A ceramifiable filler composition and its use

Abstract

The application discloses a ceramic filler composition suitable for a silicone rubber foam material and application thereof. The ceramic filler composition comprises nano magnesium-aluminum hydrotalcite, ceramic auxiliary filler and ceramic filler, and the mass ratio of the three is 1-5:13-35:3-12. The ceramic auxiliary filler comprises low-melting point glass powder, lithium carbonate and di-niobium pentoxide, and the mass ratio of the three is 6-20:2-7:3-8. The melting point of the low-melting point glass powder is 320-650 DEG C. The ceramic filler comprises one or more of titanium dioxide, mica powder, wollastonite, montmorillonite, diatomite and kaolin.

Description

Technical Field

[0001] This invention relates to the field of fire-retardant silicone rubber foam materials, specifically to a ceramicized filler composition and its application in silicone rubber foam materials. Background Technology

[0002] Silicone rubber foam, with its lightweight, soft, and highly resilient properties, is considered an ideal sealing and cushioning material, widely used in 5G base station protection, power line sealing, compression cushioning of new energy vehicle batteries, and sealing of electronic and electrical appliances. With rapid technological advancements, the demand for silicone rubber foam has expanded to aerospace, defense, and other fields, facing higher operating temperatures and thus requiring more stable and efficient thermal protection performance. However, under continuous high-temperature heat flow or flame attack, silicone rubber foam exhibits poor fire resistance, ablating to only loose SiO2 powder, completely losing its mechanical strength and self-supporting ability, making it difficult to meet the current urgent need for high-strength fire-resistant silicone foam.

[0003] Ceramicization is the main method to ensure that silicone rubber foam retains its complete structure and forms a support with a certain strength after ablation. To achieve better ceramization after ablation, a large amount of ceramic filler is usually added. This not only leads to a sharp increase in the apparent density and hardness of the ceramicized silicone rubber foam at room temperature and a sharp decrease in its mechanical strength, but also increases the foam's open-cell ratio, resulting in a decline in the foam material's thermal insulation performance. Furthermore, the foam's size undergoes significant shrinkage or expansion after ablation, causing the ceramic body to fail to support and completely cover the protective device, thus losing its thermal protection capability.

[0004] Therefore, there is an urgent need for a highly efficient ceramicized filler composition that enables foam materials to not only be lightweight, soft, and highly elastic at room temperature, but also to form a high-strength, low-shrinkage, hard ceramic body after ablation.

[0005] Chinese patent document CN108219473B discloses a room-temperature vulcanizing ceramicized silicone rubber foam sealant and its preparation method. Its components include α,ω-dihydroxypolydimethylsiloxane, precipitated silica, mica powder, ceramicizing additives, surface treatment agents, vinyl silicone oil, hydrogen-containing silicone oil, catalysts, and foaming agents. The ceramicizing additives are one or more of aluminum silicate, magnesium silicate, boric acid, zinc borate, glass powder, and TiO2. The ceramicized silicone rubber foam sealant prepared by this patent technology possesses certain mechanical properties at room temperature and forms a ceramic body under combustion or high-temperature conditions.

[0006] Chinese patent document CN115819982A discloses a flame-retardant ceramicized liquid silicone rubber foam material, its preparation method, and its application. The material includes a foaming component and a crosslinking component. The foaming component includes vinyl silicone oil, hydroxyl silicone oil, platinum catalyst, silica, flame retardant, and ceramicized filler. The crosslinking component includes vinyl silicone oil, hydrogen-containing silicone oil, silica, flame retardant, and ceramicized filler. The flame retardant includes one or more of Al(OH)3, Mg(OH)2, MgO, and Al2O3. The ceramicized filler is one or more of mica, kaolin, low-melting-point glass powder, montmorillonite, and silica fume. The silicone rubber foam provided by this patent technology forms a ceramic state after ablation.

[0007] Chinese patent document CN117866442A discloses a refractory ceramicized foamed silicone rubber, its preparation method, and its application. The refractory ceramicized foamed silicone rubber includes two forms: liquid ceramicized foamed silicone rubber and solid ceramicized foamed silicone rubber. The prepared foamed silicone rubber has good elasticity, which can play a better protective role for protective parts and achieve the purpose of buffering and shock absorption. After high temperature or open flame ablation, the foamed silicone rubber can quickly form a foam ceramic body with a self-supporting structure, while maintaining a high degree of cell structure retention rate, which can play a better role in heat insulation and flame retardancy. The foam expands in volume after ablation. Summary of the Invention

[0008] This invention provides a ceramicized filler composition suitable for silicone rubber foam materials. When used in silicone rubber foam materials, it can solve the following problems: 1) Existing technologies require too much ceramic filler, resulting in high density, poor mechanical properties, and low strength of the ceramic body in silicone rubber foam materials; 2) Existing technologies have problems such as increased foam open-cell ratio after adding ceramic filler, leading to poor thermal insulation performance; 3) Existing technologies have a large linear shrinkage rate of silicone rubber foam after ablation.

[0009] A ceramicized filler composition suitable for silicone rubber foam materials includes nano-magnesium aluminum hydrotalcite, ceramic aid filler and ceramic-forming filler in a mass ratio of 1-5 (preferably 1-4): 13-35 (preferably 13-32): 3-12 (preferably 4-8);

[0010] The ceramic filler comprises low-melting-point glass powder, lithium carbonate, and niobium pentoxide in a mass ratio of 6-20 (preferably 6-18):2-7 (preferably 3-6):3-8 (preferably 4-8); the melting point of the low-melting-point glass powder is 320-650°C.

[0011] The ceramic filler includes one or more of titanium dioxide, mica powder, wollastonite, montmorillonite, diatomite, and kaolin.

[0012] The nano-magnesium aluminum hydrotalcite is layered, with a surface hydroxyl group density of 6–9 hydroxyl groups / nm. 2.

[0013] The preparation method of the nano-magnesium aluminum hydrotalcite may include:

[0014] Dissolve magnesium nitrate and aluminum nitrate in deionized water to prepare salt solution A;

[0015] Dissolve aluminum hydroxide and sodium bicarbonate in deionized water to prepare alkaline solution B;

[0016] At room temperature, add alkaline solution B to salt solution A under stirring. After stirring evenly, the resulting mixed solution is loaded into a reaction vessel. Then, place the reaction vessel at 130-160°C (preferably 150°C) for reaction. After the reaction is completed, separate the solid and liquid, and dry the obtained solid to obtain the nano-magnesium aluminum hydrotalcite.

[0017] In the preparation method of the nano-magnesium aluminum hydrotalcite, the mass ratio of deionized water, magnesium nitrate and aluminum nitrate in the salt solution A can be 100:2.1-2.9 (preferably 2.4-2.7):1.5-2.2 (preferably 1.8-2.1).

[0018] In the preparation method of the nano-magnesium aluminum hydrotalcite, the mass ratio of deionized water, aluminum hydroxide and sodium bicarbonate in the alkaline solution B can be 100:0.6-1 (preferably 0.7-0.9):1.8-2.4 (preferably 1.9-2.1).

[0019] In the preparation method of the nano-magnesium aluminum hydrotalcite, stirring can be carried out during the preparation of salt solution A. The stirring speed can be 1500-2000 rpm and the stirring time can be 8-10 min.

[0020] In the preparation method of the nano-magnesium aluminum hydrotalcite, stirring can be carried out during the preparation of alkaline solution B. The stirring speed can be 1500-2000 rpm and the stirring time can be 8-10 min.

[0021] In the preparation method of the nano-magnesium aluminum hydrotalcite, during the process of adding alkaline solution B to the salt solution A under stirring, the stirring speed of the salt solution A can be 1300-1500 rpm.

[0022] In some embodiments, the time required for uniform stirring in the preparation method of the nano-magnesium aluminum hydrotalcite is 20-30 minutes.

[0023] In some embodiments, in the preparation method of the nano-magnesium aluminum hydrotalcite, an alkaline solution B is added to the salt solution A under stirring so that the pH of the mixed solution is 9-10;

[0024] In the preparation method of the nano-magnesium aluminum hydrotalcite, the reaction time at 130-160℃ can be 8-10 hours.

[0025] In the preparation method of the nano-magnesium aluminum hydrotalcite, the solid-liquid separation can be carried out by centrifugation, with a centrifugation speed of 4000-5000 rpm and a duration of 2-5 min.

[0026] In the preparation method of the nano-magnesium aluminum hydrotalcite, the obtained solid can be dried at 70-90℃ to obtain the nano-magnesium aluminum hydrotalcite.

[0027] This invention further provides the application of the aforementioned ceramicized filler composition in silicone rubber foam materials, wherein the nano-magnesium aluminum hydrotalcite can stabilize the cell structure and reinforce the skeleton in the silicone rubber foam material. Further, the silicone rubber foam material can be a 110-methylvinyl addition-type silicone rubber foam material. Even further, the raw material composition of the silicone rubber foam material includes methylvinyl silicone raw rubber. The mass ratio of the methylvinyl silicone raw rubber, the nano-magnesium aluminum hydrotalcite, the ceramic-forming filler, and the ceramic-forming filler can be 100:1–5:13–35:3–12.

[0028] As a general inventive concept, the present invention also provides a silicone rubber foam material, wherein the raw material composition of the silicone rubber foam material includes the ceramicized filler composition described above.

[0029] In some embodiments, the silicone rubber foam material is an addition-type fireproof and heat-insulating high-strength silicone rubber foam material, and the raw material composition includes, by weight parts:

[0030]

[0031] The benzotriazole acts as both a flame retardant and an inhibitor.

[0032] The transition metal two-dimensional sulfides act as flame retardants.

[0033] The catalyst is a platinum catalyst;

[0034] The mass ratio of the catalyst to the total mass of the benzotriazole and the inhibitor is 1:0.4 to 1.2, preferably 1:0.9 to 1.2;

[0035] The preparation method of the foaming agent includes the following steps:

[0036] S1, α,ω-dihydroxy-terminated polydimethylsiloxane and surfactant are mixed to obtain an emulsion;

[0037] S2, the emulsion is mixed with hydroxyapatite and deionized water to obtain the foaming agent in emulsion form;

[0038] The nano-magnesium aluminum hydrotalcite plays a role in stabilizing the pores and reinforcing the skeleton.

[0039] By weight, the ceramic filler comprises:

[0040] The low-melting-point glass powder is 6-20 parts.

[0041] The lithium carbonate is 2 to 7 parts.

[0042] The amount of niobium pentoxide is 3 to 8 parts.

[0043] The vinyl content in the methyl vinyl silicone raw rubber can be 0.03% to 3%.

[0044] The molecular weight of the methyl vinyl silicone raw rubber can be 45 × 10⁻⁶. 4 ~85×10 4 g / mol.

[0045] The silica may include at least one of precipitated silica and fumed silica.

[0046] The specific surface area of ​​the silica can be 120–420 m². 2 / g, which can further be 120–220m 2 / g.

[0047] The structure control agent may include hydroxyl silicone oil. The hydroxyl content of the hydroxyl silicone oil may be 4% to 10% by mass, and more particularly 4% to 8%.

[0048] The mass ratio of benzotriazole to the inhibitor can be 1:0.03 to 0.09.

[0049] The transition metal two-dimensional sulfides may include at least one of tungsten disulfide, molybdenum disulfide, and titanium disulfide.

[0050] The release agent may include stearic acid compounds.

[0051] In the raw material composition, the hydrogen-containing silicone oil can be 2 to 8 parts by weight.

[0052] The hydrogen content of the hydrogen-containing silicone oil can be 0.5% to 1.5% by mass, and more preferably 1.0% to 1.5%.

[0053] In the raw material composition, the foaming agent can be 2 to 8 parts by weight.

[0054] The foaming agent may include one or more of glycerol, hydroxytyrosol, ethylene glycol, n-butanol, and pentaerythritol.

[0055] In the raw material composition, the catalyst may be 0.3 to 0.6 parts by mass.

[0056] The catalyst may include a cassette catalyst.

[0057] The inhibitor may include one or more of acetylenol, methylbutynol, tert-butylcyclohexanol, and phenylbutynol.

[0058] In the preparation method of the foaming agent, the mass ratio of the α,ω-dihydroxy-terminated polydimethylsiloxane, the surfactant, the hydroxyapatite and the deionized water can be 100:5-15 (preferably 6-12):1-9 (preferably 1-6):50-100 (preferably 60-100).

[0059] The molecular weight of the α,ω-dihydroxy-terminated polydimethylsiloxane can be 1200–5000 g / mol.

[0060] The hydroxyl content of the α,ω-dihydroxy-terminated polydimethylsiloxane can be 0.2% to 8%, and more preferably 2% to 6%.

[0061] The hydrophilic-lipophilic balance (HLB value) of the surfactant can be 2 to 5.

[0062] The surfactant may include at least one of sorbitan tristearate, sorbitan monostearate, and dehydrated sorbitol fatty acid ester.

[0063] In step S1, the mixing temperature can be 50-55°C.

[0064] In step S1, stirring may be performed during the mixing process. The stirring speed may be 1500–2000 rpm, and the stirring time may be 8–15 minutes.

[0065] In step S2, the particle size of the hydroxyapatite can be 10–80 μm.

[0066] In step S2, hydroxyapatite and deionized water can be added to the emulsion sequentially while stirring. Further, after adding hydroxyapatite, the stirring speed can be 1500–2000 rpm, and the stirring time can be 8–15 minutes. The deionized water can be added dropwise while stirring. After the addition is complete, the stirring speed can be 2200–2500 rpm, and stirring can be continued for 15–20 minutes to obtain the emulsion-like foaming agent.

[0067] In the raw material composition, the nano-magnesium aluminum hydrotalcite may be 1 to 4 parts by weight.

[0068] In the raw material composition, the ceramic filler can be 13 to 32 parts by mass.

[0069] In the raw material composition, the ceramic filler can be 4 to 8 parts by weight.

[0070] In the ceramic filler, the low-melting-point glass powder can be 6 to 18 parts by weight.

[0071] In the ceramic filler, the lithium carbonate may be 3 to 6 parts by mass.

[0072] In the ceramic filler, the niobium pentoxide content can be 4 to 8 parts by mass.

[0073] The present invention also provides a preferred preparation method for the aforementioned silicone rubber foam material, comprising the following steps:

[0074] 1) Add methyl vinyl silicone raw rubber, fumed silica and structural control agent to a kneader for the first internal mixing, and then add benzotriazole, transition metal two-dimensional sulfides, ceramic filler, ceramic filler, nano magnesium aluminum hydrotalcite and release agent for the second internal mixing.

[0075] 2) Heat the kneader chamber temperature to 80-160℃, and mix evenly under constant temperature in a negative pressure environment of -0.03--0.08MPa to obtain silicone rubber compound.

[0076] 3) Divide the silicone rubber compound into two parts, A and B. Mix part A with inhibitor, foaming agent, foaming aid and catalyst on a two-roll mill to obtain base material A. Mix part B with hydrogen-containing silicone oil on a two-roll mill to obtain base material B. Mix base material A and base material B on a two-roll mill and roll them to obtain the compound to be foamed.

[0077] 4) The rubber compound to be foamed is pre-pressed on a flat vulcanizing machine to obtain a rubber sheet;

[0078] 5) The film is placed in a mold and subjected to a first-stage high-temperature vulcanization foaming at 120-220°C, preferably 150-170°C, and a second-stage vulcanization treatment at 170-230°C, preferably 180-220°C, and further preferably 180-200°C, to obtain the silicone rubber foam material.

[0079] In step 1), the mixture is kneaded in a kneader for a sufficient time to ensure thorough and uniform mixing of the silica, flame retardant (benzotriazole, transition metal two-dimensional sulfides), ceramic filler, ceramic-forming filler, and methyl vinyl silicone raw rubber. The structure control agent prevents the addition of silica and flame retardant, which could lead to structure formation, thus ensuring the processability and storage stability of the silicone rubber compound. Simultaneously, using an appropriate amount of release agent can improve the plasticity and release properties of the silicone rubber compound, preventing sticking to the rollers.

[0080] The purpose of maintaining the mixing temperature at 80-160℃ in step 2) is to improve the compatibility and distribution of fillers in the raw rubber, improve the flowability of the silicone rubber compound, achieve better processing plasticity, and reduce roller sticking.

[0081] The constant temperature mixing under negative pressure of -0.03 to -0.08 MPa in step 2) is to remove small molecules in silicone rubber, moisture in silica, and low-boiling-point byproducts generated during the mixing process, so as to obtain a silicone rubber compound with more stable performance.

[0082] In step 1), silica can be added to the kneader in batches and multiple times to be uniformly filled into the silicone rubber as a reinforcing filler.

[0083] In step 1), the first intensive mixing time can be 40 to 90 minutes.

[0084] In step 1), the second intensive mixing time can be 40 to 120 minutes.

[0085] In step 2), the constant temperature mixing time can be 60 to 80 minutes.

[0086] The aforementioned silicone rubber foam material uses methyl vinyl silicone raw rubber as the base material, with silica added as a reinforcing filler to ensure that the silicone rubber compound achieves good mechanical properties. Appropriate amounts of release agent and structure control agent are added to improve the processability and storage stability of the silicone rubber compound.

[0087] In step 3), when making base material A, inhibitors can be added to A first, followed by foaming agents and foaming aids, and finally catalysts. A two-roll open mill can be used, passing through the mill 2 to 3 times, then widening the roller gap and passing through the mill 2 to 5 times.

[0088] In step 3), when making base material B, a two-roll open mill can be used to pass through the material 2 to 3 times, and then the roller spacing can be widened and the material can be passed through the rollers 2 to 5 times.

[0089] In step 3), base material A and base material B can be mixed by passing them through a two-roll mill 10 to 18 times.

[0090] In step 4), the thickness of the film can be determined based on the free foaming thickness.

[0091] The target thickness of the foam material can be 0.7 to 1 times the free foaming thickness.

[0092] In some embodiments, the target thickness of the foam material may be greater than 10 mm. Further, the target thickness of the foam material may be greater than 60 mm.

[0093] The aforementioned silicone rubber foam material system and the corresponding preparation method are particularly suitable for preparing thick (the thickness can refer to a thickness greater than 10 mm, and further to a thickness greater than 60 mm) ceramicized high-temperature fireproof foam products. The prepared thick, ceramicized high-temperature fireproof foam products have a large number of cells with uniform pore size distribution, a smooth and flat surface, full contours, and a complete molded appearance.

[0094] In step 5), the time for the high-temperature vulcanization foaming can be 5 to 30 minutes, or more specifically 15 to 30 minutes.

[0095] In step 5), the time for the second-stage vulcanization treatment can be 1 to 5 hours, further 1 to 4 hours, and even further 1 to 2 hours.

[0096] In the ceramicized silicone rubber foam system containing the ceramicized filler composition described in this invention, regarding flame retardancy, benzotriazole and transition metal two-dimensional sulfides are used as compounded flame retardants; regarding strength, high molecular weight methyl vinyl silicone raw rubber is used as the base material to improve the mechanical strength of the foam material. By designing the vinyl content of the silicone raw rubber to control the crosslinking density of the foam material, the controllability of foam materials with different compressive strengths can be achieved. When preparing thick foam, the matching of platinum catalyst with benzotriazole and inhibitor is controlled. The three work together to ensure that the rubber compound has good fluidity before complete foaming and retains plasticity during foaming, which can fill the edge of the mold cavity. After full vulcanization, the foam material is fully formed, especially for mold forming, it can fill the mold cavity, resulting in foam products with complete shape, no dimensional shrinkage, and a smooth surface skin.

[0097] In terms of ceramization: Under high-temperature ablation conditions, the ceramic filler melts to generate a liquid phase. The SiO2 generated from the thermal decomposition of the foam material and the ceramic filler undergo molten eutectic reaction under the "bridging" effect of the liquid phase, forming a new eutectic. This eutectic exhibits higher high-temperature resistance and, upon cooling, forms a hard, dense ceramic shell on the surface of the foam material. Low-melting-point glass powder begins to melt during the decomposition of the foam material, promptly filling the voids created by the decomposition and connecting the SiO2 to prevent material detachment. At 1000℃, lithium carbonate not only provides a molten liquid phase to bond the ceramic filler and SiO2 into a continuous, dense whole, but also undergoes a eutectic reaction with mica powder, kaolin, wollastonite, and other ceramic fillers to generate Li(SiO3)2 crystals, and is also conducive to the formation of quartz crystals, thereby improving the ceramization performance of the foam material. The crystal phase of niobium pentoxide changes with increasing temperature, transforming from a tetragonal β-Nb₂O₅ to a high-temperature stable monoclinic α-Nb₂O₅. This phase transformation under high-temperature sintering conditions promotes anisotropic growth of α-Nb₂O₅, forming a microstructure of interwoven and overlapping fibrous crystals. These fine fibrous crystals act as a connecting skeleton, facilitating sufficient contact with the molten phase and enhancing the structural strength of the ceramic body. Furthermore, the presence of platinum catalyst and benzotriazole promotes free radical mechanisms, improving the flame retardancy and ceramic strength of the ceramicized silicone rubber foam, and positively impacting the mechanical properties of the ablated ceramic layer. Layered nano-magnesium aluminum hydrotalcite acts as a reinforcing "skeleton," with the sheets slipping through hydrogen bonds, increasing the foam's tensile toughness and preventing cracking under flame attack. This enhances the supporting strength and dimensional stability of the ablated ceramic body, resulting in a hard, intact, and high-strength ceramic body.

[0098] This invention optimizes the selection of raw materials, process formulation, and processing technology, using high-molecular-weight raw silica. While retaining the lightweight, high elasticity, and low compression set of room-temperature vulcanizing (RTV) silicone rubber foam, the high molecular weight of the raw silica compensates for the lower mechanical strength of RTV silicone rubber foam, resulting in high-temperature vulcanizing (HTV) silicone rubber foam. The crosslinking density is adjusted by controlling the molecular weight and vinyl content of the raw silica, achieving controllable hardness and compressive strength. A composite of low-melting-point glass powder, lithium carbonate, and niobium pentoxide synergistically enhances the ceramic composition, while nano-magnesium aluminum hydrotalcite acts as a connecting "skeleton" to strengthen cell stability. These components eutectic with the ceramic filler at high temperatures to form high-strength crystals, resulting in a dense, hard, and highly self-supporting ceramic body.

[0099] This invention employs benzotriazole and transition metal two-dimensional sulfides as compound flame retardants, achieving high-efficiency flame retardancy even with low addition amounts. Benzotriazole, a nitrogen-containing compound, acts as both a flame retardant and an inhibitor in the foam system of this invention. The platinum catalyst, used for addition-type silicone rubber foam, also contributes to flame retardancy. High-efficiency flame retardancy is achieved by adjusting the compatibility between the platinum catalyst and benzotriazole, and by compounding transition metal two-dimensional sulfides. Furthermore, the amount of inhibitor added is designed based on the inhibitory effect of benzotriazole, resulting in better crosslinking-foaming compatibility of silicone rubber when preparing thicker products, thus achieving excellent molding ability.

[0100] The foaming agent of this invention exhibits excellent dispersibility in silicone rubber compounds. It not only promotes heterogeneous nucleation in the foaming reaction, increasing the foaming ratio and achieving small pore size and high porosity, but also facilitates the condensation reaction between the hydroxyl groups on hydroxyapatite and hydrogen-containing silicone oil, further promoting foaming and increasing crosslinking density. Simultaneously, nano-magnesium-aluminum hydrotalcite plays a stabilizing role in the foam's pore structure, limiting excessive pore growth and preventing open-cell structures, thus ensuring a small pore size and high closed-cell structure in the foam material. The layered structure of the nano-magnesium-aluminum hydrotalcite hinders heat transfer at high temperatures, providing excellent thermal insulation. The synergistic effect of the foaming agent and nano-magnesium-aluminum hydrotalcite achieves both high porosity and high closed-cell ratio, resulting in excellent thermal insulation efficiency.

[0101] This invention utilizes a synergistic flame-retardant system of benzotriazole and transition metal two-dimensional sulfides. Based on this, it creatively optimizes the ratio of catalyst to benzotriazole and inhibitor to optimize the crosslinking-foaming matching of silicone rubber while ensuring high flame retardancy. This allows the final silicone rubber foam material to maintain excellent molding effect, flame retardant performance and comprehensive mechanical properties even at large thicknesses (e.g., thickness greater than 60 mm).

[0102] Compared with the prior art, the beneficial effects of this invention are as follows:

[0103] 1. The silicone rubber foam material of the present invention adds a low proportion of ceramic filler and ceramic aid filler, which has the advantages of low density, low hardness and high strength at room temperature. After ceramicization, it can form a ceramic body with hard texture and strong structural support, and has high mechanical strength.

[0104] 2. The silicone rubber foam material of this invention has high-efficiency flame retardant and heat insulation properties.

[0105] 3. The silicone rubber foam material of the present invention has a low linear shrinkage rate before and after ceramic formation.

[0106] 4. The silicone rubber foam material of this invention can achieve large thickness and adjustable compressive strength, meeting the special requirements under different usage conditions and is suitable for large-scale production.

[0107] 5. The silicone rubber foam material of the present invention has good storage stability, low process cost and high efficiency, and the raw materials and fillers used are non-toxic and low smoke. Attached Figure Description

[0108] Figure 1 The images show the cell distribution of the silicone rubber foam material in Example 1 and the ceramic body after ablation.

[0109] Figure 2 The images show the cell distribution of the silicone rubber foam material in Example 2 and the ceramic body after ablation.

[0110] Figure 3 The images show the cell distribution of the silicone rubber foam material in Example 3 and the ceramic body after ablation.

[0111] Figure 4 The image shows the cell distribution of the silicone rubber foam material in Comparative Example 1 and a photograph of the ceramic body after ablation.

[0112] Figure 5 The image shows the cell distribution of the silicone rubber foam material in Comparative Example 2 and the ceramic body after ablation.

[0113] Figure 6 The image shows the cell distribution of the silicone rubber foam material in Comparative Example 3 and the ceramic body after ablation.

[0114] Figure 7 The image shows the cell distribution of the silicone rubber foam material in Comparative Example 4 and the ceramic body after ablation.

[0115] Figure 8 The image shows the cell distribution of the silicone rubber foam material in Comparative Example 5 and the ceramic body after ablation. Detailed Implementation

[0116] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Operating methods not specifically specified in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer. Unless otherwise specified, the material quantities in the following embodiments and comparative examples refer to parts by weight, and the melting point of the low-melting-point glass powder is 320–650°C.

[0117] Example 1

[0118] Step 1: Preparation of foaming agent: Add 10 parts of sorbitan monostearate with an HLB of 4.7 to 100 parts of α,ω-dihydroxy-terminated polydimethylsiloxane with a molecular weight of 5000 g / mol and a hydroxyl content of 2%. Stir at 2000 rpm for 10 min in a 50°C water bath. Then add 5 parts of hydroxyapatite and stir for 8 min. Next, add 80 parts of deionized water dropwise while stirring. Finally, stir at 2500 rpm for 18 min to obtain the foaming agent.

[0119] Step 2: Preparation of nano-magnesium aluminum hydrotalcite: Add 2.6 parts magnesium nitrate and 1.9 parts aluminum nitrate to 100 parts deionized water, stir at 1800 rpm for 8 min to prepare salt solution A. Add 0.8 parts aluminum hydroxide and 1.9 parts sodium bicarbonate to 100 parts deionized water, stir at 1500 rpm for 10 min to prepare alkaline solution B. At room temperature, quickly add alkaline solution B to salt solution A at 1300 rpm to adjust the pH to 9.5, stir for 25 min, and then transfer the mixture to a reaction vessel. The reaction vessel is then placed in a 150℃ oven for 10 h. After cooling, the solid and liquid phases are separated by centrifugation at 4000 rpm for 5 min. The centrifuged product is dried in a 90℃ oven to obtain the final product, nano-magnesium aluminum hydrotalcite.

[0120] Step 3: Mix 70 parts of vinyl with a molar content of 0.08% and a molecular weight of 48×10 4 A g / mol methyl vinyl silicone rubber raw material, with a vinyl molar content of 0.22% and a molecular weight of 72 × 10⁻⁶ g / mol, is used in 30 parts of this raw material. 4 18 parts of methyl vinyl silicone rubber raw material with a specific surface area of ​​130 m² / mol g / mol 2 / g of precipitated silica, 18 parts of which have a specific surface area of ​​180m² 2 / g of precipitated silica, 5 parts of hydroxyl silicone oil with a hydroxyl content of 6% by mass are added to a kneader and mixed in an intensive kneader. The silica is added in multiple batches. After the last batch of filler is added, the mixture is continued to be intensively kneaded for 40 minutes to ensure that the rubber compound is mixed evenly.

[0121] Step 4: Add 8 parts mica powder, 15 parts low melting point glass powder, 6 parts lithium carbonate, 8 parts niobium pentoxide, 0.5 parts benzotriazole, 1.2 parts tungsten disulfide, 3.5 parts nano magnesium aluminum hydrotalcite and 0.15 parts zinc stearate to a kneader and knead for 40 minutes after adding the last batch of fillers.

[0122] Step 5: Heat the kneader chamber temperature to 150℃, and knead at a constant temperature for 60 minutes under a negative pressure of -0.05MPa. Then, maintain the vacuum and begin cooling for 30 minutes. After cooling, the silicone rubber compound is obtained. The compound is used for foaming after being left overnight for more than 12 hours.

[0123] Step 6: Divide the obtained silicone rubber compound into two equal parts, A and B. Take part A of the silicone rubber compound and grind it on a two-roll mill. Add 0.03 parts of acetylenecyclohexanol, 5 parts of ethylene glycol, 0.7 parts of the foaming agent from step 1 and 0.5 parts of caster catalyst. Pass through the mill 2 to 3 times to mix evenly. Adjust the roller spacing to produce sheet to obtain base material A.

[0124] Step 7: Take part B of silicone rubber compound and grind it on a two-roll mill. Add 3.5 parts of hydrogen-containing silicone oil with a hydrogen content of 1.5% by mass. Pass it through the two-roll mill 2-3 times to mix evenly. Adjust the roller spacing to obtain the base material B.

[0125] Step 8: Mix base material A and base material B on a two-roll mill 10 to 18 times, and roll them to obtain the foamed compound.

[0126] Step 9: Pre-press the rubber compound to be foamed on a flat vulcanizing machine to obtain a 6.0mm rubber sheet;

[0127] Step 10: Place the prepared film into a 150℃ forced-air drying oven for high-temperature foaming and vulcanization for 20 minutes, then perform secondary vulcanization at 190℃ for 1.5 hours to obtain high-temperature vulcanized silicone rubber foam material. Its cell distribution and the ceramic body after ablation are as follows... Figure 1 As shown, various performance tests were conducted.

[0128] Example 2

[0129] Step 1: Preparation of foaming agent: Add 10 parts of dehydrated sorbitol fatty acid ester with an HLB of 4.3 to 100 parts of α,ω-dihydroxy-terminated polydimethylsiloxane with a molecular weight of 4000 g / mol and a hydroxyl content of 3%. Stir at 1800 rpm for 15 min in a 55℃ water bath. Then add 5 parts of hydroxyapatite and stir for 10 min. Next, add 80 parts of deionized water dropwise while stirring. Finally, stir at 2300 rpm for 15 min to obtain the foaming agent.

[0130] Step 2: Preparation of nano-magnesium aluminum hydrotalcite: Add 2.7 parts magnesium nitrate and 2.1 parts aluminum nitrate to 100 parts deionized water, stir at 1500 rpm for 10 min to prepare salt solution A. Add 0.9 parts aluminum hydroxide and 2.1 parts sodium bicarbonate to 100 parts deionized water, stir at 2000 rpm for 8 min to prepare alkaline solution B. At room temperature, quickly add alkaline solution B to salt solution A at 1300 rpm to adjust the pH to 9.1, stir for 25 min, and then transfer the mixed solution to a reaction vessel. The reaction vessel is then placed in a 150℃ oven for 10 h. After cooling, the solid and liquid phases are separated by centrifugation at 4500 rpm for 3 min. The centrifuged product is dried in a 70℃ oven to obtain the final product, nano-magnesium aluminum hydrotalcite.

[0131] Step 3: 85 parts of vinyl with a molar content of 0.09% and a molecular weight of 48 × 10⁻⁶ 4 A g / mol methyl vinyl silicone rubber raw material, with a vinyl molar content of 0.15% and a molecular weight of 72 × 10⁻⁶ g / mol. 4 20 parts of methyl vinyl silicone rubber raw material with a specific surface area of ​​130 m² / mol g / mol have a specific surface area of ​​130 m² / mol. 2 / g of precipitated silica, 18 parts of which have a specific surface area of ​​180m² 2 / g of precipitated silica, 5 parts of hydroxyl silicone oil with a hydroxyl content of 6% by mass are added to a kneader and mixed in an intensive kneader. The silica is added in multiple batches. After the last batch of filler is added, the mixture is continued to be intensively kneaded for 40 minutes to ensure that the rubber compound is mixed evenly.

[0132] Step 4: Add 6 parts kaolin, 11 parts low melting point glass powder, 4 parts lithium carbonate, 5 parts niobium pentoxide, 0.6 parts benzotriazole, 0.8 parts molybdenum disulfide, 2 parts nano magnesium aluminum hydrotalcite and 0.15 parts zinc stearate to a kneader and knead for 40 minutes after adding the last batch of fillers.

[0133] Step 5: Heat the kneader chamber temperature to 150℃, and knead at a constant temperature for 60 minutes under a negative pressure of -0.05MPa. Then, maintain the vacuum and begin cooling for 30 minutes. After cooling, the silicone rubber compound is obtained. The compound is used for foaming after being left overnight for more than 12 hours.

[0134] Step 6: Divide the obtained silicone rubber compound into two equal parts, A and B. Take part A of the silicone rubber compound and grind it on a two-roll mill. Add 0.03 parts of acetylenecyclohexanol, 5 parts of ethylene glycol, 0.7 parts of the foaming agent from step 1 and 0.55 parts of caster catalyst. Pass through the mill 2 to 3 times to mix evenly. Adjust the roller spacing to produce sheet to obtain base material A.

[0135] Step 7: Take part B of silicone rubber compound and grind it on a two-roll mill. Add 3.5 parts of hydrogen-containing silicone oil with a hydrogen content of 1.5% by mass. Pass it through the two-roll mill 2-3 times to mix evenly. Adjust the roller spacing to obtain the base material B.

[0136] Step 8: Mix base material A and base material B on a two-roll mill 10 to 18 times, and roll them to obtain the foamed compound.

[0137] Step 9: Pre-press the rubber compound to be foamed on a flat vulcanizing machine to obtain a 50mm rubber sheet;

[0138] Step 10: Place the film into the mold and perform high-temperature foaming and vulcanization in a 170℃ forced-air drying oven for 30 minutes. Then, perform secondary vulcanization at 180℃ for 2 hours to obtain the high-temperature vulcanized silicone rubber foam material. The cell distribution and the photograph of the ceramic body after ablation are shown below. Figure 2 As shown, various performance tests were conducted.

[0139] Example 3

[0140] Step 1: Preparation of foaming agent: Add 6 parts of sorbitan tristearate with an HLB of 2.1 to 100 parts of α,ω-dihydroxy-terminated polydimethylsiloxane with a molecular weight of 5000 g / mol and a hydroxyl content of 2%. Stir at 2000 rpm for 12 min in a 55°C water bath. Then add 5 parts of hydroxyl wollastonite and stir for 12 min. Next, add 75 parts of deionized water dropwise while stirring. Finally, stir at 2400 rpm for 17 min to obtain the foaming agent.

[0141] Step 2: Preparation of nano-magnesium aluminum hydrotalcite: Add 2.4 parts magnesium nitrate and 2.0 parts aluminum nitrate to 100 parts deionized water, stir at 2000 rpm for 10 min to prepare salt solution A. Add 0.7 parts aluminum hydroxide and 1.9 parts sodium bicarbonate to 100 parts deionized water, stir at 2000 rpm for 10 min to prepare alkaline solution B. At room temperature, quickly add alkaline solution B to salt solution A at 1500 rpm to adjust the pH to 10, stir for 30 min, and then transfer the mixture to a reaction vessel. The reaction vessel is then placed in a 150℃ oven for 10 h. After cooling, the solid and liquid phases are separated by centrifugation at 5000 rpm for 2 min. The centrifuged product is dried in an 80℃ oven to obtain the final product, nano-magnesium aluminum hydrotalcite.

[0142] Step 3: 90 parts of vinyl with a molar content of 0.08% and a molecular weight of 50 × 10⁻⁶ 4 A g / mol methyl vinyl silicone rubber raw material, with a vinyl molar content of 0.23% and a molecular weight of 70 × 10⁻⁶ g / mol. 4 22 parts of methyl vinyl silicone rubber raw material with a specific surface area of ​​120 m² / mol g / mol 2 / g of precipitated silica, 23 parts of which have a specific surface area of ​​160m² 2 / g of precipitated silica, 6 parts of hydroxyl silicone oil with a hydroxyl content of 4% by mass are added to a kneader and mixed in an intensive kneader. The silica is added in multiple batches. After the last batch of filler is added, the mixture is continued to be intensively kneaded for 40 minutes to ensure that the rubber compound is mixed evenly.

[0143] Step 4: Add 4 parts wollastonite, 8 parts low melting point glass powder, 5 parts lithium carbonate, 4 parts niobium pentoxide, 0.55 parts benzotriazole, 1.5 parts tungsten disulfide, 1.5 parts nano magnesium aluminum hydrotalcite and 0.13 parts zinc stearate to a kneader and knead for 40 minutes after adding the last batch of fillers.

[0144] Step 5: Heat the kneader chamber temperature to 145℃, and knead at a constant temperature for 60 minutes under a negative pressure of -0.06MPa. Then, maintain the vacuum and begin cooling for 30 minutes. After cooling, the silicone rubber compound is obtained. The compound is used for foaming after being left overnight for more than 12 hours.

[0145] Step 6: Divide the obtained silicone rubber compound into two equal parts, A and B. Take part A of the silicone rubber compound and grind it on a two-roll mill. Add 0.04 parts of acetylenecyclohexanol, 4 parts of hydroxytyrosol, 0.9 parts of the foaming agent from step 1 and 0.6 parts of caster catalyst. Pass through the mill 2 to 3 times to mix evenly. Adjust the roller spacing to produce sheet to obtain base material A.

[0146] Step 7: Take part B of silicone rubber compound and mill it on a two-roll mill. Add 4.5 parts of hydrogen-containing silicone oil with a hydrogen content of 1.2%. Pass the mixture through the two-roll mill 2-3 times to mix evenly. Adjust the roller spacing to obtain sheet material B.

[0147] Step 8: Mix base material A and base material B on a two-roll mill 14 to 17 times, and roll them to obtain the foamed compound.

[0148] Step 9: Pre-press the rubber compound to be foamed on a flat vulcanizing machine to obtain a 41.0mm rubber sheet;

[0149] Step 10: Place the film into the mold and perform high-temperature foaming and vulcanization in a 170℃ forced-air drying oven for 15 minutes. Then, perform secondary vulcanization at 200℃ for 1 hour to obtain high-temperature vulcanized silicone rubber foam material. Its cell distribution and the ceramic body after ablation are as follows: Figure 3 As shown, various performance tests were conducted.

[0150] Comparative Example 1

[0151] The only difference from Example 1 is that mica powder was not added in step 4. The resulting high-temperature vulcanized silicone rubber foam material exhibits a different cell distribution and a more uniform ceramic body after ablation. Figure 4 As shown.

[0152] Comparative Example 2

[0153] The only difference from Example 2 is that low-melting-point glass powder was not added in step 4. The resulting high-temperature vulcanized silicone rubber foam material exhibits a different cell distribution and a more uniform ceramic body after ablation. Figure 5 As shown.

[0154] Comparative Example 3

[0155] The only difference from Example 2 is that lithium carbonate was not added in step 4. The resulting high-temperature vulcanized silicone rubber foam material exhibits a different cell distribution and a more uniform ceramic body after ablation. Figure 6 As shown.

[0156] Comparative Example 4

[0157] The only difference from Example 3 is that niobium pentoxide is not added in step 4. The resulting high-temperature vulcanized silicone rubber foam material exhibits a different cell distribution and a more uniform ceramic body after ablation. Figure 7 As shown.

[0158] Comparative Example 5

[0159] The only difference from Example 3 is that nano-magnesium aluminum hydrotalcite is not added in step 4. The resulting high-temperature vulcanized silicone rubber foam material exhibits different cell distribution and ceramic structure after ablation. Figure 8 As shown.

[0160] Performance testing

[0161] Performance tests of foam materials were conducted according to national standards. The standards for hardness testing were GB / T 10807-2006, apparent density testing was GB / T 6343-2009, flame retardancy testing was GB / T 10707-2008, compressive stress-strain testing was GB / T 18942.1-2003, compression set testing was GB / T 6669-2008 / ISO 1856:2000, and ceramic body flexural strength testing was GB / T 6569-2006. The test sample size was 100mm × 10mm × 10mm. The sample was placed in a tube furnace for ablation at a heating rate of 10℃ / min, and ablated at 1000℃ for 1 hour. The sample was then removed, and the linear shrinkage rate and flexural strength were tested. The tensile stress-strain performance testing standard was GB / T 10807-2009. 528-2009, the ablation test sample was 70mm long × 70mm wide and 10mm thick, and was ablated for 30min in a butane flame at 1300℃.

[0162] The performance test results of the high-temperature vulcanized silicone rubber foam materials provided in the above embodiments and comparative examples are shown in Table 1 below.

[0163] Table 1

[0164]

[0165] According to Table 1:

[0166] Compared with Example 1, Comparative Example 1 did not add mica powder. The density and hardness of the silicone rubber foam decreased, while the tensile strength increased. However, the bending strength decreased after ceramization, and severe cracking occurred upon ablation. This is because when the low-melting-point glass powder and lithium carbonate melt at high temperatures, there is a lack of ablation-resistant ceramic fillers to undergo eutectic reactions with these liquid phases, making it impossible to form a ceramic body with a certain strength. As the ablation time increases, the liquid phase continues to volatilize, leaving a large amount of white SiO2 powder on the ablation surface. The residual body has low strength, leading to cracking of the ceramic body and a reduction in strength.

[0167] Compared to Example 2, Comparative Example 2 did not add low-melting-point glass powder. The foam cracked significantly at the beginning of the ablation process because, at the start of the flame impact, the lack of rapid melting and filling of the gaps by low-melting-point glass powder, which connects the SiO2 powder, ceramic filler, and other high-melting-point ceramic additives, and provides a "bridging" effect in the early stages of ablation, resulted in large cracks in the foam under flame impact. This prevented the formation of a dense, continuous ceramic body after ablation, leading to a severe decrease in strength.

[0168] Compared to Example 2, Comparative Example 3 did not add lithium carbonate. Under continuous flame impact, the low-melting-point glass powder was gradually consumed, and at higher temperatures, the lack of molten lithium carbonate phase to fill the ablation gaps in time. At the same time, the lack of lithium carbonate to form Li(SiO3)2 crystals at high temperatures and to promote the formation of quartz resulted in some microcracks appearing on the ablation surface, leading to a decrease in the strength of the ceramic body.

[0169] Compared with Example 3, Comparative Example 4 did not add niobium pentoxide. Although no cracks were generated after foam ablation, the bending strength of the ceramic body was significantly reduced. This was because the lack of fibrous crystals formed by the anisotropic growth of niobium pentoxide at high temperature as a connecting skeleton caused the bending strength of the ceramic body to drop sharply.

[0170] Compared to Example 3, Comparative Example 5 did not contain nano-magnesium aluminum hydrotalcite. Without the restriction of pore size by the nano-magnesium aluminum hydrotalcite, the pore size increased. During flame attack, the lack of the reinforcing effect between the magnesium aluminum hydrotalcite layers resulted in severe cracking of the foam surface. The flame continued to attack along the cracks, leading to the ablation of the foam surface and the formation of large cracks. The foam then deformed towards these ablation cracks.

[0171] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A silicone rubber foam material, characterized by, The raw material composition includes, in mass fraction: methyl vinyl silicone gum 100 parts, white carbon black 20-80 parts, structure control agent 2-10 parts, benzotriazole 0.1-0.7 parts, transition group metal two-dimensional sulfide 0.1-2.5 parts, mold release agent 0.05-0.5 parts, hydrogen-containing silicone oil 1-10 parts, foaming agent 1-10 parts, catalyst 0.2-0.7 parts, inhibitor 0.01-0.06 parts, foaming aid 0.5-2 parts, nano magnesium-aluminum hydrotalcite 1-5 parts, auxiliary ceramic filler 13-35 parts, ceramic filler 3-12 parts; the catalyst is a platinum catalyst; the ratio of the mass of the catalyst to the total mass of the benzotriazole and the inhibitor is 1:0.4-1.2; the preparation method of the foaming aid includes the steps of: S1. uniformly mixing α, ω-dihydroxyl-terminated polydimethylsiloxane and a surfactant to obtain an emulsion; S2. uniformly mixing the emulsion with hydroxyapatite and deionized water to obtain the foaming aid in the form of an emulsion; The nano magnesium-aluminum hydrotalcite is in a sheet layer shape, and the surface hydroxyl density is 6-9 per nm 2 ; the auxiliary ceramic filler includes, in mass fraction: low-melting-point glass powder 6-20 parts, lithium carbonate 2-7 parts, niobium pentoxide 3-8 parts; the melting point of the low-melting-point glass powder is 320-650 ℃; the ceramic filler includes one or more of titanium dioxide, mica powder, wollastonite, montmorillonite, diatomite, and kaolin.

2. The silicone rubber foam material according to claim 1, characterized in that, The mass ratio of the nano magnesium-aluminum hydrotalcite, the auxiliary ceramic filler, and the ceramic filler is 1-4:13-32:4-8; the mass ratio of the low-melting-point glass powder, lithium carbonate, and niobium pentoxide is 6-18:3-6:4-8.

3. The silicone rubber foam of claim 1, wherein, The preparation method of the nano magnesium-aluminum hydrotalcite includes: dissolving magnesium nitrate and aluminum nitrate in deionized water to prepare a salt solution A; dissolving aluminum hydroxide and sodium bicarbonate in deionized water to prepare a base solution B; at room temperature, adding the base solution B to the stirring salt solution A, uniformly stirring, and then loading the obtained mixed solution into a reaction kettle, subsequently placing the reaction kettle in a 130-160 ℃ environment for reaction, after the reaction is completed, performing solid-liquid separation, and drying the obtained solid to obtain the nano magnesium-aluminum hydrotalcite.

4. The silicone rubber foam according to claim 3, characterized in that, In the preparation method of the nano magnesium-aluminum hydrotalcite: in the salt solution A, the mass ratio of deionized water, magnesium nitrate, and aluminum nitrate is 100:2.1-2.9:1.5-2.2; in the base solution B, the mass ratio of deionized water, aluminum hydroxide, and sodium bicarbonate is 100:0.6-1:1.8-2.4; stirring is performed during the preparation of the salt solution A, the stirring speed is 1500-2000 rpm, and the stirring time is 8-10 min; stirring is performed during the preparation of the base solution B, the stirring speed is 1500-2000 rpm, and the stirring time is 8-10 min; during the addition of the base solution B to the stirring salt solution A, the stirring speed of the salt solution A is 1300-1500 rpm; the uniformly stirring time is 20-30 min; adding the base solution B to the stirring salt solution A makes the pH of the mixed solution 9-10; subsequently, the reaction kettle is placed in a 130-160 ℃ environment for reaction for 8-10 h; The solid-liquid separation adopts centrifugal separation, the centrifugal rotation speed is 4000-5000 rpm, and the time length is 2-5 min; The obtained solid is dried at 70-90 ℃ to obtain the nano magnesium-aluminum hydrotalcite.

5. The silicone rubber foam according to claim 4, wherein, In the preparation method of the nano magnesium-aluminum hydrotalcite: In the salt solution A, the mass ratio of deionized water, magnesium nitrate and aluminum nitrate is 100:2.4-2.7:1.8-2.1; In the alkali solution B, the mass ratio of deionized water, aluminum hydroxide and sodium bicarbonate is 100:0.7-0.9:1.9-2.

1.

6. The silicone rubber foam of claim 3, wherein, In the preparation method of the nano magnesium-aluminum hydrotalcite: then the reaction kettle is placed at 150 ℃ for reaction.

7. The silicone rubber foam of claim 1, wherein, The methyl vinyl silicone raw rubber has a vinyl molar content of 0.03% to 3%; the molecular weight of the methyl vinyl silicone raw rubber is 45 x 10 4 ~85 x 10 4 g / mol. The white carbon black includes at least one of precipitated white carbon black and fumed white carbon black; the specific surface area of the white carbon black is 120-420 m 2 / g; The structuring control agent comprises hydroxyl silicone oil; the mass content of hydroxyl groups of the hydroxyl silicone oil is 4%-10%; The mass ratio of the benzotriazole to the inhibitor is 1:0.03-0.09; The transition group metal two-dimensional sulfide comprises at least one of tungsten disulfide, molybdenum disulfide and titanium disulfide; The release agent comprises a stearic acid compound; In the raw material composition, the hydrogen-containing silicone oil is 2-8 parts by mass; The hydrogen mass content of the hydrogen-containing silicone oil is 0.5%-1.5%; In the raw material composition, the foaming agent is 2-8 parts by mass; The foaming agent comprises one or more of glycerol, hydroxytyrosol, ethylene glycol, n-butanol and pentaerythritol; In the raw material composition, the catalyst is 0.3-0.6 parts by mass; The catalyst comprises a Kast catalyst; The mass ratio of the catalyst to the total mass of the benzotriazole and the inhibitor is 1:0.9-1.2; The inhibitor comprises one or more of ethynylcyclohexanol, methylbutynol, tert-butylcyclohexanol and phenylbutynol; In the preparation method of the foaming aid: The mass ratio of the alpha, omega-dihydroxyl-terminated polydimethylsiloxane, the surfactant, the hydroxyapatite and the deionized water is 100:5-15:1-9:50-100; The molecular weight of the alpha, omega-dihydroxyl-terminated polydimethylsiloxane is 1200-5000 g / mol, and the mass content of hydroxyl groups is 0.2%-8%; The HLB value of the surfactant is 2-5, and the surfactant comprises at least one of sorbitan tristearate, sorbitan monostearate and sorbitan fatty acid ester; In step S1, the temperature of the mixing is 50-55 ℃; the mixing is accompanied by stirring, wherein: the stirring rotation speed is 1500-2000 rpm, and the stirring time is 8-15 min; In step S2, the particle size of the hydroxyapatite is 10-80 μm; In step S2, the hydroxyapatite and the deionized water are added into the emulsion in sequence, and stirring is performed during the adding, the stirring rotation speed is 1500-2000 rpm after the hydroxyapatite is added, the stirring time is 8-15 min, the deionized water is added dropwise while stirring, the stirring rotation speed is 2200-2500 rpm after the dropwise adding is completed, and the stirring is continuously performed for 15-20 min, to obtain the foaming aid in the form of emulsion; In the raw material composition, the nano magnesium-aluminum hydrotalcite is 1-4 parts by mass; The auxiliary ceramic filler is 13-32 parts by mass in the raw material composition; The ceramic filler is 4-8 parts by mass in the raw material composition; The low-melting-point glass powder is 6-18 parts by mass in the auxiliary ceramic filler; The lithium carbonate is 3-6 parts by mass in the auxiliary ceramic filler; The niobium pentoxide is 4-8 parts by mass in the auxiliary ceramic filler.

8. The silicone rubber foam of claim 7, wherein, The specific surface area of the white carbon black is 120-220 m 2 / g; The hydroxyl mass content of the hydroxyl silicone oil is 4%-8%; The hydrogen mass content of the hydrogen-containing silicone oil is 1.0%-1.5%; The preparation method of the foaming aid comprises the following steps: The mass ratio of the α, ω-di-hydroxyl terminated polydimethylsiloxane, the surfactant, the hydroxyapatite and the deionized water is 100:6-12:1-6:60-100; The hydroxyl mass content of the α, ω-di-hydroxyl terminated polydimethylsiloxane is 2%-6%.

9. Process for the production of a silicone rubber foam material according to any one of claims 1 to 8, characterized in that The method comprises the following steps: 1) adding methyl vinyl silicone gum, white carbon black and structure control agent into a kneader for first-time mixing, then adding benzotriazole, transition metal two-dimensional sulfide, auxiliary ceramic filler, ceramic filler, nano magnesium-aluminum hydrotalcite and release agent for second-time mixing; 2) increasing the temperature of the kneader cabin to 80-160 DEG C, and uniformly mixing under the constant temperature mixing under the negative pressure environment of-0.03 to-0.08 MPa, to obtain silicone rubber mixing rubber; 3) dividing the silicone rubber mixing rubber into two parts A and B, wherein part A is mixed with inhibitor, foaming agent, foaming aid and catalyst on an open mill to obtain base A, and part B is mixed with hydrogen-containing silicone oil on an open mill to obtain base B, and the base A and the base B are mixed on an open mill to obtain a to-be-foamed mixing rubber; 4) pre-pressing the to-be-foamed mixing rubber on a flat vulcanizing machine to obtain a rubber sheet; 5) placing the rubber sheet into a mold for one-stage high-temperature vulcanization foaming at 120-220 DEG C and two-stage vulcanization treatment at 170-230 DEG C to obtain the silicone rubber foam material.

10. The method of claim 9, wherein, In step 1): The white carbon black is added into the kneader in batches and for multiple times; The first-time mixing time is 40-90 minutes; The second-time mixing time is 40-120 minutes; In step 2), the constant temperature mixing time is 60-80 minutes; In step 3): When preparing the base A, the inhibitor is added first, then the foaming agent and the foaming aid, and finally the catalyst, a double-roller open mill is adopted, and the rubber is passed through the mill 2-3 times, then the roller spacing is adjusted, and the rubber is passed through the mill 2-5 times; When preparing the base B, a double-roller open mill is adopted, and the rubber is passed through the mill 2-3 times, then the roller spacing is adjusted, and the rubber is passed through the mill 2-5 times; The base A and the base B are mixed on a double-roller open mill for 10-18 times; In step 4), the thickness of the rubber sheet is determined according to the free foaming thickness; The target thickness of the foam material is greater than 10 mm; In step 5): The rubber sheet is placed into a mold for one-stage high-temperature vulcanization foaming at 150-170 DEG C and two-stage vulcanization treatment at 180-220 DEG C; The one-stage high-temperature vulcanization foaming time is 5-30 minutes; The two-stage vulcanization treatment time is 1-5 hours.

11. The method of claim 10, wherein, In step 4), the target thickness of the foam material is greater than 60 mm; In step 5): The time of the high-temperature vulcanization foaming is 15-30 minutes; The temperature of the second vulcanization treatment is 180-200℃; The time of the second vulcanization treatment is 1-4 hours.

12. The method of claim 11, wherein, In step 5): The time of the second vulcanization treatment is 1-2 hours.

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