Flame-retardant, smoke-suppressing, deformation-resistant glulam and method of making

Abstract

This invention provides a method for preparing anti-deformation, flame-retardant, and smoke-suppressing glued laminated timber. The method involves mixing γ-methacryloyloxypropyl, o-phenylenediamine, and deionized water in a mass ratio of 1:(2-4.5):(5-7), followed by further mixing with polyvinyl acetate emulsion in a mass ratio of (1-2):10 to obtain a flame-retardant polyvinyl acetate emulsion. Multiple dried solid wood veneers are immersed in a constant-temperature water bath at 30-40°C. After removal, they are placed in an impregnation tank, and a copolymer AA / AMPS aqueous solution with a mass concentration of 40-45% and a degree of polymerization of 40-60 is injected under negative pressure to completely submerge the solid wood veneers. Pressure is then applied and maintained for 3-5 hours. After removal, cleaning, and drying at 70-80°C, the treated veneer surfaces are coated with the flame-retardant polyvinyl acetate emulsion and assembled. Cold pressing and hot pressing are then performed to obtain glued laminated timber with good anti-deformation, flame-retardant, and smoke-suppressing properties.

Description

Technical Field

[0001] This invention relates to the field of engineered wood products, and more particularly to a type of anti-deformation, flame-retardant, and smoke-suppressing glued laminated wood and its preparation method. Background Technology

[0002] Currently, flame-retardant glued laminated timber is generally produced by impregnating veneers or timber squares with flame retardants, drying them, and then applying glue to assemble the timber. However, in actual production, to achieve the flame-retardant and smoke-suppressing levels specified in national standards, it is often necessary to inject high concentrations or large amounts of flame-retardant liquid into the wood. This results in a large amount of highly absorbent flame-retardant components adhering to the surface of the dried wood. This surface condition brings fatal defects to the subsequent gluing process: when applying conventional water-based wood adhesives (such as white glue / polyvinyl acetate emulsion), the surface-enriched hydrophilic flame retardant forms an "isolation layer," preventing the adhesive from penetrating into the wood to form mechanical glue nails, leading to a decrease in glue strength. Furthermore, when exposed to fluctuations in ambient temperature and humidity, the hydrophilic groups enriched at the glue interface will rapidly absorb moisture and expand, causing an imbalance of internal stress in the wood, ultimately leading to severe warping, deformation, and even large-area delamination of the glued laminated timber. Summary of the Invention

[0003] In view of the above problems, this invention proposes a glued laminated timber with good deformation resistance, flame retardant and smoke suppression properties and its preparation method.

[0004] The method for preparing this plywood includes the following steps.

[0005] Step 1: Mix γ-methacryloxypropyl, o-phenylenediamine and deionized water in a mass ratio of 1:(2~4.5):(5~7) and stir at 700~900 r / min for 40~50 min at 50~60℃. Then, further mix with polyvinyl acetate emulsion in a mass ratio of (1-2):10 and continue stirring at 700~900 r / min for 30~50 min at 60~80℃ to obtain flame-retardant polyvinyl acetate emulsion.

[0006] Step 2: Place multiple dried solid wood veneers in a constant temperature water bath at 30-40℃ and immerse them under normal pressure for 18-24 hours. The solid wood veneers are radiata pine with a thickness of 6-9mm. To facilitate assembly into finished products, it is preferable that multiple veneers have the same length and width dimensions.

[0007] Step 3: After removing the treated veneer, place it in an impregnation tank, evacuate to -0.20 to -0.10 MPa and maintain for 20 to 40 minutes. Under this negative pressure, inject an aqueous solution of acrylic acid / 2-acrylamide-2-methylpropanesulfonic acid (AMPS) copolymer (AA / AMPS) with a mass concentration of 40 to 45% to completely immerse the solid wood veneer. Then, pressurize to 0.7 to 1.2 MPa and maintain for 3 to 5 hours. After removal and cleaning, dry at 70 to 80°C for 2 to 3 hours. The degree of copolymerization of AA / AMPS is 40 to 60.

[0008] Step 4: Coat the surface of the treated solid wood veneer with flame-retardant polyvinyl acetate emulsion and assemble the veneer. After cold pressing at 25-30℃ and 0.1-0.15MPa for 40-50 minutes, hot pressing at 125-135℃ and 0.5-0.75MPa for 35-45 minutes, the deformation-resistant, flame-retardant and smoke-suppressing glued laminated wood is obtained.

[0009] The emulsion application rate is 195–210 g / m³. 2 .

[0010] AA / AMPS contains a large number of sulfonic acid and carboxyl groups, making it highly hydrophilic, while polyvinyl acetate emulsion is also a water-based adhesive with poor water resistance. Furthermore, moisture migration is a major factor affecting deformation. AA / AMPS is also a polymer; after impregnation, it coats the microstructure of the wood, forming an interface layer. This is generally considered to be ineffective (in terms of dimensional stability and bonding strength). However, the inventors have discovered that during hot pressing at 125–135°C, the moisture inside the wood and in the adhesive layer vaporizes, generating inward vapor pressure. This causes the o-phenylenediamine in the adhesive layer to penetrate into the surface of the wood (both contain amino groups, have similar polarities, and good compatibility). When the o-phenylenediamine that has penetrated into the wood surface encounters the AA / AMPS left on the surface after the first impregnation, a cross-linking amidation reaction occurs.

[0011] Impregnation with atmospheric pressure avoids concentration polarization, strong surface tension, and swelling of the wood's microscopic channels. Dry wood is directly placed in a 40-45% high-concentration AA / AMPS aqueous solution. Wood at normal moisture content is hygroscopic; the surface layer of the wood's microstructure absorbs water rapidly, causing a localized surge in the AA / AMPS concentration, clogging pores, hindering subsequent impregnation, and making glue nail formation difficult, thus affecting bonding strength. The low-polymerization degree AA / AMPS that penetrates into the wood undergoes further polymerization in subsequent processes, forming entangled molecular chains within the wood's microstructure, providing support and resisting shrinkage and deformation from within. Simultaneously, under hot pressing at 125-135℃, o-phenylenediamine in the adhesive layer migrates into the wood interior driven by vapor pressure, undergoing a cross-linking reaction with the modified wood surface carboxyl and sulfonic acid groups, promoting glue nail formation, and improving the integrity of the adhesive layer and the wood. These two aspects together achieve an anti-deformation effect.

[0012] During combustion, AA / AMPS contains a large number of sulfonic acid groups. In the early stages of heating upon contact with fire, these sulfonic acid groups act as strong acids, catalyzing the dehydration and carbonization of cellulose and hemicellulose in the wood, altering the thermal degradation pathway of the wood and reducing the formation of combustible volatiles. Simultaneously, o-phenylenediamine, which penetrates the wood surface and participates in cross-linking, and the amide groups in AMPS, are rich in nitrogen. At high temperatures, they decompose and release non-combustible gases, diluting the oxygen concentration in the flame zone. Detailed Implementation

[0013] The following describes embodiments of the present invention; however, the present invention is not limited to these embodiments, and various modifications can be made within the scope defined by the claims. Different embodiments or preparation examples, as well as new modifications obtained by combinations of common technical means, should also be considered to be included within the scope of the present invention. Example

[0014] Step 1: Mix γ-methacryloxypropyl, o-phenylenediamine and deionized water at a mass ratio of 1:3.5 and stir at 800 r / min for 45 min at 55 °C. Then mix with polyvinyl acetate emulsion at a mass ratio of 1.5:10 and continue stirring at 800 r / min for 40 min at 70 °C to obtain flame-retardant polyvinyl acetate emulsion.

[0015] Step 2: Place the air-dried radiata pine veneer with a thickness of 7.5mm, a length of 1200mm, and a width of 800mm into a constant temperature water bath at 35℃ and immerse it under normal pressure for 21 hours.

[0016] Step 3: Place the treated veneer in an impregnation tank, evacuate to -0.15 MPa and maintain for 30 min, inject an AA / AMPS aqueous solution with a mass concentration of 42.5% and a copolymerization degree of 50, pressurize to 0.95 MPa and maintain for 4 h, remove, clean and dry at 75 °C for 2.5 h.

[0017] Step 4: Coat the surfaces of the three treated solid wood veneers with flame-retardant polyvinyl acetate emulsion (solid content 58%, viscosity 9500 mPa·s, application rate 202 g / m²). 2 The blanks were assembled and cold-pressed at 27℃ and 0.12MPa for 45 minutes, and then hot-pressed at 130℃ and 0.65MPa for 40 minutes to obtain anti-deformation, flame-retardant and smoke-suppressing glued laminated timber.

[0018] performance: Oxygen index: 33.4% 2. Deformation (test sample length 1100 mm × width 450 mm, loading parameters: load 15 kg, loading time: 15 days, loading area: (280±20) mm × (280±20) mm): 2.7 mm 3. Total flue gas emission: 116.94 m³ 2 / m 2 4- Bond strength: 0.83 MPa 5. Peak heat release rate: 212.6 kW / m 2 Example

[0019] Step 1: Mix γ-methacryloxypropyl, o-phenylenediamine and deionized water in a mass ratio of 1:2:5 and stir at 700 r / min for 40 min at 50 °C. Then mix with polyvinyl acetate emulsion in a mass ratio of 1:10 and continue stirring at 700 r / min for 30 min at 60 °C to obtain flame-retardant polyvinyl acetate emulsion.

[0020] Step 2: Place the air-dried radiata pine veneer with a thickness of 6mm, a length of 1200mm, and a width of 800mm into a constant temperature water bath at 30℃ and immerse it under normal pressure for 18 hours.

[0021] Step 3: After the veneer has been treated, it is placed in an impregnation tank, and a vacuum is drawn to -0.20 MPa and maintained for 20 min. Under this negative pressure condition, an AA / AMPS aqueous solution with a mass concentration of 40% and a copolymerization degree of 50 is injected to completely immerse the solid wood board. Then, the pressure is increased to 0.7 MPa and maintained for 3 h. After being taken out and cleaned, it is dried at 70°C for 2 h.

[0022] Step 4: Coat the surfaces of the five treated solid wood veneers with flame-retardant polyvinyl acetate emulsion (solid content 58%, viscosity 9500 mPa·s, application rate 195 g / m²). 2 The blanks are assembled and cold-pressed at 25℃ and 0.1MPa for 40 minutes, and then hot-pressed at 125℃ and 0.5MPa for 35 minutes to obtain anti-deformation, flame-retardant and smoke-suppressing glued laminated timber.

[0023] performance: Oxygen index: 31.4% 2-Deformation (test method same as in Example 1): 3.3 mm 3. Total flue gas emission: 176.11 m³ 2 / m 2 4- Bond strength: 0.76 MPa 5. Peak heat release rate: 259.1 kW / m 2 Example

[0024] Step 1: Mix γ-methacryloxypropyl, o-phenylenediamine and deionized water in a mass ratio of 1:4.5:7 and stir at 900 r / min for 50 min at 60 °C. Then mix with polyvinyl acetate emulsion in a mass ratio of 2:10 and continue stirring at 900 r / min for 50 min at 80 °C to obtain flame-retardant polyvinyl acetate emulsion.

[0025] Step 2: Place the air-dried radiata pine veneer with a thickness of 9mm, a length of 1200mm, and a width of 800mm into a constant temperature water bath at 40℃ and immerse it under normal pressure for 24 hours.

[0026] Step 3: Place the treated veneer in an impregnation tank, evacuate to -0.10 MPa and maintain for 40 min, inject an aqueous solution of AA / AMPS copolymer with a mass concentration of 45% and a copolymerization degree of 50, pressurize to 1.2 MPa and maintain for 5 h, remove, clean and dry at 80 °C for 3 h.

[0027] Step 3: After the veneer has been treated, it is placed in an impregnation tank, vacuumed to -0.10 MPa and maintained for 40 min, and then a 45% AA / AMPS aqueous solution is injected under this negative pressure to completely immerse the solid wood board. Then the pressure is increased to 1.2 MPa and maintained for 5 h. After cleaning, it is dried at 80℃ for 3 h.

[0028] Step 4: Coat the surface of the 8 treated solid wood veneers with flame-retardant polyvinyl acetate emulsion (solid content 58%, viscosity 9500 mPa·s, glue application rate 210 g / m²) and assemble them. After cold pressing at 30℃ and 0.15 MPa for 50 min, hot pressing at 135℃ and 0.75 MPa for 45 min, the deformation-resistant, flame-retardant and smoke-suppressing glued laminated wood is obtained.

[0029] performance: Oxygen index: 36.1% 2-Deformation amount (test method same as in Example 1): 2.2mm 3. Total flue gas emission: 133.21 m³ 2 / m 2 4- Bond strength: 0.89 MPa 5. Peak heat release rate: 189.4 kW / m 2 Comparative Example 1 Based on Example 1, only step 2 is omitted (no atmospheric pressure impregnation in a constant temperature water bath at 30-40°C). That is, the solid wood veneer directly enters the vacuum-pressure impregnation of AA / AMPS in step 3 in an air-dried state, and then performs hot pressing in step 4 as in Example 1.

[0030] performance: Oxygen index: 29.1% 2-Deformation amount (test method same as in Example 1): 7.1 mm 3. Total flue gas emission: 243.27 m³ 2 / m 2 4- Bond strength: 0.69 MPa 5. Peak heat release rate: 369.1 kW / m 2 Comparative Example 2 Based on Example 1, only the following changes were made: Step 3: Remove and clean the product, then allow it to air dry for 24 hours.

[0031] performance: Oxygen index: 28.2% 2-Deformation (test method same as in Example 1): 7.9 mm 3. Total flue gas emission: 261.11 m³ 2 / m 2 4- Bond strength: 0.62 MPa 5. Peak heat release rate: 384.2 kW / m 2

Claims

1. A method for preparing deformation-resistant, flame-retardant, and smoke-suppressing glued laminated timber. Its features are, include: γ-methacryloxypropyl, o-phenylenediamine and deionized water were mixed in a mass ratio of 1:(2-4.5):(5-7) and stirred at 700-900 r / min for 40-50 min at 50-60 °C. Then, it was further mixed with polyvinyl acetate emulsion in a mass ratio of (1-2):10 and stirred at 700-900 r / min for 30-50 min at 60-80 °C to obtain flame-retardant polyvinyl acetate emulsion. Multiple dried solid wood veneers were placed in a constant temperature water bath at 30-40℃ and soaked under normal pressure for 18-24 hours. After the treated solid wood veneer is removed, it is placed in an impregnation tank, and a vacuum is drawn to -0.20 to -0.10 MPa and maintained for 20 to 40 minutes. Under this negative pressure condition, an AA / AMPS aqueous solution with a mass concentration of 40 to 45% is injected to completely immerse the solid wood veneer. Subsequently, the pressure is increased to 0.7 to 1.2 MPa and maintained for 3 to 5 hours. After removal and cleaning, it is dried at 70 to 80°C for 2 to 3 hours. AA / AMPS is a copolymer of acrylic acid with a degree of polymerization of 40-60 and 2-acrylamide-2-methylpropanesulfonic acid; Multiple treated solid wood veneers are coated with flame-retardant polyvinyl acetate emulsion and assembled. After cold pressing at 25–30℃ and 0.1–0.15MPa for 40–50 min, they are hot-pressed at 125–135℃ and 0.5–0.75MPa for 35–45 min to obtain anti-deformation, flame-retardant, and smoke-suppressing glued laminated timber.

2. The preparation method according to claim 1, wherein, The thickness of solid wood veneer is 6-9mm.

3. The preparation method according to claim 1, wherein, The solid wood is radiata pine.

4. The preparation method according to claim 1, wherein, The emulsion application rate is 195–210 g / m³. 2 .

5. A type of anti-deformation, flame-retardant, and smoke-suppressing glued laminated timber prepared by the preparation method according to any one of claims 1 to 4.