High-stability silicone rubber and preparation method thereof
By plasma modification and ultrasonic field treatment of fumed silica, combined with twin-screw extruder technology, high-stability silicone rubber is prepared, which solves the stability problem of traditional silicone rubber in high-temperature environments and improves the mechanical properties and thermal aging stability.
Patent Information
- Application Number
- CN202510911586.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-02
- Publication Date
- 2025-09-12
Smart Images
Figure CN120623788A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of silicone rubber preparation, and in particular to high-stability silicone rubber and a preparation method thereof. Background Art
[0002] Silicone rubber is an elastic material with excellent properties, widely used in aerospace, electronics, automotive, medical devices, construction, and other fields. Its key features include high heat resistance, excellent electrical insulation, weather resistance, and chemical resistance. These outstanding properties have earned silicone rubber a vital position in modern industry.
[0003] In existing technologies, the silanol content in methyl vinyl silicone rubber directly affects the product's heat resistance and mechanical properties. A high silanol content results in poor heat resistance, while a low content improves heat resistance. However, when used in high-temperature environments, conventional methyl vinyl silicone rubber releases some substances, affecting its performance and even endangering the user's health. Summary of the Invention
[0004] The purpose of the present invention is to provide a high-stability silicone rubber and a preparation method thereof, which solves the technical problem of poor stability of traditional silicone rubber.
[0005] To achieve this object, the present invention adopts the following technical solutions: According to a first aspect, the present invention provides a method for preparing a high-stability silicone rubber, comprising: Step S1, performing plasma modification treatment on fumed silica to obtain modified silica with surface grafted amino groups; Step S2, putting the mixed methyl vinyl rubber, the modified silica and the structure control agent into an internal mixer and performing a primary mixing; then adding the silica microcapsules coated with blue dye and the peroxide curing agent and performing a secondary mixing to obtain a preliminary rubber compound; Step S3, placing the preliminary rubber material in a twin-screw extruder, applying an ultrasonic field with a frequency of 20 to 40 kHz in the extrusion section, and forming the extruded rubber strip by water cooling to obtain a high-stability silicone rubber.
[0006] Optionally, step S1 includes: Step S11, placing the fumed silica in a plasma reactor, applying a radio frequency electric field with a power of 800-1200 W and a frequency of 13.56 MHz, and pre-treating the fumed silica in a nitrogen atmosphere for 5-10 minutes; Step S12, introducing a gaseous medium containing a silane coupling agent into the plasma reactor, wherein the gaseous medium includes nitrogen and ammonia, wherein the silane coupling agent is converted into an aerosol by an atomizer and introduced into the plasma reactor at a flow rate of 0.5 to 1.2 L / min; Step S13: applying a radio frequency electric field with a power of 1000-1500 W between the electrodes of the plasma reactor and treating for 20-40 minutes to obtain modified silica with surface grafted amino groups.
[0007] Optionally, step S13 includes: Step S131, applying a radio frequency electric field with a frequency of 13.56 MHz and a power of 1000-1500 W between parallel electrode plates of the plasma reactor, controlling the temperature to 60-80° C. and the gas pressure to 101-103 kPa, so as to ionize the gas phase medium containing the silane coupling agent into a low-temperature plasma; Step S132: fluidizing the fumed silica at an airflow velocity of 0.8 to 1.5 m / s while applying a bias voltage of 5 to 10 kV between the parallel electrode plates to control the residence time of the silica particles in the plasma region to 25 to 40 seconds per cycle. Step S133, by adjusting the ratio K of the atomization flow rate of the silane coupling agent to the radio frequency power, the K value is maintained in the range of 1.2 to 1.8 L / (min•W), and after plasma modification treatment for 20 to 40 minutes, a modified silica with surface grafted amino groups is obtained, so that the surface grafted amino group density of the modified silica reaches 0.8 to 1.2 / nm 2 .
[0008] Optionally, in step S12, the volume ratio of nitrogen to ammonia is (3-5):1, and the silane coupling agent is γ-aminopropyltriethoxysilane.
[0009] Optionally, step S2 includes: Step S21, adding the mixed methyl vinyl rubber, the modified silica, and the structure control agent in preset weight proportions into an internal mixer, setting the rotor speed of the internal mixer to 20-40 rpm, and mixing at a temperature of 50-70° C. for 10-15 minutes to obtain a primary mixture; Step S22, adding silica microcapsules coated with blue dye and a peroxide curing agent to the primary mixture, wherein the particle size of the silica microcapsules is 5 to 20 μm; Step S23 , under the protection of inert gas, continue mixing at a rotation speed of 15-25 rpm for 5-8 minutes, control the temperature of the mixing chamber to be ≤75° C., and obtain a uniformly dispersed preliminary rubber material; wherein the inert gas is nitrogen, and the ventilation frequency is 2-4 times / min.
[0010] Optionally, the weight proportion of the mixed methyl vinyl rubber is 100 parts, the weight proportion of the modified silica is 35 to 60 parts, the weight proportion of the structure control agent is 2 to 5 parts, the weight proportion of the silica microcapsules is 1.5 to 3.5 parts, and the weight proportion of the peroxide vulcanizing agent is 0.8 to 1.5 parts.
[0011] Optionally, the mixed methyl vinyl rubber is prepared by compounding high molecular weight methyl vinyl rubber, medium molecular weight methyl vinyl rubber and low molecular weight methyl vinyl rubber in a weight ratio of 5:3:2, the structure control agent is hexamethyldisilazane or cyclic silazane, the capsule wall of the silica microcapsule is polymethylphenylsiloxane resin, the blue dye is a complex of phthalocyanine blue and an organic silicon carrier, and the peroxide vulcanizing agent is bis-(1,1-dimethylpropyl) peroxide.
[0012] Optionally, step S3 includes: Step S31, feeding the preliminary rubber material into the feed section of a twin-screw extruder, controlling the feed section temperature to 60-80°C and the screw speed to 80-120 rpm; Step S32: Install an ultrasonic transmitter array outside the extrusion section barrel, applying a frequency of 20-40 kHz and a power density of 0.3-0.5 W / cm 3 The ultrasonic field is used, and the temperature of the extrusion section is controlled at 85~110℃; Step S33, the preliminary rubber material is subjected to ultrasonic field treatment for a residence time of 40 to 90 seconds, and is extruded through a die head of a twin-screw extruder to obtain a rubber strip; In step S34, the extruded rubber strip is immersed in a cooling water tank at 15±3° C., water-cooled at a pulling speed of 10-15 m / min, and cured to obtain a high-stability silicone rubber.
[0013] Optionally, in step S33, the extrusion pressure of the twin-screw extruder is 5-8 MPa.
[0014] According to a second aspect, the present invention provides a high-stability silicone rubber, which is prepared by the preparation method of the high-stability silicone rubber as described in the first aspect, wherein the high-stability silicone rubber comprises mixed methyl vinyl rubber, modified white carbon black, a structure control agent, silica microcapsules, and a peroxide curing agent; Among them, the weight proportion of the mixed methyl vinyl rubber is 100 parts, the weight proportion of the modified silica is 35-60 parts, the weight proportion of the structure control agent is 2-5 parts, the weight proportion of the silica microcapsules is 1.5-3.5 parts, and the weight proportion of the peroxide vulcanizing agent is 0.8-1.5 parts.
[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for preparing high-stability silicone rubber. In step S1, fumed silica is subjected to plasma modification treatment to graft amino groups onto its surface. This effectively improves the interfacial compatibility of the fumed silica in the silicone rubber matrix, enhances the dispersibility and distribution uniformity of the filler, reduces agglomeration, and strengthens the physical bonding and chemical interaction between the filler and the silicone rubber matrix, thereby contributing to improved mechanical properties and thermal aging stability of the silicone rubber. In step S2, the modified silica is mixed with methyl vinyl rubber and a structure control agent in a single kneading process to form a stable network structure between the filler and the silicone rubber matrix. Subsequently, silica microcapsules coated with a blue dye and a peroxide curing agent are added to achieve sustained release and stable dispersion of the dye in a secondary kneading process, while promoting uniform distribution of the vulcanization system. This two-stage kneading method significantly improves the structural stability, color durability, and processing consistency of the product. In step S3, an ultrasonic field with a frequency of 20 to 40 kHz is applied to the twin-screw extruder. This promotes the orderly arrangement of the rubber compound's microstructure during processing, improves dispersion, and enhances crosslinking density and uniformity. This also reduces stress concentration during the mixing process in step S2. Therefore, this invention solves the technical problem of poor stability of conventional silicone rubber. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.
[0017] The structures, proportions, sizes, etc. depicted in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not intended to limit the conditions under which the present invention can be implemented and therefore have no substantive technical significance. Any structural modifications, changes in proportional relationships, or adjustments in size should still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and objectives that can be achieved by the present invention.
[0018] Figure 1 The present invention provides a flowchart of a method for preparing high-stability silicone rubber. DETAILED DESCRIPTION
[0019] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.
[0020] In the description of the present invention, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They are not intended to indicate or imply that the devices or elements referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. It should be noted that when a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a centrally located component.
[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.
[0022] Example 1: An embodiment of the present invention provides a method for preparing high-stability silicone rubber, comprising: Step S1, performing plasma modification treatment on fumed silica to obtain modified silica with amino groups grafted on the surface.
[0023] Specifically, step S1 includes: In step S11, fumed silica is placed in a plasma reactor and subjected to an RF electric field with a power of 800-1200 W and a frequency of 13.56 MHz. The fumed silica is then pretreated for 5-10 minutes under a nitrogen atmosphere. In this embodiment, nitrogen plasma pretreatment is performed under an RF electric field with a specific power (800-1200 W) and a standard frequency (13.56 MHz), effectively cleaning and activating the fumed silica surface. This process removes trace moisture, organic contaminants, and weakly bound impurities adsorbed on the fumed silica surface, improving the surface chemical purity of the fumed silica. More importantly, the active species (such as excited nitrogen atoms and ions) generated by the nitrogen plasma can physically etch the filler surface and introduce active sites (such as free radicals and unsaturated bonds), significantly enhancing the reactivity of the fumed silica surface and laying a solid foundation for subsequent efficient chemical grafting with silane coupling agents. This pretreatment step is critical to ensuring a uniform and robust grafting reaction.
[0024] In step S12, a gaseous medium containing a silane coupling agent is introduced into the plasma reactor. The gaseous medium comprises nitrogen and ammonia. The silane coupling agent is converted into an aerosol by an atomizer and then introduced into the plasma reactor at a flow rate of 0.5 to 1.2 L / min. The volume ratio of nitrogen to ammonia is 3 to 5:1, and the silane coupling agent is γ-aminopropyltriethoxysilane. In this embodiment, a gaseous medium with a specific composition (nitrogen to ammonia, volume ratio of 3 to 5:1) is used as the carrier gas and reaction atmosphere. The liquid γ-aminopropyltriethoxysilane is converted into an aerosol form by an atomizer and introduced into the reactor at a precisely controlled flow rate of 0.5 to 1.2 L / min. The aerosol form of the silane coupling agent is evenly dispersed and fully contacts the plasma area and the surface of the activated fumed silica particles, overcoming the problems of uneven dispersion and solvent residue associated with traditional liquid-phase treatments.
[0025] Specifically, ammonia decomposes in a plasma environment to produce reactive amino groups (-NH2, -NH-) and hydrogen radicals (H•), further enhancing the surface activity of fumed silica. It directly participates in the hydrolysis of the silane coupling agent or reacts with silane molecules, promoting more effective ring opening, hydrolysis, and directional anchoring of the silane coupling agent to the fumed silica surface. It also provides additional amino functional groups on the fumed silica surface, which synergize with the amino groups at the end of the silane coupling agent to significantly increase the density and uniformity of amino grafting on the final filler surface. The high density and even distribution of amino groups ensures a strong interfacial bond between the amino groups and the silicone rubber matrix (especially the vinyl groups in the raw rubber).
[0026] In step S13, a radio frequency electric field with a power of 1000-1500 W is applied between the electrodes of the plasma reactor for 20-40 minutes to obtain modified silica with surface-grafted amino groups. In this embodiment, the plasma treatment is performed at a higher radio frequency power (1000-1500 W) to provide stronger energy. The high-energy plasma environment fully fragments, excites, and ionizes the silane coupling agent aerosol molecules in the gas phase, generating a large number of highly reactive free radicals and ionic species. These highly reactive species undergo efficient and rapid covalent grafting reactions with the silica surface treated in steps S11 and S12. Step 13 ensures that the siloxane ends (-Si(OCH2CH3)3)3) of the γ-aminopropyltriethoxysilane molecules are firmly hydrolyzed and condensed to bond to the silanol (Si-OH) groups on the silica surface, while the amino groups (-NH2) at the ends are fully and densely exposed on the filler surface. Finally, modified silica with high surface amino grafting rate and uniform and firm grafting layer is obtained.
[0027] It should be noted that step S1 (especially its sub-steps S11 to S13) uses a plasma gas phase treatment process, introduces the synergistic effect of ammonia and an aerosol supply method, and performs amino functionalization treatment on the surface of the fumed silica, laying the foundation for efficient dispersion and strong interfacial bonding of the filler during mixing in the subsequent step S2, and ultimately making the silicone rubber product prepared in step S3 exhibit high stability.
[0028] In one embodiment, step S13 includes: In step S131, a radio frequency electric field with a frequency of 13.56 MHz and a power of 1000-1500 W is applied between the parallel electrode plates of the plasma reactor. The temperature is controlled between 60°C and 80°C, and the pressure is maintained between 101-103 kPa. This ionizes the gas phase containing the silane coupling agent into a low-temperature plasma. Under the conditions of a specific frequency (13.56 MHz) and high power (1000-1500 W) radio frequency electric field, combined with atmospheric pressure (101-103 kPa) and a mild temperature (60-80°C), the silane coupling agent gas phase is ionized into a highly active, low-heat-load low-temperature plasma. The atmospheric pressure environment avoids the complexity of a vacuum system, improving process efficiency and continuity. The mild temperature, far below that of traditional heat treatments, effectively prevents the deactivation of pre-formed active sites on the fumed silica surface, thermal decomposition of the silane coupling agent, and thermal damage to the final grafted amino groups, thereby preserving the integrity of the reactive groups to the greatest extent possible. This environment ensures that the plasma has sufficient energy to activate the reactants while avoiding damage to sensitive functional groups, creating an ideal environment for efficient and high-quality grafting reactions.
[0029] In step S132, the fumed silica is fluidized at an airflow velocity of 0.8 to 1.5 m / s while a bias voltage of 5 to 10 kV is applied between the parallel electrode plates. The residence time of the silica particles in the plasma region is controlled to be 25 to 40 seconds per cycle. In this embodiment, by setting the airflow velocity (0.8 to 1.5 m / s), the fluidization state of the silica particles is precisely controlled, ensuring that each particle is fully exposed to the plasma region, overcoming the drawbacks of uneven particle contact and treatment dead zones in fixed beds or simple stirred beds. By applying a bias voltage (5 to 10 kV) between the parallel electrode plates, this voltage generates a directional electrostatic force as the particles flow through the plasma region. This not only repels like-charged particles, preventing agglomeration and maintaining a single particle dispersion, but also actively controls the particle trajectory and residence time in the highly active plasma region (precisely controlled to 25 to 40 seconds per cycle), ensuring that each particle receives sufficient and equal plasma irradiation and treatment time. By combining active fluidization and electric field control, the uniformity and efficiency of plasma treatment at the particle scale are significantly improved.
[0030] Step S133, by adjusting the ratio K of the atomization flow rate of the silane coupling agent to the radio frequency power, the K value is maintained in the range of 1.2~1.8L / (min•W), and after the plasma modification treatment for 20~40min, the modified silica with surface grafted amino groups is obtained, so that the surface grafted amino group density of the modified silica reaches 0.8~1.2 / nm 2 . In this embodiment, by adjusting the ratio K of the atomization flow rate of the silane coupling agent to the radio frequency power and maintaining it in the range of 1.2~1.8, an intelligent dynamic coupling of the reactant supply (silane aerosol) and the energy input (plasma power) is achieved. When the K value is too small (the power is relatively too high), it is easy to cause excessive cracking of the silane, a short life of the active species, or damage to the grafted groups; and when the K value is too large (the silane supply is relatively excessive), it will cause the silane to be not fully activated, physical adsorption to increase, or side reactions to increase. When the K value is maintained between 1.2 and 1.8, it ensures that the plasma energy is sufficient to efficiently activate a sufficient amount of silane molecules without excessive decomposition, so that the concentration of activated silane species and the concentration of active sites on the particle surface are optimally matched, thereby maximizing the grafting reaction rate and efficiency. The surface grafted amino density of the modified silica reaches 0.8~1.2 / nm 2 This high-density and evenly distributed amino layer lays the foundation for the subsequent modified silica to form super strong covalent bonds or strong physical and chemical bonds with the silicone rubber matrix (methyl vinyl rubber).
[0031] It should be noted that through the coordinated regulation of plasma physical parameters, material retention behavior and ratio K, efficient, stable and repeatable amino grafting modification of the silica surface is achieved, so that the modified silica maintains consistent surface activity and dispersibility between different batches, greatly improving the structural consistency and performance stability of the mixed rubber in the subsequent step S2.
[0032] Step S2: putting the mixed methyl vinyl rubber, modified silica and structure control agent into an internal mixer and performing a primary mixing; then adding silica microcapsules coated with blue dye and peroxide curing agent and performing a secondary mixing to obtain a preliminary rubber compound.
[0033] Specifically, step S2 includes: In step S21, preset weight proportions of mixed methyl vinyl rubber, modified silica, and a structure control agent are placed into an internal mixer at a rotor speed of 20-40 rpm and mixed at a temperature of 50-70°C for 10-15 minutes to produce a primary mixture. In this embodiment, the silicone rubber raw material is mixed for a longer period (10-15 minutes) at a lower rotor speed (20-40 rpm) and a moderate temperature (50-70°C). This primary mixing process is conducted under low shear and low temperature conditions to ensure that the modified silica is fully wetted, deagglomerated, and initially uniformly dispersed within the mixed methyl vinyl rubber matrix. The low shear protects the fragile amino groups on the modified silica's surface from damage while also leveraging the good compatibility of the amino groups with the mixed methyl vinyl rubber matrix. The structure control agent is added during the primary mixing stage and uniformly dispersed, effectively shielding residual silanol (Si-OH) groups on the silica surface, preventing them from reaggregating due to hydrogen bonding between hydroxyl groups during subsequent storage or processing. This ensures the primary mixture produced in step S21 has good storage stability and rheological properties, laying a uniform foundation for subsequent steps. The mixing temperature of 50-70°C, far below the vulcanization temperature, avoids pre-crosslinking reactions and ensures that the amino activity on the modified silica surface is fully retained, maximizing interfacial bonding during the subsequent vulcanization stage.
[0034] In step S22, silica microcapsules coated with blue dye and a peroxide curing agent are added to the primary mixture. The silica microcapsules have a particle size of 5-20 μm. In this embodiment, the blue dye-coated silica microcapsules are added during the secondary mixing phase to prevent excessive mechanical damage and rupture of the microcapsules during the initial mixing phase, which involves high filler content and high shear forces. The silica shell (particle size 5-20 μm) is highly compatible with the silicone rubber matrix, ensuring the dispersion stability of the microcapsules in the rubber compound. The peroxide curing agent is also added during the secondary mixing phase, minimizing the risk of premature decomposition of the curing agent due to heat and shear during mixing, which could lead to localized crosslinking (scorching). This ensures the safety of the mixing process and the workability of the rubber compound.
[0035] In step S23, mixing is continued at a speed of 15-25 rpm for 5-8 minutes under an inert gas atmosphere, with the mixing chamber temperature maintained at ≤75°C, to obtain a uniformly dispersed preliminary rubber compound. The inert gas is nitrogen, and the ventilation frequency is 2-4 times / min. In this embodiment, a secondary mixing process (5-8 minutes) of the silica microcapsules and peroxide curing agent is performed at a lower speed (15-25 rpm) and strictly controlled temperature (≤75°C). This ensures uniform dispersion of the silica microcapsules and peroxide curing agent in the primary mixture. The low shear force, low temperature, and short mixing time maximize the integrity of the silica microcapsule shell, preventing leakage and migration of the blue dye during the mixing stage, which could cause contamination or affect performance. The mixing chamber temperature is well below the initial decomposition temperature of the peroxide curing agent. Combined with the inert gas atmosphere, this effectively inhibits premature decomposition of the peroxide curing agent, ensuring its uniform dispersion in the rubber compound in an unreacted state, providing uniform crosslinking sites for subsequent vulcanization.
[0036] During the implementation process, nitrogen (an inert gas) is continuously purged through the mixing chamber at a frequency of 2-4 changes per minute to completely eliminate oxygen. Oxygen is the primary cause of thermal oxidative degradation of silicone rubber during high-temperature processing, leading to molecular chain breakage and performance degradation. This inert atmosphere significantly improves the thermal stability of the rubber compound. Since oxygen can also accelerate the decomposition of peroxide curatives, the inert atmosphere eliminates this risk, further ensuring that the peroxide curative is active only during the designated curing stage, preventing oxidative discoloration or degradation of the blue dye caused by trace amounts of oxygen and heat.
[0037] It should be noted that the efficient dispersion and strong interfacial bonding of modified silica are the core of the mechanical properties and long-term stability of silicone rubber. The silica microcapsules completely coated with blue dye provide stable and permanent visual identification. The evenly dispersed and non-pre-decomposed peroxide curing agent ensures the formation of a uniform and dense cross-linked network in the subsequent vulcanization process. The inert gas protection greatly reduces the thermal oxidative aging of the rubber during the mixing process, laying the foundation for the excellent long-term aging resistance of the final silicone rubber.
[0038] In one embodiment, the mixed methyl vinyl rubber comprises 100 parts by weight, the modified silica comprises 35-60 parts by weight, the structure control agent comprises 2-5 parts by weight, the silica microcapsules comprise 1.5-3.5 parts by weight, and the peroxide curing agent comprises 0.8-1.5 parts by weight. The mixed methyl vinyl rubber is prepared by compounding high molecular weight methyl vinyl rubber, medium molecular weight methyl vinyl rubber, and low molecular weight methyl vinyl rubber in a weight ratio of 5:3:2. The structure control agent is hexamethyldisilazane or cyclic silazane. The silica microcapsule wall comprises polymethylphenylsiloxane resin. The blue dye is a composite of phthalocyanine blue and an organosilicon carrier. The peroxide curing agent is bis-(1,1-dimethylpropyl) peroxide. In this embodiment, the high molecular weight methyl vinyl rubber has a molecular weight of 550,000 to 750,000 g / mol and a vinyl content of 0.08 to 0.12 mol%. The medium molecular weight methyl vinyl rubber has a molecular weight of 300,000 to 450,000 g / mol and a vinyl content of 0.15 to 0.20 mol%. The low molecular weight methyl vinyl rubber has a molecular weight of 80,000 to 180,000 g / mol and a vinyl content of 0.10 to 0.15 mol%. The organosilicon carrier can be a phenyl-modified silicone oil or an amino-phenyl co-modified silicone oil.
[0039] It should be noted that high-molecular-weight methyl vinyl rubber provides the molecular chain backbone, contributing to its primary strength, elasticity, and creep resistance. Medium-molecular-weight methyl vinyl rubber improves processing properties (such as reducing viscosity) while still contributing good mechanical properties. Low-molecular-weight methyl vinyl rubber, as a highly effective processing aid and plasticizer, significantly reduces compound viscosity, improves fluidity during mixing (S2) and extrusion (S3), and helps eliminate internal stress. Its vinyl active sites can also participate in crosslinking.
[0040] In step S3, the preliminary rubber material is placed in a twin-screw extruder, an ultrasonic field with a frequency of 20 to 40 kHz is applied to the extrusion section, and the extruded rubber strip is water-cooled to obtain a high-stability silicone rubber. In this embodiment, the twin-screw extruder is well known in the art and will not be described in detail here.
[0041] Specifically, step S3 includes: In step S31, the preliminary rubber compound is fed into the feed section of a twin-screw extruder, with the feed section temperature controlled at 60-80°C and the screw speed at 80-120 rpm. In this embodiment, the preliminary rubber compound obtained in step S2 is fed at a relatively low feed section temperature (60-80°C) and a moderate screw speed (80-120 rpm). This feed section temperature is well below the decomposition temperature of the peroxide curative, thus avoiding the risk of pre-vulcanization (scorching) during feeding and conveying. The combination of low temperature and mild shear effectively protects the integrity of the silica microcapsules, preventing blue dye leakage due to rupture of the silica microcapsules. It also maintains a well-dispersed state of the modified silica and prevents reagglomeration under high shear. These conditions initially soften and plasticize the rubber compound, moderately reducing its viscosity and providing a uniform material foundation for efficient processing and ultrasonic treatment in the subsequent extrusion section.
[0042] Step S32: Install an ultrasonic transmitter array outside the extrusion section barrel, applying a frequency of 20-40 kHz and a power density of 0.3-0.5 W / cm 3 The ultrasonic field is applied in the extrusion section, and the temperature of the extrusion section is controlled at 85~110℃. In this embodiment, a specific frequency (20~40kHz) and power density (0.3~0.5W / cm 3 The ultrasonic field (likely a typo or a typo) creates a strong cavitation effect and high-frequency mechanical vibrations in the molten rubber. This cavitation effect generates instantaneous high-pressure, high-temperature microbubbles that violently collapse, creating a strong localized impact force that effectively breaks up any remaining micro-agglomerates of modified silica or microcapsules, achieving uniform dispersion of fillers and functional particles. High-frequency mechanical vibrations promote molecular chain motion, reducing the apparent viscosity of the melt and significantly improving melt fluidity, facilitating uniform mixing of the materials.
[0043] Specifically, ultrasonic energy can promote the interaction between the amino groups on the surface of modified silica and the raw rubber molecular chains (especially vinyl groups), further strengthening the interfacial bonding. At the same time, high-frequency mechanical vibration helps to straighten the arrangement of the polymer chains and optimize the uniformity and density of the cross-linked network structure formed by subsequent vulcanization. Ultrasonic waves can effectively eliminate the internal stress generated in the rubber during mixing and conveying, and break or expel tiny bubbles, reducing stress concentration points and defects within the product. Since the temperature in the extrusion section is 85-110°C, which is higher than the feeding section but still far below the vulcanization temperature, it ensures that the rubber is fully melted and has good fluidity, while avoiding pre-vulcanization, providing an ideal thermal environment for ultrasonic waves to maximize their effectiveness.
[0044] In step S33, the initial rubber material is subjected to ultrasonic field treatment for a residence time of 40 to 90 seconds before being extruded through the die of a twin-screw extruder to produce a rubber strip. The extrusion pressure of the twin-screw extruder is 5 to 8 MPa. In this embodiment, controlling the material's residence time in the ultrasonic field (40 to 90 seconds) is crucial. If the residence time is too short, the ultrasonic effect is insufficient; if the residence time is too long, local overheating or energy waste can easily occur. This residence time ensures that ultrasonic cavitation and vibration have sufficient time to act on the entire material system, achieving deep dispersion, homogenization, and interface optimization. Since the extrusion pressure of the twin-screw extruder is 5 to 8 MPa, the stable pressure ensures extrusion continuity and dimensional stability of the rubber strip, and also provides a uniform material shape for subsequent water cooling and shaping.
[0045] In step S34, the extruded rubber strip is immersed in a cooling water tank at 15±3°C and water-cooled at a pulling speed of 10-15 m / min to cure and form a highly stable silicone rubber. In this embodiment, the high-temperature extruded rubber strip is immediately immersed in a low-temperature (15±3°C) water tank for rapid cooling. This sudden cooling action water-cools and sets the ultrasonically optimized microstructure, preventing structural regression and maximizing the positive effects of the ultrasonic treatment. The rapid cooling shortens the rubber strip's exposure to high temperatures, protecting the integrity of the silica microcapsule wall (polymethylphenylsiloxane resin) and significantly suppressing the migration tendency of the internal dye (particularly the phthalocyanine blue / organic silicone carrier composite) in the high-temperature molten state, ensuring dyeing stability and the reliability of the anti-counterfeiting and traceability functions. By combining a constant water temperature (15±3°C) and a pulling speed (10-15m / min), a controllable and uniform cooling rate is achieved, which helps reduce internal stress and warping deformation caused by uneven cooling, ensuring the precise size, stable shape and uniform internal structure of the rubber strip. The continuous water-cooled pulling process significantly improves production efficiency.
[0046] It should be noted that the introduction of an ultrasonic field in step S3 solves the technical issues of difficulty in completely dispersing highly filled silicone rubber and the resulting internal stress during the final molding stage. By combining twin-screw continuous processing with ultrasonic technology, the present invention not only improves material uniformity, interfacial stability, and structural control during processing, but also imparts excellent mechanical properties and thermal stability to the silicone rubber products.
[0047] Working principle: The present invention provides a method for preparing high-stability silicone rubber. In step S1, by plasma-modifying fumed silica and grafting amino groups on its surface, the interfacial compatibility of fumed silica in the organosilicon system can be effectively improved, the dispersion and distribution uniformity of the filler can be enhanced, the agglomeration phenomenon can be reduced, and the physical bonding and chemical interaction between the filler and the silicone rubber matrix can be enhanced, which helps to improve the mechanical properties and thermal aging stability of the silicone rubber. In step S2, the modified silica is mixed with methyl vinyl rubber and a structure control agent once, so that the filler and the silicone rubber matrix form a stable network structure; then, silica microcapsules coated with blue dye and a peroxide curing agent are added to achieve slow release and stable dispersion of the dye in the second mixing, while promoting the uniform distribution of the vulcanization system; through this two-stage mixing method, the structural stability, color durability and processing consistency of the product are significantly improved. In step S3, an ultrasonic field with a frequency of 20 to 40 kHz is applied to the twin-screw extruder. This promotes the orderly arrangement of the rubber compound's microstructure during processing, improves dispersion, and enhances crosslinking density and uniformity. This also reduces stress concentration during the mixing process in step S2. Therefore, this invention solves the technical problem of poor stability of conventional silicone rubber.
[0048] Example 2: The embodiment of the present invention provides a high-stability silicone rubber, which is prepared by the preparation method of Example 1. The high-stability silicone rubber includes mixed methyl vinyl rubber, modified white carbon black, a structure control agent, silica microcapsules, and a peroxide curing agent; Among them, the weight portion of the mixed methyl vinyl rubber is 100 parts, the weight portion of the modified white carbon black is 35-60 parts, the weight portion of the structure control agent is 2-5 parts, the weight portion of the silica microcapsule is 1.5-3.5 parts, and the weight portion of the peroxide vulcanizing agent is 0.8-1.5 parts.
[0049] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing high-stability silicone rubber, characterized in that: include: Step S1, performing plasma modification treatment on fumed silica to obtain modified silica with surface grafted amino groups; Step S2, putting the mixed methyl vinyl rubber, the modified silica and the structure control agent into an internal mixer and performing a primary mixing; then adding the silica microcapsules coated with blue dye and the peroxide curing agent and performing a secondary mixing to obtain a preliminary rubber compound; Step S3, placing the preliminary rubber material in a twin-screw extruder, applying an ultrasonic field with a frequency of 20 to 40 kHz in the extrusion section, and forming the extruded rubber strip by water cooling to obtain a high-stability silicone rubber.
2. The method for preparing high-stability silicone rubber according to claim 1, wherein The step S1 comprises: Step S11, placing the fumed silica in a plasma reactor, applying a radio frequency electric field with a power of 800-1200 W and a frequency of 13.56 MHz, and pre-treating the fumed silica in a nitrogen atmosphere for 5-10 minutes; Step S12, introducing a gaseous medium containing a silane coupling agent into the plasma reactor, wherein the gaseous medium includes nitrogen and ammonia, wherein the silane coupling agent is converted into an aerosol by an atomizer and introduced into the plasma reactor at a flow rate of 0.5 to 1.2 L / min; Step S13: applying a radio frequency electric field with a power of 1000-1500 W between the electrodes of the plasma reactor and treating for 20-40 minutes to obtain modified silica with surface grafted amino groups.
3. The method for preparing high-stability silicone rubber according to claim 2, wherein: The step S13 includes: Step S131, applying a radio frequency electric field with a frequency of 13.56 MHz and a power of 1000-1500 W between parallel electrode plates of the plasma reactor, controlling the temperature to 60-80° C. and the gas pressure to 101-103 kPa, so as to ionize the gas phase medium containing the silane coupling agent into a low-temperature plasma; Step S132: fluidizing the fumed silica at an airflow velocity of 0.8 to 1.5 m / s while applying a bias voltage of 5 to 10 kV between the parallel electrode plates to control the residence time of the silica particles in the plasma region to 25 to 40 seconds per cycle. Step S133, by adjusting the ratio K of the atomization flow rate of the silane coupling agent to the radio frequency power, the K value is maintained in the range of 1.2 to 1.8 L / (min•W), and after plasma modification treatment for 20 to 40 minutes, a modified silica with surface grafted amino groups is obtained, so that the surface grafted amino group density of the modified silica reaches 0.8 to 1.2 / nm 2 .
4. The method for preparing high-stability silicone rubber according to claim 2, wherein: In step S12, the volume ratio of nitrogen to ammonia is (3-5):1, and the silane coupling agent is γ-aminopropyltriethoxysilane.
5. The method for preparing high-stability silicone rubber according to any one of claims 1 to 4, characterized in that: The step S2 comprises: Step S21, adding the mixed methyl vinyl rubber, the modified silica, and the structure control agent in preset weight proportions into an internal mixer, setting the rotor speed of the internal mixer to 20-40 rpm, and mixing at a temperature of 50-70° C. for 10-15 minutes to obtain a primary mixture; Step S22, adding silica microcapsules coated with blue dye and a peroxide curing agent to the primary mixture, wherein the particle size of the silica microcapsules is 5 to 20 μm; Step S23 , under the protection of inert gas, continue mixing at a rotation speed of 15-25 rpm for 5-8 minutes, control the temperature of the mixing chamber to be ≤75° C., and obtain a uniformly dispersed preliminary rubber material; wherein the inert gas is nitrogen, and the ventilation frequency is 2-4 times / min.
6. The method for preparing high-stability silicone rubber according to claim 5, characterized in that: The weight proportion of the mixed methyl vinyl rubber is 100 parts, the weight proportion of the modified silica is 35 to 60 parts, the weight proportion of the structure control agent is 2 to 5 parts, the weight proportion of the silica microcapsules is 1.5 to 3.5 parts, and the weight proportion of the peroxide vulcanizing agent is 0.8 to 1.5 parts.
7. The method for preparing high-stability silicone rubber according to claim 6, characterized in that: The mixed methyl vinyl rubber is prepared by compounding high molecular weight methyl vinyl rubber, medium molecular weight methyl vinyl rubber and low molecular weight methyl vinyl rubber in a weight ratio of 5:3:2; the structure control agent is hexamethyldisilazane or cyclic silazane; the capsule wall of the silica microcapsule is polymethylphenylsiloxane resin; the blue dye is a composite of phthalocyanine blue and an organic silicon carrier; and the peroxide vulcanizing agent is bis-(1,1-dimethylpropyl) peroxide.
8. The method for preparing high-stability silicone rubber according to claim 1, wherein: The step S3 comprises: Step S31, feeding the preliminary rubber material into the feed section of a twin-screw extruder, controlling the feed section temperature to 60-80°C and the screw speed to 80-120 rpm; Step S32: Install an ultrasonic transmitter array outside the extrusion section barrel, applying a frequency of 20-40 kHz and a power density of 0.3-0.5 W / cm 3 The ultrasonic field is used, and the temperature of the extrusion section is controlled at 85~110℃; Step S33, the preliminary rubber material is subjected to ultrasonic field treatment for a residence time of 40 to 90 seconds, and is extruded through a die head of a twin-screw extruder to obtain a rubber strip; In step S34, the extruded rubber strip is immersed in a cooling water tank at 15±3° C., water-cooled at a pulling speed of 10-15 m / min, and cured to obtain a high-stability silicone rubber.
9. The method for preparing high-stability silicone rubber according to claim 8, characterized in that: In step S33, the extrusion pressure of the twin-screw extruder is 5-8 MPa.
10. A high-stability silicone rubber, prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The high-stability silicone rubber comprises mixed methyl vinyl rubber, modified white carbon black, a structure control agent, silicon dioxide microcapsules and a peroxide curing agent; Among them, the weight proportion of the mixed methyl vinyl rubber is 100 parts, the weight proportion of the modified silica is 35-60 parts, the weight proportion of the structure control agent is 2-5 parts, the weight proportion of the silica microcapsules is 1.5-3.5 parts, and the weight proportion of the peroxide vulcanizing agent is 0.8-1.5 parts.