A highly flame-retardant and environmentally friendly urea-formaldehyde resin adhesive, its preparation process and application

Abstract

This invention discloses a preparation process for a highly flame-retardant and environmentally friendly urea-formaldehyde resin adhesive, comprising the following steps: adding formaldehyde solution to a reaction vessel, adjusting the pH value of the formaldehyde solution using sodium hydroxide, adding urea for the first time, starting a stirrer, heating the reaction, and increasing the reaction temperature, adding urea for the second time, stirring the reaction, and increasing the temperature, adding urea for the third time, stopping the reaction, adding a modified aluminum tripolyphosphate formaldehyde scavenger to the reaction vessel, stirring evenly, cooling to room temperature, and discharging the material to obtain the highly flame-retardant and environmentally friendly urea-formaldehyde resin adhesive. The preparation process of this invention is simple, and the resulting urea-formaldehyde resin adhesive is inexpensive. It not only meets the basic bonding requirements of particleboard but also reduces formaldehyde release and improves flame retardant performance, greatly enhancing the environmental friendliness and safety of particleboard.

Description

Technical Field

[0001] This invention relates to the field of engineered wood products manufacturing technology, and more specifically, to a preparation process for a urea-formaldehyde resin adhesive with low free formaldehyde content that can impart high flame retardant properties to particleboard. Background Technology

[0002] Particleboard using urea-formaldehyde resin as a binder has become one of the main types of particleboard both domestically and internationally due to its advantages such as low cost, readily available raw materials, and simple processing. However, the high free formaldehyde content in the urea-formaldehyde resin adhesive and the flammability of the particleboard itself greatly limit its downstream applications and development.

[0003] Patent CN116175715A discloses a composite inorganic flame retardant for particleboard. This composite inorganic flame retardant uses spherical calcium silicate crystals with a large specific surface area and a multi-layered lamellar structure as a carrier to adsorb and support the inorganic flame retardant. It then adheres to the particleboard surface with the help of a cross-linking agent, improving its resistance to leakage and ensuring its flame-retardant lifespan after application. Furthermore, the calcium silicate crystals are macroscopically in powder form, which can fill the gaps in the particleboard during application, also improving the density of the particleboard to some extent. The invention also discloses a flame-retardant particleboard using the aforementioned composite inorganic flame retardant and its manufacturing method. This flame-retardant particleboard uses the aforementioned anti-leakage composite inorganic flame retardant as the main flame retardant component, effectively achieving the purpose of preventing leakage while exerting a flame-retardant effect, thus extending the flame-retardant lifespan of the board. Moreover, its manufacturing method is no different from that of existing general flame-retardant particleboard, and the process is simple. This invention primarily aims to address the flammability and leaching issues of particleboard, but it fails to effectively utilize the adsorption properties of the multi-layered sheet structure of calcium silicate to solve the formaldehyde release problem from particleboard.

[0004] Patent CN115838576A discloses a formaldehyde-free adhesive and its application in the preparation of P2P12 grade particleboard, belonging to the field of plywood technology. It includes an emulsion, a crosslinking agent, and inorganic fillers. The emulsion comprises emulsion A and emulsion B. Emulsion A is obtained by solution polymerization of vinyl acetate, vinyl chloride, and ethylene; emulsion B is obtained by solution polymerization of a rigid monomer and butadiene, wherein the rigid monomer includes at least one of styrene, p-methylstyrene, o-methylstyrene, and m-methylstyrene. Through the synergistic effect of emulsions A and B, the particleboard can simultaneously possess excellent flame retardancy, water resistance, and physical and mechanical properties. This invention involves multiple chemical reactions, making the process relatively complex and difficult to control stably in actual operation. Furthermore, it fails to solve the problem of formaldehyde release from particleboard.

[0005] In summary, existing research has failed to simultaneously address the high formaldehyde content and flammability of particleboard. To address the drawbacks of existing particleboard using urea-formaldehyde resin adhesives, such as high free formaldehyde levels and flammability, a novel method for preparing urea-formaldehyde resin adhesive is proposed, aiming to simultaneously solve the problems of formaldehyde release and particleboard flammability. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing urea-formaldehyde resin adhesive to solve the problems mentioned in the background art, such as high free formaldehyde content and flammability of particleboard.

[0007] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a modified aluminum tripolyphosphate formaldehyde scavenger includes the following steps:

[0009] Aluminum tripolyphosphate suspension is added to a reaction vessel. The temperature of the aluminum tripolyphosphate suspension is increased under stirring. The composite modifier is then added to the reaction vessel. After stirring, the mixture is filtered, dried, and pulverized to obtain the modified aluminum tripolyphosphate formaldehyde scavenger.

[0010] Preferably, the dry basis weight of the aluminum tripolyphosphate suspension is 40-45%.

[0011] Preferably, the temperature of the aluminum tripolyphosphate suspension is increased to 65–70°C.

[0012] Preferably, the amount of the composite modifier added is 4.5-5% of the dry basis equivalent of aluminum tripolyphosphate.

[0013] Preferably, the preparation method of the composite modifier includes the following steps: adding deionized water to a container, then heating, adding polyvinyl alcohol under stirring conditions, and after the polyvinyl alcohol is completely dissolved, adding cycloethyl urea and m-diphenol at the same time, and after the two are completely dissolved, cooling the solution to obtain the composite modifier.

[0014] Preferably, deionized water is added to the container and then heated to 65–70°C.

[0015] Preferably, the mass ratio of deionized water, polyvinyl alcohol, cycloethylidene urea, and resorcinol is (45-50):(10-15):(20-25):(30-35).

[0016] This invention also provides a preparation process for a highly flame-retardant and environmentally friendly urea-formaldehyde resin adhesive, comprising the following steps:

[0017] Add a formaldehyde solution with a content of 35-37% to the reactor. Adjust the pH value of the formaldehyde solution to between 7.5 and 8.0 using 28-30% sodium hydroxide. Add urea for the first time, with the amount being 80-82% of the total mass of urea. Start the stirrer and heat to 70-75℃ for 1-2 hours. Increase the reaction temperature to 80-85℃. Add urea for the second time, with the amount being 13-15% of the total mass of urea. Stir and react for 1-1.5 hours. Increase the temperature to 90-95℃. Add urea for the third time, with the amount being 4-6% of the total urea. React for 1-1.5 hours and then stop the reaction. The total mass of urea added is 1.7-1.8 times the amount of formaldehyde. Add the modified aluminum tripolyphosphate formaldehyde scavenger to the reactor, stir evenly, and cool to room temperature before discharging to obtain a highly flame-retardant and environmentally friendly urea-formaldehyde resin adhesive.

[0018] This invention also provides an application of a highly flame-retardant and environmentally friendly urea-formaldehyde resin adhesive in the production of engineered wood panels.

[0019] Compared with existing technologies, this invention exhibits significant technical advantages, specifically in the following aspects:

[0020] 1. High Efficiency and Cost-Effectiveness of the Preparation Process: The preparation process of this invention is designed to be extremely simple and straightforward, not only convenient to operate but also significantly reducing the complexity and energy consumption in the production process. Through this optimized process, this invention successfully prepares a low-cost urea-formaldehyde resin adhesive. This adhesive not only fully meets the basic requirements of particleboard in terms of adhesive strength, ensuring the structural stability and durability of the product, but also achieves a qualitative leap in environmental protection and safety performance. Specifically, it significantly reduces the formaldehyde release of particleboard during use, which is of great significance for improving indoor air quality and protecting user health. At the same time, the adhesive of this invention also significantly improves the flame retardant properties of particleboard, enabling it to more effectively resist the spread of fire in the face of emergencies such as fires, thereby greatly improving the overall safety of the product. This series of improvements undoubtedly makes the urea-formaldehyde resin adhesive of this invention more competitive in the market.

[0021] 2. The Uniqueness of the Chemical Reaction and the Stability of Product Performance: The key to the high efficiency and low cost of the preparation process of this invention lies in the fact that the entire adhesive resin preparation process involves only one chemical reaction. This single reaction path not only simplifies the production process but also helps to obtain a stable adhesive resin. The meticulously designed preparation process of this invention involves a three-stage condensation reaction, each stage of which is precisely controlled and optimized to ensure a more thorough reaction. This staged reaction method not only improves the formaldehyde conversion rate and reduces the residual formaldehyde, thereby reducing environmental pollution, but also further reduces production costs, making the adhesive of this invention more price-competitive. Furthermore, this invention also includes a modified aluminum tripolyphosphate formaldehyde scavenger. This scavenger not only efficiently absorbs residual formaldehyde in the resin, further reducing the formaldehyde content, but also possesses excellent flame-retardant properties, providing additional safety for particleboard. This combination of multiple advantages represents a significant technological advancement in the urea-formaldehyde resin adhesive of this invention, bringing new development opportunities to related industries. Attached Figure Description

[0022] Figure 1 This is a SEM image of the modified aluminum tripolyphosphate formaldehyde scavenger obtained in Example 1. Detailed Implementation

[0023] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0024] In an embodiment of the present invention:

[0025] The preparation method of the composite modifier includes the following steps: adding 45-50 parts of deionized water to a container, heating to 65-70°C, adding 10-15 parts of polyvinyl alcohol under stirring, and adding 20-25 parts of cycloethylidene urea and 30-35 parts of m-diphenol at the same time after the polyvinyl alcohol is completely dissolved. After the two are completely dissolved, the solution is cooled to obtain the composite modifier.

[0026] The preparation method of the modified aluminum tripolyphosphate formaldehyde scavenger includes the following steps:

[0027] Add 40-45% (dry basis) aluminum tripolyphosphate suspension to a high-speed stirred reactor. While stirring, raise the temperature of the aluminum tripolyphosphate suspension to 65-70°C. Add 4.5-5% (dry basis) of composite modifier to the reactor. After stirring for 25-30 minutes, filter, dry, and pulverize to obtain the modified aluminum tripolyphosphate formaldehyde scavenger.

[0028] A method for preparing a highly flame-retardant and environmentally friendly urea-formaldehyde resin adhesive includes the following steps:

[0029] Add an appropriate amount of formaldehyde solution with a content of 35-37% to the reactor. Adjust the pH value of the formaldehyde solution to between 7.5 and 8.0 using 28-30% sodium hydroxide. Add urea for the first time, at a rate of 80-82% of the total urea mass. Start the stirrer and heat to 70-75℃ for 1-2 hours. Increase the reaction temperature to 80-85℃. Add urea for the second time, at a rate of 13-15% of the total urea mass. Stir and react for 1-1.5 hours. Raise the temperature to 90-95℃. Add urea for the third time, at a rate of 4-6% of the total urea mass. React for 1-1.5 hours, then stop the reaction. The total mass of urea added should be 1.7-1.8 times the amount of formaldehyde. Add modified aluminum tripolyphosphate formaldehyde scavenger to the reactor, stir evenly, and cool to room temperature before discharging to obtain a highly flame-retardant, environmentally friendly urea-formaldehyde resin adhesive.

[0030] Technical principle of the invention:

[0031] In the field of chemical synthesis, precise control of raw material dosage and optimization of process parameters are crucial for ensuring product quality, improving production efficiency, and achieving specific performance characteristics. The following is an in-depth analysis of the preparation methods of the composite modifier, modified aluminum tripolyphosphate formaldehyde scavenger, and urea-formaldehyde resin adhesive used in this invention, emphasizing the necessity and importance of controlling raw material dosage and optimizing process parameters.

[0032] I. Preparation method of composite modifier

[0033] 1. The necessity of controlling raw material usage:

[0034] Deionized water (45-50 parts): As a solvent, its amount directly affects the solubility of the subsequent solute and the concentration of the solution, thus affecting the physical properties of the modifier such as viscosity and flowability. An appropriate amount of deionized water can ensure that the solute is fully dissolved and avoid agglomeration caused by excessively high local concentrations.

[0035] Polyvinyl alcohol (10-15 parts): As one of the main components of the modifier, its dosage determines the basic skeletal structure and properties of the modifier. An appropriate amount of polyvinyl alcohol can enhance the adhesive strength and water resistance of the modifier.

[0036] Cycloethylidene urea (20-25 parts) and resorcinol (30-35 parts): These two additives work together to optimize the performance of the modifier, such as improving heat resistance and chemical corrosion resistance. Their dosage needs to be precisely controlled to ensure that the overall performance of the modifier reaches its optimal level.

[0037] 2. The process steps cannot be changed or optimized:

[0038] First, add polyvinyl alcohol and wait for it to dissolve completely, then add cycloethyl urea and resorcinol. This order ensures that the solutes dissolve gradually and avoids uneven mixing caused by differences in solubility.

[0039] The solution cooling process is also crucial, as it helps stabilize the structure of the modifier and prevents performance degradation due to high temperatures.

[0040] II. Preparation method of modified aluminum tripolyphosphate formaldehyde scavenger

[0041] 1. The necessity of controlling raw material usage:

[0042] Aluminum tripolyphosphate suspension (40-45% by dry weight): As the main material, its content directly affects the formaldehyde adsorption capacity and stability of the scavenger. An appropriate amount of aluminum tripolyphosphate ensures that the scavenger has sufficient active sites to effectively capture formaldehyde.

[0043] Composite modifier (4.5–5% of aluminum tripolyphosphate dry equivalent): Introducing a composite modifier can significantly improve the dispersibility and weather resistance of the trap. Its dosage needs to be precisely controlled to avoid performance degradation due to over- or under-dosing.

[0044] 2. The Importance of Process Parameter Optimization:

[0045] Raising the temperature to 65-70℃ helps accelerate the reaction rate and ensures that the composite modifier is uniformly dispersed in the aluminum tripolyphosphate suspension.

[0046] Precise control of stirring time (25-30 min) ensures that the reaction proceeds fully, while avoiding increased energy consumption and equipment wear caused by excessive stirring.

[0047] III. Preparation Method of Urea-Formaldehyde Resin Adhesive

[0048] 1. The necessity of controlling raw material usage:

[0049] Formaldehyde solution (35-37%): As a reaction raw material, its content directly affects the formaldehyde release and curing speed of the adhesive. An appropriate amount of formaldehyde ensures that the adhesive has suitable curing time and strength.

[0050] Urea (total amount 1.7 to 1.8 times that of formaldehyde): Added in three portions, with the amount added each time adjusted according to the reaction progress to control the degree of crosslinking and viscosity of the adhesive. An appropriate amount of urea ensures the adhesive has excellent bonding strength and water resistance.

[0051] 2. The Importance of Process Parameter Optimization:

[0052] Adjusting the pH value to 7.5–8.0 helps promote the condensation reaction of urea and formaldehyde, improving reaction efficiency and product quality.

[0053] By gradually increasing the temperature (70~75℃→80~85℃→90~95℃) and adding urea in stages, the reaction process was precisely controlled, avoiding performance degradation caused by local overheating and excessive cross-linking.

[0054] The addition of modified aluminum tripolyphosphate formaldehyde scavenger not only improves the formaldehyde scavenging ability of the adhesive, but also endows it with high flame retardant properties, achieving a dual improvement in environmental protection and performance.

[0055] In summary, this invention, through precise control of raw material dosage and optimization of process parameters, successfully prepared high-performance composite modifiers, modified aluminum tripolyphosphate formaldehyde scavengers, and urea-formaldehyde resin adhesives. These measures not only ensured the quality and stability of the products but also achieved unexpected technical effects, such as improved heat resistance, chemical corrosion resistance, and flame retardant properties, meeting the market demand for high-performance, environmentally friendly adhesives.

[0056] Formaldehyde Reduction Mechanism: During the condensation process of urea and formaldehyde, a three-stage condensation is employed to maximize polymerization and reduce the total amount of free formaldehyde. By adding the modified aluminum tripolyphosphate formaldehyde scavenger of this invention, which has a multi-layered structure and is modified by composite polyvinyl alcohol, cycloethylidene urea, and resorcinol, all three substances can react with formaldehyde under different temperatures and reaction conditions (e.g., resorcinol reacts with formaldehyde under acidic conditions, while polyvinyl alcohol reacts with formaldehyde under alkaline conditions), thereby achieving the effect of eliminating formaldehyde. The reaction conditions of the three substances with formaldehyde complement each other to maximize the reaction effect. The layered structure of aluminum tripolyphosphate has a certain adsorption effect on formaldehyde. The adsorbed formaldehyde reacts with its surface modifier; for example, polyvinyl alcohol and formaldehyde can generate polyvinyl alcohol formaldehyde, and resorcinol reacts with formaldehyde to generate phenolic resin, which solidifies the volatile formaldehyde, thus ultimately achieving the goal of completely eliminating formaldehyde.

[0057] Flame-retardant mechanism: In the early stages of particleboard ignition, aluminum tripolyphosphate effectively promotes the rapid dehydration and carbonization of hydrocarbons in the particleboard, preventing the polymer materials from producing flammable gases and thus inhibiting further escalation of the fire. Furthermore, aluminum tripolyphosphate decomposes into aluminum metaphosphate at high temperatures. Aluminum metaphosphate is a glassy substance with excellent heat resistance, which can encapsulate flammable materials, acting as a protective layer.

[0058] To make the present invention more fully disclosed, more specific embodiments are described below.

[0059] Example 1

[0060] 1. Add a 40% (dry weight) aluminum tripolyphosphate suspension to a high-speed stirred reactor. While stirring, raise the temperature of the aluminum tripolyphosphate suspension to 65°C. Add a 5% (dry weight) composite modifier (deionized water / polyvinyl alcohol / cycloethylidene urea / m-diphenol = 47 / 13 / 20 / 35) to the reactor. After stirring for 30 minutes, filter, dry, and pulverize to obtain the modified aluminum tripolyphosphate formaldehyde scavenger. See SEM image below. Figure 1 .

[0061] 2. Add an appropriate amount of 37% formaldehyde solution to the reactor. Adjust the pH of the formaldehyde solution to 7.6 using 30% sodium hydroxide. Add urea for the first time, at a rate of 80% of the total urea mass. Start the stirrer and heat to 70°C for 1 hour. Increase the reaction temperature to 80°C. Add urea for the second time, at a rate of 15% of the total urea mass. Stir and react for 1 hour. Increase the temperature to 90°C. Add urea for the third time, at a rate of 5% of the total urea mass. React for 1 hour. The reaction is then complete. The total mass of urea added is 1.8 times the effective formaldehyde content. Add the self-made modified aluminum tripolyphosphate formaldehyde scavenger from step 1 to the reactor. Stir evenly and cool to room temperature before discharging to obtain the urea-formaldehyde resin adhesive sample of Example 1.

[0062] Example 2

[0063] 1. Add a suspension of aluminum tripolyphosphate with a dry basis weight of 42% to a high-speed stirred reactor. While stirring, raise the temperature of the aluminum tripolyphosphate suspension to 67°C. Add a composite modifier (deionized water / polyvinyl alcohol / cycloethyl urea / m-diphenol = 45 / 15 / 22 / 35) with a dry basis weight of 4.5% to the reactor. After stirring for 25 minutes, filter, dry and pulverize to obtain the modified aluminum tripolyphosphate formaldehyde scavenger.

[0064] 2. Add an appropriate amount of 36% formaldehyde solution to the reactor. Adjust the pH of the formaldehyde solution to 7.7 using 29% sodium hydroxide. Add urea for the first time, at a rate of 81% of the total urea mass. Start the stirrer and heat to 72°C for 1.5 hours. Increase the reaction temperature to 82°C. Add urea for the second time, at a rate of 14% of the total urea mass. Stir and react for 1.5 hours. Increase the temperature to 92°C. Add urea for the third time, at a rate of 5% of the total urea mass. React for 1.5 hours. The reaction is then complete. The total mass of urea added is 1.7 times the effective formaldehyde content. Add the self-made modified aluminum tripolyphosphate formaldehyde scavenger from step 1 to the reactor. Stir evenly and cool to room temperature before discharging to obtain the urea-formaldehyde resin adhesive sample of Example 2.

[0065] Example 3

[0066] 1. Add a 45% dry weight aluminum tripolyphosphate suspension to a high-speed stirred reactor. While stirring, raise the temperature of the aluminum tripolyphosphate suspension to 70°C. Add a 4.8% dry weight aluminum tripolyphosphate equivalent composite modifier (deionized water / polyvinyl alcohol / cycloethyl urea / m-diphenol = 50 / 15 / 25 / 30) to the reactor. After stirring for 28 minutes, filter, dry and pulverize to obtain the modified aluminum tripolyphosphate formaldehyde scavenger.

[0067] 2. Add an appropriate amount of 35% formaldehyde solution to the reactor. Adjust the pH of the formaldehyde solution to 8.0 using 28% sodium hydroxide. Add urea for the first time, at a rate of 80% of the total urea mass. Start the stirrer and heat to 75°C for 1 hour. Increase the reaction temperature to 80°C. Add urea for the second time, at a rate of 14% of the total urea mass. Stir and react for 1.5 hours. Increase the temperature to 95°C. Add urea for the third time, at a rate of 6% of the total urea mass. React for 1.5 hours. The reaction is then complete. The total mass of urea added is 1.7 times the effective formaldehyde content. Add the self-made modified aluminum tripolyphosphate formaldehyde scavenger from step 1 to the reactor. Stir evenly and cool to room temperature before discharging to obtain the urea-formaldehyde resin adhesive sample of Example 3.

[0068] Comparative Example 1

[0069] 1. Add 40% (dry weight) aluminum tripolyphosphate suspension to a high-speed stirred reactor. While stirring, raise the temperature of the aluminum tripolyphosphate suspension to 65°C. Add 5% (dry weight) of composite modifier (deionized water / polyvinyl alcohol / cycloethylidene urea / p-toluenesulfonamide / m-diphenol = 47 / 13 / 20 / 35) to the reactor. After stirring for 30 minutes, filter, dry and pulverize to obtain modified aluminum tripolyphosphate formaldehyde scavenger.

[0070] 2. Add an appropriate amount of 37% formaldehyde solution to the reactor. Adjust the pH of the formaldehyde solution to 7.6 using 30% sodium hydroxide. Raise the temperature to 90°C and add urea all at once. The mass of urea added should be 1.8 times the effective formaldehyde content. React for 3 hours, then stop the reaction. Add the self-made modified aluminum tripolyphosphate formaldehyde scavenger from step 1 to the reactor. After stirring evenly, cool to room temperature and discharge to obtain the urea-formaldehyde resin adhesive sample of Comparative Example 1.

[0071] Comparative Example 2

[0072] A suitable amount of formaldehyde solution with a content of 37% was added to the reaction vessel. The pH value of the formaldehyde solution was adjusted to 7.6 using 30% sodium hydroxide. Urea was added for the first time, with the amount added being 80% of the total mass of urea. The stirrer was started, and the reaction was heated to 70°C for 1 hour. The reaction temperature was then increased to 80°C. Urea was added for the second time, with the amount added being 15% of the total mass of urea. The reaction was stirred for 1 hour, and the temperature was increased to 90°C. Urea was added for the third time, with the amount added being 5% of the total mass of urea. The reaction was completed after 1 hour. The total mass of urea added was 1.8 times the effective formaldehyde content. The mixture was cooled to room temperature and discharged to obtain the sample of the urea-formaldehyde resin adhesive of Comparative Example 2.

[0073] Comparative Example 3

[0074] A suitable amount of 37% formaldehyde solution was added to the reaction vessel. The pH of the formaldehyde solution was adjusted to 7.6 using 30% sodium hydroxide. Urea was added for the first time, at a rate of 80% of the total urea mass. The stirrer was started, and the mixture was heated to 70°C and reacted for 1 hour. The reaction temperature was then increased to 80°C. Urea was added for the second time, at a rate of 15% of the total urea mass. The mixture was stirred and reacted for 1 hour. The temperature was then increased to 90°C. Urea was added for the third time, at a rate of 5% of the total urea mass. The reaction was completed after 1 hour. The total mass of urea added was 1.8 times the effective formaldehyde content. Aluminum tripolyphosphate (without composite modifier) ​​was added, stirred evenly, and cooled to room temperature before being discharged to obtain the urea-formaldehyde resin adhesive sample of Comparative Example 3.

[0075] Methods for evaluating effectiveness:

[0076] 1. Determination of free formaldehyde content in adhesives

[0077] Accurately weigh approximately 2g of urea-formaldehyde resin adhesive into a beaker containing 50ml of methanol. Stir with a glass rod for 2 minutes, then add 3 drops of thymol blue indicator. Adjust the solution color to yellow-green with dilute hydrochloric acid, add 25ml of 10% hydroxylamine hydrochloride, stir well, and titrate with 1mol / L sodium hydroxide standard solution until the solution turns blue-green. The endpoint is reached when the color remains unchanged for 1 minute. The blank group is prepared by following the same procedure without adding any sample.

[0078] Formaldehyde content w = 3c(V1-V0) / m

[0079] Where: c - the actual concentration of the sodium hydroxide standard solution used, mol / L;

[0080] V0 - The volume of sodium hydroxide standard titrant consumed in the blank test, in ml;

[0081] V1 - The volume of sodium hydroxide standard titrant consumed in the test, in ml;

[0082] m - Sample mass, g.

[0083] 2. Formaldehyde emission test of particleboard

[0084] Particleboard samples prepared using the examples and comparative examples were arranged at 1m... 3 The climate chamber method for detecting formaldehyde emission is mainly based on GB18580-2017 "Formaldehyde Emission from Interior Decoration and Renovation Materials, Artificial Boards and Their Products".

[0085] 3. Flame retardant performance test of particleboard

[0086] The particleboard samples prepared using the examples and comparative examples were tested according to GB / T39032-2020 "Flame-retardant Particleboard" for THR. 600S (Total heat released during the first 600 seconds after being ignited by the main burner).

[0087] Test results:

[0088] The test was conducted using the above method, and the results are shown in Table 1:

[0089] Table 1 Sample Test Results

[0090]

[0091] (1) From the detailed data listed in Table 1, the present invention clearly demonstrates the significant advantage of Examples 1 to 3 in terms of free formaldehyde content. These values ​​are significantly lower, indicating that their formaldehyde control effect is extremely excellent. Simultaneously, the particleboard prepared in these examples also exhibits excellent formaldehyde emission, successfully meeting the E0 formaldehyde emission standard, an achievement that is undoubtedly remarkable. Upon further investigation, the present invention reveals that this is mainly due to the ingenious use of a three-stage polymerization process in the synthesis of urea-formaldehyde resin, combined with modified aluminum tripolyphosphate as an additive. The three-stage polymerization process, through precise control of reaction conditions, ensures the full reaction of formaldehyde and urea, thereby effectively reducing the generation of free formaldehyde. Furthermore, the modified aluminum tripolyphosphate, with its unique chemical structure, further captures and fixes residual formaldehyde molecules, thus achieving a significant reduction in formaldehyde emission.

[0092] In terms of flame retardant performance, Examples 1 to 3 also demonstrated impressive capabilities, all successfully meeting the requirements for flame retardant rating B1-C, with the THR600S (total heat release within 600 seconds) value controlled below 15 MJ. This achievement is largely attributed to the addition of modified aluminum tripolyphosphate. The modified aluminum tripolyphosphate not only enhances the thermal stability of the material but also forms a protective layer during combustion, effectively isolating oxygen and heat transfer, thereby significantly improving the flame retardant performance of the material.

[0093] (2) Upon further examination of the data in Table 1, the present invention reveals significant differences between Examples 1 to 3 and the comparative examples in terms of free formaldehyde content, formaldehyde release, and THR600S value. Specifically, Comparative Example 1 shows significantly higher levels of free formaldehyde and formaldehyde release. This is because a three-stage polymerization process was not used in the synthesis of urea-formaldehyde resin, resulting in low formaldehyde conversion efficiency and a large amount of formaldehyde failing to be effectively converted, thus leading to a higher residual amount. Furthermore, although modified aluminum tripolyphosphate was added in this comparative example, its absorption capacity was insufficient due to the excessive residual formaldehyde, failing to effectively reduce the formaldehyde content.

[0094] Comparative Example 2 also showed higher formaldehyde release and THR600S value than Example 2, mainly because its formulation lacked the key component modified aluminum tripolyphosphate. Modified aluminum tripolyphosphate can not only absorb volatile formaldehyde but also play a flame-retardant role during combustion. However, due to the lack of this component, the formaldehyde release in Comparative Example 2 could not be effectively controlled, and its flame-retardant performance was also greatly reduced.

[0095] As for Comparative Example 3, its formaldehyde release was significantly higher than that of Example 3. This is mainly because although aluminum tripolyphosphate was added in Example 3, it was not modified. Although unmodified aluminum tripolyphosphate also has certain adsorption properties, it cannot effectively solidify the adsorbed formaldehyde without auxiliary substances such as polyvinyl alcohol and resorcinol. Therefore, the formaldehyde release was not significantly improved. This finding further emphasizes the important role of modified aluminum tripolyphosphate in reducing formaldehyde release and improving flame retardant properties.

[0096] The above-described embodiments are some preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any modifications, equivalent changes, alterations and simplifications made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a modified aluminum tripolyphosphate formaldehyde scavenger, characterized in that, Includes the following steps: Add aluminum tripolyphosphate suspension to the reaction vessel, raise the temperature of the aluminum tripolyphosphate suspension to 65~70℃ under stirring, add the composite modifier to the reaction vessel, stir, and then filter, dry and pulverize to obtain the modified aluminum tripolyphosphate formaldehyde scavenger. The dry basis weight of the aluminum tripolyphosphate suspension is 40-45%. The amount of the composite modifier added is 4.5-5% of the dry basis equivalent of aluminum tripolyphosphate; The preparation method of the composite modifier includes the following steps: adding deionized water to a container and heating it to 65~70℃; adding polyvinyl alcohol under stirring; and adding cycloethyl urea and resorcinol after the polyvinyl alcohol has completely dissolved. After the two have completely dissolved, cooling the solution yields the composite modifier. The mass ratio of deionized water, polyvinyl alcohol, cycloethyl urea, and meta-diphenol is (45~50):(10~15):(20~25):(30~35).

2. A preparation process for a highly flame-retardant and environmentally friendly urea-formaldehyde resin adhesive, characterized in that, Includes the following steps: Add a formaldehyde solution with a content of 35-37% to the reactor. Adjust the pH value of the formaldehyde solution to between 7.5 and 8.0 using 28-30% sodium hydroxide. Add urea for the first time, with the amount being 80-82% of the total mass of urea. Start the stirrer and heat to 70-75℃ for 1-2 hours. Increase the reaction temperature to 80-85℃. Add urea for the second time, with the amount being 13-15% of the total mass of urea. Stir and react for 1-1.5 hours. Increase the temperature to 90-95℃. Add urea for the third time, with the amount being 4-6% of the total urea. React for 1-1.5 hours and then stop the reaction. The total mass of urea added is 1.7-1.8 times the amount of formaldehyde. Add the modified aluminum tripolyphosphate formaldehyde scavenger as described in claim 1 to the reactor. After stirring evenly, cool to room temperature and discharge to obtain a highly flame-retardant and environmentally friendly urea-formaldehyde resin adhesive.

3. A highly flame-retardant and environmentally friendly urea-formaldehyde resin adhesive prepared according to the process described in claim 2.

4. An application of the highly flame-retardant and environmentally friendly urea-formaldehyde resin adhesive according to claim 3, characterized in that, It is used in the production of engineered wood panels.

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