An assembled hollow silica-based soundproof composite material, a preparation method thereof and application thereof in an epoxy coating

Abstract

This invention belongs to the field of functional composite materials and coatings technology, specifically relating to an assembled hollow silica-based sound insulation composite material, its preparation method, and its application in epoxy coatings. The composite sound insulation material provided by this invention is composed of assembled hollow silica and carboxyl-terminated nitrile butadiene rubber. Its preparation involves first preparing assembled hollow silica using a template self-assembly method, then surface-modifying it with a silane coupling agent, and finally reacting it with carboxyl-terminated nitrile butadiene rubber to obtain the composite material of assembled hollow silica and carboxyl-terminated nitrile butadiene rubber. The assembled hollow silica in the composite sound insulation material of this invention has a multi-level hollow spherical shell structure. The carboxyl-terminated nitrile butadiene rubber is coated or grafted onto the surface and internal channels of the assembled hollow silica, allowing it to form a synergistic system of rigid scattering centers and viscoelastic dissipation networks. This achieves efficient blocking and dissipation of broadband sound waves, significantly improving the sound insulation and mechanical properties of epoxy coatings.

Description

Technical Field

[0001] This invention belongs to the field of functional composite materials and coatings technology, specifically relating to an assembled hollow silica-based sound insulation composite material, its preparation method, and its application in epoxy coatings. Background Technology

[0002] Sound-insulating coatings are functional materials that reduce the transmission or reflection of sound waves by coating them on structural surfaces. They are widely used in noise control in construction, transportation, and industrial equipment. Traditional sound-insulating coatings often use high-density fillers (such as barite powder, iron powder, and metal particles) or porous sound-absorbing materials (such as mineral fibers and foamed particles). The former relies on the mass law, requiring a thicker coating for effective sound insulation, resulting in heavy weight and difficult construction. The latter has a certain absorption effect on mid-to-high frequency noise, but its low-frequency sound insulation ability is weak, and its porous structure is prone to water absorption, powdering, and poor durability. In recent years, researchers have attempted to introduce hollow microspheres into coating systems, utilizing the acoustic impedance mismatch and scattering effect generated by their internal cavities to improve sound insulation performance while reducing coating density. However, ordinary hollow microspheres are mostly closed-cell single-cavity structures, where sound waves only undergo one shell reflection before passing through, resulting in a limited scattering path. Furthermore, the surface of these hollow microspheres is highly inert, with weak bonding to the resin matrix, making them prone to agglomeration, leading to actual sound insulation effects far lower than theoretical predictions.

[0003] Compared to traditional single-cavity hollow microspheres, assembled hollow silica is a novel multi-level hollow structural material prepared by template self-assembly. It is assembled from nano-silica particles, forming multiple interconnected or independent cavities within the shell. This forces sound waves to undergo multiple reflections, refractions, and interferences after entering the shell, effectively extending the propagation path and increasing sound energy dissipation. Simultaneously, its shell contains abundant nanopores, which induce viscous and thermal dissipation of sound waves, particularly showing significant absorption of mid-to-high frequency sound waves. Studies have shown that incorporating assembled hollow silica into epoxy resin coatings, at the same thickness, increases sound insulation by more than 30% compared to ordinary solid silica or single-cavity hollow glass microspheres, while reducing coating density by approximately 20%, demonstrating excellent potential for lightweighting and high-efficiency sound insulation.

[0004] Nevertheless, there are still shortcomings in the application of assembled hollow silica in sound insulation coatings. As an inorganic material, assembled hollow silica relies mainly on sound wave reflection and scattering for sound insulation, and cannot convert sound energy into heat energy like viscoelastic polymers. Therefore, the sound energy dissipation efficiency is limited when assembled hollow silica is used alone, especially in the low-frequency range where the sound insulation improvement is limited due to the larger wavelength and smaller scattering cross section. At the same time, if strong chemical bonds are not formed at the interface between assembled hollow silica and the organic matrix, debonding is likely to occur under dynamic stress, which will instead become a stress concentration point, reducing the mechanical integrity of the coating and the long-term sound insulation stability. In addition, since the scattering cross section of assembled hollow silica varies significantly with frequency, its improvement in mid-high frequencies is better than that in low frequencies. If used alone, it is difficult to achieve balanced sound insulation across the entire frequency range, so it needs to be used in combination with other damping materials.

[0005] In summary, there is an urgent need to functionalize assembled hollow silica, introduce viscoelastic components to enhance low-frequency sound energy dissipation, and optimize its dispersibility and interfacial compatibility in order to develop a composite filler for sound insulation coatings with wide bandwidth, high efficiency, and excellent overall performance. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention provides an assembled hollow silica-based sound insulation composite material, which is composed of assembled hollow silica and carboxyl-terminated nitrile rubber. When used as a filler in an epoxy resin system, it can significantly improve the sound insulation and mechanical properties of epoxy coatings, and has important application value.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides a method for preparing an assembled hollow silica-based sound-insulating composite material, the method comprising the following steps: S1. Under inert gas protection, a mixture of water, styrene, and methyl acrylate is heated to 65-80 °C, and potassium persulfate aqueous solution is added to initiate a polymerization reaction to obtain a polystyrene microsphere emulsion. Water is added to the obtained microsphere emulsion to prepare a suspension, and hexadecyltrimethylammonium bromide aqueous solution and bis(octadecyldimethylammonium chloride) ethanol solution are added sequentially and stirred to react. The pH of the system is then adjusted to 9.5-10.5, and tetraethyl orthosilicate is added. The reaction is continued to be stirred at room temperature and allowed to stand for aging. After the reaction, the product is filtered, washed, and then placed at a high temperature of 500-600 °C for 3-6 h to remove the polystyrene template, finally obtaining hollow silica material. S2. The assembled hollow silica prepared in S1 and the silane coupling agent are placed in an organic solvent, heated and stirred under reflux, the precipitate is collected by filtration, and then washed and dried to obtain the modified assembled hollow silica. S3. The assembled hollow silica modified by S2 and the carboxyl-terminated nitrile rubber were added to the solvent, heated and stirred to carry out the composite reaction. After the reaction, the composite material was filtered, washed and dried to finally obtain the assembled hollow silica-based sound insulation composite material.

[0008] This invention uses polystyrene microspheres as a template, depositing silica on the template surface via a sol-gel method to form a core-shell structure. After removing the template by high-temperature calcination, assembled hollow silica with multi-level hollow chambers and a mesoporous shell is obtained. Further surface modification with a silane coupling agent introduces active groups such as epoxy groups or double bonds onto the surface. This is then esterified or physically adsorbed with the terminal carboxyl groups of carboxyl-terminated nitrile butadiene rubber, resulting in uniform coating or grafting of the carboxyl-terminated nitrile butadiene rubber onto the surface and internal pores of the assembled hollow silica, thus forming a composite material of "rigid hollow silica shell + viscoelastic rubber core". This material can generate broadband phonon scattering effects through the multi-level hollow structure of the assembled hollow silica, induce viscous and thermal dissipation of sound waves through its mesoporous shell, and convert sound energy into heat energy through intramolecular and interfacial friction via the viscoelastic network of the carboxyl-terminated nitrile butadiene rubber. The synergistic effect of these three factors gives the coating excellent sound insulation performance over a wide frequency range. In addition, the abundant silanol groups on the surface of the assembled hollow silica facilitate chemical modification, which helps to improve its dispersibility and interfacial bonding in the resin system; furthermore, the introduction of carboxyl-terminated nitrile rubber can significantly improve the toughness and adhesion of the coating.

[0009] Preferably, the number-average molecular weight of the carboxyl-terminated nitrile rubber is 3000-4000, and the viscosity is moderate; the silane coupling agent includes silane coupling agents KH560, KH550, or KH570.

[0010] Preferably, the mass ratio of styrene, methyl acrylate, potassium persulfate, hexadecyltrimethylammonium bromide, dioctadecyldimethylammonium chloride, tetraethyl orthosilicate, silane coupling agent KH560, and carboxyl-terminated nitrile rubber is 40:5:1:6:2:14:10:30-70.

[0011] Preferably, in S1, the polymerization reaction takes 20-30 hours.

[0012] Preferably, in step S1, after adding hexadecyltrimethylammonium bromide aqueous solution and dioctadecyldimethylammonium chloride ethanol solution under stirring, the reaction is continued to be stirred for 1-3 hours.

[0013] Preferably, in S1, after adding tetraethyl orthosilicate, the mixture is stirred continuously at room temperature for 3-5 hours and then aged at room temperature for 20-30 hours.

[0014] Preferably, in S2, the temperature of the heating, reflux, and stirring reaction is 60-80°C, and the time is 4-8 hours.

[0015] Preferably, in S2, the organic solvent includes ethanol, isopropanol, or toluene.

[0016] Preferably, in S3, the composite reaction is carried out at 60-80°C with stirring at 200-400 r / min for 4-8 hours.

[0017] Preferably, in S3, the solvent includes toluene, xylene, or acetone.

[0018] The second aspect of the present invention also provides an assembled hollow silica-based sound insulation composite material prepared by the preparation method described in the first aspect.

[0019] The third aspect of the present invention also provides the application of the assembled hollow silica-based sound insulation composite material described in the second aspect in the preparation of sound insulation coatings, specifically: the assembled hollow silica-based sound insulation composite material is added as a filler to a resin matrix, wherein the resin matrix includes an epoxy resin, a polyurethane resin, or an acrylic resin matrix.

[0020] Preferably, the sound insulation coating is prepared by mixing a resin matrix (such as epoxy resin E-51), an active diluent (such as 660A), an additive (such as KH560) with the assembled hollow silica-based sound insulation composite material, mixing them thoroughly, and then adding a curing agent (such as polyamide 651).

[0021] The mass ratio of the resin matrix to the assembled hollow silica-based sound insulation composite material is 7-9:1-3.

[0022] Compared with the prior art, the beneficial effects of the present invention are: This invention discloses a method for preparing an assembled hollow silica-based sound insulation composite material. The method first prepares an assembled hollow silica with multi-level hollow chambers and mesoporous shells by template self-assembly, and then modifies the surface with a silane coupling agent and combines it with carboxyl-terminated nitrile rubber to obtain an assembled hollow silica and carboxyl-terminated nitrile rubber composite material. Compared with traditional single-cavity hollow microspheres or the use of assembled hollow silica alone, the composite material of this invention has significant advantages: Firstly, the multi-level hollow structure in the assembled hollow silica significantly extends the sound wave propagation path, and its mesoporous shell induces viscous and thermal dissipation, thereby achieving broadband and efficient sound insulation. Secondly, the viscoelastic damping of the carboxyl-terminated nitrile rubber further converts sound energy into heat energy, thus compensating for the deficiency of low-frequency energy dissipation in rigid inorganic fillers. Furthermore, the surface modification with silane coupling agent can enhance the interfacial bonding between the assembled hollow silica, the carboxyl-terminated nitrile rubber, and the resin matrix, thereby improving filler dispersibility. In addition, the flexible segments of the carboxyl-terminated nitrile rubber can improve the toughness and adhesion of the coating, and its hydrophobic properties help reduce water absorption and enhance corrosion resistance. Finally, the method of this invention is mild, the equipment is simple, and the cost is controllable, making it suitable for large-scale production and engineering applications. Attached Figure Description

[0023] Figure 1 Fourier transform infrared spectra of assembled hollow silica (ASHS) and polystyrene microspheres (PS); Figure 2 SEM images of assembled hollow silica (ASHS) and polystyrene microspheres (PS); a is an SEM image of a single polystyrene microsphere, b is an SEM image of multiple polystyrene microspheres combined, and c is an SEM image of assembled hollow silica. Detailed Implementation

[0024] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0025] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0026] This invention provides a composite sound insulation material composed of assembled hollow silica and carboxyl-terminated nitrile butadiene rubber. The preparation method involves first preparing assembled hollow silica using a template self-assembly method, then surface-modifying it with a silane coupling agent, followed by a composite reaction with carboxyl-terminated nitrile butadiene rubber in solution. After drying, the composite material of assembled hollow silica and carboxyl-terminated nitrile butadiene rubber is obtained. The assembled hollow silica in this composite sound insulation material has a multi-level hollow spherical shell structure, with the carboxyl-terminated nitrile butadiene rubber coating or grafted onto the surface and internal channels of the assembled hollow silica. This allows it to form a synergistic system of rigid scattering centers and viscoelastic dissipation networks, thereby achieving efficient blocking and dissipation of broadband sound waves. Furthermore, using this composite material as a filler in epoxy resin systems can significantly improve the sound insulation and mechanical properties of epoxy coatings.

[0027] To fully and clearly present the technical solution and significant advantages of the present invention, the present invention will be described in detail below with reference to specific embodiments.

[0028] Example 1: An assembled hollow silica / carboxyl-terminated nitrile rubber composite sound insulation filler The raw materials and their weight proportions for preparing this composite filler are as follows: Styrene (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 40 parts, methyl acrylate (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 5 parts, potassium persulfate (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 1 part, hexadecyltrimethylammonium bromide (manufacturer: Shanghai Maclean Biochemical Technology Co., Ltd.) 6 parts, dioctadecyldimethylammonium chloride (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 2 parts, tetraethyl orthosilicate (manufacturer: Shanghai Maclean Biochemical Technology Co., Ltd.) 14 parts, carboxyl-terminated nitrile butadiene rubber (number average molecular weight 3500, moderate viscosity; manufacturer: Shanghai Maclean Biochemical Technology Co., Ltd.) 50 parts, silane coupling agent KH560 (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 10 parts.

[0029] The preparation method of this composite filler includes the following steps: S1: Water (320 parts), styrene, and methyl acrylate were added to a reactor (a double-walled glass reactor equipped with a mechanical stirrer, reflux condenser, nitrogen inlet, and temperature controller). The mixture was heated to 70°C under nitrogen protection. Potassium persulfate aqueous solution (40 parts water as solvent) was added to initiate polymerization. The reaction was allowed to proceed for 24 hours to obtain a polystyrene (PS) microsphere emulsion. The obtained PS microsphere emulsion was mixed with deionized water at a volume ratio of 1:3 and ultrasonically dispersed to form a uniform suspension. A hexadecyltrimethylammonium bromide aqueous solution (5 wt.%) and a dioctadecyldimethylammonium chloride ethanol solution (1.7 wt.%) were rapidly injected into the suspension while stirring (200 rpm), and stirring was continued for 1 hour. Ammonia water (30% concentration) was then added to the mixture. The pH of the resulting mixture was adjusted to 10 by adding tetraethyl orthosilicate (wt.%), and the mixture was stirred at room temperature (300 rpm) for 4 hours, followed by aging at room temperature for 24 hours. The resulting product was then vacuum filtered and the precipitate was washed with deionized water. The washed precipitate was heated to 550°C and kept at that temperature for 4 hours (heating rate of 3°C / min) to remove the PS microsphere template, thus obtaining assembled hollow silica (ASHS). Fourier transform infrared spectra of assembled hollow silica (ASHS) and polystyrene microspheres (PS) are shown below. Figure 1 As shown, pure polystyrene microspheres exhibit characteristic peaks at 2920 cm⁻¹ and 2850 cm⁻¹, respectively, which are attributed to the C–H stretching vibrations of the methylene component. (1600, 1581, 1493, and 1450 cm⁻¹ are also mentioned.) 1 The peak at 694 cm⁻ corresponds to the C–C bending vibration in the benzene ring skeleton. 1 The peak values ​​at 1010 cm⁻¹ are attributed to out-of-plane deformation vibrations of hydrogen atoms on the benzene ring, and all these peak shapes perfectly match the structure of polystyrene. Meanwhile, the assembled hollow silica exhibits a characteristic peak near 10¹⁻¹, which belongs to the Si–O–Si bending vibration, corresponding to the SiO₂ structure. Furthermore, the characteristic peaks associated with polystyrene microspheres disappear in the assembled hollow silica, confirming the successful removal of the polystyrene microspheres and the formation of the hollow silica structure.

[0030] like Figure 2 As shown, Figure 2 SEM images of polystyrene microspheres in a confirmed that individual polystyrene microspheres were successfully synthesized and that their size distribution was uniform, with an expected size of approximately 300-400 nm. Figure 2 SEM images in b demonstrate the successful direct growth of a dense silica layer on the surface of a single polystyrene microsphere. Multiple polystyrene microspheres are bonded together as a rigid template by the action of hexadecyltrimethylammonium bromide and dioctadecyldimethylammonium chloride. Figure 2b). After the polystyrene microspheres were sintered at high temperature, the hollow silica spherical structure of the assembled hollow silica was preserved. Figure 2 c).

[0031] S2: In a reactor, the assembled hollow silica obtained in step S1 and KH560 are added to toluene (80 parts), refluxed and stirred at 70°C for 6 hours, the precipitate is collected by filtration, washed with anhydrous ethanol, and then dried under vacuum to obtain KH560 modified assembled hollow silica.

[0032] S3: The KH560 modified assembled hollow silica obtained in step S2 and carboxyl-terminated nitrile butadiene rubber were added to toluene (80 parts), and the mixture was stirred at 300 r / min for 6 h at 70 °C to carry out the composite reaction. The resulting reaction mixture was then filtered, and the precipitate was washed three times with anhydrous ethanol. The precipitate was then vacuum dried at 50 °C for 12 h to remove the solvent, yielding an assembled hollow silica and carboxyl-terminated nitrile butadiene rubber composite sound insulation filler. Example 2: An assembled hollow silica / carboxyl-terminated nitrile butadiene rubber composite sound insulation filler. The raw materials and their weight proportions for preparing this composite filler are as follows: Styrene (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 40 parts, methyl acrylate (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 5 parts, potassium persulfate (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 1 part, cetyltrimethylammonium bromide (manufacturer: Shanghai Maclean Biochemical Technology Co., Ltd.) 6 parts, dioctadecyldimethylammonium chloride (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 2 parts, tetraethyl orthosilicate (manufacturer: Shanghai Maclean Biochemical Technology Co., Ltd.) 14 parts, carboxyl-terminated nitrile butadiene rubber (number average molecular weight 3500, moderate viscosity; manufacturer: Shanghai Maclean Biochemical Technology Co., Ltd.) 30 parts, silane coupling agent KH560 (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 10 parts.

[0033] The preparation method of this composite filler includes the following steps: S1: Water (320 parts), styrene, and methyl acrylate were added to a reactor and heated to 70°C under nitrogen protection. Potassium persulfate aqueous solution (40 parts water as solvent) was added to initiate polymerization. The reaction was carried out for 24 hours to obtain a polystyrene (PS) microsphere emulsion. The obtained PS microsphere emulsion was mixed with deionized water at a volume ratio of 1:3 and ultrasonically dispersed to form a uniform suspension. A hexadecyltrimethylammonium bromide aqueous solution (5 wt.%) and a dioctadecyldimethylammonium chloride ethanol solution (1.7 wt.%) were rapidly injected into the suspension under stirring (200 rpm), and stirring was continued for 1 hour. Ammonia water (30% concentration) was then added. The pH of the resulting mixture was adjusted to 10 by adding tetraethyl orthosilicate (wt.%), and the mixture was stirred at room temperature (300 rpm) for 4 hours, followed by aging at room temperature for 24 hours. The resulting product was vacuum filtered and the precipitate was washed with deionized water. The washed precipitate was heated to 550°C and kept at that temperature for 4 hours (heating rate of 3°C / min) to remove the PS microsphere template and obtain assembled hollow silica. S2: In a reactor, the assembled hollow silica obtained in step S1 and KH560 are added to toluene (80 parts), refluxed and stirred at 70°C for 6 hours, the precipitate is collected by filtration, washed with anhydrous ethanol, and then dried under vacuum to obtain KH560 modified assembled hollow silica.

[0034] S3: The KH560 modified assembled hollow silica obtained in step S2 and the carboxyl-terminated nitrile butadiene rubber were added to toluene (80 parts) and stirred at 300 r / min for 6 h at 70 °C to carry out the composite reaction. The resulting reaction mixture was then filtered, and the precipitate was washed three times with anhydrous ethanol. The precipitate was then vacuum dried at 50 °C for 12 h to remove the solvent, resulting in the composite sound insulation filler of assembled hollow silica and carboxyl-terminated nitrile butadiene rubber.

[0035] Example 3: An assembled hollow silica / carboxyl-terminated nitrile rubber composite sound insulation filler The raw materials and their weight proportions for preparing this composite filler are as follows: Styrene (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 40 parts, methyl acrylate (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 5 parts, potassium persulfate (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 1 part, cetyltrimethylammonium bromide (manufacturer: Shanghai Maclean Biochemical Technology Co., Ltd.) 6 parts, dioctadecyldimethylammonium chloride (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 2 parts, tetraethyl orthosilicate (manufacturer: Shanghai Maclean Biochemical Technology Co., Ltd.) 14 parts, carboxyl-terminated nitrile butadiene rubber (number average molecular weight 3500, moderate viscosity; manufacturer: Shanghai Maclean Biochemical Technology Co., Ltd.) 50 parts, silane coupling agent KH570 (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 10 parts.

[0036] The preparation method of this composite filler includes the following steps: S1: Water (320 parts), styrene, and methyl acrylate were added to a reactor and heated to 70°C under nitrogen protection. Potassium persulfate aqueous solution (40 parts water as solvent) was added to initiate polymerization. The reaction was carried out for 24 hours to obtain a polystyrene (PS) microsphere emulsion. The obtained PS microsphere emulsion was mixed with deionized water at a volume ratio of 1:3 and ultrasonically dispersed to form a uniform suspension. A hexadecyltrimethylammonium bromide aqueous solution (5 wt.%) and a dioctadecyldimethylammonium chloride ethanol solution (1.7 wt.%) were rapidly injected into the suspension under stirring (200 rpm), and stirring was continued for 1 hour. Ammonia water (30% concentration) was then added. The pH of the resulting mixture was adjusted to 10 by adding tetraethyl orthosilicate (wt.%), and the mixture was stirred at room temperature (300 rpm) for 4 hours, followed by aging at room temperature for 24 hours. The resulting product was vacuum filtered, and the precipitate was washed with deionized water in the dark. The washed precipitate was heated to 550°C and kept at that temperature for 4 hours (heating rate of 3°C / min) to remove the PS microsphere template and obtain assembled hollow silica. S2: In a reactor, the assembled hollow silica obtained in step S1 and KH570 are added to toluene (80 parts), refluxed and stirred at 70°C for 6 hours, the precipitate is collected by filtration, washed with anhydrous ethanol, and then dried under vacuum to obtain KH570 modified assembled hollow silica.

[0037] S3: The KH570 modified assembled hollow silica obtained in step S2 and the carboxyl-terminated nitrile butadiene rubber were added to toluene (80 parts) and stirred at 300 r / min for 6 h at 70 °C to carry out the composite reaction. The resulting reaction mixture was then filtered, and the precipitate was washed three times with anhydrous ethanol. The precipitate was then vacuum dried at 50 °C for 12 h to remove the solvent, resulting in the composite sound insulation filler of assembled hollow silica and carboxyl-terminated nitrile butadiene rubber.

[0038] Example 4: An assembled hollow silica / carboxyl-terminated nitrile rubber composite sound insulation filler The raw materials and their weight proportions for preparing this composite filler are as follows: Styrene (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 40 parts, methyl acrylate (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 5 parts, potassium persulfate (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 1 part, hexadecyltrimethylammonium bromide (manufacturer: Shanghai Maclean Biochemical Technology Co., Ltd.) 6 parts, dioctadecyldimethylammonium chloride (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 2 parts, tetraethyl orthosilicate (manufacturer: Shanghai Maclean Biochemical Technology Co., Ltd.) 14 parts, carboxyl-terminated nitrile butadiene rubber (number average molecular weight 3500, moderate viscosity; manufacturer: Shanghai Maclean Biochemical Technology Co., Ltd.) 70 parts, silane coupling agent KH560 (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 10 parts.

[0039] The preparation method of this composite filler includes the following steps: S1: Water (320 parts), styrene, and methyl acrylate were added to a reactor and heated to 70°C under nitrogen protection. Potassium persulfate aqueous solution (40 parts water as solvent) was added to initiate polymerization. The reaction was carried out for 24 hours to obtain a polystyrene (PS) microsphere emulsion. The obtained PS microsphere emulsion was mixed with deionized water at a volume ratio of 1:3 and ultrasonically dispersed to form a uniform suspension. A hexadecyltrimethylammonium bromide aqueous solution (5 wt.%) and a dioctadecyldimethylammonium chloride ethanol solution (1.7 wt.%) were rapidly injected into the suspension under stirring (200 rpm), and stirring was continued for 1 hour. Ammonia water (30% concentration) was then added. The pH of the resulting mixture was adjusted to 10 by adding tetraethyl orthosilicate (wt.%), and the mixture was stirred at room temperature (300 rpm) for 4 hours, followed by aging at room temperature for 24 hours. The resulting product was vacuum filtered and the precipitate was washed with deionized water. The washed precipitate was heated to 550°C and kept at that temperature for 4 hours (heating rate of 3°C / min) to remove the PS microsphere template and obtain assembled hollow silica. S2: In a reactor, the assembled hollow silica obtained in step S1 and KH560 are added to toluene (80 parts), refluxed and stirred at 70°C for 6 hours, the precipitate is collected by filtration, washed with anhydrous ethanol, and then dried under vacuum to obtain KH560 modified assembled hollow silica.

[0040] S3: The KH560 modified assembled hollow silica obtained in step S2 and the carboxyl-terminated nitrile butadiene rubber were added to toluene (80 parts) and stirred at 300 r / min for 6 h at 70 °C to carry out the composite reaction. The resulting reaction mixture was then filtered, and the precipitate was washed three times with anhydrous ethanol. The precipitate was then vacuum dried at 50 °C for 12 h to remove the solvent, resulting in the composite sound insulation filler of assembled hollow silica and carboxyl-terminated nitrile butadiene rubber.

[0041] Comparative Example 1: An Assembled Hollow Silica Sound Insulation Filler The raw materials and their weight proportions for preparing this filler are as follows: Styrene (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 40 parts, methyl acrylate (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 5 parts, potassium persulfate (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 1 part, hexadecyltrimethylammonium bromide (manufacturer: Shanghai Maclean Biochemical Technology Co., Ltd.) 6 parts, dioctadecyldimethylammonium chloride (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 2 parts, tetraethyl orthosilicate (manufacturer: Shanghai Maclean Biochemical Technology Co., Ltd.) 14 parts, silane coupling agent KH560 (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.) 10 parts.

[0042] The preparation method of this filler includes the following steps: S1: Water (320 parts), styrene, and methyl acrylate were added to a reactor and heated to 70°C under nitrogen protection. Potassium persulfate aqueous solution (40 parts water as solvent) was added to initiate polymerization. The reaction was carried out for 24 hours to obtain a polystyrene (PS) microsphere emulsion. The obtained PS microsphere emulsion was mixed with deionized water at a volume ratio of 1:3 and ultrasonically dispersed to form a uniform suspension. A hexadecyltrimethylammonium bromide aqueous solution (5 wt.%) and a dioctadecyldimethylammonium chloride ethanol solution (1.7 wt.%) were rapidly injected into the suspension under stirring (200 rpm), and stirring was continued for 1 hour. Ammonia water (30% concentration) was then added. The pH of the resulting mixture was adjusted to 10 by adding tetraethyl orthosilicate (wt.%), and the mixture was stirred at room temperature (300 rpm) for 4 hours, followed by aging at room temperature for 24 hours. The resulting product was vacuum filtered, and the precipitate was washed with deionized water. The washed precipitate was heated to 550°C and kept at that temperature for 4 hours (heating rate of 3°C / min) to remove the PS microsphere template and obtain assembled hollow silica. S2: In a reactor, the assembled hollow silica from step S1 and KH560 are added to toluene (80 parts), refluxed and stirred at 70°C for 6 hours, the precipitate is collected by filtration, washed with anhydrous ethanol, and then dried under vacuum to obtain KH560 modified assembled hollow silica.

[0043] Comparative Example 2: A carboxyl-terminated nitrile butadiene rubber sound insulation filler The raw materials and their weight proportions for preparing this filler are as follows: 50 parts of carboxyl-terminated nitrile butadiene rubber (number average molecular weight 3500, moderate viscosity; manufacturer: Shanghai McLean Biochemical Technology Co., Ltd., item number: C123456) and 10 parts of silane coupling agent KH560 (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd., item number: K456789).

[0044] The preparation method of this filler includes the following steps: S1: KH560 and carboxyl-terminated nitrile butadiene rubber were added to toluene at a mass ratio of 1:5, and the mixture was stirred at 300 r / min for 6 h at 70 °C to carry out the composite reaction. The resulting reaction mixture was filtered, and the precipitate was washed three times with anhydrous ethanol. The precipitate was then vacuum dried at 50 °C for 12 h to remove the solvent, yielding carboxyl-terminated nitrile butadiene rubber sound insulation filler.

[0045] Comparative Example 3: A silica / carboxyl-terminated nitrile rubber composite sound insulation filler The raw materials and their weight proportions for preparing this composite filler are as follows: 68 parts of silica (manufacturer: Shanghai Maclean Biochemical Technology Co., Ltd.), 50 parts of carboxyl-terminated nitrile butadiene rubber (number average molecular weight 3500, moderate viscosity; manufacturer: Shanghai Maclean Biochemical Technology Co., Ltd.), and 10 parts of silane coupling agent KH560 (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.).

[0046] The preparation method of this composite filler includes the following steps: S1: Add silica and KH560 to toluene in a reactor, reflux and stir at 70°C for 6 hours, filter and collect the precipitate, wash the precipitate with anhydrous ethanol, and then dry it under vacuum to obtain KH560 modified silica.

[0047] S2: The KH560 modified silica obtained in step S1 and the carboxyl-terminated nitrile butadiene rubber were added to toluene (80 parts) and stirred at 300 r / min for 6 h at 70 °C to carry out the composite reaction. The resulting reaction mixture was then filtered, and the precipitate was washed three times with anhydrous ethanol. The precipitate was then vacuum dried at 50 °C for 12 h to remove the solvent, resulting in a composite sound insulation filler of silica and carboxyl-terminated nitrile butadiene rubber.

[0048] Experimental example: The assembled hollow silica / carboxyl-terminated nitrile rubber composite sound insulation filler was applied to an epoxy resin sound insulation coating system. Details are as follows: Epoxy resin E-51 (80 phr), reactive diluent 660A (10 phr), additive KH560 (1 phr), and composite sound-insulating filler (20 phr) were mixed. The mixture was first mechanically stirred at 400 rpm for 1 hour at room temperature until the components were initially homogenized. Then, the stirring speed was increased to 1200 rpm and continued for 12 hours. Subsequently, polyamide 651 curing agent (55 phr) was added and stirred thoroughly at 400 rpm. The mixed coating was applied to galvanized steel plate specimens and cured at 80℃ for 90 minutes. After cooling to room temperature, a sound-insulating and fire-retardant coating with a thickness of approximately 3 mm was obtained.

[0049] The composite sound insulation fillers of Examples 1-4 and Comparative Examples 1-3 were selected for performance testing. After the fillers were incorporated into the resin system according to the above method, the sound insulation (STL), adhesion, tensile strength and elongation at break of the samples were tested according to ASTM E2611, ISO 4624 and GB / T 1040 standards, respectively. The test results are shown in Table 1.

[0050] Table 1: Sound insulation performance data of composite sound insulation fillers in Examples 1-4 and Comparative Examples 1-3 According to the results in Table 1: (1) As seen in Examples 1-4, the composite sound insulation filler made by the method of the present invention, which is composed of hollow silica and carboxyl-terminated nitrile rubber, successfully enhances the broadband sound insulation performance of the epoxy coating. The average STL can reach 40-44dB at a thickness of 3mm, especially the sound insulation in the low frequency band (100-500Hz) is ≥32.8dB. It also has good adhesion (≥23MPa), tensile strength (≥56MPa) and elongation at break (≥5.9%).

[0051] (2) Comparing Example 1 and Comparative Example 1, when no assembled hollow silica is added, the coating mainly relies on the viscoelastic dissipation of the end-carboxyl nitrile rubber, but lacks a rigid scattering center. The low-frequency sound insulation is only 12.0 dB, and the average STL across the entire frequency band is only 18.0 dB. This indicates that the multi-level hollow structure of assembled hollow silica is crucial for broadband sound insulation.

[0052] (3) Comparing Example 1 and Comparative Example 2, when using assembled hollow silica alone, the coating only relies on sound wave scattering to achieve a certain sound insulation effect (average STL 24.2dB), but lacks viscoelastic dissipation, the sound insulation is less than 20dB, and the elongation at break is low (3.2%). This indicates that the introduction of carboxyl-terminated nitrile rubber not only enhances the dissipation of low-frequency sound energy, but also significantly improves the toughness of the coating.

[0053] (4) Comparing the use of solid silica instead of assembled hollow silica in Example 1 and Comparative Example 3, solid silica cannot provide a multi-level hollow structure, has a short sound wave scattering path, an average STL of only 26.5 dB, and only 20.0 dB in the low-frequency range. In addition, solid particles have a high density, increasing the coating weight. In contrast, the assembled hollow silica of the present invention achieves superior broadband sound insulation performance through its multi-level chambers and mesoporous shell.

[0054] In summary, the assembled hollow silica / carboxyl-terminated nitrile rubber composite sound insulation filler provided by this invention can achieve broadband and efficient sound insulation with a thin layer through the synergistic effect of rigid multi-level hollow structure and viscoelastic damping network. At the same time, it endows the coating with excellent mechanical properties and fire safety, making it suitable for engineering scenarios with high requirements for sound insulation, lightweighting and fire resistance.

[0055] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A method for preparing an assembled hollow silica-based sound-insulating composite material, characterized in that, Includes the following steps: S1. Under inert gas protection, a mixture of water, styrene, and methyl acrylate is heated to 65-80 °C, and potassium persulfate aqueous solution is added to initiate a polymerization reaction to obtain a polystyrene microsphere emulsion. Water is added to the obtained microsphere emulsion to prepare a suspension, and hexadecyltrimethylammonium bromide aqueous solution and bis(octadecyldimethylammonium chloride) ethanol solution are added sequentially and stirred to react. The pH of the system is then adjusted to 9.5-10.5, and tetraethyl orthosilicate is added. The reaction is continued to be stirred at room temperature and allowed to stand for aging. After the reaction, the product is filtered, washed, and then placed at a high temperature of 500-600 °C for 3-6 h to remove the polystyrene template, finally obtaining hollow silica material. S2. The assembled hollow silica prepared in S1 and the silane coupling agent are placed in an organic solvent, heated and stirred under reflux, the precipitate is collected by filtration, and then washed and dried to obtain the modified assembled hollow silica. S3. The assembled hollow silica modified by S2 and the carboxyl-terminated nitrile rubber were added to the solvent, heated and stirred to carry out the composite reaction. After the reaction, the composite material was filtered, washed and dried to finally obtain the assembled hollow silica-based sound insulation composite material.

2. The method for preparing an assembled hollow silica-based sound-insulating composite material according to claim 1, characterized in that, The number-average molecular weight of the end-carboxyl nitrile rubber is 3000-4000, and the viscosity is moderate; the silane coupling agent includes silane coupling agents KH560, KH550 or KH570.

3. The method for preparing an assembled hollow silica-based sound-insulating composite material according to claim 1, characterized in that, The mass ratio of styrene, methyl acrylate, potassium persulfate, hexadecyltrimethylammonium bromide, dioctadecyldimethylammonium chloride, tetraethyl orthosilicate, silane coupling agent KH560, and carboxyl-terminated nitrile rubber is 40:5:1:6:2:14:10:30-70.

4. The method for preparing an assembled hollow silica-based sound-insulating composite material according to claim 1, characterized in that, In S1, the polymerization reaction takes 20-30 hours.

5. The method for preparing an assembled hollow silica-based sound-insulating composite material according to claim 1, characterized in that, In S1, hexadecyltrimethylammonium bromide aqueous solution and dioctadecyldimethylammonium chloride ethanol solution are added under stirring, and the reaction is continued to be stirred for 1-3 hours after addition.

6. The method for preparing an assembled hollow silica-based sound-insulating composite material according to claim 1, characterized in that, In S1, after adding tetraethyl orthosilicate, the mixture is stirred continuously at room temperature for 3-5 hours and then aged at room temperature for 20-30 hours.

7. The method for preparing an assembled hollow silica-based sound-insulating composite material according to claim 1, characterized in that, In S2, the temperature of the heating, reflux, and stirring reaction is 60-80℃, and the time is 4-8h.

8. The method for preparing an assembled hollow silica-based sound-insulating composite material according to claim 1, characterized in that, In S3, the composite reaction is carried out at 60-80℃ with stirring at 200-400 r / min for 4-8 hours.

9. The assembled hollow silica-based sound insulation composite material prepared by the preparation method according to any one of claims 1-8.

10. The application of the assembled hollow silica-based sound-insulating composite material according to claim 9 in the preparation of sound-insulating coatings, characterized in that, The assembled hollow silica-based sound insulation composite material is added as a filler to the resin matrix, which includes epoxy resin, polyurethane resin or acrylic resin matrix.

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