Composite flame-retardant recombined decorative veneer veneered plywood and preparation method thereof

Abstract

The invention provides a composite flame-retardant recombined decorative veneer veneering plywood and a preparation method thereof, and the preparation method of the high-performance composite flame-retardant recombined decorative veneer veneering plywood is realized by adopting an adhesive layer and dipping compounding process method, an efficient novel flame retardant and a corresponding preparation process. The preparation method comprises the following steps: dipping a wood veneer into an MEL (Methyl Ester Laminate) aqueous solution, taking out and drying; dipping in an HPAA aqueous solution after treatment, taking out and drying; 3, 5-diamino-1, 2, 4-triazole and HPAA are subjected to a reaction to obtain a GH flame retardant, the GH flame retardant is added into a melamine modified urea-formaldehyde resin adhesive to obtain a flame-retardant adhesive, and the flame-retardant adhesive is applied to a recombined decorative veneer and an impregnated veneer and between the impregnated veneers; and assembling and hot-pressing to obtain the composite flame-retardant recombined decorative veneer veneering plywood.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flame-retardant decorative veneer faced plywood, in particular to a composite flame-retardant reconstituted decorative veneer faced plywood and a preparation method thereof. BACKGROUND

[0002] The traditional flame-retardant decorative veneer faced plywood adopts an impregnation process, which has the phenomenon that the flame retardant is easy to precipitate, resulting in phenomena such as surface decorative layer peeling, poor substrate bonding strength, and modification of light steel keel at the contact interface with the light steel keel. The flame-retardant decorative veneer faced plywood using a surface glue layer process adds a large amount of traditional flame retardant in the surface glue layer to achieve a qualified combustion level, and with the extension of time, there is a peeling phenomenon of the decorative layer after the aging of the surface glue layer. The flame-retardant decorative veneer faced plywood prepared by the above two processes generally has quality problems. SUMMARY

[0003] The present application is developed in view of the above problems, and provides a composite flame-retardant reconstituted decorative veneer faced plywood and a preparation method thereof, which realizes the preparation of high-performance composite flame-retardant reconstituted decorative veneer faced plywood by using a process method of glue layer and impregnation, a new type of efficient flame retardant, and a corresponding preparation process.

[0004] A preparation method of a composite flame-retardant reconstituted decorative veneer faced plywood is provided, which comprises the following steps:

[0005] Step (1): Place the wood veneer in an impregnation tank, vacuumize to -0.25 to -0.20 MPa and keep for 5 to 20 min, inject a MEL aqueous solution with a mass concentration of 2.0 to 3.5% under the negative pressure condition to completely immerse the wood veneer, then pressurize to 0.1 to 1.0 MPa and keep for 1 to 3 h, take out and clean, and then dry at 70 to 80 ℃ for 30 to 40 min; place the treated wood veneer in the impregnation tank again, vacuumize to -0.15 to -0.10 MPa and keep for 10 to 20 min, inject an HPAA aqueous solution with a mass concentration of 15 to 20% under the negative pressure to completely immerse the wood veneer, then pressurize to 0.5 to 1.0 MPa and keep for 1 to 2 h, take out and clean, and then heat to 60 to 70 ℃ at a rate of 5 to 7 ℃ / min, keep the temperature and dry for 90 to 120 min, so that the MEL, HPAA and lignin in the wood react to generate HPAA-MEL-LIGNIN, thereby obtaining a flame-retardant veneer, wherein the HPAA-MEL-LIGNIN generation reaction formula is as follows:

[0006]

[0007] Step (2): 3,5-diamino-1,2,4-triazole, 2-hydroxyphosphonoacetic acid and deionized water are mixed in a mass ratio of 1:(1.5-2):(9-10) and stirred at a speed of 800-1000 r / min at 28-32 ℃ for 40-50 min, then heated to 60-80 ℃ at a rate of 10-12 ℃ / min and continue to stir for 30-50 min, and then filtered to obtain yellow-brown precipitate, which is washed with deionized water for more than 3 times and dried at 75-85 ℃ until the weight is constant, thereby obtaining GH flame retardant; the GH flame retardant is mixed with MUF resin in a mass ratio of 2:(8-10) and stirred at 48-52 ℃ for 30-50 min, so that the GH and MUF cross-link to generate GH-MUF, thereby obtaining the flame-retardant adhesive, and the reaction formula of GH-MUF is:

[0008]

[0009] Step (3): a plurality of flame-retardant single boards are used as core layers, reconstituted decorative single boards are used as upper and lower surface layers, and the flame-retardant adhesive is used as the adhesive layer between the single boards, and then the assembly is cold-pressed at 25-30 ℃ and 0.1-0.15 MPa for 40-50 min, and then hot-pressed at 115-130 ℃ and 1.8-2.0 MPa for 25-45 min, thereby obtaining the composite flame-retardant reconstituted decorative single board veneer plywood, wherein the adhesive amount of the flame-retardant adhesive between the reconstituted decorative single board and the flame-retardant single board is 220-240 g / m 2 , and the adhesive amount of the flame-retardant adhesive between the flame-retardant single boards is 185-200 g / m 2 .

[0010] The wood single board is poplar or eucalyptus, and the thickness is 2.2-3.6 mm. The reconstituted decorative single board has a thickness of 0.28-0.4 mm. The plurality of flame-retardant single boards is 3-5.

[0011] Also provided is the composite flame-retardant reconstituted decorative single board veneer plywood prepared by the preparation method.

[0012] According to the present application, the flame-retardant efficiency and the bonding strength are considered by the synergy of the chemical action of the flame-retardant molecular structure and the wood-adhesive interface. In particular, according to the contrast test, the glue nail structure of the present application realizes the synergy in bonding strength and flame-retardant effect, which is specifically explained as follows.

[0013] In the preparation of the flame-retardant veneer, melamine and HPAA are combined with wood in the wood microstructure through ionic bonds and hydrogen bonds to form HPAA-MEL-LIGNIN. The triazine ring structure of MEL provides high nitrogen content, while the phosphonocarboxyl group in HPAA has strong dehydration-carbonization ability. Both of them react in situ in the wood vessels and pits without volume filling and blocking effect, thus retaining the original pore channels of the wood, which is beneficial to the further penetration of the adhesive and the formation of the glue-nail structure, thereby maintaining the core layer bonding strength. During pyrolysis, the MEL-HPAA composite structure is more likely to exhibit an "acid-nitrogen synergistic" effect in an oxygen-deficient environment. HPAA promotes the dehydration and carbonization of wood polysaccharides, while MEL promotes the formation of aromatic carbon layers in an oxygen-deficient environment. The expanded and dense carbon layer generated by the two synergistically forms an effective barrier to heat and oxygen transmission, achieving solid-phase flame retardation.

[0014] G-H flame retardant is a nitrogen-phosphorus hybrid structure condensed from 3,5-diamino-1,2,4-triazole and 2-hydroxyphosphonoacetic acid. Its molecular skeleton contains a polysubstituted triazole ring (providing thermal stability and gas-phase nitrogen release ability) and a phosphonocarboxyl group (providing carbonization promotion and crosslinking activity). When it is blended with melamine-modified urea-formaldehyde resin, condensation reactions occur between -NH2 and the hydroxymethyl groups of MUF, and between the phosphonic acid groups and the -CH2OH groups of the urea-formaldehyde resin, allowing the flame retardant to be uniformly embedded in the three-dimensional network structure of the adhesive. This uniform dispersion at the molecular level avoids the physical filling effect of traditional flame retardants, improving the wettability and "glue-nail" penetration continuity of the adhesive, thereby improving the bonding strength at the microstructure level. At the same time, the GH molecule can release N2, NH3, and other inert gases during thermal decomposition, which dilutes the combustible components in the combustion zone. Its nitrogen-containing heterocyclic skeleton captures free radicals in the gas phase, exhibiting a gas-phase flame-retardant characteristic, which allows it to be used in the surface layer to more efficiently inhibit flame propagation.

[0015] The core-surface assembly structure allows the gas-phase flame-retardant effect of the surface layer GH-modified adhesive and the solid-phase carbonization effect of the core layer MEL-HPAA to form a complementary synergy in the combustion kinetics. The surface layer quickly inhibits flame spread through gas-phase flame retardation at the initial stage of the flame, and the core layer forms a stable carbon layer under sustained high temperature to provide long-term barrier.

[0016] Further, in the assembly structure, MEL-HPAA reacting with the wood veneer and GH reacting with the MUF adhesive are not independent in the combustion process, but synergistic through the molecular structure of the interface glue nail. The phosphoric acid groups released by the decomposition of MEL-HPAA catalyze the dehydration of polysaccharides around the glue nail, promoting local carbonization at the interface; the nitrogen-containing radicals and inert gases (N2, NH3) generated by the thermal cracking of GH diffuse to the interface between the glue nail and the veneer, which can capture and passivate the combustion chain reaction free radicals, reducing the accumulation of interface smoke; at the same time, the polar phosphine carboxyl group of GH and the residual -OH / -NH group of MEL-HPAA carbonized network occur secondary crosslinking or association, generating a cross-linked carbon interface layer rich in P-N-C bonds, which builds a continuous and dense carbon layer on the glue nail-veneer interface. This interface layer has both physical barrier and chemical capture effects under thermal load, not only blocking the migration of volatile small molecules inside the veneer to the outside (smoke suppression), but also improving the thermal stability and carbon layer continuity between the glue nail and the veneer. DETAILED DESCRIPTION

[0017] Hereinafter, the embodiments of the present application will be described, but the present application is not limited to the embodiments, and the present application can be variously modified within the scope defined by the claims. Different embodiments or preparation examples, and new modifications obtained by combining the conventional technical means should be considered as included in the scope of the present application. The present application, unless otherwise specifically stated, the numerical range "A ~ B" means A or more (greater than or equal to A) B or less (less than or equal to B). The present application, unless otherwise specifically stated, room temperature refers to 25°C. But according to the pursuit of experimental results, room temperature is often only a controllable range, for example, in 22 ~ 25°C, the temperature in the actual control of the upper and lower floating is acceptable on the basis of not affecting the experimental results and the protection scope of the identification.

[0018] Example 1:

[0019] (1) Put 3 poplar veneers with the size of 30mm*30mm*3.6mm in an impregnation tank, vacuumize to-0.20MPa and keep for 5min, inject 2.0wt% melamine (MEL) aqueous solution under the negative pressure condition to make the veneers completely immersed, then pressurize to 0.1MPa and keep for 1h, take out and wash with clean water, and put in a blast drying oven to dry at 70℃ for 30min. Then put the treated veneers in the impregnation tank again, vacuumize to-0.10MPa and keep for 10min, inject 15wt% HPAA (2-hydroxyphosphoryl acetic acid) aqueous solution under the negative pressure condition to make the veneers completely immersed, then pressurize to 0.5MPa and keep for 1h, take out and wash with clean water, and put the veneers in a blast drying oven to increase the temperature to 60℃ at a rate of 5℃ / min and keep for 90min to obtain the flame-retardant poplar veneer.

[0020] (2) Mix 3,5-diamino-1,2,4-triazole, 2-hydroxyphosphoryl acetic acid and deionized water at a mass ratio of 1:1.5:9, stir at 28℃ and 800r / min for 40min, then increase the temperature to 60℃ at a rate of 10℃ / min and continue to stir for 30min, filter the yellow-brown precipitate after natural cooling, wash with deionized water for three times, and dry at 75℃ until the weight is constant to obtain GH flame retardant, then mix GH flame retardant and melamine modified urea-formaldehyde resin (MUF, purchased from Zhejiang Babybaby Adhesive Material Co., Ltd.) at a mass ratio of 2:8, and stir at 48℃ for 30min to prepare the flame-retardant adhesive.

[0021] (3) Assemble the flame-retardant poplar veneer as the core layer, the reconstituted decorative veneer (purchased from Han Shifu Integrated Home Co., Ltd.) as the upper and lower surface layers, and the flame-retardant adhesive as the adhesive layer between the veneers, lay 0.4mm reconstituted decorative veneer, flame-retardant adhesive, 3.6mm flame-retardant poplar veneer, flame-retardant adhesive, 3.6mm flame-retardant poplar veneer, flame-retardant adhesive, 3.6mm flame-retardant poplar veneer, flame-retardant adhesive, and 0.4mm reconstituted decorative veneer in turn, cold press at 25℃ and 0.1MPa for 40min, and then hot press at 115℃ and 1.8MPa for 45min to prepare the composite flame-retardant reconstituted decorative veneer laminated board, wherein the adhesive amount of the flame-retardant adhesive between the decorative layer and the core layer is 220g / m 2 , and the adhesive amount between the flame-retardant veneers is 185g / m 2 .

[0022] Performance:

[0023] 1- Surface bonding strength: 0.75MPa

[0024] 2- Bonding strength of flame-retardant layer adhesive layer: 1.21MPa

[0025] 3- Peak of the burning growth rate index: 158 W / s

[0026] 4- Corrosion rate on galvanized steel: 207.4 μm / a

[0027] 5- In-Grain Modulus of Elasticity and Static Bending Strength: 5120 MPa, 33 MPa

[0028] The following examples and comparative examples have the same source of basic raw materials as example 1, which will not be repeated.

[0029] Example 2:

[0030] (1) 5 pieces of eucalyptus wood veneer with a length of 30 mm, a width of 30 mm, and a thickness of 2.2 mm were placed in an impregnation tank, vacuumed to -0.25 MPa and maintained for 20 min, and then a 3.5% mass concentration of melamine aqueous solution was injected under the condition of negative pressure to completely immerse the veneer. Then, the pressure was increased to 1.0 MPa and maintained for 3 h, and after taking out, it was washed with clean water and placed in a forced air drying oven at 80°C for 40 min. Then, the treated veneer was again placed in the impregnation tank, vacuumed to -0.15 MPa and maintained for 20 min, and then a 20% mass concentration of HPAA aqueous solution was injected under the condition of negative pressure, and after the veneer was completely immersed, the pressure was increased to 1.0 MPa and maintained for 2 h, and after taking out the veneer, it was washed with clean water, and the veneer was placed in a forced air oven at a heating rate of 7°C / min to 70°C and maintained for 120 min to obtain the flame-retardant eucalyptus wood veneer.

[0031] (2) 3,5-diamino-1,2,4-triazole, 2-hydroxyphosphonoacetic acid and deionized water were mixed in a mass ratio of 1:2:10, stirred at 32°C and 1000 r / min for 50 min, then heated to 80°C at a rate of 12°C / min and continued to stir for 50 min, and then filtered after natural cooling to obtain a yellow-brown precipitate. Washed with deionized water three times and dried at 85°C to constant weight to obtain GH flame retardant. Then, the GH flame retardant and melamine modified urea-formaldehyde resin (MUF) were mixed in a mass ratio of 2:10 and stirred at 52°C for 50 min to prepare a flame-retardant adhesive.

[0032] (3) 5 pieces of fire-retardant eucalyptus wood veneer as core layer, reconstituted decorative veneer as upper and lower surface layer, fire-retardant adhesive as adhesive layer between each veneer for assembly, 0.4 mm reconstituted decorative veneer, fire-retardant adhesive, 2.2 mm fire-retardant eucalyptus wood veneer, fire-retardant adhesive, 2.2 mm fire-retardant eucalyptus wood veneer, fire-retardant adhesive, 2.2 mm fire-retardant eucalyptus wood veneer, fire-retardant adhesive, 2.2 mm fire-retardant eucalyptus wood veneer, fire-retardant adhesive, 2.2 mm fire-retardant eucalyptus wood veneer, fire-retardant adhesive, 0.4 mm reconstituted decorative veneer are laid in turn, after cold pressing at 30℃, 0.15 MPa for 50 min, hot pressing at 130℃, 2.0 MPa for 25 min, a composite fire-retardant reconstituted decorative veneer laminated board is prepared, wherein the adhesive amount of fire-retardant adhesive between the decorative layer and the core layer is 240 g / m 2 , and the adhesive amount between each fire-retardant veneer is 200 g / m 2 .

[0033] Performance:

[0034] 1 - Surface bonding strength: 0.82 MPa

[0035] 2 - Bonding strength of fire-retardant layer adhesive: 1.33 MPa

[0036] 3 - Peak value of fire growth rate index: 108 W / s

[0037] 4 - Rust rate on galvanized parts: 203.1 μm / a

[0038] 5 - Modulus of elasticity in parallel grain and static bending strength: 6350 MPa, 36.4 MPa

[0039] Example 3:

[0040] (1) 4 pieces of eucalyptus wood veneer with length, width and height of 30 mm*30 mm*2.2 mm are placed in an impregnation tank, vacuumized to -0.22 MPa and maintained for 10 min, and then a 3% mass concentration melamine aqueous solution is injected under the negative pressure condition to completely immerse the veneer; then pressurized to 0.5 MPa and maintained for 2 h, after taking out, washed with clean water, and placed in a forced air drying oven, dried at 75℃ for 35 min. Then, the treated veneer is placed in the impregnation tank again, vacuumized to -0.12 MPa and maintained for 15 min, and then an 18% mass concentration HPAA aqueous solution is injected under the negative pressure condition to completely immerse the veneer, and then pressurized to 0.8 MPa and maintained for 1.5 h, after taking out the veneer, washed with clean water, and placed in a forced air oven, heated to 65℃ at a heating rate of 6℃ / min and maintained for 100 min to obtain fire-retardant eucalyptus wood veneer.

[0041] (2) 3,5-diamino-1,2,4-triazole, 2-hydroxyphosphonoacetic acid and deionized water were mixed in a mass ratio of 1:1.8:9.5, stirred at 30°C and 900 r / min for 45 min, then heated to 70°C at 11°C / min and continued to stir for 40 min, and then filtered after natural cooling to obtain a yellow-brown precipitate, which was washed with deionized water three times and dried at 80°C to constant weight to obtain GH flame retardant. Then, the GH flame retardant and melamine modified urea-formaldehyde resin (MUF) were mixed in a mass ratio of 2:9, and stirred at 50°C for 40 min to prepare a flame-retardant adhesive.

[0042] (3) Four flame-retardant eucalyptus wood veneers were used as core layers, and reconstituted decorative veneers were used as upper and lower surface layers. Flame-retardant adhesive was used as the adhesive layer between each veneer. The reconstituted decorative veneer, flame-retardant adhesive, 2.2 mm flame-retardant eucalyptus wood veneer, flame-retardant adhesive, 2.2 mm flame-retardant eucalyptus wood veneer, flame-retardant adhesive, 2.2 mm flame-retardant eucalyptus wood veneer, flame-retardant adhesive, 2.2 mm flame-retardant eucalyptus wood veneer, flame-retardant adhesive, and 0.4 mm reconstituted decorative veneer were sequentially laid, and then cold-pressed at 28°C and 0.12 MPa for 45 min, and then hot-pressed at 120°C and 1.9 MPa for 30 min to obtain a composite flame-retardant reconstituted decorative veneer laminated board. The adhesive amount of the flame-retardant adhesive between the decorative layer and the core layer was 230 g / m 2 , and the adhesive amount between each flame-retardant veneer was 190 g / m 2 .

[0043] Performance:

[0044] 1 - Surface bonding strength: 0.78 MPa

[0045] 2 - Bonding strength of flame-retardant layer adhesive: 1.27 MPa

[0046] 3 - Peak value of flame growth rate index: 135 W / s

[0047] 4 - Rusting rate on galvanized parts: 210.8 μm / a

[0048] 5 - In-grain elastic modulus and static bending strength: 6170 MPa, 34.3 MPa

[0049] Comparative Example 1:

[0050] Comparative Example 1 and Example 2 were compared, and the only difference was that in step (1), the flame-retardant component was immersed but not reacted with the wood.

[0051] Step (1): 5 pieces of eucalyptus wood veneer with the size of 30mm*30mm*2.2mm were placed in the impregnation tank, vacuumed to -0.25MPa and kept for 20min, and then the wood veneer was completely immersed by injecting 3.5% melamine aqueous solution under the negative pressure condition. Then, the pressure was increased to 1.0MPa and kept for 3h, and then the wood veneer was washed with clean water. Then, the treated wood veneer was placed in the impregnation tank again, vacuumed to -0.15MPa and kept for 20min, and then the wood veneer was completely immersed by injecting 20% HPAA aqueous solution under the negative pressure condition. After that, the pressure was increased to 1.0MPa and kept for 2h, and then the wood veneer was washed with clean water and placed in the air-drying shed for natural air-drying for 48h, so that the HPAA and MEL reacted, but did not react with lignin, and the ordinary type flame-retardant eucalyptus wood veneer was obtained.

[0052] The other steps are the same as Example 2.

[0053] Performance:

[0054] 1-Surface bonding strength: 0.59MPa

[0055] 2-Bonding strength of flame-retardant layer: 0.69MPa

[0056] 3-Flame growth rate index peak value: 218.2W / s

[0057] 4-Rusting rate on galvanized parts: 537.1μm / a

[0058] 5-In-grain elastic modulus and static bending strength: 5410MPa, 28.1MPa

[0059] According to the comparative example 1, both MEL and HPAA do not combine with wood, and the volume filling and blocking effect occurs, which cannot retain the original pore channel of wood, affects the further penetration of the adhesive and the formation of the glue-nail structure, and the core layer bonding strength is obviously decreased. At the same time, the synergy of the glue-nail interface at the molecular structure level in the combustion process is also affected, and the flame-retardant performance is also obviously decreased.

[0060] Comparative Example 2:

[0061] The comparative example 2 was compared with the example 2, and the only difference was that the flame-retardant component did not react with the adhesive in step (2).

[0062] (1) The flame-retardant eucalyptus wood veneer was prepared by the method of the example 2.

[0063] (2) 3,5-diamino-1,2,4-triazole, 2-hydroxyphosphonoacetic acid and deionized water were mixed in a mass ratio of 1:2:10, stirred at 32°C and 1000 r / min for 50 min, then heated to 80°C and continued to stir for 50 min, and then naturally cooled and filtered to obtain a yellow-brown precipitate, which was washed with deionized water three times and then dried at 85°C to constant weight to obtain GH flame retardant. Then, the GH flame retardant and melamine modified urea-formaldehyde resin (MUF) were mixed uniformly in a mass ratio of 2:10 to prepare a blended flame-retardant adhesive.

[0064] (3) Five flame-retardant eucalyptus wood veneers were used as core layers, reconstituted decorative veneers were used as upper and lower surface layers, and the flame-retardant adhesive was used as the adhesive layer between the veneers. The reconstituted decorative veneer (0.4 mm), the blended flame-retardant adhesive, the flame-retardant eucalyptus wood veneer (2.2 mm), the blended flame-retardant adhesive, the flame-retardant eucalyptus wood veneer (2.2 mm), the blended flame-retardant adhesive, the flame-retardant eucalyptus wood veneer (2.2 mm), the blended flame-retardant adhesive, the flame-retardant eucalyptus wood veneer (2.2 mm), the blended flame-retardant adhesive, the flame-retardant eucalyptus wood veneer (2.2 mm), the blended flame-retardant adhesive, and the reconstituted decorative veneer (0.4 mm) were sequentially laid, cold-pressed at 30°C and 0.15 MPa for 50 min, and then hot-pressed at 130°C and 2.0 MPa for 25 min to prepare a composite flame-retardant reconstituted decorative veneer laminated board, wherein the adhesive amount of the flame-retardant adhesive between the decorative layer and the core layer was 240 g / m 2 , and the adhesive amount between the flame-retardant veneers was 200 g / m 2 .

[0065] Performance:

[0066] 1- Surface bonding strength: 0.51 MPa

[0067] 2- Bonding strength of the adhesive layer of the flame-retardant layer: 0.61 MPa

[0068] 3- Peak value of the rate of flame growth index: 247.1 W / s

[0069] 4- Corrosion rate on galvanized parts: 255.2 μm / a

[0070] 5- In-grain elastic modulus and static bending strength: 4710 MPa, 23.6 MPa

[0071] According to Comparative Example 2, GH and MUF were only mixed and did not react, and were not embedded in the three-dimensional network structure of the adhesive, which could not fully avoid the physical filling of the flame retardant, affected the further penetration of the adhesive and the formation of the adhesive nail structure, and the core layer bonding strength was obviously decreased. At the same time, it also affected the cooperation of the adhesive nail interface at the molecular structure level during the combustion process, and the flame retardant performance was also obviously decreased.

[0072] Comparative Example 3:

[0073] (1) Put 5 pieces of eucalyptus wood veneer with the size of 30mm*30mm*2.2mm and thickness in the impregnation tank, vacuumize to-0.25MPa and keep for 20min, inject 15% ammonium sulfate solution under the condition of negative pressure to make the veneer completely immersed, then pressurize to 1.0MPa and keep for 3h, take out and clean with water, and place in the air drying oven at 80℃ for 40min, to get ordinary type flame retardant veneer.

[0074] (2) Take the above flame retardant veneer as the core layer flame retardant layer, and use ordinary melamine modified urea-formaldehyde resin adhesive (MUF) as the common adhesive layer of the reconstituted decorative veneer and ordinary type flame retardant poplar veneer, lay 0.4mm reconstituted decorative veneer, MUF, 2.2mm ordinary type flame retardant veneer, MUF, 2.2mm ordinary type flame retardant veneer, MUF, 2.2mm ordinary type flame retardant veneer, MUF, 2.2mm ordinary type flame retardant veneer, MUF, 2.2mm ordinary type flame retardant veneer, MUF, 0.4mm reconstituted decorative veneer in turn, cold press at 30℃, 0.15MPa for 50min, then hot press at 130℃, 2.0MPa for 25min, to get composite type flame retardant reconstituted decorative veneer faced plywood, wherein the glue application amount of MUF in the surface layer is 240g / m 2 , and the glue application amount of MUF in the core layer is 200g / m 2 .

[0075] Performance:

[0076] 1- Surface bonding strength: 0.31MPa

[0077] 2- Bonding strength of flame retardant layer adhesive layer: 0.47MPa

[0078] 3- Peak value of burning growth rate index: 319.1W / s

[0079] 4- Corrosion rate on galvanized parts: 873.1μm / a

[0080] 5- Modulus of elasticity in parallel grain and static bending strength: 4410MPa, 21.6MPa.

Claims

1. A method for preparing a composite flame-retardant reconstituted decorative veneer plywood, characterized in that, The preparation method includes: Step (1): Place the wood veneer in an impregnation tank, evacuate to -0.25 to -0.20 MPa and maintain for 5 to 20 minutes. Under this negative pressure condition, inject a 2.0 to 3.5% MEL aqueous solution to completely submerge the wood veneer. Then pressurize to 0.1 to 1.0 MPa and maintain for 1 to 3 hours. Remove, clean, and dry at 70 to 80°C for 30 to 40 minutes. Place the treated wood veneer back into the impregnation tank, evacuate to -0.15 to -0.10 MPa and maintain for 10 to 20 minutes. Under negative pressure, a 15-20% (w / w) HPAA aqueous solution is injected to completely immerse the veneer. The pressure is then increased to 0.5-1.0 MPa and maintained for 1-2 hours. After removal and cleaning, the veneer is heated to 60-70°C at a rate of 5-7°C / min and maintained at this temperature for 90-120 minutes to allow the MEL, HPAA, and lignin in the wood to react and form HPAA-MEL-LIGNIN, thus obtaining a flame-retardant veneer. The HPAA-MEL-LIGNIN formation reaction formula is as follows: Step (2): Mix 3,5-diamino-1,2,4-triazole, 2-hydroxyphosphonoacetic acid, and deionized water at a mass ratio of 1:(1.5~2):(9~10) until homogeneous. Stir at 800~1000 r / min for 40~50 min at 28~32℃. Then, heat to 60~80℃ at a rate of 10~12℃ / min and continue stirring for 30~50 min. After natural cooling, filter to obtain a yellowish-brown precipitate. Wash with deionized water at least three times and dry to constant weight at 75~85℃ to obtain GH flame retardant. Mix GH flame retardant and MUF resin at a mass ratio of 2:(8~10) until homogeneous. Stir at 48~52℃ for 30~50 min to allow GH and MUF to undergo a crosslinking reaction to generate GH-MUF, thereby obtaining flame-retardant adhesive. The reaction formula for the formation of GH-MUF is: Step (3): Using multiple flame-retardant veneers as the core layer, reconstituted decorative veneers as the top and bottom surface layers, and flame-retardant adhesive as the adhesive layer between the veneers, the composite flame-retardant reconstituted decorative veneer plywood is assembled. After cold pressing at 25–30℃ and 0.1–0.15 MPa for 40–50 min, it is then hot-pressed at 115–130℃ and 1.8–2.0 MPa for 25–45 min to obtain the composite flame-retardant reconstituted decorative veneer plywood. The amount of flame-retardant adhesive applied between the reconstituted decorative veneer and the flame-retardant veneer is 220–240 g / m². 2 The application rate of flame-retardant adhesive between flame-retardant veneers is 185–200 g / m². 2 .

2. The preparation method according to claim 1, wherein, The wood veneer is made of poplar or eucalyptus and has a thickness of 2.2–3.6 mm.

3. The preparation method according to claim 1, wherein, The thickness of the reconstituted decorative veneer is 0.28–0.4 mm.

4. The preparation method according to claim 1, wherein, The number of flame-retardant veneers is 3 to 5.

5. A composite flame-retardant reconstituted decorative veneer plywood prepared by the preparation method according to any one of claims 1 to 4.

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