Silicon solid disulfide-free silica gel and preparation method thereof

Abstract

This invention belongs to the field of polymer materials technology, specifically relating to a silicon solid disulfide-free silica gel and its preparation method. The preparation method includes: heating α,ω-dihydroxypolydimethylsiloxane for vacuum dehydration, cooling it, adding silica, vanadium-doped cobalt-based imidazole zeolite framework, and imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite, and mixing under vacuum to obtain a base material; then cooling the base material, adding alkyl-terminated polydimethylsiloxane, methyl tributanone oxime silane, and dibutyltin dilaurate, and stirring under vacuum to obtain the final product. This invention, through the synergistic effect of two novel inorganic modifying compounds, achieves excellent mechanical properties and thermal stability after a single vulcanization, eliminating the need for a second vulcanization stage, simplifying the process, reducing energy consumption, and making it suitable for fields such as electronics, electrical appliances, and the automotive industry.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a silicon solid disulfide-free silica gel and its preparation method. Background Technology

[0002] Silicone rubber is a high-performance organic polymer material widely used in electronics, automotive, medical devices, and aerospace industries due to its excellent high and low temperature resistance, weather resistance, electrical insulation, and physiological inertness. In the production of silicone rubber products, vulcanization is a crucial step determining the final performance. This process chemically crosslinks the linear silicone rubber molecular chains, forming a three-dimensional network structure, thus endowing the material with good mechanical strength and elasticity. However, traditional high-temperature vulcanization of silicone rubber is not completed in one step but is divided into two stages: primary vulcanization and secondary vulcanization. Primary vulcanization is usually carried out under pressure to initially shape the rubber compound and complete basic crosslinking; secondary vulcanization is a subsequent treatment carried out in a high-temperature oven based on primary vulcanization. Its core purpose is to remove low-molecular-weight byproducts generated by the decomposition of the vulcanizing agent and further improve the crosslinking network to stabilize and enhance the overall performance of the product.

[0003] While two-stage vulcanization is crucial for improving the physical and mechanical properties of silicone rubber, reducing compression set, and ensuring the stability of products in high-temperature or clean environments, the process itself has significant limitations. First, two-stage vulcanization is an energy-intensive and time-consuming heat treatment process, typically requiring several hours at around 200 degrees Celsius, directly leading to extended production cycles and significantly increased manufacturing costs. Second, high-temperature treatment can cause yellowing in silicone rubber products, especially transparent or light-colored products, affecting their appearance and optical properties. Studies have shown that acidic impurities in silica, residual alkaline treatment agents, and excessively high vulcanization temperatures and times can all induce or exacerbate yellowing. Furthermore, for certain heat-sensitive substrates or products composited with other materials, the high-temperature conditions of two-stage vulcanization can cause irreversible thermal damage, thus limiting the application range of silicone rubber.

[0004] Therefore, simplifying the vulcanization process while ensuring or even improving the performance of silicone rubber products and effectively avoiding the drawbacks of two-stage vulcanization has always been a hot topic in the industry's research and development. The key to achieving "diceurization-free" vulcanization lies in formula design. On the one hand, it involves optimizing the crosslinking system to form a structurally sound and stable crosslinking network in a single vulcanization process. On the other hand, it requires the introduction of functional additives that can scavenge or neutralize free radicals and acidic byproducts generated by peroxide decomposition during vulcanization, while simultaneously enhancing the interfacial bonding between the filler and the matrix, thereby improving the overall performance of the material after single vulcanization. Developing novel modified compounds that can synergistically achieve these functions to address this technical need is of significant practical importance and industrial value for advancing silicone rubber processing technology and expanding its application areas. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a silicon solid disulfide-free silica gel and its preparation method.

[0006] In a first aspect, the present invention provides a method for preparing a silicon solid disulfide-free silica gel, comprising the following steps: S1. By weight, add 98-102 parts of α,ω-dihydroxypolydimethylsiloxane to a vacuum kneader, heat, and dehydrate; cool down, add 20-40 parts of silica, 0.5-3.0 parts of vanadium-doped cobalt-based imidazole zeolite framework, and 2.0-8.0 parts of imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite, and continue mixing under vacuum to obtain the base material; S2. Cool the base material to room temperature, transfer it to a planetary mixer, add 1-5 parts of alkyl-terminated polydimethylsiloxane and stir; then add 3-8 parts of methyltributyl ketone oxime silane and stir; finally add 0.05-0.5 parts of dibutyltin dilaurate and stir under vacuum.

[0007] In this invention, the preparation of the silicon solid disulfide-free silica gel uses α,ω-dihydroxypolydimethylsiloxane as the base gel, which undergoes dehydration treatment to ensure low volatile content. The base gel is heated and dehydrated in a vacuum kneader. After removing moisture, it is cooled, and then silica, vanadium-doped cobalt-based imidazole zeolite framework, and imidazole-based polyborosiloxane-intercalated sulfonated hydrotalcite are added and mixed under vacuum. The mixture is then transferred to a planetary mixer, where alkyl-terminated polydimethylsiloxane is added as a plasticizer and stirred until homogeneous. Methyltributanone oxime silane is then added as a vulcanizing agent to initiate a condensation reaction. Methyltributanone oxime silane reacts with the hydroxyl groups of the silica gel to form a silicon-oxygen bond network, simultaneously releasing byproducts. In vanadium-doped cobalt-based imidazole zeolite, vanadium in the framework catalyzes the decomposition of byproduct free radicals through multivalent state changes, reducing damage to the polymer backbone. In imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite, polyborosiloxane segments form chemical bonds with the matrix, enhancing interfacial bonding and simultaneously adsorbing and immobilizing byproducts to prevent their migration. Finally, an organotin catalyst promotes the perfection of the cross-linking network. The entire process eliminates the need for secondary vulcanization; high-mechanical-performance, high-heat-resistant silicone rubber can be obtained with a single vulcanization process, achieving a di-vulcanization-free process, significantly simplifying the production flow and enhancing the material's application value in precision electronics.

[0008] According to a preferred embodiment of the present invention, in step S1, the temperature is heated to 110-130°C and then cooled to 80-100°C.

[0009] According to a preferred embodiment of the present invention, in step S2, the alkyl-terminated polydimethylsiloxane is selected from one or more of methoxy-terminated dimethyl polysiloxane and ethoxy-terminated dimethyl polysiloxane.

[0010] According to a preferred embodiment of the present invention, the preparation method of the vanadium-doped cobalt-based imidazole zeolite framework includes: A1, dissolving 90-110 parts by weight of cobalt nitrate hexahydrate and 4-20 parts by weight of vanadium oxysulfate hydrate in methanol to obtain metal salt solution A; dissolving 50-150 parts by weight of 2-methylimidazole in methanol to obtain ligand solution B; mixing ligand solution B with metal salt solution A under stirring, and continuing stirring to obtain a mixed solution; transferring the mixed solution to a high-pressure reactor and solvothermal reaction at 100-120°C; A2, after the reaction is completed, naturally cooling to room temperature, obtaining a precipitate by centrifugation, washing the precipitate with methanol, and vacuum drying at 60-100°C.

[0011] In this invention, the core of the preparation of the vanadium-doped cobalt-based imidazole zeolite framework lies in the coordination self-assembly process of metal ions and organic ligands. Cobalt and vanadium salts are dissolved in methanol to form a metal salt solution containing cobalt and vanadium ions; simultaneously, imidazole ligands are dissolved in methanol to form a ligand solution. Under vigorous stirring, the ligand solution is rapidly poured into the metal salt solution, initiating an instantaneous coordination reaction and forming a homogeneous mixed solution. This mixed solution undergoes a solvothermal reaction in a high-pressure reactor. By controlling the temperature and time, the metal ions and ligand molecules are encouraged to self-assemble through coordination bonds, forming a metal-organic framework with a regular porous structure. Vanadium, as a dopant, replaces some cobalt sites and is uniformly distributed within the framework, significantly improving the structural thermal stability and catalytic activity. After the reaction, the mixture is naturally cooled to room temperature, centrifuged to obtain a precipitate, repeatedly washed with methanol until neutral to remove unreacted ions and impurities, and finally dried under vacuum to obtain a high-purity vanadium-doped cobalt-based imidazole zeolite framework. This framework, with its ordered pores and vanadium doping characteristics, provides a stable carrier for subsequent functional applications.

[0012] According to a preferred embodiment of the present invention, in step A1, the solvothermal reaction time at 100-120°C is 10-24 h.

[0013] According to a preferred embodiment of the present invention, in step A2, the vacuum drying time at 60-100°C is 10-24 hours.

[0014] According to a preferred embodiment of the present invention, the preparation method of the imidazolium-based polyborosiloxane intercalated sulfonated hydrotalcite includes: B1, dissolving 90-110 parts by weight of magnesium nitrate hexahydrate and 50-150 parts by weight of aluminum nitrate nonahydrate in deionized water to obtain a mixed salt solution; dissolving 20-80 parts by weight of sodium hydroxide and 30-120 parts by weight of sodium 2-acrylamido-2-methylpropanesulfonate in deionized water to obtain a mixed solution of alkali and intercalating agent; under nitrogen protection, adding the mixed salt solution dropwise to the mixed solution of alkali and intercalating agent, stirring, and adjusting the pH to 9.5-10.5; crystallizing at 50-70°C to obtain the product; and centrifuging and washing the product with deionized water. B2. Sulfonate-intercalated hydrotalcite is obtained by vacuum drying at 50-70℃. The hydrotalcite is dispersed in dimethyl sulfoxide and sonicated to obtain a suspension. 40-60 parts of hydroxyl-terminated polydimethylsiloxane and 6-12 parts of boric acid are mixed, and 0.1-0.5 parts of p-toluenesulfonic acid are added. The mixture is heated to 110-130℃ and reacted under reduced pressure to obtain imidazole-based polyborosiloxane. The imidazole-based polyborosiloxane is dissolved in dimethyl sulfoxide to obtain a mixture. The mixture is added dropwise to the suspension and stirred at 70-90℃ to obtain the reaction product. The reaction product is centrifuged, washed with ethanol, vacuum dried at 50-70℃, ground, and sieved.

[0015] In this invention, the preparation of the imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite comprises two key steps: constructing the layered structure of hydrotalcite and intercalation with polyborosiloxane. First, magnesium and aluminum salts are dissolved in deionized water to form a mixed salt solution; simultaneously, an alkaline substance and a sulfonic acid intercalating agent are dissolved in deionized water to form an alkaline mixed solution. Under nitrogen protection, the mixed salt solution is slowly added dropwise to the alkaline mixed solution, and through stirring and pH adjustment, layered hydrotalcite crystal nuclei are formed. Crystallization occurs at a suitable temperature, with sulfonate ions intercalating between the layers to form sulfonate-intercalated hydrotalcite. After centrifugation and washing with deionized water, the hydrotalcite is vacuum-dried to obtain pure hydrotalcite. Second, the sulfonate-intercalated hydrotalcite is dispersed in dimethyl sulfoxide and ultrasonically treated to form a suspension; in another reaction system, hydroxyl-terminated polydimethylsiloxane and boric acid condense under the action of a catalyst to generate polyborosiloxane segments. Polyborosiloxane was dissolved and added dropwise to a hydrotalcite suspension. The reaction was carried out at a specific temperature, allowing polyborosiloxane segments to chemically intercalate between the hydrotalcite layers, forming a stable intercalation composite. After centrifugation, ethanol washing, and vacuum drying, imidazole-based polyborosiloxane-intercalated sulfonated hydrotalcite was obtained. This composite material combines the layered structure of hydrotalcite with the flexibility of polyborosiloxane, significantly enhancing interfacial bonding.

[0016] According to a preferred embodiment of the present invention, in step B1, the crystallization time at 50-70°C is 18-30 hours.

[0017] According to a preferred embodiment of the present invention, in step B2, the reaction time at 110-130°C is 3-6 hours.

[0018] A second aspect of the present invention provides a silicon solid disulfide-free silicone obtained according to the method for preparing the silicon solid disulfide-free silicone.

[0019] Compared with the prior art, the present invention has the following beneficial effects: This invention successfully prepared a solid silicon-based disulfide-free silicone rubber that does not require two-stage vulcanization by introducing a vanadium-doped cobalt-based imidazole zeolite framework and imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite, and then compounding it with α,ω-dihydroxy polydimethylsiloxane adhesive, silica, and other additives. Compared with existing technologies, this invention achieves significant breakthroughs in mechanical properties, heat aging resistance, and process simplification, as detailed below: First, the silicone rubber prepared by this invention exhibits significantly improved mechanical properties. The results of the examples show that its tensile strength, tear strength, and elongation at break are all far superior to the comparative example without the added modifying compound. This effect stems from the synergistic effect of the two modifying compounds: the vanadium element in the vanadium-doped cobalt-based imidazole zeolite framework effectively promotes the conversion of oxime-based vulcanizing agent crosslinking byproducts through multivalent state changes, reducing their potential impact on the polymer backbone; simultaneously, the polyborosiloxane segments in the imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite can form chemical bonds with the silicone rubber matrix, significantly enhancing the interfacial bonding force between the filler and the matrix, resulting in uniformly dispersed physical crosslinking points in the crosslinking network. This allows for more efficient stress transfer and dispersion, avoiding early failure caused by localized stress concentration.

[0020] Secondly, the material of this invention exhibits excellent heat aging resistance. After prolonged high-temperature hot air aging, its tensile strength retention rate is far superior to that of the comparative sample without the added modified material. This superior performance stems from the complementary functions of the two compounds: the cobalt-nitrogen coordination structure in the vanadium-doped cobalt-based imidazole zeolite framework continuously captures free radicals generated during thermo-oxidative aging, delaying polymer chain degradation; the imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite forms a ceramic protective layer at high temperatures, effectively blocking oxygen and heat penetration. Its interlayer sulfonate ions and imidazole groups can also adsorb and neutralize residual acidic substances and acidic byproducts generated during sulfidation and pyrolysis, inhibiting acid-catalyzed degradation reactions. The synergistic effect of both compounds enables the material to maintain the stability of its molecular structure and mechanical properties under high-temperature conditions.

[0021] Most importantly, this invention achieves a true breakthrough in "disulfide-free" process. Traditional silicone rubber requires prolonged high-temperature two-stage vulcanization to remove byproducts and perfect cross-linking. However, the material of this invention achieves or surpasses the performance level of products manufactured using traditional processes after a single room-temperature or low-temperature vulcanization, with no odor or yellowing. This is thanks to the in-situ removal function of two modified compounds during the vulcanization process: the vanadium-doped cobalt-based imidazole zeolite framework helps promote the conversion of cross-linking byproducts from oxime-based vulcanizing agents; and the imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite, through a dual mechanism of chemical adsorption and physical barrier, fixes byproducts within the filler, preventing their migration to the product surface. Therefore, this invention completely eliminates the high-temperature two-stage vulcanization step, significantly reducing energy consumption and production costs, shortening the production cycle, and making silicone rubber suitable for heat-sensitive composite substrates and precision electronic components, significantly expanding its application range and demonstrating outstanding industrial promotion value and environmental benefits. Detailed Implementation

[0022] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0023] Example 1 This embodiment provides a method for preparing solid silicon disulfide-free silica gel, the steps of which include: The preparation of the vanadium-doped cobalt-based imidazole zeolite framework is carried out according to the following steps: A1. Dissolve 100g of cobalt nitrate hexahydrate and 12g of vanadium oxysulfate hydrate in 1500mL of methanol to obtain metal salt solution A; dissolve 100g of 2-methylimidazole in 1500mL of methanol to obtain ligand solution B; under stirring conditions, quickly pour ligand solution B into metal salt solution A, and continue stirring for 30 minutes to obtain a mixed solution; transfer the mixed solution to a high-pressure reactor with a polytetrafluoroethylene liner, and solvothermal react at 110℃ for 18 hours.

[0024] A2. After the reaction was completed, the mixture was naturally cooled to room temperature and centrifuged to obtain a purple precipitate. The precipitate was washed three times with methanol, and centrifuged after each wash. The washing was continued until the pH of the supernatant was 7.0. Finally, the mixture was dried in a vacuum drying oven at 80°C for 18 hours to obtain a vanadium-doped cobalt-based imidazole zeolite framework.

[0025] The preparation of imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite is carried out according to the following steps: B1. Dissolve 100g magnesium nitrate hexahydrate and 100g aluminum nitrate nonahydrate in 5000mL of deionized water to obtain a mixed salt solution; dissolve 50g sodium hydroxide and 75g sodium 2-acrylamido-2-methylpropanesulfonate in 5000mL of deionized water to obtain a mixed solution of alkali and intercalating agent; under nitrogen protection, add the mixed salt solution dropwise to the mixed solution of alkali and intercalating agent at a rate of 2mL per minute, stirring vigorously, while maintaining the pH value at 10.0±0.1 with sodium hydroxide solution; after the addition is complete, crystallize at 60℃ for 24 hours to obtain the product; separate the product by centrifugation, wash with deionized water until neutral, and dry in a vacuum drying oven at 60℃ for 24 hours to obtain sulfonate-intercalated hydrotalcite.

[0026] B2. Disperse 10g of the above-mentioned sulfonate-intercalated hydrotalcite in 300mL of dimethyl sulfoxide and sonicate for 30 minutes to obtain suspension C. In another reaction flask, add 50g of hydroxyl-terminated polydimethylsiloxane with a viscosity of 2000mPa·s and 9g of boric acid, add 0.3g of p-toluenesulfonic acid, heat to 120℃ and react for 5 hours. During the reaction, continuously reduce the pressure to remove the generated water to obtain imidazole-based polyborosiloxane. Dissolve the imidazole-based polyborosiloxane in 100mL of dimethyl sulfoxide to obtain solution D. Add solution D dropwise to suspension C at a rate of 1mL per minute and stir at 80℃ for 24 hours to obtain the reaction product. Centrifuge the reaction product, wash it three times with ethanol to remove the physically adsorbed polyborosiloxane, and finally dry it in a vacuum drying oven at 60℃ for 24 hours. Grind it through a 200-mesh sieve to obtain imidazole-based polyborosiloxane-intercalated sulfonated hydrotalcite.

[0027] The preparation of solid silicon disulfide-free silica gel follows these steps: S1. Add 100g of α,ω-dihydroxypolydimethylsiloxane with a viscosity of 5000mPa·s to a vacuum kneader, heat to 120℃, and dehydrate for 1.5 hours under a vacuum of -0.09MPa until the volatile content is ≤1.0%. Cool down to 90℃, add 30g of fumed silica with a specific surface area of ​​200m² / g, 1.8g of the above-mentioned vanadium-doped cobalt-based imidazole zeolite framework, and 5g of the above-mentioned imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite. Mix under normal pressure for 1 hour, and then continue mixing under a vacuum of -0.09MPa for 30 minutes to obtain the base material.

[0028] S2. After cooling the base material to room temperature, transfer it to a planetary mixer, add 3g of methoxy-terminated dimethyl polysiloxane with a viscosity of 100mPa·s, and stir for 15 minutes; then add 5.5g of methyl tributanone oxime silane, and stir for 15 minutes under a vacuum of -0.095MPa; finally add 0.3g of dibutyltin dilaurate, and continue stirring for 15 minutes under a vacuum of -0.095MPa. Discharge the material to obtain a one-component solid disulfide-free silicone rubber; inject the obtained rubber compound into a mold and vulcanize it for 7 days at a temperature of 23℃ and a relative humidity of 50% to obtain silicone rubber products.

[0029] Example 2 The difference between this embodiment and Embodiment 1 is that the vanadium-doped cobalt-based imidazole zeolite framework is prepared according to the following steps: A1. Dissolve 90g of cobalt nitrate hexahydrate and 4g of vanadium oxysulfate hydrate in 1500mL of methanol to obtain metal salt solution A; dissolve 50g of 2-methylimidazole in 1500mL of methanol to obtain ligand solution B; under stirring conditions, quickly pour ligand solution B into metal salt solution A, and continue stirring for 20 minutes to obtain a mixed solution; transfer the mixed solution to a high-pressure reactor with a polytetrafluoroethylene liner, and solvothermal react at 100℃ for 24 hours.

[0030] A2. After the reaction was completed, the mixture was naturally cooled to room temperature and centrifuged to obtain a purple precipitate. The precipitate was washed three times with methanol, and centrifuged after each wash. The washing was continued until the pH of the supernatant was 7.0. Finally, the mixture was dried in a vacuum drying oven at 60°C for 24 hours to obtain a vanadium-doped cobalt-based imidazole zeolite framework.

[0031] The preparation of imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite is carried out according to the following steps: B1. Dissolve 90g of magnesium nitrate hexahydrate and 50g of aluminum nitrate nonahydrate in 5000mL of deionized water to obtain a mixed salt solution; dissolve 20g of sodium hydroxide and 30g of sodium 2-acrylamido-2-methylpropanesulfonate in 5000mL of deionized water to obtain a mixed solution of alkali and intercalating agent; under nitrogen protection, add the mixed salt solution dropwise to the mixed solution of alkali and intercalating agent at a rate of 2mL per minute, stirring vigorously, while maintaining the pH value at 9.5±0.1 with sodium hydroxide solution; after the addition is complete, crystallize at 50℃ for 30 hours to obtain the product; separate the product by centrifugation, wash with deionized water until neutral, and dry in a vacuum drying oven at 50℃ for 30 hours to obtain sulfonate-intercalated hydrotalcite.

[0032] B2. Disperse 10g of the above-mentioned sulfonate-intercalated hydrotalcite in 300mL of dimethyl sulfoxide and sonicate for 20 minutes to obtain suspension C. In another reaction flask, add 40g of hydroxyl-terminated polydimethylsiloxane with a viscosity of 2000mPa·s and 6g of boric acid, add 0.1g of p-toluenesulfonic acid, heat to 110℃ and react for 6 hours. During the reaction, continuously remove the generated water under reduced pressure to obtain imidazole-based polyborosiloxane. Dissolve the imidazole-based polyborosiloxane in 100mL of dimethyl sulfoxide to obtain solution D. Add solution D dropwise to suspension C at a rate of 1mL per minute and stir at 70℃ for 30 hours to obtain the reaction product. Centrifuge the reaction product, wash it three times with ethanol to remove the physically adsorbed polyborosiloxane, and finally dry it in a vacuum drying oven at 50℃ for 30 hours. Grind it through a 200-mesh sieve to obtain imidazole-based polyborosiloxane-intercalated sulfonated hydrotalcite.

[0033] The preparation of solid silicon disulfide-free silica gel follows these steps: S1. Add 98g of α,ω-dihydroxypolydimethylsiloxane with a viscosity of 2000mPa·s to a vacuum kneader, heat to 110℃, and dehydrate for 2 hours under a vacuum of -0.08MPa until the volatile content is ≤1.0%; cool to 80℃, add 20g of fumed silica with a specific surface area of ​​200m² / g, 0.5g of the above-mentioned vanadium-doped cobalt-based imidazole zeolite framework, and 2g of the above-mentioned imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite, mix under normal pressure for 1 hour, and then continue mixing under a vacuum of -0.08MPa for 30 minutes to obtain the base material.

[0034] S2. After cooling the base material to room temperature, transfer it to a planetary mixer, add 1g of ethoxy-terminated dimethyl polysiloxane with a viscosity of 50mPa·s, and stir for 15 minutes; then add 3g of methyl tributanone oxime silane, and stir for 20 minutes under a vacuum of -0.09MPa; finally add 0.05g of dibutyltin dilaurate, and continue stirring for 20 minutes under a vacuum of -0.09MPa. Discharge the material to obtain a one-component solid disulfide-free silicone rubber; inject the obtained rubber compound into a mold and heat it at 80℃ for 1 hour to obtain a silicone rubber product.

[0035] Example 3 The difference between this embodiment and Embodiment 1 is that the vanadium-doped cobalt-based imidazole zeolite framework is prepared according to the following steps: A1. Dissolve 110g of cobalt nitrate hexahydrate and 20g of vanadium oxysulfate hydrate in 1500mL of methanol to obtain metal salt solution A; dissolve 150g of 2-methylimidazole in 1500mL of methanol to obtain ligand solution B; under stirring conditions, quickly pour ligand solution B into metal salt solution A, and continue stirring for 40 minutes to obtain a mixed solution; transfer the mixed solution to a high-pressure reactor with a polytetrafluoroethylene liner, and solvothermal react at 120℃ for 10 hours.

[0036] A2. After the reaction was completed, the mixture was naturally cooled to room temperature and centrifuged to obtain a purple precipitate. The precipitate was washed three times with methanol, and centrifuged after each wash. The washing was continued until the pH of the supernatant was 7.0. Finally, the mixture was dried in a vacuum drying oven at 100°C for 10 hours to obtain a vanadium-doped cobalt-based imidazole zeolite framework.

[0037] The preparation of imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite is carried out according to the following steps: B1. Dissolve 110g magnesium nitrate hexahydrate and 150g aluminum nitrate nonahydrate in 5000mL of deionized water to obtain a mixed salt solution; dissolve 80g sodium hydroxide and 120g sodium 2-acrylamido-2-methylpropanesulfonate in 5000mL of deionized water to obtain a mixed solution of alkali and intercalating agent; under nitrogen protection, add the mixed salt solution dropwise to the mixed solution of alkali and intercalating agent at a rate of 2mL per minute, stirring vigorously, while maintaining the pH value at 10.5±0.1 with sodium hydroxide solution; after the addition is complete, crystallize at 70℃ for 18 hours to obtain the product; separate the product by centrifugation, wash with deionized water until neutral, and dry in a vacuum drying oven at 70℃ for 20 hours to obtain sulfonate-intercalated hydrotalcite.

[0038] B2. Disperse 10g of the above-mentioned sulfonate-intercalated hydrotalcite in 300mL of dimethyl sulfoxide and sonicate for 40 minutes to obtain suspension C. In another reaction flask, add 60g of hydroxyl-terminated polydimethylsiloxane with a viscosity of 2000mPa·s and 12g of boric acid, add 0.5g of p-toluenesulfonic acid, heat to 130℃ and react for 3 hours. During the reaction, continuously reduce the pressure to remove the generated water to obtain imidazole-based polyborosiloxane. Dissolve the imidazole-based polyborosiloxane in 100mL of dimethyl sulfoxide to obtain solution D. Add solution D dropwise to suspension C at a rate of 1mL per minute and stir at 90℃ for 20 hours to obtain the reaction product. Centrifuge the reaction product, wash it three times with ethanol to remove the physically adsorbed polyborosiloxane, and finally dry it in a vacuum drying oven at 70℃ for 20 hours. Grind it through a 200-mesh sieve to obtain imidazole-based polyborosiloxane-intercalated sulfonated hydrotalcite.

[0039] The preparation of solid silicon disulfide-free silica gel follows these steps: S1. Add 102g of α,ω-dihydroxypolydimethylsiloxane with a viscosity of 20000mPa·s to a vacuum kneader, heat to 130℃, and dehydrate under a vacuum of -0.1MPa for 1 hour until the volatile matter is ≤1.0%; cool to 100℃, add 40g of fumed silica with a specific surface area of ​​300m² / g, 3g of the above-mentioned vanadium-doped cobalt-based imidazole zeolite framework, and 8g of the above-mentioned imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite, mix under normal pressure for 1 hour, and then continue mixing under a vacuum of -0.1MPa for 30 minutes to obtain the base material.

[0040] S2. After cooling the base material to room temperature, transfer it to a planetary mixer, add 5g of methoxy-terminated dimethyl polysiloxane with a viscosity of 500mPa·s, and stir for 15 minutes; then add 8g of methyl tributanone oxime silane, and stir for 10 minutes under a vacuum of -0.098MPa; finally add 0.5g of dibutyltin dilaurate, and continue stirring for 10 minutes under a vacuum of -0.098MPa. Discharge the material to obtain a one-component solid disulfide-free silicone rubber; inject the obtained rubber compound into a mold and heat it at 80℃ for 4 hours to obtain a silicone rubber product.

[0041] Comparative Example 1 The difference between this comparative example and Example 1 is that no vanadium-doped cobalt-based imidazole zeolite framework and imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite are added; the rest of the operations are exactly the same as in Example 1.

[0042] Comparative Example 2 The difference between this comparative example and Example 1 is that no vanadium-doped cobalt-based imidazole zeolite framework is added; the rest of the operations are exactly the same as in Example 1.

[0043] Comparative Example 3 The difference between this comparative example and Example 1 is that imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite is not added; all other operations are exactly the same as in Example 1.

[0044] According to relevant national and industry standards, the silicone rubber sheets prepared in Examples 1-3 and Comparative Examples 1-3 were conditioned for 24 hours at a temperature of 23℃±2℃ and a relative humidity of 50%±5% before the following performance tests were conducted.

[0045] Shore A hardness test: A Shore A hardness tester is used. The sample thickness is not less than 6 mm, and the surface is flat and smooth. The indenter of the hardness tester is pressed vertically into the sample, and the value is read within 1 second after the indenter foot makes close contact with the sample. Measurements are taken at 5 different locations on the sample with a spacing of not less than 6 mm, and the arithmetic mean is taken as the final hardness value. The result is expressed in degrees.

[0046] Tensile strength test: Type I specimens were cut using a dumbbell-shaped cutter, with a test length of 25 mm ± 0.5 mm, a width of 4 mm ± 0.1 mm, and a thickness of 2 mm ± 0.2 mm. The specimens were placed on the fixture of a universal testing machine and stretched at a tensile speed of 500 mm / min. The maximum force at which the specimen broke was recorded. At least five specimens were tested in each group, and the arithmetic mean was taken. The results were expressed in megapascals (MPa) and accurate to 0.1 MPa.

[0047] Elongation at break test: This is measured simultaneously during the tensile strength test. The gauge length elongation at break is recorded, and the elongation is calculated as: Elongation at break = (Break gauge length - Initial gauge length) / Initial gauge length × 100%. Each test group should contain at least 5 specimens, and the arithmetic mean is taken. The result is expressed as a percentage, accurate to 1%. Tear strength test: A right-angled specimen is used, with a pre-cut depth of 1.0 mm ± 0.2 mm at the right-angle vertex. The specimen is clamped in the universal testing machine fixture and stretched at a tensile speed of 500 mm / min. The maximum force during the tearing process is recorded.

[0048] Tear strength is calculated using the formula: Tear strength = Maximum force / Specimen thickness. Each test group should contain no fewer than 5 specimens, and the arithmetic mean should be taken. The result is expressed in kilonewtons per meter, accurate to 0.1 kN / m.

[0049] Hot air aging performance test: Suspend the samples in the hot aging test chamber with a distance of not less than 10 mm between samples and ensure they do not contact the chamber walls. Set the temperature to 200℃ and the aging time to 72 hours. After aging, remove the samples and adjust them for 24 hours at a temperature of 23℃±2℃ and a relative humidity of 50%±5%. Then, determine the tensile strength after aging according to the tensile strength test method described above, and calculate the tensile strength retention rate. Tensile strength retention rate = tensile strength after aging / tensile strength before aging × 100%. The result is expressed as a percentage, accurate to 1%.

[0050] Evaluation of the necessity of two-stage vulcanization: After the vulcanized sample is placed under standard conditions for 7 days, visually inspect the sample surface at a distance of 30cm under natural light to check for white precipitates or yellowing. Also, determine the presence of an irritating odor by smelling the sample at a distance of 5cm. If the sample surface is smooth, without precipitates, yellowing, or odor, then two-stage vulcanization is not required; if there are obvious precipitates, yellowing, or an irritating odor, then two-stage vulcanization is required.

[0051] The performance test data above are shown in Table 1.

[0052] Table 1 Performance Test Results

[0053] As can be seen from the above, Examples 1-3 significantly solve the technical problems of silicone rubber in the prior art, which must rely on a two-stage vulcanization process and have poor overall performance after a single vulcanization, compared with Comparative Examples 1-3.

[0054] Comparative Example 1, without any added modifying compounds, had a tensile strength of only 3.5 MPa, a tear strength of 10.2 kN / m, an elongation at break of 310%, and a tensile strength retention rate of 65% after heat aging. Furthermore, due to the presence of exudates on the surface and an irritating odor, it was determined that two-stage vulcanization was required. This fully confirms that without two-stage vulcanization, the crosslinking byproducts of traditional silicone rubber cannot be effectively removed, and its mechanical properties and heat resistance cannot meet the application requirements.

[0055] Comparative Example 2, which only added imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite without adding vanadium-doped cobalt-based imidazole zeolite framework, showed improved tensile strength (5.2 MPa), tear strength (14.8 kN / m), and tensile strength retention rate after heat aging (78%) compared to Comparative Example 1. However, it was still significantly lower than Examples 1-3 and still required two-stage vulcanization. This indicates that although adding this compound alone can partially improve interfacial bonding and byproduct adsorption, it cannot completely solve the problems of free radical residue and imperfect cross-linking network.

[0056] Comparative Example 3, which only added a vanadium-doped cobalt-based imidazole zeolite framework without adding imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite, had a tensile strength of 5.8 MPa, a tear strength of 15.6 kN / m, and a tensile strength retention rate of 75% after thermal aging. These results were also better than Comparative Example 1 but worse than Examples 1-3. Furthermore, it still required two-stage sulfidation, indicating that relying solely on free radical scavenging cannot completely eliminate the impact of acidic byproducts on performance.

[0057] Examples 1-3 simultaneously added vanadium-doped cobalt-based imidazole zeolite framework and imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite, achieving tensile strength of 7.8-9.1 MPa, tear strength of 21.3-24.1 kN / m, elongation at break of 480%-520%, and tensile strength retention rate of 90%-94% after heat aging. All samples had smooth, odorless, and yellowing surfaces, and were determined to be free from the need for secondary vulcanization.

[0058] These data fully demonstrate that the vanadium-doped cobalt-based imidazole zeolite framework and the imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite produce a significant synergistic effect: the vanadium element in the vanadium-doped cobalt-based imidazole zeolite framework effectively promotes the conversion of crosslinking byproducts of oxime-based vulcanizing agents through multivalence state changes, reducing the damage of free radicals to the polymer backbone; the polyborosiloxane segments in the imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite form chemical bonds with the silicone rubber matrix to enhance interfacial bonding, while its interlayer sulfonate ions and imidazole groups adsorb acidic byproducts and form a ceramic protective layer at high temperature.

[0059] The synergistic effect of the two processes simultaneously achieves in-situ removal of byproducts, improvement of cross-linking network, and enhancement of interfacial bonding during the single vulcanization process. This completely solves the technical problem that traditional silicone rubber must rely on a two-stage vulcanization process to obtain excellent performance, greatly simplifies the production process, reduces energy consumption, and enables silicone rubber to be applied in the field of heat-sensitive composite substrates. It has significant technological advancements and industrial application value.

Claims

1. A method for preparing a silicon solid disulfide-free silica gel, characterized in that the steps include... include: S1. By weight, 98-102 parts of α,ω-dihydroxypolydimethylsiloxane are added to a vacuum kneader, heated, and dehydrated. Cool down, add 20-40 parts of precipitated silica, 0.5-3.0 parts of vanadium-doped cobalt-based imidazole zeolite framework and 2.0-8.0 parts of imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite, and continue mixing under vacuum to obtain the base material; S2. Cool the base material to room temperature, transfer it to a planetary mixer, add 1-5 parts of alkyl-terminated polydimethylsiloxane and stir; then add 3-8 parts of methyltributyl ketone oxime silane and stir; finally add 0.05-0.5 parts of dibutyltin dilaurate and stir under vacuum.

2. The method for preparing silicon solid disulfide-free silica gel according to claim 1, characterized in that, In step S1, heat to 110-130℃; then cool to 80-100℃.

3. The method for preparing silicon solid disulfide-free silica gel according to claim 1, characterized in that, In step S2, the alkyl-terminated polydimethylsiloxane is selected from one or more of methoxy-terminated dimethyl polysiloxane and ethoxy-terminated dimethyl polysiloxane.

4. The method for preparing silicon solid disulfide-free silica gel according to claim 1, characterized in that, The preparation method of the vanadium-doped cobalt-based imidazole zeolite framework includes: A1, dissolving 90-110 parts by weight of cobalt nitrate hexahydrate and 4-20 parts by weight of vanadium oxysulfate hydrate in methanol to obtain metal salt solution A; dissolving 50-150 parts by weight of 2-methylimidazolium in methanol to obtain ligand solution B; mixing ligand solution B with metal salt solution A under stirring, and continuing stirring to obtain a mixed solution; transferring the mixed solution to a high-pressure reactor and solvothermal reaction at 100-120℃; A2, after the reaction is completed, naturally cooling to room temperature, obtaining a precipitate by centrifugation, washing the precipitate with methanol, and vacuum drying at 60-100℃.

5. The method for preparing silicon solid disulfide-free silica gel according to claim 4, characterized in that, In step A1, the solvothermal reaction time at 100-120℃ is 10-24h.

6. The method for preparing silicon solid disulfide-free silica gel according to claim 4, characterized in that, In step A2, the vacuum drying time at 60-100℃ is 10-24 hours.

7. The method for preparing silicon solid disulfide-free silica gel according to claim 1, characterized in that, The preparation method of the imidazole-based polyborosiloxane intercalated sulfonated hydrotalcite includes: B1. Dissolving 90-110 parts by weight of magnesium nitrate hexahydrate and 50-150 parts by weight of aluminum nitrate nonahydrate in deionized water to obtain a mixed salt solution; dissolving 20-80 parts by weight of sodium hydroxide and 30-120 parts by weight of sodium 2-acrylamido-2-methylpropanesulfonate in deionized water to obtain a mixed solution of alkali and intercalating agent; under nitrogen protection, adding the mixed salt solution dropwise to the mixed solution of alkali and intercalating agent, stirring, and adjusting the pH to 9.5-10.5; crystallizing at 50-70℃ to obtain the product; centrifuging the product, washing it with deionized water, and then crystallizing it at 50-70℃. Vacuum drying yields sulfonate-intercalated hydrotalcite; B2. The sulfonate-intercalated hydrotalcite is dispersed in dimethyl sulfoxide and sonicated to obtain a suspension; 40-60 parts of hydroxyl-terminated polydimethylsiloxane and 6-12 parts of boric acid are mixed, and 0.1-0.5 parts of p-toluenesulfonic acid are added. The mixture is heated to 110-130℃ and reacted. Water is removed under reduced pressure to obtain imidazole-based polyborosiloxane; the imidazole-based polyborosiloxane is dissolved in dimethyl sulfoxide to obtain a mixture; the mixture is added dropwise to the suspension and stirred at 70-90℃ to obtain the reaction product; the reaction product is separated by centrifugation, washed with ethanol, vacuum dried at 50-70℃, ground, and sieved.

8. The method for preparing silicon solid disulfide-free silica gel according to claim 7, characterized in that, In step B1, the crystallization time at 50-70℃ is 18-30 hours.

9. The method for preparing silicon solid disulfide-free silica gel according to claim 7, characterized in that, In step B2, the reaction time is 3-6 hours after heating to 110-130℃.

10. A silicon solid-state disulfide-free silica gel, characterized in that, The silicon solid disulfide-free silicone is prepared by the method according to any one of claims 1-9.

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