Silicone rubber composition with low compression set and high tear strength and preparation method of rubber compound

Abstract

The invention discloses a low-compression permanent deformation high-tear strength silicone rubber composition and a preparation method of a rubber compound, belongs to the technical field of silicone rubber, and relates to a high-performance silicone rubber composition. The composition comprises 100 parts of mixed methyl vinyl silicone rubber raw rubber (including 20-35 parts of low-vinyl raw rubber, 57-72 parts of medium-vinyl raw rubber and 8-23 parts of high-vinyl raw rubber), 40-60 parts of fumed silica, 10-20 parts of a structured control agent, 0.1-3 parts of a silane coupling agent and 0.5-3 parts of a heat-resistant agent. According to the silicone rubber prepared by taking the silicone rubber composition as a raw material, the compression permanent deformation rate lt is realized through a triple raw rubber synergistic effect and a pretreatment and step-by-step filling process; the tearing strength is gt; meanwhile, it is guaranteed that the hardness ranges from 69 Shore A to 75 Shore A, the tensile strength ranges from 8.6 MPa to 9.5 MPa, and the elongation at break is gt; the method is particularly suitable for being applied to the technical fields of new energy automobiles, aerospace, high-end industrial equipment and the like.

Description

Technical Field

[0001] This invention relates to the field of organosilicon polymer materials technology, specifically to a methyl vinyl silicone rubber composition and compound preparation method with low compression set and high tear strength, which is suitable for high-temperature seals, automotive engine parts and aerospace sealing applications. Background Technology

[0002] Silicone rubber, with its excellent resistance to high and low temperatures, weather resistance, electrical insulation, and biocompatibility, has become a core elastomer material in the automotive industry, medical devices, electronic packaging, and aerospace. However, as high-end manufacturing becomes increasingly extreme and complex, the performance limitations of traditional silicone rubber under specific harsh conditions are becoming increasingly apparent, especially in critical applications that withstand long-term dynamic loads or complex stress environments, such as battery pack sealing for new energy vehicles, vibration damping components for high-speed rail transit, and implantable medical devices. In these scenarios, the material's compression set and tear strength become key bottlenecks restricting its reliability and service life. Ideally, it should possess both low compression set (typically below 10%) and high tear strength (typically above 40 kN / m), but current technologies generally struggle to simultaneously meet these two core indicators.

[0003] Existing technologies face significant limitations in addressing this contradiction. On one hand, methods that enhance tear strength by adding high aspect ratio nanofibers, such as polyphenylene sulfide fibers, as described in publication CN110982279A, suffer from poor interfacial compatibility between the fibers and the silicone rubber matrix. This results in a significant decrease in the material's recovery ability under pressure, with a room temperature compression set residual rate typically exceeding 25%, failing to meet the application requirements for low compression set. On the other hand, solutions that focus on optimizing compression set through filler systems and formulation design, such as publication CN109337375A, while achieving lower compression set, only achieve a tear strength of approximately 13.5 kN / m, indicating relatively insufficient tear resistance. This makes the material prone to damage and shortens its lifespan under complex stress. Even increasing the crosslinking density to improve tear strength, as shown in US20220017621A1, restricts molecular chain segment movement and resilience, thus increasing the compression set rate, creating an inherent contradiction of trade-offs. Regarding raw rubber systems, neither using a single vinyl content raw rubber nor a two-component combination of high- and low-vinyl raw rubber has effectively reconciled the fundamental conflict between low tear strength and high compression set. For example, publication CN110862691A uses a specific vinyl content raw rubber compounded with physical fillers, resulting in a tear strength below 30 kN / m and a compression set above 15%. Publication CN201610721321, attempting a two-vinyl raw rubber compound, only achieved a tear strength of 32 kN / m, with a compression set still between 17.4% and 18.2%, similarly failing to effectively resolve the mutually exclusive problem of high tear strength and low compression set. Therefore, developing a new technology that can simultaneously and significantly improve the tear strength of silicone rubber and drastically reduce its compression set has become a critical technological bottleneck that urgently needs to be overcome. Summary of the Invention

[0004] To address the problems existing in the prior art, the purpose of this invention is to provide a new ternary compound silicone rubber composition. The silicone rubber made from this composition, while ensuring the basic performance indicators of the material, also has excellent properties such as low compression set and high tear strength.

[0005] To achieve the above-mentioned technical effects, the technical solution adopted by the present invention is as follows:

[0006] A silicone rubber composition with low compression set and high tear strength, comprising the following components by weight:

[0007] (1) Mixed methyl vinyl silicone rubber raw rubber: 100 parts

[0008] (A) 20-35 parts of low-vinyl raw rubber with a vinyl content of 0.08-0.10%;

[0009] (B) 57-72 parts of medium-vinyl raw rubber with a vinyl content of 0.20-0.25%;

[0010] (C) 8-23 parts of high-vinyl raw rubber with a vinyl content of 2.97-3.50%;

[0011] (2) 40-60 parts of fumed silica;

[0012] (3) 10-20 parts of structure control agent;

[0013] (4) 0.1-3 parts of silane coupling agent;

[0014] (5) 0.5-3 parts of heat resistant agent;

[0015] The molecular weight of the mixed methyl vinyl silicone rubber raw material is 57 × 10⁻⁶. 4 g / mol up to 66×10 4 g / mol.

[0016] Furthermore, the preferred composition of the above-mentioned mixed methyl vinyl silicone rubber raw rubber is:

[0017] (A) 20-25 parts of low-vinyl raw rubber with a vinyl content of 0.08-0.10%;

[0018] (B) 57-62 parts of medium-vinyl raw rubber with a vinyl content of 0.20-0.25%;

[0019] (C) 13-23 parts of high-vinyl raw rubber with a vinyl content of 2.97-3.50%.

[0020] The aforementioned structure control agent may be one or any combination of two or more of dimethyldimethoxysilane, dimethyldiethoxysilane, hexamethyldisilazane, hydroxyl silicone oil, and tetramethyldivinylsilazane.

[0021] The aforementioned silane coupling agent may be one of vinyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, vinyltriethoxysilane, γ-aminopropyltriethoxysilane, and γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

[0022] The heat-resistant agent mentioned above can be a mixture of cerium oxide and titanium oxide or a cerium-titanium composite oxide.

[0023] As a preferred technical solution, the component (2) fumed silica has a particle size of 15-50 nm and a specific surface area of ​​200-380 m². 2 / g, the structuring control agent of component (3) is a combination of dimethyldimethoxysilane, tetramethyldivinyldisilazane and hydroxyl silicone oil, the silane coupling agent of component (4) is vinyltrimethoxysilane, and the heat resistant agent of component (5) is a mixture of cerium oxide and titanium oxide, with a weight mixing ratio of 4:1.

[0024] Another objective of this invention is to provide a method for preparing methyl vinyl silicone rubber compound, ensuring that the resulting silicone rubber product simultaneously possesses excellent properties of low compression set and high tear strength. The technical solution adopted is as follows:

[0025] A method for preparing methyl vinyl silicone rubber compound using the above-mentioned silicone rubber composition as raw material includes the following steps:

[0026] (1) Filler pretreatment: 25%–30% of the total mass of fumed silica is put into a kneader, and the structure control agent and silane coupling agent are added in sequence. Kneading is carried out at ≤80℃ for 15 min.

[0027] (2) Raw rubber mixing: Add all the raw rubber of the composite methyl vinyl silicone rubber and knead for 10-15 minutes until it forms a uniform ball;

[0028] (3) Step-by-step filling: Divide the remaining fumed silica into 4 equal parts and add them to the kneader in sequence. After each part is added, knead it into a ball and continue to mix for 15 minutes.

[0029] (4) Acid-base adjustment: Add alkali metal oxide, knead into a ball and mix for 1 hour, controlling the temperature ≤100℃;

[0030] (5) High temperature dehydration: Heat to 150–165℃, start timing when the rubber compound temperature is ≥135℃, hot refining for 1.5h, then vacuuming, vacuum degree is -0.08MPa to -0.10MPa, after discharge, let stand and mature at 23±2℃ for 24-26h.

[0031] (6) Heat resistance strengthening: Put the cured rubber into a kneader, add heat resistant agent, mix at ≤80℃ for 1.5h, and filter to obtain the finished compound rubber.

[0032] Furthermore, the mixing time for each part of silica in step (3) above is strictly controlled to be 15±1 min.

[0033] Furthermore, the alkali metal oxide in step (4) above is magnesium oxide, and the amount used is 0.5-1.5% of the total mass of raw rubber.

[0034] Furthermore, during the vacuuming stage of step (5) above, the vacuum level is kept stable at -0.09±0.01MPa for 30 minutes.

[0035] This invention, through innovative molecular-level design, successfully overcomes a long-standing technical challenge in the silicone rubber field—the industry bottleneck of achieving both high tear strength and low compression set. Unlike conventional solutions relying on physical filler formulations, the core breakthrough of this invention lies in constructing a gradient vinyl raw rubber synergistic system: low-vinyl raw rubber acts as a flexible building block, endowing the material with excellent entropic elastic recovery capabilities and significantly suppressing compression set; high-vinyl raw rubber forms a dense cross-linked network, constructing a high-strength stress transfer framework; and medium-vinyl raw rubber achieves topological bridging between the flexible and rigid domains. This chemical configuration regulation, combined with specific molecular weight range control, forms a strong, tough, and highly elastic integrated three-dimensional cross-linked network during vulcanization, fundamentally reconstructing the material's stress behavior.

[0036] In the filler system and process design, the innovative application of pure fumed silica combined with a step-by-step mixing process achieves nanoscale dispersion and interface optimization. Stepwise filling technology ensures uniform filler dispersion, dynamic acid-base adjustment eliminates structural effects, and precise dehydration control guarantees compound purity. This synergistic process significantly improves processing stability and thermal aging performance, enabling the material to maintain reliable performance under high-temperature conditions. Ultimately, this invention achieves the following breakthrough performance balance while maintaining excellent processability: ultra-high tear strength: exceeding 40 kN / m, meeting the resistance to damage under extreme stress environments; extremely low compression set: less than 10%, ensuring deformation recovery capability for long-term dynamic sealing; and excellent thermal stability: significantly improved performance retention under high-temperature conditions, expanding the material's application scope.

[0037] The fundamental advancement of this invention lies in the fact that traditional techniques improve thermal stability by adding sheet-like fillers, but at the expense of molecular chain mobility, leading to a deterioration in compression set. This invention abandons the physical compounding approach, starting with the molecular cross-linking network topology and utilizing the chemical configuration differences of graded vinyl groups to achieve functional specialization. Low-vinyl segments ensure elastic recovery, while high-vinyl segments bear stress dissipation. Coupled with precise molecular weight control to optimize cross-linking kinetics, this achieves a synergistic breakthrough in the seemingly contradictory performance indicators of tear strength and compression set for the first time. This breakthrough provides a material solution for high-end fields such as aerospace sealing and new energy battery protection. Detailed Implementation

[0038] Example 1

[0039] A silicone rubber composition comprising the following components in parts by weight:

[0040] (1) Mixed methyl vinyl silicone rubber raw rubber (molecular weight 57×10 4 g / mol up to 66×10 4 g / mol): 100 parts

[0041] (A) Low-vinyl raw rubber with a vinyl content of 0.08-0.10%: 35 parts;

[0042] (B) Medium-vinyl raw rubber with a vinyl content of 0.20-0.25%: 57 parts;

[0043] (C) High-vinyl raw rubber with a vinyl content of 2.97-3.50%: 8 parts;

[0044] (2) Fumed silica (particle size 15-50nm, specific surface area 200m² / g): 55 parts;

[0045] (3) Structure control agent: 15 parts, containing:

[0046] Dimethyldimethoxysilane: 11.5 parts

[0047] Hexamethyldisilazane: 0.7 parts

[0048] Hydroxy-containing silicone oil (from Shin-Etsu KF-9701, hydroxyl content 1.0±0.1 wt%, viscosity 2500±300 mPa·s) 2.8 parts;

[0049] (4) Silane coupling agent (vinyltrimethoxysilane): 1 part;

[0050] (5) Heat resistant agent (a mixture of cerium oxide and titanium oxide in a weight ratio of 4:1): 1.5 parts.

[0051] The preparation steps of the compound rubber are as follows:

[0052] (1) Filler pretreatment: 25% (i.e. 13.75 parts) of the total mass of fumed silica was put into a kneader, and all the structure control agents and silane coupling agents were added in sequence. The mixture was kneaded at 80°C for 15 min.

[0053] (2) Raw rubber mixing: Add all the raw rubber of the composite methyl vinyl silicone rubber and knead for 10-15 minutes until it forms a uniform ball;

[0054] (3) Step-by-step filling: Divide the remaining fumed silica (41.25 parts) into 4 equal parts (each part is about 10.31 parts), add them to the kneader in sequence, knead them into a ball after each part is added and continue to knead for 15 minutes;

[0055] (4) Acid-base adjustment: Add alkali metal oxide MgO (1.0% of the total mass of raw rubber), knead into a ball, and then mix at ≤100℃ for 1 hour;

[0056] (5) High temperature dehydration: Heat to 160℃, start timing when the rubber compound temperature reaches 135℃, and heat for 1.5h; then vacuum (vacuum degree -0.08MPa to -0.10MPa) for 30min; after discharge, let stand and mature at 23±2℃ for 24h.

[0057] (6) Heat resistance strengthening: Put the cured rubber into a kneader, add heat resistant agent, mix at ≤80℃ for 1.5h, and filter through a 200-mesh stainless steel filter to obtain the finished compound rubber.

[0058] Example 2

[0059] A silicone rubber composition comprising the following components in parts by weight:

[0060] (1) Mixed methyl vinyl silicone rubber raw rubber (molecular weight 57×10 4 g / mol up to 66×10 4 g / mol): 100 parts

[0061] (A) 20 parts of low-vinyl raw rubber with a vinyl content of 0.08-0.10%;

[0062] (B) 72 parts of medium-vinyl raw rubber with a vinyl content of 0.20-0.25%;

[0063] (C) 8 parts of high-vinyl raw rubber with a vinyl content of 2.97-3.50%;

[0064] (2) 50 parts of fumed silica (particle size 15-50 nm, specific surface area 200 m²) 2 / g);

[0065] (3) Structure control agent: 18 parts, containing:

[0066] Dimethyldimethoxysilane: 13.7 parts

[0067] Hexamethyldisilazane: 0.9 parts

[0068] 3.4 parts of hydroxyl silicone oil (from Shin-Etsu KF-9701, hydroxyl content 1.0±0.1 wt%, viscosity 2500±300 mPa·s);

[0069] (4) 0.5 parts of vinyltrimethoxysilane, a silane coupling agent;

[0070] (5) 2.0 parts of heat resistant agent (the weight ratio of cerium oxide and titanium oxide is 4:1).

[0071] The preparation steps of the compound rubber are the same as in Example 1.

[0072] Example 3

[0073] A silicone rubber composition comprising the following components in parts by weight:

[0074] (1) Mixed methyl vinyl silicone rubber raw rubber (molecular weight 57×10 4 g / mol up to 66×10 4 g / mol): 100 parts

[0075] (A) 28 parts of low-vinyl raw rubber with a vinyl content of 0.08-0.10%;

[0076] (B) 63 parts of medium-vinyl raw rubber with a vinyl content of 0.20-0.25%;

[0077] (C) 9 parts of high-vinyl raw rubber with a vinyl content of 2.97-3.50%;

[0078] (2) 48 parts of fumed silica (particle size 15-50 nm, specific surface area 200 m²) 2 / g);

[0079] (3) Structure control agent: 15 parts, containing:

[0080] Dimethyldimethoxysilane: 9.9 parts

[0081] Hexamethyldisilazane: 0.6 parts

[0082] 2.5 parts of hydroxyl silicone oil (from Shin-Etsu KF-9701, hydroxyl content 1.0±0.1 wt%, viscosity 2500±300 mPa·s);

[0083] (4) 2.0 parts of vinyltrimethoxysilane, a silane coupling agent;

[0084] (5) 0.5 parts of heat resistant agent (the weight ratio of cerium oxide and titanium oxide is 4:1).

[0085] The preparation steps of the compound rubber are the same as in Example 1.

[0086] Example 4

[0087] A silicone rubber composition comprising the following components in parts by weight:

[0088] (1) Mixed methyl vinyl silicone rubber raw rubber (molecular weight 57×10 4 g / mol up to 66×10 4 g / mol): 100 parts

[0089] (A) 31 parts of low-vinyl raw rubber with a vinyl content of 0.08-0.10%;

[0090] (B) 60 parts of medium-vinyl raw rubber with a vinyl content of 0.20-0.25%;

[0091] (C) 9 parts of high-vinyl raw rubber with a vinyl content of 2.97-3.50%;

[0092] (2) 60 parts of fumed silica (particle size 15-50 nm, specific surface area 200 m²) 2 / g);

[0093] (3) Structure control agent: 10 parts, containing:

[0094] Dimethyldimethoxysilane: 7.6 parts

[0095] Methyldisilazane: 0.5 parts

[0096] 1.9 parts of hydroxyl silicone oil (from Shin-Etsu KF-9701, hydroxyl content 1.0±0.1 wt%, viscosity 2500±300 mPa·s);

[0097] (4) 0.1 parts of vinyltrimethoxysilane, a silane coupling agent;

[0098] (5) 2.2 parts of heat resistant agent (the weight ratio of cerium oxide and titanium oxide is 4:1).

[0099] The preparation steps of the compound rubber are the same as in Example 1.

[0100] Example 5

[0101] A silicone rubber composition comprising the following components in parts by weight:

[0102] (1) Mixed methyl vinyl silicone rubber raw rubber (molecular weight 57×10 4 g / mol up to 66×10 4 g / mol): 100 parts

[0103] (A) 25 parts of low-vinyl raw rubber with a vinyl content of 0.08-0.10%;

[0104] (B) 62 parts of medium-vinyl raw rubber with a vinyl content of 0.20-0.25%;

[0105] (C) 13 parts of high-vinyl raw rubber with a vinyl content of 2.97-3.50%;

[0106] (2) 45 parts of fumed silica (particle size 15-50 nm, specific surface area 200 m²) 2 / g);

[0107] (3) Structure control agent: 14 parts, containing:

[0108] Dimethyldimethoxysilane: 10.6 parts

[0109] 0.7 parts of tetramethyldivinyldisilazane

[0110] Hydroxy-hydroxy silicone oil (from Shin-Etsu KF-9701, hydroxyl content 1.0±0.1 wt%, viscosity 2500±300 mPa·s) 2.7 parts;

[0111] (4) 2.5 parts of vinyltrimethoxysilane, a silane coupling agent;

[0112] (5) 3 parts heat resistant agent (the weight ratio of cerium oxide and titanium oxide is 4:1).

[0113] Preparation of compound: The amount of fumed silica added in the filler pretreatment was increased from 25% to 30% of the total mass, and the rest was the same as in Example 1.

[0114] Example 6

[0115] A silicone rubber composition comprising the following components in parts by weight:

[0116] (1) Mixed methyl vinyl silicone rubber raw rubber (molecular weight 57×10 4 g / mol up to 66×10 4 g / mol): 100 parts

[0117] (A) 20 parts of low-vinyl raw rubber with a vinyl content of 0.08-0.10%;

[0118] (B) 57 parts of medium-vinyl raw rubber with a vinyl content of 0.20-0.25%;

[0119] (C) 23 parts of high-vinyl raw rubber with a vinyl content of 2.97-3.50%;

[0120] (2) 52 parts of fumed silica (particle size 15-50 nm, specific surface area 200 m²) 2 / g);

[0121] (3) Structure control agent: 16 parts, containing:

[0122] Dimethyldimethoxysilane: 12.2 parts

[0123] 0.8 parts of tetramethyldivinyldisilazane

[0124] Three parts of hydroxyl silicone oil (from Shin-Etsu KF-9701, hydroxyl content 1.0±0.1 wt%, viscosity 2500±300 mPa·s);

[0125] (4) 1.5 parts of vinyltrimethoxysilane, a silane coupling agent;

[0126] (5) 1.8 parts of heat resistant agent (the weight ratio of cerium oxide and titanium oxide is 4:1).

[0127] The preparation steps of the compound are the same as in Example 5.

[0128] Example 7

[0129] A silicone rubber composition comprising the following components in parts by weight:

[0130] (1) Mixed methyl vinyl silicone rubber raw rubber (molecular weight 57×10 4 g / mol up to 66×10 4 g / mol): 100 parts

[0131] (A) 28 parts of low-vinyl raw rubber with a vinyl content of 0.08-0.10%;

[0132] (B) 64 parts of medium-vinyl raw rubber with a vinyl content of 0.20-0.25%;

[0133] (C) 8 parts of high-vinyl raw rubber with a vinyl content of 2.97-3.50%;

[0134] (2) 58 parts of fumed silica (particle size 15-50 nm, specific surface area 200 m²) 2 / g);

[0135] (3) Structure control agent: 12 parts, containing:

[0136] Dimethyldimethoxysilane: 9.1 parts

[0137] 0.6 parts of hexamethyldisilazane

[0138] Hydroxy-containing silicone oil (from Shin-Etsu KF-9701, hydroxyl content 1.0±0.1 wt%, viscosity 2500±300 mPa·s) 2.3 parts;

[0139] (4) 3.0 parts of vinyltrimethoxysilane, a silane coupling agent;

[0140] (5) 1.0 part of heat resistant agent (the weight ratio of cerium oxide and titanium oxide is 4:1).

[0141] The preparation steps of the compound are the same as in Example 5.

[0142] The compound rubbers prepared in the above 7 examples were used to make test specimens with 2,5-dioxanone vulcanizing agent, and their performance was tested by numbering them. The vulcanization process parameters are as follows:

[0143] Vulcanizing agent: bis(2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane), addition amount: 0.8-1.2 phr (based on the mass of the compound);

[0144] First stage of vulcanization: 170±2℃ × t90+2min (t90 was measured by a rotorless rheometer);

[0145] Two-stage vulcanization: 200℃ × 4h (programmed temperature rise: room temperature → 200℃ / 1h → heat preservation);

[0146] Hardness is tested according to ISO 48-4:2018, tensile strength and elongation at break are tested according to ISO 37:2017, compression set is tested according to ISO 815-1:2019, and tear strength is tested according to ASTM D624 Type C.

[0147] The test results are shown in Table 1 below:

[0148] index Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Hardness (Shore A) 69.0 74.5 70.2 75.0 69.3 71.8 73.6 Tensile strength TS (MPa) 8.6 9.5 9.0 8.9 9.2 9.3 8.7 Elongation at break (EL) (%) 420 380 410 360 450 400 355 Tear strength TR (kN / m) 41.3 46.5 48.2 45.1 52.7 50.4 40.5 Compression permanent deformation rate (%) 9.2 8.5 7.8 9.8 6.5 7.3 9.9

[0149] The test results of the above 7 embodiments show that, by adopting the technical solution of the present invention, under the premise of ensuring the excellent basic properties of silicone rubber material such as hardness of 69-75HS(A), tensile strength of 8.6-9.5TS(Mpa), and elongation at break (EL) >350%, compression set <10 and tear strength >40kN / m can be achieved.

[0150] Example 8 (Comparative Example)

[0151] The mixed methyl vinyl silicone rubber raw rubber system uses 100 parts of medium vinyl raw rubber with a vinyl content of 0.20-0.25%, and the remaining components are the same as in Example 5. The preparation process steps are the same as in Example 5.

[0152] Example 9 (Comparative Example)

[0153] The mixed methyl vinyl silicone rubber raw rubber system is a two-component raw rubber, wherein there are 50 parts each of low vinyl raw rubber (A) with a vinyl content of 0.08-0.10% and high vinyl raw rubber with a vinyl content of 2.97-3.50%, for a total of 100 parts. The remaining components are the same as in Example 5, and the preparation process steps are the same as in Example 5.

[0154] Table 2 Comparative verification:

[0155] Example system Compression permanent deformation rate (%) Tear strength TR (kN / m) Reason for failure Example 8 Single vinyl raw rubber (B) 15.1 38.6 Single crosslinked network Example 9 Two-component raw rubber (A+C) 12.7 41.2 Lack of middle vinyl transition crosslinking layer

[0156] The two comparative examples above used the same test methods as Examples 1-7. The results showed that it was difficult to simultaneously meet the requirements of compression set <10% and tear strength >40kN / m.

Claims

1. A silicone rubber composition with low compression set and high tear strength, characterized in that: It contains the following components by weight: (1) Mixed methyl vinyl silicone rubber raw rubber: 100 parts (A) 20-35 parts of low-vinyl raw rubber with a vinyl content of 0.08-0.10%; (B) 57-72 parts of medium-vinyl raw rubber with a vinyl content of 0.20-0.25%; (C) 8-23 parts of high-vinyl raw rubber with a vinyl content of 2.97-3.50%; (2) Fumed silica 40-60 parts; (3) 10-20 parts of structure control agent; (4) 0.1-3 parts of silane coupling agent; (5) 0.5-3 parts of heat resistant agent; The molecular weight of the mixed methyl vinyl silicone rubber raw material is 57 × 10⁻⁶. 4 g / mol up to 66×10 4 g / mol.

2. The silicone rubber composition according to claim 1, characterized in that: The mixed methyl vinyl silicone rubber raw material has the following composition: (A) 20-25 parts of low-vinyl raw rubber with a vinyl content of 0.08-0.10%; (B) 57-62 parts of medium-vinyl raw rubber with a vinyl content of 0.20-0.25%; (C) 13-23 parts of high-vinyl raw rubber with a vinyl content of 2.97-3.50%.

3. The silicone rubber composition according to claim 1, characterized in that: The component (2), fumed silica, has a particle size of 15-50 nm and a specific surface area of ​​200-380 m². 2 / g.

4. The silicone rubber composition according to claim 1, characterized in that: The structuring control agent of component (3) is a combination of dimethyldimethoxysilane, tetramethyldivinyldisilazane and hydroxyl silicone oil.

5. The silicone rubber composition according to claim 1, characterized in that: The silane coupling agent of component (4) is vinyltrimethoxysilane.

6. The silicone rubber composition according to claim 1, characterized in that: The heat-resistant agent of component (5) is a mixture of cerium oxide and titanium oxide, with a weight mixing ratio of 4:

1.

7. A method for preparing methyl vinyl silicone rubber compound using the silicone rubber composition according to any one of claims 1-6 as a raw material, characterized in that, Includes the following steps: (1) Filler pretreatment: 25%–30% of the total mass of fumed silica is put into a kneader, and the structure control agent and silane coupling agent are added in sequence. Kneading is carried out at ≤80℃ for 15 min. (2) Raw rubber compounding: Add the raw rubber of composite methyl vinyl silicone rubber and knead until it forms a ball; (3) Step-by-step filling: Divide the remaining fumed silica into 4 equal parts and add them to the kneader in sequence. After each part is added, knead it into a ball and continue to mix for 15 minutes. (4) Acid-base adjustment: Add alkali metal oxide, knead into a ball and mix for 1 hour, controlling the temperature ≤100℃; (5) High temperature dehydration: Heat to 150–165℃, start timing when the rubber compound temperature is ≥135℃, heat for 1.5h, then vacuum, vacuum degree is -0.08MPa to -0.10MPa, after discharge, let stand and mature at 23±2℃ for 24–26h. (6) Heat resistance strengthening: Put the cured rubber into a kneader, add heat resistant agent, mix at ≤80℃ for 1.5h, and filter to obtain the finished compound rubber.

8. The method for preparing methyl vinyl silicone rubber compound according to claim 7, characterized in that: In step (3), the mixing time for each part of silica is strictly controlled at 15±1 min.

9. The method for preparing methyl vinyl silicone rubber compound according to claim 7, characterized in that: The alkali metal oxide in step (4) is magnesium oxide, and the amount used is 0.5-1.5% of the total mass of raw rubber.

10. The method according to claim 7, characterized in that: In step (5), the vacuum level is kept stable at -0.09±0.01MPa for 30 minutes.