A long-acting mildew-proof modification method for bamboo based on solid acid catalysis

Abstract

The application discloses a long-acting mildew-proof modification method for bamboo based on solid acid catalysis and belongs to the technical field of bamboo mildew-proof modification. The method is characterized in that: bamboo is immersed in a modification liquid containing solid acid and betaine and heated, so that the carboxyl group of betaine is esterified with the hydroxyl group of bamboo, and quaternary ammonium cation is introduced on the bamboo; then the bamboo is immersed in a potassium iodide solution, so that iodine ions are combined with quaternary ammonium cations through ionic bonds; and finally, modified bamboo is obtained after washing and drying. The method uses solid acid to improve the grafting degree of betaine, and uses the quaternary ammonium cation-iodine ion functional interface to improve the fixation of iodine ions, so that the obtained bamboo has the properties of mildew-proof and anti-leaching, and can be used for bamboo tableware, furniture, daily necessities and outdoor bamboo products.

Description

Technical Field

[0001] This invention belongs to the field of bamboo anti-mildew treatment technology, specifically referring to a method for long-term anti-mildew modification of bamboo based on solid acid catalysis. Background Technology

[0002] Bamboo has advantages such as a short growth cycle, high specific strength, and renewability, making it widely used in furniture, daily necessities, tableware, and architectural decoration. However, bamboo contains nutrients such as sugars and starches, and its porous structure easily absorbs moisture, making it prone to mold growth under suitable temperature and humidity conditions. Mold not only affects the appearance and lifespan of bamboo products but also limits its application in high-value-added products.

[0003] Current anti-mold treatments for bamboo commonly use anti-mold agents such as propiconazole, chlorothalonil, chromated copper arsenate, or copper azole. However, these agents raise concerns about environmental protection and safety in certain bamboo products. Betaine, an amphoteric compound with a quaternary ammonium structure, relies primarily on physical adsorption when directly impregnated into bamboo, and is easily lost due to moisture, making it difficult to maintain a long-term anti-mold effect. Therefore, there is a need for a bamboo anti-mold modification method that can improve the fixation rate and resistance to leaching of functional components. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, this invention provides a method for long-lasting anti-mold modification of bamboo based on solid acid catalysis. This method stably constructs a quaternary ammonium-iodide ion functional interface on bamboo, effectively solving the problems of low fixation rate and short anti-mold duration of functional components such as betaine in bamboo.

[0005] The technical solution adopted in this invention is as follows: This invention proposes a method for long-lasting anti-mildew modification of bamboo based on solid acid catalysis, comprising the following steps:

[0006] S1. Bamboo is immersed in a modification solution containing solid acid and betaine and heated to react. The solid acid catalyzes the esterification reaction between the carboxyl group in betaine and the hydroxyl group in cellulose and hemicellulose in bamboo, so that the quaternary ammonium cation of betaine is introduced into bamboo in a grafting manner to obtain quaternized bamboo.

[0007] S2. The quaternized bamboo is immersed in potassium iodide solution, so that iodide ions and quaternary ammonium cations are bonded together by ionic bonds and fixed on the bamboo.

[0008] S3. Wash and dry the bamboo treated with potassium iodide to obtain long-lasting mold-resistant modified bamboo.

[0009] Furthermore, the solid acid is one or more of zeolite, montmorillonite, alumina, and titanium dioxide.

[0010] Further, the mass ratio of the solid acid to betaine is 1:5 to 1:20; preferably, the mass ratio of the solid acid to betaine is 1:10. The concentration of the solid acid in the modification solution is 0.5 to 2.0 wt%, the concentration of the betaine in the modification solution is 5 to 20 wt%, and the pH value of the modification solution is 1 to 3.

[0011] Furthermore, the heating reaction temperature is 130–150°C, and the reaction time is 2–4 hours; preferably, the heating reaction temperature is 140°C, and the reaction time is 3 hours. These conditions are beneficial for improving the grafting degree of betaine and reducing the adverse effects of excessively high temperatures on the mechanical properties of bamboo.

[0012] Further, the concentration of the potassium iodide solution is 0.1–0.5 mol / L, and the impregnation time is 6–24 h; preferably, the concentration of the potassium iodide solution is 0.25 mol / L. The impregnation is performed under normal pressure or with vacuum assistance; preferably, for thick bamboo or bamboo laminated timber, vacuum assistance with a vacuum degree of 0.08 MPa is used to improve the penetration and distribution of the modified solution in the pores of the bamboo.

[0013] Furthermore, the bamboo material is bamboo blocks, bamboo strips, bamboo pith, or bamboo laminated timber processed from moso bamboo, skeinba, or light bamboo.

[0014] The present invention also provides a long-lasting mildew-resistant modified bamboo material prepared by the above method, and the application of the long-lasting mildew-resistant modified bamboo material in bamboo tableware, furniture, daily necessities and outdoor bamboo products.

[0015] The beneficial effects achieved by the invention are as follows:

[0016] 1. By using solid acid to catalyze the esterification reaction between the carboxyl groups in betaine and the hydroxyl groups in bamboo, the quaternary ammonium structure of betaine is introduced into bamboo in a grafting manner, solving the problem of easy loss of functional components during direct physical impregnation.

[0017] 2. By placing the potassium iodide treatment after the quaternization modification, iodide ions form ionic bonds with quaternary ammonium cations and are fixed on the bamboo, thus constructing a quaternary ammonium-iodide functional interface, thereby improving the iodide ion's resistance to leaching and its anti-mildew effect.

[0018] 3. Under the conditions of a solid acid to betaine mass ratio of 1:10, reaction at 140℃ for 3 hours, and vacuum-assisted impregnation with 0.25 mol / L potassium iodide solution for 12 hours, the modified bamboo exhibited a mold grade of 0 against Aspergillus niger, Penicillium citrinum, and Trichoderma viride after 30 days of cultivation. After a 14-day water loss test, the iodine ion retention rate reached 98.0%, indicating that this method can achieve both broad-spectrum anti-mold and anti-leaching performance.

[0019] 4. By controlling the esterification reaction temperature at 130-150℃ and the reaction time at 2-4h, the adverse effects of high-temperature treatment on bamboo properties can be reduced while improving the degree of betaine grafting. Under the condition of reacting at 140℃ for 3h, the decrease in bending, tensile and compressive strength of bamboo relative to untreated bamboo is less than 5%.

[0020] 5. Potassium iodide treatment can be carried out by using atmospheric pressure impregnation or vacuum-assisted impregnation to adapt to bamboo materials of different thicknesses and shapes; for thick bamboo materials or bamboo laminated timber, vacuum-assisted impregnation is beneficial to improve the iodine loading and iodine retention rate. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of a long-lasting anti-mildew modification method for bamboo based on solid acid catalysis according to the present invention.

[0022] Figure 2 This is a comparison chart showing the anti-mold properties of modified bamboo prepared using different solid acids against different molds.

[0023] Figure 3 A comparison chart showing the iodine retention rate of modified bamboo under different potassium iodide impregnation methods.

[0024] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] Example 1

[0027] Take a 20mm×20mm×5mm oven-dried bamboo specimen and place it in a reaction container. Add 36mL of modification solution. The solid acid is zeolite. The zeolite concentration in the modification solution is 1wt%, the betaine concentration is 10wt%, the mass ratio of zeolite to betaine is 1:10, and the pH is about 1.5. Add 6 pieces of bamboo per batch.

[0028] The reaction vessel was heated at 140°C for 3 hours. After the reaction was completed, the bamboo was removed and thoroughly washed with deionized water to remove unreacted betaine and solid acid. It was then dried at 60°C to constant weight to obtain quaternized bamboo.

[0029] Quaternized bamboo was immersed in a 0.25 mol / L potassium iodide solution for 12 hours at room temperature and a vacuum of 0.08 MPa. After immersion, the surface was quickly rinsed with deionized water and dried at 60°C to constant weight to obtain long-lasting anti-mildew modified bamboo.

[0030] Anti-mold tests were conducted according to GB / T 18261-2013. Modified bamboo was placed on potato dextrose agar medium inoculated with Aspergillus niger, Penicillium citrinum, and Trichoderma viride, respectively, and cultured for 30 days at 25℃ and 85% relative humidity. The coverage area of ​​the three molds on the bamboo surface was 0 for all three types, and the mold grade was 0 for all three.

[0031] Modified bamboo was immersed in deionized water, with the water changed at intervals of 6 hours, 24 hours, and 48 hours for 14 days. The iodine ion content in the runoff was measured. The iodine ion retention rate was 98.0%.

[0032] Example 2

[0033] Except for the different concentrations of potassium iodide solution, the other operations were the same as in Example 1. The potassium iodide concentrations were 0.001 mol / L, 0.01 mol / L, 0.05 mol / L, 0.10 mol / L, 0.15 mol / L, 0.25 mol / L, 0.50 mol / L, and 1.00 mol / L. Using *Aspergillus niger* as the test strain, the degree of mold growth on the bamboo was observed after 14 days of cultivation. The results are shown in Table 1.

[0034] Table 1. Effect of different potassium iodide concentrations on the antifungal properties of modified bamboo.

[0035] Potassium iodide concentration (mol / L) Aspergillus niger mold grade 0.001 4 0.01 4 0.05 3 0.10 2 0.15 1 0.25 0 0.50 0 1.00 0

[0036] As shown in Table 1, the modified bamboo exhibits enhanced control of Aspergillus niger with increasing potassium iodide concentration. When the potassium iodide concentration reaches 0.25 mol / L, the mold grade is 0, therefore 0.25 mol / L is selected as the preferred concentration.

[0037] Example 3

[0038] Except for the esterification reaction temperature, the other operations were the same as in Example 1. The reaction temperatures were set to 120℃, 140℃, and 160℃, respectively, and the degree of quaternization, mechanical properties, and antifungal properties were measured. The results are shown in Table 2. The degree of quaternization was characterized by the methyl orange adsorption rate.

[0039] Table 2. Effect of different esterification temperatures on the properties of modified bamboo.

[0040] Reaction temperature (°C) Methyl orange adsorption rate (%) Flexural strength (MPa) Tensile strength (MPa) Compressive strength (MPa) Mold level 120 51.3 102 86 61 2 140 84.2 101 85 60 0 160 78.6 95 80 57 0

[0041] The bending strength, tensile strength, and compressive strength of untreated bamboo were 104 MPa, 88 MPa, and 62 MPa, respectively. As shown in Table 2, the esterification reaction was incomplete at 120℃; the methyl orange adsorption rate was highest at 140℃, and the decrease in all mechanical properties compared to untreated bamboo was less than 5%; at 160℃, the methyl orange adsorption rate decreased, and the mechanical properties showed a significant decline. Therefore, 140℃ is the preferred esterification reaction temperature.

[0042] Example 4

[0043] Except for the potassium iodide impregnation method, the other operations were the same as in Example 1. Impregnation was carried out at room temperature and pressure for 12 hours and under vacuum-assisted impregnation at a vacuum degree of 0.08 MPa for 12 hours, respectively. The results are shown in Table 3.

[0044] Table 3. Effects of different potassium iodide impregnation methods on the properties of modified bamboo.

[0045] Impregnation method Iodine loading (kg / m³) Iodine retention rate at 14 days (%) Iodine retention rate (%) after accelerated aging at 80℃ for 7 days 30-day mold rating 60d mold level Atmospheric pressure impregnation 18.5 89.2 76.0 0 1 Vacuum-assisted impregnation 23.1 98.0 89.0 0 0

[0046] From Table 3 and Figure 3 It is evident that vacuum-assisted impregnation can improve the iodine loading and iodine retention rate, and maintain good iodine fixation ability after accelerated aging. Therefore, vacuum-assisted impregnation is the preferred method for bamboo materials that require improved long-term performance.

[0047] Example 5

[0048] Except for the different types of solid acids, the other operations were the same as in Example 1. Using *Aspergillus niger*, *Penicillium citrinum*, and *Trichoderma viride* as test strains, the modified bamboo prepared using zeolite, montmorillonite, alumina, and titanium dioxide as solid acids was evaluated for 30 days of mold resistance. The results are shown in Table 4.

[0049] Table 4. Effects of different solid acids on the 30-day anti-mildew properties of modified bamboo.

[0050] solid acid Aspergillus niger mold grade Penicillium mold spoilage grade Grades of green Trichoderma mildew zeolite 0 0 0 Montmorillonite 1 2 2 Alumina 1 1 2 Titanium oxide 0 1 3

[0051] As shown in Table 4, when zeolite is used as a solid acid, the modified bamboo exhibits a mildew grade of 0 against Aspergillus niger, Penicillium citrinum, and Trichoderma viride, demonstrating good broad-spectrum mildew resistance. Montmorillonite, alumina, and titanium dioxide exhibit mildew grades of 2, 2, and 3 against Trichoderma viride, respectively.

[0052] Example 6

[0053] Except for the different mass ratio of solid acid to betaine, the operation was the same as in Example 1. The mass ratios were 1:5, 1:10, and 1:20. The results showed that when the mass ratio was 1:10, the methyl orange adsorption rate reached 84.2%, the iodine retention rate was 98.0%, and the final mildew resistance level was 0. When the mass ratio was 1:5, the solid acid was relatively excessive, and slight degradation may occur on the bamboo surface; when the mass ratio was 1:20, the catalytic efficiency decreased, the degree of quaternization was insufficient, resulting in a decrease in the iodine ion fixation capacity. Therefore, a mass ratio of solid acid to betaine of 1:10 is preferred.

[0054] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for long-lasting anti-mildew modification of bamboo based on solid acid catalysis, characterized in that: The process includes the following steps: immersing bamboo in a modification solution containing a solid acid and betaine and heating it to react, causing the carboxyl groups of betaine to undergo esterification with the hydroxyl groups in the bamboo, thereby introducing quaternary ammonium cations onto the bamboo to obtain quaternized bamboo; immersing the quaternized bamboo in a potassium iodide solution, causing iodide ions to combine with the quaternary ammonium cations through ionic bonds and adhere to the bamboo; and finally washing and drying to obtain long-lasting anti-mildew modified bamboo.

2. The method for long-lasting anti-mildew modification of bamboo based on solid acid catalysis according to claim 1, characterized in that: The solid acid is one or more of zeolite, montmorillonite, alumina and titanium dioxide, the mass ratio of the solid acid to betaine is 1:5 to 1:20, the concentration of the solid acid in the modification solution is 0.5 to 2.0 wt%, and the concentration of the betaine in the modification solution is 5 to 20 wt%.

3. The method for long-lasting anti-mildew modification of bamboo based on solid acid catalysis according to claim 2, characterized in that: The mass ratio of the solid acid to betaine is 1:10, and the pH value of the modified solution is 1-3.

4. The method for long-lasting anti-mildew modification of bamboo based on solid acid catalysis according to claim 1, characterized in that: The heating reaction is carried out at a temperature of 130–150°C for 2–4 hours.

5. The method for long-lasting anti-mildew modification of bamboo based on solid acid catalysis according to claim 4, characterized in that: The heating reaction was carried out at a temperature of 140°C for 3 hours.

6. The method for long-lasting anti-mildew modification of bamboo based on solid acid catalysis according to claim 1, characterized in that: The concentration of the potassium iodide solution is 0.1–0.5 mol / L, and the immersion time is 6–24 h.

7. The method for long-lasting anti-mildew modification of bamboo based on solid acid catalysis according to claim 6, characterized in that: The concentration of the potassium iodide solution is 0.25 mol / L, and impregnation is carried out under normal pressure or with vacuum assistance. The vacuum degree of the vacuum assistance impregnation is 0.08 MPa.

8. The method for long-lasting anti-mildew modification of bamboo based on solid acid catalysis according to claim 1, characterized in that: The bamboo material is bamboo blocks, bamboo strips, bamboo pith, or bamboo processed into bamboo blocks, bamboo slices, bamboo strips, or bamboo laminated timber.

9. Long-lasting anti-mold modified bamboo prepared by the method of long-lasting anti-mold modification of bamboo based on solid acid catalysis as described in any one of claims 1 to 8.

10. The application of the long-lasting anti-mildew modified bamboo material according to claim 9 in the preparation of bamboo tableware, furniture, daily necessities or outdoor bamboo products.

Images