Formaldehyde-free flame-retardant adhesive, flame-retardant wood board and preparation method

Abstract

The present invention relates to the technical field of artificial boards, and in particular to a formaldehyde-free flame retardant adhesive, a flame retardant wood board and a preparation method. The process comprises the following steps: modification treatment of soybean protein; preparation of a high-viscosity antibacterial cross-linking agent; and current cross-linking and compounding of the adhesive. The present invention prepares a high-strength modifier, and then subsequently carries out a condensation reflux reaction with ammonia water and soybean meal particles. In this process, ammonia molecules act as nucleophiles to attack the carbon atoms in itaconic anhydride in the high-strength modifier, forming intermediates and losing water molecules to generate itaconic acid, thereby increasing the emulsification properties of the high-strength modifier, thereby better polymerizing with soybean meal particles at high temperatures to form nanoparticles with soybean meal particles as cores and high-strength modifiers as shells, and having good uniformity and dispersibility, significantly improving the bonding strength and waterproof properties of the formaldehyde-free flame retardant adhesive when applied to plywood.

Description

Technical Field

[0001] The present invention relates to the technical field of artificial boards, and in particular to a formaldehyde-free flame-retardant adhesive, a flame-retardant wood board and a preparation method thereof. Background Art

[0002] my country is the world's largest producer, consumer and international trader of wood-based panels, with an annual output accounting for more than 50% of the world's total. However, traditional adhesives usually use formaldehyde as a cross-linking agent, which not only pollutes the environment but also poses a potential threat to human health. In order to meet the requirements of low formaldehyde emissions, market demand has prompted the research and development of formaldehyde-free adhesives to gradually receive attention.

[0003] Formaldehyde-free flame-retardant adhesives replace the formaldehyde component in traditional adhesives with environmentally friendly materials such as polyvinyl alcohol, polyurethane, and epoxy resin. These materials not only provide good bonding properties, but can also be combined with flame retardant additives (such as inorganic phosphates, nitrogen compounds, etc.) to effectively improve the flame retardant properties of wood products and extend their service life. However, these environmentally friendly materials are often synthetic resins, most of which are highly dependent on petroleum resources, are non-renewable, and have high production costs.

[0004] Bio-based adhesives are a type of natural polymer adhesive made from degradable or renewable biomass raw materials such as starch, plant protein, tannin and lignin, which are used to replace synthetic resins. They have the advantages of abundant sources and low prices. However, these natural polymer materials often have problems such as poor thermal stability, susceptibility to mold, and poor compatibility with inorganic substances, resulting in poor performance of the prepared adhesives. Summary of the Invention

[0005] In order to solve the above technical defects, the present invention has developed a formaldehyde-free flame retardant adhesive with high bonding strength, good thermal stability and flame retardant effect, and is environmentally friendly and safe. The flame retardant wood board prepared using the formaldehyde-free flame retardant adhesive has excellent bonding strength, bonding stability and flame retardant properties.

[0006] Furthermore, the present application provides a method for preparing an aldehyde-free flame retardant adhesive, comprising the following steps:

[0007] S1: Modification of soy protein

[0008] Divinylbenzene and itaconic anhydride are mixed, isoamyl acetate is added, and the mixture is stirred. Azobisisobutyronitrile is then added and nitrogen is introduced. After heating, the mixture is reacted and centrifuged to obtain a solid. The solid is washed and dried to obtain a high-strength modifier. Soybean meal is ultrafinely ground to obtain soybean meal particles. The high-strength modifier and deionized water are added to a container equipped with a stirring device and a condensing device, and ammonia water is added. After stirring, the soybean meal particles are added, and nitrogen is introduced while stirring. The mixture is then heated and stirred to obtain modified soybean meal.

[0009] S2: Preparation of highly viscous antibacterial crosslinkers

[0010] Titanium acetylacetonate is placed in a container, toluene is added and stirred, then zinc borate powder is added and heated and stirred, and then rotary evaporated to obtain surface-modified zinc borate, and the surface-modified zinc borate and polyethylene-vinyl acetate are placed in a high-speed mixer and heated and stirred to obtain a high-viscosity antibacterial cross-linking agent;

[0011] S3: Current cross-linking compounding of adhesive

[0012] The modified soybean meal, expanded graphite and high-viscosity antibacterial cross-linking agent are mixed evenly, then placed in a container equipped with electrodes, connected to a power supply, and alternately energized and stirred at a fixed frequency to obtain a cross-linked soybean meal. The cross-linked soybean meal, inositol phosphate, sodium alginate and polyamide are mixed and placed in a container, and heated and stirred for a second time to obtain a formaldehyde-free flame retardant adhesive.

[0013] Furthermore, step S1 of modifying the soy protein comprises the following steps:

[0014] S1.1: Divinylbenzene containing 0.1-0.15wt% tert-butylcatechol as a stabilizer and itaconic anhydride are mixed in a container at a mass ratio of 1:(0.8-0.9), and then 2-3 times the mass of isoamyl acetate is added and stirred evenly. Then, 1-2wt% of azobisisobutyronitrile is added and nitrogen is introduced for 25-30 minutes. The mixture is then reacted at 70-75°C for 10-12 hours. After centrifugation, a solid substance is obtained, which is washed 2-3 times with isoamyl acetate and then 2-3 times with petroleum ether. The solid is then dried in a vacuum drying oven at 40-45°C to constant weight to obtain a high-strength modifier.

[0015] S1.2: The soybean meal is placed in an ultrafine grinder and crushed to a particle size of 10-20 μm to obtain soybean meal microparticles. 2-3 parts by weight of a high-strength modifier and 40-50 parts by weight of deionized water are added to a container equipped with a stirring device and a condensing device, and then 0.6-0.9 parts by weight of ammonia water are added. After stirring for 20-30 minutes, 9-12 parts by weight of soybean meal microparticles are added. Nitrogen is bubbled through the mixture while stirring for 20-25 minutes. The temperature is then raised to 60-65°C and stirred at a stirring speed of 200-300 rpm for 2-3 hours to obtain modified soybean meal.

[0016] Furthermore, the preparation of the highly viscous antibacterial cross-linking agent in step S2 comprises the following steps:

[0017] S2.1: Place 0.2-0.3 parts by weight of titanium acetylacetonate in a container, add 6-8 parts by weight of toluene, and stir for 20-30 minutes. Then, add 3-4 parts by weight of zinc borate powder, heat to 40-50°C, and continue stirring for 30-35 minutes. Then, place the container in a rotary evaporator at 70-75°C to evaporate the toluene to obtain surface-modified zinc borate.

[0018] S2.2: Place the surface-modified zinc borate and polyethylene-vinyl acetate in a mass ratio of 1:(20-30) into a high-speed mixer, and stir at 60-65°C and a stirring speed of 180-240 rpm for 1-1.5 hours to obtain a high-viscosity antibacterial cross-linking agent.

[0019] Furthermore, step S3 of current cross-linking and compounding the adhesive comprises the following steps:

[0020] S3.1: Modified soybean meal, expanded graphite, and a high-viscosity antibacterial crosslinking agent are mixed and stirred uniformly in a mass ratio of 1:(0.02-0.03):(0.15-0.2) at a stirring speed of 220-250 rpm. The mixture is then placed in a container and powered on. The voltage is increased at a rate of 3-5 V / min to 25-30 V and maintained thereafter. The power is turned off every 4-6 minutes and stirred for 10-15 seconds. The mixture is then restarted and powered on directly at a voltage of 25-30 V for 25-30 minutes to obtain a crosslinked soybean meal.

[0021] S3.2: Mix 15-20 parts by weight of cross-linked soybean meal, 1-2 parts by weight of inositol phosphate, 0.5-1 parts by weight of sodium alginate and 1-1.2 parts by weight of polyamide in a container, heat to 50-60°C, stir for 0.5-1 hour, then heat to 80-85°C, stir for 1-2 hours to obtain a formaldehyde-free flame retardant adhesive.

[0022] Furthermore, the soybean meal in step S1.2 is the product obtained by hot pressing soybeans to extract oil.

[0023] Furthermore, the vinyl acetate content of the polyethylene vinyl acetate in step S2.2 is 40-45%.

[0024] Furthermore, the container in step S3.1 is a rectangular parallelepiped with a length, width and height of 20 cm, 10 cm and 10 cm respectively, and 316 stainless steel electrodes are installed on the inner walls on both sides, which are respectively connected to the positive and negative poles of the power supply.

[0025] Furthermore, the present application provides a formaldehyde-free flame-retardant adhesive, which is prepared by the above-mentioned method for preparing a formaldehyde-free flame-retardant adhesive.

[0026] Furthermore, the present application provides a flame-retardant wooden board, which includes a substrate and a formaldehyde-free flame-retardant adhesive coated on the upper and lower surfaces of the substrate, the substrate is a poplar veneer, and the formaldehyde-free flame-retardant adhesive is the formaldehyde-free flame-retardant adhesive described in any one of claims 1-7.

[0027] Furthermore, the present application provides a method for preparing a flame-retardant wood board made from the above-mentioned formaldehyde-free flame-retardant adhesive, comprising the following steps:

[0028] Use manual gluing method to apply formaldehyde-free flame retardant adhesive at 200g / m 2 Apply glue to the upper and lower surfaces of the poplar veneer with a certain amount of glue. After the glue is applied, leave it for 8 minutes, then assemble it into embryos with two poplar veneers on the outside and one poplar veneer on the inside, and then place it in a hot press for 10 minutes. The hot pressing temperature is 130℃ and the hot pressing pressure is 1.2MPa. After pressing, cool it down for use.

[0029] The beneficial effects are as follows: 1. The present invention reacts divinylbenzene and itaconic anhydride under the action of an initiator, azobisisobutyronitrile, to obtain a high-strength modifier, and then subsequently performs a condensation reflux reaction with ammonia water and soybean meal particles. In this process, ammonia molecules act as nucleophiles to attack carbon atoms in itaconic anhydride in the high-strength modifier, forming intermediates and losing water molecules to generate itaconic acid, thereby increasing the emulsification performance of the high-strength modifier, thereby better performing a polymerization reaction with soybean meal particles at high temperature, forming nanoparticles with soybean meal particles as cores and the high-strength modifier as shells, and having good uniformity and dispersibility, thereby significantly improving the bonding strength and waterproof performance of the formaldehyde-free flame retardant adhesive when applied to plywood.

[0030] 2. The present invention cross-links modified soybean meal, expanded graphite, and a high-viscosity antibacterial cross-linking agent by mixing them and subjecting them to an electric current. Under the action of the electric current, the active groups of the protein in the modified soybean meal are fully exposed. At the same time, the functional groups of the high-viscosity antibacterial cross-linking agent are also activated by the electric current, generating free radicals that fully undergo cross-linking reactions with the molecular chains of the modified soybean meal and expanded graphite to form a three-dimensional network structure. The resulting cross-linked soybean meal not only has good bonding strength, but also has significantly enhanced thermal stability, thereby significantly improving the dry bonding strength and wet boiling water-resistant bonding strength of the subsequently produced plywood.

[0031] 3. The present invention obtains surface-modified zinc borate by placing zinc borate powder in toluene in which titanium acetylacetonate is dissolved, performing a heat treatment, and then performing a rotary evaporation to remove the toluene, and then mixing the surface-modified zinc borate with polyethylene-vinyl acetate to prepare a high-viscosity antibacterial cross-linking agent. During this process, titanium acetylacetonate first combines with zinc borate to form zinc borate with a functionalized surface, thereby improving the compatibility of zinc borate in organisms, so that zinc borate can fully exert its antibacterial and flame-retardant effects in the formaldehyde-free flame-retardant adhesive, and avoids the decrease in stability of the formaldehyde-free flame-retardant adhesive caused by the subsequent addition of a flame-retardant system mainly composed of phosphoinositide, sodium alginate and polyamide. The obtained formaldehyde-free flame-retardant adhesive has excellent thermal stability, antibacterial properties and flame retardancy. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a flow chart of the preparation method of the formaldehyde-free flame retardant adhesive used in the embodiments of the present invention. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0034] Example 1: A flame retardant adhesive without formaldehyde, a flame retardant wood board and a preparation method thereof, such as Figure 1 As shown, the following steps are included:

[0035] S1: Modification of soy protein

[0036] S1.1: Divinylbenzene containing 0.1 wt% of tert-butylcatechol as a stabilizer and itaconic anhydride are mixed in a mass ratio of 1:0.8 in a container, and then 2 times the mass of isoamyl acetate is added and stirred evenly. Then, 1 wt% of azobisisobutyronitrile is added and nitrogen is introduced for 25 minutes. The mixture is then reacted at 70°C for 10 hours. After centrifugation, a solid substance is obtained, which is washed twice with isoamyl acetate and then twice with petroleum ether. The solid is then dried in a vacuum drying oven at 40°C to constant weight to obtain a high-strength modifier.

[0037] S1.2: The soybean meal after hot pressing and oil extraction is placed in an ultrafine grinder and crushed to a particle size of 10 μm to obtain soybean meal microparticles. 2 parts by weight of a high-strength modifier and 40 parts by weight of deionized water are added to a container equipped with a stirring device and a condensing device, and then 0.6 parts by weight of ammonia water are added. After stirring for 20 minutes, 9 parts by weight of soybean meal microparticles are added. At the same time, nitrogen is bubbled through the mixture while stirring for 20 minutes. Then the temperature is raised to 60°C and stirred at a stirring speed of 200 rpm for 2 hours to obtain modified soybean meal.

[0038] S2: Preparation of highly viscous antibacterial crosslinkers

[0039] S2.1: 0.2 parts by weight of titanium acetylacetonate was placed in a container, 6 parts by weight of toluene was added, and the mixture was stirred for 20 minutes. Then, 3 parts by weight of zinc borate powder was added, and the mixture was heated to 40°C and stirred for 30 minutes. The toluene was then evaporated off in a rotary evaporator at 70°C to obtain surface-modified zinc borate.

[0040] S2.2: Surface-modified zinc borate and polyethylene-vinyl acetate are added into a high-speed mixer at a mass ratio of 1:20, where the vinyl acetate content in the polyethylene-vinyl acetate is 40%. The mixture is stirred at 60°C and a stirring speed of 180 rpm for 1 hour to obtain a high-viscosity antibacterial cross-linking agent.

[0041] S3: Current cross-linking compounding of adhesive

[0042] S3.1: Modified soybean meal, expanded graphite, and a high-viscosity antibacterial crosslinking agent were mixed and stirred at a mass ratio of 1:0.02:0.15 at a stirring speed of 220 rpm. The mixture was then placed in a rectangular container with a length, width, and height of 20 cm, 10 cm, and 10 cm, respectively, and 316 stainless steel electrodes connected to the positive and negative poles of a power supply were installed on the inner walls of both sides. The power was turned on and the voltage was increased at a rate of 3 V / min to 25 V and then maintained. The power was turned off every 4 minutes and stirred for 10 seconds. The mixture was then turned on again and powered on directly at 25 V for 25 minutes to obtain crosslinked soybean meal.

[0043] S3.2: Mix 15 parts by weight of cross-linked soybean meal, 1 part by weight of inositol phosphate, 0.5 part by weight of sodium alginate and 1 part by weight of polyamide in a container, heat to 50°C, stir for 0.5 hour, then heat to 80°C, stir for 1 hour to obtain a formaldehyde-free flame retardant adhesive.

[0044] Based on the formaldehyde-free flame-retardant adhesive prepared by the above-mentioned method for preparing a formaldehyde-free flame-retardant adhesive, the present application provides a flame-retardant wooden board, comprising a substrate and a formaldehyde-free flame-retardant adhesive coated on the upper and lower surfaces of the substrate, wherein the substrate is a poplar veneer; the method for preparing the flame-retardant wooden board comprises the following steps:

[0045] Use manual gluing method to apply formaldehyde-free flame retardant adhesive at 200g / m 2 Apply glue to the upper and lower surfaces of the poplar veneer with a certain amount of glue. After the glue is applied, leave it for 8 minutes, then assemble it into embryos with two poplar veneers on the outside and one poplar veneer on the inside, and then place it in a hot press for 10 minutes. The hot pressing temperature is 130℃ and the hot pressing pressure is 1.2MPa. After pressing, cool it down for use.

[0046] Example 2: A formaldehyde-free flame retardant adhesive, a flame retardant wood board and a preparation method thereof, such as Figure 1 As shown, the following steps are included:

[0047] S1: Modification of soy protein

[0048] S1.1: Divinylbenzene containing 0.15 wt% of tert-butylcatechol as a stabilizer and itaconic anhydride were mixed in a mass ratio of 1:0.9 in a container, and then 3 times the mass of isoamyl acetate was added and stirred evenly. Then, 2 wt% of azobisisobutyronitrile was added and nitrogen was introduced for 25 minutes. The mixture was then reacted at 70°C for 10 hours. After centrifugation, a solid was obtained, which was washed twice with isoamyl acetate and then twice with petroleum ether. The solid was then dried in a vacuum drying oven at 40°C to constant weight to obtain a high-strength modifier.

[0049] S1.2: The soybean meal after hot pressing and oil extraction is placed in an ultrafine grinder and crushed to a particle size of 10 μm to obtain soybean meal microparticles. 3 parts by weight of a high-strength modifier and 50 parts by weight of deionized water are added to a container equipped with a stirring device and a condensing device, and then 0.9 parts by weight of ammonia water are added. After stirring for 20 minutes, 12 parts by weight of soybean meal microparticles are added. At the same time, nitrogen is bubbled through the mixture while stirring for 20 minutes. Then the temperature is raised to 60°C and stirred at a stirring speed of 200 rpm for 2 hours to obtain modified soybean meal.

[0050] S2: Preparation of highly viscous antibacterial crosslinkers

[0051] S2.1: 0.3 parts by weight of titanium acetylacetonate was placed in a container, 8 parts by weight of toluene was added, and the mixture was stirred for 20 minutes. Then, 4 parts by weight of zinc borate powder was added, and the mixture was heated to 40°C and stirred for 30 minutes. The toluene was then evaporated off in a rotary evaporator at 70°C to obtain surface-modified zinc borate.

[0052] S2.2: Surface-modified zinc borate and polyethylene-vinyl acetate are added into a high-speed mixer at a mass ratio of 1:30, where the vinyl acetate content in the polyethylene-vinyl acetate is 45%. The mixture is stirred at 60°C and a stirring speed of 180 rpm for 1 hour to obtain a high-viscosity antibacterial cross-linking agent.

[0053] S3: Current cross-linking compounding of adhesive

[0054] S3.1: Modified soybean meal, expanded graphite, and a high-viscosity antibacterial crosslinking agent were mixed and stirred at a mass ratio of 1:0.03:0.2 at a stirring speed of 220 rpm. The mixture was then placed in a rectangular container with a length, width, and height of 20 cm, 10 cm, and 10 cm, respectively, and 316 stainless steel electrodes connected to the positive and negative poles of a power supply were installed on the inner walls of both sides. The power was turned on and the voltage was increased at a rate of 3 V / min to 25 V and then maintained. The power was turned off every 4 minutes and stirred for 10 seconds. The mixture was then turned on again and powered on directly at 25 V for 25 minutes to obtain crosslinked soybean meal.

[0055] S3.2: Mix 20 parts by weight of cross-linked soybean meal, 2 parts by weight of inositol phosphate, 1 part by weight of sodium alginate and 1.2 parts by weight of polyamide in a container, heat to 50°C, stir for 0.5 hours, then heat to 80°C, stir for 1 hour to obtain a formaldehyde-free flame retardant adhesive.

[0056] Based on the formaldehyde-free flame-retardant adhesive prepared by the above-mentioned method for preparing a formaldehyde-free flame-retardant adhesive, the present application provides a flame-retardant wooden board, comprising a substrate and a formaldehyde-free flame-retardant adhesive coated on the upper and lower surfaces of the substrate, wherein the substrate is a poplar veneer; the method for preparing the flame-retardant wooden board comprises the following steps:

[0057] Use manual gluing method to apply formaldehyde-free flame retardant adhesive at 200g / m 2 Apply glue to the upper and lower surfaces of the poplar veneer with a certain amount of glue. After the glue is applied, leave it for 8 minutes, then assemble it into embryos with two poplar veneers on the outside and one poplar veneer on the inside, and then place it in a hot press for 10 minutes. The hot pressing temperature is 130℃ and the hot pressing pressure is 1.2MPa. After pressing, cool it down for use.

[0058] Example 3: A formaldehyde-free flame retardant adhesive, a flame retardant wood board and a preparation method thereof, such as Figure 1 As shown, the following steps are included:

[0059] S1: Modification of soy protein

[0060] S1.1: Divinylbenzene containing 0.1 wt% tert-butylcatechol as a stabilizer and itaconic anhydride were mixed in a mass ratio of 1:0.8 in a container, and then 2 times the mass of isoamyl acetate was added and stirred evenly. Then, 1 wt% of azobisisobutyronitrile was added and nitrogen was introduced for 30 minutes. The mixture was then reacted at 75°C for 12 hours. After centrifugation, a solid was obtained, which was washed three times with isoamyl acetate and then three times with petroleum ether. The solid was then dried in a vacuum drying oven at 45°C to constant weight to obtain a high-strength modifier.

[0061] S1.2: The soybean meal after hot pressing and oil extraction is placed in an ultrafine grinder and crushed to a particle size of 20 μm to obtain soybean meal microparticles. 2 parts by weight of a high-strength modifier and 40 parts by weight of deionized water are added to a container equipped with a stirring device and a condensing device, and then 0.6 parts by weight of ammonia water are added. After stirring for 30 minutes, 9 parts by weight of soybean meal microparticles are added. At the same time, nitrogen is bubbled through the mixture while stirring for 25 minutes. Then the temperature is raised to 65°C and stirred at a stirring speed of 300 rpm for 3 hours to obtain modified soybean meal.

[0062] S2: Preparation of highly viscous antibacterial crosslinkers

[0063] S2.1: 0.2 parts by weight of titanium acetylacetonate was placed in a container, 6 parts by weight of toluene was added, and the mixture was stirred for 30 minutes. Then, 3 parts by weight of zinc borate powder was added, and the mixture was heated to 50°C and stirred for 35 minutes. The toluene was then evaporated off in a rotary evaporator at 75°C to obtain surface-modified zinc borate.

[0064] S2.2: Surface-modified zinc borate and polyethylene-vinyl acetate are added into a high-speed mixer at a mass ratio of 1:20, where the vinyl acetate content in the polyethylene-vinyl acetate is 40%. The mixture is stirred at 65°C and a stirring speed of 240 rpm for 1.5 hours to obtain a high-viscosity antibacterial cross-linking agent.

[0065] S3: Current cross-linking compounding of adhesive

[0066] S3.1: Modified soybean meal, expanded graphite, and a high-viscosity antibacterial crosslinking agent were mixed and stirred at a mass ratio of 1:0.02:0.15 at a stirring speed of 250 rpm. The mixture was then placed in a rectangular container with a length, width, and height of 20 cm, 10 cm, and 10 cm, respectively, and 316 stainless steel electrodes connected to the positive and negative poles of a power supply were installed on the inner walls of both sides. The power was turned on and the voltage was increased at a rate of 5 V / min to 30 V and then maintained. The power was turned off every 6 minutes and stirred for 15 seconds. The mixture was then turned on again and powered on directly at a voltage of 30 V for 30 minutes to obtain crosslinked soybean meal.

[0067] S3.2: Mix 15 parts by weight of cross-linked soybean meal, 1 part by weight of inositol phosphate, 0.5 part by weight of sodium alginate and 1 part by weight of polyamide in a container, heat to 60°C, stir for 1 hour, then heat to 85°C, stir for 2 hours to obtain a formaldehyde-free flame retardant adhesive.

[0068] Based on the formaldehyde-free flame-retardant adhesive prepared by the above-mentioned method for preparing a formaldehyde-free flame-retardant adhesive, the present application provides a flame-retardant wooden board, comprising a substrate and a formaldehyde-free flame-retardant adhesive coated on the upper and lower surfaces of the substrate, wherein the substrate is a poplar veneer; the method for preparing the flame-retardant wooden board comprises the following steps:

[0069] Use manual gluing method to apply formaldehyde-free flame retardant adhesive at 200g / m 2 Apply glue to the upper and lower surfaces of the poplar veneer with a certain amount of glue. After the glue is applied, leave it for 8 minutes, then assemble it into embryos with two poplar veneers on the outside and one poplar veneer on the inside, and then place it in a hot press for 10 minutes. The hot pressing temperature is 130℃ and the hot pressing pressure is 1.2MPa. After pressing, cool it down for use.

[0070] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 removes step S1.1 and replaces the high-strength modifier in step S1.2 with an equal mass of sodium lauryl sulfate. The remaining steps are the same as Example 1 to produce a flame-retardant wooden board, which is recorded as Comparative Example 1.

[0071] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 eliminates step S3.1, and directly stirs the modified soybean meal, expanded graphite and high-viscosity antibacterial cross-linking agent at a mass ratio of 1:0.02:0.15 at 50°C to obtain cross-linked soybean meal. The remaining steps are the same as in Example 1 to obtain a flame-retardant wooden board, which is recorded as Comparative Example 2.

[0072] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that Comparative Example 3 removes step S2.1 and replaces the surface-modified zinc borate in step S2.2 with zinc borate. The remaining steps are the same as Example 1 to produce a flame-retardant wooden board, which is recorded as Comparative Example 3.

[0073] Experiment 1: The flame-retardant wood boards prepared in the examples and comparative examples 1-3 were tested for performance according to the test requirements of GB / T11718-2009. Before testing, all test samples were allowed to stand for 12 hours in an environment of 20°C and 65% humidity for equilibrium treatment. They were then cut into 5 cm × 5 cm samples and tested using a universal mechanical testing machine for bonding strength (IB), bonding strength (20°C IB) after immersion in 20°C water for 6 hours, and bonding strength (100°C IB) after boiling in boiling water for 2 hours. Three samples were tested for each set of data, and the average value was taken. The data were calculated and recorded and tabulated, as shown in Table 1.

[0074] Table 1: Gluing strength of flame retardant panels

[0075] Bonding strength / MPa IB 20℃IB 100℃IB Example 1 1.91 1.75 1.03 Example 2 1.93 1.77 1.05 Example 3 1.96 1.79 1.08 Comparative Example 1 1.34 1.13 0.21 Comparative Example 2 1.32 1.09 0.25 Comparative Example 3 1.61 2.3 0.33

[0076] As can be seen from Table 1, the bonding strength IB, 20°C IB, and 100°C IB of the flame-retardant wood boards prepared in the examples are all greater than those of comparative examples 1-3. This demonstrates that the preparation of a high-strength modifier and modification of soybean meal particles can significantly enhance the bonding strength and waterproof properties of the formaldehyde-free flame-retardant adhesive when applied to plywood. Furthermore, it is demonstrated that cross-linking the modified soybean meal, expanded graphite, and high-viscosity antibacterial crosslinking agent under an electric current significantly enhances both the dry bonding strength and the wet boiling water-resistant bonding strength of the subsequently prepared plywood. Furthermore, it is demonstrated that the high-viscosity antibacterial crosslinking agent prepared by modifying zinc borate and reacting it with polyethylene-vinyl acetate can enhance the stability of the flame-retardant system, thereby enhancing the bonding properties of the formaldehyde-free flame-retardant adhesive.

[0077] Experiment 2: Take the flame-retardant wood board prepared in Example 3 and Comparative Example 3, and measure the flame retardant performance level of the flame-retardant wood board with reference to GB / T2408-2008, and measure the limiting oxygen index of the flame-retardant wood board with reference to GB / T2406-2008. Repeat the test three times and take the average value. Record the data and make a table, as shown in Table 2. It can be seen that the flame retardant performance and limiting oxygen index of the flame-retardant wood board prepared in Example 3 are greater than those of Comparative Example 3, and a higher performance is achieved.

[0078] Table 2: Flame retardant properties of flame retardant boards

[0079] Flame retardant properties Limiting oxygen index / % Example 1 VTM-0 40 Example 2 VTM-0 41 Example 3 VTM-0 43 Comparative Example 3 VTM-1 31

[0080] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for preparing a formaldehyde-free flame retardant adhesive, characterized in that: The following steps are involved: S1: Modification of soy protein Divinylbenzene and itaconic anhydride are mixed in a mass ratio of 1:(0.8-0.9), azobisisobutyronitrile is added, and nitrogen is introduced to react at a high temperature to obtain a solid material, which is washed and dried to obtain a high-strength modifier, soybean meal is ultrafinely ground to obtain soybean meal particles, 2-3 parts by weight of the high-strength modifier and 40-50 parts by weight of deionized water are mixed, 0.6-0.9 parts by weight of ammonia water are added and stirred, and then 9-12 parts by weight of soybean meal particles are added, the mixture is stirred and bubbling with nitrogen, and then the mixture is heated and stirred to obtain modified soybean meal; S2: Preparation of highly viscous antibacterial crosslinkers 0.2-0.3 parts by weight of titanium acetylacetonate are added to toluene and stirred uniformly, 3-4 parts by weight of zinc borate powder are added, heated and stirred, and then rotary evaporated to obtain surface-modified zinc borate, and the surface-modified zinc borate and polyethylene-vinyl acetate having a vinyl acetate content of 40-45% are added to a high-speed mixer at a mass ratio of 1:(20-30) and heated and stirred to obtain a high-viscosity antibacterial crosslinking agent. S3: Current cross-linking compounding of adhesive The modified soybean meal, expanded graphite and a high-viscosity antibacterial crosslinking agent are uniformly mixed, then placed in a container equipped with electrodes, powered on, and alternately energized and stirred at a fixed frequency to obtain a crosslinked soybean meal. The crosslinked soybean meal, inositol phosphate, sodium alginate and polyamide are mixed in a container and heated and stirred for a second time to obtain a formaldehyde-free flame retardant adhesive. Step S3 specifically includes the following steps: S3.1: Modified soybean meal, expanded graphite and high viscosity antibacterial crosslinking agent are mixed at a ratio of 1: (0.02-0.03): The mixture is stirred evenly at a mass ratio of (0.15-0.2), the stirring speed is set to 220-250 rpm, and then placed in a container, powered on, the voltage is increased at a rate of 3-5 V / min to 25-30 V, and the voltage is maintained, the power is turned off and stirred for 10-15 seconds every 4-6 minutes, and then restarted and powered directly at a voltage of 25-30 V for 25-30 minutes to obtain cross-linked soybean meal; S3.2: Mix 15-20 parts by weight of cross-linked soybean meal, 1-2 parts by weight of inositol phosphate, 0.5-1 parts by weight of sodium alginate and 1-1.2 parts by weight of polyamide in a container, heat to 50-60°C, stir for 0.5-1 hour, then heat to 80-85°C, stir for 1-2 hours to obtain a formaldehyde-free flame retardant adhesive.

2. The method for preparing a formaldehyde-free flame retardant adhesive according to claim 1, wherein: step The modification process of S1 soybean protein includes the following steps: S1.1: Divinylbenzene containing 0.1-0.15wt% of tert-butylcatechol as a stabilizer and itaconic anhydride are mixed in a mass ratio of 1:(0.8-0.9) in a container, and then 2-3 times the mass of isoamyl acetate is added and stirred evenly. Then, 1-2wt% of azobisisobutyronitrile is added and nitrogen is introduced for 25-30 minutes. Then, the mixture is reacted at 70-75°C for 10-12 hours. After centrifugation, a solid substance is obtained, which is washed with isoamyl acetate 2-3 times and then with petroleum ether 2-3 times. Then, the solid is dried in a vacuum drying oven at 40-45°C to constant weight to obtain a high-strength modifier; S1.2: The soybean meal is placed in an ultrafine grinder and crushed to a particle size of 10-20 μm to obtain soybean meal microparticles. 2-3 parts by weight of a high-strength modifier and 40-50 parts by weight of deionized water are added to a container equipped with a stirring device and a condensing device, and then 0.6-0.9 parts by weight of ammonia water are added. After stirring for 20-30 minutes, 9-12 parts by weight of soybean meal microparticles are added. Nitrogen is bubbled through the mixture while stirring for 20-25 minutes. The temperature is then raised to 60-65°C and stirred at a stirring speed of 200-300 rpm for 2-3 hours to obtain modified soybean meal.

3. The method for preparing a formaldehyde-free flame retardant adhesive according to claim 2, characterized in that: step The preparation of S2 high-viscosity antibacterial cross-linking agent comprises the following steps: S2.1: Place 0.2-0.3 parts by weight of titanium acetylacetonate in a container, add 6-8 parts by weight of toluene, and stir for 20-30 minutes. Then, add 3-4 parts by weight of zinc borate powder, heat to 40-50°C, and continue stirring for 30-35 minutes. Then, place the container in a rotary evaporator at 70-75°C to evaporate the toluene to obtain surface-modified zinc borate. S2.2: Place surface-modified zinc borate and polyethylene-vinyl acetate in a mass ratio of 1:(20-30) into a high-speed mixer, stir at 60-65°C and a stirring speed of 180-240 rpm for 1-1.5 hours to obtain a high-viscosity antibacterial crosslinking agent.

4. The method for preparing a formaldehyde-free flame retardant adhesive according to claim 2, wherein: The soybean meal in step S1.2 is the product obtained by hot pressing soybeans to extract oil.

5. The method for preparing a formaldehyde-free flame retardant adhesive according to claim 3, characterized in that: The vinyl acetate content of the polyethylene vinyl acetate in step S2.2 is 40-45%.

6. The method for preparing a formaldehyde-free flame retardant adhesive according to claim 1, characterized in that: The container in step S3.1 is a rectangular parallelepiped with a length, width, and height of 20 cm, 10 cm, and 10 cm, respectively. 316 stainless steel electrodes are installed on the inner walls on both sides, which are connected to the positive and negative poles of the power supply respectively.

7. A formaldehyde-free flame retardant adhesive, characterized in that: The adhesive is prepared by the method for preparing a formaldehyde-free flame retardant adhesive according to any one of claims 1 to 6.

8. A flame retardant wood board, characterized in that: The invention comprises a substrate and an aldehyde-free flame retardant adhesive coated on the upper and lower surfaces of the substrate, wherein the substrate is a poplar veneer and the aldehyde-free flame retardant adhesive is prepared by the preparation method of the aldehyde-free flame retardant adhesive according to any one of claims 1 to 6.

9. A method for preparing the flame-retardant wood board according to claim 8, characterized in that: The following steps are involved: Use manual gluing method to apply formaldehyde-free flame retardant adhesive at 200g / m 2 Apply glue to the upper and lower surfaces of the poplar veneer with a certain amount of glue. After the glue is applied, leave it for 8 minutes, then assemble it into embryos with two poplar veneers on the outside and one poplar veneer on the inside, and then place it in a hot press for 10 minutes. The hot pressing temperature is 130℃ and the hot pressing pressure is 1.2MPa. After pressing, cool it down for use.

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