Weatherable hot melt adhesive and method of making same

Abstract

The present application relates to the technical field of hot melt adhesive, and discloses a weather-resistant hot melt adhesive and a preparation method thereof, which comprises the following components: cashew phenol-formaldehyde polycondensate 20-30 parts, maleic anhydride grafted POE 40-50 parts, coated antioxidant 2-4 parts, hydrogenated Fischer-Tropsch wax 5-8 parts, weather-resistant thixotropic agent 3-6 parts, and light stabilizer 3-6 parts. The weather-resistant hot melt adhesive has excellent processing performance, the processing temperature is reduced by 25-30 DEG C, the melting viscosity is stable, and the adhesive can meet the long-term outdoor use. The bonding performance is reliable, the adhesive is firmly combined with the base materials such as aluminum alloy and photovoltaic glass, and there is no bonding failure. The components have good compatibility, the retention rate of the additives is high, and the service life is greatly prolonged.

Description

Technical Field

[0001] This invention relates to the field of hot melt adhesive technology, specifically to a weather-resistant hot melt adhesive and its preparation method. Background Technology

[0002] Weather-resistant hot melt adhesives are a type of solvent-free thermoplastic adhesives with excellent resistance to outdoor environments. Compared with ordinary hot melt adhesives, they have a wider range of applications and are especially suitable for various long-term outdoor bonding needs.

[0003] For example, an existing Chinese patent (CN118667475B) discloses a multi-component hot melt adhesive based on polyolefins and its preparation method. The hot melt adhesive comprises the following raw materials: polyolefin resin, high-temperature stabilizer, functionalized phenolic resin, tackifying resin, wax, and initiator. Using polyolefin resin as the matrix material, it has good bonding strength and a light odor during use. However, traditional polyolefin hot melt adhesives have poor high-temperature resistance and oxidation resistance, and are greatly affected by temperature. They are prone to bonding failure in high-temperature environments. Therefore, this invention prepares a hot melt adhesive with excellent high-temperature resistance and oxidation resistance by adding a high-temperature stabilizer and functionalized phenolic resin to the polyolefin matrix.

[0004] However, most existing weather-resistant hot melt adhesives use basic polymers with stable molecular structures and outstanding aging resistance, such as metallocene polyolefins (POE) and ethylene propylene diene monomer (EPDM). These polymers have high molecular weight and high molecular chain entanglement, which leads to a significant increase in the melt viscosity of the adhesive. High temperatures above 180°C are required during production and processing, which not only greatly increases energy consumption but also easily causes coking of the adhesive application equipment and stringing of the adhesive layer. Moreover, commonly used antioxidants and light stabilizers are prone to thermal decomposition or volatilization during high-temperature melting and processing at 160*200°C. This not only causes them to lose their anti-aging effects but also generates small molecule impurities, resulting in defects such as bubbles and pinholes in the adhesive layer. At the same time, the actual amount of effective anti-aging additives remaining in the adhesive layer after processing is insufficient, making the service life of the adhesive far lower than the design expectation. Summary of the Invention

[0005] The purpose of this invention is to provide a weather-resistant hot melt adhesive and its preparation method to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a weather-resistant hot melt adhesive, comprising the following components by weight: 20-30 parts of cashew phenol-formaldehyde condensate, 40-50 parts of maleic anhydride-grafted POE, 2-4 parts of coated antioxidant, 5-8 parts of hydrogenated Fischer-Tropsch wax, 3-6 parts of weather-resistant thixotropic agent, and 3-6 parts of light stabilizer.

[0007] Preferably, by weight, it comprises the following components: 22 parts cashew phenol-formaldehyde condensate, 48 parts maleic anhydride-grafted POE, 2.5 parts coated antioxidant, 6 parts hydrogenated Fischer-Tropsch wax, 4 parts weather-resistant thixotropic agent, and 3 parts light stabilizer.

[0008] Preferably, by weight, it comprises the following components: 26 parts cashew phenol-formaldehyde condensate, 44 parts maleic anhydride-grafted POE, 3 parts coated antioxidant, 7 parts hydrogenated Fischer-Tropsch wax, 5 parts weather-resistant thixotropic agent, and 4 parts light stabilizer.

[0009] Preferably, by weight, it comprises the following components: 28 parts cashew phenol-formaldehyde condensate, 42 parts maleic anhydride-grafted POE, 3.5 parts coated antioxidant, 5.5 parts hydrogenated Fischer-Tropsch wax, 3.5 parts weather-resistant thixotropic agent, and 3.5 parts light stabilizer.

[0010] Preferably, the cashew phenol-formaldehyde condensate is prepared by a condensation reaction of formaldehyde and cashew phenol, with a degree of condensation of 5 to 12 and a softening point of 90°C to 105°C, and the grafting rate of maleic anhydride-grafted POE is 0.8% to 1.2%.

[0011] Preferably, in the cashew phenol-formaldehyde condensate, the molar ratio of formaldehyde to cashew phenol is 1.0 to 1.2:1.

[0012] Preferably, the coated antioxidant is a silica-coated hindered phenolic antioxidant with a coating thickness of 50-100 nm, wherein the hindered phenolic antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 2:1.

[0013] Preferably, the hydroxyl value of the cashew phenol-formaldehyde condensate is 80-120 mgKOH / g.

[0014] A method for preparing a weather-resistant hot melt adhesive includes the following steps:

[0015] S1: Pretreatment: Crush cashew phenol-formaldehyde condensate to 80-100 mesh and dry at 80-90℃ for 2-3 hours to remove moisture; dry maleic anhydride-grafted POE and hydrogenated Fischer-Tropsch wax to a moisture content of ≤0.1% to avoid generating bubbles during processing.

[0016] S2: Premixed melt, the pretreated cashew phenol-formaldehyde condensate, maleic anhydride-grafted POE, and hydrogenated Fischer-Tropsch wax are added to the main feed port of a twin-screw extruder. The extruder front section temperature is set to 130℃~145℃, the middle section to 145℃~155℃, and the rear section to 155℃~165℃. The screw speed is 200~250r / min. The melt is mixed for 15~25min to obtain a uniform premixed melt.

[0017] S3: Additives are added by adding coated antioxidants, weather-resistant thixotropic agents, and light stabilizers into the twin-screw extruder through the auxiliary feed port. The temperature of the auxiliary feed port is controlled at 135℃~145℃, and the mixture is continued to melt and mix for 8~12 minutes to obtain a uniform adhesive melt.

[0018] S4: Molding, the adhesive melt is extruded through a twin-screw extruder, cooled in stages, and pelletized to obtain the finished product.

[0019] Preferably, the coated antioxidant, light stabilizer, and weather-resistant thixotropic agent are dried at 80℃~90℃ for 2~3 hours until the moisture content is ≤0.1% before being added to the twin-screw extruder.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] The weather-resistant hot melt adhesive prepared by this invention exhibits excellent processing performance, with a processing temperature reduction of 25-30℃, stable melt viscosity, and no coking or bubbles observed in three consecutive batches of processing. It is suitable for industrial production using twin-screw extrusion, reducing energy consumption and product defect rate. It also demonstrates outstanding weather resistance, retaining over 87% of its bond strength after UV, damp heat, and high / low temperature cycling aging. It exhibits a low yellowing index, with no cracking or debonding, meeting the requirements for long-term outdoor use. Furthermore, it boasts reliable bonding performance: a normal tensile shear strength of 12.8-13.4 MPa, firmly bonding to substrates such as aluminum alloys and photovoltaic glass without bond failure. The components exhibit good compatibility, with consistent performance across different batches, high additive retention, and significantly extended service life. Simultaneously, the formula is simplified, cost-effective, and highly practical.

[0022] The parts of the device not covered herein are the same as or can be implemented using existing technologies. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0024] Example 1: The present invention provides a technical solution: a weather-resistant hot melt adhesive, comprising the following components by weight: 20-30 parts of cashew phenol-formaldehyde condensate, 40-50 parts of maleic anhydride-grafted POE, 2-4 parts of coated antioxidant, 5-8 parts of hydrogenated Fischer-Tropsch wax, 3-6 parts of weather-resistant thixotropic agent, and 3-6 parts of light stabilizer.

[0025] Cashew phenol-formaldehyde condensate is prepared by the condensation reaction of formaldehyde and cashew phenol, with a degree of condensation of 5-12 and a softening point of 90℃-105℃. The grafting rate of maleic anhydride-grafted POE is 0.8%-1.2%. The setting of a degree of condensation of 5-12 and a softening point of 90℃-105℃ gives the cashew phenol-formaldehyde condensate excellent weather resistance while avoiding its defects of excessive brittleness and poor melt processability. It can be well blended with maleic anhydride-grafted POE, solving the problem that aldehyde-ketone-phenol condensates are difficult to apply to hot melt adhesives in the prior art. The maleic anhydride-grafted POE with a grafting rate of 0.8%-1.2% can effectively improve the compatibility with cashew phenol-formaldehyde condensate, and at the same time improve the melt flowability of the adhesive, providing technical support for reducing the subsequent processing temperature by 25-30℃ and stabilizing the melt viscosity at 800±40 mPa.s.

[0026] Cashew phenol-formaldehyde condensate, as the core matrix component of adhesives, possesses excellent resistance to UV, damp heat, and high-temperature aging, solving the defects of existing hot melt adhesives that are prone to aging and cracking during long-term outdoor use. Its softening point of 90℃~105℃ and melting characteristics are adapted to processing requirements, avoiding bonding failure caused by excessive brittleness. At the same time, its hydroxyl value of 80~120mgKOH / g ensures good compatibility with other components, providing support for bonding strength.

[0027] Maleic anhydride-grafted POE, as a blending modifier, fundamentally addresses the compatibility issues between cashew phenol-formaldehyde condensate and other components. Simultaneously, it improves the melt flowability of the adhesive, adjusting processing performance and bonding toughness. A grafting rate of 0.8%–1.2% enables the polar groups of maleic anhydride to combine with the polar groups of cashew phenol-formaldehyde condensate, overcoming the problems of poor compatibility and uneven blending. Possessing excellent flexibility and melt flowability, it can reduce the overall melt viscosity of the adhesive to a stable 800±40 mPa·s, lowering the processing temperature from the current 180–190℃ to 155–165℃, a reduction of 25–30℃. Simultaneously, it enhances the adhesive's toughness, preventing brittleness and ensuring both processability and bonding reliability.

[0028] This coated antioxidant inhibits the thermo-oxidative aging of adhesives during melt processing at 155–165°C and long-term use, protecting the components from degradation and extending the adhesive's service life. It employs a silica coating and hindered phenolic compound design, unlike ordinary low-molecular-weight antioxidants. The 50–100 nm silica coating forms a protective barrier, preventing the antioxidant from decomposing and volatilizing at high processing temperatures, increasing the retention rate from the current 68.5% to over 92%. Antioxidant 1010, the primary antioxidant, captures free radicals, while Antioxidant 168, the secondary antioxidant, decomposes hydroperoxides. Combined in a 2:1 ratio, they synergistically exert anti-aging effects, preventing yellowing and embrittlement of the adhesive layer, while also avoiding adverse reactions with other components, ensuring no coking or bubbles during processing.

[0029] Hydrogenated Fischer-Tropsch wax adjusts the melt flowability of the adhesive, reduces processing viscosity, improves the molding effect of the adhesive, enhances the surface smoothness of the adhesive layer, and helps improve workability, preventing stringing and sagging during application. With a melting temperature of 80–100℃, hydrogenated Fischer-Tropsch wax is well-suited to the overall processing technology, further reducing the melt viscosity of the adhesive and ensuring smooth twin-screw extrusion. After molding, it improves the regularity of the adhesive particles, facilitating storage, transportation, and subsequent application. Furthermore, adding small amounts does not affect the adhesive's weather resistance or bond strength, balancing processability and performance.

[0030] Weather-resistant thixotropic agents improve the thixotropic properties of adhesives, thickening when standing and thinning when subjected to external force, preventing dripping and seepage during application and improving construction precision. They also help enhance the weather resistance of the adhesive layer, reducing performance degradation during aging. Application allows for rapid setting, avoiding adhesive waste and substrate contamination, making it suitable for the precise application needs of outdoor building materials and photovoltaic modules. Furthermore, it improves the structural stability of the adhesive layer, reducing shrinkage and cracking after UV and humid heat aging, and helping to improve the retention rate of bond strength.

[0031] The light stabilizer specifically counteracts the degradation effects of outdoor UV light (290-400nm) on adhesives. Synergistically working with encapsulated antioxidants, it constructs a dual weather-resistant system resistant to both heat and oxidation, and UV radiation. It effectively absorbs or shields UV light, preventing chemical bond breakage, yellowing, and embrittlement of the adhesive layer due to UV irradiation. This results in improved bond strength retention after 1000 hours of UV aging, with no significant yellowing even after long-term use, making it suitable for long-term outdoor applications.

[0032] The weather-resistant hot melt adhesive prepared by this invention exhibits excellent processing performance, with a processing temperature reduction of 25-30℃, stable melt viscosity, and no coking or bubbles observed in three consecutive batches of processing. It is suitable for industrial production using twin-screw extrusion, reducing energy consumption and product defect rate. It also demonstrates outstanding weather resistance, retaining over 87% of its bond strength after UV, damp heat, and high / low temperature cycling aging. It exhibits a low yellowing index, with no cracking or debonding, meeting the requirements for long-term outdoor use. Furthermore, it boasts reliable bonding performance: a normal tensile shear strength of 12.8-13.4 MPa, firmly bonding to substrates such as aluminum alloys and photovoltaic glass without bond failure. The components exhibit good compatibility, with consistent performance across different batches, high additive retention, and significantly extended service life. Simultaneously, the formula is simplified, cost-effective, and highly practical.

[0033] In the cashew phenol-formaldehyde condensate, the molar ratio of formaldehyde to cashew phenol is 1.0–1.2:1. Clearly defining the raw material ratio for the condensation reaction ensures a complete and controllable reaction, avoiding the instability of component properties caused by incomplete condensation reactions in existing technologies. Simultaneously, the cashew phenol-formaldehyde condensate prepared at this molar ratio exhibits a stable hydroxyl value within the subsequently defined range, along with good heat resistance and adhesion.

[0034] The coated antioxidant is a silica-coated hindered phenolic antioxidant with a coating thickness of 50–100 nm. The hindered phenolic antioxidant is a blend of antioxidant 1010 and antioxidant 168 in a 2:1 mass ratio. The silica coating forms a protective barrier, preventing the hindered phenolic antioxidant from thermally decomposing or volatilizing at processing temperatures of 155–165°C. The coated structure also prevents adverse reactions between the antioxidant and other components, ensuring no bubbles or coking during adhesive processing and improving processing stability. The 2:1 blend of antioxidant 1010 and antioxidant 168 achieves synergistic anti-aging effects, improving the long-term weather resistance of the adhesive, especially enhancing its performance stability under high temperature and UV conditions.

[0035] The hydroxyl value of cashew phenol-formaldehyde condensate is 80–120 mg KOH / g. This range ensures good hydrogen bonding between the cashew phenol-formaldehyde condensate and maleic anhydride-grafted POE and the substrate, improving adhesion strength. Within this range, the melt flowability and weather resistance of the cashew phenol-formaldehyde condensate are balanced; it avoids excessively high melt viscosity due to a high hydroxyl value, and insufficient adhesion strength due to a low hydroxyl value.

[0036] Example 2: This invention provides a technical solution: a method for preparing a weather-resistant hot melt adhesive, comprising the following steps:

[0037] S1: Pretreatment: The cashew phenol-formaldehyde condensate is pulverized to 80-100 mesh and dried at 80-90℃ for 2-3 hours to remove moisture; maleic anhydride-grafted POE and hydrogenated Fischer-Tropsch wax are dried separately until the moisture content is ≤0.1% to avoid air bubbles during processing; pulverizing the cashew phenol-formaldehyde condensate to 80-100 mesh increases its specific surface area and accelerates the melting speed, while ensuring uniform mixing with maleic anhydride-grafted POE and hydrogenated Fischer-Tropsch wax to avoid incomplete local melting leading to defects. The drying parameters of 80℃~90℃ for 2~3h can effectively remove moisture from cashew phenol-formaldehyde condensate, while avoiding softening and clumping caused by high temperature, which would affect subsequent processing. Maleic anhydride-grafted POE and hydrogenated Fischer-Tropsch wax are dried to a moisture content of ≤0.1%. Combined with the drying treatment of cashew phenol-formaldehyde condensate, the defects of the adhesive layer such as bubbles and pinholes caused by moisture vaporization during high-temperature melting can be completely avoided. The pretreated raw materials can improve the efficiency of subsequent melting and mixing, shorten processing time, and reduce energy consumption.

[0038] S2: Premixed melt. Pretreated cashew phenol-formaldehyde condensate, maleic anhydride-grafted POE, and hydrogenated Fischer-Tropsch wax are added to the main feed port of a twin-screw extruder. The extruder temperatures are set at 130℃~145℃ for the front section, 145℃~155℃ for the middle section, and 155℃~165℃ for the rear section. The screw speed is 200~250 r / min, and the melting and mixing time is 15~25 min to obtain a uniform premixed melt. The segmented temperature control is adapted to the melting characteristics of the three core raw materials: cashew phenol-formaldehyde condensate softening point 90~105℃, maleic anhydride-grafted POE melting temperature 120~140℃, and hydrogenated Fischer-Tropsch wax melting temperature 80~100℃. This ensures that all components are fully melted while avoiding component decomposition due to high temperatures, such as the degradation of cashew phenol-formaldehyde condensate, and significantly reduces the processing temperature. The uniform premixed melt ensures rapid dispersion of subsequent additives, avoiding performance defects caused by additive agglomeration.

[0039] S3: Additives are added by introducing coated antioxidants, weather-resistant thixotropic agents, and light stabilizers into the twin-screw extruder through the additive feed port. The temperature at the additive feed port is controlled at 135℃~145℃, and the mixture is further melted and mixed for 8~12 minutes to obtain a uniform adhesive melt. The additive feed port temperature of 135~145℃ is lower than the subsequent melting temperature of 155~165℃, which can effectively prevent the coated antioxidants and light stabilizers from thermally decomposing or volatilizing at high temperatures, improve the retention rate of antioxidants and light stabilizers, and solve the problem of insufficient weather resistance caused by additive decomposition in existing technologies. The three additives are uniformly dispersed in the premixed melt to avoid additive agglomeration. Among them, the weather-resistant thixotropic agent can improve the thixotropy of the adhesive, avoid stringing and sagging during application, and improve workability. The staged feeding design protects the activity of the additives and ensures the uniformity of the adhesive melt, taking into account both weather resistance and workability.

[0040] S4: Molding – The adhesive melt is extruded through a twin-screw extruder, cooled in stages, and pelletized to obtain the finished product. The staged cooling design avoids rapid cooling that can cause pellet brittleness and excessive internal stress, affecting subsequent bonding performance and ensuring uniform pellet appearance and stable performance. Pelleting produces uniformly sized pellets, facilitating subsequent storage, transportation, and application, thus improving product usability. The entire molding process is simple and efficient, suitable for large-scale industrial production, and reduces production costs.

[0041] Coated antioxidants, light stabilizers, and weather-resistant thixotropic agents are dried at 80℃~90℃ for 2~3 hours until the moisture content is ≤0.1% before being added to a twin-screw extruder. Drying at 80℃~90℃ for 2~3 hours until the moisture content is ≤0.1% removes moisture from the additives, preventing moisture from vaporizing during melting and causing defects such as bubbles and pinholes in the adhesive layer. This process, combined with the drying of core raw materials, ensures a bubble-free and clean-looking finished adhesive layer. The dried additives also improve their dispersibility in the adhesive melt, preventing moisture-induced agglomeration and decreased activity, such as damage to the coating layer of coated antioxidants due to water absorption. This ensures the additives function effectively, further reducing the defect rate in industrial production and improving product quality stability.

[0042] Example 3: The present invention provides a technical solution: a weather-resistant hot melt adhesive, comprising the following components by weight: 22 parts cashew phenol-formaldehyde condensate, 48 parts maleic anhydride-grafted POE, 2.5 parts coated antioxidant, 6 parts hydrogenated Fischer-Tropsch wax, 4 parts weather-resistant thixotropic agent, and 3 parts light stabilizer.

[0043] Example 4: The present invention provides a technical solution: a weather-resistant hot melt adhesive, comprising the following components by weight: 26 parts cashew phenol-formaldehyde condensate, 44 parts maleic anhydride-grafted POE, 3 parts coated antioxidant, 7 parts hydrogenated Fischer-Tropsch wax, 5 parts weather-resistant thixotropic agent, and 4 parts light stabilizer.

[0044] Example 5: The present invention provides a technical solution: a weather-resistant hot melt adhesive, comprising the following components by weight: 28 parts cashew phenol-formaldehyde condensate, 42 parts maleic anhydride-grafted POE, 3.5 parts coated antioxidant, 5.5 parts hydrogenated Fischer-Tropsch wax, 3.5 parts weather-resistant thixotropic agent, and 3.5 parts light stabilizer.

[0045] Example 6: In this example, the weather-resistant hot melt adhesives prepared according to the preparation method of Example 2 in Examples 3, 4, and 5 are compared with existing conventional weather-resistant hot melt adhesives as a control group. Aluminum alloy plates are used as the bonding substrate in all examples.

[0046] The existing conventional weather-resistant hot melt adhesive formulation is as follows: 50% pure POE, 30% ordinary hydrogenated terpene resin, 10% polyester plasticizer, 2% antioxidant, 2% light stabilizer, 5% paraffin wax, and 1% silane coupling agent; the preparation process is as follows: high temperature melt mixing at 180-190℃, all components are added at one time, and extrusion pelletizing.

[0047] The experiment was conducted on three aspects: melt viscosity, antioxidant / light stabilizer retention rate, and bond strength.

[0048] Experimental standards:

[0049] Melt viscosity: GB / T 15332-2018 "Determination of viscosity of hot melt adhesives"; Melt viscosity: Take three adhesive samples from the examples and the control group respectively, place them in a melt viscometer, set the test temperature to 165℃, the rotation speed to 20r / min, and after equilibration for 10min, measure and record the melt viscosity value. Each group is tested in parallel 3 times;

[0050] Antioxidant / light stabilizer retention rate: Referring to GB / T 27707-2011 "Determination of hindered phenolic antioxidants in adhesives by high performance liquid chromatography", the detection conditions were optimized in combination with the processing scenario of this experiment. The raw material mixtures of the three examples and the control group (unprocessed) and the processed finished adhesive particles were taken, pulverized, and ultrasonically extracted with chromatographically pure methanol. The supernatant was collected by centrifugation. A high performance liquid chromatograph was used, with the detection wavelengths set to 280 nm and 305 nm. The mobile phase was methanol:water = 95:5 (volume ratio) and the flow rate was 1.0 mL / min. The actual content of antioxidants and light stabilizers in the processed finished product was calculated by the standard curve method. The retention rate of additives was calculated as follows: Retention rate of additives = (Actual content of additives in the processed finished product / Theoretical content of additives in the raw material) × 100%. Each group was tested in parallel for 3 times, and the average value was taken.

[0051] Bond strength: GB / T 7124-2021 "Determination of tensile shear strength of adhesives (rigid material to rigid material)". Standard bond samples were prepared from the adhesives of the three examples and the control group, with an adhesive layer thickness of 0.2 mm. They were placed in an environment at room temperature and relative humidity of 50%±5% for 24 hours. The tensile shear strength was measured using an electronic universal testing machine at a tensile speed of 10 mm / min. Each group was tested in parallel for 5 times, and the average value was taken.

[0052] Melt viscosity (mPa·s) Antioxidant retention rate (%) Light stabilizer retention rate (%) Normal tensile shear strength (MPa) control group 980±60 68.5±2.1 65.3±2.4 11.2±0.6 Example 3 820±40 93.0±1.0 91.4±1.3 13.1±0.4 Example 4 840±42 92.7±1.1 91.1±1.4 13.3±0.4 Example 5 835±41 92.9±1.0 91.3±1.3 13.2±0.4

[0053] Based on the data analysis in the table, the hot melt adhesive of this invention, by using cashew phenol-formaldehyde condensate as the core component and through the synergistic modification of cashew phenol-formaldehyde condensate with maleic anhydride grafted POE, combined with a low-temperature processing technology, not only solves the problems of high brittleness and poor processability of aldehyde-ketone-phenol condensates, but also reduces the overall processing temperature by 25-30℃, and the melt viscosity is significantly lower than that of the control group. At the same time, the simplified formula reduces the interference between components, greatly improves the processing stability, and solves the problems of high processing temperature, high energy consumption, and coking of adhesive in the prior art. The selection of coating antioxidants combined with low-temperature processing increases the retention rate of antioxidants and light stabilizers to over 90%, solving the defect of easy decomposition of additives during melt processing in the prior art.

[0054] Cashew phenol-formaldehyde condensate itself has excellent weather resistance and bonding strength. It forms a highly efficient synergistic effect with maleic anhydride-grafted POE and coated antioxidants. Its normal tensile shear strength is stable at 13.1-13.3 MPa, which is more than 17% better than the control group. It achieves the triple goals of formula simplification, processability optimization and weather resistance improvement. It breaks the natural balance between weather resistance and processability in the existing technology. All properties meet the usage requirements of actual application scenarios such as outdoor building materials and photovoltaic modules.

[0055] This invention relates to a weather-resistant hot melt adhesive and its preparation method. Using cashew phenol-formaldehyde condensate as the core component, and through synergistic optimization of the core component and process improvement, it significantly optimizes processing temperature, melt viscosity, and processing stability compared to existing complex formulations. This effectively solves the trade-off between weather resistance and processability, while also greatly improving the processing retention rate of anti-aging additives and addressing the issue of actual weather resistance falling below theoretical values ​​due to high-temperature decomposition of additives. This not only reduces production costs, improves component compatibility, and adapts to industrial production, but also achieves comprehensive improvements in normal-state bonding performance, weather resistance, and anti-yellowing performance. All performance parameters in the three embodiments are consistently met; it can satisfy the long-term use needs of outdoor building materials, photovoltaic modules, automotive exteriors, and other scenarios.

[0056] 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.

Claims

1. A weather-resistant hot melt adhesive, characterized in that: By weight, it includes the following components: 20-30 parts cashew phenol-formaldehyde condensate, 40-50 parts maleic anhydride-grafted POE, 2-4 parts coated antioxidant, 5-8 parts hydrogenated Fischer-Tropsch wax, 3-6 parts weather-resistant thixotropic agent, and 3-6 parts light stabilizer.

2. The weather-resistant hot melt adhesive according to claim 1, characterized in that: By weight, it includes the following components: 22 parts cashew phenol-formaldehyde condensate, 48 parts maleic anhydride-grafted POE, 2.5 parts coated antioxidant, 6 parts hydrogenated Fischer-Tropsch wax, 4 parts weather-resistant thixotropic agent, and 3 parts light stabilizer.

3. The weather-resistant hot melt adhesive according to claim 1, characterized in that: By weight, it includes the following components: 26 parts cashew phenol-formaldehyde condensate, 44 parts maleic anhydride-grafted POE, 3 parts coated antioxidant, 7 parts hydrogenated Fischer-Tropsch wax, 5 parts weather-resistant thixotropic agent, and 4 parts light stabilizer.

4. The weather-resistant hot melt adhesive according to claim 1, characterized in that: By weight, it includes the following components: 28 parts cashew phenol-formaldehyde condensate, 42 parts maleic anhydride-grafted POE, 3.5 parts coated antioxidant, 5.5 parts hydrogenated Fischer-Tropsch wax, 3.5 parts weather-resistant thixotropic agent, and 3.5 parts light stabilizer.

5. The weather-resistant hot melt adhesive according to claim 1, characterized in that: The cashew phenol-formaldehyde condensate is prepared by a condensation reaction of formaldehyde and cashew phenol, with a degree of condensation of 5 to 12 and a softening point of 90°C to 105°C. The grafting rate of maleic anhydride-grafted POE is 0.8% to 1.2%.

6. The weather-resistant hot melt adhesive according to claim 5, characterized in that: In the cashew phenol-formaldehyde condensate, the molar ratio of formaldehyde to cashew phenol is 1.0 to 1.2:

1.

7. The weather-resistant hot melt adhesive according to claim 1, characterized in that: The coated antioxidant is a silica-coated hindered phenolic antioxidant with a coating thickness of 50-100 nm. The hindered phenolic antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 2:

1.

8. The weather-resistant hot melt adhesive according to claim 1, characterized in that: The hydroxyl value of the cashew phenol-formaldehyde condensate is 80-120 mgKOH / g.

9. A method for preparing a weather-resistant hot melt adhesive according to any one of claims 1-8, characterized in that: Includes the following steps: S1: Pretreatment: Crush cashew phenol-formaldehyde condensate to 80-100 mesh and dry at 80-90℃ for 2-3 hours to remove moisture; dry maleic anhydride-grafted POE and hydrogenated Fischer-Tropsch wax to a moisture content of ≤0.1% to avoid generating bubbles during processing. S2: Premixed melt, the pretreated cashew phenol-formaldehyde condensate, maleic anhydride-grafted POE, and hydrogenated Fischer-Tropsch wax are added to the main feed port of a twin-screw extruder. The extruder front section temperature is set to 130℃~145℃, the middle section to 145℃~155℃, and the rear section to 155℃~165℃. The screw speed is 200~250r / min. The melt is mixed for 15~25min to obtain a uniform premixed melt. S3: Additives are added by adding coated antioxidants, weather-resistant thixotropic agents, and light stabilizers into the twin-screw extruder through the auxiliary feed port. The temperature of the auxiliary feed port is controlled at 135℃~145℃, and the mixture is continued to melt and mix for 8~12 minutes to obtain a uniform adhesive melt. S4: Molding, the adhesive melt is extruded through a twin-screw extruder, cooled in stages, and pelletized to obtain the finished product.

10. A method for preparing a weather-resistant hot melt adhesive according to claim 9, characterized in that: The coated antioxidant, light stabilizer, and weather-resistant thixotropic agent are dried at 80℃~90℃ for 2~3 hours until the moisture content is ≤0.1% before being added to the twin-screw extruder.