An anti-aging phenol-formaldehyde resin-based urea-formaldehyde glue and a preparation method thereof

Abstract

This invention relates to the field of adhesive technology and discloses an anti-aging phenolic resin-based urea-formaldehyde adhesive and its preparation method. The adhesive is composed of 95-100 parts phenol, 120-160 parts 37% formaldehyde solution, 80-110 parts urea, 3-4.5 parts modifier, 1.5-1.8 parts curing agent, and 1.8-2.2 parts anti-aging agent. The preparation method includes four steps: preparation of phenolic resin prepolymer, preparation of urea-formaldehyde resin prepolymer, composite modification, and post-treatment. This invention, through the synergistic effect of composite modification and anti-aging agent, solves the defects of traditional urea-formaldehyde adhesives, such as high formaldehyde release, poor anti-aging performance, and insufficient water resistance, while possessing excellent environmental friendliness, adhesion, and durability, making it suitable for fields such as the production of engineered wood products.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, specifically to an anti-aging phenolic resin-based urea-formaldehyde adhesive and its preparation method. Background Technology

[0002] Urea-formaldehyde resin is widely used in the production of engineered wood products due to its advantages such as readily available raw materials, low cost, and good bonding performance. However, traditional urea-formaldehyde resin has drawbacks such as high formaldehyde release, poor water resistance, and insufficient anti-aging properties. During long-term use, under the influence of environmental factors such as light and humidity, the adhesive is prone to aging and degradation, leading to problems such as cracking and delamination in engineered wood products, affecting the product's service life and safety.

[0003] Phenolic resins possess excellent high-temperature resistance, water resistance, and mechanical properties, but their high cost and brittleness when used alone limit their application in certain fields. Composite modification of phenolic resins with urea-formaldehyde resins can combine the advantages of both, improving the performance of urea-formaldehyde adhesives. While some research on phenolic-urea-formaldehyde composite adhesives exists, most composite adhesives do not show ideal results in improving anti-aging properties, and formaldehyde release still needs further reduction. Therefore, developing a phenolic resin-based urea-formaldehyde adhesive with excellent anti-aging properties, low formaldehyde release, and high bonding strength is of significant practical importance. Summary of the Invention

[0004] Technical problems to be solved To address the shortcomings of existing technologies, this invention provides an anti-aging phenolic resin-based urea-formaldehyde adhesive and its preparation method, which has good anti-aging and adhesion properties, while having low formaldehyde release.

[0005] Technical solution To achieve the above objectives, the present invention provides the following technical solution: an anti-aging phenolic resin-based urea-formaldehyde adhesive, comprising the following raw materials in parts by weight: 95-100 parts phenol, 120-160 parts formaldehyde solution, 80-110 parts urea, 3-4.5 parts modifier, 1.5-1.8 parts curing agent, and 1.8-2.2 parts anti-aging agent; wherein the formaldehyde solution has a mass fraction of 37%; the modifier is a combination of phosphorus-modified hyperbranched cashew phenol, sodium lignosulfonate, and 4-maleimide-based phenol, with a mass ratio of 1:1-2:1-1.5; the anti-aging agent is a mixture of 2,6-di-tert-butyl-p-cresol and triphenyl phosphite, with a mass ratio of 1:0.8-1.2; and the curing agent is a mixture of ammonium chloride and oxalic acid, with a mass ratio of 1:0.5-0.8.

[0006] Furthermore, the preparation method of the phosphorus-modified hyperbranched cashew phenol is as follows: S1. Under a nitrogen atmosphere, add cashew phenol and glycidol to the reactor, stir for 18-20 min, react at 75-80℃ for 1.5-2 h, then raise the temperature to 95-100℃ for 3-4 h, and finally raise the temperature to 110-120℃ for 1-2 h. After the reaction is completed, cool to room temperature to obtain hyperbranched cashew phenol polyglycerol. S2. Add 2,6,7-trioxa-1-phosphabicyclo(2.2.2)octane-4-methanol-1-oxide and mercaptoacetic acid to 30-35 mL of N,N-dimethylformamide solvent, stir and mix, continue to add p-toluenesulfonic acid catalyst, react at 100-110℃ for 7-8 h, and after the reaction is completed, distill under reduced pressure to obtain the phosphorus intermediate; S3. Add hyperbranched cashew phenol polyglycerol, phosphorus intermediate and photoinitiator 2-hydroxy-2-methylphenylacetone to a quartz glass beaker, stir evenly, react at room temperature for 10-12 h, place the quartz glass beaker under 320 nm ultraviolet light and react at room temperature for 11-12 h, and then rotary evaporate to obtain phosphorus-modified hyperbranched cashew phenol.

[0007] Furthermore, in S1, the ratio of cashew phenol to glycidol is 14-16 mmol: 45-50 mmol.

[0008] Further, in S2, the ratio of 2,6,7-trioxa-1-phosphabicyclo(2.2.2)octane-4-methanol-1-oxide, mercaptoacetic acid, and p-toluenesulfonic acid catalyst is 5-10 mmol: 5-10 mmol: 0.01-0.015 g.

[0009] Furthermore, in S3, the ratio of hyperbranched cashew polyglycerol, phosphorus intermediate, and photoinitiator 2-hydroxy-2-methylphenylacetone is 1-2 mmol: 4-7 mmol: 0.02-0.024 g.

[0010] Furthermore, the preparation method of the anti-aging phenolic resin-based urea-formaldehyde adhesive is as follows: (1) Preparation of phenolic resin prepolymer: Add phenol to the reaction vessel, heat to 40-50℃, then add formaldehyde solution accounting for 30-40% of the total weight of formaldehyde solution, adjust the pH value to 8-9, heat to 70-80℃, keep the reaction at the temperature for 1.5-2.5h to obtain phenolic resin prepolymer; (2) Preparation of urea-formaldehyde resin prepolymer: Add the remaining formaldehyde solution to another reactor, adjust the pH value to 7.5-8.5, raise the temperature to 50-60℃, add urea in two batches. The first batch is 60-70% of the total urea weight, and the reaction is stirred for 1-1.5h. The second batch is the remaining urea, and the temperature is raised to 75-85℃. The reaction is kept at this temperature for 0.5-1h to obtain urea-formaldehyde resin prepolymer. (3) Composite modification: The phenolic resin prepolymer prepared in step (1) is slowly added to the urea-formaldehyde resin prepolymer in step (2), stirred evenly, heated to 80-90℃, a modifier is added, and the reaction is kept at the temperature for 1-2 hours. Then an anti-aging agent is added, and the reaction is continued to be stirred for 0.5-1 hours. (4) Post-treatment: Cool the reaction system to 40-50℃, add curing agent, stir evenly, keep the reaction at the temperature, cool to room temperature, filter, and obtain anti-aging phenolic resin-based urea-formaldehyde glue.

[0011] Furthermore, the pH adjuster used in steps (1) and (2) is a sodium hydroxide solution with a mass fraction of 10-15%.

[0012] Furthermore, the heat preservation reaction time in step (4) is 0.3-0.5h.

[0013] Beneficial technical effects The phosphorus-modified hyperbranched cashew phenol in the modifier of this invention exhibits a branched structure that effectively reduces molecular chain entanglement, increases intermolecular porosity, absorbs and disperses external stress, thereby significantly reducing the brittleness of the adhesive layer and improving its impact and crack resistance. The long fatty chains of cashew phenol also provide excellent flexibility and hydrophobicity. Furthermore, the phosphorus element at the branch ends has good flame-retardant properties. The 4-maleimide-based phenol in the modifier participates in the reaction during resin curing, forming more stable chemical bonds and improving the thermal stability and water resistance of the resin network. The 2,6-di-tert-butyl-p-cresol (a hindered phenol) in the anti-aging agent acts as a free radical scavenger, rapidly eliminating hydroxyl and alkyl free radicals generated during aging and terminating free radical chain reactions. Triphenyl phosphite, as a hydroperoxide decomposer, decomposes the hydroperoxides generated during resin oxidation into harmless alcohol compounds, preventing further molecular chain breakage. These two components synergistically form a protective system. In the preparation of urea-formaldehyde resin, urea is added in two stages and reacts fully with sufficient formaldehyde under alkaline conditions, promoting hydroxymethylation and reducing unreacted free formaldehyde. The sodium lignosulfonate and phosphorus-modified hyperbranched cashew phenol in the modifiers contain active groups (such as phenolic hydroxyl groups and sulfonic acid groups), which can effectively react with residual free formaldehyde, effectively "capturing" it. The introduction of phenolic resin creates a more stable chemical structure, reducing the reverse decomposition and release of formaldehyde during use. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] 2,6,7-Trioxa-1-phosphabicyclo(2.2.2)octane-4-methanol-1-oxide, CAS 5301-78-0.

[0016] Example 1 An anti-aging phenolic resin-based urea-formaldehyde adhesive, comprising the following raw materials in parts by weight: 95 parts phenol, 120 parts formaldehyde solution, 80 parts urea, 3 parts modifier, 1.5 parts curing agent, and 1.8 parts anti-aging agent; wherein the formaldehyde solution has a mass fraction of 37%; the modifier is a combination of phosphorus-modified hyperbranched cashew phenol, sodium lignosulfonate, and 4-maleimide-based phenol, in a mass ratio of 1:1:1; the anti-aging agent is a mixture of 2,6-di-tert-butyl-p-cresol and triphenyl phosphite, in a mass ratio of 1:0.8; and the curing agent is a mixture of ammonium chloride and oxalic acid, in a mass ratio of 1:0.5.

[0017] The preparation method of the phosphorus-modified hyperbranched cashew phenol is as follows: S1. Under a nitrogen atmosphere, 14 mmol of cashew nut shellac and 45 mmol of glycidol were added to the reactor, stirred for 18 min, reacted at 75 °C for 1.5 h, then heated to 95 °C for 3 h, and finally heated to 110 °C for 1 h. After the reaction was completed, the mixture was cooled to room temperature to obtain hyperbranched cashew nut shellac polyglycerol. The reaction is as follows: S2. Add 5 mmol of 2,6,7-trioxa-1-phosphabicyclo(2.2.2)octane-4-methanol-1-oxide and 5 mmol of mercaptoacetic acid to 30 mL of N,N-dimethylformamide solvent, stir and mix, then add 0.01 g of p-toluenesulfonic acid catalyst, react at 100 °C for 7 h, and after the reaction is completed, distill under reduced pressure to obtain the phosphorus intermediate; S3. Add 1 mmol of hyperbranched cashew polyglycerol, 4 mmol of phosphorus intermediate and 0.02 g of photoinitiator 2-hydroxy-2-methylphenylacetone to a quartz glass beaker, stir well and react at room temperature for 10 h. Place the quartz glass beaker under ultraviolet light with a wavelength of 320 nm and react at room temperature for 11 h. Then, rotary evaporate to obtain phosphorus-modified hyperbranched cashew.

[0018] The preparation method of the anti-aging phenolic resin-based urea-formaldehyde adhesive is as follows: (1) Preparation of phenolic resin prepolymer: Phenol is added to the reaction vessel, the temperature is raised to 40°C, and then formaldehyde solution accounting for 30% of the total weight of formaldehyde solution is added. The pH value is adjusted to 8, the temperature is raised to 70°C, and the reaction is kept at the temperature for 1.5h to obtain phenolic resin prepolymer. (2) Preparation of urea-formaldehyde resin prepolymer: Add the remaining formaldehyde solution to another reactor, adjust the pH value to 7.5, raise the temperature to 50°C, add urea in two batches. The first batch is 60% of the total urea weight, and the mixture is stirred for 1 hour. The second batch is the remaining urea, and the mixture is raised to 75°C and kept at that temperature for 0.5 hours to obtain urea-formaldehyde resin prepolymer. (3) Composite modification: The phenolic resin prepolymer prepared in step (1) is slowly added to the urea-formaldehyde resin prepolymer in step (2), stirred evenly, heated to 80°C, a modifier is added, the reaction is kept warm for 1 hour, and then an anti-aging agent is added, and the reaction is continued to be stirred for 0.5 hours. (4) Post-treatment: Cool the reaction system to 40°C, add curing agent, stir evenly, keep warm for 0.3h, cool to room temperature, filter, and obtain anti-aging phenolic resin-based urea-formaldehyde glue.

[0019] The pH adjuster used in steps (1) and (2) is a 10% sodium hydroxide solution.

[0020] Example 2 An anti-aging phenolic resin-based urea-formaldehyde adhesive, comprising the following raw materials in parts by weight: 100 parts phenol, 160 parts formaldehyde solution, 110 parts urea, 4.5 parts modifier, 1.8 parts curing agent, and 2.2 parts anti-aging agent; wherein the formaldehyde solution has a mass fraction of 37%; the modifier is a combination of phosphorus-modified hyperbranched cashew phenol, sodium lignosulfonate, and 4-maleimide-based phenol, in a mass ratio of 1:2:1.5; the anti-aging agent is a mixture of 2,6-di-tert-butyl-p-cresol and triphenyl phosphite, in a mass ratio of 1:1.2; and the curing agent is a mixture of ammonium chloride and oxalic acid, in a mass ratio of 1:0.8.

[0021] The preparation method of the phosphorus-modified hyperbranched cashew phenol is as follows: S1. Under a nitrogen atmosphere, 16 mmol of cashew phenol and 50 mmol of glycidol were added to the reactor, stirred for 20 min, reacted at 80 °C for 2 h, then heated to 100 °C for 4 h, and finally heated to 120 °C for 2 h. After the reaction was completed, the mixture was cooled to room temperature to obtain hyperbranched cashew phenol polyglycerol. S2. Add 10 mmol of 2,6,7-trioxa-1-phosphabicyclo(2.2.2)octane-4-methanol-1-oxide and 10 mmol of mercaptoacetic acid to 35 mL of N,N-dimethylformamide solvent, stir and mix, then add 0.015 g of p-toluenesulfonic acid catalyst, react at 110 °C for 8 h, and after the reaction is completed, distill under reduced pressure to obtain the phosphorus intermediate; S3. Add 2 mmol of hyperbranched cashew polyglycerol, 7 mmol of phosphorus intermediate and 0.024 g of photoinitiator 2-hydroxy-2-methylphenylacetone to a quartz glass beaker, stir well and react at room temperature for 12 h. Place the quartz glass beaker under ultraviolet light with a wavelength of 320 nm and react at room temperature for 12 h. Then, rotary evaporate to obtain phosphorus-modified hyperbranched cashew.

[0022] The preparation method of the anti-aging phenolic resin-based urea-formaldehyde adhesive is as follows: (1) Preparation of phenolic resin prepolymer: Phenol is added to the reaction vessel, the temperature is raised to 50°C, and then formaldehyde solution accounting for 40% of the total weight of formaldehyde solution is added. The pH value is adjusted to 9, the temperature is raised to 80°C, and the reaction is kept at the temperature for 2.5h to obtain phenolic resin prepolymer. (2) Preparation of urea-formaldehyde resin prepolymer: Add the remaining formaldehyde solution to another reactor, adjust the pH value to 8.5, raise the temperature to 60°C, add urea in two batches. The first batch is 70% of the total urea weight, and the mixture is stirred for 1.5 hours. The second batch is the remaining urea, and the mixture is raised to 85°C and kept at that temperature for 1 hour to obtain urea-formaldehyde resin prepolymer. (3) Composite modification: The phenolic resin prepolymer prepared in step (1) is slowly added to the urea-formaldehyde resin prepolymer in step (2), stirred evenly, heated to 90°C, a modifier is added, the reaction is kept warm for 2 hours, an anti-aging agent is added, and the reaction is continued for 1 hour. (4) Post-treatment: Cool the reaction system to 50°C, add curing agent, stir evenly, keep warm for 0.5h, cool to room temperature, filter, and obtain anti-aging phenolic resin-based urea-formaldehyde adhesive.

[0023] The pH adjuster used in steps (1) and (2) is a 15% sodium hydroxide solution.

[0024] Example 3 An anti-aging phenolic resin-based urea-formaldehyde adhesive, comprising the following raw materials in parts by weight: 98 parts phenol, 140 parts formaldehyde solution, 90 parts urea, 3.6 parts modifier, 1.7 parts curing agent, and 2.0 parts anti-aging agent; wherein the formaldehyde solution has a mass fraction of 37%; the modifier is a combination of phosphorus-modified hyperbranched cashew phenol, sodium lignosulfonate, and 4-maleimide-based phenol, with a mass ratio of 1:1.5:1; the anti-aging agent is a mixture of 2,6-di-tert-butyl-p-cresol and triphenyl phosphite, with a mass ratio of 1:1.0; and the curing agent is a mixture of ammonium chloride and oxalic acid, with a mass ratio of 1:0.6.

[0025] The preparation method of the phosphorus-modified hyperbranched cashew phenol is as follows: S1. Under a nitrogen atmosphere, 15 mmol of cashew phenol and 48 mmol of glycidol were added to the reactor, stirred for 19 min, reacted at 78 °C for 1.8 h, then heated to 97 °C for 4 h, and finally heated to 115 °C for 1.5 h. After the reaction was completed, the mixture was cooled to room temperature to obtain hyperbranched cashew phenol polyglycerol. S2. Add 7 mmol of 2,6,7-trioxa-1-phosphabicyclo(2.2.2)octane-4-methanol-1-oxide and 7 mmol of mercaptoacetic acid to 32 mL of N,N-dimethylformamide solvent, stir and mix, then add 0.012 g of p-toluenesulfonic acid catalyst, react at 105 °C for 7.5 h, and after the reaction is completed, distill under reduced pressure to obtain the phosphorus intermediate; S3. Add 1.5 mmol of hyperbranched cashew polyglycerol, 5.6 mmol of phosphorus intermediate and 0.02 g of photoinitiator 2-hydroxy-2-methylphenylacetone to a quartz glass beaker, stir well, and react at room temperature for 11 h. Place the quartz glass beaker under ultraviolet light with a wavelength of 320 nm and react at room temperature for 11 h. Then, rotary evaporate to obtain phosphorus-modified hyperbranched cashew.

[0026] The preparation method of the anti-aging phenolic resin-based urea-formaldehyde adhesive is as follows: (1) Preparation of phenolic resin prepolymer: Phenol is added to the reaction vessel, the temperature is raised to 45°C, and then formaldehyde solution accounting for 35% of the total weight of formaldehyde solution is added. The pH value is adjusted to 8.5, the temperature is raised to 75°C, and the reaction is kept at the temperature for 2 hours to obtain phenolic resin prepolymer. (2) Preparation of urea-formaldehyde resin prepolymer: Add the remaining formaldehyde solution to another reactor, adjust the pH value to 8, raise the temperature to 55°C, add urea in two batches. The first batch is 65% of the total urea weight, and the mixture is stirred for 1.2 h. The second batch is the remaining urea, and the mixture is raised to 80°C and kept at that temperature for 0.75 h to obtain urea-formaldehyde resin prepolymer. (3) Composite modification: The phenolic resin prepolymer prepared in step (1) is slowly added to the urea-formaldehyde resin prepolymer in step (2), stirred evenly, heated to 85°C, a modifier is added, and the reaction is kept at the temperature for 1.5h. Then an anti-aging agent is added, and the reaction is continued to be stirred for 0.75h. (4) Post-treatment: Cool the reaction system to 45°C, add curing agent, stir evenly, keep the reaction at the temperature for 0.4h, cool to room temperature, filter, and obtain anti-aging phenolic resin-based urea-formaldehyde adhesive.

[0027] The pH adjuster used in steps (1) and (2) is a 12% sodium hydroxide solution.

[0028] Comparative Example 1 Raw material ratio: Compared with Example 3, cashew phenol is used instead of phosphorus-modified hyperbranched cashew phenol; Preparation method: Same as in Example 3.

[0029] Comparative Example 2 Raw material ratio: Compared with Example 3, the anti-aging agent is only 2.0 parts of 2,6-di-tert-butyl-p-cresol (excluding triphenyl phosphite). Preparation method: Same as in Example 3.

[0030] Comparative Example 3 Raw material ratio: Compared with Example 3, the modifier is a combination of sodium lignosulfonate and 4-maleimide phenol, with a mass ratio of 1.5:1; Preparation method: same as Example 3.

[0031] Bond strength test (normal state + water-resistant state) Test standard: The test shall be conducted in accordance with the "Test Methods for Wood Adhesives and Resins" (GB / T14074-2017); Sample preparation: Poplar boards (moisture content 8-10%, density 0.45-0.55 g / cm³) shall be processed into butt joint samples of 25 mm × 100 mm × 5 mm. The urea-formaldehyde adhesive coating amount shall be 200 g / m². After being left to dry at room temperature for 10 min, the samples shall be bonded together and cured at 0.8 MPa pressure and 25℃ for 24 h; After the water-resistant samples are cured, they shall be immersed in distilled water at (23±2)℃ for 24 h, and after being taken out, the surface moisture shall be absorbed with filter paper and tested immediately. Testing equipment: Universal testing machine (accuracy 0.01MPa), tensile rate 5mm / min, record the maximum load when the specimen breaks, calculate the result according to "bond strength = maximum load / bond area", test 5 parallel specimens in each group and take the average value.

[0032] Formaldehyde emission test standard: The test is conducted according to the "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels" (GB / T17657-2022); Sample preparation: The adhesive is coated on poplar veneer (200mm×200mm×3mm) to make three-layer plywood (total thickness 9mm). After curing, it is equilibrated for 72h at (23±2)℃ and (50±5)% relative humidity. Two 150mm×150mm samples are cut, with a total mass of (120±5)g; Test procedure: The sample is placed at the bottom of a 40L desiccator, and 50mL of distilled water is placed in the desiccator. After sealing, it is left to stand for 24h at (20±2)℃. The formaldehyde concentration in the distilled water is determined by the acetylacetone spectrophotometric method, and the formaldehyde emission is calculated. Three parallel samples are tested in each group, and the average value is taken.

[0033] Anti-aging performance test (accelerated aging) Aging conditions: A combined accelerated aging scheme of "ultraviolet light aging + damp heat aging" was adopted; Ultraviolet aging: UV lamp wavelength 320nm, irradiation intensity 0.8mW / cm², temperature (60±2)℃, continuous irradiation for 100h; Damp heat aging: Temperature (50±2)℃, relative humidity (90±5)%, continuous aging for 100h; Test procedure: Test the normal bonding strength of the sample before aging (denoted as ). After aging, the remaining bond strength is determined according to the "normal bonding strength test method" (denoted as ). The vertical flammability rating of materials is tested using a horizontal-vertical flammability testing machine.

[0034] Table 1: Performance Tests Example 1 2.9 2.5 0.08 2.3 V-0 Example 2 3.1 2.7 0.07 2.4 V-0 Example 3 3.2 2.8 0.09 2.6 V-0 Comparative Example 1 2.1 1.6 0.18 1.3 V-1 Comparative Example 2 2.5 1.8 0.12 1.4 V-0 Comparative Example 3 1.9 1.4 0.19 1.1 V-1 As shown in Table 1, the anti-aging phenolic resin-based urea-formaldehyde adhesive of the present invention has good adhesion, flame retardancy and low formaldehyde release.

[0035] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0036] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0037] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments.

Claims

1. An anti-aging phenolic resin-based urea-formaldehyde adhesive, characterized in that, The product is composed of the following raw materials in parts by weight: 95-100 parts phenol, 120-160 parts formaldehyde solution, 80-110 parts urea, 3-4.5 parts modifier, 1.5-1.8 parts curing agent, and 1.8-2.2 parts anti-aging agent; the formaldehyde solution has a mass fraction of 37%; the modifier is a combination of phosphorus-modified hyperbranched cashew phenol, sodium lignosulfonate, and 4-maleimide-based phenol, with a mass ratio of 1:1-2:1-1.5; the anti-aging agent is a mixture of 2,6-di-tert-butyl-p-cresol and triphenyl phosphite, with a mass ratio of 1:0.8-1.2; and the curing agent is a mixture of ammonium chloride and oxalic acid, with a mass ratio of 1:0.5-0.

8.

2. The anti-aging phenolic resin-based urea-formaldehyde adhesive according to claim 1, characterized in that, The preparation method of the phosphorus-modified hyperbranched cashew phenol is as follows: S1. Under a nitrogen atmosphere, add cashew phenol and glycidol to the reactor, stir for 18-20 min, react at 75-80℃ for 1.5-2 h, then raise the temperature to 95-100℃ for 3-4 h, and finally raise the temperature to 110-120℃ for 1-2 h. After the reaction is completed, cool to room temperature to obtain hyperbranched cashew phenol polyglycerol. S2. Add 2,6,7-trioxa-1-phosphabicyclo(2.2.2)octane-4-methanol-1-oxide and mercaptoacetic acid to 30-35 mL of N,N-dimethylformamide solvent, stir and mix, continue to add p-toluenesulfonic acid catalyst, react at 100-110℃ for 7-8 h, and after the reaction is completed, distill under reduced pressure to obtain the phosphorus intermediate; S3. Add hyperbranched cashew phenol polyglycerol, phosphorus intermediate and photoinitiator 2-hydroxy-2-methylphenylacetone to a quartz glass beaker, stir evenly, react at room temperature for 10-12 h, place the quartz glass beaker under 320 nm ultraviolet light and react at room temperature for 11-12 h, and then rotary evaporate to obtain phosphorus-modified hyperbranched cashew phenol.

3. The anti-aging phenolic resin-based urea-formaldehyde adhesive according to claim 2, characterized in that, In S1, the ratio of cashew phenol to glycidol is 14-16 mmol: 45-50 mmol.

4. The anti-aging phenolic resin-based urea-formaldehyde adhesive according to claim 2, characterized in that, In S2, the ratio of 2,6,7-trioxa-1-phosphabicyclo(2.2.2)octane-4-methanol-1-oxide, mercaptoacetic acid, and p-toluenesulfonic acid catalyst is 5-10 mmol: 5-10 mmol: 0.01-0.015 g.

5. The anti-aging phenolic resin-based urea-formaldehyde adhesive according to claim 2, characterized in that, In S3, the ratio of hyperbranched cashew polyglycerol, phosphorus intermediate, and photoinitiator 2-hydroxy-2-methylphenylacetone is 1-2 mmol: 4-7 mmol: 0.02-0.024 g.

6. A method for preparing an anti-aging phenolic resin-based urea-formaldehyde adhesive as described in any one of claims, characterized in that, The preparation method of the anti-aging phenolic resin-based urea-formaldehyde adhesive is as follows: (1) Preparation of phenolic resin prepolymer: Add phenol to the reaction vessel, heat to 40-50℃, then add formaldehyde solution accounting for 30-40% of the total weight of formaldehyde solution, adjust the pH value to 8-9, heat to 70-80℃, keep the reaction at the temperature for 1.5-2.5h to obtain phenolic resin prepolymer; (2) Preparation of urea-formaldehyde resin prepolymer: Add the remaining formaldehyde solution to another reactor, adjust the pH value to 7.5-8.5, raise the temperature to 50-60℃, add urea in two batches. The first batch is 60-70% of the total urea weight, and the reaction is stirred for 1-1.5h. The second batch is the remaining urea, and the temperature is raised to 75-85℃. The reaction is kept at this temperature for 0.5-1h to obtain urea-formaldehyde resin prepolymer. (3) Composite modification: The phenolic resin prepolymer prepared in step (1) is slowly added to the urea-formaldehyde resin prepolymer in step (2), stirred evenly, heated to 80-90℃, a modifier is added, and the reaction is kept at the temperature for 1-2 hours. Then an anti-aging agent is added, and the reaction is continued to be stirred for 0.5-1 hours. (4) Post-treatment: Cool the reaction system to 40-50℃, add curing agent, stir evenly, keep the reaction at the temperature, cool to room temperature, filter, and obtain anti-aging phenolic resin-based urea-formaldehyde glue.

7. The preparation method of the anti-aging phenolic resin-based urea-formaldehyde adhesive according to claim 6, characterized in that, The pH adjuster used in steps (1) and (2) is a sodium hydroxide solution with a mass fraction of 10-15%.

8. The method for preparing anti-aging phenolic resin-based urea-formaldehyde adhesive according to claim 6, characterized in that, The heat preservation reaction time in step (4) is 0.3-0.5h.

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