Preparation method of ENF grade technical wood

Abstract

This invention relates to the field of panel decoration and discloses a method for preparing ENF-grade engineered wood. The method involves adding soybean meal powder and auxiliary materials to water and stirring evenly to prepare soybean meal adhesive. Then, magnesium oxysulfate adhesive is added to the soybean meal adhesive and stirred evenly to prepare modified soybean meal adhesive. The soybean meal adhesive is then coated onto a thin layer of wood veneer, and the veneer is assembled to form a wood blank. Finally, the wood blank is cold-pressed, cured, and trimmed to produce ENF-grade engineered wood. This method modifies the soybean meal adhesive with magnesium oxysulfate adhesive, significantly improving its bonding performance. The engineered wood prepared by this method exhibits significantly improved lateral rigidity and toughness, significantly improved mildew resistance, and significantly reduced water absorption.

Description

Technical Field

[0001] This invention relates to the field of panel decoration, and in particular to a method for preparing ENF-grade engineered wood. Background Technology

[0002] The use of urea-formaldehyde resin adhesives in engineered wood products results in high formaldehyde emissions, which seriously harm human health. Therefore, to protect consumer health and promote the healthy and environmentally friendly development of the engineered wood products industry, a grading standard has been established for the formaldehyde emission levels of engineered wood products and their products. The ENF grade, also known as the F4 star environmental protection grade, is currently the highest environmental protection level for formaldehyde emission in engineered wood products and their products, with a formaldehyde emission limit of ≤0.025 mg / m³. 3 .

[0003] Currently, ENF-grade engineered wood products are mainly manufactured by replacing urea-formaldehyde resin adhesives with formaldehyde-free adhesives. For example, CN116083050B discloses a soybean meal adhesive, its preparation, and its application. This technical solution proposes a soybean meal adhesive composed of soybean meal, a penetrant, a dispersion medium, distilled water, and a crosslinking agent. Plywood made with soybean meal adhesive exhibits high strength, high water resistance, and low formaldehyde release. Soybean meal adhesive is a biomass adhesive. Soybean meal molecules have a globulin structure; denaturation allows the molecular chains to stretch and expose active groups, interacting with wood to achieve an adhesive effect. Because soybean meal adhesive is a biomass material, it is highly hydrophilic and extremely prone to spoilage and mold. Therefore, water resistance and mold prevention are important research directions for improving its performance. Currently, the existing technology for preventing mold in soybean meal adhesive mainly uses tannic acid. The anti-mold effect of tannic acid improves the corrosion resistance of soybean meal adhesive. However, tannic acid is a small molecule and is easily lost during use. After long-term use, the anti-mold properties of engineered wood will decrease significantly. Therefore, it is of great significance to provide a long-term water-resistant and mold-resistant ENF-grade engineered wood. Summary of the Invention

[0004] This invention provides a method for preparing ENF-grade engineered wood. The method uses modified soybean meal adhesive to prepare ENF-grade engineered wood. The method modifies the soybean meal adhesive with magnesium oxysulfate adhesive, which significantly improves the bonding performance of the soybean meal adhesive. The engineered wood prepared by this method has significantly improved side rigidity and toughness, significantly improved mildew resistance, and significantly reduced water absorption.

[0005] The specific technical solution of this invention is as follows: A method for preparing ENF-grade engineered wood includes the following steps: (1) Add soybean meal powder and auxiliary materials to water and stir evenly to make soybean meal glue; (2) Add magnesium oxysulfate adhesive to soybean meal adhesive and stir evenly to prepare modified soybean meal adhesive; the mass ratio of soybean meal adhesive to magnesium oxysulfate adhesive is 1:0.4~0.6. (3) Apply soybean meal glue to a thin layer of wood veneer, assemble the thin layer of wood veneer to make a wood blank, and then cold press, cure and repair the wood blank to make ENF grade engineered wood.

[0006] Preferably, the magnesium oxysulfate adhesive comprises lightly calcined magnesium oxide, magnesium sulfate, magnesium chloride, a retarder, and water.

[0007] Preferably, the activity of lightly calcined magnesium oxide is 60-70%.

[0008] As a preferred option, the soybean meal powder is 10-16 parts by weight, the auxiliary materials are 27-57 parts, and the water is 40-60 parts.

[0009] Preferably, the excipients are hexamethylene diisocyanate, polyvinyl alcohol, polyacrylamide, fly ash, water glass, inorganic thickener, and waterproofing agent.

[0010] Preferably, the waterproofing agent includes one or both of emulsified paraffin wax and sodium methylsiloxane.

[0011] Preferably, the inorganic thickener includes one or both of sepiolite fiber and bentonite.

[0012] As a preferred option, the curing conditions include: a curing temperature of 43~47 ℃, a curing humidity of 40~60%, and a curing time of 60~80 h.

[0013] Preferably, the cold pressing conditions include: 2.2~3.8 MPa, and a time of 5~10 min.

[0014] Preferably, the trimmed thickness is 0.1~2 mm.

[0015] This invention provides a method for preparing ENF-grade engineered wood, in which modified soybean meal gum is used as an adhesive for engineered wood. Soybean meal gum, as a biomass adhesive, can significantly reduce the formaldehyde release of engineered wood, enabling the formaldehyde release of engineered wood to reach the ENF level. This invention uses magnesium oxysulfate adhesive to modify soybean meal gum. Magnesium oxysulfate adhesive is alkaline and acts as a modifier for soybean meal gum, causing denaturation of the protein molecules and stretching the highly folded protein molecules to expose more active sites. Magnesium oxysulfate adhesive itself has excellent adhesive properties, and the two work synergistically. The pentahydrate magnesium oxysulfate crystals formed after hydration are tobermorite needle-like crystals. These needle-like structures penetrate into the wood fiber cells, forming a needle-like interlocking structure with the wood fibers. Simultaneously, the penetration of the pentahydrate magnesium oxysulfate crystals into the wood fibers facilitates the penetration of soybean meal gum into the interior of the wood fibers, thereby forming a tight bond between the modified soybean meal gum and the wood fibers, significantly improving the adhesive effect of the modified soybean meal gum.

[0016] Because soybean meal gum molecules contain numerous hydrophilic groups, soybean meal gum is extremely hydrophilic, resulting in highly absorbent engineered wood made from soybean meal gum adhesives. Furthermore, the biomass components of soybean meal gum can act as a substrate for mold growth, making engineered wood made from soybean meal gum adhesives prone to mold growth after absorbing water. This invention modifies soybean meal gum using magnesium oxysulfate adhesive, finding a significant reduction in water absorption and mold growth in the modified soybean meal gum. The solid adhesive layer formed after curing of magnesium oxysulfate adhesive has low porosity, significantly reducing its water absorption. In addition, the cured magnesium oxysulfate adhesive forms pentahydrate magnesium oxysulfate crystals, which provide magnesium and sulfate ions, creating a high-salt environment. This high-salt environment inhibits mold growth, thus suppressing mold growth in engineered wood.

[0017] A damp environment is a major cause of mold growth on wood. To further improve the waterproof performance of modified soybean meal adhesive, this invention utilizes fly ash. Fly ash increases the density of the cured adhesive layer and reduces its porosity, thereby reducing the water absorption of the modified soybean meal adhesive. In addition, water glass is added. Water glass, being alkaline, also acts as a modifier for soybean meal adhesive. The silica bonds formed by water glass provide a crosslinking framework for the crosslinking agent, further improving adhesion and the density of the cured adhesive layer, thus further enhancing the waterproof performance of the soybean meal adhesive.

[0018] Inorganic thickeners can adjust the viscosity of modified soybean meal gum and improve its coatability.

[0019] Waterproofing agents can improve the hydrophobicity of soybean meal gum, enhance its water resistance, and reduce its water absorption.

[0020] Polyvinyl alcohol can improve the flexibility of modified soybean meal adhesive, thus avoiding edge chipping problems during engineered wood processing.

[0021] Hexamethylene diisocyanate is a hydrophilic curing agent that can react with the active groups in modified soybean meal gum to form a cross-linking network, significantly enhancing the bonding performance of the modified soybean meal gum.

[0022] Compared with the prior art, this application has the following technical effects: (1) Magnesium sulfide adhesive can be used as a modifier for soybean meal gum to deform soybean meal gum protein molecules, so that soybean meal gum protein molecules can stretch out and expose active sites. (2) The pentahydrated magnesium oxysulfate needle-like crystals formed after the magnesium oxysulfate adhesive is hydrated can penetrate wood fibers. After the wood fibers are penetrated, it is beneficial for soybean meal adhesive to penetrate into the wood fibers, thereby forming a tight bond between the modified soybean meal adhesive and the wood fibers, significantly improving the bonding strength of the modified soybean meal adhesive. (3) The pentahydrate magnesium oxysulfate crystals of magnesium oxysulfate gelling agent have small porosity after hydration, which can significantly reduce the water absorption of soybean meal glue and significantly improve the water resistance of engineered wood. (4) The pentahydrate magnesium oxysulfate crystals of magnesium oxysulfate adhesive will release magnesium ions and sulfate ions after hydration, which can provide a high-salt environment. The osmotic pressure of the high-salt environment can inhibit the growth of mold and improve the anti-mold properties of soybean meal adhesive. Detailed Implementation

[0023] The present invention will be further described below with reference to embodiments.

[0024] To better understand the content of this invention, further explanation is provided below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of this invention.

[0025] Example 1: A method for preparing ENF-grade engineered wood includes the following steps: (1) Mix lightly calcined magnesium oxide (magnesium oxide content ≥90%, activity 70%), magnesium sulfate, magnesium chloride and water evenly in a molar ratio of 7:0.4:0.6:7, and then add a retarder (oxalic acid) to make magnesium sulfate adhesive; (2) Mix 12 parts soybean meal powder, 15 parts inorganic thickener (sepiolite fiber), 3 parts hexamethylene diisocyanate, 3 parts polyvinyl alcohol, 12 parts polyacrylamide, 3 parts fly ash, 6 parts water glass, 3 parts waterproofing agent (emulsified paraffin wax) and 50 parts water evenly to make soybean meal adhesive. (3) Mix soybean meal gum and magnesium sulfate adhesive evenly at a mass ratio of 1:0.5 to prepare modified soybean meal gum; (4) Apply glue to the thin veneer (1 mm thick, 600 mm wide, and 900 mm long) using a glue applicator, with a glue application rate of 200 g / m². 2 The glued thin layer of wood veneer is laid in an I-shaped pattern along the grain to form a engineered wood blank. During the laying process, the wood knots are removed and filled with wood veneer. (5) Place the engineered wood blank in the cold press and press it at 3MPa for 5 minutes. After the pressure index is constant, fix the mold locking device prepared inside the cold press. Then the cold press opens the mold and takes out the engineered wood blank. (6) The engineered wood blank is sent into the curing room and cured for 72 hours at a curing temperature of 45 ℃ and a curing humidity of 50% until the glue inside the engineered wood blank is completely cured and the moisture content reaches less than 10%. (7) Trim the edges of the cured engineered wood blank, apply adhesive paint to the sides, and use a planer to plan the engineered wood blank to a thickness of 0.2 mm, so as to make an ENF grade engineered wood with a size of 1300*2600 mm.

[0026] Example 2: A method for preparing ENF-grade engineered wood includes the following steps: (1) Mix lightly calcined magnesium oxide (magnesium oxide content ≥90%, activity 70%), magnesium sulfate, magnesium chloride and water evenly in a molar ratio of 7:0.4:0.6:7, and then add a retarder (oxalic acid) to make magnesium sulfate adhesive; (2) Mix 12 parts soybean meal powder, 15 parts inorganic thickener (sepiolite fiber), 3 parts hexamethylene diisocyanate, 3 parts polyvinyl alcohol, 12 parts polyacrylamide, 3 parts fly ash, 6 parts water glass, 3 parts waterproofing agent (emulsified paraffin wax) and 50 parts water evenly to make soybean meal adhesive. (3) Mix soybean meal gum and magnesium sulfate adhesive evenly at a mass ratio of 1:0.5 to prepare modified soybean meal gum; (4) Apply glue to the thin veneer (1 mm thick, 600 mm wide, and 900 mm long) using a glue applicator, with a glue application rate of 200 g / m². 2 The glued thin layer of wood veneer is laid in an I-shaped pattern along the grain to form a engineered wood blank. During the laying process, the wood knots are removed and filled with wood veneer. (5) Place the engineered wood blank in the cold press and press it at 3MPa for 5 minutes. After the pressure index is constant, fix the mold locking device prepared inside the cold press. Then the cold press opens the mold and takes out the engineered wood blank. (6) The engineered wood blank is sent into the curing room and cured for 72 hours at a curing temperature of 45 ℃ and a curing humidity of 50% until the glue inside the engineered wood blank is completely cured and the moisture content reaches less than 10%. (7) Trim the edges of the cured engineered wood blank, apply adhesive paint to the sides, and use a planer to plan the engineered wood blank to a thickness of 0.2 mm, so as to make an ENF grade engineered wood with a size of 1300*2600 mm.

[0027] Example 3: A method for preparing ENF-grade engineered wood includes the following steps: (1) Mix lightly calcined magnesium oxide (magnesium oxide content ≥90%, activity 70%), magnesium sulfate, magnesium chloride and water evenly in a molar ratio of 7:0.4:0.6:7, and then add a retarder (oxalic acid) to make magnesium sulfate adhesive; (2) Mix 12 parts soybean meal powder, 15 parts inorganic thickener (sepiolite fiber), 3 parts hexamethylene diisocyanate, 3 parts polyvinyl alcohol, 12 parts polyacrylamide, 3 parts fly ash, 6 parts water glass, 3 parts waterproofing agent (emulsified paraffin wax) and 50 parts water evenly to make soybean meal adhesive. (3) Mix soybean meal gum and magnesium sulfate adhesive evenly at a mass ratio of 1:0.6 to prepare modified soybean meal gum; (4) Apply glue to the thin veneer (1 mm thick, 600 mm wide, and 900 mm long) using a glue applicator, with a glue application rate of 200 g / m². 2 The glued thin layer of wood veneer is laid in an I-shaped pattern along the grain to form a engineered wood blank. During the laying process, the wood knots are removed and filled with wood veneer. (5) Place the engineered wood blank in the cold press and press it at 3MPa for 5 minutes. After the pressure index is constant, fix the mold locking device prepared inside the cold press. Then the cold press opens the mold and takes out the engineered wood blank. (6) The engineered wood blank is sent into the curing room and cured for 72 hours at a curing temperature of 45 ℃ and a curing humidity of 50% until the glue inside the engineered wood blank is completely cured and the moisture content reaches less than 10%. (7) Trim the edges of the cured engineered wood blank, apply adhesive paint to the sides, and use a planer to plan the engineered wood blank to a thickness of 0.2 mm, so as to make an ENF grade engineered wood with a size of 1300*2600 mm.

[0028] Example 4: A method for preparing ENF-grade engineered wood includes the following steps: (1) Mix lightly calcined magnesium oxide (magnesium oxide content ≥85%, activity 60%), magnesium sulfate, magnesium chloride and water evenly in a molar ratio of 7:0.4:0.6:7, and then add a retarder (oxalic acid) to make magnesium sulfate adhesive; (2) Mix 10 parts soybean meal powder, 20 parts inorganic thickener (sepiolite fiber), 3 parts hexamethylene diisocyanate, 1 part polyvinyl alcohol, 10 parts polyacrylamide, 2 parts fly ash, 2 parts water glass, 2 parts waterproofing agent (emulsified paraffin wax) and 40 parts water evenly to make soybean meal adhesive. (3) Mix soybean meal gum and magnesium sulfate adhesive evenly at a mass ratio of 1:0.5 to prepare modified soybean meal gum; (4) Apply glue to the thin veneer (1 mm thick, 600 mm wide, and 900 mm long) using a glue applicator, with a glue application rate of 200 g / m². 2 The glued thin layer of wood veneer is laid in an I-shaped pattern along the grain to form a engineered wood blank. During the laying process, the wood knots are removed and filled with wood veneer. (5) Place the engineered wood blank in the cold press and press it at 2.2 MPa for 5 minutes. After the pressure index is constant, fix the mold locking device prepared inside the cold press. Then the cold press opens the mold and takes out the engineered wood blank. (6) Send the engineered wood blank into the curing room and cure it for 60 hours at a curing temperature of 43 ℃ and a curing humidity of 40% until the glue inside the engineered wood blank is completely cured and the moisture content reaches less than 10%. (7) Trim the edges of the cured engineered wood blank, apply adhesive paint to the sides, and use a planer to plan the engineered wood blank to a thickness of 0.2 mm, so as to make an ENF grade engineered wood with a size of 1300*2600 mm.

[0029] Example 5: A method for preparing ENF-grade engineered wood includes the following steps: (1) Mix lightly calcined magnesium oxide (magnesium oxide content ≥90%, activity 70%), magnesium sulfate, magnesium chloride and water evenly in a molar ratio of 7:0.4:0.6:7, and then add a retarder (oxalic acid) to make magnesium sulfate adhesive; (2) Mix 16 parts soybean meal powder, 10 parts inorganic thickener (sepiolite fiber), 3 parts hexamethylene diisocyanate, 3 parts polyvinyl alcohol, 16 parts polyacrylamide, 5 parts fly ash, 10 parts water glass, 5 parts waterproofing agent (emulsified paraffin wax) and 60 parts water evenly to make soybean meal adhesive. (3) Mix soybean meal gum and magnesium sulfate adhesive evenly at a mass ratio of 1:0.5 to prepare modified soybean meal gum; (4) Apply glue to the thin veneer (1 mm thick, 600 mm wide, and 900 mm long) using a glue applicator, with a glue application rate of 200 g / m². 2 The glued thin layer of wood veneer is laid in an I-shaped pattern along the grain to form a engineered wood blank. During the laying process, the wood knots are removed and filled with wood veneer. (5) Place the engineered wood blank in the cold press and press it at 3.8 MPa for 5 minutes. After the pressure index is constant, fix the mold locking device prepared inside the cold press. Then the cold press opens the mold and takes out the engineered wood blank. (6) Send the engineered wood blank into the curing room and cure it for 80 hours at a curing temperature of 47 ℃ and a curing humidity of 60% until the glue inside the engineered wood blank is completely cured and the moisture content reaches less than 10%. (7) Trim the edges of the cured engineered wood blank, apply adhesive paint to the sides, and use a planer to plan the engineered wood blank to a thickness of 0.2 mm, so as to make an ENF grade engineered wood with a size of 1300*2600 mm.

[0030] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 uses only soybean meal gum to prepare engineered wood; it includes the following steps: (1) Mix 12 parts soybean meal powder, 15 parts inorganic thickener (sepiolite fiber), 3 parts hexamethylene diisocyanate, 3 parts polyvinyl alcohol, 12 parts polyacrylamide, 3 parts fly ash, 6 parts water glass, 3 parts waterproofing agent (emulsified paraffin wax) and 50 parts water evenly to make soybean meal adhesive. (2) Apply glue to the thin veneer (1 mm thick, 600 mm wide, and 900 mm long) using a glue applicator, with a glue application rate of 200 g / m². 2 The glued thin layer of wood veneer is laid in an I-shaped pattern along the grain to form a engineered wood blank. During the laying process, the wood knots are removed and filled with wood veneer. (3) Place the engineered wood blank in the cold press and press it at 3MPa for 5 minutes. After the pressure index is constant, fix the mold locking device prepared inside the cold press. Then the cold press opens the mold and takes out the engineered wood blank. (4) The engineered wood blank is sent into the curing room and cured for 72 hours at a curing temperature of 45 ℃ and a curing humidity of 50% until the glue inside the engineered wood blank is completely cured and the moisture content reaches less than 10%. (5) Trim the edges of the cured engineered wood blank, apply adhesive paint to the sides, and use a planer to plan the engineered wood blank to a thickness of 0.2 mm, so as to make an ENF grade engineered wood with a size of 1300*2600 mm.

[0031] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that only magnesium oxysulfate adhesive was used to prepare engineered wood; the process included the following steps: (1) Mix lightly calcined magnesium oxide (magnesium oxide content ≥90%, activity 70%), magnesium sulfate, magnesium chloride and water evenly in a molar ratio of 7:0.4:0.6:7, and then add a retarder (oxalic acid) to make magnesium sulfate adhesive; (2) Apply glue to the thin veneer (1 mm thick, 600 mm wide, and 900 mm long) using a glue applicator, with a glue application rate of 200 g / m². 2 The glued thin layer of wood veneer is laid in an I-shaped pattern along the grain to form a engineered wood blank. During the laying process, the wood knots are removed and filled with wood veneer. (3) Place the engineered wood blank in the cold press and press it at 3MPa for 5 minutes. After the pressure index is constant, fix the mold locking device prepared inside the cold press. Then the cold press opens the mold and takes out the engineered wood blank. (4) The engineered wood blank is sent into the curing room and cured for 72 hours at a curing temperature of 45 ℃ and a curing humidity of 50% until the glue inside the engineered wood blank is completely cured and the moisture content reaches less than 10%. (5) Trim the edges of the cured engineered wood blank, apply adhesive paint to the sides, and use a planer to plan the engineered wood blank to a thickness of 0.2 mm, so as to make an ENF grade engineered wood with a size of 1300*2600 mm.

[0032] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that no water glass was added; all other conditions were the same as in Example 1.

[0033] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is that no fly ash was added; all other conditions were the same as in Example 1.

[0034] Comparative Example 5: The difference between Comparative Example 5 and Example 1 is that no waterproofing agent was added; all other conditions were the same as in Example 1.

[0035] Comparative Example 6: The difference between Comparative Example 6 and Example 1 is that no polyvinyl alcohol was added; all other conditions were the same as in Example 1.

[0036] Comparative Example 7: The difference between Comparative Example 7 and Example 1 is that the amount of magnesium oxysulfate adhesive used was too small, and the mass ratio of soybean meal gum to magnesium oxysulfate adhesive was 1:0.2, including the following steps: (1) Mix lightly calcined magnesium oxide (magnesium oxide content ≥90%, activity 70%), magnesium sulfate, magnesium chloride and water evenly in a molar ratio of 7:0.4:0.6:7, and then add a retarder (oxalic acid) to make magnesium sulfate adhesive; (2) Mix 12 parts soybean meal powder, 15 parts inorganic thickener (sepiolite fiber), 3 parts hexamethylene diisocyanate, 3 parts polyvinyl alcohol, 12 parts polyacrylamide, 3 parts fly ash, 6 parts water glass, 3 parts waterproofing agent (emulsified paraffin wax) and 50 parts water evenly to make soybean meal adhesive. (3) Mix soybean meal gum and magnesium sulfate adhesive evenly at a mass ratio of 1:0.2 to prepare modified soybean meal gum; (4) Apply glue to the thin veneer (1 mm thick, 600 mm wide, and 900 mm long) using a glue applicator, with a glue application rate of 200 g / m². 2 The glued thin layer of wood veneer is laid in an I-shaped pattern along the grain to form a engineered wood blank. During the laying process, the wood knots are removed and filled with wood veneer. (5) Place the engineered wood blank in the cold press and press it at 3MPa for 5 minutes. After the pressure index is constant, fix the mold locking device prepared inside the cold press. Then the cold press opens the mold and takes out the engineered wood blank. (6) The engineered wood blank is sent into the curing room and cured for 72 hours at a curing temperature of 45 ℃ and a curing humidity of 50% until the glue inside the engineered wood blank is completely cured and the moisture content reaches less than 10%. (7) Trim the edges of the cured engineered wood blank, apply adhesive paint to the sides, and use a planer to plan the engineered wood blank to a thickness of 0.2 mm, so as to make an ENF grade engineered wood with a size of 1300*2600 mm.

[0037] Comparative Example 8: The difference between Comparative Example 8 and Example 1 is that the amount of magnesium oxysulfate adhesive used was excessive, and the mass ratio of soybean meal gum to magnesium oxysulfate adhesive was 1:0.8, including the following steps: (1) Mix lightly calcined magnesium oxide (magnesium oxide content ≥90%, activity 70%), magnesium sulfate, magnesium chloride and water evenly in a molar ratio of 7:0.4:0.6:7, and then add a retarder (oxalic acid) to make magnesium sulfate adhesive; (2) Mix 12 parts soybean meal powder, 15 parts inorganic thickener (sepiolite fiber), 3 parts hexamethylene diisocyanate, 3 parts polyvinyl alcohol, 12 parts polyacrylamide, 3 parts fly ash, 6 parts water glass, 3 parts waterproofing agent (emulsified paraffin wax) and 50 parts water evenly to make soybean meal adhesive. (3) Mix soybean meal gum and magnesium sulfate adhesive evenly at a mass ratio of 1:0.8 to prepare modified soybean meal gum; (4) Apply glue to the thin veneer (1 mm thick, 600 mm wide, and 900 mm long) using a glue applicator, with a glue application rate of 200 g / m². 2 The glued thin layer of wood veneer is laid in an I-shaped pattern along the grain to form a engineered wood blank. During the laying process, the wood knots are removed and filled with wood veneer. (5) Place the engineered wood blank in the cold press and press it at 3MPa for 5 minutes. After the pressure index is constant, fix the mold locking device prepared inside the cold press. Then the cold press opens the mold and takes out the engineered wood blank. (6) The engineered wood blank is sent into the curing room and cured for 72 hours at a curing temperature of 45 ℃ and a curing humidity of 50% until the glue inside the engineered wood blank is completely cured and the moisture content reaches less than 10%. (7) Trim the edges of the cured engineered wood blank, apply adhesive paint to the sides, and use a planer to plan the engineered wood blank to a thickness of 0.2 mm, so as to make an ENF grade engineered wood with a size of 1300*2600 mm.

[0038] Example of detection: The physical and chemical properties of the engineered wood in Examples 1-5 and Comparative Examples 1-8 were tested; The physical and chemical performance tests included: formaldehyde emission, static bending strength (transverse), modulus of elasticity (transverse), internal bond strength, and 24-hour water absorption thickness swelling rate. The test methods followed the "GB / T 17657-2022 Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels". The test results are shown in Table 1. Table 1. Results of Physicochemical Performance Tests As shown in Table 1, Examples 1 to 5 are engineered wood products prepared using the method provided by this invention, and their formaldehyde emission levels are all 0.1 mg / L, meeting the formaldehyde emission limit of ≤0.025 mg / m³ for ENF-grade engineered wood products. 3 This engineered wood meets the standards for ENF-grade engineered wood panels. Its transverse static bending strength is 14-16 MPa, and its transverse modulus of elasticity is 2435-2689 MPa. These values ​​reflect the rigidity and toughness of the engineered wood's sides under stress. High transverse static bending strength indicates strong side rigidity and structural stability, while high transverse modulus of elasticity indicates high side toughness and resistance to chipping under external forces. The internal bonding strength is 1.1-1.2 MPa. Higher internal bonding strength indicates stronger adhesion of the surface adhesive and a higher bond strength. The 24-hour thickness swelling rate after water absorption is 1.5-1.7%. A lower swelling rate indicates lower water absorption and better water resistance.

[0039] Comparative Example 1 is engineered wood made solely with soybean meal adhesive, exhibiting a transverse static bending strength of 5 MPa, a transverse elastic modulus of 761 MPa, an internal bond strength of 0.53 MPa, and a 24-hour thickness swelling rate of 15.2%. Comparative Example 2 is engineered wood made solely with magnesium oxysulfate adhesive, exhibiting a transverse static bending strength of 8 MPa, a transverse elastic modulus of 1406 MPa, an internal bond strength of 0.79 MPa, and a 24-hour thickness swelling rate of 1.1%. The results from Comparative Examples 1, 2, and Example 1 show that engineered wood made solely with soybean meal adhesive and engineered wood made solely with magnesium oxysulfate adhesive have significantly lower transverse static bending strength, transverse elastic modulus, and internal bond strength than engineered wood made with soybean meal adhesive modified with magnesium oxysulfate adhesive. This indicates that soybean meal adhesive modified with magnesium oxysulfate adhesive can significantly improve the lateral rigidity and toughness of engineered wood, and significantly enhance its bonding strength. Furthermore, the water absorption and swelling performance of engineered wood using only magnesium oxysulfate adhesive is lower than that of engineered wood made with modified soybean meal adhesive. This is because magnesium oxysulfate adhesive forms a cement-based rigid structure after hydration, which has extremely low water absorption. Engineered wood using only soybean meal adhesive has significantly higher water absorption and swelling performance than engineered wood made with both modified soybean meal adhesive and magnesium oxysulfate adhesive. This is because soybean meal adhesive has many exposed hydrophilic groups after the protein molecules unfold, resulting in extremely high water absorption. In addition, soybean meal adhesive has a high degree of expansion due to its rigid structure, leading to a very high rate of expansion change in the adhesive layer after water absorption. In contrast, soybean meal adhesive modified with magnesium oxysulfate adhesive exhibits a significantly reduced rate of expansion change in the adhesive layer due to the rigid structure formed after hydration of the magnesium oxysulfate adhesive.

[0040] In Comparative Example 3, which did not contain water glass, the transverse static bending strength, transverse elastic modulus, and internal bonding force were all lower than those of Example 1, while the water absorption swelling rate was higher than that of Example 1. These results indicate that water glass can enhance the performance of modified soybean meal adhesive and has a positive effect on increasing the rigidity and toughness of the engineered wood sides, increasing the adhesive bonding strength, and reducing the thickness of the engineered wood.

[0041] In Comparative Example 4, no ash coal powder was added, and its water absorption rate was lower than that of Example 1. Other properties did not change significantly. This indicates that the use of ash coal powder can reduce the water absorption and swelling effect of engineered wood and reduce its water absorption performance.

[0042] In Comparative Example 5, no waterproofing agent was added, and its water absorption rate was lower than that of Example 1. Other properties did not change significantly. This indicates that the use of a waterproofing agent can reduce the water absorption and swelling of engineered wood, thereby reducing its water absorption performance.

[0043] In Comparative Example 6, no polyvinyl alcohol was added, and its elastic modulus was significantly lower than that of Example 1. This indicates that polyvinyl alcohol can improve the toughness of engineered wood and can be used as a flexibility modifier.

[0044] Comparative Examples 7 and 8 investigated the ratio of soybean meal adhesive to magnesium oxysulfate adhesive. The results showed that when the amount of magnesium oxysulfate was too low, the physical and chemical properties of the engineered wood were lower than those of Example 1. When the amount of magnesium oxysulfate was too high, the elastic modulus of the engineered wood would decrease significantly and the static bending strength would increase. The decrease in elastic modulus would make the engineered wood more prone to edge chipping during cutting.

[0045] The anti-mildew properties of the engineered wood in Examples 1-5 and Comparative Examples 1-8 were tested; The mildew resistance test method was conducted in accordance with "LY / T 2230-2013 Evaluation of Mildew Resistance of Wood-based Panels". The mildew resistance levels were no growth, trace growth, small amount of growth, moderate growth and heavy growth. The test results are shown in Table 2. Table 2 Results of Anti-mildew Performance Test As shown in Table 2, the engineered wood prepared in Examples 1 to 5 did not develop mold within 15 days of the anti-mold test, but slight mold appeared after 28 days; the engineered wood prepared in Comparative Example 1 developed slight mold after 15 days, and severe mold after 20 days; the engineered wood prepared in Comparative Example 2 developed slight mold after 15 days, the mold worsened after 20 days, and severe mold after 28 days; the engineered wood prepared in Comparative Example 7 developed slight mold after 15 days, and severe mold after 20 days; the engineered wood prepared in Comparative Example 8 developed slight mold after 15 days, the mold worsened after 20 days, and severe mold after 28 days. Analysis of the above results revealed that engineered wood veneer... Antifungal agents are typically added during the manufacturing process. These agents initially have a strong antibacterial effect, preventing mold growth in engineered wood. However, as these agents are continuously lost during use, their antibacterial effect gradually decreases. For engineered wood using only soybean meal adhesive, since soybean meal adhesive is a biomass, its antibacterial effect weakens while providing conditions for mold growth, leading to faster mold development. Magnesium sulfoxylate adhesive, upon hydration, forms magnesium sulfoxylate pentahydrate, which undergoes desalination under the influence of water. This continuously releases magnesium and sulfate ions, creating a high-salt environment. This high-salt environment can, to some extent, help inhibit mold growth, thus suppressing mold growth in engineered wood. Furthermore, through the results of Comparative Examples 2, 7, and 8, this invention also found that the desalination effect of the adhesive layer formed by the combination of soybean meal adhesive and magnesium sulfoxylate adhesive is suppressed. Suppressing the desalination effect of the magnesium sulfoxylate adhesive reduces the release rate of magnesium and sulfate ions, thereby prolonging its high-salt inhibitory effect.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing ENF-grade engineered wood, characterized in that, Includes the following steps: (1) Add soybean meal powder and auxiliary materials to water and stir evenly to make soybean meal glue; (2) Add magnesium oxysulfate adhesive to soybean meal adhesive and stir evenly to prepare modified soybean meal adhesive; the mass ratio of soybean meal adhesive to magnesium oxysulfate adhesive is 1:0.4~0.

6. (3) Apply soybean meal glue to a thin layer of wood veneer, assemble the thin layer of wood veneer to make a wood blank, and then cold press, cure and repair the wood blank to make ENF grade engineered wood.

2. The preparation method according to claim 1, characterized in that, Magnesium sulfide adhesives consist of lightly calcined magnesium oxide, magnesium sulfate, magnesium chloride, a retarder, and water.

3. The preparation method according to claim 2, characterized in that, The activity of lightly calcined magnesium oxide is 60-70%.

4. The preparation method according to claim 1, characterized in that, By weight, the soybean meal powder is 10-16 parts, the auxiliary materials are 27-57 parts, and the water is 40-60 parts.

5. The preparation method according to claim 1 or 4, characterized in that, The auxiliary materials are hexamethylene diisocyanate, polyvinyl alcohol, polyacrylamide, fly ash, water glass, inorganic thickener and waterproofing agent.

6. The preparation method according to claim 5, characterized in that, Waterproofing agents include one or both of emulsified paraffin wax and sodium methylsiloxane.

7. The preparation method according to claim 5, characterized in that, Inorganic thickeners include one or both of sepiolite fiber and bentonite.

8. The preparation method according to claim 1, characterized in that, The curing conditions include: a curing temperature of 43~47 ℃, a curing humidity of 40~60%, and a curing time of 60~80 h.

9. The preparation method according to claim 1, characterized in that, The conditions for cold pressing include: 2.2~3.8 MPa, and a time of 5~10 min.

10. The preparation method according to claim 1, characterized in that, The trimmed thickness is 0.1~2 mm.

Images