Preparation method of lignin-based multi-dimensional interpenetrating network modified wood powder and application thereof in synthetic leather

Abstract

This invention relates to a method for preparing lignin-based multidimensional interpenetrating network modified wood powder and its application in synthetic leather. The invention involves reacting lignin, nano-barium sulfate, a silane coupling agent, and wood powder at low temperature in an acidic environment to form an organic-inorganic hybrid interpenetrating network, resulting in modified wood powder rich in active functional groups such as hydroxyl groups. Then, using the modified wood powder as a skeleton material, it is cross-linked with polyurethane to form a multidimensional interpenetrating network structure, producing synthetic leather with a dislocation entanglement and mechanical interlocking structure, enhancing the tensile strength, elongation at break, flexibility, hydrolysis resistance, and abrasion resistance of the synthetic leather.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive utilization technology of industrial lignin, and relates to a method for preparing lignin-based multidimensional interpenetrating network modified wood powder, as well as its application in the production of reinforcing fillers in the fields of synthetic leather and environmentally friendly packaging. Background Technology

[0002] Industrial lignin is abundant and possesses a wide range of applications due to its diverse functional groups and aromatic rings; however, the technology for its actual industrial application is limited. Large quantities of industrial lignin are byproducts of pulping, papermaking, or biorefining processes from lignocellulosic biomass containing natural lignin. Natural lignin has a very complex structure, generally formed by three basic structural units—p-hydroxyphenyl, guaiacol, and syringyl—linked by chemical bonds such as CO and C-C. The presence of various active functional groups and aromatic rings gives it broad application value.

[0003] Depending on the pulping and cooking process, industrial lignin is mainly classified into alkali lignin, lignin sulfonate, lignin sulfate, and organic solvent lignin. Among these, industrial lignin obtained by caustic soda cooking is alkali lignin; industrial lignin obtained by sulfite cooking in acid pulping processes is lignin sulfonate; lignin obtained by sulfate cooking is sulfate lignin; and industrial lignin obtained by organic solvent separation is organic solvent lignin. Currently, when lignocellulosic biomass is refined in biorefining plants, the focus is generally only on the value-added utilization of carbohydrates, such as bioethanol, pulping, and papermaking. Therefore, irreversible condensation and polymerization of lignin components easily occur during the separation and refining process. Consequently, the by-product industrial lignin has a series of characteristics such as poor water solubility, high molecular weight, and low reactivity, making its high-value utilization very challenging. Therefore, researching and developing high-value utilization methods for industrial lignin has significant economic and environmental benefits.

[0004] In the manufacturing process of PU synthetic leather, wood powder is often used as a filler or reinforcing material, reducing costs while adding environmental benefits to the product. Modification of synthetic leather through powder processing is frequently used in production, such as adding graphene and wood powder to improve the overall performance of synthetic leather, and pre-treating the synthetic leather slurry using a vacuum defoaming process. However, in the application of synthetic leather, the high fiber content, strong hydrophilicity, and low number of active functional groups of wood powder often lead to poor dispersibility and weak interfacial forces in the synthetic leather slurry, easily causing agglomeration and the formation of "powder dots" and stress concentration, resulting in pitting on the surface of the synthetic leather and a decline in mechanical properties. Therefore, it is urgent to study surface modification methods for wood powder to improve the compatibility and interfacial forces between wood powder and the resin in synthetic leather.

[0005] In summary, industrial lignin is abundant and has significant potential application value, but the technology for its actual industrial application is limited. Furthermore, the high fiber content, strong hydrophilicity, and low number of active functional groups in wood flour contribute to pitting and decreased mechanical properties on the surface of synthetic leather. Therefore, exploring how to utilize the amphiphilic properties of lignin to modify wood flour, improve its compatibility and interfacial interactions with resins in synthetic leather, and ultimately manufacture high-quality synthetic leather and achieve high-value utilization of industrial lignin, has significant economic and environmental benefits. Summary of the Invention

[0006] The purpose of this invention is to solve the problems of poor dispersibility, weak interfacial forces, easy agglomeration and stress concentration of conventional wood powder in the preparation of PU synthetic leather. By reacting lignin with amphiphilic properties, wood powder, nano-barium sulfate and silane coupling agent to form an organic-inorganic hybrid interpenetrating network, a lignin-based multidimensional interpenetrating network modified wood powder and its preparation method are provided. This makes the wood powder and PU resin more compatible, and the hydroxyl groups on the surface of the modified wood powder can be used to further crosslink with the PU resin to form a multidimensional, penetrating and mechanically interlocked leather layer, resulting in products with better mechanical properties, better uniformity and higher surface gloss.

[0007] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution.

[0008] The first aspect of this invention provides a method for preparing lignin-based multidimensional interpenetrating network modified wood powder, comprising the following steps:

[0009] (1) Add wood powder, lignin and barium sulfate to an ethanol aqueous solution, adjust the pH value with glacial acetic acid and pre-disperse, then place in a flask and heat in a water bath;

[0010] (2) Add silane coupling agent dropwise to carry out the reaction; after the reaction is completed, filter, wash and dry to obtain the product.

[0011] Preferably, the lignin in step (1) is selected from one or more of alkali lignin and enzymatically hydrolyzed lignin; more preferably, the lignin is selected from alkali lignin.

[0012] Preferably, the barium sulfate in step (1) is nano barium sulfate.

[0013] Preferably, the volume ratio of ethanol to water in the ethanol-water solution in step (1) is 1-20:1; more preferably, the volume ratio of ethanol to water in the ethanol-water solution is 5-15:1; most preferably, the volume ratio of ethanol to water in the ethanol-water solution is 8-12:1.

[0014] Preferably, the content of wood powder in the ethanol aqueous solution in step (1) is 2-15 wt%; more preferably, the content of wood powder in the ethanol aqueous solution is 4-10 wt%.

[0015] Preferably, glacial acetic acid is used to adjust the pH to 4-5 in step (1).

[0016] Preferably, a homogenizer is used for pre-dispersion in step (1).

[0017] Preferably, the water bath heating temperature in step (1) is 40-70℃ and the time is 1-10h; more preferably, the water bath heating temperature is 50-60℃ and the time is 4-8h.

[0018] Preferably, the mass ratio of wood powder, lignin, and barium sulfate in step (1) is 1-15:1-10:2; more preferably, the mass ratio of wood powder, lignin, and barium sulfate is 5-10:2-8:2.

[0019] Preferably, the mass ratio of wood powder to lignin in step (1) is 0.8-3:1; more preferably, the mass ratio of wood powder to lignin is 1-2.5:1.

[0020] Preferably, the silane coupling agent in step (2) is selected from one or more of KH550, KH560, and KH570; more preferably, the silane coupling agent is selected from KH570.

[0021] Preferably, the amount of silane coupling agent used in step (2) is 1.25-1.75% of the total mass; here, "total mass" refers to the total mass of all raw materials involved in the preparation and reaction, including aqueous ethanol solution, lignin, wood powder, barium sulfate and silane coupling agent.

[0022] Preferably, the drying temperature in step (2) is 50-80°C.

[0023] A second aspect of the present invention provides lignin-based multidimensional interpenetrating network modified wood powder prepared according to the above preparation method.

[0024] The third aspect of this invention provides the application of lignin-based multidimensional interpenetrating network modified wood powder prepared according to the above preparation method in the preparation of PU synthetic leather.

[0025] A fourth aspect of this invention provides a method for preparing modified wood powder synthetic leather, comprising the following steps:

[0026] (1) After mixing DMF and the modified wood powder prepared according to the above preparation method evenly, add polyurethane (PU), disperse evenly, and then perform vacuum defoaming to obtain wet polyurethane slurry;

[0027] (2) The wet polyurethane slurry obtained in step (1) is coated and then placed in a displacement solution for displacement reaction. After the displacement reaction is complete, it is washed with water and dried to obtain the final product.

[0028] Preferably, the mass ratio of DMF to modified wood powder in step (1) is 3-15:1; more preferably, the mass ratio of DMF to modified wood powder is 4-8:1.

[0029] Preferably, the mass ratio of polyurethane to modified wood powder in step (1) is 3-8:1.

[0030] Preferably, the replacement fluid in step (2) is composed of DMF and water; more preferably, the replacement fluid is composed of DMF and water in a mass ratio of 1:5-15.

[0031] Preferably, the coating thickness in step (2) is 100-1000 μm; more preferably, the coating thickness is 300-500 μm.

[0032] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0033] The method for preparing lignin-based multidimensional interpenetrating network modified wood powder provided by this invention involves reacting amphiphilic lignin, nano-barium sulfate, and wood powder with a silane coupling agent to form silicon-oxygen bonds, thereby obtaining lignin-based multidimensional interpenetrating network modified wood powder. This improves the compatibility between wood powder and PU resin, and allows for further cross-linking of the modified wood powder surface hydroxyl groups with PU resin to form a multidimensional, penetrating, and mechanically interlocked synthetic leather layer. This effectively solves problems such as poor dispersibility, weak interfacial forces, easy agglomeration forming "powder spots," and stress concentration in the preparation of PU synthetic leather using wood powder, resulting in synthetic leather products with better mechanical properties, better uniformity, and higher surface gloss. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the preparation process of lignin-based multidimensional interpenetrating network modified wood powder and PU synthetic leather according to the present invention.

[0035] Figure 2 The infrared spectra of the samples from Example 1 and Comparative Example 5 are shown.

[0036] Figure 3 The images are scanning electron microscope images of the surface of the synthetic leather sample obtained in Example 1 at 100, 180, and 500x magnification.

[0037] Figure 4 Scanning electron microscope images of the surface of the synthetic leather sample prepared for Comparative Example 1 at 40, 100, and 140x magnification.

[0038] Figure 5 This is a comparison chart of the tensile strength test results of synthetic leather in Example 4, Comparative Example 1, and Comparative Example 5. Detailed Implementation

[0039] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0040] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention. Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in this invention are commercially available or can be prepared by existing methods.

[0041] Example 1

[0042] A lignin-based multidimensional interpenetrating network modified wood powder, the preparation method of which includes the following steps:

[0043] (1) Add 5g wood powder, 5g alkali lignin and 2g nano barium sulfate to 100g 90% ethanol aqueous solution, adjust the pH to 4-5 with glacial acetic acid, disperse in a homogenizer at high speed (1500 rpm) for 20 minutes, and after dispersion, keep stirring at low speed (900 rpm) and heat in a 50℃ water bath for 4 hours.

[0044] (2) Slowly add 1.25% of the total mass of wood powder, alkali lignin, nano barium sulfate, ethanol aqueous solution and silane coupling agent KH570 to carry out the reaction; after the reaction is completed, filter, wash with water, dry in an oven at 60°C, and then let it dry naturally to obtain the product.

[0045] Subsequently, the lignin-based multidimensional interpenetrating network modified wood powder obtained above is used to prepare synthetic leather, specifically including the following steps:

[0046] (1) Heat the PU (090C) open explosion-proof to about 80°C, then mix DMF and lignin-based multidimensional interpenetrating network modified wood powder at a mass ratio of 5:1 and add the above PU. After dispersing evenly, vacuum defoaming is performed to obtain wet PU slurry; wherein the mass ratio of PU to modified wood powder is 4:1.

[0047] (2) Mix DMF and water at a mass ratio of 1:9 to prepare a replacement solution.

[0048] (3) Using a four-sided wet film preparation device, the wet PU slurry in step (1) is coated on the release paper to form a film with a thickness of 400 μm. Then, it is placed in the replacement solution for 5 min until the DMF in the film is replaced and the film is set. Then, it is washed with water to remove the residual DMF and dried to obtain the final product.

[0049] Example 2

[0050] A lignin-based multidimensional interpenetrating network modified wood powder, the preparation method of which includes the following steps:

[0051] (1) Add 5g wood powder, 5g alkali lignin and 2g nano barium sulfate to 100g 90% ethanol aqueous solution, adjust the pH to 4-5 with glacial acetic acid, disperse in a homogenizer at high speed (1500 rpm) for 20 minutes, and after dispersion, keep stirring at low speed (900 rpm) and heat in a 50℃ water bath for 8 hours.

[0052] (2) Slowly add 1.25% of the total mass of wood powder, alkali lignin, nano barium sulfate, ethanol aqueous solution and silane coupling agent KH570 to carry out the reaction; after the reaction is completed, filter, wash with water, dry in an oven at 60°C, and then let it dry naturally to obtain the product.

[0053] Subsequently, the lignin-based multidimensional interpenetrating network modified wood powder obtained above is used to prepare synthetic leather, specifically including the following steps:

[0054] (1) Heat the PU (090C) open explosion-proof to about 80°C, then mix DMF and lignin-based multidimensional interpenetrating network modified wood powder at a mass ratio of 5:1 and add the above PU. After dispersing evenly, vacuum defoaming is performed to obtain wet PU slurry; wherein the mass ratio of PU to modified wood powder is 4:1.

[0055] (2) Mix DMF and water at a mass ratio of 1:9 to prepare a replacement solution.

[0056] (3) Using a four-sided wet film preparation device, the wet PU slurry in step (1) is coated on the release paper to form a film with a thickness of 400 μm. Then, it is placed in the replacement solution for 5 min until the DMF in the film is replaced and the film is set. Then, it is washed with water to remove the residual DMF and dried to obtain the final product.

[0057] Example 3

[0058] A lignin-based multidimensional interpenetrating network modified wood powder, the preparation method of which includes the following steps:

[0059] (1) Add 5g wood powder, 5g alkali lignin and 2g nano barium sulfate to 100g 90% ethanol aqueous solution, adjust the pH to 4-5 with glacial acetic acid, disperse in a homogenizer at high speed (1500 rpm) for 20 minutes, and after dispersion, keep stirring at low speed (900 rpm) and heat in a 50℃ water bath for 4 hours.

[0060] (2) Slowly add 1.75% of the total mass of wood powder, alkali lignin, nano barium sulfate, ethanol aqueous solution and silane coupling agent KH570 to carry out the reaction; after the reaction is completed, filter, wash with water, dry in an oven at 60°C, and then let it dry naturally to obtain the product.

[0061] Subsequently, the lignin-based multidimensional interpenetrating network modified wood powder obtained above is used to prepare synthetic leather, specifically including the following steps:

[0062] (1) Heat the PU (090C) open explosion-proof to about 80°C, then mix DMF and lignin-based multidimensional interpenetrating network modified wood powder at a mass ratio of 5:1 and add the above PU. After dispersing evenly, vacuum defoaming is performed to obtain wet PU slurry; wherein the mass ratio of PU to modified wood powder is 4:1.

[0063] (2) Mix DMF and water at a mass ratio of 1:9 to prepare a replacement solution.

[0064] (3) Using a four-sided wet film preparation device, the wet PU slurry in step (1) is coated on the release paper to form a film with a thickness of 400 μm. Then, it is placed in the replacement solution for 5 min until the DMF in the film is replaced and the film is set. Then, it is washed with water to remove the residual DMF and dried to obtain the final product.

[0065] Example 4

[0066] A lignin-based multidimensional interpenetrating network modified wood powder, the preparation method of which includes the following steps:

[0067] (1) Add 5g wood powder, 5g alkali lignin and 2g nano barium sulfate to 100g 90% ethanol aqueous solution, adjust the pH to 4-5 with glacial acetic acid, disperse in a homogenizer at high speed (1500 rpm) for 20 minutes, and after dispersion, keep stirring at low speed (900 rpm) and heat in a water bath at 60℃ for 4 hours.

[0068] (2) Slowly add 1.25% of the total mass of wood powder, alkali lignin, nano barium sulfate, ethanol aqueous solution and silane coupling agent KH570 to carry out the reaction; after the reaction is completed, filter, wash with water, dry in an oven at 60°C, and then let it dry naturally to obtain the product.

[0069] Subsequently, the lignin-based multidimensional interpenetrating network modified wood powder obtained above is used to prepare synthetic leather, specifically including the following steps:

[0070] (1) Heat the PU (090C) open explosion-proof to about 80°C, then mix DMF and lignin-based multidimensional interpenetrating network modified wood powder at a mass ratio of 5:1 and add the above PU. After dispersing evenly, vacuum defoaming is performed to obtain wet PU slurry; wherein the mass ratio of PU to modified wood powder is 4:1.

[0071] (2) Mix DMF and water at a mass ratio of 1:9 to prepare a replacement solution.

[0072] (3) Using a four-sided wet film preparation device, the wet PU slurry in step (1) is coated on the release paper to form a film with a thickness of 400 μm. Then, it is placed in the replacement solution for 5 min until the DMF in the film is replaced and the film is set. Then, it is washed with water to remove the residual DMF and dried to obtain the final product.

[0073] Comparative Example 1

[0074] A modified wood powder, the preparation method of which includes the following steps:

[0075] Add 10g of wood powder to 100g of 90% ethanol aqueous solution, adjust the pH to 4-5 with glacial acetic acid, and disperse in a homogenizer at high speed (1500 rpm) for 20 minutes. After dispersion, maintain low-speed stirring (900 rpm) and heat in a 50℃ water bath for 4 hours. After the reaction is complete, filter, wash, dry in an oven at 60℃, and then allow to air dry naturally to obtain the final product.

[0076] The modified wood powder obtained above is then used to prepare synthetic leather, specifically including the following steps:

[0077] (1) Heat the PU (090C) open explosion-proof to about 80°C, then mix DMF and modified wood powder in a mass ratio of 5:1 and add the above PU. After dispersing evenly, vacuum defoaming is performed to obtain wet PU slurry; wherein the mass ratio of PU to modified wood powder is 4:1.

[0078] (2) Mix DMF and water at a mass ratio of 1:9 to prepare a replacement solution.

[0079] (3) Using a four-sided wet film preparation device, the wet PU slurry in step (1) is coated on the release paper to form a film with a thickness of 400 μm. Then, it is placed in the replacement solution for 5 min. After the DMF in the film is replaced and the film is set, the residual DMF is removed by washing with water and then dried.

[0080] Comparative Example 2

[0081] A modified wood powder, the preparation method of which includes the following steps:

[0082] (1) Add 5g of wood powder, 5g of sodium lignosulfonate and 2g of nano barium sulfate to 100g of 90% ethanol aqueous solution, adjust the pH to 4-5 with glacial acetic acid, disperse in a homogenizer at high speed (1500 rpm) for 20 minutes, and after dispersion, keep stirring at low speed (900 rpm) and heat in a 50℃ water bath for 4 hours.

[0083] (2) Slowly add 1.25% of the total mass of wood powder, sodium lignosulfonate, nano barium sulfate, ethanol aqueous solution and silane coupling agent KH570 to carry out the reaction; after the reaction is completed, filter, wash with water, dry in an oven at 60°C, and then let it dry naturally to obtain the product.

[0084] The modified wood powder obtained above is then used to prepare synthetic leather, specifically including the following steps:

[0085] (1) Heat the PU (090C) open explosion-proof to about 80°C, then mix DMF and modified wood powder in a mass ratio of 5:1 and add the above PU. After dispersing evenly, vacuum defoaming is performed to obtain wet PU slurry; wherein the mass ratio of PU to modified wood powder is 4:1.

[0086] (2) Mix DMF and water at a mass ratio of 1:9 to prepare a replacement solution.

[0087] (3) Using a four-sided wet film preparation device, the wet PU slurry in step (1) is coated on the release paper to form a film with a thickness of 400 μm. Then, it is placed in the replacement solution for 5 min. After the DMF in the film is replaced and the film is set, the residual DMF is removed by washing with water and then dried.

[0088] Comparative Example 3

[0089] A modified wood powder, the preparation method of which includes the following steps:

[0090] (1) Add 5g wood powder, 5g alkali lignin and 2g nano barium sulfate to 100g 90% ethanol aqueous solution, adjust the pH to 4-5 with glacial acetic acid, disperse in a homogenizer at high speed (1500 rpm) for 20 minutes, and after dispersion, keep stirring at low speed (900 rpm) and heat in a 50℃ water bath for 4 hours.

[0091] (2) Slowly add 0.9% of the total mass of wood powder, alkali lignin, nano barium sulfate, ethanol aqueous solution and silane coupling agent KH570 to carry out the reaction; after the reaction is completed, filter, wash with water, dry in an oven at 60°C, and then let it dry naturally to obtain the product.

[0092] The modified wood powder obtained above is then used to prepare synthetic leather, specifically including the following steps:

[0093] (1) Heat the PU (090C) open explosion-proof to about 80°C, then mix DMF and modified wood powder in a mass ratio of 5:1 and add the above PU. After dispersing evenly, vacuum defoaming is performed to obtain wet PU slurry; wherein the mass ratio of PU to modified wood powder is 4:1.

[0094] (2) Mix DMF and water at a mass ratio of 1:9 to prepare a replacement solution.

[0095] (3) Using a four-sided wet film preparation device, the wet PU slurry in step (1) is coated on the release paper to form a film with a thickness of 400 μm. Then, it is placed in the replacement solution for 5 min. After the DMF in the film is replaced and the film is set, the residual DMF is removed by washing with water and then dried.

[0096] Comparative Example 4

[0097] A modified lignin, the preparation method of which includes the following steps:

[0098] (1) Add 10g of alkali lignin and 2g of nano barium sulfate to 100g of 90% ethanol aqueous solution, adjust the pH to 4-5 with glacial acetic acid, disperse in a homogenizer at high speed (1500 rpm) for 20 minutes, and after dispersion, keep stirring at low speed (900 rpm) and heat in a 50℃ water bath for 4 hours.

[0099] (2) Slowly add 1.25% of the total mass of alkali lignin, nano barium sulfate, ethanol aqueous solution and silane coupling agent KH570 to carry out the reaction; after the reaction is completed, filter, wash with water, dry in an oven at 60°C, and then let it dry naturally to obtain the product.

[0100] The modified lignin obtained above is then used to prepare synthetic leather, specifically including the following steps:

[0101] (1) Heat the PU (090C) open explosion-proof to about 80°C, then mix DMF and modified lignin at a mass ratio of 5:1 and add the above PU. After dispersing evenly, vacuum defoaming is performed to obtain wet PU slurry; wherein the mass ratio of PU to modified lignin is 4:1.

[0102] (2) Mix DMF and water at a mass ratio of 1:9 to prepare a replacement solution.

[0103] (3) Using a four-sided wet film preparation device, the wet PU slurry in step (1) is coated on the release paper to form a film with a thickness of 400 μm. Then, it is placed in the replacement solution for 5 min. After the DMF in the film is replaced and the film is set, the residual DMF is removed by washing with water and then dried.

[0104] Comparative Example 5

[0105] A modified wood powder, the preparation method of which includes the following steps:

[0106] (1) Add 10g of wood powder and 2g of nano barium sulfate to 100g of 90% ethanol aqueous solution, adjust the pH to 4-5 with glacial acetic acid, disperse in a homogenizer at high speed (1500 rpm) for 20 minutes, and after dispersion, keep stirring at low speed (900 rpm) and heat in a 50℃ water bath for 4 hours.

[0107] (2) Slowly add 1.25% of the total mass of wood powder, nano barium sulfate, ethanol aqueous solution and silane coupling agent KH570 to carry out the reaction; after the reaction is completed, filter, wash with water, dry in an oven at 60°C, and then let it dry naturally to obtain the product.

[0108] The modified wood powder obtained above is then used to prepare synthetic leather, and the preparation process is as follows: Figure 1 As shown, the specific steps include the following:

[0109] (1) Heat the PU (090C) open explosion-proof to about 80°C, then mix DMF and modified wood powder in a mass ratio of 5:1 and add the above PU. After dispersing evenly, vacuum defoaming is performed to obtain wet PU slurry; wherein the mass ratio of PU to modified wood powder is 4:1.

[0110] (2) Mix DMF and water at a mass ratio of 1:9 to prepare a replacement solution.

[0111] (3) Using a four-sided wet film preparation device, the wet PU slurry in step (1) is coated on the release paper to form a film with a thickness of 400 μm. Then, it is placed in the replacement solution for 5 min. After the DMF in the film is replaced and the film is set, the residual DMF is removed by washing with water and then dried.

[0112] Verification Example 1

[0113] Infrared spectroscopy analysis was performed on the wood powders prepared in Comparative Example 5 and Example 1, respectively. The results are as follows: Figure 2 As shown. The results show 1040–1100cm -1 The peak is a marker peak for silane modification (Si-O bond). The peak at 1040 cm⁻¹ is observed in sample 5 of comparative example. -1 A significant strong peak is present at 3400 cm⁻¹, clearly pointing to the Si-OC (siloxane bond) or Si-O-Si (siloxane bridge bond) successfully introduced by silane modification. -1 The broad peak (OH) of the phenolic / alcoholic hydroxyl groups (-OH) in lignin / wood flour shows a slight decrease in peak value after silanization, indicating that some -OH groups participate in the reaction to form Si-OC. This proves that the silane coupling agent reacts with the hydroxyl groups in lignin / wood flour to form Si-OR (R represents the lignin / wood flour group, whose characteristic peak is located at 1000–1100 cm⁻¹). -11450-1600cm -1 The characteristic peak of the lignin aromatic ring structure was observed in the sample of Example 1 at 1600 cm⁻¹. -1 and 1510cm -1 The presence of a clear double peak indicates the C=C vibration of the lignin aromatic skeleton (guaiacyl / syringyl unit), meaning that silane modification did not destroy the lignin aromatic structure.

[0114] In the experiment, it was observed that the sample in Comparative Example 1 was prone to clumping and difficult to disperse, which was not conducive to production. However, the wood powder in Example 1 of this invention, after being treated with a hybrid interpenetrating network coating process modified by lignin, exhibited better dispersibility.

[0115] Verification Example 2

[0116] The morphology of the synthetic leathers prepared in Example 1 and Comparative Example 1 was examined using a scanning electron microscope. Figure 3 The images show SEM images of the sample surface in Example 1 at magnifications of 100, 180, and 500. Figure 4 The images show SEM images of the sample surface of Comparative Example 1 at magnifications of 40, 100, and 140. The results show that the synthetic leather prepared in Example 1 of this invention has a relatively smooth surface, indicating good sizing leveling properties. Figure 3 The surface of the synthetic leather sample prepared in Comparative Example 1 was relatively rough and had poor uniformity. Figure 4 Meanwhile, during the experiment, it was observed that the powder in Example 1 was easy to disperse and the dust was not easily stirred up. The slurry had good leveling properties, which helps to increase the amount of powder added, increase the solid content, and reduce the loss during the transfer process. This helps to reduce the engineering difficulty and improve the surface smoothness.

[0117] Furthermore, the mechanical properties (tensile strength (σtM) (MPa) and elongation at break (εtb) (%)) of the synthetic leather samples prepared in Examples 1-4 and Comparative Examples 1-5 were tested respectively, and the results are as follows: Figure 5 As shown in Table 1, the results demonstrate that by introducing a silane coupling agent and adjusting the ratio of wood flour to lignin and the reaction parameters, the embodiments of the present invention successfully achieved a good overall balance between tensile strength (2.16-2.40 MPa), elongation at break (180-264%), and modulus of elasticity (3.74-6.77 MPa), exhibiting excellent mechanical properties and moderate strength with flexibility. This is mainly attributed to the silane coupling agent effectively improving the interfacial compatibility between the biomass filler (wood flour / lignin) and the matrix, promoting stress transfer, and thus improving strength without significantly sacrificing toughness.

[0118] In comparison, Comparative Example 1 showed the lowest tensile strength and elongation at break, demonstrating the role of silane coupling agent and lignin, while also highlighting the specific requirements for their dosage. In Comparative Example 3, the elongation at break of the synthetic leather was significantly low when the silane coupling agent content was low. In Comparative Example 2, although sodium lignin sulfonate exhibited good solubility in ethanol aqueous solution, it performed poorly in DMF solution. In contrast, alkali lignin showed greater stability in both solutions. Comparative Example 4 shows that wood powder, as the main filler, plays a crucial role in structural support and toughness; the lack of wood powder significantly reduces its mechanical properties. Furthermore, this invention has also found through extensive experiments that excessive addition of lignin can lead to over-reaction and reduced toughness. Therefore, a suitable ratio of wood powder to lignin needs to be maintained. Extensive experimental data indicates that a wood powder to lignin mass ratio of 1-2.5:1 is optimal.

[0119] The silane coupling agent KH570 (3-(2,3-epoxypropoxy)propyltriethoxysilane) has three silanol groups per molecule. Theoretically, it can react with one, two, or three hydroxyl groups in lignin or wood powder to form single-point, double-point, or triple-point anchoring, resulting in a very strong bond. Simultaneously, the silanol groups between silane molecules also condense to form a Si-O-Si network, further encapsulating and bonding to the surface of lignin and wood powder particles. Within a certain range, increasing the amount of silane coupling agent can significantly improve the mechanical properties of modified wood powder; however, excessive amounts will significantly increase the water absorption rate of the modified wood powder. Extensive research has found that the optimal silane coupling agent concentration is between 1.25% and 1.75%. Since wood powder carries relatively few hydroxyl groups, the effect of modifying wood powder with silane alone is not significant. Therefore, introducing lignin can greatly increase the number of hydroxyl groups, resulting in an increase in the number of Si-O-Si bonds, thereby improving product performance. Simultaneously, after the reaction, the surfaces of lignin and wood powder particles are endowed with reactive epoxy groups. These epoxy groups on the biomass surface, after ring-opening at higher temperatures, can interact with polyurethane, further improving mechanical properties. Nano-barium sulfate typically contains a small number of hydroxyl groups (-OH), due to its high surface energy at the nanoscale and the adsorption of water molecules during the preparation process. These hydroxyl groups can undergo dehydration condensation with the hydrolyzed silanols (-Si-OH) of silanes, forming Si-O-Ba covalent bonds that interlock with the biomass, greatly improving the dispersion stability of modified biomass in organic polymers and effectively preventing the modified powder from agglomerating during storage. Nano-barium sulfate can also improve the drape and weight of synthetic leather, enhance weather resistance, heat resistance, and chemical corrosion resistance, improve surface gloss, and increase the hardness and abrasion resistance of synthetic leather. Synthetic leather prepared by modifying wood powder using the hybrid interpenetrating network coating process of this invention exhibits better mechanical properties, which is beneficial for improving the tensile strength and durability of the material, significantly outperforming existing processes. Simultaneously, the surface uniformity of the samples treated with the hybrid interpenetrating network coating process is significantly better than that of the original process, demonstrating better leveling properties in the slurry, which is more conducive to actual production. In summary, the addition of lignin can significantly improve the tensile strength and other mechanical properties of the product; the silane coupling agent modification can further enhance the mechanical properties while improving the product's flexibility.

[0120] Table 1

[0121] Material Sample thickness (d) (mm) Tensile strength (σtM) (MPa) Elongation at break (εtb) (%) Elastic modulus (Et) (MPa) Example 1 0.4 2.16433 180.8875 6.76836 Example 2 0.4 2.39805 240.6564 6.77495 Example 3 0.4 2.2856 263.8077 5.1163 Example 4 0.4 2.31257 228.9514 4.19847 Comparative Example 1 0.4 1.44592 113.0179 7.29686 Comparative Example 2 0.4 4.9278 170.5322 14.9689 Comparative Example 3 0.4 4.39357 91.43403 46.15512 Comparative Example 4 0.4 2.19687 74.94336 35.5478 Comparative Example 5 0.4 1.92547 125.9059 7.0275

[0122] The above detailed embodiments provide a specific description of the analytical methods involved in this invention. It should be noted that the above description is only intended to help those skilled in the art better understand the methods and ideas of this invention, and is not intended to limit the scope of the invention. Without departing from the principles of this invention, those skilled in the art can make appropriate adjustments or modifications to this invention, and such adjustments and modifications should also fall within the protection scope of this invention.

Claims

1. A method for the preparation of a lignin-based multi-dimensional interpenetrating network modified wood flour, characterized by, Includes the following steps: (1) Add wood powder, alkali lignin and nano barium sulfate to an ethanol aqueous solution, adjust the pH value with glacial acetic acid and pre-disperse, then place in a flask and heat in a water bath; (2) Add 1.25-1.75% of the total mass of wood powder, alkali lignin, nano barium sulfate, ethanol aqueous solution and silane coupling agent to react; after the reaction is completed, filter, wash and dry to obtain the product.

2. The production method according to claim 1, characterized by, The volume ratio of ethanol to water in the ethanol-water solution described in step (1) is 1-20:

1.

3. The preparation method according to claim 1, characterized in that, In step (1), the content of the wood powder in the ethanol aqueous solution is 2-15 wt%.

4. The production method according to claim 1, characterized by, In step (1), glacial acetic acid is used to adjust the pH to 4-5.

5. The preparation method according to claim 1, characterized in that, The water bath heating temperature in step (1) is 40-70℃; the time is 1-10h.

6. The preparation method according to claim 1, wherein the silane coupling agent in step (2) is selected from one or more of KH550, KH560, and KH570.

7. The lignin-based multidimensional interpenetrating network modified wood powder prepared by the preparation method according to any one of claims 1-6.

8. The application of lignin-based multidimensional interpenetrating network modified wood powder prepared by any one of claims 1-6 in the preparation of synthetic leather.

9. A method for preparing modified wood flour synthetic leather, characterized in that, Includes the following steps: (1) After mixing DMF and the modified wood powder prepared according to any one of claims 1-6 evenly, add polyurethane, disperse evenly, and then perform vacuum defoaming to obtain wet polyurethane slurry; (2) The wet polyurethane slurry obtained in step (1) is coated and then placed in a displacement solution for displacement reaction. After the displacement reaction is complete, it is washed with water and dried to obtain the final product.

10. The preparation method according to claim 9, characterized in that, The mass ratio of DMF to modified wood powder in step (1) is 3-15:1.

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