Waterproof flame-retardant adhesive as well as preparation method and application thereof

Abstract

The invention provides a waterproof flame-retardant adhesive as well as a preparation method and application thereof, and relates to the technical field of adhesives. The adhesive is prepared by mixing amino resin modified by boric acid and a silane coupling agent with magnesium chloride hexahydrate to obtain a modified amino resin inorganic premixed solution, and then adding a gelling agent and a curing agent. According to the adhesive, the water resistance of an adhesive layer is improved, compared with a magnesium oxychloride cement inorganic adhesive, the viscosity, the initial viscosity and the pre-pressing forming speed are remarkably improved, the problems of moisture absorption and halogenation caused by the fact that a magnesium chloride aqueous solution independently enters wood gaps and exists in a free state are solved, and the combustion performance of a prepared artificial board reaches the regulation of GB8624 B-level flame-retardant materials.

Description

Technical Field

[0001] The invention belongs to the technical field of adhesives, and in particular relates to a waterproof and flame-retardant adhesive, a preparation method and an application thereof. Background Art

[0002] In the field of wood processing, the adhesives widely used at present mainly include amino resin adhesives and magnesium oxychloride cement adhesives. Among them, the water resistance of artificial boards produced by amino resin is poor. Under the effects of shrinkage and swelling, outdoor and high humidity environments, the adhesive layer is easily aged and damaged, causing the product to fail, greatly limiting its application environment. At the same time, wood materials themselves are combustible materials, which do not meet the requirements of the combustion performance specifications for indoor and outdoor decoration of public buildings, and are susceptible to biological invasion, decay, mildew, and insect infestation, which has become the main technical difficulty affecting its use in high humidity and outdoor environments. Although flame retardants, preservatives, mildew inhibitors, and insect repellents are usually used to treat wood materials, and then amino resins are used to produce functional artificial boards, these additives will further deteriorate the bonding properties of amino resins, resulting in reduced physical and chemical properties of artificial boards.

[0003] On the other hand, magnesium chloride, magnesium oxide and water are used as bonding materials, and sawdust and the like are used as filling materials to prepare glass magnesium boards, which are widely used in the fields of packaging materials and building decoration. Inorganic adhesives using magnesium oxychloride cement as adhesives are also used in the production of plywood. However, magnesium oxychloride cement has problems such as moisture absorption, brine reversion, and pulverization, and has been listed as a restricted building material. In addition, magnesium oxychloride cement adhesives have poor initial viscosity and a long hydration and curing time, which seriously affects production efficiency. Even if polyurethane-modified styrene-acrylic emulsion, soy protein adhesive, polyacrylamide, etc. are added for modification, the water resistance of the inorganic adhesive plywood produced by the inorganic adhesive plywood is improved compared with the environmentally friendly amino resin adhesive plywood, but it still cannot meet the use requirements of high humidity environments and outdoor environments.

[0004] In summary, the development of a new adhesive and wood-based panel product that can meet the requirements of high humidity and outdoor environment use, and has good fire resistance, corrosion resistance, insect resistance, mildew resistance and other properties, while improving production efficiency has important practical significance and market demand. Summary of the invention

[0005] In view of the technical problems existing in the prior art, the present invention aims to provide a waterproof flame retardant adhesive, a preparation method and application thereof.

[0006] One of the purposes of the present invention is to provide a method for preparing a waterproof flame retardant adhesive, characterized in that the method for preparing the waterproof flame retardant adhesive comprises the following steps: S1 mixes formaldehyde, water and a thickener to obtain a first reaction liquid; S2: adding a mixture of melamine and urea to the first reaction solution three times to react and obtain a second reaction solution; S3: adding boric acid and a silane coupling agent to the second reaction solution to react and obtain a modified amino resin; S4 uniformly mixes the modified amino resin and magnesium chloride hexahydrate to obtain an inorganic premixed liquid of the modified amino resin; S5 adds a curing agent and a gelling agent into the modified amino resin inorganic premixed liquid in sequence to obtain a waterproof and flame-retardant adhesive.

[0007] Preferably, the mass of the thickener is 2-8% of the total mass of the formaldehyde and the water; the mass ratio of the second reaction liquid, boric acid and silane coupling agent is 100:2-5:0.1-1.

[0008] Preferably, the modified amino resin inorganic premix liquid comprises modified amino resin, magnesium chloride and water, and the mass ratio of the modified amino resin, magnesium chloride and water is 1-6:4-8:8-12.

[0009] Preferably, the mass ratio of the modified amino resin inorganic premix, the gelling agent and the curing agent is 100:50-300:0.3-5.0. Preferably, the thickener comprises one or more of alginic acid, sodium alginate, methyl cellulose, carboxymethyl cellulose or starch.

[0010] Preferably, the gelling agent includes one or more of light magnesium oxide, magnesium hydroxide, aluminum oxide, aluminum hydroxide, calcium carbonate or silicon dioxide; and the curing agent includes citric acid and / or phosphoric acid.

[0011] Preferably, the mixture of melamine and urea comprises a first mixture of melamine and urea, a second mixture of melamine and urea and a third mixture of melamine and urea; The molar ratio of the first batch of melamine and urea mixture to formaldehyde is 1:2.05-2.15; the molar ratio of the sum of the first batch of melamine and urea mixture and the second batch of melamine and urea mixture to formaldehyde is 1:1.60-1.75; the molar ratio of the sum of the first batch of melamine and urea mixture, the second batch of melamine and urea mixture and the third batch of melamine and urea mixture to formaldehyde is 1:1.15-1.30.

[0012] The second object of the present invention is to provide a waterproof flame retardant adhesive prepared by the preparation method of the waterproof flame retardant adhesive as described above.

[0013] A third object of the present invention is to provide an application of the waterproof and flame-retardant adhesive as described above on artificial boards.

[0014] Preferably, the artificial board includes waterproof and flame-retardant plywood, and the preparation method of the waterproof and flame-retardant plywood includes: The veneer is impregnated with a flame retardant, and then dried to a moisture content of 8-20%. The veneer is then dried, leveled, and spliced ​​to prepare the required size for production; the flame retardant veneer is coated with a waterproof flame retardant adhesive and assembled; the assembled veneer is placed in a press and pressurized for 48-120 hours to cure the adhesive; the adhesive is fully cured at 30-80°C to evaporate excess moisture; finally, the waterproof flame retardant plywood is prepared after edge trimming, sanding, and inspection; The flame retardant raw materials include amino resin, magnesium chloride, boric acid, borax and water.

[0015] Beneficial effects of the present invention: The invention provides a waterproof flame retardant adhesive, which is prepared by mixing an amino resin modified by boric acid and a silane coupling agent with magnesium chloride hexahydrate to obtain a modified amino resin inorganic premixed liquid, and then adding a gelling agent and a curing agent. The adhesive improves the water resistance of the adhesive layer, and compared with the magnesium oxychloride cement inorganic adhesive, the viscosity, initial viscosity and pre-pressing speed are significantly improved, and the moisture absorption and halogen return problems caused by the magnesium chloride aqueous solution entering the wood gap alone in a free state are reduced, and the combustion performance of the obtained artificial board meets the requirements of GB8624 B-level flame retardant materials. DETAILED DESCRIPTION

[0016] According to a first aspect of the present invention, the present invention provides a method for preparing a waterproof flame retardant adhesive, characterized in that the method for preparing the waterproof flame retardant adhesive comprises the following steps: S1 mixes formaldehyde, water and a thickener to obtain a first reaction liquid; S2: adding a mixture of melamine and urea to the first reaction solution three times to react and obtain a second reaction solution; S3: adding boric acid and a silane coupling agent to the second reaction solution to react and obtain a modified amino resin; S4 uniformly mixes the modified amino resin and magnesium chloride hexahydrate to obtain an inorganic premixed liquid of the modified amino resin; S5 adds a curing agent and a gelling agent into the modified amino resin inorganic premixed liquid in sequence to obtain a waterproof and flame-retardant adhesive.

[0017] In the present invention, the B-OH group in the boric acid reacts with the hydroxyl or amino group of the amino resin to form a stable borate ester bond (BOC) or boron-nitrogen coordination bond. This enhances the crosslinking density of the resin, reduces the exposure of hydrophilic groups (such as free -OH), and reduces the permeability of water molecules. The silane coupling agent is hydrolyzed to form silanol (Si-OH), which reacts with the hydroxyl group of the amino resin to form a Si-OC bond, and at the same time reacts with the Mg in the magnesium chloride hexahydrate. 2+The Si-O-Mg bond is formed, and a Si-O-Si network hydrophobic barrier is constructed at the interface between the resin and magnesium chloride, preventing water from invading the adhesive layer through capillary action. The modified amino resin also wraps the magnesium chloride hexahydrate particles through chemical bonds and physical adsorption, reducing the exposure of free MgCl2, inhibiting its moisture absorption and hydrolysis, and improving the water resistance of the adhesive layer.

[0018] Boric acid reacts with magnesium chloride during the solidification process to form magnesium borate, consuming free Cl and completing the fixation of magnesium chloride. - At the same time, the trace alkaline environment produced by the hydrolysis of the silane coupling agent can inhibit the acidic hydrolysis of MgCl2, reduce the release of HCl, and double inhibit the halogen return phenomenon.

[0019] Silane coupling agent reacts with amino resin to form Si-OC crosslinking, which increases the viscosity of the resin body and provides high shear thinning properties during the coating stage, making it easier to construct; it quickly recovers high viscosity when stationary, enhancing initial adhesion. Magnesium chloride hexahydrate is dispersed in the resin matrix as an inorganic phase, and its crystal structure can be reversibly depolymerized and reorganized under external forces (such as stirring and pressure). It gives the adhesive thixotropy and shear thinning, quickly fills the gaps in the wood during pre-compression, and quickly solidifies and forms after the external force is removed. The gelling agent combines with the resin network through hydrogen bonds to form three-dimensional physical crosslinking points, shortening the gelling time; the curing agent reacts with the active groups of the amino resin to accelerate crosslinking and curing.

[0020] Under high temperature environment, magnesium chloride hexahydrate decomposes under heat to release crystal water, diluting oxygen and combustible gas; boric acid will undergo dehydration reaction when heated, absorb heat, play a cooling role, and reduce the temperature of the material surface. At the same time, the borate formed after dehydration can generate a B2O3 glassy molten layer on the surface of the material, forming a glassy protective film, isolating the transfer of oxygen and heat, preventing the spread of flames, and further improving the flame retardant properties of the material; amino resin carbonization forms an expanded carbon layer (nitrogen-containing gas foaming), which enhances the heat insulation effect; Si-O bonds are converted into Si-C / Si-OC structures at high temperatures, improving the thermal stability of the carbon layer and preventing cracking.

[0021] At the same time, boric acid can improve the mildew and insect resistance of wood materials.

[0022] In the present invention, the viscosity of the modified amino resin is 1000-10000 cp.s and the pH value is 6.5-7.5.

[0023] In a preferred embodiment of the present invention, the mass of the thickener is 2-8% of the total mass of the formaldehyde and the water; the mass ratio of the second reaction liquid, boric acid and silane coupling agent is 100:2-5:0.1-1.

[0024] In the present invention, the silane coupling agent includes silane coupling agent KH550 and / or KH570.

[0025] In a preferred embodiment of the present invention, the modified amino resin inorganic premix liquid comprises modified amino resin, magnesium chloride and water, and the mass ratio of the modified amino resin, magnesium chloride and water is 1-6:4-8:8-12.

[0026] In a preferred embodiment of the present invention, the mass ratio of the modified amino resin inorganic premix, the gelling agent and the curing agent is 100:50-300:0.3-5.0. In a preferred embodiment of the present invention, the mass ratio of the modified amino resin inorganic premix, the gelling agent and the curing agent is 100:100-200:1.0-2.0.

[0027] In a preferred embodiment of the present invention, the thickener includes one or more of alginic acid, sodium alginate, methyl cellulose, carboxymethyl cellulose or starch.

[0028] In a preferred embodiment of the present invention, the gelling agent includes one or more of light magnesium oxide, magnesium hydroxide, aluminum oxide, aluminum hydroxide, calcium carbonate or silicon dioxide; and the curing agent includes citric acid and / or phosphoric acid.

[0029] In a preferred embodiment of the present invention, the gelling agent is light magnesium oxide, magnesium hydroxide, aluminum oxide, aluminum hydroxide, calcium carbonate and silicon dioxide; In the present invention, magnesium oxide reacts with water to generate magnesium hydroxide, which then further reacts with magnesium chloride to generate magnesium oxychloride cement 5Mg(OH)2·MgCl2·8H2O. Adding compounds such as magnesium hydroxide, aluminum oxide, aluminum hydroxide, calcium carbonate, and silicon dioxide can prevent the free magnesium chloride from absorbing moisture and returning to brine, and significantly improve the fireproof performance of wood materials.

[0030] In the present invention, the mass ratio of light magnesium oxide to the composition of magnesium hydroxide, aluminum oxide, aluminum hydroxide, calcium carbonate and silicon dioxide is 20:1-6.

[0031] In a preferred embodiment of the present invention, the mixture of melamine and urea comprises a first mixture of melamine and urea, a second mixture of melamine and urea and a third mixture of melamine and urea; The molar ratio of the first batch of melamine and urea mixture to formaldehyde is 1:2.05-2.15; the molar ratio of the sum of the first batch of melamine and urea mixture and the second batch of melamine and urea mixture to formaldehyde is 1:1.60-1.75; the molar ratio of the sum of the first batch of melamine and urea mixture, the second batch of melamine and urea mixture and the third batch of melamine and urea mixture to formaldehyde is 1:1.15-1.30.

[0032] In the present invention, the preparation method of the waterproof flame retardant adhesive specifically comprises: Mix formaldehyde and water, adjust the pH value to 9.5-10.0, add a thickener, and stir for 25-30 minutes to obtain a first reaction solution; mixing melamine and the urea to obtain a mixture of melamine and urea; Add the first batch of melamine and urea mixture to the first reaction liquid, raise the temperature to 90-94° C. within 40-50 minutes, and keep it for 45-60 minutes; adjust the pH value to 4.8-5.5, and keep it for 30-45 minutes; after adjusting the pH value to 7.5-8.5, add the second batch of melamine and urea mixture, and keep it for 30-60 minutes; finally, add the third batch of melamine and urea mixture, and keep it for 30-60 minutes to obtain a second reaction liquid; When the temperature of the second reaction liquid drops to 60-65°C, boric acid and silane coupling agent are added and stirred for 5-15 minutes to obtain a modified amino resin; After uniformly mixing the modified amino resin and water, magnesium chloride hexahydrate is added to obtain an inorganic premixed liquid of the modified amino resin; The curing agent and the gelling agent are sequentially added into the inorganic premixed liquid of the modified amino resin to obtain a waterproof and flame-retardant adhesive.

[0033] According to a second aspect of the present invention, the present invention provides a waterproof flame retardant adhesive prepared by the method for preparing the waterproof flame retardant adhesive as described above.

[0034] According to a third aspect of the present invention, the present invention provides a use of the waterproof and flame-retardant adhesive as described above on a wood-based panel.

[0035] In a preferred embodiment of the present invention, the artificial board includes a waterproof and flame-retardant plywood, and the preparation method of the waterproof and flame-retardant plywood includes: The veneer is impregnated with a flame retardant, and then dried to a moisture content of 8-20%. The veneer is then dried, leveled, and spliced ​​to prepare the required size for production; the flame retardant veneer is coated with a waterproof flame retardant adhesive and assembled; the assembled veneer is placed in a press and pressurized for 48-120 hours to cure the adhesive; the adhesive is fully cured at 30-80°C to evaporate excess moisture; finally, the waterproof flame retardant plywood is prepared after edge trimming, sanding, and inspection; The flame retardant raw materials include amino resin, magnesium chloride, boric acid, borax and water.

[0036] Example 1 Mix formaldehyde and water, adjust the pH value to 9.5-10.0, add 6% sodium alginate by mass of formaldehyde+water, and stir for 25-30 minutes to obtain a first reaction solution; mixing melamine and the urea to obtain a mixture of melamine and urea; Adding the first batch of melamine and urea mixture to the first reaction liquid, the molar ratio of the first batch of melamine and urea mixture to formaldehyde is 1:2.12, raising the temperature to 90-94°C within 40-50 minutes, and maintaining it for 45-60 minutes; adjusting the pH value to 4.8-5.5, and maintaining it for 30-45 minutes; after adjusting the pH value to 7.5-8.5, adding the second batch of melamine and urea mixture, the molar ratio of the sum of the first batch of melamine and urea mixture and the second batch of melamine and urea mixture to formaldehyde is 1:1.65, and maintaining the reaction for 30-60 minutes; finally adding the third batch of melamine and urea mixture, the molar ratio of the sum of the first batch of melamine and urea mixture, the second batch of melamine and urea mixture and the third batch of melamine and urea mixture to formaldehyde is 1:1.18, and maintaining the reaction for 30-60 minutes to obtain a second reaction liquid; When the second reaction liquid is cooled to 60-65° C., 3% of the mass of the second reaction liquid is added with boric acid and 0.2% of the mass of the second reaction liquid is added with silane coupling agent KH550, and stirred for 5-15 minutes to obtain a modified amino resin; The solid content of the modified amino resin is 60.0%, the viscosity of the resin is 3000cp.s, the water mixing ratio is 6.5 times, and the pH value is 6.5-7.5.

[0037] The modified amino resin and magnesium chloride hexahydrate are uniformly mixed to obtain a modified amino resin inorganic premixed liquid. In the modified amino resin inorganic premixed liquid, the mass ratio of the modified amino resin, magnesium chloride and water is 5.2:36.7:58.1.

[0038] Add 1.5% of the mass of citric acid curing agent to the modified amino resin inorganic premix, stir evenly, and then add 130% of the mass of the modified amino resin inorganic premix to the modified amino resin inorganic premix, the gelling agent includes 85% of light magnesium oxide, aluminum hydroxide, calcium carbonate and silicon dioxide, and the mass ratio of 85% of light magnesium oxide, aluminum hydroxide, calcium carbonate and silicon dioxide is 10:1:1:1, and finally a waterproof flame retardant adhesive is obtained.

[0039] Example 2 Mix formaldehyde and water, adjust the pH value to 9.5-10.0, add 6% of alginic acid based on the mass of formaldehyde and water, and stir for 25-30 minutes to obtain a first reaction solution; mixing melamine and the urea to obtain a mixture of melamine and urea; Adding the first batch of melamine and urea mixture to the first reaction liquid, the molar ratio of the first batch of melamine and urea mixture to formaldehyde is 1:2.12, raising the temperature to 90-94°C within 40-50 minutes, and maintaining it for 45-60 minutes; adjusting the pH value to 4.8-5.5, and maintaining it for 30-45 minutes; after adjusting the pH value to 7.5-8.5, adding the second batch of melamine and urea mixture, the molar ratio of the sum of the first batch of melamine and urea mixture and the second batch of melamine and urea mixture to formaldehyde is 1:1.65, and maintaining the reaction for 30-60 minutes; finally adding the third batch of melamine and urea mixture, the molar ratio of the sum of the first batch of melamine and urea mixture, the second batch of melamine and urea mixture and the third batch of melamine and urea mixture to formaldehyde is 1:1.18, and maintaining the reaction for 30-60 minutes to obtain a second reaction liquid; When the second reaction liquid is cooled to 60-65° C., 3% of the mass of the second reaction liquid is added with boric acid and 0.2% of the mass of the second reaction liquid is added with silane coupling agent KH550, and stirred for 5-15 minutes to obtain a modified amino resin; The solid content of the modified amino resin is 60.0%, the viscosity of the resin is 4000cp.s, the water mixing ratio is 7 times, and the pH value is 6.5-7.5.

[0040] After uniformly mixing the modified amino resin and water, magnesium chloride hexahydrate is added to obtain a modified amino resin inorganic premixed liquid. In the modified amino resin inorganic premixed liquid, the mass ratio of the modified amino resin, magnesium chloride and water is 9.2:36.0:54.7.

[0041] Add 1.5% of the mass of citric acid curing agent to the modified amino resin inorganic premix, stir evenly, and then add 120% of the mass of the modified amino resin inorganic premix to the modified amino resin inorganic premix, the gelling agent includes 85% of light magnesium oxide, magnesium hydroxide, calcium carbonate and silicon dioxide, and the mass ratio of 85% of light magnesium oxide, magnesium hydroxide, calcium carbonate and silicon dioxide is 10:1:1:1, and finally a waterproof flame retardant adhesive is obtained.

[0042] Example 3 Mix formaldehyde and water, adjust the pH value to 9.5-10.0, add 6% methylcellulose by weight of formaldehyde and water, and stir for 25-30 minutes to obtain a first reaction solution; mixing melamine and the urea to obtain a mixture of melamine and urea; Adding the first batch of melamine and urea mixture to the first reaction liquid, the molar ratio of the first batch of melamine and urea mixture to formaldehyde is 1:2.12, raising the temperature to 90-94°C within 40-50 minutes, and maintaining it for 45-60 minutes; adjusting the pH value to 4.8-5.5, and maintaining it for 30-45 minutes; after adjusting the pH value to 7.5-8.5, adding the second batch of melamine and urea mixture, the molar ratio of the sum of the first batch of melamine and urea mixture and the second batch of melamine and urea mixture to formaldehyde is 1:1.68, and maintaining the reaction for 30-60 minutes; finally adding the third batch of melamine and urea mixture, the molar ratio of the sum of the first batch of melamine and urea mixture, the second batch of melamine and urea mixture and the third batch of melamine and urea mixture to formaldehyde is 1:1.18, and maintaining the reaction for 30-60 minutes to obtain a second reaction liquid; When the second reaction liquid is cooled to 60-65° C., 3% of the mass of the second reaction liquid is added with boric acid and 0.2% of the mass of the second reaction liquid is added with silane coupling agent KH550, and stirred for 5-15 minutes to obtain a modified amino resin; The solid content of the modified amino resin is 60.0%, the viscosity of the resin is 4200cp.s, the water mixing ratio is 5 times, and the pH value is 6.5-7.5.

[0043] After uniformly mixing the modified amino resin and water, magnesium chloride hexahydrate is added to obtain a modified amino resin inorganic premixed liquid. In the modified amino resin inorganic premixed liquid, the mass ratio of the modified amino resin, magnesium chloride and water is 14:32.7:53.4.

[0044] Add 1.5% of the mass of citric acid curing agent to the modified amino resin inorganic premix, stir evenly, and then add 115% of the mass of the modified amino resin inorganic premix to the modified amino resin inorganic premix, the gelling agent includes 85% of light magnesium oxide, magnesium hydroxide and aluminum hydroxide, and the mass ratio of 85% of light magnesium oxide, magnesium hydroxide and aluminum hydroxide is 20:1:1, and finally a waterproof flame retardant adhesive is obtained.

[0045] Example 4 Mix formaldehyde and water, adjust the pH value to 9.5-10.0, add 6% carboxymethyl cellulose by weight of formaldehyde and water, and stir for 25-30 minutes to obtain a first reaction solution; mixing melamine and the urea to obtain a mixture of melamine and urea; Adding the first batch of melamine and urea mixture to the first reaction liquid, the molar ratio of the first batch of melamine and urea mixture to formaldehyde is 1:2.12, raising the temperature to 90-94°C within 40-50 minutes, and maintaining it for 45-60 minutes; adjusting the pH value to 4.8-5.5, and maintaining it for 30-45 minutes; after adjusting the pH value to 7.5-8.5, adding the second batch of melamine and urea mixture, the molar ratio of the sum of the first batch of melamine and urea mixture and the second batch of melamine and urea mixture to formaldehyde is 1:1.68, and maintaining the reaction for 30-60 minutes; finally adding the third batch of melamine and urea mixture, the molar ratio of the sum of the first batch of melamine and urea mixture, the second batch of melamine and urea mixture and the third batch of melamine and urea mixture to formaldehyde is 1:1.18, and maintaining the reaction for 30-60 minutes to obtain a second reaction liquid; When the second reaction liquid is cooled to 60-65° C., 3% of the mass of the second reaction liquid is added with boric acid and 0.2% of the mass of the second reaction liquid is added with silane coupling agent KH550, and stirred for 5-15 minutes to obtain a modified amino resin; The solid content of the modified amino resin is 60.0%, the viscosity of the resin is 4800cp.s, the water mixing ratio is 5 times, and the pH value is 6.5-7.5.

[0046] The modified amino resin and magnesium chloride hexahydrate are uniformly mixed to obtain a modified amino resin inorganic premixed liquid. In the modified amino resin inorganic premixed liquid, the mass ratio of the modified amino resin, magnesium chloride and water is 24.0:28.1:47.9.

[0047] Add 1.5% of the phosphoric acid curing agent to the modified amino resin inorganic premix, stir evenly, and then add 115% of the gelling agent to the modified amino resin inorganic premix, the gelling agent includes 85% of light magnesium oxide, magnesium hydroxide, aluminum hydroxide and silicon dioxide, and the mass ratio of 85% of light magnesium oxide, magnesium hydroxide and aluminum hydroxide is 14:1:1:1, and finally a waterproof flame retardant adhesive is obtained.

[0048] Example 5 Mix formaldehyde and water, adjust the pH value to 9.5-10.0, add 6% starch by weight of formaldehyde and water, and stir for 25-30 minutes to obtain a first reaction solution; mixing melamine and the urea to obtain a mixture of melamine and urea; Adding the first batch of melamine and urea mixture to the first reaction liquid, the molar ratio of the first batch of melamine and urea mixture to formaldehyde is 1:2.12, raising the temperature to 90-94°C within 40-50 minutes, and maintaining it for 45-60 minutes; adjusting the pH value to 4.8-5.5, and maintaining it for 30-45 minutes; after adjusting the pH value to 7.5-8.5, adding the second batch of melamine and urea mixture, the molar ratio of the sum of the first batch of melamine and urea mixture and the second batch of melamine and urea mixture to formaldehyde is 1:1.68, and maintaining the reaction for 30-60 minutes; finally adding the third batch of melamine and urea mixture, the molar ratio of the sum of the first batch of melamine and urea mixture, the second batch of melamine and urea mixture and the third batch of melamine and urea mixture to formaldehyde is 1:1.18, and maintaining the reaction for 30-60 minutes to obtain a second reaction liquid; When the second reaction liquid is cooled to 60-65° C., 3% of the mass of the second reaction liquid is added with boric acid and 0.2% of the mass of the second reaction liquid is added with silane coupling agent KH550, and stirred for 5-15 minutes to obtain a modified amino resin; The solid content of the modified amino resin is 60.0%, the viscosity of the resin is 2300 cp.s, the water mixing ratio is 6 times, and the pH value is 6.5-7.5.

[0049] The modified amino resin and magnesium chloride hexahydrate are uniformly mixed to obtain a modified amino resin inorganic premixed liquid. In the modified amino resin inorganic premixed liquid, the mass ratio of the modified amino resin, magnesium chloride and water is 30:23.4:46.6.

[0050] Add 1.5% phosphoric acid curing agent based on the mass of the modified amino resin inorganic premix, stir evenly, and then add 55% gelling agent based on the mass of the modified amino resin inorganic premix to the modified amino resin inorganic premix, the gelling agent includes 85% light magnesium oxide and silicon dioxide, and the mass ratio of 85% light magnesium oxide and silicon dioxide is 10:1, and finally a waterproof flame retardant adhesive is obtained.

[0051] Comparative Example 1 The modified amino resin was prepared in the same manner as in Example 1.

[0052] 1.5% of the mass of the modified amino resin and 85% of the phosphoric acid curing agent were added, stirred evenly, and then 25% of the mass of the modified amino resin flour was added to the modified amino resin to finally obtain a waterproof flame retardant adhesive.

[0053] Example 2 Magnesium chloride hexahydrate and water are stirred evenly, the mass ratio of magnesium chloride hexahydrate to water is 3:2, and then light magnesium oxide is added, the mass of the light magnesium oxide is the same as the total mass of magnesium chloride hexahydrate and water, and stirred evenly to obtain a waterproof flame retardant adhesive.

[0054] Performance Testing The waterproof and flame-retardant adhesives of Examples 1 to 5 and Comparative Examples 1 to 2 were used to prepare plywood according to the following process: The poplar wood core board is impregnated with a flame retardant, and the flame retardant raw materials include amino resin, magnesium chloride, boric acid, borax and water. The poplar wood core board is then dried to a moisture content of 8-20%, and then the poplar wood core board is dried, leveled, and spliced ​​to prepare the size required for production; Apply glue to the poplar core board with a glue amount of 400g / ㎡ (double-sided); assemble the blanks, with the upper and lower surfaces being un-glued poplar technical wood; send the assembled blanks to the pre-pressing machine for pre-pressing, with a unit pressure of 0.70-0.90MPa, and pre-pressing for 24-48h; hot-press the pre-pressed plywood, with a hot-pressing temperature of 50±5℃ and a hot-pressing time of 120 minutes; sand and inspect to prepare the plywood.

[0055] The plywood was subjected to Class II and Class I bonding strength tests, boiling-freezing-drying cycle tests, combustion performance, anticorrosion performance, insect resistance and mildew resistance tests. The test results are shown in Table 1.

[0056] Test standard: Class II bonding strength: According to clause 4.17.5.2.2 of GB / T 17657 “Test methods for physical and chemical properties of wood-based panels and veneered wood-based panels”, immerse the test piece in (63±3)℃ for 3h, then cool it at room temperature for 10min to test the bonding strength.

[0057] Class I bonding strength: According to GB / T 17657 "Test methods for physical and chemical properties of wood-based panels and veneer wood-based panels", the bonding strength is tested according to the requirements of Class I plywood. The test piece is immersed in boiling water for 4 hours, then dried in an oven at (63±3)℃ for 20 hours, immersed in boiling water for 4 hours, and then immersed in water at (22±2)℃ for 1 hour to test the bonding strength.

[0058] Boiling-freezing-drying cycle test: immerse the specimen in boiling water for 24 hours, take it out and freeze it at -18℃ for 24 hours, and dry it in an oven at (70±2)℃ to constant weight. Repeat 7 times and observe whether the adhesive layer of the specimen has cracks.

[0059] Combustion performance: Tested in accordance with GB8624 “Combustion performance classification of building materials and products”.

[0060] Anti-corrosion performance: Tested in accordance with GB / T 13942.1 "Durability of wood - Part 1: Laboratory test method for natural corrosion resistance".

[0061] Insect-proof performance: Tested in accordance with GBT 18260 "Laboratory test method for the toxicity of wood preservatives to termites".

[0062] Anti-mildew performance: tested according to LYT2230 "Evaluation of Anti-mildew Performance of Artificial Boards".

[0063] Table 1 Plywood performance test

[0064] Compared with Comparative Examples 1 and 2, Examples 1 to 5 use amino resin modified by boric acid and silane coupling agent mixed with magnesium chloride hexahydrate to obtain a modified amino resin inorganic premix, and then add a gelling agent and a curing agent to prepare a waterproof flame retardant adhesive with significantly improved Class II bonding strength and Class I bonding strength, greatly enhanced water resistance, and greatly improved flame retardancy, corrosion resistance, insect resistance and mildew resistance.

Claims

1. A method for preparing a waterproof flame retardant adhesive, characterized in that: The preparation method of the waterproof flame retardant adhesive comprises the following steps: S1 mixes formaldehyde, water and a thickener to obtain a first reaction liquid; S2: adding a mixture of melamine and urea to the first reaction solution three times to react and obtain a second reaction solution; S3: adding boric acid and a silane coupling agent to the second reaction solution to react and obtain a modified amino resin; S4 uniformly mixes the modified amino resin and magnesium chloride hexahydrate to obtain an inorganic premixed liquid of the modified amino resin; S5 adds a curing agent and a gelling agent into the modified amino resin inorganic premixed liquid in sequence to obtain a waterproof and flame-retardant adhesive.

2. The method for preparing the waterproof flame retardant adhesive according to claim 1, characterized in that: The mass of the thickener is 2-8% of the total mass of the formaldehyde and the water; the mass ratio of the second reaction liquid, the boric acid and the silane coupling agent is 100:2-5:0.1-1.

3. The method for preparing the waterproof flame retardant adhesive according to claim 1, characterized in that: The modified amino resin inorganic premixed liquid comprises modified amino resin, magnesium chloride and water, and the mass ratio of the modified amino resin, magnesium chloride and water is 1-6:4-8:8-12.

4. The method for preparing the waterproof flame retardant adhesive according to claim 1, characterized in that: The mass ratio of the modified amino resin inorganic premix, the gelling agent and the curing agent is 100:50-300:0.3-5.

0.

5. The method for preparing the waterproof flame retardant adhesive according to claim 1, characterized in that: The thickener includes one or more of alginic acid, sodium alginate, methyl cellulose, carboxymethyl cellulose or starch.

6. The method for preparing the waterproof flame retardant adhesive according to claim 1, characterized in that: The gelling agent includes one or more of light magnesium oxide, magnesium hydroxide, aluminum oxide, aluminum hydroxide, calcium carbonate or silicon dioxide; the curing agent includes citric acid and / or phosphoric acid.

7. The method for preparing the waterproof flame-retardant adhesive according to claim 1, characterized in that: The mixture of melamine and urea comprises a first mixture of melamine and urea, a second mixture of melamine and urea and a third mixture of melamine and urea; The molar ratio of the first batch of melamine and urea mixture to the formaldehyde is 1:2.05-2.15; the molar ratio of the sum of the first batch of melamine and urea mixture and the second batch of melamine and urea mixture to the formaldehyde is 1:1.60-1.75; the molar ratio of the sum of the first batch of melamine and urea mixture, the second batch of melamine and urea mixture and the third batch of melamine and urea mixture to the formaldehyde is 1:1.15-1.

30.

8. A waterproof flame retardant adhesive prepared by the method for preparing the waterproof flame retardant adhesive according to claims 1 to 7.

9. Use of the waterproof and flame-retardant adhesive as claimed in claim 8 on artificial boards.

10. The use according to claim 9, characterized in that The artificial board includes a waterproof and flame-retardant plywood, and the preparation method of the waterproof and flame-retardant plywood includes: The veneer is impregnated with a flame retardant, and then dried to a moisture content of 8-20%. The veneer is then dried, leveled, and spliced ​​to prepare the required size for production; the flame retardant veneer is coated with a waterproof flame retardant adhesive and assembled; the assembled veneer is placed in a press and pressurized for 48-120 hours to cure the adhesive; the adhesive is fully cured at 30-80°C to evaporate excess moisture; finally, the waterproof flame retardant plywood is prepared after edge trimming, sanding, and inspection; The flame retardant raw materials include amino resin, magnesium chloride, boric acid, borax and water.

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