Preparation method and application of water-resistant fireproof adhesive for wood-based panels

Abstract

This invention relates to the technical field of adhesives, and discloses a method for preparing and applying a water-resistant and fire-retardant adhesive for wood-based panels, comprising the following steps: S1: Modifying titanium dioxide using a titanate coupling agent or a phosphate coupling agent to obtain hydrophobically modified titanium dioxide; S2: Dissolving urea in phosphoric acid, adding soluble starch and heating to react, then drying to obtain starch ammonium phosphate; S3: Mixing and stirring epoxy resin, epoxy resin curing agent, terminal epoxy silicone oil, hydrophobically modified titanium dioxide, starch ammonium phosphate, ammonium polyphosphate and ethyl acetate to obtain a water-resistant and fire-retardant adhesive. This invention optimizes each component to better suit the epoxy resin system, achieving the construction of a multi-component synergistic functional coating system. The components exhibit good compatibility and dispersibility, significantly improving overall adhesion, water resistance, durability, and coating density, while also possessing good flame retardancy.

Description

Technical Field

[0001] This invention relates to the technical field of adhesives, and in particular to a method for preparing and applying a water-resistant and fire-retardant adhesive for wood-based panels. Background Technology

[0002] Currently, mainstream adhesives for boards are mainly divided into two categories: traditional resin-based and modified functional adhesives. Traditional products, centered on urea-formaldehyde resin, phenolic resin, and amino resin, are widely used in the production of low- to mid-range boards due to their low cost and good initial bonding properties, but they have significant performance defects. With the improvement of environmental protection and safety standards, modified adhesives such as epoxy resin and acrylate are gradually becoming the preferred choice in high-end fields. Their bonding strength and weather resistance are significantly better than traditional products, and they have better transparency, making them suitable for the decorative needs of various substrates such as wood, metal, and composite boards. However, modern boards not only need to meet the basic requirement of strong bonding, but also face multiple environmental challenges. The boards need to resist long-term moisture erosion without delamination or deformation, and they also need to have fire-retardant properties while retaining the original texture and color of the board, avoiding the "whitening and haziness" problems of traditional flame-retardant coatings.

[0003] The water resistance defects of existing board adhesives mainly stem from two major problems: "weak interfacial bonding" and "poor internal hydrophobicity." Even after epoxy resin adhesives cure, the resulting coating still contains micropores, allowing moisture to penetrate to the interface through capillary action and disrupt the chemical bond between the adhesive and the substrate. These problems are even more pronounced in environments with alternating humidity and heat, often resulting in blistering, cracking, and excessive weight loss, significantly shortening the board's service life. In addition, fire-retardant modification of boards is mainly achieved by adding flame retardants. Patent CN107722904A discloses an epoxy adhesive comprising a first component and a second component, with a weight ratio of 10:(3~6). The first component, by weight, contains: 100 parts epoxy resin; 150 to 1500 parts thermally conductive filler; 20 to 100 parts flame-retardant filler; and 1 to 3 parts coupling agent. The second component, by weight, contains: 100 parts epoxy curing agent; 100 to 1500 parts thermally conductive filler; 20 to 100 parts flame-retardant filler; and 1 to 3 parts coupling agent. However, when inorganic flame retardants (flame-retardant fillers) are used, their compatibility with organic adhesives is extremely poor, easily agglomerating into micron-sized particles, thus affecting the coating's transparency and water resistance. Furthermore, when using a single phosphorus-based flame retardant, due to the lack of synergistic effect of nitrogen, most flame retardants can only catalyze the formation of a loose char layer, resulting in limited flame retardant efficiency. The only way to meet the standard is to increase the amount added, but high amounts will lead to decreased coating adhesion and increased brittleness. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing and applying a water-resistant and fire-retardant adhesive for wood-based panels. By optimizing each component to better suit the epoxy resin system, a multi-component synergistic functional coating system is constructed. The components exhibit good compatibility and dispersibility, significantly improving overall adhesion, water resistance, durability, and coating density, while also possessing good flame retardancy.

[0005] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for preparing a water-resistant and fire-retardant adhesive for wood-based panels, comprising the following steps: S1: Titanium dioxide is modified with titanate coupling agent or phosphate coupling agent to obtain hydrophobic modified titanium dioxide. S2: Urea is dissolved in phosphoric acid, soluble starch is added and heated to react, and then dried to obtain starch ammonium phosphate ester; S3: Epoxy resin, epoxy resin curing agent, terminal epoxy silicone oil, hydrophobically modified titanium dioxide, starch ammonium phosphate, ammonium polyphosphate and ethyl acetate are mixed and stirred in a mass ratio of 1:0.2-0.3:0.2-0.4:0.03-0.07:0.3-0.6:0.1-0.3:0.1-0.3 to prepare a water-resistant and fire-retardant adhesive.

[0006] The adhesive in this invention uses an epoxy resin bonding system. Epoxy resin molecules contain epoxy groups, which can undergo ring-opening reactions with the hydroxyl and amino groups on the surface of the board to form stable chemical bonds and interfacial bonds. By adding ammonium starch phosphate and ammonium polyphosphate as flame retardants, phosphorus and nitrogen elements can be synergistically supplemented, catalyzing the dehydration and carbonization of the epoxy resin, while releasing inert gases to dilute combustible gases, thus providing gas-phase inerting to assist in flame retardancy. Simultaneously, the added terminal epoxy silicone oil decomposes at high temperatures to form a siloxane protective layer, covering the surface of the carbon layer and preventing its collapse, thereby achieving a triple synergistic flame retardancy of phosphorus, nitrogen, and silicon, improving the fireproof effect. Modified titanium dioxide can also be used as an inorganic heat-resistant material to increase the thermal conductivity resistance of the carbon layer and extend the insulation time.

[0007] Furthermore, each component contributes to improving the adhesive's bonding strength and water resistance. The starch skeleton in starch ammonium phosphate contains multiple hydroxyl groups, which form hydrogen bonds with the epoxy resin, enhancing the coating's internal cohesion. After curing with a curing agent, the epoxy resin forms a three-dimensional cross-linked network. Combined with hydrophobically modified titanium dioxide filling the tiny voids in the coating, the coupling agent on it strengthens the interfacial bonding between the inorganic filler and the organic resin, further improving the coating's density. The epoxy end groups of the terminal epoxy group silicone oil can undergo ring-opening copolymerization with the epoxy groups of the epoxy resin and the amino groups of the curing agent, forming covalent bonds that anchor the siloxane chains within the three-dimensional cross-linked network of the epoxy resin. The long-chain siloxane groups can form a hydrophobic film on the coating surface, preventing water wetting and penetration, resulting in stronger water resistance and durability of the adhesive. The addition of ethyl acetate reduces the system's viscosity, facilitating the control of the coating system's flowability to meet the requirements of roller coating. Its volatility also increases the coating's drying rate.

[0008] Therefore, by optimizing each component to better suit the epoxy resin system, the present invention achieves the construction of a multi-component synergistic functional coating system. The components have good compatibility and dispersibility, and the overall adhesion, water resistance and durability and coating density are significantly improved, while also having good flame retardancy.

[0009] Preferably, in S1, the amount of the titanate coupling agent or phosphate coupling agent is 10-15% of the mass of titanium dioxide.

[0010] Titanate / phosphate coupling agents exhibit higher reactivity with the hydroxyl groups on the TiO2 surface than silane coupling agents, resulting in stronger titanium-oxygen / phospho-oxygen bonds. Simultaneously, the organic ends of the coupling agent synergistically bond with the crosslinking network of epoxy resin and terminal epoxy-based silicone oil. Phosphate coupling agents contain phosphorus, and at high temperatures, they can synergistically catalyze char formation with ammonium starch phosphate and ammonium polyphosphate, further enhancing the flame-retardant effect of the condensed phase.

[0011] Preferably, the specific steps of S1 include: dispersing titanium dioxide powder in an ethanol solution, ultrasonically dispersing it, adding a titanate coupling agent or a phosphate coupling agent, adjusting the pH to 4-5, and heating the reaction; after the reaction is completed, centrifuging and drying are performed to obtain hydrophobically modified titanium dioxide.

[0012] Preferably, the titanium dioxide powder has a particle size of 10-100 nm; the temperature of the heating reaction is 70-90℃, and the reaction time is 3-5 h.

[0013] Preferably, the ethanol solution contains 80-90% ethanol by mass.

[0014] Preferably, the pH is adjusted to 4-5 using an acid solution; the acid solution includes one or more of acetic acid, citric acid, and oxalic acid.

[0015] Preferably, in S2, the molar ratio of urea to phosphoric acid is 1.3-1.8:1; and the mass ratio of urea to soluble starch is 1:0.5-1.

[0016] Preferably, in S2, the temperature of the heating reaction is 120-140°C and the reaction time is 30-40 min.

[0017] Preferably, in step S2, the drying temperature is 140-160°C and the reaction time is 40-70 min.

[0018] Secondly, the present invention also provides the application of a water-resistant and fire-retardant adhesive in wood-based panels.

[0019] As a preferred option, this includes: using a water-resistant and fire-retardant adhesive at a concentration of 150-250 g / m³. 2 The coating amount is applied to the surface of the board and dried at 70-80℃ for 0.3-0.5 h.

[0020] Compared with the prior art, the present invention has the following beneficial effects: (1) Starch ammonium phosphate and polyphosphate ammonium are used as dual phosphorus sources to supplement phosphorus content. Combined with terminal epoxy silicone oil and titanium dioxide, the carbon layer is more dense, resistant to high temperature collapse, and has a longer flame retardant time. At the same time, it avoids the problem of uneven dispersion that may occur with a single flame retardant. (2) After the epoxy resin is cured by the curing agent, it forms a three-dimensional cross-linked network. In addition, the covalent bonding between the components and the titanium dioxide filling make the coating more compact, so that the adhesive can form a more stable interface bond with the board surface and the bonding strength is higher. (3) The surface energy of the hydrophobic siloxane film formed by the epoxy-terminated silicone oil is lower, and it has good compatibility with epoxy resin, no risk of migration, better water resistance and durability, and the dense coating formed further blocks water penetration and has more stable resistance to damp heat. (4) Titanium dioxide itself has certain UV aging resistance properties. Combined with the weather resistance of silicone oil, the coating is not easy to age or crack in outdoor environments, making it more suitable for a wider range of scenarios. (5) The adhesive can achieve good bonding performance, water resistance and fire resistance under low coating conditions, thereby saving material costs, reducing energy consumption and making construction more convenient. Detailed Implementation

[0021] The technical solution of the present invention will be illustrated below with specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0022] The preparation method of the water-resistant and fire-retardant adhesive for wood-based panels in this invention includes the following steps: S1: Titanium dioxide powder with a particle size of 10-100 nm is dispersed in an ethanol solution (the mass fraction of ethanol in the ethanol solution is 80-90%). After ultrasonic dispersion, a titanate coupling agent or a phosphate coupling agent is added. The amount of titanate coupling agent or phosphate coupling agent is 10-15% of the mass of titanium dioxide powder. The pH is adjusted to 4-5 using an acid solution (the acid solution includes one or more of acetic acid, citric acid and oxalic acid). The temperature is raised to 70-90℃ and reacted for 3-5 hours. After the reaction is completed, the mixture is centrifuged and dried to obtain hydrophobically modified titanium dioxide. S2: Mix urea and phosphoric acid in a molar ratio of 1.3-1.8:1, heat to 80-90℃, reflux until urea is completely dissolved, add soluble starch in batches with a mass ratio of soluble starch to urea of ​​0.5-1:1, stir and heat to 120-140℃, react for 30-40 min, transfer the mixture to an oven and dry at 140-160℃ for 40-70 min, the resulting solid is ground and sieved to obtain starch ammonium phosphate ester; S3: Epoxy resin, epoxy resin curing agent, terminal epoxy silicone oil, hydrophobically modified titanium dioxide, starch ammonium phosphate, ammonium polyphosphate and ethyl acetate are mixed and stirred in a mass ratio of 1:0.2-0.3:0.2-0.4:0.03-0.07:0.3-0.6:0.1-0.3:0.1-0.3 to prepare a water-resistant and fire-retardant adhesive.

[0023] In a specific embodiment of the present invention, the epoxy resin is a bisphenol A type epoxy resin or a bisphenol F type epoxy resin.

[0024] In a specific embodiment of the present invention, the epoxy resin curing agent is one or more of diethylenetriamine, triethylenetetramine, and dipropylenetriamine.

[0025] In a specific embodiment of the present invention, the average molecular weight of the terminal epoxy group silicone oil is 10,000-20,000.

[0026] The water-resistant and fire-retardant adhesive prepared by the above method is applied at a concentration of 150-250 g / m³. 2 The coating amount is applied to the surface of the board and dried at 70-80℃ for 0.3-0.5 h to obtain a water-resistant and fire-retardant modified board.

[0027] Example 1 The preparation method of the water-resistant and fire-retardant adhesive includes the following steps: S1: Titanium dioxide powder with an average particle size of 30 nm was dispersed in an ethanol solution (the ethanol solution contained 90% ethanol by mass). After ultrasonic dispersion, a titanium dioxide solution with a mass fraction of 6% was obtained. A titanate coupling agent was added to the titanium dioxide solution, with the amount of titanate coupling agent being 11% of the mass of the titanium dioxide powder. The pH was adjusted to 4 using acid solution (acetic acid), and the temperature was raised to 70℃ for 5 hours. After the reaction was completed, the mixture was centrifuged, precipitated, washed, and dried to obtain hydrophobically modified titanium dioxide. S2: Weigh 9.8 kg of phosphoric acid and 7.8 kg of urea (molar ratio of phosphoric acid to urea is 1:1.3) and add them to the reactor. Heat to 80°C, reflux and cool until the urea is completely dissolved. Add 3.9 kg of soluble starch (mass ratio of soluble starch to urea is 0.5:1) in batches, stir and heat to 120°C. After reacting for 40 min, transfer the mixture to an oven and dry at 140°C for 70 min. The resulting solid is ground and sieved to obtain starch ammonium phosphate. S3: Bisphenol A type epoxy resin, epoxy resin curing agent, terminal epoxy silicone oil, hydrophobically modified titanium dioxide, starch ammonium phosphate, ammonium polyphosphate and ethyl acetate are mixed and stirred in a mass ratio of 1:0.2:0.4:0.03:0.3:0.1:0.1 to prepare a water-resistant and fireproof adhesive.

[0028] The water-resistant and fire-retardant adhesive prepared by the above method is applied at a concentration of 250 g / m³. 2 The coating amount was applied to the surface of the board and dried at 70℃ for 0.5 h to obtain a water-resistant and fire-retardant modified board.

[0029] Example 2 The preparation method of the water-resistant and fire-retardant adhesive includes the following steps: S1: Titanium dioxide powder with an average particle size of 30 nm was dispersed in an ethanol solution (the mass fraction of ethanol in the ethanol solution was 80%). After ultrasonic dispersion, a titanium dioxide solution with a mass fraction of 6% was obtained. A titanate coupling agent was added to the titanium dioxide solution, and the amount of titanate coupling agent was 15% of the mass of titanium dioxide powder. The pH was adjusted to 5 with acid solution (acetic acid), and the temperature was raised to 85℃ for 3 hours. After the reaction was completed, the mixture was centrifuged, precipitated, washed, and dried to obtain hydrophobically modified titanium dioxide. S2: Weigh 9.8 kg of phosphoric acid and 10.8 kg of urea (molar ratio of phosphoric acid to urea is 1:1.8) and add them to the reaction vessel. Heat to 90°C, reflux and cool until the urea is completely dissolved. Add 10.8 kg of soluble starch (mass ratio of soluble starch to urea is 1:1) in batches, stir and heat to 140°C. After reacting for 40 min, transfer the mixture to an oven and dry at 160°C for 50 min. The resulting solid is ground and sieved to obtain starch ammonium phosphate. S3: Bisphenol A type epoxy resin, epoxy resin curing agent, terminal epoxy silicone oil, hydrophobically modified titanium dioxide, starch ammonium phosphate, ammonium polyphosphate and ethyl acetate are mixed and stirred in a mass ratio of 1:0.3:0.4:0.06:0.5:0.1:0.2 to prepare a water-resistant and fireproof adhesive.

[0030] The water-resistant and fire-retardant adhesive prepared by the above method is applied at a concentration of 180 g / m³. 2 The coating amount was applied to the surface of the board and dried at 80℃ for 0.3 h to obtain a water-resistant and fire-retardant modified board.

[0031] Example 3 The preparation method of the water-resistant and fire-retardant adhesive includes the following steps: S1: Titanium dioxide powder with an average particle size of 30 nm was dispersed in an ethanol solution (the ethanol solution contained 90% ethanol by mass). After ultrasonic dispersion, a titanium dioxide solution with a mass fraction of 6% was obtained. A phosphate coupling agent was added to the titanium dioxide solution, with the amount of phosphate coupling agent being 12% of the mass of titanium dioxide powder. The pH was adjusted to 4 using acid solution (acetic acid), and the temperature was raised to 80℃ for 4 hours. After the reaction was completed, the mixture was centrifuged, precipitated, washed, and dried to obtain hydrophobically modified titanium dioxide. S2: Weigh 9.8 kg of phosphoric acid and 9 kg of urea (molar ratio of phosphoric acid to urea is 1:1.5) and add them to the reaction vessel. Heat to 90°C, reflux and cool until the urea is completely dissolved. Add 8 kg of soluble starch (mass ratio of soluble starch to urea is 0.89:1) in batches, stir and heat to 130°C. After reacting for 35 min, transfer the mixture to an oven and dry at 150°C for 60 min. The resulting solid is ground and sieved to obtain starch ammonium phosphate. S3: Bisphenol A type epoxy resin, epoxy resin curing agent, terminal epoxy silicone oil, hydrophobically modified titanium dioxide, starch ammonium phosphate, ammonium polyphosphate and ethyl acetate are mixed and stirred in a mass ratio of 1:0.2:0.2:0.05:0.4:0.3:0.3 to prepare a water-resistant and fireproof adhesive.

[0032] The water-resistant and fire-retardant adhesive prepared by the above method is applied at a concentration of 200 g / m³. 2 The coating amount was applied to the surface of the board and dried at 70℃ for 0.5 h to obtain a water-resistant and fire-retardant modified board.

[0033] Example 4 The preparation method of the water-resistant and fire-retardant adhesive includes the following steps: S1: Titanium dioxide powder with an average particle size of 30 nm was dispersed in an ethanol solution (the ethanol solution contained 90% ethanol by mass). After ultrasonic dispersion, a titanium dioxide solution with a mass fraction of 6% was obtained. A phosphate coupling agent was added to the titanium dioxide solution, with the amount of phosphate coupling agent being 12% of the mass of titanium dioxide powder. The pH was adjusted to 4 using acid solution (acetic acid), and the temperature was raised to 80℃ for 4 hours. After the reaction was completed, the mixture was centrifuged, precipitated, washed, and dried to obtain hydrophobically modified titanium dioxide. S2: Weigh 9.8 kg of phosphoric acid and 9 kg of urea (molar ratio of phosphoric acid to urea is 1:1.5) and add them to the reaction vessel. Heat to 90°C, reflux and cool until the urea is completely dissolved. Add 9 kg of soluble starch (mass ratio of soluble starch to urea is 1:1) in batches, stir and heat to 140°C. After reacting for 40 min, transfer the mixture to an oven and dry at 150°C for 60 min. The resulting solid is ground and sieved to obtain starch ammonium phosphate. S3: Bisphenol A type epoxy resin, epoxy resin curing agent, terminal epoxy silicone oil, hydrophobically modified titanium dioxide, starch ammonium phosphate, ammonium polyphosphate and ethyl acetate are mixed and stirred in a mass ratio of 1:0.2:0.2:0.06:0.5:0.3:0.3 to prepare a water-resistant and fireproof adhesive.

[0034] The water-resistant and fire-retardant adhesive prepared by the above method is applied at a concentration of 200 g / m³. 2 The coating amount was applied to the surface of the board and dried at 70℃ for 0.5 h to obtain a water-resistant and fire-retardant modified board.

[0035] Comparative Example 1 The difference from Example 1 is that ammonium polyphosphate was not added.

[0036] The preparation method of the water-resistant and fire-retardant adhesive includes the following steps: S1: Titanium dioxide powder with an average particle size of 30 nm was dispersed in an ethanol solution (the ethanol solution contained 90% ethanol by mass). After ultrasonic dispersion, a titanium dioxide solution with a mass fraction of 6% was obtained. A titanate coupling agent was added to the titanium dioxide solution, with the amount of titanate coupling agent being 11% of the mass of the titanium dioxide powder. The pH was adjusted to 4 using acid solution (acetic acid), and the temperature was raised to 70℃ for 5 hours. After the reaction was completed, the mixture was centrifuged, precipitated, washed, and dried to obtain hydrophobically modified titanium dioxide. S2: Weigh 9.8 kg of phosphoric acid and 7.8 kg of urea (molar ratio of phosphoric acid to urea is 1:1.3) and add them to the reactor. Heat to 80°C, reflux and cool until the urea is completely dissolved. Add 3.9 kg of soluble starch (mass ratio of soluble starch to urea is 0.5:1) in batches, stir and heat to 120°C. After reacting for 40 min, transfer the mixture to an oven and dry at 140°C for 70 min. The resulting solid is ground and sieved to obtain starch ammonium phosphate. S3: Bisphenol A type epoxy resin, epoxy resin curing agent, terminal epoxy silicone oil, hydrophobically modified titanium dioxide, starch ammonium phosphate and ethyl acetate are mixed and stirred in a mass ratio of 1:0.2:0.4:0.03:0.3:0.1 to prepare a water-resistant and fireproof adhesive.

[0037] The water-resistant and fire-retardant adhesive prepared by the above method is applied at a concentration of 250 g / m³. 2 The coating amount was applied to the surface of the board and dried at 70℃ for 0.5 h to obtain a water-resistant and fire-retardant modified board.

[0038] Comparative Example 2 The difference from Example 1 is that starch phosphate ester is used instead of starch ammonium phosphate ester.

[0039] The preparation method of the water-resistant and fire-retardant adhesive includes the following steps: S1: Titanium dioxide powder with an average particle size of 30 nm was dispersed in an ethanol solution (the ethanol solution contained 90% ethanol by mass). After ultrasonic dispersion, a titanium dioxide solution with a mass fraction of 6% was obtained. A titanate coupling agent was added to the titanium dioxide solution, with the amount of titanate coupling agent being 11% of the mass of the titanium dioxide powder. The pH was adjusted to 4 using acid solution (acetic acid), and the temperature was raised to 70℃ for 5 hours. After the reaction was completed, the mixture was centrifuged, precipitated, washed, and dried to obtain hydrophobically modified titanium dioxide. S2: Mix sodium tripolyphosphate solution with starch, the amount of sodium tripolyphosphate is 0.6% of the starch mass, adjust the pH value to 10 with sodium hydroxide solution, mix evenly at room temperature, then neutralize with hydrochloric acid, filter, wash with water, dry at 50℃ to the water content of 15%, then heat to 120℃ to react for 1 hour, after the reaction is complete, wash repeatedly with water 4-5 times, then dry, pulverize and sieve to obtain starch phosphate ester; S3: Bisphenol A type epoxy resin, epoxy resin curing agent, terminal epoxy silicone oil, hydrophobically modified titanium dioxide, starch phosphate, ammonium polyphosphate and ethyl acetate are mixed and stirred in a mass ratio of 1:0.2:0.4:0.03:0.3:0.1:0.1 to prepare a water-resistant and fireproof adhesive.

[0040] The water-resistant and fire-retardant adhesive prepared by the above method is applied at a concentration of 250 g / m³. 2The coating amount was applied to the surface of the board and dried at 70℃ for 0.5 h to obtain a water-resistant and fire-retardant modified board.

[0041] Comparative Example 3 The difference from Example 1 is that the amount of ammonium polyphosphate added is excessive.

[0042] The preparation method of the water-resistant and fire-retardant adhesive includes the following steps: S1: Titanium dioxide powder with an average particle size of 30 nm was dispersed in an ethanol solution (the ethanol solution contained 90% ethanol by mass). After ultrasonic dispersion, a titanium dioxide solution with a mass fraction of 6% was obtained. A titanate coupling agent was added to the titanium dioxide solution, with the amount of titanate coupling agent being 11% of the mass of the titanium dioxide powder. The pH was adjusted to 4 using acid solution (acetic acid), and the temperature was raised to 70℃ for 5 hours. After the reaction was completed, the mixture was centrifuged, precipitated, washed, and dried to obtain hydrophobically modified titanium dioxide. S2: Weigh 9.8 kg of phosphoric acid and 7.8 kg of urea (molar ratio of phosphoric acid to urea is 1:1.3) and add them to the reactor. Heat to 80°C, reflux and cool until the urea is completely dissolved. Add 3.9 kg of soluble starch (mass ratio of soluble starch to urea is 0.5:1) in batches, stir and heat to 120°C. After reacting for 40 min, transfer the mixture to an oven and dry at 140°C for 70 min. The resulting solid is ground and sieved to obtain starch ammonium phosphate. S3: Bisphenol A type epoxy resin, epoxy resin curing agent, terminal epoxy silicone oil, hydrophobically modified titanium dioxide, starch ammonium phosphate, ammonium polyphosphate and ethyl acetate are mixed and stirred in a mass ratio of 1:0.2:0.4:0.03:0.3:0.5:0.1 to prepare a water-resistant and fireproof adhesive.

[0043] The water-resistant and fire-retardant adhesive prepared by the above method is applied at a concentration of 250 g / m³. 2 The coating amount was applied to the surface of the board and dried at 70℃ for 0.5 h to obtain a water-resistant and fire-retardant modified board.

[0044] Comparative Example 4 The difference from Example 1 is that the amount of terminal epoxy silicone oil added is excessive.

[0045] The preparation method of the water-resistant and fire-retardant adhesive includes the following steps: S1: Titanium dioxide powder with an average particle size of 30 nm was dispersed in an ethanol solution (the ethanol solution contained 90% ethanol by mass). After ultrasonic dispersion, a titanium dioxide solution with a mass fraction of 6% was obtained. A titanate coupling agent was added to the titanium dioxide solution, with the amount of titanate coupling agent being 11% of the mass of the titanium dioxide powder. The pH was adjusted to 4 using acid solution (acetic acid), and the temperature was raised to 70℃ for 5 hours. After the reaction was completed, the mixture was centrifuged, precipitated, washed, and dried to obtain hydrophobically modified titanium dioxide. S2: Weigh 9.8 kg of phosphoric acid and 7.8 kg of urea (molar ratio of phosphoric acid to urea is 1:1.3) and add them to the reactor. Heat to 80°C, reflux and cool until the urea is completely dissolved. Add 3.9 kg of soluble starch (mass ratio of soluble starch to urea is 0.5:1) in batches, stir and heat to 120°C. After reacting for 40 min, transfer the mixture to an oven and dry at 140°C for 70 min. The resulting solid is ground and sieved to obtain starch ammonium phosphate. S3: Bisphenol A type epoxy resin, epoxy resin curing agent, terminal epoxy silicone oil, hydrophobically modified titanium dioxide, starch ammonium phosphate, ammonium polyphosphate and ethyl acetate are mixed and stirred in a mass ratio of 1:0.2:0.6:0.03:0.3:0.1:0.1 to prepare a water-resistant and fireproof adhesive.

[0046] The water-resistant and fire-retardant adhesive prepared by the above method is applied at a concentration of 250 g / m³. 2 The coating amount was applied to the surface of the board and dried at 70℃ for 0.5 h to obtain a water-resistant and fire-retardant modified board.

[0047] Examples 1-4 and Comparative Examples 1-4 were tested according to GB / T 12441-2018 "Decorative Fire-retardant Coatings", including adhesion grade (≤3), water resistance (no wrinkling or peeling of the paint film after 24 h test), damp heat resistance (no blistering or peeling of the paint film after 48 h test), and flame retardancy time (≥15 min). The transparency test involved placing the board in an environment with humidity ≥85% for 36 h and observing the surface changes. The results are shown in Table 1.

[0048] Table 1 As shown in Table 1, it can be seen from Examples 1-4 that the adhesives prepared according to the method of the present invention have good adhesion, water resistance, damp heat resistance, flame retardancy and transparency, indicating that adhesives with excellent comprehensive performance can be obtained through multi-component synergy, which is beneficial for wide application.

[0049] In Comparative Example 1, no ammonium polyphosphate was added to the adhesive. Since ammonium polyphosphate and starch ammonium phosphate are dual phosphorus source flame retardants, they can have a synergistic phosphorus-nitrogen effect, thereby enhancing the flame retardant effect. However, without ammonium polyphosphate, the flame retardant efficiency of starch ammonium phosphate alone is reduced, and the flame resistance time is significantly shortened. At the same time, due to the weakened overall protective ability of the coating, its resistance to damp heat will also decrease.

[0050] In Comparative Example 2, starch phosphate ester was used instead of starch ammonium phosphate ester in the adhesive. Because it lacks nitrogen, the phosphorus-nitrogen synergistic effect cannot be achieved, thus leading to a decrease in flame retardant efficiency. Furthermore, since the side chains of starch phosphate ester are phosphate groups, which are highly hydrophilic, the water resistance of the coating deteriorates.

[0051] In Comparative Example 3, the adhesive used excessive amounts of ammonium polyphosphate. While an appropriate amount of ammonium polyphosphate can enhance the flame-retardant effect, excessive addition leads to agglomeration due to its inorganic particles, resulting in an uneven char layer structure. This can even cause cracking during combustion due to internal stress, compromising the protective properties of the char layer. Furthermore, even with nano-sized powders, excessive addition increases the probability of particle collisions, leading to agglomeration, the formation of larger particles, and intense light scattering. This causes a sharp decrease in coating transparency, resulting in a noticeably white appearance.

[0052] The adhesive in Comparative Example 4 uses too much terminal epoxy silicone oil. Excessive long-chain siloxanes may accumulate on the coating surface, hindering the effective contact between the epoxy resin and the board surface. It may also reduce the crosslinking density and network strength, and may even lead to phase separation, thereby affecting water resistance, transparency and flame retardancy.

[0053] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a water-resistant and fire-retardant adhesive for wood-based panels, characterized in that, Includes the following steps: S1: Titanium dioxide is modified with titanate coupling agent or phosphate coupling agent to obtain hydrophobic modified titanium dioxide. S2: Urea is dissolved in phosphoric acid, soluble starch is added and heated to react, and then dried to obtain starch ammonium phosphate ester; S3: Epoxy resin, epoxy resin curing agent, terminal epoxy silicone oil, hydrophobically modified titanium dioxide, starch ammonium phosphate, ammonium polyphosphate and ethyl acetate are mixed and stirred in a mass ratio of 1:0.2-0.3:0.2-0.4:0.03-0.07:0.3-0.6:0.1-0.3:0.1-0.3 to prepare a water-resistant and fire-retardant adhesive.

2. The method for preparing the water-resistant and fire-retardant adhesive for wood-based panels according to claim 1, characterized in that, In S1, the amount of the titanate coupling agent or phosphate coupling agent is 10-15% of the mass of titanium dioxide.

3. The method for preparing the water-resistant and fire-retardant adhesive for wood-based panels according to claim 1 or 2, characterized in that, The specific steps of S1 include: dispersing titanium dioxide powder in an ethanol solution, ultrasonically dispersing it, adding a titanate coupling agent or a phosphate coupling agent, adjusting the pH to 4-5, and heating the reaction; after the reaction is completed, centrifuging and drying are performed to obtain hydrophobically modified titanium dioxide.

4. The method for preparing the water-resistant and fire-retardant adhesive for wood-based panels according to claim 3, characterized in that, The titanium dioxide powder has a particle size of 10-100 nm; the temperature of the heating reaction is 70-90℃, and the reaction time is 3-5 h.

5. The method for preparing the water-resistant and fire-retardant adhesive for wood-based panels according to claim 3, characterized in that, The pH is adjusted to 4-5 using an acid solution; the acid solution includes one or more of acetic acid, citric acid, and oxalic acid.

6. The method for preparing the water-resistant and fire-retardant adhesive for wood-based panels according to claim 1, characterized in that, In S2, the molar ratio of urea to phosphoric acid is 1.3-1.8:1; the mass ratio of urea to soluble starch is 1:0.5-1.

7. The method for preparing the water-resistant and fire-retardant adhesive for wood-based panels according to claim 1 or 6, characterized in that, In S2, the heating reaction temperature is 120-140℃ and the reaction time is 30-40 min.

8. The method for preparing the water-resistant and fire-retardant adhesive for wood-based panels according to claim 1 or 6, characterized in that, In S2, the drying temperature is 140-160℃ and the reaction time is 40-70 min.

9. The application of a water-resistant and fire-retardant adhesive prepared by any one of claims 1-8 in wood-based panels.

10. The application according to claim 9, characterized in that, include: Apply water-resistant and fire-retardant adhesive at a ratio of 150-250 g / m 2 The coating amount is applied to the surface of the board and dried at 70-80℃ for 0.3-0.5 h.

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