Preparation process of plywood with waterproof and flame-retardant properties

Abstract

The invention discloses a preparation technology of plywood with waterproof and flame-retardant performance, and relates to the technical field of plywood preparation, the preparation technology comprises the steps of S1, wood veneer pretreatment, S2, steeping liquor preparation, S3, veneer steeping and curing, S4, adhesive modification, S5, assembly and hot pressing, and S6, maintenance treatment. The nano composite coating with flame-retardant and hydrophobic functions is constructed through chemical reaction of phytic acid and the silane coupling agent, phosphate groups in the phytic acid provide flame retardance through catalytic carbonization, a hydrophobic silicon dioxide network is formed after the silane coupling agent is hydrolyzed, and the hydrophobic silicon dioxide network is combined with wood fibers through chemical bonds, so that long-acting water resistance is achieved, and the flame-retardant and hydrophobic functions are achieved. The contradiction that the traditional flame retardant is easy to absorb moisture and lose efficacy and the waterproof agent is poor in flame retardance is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of plywood preparation, and in particular relates to a preparation process of a plywood with waterproof and flame-retardant properties. Background Art

[0002] Plywood is one of the commonly used materials for furniture and is a man-made board. Plywood is a three-layer or multi-layer plate-like material made by peeling wood segments into veneers or planing wood squares into thin wood, and then gluing them with adhesive. It usually uses an odd number of veneers and glues the fibers of adjacent layers of veneers perpendicular to each other. Commonly used ones include three-ply boards and five-ply boards. It can improve the utilization rate of wood and is also a major way to save wood.

[0003] In ship interiors and outdoor buildings, the flame retardant and waterproof properties of plywood are key requirements. Commonly used plywood waterproofing agents, such as silicone resins and fluorocarbon resins, have poor compatibility with flame retardants, resulting in poor compatibility between flame retardants and waterproofing agents, making it difficult to achieve dual-functional synergy or long-term stability of flame retardancy and waterproofing. In response to the above problems, the following solutions are proposed. Summary of the invention

[0004] The purpose of the present invention is to provide a preparation process of plywood with waterproof and flame retardant properties. A composite coating with both flame retardant and hydrophobic functions is constructed through the reaction of phytic acid and a silane coupling agent, thereby solving the existing problem of poor compatibility between flame retardants and waterproof agents.

[0005] In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

[0006] The present invention is a process for preparing a plywood having waterproof and flame retardant properties, comprising:

[0007] Step S1, wood veneer pretreatment: removing wood knots and cracks, and performing surface treatment;

[0008] Step S2, preparation of the impregnation liquid: prepare phytic acid, silane coupling agent, nano-silicon dioxide and ethanol according to the mass ratio, and add them into the reaction kettle intermittently to prepare the impregnation liquid;

[0009] Step S3, veneer impregnation and curing: immersing the pretreated veneer in the composite sol and performing vacuum pressurization;

[0010] Step S4, adhesive modification: adding phenolic resin into the preparation device, and adding a modifier into the preparation device;

[0011] Step S5, assembling and hot pressing: gluing and assembling the veneer, and hot pressing the veneer through a hot press after the assembly is completed;

[0012] Step S6, curing treatment: immediately after the hot pressing is completed, the surface of the finished product is sprayed and cured;

[0013] In the step S2, the formula of the impregnation solution is: 40 parts of phytic acid in 50% aqueous solution, 10 parts of KH-550 silane coupling agent, 5 parts of silicon dioxide with a particle size of 20 nm, and 45 parts of ethanol.

[0014] Furthermore, the specific operation of step S1, wood veneer pretreatment is as follows:

[0015] Step S11: Select poplar or pine veneer with a thickness of 1.5-2.0 mm and a moisture content of 8%-10%, and remove knots and cracks;

[0016] Step S12: Use a constant temperature water bath to completely immerse the single board in a 5% sodium hydroxide solution, with the liquid level exceeding the top of the single board stacking layer by more than 10 cm. After treatment for 30 minutes, use a three-stage countercurrent water washing system with pure water conductivity ≤10μS / cm, and wash for 5 minutes at each stage to ensure that the residual alkali solution concentration is less than 0.01%, and then dry at 80°C to a moisture content of less than 5%.

[0017] Furthermore, the specific operation of preparing the impregnation liquid in step S2 is as follows:

[0018] Step S21: In a closed reaction vessel, the silane coupling agent is mixed with ethanol, the pH value is adjusted to 4.5-5.0 with acetic acid, the hydrolysis temperature is controlled at 25±2°C, and ultrasonic dispersion is performed for 10 minutes;

[0019] Step S22: after adding the phytic acid solution, the temperature is raised to 60°C, the linear speed of the stirring blade is ≥2.5 m / s, and the viscosity of the reaction system is monitored by an NDJ-8S rotational viscometer to stabilize it at 120-150 mPa·s, and the reaction is carried out for 2 hours to hydrolyze the silane and form Si-OP bonds with the phytic acid;

[0020] Step S23: Then, nano-silicon dioxide was added and high-speed shearing emulsification was performed at 12000 rpm for 15 minutes to form a uniform sol.

[0021] Furthermore, the specific operations of step S3, veneer impregnation and curing are as follows:

[0022] Step S31: using a vacuum-pressure impregnation machine with a maximum vacuum degree of -0.095 MPa, immersing the pretreated single board in the composite sol, evacuating to -0.08 MPa and maintaining for 20 minutes, and then pressurizing to 0.6 MPa at a rate of 0.05 MPa / s, and releasing the pressure by 0.05 MPa every 5 minutes and then re-pressurizing;

[0023] Step S32: Curing is performed in a curing box, and a step-by-step temperature increase is adopted in the pre-baking stage, 80°C / 30min→100°C / 20min→120°C / 10min, and the heating rate is 2°C / min, followed by thermal curing at 120°C for 1 hour.

[0024] Furthermore, the curing box is equipped with a humidity sensor and RH≤15%, and a forced exhaust volume ≥500m 3 / h.

[0025] Furthermore, the specific operation of step S4, adhesive modification, is as follows:

[0026] Add 3% nano-montmorillonite and 2% ammonium polyphosphate microcapsules to 45% solid content phenolic resin, disperse at 2000 rpm at 45°C for 1 hour, and then mature at 25°C for 24 hours. The maturation tank is equipped with a spiral guide plate and is used after standing to defoam.

[0027] Furthermore, the ammonium polyphosphate microcapsules are prepared by interfacial polymerization, specifically:

[0028] 15% ammonium polyphosphate aqueous solution was dispersed in white oil with an oil-water ratio of 4:1, 0.5% Span 80 emulsifier was added, and after emulsification at 2000rpm to form a W / O emulsion, melamine resin prepolymer was added dropwise, and reacted at 55°C for 3 hours. The molar ratio of melamine to formaldehyde in the melamine resin prepolymer was 1:3.

[0029] Furthermore, the rotation speed of the spiral guide plate is 5 rpm.

[0030] Furthermore, the specific operations of step S5, assembling and hot pressing are as follows:

[0031] Step S51: Double-sided coating of modified adhesive, with a coating amount of 120 g / m 2 , 5 layers of orthogonal paving, the fiber directions of adjacent veneers are perpendicular;

[0032] Step S52: Using a hot press, start the infrared heating plate synchronously during the 0-2 minute pressure increase stage to ensure that the core layer temperature of the single board reaches 110°C within 2 minutes, stabilize the pressure at 1.2 MPa during the 2-5 minute pressure stabilization stage, and start the cooling water circulation system during the 5-6 minute pressure reduction stage with an inlet water temperature of 15°C and a flow rate of 10L / min, so that the temperature of the slab drops from 135°C to 80°C within 60 seconds and the pressure is reduced to 0.5MPa.

[0033] Furthermore, the specific operation of step S6, the curing treatment, is as follows:

[0034] Immediately after hot pressing, use a high-pressure airless sprayer to spray an ethanol solution containing 1% fluorocarbon modified polysiloxane. Keep the spraying distance at 25±2cm, spray back and forth 3 times, and dry each time with an interval of 5 minutes. Monitor the coating thickness in real time using an inductive thickness meter, and then place the board blank at a constant temperature and humidity of 25°C for 72 hours.

[0035] The present invention has the following beneficial effects:

[0036] 1. The present invention constructs a nano-composite coating with both flame retardant and hydrophobic functions through the chemical reaction of phytic acid and silane coupling agent. The phosphoric acid group in the phytic acid provides flame retardancy through catalytic carbonization. The silane coupling agent forms a hydrophobic silica network after hydrolysis and combines with wood fibers through chemical bonds to achieve long-term waterproofing, thus solving the contradiction between the traditional flame retardant being easily ineffective due to moisture absorption and the poor flame retardancy of the waterproofing agent.

[0037] 2. The present invention forms Si-OP bonds through the reaction of the phosphoric acid groups in phytic acid with the hydrolyzate of silane coupling agent. This strong covalent bond tightly connects the flame retardant and hydrophobic functional components, making them firmly attached to wood fibers. The hydrogen bonds formed between phytic acid and cellulose further enhance the binding force, ensuring that the functional components will not fall off easily in the complex environment of wood. At the same time, the microencapsulation technology is used to encapsulate the flame retardant, which effectively blocks the direct contact between the flame retardant and the external environment, thereby inhibiting the migration and volatilization of the functional components.

[0038] 3. The present invention enhances the adhesion and permeability of the coating by using nano-silicon dioxide and optimizes the addition amount of functional components, thereby improving the flame retardant and waterproof properties while maintaining the mechanical properties of the plywood. At the same time, natural plant extract phytic acid and silane coupling agent are used as the main functional components, thus avoiding the use of harmful substances such as formaldehyde and halogen flame retardants in traditional processes.

[0039] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0041] Figure 1 The figure is a schematic flow chart of a process for preparing a plywood having waterproof and flame retardant properties according to the present invention;

[0042] Figure 2 This is a comparison table of the effects of the mass ratio of phytic acid to silane on various properties of the present invention;

[0043] Figure 3 This is a comparison table of the effect of the amount of nano-silicon dioxide added on the permeability of the present invention;

[0044] Figure 4 This is a comparison table of the effect of the content of the microcapsule flame retardant on water resistance of the present invention;

[0045] Figure 5 This is a vertical combustion grade comparison table of the present invention. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] In the case of no specific conditions, the operations in the examples are carried out under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used, if the manufacturer is not indicated, are all common products on the market. The parts not mentioned in the technical content of the present invention will be processed with reference to the prior art.

[0048] See also Figure 1-5 As shown, the present invention is a process for preparing a plywood with waterproof and flame retardant properties, comprising:

[0049] Step S1, wood veneer pretreatment: removing wood knots and cracks, and performing surface treatment;

[0050] Step S2, preparation of the impregnation liquid: prepare phytic acid, silane coupling agent, nano-silicon dioxide and ethanol according to the mass ratio, and add them into the reaction kettle intermittently to prepare the impregnation liquid;

[0051] Step S3, veneer impregnation and curing: immersing the pretreated veneer in the composite sol and performing vacuum pressurization;

[0052] Step S4, adhesive modification: adding phenolic resin into the preparation device, and adding a modifier into the preparation device;

[0053] Step S5, assembling and hot pressing: gluing and assembling the veneer, and hot pressing the veneer through a hot press after the assembly is completed;

[0054] Step S6, curing treatment: immediately after the hot pressing is completed, the surface of the finished product is sprayed and cured;

[0055] Step S2, the formula of the impregnation solution in the preparation of the impregnation solution is: 40 parts of phytic acid in a 50% aqueous solution, 10 parts of KH-550 silane coupling agent, 5 parts of silicon dioxide with a particle size of 20 nm, and 45 parts of ethanol;

[0056] The specific operation of step S1, wood veneer pretreatment is as follows:

[0057] Step S11: Select poplar or pine veneer with a thickness of 1.5-2.0 mm and a moisture content of 8%-10%, and remove knots and cracks;

[0058] Step S12: Use a constant temperature water bath to completely immerse the veneer in a 5% sodium hydroxide solution to remove lignin and hemicellulose. At the same time, the liquid level is more than 10 cm above the top of the veneer stacking layer to prevent uneven oxidation and expose fiber pores. After 30 minutes of treatment, a three-stage countercurrent water washing system is used, and the conductivity of pure water is ≤10μS / cm. Each stage of water washing is 5 minutes to ensure that the residual alkali concentration is <0.01%. Then, it is dried at 80°C to a moisture content of less than 5%. Accurate temperature control is used to avoid excessive fiber degradation. Three-stage water washing can remove reaction by-products.

[0059] The specific operation of step S2, preparation of the impregnation solution is as follows:

[0060] Step S21: In a closed reactor, a silane coupling agent is mixed with ethanol, the pH value is adjusted to 4.5-5.0 with acetic acid, the hydrolysis temperature is controlled at 25±2°C, and ultrasonic dispersion is performed for 10 minutes. The pH value control can inhibit silane self-polymerization and ensure a high formation rate of SiOP bonds;

[0061] Step S22: After adding the phytic acid solution, the temperature is raised to 60°C, the linear speed of the stirring blade is ≥2.5m / s, and the viscosity of the reaction system is monitored by an NDJ-8S rotational viscometer to stabilize it at 120-150mPa·s. The reaction is carried out for 2 hours to hydrolyze the silane and form Si-OP bonds with the phytic acid. The viscosity monitoring ensures that the nano-silicon dioxide is evenly dispersed and avoids particle agglomeration;

[0062] Step S23: Then, nano-silicon dioxide was added and high-speed shearing emulsification was performed at 12000 rpm for 15 minutes to form a uniform sol.

[0063] The specific operation of step S3, veneer impregnation and curing is as follows:

[0064] Step S31: using a vacuum-pressure impregnation machine with a maximum vacuum degree of -0.095 MPa, immersing the pretreated single board in the composite sol, evacuating to -0.08 MPa and maintaining for 20 minutes, and then pressurizing to 0.6 MPa at a rate of 0.05 MPa / s, and releasing the pressure by 0.05 MPa every 5 minutes and then re-pressurizing;

[0065] Step S32: Curing is carried out in a curing box. In the pre-baking stage, a step-by-step temperature increase is adopted, 80℃ / 30min→100℃ / 20min→120℃ / 10min, and the heating rate is 2℃ / min, so that the ethanol is volatilized, and then heat-curing is carried out at 120℃ for 1 hour. The silane condenses to form a three-dimensional network, and the phytic acid and cellulose are combined through hydrogen bonds. The gradient pressure increase can increase the permeability of the impregnation liquid and avoid cracking of the coating. Humidity control ensures that the condensation reaction is complete.

[0066] The curing box is equipped with a humidity sensor and RH≤15%, and the forced exhaust volume ≥500m 3 / h.

[0067] The specific operation of step S4, adhesive modification is as follows:

[0068] Add 3% nano-montmorillonite and 2% ammonium polyphosphate microcapsules to 45% solid content phenolic resin, disperse at 2000rpm at 45°C for 1 hour, then mature in a aging tank at 25°C for 24 hours, let stand and defoam before use. The addition of nano-montmorillonite can improve the water resistance of the adhesive layer. The particle size of the ammonium polyphosphate microcapsule is 5μm, and the outer shell is melamine resin, which will burst and release flame retardants when exposed to fire.

[0069] Ammonium polyphosphate microcapsules are prepared by interfacial polymerization, specifically:

[0070] 15% ammonium polyphosphate aqueous solution was dispersed in white oil with an oil-water ratio of 4:1, 0.5% Span 80 emulsifier was added, and after emulsification at 2000rpm to form a W / O emulsion, melamine resin prepolymer was added dropwise, and reacted at 55°C for 3 hours. The molar ratio of melamine to formaldehyde in the melamine resin prepolymer was 1:3.

[0071] The maturation tank is equipped with a spiral guide plate, and the rotation speed of the spiral guide plate is 5rpm.

[0072] The specific operations of step S5, assembling and hot pressing are as follows:

[0073] Step S51: Double-sided coating of modified adhesive, with a coating amount of 120 g / m 2 , 5 layers of orthogonal paving, the fiber directions of adjacent veneers are perpendicular;

[0074] Step S52: Using a hot press, start the infrared heating plate synchronously during the 0-2 minute pressure-increasing stage to ensure that the core layer temperature of the single board reaches 110°C within 2 minutes, stabilize the pressure at 1.2 MPa during the 2-5 minute pressure-stabilizing stage, and start the cooling water circulation system during the 5-6 minute pressure-reducing stage with an inlet water temperature of 15°C and a flow rate of 10 L / min, so that the slab is cooled from 135°C to 80°C within 60 seconds and the pressure is reduced to 0.5 MPa. The synergistic effect of temperature and pressure can improve the curing degree of the glue layer, and rapid cooling and pressure reduction can suppress the rebound of the wood.

[0075] The specific operation of step S6, curing treatment is as follows:

[0076] Immediately after hot pressing, use a high-pressure airless sprayer to spray an ethanol solution containing 1% fluorocarbon modified polysiloxane to improve the surface hydrophobicity. The spraying distance is maintained at 25±2cm, and the spray is repeated 3 times. Each time, the coating is dried after an interval of 5 minutes. The coating thickness is monitored in real time by an inductive thickness meter. The board is then placed at a constant temperature and humidity of 25°C for 72 hours. Three sprayings can form a gradient hydrophobic structure, and the bonding strength can be avoided by precisely controlling the film thickness.

[0077] A specific application of this embodiment is:

[0078] First, a poplar or pine veneer is selected, treated with a 5% sodium hydroxide solution (50°C) for 30 minutes to remove lignin and hemicellulose, and then washed with three-stage countercurrent water and dried to a moisture content of less than 5%. Subsequently, a flame retardant-waterproof composite impregnation solution is prepared: a silane coupling agent is mixed with ethanol, the pH is adjusted to 4.5-5.0, a phytic acid solution is added after hydrolysis, and the mixture is stirred at 60°C for 2 hours to form Si-OP bonds. Then, nano-silicon dioxide is added for high-speed shear emulsification, and the pretreated veneer is immersed in the composite sol, vacuum-pressurized (-0.08MPa for 20 minutes, then pressurized to 0.6MPa for 30 minutes), taken out, pre-baked at 80°C for 30 minutes, and thermally cured at 120°C for 1 hour. Next, a phenolic resin is mixed with 3% nano-montmorillonite and 2% ammonium polyphosphate microcapsules, dispersed at 45°C for 1 hour, and coated on the surface of the veneer (120g / m 2 ), 5 layers of orthogonal assembly were hot pressed (135°C, 1.2MPa, 6 minutes), and an ethanol solution containing 1% fluorocarbon modified polysiloxane was immediately sprayed after hot pressing. The product was maintained at a constant temperature and humidity of 25°C for 72 hours. The final product was boiled in boiling water for 4 hours and subjected to vertical burning test. The bonding strength was ≥1.10MPa, the contact angle was 118°, the LOI was ≥35.2%, the vertical burning grade reached V-0, the flame retardant migration rate was ≤4.8%, and the comprehensive performance was significantly better than that of the traditional process.

[0079] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0080] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A process for preparing a plywood having waterproof and flame retardant properties, characterized in that: The preparation process comprises the following steps: Step S1, wood veneer pretreatment: removing wood knots and cracks, and performing surface treatment; Step S2, preparation of the impregnation liquid: prepare phytic acid, silane coupling agent, nano-silicon dioxide and ethanol according to the mass ratio, and add them into the reaction kettle intermittently to prepare the impregnation liquid; Step S3, veneer impregnation and curing: immersing the pretreated veneer in the composite sol and performing vacuum pressurization; Step S4, adhesive modification: adding phenolic resin into the preparation device, and adding a modifier into the preparation device; Step S5, assembling and hot pressing: gluing and assembling the veneer, and hot pressing the veneer through a hot press after the assembly is completed; Step S6, curing treatment: immediately after the hot pressing is completed, the surface of the finished product is sprayed and cured; In the step S2, the formula of the impregnation solution is: 40 parts of phytic acid in 50% aqueous solution, 10 parts of KH-550 silane coupling agent, 5 parts of silicon dioxide with a particle size of 20 nm, and 45 parts of ethanol.

2. The process for preparing a waterproof and flame retardant plywood according to claim 1, characterized in that: The specific operation of step S1, wood veneer pretreatment is as follows: Step S11: Select poplar or pine veneer with a thickness of 1.5-2.0 mm and a moisture content of 8%-10%, and remove knots and cracks; Step S12: Use a constant temperature water bath to completely immerse the single board in a 5% sodium hydroxide solution with the liquid level being more than 10 cm above the top of the single board stacking layer. After treatment for 30 minutes, use a three-stage countercurrent water washing system with pure water conductivity ≤10μS / cm and each stage of water washing for 5 minutes.

3. The process for preparing a waterproof and flame retardant plywood according to claim 1, characterized in that: The specific operation of preparing the impregnation solution in step S2 is as follows: Step S21: In a closed reaction vessel, the silane coupling agent is mixed with ethanol, the pH value is adjusted to 4.5-5.0 with acetic acid, the hydrolysis temperature is controlled at 25±2°C, and ultrasonic dispersion is performed for 10 minutes; Step S22: after adding the phytic acid solution, the temperature is raised to 60°C, the linear speed of the stirring blade is ≥2.5 m / s, and the viscosity of the reaction system is monitored by an NDJ-8S rotational viscometer to stabilize it at 120-150 mPa·s, and the reaction is carried out for 2 hours to hydrolyze the silane and form Si-OP bonds with the phytic acid; Step S23: Then, nano-silicon dioxide was added and high-speed shearing emulsification was performed at 12000 rpm for 15 minutes to form a uniform sol.

4. The process for preparing a waterproof and flame-retardant plywood according to claim 1, characterized in that: The specific operation of step S3, veneer impregnation and curing is as follows: Step S31: using a vacuum-pressure impregnation machine with a maximum vacuum degree of -0.095 MPa, immersing the pretreated single board in the composite sol, evacuating to -0.08 MPa and maintaining for 20 minutes, and then pressurizing to 0.6 MPa at a rate of 0.05 MPa / s, and releasing the pressure by 0.05 MPa every 5 minutes and then re-pressurizing; Step S32: Curing is performed in a curing box, and a step-by-step temperature increase is adopted in the pre-baking stage, 80°C / 30min→100°C / 20min→120°C / 10min, and the heating rate is 2°C / min, followed by thermal curing at 120°C for 1 hour.

5. The process for preparing a waterproof and flame retardant plywood according to claim 1, characterized in that: The curing box is equipped with a humidity sensor and RH ≤ 15%, and the forced exhaust volume ≥ 500m 3 / h.

6. The process for preparing a waterproof and flame retardant plywood according to claim 1, characterized in that: The specific operation of step S4, adhesive modification, is as follows: Add 3% nano-montmorillonite and 2% ammonium polyphosphate microcapsules to 45% solid content phenolic resin, disperse at 2000 rpm at 45°C for 1 hour, then mature in a maturation tank at 25°C for 24 hours, and let it stand for defoaming before use.

7. The process for preparing a waterproof and flame-retardant plywood according to claim 6, characterized in that: The ammonium polyphosphate microcapsules are prepared by interfacial polymerization, specifically: 15% ammonium polyphosphate aqueous solution was dispersed in white oil with an oil-water ratio of 4:1, 0.5% Span 80 emulsifier was added, and after emulsification at 2000rpm to form a W / O emulsion, melamine resin prepolymer was added dropwise, and reacted at 55°C for 3 hours. The molar ratio of melamine to formaldehyde in the melamine resin prepolymer was 1:

3.

8. The process for preparing a waterproof and flame-retardant plywood according to claim 6, characterized in that: The ripening tank is equipped with a spiral guide plate, and the rotation speed of the spiral guide plate is 5 rpm.

9. The process for preparing a waterproof and flame retardant plywood according to claim 1, characterized in that: The specific operations of step S5, assembling and hot pressing are as follows: Step S51: Double-sided coating of modified adhesive, with a coating amount of 120 g / m 2 , 5 layers of orthogonal paving, the fiber directions of adjacent veneers are perpendicular; Step S52: Using a hot press, start the infrared heating plate synchronously during the 0-2 minute pressure increase stage to ensure that the core layer temperature of the single board reaches 110°C within 2 minutes, stabilize the pressure at 1.2 MPa during the 2-5 minute pressure stabilization stage, and start the cooling water circulation system during the 5-6 minute pressure reduction stage with an inlet water temperature of 15°C and a flow rate of 10L / min, so that the temperature of the slab drops from 135°C to 80°C within 60 seconds and the pressure is reduced to 0.5MPa.

10. The process for preparing a plywood with waterproof and flame retardant properties according to claim 1, characterized in that: The specific operation of step S6, the curing treatment, is as follows: Immediately after hot pressing, use a high-pressure airless sprayer to spray an ethanol solution containing 1% fluorocarbon modified polysiloxane. Keep the spraying distance at 25±2cm, spray back and forth 3 times, and dry each time with an interval of 5 minutes. Monitor the coating thickness in real time using an inductive thickness meter, and then place the board blank at a constant temperature and humidity of 25°C for 72 hours.

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