Weather-resistant polyurethane acrylate copolymerized hot melt adhesive

Abstract

The invention discloses a weather-resistant polyurethane acrylate copolymer hot melt adhesive and a preparation method thereof. The invention relates to a water-based polyurethane adhesive, which is prepared from the following raw materials in parts by weight: 15 to 61 parts of hydroxypropyl methacrylate, 20 to 81 parts of pentaerythritol diacrylate, 5 to 20 parts of polypropylene glycol 1000, 5 to 20 parts of polypropylene glycol 4000, 25 to 100 parts of diphenylmethane diisocyanate, 0.025 to 0.1 part of dimorpholinyl diethyl ether, 3.5 to 14 parts of first filler and 8 to 32 parts of second filler. Polyacrylate is added into polyurethane for modification, so that the weather resistance, the water resistance and the bonding strength of the hot melt adhesive can be effectively improved; by adding the first filler and the second filler, the respective reinforcing effects can be exerted, and the problems that the initial peel strength is reduced and the curing rate is reduced when the polyacrylate is added into the polyurethane hot melt adhesive can also be solved.

Description

Technical Field

[0001] This invention relates to the field of polyurethane adhesives, and particularly to a weather-resistant polyurethane acrylate copolymer hot melt adhesive. Background Technology

[0002] Hot melt adhesives come in a wide variety, mainly including EVA (ethylene-vinyl acetate copolymer), synthetic rubber, thermoplastic polyester, and PU (polyurethane). Compared with traditional solvent-based adhesives, polyurethane hot melt adhesives have advantages such as high bonding strength, low-temperature resistance, abrasion resistance, solvent resistance, and high thermal stability, and have broad application prospects in industries such as automotive, clothing, food packaging, and furniture manufacturing.

[0003] However, polyurethane hot melt adhesives have shortcomings in terms of weather resistance, bonding strength, and flame retardancy. The addition of acrylate to polyurethane can improve the weather resistance of polyurethane adhesives (Zhang Xi, Liu Jiapei, Zhang Jun, et al. Synthesis of weather-resistant and yellowing-resistant acrylate-modified polyurethane adhesives [J]. Adhesion, 2017, 38(10):3.DOI:10.3969 / j.issn.1001-5922.2017.10.010.). Related studies have also found that polyacrylate can improve the bonding strength of polyurethane hot melt adhesives (Ruan Mengmeng, Peng Fei, Wang Guiyou. Preparation and properties of polyacrylate resin / polyurethane reactive hot melt adhesives [J]. China Adhesives, 2021, 30(1):6.).

[0004] However, the following problems exist when polyacrylate is added to hot melt adhesives: (1) Polyacrylate has a high crystallization shrinkage rate and poor wetting ability on the substrate, which causes the surface of the hot melt adhesive to harden and shrink during the cooling process to room temperature, resulting in poor adhesion to the substrate. At this time, the bonding part has not yet completed the moisture assimilation reaction, leading to a decrease in the initial peel strength (Ye Qing, Lu Zhenfei, Li Jian, et al. Development of reactive polyurethane hot melt adhesive for automotive lights [J]. Chemical Industry and Engineering Progress, 2010(1):5.DOI:CNKI:SUN:HGJZ.0.2010-01-028.); (2) The addition of polyacrylate to hot melt adhesives has a dilution effect, which will reduce the curing rate and lead to a longer curing time. There is a lack of reliable solutions to the above problems in the existing technology.

[0005] On the other hand, ordinary polyurethane hot melt adhesives (PUR) have a limiting oxygen index of only about 18%, resulting in poor flame retardant properties. To improve their flame retardant performance, flame retardants are usually added. Flame retardants are mainly divided into inorganic and organic flame retardants. To achieve the ideal flame retardant effect, the amount of inorganic flame retardant added is generally larger. Excessive inorganic flame retardant content will significantly negatively affect the performance of polyurethane hot melt adhesives. Organic flame retardants are divided into additive and reactive types. Additive organic flame retardants usually have poor compatibility with polyurethane systems and are prone to partial precipitation to the surface during the curing process. Under high temperature and high humidity conditions, the precipitation is more severe, leading to decreased bond strength and increased fogging value. Reactive organic flame retardants are produced by introducing flame-retardant functional groups into the molecular structure of polyurethane through chemical reactions. This method can overcome the above-mentioned shortcomings of additive organic flame retardants (Chen Jinghua, Zhang Jianzhen, Chen Jianjun, et al. Development of flame-retardant reactive polyurethane hot melt adhesive [J]. Adhesion, 2021(11):3.). However, such reactive flame retardants are often more expensive and can also increase the complexity of the process.

[0006] Therefore, in order to improve the weather resistance of polyurethane hot melt adhesives while comprehensively improving their bonding strength and flame retardant properties, it is necessary to improve existing technologies to provide more reliable solutions. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a weather-resistant polyurethane acrylate copolymer hot melt adhesive, which addresses the shortcomings of the prior art.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a weather-resistant polyurethane acrylate copolymer hot melt adhesive, the raw materials for which are prepared by weight include: 15-61 parts of hydroxypropyl methacrylate, 20-81 parts of pentaerythritol diacrylate, 5-20 parts of polypropylene glycol 1000, 5-20 parts of polypropylene glycol 4000, 25-100 parts of diphenylmethane diisocyanate, 0.025-0.1 parts of bismorpholino diethyl ether, 3.5-14 parts of the first filler, and 8-32 parts of the second filler.

[0009] Preferably, the hot melt adhesive is prepared by: Polypropylene glycol 1000 and polypropylene glycol 4000 were mixed and dried under nitrogen protection. Hydroxypropyl methacrylate, pentaerythritol diacrylate, bismorpholino diethyl ether and the first filler were added under stirring. Diphenylmethane diisocyanate was added and stirred under heating. The second filler was then added and the temperature was raised and the reaction was continued to be stirred to obtain a weather-resistant polyurethane acrylate copolymer hot melt adhesive.

[0010] Preferably, the hot melt adhesive is prepared by: Mix polypropylene glycol 1000 and polypropylene glycol 4000, dry under nitrogen protection at 80-130℃ for 2-8 hours, cool to 50-70℃, add hydroxypropyl methacrylate, pentaerythritol diacrylate, bismorpholino diethyl ether and the first filler while stirring, stir for 1-3 hours, continue stirring, add diphenylmethane diisocyanate, stir and react at 80-95℃ for 0.5-2 hours, then add the second filler, heat to 100-110℃, continue stirring and react for 1.5-6 hours, cool to room temperature to obtain weather-resistant polyurethane acrylate copolymer hot melt adhesive.

[0011] Preferably, the first filler is prepared by the following steps: S1-1. Mesoporous silica was synthesized in situ on nano-calcium carbonate to prepare a porous silica-calcium carbonate composite. S1-2. An antioxidant was loaded onto a porous silica-calcium carbonate composite by an impregnation method to prepare a filler intermediate product. S1-3. Graft a silane coupling agent onto the intermediate product of the filler to prepare the first filler.

[0012] Preferably, the first filler is prepared by the following steps: S1-1, Preparation of porous silica-calcium carbonate composite: S1-1-1. Take nano-calcium carbonate and hexadecyltrimethylammonium bromide and add them to deionized water, then disperse them by ultrasonication to obtain a nano-calcium carbonate dispersion. S1-1-2. Add sodium hydroxide to the nano-calcium carbonate dispersion, add 5 mL of tetraethoxysilane dropwise under stirring, heat and stir to react, centrifuge, wash and dry, calcine the obtained solid product, grind it to obtain a porous silica-calcium carbonate composite. S1-2. Take porous silica-calcium carbonate composite and add it to antioxidant solution, sonicate, shake in a shaker, centrifuge, wash and dry to obtain filler intermediate product; In the antioxidant solution, the antioxidant is at least one of antioxidant 1010, antioxidant 1135, antioxidant 1076, and antioxidant BHT, and the mass concentration of the antioxidant is 2-20%. S1-3. Take the intermediate product of the packing material and deionized water, add them to ethanol, disperse them by ultrasonication, then add silane coupling agent KH-570 under stirring, heat and stir, filter, wash and dry to obtain the first packing material.

[0013] Preferably, the first filler is prepared by the following steps: S1-1, Preparation of porous silica-calcium carbonate composite: S1-1-1: Take 0.5-2g of nano-calcium carbonate and 0.15-0.7g of cetyltrimethylammonium bromide and add them to 50-200mL of deionized water. Disperse by ultrasonication for 0.5-2h to obtain a nano-calcium carbonate dispersion. S1-1-2. Add 0.06-0.24g of sodium hydroxide to the nano-calcium carbonate dispersion and stir until completely dissolved. Add 2.5-10mL of tetraethoxysilane dropwise while stirring. Stir and react at 50-70℃ for 2.5-10h. Centrifuge, wash, and dry. Calcine the obtained solid in air at 500-600℃ for 2-8h. Grind to obtain a porous silica-calcium carbonate composite. S1-2. Take 0.5-2g of porous silica-calcium carbonate composite and add it to 25-100mL of acetone solution containing 2.5-10wt% antioxidant 1010. Sonicate for 45-180min, then shake in a shaker at 30-50℃ for 6-24h. Centrifuge, wash and dry to obtain the intermediate product of the filler. S1-3. Take 0.5-2g of the intermediate product of the packing material and 5-20mL of deionized water and add them to 20-80mL of ethanol. Disperse the mixture by ultrasonication for 0.5-2h. Then, add 0.05-0.3g of silane coupling agent KH-570 under stirring. Stir at 50-70℃ for 1.5-6h. Filter, wash and dry to obtain the first packing material.

[0014] Preferably, the second filler is prepared by the following steps: S2-1. Sodium-based montmorillonite was modified with hydroxyl silicone oil to prepare hydroxyl silicone oil-grafted montmorillonite. S2-2. A composite grafted montmorillonite was prepared by modifying a silane coupling agent onto hydroxyl silicone oil-grafted montmorillonite. S2-3. Flame retardant functionalized montmorillonite is prepared by loading flame retardant onto composite grafted montmorillonite. S2-4. Coating flame-retardant functionalized montmorillonite with polyacrylate yields the second filler.

[0015] Preferably, the second filler is prepared by the following steps: S2-1. Sodium-based montmorillonite was dried and added to an ethanol-water solution, ultrasonically dispersed, hydroxyl silicone oil was added, stirred, pH was adjusted to alkaline, stirred to react, aged, centrifuged, filtered, washed, dried, and ground to obtain hydroxyl silicone oil-grafted montmorillonite. S2-2. Take hydroxyl silicone oil-grafted montmorillonite, silane coupling agent, and potassium hydroxide and add them to dimethyl sulfoxide. Heat and stir the reaction under nitrogen protection. After the reaction is completed, filter, wash, and dry to obtain composite grafted montmorillonite. S2-3. Add the composite grafted montmorillonite to the flame retardant solution, disperse it ultrasonically, shake it on a shaker, filter it, wash it, and dry it to obtain flame-retardant functionalized montmorillonite. S2-4. Coating polyacrylate onto flame-retardant functionalized montmorillonite: S2-4-1. Add flame-retardant functionalized montmorillonite to deionized water and disperse it by ultrasonication to obtain a montmorillonite dispersion. S2-4-2. Take butyl acrylate, 2-hydroxyethyl acrylate, hydroxypropyl methacrylate, and sodium dodecylbenzene sulfonate, add them to deionized water, stir, and obtain a monomer mixture. S2-4-3. Add the montmorillonite dispersion to the monomer mixture under stirring, stir, add the deionized water solution of ammonium persulfate dropwise under heating, raise the temperature, stir the reaction, centrifuge, wash, and dry to obtain the second filler.

[0016] Preferably, the silane coupling agent in step S2-2 is any one of silane coupling agents KH-570, A151, and A171; In the flame retardant solution in steps S2-3, the flame retardant is any one of diethyl phosphate, ammonium polyphosphate, and melamine, and the mass concentration of the flame retardant is 5-30%.

[0017] Preferably, the second filler is prepared by the following steps: S2-1. Take 2.5-10g of sodium montmorillonite and grind it to below 5-20μm. Dry it at 100-150℃ for 1-4h, then add it to 150-600mL of an ethanol-water solution composed of ethanol and deionized water in a volume ratio of 8:2. Disperse it ultrasonically at 60-80℃ for 1.5-6h, cool it to 25-40℃, add 1-4g of hydroxyl silicone oil, stir for 0.5-2h, adjust the pH to 9-11 with sodium hydroxide solution, continue stirring and react for 1.5-6h, age it at room temperature for 6-24h, centrifuge, filter, dry, and grind to obtain hydroxyl silicone oil-grafted montmorillonite. S2-2. Take 1.25-5g of hydroxyl silicone oil-grafted montmorillonite, 0.15-0.6g of silane coupling agent KH-570, and 0.02-0.1g of potassium hydroxide and add them to 25-100mL of dimethyl sulfoxide. Under nitrogen protection, stir and react at 70-90℃ for 2-8h. After the reaction is completed, filter, wash, and dry to obtain composite grafted montmorillonite. S2-3. Add all of the composite grafted montmorillonite prepared in step S2-2 to 100-400 mL of an ethanol solution of 5-25% diethyl phosphate, ultrasonically disperse for 1-4 h, then shake on a shaker at 50-65℃ for 12-48 h, filter, wash, and dry to obtain flame-retardant functionalized montmorillonite. S2-4. Coating polyacrylate onto flame-retardant functionalized montmorillonite: S2-4-1. Take 1-4g of flame-retardant functionalized montmorillonite and add it to 25-100mL of deionized water. Disperse it ultrasonically for 0.5-2h to obtain a montmorillonite dispersion. S2-4-2, Take 1.5-6g butyl acrylate, 1-42g 2-hydroxyethyl acrylate, 0.75-3g hydroxypropyl methacrylate, and 0.15-0.6g sodium dodecylbenzenesulfonate and add them to 35-140mL of deionized water. Stir for 30-60min to obtain a monomer mixture. S2-4-3. Add the montmorillonite dispersion to the monomer mixture under stirring, stir for 0.5-2 hours, add 10-20 mL of deionized water containing 0.025-0.1 g of ammonium persulfate dropwise at 70-78℃, and complete the addition in 45-180 minutes. Then raise the temperature to 80-85℃, stir the reaction for 2-8 hours, centrifuge, wash, and dry to obtain the second filler.

[0018] The beneficial effects of this invention are: This invention provides a weather-resistant polyurethane-acrylate copolymer hot melt adhesive. By modifying the polyurethane with polyacrylate, the weather resistance, water resistance, and bonding strength of the hot melt adhesive can be effectively improved. By adding a first filler and a second filler, in addition to their respective reinforcing effects, the invention can overcome the problems of decreased initial peel strength and decreased curing rate caused by the addition of polyacrylate to the polyurethane hot melt adhesive. Furthermore, the addition of polyacrylate can reduce the potential adverse effects of the alkalinity of nano-calcium carbonate on the hot melt adhesive. Therefore, through the interaction between the first filler, the second filler, and the polyurethane-acrylate copolymer component, this invention achieves a synergistic enhancement effect that improves the overall performance of the hot melt adhesive.

[0019] The first filler prepared in this invention is a composite of nano-calcium carbonate as the core carrier, mesoporous silica as the outer shell coating layer, and an antioxidant loaded through mesoporous structures and then grafted with a silane coupling agent. By constructing this structural system, the reinforcing effect of nano-calcium carbonate and silica fillers on hot melt adhesives can be fully utilized, and it can be endowed with excellent and long-lasting antioxidant function. It can also be compatible with the second filler and the polyacrylate component in the system. At the same time, it can overcome the defects of poor polymer compatibility and difficulty in dispersion of nano-calcium carbonate and silica fillers in the application of hot melt adhesives.

[0020] The second filler prepared in this invention is a composite system constructed by sequentially modifying montmorillonite with hydroxyl silicone oil as the base material, followed by silane coupling agent modification, functionalization by loading flame retardants, and coating with a polyacrylate organic film. This composite system overcomes the application difficulties of montmorillonite's poor dispersion in polyurethane systems through the composite modification of hydroxyl silicone oil and silane coupling agents, and the coating with polyacrylate. It fully leverages the reinforcing effect of montmorillonite on hot melt adhesive systems. Furthermore, the addition of hydroxyl silicone oil further enhances the weather resistance and water resistance of the hot melt adhesive by synergistically combining with other components in the system. The functional loading of flame retardants significantly improves the flame retardant performance of the hot melt adhesive, and the polyacrylate coating solves the application problem of easy partial separation of flame retardants. Simultaneously, polyacrylate itself also improves the performance of the polyurethane hot melt adhesive system. Therefore, the components in the composite system of the second filler can synergistically enhance the performance of the hot melt adhesive through mutual cooperation. Attached Figure Description

[0021] Figure 1 The peel strength test results of the hot melt adhesives in the examples and comparative examples are shown. Figure 2 The bonding strength test results of the hot melt adhesives in the examples and comparative examples are shown. Figure 3 The results of post-conversion performance tests for the hot melt adhesives in the examples and comparative examples are shown. Figure 4 The release curve of antioxidant 1010 in the first filler; Figure 5 The curing speed test results of the hot melt adhesives prepared in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 5; Figure 6 The flame retardant performance test results are for the examples and comparative examples; Figure 7 The TGA curve of the hot melt adhesive prepared in Example 1. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0023] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0024] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. For examples where specific conditions are not specified, conventional conditions or conditions recommended by the manufacturer are followed. For reagents or instruments whose manufacturers are not specified, they are all commercially available products.

[0025] This invention provides a weather-resistant polyurethane acrylate copolymer hot melt adhesive, the raw materials of which, by weight, include: 15-61 parts of hydroxypropyl methacrylate, 20-81 parts of pentaerythritol diacrylate, 5-20 parts of polypropylene glycol 1000, 5-20 parts of polypropylene glycol 4000, 25-100 parts of diphenylmethane diisocyanate, 0.025-0.1 parts of bismorpholino diethyl ether, 3.5-14 parts of first filler, and 8-32 parts of second filler.

[0026] In a preferred embodiment, the hot melt adhesive is prepared as follows: Mix polypropylene glycol 1000 and polypropylene glycol 4000, dry under nitrogen protection at 80-130℃ for 2-8 hours, cool to 50-70℃, add hydroxypropyl methacrylate, pentaerythritol diacrylate, bismorpholino diethyl ether and the first filler while stirring, stir for 1-3 hours, continue stirring, add diphenylmethane diisocyanate, stir and react at 80-95℃ for 0.5-2 hours, then add the second filler, heat to 100-110℃, continue stirring and react for 1.5-6 hours, cool to room temperature to obtain weather-resistant polyurethane acrylate copolymer hot melt adhesive.

[0027] In a preferred embodiment, the first filler is prepared by the following steps: S1-1. Mesoporous silica was synthesized in situ on nano-calcium carbonate to prepare a porous silica-calcium carbonate composite: S1-1-1: Take 0.5-2g of nano-calcium carbonate and 0.15-0.7g of cetyltrimethylammonium bromide and add them to 50-200mL of deionized water. Disperse by ultrasonication for 0.5-2h to obtain a nano-calcium carbonate dispersion. S1-1-2. Add 0.06-0.24g of sodium hydroxide to the nano-calcium carbonate dispersion and stir until completely dissolved. Add 2.5-10mL of tetraethoxysilane dropwise while stirring. Stir and react at 50-70℃ for 2.5-10h. Centrifuge, wash, and dry. Calcine the obtained solid in air at 500-600℃ for 2-8h. Grind to obtain a porous silica-calcium carbonate composite. S1-2. An intermediate filler product was prepared by loading an antioxidant onto a porous silica-calcium carbonate composite using an impregnation method. Take 0.5-2g of porous silica-calcium carbonate composite and add it to 25-100mL of acetone solution containing 2.5-10wt% antioxidant 1010. Sonicate for 45-180min, then shake in a shaker at 30-50℃ for 6-24h. Centrifuge, wash and dry to obtain the intermediate product of the filler. S1-3. Grafting a silane coupling agent onto the intermediate product of the filler to prepare the first filler: Take 0.5-2g of the intermediate product of the packing material and 5-20mL of deionized water and add them to 20-80mL of ethanol. Disperse the mixture by ultrasonication for 0.5-2h. Then add 0.05-0.3g of silane coupling agent KH-570 under stirring. Stir at 50-70℃ for 1.5-6h. Filter, wash and dry to obtain the first packing material.

[0028] In a preferred embodiment, the second filler is prepared by the following steps: S2-1. Hydroxyl silicone oil was used to modify sodium-based montmorillonite to prepare hydroxyl silicone oil-grafted montmorillonite: Take 2.5-10g of sodium montmorillonite and grind it to below 5-20μm. Dry it at 100-150℃ for 1-4h and then add it to 150-600mL of an ethanol-water solution composed of ethanol and deionized water in a volume ratio of 8:2. Disperse it ultrasonically at 60-80℃ for 1.5-6h. After cooling to 25-40℃, add 1-4g of hydroxyl silicone oil and stir for 0.5-2h. Adjust the pH to 9-11 with sodium hydroxide solution and continue stirring for 1.5-6h. Aging at room temperature for 6-24h, centrifuge, filter, dry, and grind to obtain hydroxyl silicone oil-grafted montmorillonite. S2-2. A composite grafted montmorillonite was prepared by modifying a silane coupling agent onto hydroxyl silicone oil-grafted montmorillonite. Take 1.25-5g of hydroxyl silicone oil-grafted montmorillonite, 0.15-0.6g of silane coupling agent KH-570, and 0.02-0.1g of potassium hydroxide and add them to 25-100mL of dimethyl sulfoxide. Under nitrogen protection, stir and react at 70-90℃ for 2-8h. After the reaction is completed, filter, wash, and dry to obtain composite grafted montmorillonite. S2-3. Flame retardant functionalized montmorillonite is prepared by loading a flame retardant onto a composite grafted montmorillonite: Add all of the composite grafted montmorillonite prepared in step S2-2 to 100-400 mL of an ethanol solution of 5-25% diethyl phosphate, ultrasonically disperse for 1-4 h, then shake on a shaker at 50-65℃ for 12-48 h, filter, wash, and dry to obtain flame-retardant functionalized montmorillonite. S2-4. Coating flame-retardant functionalized montmorillonite with polyacrylate yields the second filler: S2-4-1. Take 1-4g of flame-retardant functionalized montmorillonite and add it to 25-100mL of deionized water. Disperse it ultrasonically for 0.5-2h to obtain a montmorillonite dispersion. S2-4-2, Take 1.5-6g butyl acrylate, 1-42g 2-hydroxyethyl acrylate, 0.75-3g hydroxypropyl methacrylate, and 0.15-0.6g sodium dodecylbenzenesulfonate and add them to 35-140mL of deionized water. Stir for 30-60min to obtain a monomer mixture. S2-4-3. Add the montmorillonite dispersion to the monomer mixture under stirring, stir for 0.5-2 hours, add 10-20 mL of deionized water containing 0.025-0.1 g of ammonium persulfate dropwise at 70-78℃, and complete the addition in 45-180 minutes. Then raise the temperature to 80-85℃, stir the reaction for 2-8 hours, centrifuge, wash, and dry to obtain the second filler.

[0029] The main mechanism of the invention will be explained below to facilitate understanding of the invention.

[0030] The first filler is a composite consisting of nano-calcium carbonate as the core carrier, mesoporous silica as the outer shell coating layer, and a silane coupling agent grafted onto the mesoporous loading antioxidant. By constructing this structural system, the reinforcing effect of nano-calcium carbonate and silica fillers on hot melt adhesives can be fully utilized, and it can be endowed with excellent and long-lasting antioxidant function. It can also be compatible with the second filler and the polyacrylate component in the system. At the same time, it can overcome the defects of poor polymer compatibility and difficulty in dispersion of nano-calcium carbonate and silica fillers in the application of hot melt adhesives.

[0031] Preparation process: (1) First, silica is synthesized in situ on nano-calcium carbonate, and then the template agent (hexadecyltrimethylammonium bromide) is removed by high temperature calcination, so that silica forms a mesoporous structure and a composite structure of porous silica coated with nano-calcium carbonate in the shape of strawberry is obtained, namely porous silica-calcium carbonate composite; (2) Antioxidant is loaded on silica by impregnation method to obtain filler intermediate product; (3) Silane coupling agent KH-570 containing double bond is grafted on the surface of filler intermediate product to obtain the first filler; In this process, the silanol bond formed by hydrolysis of siloxane group in silane coupling agent can chemically bond with silanol group on silica surface to form -O- bond, thereby realizing the grafting modification of silane coupling agent.

[0032] Mechanism of action: Nano-calcium carbonate is a commonly used filler in hot melt adhesives. Its fine structure and porous properties increase the contact area between the adhesive and the bonded materials, thereby enhancing the bonding strength. Zhao Fei et al. showed that the addition of nano-calcium carbonate can improve the curing speed of moisture-curing polyurethane hot melt adhesives. This is mainly because the alkaline calcium carbonate catalyzes the cross-linking reaction of isocyanates, forming substances such as substituted urea and urethane carbamate with high cohesive energy, thereby improving the cohesive strength of the adhesive (Zhao Fei, Gu Jiyou, Li Xiaoping. Research on the application of nano-calcium carbonate in moisture-curing polyurethane hot melt adhesives [J]. Adhesion, 2005, 26(6):3.DOI:10.3969 / j.issn.1001-5922.2005.06.009.).

[0033] Silica, as an inorganic filler, can improve the tensile strength, tear strength, and elongation at break of hot melt adhesives when added. Nanoscale silica particles can penetrate into the gaps between polymer chains, enhancing the internal interaction forces of the material, thereby improving bond strength and toughness. Furthermore, the addition of highly stable silica can also improve the heat resistance and durability of polyurethane hot melt adhesives (silica hinders the thermal motion of polyurethane molecular chains, improving heat resistance; silica has the ability to absorb ultraviolet light, improving UV resistance and extending service life).

[0034] However, both nano-calcium carbonate and silica, as inorganic fillers, suffer from poor compatibility with polyurethane systems and difficulty in uniform dispersion. In this invention, by constructing a porous silica-calcium carbonate composite system and then grafting a silane coupling agent containing double bonds, the aforementioned defects of both can be solved simultaneously. KH-570 achieves strong grafting through chemical bonding with the surface hydroxyl groups of silica. In the subsequent hot melt adhesive preparation process, the double bonds in KH-570 can participate in the polymerization reaction, thereby enabling the porous silica-calcium carbonate composite to form chemical bonds with the organic components in the hot melt adhesive. This greatly improves the compatibility of the porous silica-calcium carbonate composite with the polyurethane system and achieves chemical mixing, thus enabling it to achieve uniform and stable dispersion in the hot melt adhesive to better exert its reinforcing effect.

[0035] Antioxidants, loaded into the mesoporous structure of silica, can achieve a slow-release effect, thus providing the system with long-lasting antioxidant function, which significantly improves the weather resistance of hot melt adhesives. At the same time, since antioxidants can enter the hot melt adhesive system in small amounts and continuously, they can also reduce the negative impact of antioxidants on the curing speed of hot melt adhesives.

[0036] The second filler is a composite system constructed by using hydroxyl silicone oil-modified montmorillonite as the base material, followed by silane coupling agent modification, functionalization with loaded flame retardants, and coating with a polyacrylate organic film. This composite system overcomes the difficulty of dispersing montmorillonite in polyurethane systems through the composite modification with hydroxyl silicone oil and silane coupling agents, and the coating with polyacrylate. It fully leverages the reinforcing effect of montmorillonite on hot melt adhesive systems. Furthermore, the addition of hydroxyl silicone oil further enhances the weather resistance and water resistance of the hot melt adhesive by synergistically enhancing the components in the system. The functional loading of flame retardants significantly improves the flame retardant performance of the hot melt adhesive, and the polyacrylate coating solves the application problem of easy partial separation of flame retardants. Simultaneously, polyacrylate itself also improves the performance of the polyurethane hot melt adhesive system. Therefore, the components in the second filler composite system work together synergistically to enhance the performance of the hot melt adhesive.

[0037] Preparation process: (1) First, under alkaline conditions, hydroxyl silicone oil is modified onto sodium montmorillonite by reacting with the hydroxyl groups on the surface of sodium montmorillonite, thus obtaining hydroxyl silicone oil-grafted montmorillonite. Hydroxy silicone oil molecules contain a large number of Si-O-Si bonds, which are relatively stable under neutral conditions, but are easily hydrolyzed into a large number of silanol groups under acidic and alkaline conditions, which can condense with hydroxyl groups (Ma Zhiling, Hao Xuehui, He Jiayin, et al. Preparation of hydrophobic precipitated silica by in-situ modification of hydroxyl silicone oil [J]. Inorganic Salt Industry, 2011, 43(3):36.DOI:10.3969 / j.issn.1006-4990.2011.03.011.). Sodium montmorillonite has abundant hydroxyl groups on its surface. In this step, the hydroxyl silicone oil is grafted onto the surface of sodium montmorillonite by utilizing this reaction principle.

[0038] (2) Then, a silane coupling agent was modified on the hydroxyl silicone oil-grafted montmorillonite to prepare a composite grafted montmorillonite. Under the action of potassium hydroxide as an alkaline catalyst, the hydroxyl silicone oil can undergo a condensation reaction with the silane coupling agent KH-570 (Gao Futang, Zhang Xiaolei, Feng Jianyan, et al. Synthesis and application of hydroxyl silicone oil-modified acrylic resin leather finishing agent [J]. Leather Science and Engineering, 2006, 16(1):63-66.DOI:10.3969 / j.issn.1004-7964.2006.01.015.), so that the silane coupling agent KH-570 can be firmly modified onto the hydroxyl silicone oil-grafted montmorillonite.

[0039] (3) Grafting: By using the impregnation method, flame retardant diethyl phosphate is loaded into the voids between the layers of sodium-based montmorillonite with a layered structure to obtain flame-retardant functionalized montmorillonite.

[0040] (4) Finally, butyl acrylate, 2-hydroxyethyl acrylate, and hydroxypropyl methacrylate were used as acrylate monomers and polymerized in situ on flame-retardant functionalized montmorillonite to coat polyacrylate onto the flame-retardant functionalized montmorillonite, thus obtaining the second filler. In this process, the double bonds in the silane coupling agent KH-570 can participate in the polymerization reaction of acrylate, and the hydroxyl groups in the hydroxyl silicone oil and the hydroxyl groups in the acrylic monomers can also undergo condensation reactions, ultimately enabling montmorillonite to be chemically bonded to the polyacrylate coating film, promoting the coating process and ensuring the coating strength.

[0041] Mechanism of action: Montmorillonite is a natural silicate mineral widely used as a filler in adhesive materials. In hot melt adhesives, it has the following reinforcing effects: (1) It exhibits significant charring properties, effectively isolating gases and heat, reducing the heat release rate during polymer combustion, and improving flame retardant performance; (2) The layered structure of montmorillonite enhances barrier properties, thereby improving the sealing effect of hot melt adhesives. It also improves weather resistance by blocking oxygen and other substances; (3) Montmorillonite can also improve the thermal stability of hot melt adhesives and delay high-temperature softening. However, montmorillonite has poor compatibility with organic hot melt adhesive systems, making it difficult to achieve uniform dispersion within the system and limiting its reinforcing effect. In this invention, the composite modification of hydroxyl silicone oil and silane coupling agent, followed by further coating with polyacrylate, significantly improves the compatibility of montmorillonite with the hot melt adhesive system and achieves its chemical dispersion within the system, thereby fully leveraging the reinforcing effect of montmorillonite.

[0042] Hydroxyl silicone oil: (1) Grafting hydroxy silicone oil onto montmorillonite can improve the dispersibility of montmorillonite and facilitate the firm modification of silane coupling agent KH-570 on montmorillonite (hydroxy silicone oil can undergo a condensation reaction with KH-570). It can also promote the coating of polyacrylate onto montmorillonite (the hydroxyl groups in hydroxy silicone oil can undergo a condensation reaction with the hydroxyl groups in acrylic monomers), which is beneficial for achieving the organic modification of montmorillonite. (2) Hydroxyl silicone oil can introduce organosilicon functional groups into the molecular chains of polyurethane and polyacrylate, thereby significantly improving the weather resistance and water resistance of hot melt adhesives.

[0043] The silane coupling agent KH-570 can introduce double bonds into the surface of montmorillonite, which can participate in the copolymerization reaction of polyurethane and acrylate, thereby promoting the chemical mixing of montmorillonite in hot melt adhesive systems. On the other hand, the silane coupling agent KH-570 in the first and second fillers can also play the following role: the silane group in the silane coupling agent replaces part of the original isocyanate group (-NCO) in the wet curing reaction. In this wet curing reaction, the silane group will first react with water to generate silanol. The generated silanol is unstable and will form hydrogen bonds or Si-O-R (R is the adhesive) with the hydroxyl groups on the surface of the adhesive. In this way, the silane exists in the form of chemical bonds between the PUR hot melt adhesive and the adhesive, thereby increasing the strength of the cohesive point of the polyurethane hot melt adhesive, which macroscopically manifests as an increase in adhesive strength. At the same time, the silanols can condense with each other to form a three-dimensional network structure, which increases the crosslinking degree of the polyurethane hot melt adhesive, and ultimately effectively improves the adhesive strength and heat resistance of the polyurethane (Zhang Xu. Preparation and performance study of novel reactive polyurethane (PUR) hot melt adhesive [D]. Beijing University of Chemical Technology, 2020.) Ordinary polyurethane hot melt adhesives (PUR) have a limiting oxygen index of only around 18%, resulting in poor flame retardant properties. Adding flame retardants is a common method to improve their flame retardant performance. Flame retardants are mainly divided into inorganic and organic flame retardants. To achieve the ideal flame retardant effect, the amount of inorganic flame retardant added is generally larger. Excessive inorganic flame retardant content will significantly negatively impact the performance of polyurethane hot melt adhesives. Organic flame retardants are divided into additive and reactive types. Additive organic flame retardants usually have poor compatibility with the polyurethane system and are prone to partial precipitation to the surface during the curing process. Under high temperature and high humidity conditions, the precipitation is more severe, leading to decreased bond strength and increased fogging value. Reactive organic flame retardants are produced by introducing flame-retardant functional groups into the molecular structure of polyurethane through chemical reactions. This method can overcome the above-mentioned shortcomings of additive organic flame retardants (Chen Jinghua, Zhang Jianzhen, Chen Jianjun, et al. Development of flame-retardant reactive polyurethane hot melt adhesive [J]. Adhesion, 2021(11):3.). However, such reactive flame retardants are often more expensive and can also increase the complexity of the process. In this invention, conventional additive organic flame retardants are used to construct a composite system, which can also overcome the above-mentioned defects of additive organic flame retardants. Specifically: In the second filler of this invention, the flame retardant diethyl phosphate is loaded into the interlayer gaps of the layered montmorillonite structure, and then coated with polyacrylate. This ensures that during normal use, the flame retardant is relatively isolated from the main hot melt adhesive system (polyurethane-acrylate copolymer), effectively preventing the flame retardant from precipitating out of the polyurethane-acrylate copolymer, which would lead to decreased flame retardant performance and deterioration of bond strength. The polyacrylate coating greatly improves the compatibility between the second filler and the main hot melt adhesive system: the polyurethane-acrylate copolymer. During combustion, the polyacrylate film ruptures and melts at high temperatures, rapidly releasing the flame retardant diethyl phosphate loaded in the interlayers of the montmorillonite, which then works synergistically with the montmorillonite to exert its flame-retardant effect.

[0044] The polyacrylate used as a coating layer in the second filler and the polyacrylate copolymerized with polyurethane in the hot melt adhesive system can play the following roles: Polyacrylate has excellent weather resistance, water resistance and alkali resistance. The ester group and hydroxyl group in the molecule have strong hydrogen bonds and excellent adhesion. The doping of polyacrylate in polyurethane hot melt adhesive can improve the weather resistance and bonding strength of hot melt adhesive (Zhang Xi, Liu Jiapei, Zhang Jun, et al. Synthesis of weather-resistant and yellowing-resistant acrylic modified polyurethane adhesive [J]. Adhesion, 2017, 38(10):3.DOI:10.3969 / j.issn.1001-5922.2017.10.010.). Furthermore, the improvement of alkali resistance by acrylic resin can reduce the potential adverse effects of the alkalinity of nano-calcium carbonate on hot melt adhesive.

[0045] However, polyacrylate as a dopant component in hot melt adhesive systems has the following shortcomings: (1) Polyacrylate has a high crystallization shrinkage rate and poor wetting ability on the substrate, which causes the surface of the hot melt adhesive to harden and shrink during the cooling process to room temperature, resulting in poor adhesion to the substrate. At this time, the bonding part has not yet completed the moisture assimilation reaction, leading to the problem of reduced initial peel strength (Ye Qing, Lu Zhenfei, Li Jian, et al. Development of reactive polyurethane hot melt adhesive for automotive lights [J]. Chemical Industry Progress, 2010(1):5.DOI:CNKI:SUN:HGJZ.0.2010-01-028.); (2) The addition of polyacrylate to hot melt adhesive has a dilution effect, which will reduce the curing rate and lead to a longer curing time.

[0046] In this invention, the combination of the first filler and the second filler can effectively overcome the above-mentioned defects of polyacrylate: (1) In the second filler, the layered structure of montmorillonite can restrict the free movement of resin molecular chains, reduce the crystallinity of polymer, thereby reducing the crystallization shrinkage rate of acrylic resin, thereby improving the initial peel strength; (2) In the first filler, alkaline nano-calcium carbonate produces a catalytic cross-linking reaction of isocyanate, forming high cohesive energy substituted urea and urea carbamate, etc., which accelerate the curing rate and improve the cohesive strength of the adhesive.

[0047] Preparation Process: In the hot melt adhesive system, acrylate monomers are first mixed with polypropylene glycol, the first filler, and the catalyst bismorpholino diethyl ether. Then, diphenylmethane diisocyanate is added for prepolymerization. During this process, the acrylate and polyurethane form a copolymer. Simultaneously, the first filler participates in the polymerization reaction through the double bonds in the silane coupling agent KH-570, dispersing the first filler into the copolymer system in a chemically mixed manner. Then, the second filler is added and the temperature is raised to continue polymerization. At this time, the residual double bonds in the silane coupling agent KH-570 in the second filler participate in the polymerization reaction, and the hydroxyl groups in the hydroxyl silicone oil undergo a condensation reaction with the hydroxyl groups in the acrylate monomer, thus dispersing the second filler into the copolymer system in a chemically mixed manner as well. Ultimately, the spherical first filler and the layered second filler form a cross-linked network structure with the polymer system. The two different fillers are uniformly dispersed in the polymer system and form a network structure, thereby significantly enhancing the bonding strength, barrier properties, weather resistance, and flame retardant properties of the hot melt adhesive system.

[0048] The combination of the first filler and the second filler can overcome the problems of decreased initial peel strength and decreased curing rate caused by the addition of polyacrylate to polyurethane hot melt adhesive. The addition of polyacrylate can also reduce the potential adverse effects of the alkalinity of nano-calcium carbonate on hot melt adhesive. Therefore, in this invention, the synergistic enhancement effect of improving the overall performance of hot melt adhesive is achieved through the mutual cooperation between the first filler, the second filler and the polyurethane-acrylate copolymer component.

[0049] The above is the overall concept of the present invention. The present invention will be further described below with reference to specific embodiments and comparative examples.

[0050] The main sources of raw materials in the examples and comparative examples are described below: Hydroxypropyl methacrylate, pentaerythritol diacrylate, butyl acrylate, 2-hydroxyethyl acrylate, Shanghai Maclean Biochemical Technology Co., Ltd. Polypropylene glycol 1000 and polypropylene glycol 4000, Jiangsu Haolong Chemical Co., Ltd.; Diphenylmethane diisocyanate, Jiangsu Haolong Chemical Co., Ltd.; Bismorpholino diethyl ether, Nantong Shenglun Chemical Technology Co., Ltd.; Nano-calcium carbonate, average particle size 200nm, Suzhou Kaifa New Materials Technology Co., Ltd. Tetraethoxysilane, Jiangsu Haolong Chemical Co., Ltd.; Antioxidant 1010, Jiangsu Runfeng Synthetic Technology Co., Ltd.; Silane coupling agent KH-570, Nanjing Xuanhao New Material Technology Co., Ltd.; Sodium-based montmorillonite, Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.; Hydroxysilicone oil, molecular weight 2000, Guangdong Wengjiang Chemical Reagent Co., Ltd. Diethyl phosphate, Jiangsu Runfeng Synthetic Technology Co., Ltd. Example 1

[0051] A weather-resistant polyurethane acrylate copolymer hot melt adhesive, the raw materials for which are prepared by weight include: 30.5 parts hydroxypropyl methacrylate, 40.5 parts pentaerythritol diacrylate, 10 parts polypropylene glycol 1000, 10 parts polypropylene glycol 4000, 50 parts diphenylmethane diisocyanate, 0.05 parts bismorpholino diethyl ether, 7 parts first filler, and 16 parts second filler.

[0052] The preparation method of this hot melt adhesive is as follows: Polypropylene glycol 1000 and polypropylene glycol 4000 were mixed, dried at 110°C for 4 hours under nitrogen protection, and then cooled to 60°C. Hydroxypropyl methacrylate, pentaerythritol diacrylate, bismorpholino diethyl ether and the first filler were added while stirring. The mixture was stirred for 1.5 hours while stirring was maintained. Diphenylmethane diisocyanate was added and stirred at 90°C for 1 hour. The second filler was then added, the temperature was raised to 100°C, and the mixture was stirred for another 3 hours. The mixture was then cooled to room temperature to obtain a weather-resistant polyurethane acrylate copolymer hot melt adhesive.

[0053] The first filler is prepared through the following steps: S1-1. Mesoporous silica was synthesized in situ on nano-calcium carbonate to prepare a porous silica-calcium carbonate composite: S1-1-1. Take 1g of nano calcium carbonate and 0.35g of cetyltrimethylammonium bromide and add them to 100mL of deionized water. Disperse by ultrasonication for 1h to obtain nano calcium carbonate dispersion. S1-1-2. Add 0.12g sodium hydroxide to the nano-calcium carbonate dispersion and stir until completely dissolved. Add 5mL tetraethoxysilane dropwise while stirring. Stir and react at 60℃ for 5h. Centrifuge, wash the solid product with deionized water, dry under vacuum at 100℃ for 8h, and then calcine at 550℃ in air for 4h. Grind to obtain porous silica-calcium carbonate composite. S1-2. An intermediate filler product was prepared by loading an antioxidant onto a porous silica-calcium carbonate composite using an impregnation method. 1 g of porous silica-calcium carbonate composite was added to 50 mL of acetone solution containing 5 wt% antioxidant 1010, and ultrasonically treated for 90 min. Then, it was shaken in a shaker at 40 °C for 12 h. After centrifugation, the solid product was washed with acetone and ethanol in sequence, and vacuum dried at 90 °C overnight to obtain the intermediate product of the filler. S1-3. Grafting a silane coupling agent onto the intermediate product of the filler to prepare the first filler: Take 1g of the intermediate product of the packing material and 10mL of deionized water and add them to 40mL of ethanol. Disperse the mixture by ultrasonication for 1h. Then, add 0.15g of silane coupling agent KH-570 under stirring. Stir at 60℃ for 3h. Filter the mixture. Wash the solid product with ethanol and dry it under vacuum at 80℃ for 12h to obtain the first packing material.

[0054] The second filler is prepared through the following steps: S2-1. Hydroxyl silicone oil was used to modify sodium-based montmorillonite to prepare hydroxyl silicone oil-grafted montmorillonite: 5g of sodium-based montmorillonite was ground to below 10μm and dried at 120℃ for 2h. Then, it was added to 300mL of an ethanol-water solution composed of ethanol and deionized water in a volume ratio of 8:2. The mixture was ultrasonically dispersed at 70℃ for 3h. After cooling to 30℃, 2g of hydroxyl silicone oil was added and stirred at 1500rpm for 1h. The pH was adjusted to 10 with 1mol / L sodium hydroxide solution, and the reaction was continued for 3h. The mixture was aged at room temperature for 12h, centrifuged and filtered, and the solid product was washed with deionized water. It was then vacuum dried at 90℃ overnight and ground to obtain hydroxyl silicone oil-grafted montmorillonite. S2-2. A composite grafted montmorillonite was prepared by modifying a silane coupling agent onto hydroxyl silicone oil-grafted montmorillonite. Take 2.5g of hydroxyl silicone oil-grafted montmorillonite, 0.3g of silane coupling agent KH-570, and 0.05g of potassium hydroxide and add them to 50mL of dimethyl sulfoxide. Under nitrogen protection, stir and react at 85℃ for 4h. After the reaction is completed, filter, wash the solid product with methanol, and dry it under vacuum at 70℃ for 12h to obtain composite grafted montmorillonite. S2-3. Flame retardant functionalized montmorillonite is prepared by loading a flame retardant onto a composite grafted montmorillonite: The composite grafted montmorillonite prepared in step S2-2 was added to 200 mL of ethanol solution of 20% diethyl ethyl phosphate, ultrasonically dispersed for 2 h, then shaken on a shaker at 60 °C for 24 h, filtered, washed with ethanol, and vacuum dried at 70 °C for 12 h to obtain flame-retardant functionalized montmorillonite. S2-4. Coating flame-retardant functionalized montmorillonite with polyacrylate yields the second filler: S2-4-1. Take 2g of flame-retardant functionalized montmorillonite and add it to 50mL of deionized water. Disperse it ultrasonically for 1h to obtain a montmorillonite dispersion. S2-4-2, Take 3g butyl acrylate, 2g 2-hydroxyethyl acrylate, 1.5g hydroxypropyl methacrylate, and 0.3g sodium dodecylbenzene sulfonate and add them to 70mL of deionized water. Stir for 45min to obtain a monomer mixture. S2-4-3. Add the montmorillonite dispersion to the monomer mixture under stirring, stir for 1 hour, add 10 mL of deionized water containing 0.05 g ammonium persulfate dropwise at 75°C, and complete the addition in 90 minutes. Then raise the temperature to 82°C, stir and react for 4 hours, centrifuge, wash the solid product with deionized water, and vacuum dry at 90°C for 12 hours to obtain the second filler. Example 2

[0055] A weather-resistant polyurethane acrylate copolymer hot melt adhesive, the raw materials for which are prepared by weight include: 30.5 parts of hydroxypropyl methacrylate, 41 parts of pentaerythritol diacrylate, 10 parts of polypropylene glycol 1000, 10 parts of polypropylene glycol 4000, 50 parts of diphenylmethane diisocyanate, 0.05 parts of bismorpholino diethyl ether, 6.5 parts of first filler, and 17 parts of second filler.

[0056] The preparation method of this hot melt adhesive is as follows: Polypropylene glycol 1000 and polypropylene glycol 4000 were mixed, dried at 110°C for 4 hours under nitrogen protection, and then cooled to 60°C. Hydroxypropyl methacrylate, pentaerythritol diacrylate, bismorpholino diethyl ether and the first filler were added while stirring. The mixture was stirred for 1.5 hours while maintaining stirring. Diphenylmethane diisocyanate was then added and stirred at 90°C for 1 hour. The second filler was then added, and the mixture was heated to 105°C and stirred for another 2.5 hours. The mixture was then cooled to room temperature to obtain a weather-resistant polyurethane acrylate copolymer hot melt adhesive.

[0057] The preparation methods for the first and second packing materials are the same as in Example 1. Example 3

[0058] A weather-resistant polyurethane acrylate copolymer hot melt adhesive, the raw materials for which are prepared by weight include: 30.5 parts of hydroxypropyl methacrylate, 41 parts of pentaerythritol diacrylate, 10 parts of polypropylene glycol 1000, 10 parts of polypropylene glycol 4000, 50 parts of diphenylmethane diisocyanate, 0.05 parts of bismorpholino diethyl ether, 7.5 parts of first filler, and 15 parts of second filler.

[0059] The preparation method of this hot melt adhesive is as follows: Polypropylene glycol 1000 and polypropylene glycol 4000 were mixed, dried at 110°C for 4 hours under nitrogen protection, and then cooled to 60°C. Hydroxypropyl methacrylate, pentaerythritol diacrylate, bismorpholino diethyl ether and the first filler were added while stirring. The mixture was stirred for 1.5 hours while maintaining stirring. Diphenylmethane diisocyanate was then added and stirred at 90°C for 1 hour. The second filler was then added, the temperature was raised to 90°C, and the mixture was stirred for another 3.5 hours. The mixture was then cooled to room temperature to obtain a weather-resistant polyurethane acrylate copolymer hot melt adhesive.

[0060] The preparation methods for the first and second packing materials are the same as in Example 1.

[0061] Comparative Example 1

[0062] The only difference between this example and Example 1 is that the raw materials for preparing the hot melt adhesive in this example include, by weight, 10 parts of polypropylene glycol 1000, 10 parts of polypropylene glycol 4000, 50 parts of diphenylmethane diisocyanate, 0.05 parts of bismorpholino diethyl ether, 7 parts of the first filler, and 16 parts of the second filler.

[0063] The preparation method of this hot melt adhesive is as follows: Polypropylene glycol 1000 and polypropylene glycol 4000 were mixed, dried at 110°C for 4 hours under nitrogen protection, cooled to 60°C, and then bismorpholino diethyl ether and the first filler were added with stirring. The mixture was stirred for 1.5 hours, and then diphenylmethane diisocyanate was added. The mixture was stirred at 90°C for 1 hour. The second filler was then added, the temperature was raised to 100°C, and the mixture was stirred for another 3 hours. The mixture was then cooled to room temperature to obtain a hot melt adhesive.

[0064] The preparation methods for the first and second packing materials are the same as in Example 1.

[0065] Comparative Example 2

[0066] The only difference between this example and Example 1 is that the hot melt adhesive preparation materials in this example do not include the first filler.

[0067] Comparative Example 3 The only difference between this example and Example 1 is that the hot melt adhesive preparation materials in this example do not include a second filler.

[0068] Comparative Example 4

[0069] The only difference between this example and Example 1 is that this example uses the intermediate packing product prepared in Example 1 as the first packing.

[0070] Comparative Example 5

[0071] The only difference between this example and Example 1 is that the first filler in this example is prepared through the following steps: S1-1. Porous silica was prepared: S1-1-1. Take 0.35g of cetyltrimethylammonium bromide and add it to 100mL of deionized water. Disperse it by ultrasonication for 1h to obtain a dispersion. S1-1-2. Add 0.12g sodium hydroxide to the dispersion and stir until completely dissolved. Add 5mL tetraethoxysilane dropwise while stirring. Stir the reaction at 60℃ for 5h. Centrifuge and wash the solid product with deionized water. Dry it under vacuum at 100℃ for 8h. Then calcine it in air at 550℃ for 4h. Grind it to obtain porous silica. S1-2. An intermediate filler product is prepared by loading an antioxidant onto porous silica using an impregnation method: 1 g of porous silica was added to 50 mL of acetone solution containing 5 wt% antioxidant 1010, and ultrasonically treated for 90 min. Then, it was shaken in a shaker at 40 °C for 12 h. After centrifugation, the solid product was washed with acetone and ethanol in sequence, and vacuum dried at 90 °C overnight to obtain the intermediate product of the filler. S1-3. Graft a silane coupling agent onto the intermediate product of the filler to prepare the first filler. The specific preparation steps are the same as in Example 1.

[0072] Comparative Example 6

[0073] A weather-resistant polyurethane acrylate copolymer hot melt adhesive, the raw materials for which are prepared by weight include: 30.5 parts hydroxypropyl methacrylate, 40.5 parts pentaerythritol diacrylate, 10 parts polypropylene glycol 1000, 10 parts polypropylene glycol 4000, 50 parts diphenylmethane diisocyanate, 0.05 parts bismorpholino diethyl ether, 7 parts first filler, 16 parts second filler, and 0.75 parts antioxidant.

[0074] The preparation method of this hot melt adhesive is as follows: Polypropylene glycol 1000 and polypropylene glycol 4000 were mixed, dried at 110°C for 4 hours under nitrogen protection, and then cooled to 60°C. Hydroxypropyl methacrylate, pentaerythritol diacrylate, bismorpholino diethyl ether and the first filler were added while stirring. The mixture was stirred for 1.5 hours while stirring was maintained. Diphenylmethane diisocyanate was added and stirred at 90°C for 1 hour. The second filler was then added, and the mixture was heated to 100°C. An antioxidant was added, and the mixture was stirred and reacted for another 3 hours. The mixture was then cooled to room temperature to obtain a weather-resistant polyurethane acrylate copolymer hot melt adhesive.

[0075] Comparative Example 7

[0076] The only difference between this example and Example 1 is that the second filler in this example is prepared through the following steps: S2-1. Grafted montmorillonite is prepared by modifying silane coupling agents onto montmorillonite: Take 2.5g of sodium montmorillonite (pre-ground to below 10μm and dried at 120℃ for 2h), 0.3g of silane coupling agent KH-570, and 0.05g of potassium hydroxide and add them to 50mL of dimethyl sulfoxide. Under nitrogen protection, stir and react at 85℃ for 4h. After the reaction is completed, filter, wash the solid product with methanol, and dry it under vacuum at 70℃ for 12h to obtain grafted montmorillonite. S2-2. Flame retardant functionalized montmorillonite is prepared by loading a flame retardant onto grafted montmorillonite: All of the grafted montmorillonite prepared in step S2-1 was added to 200 mL of an ethanol solution of 20% diethyl ethyl phosphate, ultrasonically dispersed for 2 h, then shaken on a shaker at 60 °C for 24 h, filtered, washed with ethanol, and vacuum dried at 70 °C for 12 h to obtain flame-retardant functionalized montmorillonite. S2-3. Coating flame-retardant functionalized montmorillonite with polyacrylate to obtain the second filler, the specific steps are the same as step S2-4 of Example 1.

[0077] Comparative Example 8

[0078] The only difference between this example and Example 1 is that the second filler in this example is prepared through the following steps: S2-1. Sodium-based montmorillonite was modified with hydroxyl silicone oil to prepare hydroxyl silicone oil-grafted montmorillonite. The specific steps were the same as in Example 1. S2-2. Flame retardant functionalized montmorillonite is prepared by loading a flame retardant onto hydroxyl silicone oil-grafted montmorillonite: The hydroxyl silicone oil-grafted montmorillonite prepared in step S2-1 was added to 200 mL of an ethanol solution of 20% diethyl ethyl phosphate, ultrasonically dispersed for 2 h, then shaken on a shaker at 60 °C for 24 h, filtered, washed with ethanol, and vacuum dried at 70 °C for 12 h to obtain flame-retardant functionalized montmorillonite. S2-3. Coating flame-retardant functionalized montmorillonite with polyacrylate to obtain the second filler, the specific steps are the same as step S2-4 of Example 1.

[0079] Comparative Example 9

[0080] The only difference between this example and Example 1 is that this example uses the flame-retardant functionalized montmorillonite prepared in Example 1 as the second filler.

[0081] Comparative Example 10

[0082] A weather-resistant polyurethane acrylate copolymer hot melt adhesive, the raw materials for which are prepared by weight include: 30.5 parts hydroxypropyl methacrylate, 40.5 parts pentaerythritol diacrylate, 10 parts polypropylene glycol 1000, 10 parts polypropylene glycol 4000, 50 parts diphenylmethane diisocyanate, 0.05 parts bismorpholino diethyl ether, 7 parts first filler, 16 parts second filler, and 10 parts diethyl ethyl phosphate.

[0083] The preparation method of this hot melt adhesive is as follows: Polypropylene glycol 1000 and polypropylene glycol 4000 were mixed, dried at 110°C for 4 hours under nitrogen protection, and then cooled to 60°C. Hydroxypropyl methacrylate, pentaerythritol diacrylate, bismorpholino diethyl ether and the first filler were added while stirring. The mixture was stirred for 1.5 hours while maintaining stirring. Diphenylmethane diisocyanate was added and stirred at 90°C for 1 hour. The second filler and diethyl ethyl phosphate were then added, and the mixture was heated to 100°C and stirred for another 3 hours. The mixture was then cooled to room temperature to obtain a weather-resistant polyurethane acrylate copolymer hot melt adhesive.

[0084] The preparation method of the first filler is the same as in Example 1.

[0085] The second filler is prepared through the following steps: S2-1. Sodium-based montmorillonite was modified with hydroxyl silicone oil to prepare hydroxyl silicone oil-grafted montmorillonite. The specific steps were the same as in Example 1. S2-2. Modify silane coupling agent on hydroxyl silicone oil-grafted montmorillonite to prepare composite grafted montmorillonite. The specific steps are the same as in Example 1. S2-4. Coating the composite-grafted montmorillonite with polyacrylate yields the second filler: S2-4-1. Take 2g of composite grafted montmorillonite and add it to 50mL of deionized water. Disperse it ultrasonically for 1h to obtain a montmorillonite dispersion. S2-4-2, Take 3g butyl acrylate, 2g 2-hydroxyethyl acrylate, 1.5g hydroxypropyl methacrylate, and 0.3g sodium dodecylbenzene sulfonate and add them to 70mL of deionized water. Stir for 45min to obtain a monomer mixture. S2-4-3. Add the montmorillonite dispersion to the monomer mixture under stirring, stir for 1 hour, add 10 mL of deionized water containing 0.05 g ammonium persulfate dropwise at 75°C, and complete the addition in 90 minutes. Then raise the temperature to 82°C, stir and react for 4 hours, centrifuge, wash the solid product with deionized water, and vacuum dry at 90°C for 12 hours to obtain the second filler.

[0086] 1. Peel strength The prepared hot melt adhesive was melted and applied to test pieces. After curing at RH=60% and T=25℃ for different times, the peel strength was tested according to the standard GB / T 2790 Adhesives 180° Peel Strength Test Method. The test pieces were PC boards / aramid strips. The peel strength after 1 hour of curing was taken as the initial peel strength, and the peel strength after 60 hours of curing was taken as the final peel strength. The test results are shown in Table 1 and below. Figure 1 As shown: Table 1 Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 Initial peel strength (25mm) / N 97 94 95 94 76 74 85 78 91 92 89 93 90 Final peel strength (25mm) / N 895 882 886 672 655 701 834 812 825 844 847 855 851 The test results show that the initial and final peel strengths of Examples 1-3 are very high, while the comparative examples show varying degrees of decrease. Specifically: The significant decrease in final peel strength in Comparative Example 1 was attributed to the absence of acrylate polymer in the hot melt adhesive raw material system. In Comparative Example 2, the absence of a first filler containing nano-calcium carbonate resulted in a decrease in curing rate, leading to a significant decrease in both initial and final peel strength. In Comparative Example 3, the absence of a second filler containing montmorillonite failed to effectively reduce the crystallization shrinkage of the acrylic resin, resulting in a significant decrease in initial peel strength and also impairing the final peel strength. In Comparative Example 4, the lack of silane coupling agent modification on the first filler affected its dispersibility, leading to a decrease in strength. In Comparative Example 5, the absence of nano-calcium carbonate in the first filler resulted in a decrease in curing rate and a significant decrease in initial peel strength. The results of Comparative Examples 6 and 7 indicate that modification with hydroxyl silicone oil and silane coupling agent in the second filler both contribute to peel strength. In Comparative Example 9, the absence of polyacrylate coating on the second filler affected its dispersibility, resulting in a decrease in final peel strength. In Comparative Example 10, the main reason for the decrease in final peel strength was the direct addition of flame retardant to the hot melt adhesive raw material system, which precipitated out during curing.

[0087] 2. Bond strength The prepared hot melt adhesive was heated and melted, then applied to a test piece (stainless steel plate / stainless steel sheet). It was cured at RH=50% and T=25℃, and then the tensile shear strength was tested according to standard GB / T 7124—2008. The tensile shear strength after 10 minutes of curing was taken as the initial bond strength; the tensile shear strength after 3 days of curing was taken as the final bond strength.

[0088] The test results are shown in Table 2 below. Figure 2 As shown: Table 2 Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 Initial Tack Strength / MPa 3.26 3.14 3.17 3.14 2.58 2.67 2.91 2.58 3.04 3.07 2.96 3.13 3.07 Final Tack Strength / MPa 11.43 11.28 11.30 8.61 8.43 8.94 10.70 10.36 10.52 10.64 10.85 10.90 10.92 The test results show that Examples 1-3 have high initial and final tack strengths, while the comparative examples show varying degrees of decrease, and the decreasing trend is similar to that of the peel strength.

[0089] 3. Post-continuity performance test The prepared hot melt adhesive was heated and melted, and then applied to the test piece (stainless steel plate / stainless steel sheet). It was cured for 3 days at RH=50% and T=25℃. Then, it was accelerated to age for 7 days at 85℃ and RH=85%. The tensile shear strength before and after aging was tested according to the standard GB / T 7124—2008. The bond strength retention rate after aging was calculated as (tensile shear strength after aging / tensile shear strength before aging)*100%.

[0090] The test results are shown in Table 3 below. Figure 3 As shown: Table 3 Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 Bond strength retention rate after aging / % 99.2 98.5 98.9 88.3 82.7 89.1 92.5 97.4 86.3 91 92.7 90.4 92.3 The test results show that the bonding strength of Examples 1-3 decreased very little after 7 days of aging with double 85, indicating excellent weather resistance.

[0091] In Comparative Example 1, the hot melt adhesive raw material system without acrylate polymers showed a significant decrease in weather resistance. In Comparative Example 2, the first filler without added antioxidant showed a significant decrease in weather resistance. The decrease in weather resistance shown in Comparative Example 3 indicates that the addition of the second filler can improve the weather resistance of the hot melt adhesive. The reason for the decrease in the bond strength retention rate after aging in Comparative Example 4 is that the first filler was not modified with a silane coupling agent, which affected its dispersibility. In Comparative Example 6, the antioxidant was directly added to the hot melt adhesive raw material system, which resulted in the loss of the antioxidant's slow-release effect and a significant decrease in weather resistance. In Comparative Example 7, the second filler was not grafted with hydroxyl silicone oil, thus losing the effect of the organosilicon functional groups introduced by the hydroxyl silicone oil on improving weather resistance, resulting in a decrease in the retention rate of bond strength after aging. Comparative Example 8 did not graft silane coupling agent onto the second filler, which affected the dispersion effect and reduced the weather resistance. In Comparative Example 9, the second filler was not coated with polyacrylate, which affected its dispersibility. Furthermore, due to the lack of coating, the flame retardant loaded in the second filler gradually precipitated out under high temperature and high humidity aging conditions, which reduced the bonding strength and ultimately resulted in a decrease in weather resistance. The bonding strength of Comparative Example 10 decreased significantly after aging. The reason for this was that the flame retardant was directly added to the hot melt adhesive raw material system. Under the aging conditions of high temperature and high humidity, the flame retardant was released from the system, resulting in a rapid decrease in bonding strength.

[0092] To further analyze the mechanism by which the first filler improves aging resistance, the antioxidant release performance of the first filler prepared in Example 1 was further tested. The test method is as follows: 1g of the first packing material prepared in Example 1 was added to 100mL of acetone. The concentration of antioxidant 1010 in the soaking solution after different soaking times was detected by gas chromatography. The release amount at different time points was calculated. The test was continued for 24 hours. A release curve was plotted with the cumulative release percentage as the ordinate and the soaking time as the abscissa. Wherein, the cumulative release percentage K= Q T Q represents the cumulative release over a soaking time T. Z The total loading of antioxidant 1010 is indicated by subtracting the mass of antioxidant 1010 remaining in the impregnation solution after impregnation from the total mass of antioxidant 1010 in steps S1-2 of Example 1. Test results are as follows... Figure 4 As shown, this illustrates that the first filler can achieve the sustained release of antioxidant 1010.

[0093] 4. Curing speed The hot melt adhesives prepared in Examples 1, 1, 2, and 5 were heated and melted, and then applied to test pieces (stainless steel plates). The adhesives were cured at RH=50% and T=25℃, and the tensile shear strength at different curing times was tested in accordance with the standard GB / T 7124—2008.

[0094] Test results are as follows Figure 5 As shown, it can be seen that compared with Comparative Examples 2 and 5, Example 1 and Comparative Example 1 have a faster curing speed. The comparison of the results shows that the nano-calcium carbonate in the first filler can improve the curing speed.

[0095] 5. Flame retardant properties The limiting oxygen index of hot melt adhesives was tested according to standard GB / T 10707—2008. The test results are shown in Table 4 below. Figure 6 As shown: Table 4 Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 Limiting oxygen index / % 41.6 40.9 41.3 40.7 38.2 25.1 39.7 40.3 38.5 37.8 35.2 33.7 39.4 The test results show that Examples 1-3 have excellent flame retardant properties, while the comparative examples show varying degrees of decline.

[0096] 6. Thermal stability The hot melt adhesive prepared in Example 1 was applied and cured for 3 days at RH=50% and T=25℃. Its TGA curve was then measured using a thermogravimetric analyzer (nitrogen atmosphere, scanning range 30~600℃, heating rate 10℃ / min) to characterize its thermal stability. The test results are as follows: Figure 7 As shown in the figure, its thermogravimetric initiation temperature is around 330℃, indicating good thermal stability.

[0097] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. A weather-resistant polyurethane-acrylate copolymer hot melt adhesive, characterized in that, The raw materials for its preparation include, by weight, 15-61 parts of hydroxypropyl methacrylate, 20-81 parts of pentaerythritol diacrylate, 5-20 parts of polypropylene glycol 1000, 5-20 parts of polypropylene glycol 4000, 25-100 parts of diphenylmethane diisocyanate, 0.025-0.1 parts of bismorpholino diethyl ether, 3.5-14 parts of the first filler, and 8-32 parts of the second filler.

2. The weather-resistant polyurethane acrylate copolymer hot melt adhesive according to claim 1, characterized in that, The preparation method of this hot melt adhesive is as follows: Polypropylene glycol 1000 and polypropylene glycol 4000 were mixed and dried under nitrogen protection. Hydroxypropyl methacrylate, pentaerythritol diacrylate, bismorpholino diethyl ether and the first filler were added under stirring. Diphenylmethane diisocyanate was added and stirred under heating. The second filler was then added and the temperature was raised and the reaction was continued to be stirred to obtain a weather-resistant polyurethane acrylate copolymer hot melt adhesive.

3. The weather-resistant polyurethane acrylate copolymer hot melt adhesive according to claim 2, characterized in that, The preparation method of this hot melt adhesive is as follows: Mix polypropylene glycol 1000 and polypropylene glycol 4000, dry under nitrogen protection at 80-130℃ for 2-8 hours, cool to 50-70℃, add hydroxypropyl methacrylate, pentaerythritol diacrylate, bismorpholino diethyl ether and the first filler while stirring, stir for 1-3 hours, continue stirring, add diphenylmethane diisocyanate, stir and react at 80-95℃ for 0.5-2 hours, then add the second filler, heat to 100-110℃, continue stirring and react for 1.5-6 hours, cool to room temperature to obtain weather-resistant polyurethane acrylate copolymer hot melt adhesive.

4. The weather-resistant polyurethane acrylate copolymer hot melt adhesive according to claim 1, characterized in that, The first filler is prepared through the following steps: S1-1. Mesoporous silica was synthesized in situ on nano-calcium carbonate to prepare a porous silica-calcium carbonate composite. S1-2. An antioxidant was loaded onto a porous silica-calcium carbonate composite by an impregnation method to prepare a filler intermediate product. S1-3. Graft a silane coupling agent onto the intermediate product of the filler to prepare the first filler.

5. The weather-resistant polyurethane acrylate copolymer hot melt adhesive according to claim 4, characterized in that, The first filler is prepared through the following steps: S1-1, Preparation of porous silica-calcium carbonate composite: S1-1-1. Take nano-calcium carbonate and hexadecyltrimethylammonium bromide and add them to deionized water, then disperse them by ultrasonication to obtain a nano-calcium carbonate dispersion. S1-1-2. Add sodium hydroxide to the nano-calcium carbonate dispersion, add 5 mL of tetraethoxysilane dropwise under stirring, heat and stir to react, centrifuge, wash and dry, calcine the obtained solid product, grind it to obtain a porous silica-calcium carbonate composite. S1-2. Take porous silica-calcium carbonate composite and add it to antioxidant solution, sonicate, shake in a shaker, centrifuge, wash and dry to obtain filler intermediate product; In the antioxidant solution, the antioxidant is at least one of antioxidant 1010, antioxidant 1135, antioxidant 1076, and antioxidant BHT, and the mass concentration of the antioxidant is 2-20%. S1-3. Take the intermediate product of the packing material and deionized water, add them to ethanol, disperse them by ultrasonication, then add silane coupling agent KH-570 under stirring, heat and stir, filter, wash and dry to obtain the first packing material.

6. The weather-resistant polyurethane acrylate copolymer hot melt adhesive according to claim 5, characterized in that, The first filler is prepared through the following steps: S1-1, Preparation of porous silica-calcium carbonate composite: S1-1-1: Take 0.5-2g of nano-calcium carbonate and 0.15-0.7g of cetyltrimethylammonium bromide and add them to 50-200mL of deionized water. Disperse by ultrasonication for 0.5-2h to obtain a nano-calcium carbonate dispersion. S1-1-2. Add 0.06-0.24g of sodium hydroxide to the nano-calcium carbonate dispersion and stir until completely dissolved. Add 2.5-10mL of tetraethoxysilane dropwise while stirring. Stir and react at 50-70℃ for 2.5-10h. Centrifuge, wash, and dry. Calcine the obtained solid in air at 500-600℃ for 2-8h. Grind to obtain a porous silica-calcium carbonate composite. S1-2. Take 0.5-2g of porous silica-calcium carbonate composite and add it to 25-100mL of acetone solution containing 2.5-10wt% antioxidant 1010. Sonicate for 45-180min, then shake in a shaker at 30-50℃ for 6-24h. Centrifuge, wash and dry to obtain the intermediate product of the filler. S1-3. Take 0.5-2g of the intermediate product of the packing material and 5-20mL of deionized water and add them to 20-80mL of ethanol. Disperse the mixture by ultrasonication for 0.5-2h. Then, add 0.05-0.3g of silane coupling agent KH-570 under stirring. Stir at 50-70℃ for 1.5-6h. Filter, wash and dry to obtain the first packing material.

7. The weather-resistant polyurethane acrylate copolymer hot melt adhesive according to claim 1, characterized in that, The second filler is prepared by the following steps: S2-1. Sodium-based montmorillonite was modified with hydroxyl silicone oil to prepare hydroxyl silicone oil-grafted montmorillonite. S2-2. A composite grafted montmorillonite was prepared by modifying a silane coupling agent onto hydroxyl silicone oil-grafted montmorillonite. S2-3. Flame retardant functionalized montmorillonite is prepared by loading flame retardant onto composite grafted montmorillonite. S2-4. Coating flame-retardant functionalized montmorillonite with polyacrylate yields the second filler.

8. The weather-resistant polyurethane acrylate copolymer hot melt adhesive according to claim 7, characterized in that, The second filler is prepared by the following steps: S2-1. Sodium-based montmorillonite was dried and added to an ethanol-water solution, ultrasonically dispersed, hydroxyl silicone oil was added, stirred, pH was adjusted to alkaline, stirred to react, aged, centrifuged, filtered, washed, dried, and ground to obtain hydroxyl silicone oil-grafted montmorillonite. S2-2. Take hydroxyl silicone oil-grafted montmorillonite, silane coupling agent, and potassium hydroxide and add them to dimethyl sulfoxide. Heat and stir the reaction under nitrogen protection. After the reaction is completed, filter, wash, and dry to obtain composite grafted montmorillonite. S2-3. Add the composite grafted montmorillonite to the flame retardant solution, disperse it ultrasonically, shake it on a shaker, filter it, wash it, and dry it to obtain flame-retardant functionalized montmorillonite. S2-4. Coating polyacrylate onto flame-retardant functionalized montmorillonite: S2-4-1. Add flame-retardant functionalized montmorillonite to deionized water and disperse it by ultrasonication to obtain a montmorillonite dispersion. S2-4-2. Take butyl acrylate, 2-hydroxyethyl acrylate, hydroxypropyl methacrylate, and sodium dodecylbenzene sulfonate, add them to deionized water, stir, and obtain a monomer mixture. S2-4-3. Add the montmorillonite dispersion to the monomer mixture under stirring, stir, add the deionized water solution of ammonium persulfate dropwise under heating, raise the temperature, stir the reaction, centrifuge, wash, and dry to obtain the second filler.

9. The weather-resistant polyurethane acrylate copolymer hot melt adhesive according to claim 8, characterized in that, The silane coupling agent in step S2-2 is any one of the silane coupling agents KH-570, A151, and A171; In the flame retardant solution in steps S2-3, the flame retardant is any one of diethyl phosphate, ammonium polyphosphate, and melamine, and the mass concentration of the flame retardant is 5-30%.

10. The weather-resistant polyurethane acrylate copolymer hot melt adhesive according to claim 9, characterized in that, The second filler is prepared by the following steps: S2-1. Take 2.5-10g of sodium montmorillonite and grind it to below 5-20μm. Dry it at 100-150℃ for 1-4h, then add it to 150-600mL of an ethanol-water solution composed of ethanol and deionized water in a volume ratio of 8:

2. Disperse it ultrasonically at 60-80℃ for 1.5-6h, cool it to 25-40℃, add 1-4g of hydroxyl silicone oil, stir for 0.5-2h, adjust the pH to 9-11 with sodium hydroxide solution, continue stirring and react for 1.5-6h, age it at room temperature for 6-24h, centrifuge, filter, dry, and grind to obtain hydroxyl silicone oil-grafted montmorillonite. S2-2. Take 1.25-5g of hydroxyl silicone oil-grafted montmorillonite, 0.15-0.6g of silane coupling agent KH-570, and 0.02-0.1g of potassium hydroxide and add them to 25-100mL of dimethyl sulfoxide. Under nitrogen protection, stir and react at 70-90℃ for 2-8h. After the reaction is completed, filter, wash, and dry to obtain composite grafted montmorillonite. S2-3. Add all of the composite grafted montmorillonite prepared in step S2-2 to 100-400 mL of an ethanol solution of 5-25% diethyl phosphate, ultrasonically disperse for 1-4 h, then shake on a shaker at 50-65℃ for 12-48 h, filter, wash, and dry to obtain flame-retardant functionalized montmorillonite. S2-4. Coating polyacrylate onto flame-retardant functionalized montmorillonite: S2-4-1. Take 1-4g of flame-retardant functionalized montmorillonite and add it to 25-100mL of deionized water. Disperse it ultrasonically for 0.5-2h to obtain a montmorillonite dispersion. S2-4-2, Take 1.5-6g butyl acrylate, 1-42g 2-hydroxyethyl acrylate, 0.75-3g hydroxypropyl methacrylate, and 0.15-0.6g sodium dodecylbenzenesulfonate and add them to 35-140mL of deionized water. Stir for 30-60min to obtain a monomer mixture. S2-4-3. Add the montmorillonite dispersion to the monomer mixture under stirring, stir for 0.5-2 hours, add 10-20 mL of deionized water containing 0.025-0.1 g of ammonium persulfate dropwise at 70-78℃, and complete the addition in 45-180 minutes. Then raise the temperature to 80-85℃, stir the reaction for 2-8 hours, centrifuge, wash, and dry to obtain the second filler.

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