Hydrophobic anti-leaching flame-retardant plywood and method for preparing the same

Abstract

The application provides a preparation method of a hydrophobic anti-leaching fire-retardant plywood, comprising the following steps: (1) impregnating wood veneers in a fire-retardant liquid and a silica sol polymer resin mixed emulsion in sequence to obtain fire-retardant veneers; (2) assembling the fire-retardant veneers in a longitudinal and transverse interlaced manner to obtain a fire-retardant plywood base material; and (3) coating a hydrophobic coating on the surface of the fire-retardant plywood base material to form a hydrophobic coating layer, thereby obtaining the hydrophobic anti-leaching fire-retardant plywood. The wood veneers are impregnated in the fire-retardant liquid and the silica sol polymer resin mixed emulsion in sequence to fill the interior of the wood units, the polymer resin is used as a coating material in the silica sol, the anti-leaching performance of the fire retardant is enhanced, and the hardness and water resistance of the entire plywood are enhanced. The fire-retardant plywood base material is subjected to hydrophobic treatment, so that the plywood is endowed with self-cleaning ability, and the occurrence of adverse phenomena such as corrosion and insect damage is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flame-retardant plywood manufacturing, in particular to a hydrophobic and anti-leaching flame-retardant plywood and a preparation method thereof. BACKGROUND

[0002] As a common building and furniture material, the flame-retardant performance of plywood is crucial for consumer safety. Various flame-retardant plywoods are available on the market. Common methods for preparing flame-retardant plywood include impregnation, inorganic glue layer, and surface coating. However, conventional flame-retardant methods have some problems, such as: conventional impregnation methods usually use phosphates and sulfates as impregnation flame retardants, which often leads to moisture absorption, mold growth, and other adverse phenomena. The inorganic glue layer method for preparing flame-retardant plywood has a long process time and heavy weight, which affects transportation and construction. The coating method for preparing flame-retardant plywood has high cost, and the glue layer is prone to aging.

[0003] A "mildew-resistant flame-retardant plywood and its production method" is disclosed in Chinese patent literature, with publication number CN116175705A. The invention sets up a carbon sandwich board in the panel, and sets up a flame-retardant layer composed of carbon powder layer and intumescent flame retardant on the carbon sandwich board. Moreover, the panel is subjected to carburizing treatment, and carbon molecules enter the interior of the panel, changing the internal environment, and carbon does not appear to be moldy, thus reducing the growth of bacteria. However, the preparation process of the mildew-resistant flame-retardant plywood of the invention is complex, has special requirements for equipment, and the prepared mildew-resistant flame-retardant plywood does not have hydrophobicity and still has the problem of easy moisture absorption. SUMMARY

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a hydrophobic and anti-leaching flame-retardant plywood and a preparation method thereof, to solve the problems of easy moisture absorption, mold growth, and complex preparation process of existing flame-retardant plywood, and low production efficiency.

[0005] To achieve the above-mentioned purposes and other related purposes, the present application provides a preparation method of a hydrophobic and anti-leaching flame-retardant plywood, comprising the following steps:

[0006] (1) Impregnate the wood veneer successively in the flame-retardant liquid and the silica sol high molecular resin mixed emulsion to obtain flame-retardant veneer;

[0007] (2) Assemble the flame-retardant veneer in a longitudinal and transverse interlaced manner to obtain a flame-retardant plywood base material;

[0008] (3) Coat a hydrophobic coating on the surface of the flame-retardant plywood base material to form a hydrophobic coating layer, and obtain a hydrophobic and anti-leaching flame-retardant plywood.

[0009] From the perspective of energy efficiency and preparation process, the impregnation method is an efficient and mature process for flame retardation. However, due to the hygroscopic property of the flame retardant, the final product may be affected; at the same time, the wood material itself has water absorption, which may cause the deformation of the wood board. To solve the above technical problems, the wood veneer is sequentially immersed in the flame retardant liquid and the silica sol polymer resin mixed emulsion in the method, to fill the inside of the wood unit, and the polymer resin is used as the coating material in the silica sol to enhance the anti-loss performance of the flame retardant, and at the same time, the hardness and water resistance of the entire plywood are enhanced. In addition, the flame-retardant plywood substrate is subjected to hydrophobic treatment, thereby imparting self-cleaning ability to the plywood, and reducing the occurrence of corrosion, insect damage and other adverse phenomena.

[0010] Preferably, the flame retardant liquid is one or more mixed aqueous solutions of ammonium polyphosphate, diammonium phosphate and borax.

[0011] Preferably, based on 100 parts by weight of water, the flame retardant liquid comprises the following components by weight: 4-6 parts of ammonium polyphosphate, 2-3 parts of diammonium phosphate and 1-2 parts of borax; and the silica sol polymer resin mixed emulsion is a dispersion of aqueous polyurethane and silane coupling agent in silica sol.

[0012] Preferably, in step (1), the wood veneer is sequentially immersed in the flame retardant liquid and the silica sol polymer resin mixed emulsion by using the full cell method; the process of the full cell method comprises: pre-vacuum, pressure impregnation and post-vacuum.

[0013] Preferably, the vacuum degree of the pre-vacuum is -0.05 to -0.10 Mpa, and the time is 25-45 min; the pressure of the pressure impregnation is 1.0-1.5 Mpa; the vacuum degree of the post-vacuum is -0.05 to -0.10 Mpa, and the time is 30-35 min.

[0014] Preferably, the silica sol polymer resin mixed emulsion is impregnated by using the cyclic impregnation method to increase the loading amount of the silica sol polymer resin mixed emulsion in the wood veneer, enhance the anti-loss performance of the flame retardant, and at the same time, enhance the hardness and water resistance of the entire plywood.

[0015] Preferably, the moisture content of the wood veneer before impregnation is not more than 5%.

[0016] Preferably, in step (1), based on the total mass of the silica sol polymer resin mixed emulsion, the mass percentage concentration of the silica sol is 20-40%, the mass percentage concentration of the aqueous polyurethane is 8-15%, and the mass percentage concentration of the silane coupling agent is 0.5-1.5%.

[0017] Preferably, in step (3), the hydrophobic coating is a hydrophobic nano-silica layer; the coating is performed by spray coating using a spray gun with a spray pressure of 0.05-0.10 MPa, a distance of 10-15 cm between the spray gun and the fire-retardant plywood substrate, and a moving speed of the spray gun of 20-25 cm / min.

[0018] Preferably, in step (3), the hydrophobic coating is a composite emulsion prepared by mixing hydrophobic nano-silica particles, compatibly modified polydimethylsiloxane, and epoxy resin at a mass ratio of (3-5):(4-5):20.

[0019] Preferably, the compatibly modified polydimethylsiloxane is prepared by modifying hydroxyl-terminated polydimethylsiloxane with KH-550 silane coupling agent, epoxy resin, and dibutyltin dilaurate.

[0020] Mixing polydimethylsiloxane directly with epoxy resin can cause delamination and phase separation. In the present application, the compatibly modified polydimethylsiloxane is obtained by modifying the above-mentioned reagents, and the epoxy groups are grafted onto the hydroxyl-terminated polydimethylsiloxane, which is conducive to forming an interpenetrating network structure with the epoxy resin, improving the compatibility of the system, and improving the stability of the hydrophobic coating.

[0021] More preferably, the preparation method of the modified polydimethylsiloxane comprises the following steps: mixing 10-15 parts by mass of hydroxyl-terminated polydimethylsiloxane with 30-40 parts by mass of epoxy resin, 0.5-1 part by mass of KH-550, and 1-1.5 parts by mass of dibutyltin dilaurate, and reacting for 6 h under the condition of water bath heating at 80℃ to obtain the compatibly modified polydimethylsiloxane.

[0022] Preferably, the particle size of the hydrophobic nano-silica particles is 50-75 μm.

[0023] Preferably, the hydrophobic nano-silica particles are prepared by the method comprising the following steps: dispersing alkoxysilane in a mixed solution of ammonia and ethanol, slowly adding a mixed solution of hydrophobic group-containing silane and anhydrous ethanol, aging, and centrifugally separating to obtain the hydrophobic nano-silica particles.

[0024] More preferably, the hydrophobic group-containing silane is methyl triethoxysilane.

[0025] Preferably, the hydrophobic nano-silica particles are prepared by the method comprising the following steps: adding a composite silicon source to an aqueous ethanol solution, adding oxalic acid catalyst to perform hydrolysis, adding ammonia catalyst to form a gel, aging the gel in a trimethylchlorosilane ethanol solution to obtain a silica gel, and crushing and drying the silica gel to obtain the hydrophobic nano-silica particles.

[0026] The application further provides the hydrophobic anti-leaching fire-retardant plywood prepared by the preparation method.

[0027] Preferably, the hydrophobic anti-leaching fire-retardant plywood comprises a fire-retardant plywood substrate and a hydrophobic coating covering the surface of the fire-retardant plywood substrate.

[0028] As described above, the hydrophobic anti-leaching fire-retardant plywood and the preparation method thereof have the following beneficial effects: the wood veneer is sequentially immersed in the fire-retardant liquid and the silica sol polymer resin mixed emulsion, and the immersion of the silica sol polymer resin mixed emulsion is completed in a cyclic immersion manner, so as to increase the loading amount of the silica sol polymer resin mixed emulsion in the wood veneer, enhance the anti-leaching performance of the fire retardant, and simultaneously enhance the hardness and water resistance of the entire plywood; the fire-retardant plywood substrate is subjected to hydrophobic treatment, so as to endow the plywood with self-cleaning ability, and simultaneously reduce the occurrence of adverse phenomena such as corrosion and insect damage. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The structure of the hydrophobic anti-leaching fire-retardant plywood is shown.

[0030] Explanation of reference numerals: 1, fire-retardant plywood substrate; 2, hydrophobic coating. DETAILED DESCRIPTION

[0031] The embodiments of the present application will be described in detail below with specific reference to the drawings. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in the specification. The present application can also be implemented or applied in other different specific embodiments, and various modifications or changes can be made to the details in the specification without departing from the spirit of the present application.

[0032] It should be noted that the process equipment or device not specifically mentioned in the following examples is the conventional equipment or device in the art.

[0033] In addition, it should be understood that the one or more method steps mentioned in the present application do not exclude the presence of other method steps before and after the combination steps or the insertion of other method steps between the explicitly mentioned steps, unless otherwise specified; it should also be understood that the combination connection relationship between the one or more devices / apparatuses mentioned in the present application does not exclude the presence of other devices / apparatuses before and after the combination devices / apparatuses or the insertion of other devices / apparatuses between the two explicitly mentioned devices / apparatuses, unless otherwise specified. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not a limitation on the arrangement order of each method step or a limitation on the range of implementation of the present application. The change or adjustment of the relative relationship, without substantial change of the technical content, is also regarded as the implementation scope of the present application.

[0034] Example 1

[0035] The embodiment of the present application provides a preparation method of a hydrophobic anti-leaching flame-retardant plywood, comprising the following steps:

[0036] (1) 5 parts of ammonium polyphosphate, 3 parts of diammonium phosphate and 2 parts of borax are dissolved in 100 parts of water and stirred uniformly to prepare a flame-retardant liquid; wood veneers are dried to reduce the moisture content of the wood veneers to 5% or below; the dried wood veneers are placed into a vacuum impregnation tank, the parameters of the vacuum impregnation tank are set as follows: vacuum degree-0.08 Mpa, pre-vacuum for 30 min, after the vacuum is completed, the flame-retardant liquid is poured into the tank body of the vacuum impregnation tank, and pressure impregnation is performed for 2 h with a pressure of 1.2 Mpa; the impregnated veneers are taken out and dried, and a mesh belt dryer is used to dry the veneers to a moisture content of 5% or below, so that wood veneers with flame-retardant properties are obtained;

[0037] Preparation of a silica sol high polymer resin mixed emulsion: the silica sol is diluted to 30% with distilled water, and 15% of the water-based polyurethane and 1.5% of the silane coupling agent are added to the silica sol diluent based on the total mass of the silica sol high polymer resin mixed emulsion, and the two are uniformly mixed by magnetic stirring to obtain the silica sol high polymer resin mixed emulsion;

[0038] The dried wood veneers with flame-retardant properties are placed into a vacuum impregnation tank, vacuum is drawn for 20 min, after the vacuum is completed, the silica sol high polymer resin mixed emulsion is injected into the tank body of the vacuum impregnation tank, and pressure impregnation is performed, the impregnation time is 3 h; the method of cyclic impregnation is adopted, and vacuum-pressure cyclic impregnation is continuously performed, which is repeated for 3 times to increase the sol load; the impregnated veneers are taken out, the residual impregnation emulsion on the surface of the veneers is removed, the surface liquid is dried, and then a mesh belt dryer is used for drying, so that the veneers are dried to a moisture content of 20% or below, and flame-retardant veneers are obtained;

[0039] (2) the surface curing layer sand of the flame-retardant veneers is removed by using a thickness sander, the sanded veneers are assembled in a longitudinal and transverse interlaced manner, the veneer assembly is glued by using conventional urea-formaldehyde resin glue and is cold-pressed and hot-pressed, and after hot pressing, the veneer assembly is scraped and aged; 0.7 mm thin veneers are selected as veneer layers, the surface of the thin veneers is washed clean by using distilled water, and the thin veneers are dried by using a mesh belt dryer; the thin veneers after cleaning are veneered to the plywood substrate, the veneering process is consistent with the existing plywood production process, and a flame-retardant plywood substrate is obtained;

[0040] (3) Preparation of hydrophobic silica nanoparticles: 0.5 mol / L dilute ammonia water was added to 100 parts by mass of anhydrous ethanol, the pH was adjusted to 7, the temperature was slowly raised to 50°C and magnetically stirred to mix thoroughly; 20 parts by mass of tetraethyl orthosilicate was slowly added dropwise, and magnetic stirring was continued at room temperature; after stirring, 50 parts by mass of methyltriethoxysilane and 10 parts by mass of a mixture of dimethyldiethoxysilane and anhydrous ethanol were added, and after aging for a period of time, anhydrous ethanol containing 15% by mass of trimethylchlorosilane was added, and aging was continued for 24 hours to obtain the desired alcohol sol; the obtained alcohol sol was centrifuged using a high-speed centrifuge to separate the silica sol to obtain hydrophobic silica nanoparticles, which were then vacuum dried at 80°C for 10 hours for later use;

[0041] Preparation of hydrophobic coatings:

[0042] Preparation of compatibilized modified polydimethylsiloxane: 10 parts by mass of hydroxyl-terminated polydimethylsiloxane are mixed with 35 parts by mass of epoxy resin, 1 part by mass of KH-550 and 1.5 parts by mass of dibutyltin dilaurate, and reacted in a water bath at 80°C for 6 hours to obtain compatibilized modified polydimethylsiloxane.

[0043] Hydrophobic silica nanoparticles are mixed with compatibilized modified polydimethylsiloxane and epoxy resin in a mass ratio of 3:5:20, and ultrasonic dispersion is used to obtain a uniformly mixed composite emulsion, which is the hydrophobic coating.

[0044] The hydrophobic coating was sprayed onto the surface of the flame-retardant plywood substrate using a spray gun. The specific spraying parameters were: pressure 0.1 MPa, distance between the spray gun and the substrate 15 cm, and spray gun moving speed 20 cm / min. This allowed the polydimethylsiloxane-silica nanoparticles to be fully deposited on the wood surface. After being left at room temperature for 2 hours, the substrate was pushed into a hot press and dried and cured using the platen temperature without pressure, resulting in a hydrophobic, anti-leakage, flame-retardant plywood.

[0045] The hydrophobic, anti-leakage, and flame-retardant plywood prepared in this embodiment is as follows: Figure 1 As shown, it includes a flame-retardant plywood substrate 1 and a hydrophobic coating 2 covering the surface of the flame-retardant plywood substrate, wherein the thickness of the flame-retardant plywood substrate 1 is 9 mm and the thickness of the hydrophobic coating 2 is 0.45 mm.

[0046] Example 2

[0047] This application provides a method for preparing hydrophobic, anti-leakage, and flame-retardant plywood, comprising the following steps:

[0048] (1) Take 5 parts of ammonium polyphosphate, 3 parts of diammonium phosphate, and 2 parts of borax, and dissolve them in 100 parts of water by mass and stir uniformly to prepare a fire-retardant liquid; dry the wood veneer to reduce the moisture content of the wood veneer to 5% or less; place the dried wood veneer into a vacuum impregnation tank, set the vacuum degree of the vacuum impregnation tank to -0.08 Mpa, and vacuum for 30 minutes; after the vacuum is completed, pour the impregnation liquid into the tank body, pressurize for 2 hours, and the pressure is 1.2 Mpa; take out the impregnated veneer, dry it, and use a mesh belt dryer to dry the veneer to a moisture content of 5% or less, to obtain a wood veneer with fire-retardant properties;

[0049] Preparation of silica sol high polymer resin mixed emulsion: dilute the silica sol to a concentration of 30% with distilled water, and based on the total mass of the silica sol high polymer resin mixed emulsion, add 15% water-based polyurethane and 1.0% silane coupling agent to the silica sol diluent, mix them uniformly by magnetic stirring to obtain the silica sol high polymer resin mixed emulsion;

[0050] Place the dried wood veneer with fire-retardant properties into a vacuum impregnation tank, and vacuum for 20 minutes. After the vacuum is completed, inject the silica sol high polymer resin mixed emulsion into the tank body of the vacuum impregnation tank, and pressurize and impregnate for 3 hours; use the method of circulating impregnation to continuously vacuum-pressurize and circulate impregnation, repeat 3 times to increase the sol load; take out the impregnated veneer, remove the residual impregnation emulsion on the surface of the veneer, dry the surface liquid, and then use a mesh belt dryer to dry the veneer to a moisture content of 20% or less, to obtain a fire-retardant veneer;

[0051] (2) Use a thickness sander to sand the surface of the fire-retardant veneer to remove the sanding layer, and use the veneer after sanding in a longitudinal and transverse interlaced way to form a stack, use conventional urea-formaldehyde resin glue to glue the stack and perform cold pressing and hot pressing, and after hot pressing, perform scraping and aging; select a 0.7 mm thin veneer as a veneer layer, wash its surface with distilled water, and dry it with a mesh belt dryer, and then use the cleaned thin veneer as a veneer on the plywood substrate, the veneering process is consistent with the existing technology of plywood production process, to obtain a fire-retardant plywood substrate;

[0052] (3) Preparation of hydrophobic silica nanoparticles: 0.5 mol / L dilute aqueous ammonia was added to 100 parts by mass of anhydrous ethanol, the pH was adjusted to 7, and it was slowly warmed to 50°C and magnetically stirred to mix thoroughly. 20 parts by mass of tetraethyl orthosilicate was slowly added thereto, and the magnetic stirring was continued at room temperature. After the stirring was completed, 50 parts by mass of a mixture of methyltriethoxysilane and anhydrous ethanol was added thereto, and after standing for a period of time, 15% by mass of trimethylchlorosilane in anhydrous ethanol was added thereto, and it was further allowed to stand for 24 h to obtain the desired alcohol sol; the obtained alcohol sol was centrifuged to separate the silica sol using a high-speed centrifuge, and the nanoparticles were vacuum fractionally dried for 10 h and reserved for use;

[0053] Preparation of hydrophobic coating:

[0054] Preparation of compatibilized modified polydimethylsiloxane: 10 parts by mass of hydroxyl-terminated polydimethylsiloxane was mixed with 30 parts by mass of epoxy resin, 0.5 parts by mass of KH-550, and 1 part by mass of dibutyltin dilaurate, and the mixture was reacted at 80°C in a water bath for 6 h to obtain the compatibilized modified polydimethylsiloxane;

[0055] The hydrophobic silica nanoparticles, the compatibilized modified polydimethylsiloxane, and the epoxy resin were mixed in a mass ratio of 3:4:20, and a uniformly mixed composite emulsion was obtained by ultrasonic dispersion, which was the hydrophobic coating;

[0056] The hydrophobic coating was sprayed onto the surface of the flame-retardant plywood substrate by a spray gun, and the specific spraying parameters were: pressure 0.1 MPa, distance between the spray gun and the substrate 15 cm, and spray gun moving speed 20 cm / min. In order to allow the polydimethylsiloxane-silica nanoparticles to fully deposit on the surface of the wood, the substrate was placed in a hot press after standing at room temperature for 2 h, and the substrate was dried and cured at the plate temperature without pressure to obtain the hydrophobic and anti-leaching flame-retardant plywood.

[0057] The hydrophobic and anti-leaching flame-retardant plywood prepared in this example includes a flame-retardant plywood substrate and a hydrophobic coating layer covering the surface of the flame-retardant plywood substrate, wherein the thickness of the flame-retardant plywood substrate is 9 mm, and the thickness of the hydrophobic coating layer is 0.38 mm.

[0058] Example 3

[0059] Example 3 differs from Example 1 in that the preparation method of the hydrophobic coating in step (3) is different, and the remaining process steps are exactly the same.

[0060] The preparation method of the hydrophobic coating in step (3) includes the following steps:

[0061] Preparation of hydrophobic silica nanoparticles: methyl triethoxysilane (MTES) is added to a mixed solution containing ethanol and distilled water, 0.5 mol / L oxalic acid catalyst and tetraethoxysilane (TEOS) are added and continuously stirred at a speed of 650 rpm for 8 h for hydrolysis; the mass ratio of MTES: TEOS: ethanol is fixed at 3:1:5; the solution is transferred to a mold, 0.5 mol / L dilute ammonia water is added to adjust the pH to 7, and a gel is formed within 30 minutes, the formed gel is aged and soaked in anhydrous ethanol solution containing 15% trimethylchlorosilane (MTES) for 48 h to strengthen the gel network; the obtained silica gel is crushed and dried in sections using a hot press, the drying temperature is 40℃, 60℃, 80℃, and the hot pressing time for each section is 4 h. After hot pressing, white micro-translucent powder hydrophobic aerogel is obtained; the powder aerogel is placed in an oven and dried at 80℃ for 12 h. The hydrophobic SiO2 aerogel particles after drying are placed in a sieve for screening to remove larger particles, and hydrophobic silica nanoparticles with a particle size of 50-75 μm are obtained;

[0062] Preparation of hydrophobic coating:

[0063] Preparation of compatibilized modified polydimethylsiloxane: 15 parts by mass of hydroxyl-terminated polydimethylsiloxane is mixed with 40 parts by mass of epoxy resin, 1 part by mass of KH-550, and 1.5 parts by mass of dibutyltin dilaurate, and reacted at 80℃ in a water bath for 6 h to obtain compatibilized modified polydimethylsiloxane;

[0064] The hydrophobic silica nanoparticles, compatibilized modified polydimethylsiloxane, and epoxy resin are mixed in a mass ratio of 4:5:20, and ultrasonic dispersion is used to obtain a uniformly mixed composite emulsion, which is the hydrophobic coating.

[0065] The hydrophobic anti-run-off flame-retardant plywood prepared in this example includes a flame-retardant plywood substrate and a hydrophobic coating layer covering the surface of the flame-retardant plywood substrate, wherein the thickness of the flame-retardant plywood substrate is 9 mm, and the thickness of the hydrophobic coating layer is 0.51 mm.

[0066] The performance of the experimental sample of the hydrophobic anti-run-off flame-retardant plywood prepared in this example is detected, and the results show that after the above steps, the hardness and strength of the hydrophobic anti-run-off flame-retardant plywood are improved by 5%, and it has certain anti-run-off performance, the mass increases by 20% after sol immersion, the oxygen index reaches 36%, and the water contact angle is 115°, which meets the preset requirements of the performance of the hydrophobic flame-retardant plywood.

[0067] Comparative Example 1

[0068] The difference between Comparative Example 1 and Example 1 is that the flame-retardant liquid is directly used for impregnation without using the silica sol polymer resin mixed emulsion for impregnation, and the surface is not treated with a hydrophobic coating, and the rest of the process is exactly the same.

[0069] Comparative Example 2

[0070] The difference between Comparative Example 2 and Example 1 is that the silica sol is directly used for impregnation without adding a polymer resin and a silane coupling agent, and the surface is not treated with a hydrophobic coating, and the rest of the process is exactly the same.

[0071] The properties of the flame-retardant plywood prepared in Examples 1-3 and Comparative Examples 1-2 were characterized, and the characterization method was as follows: the hydrophobic and anti-leaching flame-retardant plywood was dried before and after impregnation, and the weight gain rate of the board was calculated by the difference; and the weight loss rate of the board was detected by 24h water soaking test, so as to judge the leaching amount of the flame retardant; the oxygen index of the test piece was detected according to GB / t2406.2-2009, the strength of the board was detected according to GB / T 17657-2022, and the hydrophobic property was tested by water contact angle tester. The characterization results are shown in Table 1:

[0072] Table 1. Performance results of flame-retardant plywood prepared in Examples 1-3 and Comparative Examples 1-2

[0073]

[0074] As can be seen from Table 1, by comparing the data of Example 1 and Comparative Example 1, after adding the silica sol and polymer resin mixed impregnation liquid, the strength of the board increases, the water soaking test shows that the weight loss rate of the board decreases, and the anti-leaching property is enhanced. And the water contact angle of the wood after coating treatment is improved, showing good hydrophobic property, and the flame-retardant property of the board is improved. By comparing Example 1 with Comparative Example 2, it can be seen that the effect of hydrophobic coating is obvious, which further reduces the leaching of the flame retardant in the board, and the flame-retardant property is obviously improved, because the board is not treated with a flame-retardant impregnation. By comparing Comparative Example 1 and Comparative Example 2, it can be seen that using silica sol impregnation can improve the strength of the board, but the improvement of the flame-retardant effect is not significant. By comparing Example 1 with Example 3, it can be seen that the hydrophobic nano-silicon dioxide particles prepared by the two methods both have good hydrophobic effect.

[0075] The foregoing examples are to be construed as merely illustrative of the presently disclosed embodiments, and do not exhaust the scope of the present application. Furthermore, various modifications to both the examples listed herein and the methods and compositions of the application will be apparent to those skilled in the art, and this application is intended to encompass such modifications within the scope and spirit of the application. Although the application has been described in conjunction with specific preferred embodiments thereof, it will be understood that the application is not limited to these embodiments. In fact, various modifications to the described embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments. Therefore, to the extent that modifications of the described embodiments incorporating some but not other features of the application are within the spirit and scope of the application, they should be and are intended to be included within the scope of the application.

Claims

1. A method for preparing a hydrophobic and anti-leaching fire-retardant plywood, characterized in that, comprising the following steps: (1) sequentially immersing wood veneers in a fire-retardant solution and a silica sol polymer resin mixed emulsion to obtain fire-retardant veneers; (2) assembling the fire-retardant veneers in a longitudinal and transverse staggered manner to obtain a fire-retardant plywood base material; (3) coating a hydrophobic coating on the surface of the fire-retardant plywood base material to form a hydrophobic coating layer, thereby obtaining a hydrophobic and anti-leaching fire-retardant plywood; wherein the silica sol polymer resin mixed emulsion is a dispersion of waterborne polyurethane and silane coupling agent in silica sol. 2.The method according to claim 1, characterized in that: the fire-retardant solution is one or more mixed aqueous solutions of ammonium polyphosphate, diammonium phosphate and borax. 3.The method according to claim 2, characterized in that: based on 100 parts by weight of water, the fire-retardant solution comprises the following components by weight: 4-6 parts of ammonium polyphosphate, 2-3 parts of diammonium phosphate and 1-2 parts of borax. 4.The method according to claim 1, characterized in that: in step (1), the wood veneers are sequentially immersed in the fire-retardant solution and the silica sol polymer resin mixed emulsion by using a full-cell method; the immersion of the silica sol polymer resin mixed emulsion is completed by using a cyclic immersion method; the full-cell method comprises the following processes: pre-vacuum, pressure immersion and post-vacuum, wherein the pre-vacuum degree is-0.05 to-0.10 MPa and the time is 25-45 min; the pressure of the pressure immersion is 1.0-1.5 MPa; the post-vacuum degree is-0.05 to-0.10 MPa and the time is 30-35 min; the moisture content of the wood veneers before immersion is not more than 5%. 5.The method according to claim 3, characterized in that: in step (1), based on the total mass of the silica sol polymer resin mixed emulsion, the mass percentage concentration of the silica sol is 20-40%, the mass percentage concentration of the waterborne polyurethane is 8-15%, and the mass percentage concentration of the silane coupling agent is 0.5-1.5%. 6.The method according to claim 1, characterized in that: in step (3), the hydrophobic coating layer is a hydrophobic nano-silicon dioxide layer; the coating is performed by using a spray gun spraying method, wherein the spraying pressure of the spray gun is 0.05-0.10 MPa, the distance between the spray gun and the fire-retardant plywood base material is 10-15 cm, and the moving speed of the spray gun is 20-25 cm / min. 7.The method according to claim 1, characterized in that: in step (3), the hydrophobic coating is a composite emulsion prepared by mixing hydrophobic silicon dioxide nanoparticles, compatibly modified polydimethylsiloxane and epoxy resin according to a mass ratio of (3-5) :(4-5) :20; the compatibly modified polydimethylsiloxane is prepared by modifying hydroxyl-terminated polydimethylsiloxane with KH-550 silane coupling agent, epoxy resin and dibutyltin dilaurate; the particle size of the hydrophobic silicon dioxide nanoparticles is about 50-75 μm. 8.The method according to claim 7, characterized in that: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ In step (3), the hydrophobic silica nanoparticles are prepared by a method comprising the following steps: dispersing alkoxysilane in a mixture of ammonia and ethanol, slowly adding a mixture of silane with hydrophobic group and anhydrous ethanol, aging, centrifugal separation and drying, and the obtained solid is the hydrophobic silica nanoparticles.

9. The preparation method according to claim 7, characterized in that: In step (3), the hydrophobic silica nanoparticles are prepared by a method comprising the following steps: adding a composite silicon source into an aqueous ethanol solution, adding oxalic acid catalyst for hydrolysis, adding ammonia catalyst, forming a gel, aging the gel in a trimethylchlorosilane ethanol solution to obtain a silica gel, crushing and drying the silica gel to obtain the hydrophobic silica nanoparticles.

10. A hydrophobic and anti-leaching fire-retardant plywood prepared by the preparation method according to any one of claims 1-9, characterized in that: The hydrophobic and anti-leaching fire-retardant plywood comprises a fire-retardant plywood substrate (1) and a hydrophobic coating layer (2) covering the surface of the fire-retardant plywood substrate.

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