Crosslinked reinforced flame retardant facing panel and method of making same

Abstract

A cross-linked reinforced flame-retardant decorative panel and its preparation method are disclosed. The cross-linking reinforcement ensures both flame-retardant and adhesive properties. The preparation includes: impregnating wood veneer in a mixture of thiourea and ammonium polyphosphate under pressure; then impregnating it in an aqueous solution of trisodium methylglycine diacetate; then impregnating it successively in an aqueous solution of Fe(NO3)3 and KH560; drying to obtain a flame-retardant wood board; mixing a modified urea-formaldehyde resin adhesive with flour, applying the adhesive to the flame-retardant wood board to form an adhesive layer, covering the adhesive layer with decorative wood veneer, and pressing the board. Modified adhesive preparation: formaldehyde, xanthan gum, and OP-10 are mixed and stirred, the pH is adjusted to 7.7–8.2, the temperature is increased, and stirring continues; the first batch of urea is added, the temperature is increased, and stirring continues until the pH reaches 5.7–5.9, then the mixture is cooled; the remaining urea is added, and stirring continues, after cooling, the pH is adjusted to 7.7–8.2, and stirring is stopped.

Description

Technical Field

[0001] This invention relates to wood processing technology, and more particularly to a cross-linked reinforced flame-retardant decorative panel and its preparation method. Background Technology

[0002] Regarding flame-retardant treatment technologies for decorative panels, for example, flame retardants are added to the adhesive layer between the decorative layer and the substrate to attempt to improve the flammability rating of the decorative panel. However, decorative panels using ordinary flame-retardant adhesives in the past have not yet ideally met the flammability rating requirements. Summary of the Invention

[0003] In view of the problems of the past, the present invention proposes a cross-linked reinforced flame-retardant decorative panel and its preparation method, which aims to meet the requirements of flame retardancy rating and bonding ability.

[0004] A method for preparing a cross-linked reinforced flame-retardant decorative panel is provided, the method comprising:

[0005] (1) Impregnating the wood veneer: First, immerse the wood veneer in a mixture of thiourea and ammonium polyphosphate at a mass ratio of 1:(7-8) and apply vacuum pressure at a vacuum degree of -0.15 to -0.1 MPa for 20-25 min. Then, pressurize to 0.8-0.9 MPa and hold for 1-2 h. Next, impregnate the wood veneer in a 2-2.5% aqueous solution of trisodium methylglycine diacetate for 4-5 h at room temperature and pressure. Then, impregnate the wood veneer in a 1-2% aqueous solution of Fe(NO3)3 and a 0.5-0.6% aqueous solution of KH560 for 2-3 h at room temperature and pressure. Finally, dry the impregnated wood veneer to a moisture content of 9-11% to obtain flame-retardant wood board.

[0006] (2) After uniformly mixing the modified urea-formaldehyde resin adhesive with flour at a mass ratio of 100:(20-80), the mixture is applied to the flame-retardant wood board to form an adhesive layer. Decorative wood veneer is then applied to the adhesive layer, and the flame-retardant decorative panel is obtained through a pressing process. The modified urea-formaldehyde resin adhesive is prepared by the following method: raw materials are prepared: formaldehyde aqueous solution, urea, xanthan gum, and OP-10, wherein the molar ratio of formaldehyde solute, urea, xanthan gum, and OP-10 is (440-520):(380-420):(0.6-1.0):(0.1-0.3); Aldehyde aqueous solution, xanthan gum, and OP-10 are poured into a container and stirred. The pH of the mixture is adjusted to 7.7–8.2 with alkali solution, then heated to 48–55°C and held for 2–5 minutes. 10–15% of the total urea raw material is added, and the temperature is further increased to 80–85°C and held until the pH of the mixture reaches 5.7–5.9. The mixture is then cooled to 50–55°C. The remaining urea is added and the mixture is kept at this temperature for 3–6 hours. The mixture is then cooled to 40–45°C, and the pH is adjusted to 7.7–8.2 with alkali solution. Stirring is then stopped to obtain the modified urea-formaldehyde resin adhesive.

[0007] Furthermore, the alkaline solution is an aqueous solution of NaOH.

[0008] Furthermore, the adhesive application is carried out by coating, with an adhesive application amount of 200–220 g / m³. 2 The pressing process includes: first, cold pressing at a pressure of 0.1-0.2 MPa and a temperature of 22-25°C for 40-50 minutes, and then hot pressing at a temperature of 110-120°C for 300-400 seconds, with a pressure of 0.2-0.3 MPa.

[0009] Furthermore, the decorative wood veneer is a planed solid wood veneer or a reconstituted decorative veneer.

[0010] Furthermore, the thickness of the decorative wood veneer is 0.2 to 0.4 mm.

[0011] Furthermore, a flame-retardant decorative panel prepared by the above preparation method is also provided.

[0012] The modified urea-formaldehyde resin adhesive layer and flame-retardant treated substrate veneer demonstrate excellent flame-retardant properties. The flame-retardant performance is reflected in the cross-linking reinforcement effect:

[0013] First, the modified urea-formaldehyde resin adhesive exhibits increased fluidity during the initial hot-pressing phase as the surface temperature of the board rises (around 50°C). This fluidity, reaching 50°C at the initial hot-pressing stage, further enhances the cross-linking effect. During the synthesis of urea-formaldehyde resin, xanthan gum reacts with some of the hydroxyl groups in the proteourea to form a new modified proteourea. This modified proteourea further improves the bonding performance during the later hot-pressing cross-linking process through the formation of a macromolecular network structure.

[0014] Secondly, the flame retardant in the flame-retardant veneer has an adsorption effect on the modified urea-formaldehyde resin, making it easier for the adhesive to penetrate into the porous structure of the wood, thus better promoting the formation of glued nails. Simultaneously, the cross-linked macromolecular network structure of the adhesive itself enhances the bonding strength. The addition of interlayer coupling agent KH560 allows for adsorption between the KH560 coupling agent and the xanthan gum-modified urea-formaldehyde resin during cold pressing after the veneer has been glued, further promoting glued nail formation. At the same time, the addition of OP-10 reduces surface tension, further promoting the penetration of glued nails.

[0015] Third, during the hot pressing process, the coupling agent-modified impregnated veneer undergoes a chemical reaction at the interface with the penetrating glue nails, which allows the wood material and the glue nails to bond through chemical action, further improving the bonding performance.

[0016] Fourth, in terms of combustion, in addition to the synergistic flame-retardant effect of thiourea and polyphosphate, the foot nails with good permeability in the multi-pore wood form a blocking char layer during combustion, reducing the combustion chamber of the wood itself. Furthermore, a complex multi-char layer structure is formed at the interface during combustion, which can correspond to different combustion states, thus enhancing the flame-retardant effect from the microscopic interface. Detailed Implementation

[0017] Example 1:

[0018] (1) Prepare a total of 200 mol of urea. Add 0.4 mol of xanthan gum with a degree of polymerization of 500 and 0.05 g of polyoxyethylene octylphenol ether-10 (polyoxyethylene octylphenol (10) ether, also referred to as OP-10 in this article) with a degree of polymerization of 800 to a three-necked flask containing a formaldehyde aqueous solution with a solute content of 260 mol (concentration of 37 mol / mL) with a stirrer and start stirring at 800 r / min. Adjust the pH to 7.7 with 350 g / kg NaOH solution, heat to 50 ℃ and keep warm (continue stirring) for 2 min. Then add 10% of the total amount of urea, heat to 80 ℃ and continue stirring (keep warm). When the reaction reaches pH 5.7, cool to 50 ℃. Finally, add the remaining amount of urea and keep warm (continue stirring) for 3 h. Cool to 40 ℃, adjust the pH to 7.7 with 350 g / kg NaOH solution and stop stirring to obtain modified urea-formaldehyde resin adhesive.

[0019] (2) Immerse 2.6 mm thick eucalyptus veneers in a 1:7 mixture of thiourea and ammonium polyphosphate (degree of polymerization 35) in an impregnation tank. Perform vacuum impregnation at -0.1 MPa for 20 min, then pressurize to 0.9 MPa and maintain for 1 h. Drain the mixture and add 2% (w / w) trisodium methylglycine diacetate solution to the impregnation tank until the veneers are submerged. Maintain at room temperature (25°C) and standard atmospheric pressure for 4 h before removing the eucalyptus veneers. The eucalyptus veneer is then post-treated: first, it is immersed in a 1% Fe(NO3)3 aqueous solution at room temperature (25℃) and standard atmospheric pressure for 2 hours; then, it is immersed in a 0.5% γ-glycidyl etheroxypropyltrimethoxysilane (KH560) aqueous solution at room temperature (25℃) and standard atmospheric pressure for 2 hours; finally, the veneer is removed and dried in a drying room at 25℃ until the moisture content is 11% to obtain flame-retardant wood board.

[0020] (3) Add flour to the above modified urea-formaldehyde resin adhesive at a mass ratio of 100:30, stir evenly, and then apply the adhesive to the upper surface of the flame-retardant wood board. The amount of adhesive applied is 210 g / m². 2 A 0.4mm thick reconstituted decorative veneer (obtained by lamination and molding of rotary-cut eucalyptus veneer) was applied to the surface of the adhesive layer. After cold pressing at 25°C for 40 minutes under a pressure of 0.1MPa, it was hot-pressed at 120°C for 300 seconds under a pressure of 0.2MPa to obtain flame-retardant reconstituted decorative veneer panel A1 with cross-linking reinforcement.

[0021] Example 2:

[0022] (1) Prepare a total of 200 mol of urea. Add 0.3 mol of xanthan gum with a degree of polymerization of 500 and 0.15 g of polyoxyethylene octylphenol ether-10 (OP-10) with a degree of polymerization of 800 to a three-necked flask containing a formaldehyde aqueous solution with a solute content of 220 mol (concentration of 37 mol / mL) with a stirrer. Start stirring at 800 r / min. Adjust the pH to 7.8 with 350 g / kg NaOH solution. Heat to 55℃ and keep warm (continue stirring) for 2 min. Then add 15% of the total amount of urea. Heat to 85℃ and keep warm (continue stirring). When the reaction reaches pH 5.8, cool to 55℃. Finally, add the remaining amount of urea and keep warm (continue stirring) for 4 h. Cool to 45℃, adjust the pH to 7.8 with 350 g / kg NaOH solution and stop stirring to obtain modified urea-formaldehyde resin adhesive.

[0023] (2) 2.8 mm thick poplar veneer was immersed in a 1:8 mixture of thiourea and ammonium polyphosphate (degree of polymerization 35) in an impregnation tank under vacuum pressure (-0.15 MPa, 25 min), followed by pressurization to 0.8 MPa for 2 h. The mixture was then drained, and a 2.5% aqueous solution of trisodium methylglycine diacetate was added to the impregnation tank until the veneer was submerged. The veneer was then removed after 5 h at room temperature (25°C) and standard atmospheric pressure. The veneer was then subsequently immersed in a 2% aqueous solution of Fe(NO3)3 and a 0.6% aqueous solution of γ-glycidyl etheroxypropyltrimethoxysilane (KH560) for post-treatment, respectively, at room temperature (25°C) and standard atmospheric pressure for 2.5 h. Finally, the veneer was removed and dried in a drying chamber at 25°C until the moisture content was 9% to obtain flame-retardant wood board.

[0024] (3) Add flour to the modified urea-formaldehyde resin adhesive at a mass ratio of 100:40, stir evenly, and then apply the adhesive to the upper surface of the flame-retardant wood board. The amount of adhesive applied is 215 g / m². 2 A 0.4mm thick reconstituted decorative veneer (obtained by lamination molding of rotary-cut poplar veneer) was applied to the adhesive layer surface. After cold pressing at 28℃ for 50 minutes under a pressure of 0.2MPa, it was hot-pressed at 110℃ for 400 seconds under a pressure of 0.3MPa to obtain flame-retardant reconstituted decorative veneer panel A2 with cross-linking reinforcement.

[0025] In the above embodiments, although the concentration of the NaOH aqueous solution is 350 g / kg, it should be understood that it can also be 300-400 g / kg; although the concentration of the formaldehyde aqueous solution is 37 mol / mL, it can generally be 35-40 mol / mL. Furthermore, the stirring from the start to the stop is carried out at 800 r / min, but it can also be carried out by a stirrer at 500-1000 r / min; it should be understood that stirring does not need to be interrupted during this process. Additionally, the modified urea-formaldehyde resin adhesive and flour can be uniformly mixed at a mass ratio of 100:(20-80), or further, 100:(20-70) or 100:(30-40). Here, the flour at least serves as a thickener and provides a carbon source for combustion.

[0026] In addition, a decorative wood veneer is applied to the adhesive layer surface. This decorative wood veneer can be a planed solid wood veneer or a reconstituted decorative veneer, with a preferred thickness of 0.2–0.4 mm. The solid wood veneer is made from thin slices of log material, which can be produced through multiple processes such as high-temperature painting. The reconstituted decorative veneer is obtained by laminating or molding planed or rotary-dried solid wood chips. The species of solid wood material is not limited here; for example, poplar, teak, walnut, birch, eucalyptus, ash, etc., any wood species that can be used for decorative surfaces within the industry and possesses the corresponding properties are included in the solid wood material used for the reconstituted decorative veneer.

[0027] The above embodiments illustrate the application of the adhesive of the present invention in the preparation of decorative panels by applying the synergistic flame-retardant urea-formaldehyde resin adhesive to one side of a wood substrate. However, it is easy to understand that this application can also include applying the adhesive of the present invention to both sides of the substrate, and further covering it with decorative wood veneer and performing a pressing process to prepare a double-sided flame-retardant decorative panel.

[0028] The resulting decorative panel has improved flame retardant properties. The definition of decorative panel should be regarded as a recognized term in the field, specifically a type of artificial board for decoration, also called veneer panel, which is made by pressing a decorative layer onto a substrate through a certain pressing process. However, in this invention, the decorative layer is especially a decorative wood veneer, such as planed solid wood veneer or reconstituted decorative veneer.

[0029] Comparative Example 1:

[0030] (1) A 2.6 mm thick eucalyptus veneer was immersed in a 1:7 mixture of thiourea and ammonium polyphosphate (degree of polymerization 35) in an impregnation tank under vacuum pressure (-0.1 MPa) for 20 min, followed by pressurization to 0.9 MPa for 1 h. The mixture was then drained, and a 2% (w / w) solution of trisodium methylglycine diacetate was added to the impregnation tank until the veneer was submerged. The veneer was then removed after being kept under standard atmospheric pressure (25°C) for 4 h. The veneer was then immersed in a 1% (w / w) Fe(NO3)3 aqueous solution and a 0.5% (w / w) γ-glycidyl etheroxypropyltrimethoxysilane (KH560) aqueous solution for post-treatment, respectively, under standard atmospheric pressure (25°C) for 2 h. Finally, the veneer was removed and dried in a drying chamber at 25°C until the moisture content was 15% to obtain flame-retardant wood board.

[0031] (2) Add flour to unmodified urea-formaldehyde resin with a solid content of 58% at a ratio of 100:30, stir evenly, and then apply the adhesive to the upper surface of the flame-retardant wood board. The amount of adhesive applied is 210g / m². 2A 0.4mm thick reconstituted decorative veneer (obtained by lamination and molding of rotary-cut eucalyptus veneer) is applied to the surface of the adhesive layer. After cold pressing at 25°C for 40 minutes under a pressure of 0.1MPa, it is hot-pressed at 120°C for 300 seconds under a pressure of 0.2MPa. After cooling and settling, flame-retardant reconstituted decorative veneer panel B1 is obtained.

[0032] Comparative Example 2:

[0033] (1) Prepare a total of 200 mol of urea. Add 10 g of polystyrene powder and 0.15 g of polyoxyethylene octylphenol ether-10 (OP-10) with a degree of polymerization of 800 to a three-necked flask containing a formaldehyde aqueous solution with a solute content of 220 mol (concentration of 37 mol / mL) with a stirrer. Start stirring at 800 r / min. Adjust the pH to 7.8 with 350 g / kg NaOH solution. Heat to 55 °C and keep warm (continue stirring) for 2 min. Then add 15% of the total amount of urea. Heat to 85 °C and keep warm (continue stirring). When the reaction reaches pH 5.8, cool to 55 °C. Finally, add the remaining amount of urea and keep warm (continue stirring) for 4 h. Cool to 45 °C and adjust the pH to 7.8 with 350 g / kg NaOH solution and stop stirring to obtain modified urea-formaldehyde resin adhesive.

[0034] (2) Immerse 2.8 mm thick poplar veneer in a 1:8 mixture of thiourea and ammonium polyphosphate (degree of polymerization 35) in an impregnation tank. Vacuum pressure impregnation is performed at -0.15 MPa for 25 min, followed by pressurization to 0.8 MPa for 2 h. Then drain the mixture and add 2.5% trisodium methylglycine diacetate aqueous solution to the impregnation tank until the veneer is submerged. Maintain the solution at room temperature (25℃) and standard atmospheric pressure for 5 h before removing the veneer. Subsequently immerse the veneer in a 2% Fe(NO3)3 aqueous solution and a 0.6% γ-glycidyl etheroxypropyltrimethoxysilane (KH560) aqueous solution for post-treatment. Each veneer is impregnated at room temperature (25℃) and standard atmospheric pressure for 2.5 h. Finally, remove the veneer and dry it in a drying chamber at 25℃ until the moisture content is 11% to obtain flame-retardant wood board.

[0035] (3) Add flour to the above-mentioned blended urea-formaldehyde adhesive at a mass ratio of 100:40, stir evenly, and then apply the adhesive to the upper surface of the flame-retardant wood board. The amount of adhesive applied is 215g / m². 2 A 0.4mm thick reconstituted decorative veneer (obtained by lamination and molding of rotary-cut poplar veneer) was applied to the surface of the adhesive layer. After cold pressing at 28°C for 50 minutes under a pressure of 0.2MPa, it was hot-pressed at 110°C for 400 seconds under a pressure of 0.3MPa to obtain flame-retardant reconstituted decorative veneer panel B2 with cross-linking reinforcement.

[0036] Comparative Example 3:

[0037] (1) Prepare a total of 200 mol of urea. Add 0.3 mol of xanthan gum with a degree of polymerization of 500 and 0.15 g of polyoxyethylene octylphenol ether-10 (OP-10) with a degree of polymerization of 800 to a three-necked flask containing a formaldehyde aqueous solution with a solute content of 220 mol (concentration of 37 mol / mL) with a stirrer. Start stirring at 800 r / min. Adjust the pH to 10.5 with 350 g / kg NaOH solution. Heat to 55℃ and keep warm (continue stirring) for 2 min. Then add 15% of the total amount of urea. Heat to 85℃ and keep warm (continue stirring). When the pH reaches 5.8, cool to 55℃. Finally, add the remaining amount of urea and keep warm (continue stirring) for 4 h. Cool to 45℃, adjust the pH to 7.8 with 350 g / kg NaOH solution and stop stirring to obtain modified urea-formaldehyde resin adhesive.

[0038] (2) 2.8 mm thick poplar veneer was immersed in a 1:8 mixture of thiourea and ammonium polyphosphate (degree of polymerization 35) in an impregnation tank under vacuum pressure (-0.15 MPa, 25 min), followed by pressurization to 0.8 MPa for 2 h. The mixture was then drained, and a 2.5% aqueous solution of trisodium methylglycine diacetate was added to the impregnation tank until the veneer was submerged. The veneer was then removed after 5 h at room temperature (25°C) and standard atmospheric pressure. The veneer was then subsequently immersed in a 2% aqueous solution of Fe(NO3)3 and a 0.6% aqueous solution of γ-glycidyl etheroxypropyltrimethoxysilane (KH560) for post-treatment, respectively, at room temperature (25°C) and standard atmospheric pressure for 2.5 h. The veneer was then removed and dried in a drying chamber at 25°C until the moisture content reached 11%, yielding flame-retardant wood panels.

[0039] (3) Add flour to the modified urea-formaldehyde adhesive at a mass ratio of 100:40, stir evenly, and then apply the adhesive to the upper surface of the flame-retardant wood board. The amount of adhesive applied is 215 g / m². 2 A 0.4mm thick reconstituted decorative veneer (obtained by lamination and molding of rotary-cut poplar veneer) was applied to the surface of the adhesive layer. After cold pressing at 28°C for 50 minutes under a pressure of 0.2MPa, it was hot-pressed at 110°C for 400 seconds under a pressure of 0.3MPa to obtain flame-retardant reconstituted decorative veneer panel B3 with cross-linking reinforcement.

[0040] Flame retardancy tests were conducted on the different decorative panels obtained in Examples 1-2 and Comparative Examples 1-3, and the results are shown in Table 1. The synergy ratio was calculated according to A1.

[0041] Table 1:

[0042] A1 A2 B1 B2 B3 Surface bonding strength (MPa) 0.85 0.86 0.61 0.41 0.57 <![CDATA[Peak value of the first heat release rate (kW / m 2 )]]> 131.87 145.62 216.5 347.75 205.66

[0043] According to Table 1, the modification of the substrate veneer based on the modified urea-formaldehyde resin adhesive layer and flame-retardant treatment demonstrates excellent flame-retardant performance. The flame-retardant performance is reflected in the cross-linking enhancement effect: the cross-linking effect of the modified urea-formaldehyde resin adhesive during the hot pressing process and the enhanced fluidity in the early stage of hot pressing (around 50℃), the flame retardant of the flame-retardant veneer has an adsorption effect on the modified urea-formaldehyde resin, making it easier for the adhesive to penetrate into the pore structure of the wood, better promoting the formation of glue nails, and at the same time, the cross-linked macromolecular network structure of the adhesive itself enhances the bonding strength.

Claims

1. A method for preparing a cross-linked reinforced flame-retardant decorative panel, Its features are, The preparation method includes: (1) Impregnate the wood veneer: First, the wood veneer is immersed in a mixture of thiourea and ammonium polyphosphate at a mass ratio of 1:(7-8) and vacuum pressure is applied at a vacuum degree of -0.15 to -0.1 MPa for 20 to 25 minutes. Then, the pressure is increased to 0.8 to 0.9 MPa and maintained for 1 to 2 hours. Then the wood veneer was impregnated in a 2-2.5% aqueous solution of trisodium methylglycine diacetate for 4-5 hours at room temperature and pressure. Then, the wood veneer was successively immersed in a 1-2% Fe(NO3)3 aqueous solution and a 0.5-0.6% KH560 aqueous solution, and kept at room temperature and pressure for 2-3 hours respectively. The impregnated wood veneer is dried to a moisture content of 9-11% to obtain flame-retardant wood board; (2) After uniformly mixing the modified urea-formaldehyde resin adhesive with flour at a mass ratio of 100:(20-80), the mixture is applied to the flame-retardant wood board to form an adhesive layer. Decorative wood veneer is then applied to the adhesive layer, and the flame-retardant decorative panel is obtained through a pressing process. The modified urea-formaldehyde resin adhesive is prepared by the following method: Prepare the following raw materials: formaldehyde solution, urea, xanthan gum, and OP-10. The molar ratio of formaldehyde solute, urea, xanthan gum and OP-10 is (440~520):(380~420):(0.6~1.0):(0.1~0.3); Formaldehyde aqueous solution, xanthan gum, and OP-10 are poured into a container and stirred. The pH of the mixture is adjusted to 7.7–8.2 with an alkaline solution, then heated to 48–55°C and held for 2–5 minutes. Urea (10–15% of the total amount of urea raw material) is added, and the temperature is further increased to 80–85°C and held until the pH of the mixture reaches 5.7–5.

9. The mixture is then cooled to 50–55°C. The remaining amount of urea is added and the mixture is held for 3–6 hours. The mixture is then cooled to 40–45°C, and the pH of the mixture is adjusted to 7.7–8.2 with an alkaline solution. Stirring is then stopped to obtain the modified urea-formaldehyde resin adhesive.

2. The preparation method according to claim 1, wherein, The alkaline solution is an aqueous solution of NaOH.

3. The preparation method according to claim 1, wherein, The adhesive is applied by coating, with a coating amount of 200–220 g / m². 2 ; The pressing process includes: first, cold pressing at a pressure of 0.1-0.2 MPa and a temperature of 22-25°C for 40-50 minutes, followed by hot pressing at a temperature of 110-120°C for 300-400 seconds and a pressure of 0.2-0.3 MPa.

4. The preparation method according to claim 1, wherein, The decorative wood veneer is a planed solid wood veneer or a reconstituted decorative veneer.

5. The preparation method according to claim 1, wherein, The thickness of the decorative wood veneer is 0.2 to 0.4 mm.

6. A flame-retardant decorative panel, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 5.