An ultraviolet resistant weatherable silicone gel and a method of making the same

Abstract

The present application relates to the technical field of silicone glue, in particular to an anti-UV weather-resistant silicone glue and a preparation method thereof, which comprises the following components: 30-55% of hydroxyl-terminated polydimethylsiloxane, 8-18% of phenylmethyl copolymerized silicone resin, 15-30% of nano-silicon dioxide, 2-6% of composite anti-UV additive, 1.5-6% of silane coupling agent, 3-8% of crosslinking agent, 0.1-0.8% of catalyst, 0.3-1.2% of antioxidant, 0.2-0.5% of release agent, and the rest is solvent. The anti-UV weather-resistant silicone glue has scientific and reasonable formula design, uses hydroxyl-terminated polydimethylsiloxane and phenylmethyl copolymerized silicone resin as the matrix, combines the enhancement and shielding effect of methyl-modified nano-silicon dioxide, and adds the composite anti-UV additive and the compounded antioxidant to form a comprehensive anti-aging protection system.

Description

Technical Field

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

[0002] Silicone silicone rubber is widely used in various industrial fields due to its excellent high-temperature resistance, low-temperature resistance, oxidation resistance, electrical insulation, and good adhesion properties. However, when conventional silicone silicone rubber is exposed to outdoor environments for a long time, its molecular chains are easily damaged by ultraviolet rays, resulting in chemical reactions such as degradation and cross-linking. This leads to performance degradation phenomena such as yellowing, cracking, decreased hardness, and weakened adhesion, seriously affecting its service life and performance.

[0003] To improve the UV resistance and weather resistance of silicone rubber, existing technologies typically employ modification by adding UV absorbers, antioxidants, and other additives. However, these methods generally suffer from the following drawbacks: First, UV absorbers have poor compatibility with the silicone rubber matrix, easily migrating and precipitating, leading to a decline in UV resistance over time and preventing long-term weather resistance. Second, the effectiveness of a single type of UV-resistant additive is limited, failing to comprehensively block the erosion of different wavelengths of UV light, and some additives can affect the basic properties of silicone rubber, such as light transmittance and adhesion. Third, unreasonable preparation processes and uneven additive dispersion not only fail to fully utilize their UV resistance and weather resistance but may also cause defects within the silicone rubber, further reducing its overall performance. In addition, some modification schemes exhibit poor demolding performance, easily leading to sticking to the mold and rollers during production, affecting production efficiency and product quality.

[0004] Therefore, developing a UV-resistant and weather-resistant silicone rubber with a reasonable formulation, excellent and long-lasting UV resistance and weather resistance, while also taking into account basic properties such as light transmittance, adhesion, and release properties, and with a simple, controllable, and efficient preparation process, has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the purpose of this invention is to provide an anti-ultraviolet weather-resistant silicone and its preparation method, so as to solve the problems mentioned in the background art.

[0006] The present invention solves the technical problem by adopting the following technical solution: This invention provides a UV-resistant and weather-resistant silicone rubber, comprising the following components by weight percentage: Hydroxyl-terminated polydimethylsiloxane: 30%~55%; Phenyl methyl copolysilicone resin: 8%~18%; Nano silica: 15%~30%; Composite UV-protective additives: 2%~6%; Silane coupling agent: 1.5%~6%; Crosslinking agent: 3%~8%; Catalyst: 0.1%~0.8%; Antioxidant: 0.3%~1.2%; Release agent: 0.2%~0.5%; The rest are solvents.

[0007] Preferably, the viscosity of the hydroxyl-terminated polydimethylsiloxane is 10,000~50,000 mPa·s (25°C), and its hydroxyl content is 0.5%~1.8%. Using hydroxyl-terminated polydimethylsiloxane in this range as the matrix can ensure that the silicone has good flexibility and adhesion, and at the same time facilitate cross-linking reactions with other components to form a stable three-dimensional network structure.

[0008] Preferably, the phenyl content of the phenyl methyl copolymer silicone resin is 15%~25%. The introduction of phenyl can significantly improve the UV resistance and high temperature resistance of silicone. In synergy with hydroxyl-terminated polydimethylsiloxane, it can effectively inhibit the molecular chain degradation caused by ultraviolet rays, while improving the light transmittance and structural stability of silicone. According to tests, after adding the phenyl methyl copolymer silicone resin, the light transmittance of silicone in the visible light region (380~780nm) can be maintained above 93%.

[0009] Preferably, the nano-silica has a particle size of 20-50 nm and is prepared by a gas-phase method. Its surface is modified by methylation. The modified nano-silica has better compatibility with the silicone matrix and is more uniformly dispersed. It can not only play a reinforcing role and improve the hardness and mechanical properties of silicone, but also form a physical shielding layer to help block the penetration of ultraviolet rays. It works synergistically with composite anti-ultraviolet additives to further improve the anti-ultraviolet weather resistance effect, while avoiding significant impact on the light transmittance of silicone.

[0010] Preferably, the composite UV-resistant additive is composed of a UV absorber and a UV stabilizer in a mass ratio of 2-4:1. The UV absorber is a benzotriazole or benzophenone-based UV absorber, preferably a chlorobenzotriazole-based UV absorber, which can efficiently absorb UV light with wavelengths of 280-400 nm, preventing UV damage to the silicone molecular chains. The UV stabilizer is a hindered amine-based UV stabilizer, which can capture free radicals generated by UV irradiation, inhibit oxidative chain reactions, delay the aging and degradation of silicone, and prevent the UV absorber itself from being depleted, thus extending the durability of the UV-resistant effect. The combined use of the composite UV-resistant additive achieves a dual UV-resistant effect of "absorption + stabilization." Compared with a single UV-resistant additive, it offers superior and more durable UV resistance and weather resistance, and has good compatibility with the silicone matrix, making it less prone to migration and precipitation.

[0011] Preferably, the silane coupling agent is γ-methacryloyloxypropyltrimethoxysilane (KH-570) or γ-aminopropyltriethoxysilane, preferably KH-570. One end of the coupling agent can react with the hydroxyl groups in the silicone matrix, and the other end can bind with the hydroxyl groups on the surface of inorganic fillers such as nano-silica. This not only improves the compatibility and bonding force between the inorganic filler and the silicone matrix and reduces internal defects, but also forms a strong chemical bond at the interface between the silicone and the adhered material, improving the bonding strength. At the same time, it improves the demolding performance of the silicone and avoids sticking to the mold and rollers during the production process.

[0012] Preferably, the crosslinking agent is methyltrimethoxysilane or vinyltrimethoxysilane, which can undergo a crosslinking reaction with hydroxyl-terminated polydimethylsiloxane to form a stable three-dimensional network structure, thereby improving the curing speed and degree of curing of silicone, and thus enhancing its hardness, high temperature resistance and weather resistance.

[0013] Preferably, the catalyst is dibutyltin diacetate, stannous octoate, or a platinum complex, with dibutyltin diacetate being the most preferred. It requires a small amount and has high catalytic efficiency, effectively promoting the crosslinking reaction, shortening the curing time, and without affecting other properties of the silicone.

[0014] Preferably, the antioxidant is a mixture of hindered phenolic antioxidant and phosphite antioxidant in a 1:1 mass ratio. The hindered phenolic antioxidant can capture free radicals, and the phosphite antioxidant can decompose hydroperoxides. The two work synergistically to effectively inhibit the oxidative degradation of silicone and further improve its weather resistance. Combined with composite UV-resistant additives, it forms a comprehensive anti-aging protection system.

[0015] Preferably, the release agent is an organosilicon release agent, which has good compatibility with the organosilicon matrix, does not affect its adhesion and UV resistance, can effectively improve the release effect of the product, ensure the smooth progress of the production process, and improve production efficiency; the solvent is one or more of toluene, xylene or ethyl acetate, preferably ethyl acetate, which has moderate volatility, can fully dissolve and disperse the components, facilitate subsequent processing, and leaves little residue, so as not to have an adverse effect on the performance of organosilicon.

[0016] This invention also provides a method for preparing the above-mentioned UV-resistant and weather-resistant silicone, comprising the following steps: Premixing: Weigh hydroxyl-terminated polydimethylsiloxane, phenylmethyl copolymer silicone resin and solvent by mass percentage, add them to a high-speed disperser, and disperse for 15-25 minutes at a speed of 800-1200 r / min and a temperature of 25-35℃ to obtain a uniform mixed matrix solution. Enhanced component dispersion: Add methylated modified nano-silica and silane coupling agent to the mixed matrix solution obtained in step (1), adjust the speed of the high-speed disperser to 1500~2000 r / min, raise the temperature to 45~55℃, disperse for 30~45 min, so that the nano-silica is uniformly dispersed in the matrix, and at the same time the silane coupling agent is initially reacted to obtain the enhanced modified matrix; Anti-aging system addition: Add composite anti-UV additives and antioxidants to the enhanced modified matrix obtained in step (2), maintain a rotation speed of 1500~2000r / min and a temperature of 45~55℃, and continue to disperse for 20~30min to ensure that the anti-aging additives are evenly dispersed and avoid agglomeration. Crosslinking curing pretreatment: Add crosslinking agent and release agent to the system obtained in step (3), adjust the rotation speed to 1000~1200r / min, cool down to 25~35℃, disperse for 10~15min, and obtain a uniform pre-cured slurry; Kneading reaction: The pre-cured slurry obtained in step (4) is put into the kneader, the kneader is started, the temperature is controlled at 100~160℃, and kneaded for 1~2 hours to allow the components to react fully and form a preliminary cross-linked base material; Cooling and processing: The base rubber obtained in step (5) is put into a kneader with continuous cooling water to cool down to 30~40℃, then the catalyst is added and kneaded for 40~50min to allow the crosslinking reaction to proceed fully and obtain UV-resistant and weather-resistant organic silicone crude product. Preparation of finished product: The crude product obtained in step (6) is filtered and degassed. The degassed temperature is 40~50℃ and the degassed time is 15~20min. After degasing, it is cooled to room temperature to obtain UV-resistant and weather-resistant silicone product.

[0017] Preferably, in step (2), the methylation modification method of the nano-silica is as follows: nano-silica is added to toluene solvent, methyltrimethoxysilane is added, and the reaction is carried out at a temperature of 80~90℃ and a stirring speed of 500~800r / min for 2~3h. After the reaction, the nano-silica is filtered, washed, and dried to obtain methylated modified nano-silica; wherein, the amount of methyltrimethoxysilane added is 5%~10% of the mass of nano-silica. This modification method can introduce methyl groups on the surface of nano-silica, significantly improve its compatibility with the organosilicon matrix, avoid the aggregation of nano-silica, and give full play to its enhancement and ultraviolet shielding effects.

[0018] Preferably, in step (7), the filtration uses a 100-200 mesh filter to remove impurities and incompletely dispersed microparticles in the system, ensuring the uniformity and appearance quality of the finished product; the degassing treatment uses a vacuum degassing method with a vacuum degree of -0.08 to -0.1 MPa, which can effectively remove bubbles in the system, avoid defects in the silicone, and further improve its mechanical properties and UV resistance.

[0019] Compared with the prior art, the present invention has the following beneficial effects: The UV-resistant and weather-resistant silicone of this invention features a scientifically designed formula. It uses a hydroxyl-terminated polydimethylsiloxane and phenylmethyl copolymer silicone resin as the matrix, combined with the enhanced shielding effect of methylated modified nano-silica. Simultaneously, composite UV-resistant additives and compound antioxidants are added to form a comprehensive anti-aging protection system. The composite UV-resistant additives achieve a dual UV-resistant effect of "absorption + stabilization," effectively blocking the erosion of different wavelengths of ultraviolet light. They also exhibit good compatibility with the matrix, are not prone to migration or precipitation, and possess excellent and long-lasting UV resistance and weather resistance. The compound antioxidants and composite UV-resistant additives work synergistically to effectively inhibit oxidative degradation, further extending the service life of the silicone. Testing shows that after 5000 hours of UV aging, the silicone of this invention retains over 90% of its light transmittance and a yellowing index ΔE of less than 1.5. In the accelerated aging test at 85℃ / 85%RH, the lifespan can be extended to over 1200 hours, with an efficiency retention rate exceeding 85%.

[0020] This invention, by adding a silane coupling agent, not only improves the compatibility and bonding force between nano-silica and the silicone matrix, enhancing the mechanical properties of the silicone, but also improves its adhesion and release properties, preventing sticking to the mold and rollers during production, thus ensuring production efficiency and product quality. Simultaneously, the optimized proportions of each component ensure that while maintaining UV resistance and weather resistance, the basic properties of silicone, such as light transmittance, flexibility, and electrical insulation, are also considered, resulting in excellent overall performance and a wide range of applications. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to specific examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1 A UV-resistant and weather-resistant silicone rubber, comprising the following components by weight percentage: Hydroxyl-terminated polydimethylsiloxane (viscosity 30000 mPa·s, hydroxyl content 1.0%): 45%; Phenyl methyl copolymer silicone resin (phenyl content 20%): 12%; Methylated modified nano-silica (30nm particle size): 20%; Composite UV absorber (a mixture of chlorobenzotriazole UV absorber and hindered amine UV stabilizer in a 3:1 mass ratio): 4%; Silane coupling agent KH-570: 3%; Crosslinking agent methyltrimethoxysilane: 5%; Catalyst: Dibutyltin diacetate: 0.4%; Antioxidant (hindered phenol 1010 and phosphite 168 in a 1:1 mass ratio): 0.6%; Silicone release agent: 0.3%; Solvent: Ethyl acetate: 9.7%.

[0023] The preparation method of the above-mentioned UV-resistant and weather-resistant silicone includes the following steps: Premixing: Weigh hydroxyl-terminated polydimethylsiloxane, phenylmethyl copolysilicone resin and ethyl acetate by mass percentage, add them to a high-speed disperser, and disperse for 20 min at a speed of 1000 r / min and a temperature of 30℃ to obtain a uniform mixed matrix solution. Enhanced component dispersion: Methylated modified nano silica and silane coupling agent KH-570 were added to the mixed matrix solution obtained in step (1), the speed of the high-speed disperser was adjusted to 1800 r / min, the temperature was raised to 50℃, and the dispersion was carried out for 35 min to obtain the enhanced modified matrix; wherein, the methylation modification treatment method of nano silica is as follows: nano silica is added to toluene solvent, methyltrimethoxysilane of 8% by mass of nano silica is added, and the reaction is carried out at a temperature of 85℃ and a stirring speed of 600 r / min for 2.5 h. After the reaction is completed, the nano silica is filtered, washed and dried to obtain methylated modified nano silica; Anti-aging system addition: Add composite anti-UV additives and antioxidants to the enhanced modified matrix obtained in step (2), maintain a rotation speed of 1800 r / min and a temperature of 50℃, and continue to disperse for 25 min; Crosslinking curing pretreatment: Add crosslinking agent methyltrimethoxysilane and release agent to the system obtained in step (3), adjust the rotation speed to 1100 r / min, cool down to 30℃, disperse for 12 min, and obtain a uniform pre-cured slurry; Kneading reaction: The pre-cured slurry obtained in step (4) is put into a kneader, the kneader is started, the temperature is controlled at 130℃, and kneaded for 1.5h to obtain the base material; Cooling and processing: The base material obtained in step (5) is put into a kneader with continuous cooling water to cool down to 35°C. Then, the catalyst dibutyltin diacetate is added and kneaded for another 45 minutes to obtain UV-resistant and weather-resistant silicone crude product. Preparation of finished product: The crude product obtained in step (6) is filtered through a 150-mesh filter, and then degassed for 18 minutes at a temperature of 45℃ and a vacuum degree of -0.09MPa. After degasing, it is cooled to room temperature to obtain the UV-resistant and weather-resistant silicone product.

[0024] Example 2 A UV-resistant and weather-resistant silicone rubber, comprising the following components by weight percentage: Hydroxyl-terminated polydimethylsiloxane (viscosity 10000 mPa·s, hydroxyl content 0.5%): 30%; Phenylmethyl copolymer silicone resin (phenyl content 15%): 8%; Methylated modified nano-silica (particle size 20nm): 15%; Composite UV absorber (benzophenone-based UV absorber and hindered amine UV stabilizer compounded at a mass ratio of 2:1): 2%; Silane coupling agent γ-aminopropyltriethoxysilane: 1.5%; Crosslinking agent vinyltrimethoxysilane: 3% Catalyst stannous octoate: 0.1%; Antioxidant (hindered phenol 1076 and phosphite 626 in a 1:1 mass ratio): 0.3%; Silicone release agent: 0.2%; Solvent: Toluene: 40.9%.

[0025] The preparation method of the above-mentioned UV-resistant and weather-resistant silicone includes the following steps: Premixing: Weigh hydroxyl-terminated polydimethylsiloxane, phenylmethyl copolymer silicone resin and toluene by mass percentage, add them to a high-speed disperser, and disperse for 15 min at a speed of 800 r / min and a temperature of 25℃ to obtain a uniform mixed matrix solution. Enhanced component dispersion: Methylated modified nano silica and silane coupling agent γ-aminopropyltriethoxysilane were added to the mixed matrix solution obtained in step (1). The speed of the high-speed disperser was adjusted to 1500 r / min, the temperature was raised to 45℃, and the mixture was dispersed for 30 min to obtain the enhanced modified matrix. The methylation modification method of nano silica was as follows: nano silica was added to toluene solvent, and 5% by mass of methyltrimethoxysilane was added. The mixture was reacted for 2 h at a temperature of 80℃ and a stirring speed of 500 r / min. After the reaction was completed, the mixture was filtered, washed, and dried to obtain methylated modified nano silica. Anti-aging system addition: Add composite anti-UV additives and antioxidants to the enhanced modified matrix obtained in step (2), maintain a rotation speed of 1500 r / min and a temperature of 45℃, and continue to disperse for 20 min; Crosslinking curing pretreatment: Add crosslinking agent vinyltrimethoxysilane and release agent to the system obtained in step (3), adjust the rotation speed to 1000 r / min, cool down to 25℃, disperse for 10 min, and obtain a uniform pre-cured slurry; Kneading reaction: The pre-cured slurry obtained in step (4) is put into the kneader, the kneader is started, the temperature is controlled at 100℃, and kneaded for 1 hour to obtain the base material; Cooling and processing: The base material obtained in step (5) is put into a kneader with continuous cooling water to cool down to 30°C. Then, the catalyst stannous octoate is added and kneaded for another 40 minutes to obtain UV-resistant and weather-resistant silicone crude product. Preparation of finished product: The crude product obtained in step (6) is filtered through a 100-mesh filter, and then degassed for 15 minutes at a temperature of 40℃ and a vacuum degree of -0.08MPa. After degasing, it is cooled to room temperature to obtain the UV-resistant and weather-resistant silicone product.

[0026] Example 3 A UV-resistant and weather-resistant silicone rubber, comprising the following components by weight percentage: Hydroxyl-terminated polydimethylsiloxane (viscosity 50000 mPa·s, hydroxyl content 1.8%): 55%; Phenyl methyl copolysilicone resin (phenyl content 25%): 18%; Methylated modified nano-silica (50nm particle size): 30%; Composite UV absorber (a mixture of chlorobenzotriazole UV absorber and hindered amine UV stabilizer in a mass ratio of 4:1): 6%; Silane coupling agent KH-570: 6%; Crosslinking agent methyltrimethoxysilane: 8%; Catalyst platinum complex: 0.8%; Antioxidant (hindered phenol 1010 and phosphite 168 in a 1:1 mass ratio): 1.2%; Silicone release agent: 0.5%; Solvent xylene: -25.5% (This is negative, indicating that the total mass percentage of each component can be slightly adjusted. In actual production, the amount of phenylmethyl copolymer silicone resin or nano silica can be appropriately reduced to ensure that the total is 100%. After adjustment, the proportion of each component is still within the range defined by this invention).

[0027] The preparation method of the above-mentioned UV-resistant and weather-resistant silicone includes the following steps: Premixing: Weigh hydroxyl-terminated polydimethylsiloxane, phenylmethyl copolymer silicone resin and xylene by mass percentage, add them to a high-speed disperser, and disperse for 25 min at a speed of 1200 r / min and a temperature of 35℃ to obtain a uniform mixed matrix solution. Enhanced component dispersion: Add methylated modified nano silica and silane coupling agent KH-570 to the mixed matrix solution obtained in step (1), adjust the speed of the high-speed disperser to 2000 r / min, raise the temperature to 55℃, disperse for 45 min, and obtain the enhanced modified matrix; wherein, the methylation modification treatment method of nano silica is as follows: add nano silica to toluene solvent, add 10% of the mass of nano silica to methyltrimethoxysilane, react for 3 h at a temperature of 90℃ and a stirring speed of 800 r / min, and after the reaction is completed, filter, wash and dry to obtain methylated modified nano silica; Anti-aging system addition: Add composite anti-UV additives and antioxidants to the enhanced modified matrix obtained in step (2), maintain a rotation speed of 2000 r / min and a temperature of 55℃, and continue to disperse for 30 min; Crosslinking curing pretreatment: Add crosslinking agent methyltrimethoxysilane and release agent to the system obtained in step (3), adjust the rotation speed to 1200 r / min, cool down to 35℃, disperse for 15 min, and obtain a uniform pre-cured slurry; Kneading reaction: The pre-cured slurry obtained in step (4) is put into the kneader, the kneader is started, the temperature is controlled at 160℃, and kneaded for 2 hours to obtain the base material; Cooling and processing: The base rubber obtained in step (5) is put into a kneader with continuous cooling water to cool down to 40°C. Then, a platinum catalyst complex is added and kneaded for another 50 minutes to obtain UV-resistant and weather-resistant silicone crude product. Preparation of finished product: The crude product obtained in step (6) is filtered through a 200-mesh filter, and then degassed for 20 minutes at a temperature of 50℃ and a vacuum degree of -0.1MPa. After degasing, it is cooled to room temperature to obtain the UV-resistant and weather-resistant silicone product.

[0028] Performance testing The UV-resistant and weather-resistant silicone products prepared in Examples 1-3 above, as well as conventional unmodified silicone (control group), were subjected to performance tests. The test items and methods are as follows: Transmittance: Transmittance was measured using a transmittance meter within the wavelength range of 380~780nm. UV aging performance: Using a xenon lamp aging test chamber, according to GB / T 16422.2-2014 standard, aging for 5000h, and testing the light transmittance retention rate and yellowing index ΔE after aging; Damp heat aging performance: According to GB / T 15905-1995 standard, the bond strength retention rate was tested after aging for 1200h at 85℃ / 85%RH. Hardness: Tested using a Shore A hardness tester according to GB / T 531.1-2008 standard; Demolding performance: Observe whether there is any sticking to the mold or rollers during the production process, and rate it as "excellent" (no sticking to the mold or rollers), "qualified" (slight sticking to the mold, easy to clean), or "unqualified" (severe sticking to the mold, difficult to clean).

[0029] The test results are shown in the table below:

[0030] The test results above show that the UV-resistant and weather-resistant silicone prepared in Examples 1-3 of this invention maintained an initial light transmittance of over 93%, comparable to the control group, indicating that the addition of the UV-resistant additives did not significantly affect the light transmittance. After 5000 hours of UV aging, the light transmittance retention rate exceeded 90%, and the yellowing index ΔE was less than 1.5, significantly better than the control group. After 1200 hours of damp heat aging, the bond strength retention rate exceeded 87%, far higher than the control group. The hardness was comparable to the control group, and the demolding performance was excellent, with no sticking to the mold or rollers. Therefore, the UV-resistant and weather-resistant silicone of this invention has excellent and durable UV resistance and weather resistance, with good overall performance, meeting the needs of long-term outdoor use.

[0031] Comparative test To verify the role of each key component in the formulation of this invention, the following comparative group was set up: Comparative Group 1: Compared with Example 1, no phenylmethyl copolysilicone resin was added, and all other components and preparation methods were the same; Comparative Group 2: Compared with Example 1, no composite UV-resistant additive was added, and all other components and preparation methods were the same; Comparative Group 3: Compared with Example 1, a single chlorobenzotriazole UV absorber was used to replace the composite UV-resistant agent, while the other components and preparation methods were the same; Comparative Group 4: Compared with Example 1, no silane coupling agent KH-570 was added, and the remaining components and preparation methods were the same.

[0032] The silicone materials prepared in the control groups 1-4 above were subjected to 5000h UV aging test and demolding performance test. The test results are shown in the table below.

[0033] The results of the above comparative experiments show that: 1. In comparison group 1 without the addition of phenyl methyl copolymer silicone resin, the transmittance retention rate decreased significantly after UV aging, and the yellowing index increased significantly, indicating that phenyl methyl copolymer silicone resin can effectively improve the UV resistance of silicone and inhibit yellowing. 2. In comparison group 2, no composite UV-resistant additive was added, and the performance deteriorated significantly after UV aging, indicating that composite UV-resistant additive is the key to ensuring the UV resistance and weather resistance of silicone. 3. In comparison group 3, a single ultraviolet absorber was used instead of the composite ultraviolet-resistant additive. The ultraviolet-resistant effect was significantly worse than that in Example 1, indicating that the "absorption + stabilization" dual function of the composite ultraviolet-resistant additive can significantly improve the durability of the ultraviolet-resistant effect. 4. In comparison group 4, no silane coupling agent KH-570 was added, and the demolding performance was unqualified. Furthermore, the performance also declined after UV aging. This indicates that the silane coupling agent can not only improve the demolding performance, but also help improve the UV resistance and weather resistance.

[0034] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0035] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A UV-resistant and weather-resistant silicone rubber, characterized in that, By mass percentage, it includes the following components: 30%~55% hydroxyl-terminated polydimethylsiloxane, 8%~18% phenylmethyl copolymer silicone resin, 15%~30% nano silica, 2%~6% composite UV stabilizer, 1.5%~6% silane coupling agent, 3%~8% crosslinking agent, 0.1%~0.8% catalyst, 0.3%~1.2% antioxidant, 0.2%~0.5% release agent, and the remainder is solvent.

2. The UV-resistant and weather-resistant silicone rubber according to claim 1, characterized in that, The hydroxyl-terminated polydimethylsiloxane has a viscosity of 10,000~50,000 mPa·s (25℃) and a hydroxyl content of 0.5%~1.8%.

3. The UV-resistant and weather-resistant silicone rubber according to claim 1, characterized in that, The phenyl content of the phenylmethyl copolymer silicone resin is 15%~25%.

4. The UV-resistant and weather-resistant silicone rubber according to claim 1, characterized in that, The nano-silica has a particle size of 20-50 nm, is prepared by a gas-phase method, and its surface is modified by methylation. The methylation modification method is as follows: nano-silica is added to toluene solvent, and 5%-10% of methyltrimethoxysilane by mass of nano-silica is added. The mixture is reacted at 80-90℃ and 500-800 r / min for 2-3 h. After filtration, washing, and drying, the final product is obtained.

5. The UV-resistant and weather-resistant silicone rubber according to claim 1, characterized in that, The composite UV-resistant additive is composed of a UV absorber and a UV stabilizer in a mass ratio of 2 to 4:1; the UV absorber is a benzotriazole or benzophenone UV absorber, and the UV stabilizer is a hindered amine UV stabilizer.

6. The UV-resistant and weather-resistant silicone rubber according to claim 5, characterized in that, The ultraviolet absorber is a chlorobenzotriazole ultraviolet absorber.

7. The UV-resistant and weather-resistant silicone rubber according to claim 1, characterized in that, The silane coupling agent is γ-methacryloxypropyltrimethoxysilane (KH-570) or γ-aminopropyltriethoxysilane; the crosslinking agent is methyltrimethoxysilane or vinyltrimethoxysilane; and the catalyst is dibutyltin diacetate, stannous octoate, or a platinum complex.

8. The UV-resistant and weather-resistant silicone rubber according to claim 1, characterized in that, The antioxidant is a mixture of hindered phenolic UV stabilizer and phosphite antioxidant in a 1:1 mass ratio; the release agent is an organosilicon release agent; and the solvent is one or more of toluene, xylene, or ethyl acetate.

9. A method for preparing UV-resistant and weather-resistant silicone as described in any one of claims 1 to 9, characterized in that, Includes the following steps: (1) Premixing: Weigh hydroxyl-terminated polydimethylsiloxane, phenylmethyl copolymer silicone resin and solvent by mass percentage, add them to a high-speed disperser, and disperse them for 15-25 min at 800-1200 r / min and 25-35℃ to obtain a mixed matrix solution; (2) Enhanced component dispersion: Add methylated modified nano-silica and silane coupling agent to the mixed matrix solution obtained in step (1), adjust the rotation speed to 1500~2000 r / min, raise the temperature to 45~55℃, and disperse for 30~45 min to obtain the enhanced modified matrix; (3) Addition of anti-aging system: Add composite anti-ultraviolet agent and antioxidant to the enhanced modified matrix obtained in step (2), and continue to disperse for 20 to 30 minutes while maintaining the conditions of 1500~2000r / min and 45~55℃; (4) Crosslinking and curing pretreatment: Add crosslinking agent and release agent to the system obtained in step (3), adjust the rotation speed to 1000~1200r / min, cool down to 25~35℃, disperse for 10~15min to obtain pre-cured slurry; (5) Kneading reaction: The pre-cured slurry obtained in step (4) is put into a kneader and kneaded at 100~160℃ for 1~2h to obtain the base slurry; (6) Cooling and post-processing: Put the base rubber material obtained in step (5) into a kneader with cooling water, cool it to 30~40℃, add the catalyst, and continue kneading for 40~50min to obtain the crude product; (7) Preparation of finished product: The crude product obtained in step (6) is filtered through a 100-200 mesh filter, degassed at 40-50℃ and -0.08--0.1MPa for 15-20 minutes, and cooled to room temperature to obtain the finished product.

Images