A method for improving dimensional stability of wood

Abstract

This invention relates to a method for improving the dimensional stability of wood, comprising the following steps: S1, a double-bonded acyl halide compound, an acid-binding agent, and a catalyst are dissolved in an inert solvent to form a reaction solution, and the wood after anhydrous treatment is vacuum impregnated; after removing the residual liquid, a grafting reaction is carried out by heating to obtain grafted modified wood; S2, molten paraffin is mixed with an oleophilic surfactant to form an oil phase, and a hydrophilic surfactant, silica sol, and polyethylene glycol diacrylate are dissolved in water to form an aqueous phase. The oil phase is added dropwise to the aqueous phase at a temperature higher than the melting point of paraffin to emulsify, obtaining an oil-in-water emulsion; S3, the grafted modified wood is vacuum impregnated in the emulsion and an initiator to obtain impregnated wood; S4, the impregnated wood is subjected to heat treatment. The method of this invention treats scabbard woods such as wenge, ipe, or windmill wood, exhibiting good dimensional stability, with a warpage of 4%~5%, a twist of 2%~4%, a fork deformation of <0.3%, and no obvious discoloration.

Description

Technical Field

[0001] This invention belongs to the field of wood processing technology, and specifically relates to a method for improving the dimensional stability of wood. Background Technology

[0002] A scabbard, also known as a sword sheath or sword chamber, is a sheath-shaped container used to hold and protect the sword. It is typically made of wood, and its internal shape must fit the sword precisely to secure it and facilitate drawing and sheathing. Scabbards are usually made of high-grade hardwoods such as ebony, rosewood, padauk, and wenge, and are crafted through intricate carving, gilding, and lacquering. However, scabbards are prone to cracking or warping in drier regions, affecting their dimensional stability. Impregnating the wood with paraffin wax is a common method to improve its dimensional stability; however, for high-grade hardwoods like ebony, wenge, or padauk, due to their high density and fine grain, conventional paraffin melt impregnation or paraffin emulsion impregnation methods suffer from limitations such as difficulty in penetration and uneven treatment.

[0003] Patent CN118752571A discloses a wood dimensional stabilizer, its preparation method, and its application. The dimensional stabilizer comprises, by weight, 50-70 parts paraffin wax and 10-20 parts polyethylene glycol as a solubilizer. The melted paraffin wax flows into the internal pores of the wood to block moisture channels, and the solubilizer replaces the moisture in the wood, keeping it in a swollen state, thereby maintaining the dimensional stability of the wood. However, this technical solution mainly targets the dimensional stabilization treatment of conventional wood and does not address high-grade hardwoods used for sword sheaths. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for improving the dimensional stability of wood. The method first involves an esterification reaction between a double-bonded acyl halide compound and the hydroxyl groups in the wood under anhydrous conditions, introducing active double bonds into the wood, thus achieving graft modification. Next, a composite emulsion comprising paraffin wax, polyethylene glycol diacrylate, and silica sol is prepared and impregnated to allow the emulsion components to penetrate into the wood. Finally, heat treatment causes the polyethylene glycol diacrylate to copolymerize with the grafted double-bonded acyl halide compound, forming a chemical anchor. Simultaneously, paraffin wax fills the pores within the wood, and silica sol forms an inorganic reinforcing skeleton, thereby achieving a synergistic effect of chemical anchoring, physical filling, and inorganic reinforcement, effectively improving the dimensional stability of the wood.

[0005] Specifically, the present invention adopts the following technical solutions to achieve the above objectives:

[0006] A method for improving the dimensional stability of wood includes the following steps:

[0007] S1. Dissolve the double-bonded acyl halide compound, acid binder, and catalyst in a solvent inert to the acyl halide to form a reaction solution; place the anhydrous wood in a sealed container, evacuate it, add the reaction solution for impregnation, remove the residual reaction solution and rinse the wood surface, then heat it to carry out a grafting reaction to obtain grafted modified wood.

[0008] S2. Paraffin wax is heated and melted, and an oleophilic nonionic surfactant is added to form an oil phase; a hydrophilic nonionic surfactant is dissolved in water, and silica sol and polyethylene glycol diacrylate are added to form an aqueous phase; the oil phase is added dropwise to the aqueous phase at a temperature higher than the melting point of paraffin wax to emulsify and obtain an oil-in-water emulsion.

[0009] S3. Place the grafted modified wood obtained in step S1 into a sealed container, vacuum it, add the emulsion and initiator prepared in step S2, and perform impregnation treatment to obtain impregnated wood.

[0010] S4. Heat-treat the impregnated wood.

[0011] Further, in step S1, based on the dry weight of the anhydrous wood, the amount of the double-bonded acyl halide compound is 3-5 wt%, and the double-bonded acyl halide compound is selected from at least one of acryloyl chloride, methacryloyl chloride, and chlorobutenoate; the amount of the acid-binding agent is 1.3-2 times the mass of the double-bonded acyl halide compound, and the acid-binding agent is selected from at least one of pyridine and triethylamine; the amount of the catalyst is 0.5-1.5 wt% of the double-bonded acyl halide compound, and the catalyst is 4-dimethylaminopyridine; the solvent inert to the acyl halide is selected from dichloromethane (DCM) or acetonitrile, and the concentration of the reaction solution is 8-15 wt%. "Based on the dry weight of the anhydrous wood" means that the dry weight of the anhydrous wood is 100%, and the mass percentage of other substances relative to the dry weight of the wood.

[0012] Further, in step S1, the wood is selected from wenge, ipe, or windmill wood, and is sawn into boards 100-200mm long × 20-40mm wide × 20-40mm thick; the anhydrous treatment conditions are: soaking the wood in anhydrous acetone for 12-24 hours, and then vacuum drying at 40-60℃ to constant weight. Acyl halide compounds containing double bonds are sensitive to water, therefore anhydrous treatment of the wood is necessary.

[0013] Further, in step S1, the vacuuming conditions are: vacuuming to -0.08~-0.095MPa and maintaining it for 20~60min; the impregnation conditions are: impregnation temperature 20~30℃, impregnation time 1~4h; the rinsing is rinsing the wood surface with acetone.

[0014] Further, in step S1, the grafting reaction conditions are: heat treatment at 50~60℃ for 2~4 hours, after the reaction is completed, the wood is taken out, the surface of the wood is rinsed with acetone, and vacuum dried at 40~60℃ to constant weight.

[0015] In step S1, air is first removed from the pores of the wood by vacuuming. The wood is then immersed in the reaction solution, and under vacuum, the reaction solution fully fills the pores of the wood. Afterward, the residual reaction solution is drained, and the wood is washed with acetone to remove the adsorbed reaction solution from the wood surface. The wood is then heated, and the acyl halide compounds containing double bonds in the pores undergo an acylation reaction with the hydroxyl groups in the wood to generate ester groups. This chemically introduces the double-bonded acyl halide compounds into the interior of the wood pores. This invention is not suitable for using alkenylsilane coupling agents. Alkenylsilanes are generally more suitable for particulate materials. For large, planar wood, alkenylsilanes have low grafting rates and are prone to self-polymerization. Acyl halide compounds containing double bonds have high grafting efficiency, and their double bonds have higher copolymerization activity.

[0016] Further, in step S2, based on the dry weight of the grafted and modified wood from step S1, the amounts of each component are: paraffin 15-25 wt%, polyethylene glycol diacrylate 5-10 wt%, and silica sol 3-7 wt% (by solids weight), preferably 20-25 wt% paraffin, 5-8 wt% polyethylene glycol diacrylate, and 3-5 wt% silica sol (by solids weight). The amount of the lipophilic nonionic surfactant is 1 wt%-3 wt% of paraffin; the amount of the hydrophilic nonionic surfactant is 1 wt%-4 wt% of polyethylene glycol diacrylate. "Based on the dry weight of the grafted and modified wood from step S1" means that the dry weight of the grafted and modified wood from step S1 is 100%, and the mass percentage of other substances relative to the dry weight of the grafted and modified wood.

[0017] Further, in step S2, the paraffin wax has a melting point of 50-65°C; the lipophilic nonionic surfactant has an HLB value ≤6, specifically selected from at least one of Span-80 and Span-60; the polyethylene glycol diacrylate has a number-average molecular weight of 400-700 for the polyethylene glycol segments; the hydrophilic nonionic surfactant has an HLB value of 12-14, specifically selected from alkyl glycosides (APG); and the silica sol has a median particle size D50 of 10-50 nm and a solid content of 20-30 wt%.

[0018] Further, in step S2, the temperatures of the oil phase and the aqueous phase are each independently set to 75~85℃. In the emulsion, by adjusting the amount of water used in the aqueous phase, the paraffin content in the emulsion is made to be 20~30wt% of the total emulsion mass, and the median particle size D50 of the emulsion is 100~300nm.

[0019] Further, in step S3, the vacuuming conditions are: vacuuming to -0.08~-0.095 MPa and maintaining it for 20~60 minutes; the initiator is at least one of ammonium persulfate, potassium persulfate, and sodium persulfate, and the amount of initiator is 1~2 wt% of polyethylene glycol diacrylate; the impregnation conditions are: impregnation temperature 25~40℃, impregnation time 1~4 hours. Through the impregnation treatment in step S3, the emulsion containing paraffin in the oil phase and polyethylene glycol diacrylate and silica sol in the aqueous phase fully penetrates into the pores inside the wood. Those skilled in the art will understand that the initiator should not be added in step S2 to avoid premature self-polymerization of polyethylene glycol diacrylate at the emulsification temperature.

[0020] Further, in step S4, the heat treatment conditions are as follows: first, hold at 40-50℃ for 4-6 hours, then raise the temperature to 65-75℃ and hold for 6-8 hours, and finally hold at 90-110℃ for 1-2 hours. During the heat treatment in step S4, the emulsion breaks down, the water slowly evaporates, and the polyethylene glycol diacrylate in the aqueous phase undergoes a copolymerization reaction with the acyl halide compounds containing double bonds that have been grafted into the pores of the wood under heating, forming a high-molecular cross-linked network. This network is chemically anchored to the wood, occupying part of the space within the pores and producing a permanent and stable swelling effect. At the same time, paraffin melts and fills the pores and capillaries of the wood, physically filling them and cutting off the entry path of water. The nano-silica particles in the silica sol penetrate and fill the finer micropores in the wood, thus acting as a support like a skeleton and further preventing the entry of water. The synergistic effect of the above factors effectively improves the dimensional stability of the wood.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The method of this invention treats scabbard woods such as chicken wing wood, ipe wood, or windmill wood with good dimensional stability. The warping of the treated wood is only 4% to 5%, and the twisting is only 2% to 4%. When the treated wood is chicken wing wood, the relative deformation of the fork teeth is only 0.02% to 0.04%. When the treated wood is ipe wood or windmill wood, the deformation of the fork teeth does not exceed 0.3%. Moreover, the treatment method of this invention has no significant adverse effect on the color of the wood. The total color difference value ΔE is less than 15, and no blue tone appears. Attached Figure Description

[0023] Figure 1 These are comparative photographs of the wood from Examples 1, 6, and 7 before and after treatment by the method of the present invention.

[0024] Figure 2 This is a schematic diagram of a fork-tooth stress test piece. Detailed Implementation

[0025] The present invention will be described below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0026] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available; and the parts are parts by weight.

[0027] Paraffin wax has a melting point of approximately 58°C.

[0028] Chicken wing wood comes from Congo in Africa; Ipe wood comes from Brazil; and windmill wood comes from Mozambique.

[0029] Polyethylene glycol diacrylate, PEG400-DA and PEG700-DA, were purchased from Proon (Tianjin) Technology Co., Ltd., with number-average molecular weights of 400 and 700 for their polyethylene glycol segments, respectively.

[0030] Silica sol, McLean brand, purchased from Hefei Shangcheng Experimental Supplies Co., Ltd., with a solid content of 20 wt% and a median particle size D50 of 30 nm.

[0031] Example 1

[0032] A method for improving the dimensional stability of wood includes the following steps:

[0033] S1. Cut the chicken wing wood into boards 100mm long × 20mm wide × 20mm thick, then soak them in anhydrous acetone for 12 hours. After soaking, remove the boards and vacuum dry them at 50℃ to constant weight. Based on the dry weight of the chicken wing wood boards, weigh 3wt% of methacryloyl chloride. Dissolve methacryloyl chloride, triethylamine, and 4-dimethylaminopyridine in acetonitrile at a mass ratio of 1:1.5:0.01 to form a 10wt% reaction solution. Place the solution in an impregnation tank, evacuate to -0.09MPa and maintain for 30 minutes. Then add the reaction solution to immerse the chicken wing wood boards at 25℃ for 3 hours. After impregnation, drain the residual reaction solution and rinse the wood surface three times with acetone. Then keep the solution at 50℃ for 2 hours to carry out the grafting reaction. After the reaction, remove the chicken wing wood boards, wash the wood surface twice with acetone, and vacuum dry them at 50℃ to constant weight to obtain grafted modified chicken wing wood.

[0034] S2. Based on the dry weight of the grafted and modified chicken wing wood from step S1, weigh 20 wt% paraffin wax, 5 wt% PEG400-DA, and 3 wt% silica sol (by solids mass). Heat the paraffin wax to 75°C until completely melted, then add 2 wt% Span-80 (by mass of paraffin wax) and stir until homogeneous to form an oil phase. Dissolve alkyl glycoside (2 wt% by mass of PEG400-DA) in pure water, add the silica sol and stir until homogeneous, then add the PEG400-DA and stir until homogeneous to form an aqueous phase. Subsequently, raise the temperature of the aqueous phase to 75°C, and add all the oil phase dropwise to the aqueous phase within 30 minutes while stirring at 8000 r / min. After the dropwise addition is complete, continue stirring and emulsifying for 30 minutes, then add pure water to adjust the concentration to obtain an oil-in-water emulsion with a paraffin wax content of 25 wt% (the median particle size D50 of the emulsion is approximately 220 nm).

[0035] S3. Place the grafted modified chicken wing wood obtained in step S1 into an impregnation tank, evacuate to -0.09MPa and maintain for 30 minutes, then add all the emulsion obtained in step S2 and potassium persulfate (1.5wt% of PEG400-DA), impregnate at 40°C for 3 hours, release the pressure after impregnation, drain the residual liquid, and obtain impregnated chicken wing wood.

[0036] S4. First, heat the soaked chicken wing wood at 45℃ for 4 hours, then raise the temperature to 70℃ and heat for 6 hours, and finally heat it at 95℃ for 1 hour for heat treatment.

[0037] Example 2

[0038] The rest is the same as in Example 1, except that in step S2, based on the dry weight of the grafted and modified chicken wing wood in step S1, the amount of each component is: paraffin 15wt%, PEG400-DA 5wt%, and silica sol (by solids mass) 3wt%.

[0039] Example 3

[0040] The rest is the same as in Example 1, except that in step S2, based on the dry weight of the grafted modified chicken wing wood in step S1, the amount of each component is: paraffin 25wt%, PEG400-DA 8wt%, and silica sol (by solids mass) 5wt%.

[0041] Example 4

[0042] The rest is the same as in Example 1, except that in step S2, based on the dry weight of the grafted and modified chicken wing wood in step S1, the amount of each component is: paraffin 25wt%, PEG400-DA 10wt%, and silica sol (by solids mass) 7wt%.

[0043] Example 5

[0044] The rest is the same as in Example 1, except that the mass of the methacryloyl chloride in step S1 is 5 wt% of the dry weight of the chicken wing wood board.

[0045] Example 6

[0046] The rest is the same as in Example 1, except that: Ipe wood is used instead of chicken wing wood, and methacryloyl chloride is used instead of butenoic acid chloride in step S1.

[0047] Example 7

[0048] The rest is the same as in Example 1, except that windmill wood is used instead of chicken wing wood; and PEG700-DA is used instead of PEG400-DA in step S2.

[0049] Comparative Example 1

[0050] The rest is the same as in Example 1, except that: the chemical grafting modification in step S1 is omitted, and chicken wing wood is used instead of grafted and modified chicken wing wood in step S3; specifically:

[0051] S1. Cut the chicken wing wood into boards with a length of 100mm, a width of 20mm, and a thickness of 20mm. Then soak them in anhydrous acetone for 12 hours. After soaking, take out the boards and vacuum dry them at 50℃ to constant weight to obtain pretreated chicken wing wood.

[0052] S2. Based on the dry weight of the pretreated chicken wing wood in step S1, the other conditions are the same as in Example 1.

[0053] S3. Place the pretreated chicken wing wood from step S1 into an impregnation tank, and keep the other conditions the same as in Example 1.

[0054] S4, Same as Example 1.

[0055] Comparative Example 2

[0056] The rest is the same as in Example 1, except that PEG400-DA is not added in step S2; specifically:

[0057] S1, Same as Example 1;

[0058] S2. Based on the dry weight of the grafted and modified chicken wing wood in step S1, weigh 20 wt% paraffin wax and 5 wt% silica sol (by solids mass). Heat the paraffin wax to 75°C until completely melted, then add 2 wt% Span-80 (by weight of paraffin wax) and stir until homogeneous to form an oil phase. Dissolve alkyl glycosides (consistent with the absolute amount of alkyl glycosides in Example 1) in pure water, add the silica sol, and stir until homogeneous to form an aqueous phase. Then raise the temperature of the aqueous phase to 75°C, and add all the oil phase dropwise to the aqueous phase within 30 minutes while stirring at 8000 r / min. After the dropwise addition is complete, continue stirring and emulsifying for 30 minutes, and add pure water to adjust the concentration to obtain an oil-in-water emulsion with a paraffin wax content of 25 wt%.

[0059] S3. Place the grafted modified chicken wing wood obtained in step S1 into an impregnation tank, evacuate to -0.09MPa and maintain for 30 minutes, then add all the emulsion obtained in step S2, impregnate at 40°C for 3 hours, release the pressure after impregnation, drain the residual liquid, and obtain impregnated chicken wing wood.

[0060] S4, Same as Example 1.

[0061] Comparative Example 3

[0062] The rest is the same as in Example 1, except that silica sol is not added in step S2.

[0063] Comparative photographs of the wood from Examples 1, 6, and 7 before and after treatment by the method of the present invention are shown below. Figure 1 As shown.

[0064] Testing and Analysis

[0065] The wood samples obtained from the above examples and comparative examples were subjected to the following performance tests.

[0066] 1) Warping deformation test

[0067] The wood samples obtained from the above embodiments and comparative examples were placed in a standard environment (temperature 20±2℃, relative humidity 65±5%) for 24 hours, and then subjected to warping deformation tests. Warping deformation mainly includes warping and twisting. Warping degree (WP) refers to the ratio of the maximum bending arch height to the horizontal length of the inner curved surface, and the calculation formula is as follows:

[0068]

[0069] In the formula, h is the maximum bending arch height (mm), and L is the inner curvature length (mm).

[0070] Twist (TW) is the ratio of the maximum height by which a board deviates from its flat surface to the length of the test board. The calculation formula is as follows:

[0071]

[0072] In the formula, h is the maximum height of the plate deviating from the plane (mm); L is the length of the test material (mm).

[0073] 2) Fork tooth deformation test

[0074] The wood samples obtained from the above embodiments and comparative examples were sawn into fork-tooth stress test pieces (see schematic diagram). Figure 2 As shown in the figure, after sawing, the fork teeth are dried in a drying oven at 103±2℃ for 2 hours, and then conditioned in a constant temperature and humidity chamber (temperature 20±2℃, relative humidity 65±5%) for 24 hours to ensure a uniform moisture content distribution and fully release internal stress. The relative deformation (Y) of the fork teeth is calculated according to the following formula as an evaluation index of residual stress in the wood.

[0075] Y=

[0076] In the formula, H is the original tooth width (mm) of the sawn fork tooth, H1 is the tooth width (mm) at the same position after stress release deformation, and S is the length of the fork tooth (mm). The larger the Y value, the greater the residual stress inside the wood.

[0077] 3) Color difference test

[0078] The wood samples obtained from the above embodiments and comparative examples were placed in a standard environment (temperature 20±2℃, relative humidity 65±5%) for 24 hours, and then measured using a colorimeter (such as a Konica Minolta CM-2300d) under D65 light source and 10° viewing angle. Untreated sword sheath wood from the same batch of raw materials was used as a control (standard reference sample). The L, a, and b values ​​of untreated wood (control group) and wood treated according to the embodiments or comparative examples of this invention (treated group) were measured respectively. Three parallel samples were set for each treated group, and three different locations were randomly measured for each sample, and the average value was taken. The color difference between the treated group and the control group was calculated using the following formula: ΔL is the lightness difference, Δa is the red-green difference, Δb is the yellow-blue difference, and ΔE is the total color difference value, reflecting the overall change in color before and after treatment. The smaller the value, the less the treatment method affects the original color of the wood.

[0079] ΔL= L 处理- L 对照

[0080] Δa = a 处理 - a 对照

[0081] Δb=b 处理 - b 对照

[0082] ΔE=

[0083] The specific data on warpage, twist, fork tooth deformation, and total color difference ΔE of the above-mentioned embodiments and comparative samples are summarized in Table 1.

[0084] Table 1. Warping, Tooth Deformation, and Color Difference Tests

[0085]

[0086] As shown in Table 1, the *Zanthoxylum bungeanum* wood treated by the method of the present invention in Examples 1-5 exhibits excellent dimensional stability, with warpage of only 4%–5%, twist of only 2%–4%, and fork deformation of only 0.02%–0.04%, far superior to Comparative Examples 1-3. The present invention also shows good applicability to sword sheath wood from *Ipe* and *Pterocarpus serratus*. *Ipe* wood in Example 6 and *Pterocarpus serratus* wood in Example 7 are high-growth-stress species, and their fork deformation after treatment does not exceed 0.3%, which is higher than that of *Zanthoxylum bungeanum*, but this is due to the differences in material properties inherent to the tree species; moreover, their warpage and twist are at the same excellent level as *Zanthoxylum bungeanum*. Furthermore, the treatment method of the present invention has no significant adverse effect on the color of the wood, with the total color difference value ΔE being less than 15, and no blue tint appearing.

Claims

1. A method for improving the dimensional stability of wood, characterized in that, Includes the following steps: S1. Dissolve the double-bonded acyl halide compound, acid binder, and catalyst in a solvent inert to the acyl halide to form a reaction solution; place the anhydrous wood in a sealed container, evacuate it, add the reaction solution for impregnation, remove the residual reaction solution and rinse the wood surface, then heat it to carry out a grafting reaction to obtain grafted modified wood. S2. Paraffin wax is heated and melted, and an oleophilic nonionic surfactant is added to form an oil phase; a hydrophilic nonionic surfactant is dissolved in water, and silica sol and polyethylene glycol diacrylate are added to form an aqueous phase; the oil phase is added dropwise to the aqueous phase at a temperature higher than the melting point of paraffin wax to emulsify and obtain an oil-in-water emulsion. S3. Place the grafted modified wood obtained in step S1 into a sealed container, vacuum it, add the emulsion and initiator prepared in step S2, and perform impregnation treatment to obtain impregnated wood. S4. Heat-treat the impregnated wood.

2. The method according to claim 1, characterized in that, In step S1, based on the dry weight of the anhydrous wood, the amount of the double-bonded acyl halide compound is 3-5 wt%, and the double-bonded acyl halide compound is selected from at least one of acryloyl chloride, methacryloyl chloride, and chlorobutenoate; the amount of the acid-binding agent is 1.3-2 times the mass of the double-bonded acyl halide compound, and the acid-binding agent is selected from at least one of pyridine and triethylamine; the amount of the catalyst is 0.5-1.5 wt% of the double-bonded acyl halide compound, and the catalyst is 4-dimethylaminopyridine; the solvent that is inert to the acyl halide is selected from dichloromethane (DCM) or acetonitrile, and the concentration of the reaction solution is 8-15 wt%.

3. The method according to claim 1, characterized in that, In step S1, the wood is selected from chicken wing wood, ipe wood or windmill wood, and the wood is sawn into boards with a length of 100~200mm × width of 20~40mm × thickness of 20~40mm; the conditions for the waterless treatment are: soaking the wood in anhydrous acetone for 12~24h, and then vacuum drying at 40~60℃ to constant weight.

4. The method according to claim 1, characterized in that, In step S1, the vacuuming conditions are: vacuuming to -0.08~-0.095MPa and maintaining it for 20~60 minutes; the impregnation conditions are: impregnation temperature 20~30℃, impregnation time 1~4h; the rinsing is to rinse the wood surface with acetone; the grafting reaction conditions are: holding the reaction at 50~60℃ for 2~4h, after the reaction is completed, the wood is taken out, the wood surface is rinsed with acetone, and vacuum dried at 40~60℃ to constant weight.

5. The method according to claim 1, characterized in that, In step S2, based on the dry weight of the grafted modified wood from step S1, the amounts of each component are as follows: paraffin 15-25 wt%, polyethylene glycol diacrylate 5-10 wt%, and silica sol 3-7 wt% (by solid mass); the amount of the lipophilic nonionic surfactant is 1 wt%-3 wt% of paraffin; and the amount of the hydrophilic nonionic surfactant is 1 wt%-4 wt% of polyethylene glycol diacrylate.

6. The method according to claim 1, characterized in that, In step S2, based on the dry weight of the grafted modified wood from step S1, the amounts of each component are: paraffin 20-25 wt%, polyethylene glycol diacrylate 5-8 wt%, and silica sol 3-5 wt% (by solid mass).

7. The method according to claim 1, characterized in that, In step S2, the paraffin wax has a melting point of 50-65°C; the lipophilic nonionic surfactant has an HLB value ≤6, specifically selected from at least one of Span-80 and Span-60; the polyethylene glycol diacrylate has a number-average molecular weight of 400-700 for the polyethylene glycol segments; the hydrophilic nonionic surfactant has an HLB value of 12-14, specifically selected from alkyl glycosides (APG); and the silica sol has a median particle size D50 of 10-50 nm and a solid content of 20-30 wt%.

8. The method according to claim 1, characterized in that, In step S2, the temperatures of the oil phase and the water phase are each independently 75~85℃. In the emulsion, by adjusting the amount of water used in the aqueous phase, the paraffin content in the emulsion is 20-30 wt% of the total emulsion mass, and the median particle size D50 of the emulsion is 100-300 nm.

9. The method according to claim 1, characterized in that, In step S3, the vacuuming conditions are: vacuuming to -0.08~-0.095MPa and maintaining it for 20~60min; the initiator is at least one of ammonium persulfate, potassium persulfate, and sodium persulfate, and the amount of initiator is 1~2wt% of polyethylene glycol diacrylate; the impregnation conditions are: impregnation temperature 25~40℃, impregnation time 1~4h.

10. The method according to claim 1, characterized in that, In step S4, the heat treatment conditions are as follows: first, keep the temperature at 40~50℃ for 4~6 hours, then raise the temperature to 65~75℃ and keep it for 6~8 hours, and finally keep it at 90~110℃ for 1~2 hours.

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