Method for curing and impregnating solid wood floor at low temperature through melamine-furfuryl alcohol

Abstract

The invention provides a method for curing and impregnating a solid wood floor at a low temperature by using melamine-furfuryl alcohol, which comprises the following steps: carrying out secondary balance humidifying treatment on a solid wood floor blank to obtain a wood blank; the wood blank is subjected to interface pre-modification treatment, a modified interface layer is formed, and a pre-modified wood blank is obtained; the preparation method comprises the following steps: taking melamine, urea and furfuryl alcohol as raw materials, and reacting according to a molar ratio of 1: 0.5: 1.2 to obtain furfuryl alcohol resin; the pre-modified wood blank and furfuryl alcohol resin are subjected to pre-distribution treatment through a precision metering impregnation system, and a resin layer with the pre-distribution thickness being 0.3-0.5 mm is formed on the surface of the wood; carrying out sectional gradient vacuum-ultrasonic immersion treatment on the wood with the formed resin layer to obtain impregnated wood with sufficient resin permeation; and the impregnated wood is subjected to catalyst-assisted low-temperature curing treatment, and a solid wood floor finished product with the curing degree reaching 85% or above is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of solid wood floor manufacturing, in particular to a method for low-temperature curing and impregnating solid wood flooring with melamine-furfuryl alcohol. Background Art

[0002] Traditional impregnation modification technologies for solid wood flooring suffer from issues such as uneven resin penetration and incomplete curing, resulting in poor dimensional stability and high formaldehyde emissions. While existing vacuum-ultrasonic impregnation techniques improve penetration efficiency, they struggle to achieve uniform distribution within complex wood textures, and low-temperature curing conditions lead to incomplete cross-linking. Furthermore, insufficient interfacial bonding strength between the wood and the resin compromises the overall performance of the floor.

[0003] The existing technology has the following main defects: the impregnation depth and uniformity are difficult to accurately control, resulting in large differences in performance between different areas of the wood; the cross-linking reaction of melamine-furfuryl alcohol resin is incomplete under low-temperature curing conditions, affecting the mechanical properties of the cured product; the interface bonding mechanism between wood fibers and resin is unclear, and the interface bonding strength is limited. Summary of the Invention

[0004] The present invention aims to provide a method for low-temperature curing of melamine-furfuryl alcohol impregnated solid wood flooring, aiming to solve the technical problems existing in the prior art, such as uneven impregnation, incomplete curing reaction, and insufficient interface bonding strength between wood and resin.

[0005] To achieve the above objectives, the present invention provides a method for low-temperature curing and impregnating solid wood flooring with melamine-furfuryl alcohol, comprising: subjecting a solid wood flooring blank to a secondary equilibrium moisture control treatment to obtain a wood blank with a moisture content stabilized at 8±0.5%; subjecting the wood blank with a moisture content stabilized at 8±0.5% to an interface pre-modification treatment to form a modified interface layer and obtain a pre-modified wood blank; using melamine, urea, and furfuryl alcohol as raw materials, reacting in a molar ratio of 1:0.5:1.2 to prepare a MUF-furfuryl alcohol resin with a solid content of 60±2%; subjecting the pre-modified wood blank and the MUF-furfuryl alcohol resin to a pre-distributed treatment using a precision metering impregnation system to form a resin layer with a pre-distributed thickness of 0.3-0.5 mm on the wood surface; subjecting the wood forming the resin layer to a segmented gradient vacuum-ultrasonic impregnation treatment to obtain impregnated wood with sufficient resin penetration; and subjecting the impregnated wood to a catalyst-assisted low-temperature curing treatment to obtain a finished solid wood flooring product with a curing degree of more than 85%.

[0006] Preferably, the solid wood flooring blank is subjected to a secondary balanced humidity control treatment to obtain a wood blank with a moisture content stabilized at 8±0.5%, comprising: subjecting the solid wood flooring blank to a first humidity control treatment at a temperature of 45±2°C and a relative humidity of 65±3% for 48 hours to reduce the moisture content of the wood to 10±1%; subjecting the wood blank with the moisture content reduced to 10±1% to a second precision humidity control treatment at a temperature of 40±1°C and a relative humidity of 55±2% for 24 hours to stabilize the moisture content to 8±0.5%; and measuring the moisture content every 6 hours during the humidity control process to ensure that the moisture content fluctuation does not exceed ±0.2%, thereby obtaining the wood blank with a moisture content stabilized at 8±0.5%.

[0007] Preferably, the interface pre-modification treatment of the wood blank with a moisture content stabilized at 8±0.5% to form a modified interface layer and obtain a pre-modified wood blank comprises: immersing the wood blank with a moisture content stabilized at 8±0.5% in an interface modification liquid, treating it in a constant temperature water bath at 60±2°C for 2 hours to allow the silane molecules to fully penetrate and react with the hydroxyl groups on the surface of the wood fibers; drying the treated wood blank in an oven at 105°C for 30 minutes to completely cure the silane coupling agent to form a modified interface layer with a thickness of 5-10 nm; and verifying the modification effect through a contact angle test to obtain the pre-modified wood blank with a surface contact angle reduced from 85° to 65°.

[0008] Preferably, the preparation method of the interface modification liquid is: dissolving γ-aminopropyltriethoxysilane APTES at a concentration of 3wt% in an ethanol-water mixed solvent with a volume ratio of 7:3 to obtain a silane solution; adding 0.1% acetic acid to the silane solution to adjust the pH to 4.5-5.0 to obtain the interface modification liquid that promotes silane hydrolysis.

[0009] Preferably, the preparation method of melamine, urea, and furfuryl alcohol as raw materials in a molar ratio of 1:0.5:1.2 to obtain a MUF-furfuryl alcohol resin with a solid content of 60±2% comprises: first adding furfuryl alcohol to a reactor, heating to 80°C, then sequentially adding urea and melamine, and reacting for 2 hours at pH=8.5-9.0 to obtain a preliminary reaction product; cooling the preliminary reaction product to 60°C, adjusting the pH to 7.5-8.0, and continuing the reaction for 1 hour until the resin viscosity reaches 200-300 mPa·s; adding water to the reaction product with a resin viscosity of 200-300 mPa·s to dilute it to a solid content of 60±2%, adding 0.3% citric acid as a low-temperature curing catalyst, and fully stirring to obtain the MUF-furfuryl alcohol resin with a free formaldehyde content of less than 0.1%.

[0010] Preferably, the specific control of the reaction conditions is that: during the reaction, a pH automatic adjusting system is used to maintain the pH stability ±0.1, a precision temperature control system is used to ensure the temperature fluctuation ±1℃, and the precise control of the reaction conditions is ensured; an online viscosity monitoring system is used to monitor the viscosity change of the resin in real time, and the reaction is automatically stopped when the viscosity reaches the target range, so that the MUF-furfuryl alcohol resin with qualified viscosity is obtained.

[0011] Preferably, the precision metering impregnation system comprises: a precision scraper system using a stainless steel scraper, the gap adjustment precision is ±0.05mm, the pressure of the scraper on the wood surface is 10-15N / cm 2 ; a slit supply system with a slit width of 0.2-0.5mm adjustable, the resin supply flow is controlled by a precision gear pump, and the flow stability is ±2%; a tension control system applies a tensile tension of 10-20N / cm to both ends of the wood board.

[0012] Preferably, the pre-distribution treatment by the precision metering impregnation system forms a resin layer with a pre-distribution thickness of 0.3-0.5mm on the wood surface, which comprises: the pre-modified wood blank and the MUF-furfuryl alcohol resin pass through the precision scraper system at a wood moving speed of 2-3m / min, the resin temperature is controlled at 50±2℃, and the scraper gap is 1.2-1.5 times the thickness of the wood; the pre-distribution of the resin on the surface is controlled by the precision scraper system, and the resin layer with a pre-distribution thickness of 0.3-0.5mm is obtained.

[0013] Preferably, the first stage surface layer impregnation of the segmented gradient vacuum-ultrasonic impregnation is that the wood forming the resin layer is impregnated under the conditions of a vacuum degree of -0.3±0.05MPa, an ultrasonic frequency of 35kHz, and a power density of 0.5W / cm 3 for 10 minutes, so as to realize the resin penetration in the 0-3mm depth area of the wood surface layer.

[0014] Preferably, the second stage deep layer impregnation of the segmented gradient vacuum-ultrasonic impregnation is that the wood treated by the first stage is impregnated under the conditions of a vacuum degree of -0.7±0.05MPa, an ultrasonic frequency of 45kHz, and a power density of 0.8W / cm 3 for 20 minutes, so as to realize the resin penetration in the 3-10mm depth area, and obtain the impregnated wood with sufficient resin penetration.

[0015] The beneficial effects of the present invention are as follows: the interface modification technology improves the wood-resin bonding strength and significantly enhances the anti-expansion efficiency; the precision metering system enables accurate control of the resin dosage and reduces waste; the segmented gradient impregnation improves the penetration uniformity and effectively controls the water absorption thickness expansion rate; the catalyst-assisted curing ensures the completeness of the reaction at low temperatures and significantly reduces the TVOC emission; the overall process energy consumption is reduced and the VOC emission of the curing tail gas is reduced, providing a new technical path for the industrialized production of high-performance and environmentally friendly solid wood flooring. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. The drawings herein are incorporated into and constitute a part of the specification. These drawings illustrate embodiments consistent with the present disclosure and, together with the specification, are used to illustrate the technical solutions of the present disclosure. It should be understood that the following drawings only illustrate certain embodiments of the present disclosure and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without inventive effort.

[0017] Figure 1 This is a flow chart of the method for low-temperature curing and impregnation of solid wood flooring with melamine-furfuryl alcohol according to the present invention; Figure 2 This is a schematic diagram of the secondary balanced humidity control process of the present invention; Figure 3 Schematic diagram of the interface pre-modification treatment mechanism of the present invention; Figure 4 Schematic diagram of the synthesis reaction of MUF-furfuryl alcohol resin of the present invention; Figure 5 This is a structural diagram of the precision metering impregnation system of the present invention; Figure 6 This is a schematic diagram of the principle of the segmented gradient vacuum-ultrasonic impregnation of the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. The components of the embodiments of the present disclosure generally described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present disclosure provided in the drawings is not intended to limit the scope of the disclosure for which protection is sought, but merely represents selected embodiments of the present disclosure. Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present disclosure.

[0019] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0020] The term "and / or" herein simply describes an association relationship, indicating that three relationships can exist. For example, A and / or B can represent the existence of A alone, the simultaneous existence of A and B, and the existence of B alone. In addition, the term "at least one" herein refers to any combination of at least two of any one or more of a plurality of items. For example, "at least one of A, B, and C" can represent any one or more elements selected from the set consisting of A, B, and C.

[0021] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0022] like Figure 1 As shown, the present invention provides a method for low-temperature curing of melamine-furfuryl alcohol impregnated solid wood flooring, comprising: S1: The solid wood flooring blank is subjected to a secondary balance moisture control treatment to obtain a wood blank with a moisture content stabilized to 8±0.5%; The secondary balanced moisture conditioning treatment of solid wood flooring blanks is a key pre-treatment step to ensure the effect of impregnation modification.

[0023] During the first stage of humidity adjustment, the solid wood flooring blanks are placed in an environment with a temperature of 45±2°C and a relative humidity of 65±3% for 48 hours, so that the moisture inside the wood is gradually and evenly released, and the moisture content is reduced to 10±1%. The main purpose of this stage is to remove excess moisture inside the wood and create conditions for subsequent fine humidity adjustment. The second stage of precision humidity adjustment is carried out at a more precise temperature of 40±1°C and a relative humidity of 55±2% for 24 hours, further stabilizing the moisture content of the wood to 8±0.5%. During the entire humidity adjustment process, the moisture content is measured every 6 hours to ensure that the moisture content fluctuation does not exceed ±0.2%. This precise control ensures the stability of the internal structure of the wood and creates ideal basic conditions for subsequent resin impregnation.

[0024] S2: performing interface pre-modification treatment on the wood blank having a moisture content stabilized at 8±0.5% to form a modified interface layer and obtain a pre-modified wood blank; Interfacial pre-modification is a key innovative step in improving the bonding strength between wood and resin. This step first prepares an interfacial modification liquid, dissolves γ-aminopropyltriethoxysilane (APTES) at a concentration of 3wt% in an ethanol-water mixed solvent (volume ratio 7:3), and adds 0.1% acetic acid to adjust the pH to 4.5-5.0. The wood blank with stable moisture content is immersed in this modification liquid and treated in a constant temperature water bath at 60±2℃ for 2 hours to allow the silane molecules to fully penetrate the wood surface and react chemically with the hydroxyl groups on the surface of the wood fibers. It is then dried in an oven at 105℃ for 30 minutes to promote the complete curing of the silane coupling agent and form a modified interface layer 5-10nm thick. The modification effect can be verified by contact angle testing. After modification, the contact angle of the wood surface drops from 85° to 65°, indicating that the surface properties of the wood have changed significantly, laying a molecular foundation for the subsequent strong bonding between the resin and the wood.

[0025] S3: Using melamine, urea, and furfuryl alcohol as raw materials, a molar ratio of 1:0.5:1.2 was reacted to obtain MUF-furfuryl alcohol resin with a solid content of 60±2%; The preparation of MUF-furfuryl alcohol resin is the core technical step of this method and directly determines the performance of the impregnated wood. The preparation process follows strictly controlled reaction conditions: First, furfuryl alcohol is added to the reactor and heated to 80°C. Urea and melamine are then added sequentially, and the reaction proceeds for two hours at a pH of 8.5-9.0 to form a preliminary reaction product. The reaction system is then cooled to 60°C, the pH adjusted to 7.5-8.0, and the reaction continues for one hour until the resin viscosity reaches 200-300 mPa·s. Finally, the resin is diluted with water to a solids content of 60±2%, and 0.3% citric acid is added as a low-temperature curing catalyst, followed by thorough stirring. The entire reaction process is controlled by an automatic pH adjustment system and a precision temperature control system to ensure precise and stable reaction conditions. The resin viscosity is monitored in real time using an online viscosity monitoring system. The resulting high-performance MUF-furfuryl alcohol resin contains less than 0.1% free formaldehyde.

[0026] S4: pre-distributing the pre-modified wood blank and the MUF-furfuryl alcohol resin through a precision metering impregnation system to form a pre-distributed resin layer with a thickness of 0.3-0.5 mm on the wood surface; The pre-distribution treatment by precision metering impregnation system is an important process to ensure the uniform distribution of resin. The system is composed of precision doctor blade system, slit feeding system and tension control system, which can accurately control the distribution of resin on the wood surface. The pre-modified wood blank passes through the system at a speed of 2-3 m / min, the resin temperature is maintained at 50±2℃, and the doctor blade gap is set to 1.2-1.5 times the thickness of the wood. The stainless steel doctor blade maintains a pressure of 10-15 N / cm2 on the wood surface to ensure uniform distribution of resin. The slit feeding system controls the resin feeding flow rate through a precision gear pump, with a flow rate stability of ±2%, and applies a tensile tension of 10-20 N / cm to the two ends of the wood board to prevent wood deformation during the treatment. This pre-distribution treatment process forms a uniform resin layer with a thickness of 0.3-0.5 mm on the wood surface, laying the foundation for subsequent deep penetration.

[0027] S5: The wood forming the resin layer is subjected to a segmented gradient vacuum-ultrasonic impregnation treatment to obtain an impregnated wood with sufficient resin penetration; The segmented gradient vacuum-ultrasonic impregnation treatment is an innovative technology to achieve deep resin penetration. The process is divided into two stages: the first stage of surface impregnation is carried out under the conditions of vacuum degree -0.3±0.05 MPa, ultrasonic frequency 35 kHz, power density 0.5 W / cm 3 for 10 minutes, mainly acting on the 0-3 mm deep area of the wood surface; the second stage of deep impregnation is carried out under the conditions of higher vacuum degree -0.7±0.05 MPa, ultrasonic frequency 45 kHz, power density 0.8 W / cm 3 for 20 minutes to achieve resin penetration in the 3-10 mm deep area. The action of ultrasonic waves can significantly enhance the flowability of resin in the micro-pores of wood, reducing the obstruction of air bubbles, while the gradient vacuum design ensures uniform penetration from the surface to the deep layer. The entire process is monitored in real time by micro-electrodes embedded at different depths, and when the electrical impedance decreases by 80%, it indicates that the resin has penetrated sufficiently at that depth. The system automatically adjusts the ultrasonic power and frequency based on the monitoring data to ensure accurate control of the penetration effect.

[0028] S6: The impregnated wood is subjected to catalyst-assisted low-temperature curing treatment to obtain a solid wood floor product with a curing degree of more than 85%.

[0029] Catalyst-assisted low-temperature curing treatment is the last process step to ensure complete curing of the resin. The process first preheats the impregnated wood at 80°C for 5 minutes to activate the activity of the citric acid catalyst; then enters the main curing stage, which is treated at a temperature of 105±2°C, a saturated steam pressure of 0.12±0.02 MPa for 12 minutes, with a heating rate controlled at 5°C / min to ensure uniform temperature rise and prevent stress accumulation in the wood; after curing, the curing degree is confirmed to be more than 85% by DSC test, and then naturally cooled to room temperature under the condition of relative humidity 45-55% to complete the entire curing process. This low-temperature curing process not only reduces energy consumption, but also effectively avoids the deformation and cracking of wood that may occur during high-temperature curing. The use of citric acid catalyst ensures the completeness of the resin crosslinking reaction at relatively low temperature, and the finished product of solid wood flooring with stable performance and low environmental emission is obtained.

[0030] The secondary equilibrium moisture conditioning of solid wood flooring blanks is a key step to ensure the subsequent impregnation effect. As shown in Figure 2 , the process first performs the first moisture conditioning in an accurately controlled environment at a temperature of 45±2°C and a relative humidity of 65±3% for 48 hours to uniformly reduce the moisture content of the wood to 10±1%. Then, the preliminarily conditioned wood blanks are transferred to a more precise environment (temperature 40±1°C, relative humidity 55±2%) for the second precise moisture conditioning for 24 hours until the moisture content is stabilized in the ideal range of 8±0.5%. During the entire moisture conditioning process, the technician measures the moisture content every 6 hours to ensure that the moisture content fluctuation does not exceed ±0.2%, thereby obtaining high-quality wood blanks with uniform internal moisture distribution and stable moisture content. The interface pre-modification treatment of the stabilized wood blanks is an innovative link to improve the bonding force between the resin and the wood. As shown in Figure 3As shown, wood blanks with a moisture content of 8±0.5% were completely immersed in a specially formulated interfacial modification solution and treated in a constant-temperature water bath at 60±2°C for a precise 2 hours. This ensured that the silane molecules fully penetrated the wood surface and reacted with the hydroxyl groups on the wood fiber surfaces. The treated wood blanks were then dried in a 105°C oven for 30 minutes to fully cure the silane coupling agent, forming a modified interfacial layer 5-10 nm thick on the wood surface. The modification effect was clearly observed through contact angle measurements, which significantly decreased from 85° to 65° after treatment, demonstrating the desired change in the surface properties of the pre-modified wood blanks. The interfacial modification solution was prepared using a precise stoichiometric method. First, γ-aminopropyltriethoxysilane (APTES) was dissolved in an ethanol-water mixture (with a strictly controlled volume ratio of 7:3) at a precise concentration of 3 wt% to form a preliminary silane solution. 0.1% acetic acid is then added to the solution, precisely adjusting the pH to the optimal range of 4.5-5.0, resulting in a highly effective interfacial modification solution that promotes silane hydrolysis. The addition of acetic acid plays a key catalytic role in this process, significantly accelerating the hydrolysis of silane and generating highly active silanol groups. This significantly enhances the chemical reactivity of the modification solution with the hydroxyl groups on the wood surface, laying a solid molecular foundation for subsequent resin impregnation.

[0031] Melamine, urea and furfuryl alcohol were used as raw materials and reacted in a molar ratio of 1:0.5:1.2 to obtain MUF-furfuryl alcohol resin with a solid content of 60±2%. Figure 4 As shown, furfuryl alcohol is first added to a reactor, the temperature is raised to 80°C, and then urea and melamine are added in sequence. The mixture is reacted at pH = 8.5-9.0 for 2 hours to obtain a preliminary reaction product; the preliminary reaction product is cooled to 60°C, the pH is adjusted to 7.5-8.0, and the reaction is continued for 1 hour until the resin viscosity reaches 200-300 mPa·s; water is added to the reaction product with a resin viscosity of 200-300 mPa·s to dilute the solid content to 60±2%, 0.3% citric acid is added as a low-temperature curing catalyst, and the mixture is thoroughly stirred to obtain a MUF-furfuryl alcohol resin with a free formaldehyde content of less than 0.1%.

[0032] In the synthesis process of MUF-furfuryl alcohol resin, precise control of reaction conditions is a key factor in ensuring product quality. The entire reaction process adopts an advanced pH automatic adjustment system, which can control the pH fluctuation within a precise range of ±0.1, effectively avoiding the adverse effects of pH fluctuations on the molecular structure of the resin. At the same time, the precision temperature control system ensures that the reaction temperature fluctuation does not exceed ±1°C, providing stable conditions for the uniformity of the resin molecular weight distribution. It is particularly worth mentioning that the entire production line is equipped with an online viscosity monitoring system, which can track the resin viscosity change curve in real time. When it is detected that the viscosity reaches the target range of 200-300mPa·s, the system will automatically adjust the reaction parameters or stop the reaction to obtain MUF-furfuryl alcohol resin with precisely controllable viscosity. This multi-parameter coordinated precise control mechanism significantly improves the batch consistency and performance stability of resin products, and lays a solid foundation for the reliable implementation of subsequent impregnation processes. The precision metering impregnation system used in the present invention is the core device for achieving uniform distribution of resin. As Figure 5 As shown, the system consists of three subsystems with coordinated functions: the precision scraper system uses a special stainless steel scraper with a gap adjustment accuracy of up to ±0.05mm, while maintaining a pressure of 10-15N / cm with the wood surface. 2 The system maintains constant pressure to ensure stability during the coating process. The slit feed system features an adjustable glue slit with a width range of 0.2-0.5mm. A high-precision gear pump controls the resin flow rate, achieving a flow stability of ±2%, enabling precise metering of resin dosage. The tension control system applies a uniform tensile force of 10-20N / cm to both ends of the wood panel, effectively preventing deformation or twisting during processing. These three subsystems work together to ensure uniform resin distribution across the wood surface, creating ideal initial conditions for subsequent deep penetration. During operation, pre-modified wood blanks pass through the precision metering impregnation system at a constant speed of 2-3m / min. Simultaneously, the MUF-furfuryl alcohol resin is precisely heated to an optimal temperature of 50±2°C, ensuring good resin flow without premature cross-linking. The blade gap is precisely set to 1.2-1.5 times the wood thickness, a ratio verified through extensive experimentation to ensure sufficient resin flow while avoiding excess waste. Through this precise control, a uniform resin layer with a thickness of 0.3-0.5mm is formed on the wood surface. This pre-distribution not only enables the resin to form a continuous and complete liquid film on the wood surface, but also provides a sufficient and uniform resin source for the subsequent vacuum-ultrasonic impregnation process, significantly improving the overall impregnation efficiency and uniformity.

[0033] The first stage of segmented gradient vacuum-ultrasonic impregnation is surface impregnation. Figure 6 As shown in the figure, the wood with resin layer was placed under vacuum degree -0.3±0.05MPa, ultrasonic frequency 35kHz, power density 0.5W / cm3 The wood is immersed for 10 minutes under the condition to realize resin penetration in the area of 0-3 mm depth of the surface layer of the wood. The main purpose of this stage is to ensure that the surface layer of the wood is fully immersed, and to avoid stress concentration caused by uneven immersion between the surface and the internal structure of the wood.

[0034] The second stage of the segmented gradient vacuum-ultrasonic immersion is deep immersion. The wood treated in the first stage is immersed for 20 minutes under the condition of vacuum degree-0.7±0.05 MPa, ultrasonic frequency 45 kHz, power density 0.8 W / cm 3 The wood is immersed for 20 minutes under the condition to realize resin penetration in the area of 3-10 mm depth, and to obtain the immersed wood with sufficient resin penetration. In this stage, the higher vacuum degree and ultrasonic power can promote the penetration of resin into the deep layer of the wood, and the ultrasonic vibration can break the bubbles in the deep structure of the wood to improve the uniformity of penetration.

[0035] The catalyst-assisted low-temperature curing treatment. The immersed wood is preheated at 80°C for 5 minutes to activate the catalyst activity, and then the main curing stage is carried out at a temperature of 105±2°C and a saturated steam pressure of 0.12±0.02 MPa for 12 minutes, with a heating rate controlled at 5°C / min to ensure uniform temperature rise. The curing degree is confirmed by DSC test to be above 85%. Finally, the product of the solid wood floor with a curing degree of above 85% is obtained by natural cooling to room temperature under the condition of relative humidity of 45-55%. This low-temperature curing process not only reduces energy consumption, but also reduces the deformation and cracking problems of the wood that may occur in the high-temperature curing process.

[0036] Through the combined application of the above embodiments, the method of the melamine-furfuryl alcohol low-temperature curing and immersion of the solid wood floor solves the key technical problems existing in the traditional immersion process. The interfacial modification technology improves the wood-resin bonding strength by more than 30%, and the anti-swelling efficiency (ASE) is increased to more than 80%. The precise metering system realizes accurate control of the amount of resin, reducing waste by 15-20%. The segmented gradient immersion improves the uniformity of penetration, and the 24-hour water absorption thickness expansion rate is controlled within 1.5%. The catalyst-assisted curing ensures the completeness of the reaction at low temperature, and the TVOC emission is reduced by more than 45%. The overall process energy consumption is reduced by 20%, and the VOC emission of the curing tail gas is less than 0.08%. The method provides a new technical path for the industrial production of high-performance and environmentally friendly solid wood floors through the integration of multiple technologies.

Claims

1. A method for low-temperature curing of melamine-furfuryl alcohol impregnated solid wood flooring, characterized in that: include: The solid wood flooring blanks were subjected to a secondary balance moisture control treatment to obtain wood blanks with a moisture content stabilized at 8±0.5%; Performing interface pre-modification treatment on the wood blank with a moisture content stabilized at 8±0.5% to form a modified interface layer and obtain a pre-modified wood blank; Melamine, urea and furfuryl alcohol were used as raw materials and reacted in a molar ratio of 1:0.5:1.2 to obtain MUF-furfuryl alcohol resin with a solid content of 60±2%. The pre-modified wood blank and the MUF-furfuryl alcohol resin are pre-distributed by a precision metering impregnation system to form a pre-distributed resin layer with a thickness of 0.3-0.5 mm on the wood surface; The wood forming the resin layer is subjected to a segmented gradient vacuum-ultrasonic impregnation treatment to obtain impregnated wood with sufficient resin penetration; The impregnated wood is subjected to a catalyst-assisted low-temperature curing treatment to obtain a finished solid wood flooring product with a curing degree of more than 85%.

2. The method according to claim 1, characterized in that The method of subjecting the solid wood flooring blank to a secondary balanced moisture conditioning treatment to obtain a wood blank having a moisture content stabilized at 8±0.5% comprises: The solid wood flooring blank is subjected to a first humidity conditioning treatment at a temperature of 45±2° C. and a relative humidity of 65±3% for 48 hours to reduce the moisture content of the wood to 10±1%; The wood blank with the moisture content reduced to 10±1% is subjected to a second precision humidity control treatment at a temperature of 40±1°C and a relative humidity of 55±2% for 24 hours to stabilize the moisture content to 8±0.5%; During the humidity adjustment process, the moisture content was measured every 6 hours to ensure that the moisture content fluctuation did not exceed ±0.2%, thereby obtaining a wood blank with a moisture content stabilized at 8±0.5%.

3. The method according to claim 1, characterized in that The method of performing interface pre-modification treatment on a wood blank having a moisture content stabilized at 8±0.5% to form a modified interface layer and obtain a pre-modified wood blank comprises: The wood blank with a moisture content stabilized to 8±0.5% is immersed in the interfacial modification liquid and treated in a constant temperature water bath at 60±2°C for 2 hours to allow the silane molecules to fully penetrate and react with the hydroxyl groups on the surface of the wood fibers; The treated wood blank was dried in an oven at 105° C. for 30 minutes to completely cure the silane coupling agent and form a modified interface layer with a thickness of 5-10 nm; The modification effect was verified by contact angle testing, and the pre-modified wood blank was obtained in which the surface contact angle was reduced from 85° to 65°.

4. The method according to claim 3, characterized in that The preparation method of the interface modification liquid is: γ-aminopropyltriethoxysilane (APTES) was dissolved in an ethanol-water mixed solvent at a volume ratio of 7:3 at a concentration of 3 wt % to obtain a silane solution; 0.1% acetic acid is added to the silane solution to adjust the pH to 4.5-5.0 to obtain the interface modification solution that promotes silane hydrolysis.

5. The method according to claim 1, wherein The method comprises reacting melamine, urea and furfuryl alcohol as raw materials in a molar ratio of 1:0.5:1.2 to obtain a MUF-furfuryl alcohol resin having a solid content of 60±2%, comprising: First, furfuryl alcohol was added to the reactor, and the temperature was raised to 80°C. Then, urea and melamine were added in sequence, and the reaction was carried out at pH = 8.5-9.0 for 2 hours to obtain a preliminary reaction product. The preliminary reaction product was cooled to 60° C., the pH was adjusted to 7.5-8.0, and the reaction was continued for 1 hour until the viscosity of the resin reached 200-300 mPa·s; Water was added to the reaction product with a resin viscosity of 200-300 mPa·s to dilute the solid content to 60±2%, 0.3% citric acid was added as a low-temperature curing catalyst, and the mixture was thoroughly stirred to obtain the MUF-furfuryl alcohol resin with a free formaldehyde content of less than 0.1%.

6. The method according to claim 5, characterized in that The specific control of the reaction conditions is: During the reaction, an automatic pH adjustment system was used to maintain pH stability within ±0.1, and a precision temperature control system was used to ensure temperature fluctuations within ±1°C, thereby ensuring precise control of reaction conditions. The resin viscosity change is monitored in real time by an online viscosity monitoring system, and the reaction is automatically stopped when the viscosity reaches the target range to obtain the MUF-furfuryl alcohol resin with qualified viscosity.

7. The method according to claim 1, characterized in that The precision metering impregnation system includes: Precision scraper system, using stainless steel scraper, gap adjustment accuracy ±0.05mm, scraper and wood surface pressure 10-15N / cm 2 ; Slit supply system, slit width 0.2-0.5mm adjustable, resin supply flow rate is controlled by a precision gear pump, flow rate stability is ±2%; The tension control system applies a tensile tension of 10-20N / cm to both ends of the wood board.

8. The method according to claim 7, characterized in that The method of performing pre-distribution treatment by a precision metering impregnation system to form a pre-distributed resin layer with a thickness of 0.3-0.5 mm on the wood surface includes: The pre-modified wood blank and the MUF-furfuryl alcohol resin pass through a precision scraper system at a wood moving speed of 2-3 m / min, controlling the resin temperature at 50±2°C and the scraper gap at 1.2-1.5 times the wood thickness; The resin is pre-distributed on the surface by controlling the precision scraper system to obtain the resin layer with a pre-distributed thickness of 0.3-0.5 mm.

9. The method according to claim 1, characterized in that The first stage of surface impregnation of the segmented gradient vacuum-ultrasonic impregnation is: The wood forming the resin layer was placed under vacuum at -0.3±0.05 MPa, ultrasonic frequency at 35 kHz, and power density at 0.5 W / cm 3 Impregnate for 10 minutes under the appropriate conditions to achieve resin penetration into the wood surface area at a depth of 0-3mm.

10. The method according to claim 1, characterized in that The second stage deep impregnation of the segmented gradient vacuum-ultrasonic impregnation is: The wood treated in the first stage was placed under vacuum of -0.7±0.05MPa, ultrasonic frequency of 45kHz, and power density of 0.8W / cm 3 The resin was immersed in the wood for 20 minutes under the above conditions to achieve resin penetration in the 3-10 mm depth region, thereby obtaining the impregnated wood with sufficient resin penetration.

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