Chemical etching method for bamboo wood

Abstract

The invention provides a chemical etching method for bamboo wood, which comprises the following steps: processing raw bamboo into bamboo wood, soaking the bamboo wood in a ferric salt aqueous solution with the temperature of 10-30 DEG C and the concentration of 1-15 mmol / L for 2-48 hours, taking out the bamboo wood, drying the bamboo wood until the water content is 15-45%, then soaking the bamboo wood in a hydrogen peroxide aqueous solution with the temperature of 10-30 DEG C and the mass fraction of 5-15% for 2-96 hours, taking out the bamboo wood, and drying the bamboo wood to obtain the chemical etching bamboo wood. The porosity of the chemically etched bamboo material prepared by the method is 55-67%, the etching of the bamboo material at low temperature and low-concentration hydrogen peroxide is realized, the method has the advantages of energy conservation and environmental protection, the porosity of the bamboo material is increased after the bamboo material is chemically etched, the bonding strength is remarkably improved, nutritional ingredients which are easy to cause mildew in the bamboo material are reduced, the ageing resistance and mildew resistance of the bamboo material are enhanced, and the service life of the bamboo material is prolonged. The service life is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of bamboo modification, and particularly relates to a bamboo chemical etching method. Background Art

[0002] Bamboo is a natural biomass material that can be processed into reconstituted bamboo, bamboo laminates, bamboo particleboard, and bamboo fiber molded products. However, due to its poor permeability and abundance of nutrients like starch, bamboo often suffers from quality issues such as debonding and mildew. To improve the processing and performance of bamboo products, treatment is often required on the basic bamboo units (bamboo bundles, bamboo strips, bamboo sheets, bamboo shavings, and bamboo fibers). This improves permeability, allowing the penetration of fluids like resins, mildew inhibitors, and preservatives, while also reducing the starch and sugar content. Heat treatment and bleaching are common methods used to modify bamboo. However, all of these methods present challenges: high-temperature heat treatment reduces the mechanical strength of bamboo; bleaching, typically performed at 50-80°C with a 20-30% (mass fraction) hydrogen peroxide (H2O2) steaming process, is energy-intensive and consumes large amounts of hydrogen peroxide. Furthermore, to promote the reaction, alkaline substances such as ammonia and sodium hydroxide are often added, which can cause environmental pollution and pose a health risk to workers. Therefore, there is an urgent need to develop a new bamboo modification method to address these technical issues. Summary of the Invention

[0003] In response to the shortcomings of the above-mentioned technologies, the present invention provides a bamboo chemical etching method, which realizes low-temperature (10°C~30°C) and low-concentration (mass fraction 5%~15%) bamboo etching with hydrogen peroxide. After chemical etching, the porosity of the bamboo increases, significantly improving the bonding strength, and reducing the nutrients in the bamboo that are prone to mildew, thereby enhancing the aging and mildew resistance of the bamboo and extending its service life.

[0004] The present invention provides a technical solution: a bamboo chemical etching method, The method comprises: processing raw bamboo to prepare bamboo materials, then soaking the bamboo materials in an iron salt aqueous solution at normal pressure, and then soaking the bamboo materials in a hydrogen peroxide aqueous solution at normal pressure; The method for soaking bamboo in an iron salt aqueous solution at normal pressure comprises: soaking the bamboo in an iron salt aqueous solution at normal pressure, taking out the bamboo, and drying the bamboo until the moisture content is 15% to 45%, thereby obtaining iron salt-containing bamboo; the concentration of the iron salt aqueous solution is 1 mmol / L to 15 mmol / L, the soaking temperature is 10° C. to 30° C., and the soaking time is 2 hours to 48 hours; The method for soaking bamboo in hydrogen peroxide aqueous solution at normal pressure comprises: soaking the iron salt-containing bamboo in hydrogen peroxide aqueous solution at normal pressure, taking it out, and drying it to obtain chemically etched bamboo; the mass fraction of the hydrogen peroxide aqueous solution is 5% to 15%, the soaking temperature is 10° C. to 30° C., and the soaking time is 2 hours to 96 hours.

[0005] Preferably, the method for processing raw bamboo into bamboo materials is: using mechanical processing to prepare raw bamboo into bamboo materials, wherein the bamboo materials are bamboo shavings, bamboo fibers, bamboo bundles, bamboo slices or fiberized bamboo veneers.

[0006] Preferably, the iron salt in the iron salt aqueous solution is ferric sulfate or ferrous sulfate.

[0007] Preferably, the moisture content of the chemically etched bamboo material is 5% to 12%.

[0008] Preferably, the porosity of the chemically etched bamboo material is 55% to 67%.

[0009] Preferably, the starch content of the chemically etched bamboo material is 0-3%, and the soluble sugar content is 1%-7%.

[0010] Preferably, the normal pressure immersion is replaced by pressurized immersion, and the pressure of the pressurized immersion is 0.1 MPa to 1.5 MPa.

[0011] Compared with the prior art, the present invention has the following advantages: 1. The present invention realizes low-temperature (10-30°C) and low-concentration (mass fraction 5% to 15%) hydrogen peroxide bamboo etching.

[0012] 2. The porosity of the bamboo material of the present invention increases after etching, which can significantly improve the bonding strength, solve the problem of poor bonding performance of bamboo material, and broaden its application in structural materials.

[0013] 3. The present invention reduces the nutrients in bamboo that are prone to mildew, enhances the aging resistance and mildew resistance of bamboo, and extends the service life by 5 to 10 years.

[0014] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 : These are SEM spectra of the pore structure of the cell wall of vascular cells in the bamboo piece before and after etching in Example 1 of the present invention (a is a bamboo piece without chemical etching, c is a partial enlarged view of a, b is a bamboo piece after chemical etching, and d is a partial enlarged view of b).

[0016] Figure 2 shows the changes in starch in parenchyma cells before and after etching in Example 1 of the present invention. A: original bamboo; B: bamboo after etching.

[0017] Figure 3 3. This is a diagram of the color change of the bamboo pieces before and after etching in Examples 1-3 of the present invention (the first row shows the color of the bamboo materials in Examples 1-3 before etching, and the second row shows the color of the bamboo materials in Examples 1-3 after etching).

[0018] Figure 4 shows the damage to the adhesive layer of the bamboo composite material made from bamboo material before and after chemical etching in Example 1 of the present invention. The left figure shows the damage to the adhesive layer of the bamboo composite material made from bamboo material before etching, and the right figure shows the damage to the adhesive layer of the bamboo composite material made from bamboo material after chemical etching.

[0019] Figure 5 shows the anti-mildew efficacy of the bamboo composite material prepared before and after chemical etching of bamboo materials in Example 1 of the present invention. The left figure shows the anti-mildew efficacy of the bamboo composite material prepared before chemical etching, and the right figure shows the anti-mildew efficacy of the bamboo composite material prepared after chemical etching. DETAILED DESCRIPTION

[0020] Example 1 The bamboo chemical etching method of this embodiment is as follows: S1, preparing raw bamboo into bamboo chips with a moisture content of 8%; The preparation method of bamboo chips is as follows: sawing the original bamboo into bamboo tubes, and splitting the bamboo into bamboo chips along the longitudinal direction; The original bamboo in this embodiment is 5-year-old moso bamboo; S2. Chemical etching: The bamboo slices obtained in S1 were soaked in an aqueous solution of ferric sulfate at a temperature of 10°C and a concentration of 12.5 mmol / L. After soaking for 48 hours, the slices were taken out and dried to a moisture content of 15%. Then, the slices were soaked in an aqueous solution of hydrogen peroxide at a temperature of 10°C and a mass fraction of 15%. After soaking for 24 hours, the slices were taken out and dried to obtain chemically etched bamboo slices with a moisture content of 12%. The porosity of the chemically etched bamboo slices was 67%, while the porosity of the bamboo slices without chemical etching was 55%. The porosity of the bamboo slices increased by 12%; the starch content was reduced by 50%, the sugar content was reduced by 12%, and the total removal rate of lignin and hemicellulose in the cell wall was 4%.

[0021] The chemically etched bamboo material has a starch content of 1% and a soluble sugar (Ara, Gal, Glc, Xyl) content of 6%; The bamboo is immersed in the ferric sulfate aqueous solution by pressurized immersion, and the immersion pressure is 1.5 MPa.

[0022] Depend on Figure 1As can be seen, the cell wall structure of the chemically etched bamboo slices was not significantly damaged. Figure a shows the unetched bamboo slice, c is a zoomed-in view of a, b shows the chemically etched bamboo slice, and d is a zoomed-in view of b. The porosity of the chemically etched bamboo slices is 67%, indicating that the cell walls of the bamboo slices have been etched, and the pores within the cell walls have increased.

[0023] Depend on Figure 2 The changes in starch in the thin-walled cells before (A) and after (B) etching show that the starch content in the thin-walled cells of the bamboo slices is significantly reduced after etching.

[0024] Table 1 shows the changes in sugar content in bamboo slices before and after etching. The sugar content in bamboo slices decreases after etching.

[0025] Table 1 Changes in sugar content in bamboo before and after etching Through chemical etching treatment, the macromolecules in the weak parts of the bamboo cell wall can be destroyed, causing the cell wall to be damaged and the cell wall components to be etched to increase the pore size; at the same time, nutrients such as starch and polysaccharides are removed, which is conducive to the subsequent modification reagents such as glue and mildew inhibitors to better penetrate into the bamboo.

[0026] Figure 4 shows the adhesive layer damage of the bamboo composite material prepared from bamboo before and after chemical etching in this example. The adhesive layer of the bamboo composite material prepared before etching (left image) is broken, while the adhesive layer of the bamboo composite material after etching (right image) remains intact. This indicates that the bonding strength of the bamboo is increased after etching. The adhesive layer of the bamboo composite material prepared before etching is completely cracked, while the adhesive layer of the bamboo composite material prepared after chemical etching is largely intact, with cracks primarily occurring in the bamboo material.

[0027] Figure 5 shows the bamboo composite material prepared before and after chemical etching of bamboo in this example. Etching improves the anti-mildew performance. The bamboo composite material prepared before etching (left image) exhibits mildew, while the bamboo composite material prepared after etching (right image) does not. Laboratory testing shows that the anti-mildew performance of the bamboo composite material after chemical etching improves from level 4 (unetched material) to level 0, according to the evaluation criteria shown in Table 2.

[0028] Table 2 Evaluation criteria Example 2 The bamboo chemical etching method of this embodiment is as follows: S1, preparing raw bamboo into bamboo chips with a moisture content of 30%; The original bamboo in this embodiment is 5-year-old moso bamboo; The preparation method of bamboo chips is as follows: sawing the original bamboo into bamboo tubes, and splitting the bamboo into bamboo chips along the longitudinal direction; S2. Chemical etching: The bamboo pieces obtained in S1 were immersed in a 15 mmol / L ferrous sulfate aqueous solution at a temperature of 25°C for 30 hours, removed, and dried to a moisture content of 30%. The bamboo pieces were then immersed in a 10% hydrogen peroxide aqueous solution at a temperature of 25°C for 2 hours, removed, and dried to obtain chemically etched bamboo pieces with a moisture content of 12%. The bamboo is immersed in the ferrous sulfate aqueous solution by pressurized immersion, and the immersion pressure is 0.1 MPa.

[0029] The porosity of the chemically etched bamboo strips was 60%, which was 7% higher than that before chemical etching. The starch content was reduced by 30%, the sugar content was reduced by 8%, and the total removal rate of lignin and hemicellulose in the cell wall was 3%.

[0030] In this embodiment, the starch content of the chemically etched bamboo strips is 0, and the soluble sugar content is 1%.

[0031] Example 3 The bamboo chemical etching method of this embodiment is as follows: S1. Prepare raw bamboo into bamboo chips with a moisture content of 35%; The preparation method of bamboo chips is as follows: sawing the original bamboo into bamboo tubes, and splitting the bamboo into bamboo chips along the longitudinal direction; The original bamboo in this embodiment is 5-year-old moso bamboo; S2. Chemical etching: The bamboo slices obtained in S1 were soaked in a 1 mmol / L ferric sulfate aqueous solution at a temperature of 30°C for 2 hours, taken out, and dried to a moisture content of 45%. They were then soaked in a 5% hydrogen peroxide aqueous solution at a temperature of 30°C for 96 hours, taken out, and dried to obtain chemically etched bamboo slices with a moisture content of 5%.

[0032] The porosity of the bamboo after chemical etching is 55%, which is 2% higher than that before chemical etching. The starch content is reduced by 10%, the sugar content is reduced by 4%, and the total removal rate of lignin and hemicellulose in the cell wall is 1%.

[0033] In this embodiment, the starch content of the chemically etched bamboo slices is 3%, and the soluble sugar content is 7%.

[0034] In this embodiment, the bamboo pieces can also be processed mechanically to prepare bamboo materials from raw bamboo, and the bamboo materials are bamboo shavings, bamboo fibers, bamboo bundles, bamboo pieces or fiberized bamboo veneers.

[0035] The porosity of the bamboo material after chemical etching is increased, which is conducive to the subsequent improvement of the glue, mildewproof agent and other modifying agents to better penetrate into the bamboo material. The chemically etched bamboo material of the present invention can be used to prepare weather-resistant bamboo products.

[0036] The chemical etching method of the present invention lays the foundation for optimizing bamboo bleaching, gluing and other processing technologies, as well as developing bamboo product protection technologies such as light aging resistance and anti-corrosion, and provides a theoretical basis for the efficient utilization of bamboo materials such as high-performance bamboo engineering materials, high-weather-resistant bamboo materials, and green bamboo daily products.

[0037] The bamboo chemical etching method of the present invention can controllably etch bamboo using a low-concentration (5%~15%) solution under a low-temperature (10-30°C) environment. By precisely regulating the surface / interface structure of the bamboo (such as increasing the porosity), the permeability of the bamboo is fundamentally improved, providing a new approach to solving bottleneck problems such as poor gluing properties and difficulty in functional processing, and laying the foundation for the development of high-performance and high-durability bamboo products.

[0038] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent variation made to the above embodiment based on the essence of the invention technology shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A bamboo chemical etching method, characterized in that: The method comprises: processing raw bamboo to prepare bamboo materials, then soaking the bamboo materials in an iron salt aqueous solution at normal pressure, and then soaking the bamboo materials in a hydrogen peroxide aqueous solution at normal pressure; The method for soaking bamboo in an iron salt aqueous solution at normal pressure comprises: soaking the bamboo in an iron salt aqueous solution at normal pressure, taking out the bamboo, and drying the bamboo until the moisture content is 15% to 45%, thereby obtaining iron salt-containing bamboo; the concentration of the iron salt aqueous solution is 1 mmol / L to 15 mmol / L, the soaking temperature is 10° C. to 30° C., and the soaking time is 2 hours to 48 hours; The method for soaking bamboo in hydrogen peroxide aqueous solution at normal pressure comprises: soaking the iron salt-containing bamboo in hydrogen peroxide aqueous solution at normal pressure, taking it out, and drying it to obtain chemically etched bamboo; the mass fraction of the hydrogen peroxide aqueous solution is 5% to 15%, the soaking temperature is 10° C. to 30° C., and the soaking time is 2 hours to 96 hours.

2. The bamboo chemical etching method according to claim 1, characterized in that: The method for preparing bamboo materials by processing raw bamboo is as follows: The raw bamboo is prepared into bamboo materials by mechanical processing, and the bamboo materials are bamboo shavings, bamboo fibers, bamboo bundles, bamboo slices or fiberized bamboo veneers.

3. The bamboo chemical etching method according to claim 1, characterized in that: The iron salt in the iron salt aqueous solution is ferric sulfate or ferrous sulfate.

4. The bamboo chemical etching method according to claim 1, characterized in that: The moisture content of the chemically etched bamboo material is 5% to 12%.

5. The bamboo chemical etching method according to claim 1, characterized in that: The porosity of the chemically etched bamboo material is 55% to 67%.

6. The bamboo chemical etching method according to claim 1, characterized in that: The chemically etched bamboo material has a starch content of 0-3% and a soluble sugar content of 1%-7%.

7. The bamboo chemical etching method according to claim 1, characterized in that: The normal pressure immersion is replaced by pressurized immersion, and the pressure of the pressurized immersion is 0.1 MPa to 1.5 MPa.

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