Wood adhesive and method for preparing wood with flame retardant, hydrophobic and self-adhesive properties

Abstract

The present invention relates to a wood adhesive and a method for preparing wood with flame retardant, hydrophobic and self-adhesive properties. The present invention belongs to the technical field of wood adhesives. The present invention provides a wood adhesive, comprising component A and component B, wherein component A is a chitosan solution, and component B is a soy protein isolate solution. The present invention provides a method for preparing wood, wherein the layer-by-layer self-assembly technology is adopted, and fast-growing wood is cyclically immersed in a chitosan solution and a soy protein isolate solution respectively, and after drying, the surface of the fast-growing wood adsorbs chitosan and soy protein isolate by electrostatic action, and the prepared wood has self-adhesive properties, and no modification or adhesive supplementation is required, and plywood can be obtained by hot pressing. The raw materials used in the present invention are all natural biomass materials, which are widely available, and the preparation process and principle are simple. While improving the hydrophobic and flame retardant properties of the wood, the preparation method of the plywood is also developed.

Description

Technical Field

[0001] The invention relates to a wood adhesive and a method for preparing wood with flame retardant, hydrophobic and self-adhesive properties, belonging to the technical field of wood adhesives. Background Art

[0002] As people's requirements for the safety and comfort of living environment continue to increase, higher requirements are also placed on the performance of building and decorative materials. Wood is a renewable green and environmentally friendly material that is widely used in furniture and construction. Traditional wood has good texture, feel and processability, but it has obvious deficiencies in fire resistance and waterproofing. It is prone to dimensional deformation, decay and discoloration, and there are fire safety hazards.

[0003] First, wood is flammable and needs to be treated with flame retardant. However, most existing flame retardants have problems such as toxicity and the generation of harmful gases.

[0004] Secondly, wood has strong water absorption and is easily deformed by moisture, which affects the structural stability and aesthetics. However, existing waterproof treatment methods have many problems in terms of preparation process, functionality and practical application.

[0005] To overcome the above problems, there are also ways to improve the flame retardancy and water resistance of wood through chemical modification, surface coating, etc. However, these methods often cannot solve multiple problems at the same time, and in practical applications, there may be problems such as single function, poor environmental protection, expensive reagents and equipment, etc.

[0006] Therefore, providing an adhesive that can meet the flame retardant and hydrophobic requirements of wood, and the wood board treated with the adhesive has the advantage of good bonding strength, has become an urgent problem to be solved in the field. Summary of the invention

[0007] In order to solve the above problems, the present invention provides a wood adhesive. Wood using the adhesive has good flame retardant and hydrophobic effects.

[0008] The technical solution of the present invention to solve the above problems is as follows:

[0009] A wood adhesive comprises component A and component B, wherein component A is a chitosan solution and component B is a soy protein isolate solution;

[0010] The concentration of the chitosan solution is 4-6 g / L, and the pH is 3-4; the deacetylation degree of the chitosan used is ≥95%, and the viscosity is 100-200 mPa·s; and the concentration of the soy protein isolate solution is 1-10 g / L.

[0011] The adhesive provided by the present invention, when used, self-assembles the positively charged chitosan polyelectrolyte and the negatively charged soy protein isolate polyelectrolyte on the wood surface by dipping or roller coating, forming a functional film on the wood surface; making it flame retardant and hydrophobic. At the same time, since the surfaces of adjacent veneers have opposite charges, there is no need to add adhesive, and plywood can be obtained after hot pressing.

[0012] Another object of the present invention is to provide a method for preparing wood having flame retardant, hydrophobic and self-adhesive properties.

[0013] A method for preparing wood with flame retardant, hydrophobic and self-adhesive properties comprises the following steps:

[0014] S1, dipping or roller coating a fast-growing wood veneer with a chitosan solution, then taking it out, cleaning it, and drying it to obtain a first treated veneer;

[0015] S2, dipping or roller coating the first treated veneer with the soy protein isolate solution, then taking it out after dipping, cleaning and drying it to obtain a second treated veneer;

[0016] S3, divide the plurality of second processing boards into two groups, respectively according to A-(-BA-) n –B and A-(-BA-) n -BA method to repeat steps S1-S2 to obtain two different types of modified veneers; n is 1-15;

[0017] S4, two different types of modified veneers are divided into X-(-YX-) m –Y or X-(-YX-) m -YX method for assembling, and then hot pressing to obtain a wood with flame retardant, hydrophobic and self-adhesive properties; m is 0~10.

[0018] In the above technical solution of the present invention, in step S3, firstly, a plurality of second processing boards are prepared, and then these boards are divided into two groups. The first group is arranged according to A-(-BA-) n -B, repeating steps S1-S2 to obtain a modified veneer covered with soy protein isolate (referred to as the first modified veneer). The second group was prepared according to A-(-BA-) n -BA method, repeating steps S1-S2 to obtain a chitosan-coated modified veneer (referred to as the second modified veneer); in step S4, the first modified veneer and the second modified veneer are subjected to X-(-YX-) m -Y or X- (-YX-) m -YX method for assembly and then hot pressing.

[0019] As a preferred embodiment of the above technical solution, in step S1, the fast-growing wood is preliminarily cleaned and dried before being immersed in the chitosan solution.

[0020] As a preferred embodiment of the above technical solution, in step S1, the concentration of the chitosan solution is 4-6 g / L, and the pH is 3-4; the deacetylation degree of the chitosan used is ≥95%, and the viscosity is 100-200 mPa·s.

[0021] As a preferred embodiment of the above technical solution, in step S2, the concentration of the soy protein isolate solution is 1-10 g / L.

[0022] As a preferred embodiment of the above technical solution, in steps S1 and S2, the cleaning is performed with water; and the drying temperature is 40-80°C.

[0023] As a preferred embodiment of the above technical solution, in step S4, the hot pressing temperature is 100°C to 130°C, the hot pressing pressure is 1.1 to 1.5 MPa, and the hot pressing time is 30 to 50 min.

[0024] In summary, the present invention has the following beneficial effects:

[0025] 1. A wood adhesive provided by the present invention, when used, firstly attaches a positively charged chitosan polyelectrolyte to a wood board by dipping or roller coating, preferably a fast-growing wood, and then immerses or roller-coats a soy protein isolate solution after drying, so that chitosan and soy protein isolate are self-assembled layer by layer in this way, and a functional film is formed on the surface of the wood, so that it has flame retardant and hydrophobic properties; at the same time, after the last dipping or roller coating of the wood, it is not dried or lightly dried to keep its surface moist, and the wood is assembled and hot-pressed, and the surfaces of adjacent veneers are oppositely charged during assembly, and no adhesive needs to be added, and plywood can be obtained after the hot pressing is completed;

[0026] 2. The present invention adopts the above method to prepare a wood with flame retardant, hydrophobic and self-adhesive properties, and a composite film composed of chitosan-soy protein isolate is attached to the surface of the wood. Among them, the chitosan and soy protein isolate used in the modification process of the present invention are both natural and degradable polyelectrolyte biomass materials with wide sources, low cost and high safety. At the same time, the present invention has low equipment requirements in the preparation process and high feasibility of industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is an exposure combustion test diagram of the wood with flame retardant, hydrophobic and self-adhesive properties prepared in Example 1 of the present invention;

[0028] Figure 2 This is a diagram of an exposure combustion test of the wood with flame retardant, hydrophobic and self-adhesive properties prepared in Example 2 of the present invention;

[0029] Figure 3 This is the exposure combustion test diagram of the original wood of Comparative Example 1;

[0030] Figure 4 This is an exposure combustion test diagram of the chitosan-modified wood prepared in Comparative Example 2;

[0031] Figure 5 The water contact angle of the wood with flame retardant, hydrophobic and self-adhesive properties obtained in Example 1 of the present invention;

[0032] Figure 6 The water contact angle of the wood with flame retardant, hydrophobic and self-adhesive properties obtained in Example 2 of the present invention;

[0033] Figure 7 The water contact angle of the original wood surface in Comparative Example 1;

[0034] Figure 8 This is the water contact angle of the chitosan-modified wood surface obtained in Comparative Example 2. DETAILED DESCRIPTION

[0035] In order to make the technical purpose, technical solution and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0036] Example 1

[0037] This embodiment provides a wood adhesive and a method for preparing wood with flame retardant, hydrophobic and self-adhesive properties.

[0038] The wood adhesive comprises component A and component B; component A is a chitosan solution with positive charge; component B is a soy protein isolate solution with negative charge.

[0039] A method for preparing wood with flame retardant, hydrophobic and self-adhesive properties, comprising the following steps:

[0040] (1) Material preparation:

[0041] The fast-growing poplar wood with a size of 120 mm×10 mm×1 mm was washed and dried at a drying temperature of 60° C. to obtain pretreated fast-growing poplar wood;

[0042] Preparation of chitosan solution: Dissolve 1 g of low-viscosity chitosan (degree of deacetylation ≥ 95%, viscosity 100-200 mPa·s) in 200 mL of deionized water, adjust the pH to 3-4 with acetic acid, and stir magnetically until the solution is clear and transparent to obtain a chitosan solution with a concentration of 5 g / L.

[0043] Preparation of soy protein isolate solution: dissolve 1 g of soy protein isolate in 200 mL of deionized water, and stir magnetically until the soy protein isolate is evenly dispersed to obtain a 5 g / L soy protein isolate solution;

[0044] (2) The pretreated fast-growing poplar wood was first immersed in a chitosan solution (5 g / L) for immersion treatment at room temperature for 1 hour, then repeatedly rinsed with deionized water, and dried at 60°C; the dried fast-growing poplar wood was then immersed in a soy protein isolate solution (5 g / L) for immersion treatment for 1 hour, taken out and repeatedly rinsed with deionized water and dried at 60°C, which was considered as one immersion cycle. The cyclic immersion was repeated for 5 cycles, and after drying, a flame retardant and hydrophobic wood of this embodiment was obtained.

[0045] Example 2

[0046] This embodiment provides a wood adhesive and a method for preparing wood with flame retardant, hydrophobic and self-adhesive properties.

[0047] The wood adhesive comprises component A and component B; component A is a chitosan solution with positive charge; component B is a soy protein isolate solution with negative charge.

[0048] A method for preparing wood with flame retardant, hydrophobic and self-adhesive properties, comprising the following steps:

[0049] (1) Material preparation:

[0050] The fast-growing poplar wood with a size of 120 mm×10 mm×1 mm was washed and dried at a drying temperature of 60° C. to obtain pretreated fast-growing poplar wood;

[0051] Preparation of chitosan solution: Dissolve 1 g of low-viscosity chitosan (degree of deacetylation ≥ 95%, viscosity 100-200 mPa·s) in 200 mL of deionized water, adjust the pH to 3-4 with acetic acid solution, and stir magnetically until the solution is clear and transparent to obtain a chitosan solution with a concentration of 5 g / L.

[0052] Preparation of soy protein isolate solution: 2 g of soy protein isolate was dissolved in 200 mL of deionized water, and magnetic stirring was performed until the soy protein isolate was evenly dispersed to obtain a 10 g / L soy protein isolate solution;

[0053] (2) The pretreated fast-growing poplar wood was first immersed in a chitosan solution (5 g / L) for 1 hour, then repeatedly rinsed with deionized water, and dried at 60°C; the dried fast-growing poplar wood was then immersed in a soy protein isolate solution (10 g / L) for 1 hour, taken out and repeatedly rinsed with deionized water and dried at 60°C, which was considered as one immersion cycle. The cyclic immersion was repeated for 5 cycles to obtain a flame retardant and hydrophobic wood of this embodiment.

[0054] Example 3

[0055] This embodiment provides a wood adhesive and a method for preparing wood with flame retardant, hydrophobic and self-adhesive properties.

[0056] The wood adhesive comprises component A and component B; component A is a chitosan solution with positive charge; component B is a soy protein isolate solution with negative charge.

[0057] A method for preparing wood with flame retardant, hydrophobic and self-adhesive properties, comprising the following steps:

[0058] (1) Material preparation:

[0059] Three poplar veneers with a size of 300 mm × 300 mm × 2 mm were taken, washed and dried at a drying temperature of 60° C. to obtain pretreated eucalyptus veneers;

[0060] Preparation of chitosan solution: Dissolve 5 g of low-viscosity chitosan (deacetylation degree ≥ 95%, viscosity 100-200 mPa·s) in 1 L of deionized water, adjust the pH to 3-4 with acetic acid solution, and stir magnetically until the solution is clear and transparent to obtain a chitosan solution with a concentration of 10 g / L.

[0061] Preparation of soy protein isolate solution: dissolve 10 g of soy protein isolate in 1 L of deionized water, and stir magnetically until the soy protein isolate is evenly dispersed to obtain a 10 g / L soy protein isolate solution;

[0062] (2) The poplar wood veneer was immersed in a chitosan solution for 1 hour and dried at 60°C; after drying, the veneer was immersed in a soy protein isolate solution for 1 hour, and dried again at 60°C. The immersion in two solutions and drying was considered a cycle, and the cycle was repeated for 5 times. After the last immersion in the soy protein isolate solution, no drying was required, and one of the veneers was immersed in a chitosan solution again to make its surface positively charged;

[0063] (3) Eucalyptus plywood was prepared by pressing according to GB / T 9846.7-2015 "Ordinary Plywood" standard. The veneers were all in a wet state during hot pressing. Three layers of plywood were assembled based on the vertical grain. The hot pressing process parameters were: hot pressing temperature of 120°C, pressure of 1.3MPa, and hot pressing time of 30min. The test was carried out according to the bonding strength test method for Class II plywood specified in 4.17 of GB / T 17657-2022 "Test methods for physical and chemical properties of wood-based panels and veneered wood-based panels". The bonding strength of the product was 0.87MPa, which met the relevant national standards for Class II plywood.

[0064] Example 4

[0065] This embodiment provides a wood adhesive and a method for preparing wood with flame retardant, hydrophobic and self-adhesive properties.

[0066] The wood adhesive comprises component A and component B; component A is a chitosan solution with positive charge; component B is a soy protein isolate solution with negative charge.

[0067] A method for preparing wood with flame retardant, hydrophobic and self-adhesive properties, comprising the following steps:

[0068] (1) Material preparation:

[0069] Three poplar veneers with a size of 300 mm × 300 mm × 2 mm were taken, washed and dried at a drying temperature of 60° C. to obtain pretreated eucalyptus veneers;

[0070] Preparation of chitosan solution: Dissolve 5 g of low-viscosity chitosan (deacetylation degree ≥ 95%, viscosity 100-200 mPa·s) in 1 L of deionized water, adjust the pH to 3-4 with acetic acid solution, and stir magnetically until the solution is clear and transparent to obtain a chitosan solution with a concentration of 10 g / L.

[0071] Preparation of soy protein isolate solution: dissolve 10 g of soy protein isolate in 1 L of deionized water, and stir magnetically until the soy protein isolate is evenly dispersed to obtain a 10 g / L soy protein isolate solution;

[0072] (2) The poplar wood veneer was immersed in a chitosan solution for 1 hour and dried at 60°C; after drying, the veneer was immersed in a soy protein isolate solution for 1 hour, and dried again at 60°C. The immersion in two solutions and drying was considered a cycle, and the cycle was repeated for 5 times. After the last immersion in the soy protein isolate solution, no drying was required, and one of the veneers was immersed in a chitosan solution again to make its surface positively charged;

[0073] (3) Eucalyptus plywood was prepared by pressing according to GB / T 9846.7-2015 "Ordinary Plywood" standard. The veneers were all in a wet state during hot pressing. Three layers of plywood were assembled based on the vertical grain. The hot pressing process parameters were: hot pressing temperature of 120°C, pressure of 1.3MPa, and hot pressing time of 40min. The test was carried out according to the bonding strength test method for Class II plywood specified in 4.17 of GB / T 17657-2022 "Test methods for physical and chemical properties of wood-based panels and veneered wood-based panels". The bonding strength of the product was 0.77MPa, which met the relevant national standards for Class II plywood.

[0074] Comparative Example 1

[0075] This comparative example provides an unmodified wood, which uses the same fast-growing poplar wood as that in Example 1, which is first cleaned and then dried at 60° C., to obtain the unmodified wood of Comparative Example 1.

[0076] Comparative Example 2

[0077] This comparative example provides a chitosan-modified wood, and the preparation method thereof comprises the following steps:

[0078] (1) Material preparation:

[0079] Three poplar veneers with a size of 300 mm×300 mm×2 mm were washed and dried at a drying temperature of 60° C. to obtain pretreated fast-growing poplar wood;

[0080] Preparation of chitosan solution: Dissolve 1 g of low-viscosity chitosan (degree of deacetylation ≥ 95%, viscosity 100-200 mPa·s) in 200 mL of deionized water, adjust the pH to 3-4 with acetic acid solution, and stir magnetically until the solution is clear and transparent to obtain a chitosan solution with a concentration of 5 g / L.

[0081] (2) The pretreated fast-growing poplar wood was immersed in a chitosan solution (5 g / L) for 1 hour, and then repeatedly rinsed with deionized water and dried at 60°C. The chitosan solution was repeatedly immersed for 5 cycles to obtain the chitosan-modified wood of the comparative example;

[0082] (3) Plywood was prepared by pressing according to GB / T 9846.7-2015 "Ordinary Plywood" standard, and three layers of plywood were assembled based on the vertical grain. The hot pressing process parameters were: hot pressing temperature of 120°C, pressure of 1.3 MPa, and hot pressing time of 30 min. After hot pressing, the veneer had no adhesiveness and could not be self-glued.

[0083] Comparative Example 3

[0084] This comparative example provides a soy protein isolate modified wood, and the preparation method thereof comprises the following steps:

[0085] (1) Material preparation:

[0086] Three poplar veneers with a size of 300 mm×300 mm×2 mm were washed and dried at a drying temperature of 60° C. to obtain pretreated fast-growing poplar wood;

[0087] Preparation of soy protein isolate solution: dissolve 5 g of soy protein isolate in 1 L of deionized water, and stir magnetically until the soy protein isolate is evenly dispersed to obtain a 5 g / L soy protein isolate solution;

[0088] (2) Immerse the pretreated fast-growing poplar wood in the soy protein isolate solution for 1 hour, then rinse repeatedly with deionized water, and dry at 60°C. Repeat the immersion for 5 cycles to obtain the modified wood of this comparative example;

[0089] (3) Plywood was prepared by pressing according to GB / T 9846.7-2015 "Ordinary Plywood" standard. Three layers of plywood were assembled based on the vertical grain. The hot pressing process parameters were: hot pressing temperature of 120°C, pressure of 1.3 MPa, and hot pressing time of 30 min. After hot pressing, the veneer had a certain degree of stickiness, but the stickiness was not enough to prepare plywood, and the veneer could be directly torn off.

[0090] Test Example 1: Flame retardant performance test

[0091] The wood obtained in Examples 1-2 and Comparative Examples 1-2 was subjected to a vertical exposure combustion test. The entire test was timed. An ignition source was applied to the wood so that a flame of about 6 mm covered the top of the wood. The ignition source was removed after 15±1 s. The self-extinguishing time or the combustion process of the wood in Examples 1-2 and Comparative Examples 1-2 was as follows: Figure 1~Figure 4 shown.

[0092] Depend on Figure 1 It can be seen that the wood with flame retardant, hydrophobic and self-adhesive properties prepared in Example 1 is not easy to ignite and extinguishes itself 12.6 seconds after the fire source is removed. Figure 2 It can be seen that the wood with flame retardant, hydrophobic and self-adhesive properties prepared in Example 2 is not easy to ignite and extinguishes itself 11.3 seconds after the fire source is removed. Figure 3 Comparative Example 1 is a modified wood combustion process. It can be seen that the wood that has not been treated with chitosan-soy protein isolate impregnation continues to burn after 15 seconds of ignition. Figure 4It can be seen from the wood burning process of Comparative Example 2 that only the wood modified by chitosan will continue to burn and will not self-extinguish. It can be seen that the modified wood prepared by the present invention is more difficult to ignite than unmodified fast-growing wood, and the flame becomes smaller after the fire source is removed, and self-extinguishing phenomenon occurs after a certain period of time, and the flame retardant performance of the wood is significantly improved. Chitosan and soy protein isolate have high carbon content and both have nitrogen elements. When the modified wood is ignited and thermally decomposed, the film adsorbed by the self-assembly of chitosan and soy protein isolate on the wood surface will preferentially decompose, forming a dense carbon layer while also isolating external heat and combustible gases. At the same time, chitosan and soy protein isolate will decompose N2, NO2 and other non-combustible gases when heated to prevent the combustion of wood.

[0093] Test Example 2: Hydrophobicity Test

[0094] The wood obtained in Examples 1-2 and Comparative Examples 1-2 was subjected to a water contact angle test. The water contact angle test results of Examples 1-2 and Comparative Examples 1-2 are shown in FIG. Figure 5~Figure 8 And as shown in Table 1.

[0095] Table 1

[0096] Test group number Initial water contact angle 60s water contact angle Example 1 114.8° 112.3° Example 2 122.8° 120.9° Comparative Example 1 60.8° 0° Comparative Example 2 101.2° 57.3°

[0097] Depend on Figure 5~Figure 8 As can be seen from Table 1, the modified wood in Example 1 of the present invention has good hydrophobic properties, and its initial water contact angle is 114.8°, and the water contact angle maintained for 60s is 112.3°. The modified wood in Example 2 of the present invention has good hydrophobic properties, and its initial water contact angle is 122.8°, and the water contact angle maintained for 60s is 120.9°. The unmodified fast-growing wood prepared in Comparative Example 1 is hydrophilic, and its contact angle is 60.8°. The hydrophobic properties of the wood modified only by chitosan prepared in Comparative Example 2 are unstable, and the initial contact angle is 101.2°, but after continuous measurement for 60s, the water contact angle of the modified wood is 57.3°, which is hydrophilic. The above results prove that the wood prepared by self-assembly by impregnation of chitosan-soy protein isolate solution has good hydrophobicity, and the preparation process and materials are simple.

[0098] Test Example 3: Gluing Performance Test

[0099] The wood obtained in Examples 3-4 and Comparative Examples 2-3 was tested for gluing performance, and the gluing strength results are shown in Table 2.

[0100] Table 2

[0101] Bonding strength (MPa) Example 3 0.87 Example 4 0.77 Comparative Example 2 none Comparative Example 3 none Class II plywood standard value ≥0.7

[0102] The plywood obtained in Examples 3 and 4 was tested according to the Class II plywood bonding strength test method specified in 4.17 of GB / T 17657-2022 "Test Methods for Physical and Chemical Properties of Artificial Boards and Faced Artificial Boards", and the obtained bonding properties all met the standard values. And the experiment proved that only chitosan or soy protein isolate could not make the wood self-glued into plywood. The wood impregnated with soy protein isolate solution alone has a certain viscosity, but if chitosan solution is used in combination to self-assemble the cation and cation polyelectrolytes, in addition to the electrostatic adsorption force between the two, under high temperature conditions, their functional groups will also interact non-covalently, so that the soy protein isolate molecules and the chitosan molecules form a stable three-dimensional cross-linked network structure, which enhances the bonding force between the veneers. The results show that the present invention provides a flame-retardant, hydrophobic and self-gluing wood and a preparation method thereof, without the need to apply an adhesive separately, and the plywood can be obtained by hot pressing the wood impregnated with chitosan-soy protein isolate solution, and the modified wood has good self-gluing properties.

[0103] In summary, the present invention provides a flame-retardant, hydrophobic and self-adhesive wood and a preparation method thereof. The fast-growing wood is respectively immersed in a chitosan solution with polycations and a soy protein isolate solution with polyanions by layer-by-layer self-assembly impregnation. After drying, the surface of the fast-growing wood forms a hydrophobic flame-retardant surface by electrostatically adsorbing chitosan and soy protein isolate. At the same time, the fast-growing wood veneer is not dried after impregnation, that is, the fast-growing wood veneer is assembled and hot-pressed while keeping the wood surface moist, so that plywood can be obtained. No additional adhesive is required during the preparation process, indicating that it has self-adhesive properties. The preparation process of the present invention is simple, the raw material cost is low, and all of them are biomass raw materials, the safety is high, the equipment used in the preparation process is low, and the texture characteristics of the wood itself are retained after modification, the color is natural and beautiful, and it has highly competitive industrial production feasibility in the field of high-quality multifunctional wood preparation.

Claims

1. A method for preparing wood with flame retardant, hydrophobic and self-adhesive properties, comprising the following steps: S1, dipping or roller coating a fast-growing wood veneer with a chitosan solution, then taking it out, cleaning it, and drying it to obtain a first treated veneer; S2, dipping or roller coating the first treated veneer with the soy protein isolate solution, then taking it out, washing it, and drying it to obtain a second treated veneer; S3, divide the plurality of second processing boards into two groups, respectively according to A-(-BA-) n -B and A-(-BA-) n -BA method to repeat steps S1-S2 to obtain two different types of modified veneers; n is 1-15; S4, two different types of modified veneers are divided into X-(-YX-) m -Y or X- (-YX-) m -YX method for assembling, and then hot pressing to obtain a wood with flame retardant, hydrophobic and self-adhesive properties; m is 0~10.

2. The preparation method according to claim 1, characterized in that: In step S1, the fast-growing wood is cleaned and dried before being immersed in the chitosan solution.

3. The preparation method according to claim 1, characterized in that: In step S1, the concentration of the chitosan solution is 4-6 g / L, and the pH is 3-4; the deacetylation degree of the chitosan used is ≥95%, and the viscosity is 100-200 mPa·s.

4. The preparation method according to claim 1, characterized in that: In step S2, the concentration of the soy protein isolate solution is 1-10 g / L.

5. The preparation method according to claim 1, characterized in that: In steps S1 and S2, the cleaning is performed with water; and the drying temperature is 40-80°C.

6. The preparation method according to claim 1, characterized in that: In step S4, the hot pressing temperature is 100° C. to 130° C., the hot pressing pressure is 1.1 to 1.5 MPa, and the hot pressing time is 30 to 50 min.

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