Adhesive for solid wood composite floor, preparation method of adhesive and solid wood composite floor

Abstract

The invention belongs to the technical field of solid wood composite floors, and particularly relates to an adhesive for a solid wood composite floor, a preparation method of the adhesive and the solid wood composite floor, and the adhesive is prepared from water glass, active silica-alumina filler, nano-silica sol, nano-zinc oxide, a silane coupling agent, cellulose ether and a water reducing agent. The front and back faces of the middle-layer wood veneer are evenly coated with an adhesive in a roller mode, then the middle-layer wood veneer, the surface-layer wood veneer and the bottom-layer wood veneer are subjected to veneer assembly, and a plate blank is obtained; and the plate blank is pressed and formed through a cold pressing process, and then the solid wood composite floor is obtained after drying treatment, balancing treatment, sawing and grooving and stabilizing treatment. The formaldehyde-free flame-retardant inorganic adhesive is adopted for cold pressing to prepare the solid wood composite floor, the solid wood composite floor which is good in flame retardant property and free of formaldehyde release is prepared on the premise that the low cost is maintained and the process complexity is not increased, the preparation process is environmentally friendly, and the prepared formaldehyde-free solid wood composite floor meets the requirement for the B1-level flame retardant property.

Description

Technical Field

[0001] This invention belongs to the field of engineered wood flooring technology, specifically relating to an adhesive for engineered wood flooring, its preparation method, and engineered wood flooring. Background Technology

[0002] In recent years, with the improvement of people's living standards, fire accidents have shown an upward trend. In order to reduce the occurrence of fires, it is stipulated that "the interior decoration of high-rise buildings such as high-end hotels, restaurants, hospital wards and residential buildings, as well as the paneling used for various fire doors and the manufacture of fire-resistant furniture, must be made of non-combustible or flame-retardant materials"; standard GB20286-2006 clarifies that "building materials and decoration materials used for ceilings, walls, floors and fixed furniture in public places must be flame-retardant products that meet the requirements of this standard" and "furniture and components such as beds, mattresses, cabinets, boxes, tables, sofas, junction boxes, and coffee tables used in public places must be flame-retardant products or components that meet the requirements of this standard".

[0003] One measure to prevent indoor fires is the use of fire-retardant materials and products, such as flame-retardant boards, flame-retardant flooring, and fire-resistant furniture. Among these, engineered wood flooring is a commonly used interior decoration material, but its flame-retardant properties are currently poor. Furthermore, engineered wood flooring, also known as multi-layer engineered wood flooring or three-layer engineered wood flooring, is made by bonding multiple or three layers of solid wood veneers together. It is generally manufactured using formaldehyde-based thermosetting adhesives such as urea-formaldehyde resin, modified urea-formaldehyde resin, phenolic resin, and melamine-formaldehyde resin. The use of formaldehyde-based adhesives is the main reason for the release of formaldehyde during the use of engineered wood flooring. In recent years, the implementation of a series of standards, including GB / T 39600-2021 "Classification of Formaldehyde Emission from Wood-based Panels and Their Products", GB / T39598-2021 "Guidelines for Indoor Load-bearing Capacity Limits of Wood-based Panels Based on Limiting Formaldehyde Emission", T / CNFPIA 1001-2019 "Formaldehyde Emission Limits for Wood-based Panels", and T / CNFPIA 3002-2018 "Formaldehyde-Free Wood-based Panels and Their Products", has placed stricter requirements on formaldehyde emission from engineered wood flooring. Low-formaldehyde and formaldehyde-free engineered wood flooring have become the inevitable development direction for the flooring industry in the future. While using formaldehyde-free adhesives can avoid the problem of formaldehyde release, the performance of engineered wood flooring currently using formaldehyde-free adhesives is not yet satisfactory and cannot reach the performance level of products currently using formaldehyde-based adhesives. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides an adhesive for engineered wood flooring, its preparation method, and the resulting engineered wood flooring. The adhesive is derived from inorganic materials, has a simple preparation process, and contains no formaldehyde or other harmful components added or released. It exhibits good flame retardancy, is environmentally friendly, and possesses excellent bonding and flame retardancy, as well as high water resistance and aging resistance. It significantly improves the water-resistant bonding strength and flame retardant properties of engineered wood flooring. No formaldehyde or other harmful substances are added or released during the preparation of the adhesive and the use of the bonded engineered wood flooring, thus conforming to green and environmentally friendly principles.

[0005] This invention is specifically achieved through the following technical solutions: The first object of the present invention is to provide an adhesive for engineered wood flooring, which is made of the following components in parts by weight: The water glass (calculated as SiO2) comprises 100 parts, active silica-alumina filler 30-60 parts, nano silica sol 5-20 parts, nano zinc oxide 2-10 parts, silane coupling agent 1-5 parts, cellulose ether 0.1-2 parts, and water-reducing agent 0.2-1.5 parts.

[0006] The water glass is potassium water glass or sodium-potassium composite water glass, with a modulus of 3.0 to 3.8 and a solid content of 35% to 45%. The modulus refers to SiO2 / M2O, where M is Na or K.

[0007] The activated silica-alumina filler is one or more of metakaolin, silica powder, and fly ash microspheres, with a particle size D50 ≤ 15 μm and a total SiO2 and Al2O3 content of not less than 85%; the nano silica sol has a particle size of 10 nm to 30 nm and a solid content of 20% to 30%; the nano zinc oxide has a particle size of 30 nm to 70 nm; the silane coupling agent is at least one of γ-aminopropyltriethoxysilane (KH-550) and γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560); the cellulose ether is hydroxypropyl methylcellulose (HPMC); and the water-reducing agent is a polycarboxylate-based water-reducing agent.

[0008] A second objective of this invention is to provide a method for preparing an adhesive for engineered wood flooring, comprising the following steps: The silane coupling agent and water glass are mixed, and the water glass is pretreated and modified by using 0.5%-2% of the total weight of the water glass as the silane coupling agent to obtain the modified base liquid. The active silica-alumina filler, nano zinc oxide and cellulose ether are mixed evenly to obtain a premixed powder. Under stirring conditions (preferably 400 rpm to 600 rpm), add nano-silica sol and water-reducing agent to the modified base liquid and stir for 10 to 15 minutes until the mixture is uniform. After increasing the speed (preferably 800 rpm to 1200 rpm), slowly and evenly add the premixed powder, then reduce the speed (preferably 300 rpm to 400 rpm) and continue stirring for 20 to 40 minutes for aging and defoaming to obtain a uniform and delicate paste-like adhesive for solid wood composite flooring.

[0009] The third objective of this invention is to provide a solid wood composite flooring, comprising a surface wood veneer, a middle wood veneer, and a bottom wood veneer, wherein the middle wood veneer is bonded to the surface wood veneer and the bottom wood veneer on both sides by the aforementioned solid wood composite flooring adhesive.

[0010] Preferably, the above-mentioned engineered wood flooring is prepared by the following method: The adhesive is evenly rolled onto both sides of the middle layer of wood veneer, and then assembled with the surface layer and bottom layer of wood veneer to obtain the board blank. The slab is pressed into shape using a cold pressing process, and then undergoes drying, balancing, sawing and grooving, and stabilization treatments to obtain engineered wood flooring.

[0011] Preferably, the adhesive application rate is 300 g / m². 2 ~350g / m 2 .

[0012] Preferably, in the cold pressing process, the pressing temperature is room temperature, the pressure is 1.2MPa~1.5MPa, and the time is 12h~24h.

[0013] Preferably, the drying process is as follows: First, the cold-pressed sheet is clamped with C-clamps and placed in a drying chamber at a temperature of 65℃~70℃ for 24h~48h; then the sheet is placed in a drying chamber at a temperature of 45℃~50℃ for 24h~48h.

[0014] Preferably, the balancing process involves placing the board in an environment with a temperature of 25°C and a relative humidity of 50% for 24 hours to equilibrate.

[0015] Preferably, the stabilization process involves placing the board in an environment with a temperature of 25°C and a relative humidity of 50% for 24 hours to stabilize it.

[0016] Preferably, the surface wood is a broad-leaved tree species, and the thickness of the surface wood veneer is 1.8mm~2.5mm, with a density of 0.6g / cm³. 3 ~0.8g / cm 3The middle layer wood is made of coniferous trees, with a veneer thickness of 7.5mm~9.0mm and a density of 0.4g / cm³. 3 ~0.7g / cm 3 The bottom layer of wood is made of broad-leaved tree species, with a veneer thickness of 1.8mm~2.5mm and a density of 0.6g / cm³. 3 ~0.8g / cm 3 The moisture content of the surface veneer, middle veneer, and bottom veneer is all 8% to 12%.

[0017] Hardwood species include ash, oak, teak, birch, beech, maple, catalpa, and black walnut; coniferous species include pine and fir.

[0018] Preferably, before veneer assembly, the surface veneer, middle veneer and bottom veneer are dried separately to adjust the moisture content to 8%~10%.

[0019] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a formaldehyde-free flame-retardant inorganic adhesive, in which water glass serves as the main bonding matrix. Using water glass with a high modulus and pre-modifying it with a silane coupling agent reduces the system's alkalinity and minimizes efflorescence. Simultaneously, the organic functional groups of the silane improve interfacial compatibility with wood. The active silica-alumina filler not only serves as an inexpensive filler, but more importantly, its active SiO2 and Al2O3 react with alkali metal ions in the water glass to generate a three-dimensional network structure (Si-O-Al-O-) similar to a geopolymer. This is crucial for the adhesive to achieve high strength and water resistance. Nano-silica sol, as a nano-reinforcing phase, has silanol groups on its surface that react with the water glass and active filler, filling micropores and defects within the sol and significantly improving the density, hardness, and bonding strength of the adhesive layer. Nano-zinc oxide has multiple functions, including acting as a functional filler to improve the toughness and... The adhesive offers several advantages: durability, antibacterial properties, and the ability to react with water glass to consume some free alkali and help inhibit alkali return. Silane coupling agents act as "molecular bridges," with their inorganic ends (-Si(OR)4) chemically bonded to inorganic colloids and their organic ends (-NH2,-CH2CH2CH2O-) forming strong bonds or hydrogen bonds with the hydroxyl groups on wood cellulose, significantly improving the adhesion at the inorganic-organic interface. Cellulose ethers act as water-retaining and thickening agents, preventing the adhesive from losing water too quickly or being excessively absorbed by the wood after application, ensuring sufficient open aging time, and improving application performance. Water-reducing agents effectively reduce mixing water without lowering viscosity, thereby increasing the density and strength of the cured adhesive layer and reducing shrinkage and cracking caused by excessive moisture.

[0020] The adhesive used in this invention for solid wood composite flooring is derived from inorganic materials. The preparation process is simple, with no formaldehyde or other harmful components added or released. It exhibits good flame retardancy, is environmentally friendly, and possesses excellent bonding and flame retardancy, as well as high water resistance and aging resistance. It significantly improves the water-resistant bonding strength and flame retardant properties of solid wood composite flooring. No formaldehyde or other harmful substances are added or released during the preparation of the adhesive and the use of the bonded solid wood composite flooring, complying with green and environmentally friendly principles.

[0021] This invention utilizes a formaldehyde-free, flame-retardant inorganic adhesive for cold-pressing solid wood composite flooring. While maintaining low costs and without increasing process complexity, it produces solid wood composite flooring with good flame retardant properties and no formaldehyde release. The manufacturing process is green and environmentally friendly. The solid wood composite flooring substrate prepared using the adhesive of this invention achieves the B1 level flame retardant performance requirement; its water-resistant bonding strength meets the requirements for Class I boards in the national standard GB17657-2022 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels" (boiling water treatment shear strength ≥ 0.7 MPa); and its environmental performance meets the requirements of GB / T 39600-2021 "Classification of Formaldehyde Emission from Wood-based Panels and Their Products" (E...). NF (Formaldehyde-free) grade requirement. Detailed Implementation

[0022] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below with reference to specific embodiments. However, the embodiments are not intended to limit the present invention. Unless otherwise specified, the experimental methods and detection methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0023] The test materials used in the embodiments of this invention are all conventional test materials in the art and can be purchased through commercial channels.

[0024] Example 1 The raw material composition (by weight) of the formaldehyde-free inorganic adhesive in this embodiment is as follows: 250 parts of potassium silicate with a modulus of 3.3 (SiO2 mass content 40%) (equivalent to 100 parts of SiO2), 45 parts of metakaolin (active silica-alumina filler, D50=8μm), 20 parts of nano silica sol (20nm, 25wt%), 5 parts of nano zinc oxide (50nm), 3 parts of γ-aminopropyltriethoxysilane (KH-550), 0.5 parts of hydroxypropyl methylcellulose (HPMC, viscosity 40000mPa•s), and 0.5 parts of polycarboxylate superplasticizer (40% solid content).

[0025] The method for preparing the formaldehyde-free inorganic adhesive in this embodiment includes the following steps: (1) In a 60°C water bath, KH-550 was slowly added to potassium silicate and stirred at 400 rpm for 45 minutes to obtain the modified base solution.

[0026] (2) Mix metakaolin, nano zinc oxide and HPMC in a mixer for 15 minutes to obtain premixed powder.

[0027] (3) Pour the modified base liquid from step (1) into a planetary mixer, add nano silica sol and water-reducing agent in sequence at 500 rpm, and stir for 12 minutes.

[0028] (4) Increase the rotation speed to 1000 rpm and slowly add the premixed powder. The feeding time is about 10 minutes.

[0029] (5) After adding all the powder, reduce the speed to 350 rpm and continue stirring for 30 minutes until it becomes a uniform paste without bubbles, then discharge.

[0030] Example 2 The raw material composition (by weight) of the formaldehyde-free inorganic adhesive in this embodiment is as follows: 250 parts of potassium silicate with a modulus of 3.3 (40% SiO2 content) (equivalent to 100 parts of SiO2), 30 parts of metakaolin (active silica-alumina filler, D50=8μm), 5 parts of nano silica sol (20nm, 25wt%), 10 parts of nano zinc oxide (50nm), 5 parts of γ-aminopropyltriethoxysilane (KH-550), 0.1 parts of hydroxypropyl methylcellulose (HPMC, viscosity 40000mPa•s), and 0.2 parts of polycarboxylate superplasticizer (40% solid content).

[0031] The preparation method is the same as in Example 1.

[0032] Example 3 The raw material composition (by weight) of the formaldehyde-free inorganic adhesive in this embodiment is as follows: 250 parts of potassium silicate with a modulus of 3.3 (40% SiO2 content) (equivalent to 100 parts of SiO2), 60 parts of metakaolin (active silica-alumina filler, D50=8μm), 10 parts of nano silica sol (20nm, 25wt%), 2 parts of nano zinc oxide (50nm), 1 part of γ-aminopropyltriethoxysilane (KH-550), 2 parts of hydroxypropyl methylcellulose (HPMC, viscosity 40000mPa•s), and 1.5 parts of polycarboxylate superplasticizer (40% solid content).

[0033] The preparation method is the same as in Example 1.

[0034] The formaldehyde-free inorganic adhesives prepared in Examples 1 to 3 above have similar properties. The following example only uses Example 1 to prepare solid wood composite flooring and tests its performance.

[0035] Application Example 1 The preparation of highly flame-retardant formaldehyde-free solid wood composite flooring, using the formaldehyde-free inorganic adhesive prepared in Example 1, includes the following steps: (1) The surface veneer, the middle veneer, and the bottom veneer are dried separately to adjust their moisture content to 8%, wherein the surface veneer is oak veneer with a thickness of 1.8 mm and a density of 0.75 g / cm³. 3 The middle layer of wood veneer is made of fir veneer, with a thickness of 8.5mm and a density of 0.6g / cm³. 3 The bottom layer is made of oak veneer, 1.8mm thick, with a density of 0.75g / cm³. 3 ; The formaldehyde-free inorganic adhesive prepared in Example 1 was applied to both the top and bottom surfaces of the intermediate layer wood veneer using a roller coating method. The application amount of the formaldehyde-free inorganic adhesive was 300 g / m². 2 (Double-sided), then the glued middle layer wood veneer is sequentially and alternately combined with the surface wood veneer and the bottom layer wood veneer to form a veneer blank.

[0036] (2) The slab is fed into a cold press for pressing and forming, wherein the temperature is room temperature, the pressure is 1.2 MPa, and the time is 12 h.

[0037] (3) Remove the cold-pressed board from the cold press, clamp it with C-clamps, and place it in a drying chamber at 65℃ for 48 hours; then place the board in a drying chamber at 45℃ for 24 hours. Place the board in an environment at 25℃ and 50% relative humidity for 24 hours to equilibrate. Cut the equilibrated board into grooves according to the specified dimensions, and place it in an environment at 25℃ and 50% relative humidity for 24 hours to stabilize it, thus obtaining the high flame-retardant formaldehyde-free solid wood composite flooring.

[0038] Application Example 2 The preparation of highly flame-retardant formaldehyde-free engineered wood flooring includes the following steps: (1) The surface veneer, the middle veneer, and the bottom veneer are dried separately to adjust their moisture content to 10%, wherein the surface veneer is teak veneer with a thickness of 2.0 mm and a density of 0.72 g / cm³. 3 The middle layer is made of pine veneer, with a thickness of 8.3mm and a density of 0.65g / cm³. 3 The bottom veneer is teak veneer, 2.0mm thick, with a density of 0.72g / cm³. 3 ; The formaldehyde-free inorganic adhesive prepared in Example 1 was applied to both the top and bottom surfaces of the intermediate layer wood veneer using a roller coating method. The application amount of the formaldehyde-free inorganic adhesive was 320 g / m². 2 (Double-sided), then the glued middle layer wood veneer is sequentially and alternately combined with the surface wood veneer and the bottom layer wood veneer to form a veneer blank.

[0039] (2) The slab is fed into a cold press for pressing and forming, wherein the temperature is room temperature, the pressure is 1.2 MPa, and the time is 18 h.

[0040] (3) Remove the cold-pressed board from the cold press, clamp it with C-clamps, and place it in a drying chamber at 65℃ for 36 hours; then place it in a drying chamber at 45℃ for 24 hours. Place the board in an environment at 25℃ and 50% relative humidity for 24 hours to equilibrate. Cut the equilibrated board into grooves according to the specified dimensions, and place it in an environment at 25℃ and 50% relative humidity for 24 hours to stabilize it, thus obtaining the high flame-retardant formaldehyde-free solid wood composite flooring.

[0041] Application Example 3 The preparation of highly flame-retardant formaldehyde-free engineered wood flooring includes the following steps: (1) The surface veneer, the middle veneer, and the bottom veneer are dried separately to adjust their moisture content to 8%, wherein the surface veneer is ash veneer with a thickness of 2.5 mm and a density of 0.76 g / cm³. 3 The middle layer is made of pine veneer, with a thickness of 7.8mm and a density of 0.65g / cm³. 3 The bottom veneer is teak veneer, 2.5mm thick, with a density of 0.76g / cm³. 3 ; The formaldehyde-free inorganic adhesive prepared in Example 1 was applied to both the top and bottom surfaces of the intermediate layer wood veneer using a roller coating method. The application amount of the formaldehyde-free inorganic adhesive was 350 g / m². 2 (Double-sided), then the glued middle layer wood veneer is sequentially and alternately combined with the surface wood veneer and the bottom layer wood veneer to form a veneer blank.

[0042] (2) The board blank is fed into a cold press for pressing and forming at room temperature, pressure of 1.2 MPa, and time of 24 hours. The cold-pressed board is removed from the cold press, clamped with C-clamps, and placed in a drying chamber at 65°C for 24 hours; then the board is placed in a drying chamber at 45°C for 24 hours. The board is then placed in an environment at 25°C and 50% relative humidity for 24 hours to equilibrate. The equilibrated board is then sawn into grooves according to the specified dimensions and placed in an environment at 25°C and 50% relative humidity for 24 hours to stabilize, thus obtaining the high flame-retardant formaldehyde-free solid wood composite flooring.

[0043] Application Comparative Example 1 The preparation of engineered wood flooring includes the following steps: The difference between this comparative example and application example 1 is that the adhesive used is a urea-formaldehyde resin adhesive prepared and produced by Lanling Jason Decoration Materials Co., Ltd., which is prepared using the commonly used formaldehyde / urea molar ratio of 1.05 and has a solid content of 50.05%. This urea-formaldehyde resin adhesive is currently used in the production of conventional solid wood composite flooring.

[0044] (1) The surface veneer, the middle veneer, and the bottom veneer are dried separately to adjust their moisture content to 8%, wherein the surface veneer is oak veneer with a thickness of 1.8 mm and a density of 0.75 g / cm³. 3 The middle layer of wood veneer is made of fir veneer, with a thickness of 8.5mm and a density of 0.6g / cm³. 3 The bottom layer is made of oak veneer, 1.8mm thick, with a density of 0.75g / cm³. 3 ; Urea-formaldehyde resin adhesive was applied to both the top and bottom surfaces of the intermediate layer wood veneer using a roller coating method, with an application rate of 300 g / m². 2 (Double-sided), then the glued middle layer wood veneer is sequentially and alternately combined with the surface wood veneer and the bottom layer wood veneer to form a veneer blank.

[0045] (2) The slab is fed into a cold press for pressing and forming, wherein the temperature is room temperature, the pressure is 1.2 MPa, and the time is 12 h.

[0046] (3) Remove the cold-pressed boards from the cold press, clamp them with C-clamps, and place them in a drying chamber at 65°C for 48 hours; then place them in a drying chamber at 45°C for 24 hours. Place the boards in an environment at 25°C and 50% relative humidity for 24 hours to equilibrate. Cut the equilibrated boards into grooves according to the specified dimensions, and place them in an environment at 25°C and 50% relative humidity for 24 hours to stabilize them, thus obtaining the solid wood composite flooring.

[0047] Application Comparative Example 2 The preparation of highly flame-retardant formaldehyde-free engineered wood flooring includes the following steps: The difference between this comparative example and application example 1 is that the pressing molding is a conventional hot pressing molding process for solid wood composite flooring.

[0048] (1) The surface veneer, the middle veneer, and the bottom veneer are dried separately to adjust their moisture content to 8%, wherein the surface veneer is oak veneer with a thickness of 1.8 mm and a density of 0.75 g / cm³. 3 The middle layer of wood veneer is made of fir veneer, with a thickness of 8.5mm and a density of 0.6g / cm³. 3 The bottom layer is made of oak veneer, 1.8mm thick, with a density of 0.75g / cm³. 3 ; The formaldehyde-free inorganic adhesive prepared in Example 1 was applied to both the top and bottom surfaces of the intermediate layer wood veneer using a roller coating method. The application amount of the formaldehyde-free inorganic adhesive was 300 g / m². 2 (Double-sided), then the glued middle layer wood veneer is sequentially and alternately combined with the surface wood veneer and the bottom layer wood veneer to form a veneer blank.

[0049] (2) The blank is fed into a hot press for pressing and forming, wherein the temperature is 120℃ (common hot pressing temperature for solid wood composite flooring), the pressure is 1.2MPa (common hot pressing pressure for solid wood composite flooring), and the time is 10min (common hot pressing time for solid wood composite flooring).

[0050] (3) Remove the hot-pressed boards from the hot press, clamp them with C-clamps, and place them in a drying chamber at 65°C for 48 hours; then place them in a drying chamber at 45°C for 24 hours. Place the boards in an environment at 25°C and 50% relative humidity for 24 hours to equilibrate. Cut the equilibrated boards into grooves according to the specified dimensions, and place them in an environment at 25°C and 50% relative humidity for 24 hours to stabilize them, thus obtaining the solid wood composite flooring.

[0051] Application Comparative Example 3 The preparation of engineered wood flooring includes the following steps: The difference between this comparative example and application example 1 is that the adhesive used is the urea-formaldehyde resin adhesive prepared and produced by Lanling Jason Decoration Materials Co., Ltd., and the pressing molding is a conventional hot pressing molding process for solid wood composite flooring.

[0052] (1) The surface veneer, the middle veneer, and the bottom veneer are dried separately to adjust their moisture content to 8%, wherein the surface veneer is oak veneer with a thickness of 1.8 mm and a density of 0.75 g / cm³.3 The middle layer of wood veneer is made of fir veneer, with a thickness of 8.5mm and a density of 0.6g / cm³. 3 The bottom layer is made of oak veneer, 1.8mm thick, with a density of 0.75g / cm³. 3 ; Urea-formaldehyde resin adhesive was applied to both the top and bottom surfaces of the intermediate layer wood veneer using a roller coating method, with an application rate of 300 g / m². 2 (Double-sided), then the glued middle layer wood veneer is sequentially and alternately combined with the surface wood veneer and the bottom layer wood veneer to form a veneer blank.

[0053] (2) The board is fed into a hot press for pressing and molding. The temperature is 120℃ (common hot pressing temperature for solid wood composite flooring), the pressure is 1.2MPa (common hot pressing pressure for solid wood composite flooring), and the time is 10min (common hot pressing time for solid wood composite flooring).

[0054] (3) Remove the hot-pressed board from the hot press and place it in an environment with a temperature of 25℃ and a relative humidity of 50% for 24 hours to equilibrate. Cut the equilibrated board into grooves according to the specified dimensions and place it in an environment with a temperature of 25℃ and a relative humidity of 50% for 24 hours to stabilize it, thus obtaining solid wood composite flooring.

[0055] Application Comparative Example 4 The preparation of highly flame-retardant formaldehyde-free engineered wood flooring includes the following steps: The difference between this comparative example and application example 1 is that the sheet material was not clamped during the drying process after pressing.

[0056] (1) The surface veneer, the middle veneer, and the bottom veneer are dried separately to adjust their moisture content to 8%, wherein the surface veneer is oak veneer with a thickness of 1.8 mm and a density of 0.75 g / cm³. 3 The middle layer of wood veneer is made of fir veneer, with a thickness of 8.5mm and a density of 0.6g / cm³. 3 The bottom layer is made of oak veneer, 1.8mm thick, with a density of 0.75g / cm³. 3 ; The formaldehyde-free inorganic adhesive prepared in Example 1 was applied to both the top and bottom surfaces of the intermediate layer wood veneer using a roller coating method. The application amount of the formaldehyde-free inorganic adhesive was 300 g / m². 2 (Double-sided), then the glued middle layer wood veneer is sequentially and alternately combined with the surface wood veneer and the bottom layer wood veneer to form a veneer blank.

[0057] (2) The sheet material is fed into a cold press for pressing and forming, wherein the temperature is room temperature, the pressure is 1.2 MPa, and the time is 12 h.

[0058] (3) Remove the cold-pressed boards from the cold press and place them in a drying room at 65°C for 48 hours; then place them in a drying room at 45°C for 24 hours. Place the boards in an environment at 25°C and 50% relative humidity for 24 hours to equilibrate. Cut the equilibrated boards into grooves according to the specified dimensions and place them in an environment at 25°C and 50% relative humidity for 24 hours to stabilize them, thus obtaining the high flame-retardant formaldehyde-free solid wood composite flooring.

[0059] Application Comparative Example 5 The preparation of highly flame-retardant formaldehyde-free engineered wood flooring includes the following steps: The difference between this comparative example and application example 1 is that the sheet material was not dried after pressing.

[0060] (1) The surface veneer, the middle veneer, and the bottom veneer are dried separately to adjust their moisture content to 8%, wherein the surface veneer is oak veneer with a thickness of 1.8 mm and a density of 0.75 g / cm³. 3 The middle layer of wood veneer is made of fir veneer, with a thickness of 8.5mm and a density of 0.6g / cm³. 3 The bottom layer is made of oak veneer, 1.8mm thick, with a density of 0.75g / cm³. 3 ; The formaldehyde-free inorganic adhesive prepared in Example 1 was applied to both the top and bottom surfaces of the intermediate layer wood veneer using a roller coating method. The application amount of the formaldehyde-free inorganic adhesive was 300 g / m². 2 (Double-sided), then the glued middle layer wood veneer is sequentially and alternately combined with the surface wood veneer and the bottom layer wood veneer to form a veneer blank.

[0061] (2) The sheet material is fed into a cold press for pressing and forming, wherein the temperature is room temperature, the pressure is 1.2 MPa, and the time is 12 h.

[0062] (3) Take the cold-pressed board out of the cold press and place it in an environment with a temperature of 25℃ and a relative humidity of 50% for 24 hours to equilibrate. Cut the equilibrated board into grooves according to the specified size and place it in an environment with a temperature of 25℃ and a relative humidity of 50% for 24 hours to stabilize it, thus obtaining the high flame retardant formaldehyde-free solid wood composite flooring.

[0063] Application Comparative Example 6 The difference between this comparative example and application example 1 is that the adhesive formulation does not contain a silane coupling agent, that is, the water glass has not been modified.

[0064] (1) The surface veneer, the middle veneer, and the bottom veneer are dried separately to adjust their moisture content to 8%, wherein the surface veneer is oak veneer with a thickness of 1.8 mm and a density of 0.75 g / cm³. 3 The middle layer of wood veneer is made of fir veneer, with a thickness of 8.5mm and a density of 0.6g / cm³. 3 The bottom layer is made of oak veneer, 1.8mm thick, with a density of 0.75g / cm³. 3 ; A formaldehyde-free inorganic adhesive, made from unmodified water glass, was applied to both the top and bottom surfaces of the interlayer wood veneer using a roller coating method. The application rate of the formaldehyde-free inorganic adhesive was 300 g / m². 2 (Double-sided), then the glued middle layer wood veneer is sequentially and alternately combined with the surface wood veneer and the bottom layer wood veneer to form a veneer blank.

[0065] (2) The sheet material is fed into a cold press for pressing and forming, wherein the temperature is room temperature, the pressure is 1.2 MPa, and the time is 12 h.

[0066] (3) Remove the cold-pressed board from the cold press, clamp it with C-clamps, and place it in a drying chamber at 65℃ for 48 hours; then place the board in a drying chamber at 45℃ for 24 hours. Place the board in an environment at 25℃ and 50% relative humidity for 24 hours to equilibrate. Cut the equilibrated board into grooves according to the specified dimensions, and place it in an environment at 25℃ and 50% relative humidity for 24 hours to stabilize it, thus obtaining the high flame-retardant formaldehyde-free solid wood composite flooring.

[0067] Application Comparative Example 7 The difference between this comparative example and application example 1 is that the adhesive formulation does not contain metakaolin.

[0068] (1) The surface veneer, the middle veneer, and the bottom veneer are dried separately to adjust their moisture content to 8%, wherein the surface veneer is oak veneer with a thickness of 1.8 mm and a density of 0.75 g / cm³. 3 The middle layer of wood veneer is made of fir veneer, with a thickness of 8.5mm and a density of 0.6g / cm³. 3 The bottom layer is made of oak veneer, 1.8mm thick, with a density of 0.75g / cm³. 3 ; A formaldehyde-free inorganic adhesive, made without metakaolin, was applied to both the top and bottom surfaces of the intermediate layer wood veneer using a roller coating method. The application rate of the formaldehyde-free inorganic adhesive was 300 g / m². 2 (Double-sided), then the glued middle layer wood veneer is sequentially and alternately combined with the surface wood veneer and the bottom layer wood veneer to form a veneer blank.

[0069] (2) The sheet material is fed into a cold press for pressing and forming, wherein the temperature is room temperature, the pressure is 1.2 MPa, and the time is 12 h.

[0070] (3) Remove the cold-pressed board from the cold press, clamp it with C-clamps, and place it in a drying chamber at 65℃ for 48 hours; then place the board in a drying chamber at 45℃ for 24 hours. Place the board in an environment at 25℃ and 50% relative humidity for 24 hours to equilibrate. Cut the equilibrated board into grooves according to the specified dimensions, and place it in an environment at 25℃ and 50% relative humidity for 24 hours to stabilize it, thus obtaining the high flame-retardant formaldehyde-free solid wood composite flooring.

[0071] Application Comparative Example 8 The difference between this comparative example and application example 1 is that the adhesive formulation does not contain nano-silica sol.

[0072] (1) The surface veneer, the middle veneer, and the bottom veneer are dried separately to adjust their moisture content to 8%, wherein the surface veneer is oak veneer with a thickness of 1.8 mm and a density of 0.75 g / cm³. 3 The middle layer of wood veneer is made of fir veneer, with a thickness of 8.5mm and a density of 0.6g / cm³. 3 The bottom layer is made of oak veneer, 1.8mm thick, with a density of 0.75g / cm³. 3 ; A formaldehyde-free inorganic adhesive, prepared without nano-silica sol, was applied to both the top and bottom surfaces of the intermediate layer wood veneer using a roller coating method. The application rate of the formaldehyde-free inorganic adhesive was 300 g / m². 2 (Double-sided), then the glued middle layer wood veneer is sequentially and alternately combined with the surface wood veneer and the bottom layer wood veneer to form a veneer blank.

[0073] (2) The sheet material is fed into a cold press for pressing and forming, wherein the temperature is room temperature, the pressure is 1.2 MPa, and the time is 12 h.

[0074] (3) Remove the cold-pressed board from the cold press, clamp it with C-clamps, and place it in a drying chamber at 65℃ for 48 hours; then place the board in a drying chamber at 45℃ for 24 hours. Place the board in an environment at 25℃ and 50% relative humidity for 24 hours to equilibrate. Cut the equilibrated board into grooves according to the specified dimensions, and place it in an environment at 25℃ and 50% relative humidity for 24 hours to stabilize it, thus obtaining the high flame-retardant formaldehyde-free solid wood composite flooring.

[0075] Application Comparison Example 9 The difference between this comparative example and application example 1 is that the adhesive formulation does not contain nano zinc oxide.

[0076] (1) The surface veneer, the middle veneer, and the bottom veneer are dried separately to adjust their moisture content to 8%, wherein the surface veneer is oak veneer with a thickness of 1.8 mm and a density of 0.75 g / cm³. 3 The middle layer of wood veneer is made of fir veneer, with a thickness of 8.5mm and a density of 0.6g / cm³. 3 The bottom layer is made of oak veneer, 1.8mm thick, with a density of 0.75g / cm³. 3 ; A formaldehyde-free inorganic adhesive, made without nano-zinc oxide, was applied to both the top and bottom surfaces of the intermediate layer wood veneer using a roller coating method. The application rate of the formaldehyde-free inorganic adhesive was 300 g / m². 2 (Double-sided), then the glued middle layer wood veneer is sequentially and alternately combined with the surface wood veneer and the bottom layer wood veneer to form a veneer blank; (2) The sheet material is fed into a cold press for pressing and forming, wherein the temperature is room temperature, the pressure is 1.2 MPa, and the time is 12 h.

[0077] (3) Remove the cold-pressed board from the cold press, clamp it with C-clamps, and place it in a drying chamber at 65℃ for 48 hours; then place the board in a drying chamber at 45℃ for 24 hours. Place the board in an environment at 25℃ and 50% relative humidity for 24 hours to equilibrate. Cut the equilibrated board into grooves according to the specified dimensions, and place it in an environment at 25℃ and 50% relative humidity for 24 hours to stabilize it, thus obtaining the high flame-retardant formaldehyde-free solid wood composite flooring.

[0078] Application Comparison Example 10 The difference between this comparative example and application example 1 is that the adhesive formulation does not contain hydroxypropyl methylcellulose.

[0079] (1) The surface veneer, the middle veneer, and the bottom veneer are dried separately to adjust their moisture content to 8%, wherein the surface veneer is oak veneer with a thickness of 1.8 mm and a density of 0.75 g / cm³. 3 The middle layer of wood veneer is made of fir veneer, with a thickness of 8.5mm and a density of 0.6g / cm³. 3 The bottom layer is made of oak veneer, 1.8mm thick, with a density of 0.75g / cm³. 3 ; A formaldehyde-free inorganic adhesive, made without hydroxypropyl methylcellulose, was applied to both the top and bottom surfaces of the intermediate layer wood veneer using a roller coating method. The application rate of the formaldehyde-free inorganic adhesive was 300 g / m². 2(Double-sided), then the glued middle layer wood veneer is sequentially and alternately combined with the surface wood veneer and the bottom layer wood veneer to form a veneer blank.

[0080] (2) The sheet material is fed into a cold press for pressing and forming, wherein the temperature is room temperature, the pressure is 1.2 MPa, and the time is 12 h.

[0081] (3) Remove the cold-pressed board from the cold press, clamp it with C-clamps, and place it in a drying chamber at 65℃ for 48 hours; then place the board in a drying chamber at 45℃ for 24 hours. Place the board in an environment at 25℃ and 50% relative humidity for 24 hours to equilibrate. Cut the equilibrated board into grooves according to the specified dimensions, and place it in an environment at 25℃ and 50% relative humidity for 24 hours to stabilize it, thus obtaining the high flame-retardant formaldehyde-free solid wood composite flooring.

[0082] Application Comparative Example 11 The difference between this comparative example and application example 1 is that the adhesive formulation does not contain polycarboxylate superplasticizer.

[0083] (1) The surface veneer, the middle veneer, and the bottom veneer are dried separately to adjust their moisture content to 8%, wherein the surface veneer is oak veneer with a thickness of 1.8 mm and a density of 0.75 g / cm³. 3 The middle layer of wood veneer is made of fir veneer, with a thickness of 8.5mm and a density of 0.6g / cm³. 3 The bottom layer is made of oak veneer, 1.8mm thick, with a density of 0.75g / cm³. 3 ; A formaldehyde-free inorganic adhesive, prepared without polycarboxylate superplasticizer, was applied to both the top and bottom surfaces of the interlayer wood veneer using a roller coating method. The application rate of the formaldehyde-free inorganic adhesive was 300 g / m². 2 (Double-sided), then the glued middle layer wood veneer is sequentially and alternately combined with the surface wood veneer and the bottom layer wood veneer to form a veneer blank.

[0084] (2) The sheet material is fed into a cold press for pressing and forming, wherein the temperature is room temperature, the pressure is 1.2 MPa, and the time is 12 h.

[0085] (3) Remove the cold-pressed board from the cold press, clamp it with C-clamps, and place it in a drying chamber at 65℃ for 48 hours; then place the board in a drying chamber at 45℃ for 24 hours. Place the board in an environment at 25℃ and 50% relative humidity for 24 hours to equilibrate. Cut the equilibrated board into grooves according to the specified dimensions, and place it in an environment at 25℃ and 50% relative humidity for 24 hours to stabilize it, thus obtaining the high flame-retardant formaldehyde-free solid wood composite flooring.

[0086] Experimental Example 1 The physical and mechanical properties of the high flame-retardant formaldehyde-free solid wood composite flooring prepared in Examples 1 to 3 and the solid wood composite flooring prepared in Comparative Examples 1 to 11 were tested in accordance with GB / T 18103-2022 "Solid Wood Composite Flooring", GB / T 17657-2013 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels", and GB / T 39600-2021 "Classification of Formaldehyde Emission of Wood-based Panels and Their Products". The results are shown in Table 1.

[0087] Table 1. Test results of physical and mechanical properties of engineered wood flooring As can be seen from Table 1, the high flame-retardant formaldehyde-free solid wood composite flooring prepared by this invention has a 63% efficiency. ℃ The water-treated shear strength can reach up to 3.87 MPa (the national standard for Class II flooring substrates requires ≥0.7 MPa), and the boiling water-treated shear strength can reach up to 1.78 MPa (the national standard for Class I flooring substrates requires ≥0.7 MPa), far exceeding the national standard requirements. Therefore, the high flame-retardant formaldehyde-free solid wood composite flooring produced by this invention has excellent water resistance and shear strength.

[0088] Compared to the application examples, Comparative Example 1 used a commercially available conventional urea-formaldehyde resin adhesive for engineered wood flooring, which is unsuitable for the cold-pressing process used in this invention. Therefore, the urea-formaldehyde resin did not cure completely during cold pressing, leading to delamination of the boards and failure of the preparation. Comparative Example 2 used a conventional hot-pressing process for engineered wood flooring, which is unsuitable for the curing conditions of the formaldehyde-free inorganic adhesive used in this invention. The inorganic formaldehyde-free adhesive generated a large number of bubbles during hot pressing, leading to delamination of the boards and failure of the preparation. Comparative Example 3 used a commercially available conventional urea-formaldehyde resin adhesive for engineered wood flooring and a conventional hot-pressing process for engineered wood flooring, which successfully produced engineered wood flooring. However, the urea-formaldehyde resin is not resistant to boiling water, and the bonded boards have formaldehyde release issues, affecting the performance of the engineered wood flooring. In Comparative Example 4, the boards were not clamped tightly during the drying process after pressing, causing significant warping of the boards during drying, rendering the engineered wood flooring unusable. The boards used in Comparative Example 5 were not dried after pressing, resulting in significant warping during warehouse storage and rendering the engineered wood flooring unusable. The boards used in Comparative Examples 6 through 11 all failed to meet the national standard requirements for Class I flooring substrates (≥0.7 MPa) after boiling water treatment.

[0089] Experimental Example 2 The flame retardancy of the high flame retardant formaldehyde-free solid wood composite flooring prepared in Application Examples 1 to 3 and the solid wood composite flooring prepared in Comparative Examples 1 to 11 were tested according to GB / T 5454-1997 "Test for Burning Performance of Textiles - Oxygen Index Method". The burning performance level was judged according to GB8624-2012 "Classification Standard for Burning Performance". The results are shown in Table 2.

[0090] Table 2. Test results of flame retardant properties of engineered wood flooring As can be seen from Table 2, the oxygen index of the high flame-retardant formaldehyde-free solid wood composite flooring prepared by this invention can reach up to 44%, the damage length is as low as 129 mm, and the afterflame time is as low as 3.6 s, which meets the requirements of the B1 flammability rating.

[0091] Compared to the application examples, Comparative Examples 1 and 2 showed delamination of the boards, indicating preparation failure and making flame retardant performance testing impossible. Comparative Example 3 used commercially available urea-formaldehyde resin adhesive for engineered wood flooring and a conventional hot-pressing process for engineered wood flooring, successfully producing engineered wood flooring. However, it lacked flame retardant properties and failed to meet the requirements of flammability rating B1. Comparative Examples 4 and 5 both met the requirements of flammability rating B1; however, they were unusable due to significant warping. Comparative Example 6 showed delamination of the boards, indicating preparation failure and making flame retardant performance testing impossible. Comparative Examples 7 through 11 all met the requirements of flammability rating B1; however, their water shear strength was significantly lower than that of Comparative Examples 1 through 3.

[0092] In summary, the raw materials and preparation method of the high flame-retardant formaldehyde-free solid wood composite flooring of the present invention form an organic whole. Reducing or changing the composition of the raw materials or reducing a certain step in the preparation method will significantly reduce the performance of the prepared flooring.

[0093] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, it is intended to include any modifications and variations that fall within the scope of the claims and their equivalents.

Claims

1. An adhesive for engineered wood flooring, characterized in that, Made from the following components in parts by weight: The composition includes 100 parts of water glass (based on SiO2), 30 to 60 parts of active silica-alumina filler, 5 to 20 parts of nano silica sol, 2 to 10 parts of nano zinc oxide, 1 to 5 parts of silane coupling agent, 0.1 to 2 parts of cellulose ether, and 0.2 to 1.5 parts of water-reducing agent.

2. The adhesive for solid wood composite flooring according to claim 1, characterized in that, The water glass is potassium water glass or sodium-potassium composite water glass, with a modulus of 3.0~3.8 and a solid content of 35%~45%. The modulus refers to SiO2 / M2O, where M is Na or K.

3. The adhesive for solid wood composite flooring according to claim 1, characterized in that, The activated silica-alumina filler is one or more of metakaolin, silica powder, and fly ash microspheres. The particle size D50 of the activated silica-alumina filler is ≤15μm, and the total content of SiO2 and Al2O3 is not less than 85%. The particle size of the nano-silica sol is 10nm~30nm, and the solid content is 20%~30%. The particle size of nano zinc oxide is 30nm~70nm.

4. A method for preparing an adhesive for solid wood composite flooring, characterized in that, The method for preparing the adhesive for solid wood composite flooring according to claim 1 comprises the following steps: A silane coupling agent and water glass are mixed, and the water glass is pretreated and modified using the silane coupling agent to obtain a modified base solution. The active silica-alumina filler, nano zinc oxide and cellulose ether are mixed evenly to obtain a premixed powder. Under stirring conditions, nano-silica sol and water-reducing agent are added to the modified base liquid; after increasing the speed, premixed powder is added, and then the speed is reduced and stirred evenly to obtain an adhesive for solid wood composite flooring.

5. A type of engineered wood flooring, comprising a surface veneer, a middle veneer, and a bottom veneer, characterized in that, The middle layer of wood veneer is bonded to the surface wood veneer and the bottom wood veneer on both sides by the adhesive for solid wood composite flooring as described in claim 1.

6. The engineered wood flooring according to claim 5, characterized in that, Prepared by the following method: The adhesive is evenly rolled onto both sides of the middle layer of wood veneer, and then assembled with the surface layer and bottom layer of wood veneer to obtain the board blank. The slab is pressed into shape using a cold pressing process, and then undergoes drying, balancing, sawing and grooving, and stabilization treatments to obtain engineered wood flooring.

7. The engineered wood flooring according to claim 6, characterized in that, The adhesive application rate is 300g / m² on both sides. 2 ~350g / m 2 .

8. The engineered wood flooring according to claim 6, characterized in that, In the cold pressing process, the pressing temperature is room temperature, the pressure is 1.2MPa~1.5MPa, and the time is 12h~24h.

9. The engineered wood flooring according to claim 6, characterized in that, The drying process is as follows: First, use C-clamps to clamp the cold-pressed sheet and place it in a drying chamber at a temperature of 65℃~70℃ for 24h~48h; then place the sheet in a drying chamber at a temperature of 45℃~50℃ for 24h~48h. The equilibration process involves placing the board in an environment with a temperature of 25°C and a relative humidity of 50% for 24 hours to equilibrate. The stabilization process involves placing the board in an environment with a temperature of 25°C and a relative humidity of 50% for 24 hours to stabilize it.

10. The engineered wood flooring according to claim 6, characterized in that, The surface wood is made of broad-leaved tree species, with a veneer thickness of 1.8mm~2.5mm and a density of 0.6g / cm³. 3 ~0.8g / cm 3 The middle layer wood is made of coniferous trees, with a veneer thickness of 7.5mm~9.0mm and a density of 0.4g / cm³. 3 ~0.7g / cm 3 The bottom layer of wood is made of broad-leaved tree species, with a veneer thickness of 1.8mm~2.5mm and a density of 0.6g / cm³. 3 ~0.8g / cm 3 ; Before veneer assembly, the surface veneer, middle veneer and bottom veneer are dried separately to adjust the moisture content to 8%~10%.

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