High weatherable acrylic resin composition and method of making same

Abstract

This invention relates to the field of polymer materials technology, specifically to a high weather-resistant acrylic resin composition and its preparation method. The composition comprises an acrylic copolymer matrix, an in-situ surface-modified composite nano-weather-resistant filler, composite functional additives, and an organic solvent. The acrylic copolymer matrix is ​​obtained by copolymerization of functional acrylate monomers, with chemically bonded reactive UV-absorbing groups and fluorinated weather-resistant segments in its molecular chains. The in-situ modified composite nano-weather-resistant filler is a silane coupling agent-modified nano-inorganic filler composite. The composite functional additives include light stabilizers, antioxidants, and leveling agents. The composition exhibits excellent artificially accelerated weathering resistance. This invention improves resin weather resistance at the molecular level, solving the problems of easy precipitation of traditional additives and easy agglomeration of fillers. The synergistic effect of multiple systems significantly improves artificially accelerated weathering resistance and overall service performance, making it suitable for high-end outdoor applications.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a high weather-resistant acrylic resin composition and its preparation method. Background Technology

[0002] Acrylic resins are widely used in various fields such as outdoor architectural coatings, automotive topcoats, photovoltaic protective coatings, and outdoor decorative materials due to their excellent light color transparency, gloss and color retention, chemical resistance, and substrate adhesion. With the continuous expansion of outdoor applications, coatings face harsh environments such as strong ultraviolet radiation, high and low temperature cycling, acid rain and salt spray, and high humidity and high heat, placing higher demands on the weather resistance, service stability, and overall performance of acrylic resins.

[0003] Currently available commercially available acrylic resins are prone to chain breakage and degradation under ultraviolet radiation during long-term outdoor service, resulting in problems such as yellowing, loss of gloss, chalking, and cracking, which cannot meet the requirements for long-term outdoor use. Existing technologies often improve weather resistance by physically adding UV absorbers, light stabilizers, and other additives. However, these physically added additives have limited compatibility with the resin matrix and are prone to migration, precipitation, and volatilization, leading to rapid degradation of long-term weather resistance. They also affect the mechanical properties and appearance of the coating.

[0004] Other technologies modify resins by introducing fluorinated monomers and nanofillers. However, fluorinated monomers generally suffer from high addition amounts and high production costs. Furthermore, the excessive hydrophobicity of fluorinated segments can lead to decreased resin system stability, and fluorine elements easily migrate to the coating surface, failing to achieve overall weather resistance modification of the resin. Nanofillers, on the other hand, are mostly added directly or through simple offline modification, easily agglomerating in the resin matrix. This not only fails to achieve weather resistance modification but also creates stress concentration points, reducing the coating's mechanical strength and impact resistance. Simultaneously, the weak interfacial bonding between the filler and the resin matrix leads to phase separation over long-term use, further degrading coating performance. In addition, existing modified acrylic resins struggle to balance low-temperature flexibility with high-temperature anti-sticking properties. A balance cannot be achieved between weather resistance, adhesion, and chemical resistance, resulting in a significantly shortened service life in harsh outdoor environments, failing to meet the demands of high-end outdoor applications. Summary of the Invention

[0005] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a high weather-resistant acrylic resin composition and its preparation method.

[0006] (II) Technical Solution A high weather-resistant acrylic resin composition, by weight, comprises the following components: 65-85 parts of acrylic copolymer matrix, 3-8 parts of in-situ surface-modified composite nano weather-resistant filler, 2-7 parts of composite functional additives, and 10-25 parts of organic solvent. The acrylic copolymer matrix is ​​prepared by free radical polymerization of the following comonomers in parts by weight: 15-30 parts methyl methacrylate, 8-18 parts isoborneol methacrylate, 10-22 parts isooctyl acrylate, 2-6 parts tridecafluorooctylpropyl methacrylate, 3-7 parts reactive UV-absorbing acrylate monomer, 4-10 parts hydroxyethyl methacrylate, and 0.5-2 parts acrylic acid. The hydroxyl value of the acrylic copolymer matrix is ​​30~60 mgKOH / g, the glass transition temperature is 15~35℃, the weight-average molecular weight is 12000~35000, and the molecular weight distribution index is ≤2.3; The in-situ surface-modified composite nano-weather-resistant filler is a composite of nano-titanium dioxide and nano-zinc oxide modified in-situ by silane coupling agent KH570, with a mass ratio of 3:1 to 5:1 and an average particle size of 20 to 50 nm. The composite functional additives, by weight, include 1-3 parts hindered amine light stabilizer, 0.5-2 parts thioester antioxidant, and 0.5-2 parts acrylate leveling agent.

[0007] Preferably, the reactive UV-absorbing acrylate monomer is either 2-hydroxy-4-(3-methacryloyloxy-2-hydroxypropoxy)benzophenone or 2-(2'-hydroxy-5'-methacryloyloxyphenyl)benzotriazole.

[0008] Preferably, in the in-situ surface-modified composite nano-weather-resistant filler, the amount of silane coupling agent KH570 is 2-5% of the total mass of the nano-filler.

[0009] Preferably, in the comonomer of the acrylic copolymer matrix, the amount of tridecafluorooctylpropyl methacrylate is 3-5 parts, and the amount of reactive ultraviolet-absorbing acrylate monomer is 4-6 parts.

[0010] Preferably, in the composite functional additive, the hindered amine light stabilizer is at least one of light stabilizer 944 and light stabilizer 622; and the thioester antioxidant is at least one of antioxidant DLTP and antioxidant DSTP.

[0011] Preferably, the organic solvent is a mixed solvent composed of xylene, butyl acetate, and propylene glycol methyl ether acetate in a mass ratio of 2:2:1.

[0012] Preferably, the method for preparing the high weather-resistant acrylic resin composition includes the following steps: Preparation of S1 premix: Mix all comonomers evenly according to the weight parts to obtain monomer premix; dissolve the initiator in a portion of the organic solvent to obtain an initiator solution for later use; Preparation of S2 acrylic copolymer matrix: Add the remaining organic solvent to the reactor, purge with nitrogen for protection, heat to 105~120℃, and under the condition of heat preservation and stirring, first add 10~15% of monomer premix and 15~20% of initiator solution dropwise, and keep the reaction at the temperature for 30~60 min; then add the remaining monomer premix and initiator solution dropwise at a uniform rate, controlling the dropwise addition time to 3~5 h, and keep the reaction at the temperature for 2~4 h after the dropwise addition is completed; then cool to 80~90℃, add the remaining initiator solution, keep the reaction at the temperature for 1~2 h for ripening reaction, and cool to room temperature to obtain acrylic copolymer matrix solution; Preparation of S3 in-situ surface modified composite nano-weather-resistant filler: Nano-titanium dioxide and nano-zinc oxide are dispersed in an organic solvent according to the ratio. After high-speed dispersion for 30-60 min, silane coupling agent KH570 is added, the temperature is raised to 60-80℃, and the mixture is kept warm and stirred for 1-3 h to obtain the modified filler dispersion. S4 composition compounding: Add acrylic copolymer matrix solution, modified filler dispersion and composite functional additives to a stirring tank according to the ratio, stir at 800~1200 rpm for 60~90 min at room temperature, filter after uniform mixing to obtain high weather-resistant acrylic resin composition.

[0013] Preferably, the initiator in S1 is at least one of benzoyl peroxide and azobisisobutyronitrile, and the total amount of initiator is 0.8 to 2.0% of the total weight of the comonomer.

[0014] Preferably, in step S2, the reaction temperature fluctuation during the monomer and initiator dropwise addition process is controlled within ±2℃, and the constant temperature for the ripening reaction is 85℃.

[0015] Preferably, in step S4, a 200-400 mesh filter cloth is used for filtration, and the solid content of the final high weather-resistant acrylic resin composition is 50-70%.

[0016] (iii) Beneficial technical effects Compared with existing technologies, the beneficial effects of this invention are: Through targeted molecular structure design, reactive UV-absorbing functional monomers, fluorinated functional monomers, and cyclic functional monomers are chemically bonded into the molecular chain of the acrylic copolymer matrix. This enhances the resin's resistance to UV degradation and weather stability from the molecular level, avoiding the defects of traditional physical additives such as easy migration and precipitation. At the same time, by precisely controlling the resin's molecular weight, hydroxyl value, and glass transition temperature, a good balance is achieved between the resin's film-forming properties, low-temperature flexibility, and high-temperature anti-sticking properties, making it suitable for a variety of complex outdoor application scenarios.

[0017] In-situ surface-modified composite nano-weather-resistant fillers are used. Through in-situ modification with silane coupling agents, reactive active groups are introduced on the surface of the nano-fillers, which significantly improves the dispersibility of the fillers in the resin matrix and effectively solves the industry pain point of easy agglomeration of nano-fillers. At the same time, chemical bonding between the filler and the resin matrix is ​​achieved, enhancing the interfacial bonding force between the two phases. It can form a synergistic protective effect with the weather-resistant structure in the molecular chain, further enhancing the anti-aging and anti-yellowing properties of the resin, and also effectively improving the mechanical strength, impact resistance and scratch resistance of the coating.

[0018] Through the synergistic compounding of various components, a multi-layered weather protection system was constructed. The composite functional additives have excellent compatibility with the resin matrix and form a synergistic effect with the weather-resistant functional monomers and modified nanofillers, which greatly improves the gloss and color retention and long-term service stability of the resin composition, while optimizing the film-forming flowability and substrate adhesion of the resin. Attached Figure Description

[0019] Figure 1 This is a flowchart of a method for preparing a high weather-resistant acrylic resin composition disclosed in this invention; Figure 2 This is a bar chart comparing the core weathering indicators of the embodiment and the comparative example after 3000h artificial accelerated aging under xenon lamps. Figure 3 These are line graphs showing the trend of light loss rate under different aging times for the examples and comparative examples; Figure 4 The images show radar charts of the overall weather resistance performance of the examples and comparative examples after 3000 hours of aging. Detailed Implementation

[0020] according to Figures 1 to 4 The specific embodiments of the present invention are as follows: This invention discloses a high weather-resistant acrylic resin composition and its preparation method. Through molecular structure orientation design, in-situ modified nanofiller compounding, and synergistic effect of multiple weather-resistant systems, the weather resistance and comprehensive service performance of acrylic resin are improved simultaneously. The following detailed description of the invention is based on specific embodiments. The described embodiments are some, but not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0021] The high weather-resistant acrylic resin composition of the present invention comprises, by weight, 65-85 parts of acrylic copolymer matrix, 3-8 parts of in-situ surface-modified composite nano weather-resistant filler, 2-7 parts of composite functional additives, and 10-25 parts of organic solvent. The acrylic copolymer matrix serves as the film-forming core, prepared by free radical polymerization of functional comonomers in a specific ratio. The monomer composition is 15-30 parts methyl methacrylate, 8-18 parts isoborneol methacrylate, 10-22 parts isooctyl acrylate, 2-6 parts tridecafluorooctylpropyl methacrylate, 3-7 parts reactive UV-absorbing acrylate monomer, 4-10 parts hydroxyethyl methacrylate, and 0.5-2 parts acrylic acid. Through precise control of the monomer ratio, the resulting acrylic copolymer matrix has a hydroxyl value of 30-60 mgKOH / g, a glass transition temperature of 15-35℃, a weight-average molecular weight of 12000-35000, and a molecular weight distribution index ≤2.3, taking into account the resin's crosslinking activity, film-forming properties, high and low temperature adaptability, and performance uniformity.

[0022] The in-situ surface-modified composite nano-weather-resistant filler is a nano-titanium dioxide and nano-zinc oxide composite modified in-situ with silane coupling agent KH570, with a mass ratio of 3:1 to 5:1. The average particle size of the filler is 20 to 50 nm, and the amount of silane coupling agent KH570 is 2 to 5% of the total mass of the nano-filler. By introducing reactive double bonds on the surface of the filler through in-situ modification, a synergistic effect of full shielding in the ultraviolet band is achieved, and the pain points of easy agglomeration of nano-fillers and weak interfacial bonding with the resin matrix are solved. The composite functional additives, by weight, include 1-3 parts of hindered amine light stabilizer, 0.5-2 parts of thioester antioxidant, and 0.5-2 parts of acrylate leveling agent. The hindered amine light stabilizer is at least one of light stabilizer 944 and light stabilizer 622, and the thioester antioxidant is at least one of antioxidant DLTP and antioxidant DSTP. It exhibits excellent compatibility with the resin matrix and can form a triple synergistic protection system with weather-resistant functional monomers and modified nanofillers. The organic solvent is a mixed solvent composed of xylene, butyl acetate, and propylene glycol methyl ether acetate in a mass ratio of 2:2:1. Matching the dissolution parameters of the acrylic resin, it allows for precise control of the solvent evaporation rate and optimization of film formation.

[0023] The preparation method of the high weather-resistant acrylic resin composition of the present invention is as follows: Preparation of S1 premix: Add all comonomers to the mixing tank according to the weight parts, and stir at 300~500 rpm for 20~30 min to mix evenly to obtain a monomer premix; dissolve the initiator in a portion of the organic solvent, and stir at 200~400 rpm for 10~20 min until completely dissolved to obtain an initiator solution for later use; wherein the initiator is at least one of benzoyl peroxide and azobisisobutyronitrile, and the total amount is 0.8~2.0% of the total weight of the comonomers, and the amount of organic solvent used to dissolve the initiator is 20~30% of the total weight of the organic solvent.

[0024] S2 Preparation of acrylic copolymer matrix: The remaining organic solvent is added to a reactor equipped with a reflux condenser, nitrogen inlet, stirring, and dropping device. High-purity nitrogen is introduced to replace the air in the reactor for at least 30 minutes, ensuring the oxygen content is below 100 ppm. Stirring is started and the temperature is raised to 105-120°C. Under this stirring and temperature-controlled condition, 10-15% of the monomer premix and 15-20% of the initiator solution are added dropwise over 15-30 minutes. After the addition is complete, the reaction is maintained at this temperature for 30-60 minutes to complete seed polymerization. The remaining monomer premix and initiator solution are then added dropwise at a uniform rate over 3-5 hours, with the temperature fluctuation controlled within ±2°C. After the addition is complete, the reaction is maintained at this temperature for 2-4 hours. The temperature is then lowered to 80-90°C, and the remaining initiator solution is added. The reaction is maintained at this temperature for 1-2 hours for maturation, preferably at a constant temperature of 85°C. After the reaction is complete, the mixture is cooled to room temperature by cooling water. A small amount of gel impurities is removed by filtration to obtain the acrylic copolymer matrix solution.

[0025] Preparation of S3 in-situ surface-modified composite nano-weather-resistant filler: Nano-titanium dioxide and nano-zinc oxide are added to a portion of organic solvent according to the specified ratio. First, the mixture is dispersed at high speed at 1500~2000 rpm for 30~60 min to complete the initial dispersion. Then, silane coupling agent KH570 is added, stirring is started and the temperature is raised to 60~80℃. The mixture is kept at this temperature and stirred for 1~3 h to complete the in-situ surface modification and obtain the modified filler dispersion for later use. The amount of organic solvent used to disperse the filler is 10~20% of the total organic solvent weight.

[0026] S4 Composition Blending: The prepared acrylic copolymer matrix solution, modified filler dispersion, and composite functional additives are added to a mixing tank according to the ratio. The mixture is stirred at 800-1200 rpm for 60-90 minutes at room temperature until fully mixed. After mixing, the mixture is filtered through a 200-400 mesh filter cloth to remove undispersed filler aggregates and impurities, finally obtaining a high weather-resistant acrylic resin composition with a solid content of 50-70%.

[0027] Example 1

[0028] The high weather-resistant acrylic resin composition of this embodiment includes, by weight, 75 parts of acrylic copolymer matrix, 5 parts of in-situ surface-modified composite nano weather-resistant filler, 4 parts of composite functional additives, and 16 parts of organic solvent.

[0029] The acrylic copolymer matrix was prepared from the following comonomers in parts by weight: 22 parts methyl methacrylate, 13 parts isoborneol methacrylate, 16 parts isooctyl acrylate, 4 parts tridecafluorooctylpropyl methacrylate, 5 parts reactive UV-absorbing acrylate monomer, 7 parts hydroxyethyl methacrylate, and 1.2 parts acrylic acid. In this embodiment, the reactive UV-absorbing acrylate monomer is 2-hydroxy-4-(3-methacryloyloxy-2-hydroxypropoxy)benzophenone. The final acrylic copolymer matrix had a hydroxyl value of 45 mg KOH / g, a glass transition temperature of 25°C, a weight-average molecular weight of 22,000, and a molecular weight distribution index of 2.1.

[0030] The in-situ surface-modified composite nano-weather-resistant filler is a nano-titanium dioxide and nano-zinc oxide composite modified in-situ with silane coupling agent KH570, with a mass ratio of 4:1. The average particle size of the filler is 30nm, and the amount of silane coupling agent KH570 is 3.5% of the total mass of the nano-filler.

[0031] The composite functional additives, by weight, include 2 parts hindered amine light stabilizer 944, 1 part antioxidant DLTP, and 1 part acrylate leveling agent.

[0032] The organic solvent is a mixed solvent composed of xylene, butyl acetate, and propylene glycol methyl ether acetate in a mass ratio of 2:2:1.

[0033] The specific steps of the preparation method in this embodiment are as follows: Preparation of S1 premix: Add all comonomers to the mixing tank according to the above weight parts, stir at 400 rpm for 25 min to mix evenly, and obtain a monomer premix; dissolve the initiator azobisisobutyronitrile in a portion of the organic solvent, stir at 300 rpm for 15 min until completely dissolved, and obtain an initiator solution for later use; wherein the total amount of initiator is 1.2% of the total weight of the comonomers, and the amount of organic solvent used to dissolve the initiator is 25% of the total weight of the organic solvent.

[0034] Preparation of S2 acrylic copolymer matrix: Add the remaining organic solvent to the reactor, purge the air in the reactor with high-purity nitrogen for 35 min to ensure that the oxygen content in the reactor is below 100 ppm, start stirring and heat to 112℃; under the condition of heat preservation and stirring, first add 12% monomer premix and 18% initiator solution dropwise over 20 min, and then keep the reaction temperature for 45 min to complete the seed polymerization; then add the remaining monomer premix and initiator solution dropwise at a uniform rate over 4 h, and control the reaction temperature fluctuation within ±2℃ during the dropwise addition, and keep the reaction temperature for 3 h after the dropwise addition; then cool to 85℃, add the remaining initiator solution, and keep the temperature for 1.5 h for the ripening reaction; after the reaction is completed, cool to room temperature with cooling water, filter with a 200 mesh filter cloth to remove gel impurities, and obtain acrylic copolymer matrix solution.

[0035] Preparation of S3 in-situ surface modified composite nano-weathering filler: Nano-titanium dioxide and nano-zinc oxide were added to a portion of organic solvent at a mass ratio of 4:1. Initial dispersion was completed by high-speed dispersion at 1800 rpm for 45 min. Then, silane coupling agent KH570 was added, stirring was started and the temperature was raised to 70℃. The modified filler dispersion was maintained at this temperature for 2 h to obtain the modified filler dispersion for later use. The amount of organic solvent used to disperse the filler was 15% of the total organic solvent weight.

[0036] S4 Composition Blending: Add the acrylic copolymer matrix solution, modified filler dispersion, and composite functional additives to a mixing tank according to the specified ratio, and stir at 1000 rpm for 75 minutes at room temperature until fully mixed. After mixing, filter the mixture through a 300-mesh filter cloth to obtain a high weather-resistant acrylic resin composition with a solid content of 60%.

[0037] Example 2

[0038] The high weather-resistant acrylic resin composition of this embodiment includes, by weight, 85 parts of acrylic copolymer matrix, 8 parts of in-situ surface-modified composite nano weather-resistant filler, 7 parts of composite functional additives, and 25 parts of organic solvent.

[0039] The acrylic copolymer matrix is ​​prepared from the following parts by weight of comonomers: 30 parts methyl methacrylate, 18 parts isobornyl methacrylate, 22 parts isooctyl acrylate, 6 parts tridecafluorooctylpropyl methacrylate, 7 parts reactive UV-absorbing acrylate monomer, 10 parts hydroxyethyl methacrylate, and 2 parts acrylic acid. In this embodiment, the reactive UV-absorbing acrylate monomer is 2-(2'-hydroxy-5'-methacryloyloxyphenyl)benzotriazole. The final acrylic copolymer matrix has a hydroxyl value of 60 mg KOH / g, a glass transition temperature of 35°C, a weight-average molecular weight of 35,000, and a molecular weight distribution index of 2.2.

[0040] The in-situ surface-modified composite nano-weather-resistant filler is a nano-titanium dioxide and nano-zinc oxide composite modified in-situ with silane coupling agent KH570, with a mass ratio of 5:1. The average particle size of the filler is 50nm, and the amount of silane coupling agent KH570 is 5% of the total mass of the nano-filler.

[0041] The composite functional additives, by weight, include 3 parts hindered amine light stabilizer 622, 2 parts antioxidant DSTP, and 2 parts acrylate leveling agent.

[0042] The organic solvent is a mixed solvent composed of xylene, butyl acetate, and propylene glycol methyl ether acetate in a mass ratio of 2:2:1.

[0043] The specific steps of the preparation method in this embodiment are as follows: Preparation of S1 premix: Add all comonomers to the mixing tank according to the above weight parts, stir at 500 rpm for 30 min to mix evenly, and obtain monomer premix; dissolve the initiator benzoyl peroxide in a portion of the organic solvent, stir at 400 rpm for 20 min until completely dissolved, and obtain the initiator solution for later use; wherein the total amount of initiator is 2.0% of the total weight of comonomers, and the amount of organic solvent used to dissolve the initiator is 30% of the total weight of organic solvents.

[0044] Preparation of S2 acrylic copolymer matrix: Add the remaining organic solvent to the reactor, purge the air in the reactor with high-purity nitrogen for 40 min to ensure that the oxygen content in the reactor is below 100 ppm, start stirring and heat to 120℃; under the condition of heat preservation and stirring, first add 15% monomer premix and 20% initiator solution dropwise over 30 min, and then keep the reaction at the temperature for 60 min to complete seed polymerization; then add the remaining monomer premix and initiator solution dropwise at a uniform rate over 5 h, and control the reaction temperature fluctuation within ±2℃ during the dropwise addition, and keep the reaction at the temperature for 4 h after the dropwise addition; then cool to 90℃, add the remaining initiator solution, and keep the reaction at the temperature for 2 h for ripening reaction; after the reaction is completed, cool to room temperature with cooling water, filter with a 200 mesh filter cloth to remove gel impurities, and obtain acrylic copolymer matrix solution.

[0045] Preparation of S3 in-situ surface modified composite nano-weathering filler: Nano-titanium dioxide and nano-zinc oxide were added to a portion of organic solvent at a mass ratio of 5:1. Initial dispersion was completed by high-speed dispersion at 2000 rpm for 60 min. Then, silane coupling agent KH570 was added, stirring was started and the temperature was raised to 80℃. The modified filler dispersion was maintained at this temperature for 3 h to obtain the modified filler dispersion for later use. The amount of organic solvent used to disperse the filler was 20% of the total organic solvent weight.

[0046] S4 Composition Blending: Add the acrylic copolymer matrix solution, modified filler dispersion, and composite functional additives to a mixing tank according to the specified ratio. Stir at 1200 rpm for 90 minutes at room temperature until fully mixed. After mixing, filter through a 400-mesh filter cloth to obtain a high weather-resistant acrylic resin composition with a solid content of 70%.

[0047] Example 3

[0048] The high weather-resistant acrylic resin composition of this embodiment includes, by weight, 65 parts of acrylic copolymer matrix, 3 parts of in-situ surface-modified composite nano weather-resistant filler, 2 parts of composite functional additive, and 10 parts of organic solvent.

[0049] The acrylic copolymer matrix is ​​prepared from the following comonomers in parts by weight: 15 parts methyl methacrylate, 8 parts isobornyl methacrylate, 10 parts isooctyl acrylate, 2 parts tridecafluorooctylpropyl methacrylate, 3 parts reactive UV-absorbing acrylate monomer, 4 parts hydroxyethyl methacrylate, and 0.5 parts acrylic acid. In this embodiment, the reactive UV-absorbing acrylate monomer is 2-hydroxy-4-(3-methacryloyloxy-2-hydroxypropoxy)benzophenone. The final acrylic copolymer matrix has a hydroxyl value of 30 mg KOH / g, a glass transition temperature of 15°C, a weight-average molecular weight of 12000, and a molecular weight distribution index of 2.0.

[0050] The in-situ surface-modified composite nano-weather-resistant filler is a nano-titanium dioxide and nano-zinc oxide composite modified in-situ with silane coupling agent KH570, with a mass ratio of 3:1. The average particle size of the filler is 20nm, and the amount of silane coupling agent KH570 is 2% of the total mass of the nano-filler.

[0051] The composite functional additives, by weight, include 1 part of a mixture of hindered amine light stabilizers 944 and 622 in a 1:1 ratio, 0.5 parts of a mixture of antioxidants DLTP and DSTP in a 1:1 ratio, and 0.5 parts of an acrylate leveling agent.

[0052] The organic solvent is a mixed solvent composed of xylene, butyl acetate, and propylene glycol methyl ether acetate in a mass ratio of 2:2:1.

[0053] The specific steps of the preparation method in this embodiment are as follows: Preparation of S1 premix: Add all comonomers to the mixing tank according to the above weight proportions, and stir at 300 rpm for 20 min to mix evenly to obtain a monomer premix; dissolve the initiator, a mixture of azobisisobutyronitrile and benzoyl peroxide in a 1:1 ratio, in a portion of the organic solvent, and stir at 200 rpm for 10 min until completely dissolved to obtain an initiator solution for later use; wherein the total amount of initiator is 0.8% of the total weight of the comonomers, and the amount of organic solvent used to dissolve the initiator is 20% of the total weight of the organic solvent.

[0054] Preparation of S2 acrylic copolymer matrix: Add the remaining organic solvent to the reactor, purge the air in the reactor with high-purity nitrogen for 30 min to ensure that the oxygen content in the reactor is below 100 ppm, start stirring and heat to 105℃; under the condition of heat preservation and stirring, first add 10% monomer premix and 15% initiator solution dropwise over 15 min, and then keep the reaction temperature for 30 min to complete the seed polymerization; then add the remaining monomer premix and initiator solution dropwise at a uniform rate over 3 h, and control the reaction temperature fluctuation within ±2℃ during the dropwise addition, and keep the reaction temperature for 2 h after the dropwise addition; then cool to 80℃, add the remaining initiator solution, and keep the temperature for 1 h for the ripening reaction; after the reaction is completed, cool to room temperature with cooling water, filter with a 200 mesh filter cloth to remove gel impurities, and obtain acrylic copolymer matrix solution.

[0055] Preparation of S3 in-situ surface modified composite nano-weathering filler: Nano-titanium dioxide and nano-zinc oxide were added to a portion of organic solvent at a mass ratio of 3:1. The mixture was first dispersed at high speed at 1500 rpm for 30 min to complete the initial dispersion. Then, silane coupling agent KH570 was added, the mixture was stirred and heated to 60℃, and the mixture was kept at this temperature and stirred for 1 h to obtain the modified filler dispersion for later use. The amount of organic solvent used to disperse the filler was 10% of the total weight of organic solvent.

[0056] S4 Composition Blending: Add the acrylic copolymer matrix solution, modified filler dispersion, and composite functional additives to a mixing tank according to the specified ratio, and stir at 800 rpm for 60 minutes at room temperature until fully mixed. After mixing, filter through a 200-mesh filter cloth to obtain a high weather-resistant acrylic resin composition with a solid content of 50%.

[0057] Example 4

[0058] The high weather-resistant acrylic resin composition of this embodiment includes, by weight, 70 parts of acrylic copolymer matrix, 6 parts of in-situ surface-modified composite nano weather-resistant filler, 5 parts of composite functional additives, and 19 parts of organic solvent.

[0059] The acrylic copolymer matrix is ​​prepared from the following parts by weight of comonomers: 20 parts methyl methacrylate, 12 parts isobornyl methacrylate, 15 parts isooctyl acrylate, 3.5 parts tridecafluorooctylpropyl methacrylate, 4.5 parts reactive UV-absorbing acrylate monomer, 6 parts hydroxyethyl methacrylate, and 1 part acrylic acid. In this embodiment, the reactive UV-absorbing acrylate monomer is 2-(2'-hydroxy-5'-methacryloyloxyphenyl)benzotriazole. The final acrylic copolymer matrix has a hydroxyl value of 38 mgKOH / g, a glass transition temperature of 22°C, a weight-average molecular weight of 20,000, and a molecular weight distribution index of 2.1.

[0060] The in-situ surface-modified composite nano-weather-resistant filler is a nano-titanium dioxide and nano-zinc oxide composite modified in-situ with silane coupling agent KH570, with a mass ratio of 3.5:1. The average particle size of the filler is 35nm, and the amount of silane coupling agent KH570 is 3% of the total mass of the nano-filler.

[0061] The composite functional additives, by weight, include 2.2 parts of hindered amine light stabilizer 622, 1.3 parts of antioxidant DLTP, and 1.5 parts of acrylate leveling agent.

[0062] The organic solvent is a mixed solvent composed of xylene, butyl acetate, and propylene glycol methyl ether acetate in a mass ratio of 2:2:1.

[0063] The specific steps of the preparation method in this embodiment are as follows: Preparation of S1 premix: Add all comonomers to the mixing tank according to the above weight parts, and stir at 350 rpm for 22 min to mix evenly to obtain a monomer premix; dissolve the initiator azobisisobutyronitrile in a portion of the organic solvent, and stir at 250 rpm for 12 min until completely dissolved to obtain an initiator solution for later use; wherein the total amount of initiator is 1.0% of the total weight of the comonomers, and the amount of organic solvent used to dissolve the initiator is 22% of the total weight of the organic solvent.

[0064] Preparation of S2 acrylic copolymer matrix: Add the remaining organic solvent to the reactor, purge the air in the reactor with high-purity nitrogen for 32 min to ensure that the oxygen content in the reactor is below 100 ppm, start stirring and heat to 110℃; under the condition of heat preservation and stirring, first add 11% monomer premix and 16% initiator solution dropwise over 18 min, and then keep the reaction at the temperature for 40 min to complete seed polymerization; then add the remaining monomer premix and initiator solution dropwise at a uniform rate over 3.5 h, and control the reaction temperature fluctuation within ±2℃ during the dropwise addition, and keep the reaction at the temperature for 2.5 h after the dropwise addition; then cool to 82℃, add the remaining initiator solution, and keep the reaction at the temperature for 1.2 h for ripening reaction; after the reaction is completed, cool to room temperature with cooling water, filter with a 200 mesh filter cloth to remove gel impurities, and obtain acrylic copolymer matrix solution.

[0065] Preparation of S3 in-situ surface modified composite nano-weather-resistant filler: Nano-titanium dioxide and nano-zinc oxide were added to a portion of organic solvent at a mass ratio of 3.5:1. Initial dispersion was completed by high-speed dispersion at 1600 rpm for 35 min. Then, silane coupling agent KH570 was added, stirring was started and the temperature was raised to 65℃. The modified filler dispersion was maintained at this temperature for 1.5 h to obtain the modified filler dispersion for later use. The amount of organic solvent used to disperse the filler was 13% of the total organic solvent weight.

[0066] S4 Composition Blending: Add the acrylic copolymer matrix solution, modified filler dispersion, and composite functional additives to a mixing tank according to the specified ratio. Stir at 900 rpm for 70 minutes at room temperature until fully mixed and homogeneous. After mixing, filter through a 300-mesh filter cloth to obtain a high weather-resistant acrylic resin composition with a solid content of 58%.

[0067] Comparative Example 1 The only difference between this comparative example and Example 1 is that, instead of adding reactive UV-absorbing acrylate monomers to the comonomers of the acrylic copolymer matrix, an equal amount of non-reactive UV absorber UV-531 is physically added in step S4 of the composition compounding process. The remaining components, proportions, and preparation methods are completely consistent with those of Example 1.

[0068] Comparative Example 2 The only difference between this comparative example and Example 1 is that the in-situ surface-modified composite nano-weather-resistant filler is not used. Instead, an equal amount of nano-titanium dioxide and nano-zinc oxide composite that has not been modified by silane coupling agent KH570 is added. The mass ratio of the two is the same as in Example 1. All other components, ratios and preparation methods are completely the same as in Example 1.

[0069] Comparative Example 3 The only difference between this comparative example and Example 1 is that tridecafluorooctylpropyl methacrylate is not added to the comonomer of the acrylic copolymer matrix; the other components, proportions, and preparation methods are completely consistent with Example 1.

[0070] Comparative Example 4 This comparative example uses commercially available common acrylic resin, prepared by conventional free radical polymerization. The comonomers are 25 parts methyl methacrylate, 20 parts butyl acrylate, 15 parts styrene, 6 parts hydroxyethyl methacrylate, and 1 part acrylic acid. The initiator is azobisisobutyronitrile (AIBN), used at 1.2% of the total monomer weight. The preparation method is conventional solution polymerization. The final product has a solid content of 60%. No nanofillers or weather-resistant functional monomers are added. Only light stabilizer 944 and UV absorber UV-531 are physically added to the finished product in the same amounts as in Example 1.

[0071] The basic performance comparison between the examples and the comparative examples is shown in the table below: Table 1

[0072] The comparison of the artificially accelerated weathering resistance performance of the examples and comparative examples is shown in the table below: Table 2

[0073] As can be seen from the above two test results, the high weather-resistant acrylic resin composition prepared in the embodiments of the present invention is superior to all comparative examples and commercially available ordinary acrylic resin products in terms of basic physicochemical properties and artificial accelerated weathering resistance. Regarding basic properties, the products in all embodiments of the present invention exhibit excellent storage stability, substrate adhesion, mechanical strength, and media resistance, without problems such as filler agglomeration or additive precipitation. They perfectly achieve a balance between film hardness, flexibility, and impact resistance, and demonstrate outstanding acid and alkali resistance and water resistance. This solves the problems in the comparative examples where mechanical properties decreased due to unmodified fillers and media resistance deteriorated due to the lack of functional monomer modification.

[0074] In the core artificial accelerated weathering test, after 3000 hours of accelerated aging under a xenon arc lamp, the gloss loss rate of each embodiment of the present invention was less than 5%, the yellowing index ΔYI was less than 2.0, and there were no aging phenomena such as powdering, cracking, or blistering throughout the process, demonstrating excellent long-term weathering stability. In contrast, comparative examples show that Comparative Example 1, due to its conventional modification method of physically adding non-reactive UV absorbers, exhibited problems such as additive migration and precipitation, resulting in a rapid decline in weather resistance with prolonged aging time. After 3000 hours of aging, the gloss loss rate and yellowing index increased significantly, and obvious chalking occurred. Comparative Example 2, due to the lack of in-situ surface modification of nanofillers, suffered from severe agglomeration in the resin matrix and weak interfacial bonding between the two phases. This not only significantly reduced the basic mechanical properties but also made the gloss loss, yellowing, and chalking problems more prominent after aging. Comparative Example 3, lacking the introduction of fluorinated functional monomers, showed a significant decline in both weather resistance and media resistance. Comparative Example 4, made of commercially available ordinary acrylic resin, exhibited the worst aging performance, with large-area cracking, chalking, and peeling of the paint film after 3000 hours of aging, completely losing its usability.

[0075] The overall test results fully verify that the present invention, through the chemical bonding of reactive weather-resistant monomers, the compounding of in-situ modified nanofillers, and the synergistic modification of fluorinated functional monomers, constructs a multi-layer weather-resistant protection system that fundamentally solves the industry pain points of traditional acrylic resins, such as easy precipitation of physical additives, easy agglomeration of fillers, and poor long-term weather resistance. It achieves a significant improvement in the comprehensive performance and long-term outdoor service stability of the resin composition, and can fully meet the long-term use requirements of high-end outdoor scenarios.

[0076] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high weather-resistant acrylic resin composition, characterized in that, By weight, it includes the following components: 65-85 parts of acrylic copolymer matrix, 3-8 parts of in-situ surface modified composite nano weather-resistant filler, 2-7 parts of composite functional additives, and 10-25 parts of organic solvent. The acrylic copolymer matrix is ​​prepared by free radical polymerization of the following comonomers in parts by weight: 15-30 parts methyl methacrylate, 8-18 parts isoborneol methacrylate, 10-22 parts isooctyl acrylate, 2-6 parts tridecafluorooctylpropyl methacrylate, 3-7 parts reactive UV-absorbing acrylate monomer, 4-10 parts hydroxyethyl methacrylate, and 0.5-2 parts acrylic acid. The hydroxyl value of the acrylic copolymer matrix is ​​30~60 mgKOH / g, the glass transition temperature is 15~35℃, the weight-average molecular weight is 12000~35000, and the molecular weight distribution index is ≤2.3; The in-situ surface-modified composite nano-weather-resistant filler is a composite of nano-titanium dioxide and nano-zinc oxide modified in-situ by silane coupling agent KH570, with a mass ratio of 3:1 to 5:1 and an average particle size of 20 to 50 nm. The composite functional additives, by weight, include 1-3 parts hindered amine light stabilizer, 0.5-2 parts thioester antioxidant, and 0.5-2 parts acrylate leveling agent.

2. The high weather-resistant acrylic resin composition according to claim 1, characterized in that, The reactive UV-absorbing acrylate monomer is either 2-hydroxy-4-(3-methacryloyloxy-2-hydroxypropoxy)benzophenone or 2-(2'-hydroxy-5'-methacryloyloxyphenyl)benzotriazole.

3. The high weather-resistant acrylic resin composition according to claim 1, characterized in that, In the in-situ surface-modified composite nano-weather-resistant filler, the amount of silane coupling agent KH570 is 2-5% of the total mass of the nano-filler.

4. The high weather-resistant acrylic resin composition according to claim 1, characterized in that, In the comonomer of the acrylic copolymer matrix, the amount of tridecafluorooctylpropyl methacrylate is 3-5 parts, and the amount of reactive ultraviolet-absorbing acrylate monomer is 4-6 parts.

5. The high weather-resistant acrylic resin composition according to claim 1, characterized in that, In the composite functional additive, the hindered amine light stabilizer is at least one of light stabilizer 944 and light stabilizer 622; the thioester antioxidant is at least one of antioxidant DLTP and antioxidant DSTP.

6. The high weather-resistant acrylic resin composition according to claim 1, characterized in that, The organic solvent is a mixed solvent composed of xylene, butyl acetate, and propylene glycol methyl ether acetate in a mass ratio of 2:2:

1.

7. A method for preparing a high weather-resistant acrylic resin composition according to any one of claims 1 to 6, characterized in that, Includes the following steps: Preparation of S1 premix: Mix all comonomers evenly according to the weight parts to obtain monomer premix; dissolve the initiator in a portion of the organic solvent to obtain an initiator solution for later use; Preparation of S2 acrylic copolymer matrix: Add the remaining organic solvent to the reactor, purge with nitrogen for protection, heat to 105~120℃, and under the condition of heat preservation and stirring, first add 10~15% of monomer premix and 15~20% of initiator solution dropwise, and keep the reaction at the temperature for 30~60 min; then add the remaining monomer premix and initiator solution dropwise at a uniform rate, controlling the dropwise addition time to 3~5 h, and keep the reaction at the temperature for 2~4 h after the dropwise addition is completed; then cool to 80~90℃, add the remaining initiator solution, keep the reaction at the temperature for 1~2 h for ripening reaction, and cool to room temperature to obtain acrylic copolymer matrix solution; Preparation of S3 in-situ surface modified composite nano-weather-resistant filler: Nano-titanium dioxide and nano-zinc oxide are dispersed in an organic solvent according to the ratio. After high-speed dispersion for 30-60 min, silane coupling agent KH570 is added, the temperature is raised to 60-80℃, and the mixture is kept warm and stirred for 1-3 h to obtain the modified filler dispersion. S4 composition compounding: Add acrylic copolymer matrix solution, modified filler dispersion and composite functional additives to a stirring tank according to the ratio, stir at 800~1200 rpm for 60~90 min at room temperature, filter after uniform mixing to obtain high weather-resistant acrylic resin composition.

8. The method for preparing the high weather-resistant acrylic resin composition according to claim 7, characterized in that, The initiator in S1 is at least one of benzoyl peroxide and azobisisobutyronitrile, and the total amount of initiator is 0.8 to 2.0% of the total weight of the comonomer.

9. The method for preparing the high weather-resistant acrylic resin composition according to claim 7, characterized in that, In S2, the reaction temperature fluctuation during the monomer and initiator dropwise addition process is controlled within ±2℃, and the constant temperature of the ripening reaction is 85℃.

10. The method for preparing the high weather-resistant acrylic resin composition according to claim 7, characterized in that, In step S4, filtration is performed using a 200-400 mesh filter cloth, and the final high weather-resistant acrylic resin composition has a solid content of 50-70%.

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