Method for preparing mildew-proof and insect-resistant wood by adopting sulfuryl fluoride modification strategy
Modified wood is prepared by covalent reaction of sulfuryl fluoride with the phenolic hydroxyl groups of wood lignin, which solves the risks of chemical migration and environmental protection, and achieves long-lasting anti-mildew and anti-insect effects.
Patent Information
- Application Number
- CN202511774171.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-28
- Publication Date
- 2026-01-16
AI Technical Summary
Existing methods for preventing mold and insect infestation in wood have problems such as pesticide migration, environmental risks, and short-lasting protective effects.
Modified wood is prepared by chemically reacting sulfuryl fluoride with the phenolic hydroxyl groups of lignin in wood under alkaline conditions to achieve covalent bonding between wood and aryl fluorosulfate groups.
It significantly improves the anti-mildew and anti-insect properties of wood, prevents the migration of pesticides into the environment, and does not damage the wood structure.
Smart Images
Figure CN121340419A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of chemical modification of wood, specifically to a method and its application for in-situ covalent functionalization of wood by reacting sulfuryl fluoride (SO2F2) with the phenolic hydroxyl groups of lignin in wood to prepare mold-resistant and insect-resistant modified wood. Technical Background
[0002] Wood, as a renewable natural resource, is widely used in the construction and furniture industries and is favored for its excellent mechanical properties and appearance. However, wood is susceptible to damage from microorganisms, fungi, and insects during use, especially in humid environments. Wood easily absorbs water, providing conditions for the growth of mold and decay fungi, leading to rot, mildew, and discoloration. Furthermore, insect infestations such as termites can damage the wood structure and shorten its lifespan. Therefore, enhancing the mold and insect resistance of wood is crucial.
[0003] Currently, pesticide impregnation is a common method for treating wood to prevent mold and insects. This involves immersing the wood in a pesticide solution containing bactericides, insecticides, and preservatives, allowing the pesticides to penetrate the wood. Commonly used pesticides include pyrethroids, pentachlorophenol, and copper chromium arsenide (CCA). However, this method inevitably releases small-molecule active ingredients into the environment. This not only reduces the material's anti-mold and insect-resistant effects but also pollutes the environment and harms human health. For example, the research by Ahn SH et al. highlighted the controversial toxicity of chromium and arsenic released from CCA-treated wood to human health and the environment (J. Hazard. Mater., 2010, 175(1-3), 825-832). Therefore, although this method is simple to operate and low in cost, it poses environmental risks, pesticide residues, and short-lasting protective effects.
[0004] To overcome the aforementioned drawbacks, this invention proposes a method for modifying wood by covalently binding bioactive groups. Through a chemical reaction between sulfuryl fluoride and the phenolic hydroxyl groups of lignin in wood under alkaline conditions, covalent bonding between the wood and aryl fluorosulfate groups is achieved. Bioactivity tests show that this method of sulfuryl fluoride covalent modification can simultaneously improve the wood's resistance to mold and insects, while the covalent bonding effectively avoids the problem of active substances migrating into the environment associated with traditional impregnation treatments. Summary of the Invention
[0005] The purpose of this invention is to provide a method for modifying wood by reacting sulfuryl fluoride with phenolic hydroxyl groups in wood under specific conditions to prepare modified wood with aryl fluorosulfate groups, thereby solving the problems of agent migration, environmental risks, and short-lasting protective effects in existing anti-mildew and anti-insect treatment technologies.
[0006] To achieve the above objectives, the technical solution of the present invention is as follows:
[0007] Experimental equipment:
[0008] (1) Reaction vessel: a wide-mouth reaction flask made of glass or lined with PTFE, preferably 200-1000 mL;
[0009] (2) Vacuum device: A circulating water vacuum pump (ultimate vacuum degree ≤10 kPa) is connected in series with a vacuum dryer (volume 5-10L);
[0010] (3) Stirring device: magnetic stirrer with a speed range of 50-1500 rpm, equipped with a cylindrical stir bar covered with polytetrafluoroethylene.
[0011] Experimental steps:
[0012] (1) Soak the wood chips in a reaction flask containing alkaline reagents and organic solvents, and place the reaction flask in a vacuum dryer. After evacuating the vacuum device, fill it with sulfuryl fluoride gas.
[0013] (2) The reaction temperature is 10-40 ℃, and the reaction is continuously stirred with a magnetic stirrer for 1-48 hours;
[0014] (3) After the reaction is complete, the wood chips are cleaned with an organic solvent;
[0015] (4) The cleaned wood chips are air-dried naturally to obtain modified wood chips.
[0016] The alkaline reagent is selected from at least one of triethylamine, sodium hydroxide, potassium hydroxide, ammonia, calcium hydroxide, aluminum hydroxide, and lithium hydroxide.
[0017] The organic solvent is selected from at least one of acetonitrile, dichloromethane, tetrahydrofuran, acetone, methanol, ethanol, isopropanol, dimethyl sulfoxide, dimethylformamide, cyclohexanone, methyl ethyl ketone, ethyl acetate, chloroform, benzene, toluene, xylene, or water.
[0018] Preferably, the alkaline reagent in step (1) is triethylamine and the organic solvent is acetonitrile.
[0019] Preferably, the reaction in step (2) lasts for 24 hours.
[0020] Preferably, step (3) involves cleaning once every 48 hours, for a total of 3 cleanings.
[0021] Preferably, the natural drying conditions in step (4) are 25 ℃ and 50% RH, and the drying time is one week.
[0022] This invention also provides an application of the modified wood prepared by the method described above in the fields of mildew prevention and insect resistance.
[0023] Beneficial effects:
[0024] This invention achieves the connection between sulfuryl fluoride and wood through covalent bonding, effectively avoiding the problem of free small molecule active ingredients migrating into the environment in traditional impregnation methods, significantly improving the anti-mildew and anti-insect properties of wood, while not significantly affecting the structure of the wood itself. Detailed Implementation
[0025] This invention provides a novel method for modifying wood to resist mold and insects. The reaction system includes an alkaline reagent, an organic solvent, and reaction reagents. The specific implementation of this invention is further described in detail below with reference to examples.
[0026] Example 1
[0027] Pine wood chips measuring 50 mm × 50 mm × 2 mm were soaked in a solution containing triethylamine (8.35 g) and acetonitrile (130 g). After evacuation using a vacuum device, sulfuryl fluoride gas was introduced to ensure the reaction proceeded in a sulfuryl fluoride-filled environment. After magnetic stirring for 24 hours, the reaction was complete. The pine wood chips were then washed with acetonitrile, once every 48 hours for a total of 3 washes. They were then air-dried naturally for one week and then vacuum-dried for 12 hours to remove residual volatiles, yielding modified pine wood chips that retained the original wood texture. (See attached image) Figure 1 ).
[0028] Comparative Example 1
[0029] Pine wood chips measuring 50 mm × 50 mm × 2 mm were soaked in a solution containing triethylamine (8.35 g) and acetonitrile (130 g) without the introduction of sulfuryl fluoride gas. After magnetic stirring for 24 hours, the reaction was completed. The pine wood chips were then washed with acetonitrile, once every 48 hours for a total of 3 times. They were then air-dried naturally for 1 week and then desiccated in a vacuum desiccator for 12 hours to remove residual volatiles, yielding control pine wood chips A.
[0030] Comparative Example 2
[0031] Pine wood chips measuring 50 mm × 50 mm × 2 mm were soaked in a solution of acetonitrile (130 g) without the addition of alkaline reagents. The reaction was carried out under vacuum, followed by the introduction of sulfuryl fluoride gas to ensure a sulfuryl fluoride-filled environment. After magnetic stirring for 24 hours, the reaction was complete. The pine wood chips were then washed with acetonitrile, once every 48 hours for a total of 3 times. They were then air-dried naturally for one week and then vacuum-dried for 12 hours to remove residual volatiles, yielding control pine wood chips B (attached). Figure 1 ).
[0032] Comparative Example 3
[0033] Pine wood chips with dimensions of 50 mm × 50 mm × 2 mm were soaked in acetonitrile (130 g) solution without the introduction of sulfuryl fluoride gas for reaction. After magnetic stirring for 24 hours, the reaction was completed. The pine wood chips were washed with acetonitrile once every 48 hours for a total of 3 times, then air-dried naturally for 1 week, and finally desiccated in a vacuum desiccator for 12 hours to remove residual volatiles, yielding control pine wood chips C.
[0034] Example 2
[0035] Characterization and Testing
[0036] Surface SEM morphology analysis:
[0037] The logs from Example 1, Comparative Example 2, and the untreated logs were then cut into 5 mm × 5 mm pieces using a table saw. After gold spraying using a HITACHI MC1000 spray gun, the surface morphology of the wood was observed using a scanning electron microscope (SEM, Hitachi SU8020, accelerating voltage 5 kV). The results showed that there were no significant differences in the surface morphology of the three groups of samples: the log chips, the control pine chips B of Comparative Example 2, and the modified pine chips of Example 1, indicating that this method did not damage the microstructure of the wood (see Appendix). Figure 2 ).
[0038] Surface EDS elemental analysis:
[0039] Elemental composition was determined by energy-dispersive X-ray spectroscopy (EDS, HORIBA EMAX micro). Under the same testing conditions and detection limits, the EDS results showed that: no fluorine was detected on the surface of the untreated log sample (below the detection limit); the control pine chip B of Comparative Example 2 (introduced with sulfuryl fluoride, without the addition of alkali) also showed no fluorine after 12 h of vacuum residue removal; while the sample of Example 1 (introduced with sulfuryl fluoride and with the addition of organic alkali) showed stable detection of fluorine after 12 h of vacuum residue removal, with a fluorine atomic fraction of approximately 1.21 At% (see Table 1 and Appendix). Figure 3 ).
[0040] The above results indicate that fluorine can only be stably detected on the sample surface under the condition of "thioyl fluoride + alkali"; while in the absence of alkali, no detectable fluorine-containing groups are formed even when thioyl fluoride is introduced. Based on the reaction pathway, it can be inferred that the detected fluorine originates from the aryl fluorosulfate (Ar–O–SO2F) generated by the reaction of thioyl fluoride with the phenolic hydroxyl groups of lignin; this inference is consistent with the mechanism description of "bonding to the active sites of wood in the presence of an organic base and fixing it in a covalent form".
[0041] Table 1. Comparison of EDS elemental composition on the surface of logs, Comparative Example 2, and wood chips from Example 1.
[0042]
[0043] Cross-sectional EDS elemental analysis:
[0044] Line scanning of the interior (freshly cut sections of the upper and lower surfaces) of the modified pine chips in Example 1 after vacuum treatment was performed using an energy dispersive spectroscopy (EDS, Oxford Xplore 30). F (wt%≈0.43, At%≈0.30) was detected in the freshly cut sections of the pine chips, consistent with the inference that bonding also occurred in the inner layers. (See Table 2 and appendix) Figure 4 ).
[0045] Table 2. Elemental distribution within modified pine chips from Example 1
[0046]
[0047] Example 3
[0048] Antifungal test
[0049] Test operation reference standards:
[0050] The process references antibacterial coatings (HG / T 3950-2007), and the rating references the test method for mildew resistance of paint film (GB / T1741-2020).
[0051] Materials and experimental conditions:
[0052] The strain used was Aspergillus niger.
[0053] The substrate is nutrient salt agar medium;
[0054] The negative control sample was sterile filter paper (50 mm in diameter).
[0055] The blank sample is an untreated pine chip (50 mm × 50 mm × 2 mm);
[0056] The sample was the modified pine wood chip from Example 1;
[0057] The control samples were control pine wood chips A of Comparative Example 1 and control pine wood chips B of Comparative Example 2.
[0058] Test replication: Three replicates were set up for each sample and control sample;
[0059] Material pretreatment: Irradiate under ultraviolet light for 1 hour, then turn over and continue irradiation for 1 hour;
[0060] Sterilization conditions: The culture medium, petri dishes, sterile water and other materials used in the experiment were sterilized by autoclaving at 121 °C for 30 min.
[0061] Test method:
[0062] Activation of the strain: The strain was cultured in PDA slant medium at 28 ℃ for 12 days. After a clear mold layer appeared on the surface and a large number of spores were generated, it was taken out for use.
[0063] Preparation of spore suspension: Add a small amount of sterile water to the culture slant medium after culture. Gently scrape the surface mold spores with an inoculation needle and transfer them to an Erlenmeyer flask. Add approximately 50 mL of 0.05% Tween 80 physiological saline solution. Add 10-15 glass beads with a diameter of 5 mm to the Erlenmeyer flask and gently shake for 15 min. Then, plug the glass funnel with absorbent cotton, filter, count and observe under a microscope using a hemocytometer, and store for later use.
[0064] Preparation of plate culture medium: Evenly pour nutrient salt agar culture medium into a sterile petri dish (90 mm in diameter) to a thickness of 3 mm to 6 mm, and let it solidify before use.
[0065] Mold activity control: Place the negative control sample (sterile filter paper) on a plate culture medium. Spray the spore suspension with a sprayer containing freshly prepared spore suspension, ensuring it is thoroughly and evenly distributed on the culture medium and filter paper. Incubate for 7 days at 28°C and a relative humidity of 90% RH or higher. Clear fungal growth should be observed on the filter paper strip; otherwise, the test should be considered invalid and repeated.
[0066] Sample testing: Simultaneously, blank samples, Example 1, Comparative Example 1, and Comparative Example 2 were also spread on nutrient agar medium, and spore suspension was sprayed onto them, ensuring thorough and even coverage of the medium and samples. All samples were cultured for 28 days at a temperature of 28 ℃ and a relative humidity of 90% RH or higher.
[0067] Results observation: After the culture is completed, the test samples are taken out of the constant temperature and humidity incubator and visually inspected first. When the area with mold growth is less than 10%, they are observed under a microscope at 50x magnification. The mold resistance level is evaluated according to the following standards.
[0068] Sample mold resistance grade:
[0069] Level 0: No growth, meaning no growth is visible to the naked eye;
[0070] Level 1: Trace growth, the percentage of moldy area in the test sample is <10%;
[0071] Level 2: Small amount of growth, with the area of mold growth on the test sample ≥10% and <30%;
[0072] Level 3: Moderate growth, with the percentage of moldy area in the test sample ≥30% and <60%;
[0073] Level 4: Severe growth, with mold covering ≥60% of the test sample.
[0074] The statistical results of the antifungal test are shown in Table 3, and the specific comparison of antifungal effects is shown in the appendix. Figure 5 .
[0075] Table 3 Results of antifungal test
[0076]
[0077] The results of the anti-mold test showed that the negative control, blank sample (log) and comparative examples 1 and 2 were severely moldy (level 4), while Example 1 remained at level 0 for 28 days, showing stable anti-mold performance.
[0078] Example 4
[0079] Insect control test
[0080] Test operation reference standards:
[0081] Refer to the Technical Specification for Insect (Termite) Control of Wood (GB / T 29399-2012) and the Laboratory Test Method for the Toxicity of Wood Preservatives to Termites (GB / T 18260-2015).
[0082] Materials and experimental conditions:
[0083] Termites were selected as the test insect species.
[0084] The control group was the control pine wood chip C (50 mm × 50 mm × 2 mm) obtained from Comparative Example 3.
[0085] The sample was the modified pine wood chip (50 mm × 50 mm × 2 mm) obtained in Example 1.
[0086] Test replication: Five replicates were set up for each sample;
[0087] Sample pretreatment: Dry in a 40 ℃ constant temperature drying oven until constant weight;
[0088] Note: The dimensions used in this test are different from those commonly used in GB / T 18260-2015, and are set for this invention; other conditions are controlled according to standard caliber.
[0089] Test method:
[0090] Sample preparation: Clean the surface of the wood chips from Comparative Example 3 and Example 1 to remove debris and other adhering substances, ensuring that the sample surface is free of contamination.
[0091] Sample placement: Place the treated wood chips from Comparative Example 3 and Example 1 into culture bottles, ensuring that there is adequate space between the sample and the bottle wall.
[0092] Termite introduction: Add an appropriate amount of termites to the culture bottle, ensuring that the termites can freely contact the wood chips.
[0093] Environmental settings: Place the culture flasks in an environment with controllable temperature and humidity, at a temperature of (28±2)℃, relative humidity of (80±5)%, and without external sunlight.
[0094] Observations were conducted weekly throughout the four-week experiment. During observations, efforts were made to avoid disturbing the termites' normal activities, and data was recorded and analyzed through photography.
[0095] Insect-resistant properties of wood and the integrity level of the sample after being infested with insects:
[0096] Grade 0: The sample was almost completely destroyed by insects.
[0097] Level 4: Extremely severe decay. 50%–75% of the cross-sectional area is decayed.
[0098] Level 6: Severe borer damage, with 30%–50% of the cross-sectional area decayed.
[0099] Level 7: Moderate borer damage, with 10%–30% of the cross-sectional area showing signs of decay.
[0100] Level 8: Moderate borer damage. 3%–10% of the cross-sectional area is infested.
[0101] Level 9: Slight insect infestation, with a cross-sectional area of less than 3% infestation.
[0102] Grade 9.5: Minor ant trails or borer marks, with only 1-2 trails or borer marks.
[0103] Level 10: Sample intact
[0104] Determination of experimental validity:
[0105] The experiment is considered valid if the termites in the control group are active, at least three of the five control samples are at level 4, the average mass loss rate is above 40%, and the termite survival rate is above 50% at the end of the experiment.
[0106] The statistical results of the insect resistance experiment are shown in Table 4, and the specific comparison of insect resistance effects is shown in the appendix. Figure 6 .
[0107] Table 4 Insect control experiment results
[0108]
[0109] The results of the insect control test showed that the insect damage level of Example 1 after being infested by termites was 7-10, while that of Comparative Example 3 was 0-7, indicating that this method can significantly improve the resistance of wood to termites. Attached Figure Description
[0110] Figure 1 Examples and comparative examples show the macroscopic structures; where A represents the macroscopic effect of Example 1; B represents the macroscopic effect of Comparative Example 2; and C represents the macroscopic effect of the log.
[0111] Figure 2 The images show the material morphology of pine wood surfaces magnified 150 times using a scanning electron microscope; where A is the surface of untreated raw wood chips; B is the surface of modified wood chips B in Comparative Example 2; and C is the surface of modified pine wood chips from Example 1.
[0112] Figure 3 The EDS elemental analysis results show the distribution of six elements (C, N, O, F, S, P) on the surface of different samples, as shown in Table 1. A represents the elemental distribution on the surface of untreated raw wood chips; B represents the elemental distribution on the surface of control pine wood chips B in Comparative Example 2; and C represents the elemental distribution on the surface of modified pine wood chips in Example 1.
[0113] Figure 4 The images shown are scanning electron microscope (SEM) images and EDS line spectrum scan images of the cross-section of the modified pine wood chips in Example 1, magnified 500 times. Among them, A is a scanning electron microscope image of the internal cross-section of the modified pine wood chips, B is the distribution of C, O, F and S elements in the cross-section, and C is the distribution of F element.
[0114] Figure 5 This is a comparison chart of the antifungal test results. From left to right, the columns are: column a: negative control sample (sterile filter paper); column b: blank sample (logiced wood chips); column c: modified wood chips from Example 1; column d: control pine wood chip A from Comparative Example 1; and column e: control pine wood chip B from Comparative Example 2. Each column contains results from three parallel experiments.
[0115] Figure 6 This is the result of an insect control experiment; Figure 6 In Figure A, the results of five parallel insect control experiments of Example 1 are shown; in Figure B, the results of five parallel insect control experiments of Comparative Example 3 are shown.
Claims
1. A method for modifying wood, characterized in that: sulfuryl fluoride (SO2F2) is chemically reacted with the phenolic hydroxyl groups of wood in the presence of an alkaline reagent and an organic solvent or water to form a stable covalent bond, and the modified wood with antifungal and insect resistance is obtained after cleaning and drying; the alkaline reagent is at least one of triethylamine, sodium hydroxide, potassium hydroxide, aqueous ammonia, calcium hydroxide, aluminum hydroxide, and lithium hydroxide; the organic solvent is at least one of acetonitrile, dichloromethane, tetrahydrofuran, acetone, methanol, ethanol, isopropanol, dimethyl sulfoxide, dimethylformamide, cyclohexanone, methyl ethyl ketone, ethyl acetate, chloroform, benzene, toluene, xylene, or water.
2. The method of modifying wood of claim 1, characterized in that, The reaction system includes the following devices: (1) Reaction vessel: glass or PTFE-lined wide-mouth reaction bottle; (2) Vacuum device: a circulating water vacuum pump connected in series with a vacuum dryer; (3) Stirring device: magnetic stirrer with a speed range of 50-1500 rpm, equipped with a polytetrafluoroethylene-coated cylindrical stirrer.
3. The method of modifying wood of claim 1, characterized in that The method includes the following steps: Step S1: Soak the wood chips in a reaction bottle containing an alkaline reagent and an organic solvent, and place the reaction bottle in a vacuum dryer. After vacuumizing by the vacuum device, fill the sulfuryl fluoride gas; the alkaline reagent is at least one of triethylamine, sodium hydroxide, potassium hydroxide, aqueous ammonia, calcium hydroxide, aluminum hydroxide, and lithium hydroxide; Step S2: Continuously stir the solution using a magnetic stirrer for 1-48 hours at a reaction temperature of 10-40℃; Step S3: After the reaction is completed, the wood chips are cleaned with an organic solvent; Step S4: The treated wood chips are naturally air-dried to obtain modified wood chips.