Preparation method and application of ultra-long room-temperature phosphorescent modified urea-formaldehyde resin adhesive

Abstract

The invention belongs to the technical field of functional adhesives, and relates to a preparation method and application of an ultra-long room-temperature phosphorescent modified urea-formaldehyde resin adhesive. Comprising the following steps: by taking urea and formaldehyde as main raw materials, carrying out hydroxymethylation reaction under an alkaline condition to obtain a reaction product; then, a reaction type phosphorescence light-emitting unit is introduced in the polycondensation process, and the reaction type phosphorescence light-emitting unit participates in a resin polycondensation reaction and is fixed in a resin network; further polycondensation of the system is promoted through multi-stage pH regulation and control and heating reaction; melamine and multi-step urea are added in the subsequent reaction stage to regulate and control the resin structure, and finally the modified urea-formaldehyde resin adhesive with the room-temperature phosphorescence characteristic is prepared. After being cured, the synthesized adhesive can generate stable room-temperature phosphorescence emission under the excitation of ultraviolet light, meanwhile, good bonding performance is kept, and the characteristics of light emitting color and light emitting service life can be changed by regulating and controlling the types and the content of light emitting units. The adhesive has an identifiable room-temperature phosphorescence function while keeping the adhesive performance, and can be applied to anti-counterfeiting and tracing of wood composite materials and related interface systems.

Description

Technical Field

[0001] This invention belongs to the field of functional adhesives and optical information materials technology, specifically relating to a method for preparing an ultra-long room temperature phosphorescent modified urea-formaldehyde resin adhesive. Background Technology

[0002] Wood-based composite materials are widely used in furniture, construction, and packaging. Adhesives, as key components for achieving interfacial bonding and structural stability, directly affect the performance and reliability of the finished products. With the development of functional adhesives, adding additional functions such as optical identification and anti-counterfeiting features is gradually becoming a growth point in market demand.

[0003] Room temperature phosphorescent materials have potential applications in optical identification, anti-counterfeiting, and information storage due to their long luminescence lifetime and high recognizability. However, for adhesive systems, introducing the luminescent component externally often fails to form a stable bond with the resin network, easily affecting luminescence stability and system uniformity, and hindering the integrated construction of adhesive function and structure.

[0004] Therefore, how to introduce reactive phosphorescent units into the synthesis process of urea-formaldehyde resin adhesives, so that they can participate in the resin polycondensation reaction and be fixed in the adhesive network, thereby giving the adhesive stable and identifiable room temperature phosphorescence function while maintaining the adhesive properties, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The main objective of this invention is to provide an ultra-long room temperature phosphorescent modified urea-formaldehyde resin adhesive, its preparation method, and its application. The technical problem to be solved is how to introduce reactive phosphorescent units into the synthesis process of urea-formaldehyde resin adhesive, so that they participate in the resin condensation reaction and are fixed in the adhesive network, thereby endowing it with stable and identifiable room temperature phosphorescent function without reducing the adhesive performance.

[0006] This invention proposes introducing reactive luminescent units during a multi-stage pH-controlled polycondensation reaction, enabling the adhesive molecular structure to be progressively constructed and form a stable three-dimensional cross-linked network at different reaction stages. This method eliminates the need for additional external luminescent fillers, integrating the luminescent structure with the adhesive network, resulting in high luminescent stability, minimal migration, and strong structural stability. Furthermore, the resulting adhesive exhibits significant room-temperature phosphorescence emission under ultraviolet light excitation while maintaining good bonding properties and process adaptability.

[0007] The objective of this invention and the technical problem it solves are achieved through the following technical solutions: According to the present invention, a method for preparing an ultra-long room temperature phosphorescent modified urea-formaldehyde resin adhesive includes the following steps: Step 1, adding urea and formaldehyde, adjusting the pH to 8-9 using a 20-30% sodium hydroxide solution, raising the temperature to 90-95℃ within 30-40 minutes, and maintaining the temperature for 40-60 minutes to obtain a first reaction product; Step 2, adding reactive phosphorescent luminescent units to the first reaction product, stabilizing and dispersing them, adjusting the pH of the system to 5.2-5.5 using formic acid, and maintaining the temperature at 85-90℃ until the viscosity of the reactant measured at 50℃ is 11.8-12.2 s, to obtain a second reaction product; Step 3, adjusting the pH of the second reaction product system to 4.8-5.0 using formic acid, and maintaining the temperature at 83-85℃ until the viscosity of the reactant measured at 50℃ is 12.8-13.5 s, to obtain a third reaction product; Step 4, using a 20-30% sodium hydroxide solution to... Adjust the pH of the third reaction product system to 7.0-7.5 with sodium hydroxide solution, add melamine and formaldehyde from the second step, and maintain the reaction temperature at 80-85℃ until the viscosity of the reactants measured at 50℃ in a Forck-4 cup is 14.5-15.0 s, thus obtaining the fourth reaction product; Step 5, adjust the pH of the fourth reaction product system to 8.0-8.5 with 20-30% sodium hydroxide solution, add urea from the second step, and maintain the reaction temperature at 78-80℃ until the viscosity of the reactants measured at 50℃ in a Forck-4 cup is 14.5-15.0 s, thus obtaining the fourth reaction product; The viscosity of the fifth reaction product was tested at 50℃ and found to be 15.0~16.0 s⁻¹ in a Forte 4 cup, yielding the fifth reaction product. In step 6, the fifth reaction product was cooled to 65~70℃, and the pH of the system was adjusted to 8.5~9.0 using a 20~30% sodium hydroxide solution. Urea from step 3 was added, and the reaction was maintained at this temperature for 15~30 min until the viscosity of the reactant was tested at 25℃ and found to be 19.0~25.0 s⁻¹ in a Forte 4 cup, resulting in an ultra-long room temperature phosphorescent modified urea-formaldehyde resin adhesive.

[0008] The molar ratio of formaldehyde to urea in step 1 is 1.9 to 2.2:1.

[0009] Preferably, the molar ratio of formaldehyde to urea in step 1 is 2.0 to 2.1:1; The reactive phosphorescent unit in step 2 is one or more of tannic acid, tannic acid, alkali lignin, lignin sulfonate, gallic acid, aminophenanthrene or aminopyrene, and p-aminobenzonitrile; and the amount of reactive phosphorescent unit added is 0.1% to 5.0% of the total mass of the synthetic material.

[0010] Preferably, in step 2, the reactive phosphorescent luminescent unit is one or more of tannic acid, alkali lignin, lignin sulfonate, aminopyrene, and p-aminobenzonitrile, and the amount of reactive phosphorescent luminescent unit added is 0.5% to 3.0% of the total mass of the synthesized material; The amount of melamine added in step 4 is 1.0% to 18% of the total mass of the synthetic materials; after the addition of formaldehyde in the second step, the theoretical molar ratio of formaldehyde to urea in the added materials is 2.2 to 2.5:1.

[0011] Preferably, the amount of melamine added in step 4 is 3% to 12% of the total mass of the synthetic materials; after the formaldehyde is added in the second step, the theoretical molar ratio of formaldehyde to urea in the added materials is 2.3 to 2.4:1.

[0012] After the addition of urea in the second step of step 5, the theoretical molar ratio of formaldehyde to urea in the added material is 1.4~1.6:1.

[0013] Preferably, after the addition of urea in the second step of step 5, the theoretical molar ratio of formaldehyde to urea in the added material is 1.4~1.5:1.

[0014] After adding urea in the third step of step 6, the theoretical molar ratio of formaldehyde to urea in the added material is 1.0~1.2:1.

[0015] Preferably, after the third step of step 6, when urea is added, the theoretical molar ratio of formaldehyde to urea in the added material is 1.0~1.1:1.

[0016] The present invention also provides an ultra-long room temperature phosphorescent modified urea-formaldehyde resin adhesive prepared by the above preparation method. In the adhesive, the luminescent structural unit is fixed in the resin crosslinking network by participating in the condensation reaction of urea-formaldehyde resin. After the adhesive is fully cured, it can exhibit ultra-long room temperature phosphorescence characteristics under ultraviolet light excitation.

[0017] The aforementioned ultra-long room temperature phosphorescent modified urea-formaldehyde resin adhesive can be used in optical identification, anti-counterfeiting traceability, or environmental response monitoring in wood composite materials, paper-based composite materials, and related interfacial bonding systems.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention innovatively uses a rigid structure of urea-formaldehyde resin adhesive to covalently anchor phosphorescent luminescent units. It utilizes the lone pair electrons on the N atom of the urea-formaldehyde resin polymer structure to occupy the non-bonded n orbitals, which promotes the formation of n→π* transition when the luminescent unit is excited by light, effectively enhancing spin-orbit coupling and greatly promoting the intersystem crossing process from singlet to triplet state, thus providing sufficient excited state particles for phosphorescence emission. Meanwhile, the rigid three-dimensional cross-linked network structure and hydrogen bond system of urea-formaldehyde resin bind the movement of the luminescent molecules and stabilize the triplet excitons to suppress non-radiative transitions, thereby giving the urea-formaldehyde resin adhesive ultra-long room temperature phosphorescence properties, so that the cured adhesive layer has both reliable bonding function and optical recognition function; (2) The luminescence color and lifespan characteristics of the adhesive can be adjusted by setting the type of reactive phosphorescent luminescent unit and its content in the synthesis formula, and the addition of reactive phosphorescent luminescent unit does not affect the appearance, storage stability and bonding performance of the adhesive; (3) The adhesive layer formed after the adhesive is cured is bound to the bonded material throughout the entire service life and cannot be easily covered or wiped off; (4) The adhesive has the potential to give the artificial board product traceability-level anti-counterfeiting function and has broad prospects for industrial application. Detailed Implementation

[0019] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following detailed embodiments further illustrate the preparation method of an ultra-long room temperature phosphorescent modified urea-formaldehyde resin adhesive proposed in this invention. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Non-substantial improvements and adjustments made by those skilled in the art under the guidance of this invention should fall within the scope of protection of this invention. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific technical features, structures, or characteristics in one or more embodiments can be combined in an appropriate manner.

[0020] Unless otherwise specified, all raw materials, reagents, and instruments mentioned below are conventional commercially available products well-known to those skilled in the art; unless otherwise specified, all methods employed are methods known in the art. Unless otherwise defined, the technical or scientific terms used herein should be understood in the manner of those skilled in the art to which this invention pertains.

[0021] This invention proposes a method for preparing an ultra-long room temperature phosphorescent modified urea-formaldehyde resin adhesive. The key lies in introducing reactive phosphorescent units during the multi-stage polycondensation process of urea-formaldehyde resin, allowing them to participate in the resin polycondensation reaction and be fixed in the cross-linking network, thereby endowing the adhesive with stable room temperature phosphorescent function.

[0022] Specifically, this invention employs a step-by-step feeding and staged pH control method for preparation. First, under alkaline conditions, urea and formaldehyde undergo an initial condensation reaction to form a first-stage resin system. Subsequently, reactive phosphorescent luminescent units are added, and their participation in resin network construction is promoted through further condensation reactions under acidic conditions. Then, the viscosity of the system is adjusted through further acidic condensation. Subsequently, melamine and formaldehyde are added for a co-condensation reaction, and the theoretical molar ratio of formaldehyde to urea in the system is adjusted in stages by adding urea in the second and third steps, ultimately yielding an ultra-long room temperature phosphorescent modified urea-formaldehyde resin adhesive.

[0023] This invention employs a multi-stage pH control and stepwise feeding strategy to gradually construct the resin molecular structure at different reaction stages, thereby facilitating the formation of a stable cross-linked network and a light-emitting confinement environment. This avoids the local aggregation or quenching problems that easily occur when light-emitting components are introduced through simple physical doping.

[0024] Example 1 The following reaction is carried out in a reaction vessel equipped with a thermometer, a mechanical stirrer, and a reflux condenser: Step 1: Add 300 g of urea and 810 g of formaldehyde solution (37% by mass) to the reaction vessel, stir and mix evenly, adjust the pH of the system to 8.5 using 30% sodium hydroxide solution, raise the temperature to 92 ℃ in 35 min, and keep the temperature for 50 min to obtain the first stage reaction product.

[0025] Step 2: Add 10 g of tannic acid to the first-stage reaction product obtained in Step 1, stir and mix evenly, then adjust the pH of the system to 5.3 with formic acid, and keep the reaction at 88 ℃ until the viscosity of the reactant is 12.0 s when tested at 50 ℃ in a Forbes-4 cup, to obtain the second-stage reaction product.

[0026] Step 3: Continue to adjust the pH of the second-stage reaction product to 4.9 using formic acid, and keep the reaction at 84 °C until the viscosity of the reactant is 13.2 s when tested at 50 °C using a Forte 4 cup, thus obtaining the third-stage reaction product.

[0027] Step 4: Adjust the pH of the third-stage reaction product to 7.2 using 30% sodium hydroxide solution, add 60 g of melamine and 122 g of formaldehyde from the second step, and keep the reaction at 82 ℃ until the viscosity of the reactant measured at 50 ℃ in a Forte 4 cup is 14.8 s, thus obtaining the fourth-stage reaction product.

[0028] Step 5: Adjust the pH of the system to 8.2 using 30% sodium hydroxide solution, add 159g of urea from the second step, and keep the reaction at 79 ℃ until the viscosity of the reactant measured at 50 ℃ using a Forte 4 cup is 15.5 s, thus obtaining the product of the fifth stage reaction.

[0029] Step 6: Cool the product of the fifth stage reaction to 68 ℃, adjust the pH of the system to 8.8 using 30% sodium hydroxide solution, add 148g of urea from the third step, keep the reaction at the temperature for 20 min, until the viscosity of the reactant tested at 25 ℃ in a Forte 4 cup is 21.0 s, cool to room temperature, and obtain ultra-long room temperature phosphorescent modified urea-formaldehyde resin adhesive.

[0030] Flour (25% by weight) was added to the above adhesive to prepare the adhesive solution, which was then applied to 2.2 mm thick eucalyptus veneers at an application rate of 340 g / m² (double-sided). This resulted in the assembly of three-layer eucalyptus plywood sheets. The sheets were then hot-pressed at 120 ℃ and 1.0 MPa for 10 min to obtain three-layer eucalyptus plywood. The Class II bond strength, formaldehyde emission, and phosphorescence properties were then tested. Example 2 The following reaction was carried out in the same reaction apparatus as in Example 1: Step 1: Add 300 g of urea and 770 g of formaldehyde solution (37% by mass) to the reaction vessel, stir and mix evenly, adjust the pH of the system to 8.3 using 25% sodium hydroxide solution, raise the temperature to 90 ℃ within 30 min, and keep the temperature for 45 min to obtain the first stage reaction product.

[0031] Step 2: Add 8 g of lignin sulfonate to the first-stage reaction product obtained in Step 1, stir and mix evenly, so that the light-emitting unit participates in the urea-formaldehyde resin condensation reaction and is embedded in the network structure. Then, adjust the pH of the system to 5.4 with formic acid, and keep the reaction at 87 °C until the viscosity of the reactant is 11.9 s when tested at 50 °C in a Forte 4 cup, to obtain the second-stage reaction product.

[0032] Step 3: Continue to adjust the pH of the second-stage reaction product to 4.8 using formic acid, and keep the reaction at 83 °C until the viscosity of the reactant is 13.0 s when tested at 50 °C using a Forte 4 cup, thus obtaining the third-stage reaction product.

[0033] Step 4: Adjust the pH of the system to 7.1 using 25% sodium hydroxide solution, add 50 g of melamine and 122 g of formaldehyde from the second step, and keep the reaction at 81 °C until the viscosity of the reactants measured at 50 °C in a Forte 4 cup is 14.6 s, thus obtaining the fourth stage reaction product.

[0034] Step 5: Adjust the pH of the fourth-stage reaction product to 8.1 using a 25% sodium hydroxide solution, add 171g of urea from the second step, and keep the reaction at 78 ℃ until the viscosity of the reactant measured at 50 ℃ using a Forte 4 cup is 15.2 s, thus obtaining the fifth-stage reaction product.

[0035] Step 6: Cool the system obtained in Step 5 to 66 ℃, adjust the pH of the system to 8.7 using 25% sodium hydroxide solution, add 103g of urea from Step 3, keep the reaction at this temperature for 20 min, until the viscosity of the reactant measured at 25 ℃ in a Forte 4 cup is 20.5 s, cool to room temperature, and obtain ultra-long room temperature phosphorescent modified urea-formaldehyde resin adhesive.

[0036] Flour (25% by weight) was added to the above adhesive to prepare the adhesive solution, which was then applied to 2.2 mm thick eucalyptus veneers at an application rate of 340 g / m² (double-sided). This resulted in the assembly of three-layer eucalyptus plywood sheets. The sheets were then hot-pressed at 120 ℃ and 1.0 MPa for 10 min to obtain three-layer eucalyptus plywood. The Class II bond strength, formaldehyde emission, and phosphorescence properties were then tested.

[0037] Example 3 The following reaction is carried out in a reaction vessel equipped with a thermometer, a mechanical stirrer, and a reflux condenser: Step 1: Add 300 g of urea and 891 g of formaldehyde solution (37% by mass) to the reaction vessel. After stirring and mixing evenly, adjust the pH of the system to 8.5 using 30% sodium hydroxide solution. Raise the temperature to 92 °C within 36 min and keep the temperature for 50 min to obtain the first stage reaction product.

[0038] Step 2: Add 20 g of tannic acid to the first-stage reaction product obtained in Step 1, stir and mix evenly, so that the light-emitting unit participates in the urea-formaldehyde resin condensation reaction and is embedded in the network structure. Then, adjust the pH of the system to 5.3 with formic acid, and keep the reaction at 88°C until the viscosity of the reactant is 11.9 s when tested at 50°C in a Forte 4 cup, to obtain the second-stage reaction product.

[0039] Step 3: Continue to adjust the pH of the second-stage reaction product to 4.9 using formic acid, and keep the reaction at 84 °C until the viscosity of the reactant is 13.0 s when tested at 50 °C using a Forte 4 cup, thus obtaining the third-stage reaction product.

[0040] Step 4: Adjust the pH of the third-stage reaction product to 7.2 using 30% sodium hydroxide solution, add 80 g of melamine and 104 g of formaldehyde from the second step, and keep the reaction at 82 ℃ until the viscosity of the reactant measured at 50 ℃ in a Forte 4 cup is 14.9 s, thus obtaining the fourth-stage reaction product.

[0041] Step 5: Adjust the pH of the system to 8.1 using 30% sodium hydroxide solution, add 175g of urea from the second step, and keep the reaction at 79 ℃ until the viscosity of the reactant is 15.4 s when tested at 50 ℃ using a Forte 4 cup, thus obtaining the product of the fifth stage reaction.

[0042] Step 6: Cool the fifth stage reaction product obtained in Step 5 to 67 ℃, adjust the pH of the system to 8.7 using 30% sodium hydroxide solution, add 139g of urea from Step 3, keep the reaction at this temperature for 25 min, until the viscosity of the reactant measured at 25 ℃ is 22.0 s in a Forte 4 cup, cool to room temperature, and obtain an ultra-long room temperature phosphorescent modified urea-formaldehyde resin adhesive.

[0043] Flour (25% by weight) was added to the above adhesive to prepare the adhesive solution, which was then applied to 2.2 mm thick eucalyptus veneers at an application rate of 340 g / m² (double-sided). This resulted in the assembly of three-layer eucalyptus plywood sheets. The sheets were then hot-pressed at 120 ℃ and 1.0 MPa for 10 min to obtain three-layer eucalyptus plywood. The Class II bond strength, formaldehyde emission, and phosphorescence properties were then tested. Comparative Example 1 The following reaction was carried out in the same reaction apparatus as in Example 1: The following reaction is carried out in a reaction vessel equipped with a thermometer, a mechanical stirrer, and a reflux condenser: Step 1: Add 300 g of urea and 810 g of formaldehyde solution (37% by mass) to the reaction vessel, stir and mix evenly, adjust the pH of the system to 8.5 using 30% sodium hydroxide solution, raise the temperature to 92 ℃ in 35 min, and keep the temperature for 50 min to obtain the first stage reaction product.

[0044] Step 2: Adjust the pH of the first-stage reaction product to 5.3 using formic acid, and keep the reaction at 88 °C until the viscosity of the reactant is 12.0 s when tested at 50 °C using a Forte 4 cup, thus obtaining the second-stage reaction product.

[0045] Step 3: Continue to adjust the pH of the second-stage reaction product to 4.9 using formic acid, and keep the reaction at 84 °C until the viscosity of the reactant is 13.2 s when tested at 50 °C using a Forte 4 cup, thus obtaining the third-stage reaction product.

[0046] Step 4: Adjust the pH of the third-stage reaction product to 7.2 using 30% sodium hydroxide solution, add 122g of formaldehyde from the second step, and keep the reaction at 82 ℃ until the viscosity of the reactant measured at 50 ℃ using a Forte 4 cup is 14.8 s, thus obtaining the fourth-stage reaction product.

[0047] Step 5: Adjust the pH of the system to 8.2 using 30% sodium hydroxide solution, add 159g of urea from the second step, and keep the reaction at 79 ℃ until the viscosity of the reactant measured at 50 ℃ using a Forte 4 cup is 15.5 s, thus obtaining the product of the fifth stage reaction.

[0048] Step 6: Cool the product of the fifth stage reaction to 68 ℃, adjust the pH of the system to 8.8 using 30% sodium hydroxide solution, add 148g of urea from the third step, keep the reaction at this temperature for 20 min, until the viscosity of the reactant measured at 25 ℃ in a Forte 4 cup is 21.0 s, cool to room temperature, and obtain urea-formaldehyde resin adhesive.

[0049] Flour (25% by weight) was added to the above adhesive to prepare the adhesive solution, which was then applied to 2.2 mm thick eucalyptus veneers at an application rate of 340 g / m² (double-sided). This resulted in the assembly of three-layer eucalyptus plywood sheets. The sheets were then hot-pressed at 120 ℃ and 1.0 MPa for 10 min to obtain three-layer eucalyptus plywood. The Class II bond strength, formaldehyde emission, and phosphorescence properties were then tested.

[0050] Table 1. Properties and phosphorescence characteristics of adhesive-bonded boards prepared in the examples and comparative examples.

[0051] Note: The plywood strength in Table 1 is the test result of 14 specimens. The numerator is the average bond strength and the denominator is the minimum bond strength.

[0052] The strength of the plywood was tested according to the Class II strength test method in GB / T 9846-2015 "Ordinary Plywood": the specimen was soaked in water for 3 hours, then removed and soaked in hot water at 63 ℃ for another 3 hours before the bonding strength test was conducted. Formaldehyde emission was determined according to the desiccator method in GB / T 17657-1999 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels".

[0053] The three-layer eucalyptus plywood prepared in Examples 1 to 3 all exhibited better bonding strength, environmental friendliness, and good room temperature phosphorescence emission performance than the comparative examples. This indicates that the reactive phosphorescent unit described in this invention can be effectively embedded in the urea-formaldehyde resin molecular network and has the ability to impart room temperature phosphorescence without degrading the adhesive bonding performance and environmental friendliness.

[0054] The plywood obtained in Comparative Example 1 did not show significant room-temperature phosphorescence emission under the same test conditions, indicating that the phosphorescence performance comes from the embedding of reactive phosphorescent units into the adhesive structure.

Claims

1. A method for preparing an ultra-long-lasting room-temperature phosphorescent modified urea-formaldehyde resin adhesive, characterized in that, Includes the following steps: Step 1: Add urea and formaldehyde from the first step, adjust the pH to 8-9 using a 20-30% sodium hydroxide solution, raise the temperature to 90-95℃ within 30-40 minutes, and maintain the temperature for 40-60 minutes to obtain the first reaction product. Step 2: Add a reactive phosphorescent luminescent unit to the first reaction product, and after stable dispersion, adjust the pH to 5.2-5.5 using formic acid, and maintain the temperature at 85-90℃ until the viscosity of the reactant measured in a Ford cup at 50℃ is 11.8-12.2 s, obtaining the second reaction product. Step 3: Adjust the pH of the second reaction product system to 4.8-5.0 using formic acid, and maintain the temperature at 83-85℃ until the viscosity of the reactant measured in a Ford cup at 50℃ is 12.8-13.5 s, obtaining the third reaction product. Step 4: Adjust the pH of the third reaction product system to 7 using a 20-30% sodium hydroxide solution. Step 5: Add melamine and formaldehyde (from step 2) to a pH of 8.0-7.5, and react at 80-85°C until the viscosity of the reactant measured in a Forte 4 cup at 50°C is 14.5-15.0 s, obtaining the fourth reaction product; Step 6: Adjust the pH of the fourth reaction product system to 8.0-8.5 using a 20-30% sodium hydroxide solution, add urea (from step 2), and react at 78-80°C until the viscosity of the reactant measured in a Forte 4 cup at 50°C is 15.0-16.0 s, obtaining the fifth reaction product; Step 7: Cool the fifth reaction product to 65-70°C, adjust the pH of the system to 8.5-9.0 using a 20-30% sodium hydroxide solution, add urea (from step 3), and react at 15-30 min until the viscosity of the reactant measured in a Forte 4 cup at 25°C is 19.0-25.0 s, obtaining an ultra-long room temperature phosphorescent modified urea-formaldehyde resin adhesive.

2. The preparation method of the ultra-long room temperature phosphorescent modified urea-formaldehyde resin adhesive according to claim 1, characterized in that, The molar ratio of formaldehyde to urea in step 1 is 1.9 to 2.2:

1.

3. The preparation method of an ultra-long room temperature phosphorescent modified urea-formaldehyde resin adhesive according to claim 1, characterized in that, The reactive phosphorescent unit mentioned in step 2 is one or more of tannic acid, tannic acid, alkali lignin, lignin sulfonate, gallic acid, aminophenanthrene or aminopyrene, and p-aminobenzonitrile; and the amount of reactive phosphorescent unit added is 0.1% to 5.0% of the total mass of the synthetic material.

4. The preparation method of an ultra-long room temperature phosphorescent modified urea-formaldehyde resin adhesive according to claim 1, characterized in that, The amount of melamine added in step 4 is 1.0% to 18% of the total mass of the synthetic materials; after the addition of formaldehyde in the second step, the theoretical molar ratio of formaldehyde to urea in the added materials is 2.2 to 2.5:

1.

5. The preparation method of an ultra-long room temperature phosphorescent modified urea-formaldehyde resin adhesive according to claim 1, characterized in that, After adding urea in the second step described in step 5, the theoretical molar ratio of formaldehyde to urea in the added material is 1.4~1.6:

1.

6. The preparation method of an ultra-long room temperature phosphorescent modified urea-formaldehyde resin adhesive according to claim 1, characterized in that, After adding urea in the third step described in step 6, the theoretical molar ratio of formaldehyde to urea in the added material is 1.0~1.2:

1.

7. The product prepared by the method according to any one of claims 1-6 is an ultra-long room temperature phosphorescent modified urea-formaldehyde resin adhesive, and after the adhesive is fully cured, it can exhibit ultra-long room temperature phosphorescence characteristics under ultraviolet light excitation.

8. The application of the ultra-long room temperature phosphorescent modified urea-formaldehyde resin adhesive as described in claim 7 in optical identification, anti-counterfeiting traceability, or environmental response monitoring in wood composite materials, paper-based composite materials, and related interfacial bonding systems.

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