High-weather-resistance anti-aging silicone rubber, preparation method and application thereof

Abstract

The application provides a high-weather-resistance anti-aging silicone rubber as well as a preparation method and application thereof. The high-weather-resistance anti-aging silicone rubber comprises the following raw materials in parts by mass: 100 parts of methyl vinyl silicone rubber, 30-60 parts of white carbon black, 6-8 parts of alkyl silane coupling agent, 0.5-2 parts of hindered amine silane coupling agent, 0.5-2 parts of vinyl silane coupling agent, 3-5 parts of vinyl MQ silicone resin, 1-1.5 parts of vinyl hydroxyl silicone oil and 1-3 parts of organic peroxide. The hindered amine silane coupling agent is obtained by the reaction of a hindered amine with an isocyanate silane coupling agent. Through the above formula design, the long-term weather resistance and mechanical property retention rate of the material under ultraviolet irradiation and hygrothermal conditions can be significantly improved while the excellent toughness of the silicone rubber is maintained.

Description

Technical Field

[0001] This application relates to the field of organosilicon technology, specifically to a highly weather-resistant and anti-aging silicone rubber, its preparation method, and its application. Background Technology

[0002] Silicone rubber is a type of polymeric elastomer primarily composed of polysiloxanes. It possesses excellent resistance to high and low temperatures, superior electrical insulation, and chemical stability, making it widely used in automotive, construction, power, and aerospace industries. In practical applications, silicone rubber often requires the addition of inorganic fillers such as silica to achieve the desired mechanical strength and reinforcing effect; this is a key component of silicone rubber formulations.

[0003] However, extensive research and practical applications have shown that the aging of silicone rubber under long-term ultraviolet irradiation, thermo-oxidative effects, and humid heat conditions does not first occur in the polysiloxane matrix, but rather concentrates in the interface region between the filler and the matrix. The surface of inorganic fillers such as silica contains a large number of polar silanol groups, which have insufficient interfacial bonding force with the non-polar silicone rubber backbone. When subjected to external environmental effects, this interface is more likely to become an active site for free radical reactions, leading to the gradual destruction of interfacial bonds, which in turn causes filler debonding, surface pulverization, and crack formation, resulting in a significant decrease in the mechanical properties and weather resistance of the material.

[0004] To improve interfacial stability and enhance the weather resistance of silicone rubber, existing technologies mainly rely on adding silane coupling agents, light stabilizers, or resin-based additives. Silane coupling agents can alleviate the polarity difference between the filler and the matrix to some extent, but they are still prone to hydrolysis or breakage under long-term service conditions, making it difficult to maintain interfacial stability. Small-molecule light stabilizers, such as hindered amines or UV absorbers, can capture free radicals and delay the aging process, but since they exist only in a physical blending manner, they are prone to migration or volatilization, leading to a decline in anti-aging effects over time. In addition, components such as adding MQ resin and vinyl silicone oil are often used to improve filler dispersion and adjust the reinforcing structure, but these methods have limited inhibitory effects on free radicals at the interface and cannot fundamentally solve the problem of interfacial aging.

[0005] Therefore, how to significantly improve the high weather resistance and anti-aging properties of silicone rubber while maintaining its inherent advantages remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] This application provides a high weather-resistant and anti-aging silicone rubber, its preparation method and application. By improving the bonding mode of the filler-matrix interface and introducing a stable free radical inhibition effect in the interface region, the interface compatibility and anti-aging function are synergistically improved, thereby significantly improving the high weather-resistant and anti-aging performance of silicone rubber in complex environments.

[0007] In a first aspect, this application provides a highly weather-resistant and anti-aging silicone rubber, comprising the following raw materials in parts by weight: 100 parts methyl vinyl silicone rubber, 30-60 parts silica, 6-8 parts alkyl silane coupling agent, 0.5-2 parts hindered amine silane coupling agent, 0.5-2 parts vinyl silane coupling agent, 3-5 parts vinyl MQ silicone resin, 1-1.5 parts vinyl hydroxyl silicone oil, and 1-3 parts organic peroxide; wherein the hindered amine silane coupling agent is obtained by reacting a hindered amine with an isocyanate silane coupling agent.

[0008] According to this application, the above-mentioned formulation design can significantly improve the long-term weather resistance and mechanical property retention rate of the material under ultraviolet irradiation and humid heat conditions while maintaining the excellent toughness of silicone rubber.

[0009] Specifically, methyl vinyl silicone rubber serves as the matrix, providing excellent toughness and resistance to high and low temperatures. Silica, as the main reinforcing filler, significantly improves the tensile strength and modulus of the material; however, its surface hydroxyl groups have poor compatibility with non-polar silicone rubber segments, easily becoming aging-sensitive points. This application introduces alkylsilane coupling agents, vinylsilane coupling agents, and hindered amine silane coupling agents. The alkylsilane coupling agent forms a hydrophobic layer on the filler surface, reducing interfacial polarity differences and stabilizing filler dispersion. The vinylsilane coupling agent introduces reactive vinyl groups on the filler surface, allowing them to co-crosslink with matrix segments during peroxide vulcanization, forming stronger interfacial chemical bonds. The hindered amine molecules interact with isocyanate groups through their side chain amino or hydroxyl groups. The hindered amine undergoes a group reaction to generate stable urea bonds or urethane bonds, allowing the hindered amine to be firmly grafted onto the silane coupling agent molecule, resulting in a hindered amine silane coupling agent. The silane portion of the hindered amine silane coupling agent is anchored to the surface of silica, while the amine nitrogen on the piperidine ring of the hindered amine portion can capture free radicals generated by ultraviolet light or thermo-oxidative action in the interfacial region, blocking the degradation chain reaction. This design ensures that the light stabilizer remains fixed at the interfacial position for a long time and is not easily migrated or lost. The synergistic effect of the three types of coupling agents gives the filler-matrix interface both flexible buffering and chemical cross-linking stability, as well as anti-aging function, thereby effectively delaying interfacial aging.

[0010] Vinyl MQ silicone resin, as a resinous filler component, can co-crosslink with the matrix and vinyl silane coupling agent during peroxide vulcanization to form a uniformly distributed microphase network. This micronetwork reinforces the rubber matrix and provides spatial confinement for filler dispersion, resulting in more stable interfacial bonding. Vinyl hydroxy silicone oil acts as a structure control agent during compounding, regulating the interaction between silica and the matrix and preventing excessive agglomeration. It also participates in network construction as an active segment during vulcanization, further improving crosslinking uniformity. Organic peroxides, as vulcanizing agents, initiate vinyl free radical reactions during vulcanization, enabling the methyl vinyl silicone rubber backbone, vinyl silane coupling agent, and vinyl MQ silicone resin to synergistically crosslink, constructing a dense and stable three-dimensional network. Because hindered amines inhibit the accumulation of aging free radicals in the interfacial region, this network maintains high stability even under long-term aging conditions.

[0011] Through the reasonable combination of the above components, not only is a balance between matrix strength and toughness achieved, but also compatibility and free radical inhibition are taken into account at the interface level. Furthermore, combined with the micro-network reinforcement and structural control effects, the silicone rubber provided in this application can still maintain excellent weather resistance and mechanical properties under long-term complex environments.

[0012] In some embodiments, the hindered amine includes at least one of 4-amino-2,2,6,6-tetramethylpiperidine, 1-hydroxy-2,2,6,6-tetramethylpiperidine, and 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidine.

[0013] In some of the above embodiments, in 4-amino-2,2,6,6-tetramethylpiperidine, since the primary amine has higher reactivity than the secondary amine on the piperidine ring, and there is a steric effect, the hindered amine molecule can effectively avoid the secondary amine nitrogen on the piperidine ring from participating in the reaction, thereby maintaining its free radical scavenging activity; the piperidine ring of 1-hydroxy-2,2,6,6-tetramethylpiperidine and 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidine alcohol has a tertiary amine nitrogen, which has no reactivity with isocyanate, so it can also maintain free radical scavenging activity. At the same time, its side chain hydroxyl group reacts with isocyanate to form a carbamate bond, thereby achieving molecular immobilization.

[0014] Compared with directly blended hindered amine additives, this coupling fixation method ensures that the hindered amine is anchored on the filler surface for a long time, making it less prone to migration or failure. It can continuously capture free radicals generated during aging in the interfacial region, providing long-lasting UV and heat-oxidation resistance. At the same time, the silane structure of the coupling agent can also condense with the silanol groups on the surface of silica, further enhancing the bonding stability of the filler-matrix interface. Thus, the interfacial bonding strength and weather resistance of silicone rubber are improved simultaneously.

[0015] In some embodiments, the hindered amine silane coupling agent is prepared by dispersing a hindered amine and an isocyanate silane coupling agent in toluene and reacting them at 25-35°C for 1-3 hours to obtain the hindered amine silane coupling agent.

[0016] The hindered amine includes at least one of 1-hydroxy-2,2,6,6-tetramethylpiperidine and 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidineol.

[0017] In some of the above embodiments, the inventors found that using 1-hydroxy-2,2,6,6-tetramethylpiperidine and / or 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol as a hindered amine silane coupling agent obtained by reacting a hindered amine with an isocyanate silane coupling agent can further improve the weather resistance of silicone rubber compared to using 4-amino-2,2,6,6-tetramethylpiperidine; the reason may be that using 1-hydroxy-2,2,6,6-tetramethylpiperidine and / or 1-( When 2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol is used as a hindered amine molecule, the urethane bond formed by the reaction of the side chain hydroxyl group with isocyanate is superior in terms of chemical stability and hydrolysis resistance compared to the urea bond formed by the primary amine and isocyanate, and is less prone to breakage in humid or aging environments. At the same time, the hydrogen bond density of the urethane structure is lower than that of the urea structure, which avoids excessive rigidity of the interface layer, so that the interface has both strong chemical bonding and a certain degree of toughness, thus helping to further improve the weather resistance of silicone rubber.

[0018] In some embodiments, the isocyanate silane coupling agent comprises propyltriethoxysilane isocyanate.

[0019] In some embodiments, the hindered amine includes 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol, and the molar ratio of 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol to isocyanate silane coupling agent is 1:1 to 1.02, and the solid content of the reaction system is 40wt% to 50wt%.

[0020] In some of the above embodiments, when 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol is used as the hindered amine and its molar ratio with isocyanate is controlled within the above range, the resulting silicone rubber exhibits better weather resistance. This may be because the 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol molecule contains a hydroxyethyl group attached to the nitrogen atom of the piperidine ring and a hydroxyl group located at the 4-carbon position. The former is a primary alcohol, exhibiting significantly higher reactivity than the secondary alcohol at the 4-carbon position. Under the above reaction conditions, the primary alcohol on the hydroxyethyl group preferentially reacts with the isocyanate. Ester-silane coupling agents are reacted to obtain hindered amine silane coupling agents with predominantly single-end silanization. These single-end silanization-based hindered amine silane coupling agents retain the secondary alcohol at the 4-position while providing additional polar sites during subsequent grafting. This facilitates hydrogen bonding or further condensation with other active groups in the system, enhancing the anchoring strength of the hindered amine filler surface and enabling the hindered amine to exert a long-lasting anti-aging effect at the interface. Simultaneously, reducing the risk of intermolecular self-crosslinking and polycondensation due to simultaneous double-end silanization results in a more uniform and stable coupling layer structure, thereby further improving the weather resistance of silicone rubber.

[0021] In some embodiments, the raw materials further include: 0.5 to 2 parts of epoxy silane coupling agent.

[0022] In some of the above embodiments, the inventors discovered that adding a certain amount of epoxy silane coupling agent to the raw materials can further improve the weather resistance of silicone rubber. The reason may be that during the mixing stage, the alkoxy groups on the epoxy silane coupling agent preferentially undergo condensation reactions, thus firmly grafting onto the surface of silica. In subsequent vulcanization and post-curing processes, the hydroxyl components in the system can undergo ring-opening reactions with the epoxy groups, thereby introducing additional chemical crosslinking points at the filler-matrix interface, significantly improving the density, stability, and mechanical strength of the interfacial bonding. In particular, when using 1-(2'- When hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol is used as a hindered amine to obtain a hindered amine coupling agent, the epoxy group can bond with the hydroxyl sites retained on the hindered amine molecule, further anchoring the hindered amine molecule at the filler interface, thereby better exerting its anti-aging properties. At the same time, the unreacted epoxy group can also act as a sacrificial group under ultraviolet or thermo-oxidative environments, preferentially reacting with free radicals, inhibiting the diffusion and accumulation of free radicals in the interface layer, and further delaying the aging of the matrix. Therefore, further addition of epoxy silane coupling agents can improve the bonding stability of the interface and the overall weather resistance of silicone rubber.

[0023] In some embodiments, the alkylsilane coupling agent includes at least one of dimethyldimethoxysilane and methyltrimethoxysilane; the vinylsilane coupling agent includes at least one of vinyltrimethoxysilane and vinyltriethoxysilane; and the epoxysilane coupling agent includes γ-glycidoxypropyltrimethoxysilane.

[0024] In some of the above embodiments, dimethyldimethoxysilane and methyltrimethoxysilane can effectively cap surface hydroxyl groups, reduce filler agglomeration, and improve the dispersion uniformity of the system; vinyltrimethoxysilane and vinyltriethoxysilane provide vinyl reaction sites at the interface while anchoring the filler, which is beneficial for synergistic crosslinking with the matrix or MQ silicone resin; γ-glycidoxypropyltrimethoxysilane can further introduce secondary crosslinking sites and sacrificial groups on the filler surface; the combination of these preferred coupling agents not only improves the dispersibility and interfacial bonding strength of the filler, but also further enhances the weather resistance of silicone rubber through the stratified synergy of multiple types of functional groups.

[0025] In some embodiments, the methyl vinyl silicone rubber has a weight-average molecular weight of 400,000 to 600,000 and a vinyl content of 0.05 wt% to 0.5 wt%. Based on the above embodiments, the higher molecular weight ensures good mechanical strength of the silicone rubber, while the moderate vinyl content enables the formation of an appropriate number of crosslinking points during peroxide vulcanization.

[0026] In some embodiments, the average particle size of the silica is 10-30 nm. Based on the above embodiments, silica with a particle size in this range has a large specific surface area and a high surface hydroxyl density, which is conducive to the full reaction of the coupling agent and the formation of an interfacial layer, thereby improving the bonding strength between the filler and the matrix and its aging resistance.

[0027] In some embodiments, the vinyl MQ silicone resin has a viscosity of 5000~15000 at 25°C, an M / Q ratio of 0.7~0.9, and a vinyl content of 0.5~2wt%. Based on the above embodiments, the vinyl MQ silicone resin has a moderate molecular weight and suitable viscosity, enabling it to effectively copolymerize with the matrix segments during vulcanization. When the M / Q ratio is within a reasonable range, the resin structure has both a sufficiently rigid framework and good compatibility. Combined with an appropriate vinyl content, a uniform micro-network structure can be formed at the interface, thereby significantly improving the dimensional stability and weather resistance of the material.

[0028] In some embodiments, the vinyl hydroxyl silicone oil has a viscosity of 20~100 mPa·s at 25°C, a vinyl content of 6mol%~7mol%, and a hydroxyl content of 5.5mol%~6.5mol%. Based on the above embodiments, this vinyl hydroxyl silicone oil can adjust the viscosity of the system during the mixing process, improve the dispersibility of silica, and introduce flexible crosslinking points during the vulcanization and post-curing stages with appropriate amounts of vinyl and hydroxyl groups, thereby improving network uniformity, avoiding local stress concentration, and thus enhancing the durability and anti-aging properties of silicone rubber.

[0029] In some embodiments, the organic peroxide includes at least one of dicumyl peroxide, benzoyl peroxide, tert-butyl peracetate, and tert-butyl perbenzoate. Based on the above embodiments, the selection of these commonly used peroxides can provide a stable and controllable source of free radicals during the vulcanization process, ensuring uniform crosslinking of vinyl double bonds; different types of peroxides can be combined and optimized according to decomposition temperature and reaction rate to make the crosslinking process more stable, thereby further improving the integrity and weather resistance of the crosslinked network.

[0030] Secondly, this application provides a method for preparing highly weather-resistant and anti-aging silicone rubber, comprising:

[0031] Provide raw materials for the silicone rubber according to any embodiment of the first aspect;

[0032] The raw materials are mixed and cured to obtain a highly weather-resistant and anti-aging silicone rubber.

[0033] According to this application, the above method preferentially reacts with and firmly grafts various silane coupling agents onto the hydroxyl groups on the surface of silica during the mixing stage, and then introduces peroxides to induce crosslinking of vinyl double bonds during the subsequent curing process, thereby constructing a dense and stable chemical bond network at the filler-matrix interface. This method is simple and the steps are controllable, and it can significantly improve the weather resistance of silicone rubber while maintaining its basic mechanical properties.

[0034] In some embodiments, the method includes:

[0035] Methyl vinyl silicone rubber, silica, alkyl silane coupling agent, vinyl silane coupling agent, epoxy silane coupling agent and hindered amine silane coupling agent are mixed at 120~140℃ for 10~15min, and then dried at 140~150℃ for 1~2h to obtain masterbatch.

[0036] After the masterbatch cools, vinyl MQ silicone resin, vinyl hydroxyl silicone oil and organic peroxide are added. The mixture is then molded and vulcanized at 160~180℃ for 10~15 min. After vulcanization, it is post-cured at 190~210℃ for 2~4 h to obtain a silicone rubber with high weather resistance and anti-aging properties.

[0037] In some of the above embodiments, during the mixing and drying stages, the silane coupling agent preferentially undergoes a condensation reaction with the silanol groups on the surface of silica, forming a stable interfacial bonding layer. Hindered amine molecules are firmly anchored to the filler surface and maintain free radical scavenging activity. The preferential mixing and drying of the silane coupling agent and filler reduces the adverse effects of small-molecule byproducts on material properties. In the subsequent compression molding and vulcanization stage, organic peroxides decompose to generate free radicals, initiating a cross-linking reaction between the silicone rubber segments and vinyl MQ silicone resin, forming a uniform network structure. During the final post-curing process, functional groups such as epoxy groups can further react with the residual hydroxyl groups in the system to form additional cross-linking points, while completely eliminating small-molecule byproducts, thereby significantly improving interfacial density and the long-term stability of the material. Based on this process, the resulting silicone rubber not only exhibits excellent mechanical properties but also good weather resistance.

[0038] It should also be noted that in this application, most of the fixed grafts are on the surface of the filler, the amount is small and the location is limited. During the vulcanization process, the free radical yield of the peroxide is much higher than the hindered amine capture ability. Therefore, the peroxide vulcanization process has almost no negative impact. On the contrary, it can play a long-term role in capturing free radicals and enhancing weather resistance during long-term service after curing.

[0039] Thirdly, this application provides a silicone rubber article comprising silicone rubber according to any embodiment of the first aspect or silicone rubber prepared by the method according to any embodiment of the second aspect.

[0040] According to this application, because the aforementioned silicone rubber forms a dense and stable chemical bonding network at both the molecular structure and the filler interface, and introduces multiple structural features such as hindered amine free radical scavenging, epoxy group delayed reaction, and vinyl MQ silicone resin micronetwork reinforcement in the interface region, the silicone rubber product can maintain high mechanical properties even under long-term ultraviolet irradiation, thermo-oxidative environments, and humid and hot conditions. Specifically, the product exhibits excellent anti-aging properties and dimensional stability in harsh environments such as outdoor exposure, electronic and electrical packaging, transportation, and building sealing, thereby significantly extending its service life and reducing maintenance costs.

[0041] Compared with the prior art, the beneficial effects of this application are at least as follows:

[0042] By synergistically introducing alkylsilane coupling agents, vinylsilane coupling agents, and hindered amine silane coupling agents into the silicone rubber system, and combining the network regulation effects of vinyl MQ silicone resin and vinyl hydroxyl silicone oil, both chemical bonding enhancement and free radical capture protection are simultaneously achieved at the filler-matrix interface, significantly improving the interfacial bonding density and long-term stability. As a result, the prepared silicone rubber not only possesses excellent mechanical and processing properties but also good weather resistance and anti-aging capabilities, meeting the requirements for long-term outdoor service and high-end applications. Detailed Implementation

[0043] The various embodiments or implementation schemes in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments.

[0044] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0045] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0046] In this specification, unless otherwise specified, "parts" refers to "parts by weight".

[0047] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0048] 4-Amino-2,2,6,6-Tetramethylpiperidine, CAS: 36768-62-4;

[0049] 1-Hydroxy-2,2,6,6-Tetramethylpiperidine, CAS:7031-93-8;

[0050] 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol, CAS: 52722-86-8;

[0051] Propyltrimethoxysilane isocyanate, CAS: 24801-88-5;

[0052] Methyl vinyl silicone rubber, with a weight average molecular weight of 500,000 and a vinyl content of 0.25 wt%;

[0053] Silica with an average particle size of 20 nm;

[0054] Vinyl MQ silicone resin, also known as methyl vinyl MQ silicone resin, has a viscosity of 9000 mPa·s at 25°C, an M / Q ratio of 0.8, and a vinyl content of 1.5 wt%.

[0055] Vinyl hydroxyl silicone oil with a viscosity of 35 mPa·s at 25°C, a vinyl content of 6.5 mol%, and a hydroxyl content of 6 mol%.

[0056] Preparation Example 1

[0057] Preparation of hindered amine silane coupling agents:

[0058] 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol and propyltrimethoxysilane isocyanate were dispersed in toluene, with the molar ratio of 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol to propyltrimethoxysilane controlled at 1:1.01. The solid content of the system was 45 wt%. The reaction was carried out at 30 °C for 2 h under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature, and the solvent was removed by rotary evaporation to obtain hindered amine silane coupling agent A.

[0059] Preparation Example 2

[0060] Preparation of hindered amine silane coupling agents:

[0061] 4-Amino-2,2,6,6-Tetramethylpiperidine and propyltrimethoxysilane isocyanate were dispersed in toluene, with the molar ratio of 4-amino-2,2,6,6-tetramethylpiperidine to propyltrimethoxysilane controlled at 1:1.01. The solid content of the system was 45 wt%. The reaction was carried out at 30 °C for 2 h under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature, and the solvent was removed by rotary evaporation to obtain hindered amine silane coupling agent B.

[0062] Preparation Example 3

[0063] Preparation of hindered amine silane coupling agents:

[0064] 1-Hydroxy-2,2,6,6-Tetramethylpiperidine and propyltrimethoxysilane isocyanate were dispersed in toluene, with the molar ratio of 1-hydroxy-2,2,6,6-tetramethylpiperidine to propyltrimethoxysilane controlled at 1:1.01. The solid content in the system was 45 wt%. The reaction was carried out at 30 °C for 2 h under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature, and the solvent was removed by rotary evaporation to obtain hindered amine silane coupling agent C.

[0065] Preparation Example 4

[0066] Preparation of hindered amine silane coupling agents:

[0067] 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol and propyltrimethoxysilane isocyanate were dispersed in toluene, with the molar ratio of 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol to propyltrimethoxysilane controlled at 1:1.3. The solid content of the system was 45 wt%. The reaction was carried out at 30 °C for 2 h under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature, and the solvent was removed by rotary evaporation to obtain hindered amine silane coupling agent D.

[0068] Example 1

[0069] Preparation of highly weather-resistant and anti-aging silicone rubber:

[0070] 100 parts of methyl vinyl silicone rubber were put into a mixer and mixed at 130°C. 45 parts of silica were added sequentially, followed by 7 parts of dimethyl dimethoxysilane, 1.5 parts of vinyltriethoxysilane, 1 part of γ-glycidoxypropyltrimethoxysilane, and 1 part of hindered amine silane coupling agent A. The mixture was mixed at 130°C for 15 minutes to ensure uniform dispersion of the filler and in-situ condensation with the coupling agent. The mixture was then placed in a 145°C hot air oven and dried for 2 hours to remove low-molecular-weight byproducts, yielding the masterbatch.

[0071] The cooled masterbatch was placed in a mixer, and 4 parts of vinyl MQ silicone resin, 1 part of vinyl hydroxyl silicone oil and 1.5 parts of dicumyl peroxide were added. After mixing at 130°C for 1 minute, the mixture was molded at 170°C using a flat vulcanizing machine at a pressure of 10 MPa for 12 minutes to obtain a pre-formed silicone rubber product.

[0072] The product was placed in a 200℃ hot air circulating oven for post-curing for 3 hours to obtain a silicone rubber with high weather resistance and anti-aging properties.

[0073] Example 2

[0074] Preparation of highly weather-resistant and anti-aging silicone rubber:

[0075] Similar to Example 1, except that hindered amine silane coupling agent B is used instead of hindered amine silane coupling agent A.

[0076] Example 3

[0077] Preparation of highly weather-resistant and anti-aging silicone rubber:

[0078] Similar to Example 1, except that hindered amine silane coupling agent C is used instead of hindered amine silane coupling agent A.

[0079] Example 4

[0080] Preparation of highly weather-resistant and anti-aging silicone rubber:

[0081] Similar to Example 1, except that hindered amine silane coupling agent D is used instead of hindered amine silane coupling agent A.

[0082] Example 5

[0083] Preparation of highly weather-resistant and anti-aging silicone rubber:

[0084] 100 parts of methyl vinyl silicone rubber were put into an internal mixer and mixed at 130°C. 45 parts of silica were added sequentially, followed by 7 parts of dimethyldimethoxysilane, 1.5 parts of vinyltriethoxysilane, and 1 part of hindered amine silane coupling agent A. The mixture was mixed at 130°C for 15 minutes to ensure uniform dispersion of the filler and in-situ condensation with the coupling agent. The mixture was then placed in a 145°C hot air oven and dried for 2 hours to remove low-molecular-weight byproducts, yielding the masterbatch.

[0085] The cooled masterbatch was placed in a mixer, and 4 parts of vinyl MQ silicone resin, 1 part of vinyl hydroxyl silicone oil and 1.5 parts of dicumyl peroxide were added. After mixing at 130°C for 1 minute, the mixture was molded at 170°C using a flat vulcanizing machine at a pressure of 10 MPa for 12 minutes to obtain a pre-formed silicone rubber product.

[0086] The product was placed in a 200℃ hot air circulating oven for post-curing for 3 hours to obtain a silicone rubber with high weather resistance and anti-aging properties.

[0087] Comparative Example 1

[0088] Preparation of highly weather-resistant and anti-aging silicone rubber:

[0089] 100 parts of methyl vinyl silicone rubber were put into a mixer and mixed at 130°C. 45 parts of silica were added sequentially, followed by 8.5 parts of dimethyl dimethoxysilane, 1 part of γ-glycidyl etheroxypropyltrimethoxysilane, and 1 part of hindered amine silane coupling agent A. The mixture was mixed at 130°C for 15 minutes to ensure uniform dispersion of the filler and in-situ condensation with the coupling agent. The mixture was then placed in a 145°C hot air oven and dried for 2 hours to remove low-molecular-weight byproducts, yielding the masterbatch.

[0090] The cooled masterbatch was placed in a mixer, and 4 parts of vinyl MQ silicone resin, 1 part of vinyl hydroxyl silicone oil and 1.5 parts of dicumyl peroxide were added. After mixing at 130°C for 1 minute, the mixture was molded at 170°C using a flat vulcanizing machine at a pressure of 10 MPa for 12 minutes to obtain a pre-formed silicone rubber product.

[0091] The product was placed in a 200℃ hot air circulating oven for post-curing for 3 hours to obtain a silicone rubber with high weather resistance and anti-aging properties.

[0092] Comparative Example 2

[0093] Preparation of highly weather-resistant and anti-aging silicone rubber:

[0094] 100 parts of methyl vinyl silicone rubber were put into a mixer and mixed at 130°C. 45 parts of silica were added sequentially, followed by 7.5 parts of dimethyl dimethoxysilane, 1.5 parts of vinyltriethoxysilane, 1 part of γ-glycidoxypropyltrimethoxysilane, and 0.5 parts of 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol. The mixture was mixed at 130°C for 15 minutes to ensure uniform dispersion of the filler and in-situ condensation with the coupling agent. The mixture was then placed in a 145°C hot air oven and dried for 2 hours to remove low-molecular-weight byproducts, yielding the masterbatch.

[0095] The cooled masterbatch was placed in a mixer, and 4 parts of vinyl MQ silicone resin, 1 part of vinyl hydroxyl silicone oil and 1.5 parts of dicumyl peroxide were added. After mixing at 130°C for 1 minute, the mixture was molded at 170°C using a flat vulcanizing machine at a pressure of 10 MPa for 12 minutes to obtain a pre-formed silicone rubber product.

[0096] The product was placed in a 200℃ hot air circulating oven for post-curing for 3 hours to obtain a silicone rubber with high weather resistance and anti-aging properties.

[0097] Comparative Example 3

[0098] Preparation of highly weather-resistant and anti-aging silicone rubber:

[0099] 104 parts of methyl vinyl silicone rubber were put into a mixer and mixed at 130°C. 45 parts of silica were added sequentially, followed by 7 parts of dimethyl dimethoxysilane, 1.5 parts of vinyltriethoxysilane, 1 part of γ-glycidoxypropyltrimethoxysilane, and 1 part of hindered amine silane coupling agent A. The mixture was mixed at 130°C for 15 minutes to ensure uniform dispersion of the filler and in-situ condensation with the coupling agent. The mixture was then placed in a 145°C hot air oven and dried for 2 hours to remove low-molecular-weight byproducts, yielding the masterbatch.

[0100] The cooled masterbatch was placed in a mixer, and 1 part of vinyl hydroxyl silicone oil and 1.5 parts of dicumyl peroxide were added. After mixing at 130°C for 1 minute, the masterbatch was molded at 170°C using a flat vulcanizing machine with a pressure of 10 MPa for 12 minutes to obtain a pre-formed silicone rubber product.

[0101] The product was placed in a 200℃ hot air circulating oven for post-curing for 3 hours to obtain a silicone rubber with high weather resistance and anti-aging properties.

[0102] Test section

[0103] Tensile strength: The tensile strength σ0 (MPa) of the high weather-resistant and anti-aging silicone rubbers obtained in each example and comparative example was determined according to GB / T 1040-2006, and the results are shown in Table 1.

[0104] Water-UV light irradiation tensile strength retention rate: The sample was placed in a water-UV test chamber, immersed in deionized water, and subjected to 60W / m at 45℃. 2 After being irradiated with a 340nm ultraviolet lamp for 1000h and dried, the tensile strength σ1 (MPa) was tested after being left to stand for 24h at 23℃ and 50%RH. The tensile strength retention rate of water-ultraviolet light irradiation δ (%) was calculated as σ1 / σ0×100%, and the results are shown in Table 1.

[0105] Table 1

[0106]

[0107] According to Table 1, all embodiments exhibit higher tensile strength and tensile strength retention rate compared to Comparative Examples 1-3, indicating that the technical solution provided in this application can significantly improve the weather resistance and anti-aging properties of silicone rubber. The possible reasons are as follows: In Comparative Example 1, the absence of a vinyl silane coupling agent resulted in insufficient filler-matrix interface bonding points, making the interface region more prone to free radical accumulation during aging, thus accelerating performance degradation; in Comparative Example 2, the hindered amine was directly incorporated in the form of free small molecules, which inhibited the peroxide-induced reaction during vulcanization, leading to a decrease in tensile strength, and was also prone to migration or loss during aging, resulting in a significant reduction in aging resistance; in Comparative Example 3, the absence of vinyl MQ silicone resin resulted in a lack of micro-network constraint in the interface structure, low tensile strength, and a low mechanical retention rate after aging, indicating that MQ silicone resin plays an important role in stabilizing the interface.

[0108] As shown in Examples 1-3, different types of hindered amine silane coupling agents have a certain impact on the mechanical properties and weather resistance of silicone rubber. Specifically, when using urethane-type coupling agents prepared with 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol and 1-hydroxy-2,2,6,6-tetramethylpiperidine (Examples 1 and 3), the tensile strength retention rate is significantly higher than that of urea-type coupling agents prepared with 4-amino-2,2,6,6-tetramethylpiperidine (Example 2). This indicates that urethane bonds are superior in hydrolysis resistance and chemical stability, making them more suitable for damp heat and UV aging. Environment; Furthermore, the coupling agent prepared by the hindered amine 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol exhibits better tensile strength and resistance to damp heat and aging compared to the coupling agent prepared by 1-hydroxy-2,2,6,6-tetramethylpiperidine when used in the silicone rubber of this application. This may be because when using 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol as the hindered amine to obtain the hindered amine coupling agent, the epoxy group can bond with the hydroxyl site retained on the hindered amine molecule, further anchoring the hindered amine molecule at the filler interface, thereby better exerting anti-aging properties.

[0109] As can be seen from Examples 1 and 4, when the raw material molar ratio is controlled at 1:1.01 (Example 1), the hindered amine has a more uniform structure in the filler interface layer, resulting in the best aging resistance. However, when NCO is in excess (Example 4), excessive cross-linking or side reactions are easily formed, leading to a decrease in retention rate.

[0110] As shown in Examples 1 and 5, the further introduction of epoxy-based silane coupling agents can improve the tensile strength and tensile strength retention rate of silicone rubber. This indicates that when epoxy-based silane coupling agents are used to introduce epoxy groups onto the surface of silica, they can react with hydroxyl groups in the system during subsequent vulcanization or aging to form additional chemical anchoring sites, thereby enhancing the stability of the interfacial layer. In contrast, without the addition of epoxy-based silane coupling agents (Example 5), the tensile strength and tensile strength retention rate decreased, indicating that the further introduction of epoxy-based silane coupling agents can improve the weather resistance of silicone rubber.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A highly weather resistant and age resistant silicone rubber, characterized by, The raw materials include the following quality parts: 100 parts of methyl vinyl silicone rubber, 30-60 parts of white carbon black, 6-8 parts of alkyl silane coupling agent, 0.5-2 parts of hindered amine silane coupling agent, 0.5-2 parts of vinyl silane coupling agent, 3-5 parts of vinyl MQ silicone resin, 1-1.5 parts of vinyl hydroxyl silicone oil, 1-3 parts of organic peroxide; The hindered amine silane coupling agent is obtained by reacting a hindered amine with an isocyanate silane coupling agent; the hindered amine includes at least one of 4-amino-2,2,6,6-tetramethylpiperidine, 1-hydroxy-2,2,6,6-tetramethylpiperidine, and 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol.

2. The silicone rubber according to claim 1, characterized in that, The hindered amine silane coupling agent is prepared by the following method: The hindered amine and the isocyanate silane coupling agent are dispersed in toluene, and reacted at 25-35℃ for 1-3h to obtain the hindered amine silane coupling agent; The hindered amine includes at least one of 1-hydroxy-2,2,6,6-tetramethylpiperidine and 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol.

3. The silicone rubber according to claim 2, characterized in that, The hindered amine includes 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol, and the molar ratio of 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol to the isocyanate silane coupling agent is 1:1-1.02, and the solid content of the reaction system is 40wt%-50wt%.

4. The silicone rubber according to claim 1, characterized in that, The raw materials further include 0.5-2 parts of epoxy silane coupling agent.

5. The silicone rubber according to claim 4, characterized in that, The alkyl silane coupling agent includes at least one of dimethyldimethoxysilane and methyltrimethoxysilane; The vinyl silane coupling agent includes at least one of vinyltrimethoxysilane and vinyltriethoxysilane; The epoxy silane coupling agent includes γ-glycidoxypropyltrimethoxysilane.

6. The silicone rubber according to any one of claims 1 to 5, characterized in that, The silicone rubber satisfies at least one of the following conditions: 1) the weight average molecular weight of the methyl vinyl silicone rubber is 400000-600000, and the vinyl content is 0.05wt%-0.5wt%; 2) the average particle size of the white carbon black is 10-30nm; 3) the viscosity of the vinyl MQ silicone resin at 25℃ is 5000-15000mPa·s, the value of M / Q is 0.7-0.9, and the vinyl content is 0.5-2wt%; 4) the viscosity of the vinyl hydroxyl silicone oil at 25℃ is 20-100mPa·s, the vinyl content is 6mol%-7mol%, and the hydroxyl content is 5.5mol%-6.5mol%; 5) the organic peroxide includes at least one of dicumyl peroxide, benzoyl peroxide, tert-butyl peroxyacetate, and tert-butyl perbenzoate.

7. A method of preparing a highly weather resistant and age resistant silicone rubber, characterized by, The raw materials include the following quality parts: The raw materials include the following quality parts: The raw materials include the following quality parts:

8. The method of claim 7, wherein, ​ The methyl vinyl silicone rubber, white carbon black, alkyl silane coupling agent, vinyl silane coupling agent, epoxy silane coupling agent and hindered amine silane coupling agent are mixed at 120-140℃ for 10-15min, and after mixing, the mixture is dried at 140-150℃ for 1-2h to obtain a masterbatch; After the masterbatch is cooled, vinyl MQ silicone resin, vinyl hydroxyl silicone oil and organic peroxide are added, and the mixture is molded and vulcanized at 160-180℃ for 10-15min, and after vulcanization, the mixture is post-cured at 190-210℃ for 2-4h to obtain a high-weathering and anti-aging silicone rubber.

9. A silicone rubber article, characterized by, The silicone rubber according to any one of claims 1-6 or prepared according to the method of claims 7 or 8.

Images