulate form and be unevenly distributed.

[0059] PE1: The addition of modified lignin 1 significantly improves the interface of the composite material, resulting in a tighter bond between wood flour and plastic and reduced gaps. Lignin may also be more evenly dispersed, forming a transition layer.

[0060] PE4: With the addition of modified lignin 4, the composite material interface is the most continuous and dense, with almost no visible gaps. Lignin forms a good bond with the plastic, possibly exhibiting a "bridging" structure.

[0061] PE5: The addition of modified lignin 5 resulted in limited improvement in the composite material interface, with obvious gaps or interface delamination still present, indicating poor performance of the non-functionalized ionic liquid.

[0062] PE7: The addition of modified lignin 7 improves the interface of the composite material, but it is not as uniform as that produced by microwave method (such as PE4), and there may be local agglomeration or uneven reaction.

[0063] The properties of the prepared composite materials are shown in Table 3. Compared with the wood-plastic composite material without lignin (PE0), the wood-plastic composite material made with unmodified lignin (PE0) has better performance. 未改性 It can improve tensile strength and other mechanical properties to some extent, but the impact strength decreases significantly. Compared with wood-plastic composites (PE) made from unmodified lignin... 未改性Compared to other methods, the wood-plastic composites (PE1, PE4) made from lignin modified by carboxyl-functionalized ionic liquids provided in this invention can further improve the mechanical properties of wood-plastic composites. In particular, PE4 can also restore impact strength, which is 14% higher than the blank group (13.80 vs 12.14 KJ / m²), breaking the dilemma of "reinforcement inevitably leads to embrittlement". On the contrary, some mechanical properties of wood-plastic composites (PE2, PE3, PE5, PE6) made from lignin modified by other ionic liquids decreased. Compared with PE7, PE1 has higher mechanical properties, indicating that microwave-assisted carboxyl-functionalized ionic liquids can achieve rapid homogeneous modification of lignin. By utilizing the interaction between carboxyl functional groups and phenolic hydroxyl groups of the lignin matrix, it can covalently graft them onto the lignin surface, realizing the interfacial chemical bonding and physical synergistic reinforcement of wood-plastic composites.

[0064] Table 3. Properties of wood-plastic composites made with no lignin, unmodified lignin, and lignin modified with different ionic liquids.

[0065] Example 3: Preparation of wood-plastic composite materials Referring to the preparation method of modified lignin 4 in Table 1, the carboxyl functionalized ionic liquid used in the modified lignin was replaced with other carboxylmethyl and carboxylethyl series functionalized ionic liquids. The properties of the resulting wood-plastic composite material are shown in Table 4.

[0066] Table 4. Properties of wood-plastic composites made from other carboxymethyl and carboxyethyl functionalized ionic liquid-modified lignin.

[0067] Example 4: Preparation of wood-plastic composite materials Referring to the preparation method of modified lignin 4 in Table 1, 1-carboxyethyl-3-methylimidazolium chloride was used as the functionalized ionic liquid for modification. The amount of 1-carboxyethyl-3-methylimidazolium chloride used was 0%, 0.3% and 0.5% of the lignin quality, respectively. The resulting lignins were named IL-0, IL-0.3 and IL-0.5, respectively.

[0068] (1) Take 39.5 parts of polypropylene, 55 parts of bamboo powder, 5 parts of the aforementioned different lignins and 0.5 parts of antioxidant to prepare wood-plastic composite material according to the method of Example 2. The experimental results are shown in Table 5.

[0069] As shown in Table 5, when PP is used as the matrix, the impact performance of wood-plastic composites made with modified lignin IL-0.3 and IL-0.5 is significantly improved compared with wood-plastic composites made with unmodified lignin. In particular, the mechanical properties of wood-plastic composites made with modified lignin IL-0.5 are better than those of wood-plastic composites made with unmodified lignin.

[0070] (2) Take 39.5 parts of polypropylene, bamboo powder and lignin IL-0.5 (the specific parts of bamboo powder and lignin are as shown in Table 6) and 0.5 parts of antioxidant to prepare wood-plastic composite material according to the method of Example 2. The experimental results are shown in Table 6.

[0071] As shown in Table 6, when using PP as the matrix, compared to wood-plastic composites without lignin, the wood-plastic composites prepared by the modified lignin IL-0.5 of this invention at dosages of 1 part and 3 parts can effectively improve the various mechanical properties of the wood-plastic composites, especially at a dosage of 1 part, where the impact strength reaches as high as 3.94 kJ / m. 2 .

[0072] Table 5 Properties of Polypropylene Wood-Plastic Composites

[0073] Table 6 Properties of Polypropylene Wood-Plastic Composites

[0074] This invention achieves rapid homogeneous modification of lignin by using microwave-assisted carboxyl-functionalized ionic liquids. By utilizing the interaction between carboxyl functional groups and phenolic hydroxyl groups of the lignin matrix, the carboxyl functional groups are covalently grafted onto the lignin surface, thereby achieving chemical bonding and physical synergistic enhancement of the wood-plastic composite interface.

[0075] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A lignin modified with a carboxyl-functionalized ionic liquid, characterized in that, The carboxyl groups of the carboxyl-functionalized ionic liquid are grafted onto the surface of lignin by forming covalent bonds through interaction with the phenolic hydroxyl groups of lignin.

2. The modified lignin according to claim 1, characterized in that, The carboxyl-functionalized ionic liquid is any one or a combination of several of the following: 1-carboxymethyl-3-methylimidazolium chloride, 1-carboxymethyl-3-methylimidazolium bromide, 1-carboxymethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine, 1-carboxymethyl-3-methylimidazolium trifluoromethanesulfonate, 1-carboxymethyl-3-methylimidazolium hydrogen sulfate, 1-carboxyethyl-3-methylimidazolium chloride, 1-carboxyethyl-3-methylimidazolium bromide, 1-carboxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine, and 1-carboxyethyl-3-methylimidazolium trifluoromethanesulfonate.

3. The method for preparing the modified lignin according to claim 1 or 2, characterized in that, Carboxyl-functionalized ionic liquids were covalently grafted with lignin in a microwave reactor.

4. The preparation method according to claim 3, characterized in that, The mass of the carboxyl-functionalized ionic liquid is 0.03%-1% of the lignin content.

5. The preparation method according to claim 3, characterized in that, The power of the microwave reactor is 200-800W.

6. The preparation method according to claim 3, characterized in that, The temperature for the covalent grafting reaction is 60-140℃.

7. A wood-plastic composite material, characterized in that, The modified lignin produced by the method described in claim 1 or 2 or any one of claims 3-6 is made with a plastic matrix, biomass powder and excipients.

8. The wood-plastic composite material according to claim 7, characterized in that, The modified lignin comprises 0.5%-20% of the total mass of modified lignin, plastic matrix, biomass powder, and auxiliary materials.

9. The wood-plastic composite material according to claim 7 or 8, characterized in that, The mass ratio of the plastic matrix to the biomass powder is 4:(5-6).

10. The wood-plastic composite material according to claim 7 or 8, characterized in that, The auxiliary materials include antioxidants; the mass ratio of the modified lignin to the antioxidant is (1-5):(0.5-1).

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