Environmentally friendly particle board and method for producing the same

Abstract

The application provides an environment-friendly shaving board and a preparation method thereof, which replaces a formaldehyde adhesive system for preparing a shaving board and further guarantees high mechanical properties and water resistance. The preparation comprises the following steps: mixing chitosan and water, dropping appropriate acetic acid into the mixture, and stirring until the mixture is completely dissolved to obtain a water-based biomass adhesive; oxidizing and activating wood shavings by using an oxidizing agent to obtain activated shavings in which aldehyde groups are generated on the surface interface cellulose of the shavings, and performing drying treatment on the activated shavings; uniformly applying the water-based biomass adhesive to the dried activated shavings, and laying and hot-pressing the shavings to form a board, so that the amino groups in the chitosan and the aldehyde groups on the surface interface cellulose of the shavings generate Schiff base reaction, and the hydroxyl groups in the chitosan and the aldehyde groups on the surface interface cellulose of the shavings generate esterification reaction, thereby forming covalent cross-linking.

Description

Technical Field

[0001] This invention relates to the manufacturing process of particleboard, and more particularly to an environmentally friendly particleboard and its manufacturing method. Background Technology

[0002] In recent years, due to the continuous improvement of social living standards, customized home furnishings have become increasingly popular, further driving the progress and development of the engineered wood products industry. According to 2020 data, my country ranks first in the world in both engineered wood product production and consumption, accounting for more than half of the world's annual production. Particleboard accounts for approximately 10% of this, and demand continues to rise rapidly. In terms of production and processing, the use of continuous flat-press particleboard automated production lines allows for large-scale production of particleboard while maintaining advantages such as quality stability and structural uniformity. Furthermore, the good sound absorption and insulation properties, as well as excellent mechanical properties, are also important factors contributing to its widespread application in customized home furnishings. With the booming development of the downstream furniture industry, the traditional particleboard industry is also moving towards producing new, environmentally friendly, formaldehyde-free, lightweight, and high-strength high-quality particleboard, further enhancing the consumer image of Chinese particleboard and propelling its products towards a new level of high-quality development.

[0003] Because wood shavings often require large amounts of adhesives to achieve excellent mechanical properties in the manufacturing of reconstituted composite materials, the adhesives used for particleboard are currently primarily formaldehyde-based adhesives (phenolic resin adhesives, urea-formaldehyde resin adhesives, and melamine-formaldehyde resin adhesives), accounting for over 90% of the market. Boards made with these adhesives release large amounts of formaldehyde and volatile organic pollutants during use, posing significant harm to human health and the environment. Furthermore, the raw materials used to prepare formaldehyde-based adhesives are all petrochemical resource derivatives, which are primary energy sources and cause irreversible pollution to the environment and atmosphere during their development and production. Therefore, producing green and environmentally friendly engineered wood products that meet the needs of modern development is a crucial step for the vigorous development of the engineered wood products industry.

[0004] Biomass-based adhesives offer advantages such as being environmentally friendly, using renewable raw materials, and eliminating the release of formaldehyde and volatile organic pollutants during preparation and use, making them a promising alternative to formaldehyde-based adhesives. However, current biomass-based adhesives still suffer from several drawbacks, including insufficient bonding strength, poor water resistance, and high cost, hindering their complete replacement of existing formaldehyde-based adhesives and limiting their industrial application and promotion. Adhesive-free bonding technology has garnered widespread attention due to its adhesive-free, environmentally friendly, and pollution-free characteristics. However, current adhesive-free bonding technologies also suffer from drawbacks such as insufficient bonding strength, poor water resistance, especially in hot water, and long hot-pressing times. Summary of the Invention

[0005] This invention addresses the problems of low bonding strength and poor water resistance in particleboard prepared with existing biomass-based adhesives by proposing a high-performance particleboard and its preparation method.

[0006] This invention utilizes a chemical modification method in glueless bonding technology to activate the surface and interface of wood shavings, transforming the hydroxyl groups on the cellulose surface of the wood shavings into more active aldehyde groups. These aldehyde groups then react chemically with biomass-based adhesives to form a cross-linked network, achieving a bonding effect and resulting in a green and environmentally friendly high-performance particleboard.

[0007] The present invention provides a method for preparing an environmentally friendly particleboard, comprising: mixing chitosan and water, adding an appropriate amount of acetic acid, and stirring until completely dissolved to obtain an aqueous biomass adhesive; subjecting wood shavings to oxidative activation treatment with an activator to obtain activated shavings with aldehyde-modified cellulose at the shaving surface, and drying them; uniformly applying the aqueous biomass adhesive to the dried activated shavings, and laying and hot-pressing them into a board, so that the amino groups in chitosan react with the aldehyde groups on the cellulose at the shaving surface to form covalent bonds through a Schiff base reaction, while the hydroxyl groups in chitosan react with the aldehyde groups on the cellulose at the shaving surface to form covalent crosslinks through an esterification reaction.

[0008] Furthermore, in the preparation of the aqueous biomass adhesive, the mass ratio of chitosan to water is (0.5–5):100. Furthermore, the application rate of the aqueous biomass adhesive relative to dry wood shavings is 1%–6%. Furthermore, the oxidation degree of the activated wood shavings is 0.2–0.4. The oxidation degree is controlled by selecting an activator and controlling the activation temperature and activation time. The activator is a 0.05–1 mol / L sodium periodate aqueous solution. Wood shavings are immersed in this sodium periodate aqueous solution and activated for 2–12 hours under light-protected conditions and at a temperature of 25–90°C.

[0009] This method and the particleboard prepared by it provide a new possibility for preparing particleboard, replacing the previous formaldehyde-based adhesive system.

[0010] Further, in the preparation of the aqueous biomass adhesive, the mass ratio of chitosan to water is (0.5-2):100, and the volume ratio of acetic acid to water is (0.5-2):100. Further, the application rate of the aqueous biomass adhesive relative to dry wood shavings is 1%-3%. Further, the activator is an aqueous sodium periodate solution with a concentration of 0.05-0.2 mol / L and a pH of 4-5.5. The oxidation activation treatment is completed by completely immersing the wood shavings in this sodium periodate solution and activating them under light-protected conditions at a temperature of 25-32°C for 5-11 hours. Preferably, the activation time is 5-7 hours. More preferably, the activation time is 6 hours.

[0011] Further, the activated wood shavings are dried to a moisture content of less than 15%. Further, the hot-pressing pressure is 0.5–10 MPa, the hot-pressing temperature is 120–250℃, and the hot-pressing time is 30–120 s / mm. Further, the wood shavings consist of coarse shavings and fine shavings in a mass ratio of (1.5–2.5):1, wherein the coarse shavings have dimensions of 5–35 mm in length, 1–3 mm in width, and 0.15–0.5 mm in thickness, and the fine shavings have lengths, widths, and thicknesses of 0.1–1 mm.

[0012] After the oxidation activation treatment, the process may also include adding ethylene glycol to quench the reaction and remove unreacted sodium periodate, and then washing the activated wood shavings to neutrality using a vacuum filter.

[0013] Based on this method and the particleboard prepared by this method, it is possible to ensure high mechanical properties and water resistance, which can meet the various performance requirements of load-bearing particleboard (P3 type) used in a dry state.

[0014] According to the preparation method of the present invention, activated wood shavings are obtained by immersing wood shavings in an activator for oxidative activation. After drying the activated wood shavings, a self-made water-based biomass-based adhesive is evenly sprayed onto the surface of the shavings, followed by laying and hot pressing. This utilizes the aldehyde groups on the surface of the activated wood to react with the amino groups in the bio-based adhesive through a Schiff base reaction, forming a stable cross-linked network, thus endowing the particleboard with high mechanical properties and water resistance. Simultaneously, by seeking to control the degree of oxidation, the mechanical properties and water resistance of the wood meet the standards and achieve optimal performance.

[0015] Because the hydroxyl groups in cellulose are converted into more reactive aldehyde groups, covalent bonds can be formed through aldol condensation to improve bonding strength. Furthermore, particleboard made from oxidized and glued wood chips can form a large number of covalent bonds in a short time through the Schiff base reaction, significantly increasing bonding strength. On the other hand, the oxidized wood chips undergo a chemical reaction during hot pressing, consuming the hydrophilic hydroxyl groups on the cellulose, resulting in extremely improved water resistance, meeting national standards.

[0016] Furthermore, the properties of particleboard prepared after sizing vary significantly depending on the oxidation activation time. Shorter oxidation times result in poorer oxidation effects, leading to less aldehyde group conversion and thus fewer bonds with the biomass adhesive, resulting in poor mechanical properties. Conversely, excessively long oxidation times can damage the cellulose molecular chains, causing a decrease in the mechanical properties of the particleboard itself, which in turn reduces the mechanical properties of the board. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the process for preparing high-performance environmentally friendly particleboard according to the present invention.

[0018] Figure 2 This is a diagram illustrating the reaction principle between the water-based biomass adhesive and the cellulose at the surface of the wood chips in the preparation of particleboard according to the present invention.

[0019] Figure 3a ,3b is a comparison photo of natural wood shavings and activated wood shavings.

[0020] Figure 4 It is a curve comparing the crystallinity of natural wood shavings and activated wood shavings.

[0021] Figure 5 This is a graph showing the change in the degree of acetal oxidation over time. Detailed Implementation

[0022] To make the technical methods, objectives, and effects of this invention easier to understand, the invention is further described below with reference to specific embodiments. The technical solution of this invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0023] It should be understood that, in any work involving the definition of the scope of the claims of this invention, the specific embodiments provided by this invention can fully support the generalization of equivalent or superior suitable solutions derived therefrom, and the scope of the claims should never be construed as not exceeding the examples themselves. It must also be understood that, with the development of technology and the emergence of new scenarios, the technical solutions provided by the embodiments of this application will also be equally applicable to similar technical problems without any inventive effort by those skilled in the art, and the scope of protection of this invention should not be limited to the examples described in the specific embodiments of this invention.

[0024] The terms "comprising" and "having," and any variations thereof, in the specification, claims, and drawings of this application are intended to cover a non-exclusive inclusion, so that a process, method, system, product, or apparatus that comprises a series of units is not necessarily limited to those units, but may include other units not explicitly listed or inherent to those processes, methods, products, or apparatuses. Unless otherwise stated, the numerical range "A-B" means A or greater than (greater than or equal to) and B or less than (less than or equal to) B. When room temperature or ambient temperature is mentioned, it usually refers to 22-25°C, and sometimes 20-28°C depending on the process. For some processes where temperature is specified, it is generally considered that the process is carried out at the stated room temperature or ambient temperature. Different fields in actual industry have different understandings of room temperature or ambient temperature, but for the implementation and application of patent law, the specific scope of application should be based on achieving the purpose of the invention, and should not be limited to the narrow experience of a particular field. Those skilled in the art should also understand that when referring to a certain temperature, it means that the temperature control is not absolutely constant and there will often be some fluctuation. This fluctuation may exceed one degree or even more in a certain scenario. As long as the experimental purpose can be achieved, it should be regarded as being at that temperature.

[0025] In this embodiment, wood shavings are immersed in an activator to obtain activated shavings. After the activated shavings are dried, a self-made water-based biomass adhesive is evenly applied to the surface of the shavings, and then laid and hot-pressed to obtain high-performance particleboard.

[0026] Unless otherwise specified, all materials and reagents used in this invention are commercially available. The wood shavings can be obtained in predetermined size ranges through mechanical processing of natural wood. The raw materials used include all coniferous and broadleaf woods, bamboo, and agricultural and forestry waste (straw, bagasse, etc.). This embodiment uses engineered wood shavings provided by Shandong Xingang Group, including coarse shavings with a length of 5–35 mm, a width of 1–3 mm, and a thickness of 0.15–0.5 mm, and fine shavings with a length, width, and thickness of 0.1–1 mm. The coarse and fine shavings are mixed uniformly at a mass ratio of (1.5–2.5):1, preferably 2:1, to obtain the wood shavings for preparation.

[0027] The activator is an aqueous solution of sodium periodate. The wood shavings are immersed in the sodium periodate solution under light-protected conditions to achieve oxidation and activation, converting the hydroxyl groups on the cellulose surface of the shavings into more reactive aldehyde groups. After activation, the shavings turn brownish-red due to partial oxidation of the lignin components. The oxidation degree is controlled to 0.2–0.4 by adjusting the activation temperature, activator concentration, and immersion time. In this embodiment, the concentration of the sodium periodate aqueous solution is 0.05–1 mol / L, the activation temperature is 25–90°C, the activator concentration is 0.05–1 mol / L, and the activation time is 2–12 h. The oxidation degree of activated wood shavings is preferably 0.24 to 0.31. To further ensure the high performance of the particleboard, the activator is a sodium periodate aqueous solution with a concentration of 0.05 to 0.2 mol / L and a pH value of 4 to 5.5. The wood shavings are completely immersed in the sodium periodate aqueous solution and activated at 25 to 32°C for 5 to 11 hours under light-protected conditions to complete the oxidation activation treatment. Preferably, the activation time is 5 to 10 hours, more preferably 5 to 7 hours, and more preferably 6 hours.

[0028] As the pH of the sodium periodate aqueous solution increases, the oxidation degree increases slightly; when the pH value becomes moderately alkaline, the oxidation degree decreases. The activator used in this invention exhibits minimal pH variation within its concentration range, remaining weakly acidic, with pH values ​​between 4 and 5.5. When the pH value exceeds 6, the oxidation degree decreases rapidly with increasing pH.

[0029] The self-made water-based biomass-based adhesive consists of chitosan, acid, and water. It is prepared by mixing weighed chitosan with a certain volume of water, then adding an appropriate amount of acid dropwise, and stirring until completely dissolved. The ratio of chitosan (g): acid (ml): water (ml) is (0.5–5):(0.5–5):100, resulting in a solid content of 0.5–5% for the biomass-based adhesive. Further, the mass ratio of chitosan to water is (0.5–2):100, and the volume ratio of acetic acid to water is (0.5–2):100. The water-based biomass-based adhesive is applied to activated wood shavings in a mixer, such as a high-speed mixer, at a speed of, for example, 800 rpm. The amount of adhesive applied relative to the dry wood shavings is 1%–6%, preferably 1–3%, and more preferably 2%.

[0030] After wood shavings are impregnated with a sodium periodate aqueous solution, unreacted sodium periodate can be removed by adding ethylene glycol to quench the reaction. The activated shavings are then washed to neutrality using a vacuum filtration device. The washed shavings are then dried until the moisture content is below 15%. Activated shavings can be dried at room temperature or in an oven. For room temperature drying, the activated shavings, washed to neutrality, are placed under ambient conditions to dry; they are ready for use when the moisture content is below 15%. For oven drying, the activated shavings are placed in an oven at 30–60°C to dry; they are ready for use when the moisture content is below 15%.

[0031] After applying the adhesive, the wood shavings are laid into a pavement, and then hot-pressed at a pressure of 0.5–10 MPa, a temperature of 120–250℃, and a time of 30–120 s / mm. The thickness is controlled at 4–6 mm, and the density is controlled at 800–850 kg / m³. 3 It may also include a pre-compression process, with a pre-compression unit pressure of 2.5–3.5 MPa and a pre-compression time of 20–30 seconds.

[0032] According to the present invention, the amino groups in chitosan react with the aldehyde groups on the cellulose surface of the chitosan chip to form covalent bonds through a Schiff base reaction, while the hydroxyl groups in chitosan react with the aldehyde groups on the cellulose surface of the chitosan chip to form covalent crosslinks through an esterification reaction (e.g., ...). Figure 2 (Schematic diagram revealed).

[0033] Example 1:

[0034] (1) Mix 5g of chitosan with 1L of water, then slowly add 5ml of acetic acid and stir until completely dissolved to obtain a standby biomass-based adhesive with a solid content of 0.5%.

[0035] (2) The dry poplar wood shavings provided by Shandong Xingang Group, including 33 kg of coarse shavings and 17 kg of fine poplar shavings, were mixed evenly as wood shavings for preparation. The coarse shavings were 35 mm in length, 3 mm in width, and 0.5 mm in thickness, while the fine shavings were 1 mm in length, width, and thickness.

[0036] (3) Using a sodium periodate aqueous solution with a concentration of 0.05 mol / L and a pH of 4 as an activator, the wood shavings were completely immersed in the sodium periodate aqueous solution and activated for 6 hours under dark conditions and at a temperature of 25°C.

[0037] (4) After impregnation, add an appropriate amount of ethylene glycol to quench the reaction and remove unreacted sodium periodate. Then use a vacuum filter to wash the activated wood shavings until neutral.

[0038] (5) The washed wood shavings are dried in an oven at 60°C until the activated wood shavings have a moisture content of 12%.

[0039] (6) Apply water-based biomass-based adhesive to activated wood shavings in a high-speed mixer at a rate of 2% relative to dry wood shavings and a mixer speed of 800 r / min.

[0040] (7) The glued wood shavings are laid into veneers for pre-pressing and hot-pressing. The pre-pressing pressure is 2.5 MPa, the pre-pressing time is 20 s, the hot-pressing pressure is 5 MPa, the hot-pressing temperature is 160℃, the hot-pressing time is 10 min, the thickness is controlled at 5 mm, and the density is controlled at 800 kg / m³. 3 .

[0041] Actual images of natural wood shavings and activated wood shavings are shown below. Figure 3a and Figure 3b As shown, the color of wood shavings darkens under the action of sodium periodate oxidant.

[0042] In addition, X-ray diffraction signals in crystals are used to analyze the crystal structure of natural and activated wood shavings, such as... Figure 4 As shown in the XRD patterns of natural and activated cellulose shavings, the crystallinity of cellulose remained almost unchanged before and after activation. This indicates that the activation reaction only occurred in the non-crystalline region of cellulose and did not affect the crystalline region. It also shows that activation does not damage the material.

[0043] In the following Examples 2 to 5, the effect of particleboard activation time on particleboard performance is explored. Similarities with Example 1 include omissions in the description.

[0044] Example 2:

[0045] Poplar wood was selected as the raw material, and poplar wood shavings of a predetermined size range were obtained through mechanical processing. Activated shavings were obtained by activating the shavings with a 0.05 mol / L activator for 2 hours in the dark. The dried activated shavings were then sizinged under the stirring of a high-speed mixer and hot-pressed at 160℃ and 5 MPa for 10 minutes to obtain particleboard.

[0046] Example 3:

[0047] Poplar wood was selected as the raw material, and poplar wood shavings within a predetermined size range were obtained through mechanical processing. Activated shavings were obtained by activating the shavings with a 0.05 mol / L activator for 4 hours in the dark. The dried activated shavings were then sizinged under the stirring of a high-speed mixer and hot-pressed at 160℃ and 5 MPa for 10 minutes to obtain particleboard.

[0048] Example 4:

[0049] Poplar wood was selected as the raw material, and poplar wood shavings within a predetermined size range were obtained through mechanical processing. Activated shavings were obtained by activating the shavings with a 0.05 mol / L activator for 8 hours in the dark. The dried activated shavings were then sizinged under the stirring of a high-speed mixer and hot-pressed at 160℃ and 5 MPa for 10 minutes to obtain particleboard.

[0050] Example 5:

[0051] Poplar wood was selected as the raw material, and poplar wood shavings of a predetermined size range were obtained through mechanical processing. Activated shavings were obtained by activating the shavings with a 0.05 mol / L activator for 10 hours in the dark. The dried activated shavings were then sizinged under the stirring of a high-speed mixer and hot-pressed at 160℃ and 5 MPa for 10 minutes to obtain particleboard.

[0052] The following Comparative Examples 1 to 3 explore the performance of particleboard under several comparative conditions. Similarities with Example 1 include omissions in the description.

[0053] Comparative Example 1:

[0054] Poplar wood was selected as the raw material, and poplar wood shavings within a predetermined size range were obtained through mechanical processing and then laid out. The shavings were then hot-pressed at 160℃ and 5MPa for 10 minutes to obtain particleboard.

[0055] Comparative Example 2:

[0056] Poplar wood was selected as the raw material, and poplar wood shavings of a predetermined size range were obtained through mechanical processing. The shavings were then mixed with glue in a high-speed mixer, laid out, and hot-pressed at 160℃ and 5MPa for 10 minutes to obtain particleboard.

[0057] Comparative Example 3:

[0058] Poplar wood was selected as the raw material, and poplar wood shavings within a predetermined size range were obtained through mechanical processing. Activated shavings were obtained by activating the shavings with a 0.05 mol / L activator for 6 hours in the dark. The shavings were then hot-pressed at 160℃ and 5 MPa for 10 minutes to obtain particleboard.

[0059] The degree of oxidation activation in oxidative activation reactions can be easily controlled by adjusting the activation time. Figure 5 It can be seen that the degree of oxidation increases with the extension of time.

[0060] According to the national standard GB / T 4897-2015 Particleboard, the relevant mechanical properties and water resistance properties of particleboard prepared in different samples were tested, and the results are shown in Table 1.

[0061] Table 1

[0062] Performance comparison of particleboard made from natural wood shavings and activated wood shavings

[0063]

[0064] The particleboard prepared after oxidation and sizing (Example 1) has a static bending strength and elastic modulus of 19.56 MPa and 4154.29 MPa, respectively, and an internal bond strength of 0.58 MPa, all of which meet the relevant performance requirements in the national standard.

[0065] The particleboard prepared from oxidized wood chips without adhesive (Comparative Example 3) had a static bending strength and modulus of elasticity of 15.21 MPa and 1659.64 MPa, respectively, and an internal bond strength of only 0.29 MPa, all of which failed to meet the national standard requirements. Activated wood chips, whether unadhesive or adhesive, showed significantly improved water resistance compared to particleboard made from natural wood chips. Their 24-hour water absorption thickness expansion rates were 14.29% and 11.25%, respectively, both meeting the national standard requirements. The particleboard prepared after oxidation and adhesive application exhibited the best water resistance.

[0066] The static bending strength and elastic modulus of unoxidized natural wood shavings without sizing (Comparative Example 1) are 7.63 MPa and 1328.22 MPa, respectively, and the internal bond strength is 0.065 MPa, which cannot meet the national standard requirements of 15 MPa, 2200 MPa and 0.45 MPa.

[0067] After sizing (Comparative Example 2), the static bending strength and modulus of elasticity of untreated natural wood shavings were 11.94 MPa and 2159.14 MPa, respectively, with an internal bond strength of 0.37 MPa. Although the mechanical properties were improved compared to particleboard made from unsized natural wood shavings, they still did not meet the national standards. The water resistance of both unsized and sized natural wood shavings was poor, with 24-hour thickness swelling rates of 53.21% and 37.95% respectively, both failing to meet national standards.

[0068] The reason for the above phenomenon is that the particleboard prepared from unadhesive natural wood shavings (Comparative Example 1) achieves a bonding effect through hydrogen bonding. This intermolecular force is relatively weak and cannot provide a sufficiently strong bonding ability, and it is easily destroyed in water. For particleboard prepared from natural wood shavings after adhesion (Comparative Example 2), the amino groups in the biomass-based adhesive are difficult to form a large number of covalent bonds with the hydroxyl groups on cellulose, and the bonding strength is still provided by intermolecular forces and hydrogen bonds, thus failing to provide a strong bonding ability. Activated wood shavings, although not using adhesives (Comparative Example 3), have their hydroxyl groups in cellulose transformed into more reactive aldehyde groups, thus forming covalent bonds through aldol condensation to improve bonding strength. Particleboard prepared from oxidized and adhesive-adhesive wood shavings (Example 1) can form a large number of covalent bonds in a short time through Schiff base reaction, resulting in a significant increase in bonding strength. On the other hand, the shavings after oxidation treatment have a significantly improved water resistance due to the chemical reaction that consumes the hydrophilic hydroxyl groups on the cellulose during the hot pressing process, which meets the national standard requirements.

[0069] Meanwhile, according to the experimental results, the properties of the particleboard prepared after sizing varied greatly depending on the oxidation time. The best properties were observed when the oxidation time was 6 hours (Example 1). When the oxidation time was less than 6 hours (2 hours, Example 2) and 4 hours (Example 3), the mechanical properties were low and failed to meet national standards. When the oxidation time exceeded 6 hours (8 hours, Example 4) and 10 hours (Example 5), although the mechanical properties met national standards, they were still lower than those after a 6-hour oxidation time. However, all particleboards prepared from shavings that underwent oxidation treatment and then sizing exhibited excellent water resistance and met national standards.

[0070] The above phenomenon occurs because a shorter oxidation time results in a poorer oxidation effect, leading to less aldehyde group conversion and thus fewer bonds forming with the biomass adhesive, resulting in poor mechanical properties. Conversely, excessively long oxidation times damage the cellulose molecular chains, causing a decrease in the mechanical properties of the wood chips themselves, which in turn reduces the mechanical properties of the board. The fact that particleboard made from oxidized and sizing wood chips meets national standards for 24-hour water absorption thickness swelling rate is because the chemical reaction during hot pressing consumes the hydrophilic hydroxyl groups on the cellulose, improving water resistance.

[0071] In summary, the present invention has the following advantages: (1) The present invention uses biomass-based adhesive to prepare high-performance, water-resistant particleboard; (2) The biomass-based adhesive used in the present invention is simple to prepare, and the raw materials are green, environmentally friendly, and abundant; (3) Due to the use of water-based adhesive, the amount of adhesive applied is low (approximately 2% of the dry particleboard mass), resulting in low manufacturing costs; (4) During the preparation process, since no formaldehyde is added, the invention is environmentally friendly, pollution-free, and harmless to the human body.

Claims

1. A method for preparing environmentally friendly particleboard, characterized in that, include: A water-based biomass adhesive was prepared by mixing chitosan and water, adding an appropriate amount of acetic acid, and stirring until completely dissolved. Wood shavings are oxidized and activated with an activator to obtain activated shavings with aldehyde-modified cellulose at the shaving surface, and then dried. A water-based biomass adhesive is then evenly applied to the dried activated shavings, and they are laid out and hot-pressed into boards. This allows the amino groups in chitosan to undergo a Schiff base reaction with the aldehyde groups on the cellulose at the shaving surface, and the hydroxyl groups in chitosan to undergo an esterification reaction with the aldehyde groups on the cellulose at the shaving surface, thereby forming covalent crosslinks. The oxidation degree of activated wood shavings is 0.2~0.

4. In the preparation of the water-based biomass adhesive, the mass ratio of chitosan to water is (0.5~2):100, and the volume ratio of acetic acid to water is (0.5~2):100; the application rate of the water-based biomass adhesive relative to dry wood shavings is 1~3%; the activator is a sodium periodate aqueous solution with a concentration of 0.05~0.2mol / L and a pH value of 4~5.

5. The oxidation activation treatment is completed by completely immersing the wood shavings in this sodium periodate aqueous solution and activating them under light-protected conditions at a temperature of 25~32℃ for 5~7 hours. Dry the activated wood shavings until the moisture content is less than 15%. The hot pressing pressure is 0.5~10MPa, the hot pressing temperature is 120~250℃, and the hot pressing time is 30~120s / mm.

2. The preparation method according to claim 1, wherein, After oxidation and activation treatment, ethylene glycol is added to quench the reaction and remove unreacted sodium periodate. The activated wood shavings are then washed to neutrality using a vacuum filter.

3. An environmentally friendly particleboard, characterized in that, Prepared by the preparation method described in claim 1 or 2.

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