A method for producing a glue-free and formaldehyde-free shaving board

Abstract

This invention provides a method for producing glue-free and formaldehyde-free particleboard, belonging to the field of particleboard technology. This invention uses bamboo willow branches, *Ligustrum lucidum* branches, dried leaves, and *Eucommia ulmoides* waste as raw materials after chipping. No adhesives are needed. Through practice, it has been found that *Ligustrum lucidum*, also known as "sheep's milk strip," contains rubber components in its stems and leaves. Sulfur water-dispersible granules, originally used for antibacterial and insecticidal purposes, undergo a vulcanization cross-linking reaction with the rubber components in the *Ligustrum lucidum* branches and dried leaves during continuous hot pressing of the layered particleboard blanks. Furthermore, some rubber components remain in the *Eucommia ulmoides* waste. This vulcanization cross-linking reaction creates a tightly connected cross-linked network between the raw materials, acting as an adhesive for the particleboard. This method not only reduces energy consumption but also facilitates processing, reduces production costs, and provides excellent performance, completely eliminating pollution sources at a low cost.

Description

Technical Field

[0001] This invention belongs to the field of particleboard technology, and in particular to a method for producing glue-free and formaldehyde-free particleboard. Background Technology

[0002] Traditional adhesives can improve the mechanical properties of particleboard, but they have drawbacks such as formaldehyde release. Research on glue-free particleboard began in the 1980s, using sugarcane bagasse to prepare glue-free cellulose composites, or using the enzyme modification technology adopted by German scholar Kuhne G in 1998 to treat wood particleboard, followed by pressure or molding to prepare glue-free wood particleboard. Ke Cuifang et al. placed wood fibers in a closed high-pressure container, treated them with steam heating, and then hot-pressed them to prepare glue-free particleboard. Wang Kaiwen et al. disclosed a process study on the preparation of glue-free particleboard by co-grinding soybeans and wood chips. On December 12, 2017, CN201710833090.6 disclosed a method for producing glue-free particleboard using white-rot mycelium, using straw or wood shavings as raw materials, and obtaining mycelium through liquid fermentation of white-rot fungi. However, during the rainy season, the air humidity is high and the temperature is high, making medium-density particleboard and other materials prone to mold. Robles et al. developed high-performance glue-free particleboard using wheat straw residue. Glue-free particleboard has advantages such as no formaldehyde release and lower cost, but it also has some drawbacks, such as lower mechanical strength, which greatly limits its application and makes industrial production difficult. Glue-free particleboard can be prepared into multifunctional composite glue-free particleboard through methods such as adding nanoparticles and surface modification, and can be widely used in home decoration materials and other fields. Those skilled in the art urgently need to develop a production method for glue-free, formaldehyde-free particleboard to meet current usage needs and performance requirements. Summary of the Invention

[0003] To address the above problems, the present invention aims to provide a method for producing glue-free and formaldehyde-free particleboard.

[0004] This invention is achieved through the following technical solution:

[0005] A method for producing glue-free and formaldehyde-free particleboard includes the following steps:

[0006] Step 1: Using bamboo willow branches, willow branches, dried willow leaves, and Eucommia ulmoides waste as raw materials, the bamboo willow branches and willow branches are shaving, screened, steamed, and then hot-milled, fed into a hot mill via a screw feeder. Further, the Eucommia ulmoides waste has a gum content of 2%–3%, with a screw feeder compression ratio of 1.9–2.2, a hot mill speed of 1700–1900 rpm, and a gap of 0.15–0.30 mm between the moving and stationary grinding discs. Hot milling is performed at 175–195℃, followed by pneumatic air separation to obtain granular shavings. Steam is then steamed at 90–95℃ at a pressure of 7.0–8.5 MPa for 2–5 minutes. After extracting the effective medicinal components of Eucommia ulmoides, most of the Eucommia ulmoides waste will accumulate and degrade naturally or be directly incinerated, leading to environmental pollution and resource waste. Currently, the waste is mainly used for composting or edible fungi cultivation.

[0007] Willow shrubs were previously used for vertical greening and sand fixation. They are drought-resistant, cold-resistant, alkali-resistant, easy to grow, fast-growing, and useful as firewood.

[0008] Step 2: The dried leaves of *Ligustrum lucidum*, waste residue of *Eucommia ulmoides*, and hot-ground granular wood shavings are mixed to obtain surface layer wood shavings and core layer wood shavings, respectively. Further, the mass ratio of dried leaves of *Ligustrum lucidum*, waste residue of *Eucommia ulmoides*, and wood shavings in the surface layer wood shavings is 8–9:35–37:41–43, and the mass ratio of dried leaves of *Ligustrum lucidum*, waste residue of *Eucommia ulmoides*, and granular wood shavings in the core layer wood shavings is 11–13:29–31:27–29. After atomization through a pressurized nozzle, the mixture is applied to the surface layer... Sulfur water-dispersible granules are sprayed onto the surface layer and core layer wood shavings. Then, the surface layer and core layer wood shavings are dried until their moisture content is 8%–10%. After drying, they are laid in layers to form a layered paving board with a lower surface layer / core layer / upper surface layer. The sulfur water-dispersible granules account for 0.03%–0.04% of the surface layer wood shavings and 0.04%–0.05% of the core layer wood shavings.

[0009] Step 3: The layered slab blanks are continuously hot-pressed, with a hot-pressing factor of 16-20 s / mm. The pressure is increased to high pressure in 10-20 seconds, with a high pressure of 5.0-5.2 MPa. Under high pressure, the blanks are hot-pressed at 230-240℃ for 30-35 seconds, and then the pressure is reduced to low pressure in 15-20 seconds, with a low pressure of 3.5-4.5 MPa. Under low pressure, the blanks are hot-pressed at 195-200℃ for 30-35 seconds, and then cooled to room temperature to obtain a semi-finished particleboard product. The semi-finished particleboard product is cooled by a flip-plate cooling machine to bring the core layer temperature to 30-50℃. After stacking and conditioning for 24-48 hours, the blanks are sanded, inspected, graded, and packaged to obtain glue-free and formaldehyde-free particleboard.

[0010] Furthermore, in the step one, the granular wood shavings after hot grinding account for 7.5% to 10% of the total weight if the granular wood shavings are larger than 3mm, 80% to 85% of the total weight if the granular wood shavings are 2 to 3mm, and 7.5% to 10% of the total weight if the granular wood shavings are smaller than 2mm.

[0011] Furthermore, in step two, the thickness ratio of the lower surface layer / core layer / upper surface layer in the layered paving slab is 2-3:5-7:2-3.

[0012] Furthermore, the thickness of the particleboard in step three is 18–35 mm.

[0013] Furthermore, the sulfur water-dispersible granule solution is obtained by diluting 80% sulfur water-dispersant with water 200-300 times.

[0014] This highly water-dispersible 80% sulfur water-dispersible granule can quickly disperse in water to form a stable suspension. It does not settle, clump, or clog nozzles, making it easy, safe, and efficient to use. Its particles are approximately 150 micrometers in diameter and immediately and completely disperse into particles upon contact with water, thus forming a stable suspension. Previously used to control powdery mildew, rust, and other fungal diseases in crops, it also controls mites. It has the advantages of low dosage and no dust.

[0015] In production practice, a small amount of sulfur water-dispersible granules was used in particleboard processing in an attempt to achieve antibacterial and insecticidal effects. However, it was unexpectedly discovered that the sulfur water-dispersible granules could act as a binder for particleboard without the need for adhesives. This allowed for the production of formaldehyde-free and glue-free particleboard, with all properties meeting the requirements of the national standard for medium-density particleboard.

[0016] The beneficial effects of this invention are:

[0017] The method for producing formaldehyde-free and glue-free particleboard disclosed in this invention uses bamboo willow branches, *Ligustrum lucidum* branches, dried leaves of *Ligustrum lucidum*, and *Eucommia ulmoides* waste as raw materials. No adhesives are required. Through practice, it has been found that *Ligustrum lucidum*, also known as "sheep's milk strip," contains rubber components in its stems and leaves. Sulfur water-dispersible granules, originally used for antibacterial and insecticidal purposes, undergo a vulcanization cross-linking reaction with the rubber components in the *Ligustrum lucidum* branches and dried leaves during continuous hot pressing of the layered particleboard. Furthermore, some rubber components remain in the *Eucommia ulmoides* waste. This vulcanization cross-linking reaction creates a tightly connected cross-linked network between the raw materials, effectively bonding the particleboard. The agent not only reduces energy consumption but also facilitates processing, reduces production costs, and enhances performance. The rubber components are cross-linked through a sulfur cross-linking agent, altering their properties. During heating, they lose their viscosity, transforming from plastic rubber into elastic and hard rubber. Consequently, particleboard does not require additional adhesives. Previously, most particleboard production in my country relied on wood as raw material, and the shortage of raw materials significantly limited the development of particleboard. Due to the shortage and rising prices of raw materials, the formaldehyde-free and glue-free particleboard production method disclosed in this invention completely eliminates pollution sources and is cost-effective. Detailed Implementation

[0018] The present invention is illustrated below with specific embodiments, but these are not intended to limit the scope of the invention. Example 1

[0019] Raw materials: 3-year-old bamboo and willow branches; 3-year-old willow branches; stockpiled in the raw material yard; Zhongshan Chemical 80% sulfur water dispersant;

[0020] The production method of glue-free and formaldehyde-free particleboard includes the following steps:

[0021] (1) Bamboo and willow branches, willow branches, dried willow leaves, and Eucommia ulmoides residue are used as raw materials. The bamboo and willow branches are shaving, screened, steamed, and then hot-ground. The bamboo and willow branches in the raw material yard are coarsely processed and cut into wood chips. The branches are chipped by a chipper for crushing. At the same time, the raw materials are detected by a metal detector and iron remover to remove metal impurities before use. Screening and impurity removal: This is to separate the stones, dust, food particles, some stalks and leaves, stalk nodes and other "impurities" in the raw materials such as straw. The straw after screening is cleaner, which can reduce the ash content in the raw materials and improve the quality of the raw materials. Crushing: The coarse material after cutting is crushed into a shape that meets the requirements of the crushed material for the preparation of straw board.Branches are fed by forklift onto a belt conveyor and then into a drum chipper for chipping. The chips are then processed by a ring shaving machine and transported by belt conveyor to a wood chip sieve. Qualified wood shavings are 16–25 mm long, 15–20 mm wide, and 3–4 mm thick. They then enter a hot mill via a screw feeder. Further processing is performed in a hot mill with a screw feeder compression ratio of 1.9, a hot mill speed of 1700 rpm, and a 0.15 mm gap between the moving and stationary grinding discs. The mill is then hot-milled at 175°C, followed by pneumatic air separation to obtain granular wood shavings. Finally, the wood is steam-cooked at 90°C at a pressure of 7.0 MPa. a. The cooking time is 2 minutes; after hot grinding, the granular shavings larger than 3 mm account for 7.5% of the total weight, the granular shavings of 2~3 mm account for 85% of the total weight, and the fibers smaller than 2 mm account for 7.5% of the total weight; (2) The dried leaves of *Ligustrum lucidum*, the waste residue of *Eucommia ulmoides* and the granular shavings after hot grinding are mixed to prepare the surface layer shavings and the core layer shavings respectively; the *Eucommia ulmoides* waste residue of Qingzhou Miaozi contains 2% glue, wherein the mass ratio of dried leaves of *Ligustrum lucidum*, waste residue of *Eucommia ulmoides* and shavings in the surface layer shavings is 8:35:41, and the mass ratio of dried leaves of *Ligustrum lucidum*, waste residue of *Eucommia ulmoides* and granular shavings in the core layer shavings is 8:35:41. The ratio is 11:29:27; after atomization by a pressurized nozzle, sulfur water-dispersible granules are sprayed onto the surface layer shavings and the core layer shavings, and then the surface layer shavings and the core layer shavings are dried until the moisture content of the surface layer shavings and the core layer shavings is 8%; after drying, they are laid in layers to form a layered paving board blank with a lower surface layer / core layer / upper surface layer, wherein the sulfur water-dispersible granules account for 0.03% of the surface layer shavings and the sulfur water-dispersible granules account for 0.04% of the core layer shavings, and the thickness ratio of the lower surface layer / core layer / upper surface layer in the layered paving board blank is 2:5:2; (3) the layered paving board blank is laid in layers. The blank is continuously hot-pressed, with a hot-pressing factor of 16s / mm. The pressure is increased to high pressure in 10s, with a high pressure of 5.0MPa. It is then hot-pressed at 230℃ for 30s under high pressure, followed by a 15s reduction to low pressure, with a low pressure of 3.5MPa. After hot-pressing at 195℃ for 30s under low pressure, it is cooled to room temperature. After thickness and weight testing, a semi-finished particleboard is obtained. The semi-finished particleboard is then cooled using a flip-plate cooling machine to bring the core layer temperature to 30℃. After stacking and conditioning for 48 hours, it is sanded, inspected, graded, and packaged to obtain glue-free and formaldehyde-free particleboard with a thickness of 18mm.

[0022] Product: Odor rating: 0 (odorless); Dimensions: 1220×2440×18mm; Static bending strength: 12.1MPa; Elastic modulus: 2152MPa; Internal bond strength: 0.59MPa; Surface bond strength: 1.23MPa; 2-hour water absorption thickness swelling rate: 0%; Moisture content: 5.1%; Density: 0.71g / cm³; Internal density deviation: +1.4%~2.8%; Screw holding force: 1280N on the board surface, 1060N on the edge; Formaldehyde emission: mg / m³ 3 Not detected. Example 2

[0023] Raw materials: 3-year-old small-diameter bamboo willow timber, 3-year-old bamboo willow branches; willow branches; Eucommia ulmoides waste residue with 3% glue content from Qingzhou Miaozi, piled up in the raw material stockpile; Shuangji Chemical 80% sulfur water dispersant.

[0024] The production method of glue-free and formaldehyde-free particleboard includes the following steps:

[0025] (1) Bamboo and willow branches, willow branches, dried willow leaves, and Eucommia ulmoides residue are used as raw materials. The bamboo and willow branches are shaving, screened, steamed, and then hot-ground. The bamboo and willow branches in the raw material yard are coarsely processed and cut into wood chips. The branches are chipped by a chipper for crushing. At the same time, the raw materials are detected by a metal detector and iron remover to remove metal impurities before use. Screening and impurity removal: This is to separate the stones, dust, food particles, some stalks and leaves, stalk nodes and other "impurities" in the raw materials such as straw. The straw after screening is cleaner, which can reduce the ash content in the raw materials and improve the quality of the raw materials. Crushing: The coarse material after cutting is crushed into a shape that meets the requirements of the crushed material for the preparation of straw board.Branches are fed by forklift onto a belt conveyor and then into a drum chipper for chipping. The chips are then processed by a ring shaving machine and transported by belt conveyor to a wood chip sieve. Qualified wood chips have a length of 16–25 mm, a width of 15–20 mm, and a thickness of 3–4 mm. These chips are then fed into a hot mill via a screw feeder. Further processing is performed, with the screw feeder having a compression ratio of 2.2, the hot mill rotating at 1900 rpm, and a 0.30 mm gap between the moving and stationary grinding discs. The mill is then hot-milled at 195°C, followed by pneumatic air separation to obtain granular wood chips. Finally, the chips are steam-cooked at 95°C at a pressure of 8.5 MPa. Pa, the cooking time is 5 min; the granular shavings after hot grinding are 10% of the total weight of granular shavings with a mesh size greater than 70, 80% of the total weight of granular shavings with a mesh size of 2-3 mm, and 10% of the total weight of granular shavings with a mesh size less than 2 mm; (2) the dried leaves of *Ligustrum lucidum*, the waste residue of *Eucommia ulmoides*, and the granular shavings and wood chips after hot grinding are mixed to prepare surface shavings and core shavings respectively; further, the mass ratio of dried leaves of *Ligustrum lucidum*, waste residue of *Eucommia ulmoides*, and wood chips in the surface shavings is 9:37:43, and the mass ratio of dried leaves of *Ligustrum lucidum*, waste residue of *Eucommia ulmoides*, and granular shavings in the core shavings is 13∶31∶29;After atomization by pressurized nozzle, sulfur water-dispersible granules are sprayed onto the surface layer shavings and the core layer shavings. Then, the surface layer shavings and the core layer shavings are dried until the moisture content of the surface layer shavings and the core layer shavings is 10%. After drying, they are laid in layers to form a layered paving board blank with a lower surface layer / core layer / upper surface layer. The sulfur water-dispersible granules account for 0.4% of the surface layer shavings and 0.5% of the core layer shavings. The thickness ratio of the lower surface layer / core layer / upper surface layer in the layered paving board blank is 3∶7∶3; (3) The layered paving board blank is continuously processed by… The process involves hot pressing, with a hot pressing factor of 20s / mm. The pressure is increased to high pressure (5.2MPa) in 20 seconds, then hot-pressed at 240℃ for 35 seconds. The pressure is then reduced to low pressure (4.5MPa) in 20 seconds, and finally hot-pressed at 200℃ for 35 seconds before cooling to room temperature. Thickness and weight are then measured to obtain a semi-finished particleboard product. This semi-finished product is then cooled using a flip-plate cooling machine to achieve a core layer temperature of 50℃. After stacking and conditioning for 48 hours, it undergoes sanding, inspection, grading, and packaging to obtain glue-free and formaldehyde-free particleboard with a thickness of 35mm.

[0026] Product: Odor rating: 0 (odorless); Dimensions: 1220×2440×35mm; Static bending strength: 12.9MPa; Elastic modulus: 2111MPa; Internal bond strength: 0.57MPa; Surface bond strength: 1.17MPa; 2-hour water absorption thickness swelling rate: 0%; Moisture content: 4.8%; Density: 0.72g / cm³ 3 Internal density deviation of the board: +1.5%~2.7%; Screw holding force: 1240N on the board surface, 1040N on the board edge; Formaldehyde emission: mg / m³ 3 Not detected.

[0027] Note: Refer to GB / T15102-2017: static bending strength, modulus of elasticity, internal bond strength, surface bond strength, 2h water absorption thickness swelling rate, moisture content, density, density deviation within the board, screw holding force; GB18580-2017 Formaldehyde emission limits in wood-based panels and their products for interior decoration and renovation: formaldehyde emission.

Claims

1. A method for producing glue-free and formaldehyde-free particleboard, characterized in that, Includes the following steps: Step 1: Using bamboo and willow branches, willow branches, dried willow leaves, and eucommia residue as raw materials, the bamboo and willow branches are shaving, screened, and steamed to obtain wood shavings, which are then hot-milled. The shavings are fed into a hot mill via a screw feeder and subjected to pneumatic air separation to obtain granular wood shavings. The granular wood shavings larger than 3mm account for 7.5%–10% of the total weight, those 2–3mm account for 80%–85%, and those smaller than 2mm account for 7.5%–10%. The milling process is carried out at 90–95℃. Steam cooking is performed at a pressure of 7.0–8.5 MPa for 2–5 minutes. In step two, dried willow leaves, Eucommia ulmoides residue, and granular wood shavings are mixed to prepare surface and core wood shavings. The mass ratio of dried willow leaves, Eucommia ulmoides residue, and wood shavings in the surface layer is 8–9:35–37:41–43, while the mass ratio of dried willow leaves, Eucommia ulmoides residue, and granular wood shavings in the core layer is 11–13:29–31:27–29. The surface and core wood shavings are then sprayed through a pressurized nozzle after atomization. Sulfur water-dispersible granules are prepared, and then the surface layer and core layer wood shavings are dried to a moisture content of 8%–10%. After drying, they are laid in layers to form a layered paving board with a lower surface layer / core layer / upper surface layer. The sulfur water-dispersible granules account for 0.03%–0.04% of the surface layer wood shavings and 0.04%–0.05% of the core layer wood shavings. Step 3: The layered paving board is continuously hot-pressed at a hot-pressing factor of 16–20 s / mm and a pressure increase of 10–20 s. The material is then heated to high pressure (5.0–5.2 MPa) at 230–240°C for 30–35 seconds, followed by a 15–20 second reduction in pressure to low pressure (3.5–4.5 MPa). This low pressure is then further reduced to 195–200°C for 30–35 seconds, followed by cooling to room temperature to obtain a semi-finished particleboard product. This semi-finished product is then cooled using a flip-plate cooling machine to achieve a core layer temperature of 30–50°C. After stacking and conditioning for 24–48 hours, the product is sanded, inspected, graded, and packaged to obtain glue-free and formaldehyde-free particleboard.

2. The method for producing glue-free and formaldehyde-free particleboard according to claim 1, characterized in that, In step one, the compression ratio of the screw feeder is 1.9 to 2.2, the rotation speed of the hot mill is 1700 to 1900 rpm, the gap between the moving grinding disc and the fixed disc is 0.15 to 0.30 mm, and the hot milling treatment is carried out at 175 to 195℃.

3. The method for producing glue-free and formaldehyde-free particleboard according to claim 1, characterized in that, The thickness ratio of the lower surface layer / core layer / upper surface layer in the layered paving slab in step two is 2-3:5-7:2-3.

4. The method for producing glue-free and formaldehyde-free particleboard according to claim 1, characterized in that, The thickness of the particleboard in step three is 18-30mm.

5. The method for producing glue-free and formaldehyde-free particleboard according to claim 1, characterized in that, The sulfur water-dispersible granule solution in step two is obtained by diluting 80% sulfur water-dispersant with water 200-300 times.