Silicone sealant prepared from silicon dioxide and preparation method thereof

Abstract

The invention discloses a silicone sealant prepared from silicon dioxide and a preparation method of the silicone sealant, and belongs to the technical field of adhesive materials. Firstly, the organic silicon waste residues are converted into high-quality powder through the steps of screening, iron removal, high-temperature calcination, water washing, drying, smashing and the like. Then, modifying the surface of the powder by adopting a modifying additive to reduce the oil absorption value and improve the compatibility with an organic phase; finally, the modified powder is mixed with a composite thixotropic agent, light calcium carbonate, alpha, omega-dihydroxy polydimethylsiloxane, white oil and other components, and the high-performance silicone sealant is prepared through stirring, vacuumizing, polymerization and other processes. Compared with the prior art, the sealant has the advantages of high tensile strength, high elastic recovery rate and excellent thixotropy, the production cost is reduced, the resource utilization of the organic silicon waste residues is realized, the environmental pollution is reduced, and the sealant has remarkable economic and environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of adhesive materials technology, and in particular to a silicone sealant made of silica and its preparation method. Background Technology

[0002] With the widespread application of organosilicon materials, the disposal of organosilicon waste has become increasingly prominent. Organosilicon waste mainly originates from the pyrolysis process of waste silicone rubber, and its components include unreacted silicon powder, byproduct siloxane polymers, and small amounts of metallic impurities. Traditional disposal methods such as landfilling or incineration not only occupy land and pollute the environment but also result in a serious waste of silicon resources. Therefore, how to transform these wastes into useful materials and achieve resource utilization has become a problem that needs attention.

[0003] In the field of adhesive materials, silicone sealants are widely used due to their excellent sealing, waterproofing, weather resistance, and resistance to high and low temperatures. However, the production cost of traditional silicone sealants is relatively high, and their mechanical and thixotropic properties still need improvement. For example, Chinese patent application CN107815266A discloses a method for preparing reinforcing fillers for silicone sealants using waste silicone rubber acid pyrolysis residue and crude oil alkali pyrolysis ash. While this solves some waste disposal problems, it still has limitations in performance improvement. Another example is Chinese patent application CN113930215A, which discloses a high elastic recovery rate pyrolysis silicone sealant and its preparation method. This improves the sealant's performance by adding a high elastic recovery rate additive, but its raw material cost is high, hindering large-scale application.

[0004] Existing technologies for treating organosilicon waste typically involve steps such as impurity removal, high-temperature calcination, washing, drying, pulverization, and surface treatment to convert the waste into silica. However, this process presents several challenges. First, traditional methods for preparing fumed silica are prohibitively expensive, costing 20,000-30,000 yuan per ton, limiting their large-scale application. Second, while surface treatment and additive modifications can reduce the oil absorption value of the powder, existing technologies still offer significant room for improvement in enhancing silica performance and reducing costs. Furthermore, current technologies often fail to fully utilize the potential value of organosilicon waste when converting it into useful materials for product applications, leading to resource waste and environmental pollution. Therefore, how to efficiently convert this waste into high-value-added products while adhering to environmental protection principles to maximize economic benefits is a pressing issue that needs to be addressed. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to provide a method for preparing silicone sealant using organosilicon waste to produce silica, which is then applied to silicone sealant with high tensile strength, high elastic recovery rate, and excellent thixotropic properties.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A method for preparing a silicone sealant made of silica includes the following steps: Step 1: High-speed screening is used to remove large particulate impurities from the silicone rubber pyrolysis residue and remove iron from the powder. The powder is then sieved to obtain a powder for later use. Step 2: The powder prepared in Step 1 is fed into a high-temperature calcining furnace for calcination and then cooled to obtain powder for later use. Step 3: Add water to the powder prepared in Step 2, heat and stir, wash with water, control the pH of the powder, dry it in a rotary dryer, then pulverize and sieve it to obtain powder for later use. Step 4: Add the modified additive to the powder prepared in Step 3, heat, stir, disperse, and cool to room temperature to obtain the modified powder. Step 5: Add the modified powder prepared in Step 4 to the composite thixotropic agent, then add light calcium carbonate, α,ω-dihydroxypolydimethylsiloxane, and white oil and stir to obtain the base material for later use; Step 6: Heat the base material prepared in Step 5, then vacuum and continue stirring. Add color paste, additives, and catalyst, stir, and package to obtain silicone sealant.

[0007] Preferably, the method for preparing the silicone sealant made of silica is as follows, in parts by weight: Step 1: Remove large particulate impurities from the silicone rubber pyrolysis residue by high-speed screening, remove iron from the powder by permanent magnet machine, and pass it through a 50-100 mesh sieve to obtain powder for later use. Step 2: The powder prepared in Step 1 is fed into a high-temperature calcining furnace by a blower and calcined at 1000-1400℃ for 0.5-2 hours. After cooling, the powder is ready for use. Step 3: Add water to the powder prepared in Step 2 and heat it to 50-80℃. The amount of water added is 15-25 times the weight of the powder. Stir for 0.5-2 hours, then wash with water to control the pH of the powder to 6-8. Dry it in a rotary drying oven at 100-150℃ for 2-3 hours, then pulverize it and pass it through a 200-500 mesh sieve to obtain the powder for later use. Step 4: Weigh 200-300 parts of the powder prepared in Step 3 into a mixer, add 5-10 parts of the modifying additive, heat to 80-110℃, stir at 300-500 rpm for 0.5-1h, then disperse, cool to room temperature to obtain the modified powder. Step 5: Weigh 200-300 parts of the modified powder prepared in Step 4, then add 5-15 parts of the composite thixotropic agent, and then add it to 250-450 parts of light calcium carbonate, 250-450 parts of α,ω-dihydroxypolydimethylsiloxane, and 50-100 parts of white oil. Stir at 300-500 rpm for 2-5 hours to obtain the base material for later use. Step 6: Heat the base material prepared in Step 5 to 110-130℃, then vacuum and continue stirring. Add 50-100 parts of color paste, 50-80 parts of additives, and 0.3-0.8 parts of catalyst, then stir and package to obtain silicone sealant.

[0008] The modified additive is n-propyltrimethoxysilane.

[0009] The catalyst is dibutyltin dilaurate.

[0010] The light calcium is nano-calcium carbonate.

[0011] The adjuvant is composed of γ-glycidyl etheroxypropyltrimethoxysilane, bisaminosilane KH-792, and methyltributanone oxime silane in a mass ratio of 1:1:8-12.

[0012] The preparation method of the composite thixotropic agent is as follows: S1. Carboxylated multi-walled carbon nanotubes were added to an aqueous solution containing an amine polymer, refluxed, vacuum filtered, washed with water, and freeze-dried to obtain grafted carbon nanotube powder. S2. Graphene oxide is dispersed in an ethanol-water solution, sonicated in an ice bath, and an aminosilane coupling agent is added dropwise. The mixture is then sonicated in an ice bath, stirred, centrifuged, washed, and vacuum dried to obtain pretreated graphene oxide. The pretreated graphene oxide is dispersed in xylene and sonicated to obtain a dispersion. Hydrogenated castor oil is added to xylene, the dispersion is added dropwise, the mixture is reacted, washed with cyclohexanone, and vacuum dried to obtain modified graphene oxide. The modified graphene oxide is mixed with grafted carbon nanotube powder to obtain the composite thixotropic agent.

[0013] Preferably, the preparation method of the composite thixotropic agent is as follows, in parts by weight: S1. Add 0.5-2 parts of carboxylated multi-walled carbon nanotubes to 800-1200 parts of an aqueous solution containing 30-70 mg / mL of amine polymer, reflux at 90-100℃ for 5-24 hours, vacuum filter the product, wash with water 1-5 times, freeze dry to obtain grafted carbon nanotube powder. S2. Disperse 0.8-1.5 parts of graphene oxide in 800-1200 parts of 70-90wt% ethanol aqueous solution, sonicate in an ice bath for 20-40 min, add 5-10 parts of aminosilane coupling agent, sonicate in an ice bath for 20-40 min, stir at 70-90℃ and 200-500 rpm for 12-30 h, centrifuge and wash, and vacuum dry at 30-50℃ to obtain pretreated graphene oxide; disperse 0.8-1.5 parts of pretreated graphene oxide in 200-400 parts of xylene, sonicate for 20-40 min to obtain a dispersion; add 2-6 parts of hydrogenated castor oil to 8000-12000 parts of xylene, add the dispersion, react at 70-90℃ for 24-72 h, wash with cyclohexanone, and vacuum dry at 30-50℃ to obtain modified graphene oxide; mix the modified graphene oxide with grafted carbon nanotube powder to obtain the composite thixotropic agent.

[0014] The amine-containing polymer is at least one of polyamide amine and polyether amine.

[0015] The aminosilane coupling agent is at least one of 3-(diethoxymethylsilyl)propylamine, 4-aminobutyltriethoxysilane, and bisaminosilane KH-792.

[0016] The roles of each substance in the silicone sealant preparation method are as follows: Silicone rubber pyrolysis residue, as a source of recycled silica, is processed and used as a base filler for sealants, thus realizing resource reuse.

[0017] n-Propyltrimethoxysilane, as a surface modifier, improves the dispersibility and compatibility of powders in organic phases.

[0018] The composite thixotropic agent is composed of modified graphene oxide and grafted carbon nanotube powder. It constructs a three-dimensional network structure in the sealant, improving the mechanical properties of the sealant and providing anti-sagging and application thixotropic properties.

[0019] Nano-calcium carbonate, as a reinforcing filler, improves the mechanical properties (such as elasticity and strength) and rheological properties (flowability and extrudability) of sealants.

[0020] α,ω-dihydroxypolydimethylsiloxane is a base polymer for silicone sealants, providing basic sealing, waterproofing, weather resistance, and resistance to high and low temperatures.

[0021] White oil acts as a plasticizer, improving the elasticity, consistency, and extrudability of sealants.

[0022] Pigments provide the desired color.

[0023] It is one of the auxiliary components of γ-glycidyl etheroxypropyltrimethoxysilane, whose epoxy and methoxy groups can improve adhesion to the substrate and water resistance of the sealant.

[0024] N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane is one of the auxiliary components. Its diamine structure can enhance the adhesion and compatibility with fillers and inorganic substrates.

[0025] Methyltributylone oxime silane is one of the auxiliary components. As a crosslinking agent, it reacts with the base polymer to form a three-dimensional network structure, which cures the sealant.

[0026] Carboxylated multi-walled carbon nanotubes provide a one-dimensional nanostructure that is entangled with polymer chains, serving to reinforce and enhance thixotropy.

[0027] Polyamide amine is an amine-containing polymer. Its amine groups react with the carboxyl groups on the surface of carbon nanotubes to achieve surface grafting modification of carbon nanotubes and improve their dispersibility.

[0028] Graphene oxide provides a two-dimensional sheet structure, which acts as a physical barrier, reinforcement, and thixotropic agent in sealants.

[0029] Diaminosilane KH-792 is an aminosilane coupling agent that reacts with graphene oxide and hydrogenated castor oil to achieve surface organic modification of graphene oxide.

[0030] Hydrogenated castor oil enhances compatibility with silicone matrices.

[0031] The technical concept of this invention is to transform organosilicon waste into high-performance silica through a series of treatments and apply it to the production of silicone sealants. Specifically, the organosilicon waste is first screened and treated to remove large particles and iron, obtaining pure silica powder. Next, the powder is calcined at high temperature to remove organic impurities and activate the silica surface. The calcined powder is then washed, dried, and ground to further purify it and adjust its particle size distribution. Subsequently, surface modification additives are added to the powder to reduce its oil absorption value and improve its compatibility with organic phases. Finally, the modified silica powder is mixed with a composite thixotropic agent, light calcium carbonate, silicone oil, white oil, and other components, and through processes such as stirring, vacuuming, and polymerization, a high-performance silicone sealant is prepared. This process not only realizes the resource utilization of organosilicon waste and reduces production costs, but also significantly improves the mechanical and thixotropic properties of silicone sealant, giving it higher tensile strength, better elastic recovery rate and better extrudability, while maintaining a good appearance and low specific gravity.

[0032] Compared with the prior art, the present invention has the following beneficial technical effects: 1) This invention uses silicone rubber pyrolysis residue as the main raw material, transforming it into high-quality silica powder through a series of processing steps for the preparation of silicone sealant. This process not only achieves resource utilization of waste and reduces environmental pollution, but also lowers production costs. Furthermore, this invention uses various environmentally friendly additives and auxiliaries in the preparation process, further improving the environmental performance of the sealant and making it safer and more environmentally friendly during production and use. This efficient use of resources and environmental friendliness gives this invention a significant advantage in sustainable development.

[0033] 2) This invention significantly enhances the mechanical properties of silicone sealants through the preparation and application of a unique composite thixotropic agent. The modified graphene oxide and grafted carbon nanotube powder in the composite thixotropic agent work synergistically to construct a three-dimensional network structure within the sealant. This structure not only improves the tensile strength of the sealant but also enhances its elastic recovery rate, allowing it to better return to its original shape under external forces, thereby improving the sealant's durability and reliability. This improvement in mechanical properties is particularly important for applications such as building sealants, effectively extending the sealant's service life and reducing maintenance costs.

[0034] 3) The composite thixotropic agent of this invention also significantly improves the thixotropic properties of silicone sealants. Thixotropy refers to the characteristic of a material whose viscosity decreases under shear force but recovers to a higher viscosity after standing. This characteristic gives the sealant good flowability and workability during application, while allowing it to quickly recover a higher viscosity after application, preventing sagging and deformation. This invention optimizes the preparation process of the composite thixotropic agent, making the sealant easy to apply and shape during application, and maintaining a stable shape after application, greatly improving application efficiency and quality. Detailed Implementation

[0035] Main source of materials: Silicone rubber pyrolysis residue is a byproduct of extracting oil from waste silicone rubber through pyrolysis with sulfuric acid and sulfonic acid.

[0036] α,ω-Dihydroxypolydimethylsiloxane, model: BSM-OH207-50, Qingdao Baisenmao New Materials Co., Ltd.

[0037] Carboxylated multi-walled carbon nanotubes, item number: 008, fineness: 10-20nm, Shenzhen Guosen Leading Technology Co., Ltd.

[0038] Polyamidoamine, molecular weight: 58048, product name: PAMAM G6-NH2, sixth generation dendritic polyamidoamine with amino groups, Hangzhou Xinqiao Biotechnology Co., Ltd.

[0039] Polyetheramine, product specification: D230, brand: Huntsman.

[0040] Branched polyethyleneimine, product number: WG-PEI99-4500, Guangzhou Xiangbo Biotechnology Co., Ltd.

[0041] Graphene oxide, item number: NCT-SE2430, Suqian Nakaite New Material Technology Co., Ltd.

[0042] Diaminosilane KH-792, molecular formula: C8H 22 N2O3Si, CAS: 1760-24-3, Hubei Jianghao New Material Technology Co., Ltd.

[0043] Hydrogenated castor oil, product number: YN615395464480, Jinan Yuno Chemical Co., Ltd.

[0044] Nano calcium carbonate, product number: JLD-5000, specification: 5000 mesh, Foshan Jinlinda Chemical Co., Ltd.

[0045] White oil, specification: 26#, pour point: -32, specific gravity: 0.851, viscosity index: 121, Suzhou Hesen Special Oils Co., Ltd.

[0046] Pigment paste, grade: 3306, application scope: pigment carbon black, Guangzhou Shuangli Rubber Raw Material Trading Co., Ltd.

[0047] All other raw materials used in the embodiments and comparative examples of this invention are commercially available products.

[0048] Example 1 A method for preparing a silicone sealant made of silica is as follows, in parts by weight: Step 1: High-speed screening is used to remove large particulate impurities from the silicone rubber pyrolysis residue. Iron is removed from the powder by a permanent magnet machine and then passed through an 80-mesh sieve to obtain powder for later use. Step 2: The powder prepared in Step 1 is fed into a high-temperature calcining furnace by a blower and calcined at 1250℃ for 1.5 hours. After cooling, the powder is obtained for later use. Step 3: Add water to the powder prepared in Step 2 and heat it to 65°C. The amount of water added is 18 times the weight of the powder. Stir for 1 hour, then wash with water to control the pH of the powder at 7. Dry it in a rotary dryer at 120°C for 2 hours, then pulverize it and pass it through a 400-mesh sieve to obtain powder for later use. Step 4: Weigh 250 parts of the powder prepared in Step 3 into a mixer, add 6.25 parts of n-propyltrimethoxysilane, heat to 100℃, stir at 350 rpm for 1 hour, then disperse, cool to room temperature to obtain modified powder. Step 5: Weigh 250 parts of the modified powder prepared in Step 4, then add 10 parts of the composite thixotropic agent, and then add it to 350 parts of nano calcium carbonate, 320 parts of α,ω-dihydroxypolydimethylsiloxane, and 70 parts of white oil. Stir at 400 rpm for 3 hours to obtain the base material for later use. Step 6: Heat the base material prepared in Step 5 to 120°C, then vacuum and continue stirring. Add 70 parts of color paste, 62 parts of additives, and 0.5 parts of dibutyltin dilaurate, then stir and package. The additives are composed of γ-glycidyl etheroxypropyltrimethoxysilane, bisaminosilane KH-792, and methyl tributanone oxime silane in a mass ratio of 1:1:10, thus obtaining the silicone sealant.

[0049] The preparation method of the composite thixotropic agent is as follows, in parts by weight: S1. Add 1 part of carboxylated multi-walled carbon nanotubes to 1000 parts of 50 mg / mL polyamide amine aqueous solution, reflux at 100℃ for 12 hours, vacuum filter the product, wash with water 5 times, freeze dry to obtain grafted carbon nanotube powder. S2. 1.2 parts of graphene oxide were dispersed in 1000 parts of 80wt% ethanol aqueous solution, sonicated in an ice bath for 30 min, 8 parts of diaminosilane KH-792 were added dropwise, sonicated in an ice bath for 30 min, stirred at 80℃ and 400rpm for 24 h, centrifuged and washed, and then vacuum dried at 40℃ to obtain pretreated graphene oxide; 1 part of pretreated graphene oxide was dispersed in 300 parts of xylene, sonicated for 30 min to obtain a dispersion; 4 parts of hydrogenated castor oil were added to 10000 parts of xylene, the dispersion was added dropwise, reacted at 80℃ for 48 h, washed with cyclohexanone, and vacuum dried at 40℃ to obtain modified graphene oxide; the modified graphene oxide was mixed with grafted carbon nanotube powder to obtain the composite thixotropic agent.

[0050] Example 2 The preparation method of the silicone sealant made of silica is basically the same as that in Example 1, except that the preparation method of the composite thixotropic agent is different.

[0051] The preparation method of the composite thixotropic agent is as follows, in parts by weight: S1. Add 1 part of carboxylated multi-walled carbon nanotubes to 1000 parts of 50 mg / mL polyetheramine aqueous solution, reflux at 100°C for 12 hours, vacuum filter the product, wash with water 5 times, freeze dry to obtain grafted carbon nanotube powder. S2. 1.2 parts of graphene oxide were dispersed in 1000 parts of 80wt% ethanol aqueous solution, sonicated in an ice bath for 30 min, 8 parts of diaminosilane KH-792 were added dropwise, sonicated in an ice bath for 30 min, stirred at 80℃ and 400rpm for 24 h, centrifuged and washed, and then vacuum dried at 40℃ to obtain pretreated graphene oxide; 1 part of pretreated graphene oxide was dispersed in 300 parts of xylene, sonicated for 30 min to obtain a dispersion; 4 parts of hydrogenated castor oil were added to 10000 parts of xylene, the dispersion was added dropwise, reacted at 80℃ for 48 h, washed with cyclohexanone, and vacuum dried at 40℃ to obtain modified graphene oxide; the modified graphene oxide was mixed with grafted carbon nanotube powder to obtain the composite thixotropic agent.

[0052] Example 3 The preparation method of the silicone sealant made of silica is basically the same as that in Example 1, except that the preparation method of the composite thixotropic agent is different.

[0053] The preparation method of the composite thixotropic agent is as follows, in parts by weight: S1. Add 1 part of carboxylated multi-walled carbon nanotubes to 1000 parts of 50 mg / mL polyamide amine aqueous solution, reflux at 100℃ for 12 hours, vacuum filter the product, wash with water 5 times, freeze dry to obtain grafted carbon nanotube powder. S2. 1.2 parts of graphene oxide were dispersed in 1000 parts of 80wt% ethanol aqueous solution, sonicated in an ice bath for 30 min, 8 parts of 4-aminobutyltriethoxysilane were added dropwise, sonicated in an ice bath for 30 min, stirred at 80℃ and 400rpm for 24 h, centrifuged and washed, and then vacuum dried at 40℃ to obtain pretreated graphene oxide; 1 part of pretreated graphene oxide was dispersed in 300 parts of xylene, sonicated for 30 min to obtain a dispersion; 4 parts of hydrogenated castor oil were added to 10000 parts of xylene, the dispersion was added dropwise, reacted at 80℃ for 48 h, washed with cyclohexanone, and vacuum dried at 40℃ to obtain modified graphene oxide; the modified graphene oxide was mixed with grafted carbon nanotube powder to obtain the composite thixotropic agent.

[0054] Example 4 The preparation method of the silicone sealant made of silica is basically the same as that in Example 1, except that the preparation method of the composite thixotropic agent is different.

[0055] The preparation method of the composite thixotropic agent is as follows, in parts by weight: S1. Add 1 part of carboxylated multi-walled carbon nanotubes to 1000 parts of 50 mg / mL polyamide amine aqueous solution, reflux at 100℃ for 12 hours, vacuum filter the product, wash with water 5 times, freeze dry to obtain grafted carbon nanotube powder. S2. 1.2 parts of graphene oxide were dispersed in 1000 parts of 80wt% ethanol aqueous solution, sonicated in an ice bath for 30 min, 8 parts of 3-(diethoxymethylsilyl)propylamine were added dropwise, sonicated in an ice bath for 30 min, stirred at 80℃ and 400rpm for 24 h, centrifuged and washed, and then vacuum dried at 40℃ to obtain pretreated graphene oxide; 1 part of pretreated graphene oxide was dispersed in 300 parts of xylene, sonicated for 30 min to obtain a dispersion; 4 parts of hydrogenated castor oil were added to 10000 parts of xylene, the dispersion was added dropwise, reacted at 80℃ for 48 h, washed with cyclohexanone, and vacuum dried at 40℃ to obtain modified graphene oxide; the modified graphene oxide was mixed with grafted carbon nanotube powder to obtain the composite thixotropic agent.

[0056] Comparative Example 1 The preparation method of the silicone sealant made of silica is basically the same as that in Example 1, except that the preparation method of the composite thixotropic agent is different.

[0057] The preparation method of the composite thixotropic agent is as follows, in parts by weight: S1. Add 1 part of carboxylated multi-walled carbon nanotubes to 1000 parts of 50 mg / mL branched polyethyleneimine aqueous solution, reflux at 100°C for 12 hours, vacuum filter the product, wash with water 5 times, freeze dry to obtain grafted carbon nanotube powder. S2. 1.2 parts of graphene oxide were dispersed in 1000 parts of 80wt% ethanol aqueous solution, sonicated in an ice bath for 30 min, 8 parts of diaminosilane KH-792 were added dropwise, sonicated in an ice bath for 30 min, stirred at 80℃ and 400rpm for 24 h, centrifuged and washed, and then vacuum dried at 40℃ to obtain pretreated graphene oxide; 1 part of pretreated graphene oxide was dispersed in 300 parts of xylene, sonicated for 30 min to obtain a dispersion; 4 parts of hydrogenated castor oil were added to 10000 parts of xylene, the dispersion was added dropwise, reacted at 80℃ for 48 h, washed with cyclohexanone, and vacuum dried at 40℃ to obtain modified graphene oxide; the modified graphene oxide was mixed with grafted carbon nanotube powder to obtain the composite thixotropic agent.

[0058] Comparative Example 2 The preparation method of the silicone sealant made of silica is basically the same as that in Example 1, except that the preparation method of the composite thixotropic agent is different.

[0059] The preparation method of the composite thixotropic agent is as follows, in parts by weight: S1. Add 1 part of carboxylated multi-walled carbon nanotubes to 1000 parts of 50 mg / mL polyamide amine aqueous solution, reflux at 100℃ for 12 hours, vacuum filter the product, wash with water 5 times, freeze dry to obtain grafted carbon nanotube powder. S2. 1.2 parts of graphene oxide were dispersed in 1000 parts of 80wt% ethanol aqueous solution, sonicated in an ice bath for 30 min, 8 parts of 3-aminopropyltriethoxysilane were added dropwise, sonicated in an ice bath for 30 min, stirred at 80℃ and 400rpm for 24 h, centrifuged and washed, and then vacuum dried at 40℃ to obtain pretreated graphene oxide; 1 part of pretreated graphene oxide was dispersed in 300 parts of xylene, sonicated for 30 min to obtain a dispersion; 4 parts of hydrogenated castor oil were added to 10000 parts of xylene, the dispersion was added dropwise, reacted at 80℃ for 48 h, washed with cyclohexanone, and vacuum dried at 40℃ to obtain modified graphene oxide; the modified graphene oxide was mixed with grafted carbon nanotube powder to obtain the composite thixotropic agent.

[0060] Comparative Example 3 The preparation method of a silicone sealant made of silica is basically the same as that in Example 1, except that the composite thixotropic agent is a mixture of graphene oxide and carboxylated multi-walled carbon nanotubes in equal weight.

[0061] Comparative Example 4 The preparation method of a silicone sealant made of silica is basically the same as that in Example 1, except that the composite thixotropic agent is not added.

[0062] Test Example 1 The silicone sealants prepared in the examples and comparative examples were used to prepare mechanical I-beam samples for testing according to the requirements of the national standard GB / T14683-2017 "Silicone and Modified Silicone Building Sealants" (Gn-20HM). The key indicators were tested, and the test results are shown in Table 1 below:

[0063] Test Example 2 Thixotropic performance test: The thixotropic properties of the silicone sealant prepared in this invention were evaluated using a Brookfield rotational viscometer (rotor model: TE 95).

[0064] The specific steps are as follows: Evenly fill the measuring cup with the sealant sample to be tested, avoiding air bubbles. Measure the apparent viscosity of the sample at a low shear rate (rotor speed 20 rpm), and record it as η1 (unit: mPa·s). Quickly switch to a high shear rate (rotor speed 200 rpm) and measure the apparent viscosity, recording it as η2.

[0065] Thixotropic index = (η1-η2) / 10.

[0066] This value reflects the ability of a sample to recover its original structure after its viscosity decreases under shear force; a higher value indicates better thixotropy.

[0067] Each group of samples was tested three times, and the average value was taken as the final result. The results are shown in Table 2.

[0068]

[0069] The performance advantage of Example 1 primarily stems from the superior synergistic effect provided by the molecular structures of polyamide amine and bis(amino)silane KH-792. Compared to polyether amine and branched polyethyleneimine, polyamide amine typically exhibits a higher functional group density and a more rigid framework. This allows it to form a denser and more stable covalent network during the amidation condensation reaction with carboxylated carbon nanotubes, thereby more effectively transferring stress and significantly improving the tensile strength of the sealant. The key to bis(amino)silane KH-792 lies in its two amino groups (primary and secondary amines). This characteristic enables it to form strong Si-OC covalent bonds with the hydroxyl groups on the surface of graphene oxide via silanol groups (Si-OH) after hydrolysis. Furthermore, its bis(amino) groups provide more reaction sites and stronger intermolecular forces (such as hydrogen bonds), resulting in broader and stronger bridging interactions with polymer chains and inorganic fillers during the final silicone sealant curing process. This enhanced interfacial adhesion and network crosslinking density collectively lead to higher elastic recovery and thixotropic index. The combination of polyamide amine and KH-792 creates a more robust three-dimensional network structure.

Claims

1. A method for preparing a silicone sealant made of silica, characterized in that, Includes the following steps: Step 1: High-speed screening is used to remove large particulate impurities from the silicone rubber pyrolysis residue and remove iron from the powder. The powder is then sieved to obtain a powder for later use. Step 2: The powder prepared in Step 1 is fed into a high-temperature calcining furnace for calcination and then cooled to obtain powder for later use. Step 3: Add water to the powder prepared in Step 2, heat and stir, wash with water, control the pH of the powder, dry it in a rotary dryer, then pulverize and sieve it to obtain powder for later use. Step 4: Add the modified additive to the powder prepared in Step 3, heat, stir, disperse, and cool to room temperature to obtain the modified powder. Step 5: Add the modified powder prepared in Step 4 to the composite thixotropic agent, then add light calcium carbonate, α,ω-dihydroxypolydimethylsiloxane, and white oil and stir to obtain the base material for later use; Step 6: Heat the base material prepared in Step 5, then vacuum and continue stirring. Add color paste, additives, and catalyst, stir, and package to obtain silicone sealant. The preparation method of the composite thixotropic agent is as follows: S1. Carboxylated multi-walled carbon nanotubes were added to an aqueous solution containing an amine polymer, refluxed, vacuum filtered, washed with water, and freeze-dried to obtain grafted carbon nanotube powder. S2. Graphene oxide is dispersed in an aqueous ethanol solution, sonicated in an ice bath, aminosilane coupling agent is added dropwise, sonicated in an ice bath, stirred and reacted, centrifuged, washed and vacuum dried to obtain pretreated graphene oxide. Pretreated graphene oxide was dispersed in xylene and sonicated to obtain a dispersion. Hydrogenated castor oil was added to xylene, the dispersion was added dropwise, the mixture was reacted, washed with cyclohexanone, and dried under vacuum to obtain modified graphene oxide. The modified graphene oxide was mixed with grafted carbon nanotube powder to obtain the composite thixotropic agent.

2. The method for preparing the silicone sealant made of silica as described in claim 1, characterized in that, The preparation method is as follows, in parts by weight: Step 1: Remove large particulate impurities from the silicone rubber pyrolysis residue by high-speed screening, remove iron from the powder by permanent magnet machine, and pass it through a 50-100 mesh sieve to obtain powder for later use. Step 2: The powder prepared in Step 1 is fed into a high-temperature calcining furnace by a blower and calcined at 1000-1400℃ for 0.5-2 hours. After cooling, the powder is ready for use. Step 3: Add water to the powder prepared in Step 2 and heat it to 50-80℃. The amount of water added is 15-25 times the weight of the powder. Stir for 0.5-2 hours, then wash with water to control the pH of the powder to 6-8. Dry it in a rotary drying oven at 100-150℃ for 2-3 hours, then pulverize it and pass it through a 200-500 mesh sieve to obtain the powder for later use. Step 4: Weigh 200-300 parts of the powder prepared in Step 3 into a mixer, add 5-10 parts of the modifying additive, heat to 80-110℃, stir at 300-500 rpm for 0.5-1h, then disperse, cool to room temperature to obtain the modified powder. Step 5: Weigh 200-300 parts of the modified powder prepared in Step 4, then add 5-15 parts of the composite thixotropic agent, and then add it to 250-450 parts of light calcium carbonate, 250-450 parts of α,ω-dihydroxypolydimethylsiloxane, and 50-100 parts of white oil. Stir at 300-500 rpm for 2-5 hours to obtain the base material for later use. Step 6: Heat the base material prepared in Step 5 to 110-130℃, then vacuum and continue stirring. Add 50-100 parts of color paste, 50-80 parts of additives, and 0.3-0.8 parts of catalyst, then stir and package to obtain silicone sealant.

3. The method for preparing the silicone sealant made of silica as described in claim 1 or 2, characterized in that, The modified additive is n-propyltrimethoxysilane.

4. The method for preparing the silicone sealant made of silica as described in claim 1 or 2, characterized in that, The catalyst is dibutyltin dilaurate.

5. The method for preparing the silicone sealant made of silica as described in claim 1 or 2, characterized in that, The light calcium is nano-calcium carbonate.

6. The method for preparing the silicone sealant made of silica as described in claim 1 or 2, characterized in that, The adjuvant is composed of γ-glycidyl etheroxypropyltrimethoxysilane, bisaminosilane KH-792, and methyltributanone oxime silane in a mass ratio of 1:1:8-12.

7. The method for preparing the silicone sealant made of silica as described in claim 1 or 2, characterized in that, The preparation method of the composite thixotropic agent is as follows, in parts by weight: S1. Add 0.5-2 parts of carboxylated multi-walled carbon nanotubes to 800-1200 parts of an aqueous solution containing 30-70 mg / mL of amine polymer, reflux at 90-100℃ for 5-24 hours, vacuum filter the product, wash with water 1-5 times, freeze dry to obtain grafted carbon nanotube powder. S2. Disperse 0.8-1.5 parts of graphene oxide in 800-1200 parts of 70-90wt% ethanol aqueous solution, sonicate in an ice bath for 20-40 min, add 5-10 parts of aminosilane coupling agent, sonicate in an ice bath for 20-40 min, stir at 70-90℃ and 200-500 rpm for 12-30 h, centrifuge and wash, and vacuum dry at 30-50℃ to obtain pretreated graphene oxide; disperse 0.8-1.5 parts of pretreated graphene oxide in 200-400 parts of xylene, sonicate for 20-40 min to obtain a dispersion; add 2-6 parts of hydrogenated castor oil to 8000-12000 parts of xylene, add the dispersion, react at 70-90℃ for 24-72 h, wash with cyclohexanone, and vacuum dry at 30-50℃ to obtain modified graphene oxide; mix the modified graphene oxide with grafted carbon nanotube powder to obtain the composite thixotropic agent.

8. The method for preparing the silicone sealant made of silica as described in claim 7, characterized in that, The amine-containing polymer is at least one of polyamide amine and polyether amine.

9. The method for preparing the silicone sealant made of silica as described in claim 7, characterized in that, The aminosilane coupling agent is at least one of 3-(diethoxymethylsilyl)propylamine, 4-aminobutyltriethoxysilane, and bisaminosilane KH-792.

10. A silicone sealant prepared from silica, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.

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