Laminated wood reinforced based on impregnated gauze and preparation method of laminated wood

Abstract

The invention provides laminated wood based on impregnated gauze reinforcement and a preparation method of the laminated wood, and relates to the technical field of artificial boards. The preparation method of the laminated wood comprises the steps that S1, a wood veneer is subjected to gradient drying and plasma treatment, then the surface of the wood veneer is coated with modified phenolic resin glue, standing is conducted, and a pretreated wood veneer is obtained; s2, lignin fiber gauze is subjected to dipping treatment in the dipping liquid, and dipped gauze is obtained; s3, the wood veneers and the lignin fiber gauze are alternately stacked and arranged in the 0-degree / 90-degree / 0-degree texture direction, one layer of dipping gauze is clamped between every 2-4 layers of veneers, segmented hot pressing is conducted, and hot-pressed laminated wood is obtained; and S4, the hot-pressed laminated wood is subjected to hot-pile curing, then double-face sanding is conducted, a residual adhesive layer on the surface is removed, and the wood is obtained. The laminated wood is high in interface bonding strength and excellent in mechanical property and durability.

Description

Technical Field

[0001] This application relates to the field of engineered wood technology, and in particular to a laminated wood based on impregnated gauze reinforcement and its preparation method. Background Technology

[0002] As the global supply and demand imbalance for timber resources intensifies, fast-growing timber (such as poplar and eucalyptus) has become an important alternative to rare hardwoods due to its short growth cycle (5-8 years) and large reserves. However, fast-growing timber itself has significant drawbacks: ① It has a loose texture (air-dry density is usually ≤0.5g / cm³) and low mechanical properties (poplar bending strength is about 60-80MPa, and eucalyptus is about 70-90MPa), making it difficult to meet the strength requirements of structural components when used directly in laminated wood; ② Its moisture content fluctuates greatly, making it prone to warping and cracking, affecting product stability; ③ Traditional lamination processes have limited performance improvement for fast-growing timber, leading to its use in low-value-added fields (such as packaging materials and fiberboard raw materials), limiting its high-value utilization.

[0003] To address the performance shortcomings of fast-growing laminated wood, existing technologies in the market mainly improve it through three approaches: ① Veneer modification (such as compression compaction and chemical impregnation), which leads to a decrease in wood toughness or insufficient environmental friendliness; ② Adhesive upgrades (such as the use of phenolic resin and epoxy resin), but these are costly and offer limited improvement in interlayer bonding strength; ③ The introduction of reinforcing materials (such as glass fiber and carbon fiber), but these have poor compatibility with the wood interface, easily resulting in "delamination," and the reinforcement effect is unstable.

[0004] Therefore, developing a technology that can balance the high-value utilization of fast-growing timber with the improvement of the mechanical properties of laminated wood has become an urgent problem to be solved in the industry. Summary of the Invention

[0005] The purpose of this application is to address the shortcomings of existing technologies by providing a laminated wood reinforced with impregnated gauze and its preparation method, which solves the problem of poor interfacial compatibility between traditional impregnated gauze and wood, and improves the mechanical properties and durability of laminated wood.

[0006] To achieve the above objectives, the technical solution adopted in this application is as follows: According to one aspect of this application, a method for preparing laminated wood based on impregnated gauze reinforcement is provided, comprising the following steps: S1. The wood veneer is subjected to gradient drying and plasma treatment, and then modified phenolic resin glue is coated on both sides of the wood monomer and left to stand to obtain pretreated wood veneer. S2. The lignin fiber gauze is impregnated in the impregnation solution to obtain impregnated gauze; S3. Alternately layer wood veneer and impregnated gauze, arranged in the "0° / 90° / 0°" grain direction, with one layer of impregnated gauze sandwiched between every 2 to 4 layers of veneer, and hot press in sections to obtain hot-pressed laminated wood; S4. Perform hot-pressed laminated wood curing, then sand both sides to remove residual adhesive layer on the surface, and the product is obtained.

[0007] Furthermore, in step S1, the wood veneer is selected from poplar or eucalyptus, and the thickness of the wood veneer is 1.5 to 2.0 mm.

[0008] Further, in step S1, the gradient drying step is as follows: first, dry at 55-60℃ and 50-60% relative humidity for 4-5 hours, then raise the temperature to 80-90℃ and 30-40% relative humidity for 6-8 hours, controlling the moisture content to 8-10%.

[0009] Furthermore, in step S1, the plasma treatment conditions are: power 300-500W, argon flow rate 10-25 L / min, and time 15-20s.

[0010] Further, in step S1, the modified phenolic resin adhesive has a solid content of 45-55%, and is prepared by the following method: (1) Mix the catalyst, phenol and resorcinol, and activate for 10-30 min to obtain a mixture; (2) Formaldehyde aqueous solution and mixture are passed into a microchannel reactor for reaction. After the reaction is completed, the mixture is cooled and discharged to obtain modified phenolic resin glue.

[0011] Optionally, in the preparation process of the above-mentioned modified phenolic resin adhesive, the catalyst is selected from any one of magnesium hydroxide, potassium hydroxide, and sodium hydroxide; the OH group of the base in the catalyst... - The molar ratio of the amount of the substance to the molar amount of phenol is (0.1–0.5):1; the activation temperature is 40–50°C. The mass fraction of formaldehyde aqueous solution is 25-35%; When formaldehyde aqueous solution and mixed solution are introduced into the microchannel reactor, the flow rates of formaldehyde aqueous solution and mixed solution are controlled to be 10-20 mL / min and 20-30 mL / min, respectively. The reaction temperature is 70–95℃, and the reaction time is 7–9 min; The molar ratio of formaldehyde to phenol in an aqueous formaldehyde solution is (1.5–2.5):1; The molar ratio of the hydroxyl group in resorcinol to the molar ratio of the phenol is (0.1–0.5):1.

[0012] Further, in step S1, the coating amount of the modified phenolic resin is 220-240 g / m².2 .

[0013] Furthermore, in step S2, the basis weight of the lignin fiber gauze is 30–50 g / m². 2 The latitude and longitude density is (18~22)×(18~22) roots / cm.

[0014] Further, in step S2, the impregnation solution comprises, by mass percentage, the following raw materials: 55-65% phenolic resin, 8-12% lignin, and 0.16-0.3% hyperbranched polyamide functionalized graphene (HGNP) suspension; the viscosity of the impregnation solution is 200-300 mPa. s (23±2℃); the impregnation solution is obtained by uniformly mixing the above materials; The sizing retention of the impregnated lignin fiber gauze is 30-40%. The impregnation treatment method is as follows: one dip and one roll are used, with a roll pressure of 0.2 to 0.4 MPa. After impregnation, the mixture is pre-cured at 75 to 85°C for 8 to 12 minutes.

[0015] Preferably, in the impregnation solution: the lignin has a particle size of 40-60 μm, and the hyperbranched polyamide in the hyperbranched polyamide functionalized graphene (HGNP) is any one of terminal amino type, terminal hydroxyl type, HYPAM type, and terminal carboxyl type. The terminal amino type, terminal hydroxyl type, HYPAM type, and terminal carboxyl type hyperbranched polyesters are all hyperbranched polyesters well known in the art, which can be directly purchased commercially or prepared by methods well known in the art.

[0016] More preferably, the amino-terminated hyperbranched polyamide functionalized graphene is prepared by the following method: (1) Under nitrogen protection, triethylenetetramine was reacted with a mixed solution of methyl acrylate and methanol at a mass ratio of 1:(2-3). The reaction was first carried out at 30-40℃ for 4-5 hours, and then the temperature was raised to 90-95℃ to continue the reaction for 5-6 hours to obtain amino-terminated hyperbranched polyamide. (2) The graphene oxide dispersion was ultrasonically mixed with an equal mass of deionized water, amino acids were added, and the mixture was reacted at 30-40℃ for 5-6 hours to obtain a carboxylated graphene oxide dispersion. (3) The amino-terminated hyperbranched polyamide was mixed with the carboxylated graphene oxide dispersion, stirred at room temperature for 4–5 h, and then ultrasonically dispersed for 40–60 min to finally obtain a hyperbranched polyamide functionalized graphene suspension.

[0017] Optionally, in step (1) of preparing hyperbranched polyamide functionalized graphene, the mixed solution of methyl acrylate and methanol is prepared by methyl acrylate and methanol at a mass ratio of 1:(2-3); Optionally, in step (2) of preparing hyperbranched polyamide functionalized graphene, the graphene oxide dispersion is prepared by the Hummers method, and the content of graphene oxide is 0.5%; The mass ratio of amino acids to graphene oxide in the graphene oxide dispersion was (2-3):1.

[0018] Furthermore, in step S3, the segmented hot pressing step is as follows: Pre-compression: Heat to 100℃ and pre-compress for 2-3 minutes at a pressure of 0.7-0.9MPa; during this process, automatically vent 2-3 times, each time for 2-3 seconds; Main pressure: Heat to 130-140℃, increase pressure to 1.2-1.5MPa, and adjust the holding time according to the thickness of the plate. For every 1mm increase in thickness, increase the time by 0.6-0.8min. Insulation and pressure reduction: The pressure is reduced to 0.9-1.1 MPa, and the pressure is released naturally when the temperature drops below 60°C.

[0019] Preferably, during the segmented hot pressing process of poplar veneer, the temperature is raised to 130°C during the main pressing stage; during the segmented hot pressing process of eucalyptus veneer, the temperature is raised to 140°C during the main pressing stage.

[0020] Furthermore, in step S4, the conditions for hot-press curing are: temperature of 20-25℃, relative humidity of 50±5%, and time of 8-10 days; the wood is turned over every 2 days during the hot-press curing process to ensure that the moisture content of the hot-pressed laminated wood is stable at 9-11%.

[0021] Further, in step S4, the hot-pressed laminated wood is sanded on both sides to remove residual adhesive layer on the surface and control the surface roughness Ra≤3.2μm.

[0022] According to another aspect of this application, a laminated wood based on impregnated gauze reinforcement is provided, wherein the thickness of the laminated wood is ≥12mm, the warping deformation rate is <1.5%, the 24h water absorption swelling rate is ≤5%, and the formaldehyde release is ≤0.1mg / L.

[0023] Compared with the prior art, this application has the following beneficial effects: 1. This application uses fast-growing wood such as poplar / eucalyptus as raw materials to prepare laminated wood. By adopting the treatment method of "gradient drying + plasma etching", the surface hardness, bonding interface polarity and glue layer penetration uniformity of fast-growing wood are significantly improved, and the bonding strength of phenolic resin is increased by 20%, which meets the performance requirements of outdoor-grade laminated wood.

[0024] 2. This application uses impregnated lignin fiber gauze to reinforce laminated wood. The lignin fiber gauze has both biodegradability and mechanical reinforcement potential, solving the problem of poor environmental performance of traditional reinforcement materials. The impregnation solution and impregnation treatment method are combined to improve the interfacial bonding between the impregnated gauze and the wood, thereby improving the mechanical properties of the laminated wood.

[0025] 3. The directional plywood structure design of this application adopts alternating layers of "fast-growing veneer - impregnated gauze" with a cross arrangement of "0° parallel grain / 90° cross grain / 0° parallel grain" to balance longitudinal bending resistance and transverse shear resistance, solving the defect of weak transverse strength in traditional parallel grain plywood. The directional plywood structure design, combined with the segmented hot pressing process, improves the uniformity of resin penetration and interfacial shear strength, making the longitudinal bending strength of the laminated wood ≥120 MPa and the transverse shear strength ≥14 MPa. At the same time, it eliminates surface cracking and inner blistering defects, realizing the efficient utilization of fast-growing outdoor structural laminated wood. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of laminated wood in Embodiment 1 of this application. Detailed Implementation

[0027] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of this application, but do not limit this application in any way. The following content is merely an exemplary description of the scope of protection claimed in this application, and those skilled in the art can make various changes and modifications to the invention based on the disclosed content, which should also fall within the scope of protection claimed in this application.

[0028] The present application will be further described below by way of specific embodiments. Unless otherwise specified, all chemical reagents used in the embodiments of this application are obtained through conventional commercial means.

[0029] Example 1 This embodiment uses poplar wood pressed into 16mm thick laminated wood. The preparation method of the laminated wood includes the following steps: S1. Select nine poplar veneers with a thickness of 2.0±0.2mm and dry them at 60℃ and 60% relative humidity for 4 hours. Then, raise the temperature to 80℃ and dry them at 40% relative humidity for 8 hours, finally controlling the moisture content to be approximately 10%, with a moisture content difference of ≤1.5% between veneers. Next, use an atmospheric pressure plasma treatment device (power 500W, argon flow rate 10L / min) to treat the surface of the veneers for 25 seconds to etch the micropores on the surface. Finally, apply a 240g / m² modified phenolic resin adhesive containing 45% to the surface of the veneers. 2 After standing for 10 minutes, pretreated wood veneer is obtained; The modified phenolic resin adhesive was prepared by the following method: Magnesium hydroxide, phenol, and resorcinol were mixed and activated at 40°C for 10–30 min to obtain a mixed solution. The molar ratio of the hydroxyl groups in the magnesium hydroxide base to the molar ratio of the hydroxyl groups in the resorcinol to the phenol was 0.1:0.1:1. A 25% formaldehyde aqueous solution and the mixed solution were introduced into a microchannel reactor and reacted at 70°C. The molar ratio of formaldehyde to phenol in the formaldehyde aqueous solution was 1.5:1. The flow rates of the formaldehyde aqueous solution and the mixed solution were controlled at 10 mL / min and 20 mL / min, respectively. After the reaction was completed, the mixture was cooled and discharged to obtain modified phenolic resin adhesive. S2, Select a weight of 30g / m 2 A lignin fiber gauze with a warp and weft density of 18×18 threads / cm was impregnated in an impregnation solution using a one-dip-one-roll method. The roll pressure was 0.2 MPa, and the glue holding capacity of the gauze was controlled at 50%. After impregnation, it was pre-cured at 85℃ for 12 minutes to obtain the impregnated gauze. The impregnation solution contained the following raw materials: 55% phenolic resin, 12% lignin, and 0.16% amino-terminated HGNP suspension. The viscosity of the impregnation solution was 200 mPa. s; The amino-terminated HGNP suspension was prepared by the following method: (1) Under nitrogen protection, triethylenetetramine was reacted with a mixed solution of methyl acrylate and methanol (prepared by mixing methyl acrylate and methanol at a mass ratio of 1:3) at a mass ratio of 1:2. The reaction was first carried out at 30°C for 5 hours, and then the temperature was raised to 90°C for another 6 hours to obtain amino-terminated hyperbranched polyamide; (2) Graphene oxide dispersion was ultrasonically mixed with an equal mass of deionized water, and amino acids at a mass ratio of 2 times that of graphene oxide were added. The mixture was then reacted at 30°C for 6 hours to obtain carboxylated graphene oxide dispersion; (3) The amino-terminated hyperbranched polyamide was mixed with the carboxylated graphene oxide dispersion and stirred at room temperature for 4 hours. The mixture was then ultrasonically dispersed for 60 minutes to finally obtain a hyperbranched polyamide functionalized graphene suspension, namely an amino-terminated HGNP suspension; S3. Alternately layer pretreated wood veneers and impregnated gauze, arranging them according to the "0° / 90° / 0°" grain direction, with one layer of impregnated gauze sandwiched between every three layers of veneers, ensuring an edge alignment error of ≤0.5mm; then perform segmented hot pressing to obtain hot-pressed laminated wood. The segmented hot pressing steps are as follows: Pre-compression: First, maintain at 100℃ and 0.8Mpa pressure for 2 minutes, during which automatic venting is performed; Main pressure: Heat to 130℃, increase pressure to 1.2MPa, and maintain for 30 minutes; Pressure holding and cooling: The pressure is reduced to 1.0 MPa, and the pressure is released naturally when the temperature drops below 60°C; S4. Hot-pressed laminated wood is placed in an environment of 20℃ and 50±5% relative humidity for 10 days, turning it over every 2 days to ensure the moisture content remains stable at around 11%. Then, it is sanded on both sides with a 400-grit sandpaper to obtain the laminated wood. Figure 1 As shown.

[0030] Example 2 This embodiment uses eucalyptus wood pressed into 12mm thick laminated wood. The preparation method of the laminated wood includes the following steps: S1. Select 7 poplar veneers with a thickness of 2.0±0.2mm and dry them at 55℃ and 50% relative humidity for 5 hours, then raise the temperature to 90℃ and 30% relative humidity for 6 hours, finally controlling the moisture content to be about 8%, with a moisture content difference of ≤1.5% between veneers; then use an atmospheric pressure plasma treatment device (power 300W, argon flow rate 20L / min) to treat the surface of the veneers for 20 seconds to etch the micropores on the surface; then coat the surface of the veneers with 220g / m² of modified phenolic resin adhesive containing 55%. 2 After standing for 10 minutes, pretreated wood veneer is obtained; The modified phenolic resin adhesive was prepared by the following method: Potassium hydroxide, phenol, and resorcinol were mixed and activated at 50°C for 10–30 min to obtain a mixed solution. The molar ratio of the hydroxyl groups in the potassium hydroxide base to the molar ratio of the hydroxyl groups in the resorcinol to the phenol was 0.5:0.5:1. A 35% formaldehyde aqueous solution and the mixed solution were introduced into a microchannel reactor and reacted at 95°C. The molar ratio of formaldehyde to phenol in the formaldehyde aqueous solution was 2.5:1. The flow rates of the formaldehyde aqueous solution and the mixed solution were controlled at 20 mL / min and 30 mL / min, respectively. After the reaction was completed, the mixture was cooled and discharged to obtain modified phenolic resin adhesive. S2, Select a weight of 40g / m 2 A lignin fiber gauze with a warp and weft density of 22×22 threads / cm was impregnated in an impregnation solution using a one-dip-one-roll method. The roll pressure was 0.4 MPa, and the glue holding capacity of the gauze was controlled at 33%. After impregnation, it was pre-cured at 75℃ for 8 minutes to obtain the impregnated gauze. The impregnation solution contained the following raw materials: 55% phenolic resin, 12% lignin, and 0.3% amino-terminated HGNP suspension. The viscosity of the impregnation solution was 200 mPa. s; The amino-terminated HGNP suspension was prepared by the following method: (1) Under nitrogen protection, triethylenetetramine was reacted with a mixed solution of methyl acrylate and methanol (prepared by mixing methyl acrylate and methanol at a mass ratio of 1:2) at a mass ratio of 1:3. The reaction was carried out at 40°C for 4 hours, and then the temperature was raised to 95°C for 5 hours to obtain amino-terminated hyperbranched polyamide; (2) Graphene oxide dispersion was ultrasonically mixed with an equal mass of deionized water, and amino acids were added at 3 times the mass of graphene oxide. The mixture was reacted at 40°C for 5 hours to obtain carboxylated graphene oxide dispersion; (3) The amino-terminated hyperbranched polyamide was mixed with the carboxylated graphene oxide dispersion and stirred at room temperature for 5 hours. The mixture was then ultrasonically dispersed for 40 minutes to finally obtain hyperbranched polyamide functionalized graphene suspension, i.e., amino-terminated HGNP suspension; S3. Alternately layer the pretreated wood veneer with impregnated gauze, arranging them according to the "0° / 90° / 0°" grain direction, with one layer of impregnated gauze sandwiched between every two layers of veneer, ensuring an edge alignment error of ≤0.5mm; then perform segmented hot pressing to obtain hot-pressed laminated wood. The segmented hot pressing steps are as follows: Pre-compression: First, maintain at 100℃ and 0.9Mpa pressure for 3 minutes, during which automatic venting is performed; Main pressure: Heat to 140℃, increase pressure to 1.5MPa, and maintain for 25 minutes; Pressure holding and cooling: The pressure is reduced to 1.0 MPa, and the pressure is released naturally when the temperature drops below 60°C; S4. Hot-pressed laminated wood is placed in an environment with a temperature of 25℃ and a relative humidity of 50±5% for 10 days, and turned over every 2 days during this period to ensure that the moisture content is stable at about 9%. Then, it is sanded on both sides with a 400-mesh sanding belt to obtain laminated wood.

[0031] Example 3 This embodiment uses eucalyptus wood pressed into a 35mm thick laminate. The preparation method of the laminate includes the following steps: S1. Select 27 poplar veneers with a thickness of 1.5±0.2mm and dry them at 60℃ and 60% relative humidity for 4 hours, then raise the temperature to 80℃ and 40% relative humidity for 8 hours, finally controlling the moisture content to be approximately 10%, with a moisture content difference of ≤1.5% for each veneer. Next, use an atmospheric pressure plasma treatment device (power 400W, argon flow rate 15L / min) to treat the veneer surface for 15 seconds to etch the micropores on the surface. Then, apply a 240g / m² modified phenolic resin adhesive containing 55% to the veneer surface for fixation. 2 After standing for 10 minutes, pretreated wood veneer is obtained; The modified phenolic resin adhesive was prepared by the following method: Potassium hydroxide, phenol, and resorcinol were mixed and activated at 50°C for 10–30 min to obtain a mixed solution. The molar ratio of the hydroxyl groups in the potassium hydroxide base to the molar ratio of the hydroxyl groups in the resorcinol to the phenol was 0.5:0.5:1. A 35% formaldehyde aqueous solution and the mixed solution were introduced into a microchannel reactor and reacted at 95°C. The molar ratio of formaldehyde to phenol in the formaldehyde aqueous solution was 2.5:1. The flow rates of the formaldehyde aqueous solution and the mixed solution were controlled at 20 mL / min and 30 mL / min, respectively. After the reaction was completed, the mixture was cooled and discharged to obtain modified phenolic resin adhesive. S2, Select a weight of 50g / m 2 A lignin fiber gauze with a warp and weft density of 22×22 threads / cm was impregnated in an impregnation solution using a one-dip-one-roll method with a roll pressure of 0.4MPa and a glue holding capacity of 30%. After impregnation, it was pre-cured at 75°C for 8 minutes to obtain the impregnated gauze. The impregnation solution included the following raw materials: 65% phenolic resin (solid content of 45%), 8% lignin (particle size of 40μm), and an amino-terminated HGNP suspension (same as in Example 1). S3. Alternately layer pretreated wood veneers and impregnated gauze, arranging them according to the "0° / 90° / 0°" grain direction, with one layer of impregnated gauze sandwiched between every three layers of veneers, ensuring an edge alignment error of ≤0.5mm; then perform segmented hot pressing to obtain hot-pressed laminated wood. The segmented hot pressing steps are as follows: Pre-compression: First, maintain at 100℃ and 0.8Mpa pressure for 10 minutes, during which automatic venting is performed; Main pressure: Heat to 130℃, increase pressure to 1.8MPa, and maintain for 65 minutes; Pressure holding and cooling: The pressure is reduced to 1.0 MPa, and the pressure is released naturally when the temperature drops below 60°C; S4. Hot-pressed laminated wood is placed in an environment with a temperature of 25℃ and a relative humidity of 50±5% for 10 days, and turned over every 2 days during this period to ensure that the moisture content is stable at about 9%. Then, it is sanded on both sides with a 400-mesh sanding belt to obtain laminated wood.

[0032] Example 4 The difference from Example 2 is that the modified phenolic resin adhesive is replaced with an equal amount of commercially available phenolic resin adhesive.

[0033] Example 5 The difference from Example 2 is that the terminal amino-type HGNP suspension in the impregnation solution is replaced with a suspension of unmodified graphene and water, wherein the amount of graphene and terminal amino-type HGNP is equal.

[0034] Example 6 The difference from Example 2 is that the terminal amino hyperbranched polyamide in the terminal amino HGNP suspension in the impregnation solution is replaced with an equal amount of KH550.

[0035] Comparative Example 1 The difference from Example 2 is that the poplar veneer was not subjected to plasma treatment.

[0036] Comparative Example 2 The difference from Example 2 is that the pretreated wood veneers obtained in step S1 were not reinforced with impregnated gauze, but were directly used for segmented hot pressing by alternating layers, while the segmented hot pressing conditions remained unchanged.

[0037] Comparative Example 3 The difference from Example 2 is that in step S3, the pretreated wood veneer and impregnated gauze are alternately layered and arranged in the direction of the grain.

[0038] Comparative Example 4 The difference from Example 2 is that the segmented hot pressing step S3 is as follows: directly heat to 130°C, maintain at 1.2MPa for 30 minutes, then reduce the pressure to 1.0MPa, and naturally cool down to below 60°C to release the pressure.

[0039] Comparative Example 5 The difference from Example 2 is that the segmented hot pressing step S3 is as follows: maintain at 100°C and 0.8 MPa pressure for 30 minutes, during which automatic venting is performed, and then the pressure is reduced to 1.0 MPa and naturally cooled to below 60°C to release the pressure.

[0040] Comparative Example 6 The difference from Example 2 is that the segmented hot pressing step in step S3 is as follows: Pre-compression: Maintain at 100℃ and 0.8Mpa pressure for 2 minutes, during which automatic venting is performed; Main pressure: directly raise the temperature to 130℃ and maintain it at 1.2MPa for 30 minutes; Cooling: Depressurize and allow to cool naturally to 60℃.

[0041] Comparative Example 7 The difference from Example 2 is that in step S1, the poplar veneer was not subjected to gradient drying, but was directly dried at 80°C and 40% relative humidity until the moisture content was about 10% and the moisture content difference was ≤1.5%.

[0042] Test case The surface contact angle, interlayer bonding force, interfacial shear strength, tensile strength, bending strength, warpage rate, 24-hour water absorption swelling rate, and boiling water immersion peeling rate of the laminated wood prepared in the above embodiments and comparative examples were tested. The test standards are shown in Table 1 below.

[0043] Table 1. Testing Standards

[0044] The test results are shown in Table 2 below.

[0045] Table 2. Properties of laminated wood

[0046] As can be seen from the data in the table, the laminated wood obtained in Examples 1-3 has excellent interlayer bonding force, interfacial shear strength, and mechanical properties, and the warping deformation rate (warping degree) meets the requirements (length direction ≤ 1.0%, width direction ≤ 0.2%).

[0047] Compared to Examples 1-3, in Example 4, the impregnating solution was changed to phenolic resin adhesive, resulting in a decrease of over 20% in the interlayer bonding strength of the resulting laminated wood. In Example 5, the graphene was not modified, leading to a significant decrease in the interlayer bonding strength and interfacial shear strength of the resulting laminated wood, as well as a slight decrease in tensile strength and flexural strength, and a boiling water peeling rate exceeding 5%. In Example 6, replacing the amino-terminated HGNP with KH550, while still achieving a relatively high interlayer bonding strength, resulted in a significant decrease in flexural strength and an increase in boiling water peeling rate. This indicates that impregnating with a specific formulation of impregnating solution for fiber-based fabrics helps improve the bonding strength and mechanical properties of laminated wood.

[0048] In Comparative Example 1, the poplar veneer was not subjected to plasma treatment, resulting in a decrease in interlayer bonding strength, interfacial strength, and mechanical properties of the laminated wood. In Comparative Example 2, the lack of impregnated gauze reinforcement led to a significant decrease in interfacial shear strength and mechanical properties. In Comparative Example 3, the absence of a "0° / 90° / 0°" grain orientation and the failure to laminate the impregnated gauze with the veneer colloid resulted in improved interlayer bonding strength and interfacial strength, but a significant decrease in mechanical properties and an increased warping rate, failing to meet requirements. In Comparative Examples 4-6, the altered segmented hot-pressing conditions led to varying degrees of decrease in interlayer bonding strength and interfacial strength, while mechanical properties decreased significantly. In Comparative Example 4, direct high-temperature pressing without steam venting resulted in material bursting.

[0049] Compared with Example 1, the interlayer bonding strength, interfacial shear strength and mechanical properties of Comparative Example 7 were reduced. Furthermore, because the laminated wood in Comparative Example 7 was dried directly in the high-temperature section, the rapid water loss caused the wood layers of the material to be damaged during the bonding strength and interlayer shear strength testing process.

[0050] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, this application is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of this application without departing from the scope of this application should be within the protection scope of this application.

Claims

1. A method for preparing laminated wood based on impregnated gauze reinforcement, characterized in that, Includes the following steps: S1. The wood veneer is subjected to gradient drying and plasma treatment, and then a modified phenolic resin adhesive is coated on the surface and left to stand to obtain pretreated wood veneer. S2. The lignin fiber gauze is impregnated in the impregnation solution to obtain impregnated gauze; S3. Alternately layer wood veneer and impregnated gauze, arranged in the "0° / 90° / 0°" grain direction, with one layer of impregnated gauze sandwiched between every 2 to 4 layers of veneer, and hot press in sections to obtain hot-pressed laminated wood; S4. Perform hot-pressed laminated wood curing, then sand both sides to remove residual adhesive layer on the surface, and the product is obtained.

2. The preparation method according to claim 1, characterized in that, The wood veneer is selected from poplar or eucalyptus, and the thickness of the wood veneer is 1.5 to 2.0 mm.

3. The preparation method according to claim 1, characterized in that, In step S1, the gradient drying process is as follows: first, dry at 55-60℃ and 50-60% relative humidity for 4-5 hours, then raise the temperature to 80-90℃ and 30-40% relative humidity for 6-8 hours, controlling the moisture content to 8-10%.

4. The preparation method according to claim 1, characterized in that, In step S1, the plasma treatment conditions are: power 300-500W, argon flow rate 10-25 L / min, and time 15-20s.

5. The preparation method according to claim 1, characterized in that, In step S1, the modified phenolic resin adhesive has a solid content of 45-55%, and is prepared by the following method: (1) Mix the catalyst, phenol and resorcinol, and activate for 10-30 min to obtain a mixture; (2) Formaldehyde aqueous solution and mixture are passed into a microchannel reactor for reaction. After the reaction is completed, the mixture is cooled and discharged to obtain modified phenolic resin glue.

6. The preparation method according to claim 1, characterized in that, In step S2, the basis weight of the lignin fiber gauze is 30–50 g / m². 2 The latitude and longitude density is (18~22)×(18~22) roots / cm.

7. The preparation method according to claim 1, characterized in that, The impregnation solution, by mass percentage, includes the following raw materials: 55-65% phenolic resin, 8-12% lignin, and 0.16-0.3% hyperbranched polyamide functionalized graphene suspension; the lignin fiber gauze after impregnation has a resin holding capacity of 30-40%.

8. The preparation method according to claim 1, characterized in that, In step S3, the segmented hot pressing process is as follows: Pre-compression: Heat to 100℃ and pre-compress for 2-3 minutes at a pressure of 0.7-0.9MPa; during this process, automatically vent 2-3 times, each time for 2-3 seconds; Main pressure: Heat to 130-140℃, increase pressure to 1.2-1.5MPa, and adjust the holding time according to the thickness of the plate. For every 1mm increase in thickness, increase the time by 0.6-0.8min. Insulation and pressure reduction: The pressure will be reduced to 0.9-1.1 MPa, and the pressure will be released naturally when the temperature drops below 60°C.

9. The preparation method according to claim 1, characterized in that, In step S4, the conditions for hot-press curing are: temperature of 20-25℃, relative humidity of 50±5%, and time of 8-10 days; the wood is turned over every 2 days during the hot-press curing process to ensure that the moisture content of the hot-pressed laminated wood is stable at 9-11%.

10. The laminated wood reinforced with impregnated gauze prepared by the preparation method according to any one of claims 1-9, characterized in that, The thickness of the laminated wood is ≥12mm, the warping deformation rate is <1.5%, the 24h water absorption swelling rate is ≤5%, and the formaldehyde release is ≤0.1mg / L.

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