Multi-layer structure medicinal herb fiber environment-friendly plate and preparation method thereof

Abstract

The invention discloses a multi-layer structure medicinal herb fiber environment-friendly plate and a preparation method thereof, and relates to the technical field of environment-friendly composite materials, the multi-layer structure medicinal herb fiber environment-friendly plate comprises an upper layer panel, a middle functional sandwich layer and a lower layer bottom plate; each of the upper-layer panel and the lower-layer bottom plate takes bark fibers as a framework and wormwood straw powder and medicinal plant straw powder as main fillers, and the frameworks and the main fillers are bonded through an environment-friendly adhesive and then are subjected to hot press molding; the middle functional sandwich layer comprises the following components: 65 wt% of moxa residues, 10 wt% of hedera helix powder, 11 wt% of mixed powder of peach branches and acorus calamus leaves, 8 wt% of eucalyptus and paper tree bark powder, 6 wt% of bamboo powder and fiber cloth embedded in the middle functional sandwich layer; the environment-friendly adhesive is selected from polymerized MDI glue or biomass-based glue, and the dosage of the environment-friendly adhesive is 8-12% of the total dry material mass in the upper-layer panel, the lower-layer bottom plate and the middle functional sandwich layer; the total thickness of the upper-layer panel and the lower-layer bottom plate accounts for 65% of the overall thickness of the plate, and the thickness of the middle functional sandwich layer accounts for 35% of the overall thickness of the plate; and the length of the bark fiber is 15-20 mm.

Description

Technical Field

[0001] This invention relates to the field of environmentally friendly composite materials technology, and in particular to a multi-layered herbal fiber environmentally friendly board and its preparation method. Background Technology

[0002] The field of environmentally friendly composite materials technology refers to a new type of material technology system that combines excellent performance with environmental friendliness, based on renewable resources, waste materials, or low-environmental-impact raw materials and compounded through physical, chemical, or biological methods. This field focuses on reducing dependence on petrochemical resources, lowering energy consumption and emissions during production, improving the biodegradability or recyclability of materials, and ensuring that products are harmless to human health and the ecological environment throughout their entire life cycle. Typical materials include natural fiber-reinforced composite materials, bio-based resin-based composite materials, recycled plastic / rubber composite materials, and functional panels prepared using agricultural, forestry, or industrial solid waste, which are widely used in construction, transportation, packaging, home furnishings, and electronics.

[0003] Fiberboard made from single agricultural waste generally suffers from problems such as low internal bond strength, poor static bending strength, and high thickness expansion rate after water absorption, which limits its application in high humidity or load-bearing environments. Furthermore, medicinal plants such as mugwort, calamus, peach branches, and ivy generate a large amount of residue after extraction for traditional Chinese medicine or pruning in gardens. These residues are usually incinerated or landfilled, resulting in resource waste and environmental pollution, and there is a lack of high-value utilization pathways. Summary of the Invention

[0004] In view of the aforementioned existing problems, the present invention is proposed.

[0005] Therefore, this invention provides a multi-layer structured herbal fiber environmentally friendly board to solve the problems of low internal bond strength, poor static bending strength, and high thickness expansion rate after water absorption that are common in fiberboards made from single agricultural waste, which limit their application in high humidity or load-bearing environments. In addition, medicinal plants such as mugwort, calamus, peach branches, and ivy generate a lot of residue after Chinese medicine extraction or garden pruning, which is usually incinerated or landfilled, causing resource waste and environmental pollution, and lacking high-value utilization pathways.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: In a first aspect, the present invention provides a multi-layered herbal fiber environmentally friendly board, comprising: Upper panel, middle functional sandwich layer and lower base plate; Both the upper panel and the lower base plate are made of bark fiber as the skeleton, and mugwort straw powder and medicinal plant stalk powder as the main filler. They are bonded together with environmentally friendly adhesive and then hot-pressed. The intermediate functional core layer comprises the following components: 65 wt% Artemisia argyi residue, 10 wt% ivy powder, 11 wt% mixed powder of peach branches and calamus leaves, 8 wt% eucalyptus and paper bark powder, 6 wt% bamboo powder, and fiber cloth embedded therein. The environmentally friendly adhesive is selected from polymeric MDI adhesive or biomass-based adhesive, and its usage is 8%–12% of the total dry material mass of the upper panel, lower bottom plate and middle functional sandwich layer.

[0007] In a preferred embodiment of the multi-layer herbal fiber environmentally friendly board of the present invention, the total thickness of the upper panel and the lower base plate accounts for 65% of the overall thickness of the board, and the thickness of the middle functional sandwich layer accounts for 35% of the overall thickness of the board. The bark fibers are 15–20 mm in length and have a moisture content of 8%–12%. The particle sizes of the mugwort residue, medicinal plant stalk powder, and bamboo powder are 40 mesh, 80 mesh, and 100 mesh, respectively. The board also contains coupling agent, flame retardant and waterproofing agent, which are added at 1%, 0.3% and 2% of the total dry material mass, respectively.

[0008] As a preferred embodiment of the multi-layer structure herbal fiber environmentally friendly board of the present invention, the medicinal plant stalk powder is selected from at least two of the following: Artemisia argyi stalk powder, Acorus calamus stalk powder, Prunus persica twig powder, and Ivy stem powder.

[0009] As a preferred embodiment of the multi-layer structured herbal fiber environmentally friendly board of the present invention, wherein: the fiber cloth is a natural plant fiber non-woven fabric with a surface density of 80–120 g / m². 2 It is embedded in the middle of the intermediate functional sandwich layer.

[0010] Secondly, the present invention provides a method for preparing a multi-layered herbal fiber environmentally friendly board, comprising: S1. After softening the bark fiber by steaming, soak it in wood ash water or gypsum water solution, then pulp it until the fiber length is 15–20 mm, and adjust the moisture content to 8%–12% to obtain the skeleton fiber. S2. Dry and pulverize the mugwort stalks, medicinal plant stalks, mugwort residue, ivy, peach branches, calamus leaves, eucalyptus and paper bark tree bark, and bamboo separately, and sieve them to obtain 40 mesh, 80 mesh or 100 mesh powder; S3. Mix the powders, coupling agents, flame retardants, waterproofing agents and environmentally friendly adhesives evenly according to the formula to prepare the upper panel material, the middle functional sandwich layer material and the lower bottom plate material respectively. S4. Lay the lower base plate material, the middle functional sandwich layer material (embedded fiber cloth) and the upper panel material in sequence in the mold to form a three-layer blank; S5. Place the blank in a hot press and hot press for 10–20 minutes at a temperature of 140–160℃ and a pressure of 3–5 MPa. Cool and demold to obtain the multi-layer structured herbal fiber environmentally friendly board.

[0011] In a preferred embodiment of the preparation method of the multi-layer structure herbal fiber environmentally friendly board of the present invention, in step S1, the mass concentration of the wood ash aqueous solution is 3%–5% and the soaking time is 2–4 hours; the concentration of the gypsum aqueous solution is 2%–4% and the soaking time is 1–3 hours.

[0012] As a preferred embodiment of the preparation method of the multi-layer structure herbal fiber environmentally friendly board of the present invention, in step S3, when the environmentally friendly adhesive is polymeric MDI adhesive, the mixing temperature is controlled at 25–35℃; when it is biomass-based adhesive, the mixing temperature is controlled at 40–50℃, and 0.5%–1% of curing accelerator is added.

[0013] In a preferred embodiment of the preparation method of the multi-layer herbal fiber environmentally friendly board of the present invention, wherein: in step S4, the fiber cloth has an areal density of 80–120 g / m² 2 The natural plant fiber nonwoven fabric is laid in the middle of the intermediate functional sandwich layer material, and its width is 5–10 mm smaller than the width of the board to avoid edge overflow.

[0014] As a preferred embodiment of the preparation method of the multi-layer structure herbal fiber environmentally friendly board of the present invention, in step S5, the hot pressing process adopts a segmented pressurization method: first, pre-press at 1–2 MPa for 2–3 minutes to exhaust air, then increase the pressure to 3–5 MPa and hold the pressure for 8–15 minutes, and finally depressurize and cool to below 50°C for demolding.

[0015] As a preferred embodiment of the preparation method of the multi-layer structure herbal fiber environmentally friendly board of the present invention, in step S2, the pulverized powder is dried at 60–80℃ for 2–4 hours before mixing to make its moisture content ≤5%.

[0016] The beneficial effects of this invention are as follows: By adopting a multi-layer composite structure design, combining medicinal plant fibers such as Artemisia argyi residue, ivy, peach branches, and calamus leaves with bark fiber skeletons, and introducing environmentally friendly adhesives and functional additives, it not only effectively improves the mechanical strength, dimensional stability, and water resistance and flame retardant properties of the board, but also endows it with natural antibacterial, insect-repellent, and slow-release aromatic health and environmental protection functions. At the same time, by optimizing the raw material ratio, powder particle size, fiber cloth embedding method, and segmented hot pressing process, it effectively solves the problems of easy cracking, low bonding strength, and high formaldehyde release of traditional plant fiber boards, and realizes the preparation of green building materials with high added value, all bio-based, and near-zero formaldehyde emissions. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of the preparation method of the multi-layer structure herbal fiber environmentally friendly board in Example 1. Detailed Implementation

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0020] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0021] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0022] Example 1, referring to Figure 1 This is the first embodiment of the present invention, which provides a multi-layer structured herbal fiber environmentally friendly board, comprising: The structure comprises an upper panel, a middle functional sandwich layer, and a lower base plate. Both the upper panel and the lower base plate use bark fiber as a skeleton, with Artemisia argyi straw powder and medicinal plant stalk powder as the main fillers, and are bonded together with an environmentally friendly adhesive and then hot-pressed. The middle functional sandwich layer includes the following components: 65 wt% Artemisia argyi residue, 10 wt% ivy powder, 11 wt% mixed powder of peach branches and calamus leaves, 8 wt% eucalyptus and paper bark powder, 6 wt% bamboo powder, and fiber cloth embedded therein. The environmentally friendly adhesive is selected from polymeric MDI adhesive or biomass-based adhesive, and its usage is 8%–12% of the total dry mass of the upper panel, lower base plate, and middle functional sandwich layer.

[0023] Furthermore, the total thickness of the upper panel and the lower base plate accounts for 65% of the overall thickness of the board, and the thickness of the intermediate functional core layer accounts for 35% of the overall thickness of the board; the length of the bark fiber is 15–20 mm, and the moisture content is 8%–12%; the particle sizes of the mugwort residue, medicinal plant stalk powder, and bamboo powder are 40 mesh, 80 mesh, and 100 mesh, respectively; the board also contains coupling agent, flame retardant, and waterproofing agent, with the addition amounts accounting for 1%, 0.3%, and 2% of the total dry material mass, respectively; the medicinal plant stalk powder is selected from at least two of the following: mugwort stalk powder, calamus stalk powder, peach tree branch powder, and ivy stem powder; the fiber cloth is a natural plant fiber nonwoven fabric with a surface density of 80–120 g / m². 2 It is embedded in the middle of the intermediate functional sandwich layer.

[0024] It should be noted that the bark fiber content should be controlled at 15–20. By adjusting the fiber length to mm and the moisture content to 8%–12%, sufficient flexibility and interweaving ability are ensured to form a stable skeleton structure, while avoiding bubbling or delamination caused by excessive moisture during hot pressing due to steam accumulation. This significantly improves the internal bonding strength and surface smoothness of the board. By crushing different raw materials to specific particle sizes according to functional requirements (coarse particles provide skeleton support, and fine powder fills the pores), and with the precise addition of 1% coupling agent, 0.3% flame retardant, and 2% waterproofing agent, the interfacial compatibility between fillers and adhesives is effectively enhanced, improving the mechanical properties, water resistance, and fire safety of the board, while avoiding excessive additives that could affect environmental friendliness. At least two combinations of Artemisia argyi stalk powder, Acorus calamus stalk powder, Prunus persica branch powder, and Ivy stem powder are selected. This not only fully utilizes the volatile aromatic components and natural antibacterial substances (such as eucalyptol, calamus ketone, and safflower glycoside) contained in various medicinal plants, but also achieves long-lasting insect repellent, antibacterial, and air-freshening functions through the synergistic effect of multiple components, giving the board a unique health and environmental protection value.

[0025] This embodiment also provides a method for preparing a multi-layered herbal fiber environmentally friendly board, including: S1. After softening the bark fibers by steaming, soak them in wood ash water or gypsum water solution, then pulp them until the fiber length is 15–20 mm, and adjust the moisture content to 8%–12% to obtain the skeleton fiber.

[0026] Furthermore, in step S1, the mass concentration of the wood ash aqueous solution is 3%–5%, and the soaking time is 2–4 hours; the concentration of the gypsum aqueous solution is 2%–4%, and the soaking time is 1–3 hours.

[0027] It should be noted that soaking in a 3%–5% wood ash aqueous solution for 2–4 hours, or a 2%–4% gypsum aqueous solution for 1–3 hours, can effectively remove wax, pectin, and some hemicellulose from the surface of bark fibers under mild conditions, improving their hydrophilicity and adhesive activity, while avoiding fiber strength loss caused by strong acid and alkali treatment. This treatment method is not only environmentally friendly and pollution-free, but also enhances the interfacial bonding force between fibers and adhesives, thereby improving the overall mechanical properties and durability of the board.

[0028] S2. Dry and pulverize the mugwort stalks, medicinal plant stems, mugwort residue, ivy, peach branches, calamus leaves, eucalyptus and paper bark bark, and bamboo separately, and sieve them to obtain 40 mesh, 80 mesh or 100 mesh powder.

[0029] Furthermore, in step S2, the pulverized powder is dried at 60–80°C for 2–4 hours before mixing to reduce its moisture content to ≤5%.

[0030] It should be noted that drying the pulverized plant powders at 60–80℃ for 2–4 hours to control their moisture content to below 5% can effectively prevent bubbles, delamination, or internal voids caused by moisture vaporization during subsequent mixing and hot pressing, ensuring uniform distribution and full curing of the adhesive. This measure improves the density uniformity, internal bond strength, and dimensional stability of the board, while also helping to reduce the formaldehyde release of the final product.

[0031] S3. Mix the powders, coupling agents, flame retardants, waterproofing agents and environmentally friendly adhesives evenly according to the formula to prepare the upper panel material, the middle functional sandwich layer material and the lower base plate material respectively.

[0032] Furthermore, in step S3, when the environmentally friendly adhesive is polymeric MDI adhesive, the mixing temperature is controlled at 25–35°C; when it is biomass-based adhesive, the mixing temperature is controlled at 40–50°C, and 0.5%–1% of curing accelerator is added.

[0033] It should be noted that, depending on the type of adhesive selected (polymeric MDI adhesive or biomass-based adhesive), the mixing temperature can be controlled at 25–35℃ or 40–50℃, and 0.5%–1% of curing accelerator can be added to optimize the flowability and reactivity of the adhesive, ensuring good dispersibility during the room temperature mixing stage and achieving rapid and full cross-linking and curing during hot pressing. This process not only guarantees the bonding strength but also avoids premature gelation or incomplete curing of the adhesive due to improper temperature, thereby improving the yield and environmental performance.

[0034] S4. Lay the lower base plate material, the middle functional sandwich layer material (embedded fiber cloth) and the upper panel material in sequence in the mold to form a three-layer blank.

[0035] Furthermore, in step S4, the fiber cloth has an areal density of 80–120 g / m². 2 The natural plant fiber nonwoven fabric is laid in the middle of the intermediate functional sandwich layer material, and its width is 5–10 mm smaller than the width of the board to avoid edge overflow.

[0036] It should be noted that a surface density of 80–120 g / m³ is used. 2 The natural plant fiber nonwoven fabric is precisely laid in the middle of the functional core layer, and its width is 5-10 mm smaller than the overall width of the board. This can give full play to the reinforcing effect of the fiber fabric, effectively suppress the shrinkage and deformation of the core layer, improve the bending and impact resistance, and prevent it from overflowing the edge of the board due to stretching during hot pressing, avoiding edge burrs, uneven thickness or subsequent processing difficulties, and ensuring that the board has a neat appearance and structural integrity.

[0037] S5. Place the blank in a hot press and hot press for 10–20 minutes at a temperature of 140–160℃ and a pressure of 3–5 MPa. Cool and demold to obtain the multi-layer structured herbal fiber environmentally friendly board.

[0038] Furthermore, in step S5, the hot pressing process adopts a segmented pressurization method: first, pre-press at 1–2 MPa for 2–3 minutes to release the air, then increase the pressure to 3–5 MPa and hold the pressure for 8–15 minutes, and finally depressurize and cool to below 50°C for demolding.

[0039] It should be noted that the hot pressing process adopts a segmented pressurization method, which first pre-presses at low pressure (1–2 MPa) for 2–3 minutes to exhaust air, and then increases the pressure to 3–5 MPa and holds it for 8–15 minutes. This method can efficiently remove air and volatile substances from the interior of the blank, preventing bulges, voids, or delamination defects from forming inside the board. At the same time, this process is conducive to the uniform penetration and full curing of adhesives, effectively improving the density, mechanical strength, and surface smoothness of the board, and ultimately obtaining high-quality environmentally friendly boards with uniform structure and stable performance.

[0040] In summary, this invention, through the adoption of a multi-layer composite structure design, combines medicinal plant fibers such as Artemisia argyi residue, ivy, peach branches, and calamus leaves with bark fiber skeletons, and introduces environmentally friendly adhesives and functional additives. This not only effectively improves the mechanical strength, dimensional stability, and water resistance and flame retardancy of the board, but also endows it with natural antibacterial, insect-repellent, and slow-release aromatic health and environmental protection functions. At the same time, by optimizing the raw material ratio, powder particle size, fiber cloth embedding method, and segmented hot pressing process, it effectively solves the problems of easy cracking, low bonding strength, and high formaldehyde release of traditional plant fiber boards, and realizes the preparation of green building materials with high added value, all bio-based, and near-zero formaldehyde emissions.

[0041] Example 2 is the second embodiment of the present invention. This embodiment provides a multi-layered herbal fiber environmentally friendly board material mainly based on biomass-based adhesive and its preparation method, including: The structure consists of an upper panel, a middle functional sandwich layer, and a lower bottom plate. The upper panel and lower bottom plate are constructed with a framework of bark fiber (18 mm in length, 10% moisture content), and the main filler is a mixture of Artemisia argyi straw powder (80 mesh), Acorus calamus straw powder, and peach branch powder (mass ratio 1:1). The middle functional sandwich layer comprises 65 wt% Artemisia argyi residue, 10 wt% ivy powder, 11 wt% mixed powder of peach branches and Acorus calamus leaves, 8 wt% eucalyptus and paper bark powder, and 6 wt% bamboo powder (100 mesh), with an embedded surface density of 100 g / m³. 2 The core layer is made of hemp fiber nonwoven fabric; the environmentally friendly adhesive used is soybean protein modified biomass-based adhesive, which accounts for 10% of the total dry material mass; 1% silane coupling agent, 0.3% ammonium polyphosphate flame retardant, and 2% paraffin emulsion waterproofing agent are also added to the board.

[0042] During preparation, bark fibers were soaked in 4% wood ash water for 3 hours and then pulped. All plant materials were pulverized and dried at 70℃ for 3 hours (moisture content ≤5%). The mixing stage was controlled at 45℃, and 0.8% organic amine curing accelerator was added. During layering, the fiber cloth width was 8 mm smaller than the board width. Hot pressing was performed in stages: a pre-press of 1.5 MPa for 2.5 minutes to remove air, then increased to 4 MPa and held for 12 minutes, followed by cooling to 45℃ for demolding. The resulting board was 12 mm thick, with a smooth surface without bulges, and a formaldehyde release of 0.003 mg / m³. 3 It has a static bending strength of 28 MPa, a 24-hour water absorption thickness expansion rate of ≤6%, and a distinct aroma of mugwort and calamus, which provides good insect repellent effect.

[0043] Example 3 is the third embodiment of the present invention. This embodiment provides a highly flame-retardant multi-layer structure herbal fiber environmentally friendly board and its preparation method, including: The structure consists of an upper panel, a middle functional sandwich layer, and a lower base plate. The upper / lower panels are constructed with bark fiber (16 mm, 9% moisture content) as the framework, and the main filler is a mixture of Artemisia argyi straw powder (40 mesh) and ivy stem powder and Artemisia argyi straw powder. The middle functional sandwich layer is composed of: 63 wt% Artemisia argyi residue, 12 wt% ivy powder, 10 wt% mixed powder of peach branches and calamus leaves, 9 wt% eucalyptus and paper bark powder, and 6 wt% bamboo powder, with an embedded surface density of 120 g / m². 2 Jute nonwoven fabric; environmentally friendly adhesive is selected from polymeric MDI adhesive, with a dosage of 11%; flame retardant dosage is increased to 0.5% (compounded with ammonium polyphosphate and zinc borate), coupling agent 1%, and waterproofing agent 2%.

[0044] During the preparation process, bark fibers were soaked in 3% gypsum water for 2 hours; the powder was dried at 75℃ for 2.5 hours; the MDI adhesive mixing temperature was controlled at 30℃; during layup, the fiber cloth was laid in the center with a width of 7 mm (smaller than the board width); the hot-pressing parameters were 150℃ and 4.5 MPa, with segmented pressing (1.8 MPa / 2 min → 4.5 MPa / 10 min), and demolding was performed after cooling to 50℃. The resulting board had an oxygen index of 32%, meeting the B1 flame retardant standard, a static bending strength of 26 MPa, and a formaldehyde release of 0.004 mg / m². 3 It is suitable for interior decoration scenarios with high fire protection requirements.

[0045] Example 4, the third embodiment of the present invention, provides a thin, high-strength, multi-layered herbal fiber environmentally friendly board (6 mm thick), suitable for furniture veneer panels, comprising: The structure consists of an upper panel, a middle functional sandwich layer, and a lower base plate. The upper and lower panels together account for 70% of the total thickness (35% each), and the core layer accounts for 30%. The bark fiber length is 15 mm, and the moisture content is 8%. The main filler for the upper and lower panels is 80-mesh Artemisia argyi straw powder and peach branch powder. The middle layer is composed of 66 wt% Artemisia argyi residue, 9 wt% ivy powder, 12 wt% mixed powder of peach branches and calamus leaves, 7 wt% eucalyptus and paper bark powder, and 6 wt% bamboo powder (100 mesh), with an 80 g / m² layer. 2 Linen nonwoven fabric; adhesive is polymeric MDI glue, used at 9%; additives are the same as in Example 1.

[0046] The preparation process employs more precise hot-pressing control: 140℃, 5 MPa, segmented pressurization (1 MPa / 2 min → 5 MPa / 8 min), followed by rapid cooling to 40℃ for demolding to maintain dimensional accuracy. The resulting 6 mm thick board has a dense surface, can be directly laminated, has a static bending strength of 30 MPa, an elastic modulus of 4200 MPa, and a 24-hour water absorption thickness expansion rate of only 4.8%, meeting the requirements for high-density fiberboard in GB / T 11718-202X, while retaining the slow-release function of natural herbs.

[0047] Comparative Example 1 is a comparative embodiment of the present invention, which provides a three-layer fiberboard without medicinal plant active ingredients, comprising: The product consists of an upper panel, a middle layer, and a lower base plate. The upper and lower panels are filled with bark fiber and ordinary rice husk powder. The middle layer is composed of 70 wt% sawdust, 20 wt% bamboo powder, and 10 wt% starch glue. No medicinal ingredients such as Artemisia argyi residue, ivy, peach branches, or calamus are added, and no fiber cloth is used for reinforcement. The adhesive is urea-formaldehyde resin (12%). The remaining processes are as described in Example 1.

[0048] Although the resulting board has a certain strength (static bending strength 20 MPa), its formaldehyde emission is as high as 0.12 mg / m². 3 (Super E1 grade), lacks antibacterial and insect-repellent functions, and exhibits a 12% thickness expansion rate after 24 hours of water absorption, making it prone to deformation. This result indicates that the synergy between medicinal plant components and environmentally friendly adhesives is key to achieving low formaldehyde and multifunctionality.

[0049] Comparative Example 2 is another comparative embodiment of the present invention. This comparative example provides a herbal fiberboard that does not use a segmented hot pressing process. Its raw material formula is exactly the same as that of Example 1, but in step S5, it is directly hot-pressed at a constant pressure of 4 MPa for 15 minutes without a pre-pressurization and degassing stage.

[0050] The results showed that the board contained obvious air bubbles and micro-delamination, with localized bulging on the surface. The static bending strength dropped to 22 MPa, and the internal bond strength was only 0.45 MPa (compared to 0.72 MPa in Example 1). This indicates that segmented pressurization plays an irreplaceable role in removing volatiles and ensuring structural density.

[0051] Comparative Example 3 is another comparative embodiment of the present invention. This comparative example provides a single-layer homogeneous herbal fiberboard, which is formed by uniformly mixing all components (including Artemisia argyi residue, ivy powder, bark fiber, bamboo powder, etc.) and hot-pressing them in one go. It does not have a functional core layer to distinguish it from the surface layer, nor does it have fiber cloth embedded in it.

[0052] The resulting boards are environmentally friendly (formaldehyde 0.005 mg / m³). 3 However, the mechanical properties decreased significantly (static bending strength was only 18 MPa), and the medicinal components were easily worn away and lost on the surface, resulting in a sustained-release effect lasting less than 7 days (Example 1 can last for more than 30 days). This demonstrates that the multi-layer gradient structure design of the present invention is crucial for the synergistic improvement of functional durability and mechanical properties.

[0053] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A multi-layered herbal fiber environmentally friendly board, characterized in that: include: Upper panel, middle functional sandwich layer and lower base plate; Both the upper panel and the lower base plate are made of bark fiber as the skeleton, and mugwort straw powder and medicinal plant stalk powder as the main filler. They are bonded together with environmentally friendly adhesive and then hot-pressed. The intermediate functional core layer comprises the following components: 65 wt% Artemisia argyi residue, 10 wt% ivy powder, 11 wt% mixed powder of peach branches and calamus leaves, 8 wt% eucalyptus and paper bark powder, 6 wt% bamboo powder, and fiber cloth embedded therein. The environmentally friendly adhesive is selected from polymeric MDI adhesive or biomass-based adhesive, and its usage is 8%–12% of the total dry material mass of the upper panel, lower bottom plate and middle functional sandwich layer.

2. The multi-layer structure herbal fiber environmentally friendly board as described in claim 1, characterized in that: The total thickness of the upper panel and the lower base plate accounts for 65% of the overall thickness of the board, and the thickness of the middle functional sandwich layer accounts for 35% of the overall thickness of the board. The bark fibers are 15–20 mm in length and have a moisture content of 8%–12%. The particle sizes of the mugwort residue, medicinal plant stalk powder, and bamboo powder are 40 mesh, 80 mesh, and 100 mesh, respectively. The board also contains coupling agent, flame retardant and waterproofing agent, which are added at 1%, 0.3% and 2% of the total dry material mass, respectively.

3. The method for preparing the multi-layer structured herbal fiber environmentally friendly board as described in claim 2, characterized in that: The medicinal plant stalk powder is selected from at least two of the following: Artemisia argyi stalk powder, Acorus calamus stalk powder, Prunus persica twig powder, and Ivy stem powder.

4. The method for preparing multi-layered herbal fiber environmentally friendly board as described in claim 3, characterized in that: The fiber cloth is a nonwoven fabric made of natural plant fibers with a surface density of 80–120 g / m². 2 It is embedded in the middle of the intermediate functional sandwich layer.

5. A method for preparing a multi-layered herbal fiber environmentally friendly board, as described in any one of claims 1-4, characterized in that: include: S1. After softening the bark fiber by steaming, soak it in wood ash water or gypsum water solution, then pulp it until the fiber length is 15–20 mm, and adjust the moisture content to 8%–12% to obtain the skeleton fiber. S2. Dry and pulverize the mugwort stalks, medicinal plant stalks, mugwort residue, ivy, peach branches, calamus leaves, eucalyptus and paper bark tree bark, and bamboo separately, and sieve them to obtain 40 mesh, 80 mesh or 100 mesh powder; S3. Mix the powders, coupling agents, flame retardants, waterproofing agents and environmentally friendly adhesives evenly according to the formula to prepare the upper panel material, the middle functional sandwich layer material and the lower bottom plate material respectively. S4. Lay the lower base plate material, the middle functional sandwich layer material (embedded fiber cloth) and the upper panel material in sequence in the mold to form a three-layer blank; S5. Place the blank in a hot press and hot press for 10–20 minutes at a temperature of 140–160℃ and a pressure of 3–5 MPa. Cool and demold to obtain the multi-layer structured herbal fiber environmentally friendly board.

6. The method for preparing the multi-layer structured herbal fiber environmentally friendly board as described in claim 5, characterized in that: In step S1, the mass concentration of the wood ash aqueous solution is 3%–5%, and the soaking time is 2–4 hours; the concentration of the gypsum aqueous solution is 2%–4%, and the soaking time is 1–3 hours.

7. The method for preparing the multi-layer structured herbal fiber environmentally friendly board as described in claim 6, characterized in that: In step S3, when the environmentally friendly adhesive is polymeric MDI adhesive, the mixing temperature is controlled at 25–35℃; when it is biomass-based adhesive, the mixing temperature is controlled at 40–50℃, and 0.5%–1% of curing accelerator is added.

8. The method for preparing the multi-layer structured herbal fiber environmentally friendly board as described in claim 7, characterized in that: In step S4, the fiber cloth has a surface density of 80–120 g / m². 2 The natural plant fiber nonwoven fabric is laid in the middle of the intermediate functional sandwich layer material, and its width is 5–10 mm smaller than the width of the board to avoid edge overflow.

9. The method for preparing the multi-layer structured herbal fiber environmentally friendly board as described in claim 8, characterized in that: In step S5, the hot pressing process adopts a segmented pressurization method: first, pre-press at 1–2 MPa for 2–3 minutes to release the air, then increase the pressure to 3–5 MPa and hold the pressure for 8–15 minutes, and finally depressurize and cool to below 50°C for demolding.

10. The method for preparing the multi-layer structured herbal fiber environmentally friendly board as described in claim 9, characterized in that: In step S2, the pulverized powder is dried at 60–80°C for 2–4 hours before mixing to reduce its moisture content to ≤5%.

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