A preparation process for preparing super-hydrophobic aerogel in situ by using glass wool waste yarn

Abstract

The present application relates to glass wool waste silk recycling technical field, specifically to a kind of preparation process of super-hydrophobic aerogel prepared in situ using glass wool waste silk, the integrated process of super-hydrophobic aerogel prepared in situ using glass wool cutting waste silk as only silicon source, first on-line collection waste silk and through microwave pretreatment to remove dust and binder to complete pre-cleaning;Then the surface of waste silk is roughened by combining plasma and chemical gradient etching, so that the roughness of the substrate reaches the standard Ra≥800nm;Subsequently, the roughened waste silk is grafted and modified using a fluorosilane-nano titanium dioxide composite system to construct a micro-nano composite low surface energy hydrophobic interface;Finally, the modified waste silk is mixed with an alcohol solvent, and the microwave-induced silicon component dissolution and reorganization and supercritical CO2 non-collapsing hole drying integrated forming are completed in the same closed reactor, without additional high-purity silicon source throughout, with high process integration, to stably produce super-hydrophobic aerogel materials with complete structure and excellent performance.

Description

Technical Field

[0001] This invention relates to the field of glass wool waste recycling technology, specifically to a preparation process for in-situ preparation of superhydrophobic aerogels using glass wool waste. Background Technology

[0002] Glass wool, due to its excellent thermal insulation and fireproofing properties, is widely used in building exterior wall insulation, industrial pipeline insulation, and other fields. During the production of glass wool boards, the cutting process generates approximately 20-30% short fiber waste. Currently, the main methods for treating this waste are landfilling or remelting. The former causes land occupation and environmental pollution, while the latter is energy-intensive, has high carbon emissions, and the fiber length and performance are significantly reduced during remelting, representing a typical case of degraded utilization. Therefore, how to achieve high-value recycling and utilization of glass wool waste is a long-standing but unresolved technical challenge in this field.

[0003] On the other hand, silica aerogels, due to their extremely high porosity and extremely low thermal conductivity, are considered to be the next generation of super insulation materials. However, traditional aerogel preparation typically uses tetraethyl orthosilicate, water glass, or silica sol as silicon sources, resulting in high raw material costs and requiring supercritical drying or complex atmospheric pressure drying processes, which are time-consuming and involve large equipment investments, limiting their large-scale application. Furthermore, existing aerogel materials themselves have low strength and high brittleness, making them difficult to use directly as structural insulation materials; they usually need to be composited with fiber-based substrates.

[0004] In recent years, researchers have made some progress in preparing aerogels using inexpensive silicon sources as an alternative to organosilicon sources. However, these methods usually still require the addition of acid / base catalysts, surface modifiers, etc., and the hydrophobic and mechanical properties of the resulting aerogels are often lower than those of organosilicon-based products. In particular, research on preparing aerogels using waste glass wool as a silicon source is extremely limited. The main component of waste glass wool is SiO2, and it also contains fluxing agents such as CaO, MgO, Al2O3, and B2O3. Its chemical composition differs significantly from pure silica, and impurity ions can easily cause uneven gel networks or even precipitation during the sol-gel process, increasing the difficulty of aerogel preparation.

[0005] To address the aforementioned issues, researchers have attempted to combine glass wool with aerogels, for example, by using physical doping to attach commercially available aerogel particles to the surface of glass wool, or by using the sol-gel method to grow aerogels in situ on glass wool fibers. However, these methods all use virgin glass wool and an external silicon source as raw materials, and have never addressed the recycling of glass wool waste fibers. A search revealed no existing technologies that report a closed-loop process that uses glass wool waste fibers as the sole silicon source, without requiring any external commercial aerogel or organosilicon source, to directly and in situ convert it into a high-performance superhydrophobic aerogel for reuse in the production line. Therefore, developing a closed-loop process that can both solve the problem of glass wool waste pollution and produce high-performance aerogels at low cost has significant industrial value and environmental implications. Summary of the Invention

[0006] This application provides a preparation process for superhydrophobic aerogels prepared in situ using waste glass wool fibers, in order to solve the problems of poor treatment effect of waste glass wool fibers, high cost of aerogel preparation, and lack of closed-loop recycling process for waste fiber aerogel preparation in the prior art.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The present invention provides a preparation process for in-situ preparation of superhydrophobic aerogels using waste glass wool fibers. The preparation process uses cut waste glass wool fibers as the sole silicon source and includes the following steps: (1) Online collection and pre-cleaning of waste filaments: Waste filaments are collected at the glass wool cutting station and sent into the microwave pretreatment chamber. Microwave treatment is used to remove surface dust particles and adhesives. (2) Plasma-chemical gradient etching: The pre-cleaned waste wire is subjected to plasma treatment and chemical etching solution treatment in sequence to roughen the surface of the waste wire, with an arithmetic mean roughness Ra≥800nm; (3) Grafting of fluorosilane-titanium dioxide composite coating: The etched waste wire is immersed in a solution containing fluorosilane and nano-titanium dioxide to carry out a grafting reaction and obtain modified waste wire; (4) Microwave-induced dissolution-supercritical drying integrated recombination: The modified waste filaments are mixed with an alcohol-containing solvent and placed in a closed reactor. First, microwave digestion is carried out at a temperature of 110℃-130℃ and a pressure of 0.2-0.4MPa. Then, supercritical CO2 drying is carried out in the same reactor to obtain the superhydrophobic aerogel.

[0008] Preferably, the plasma treatment in step (2) is carried out in a nitrogen / oxygen mixed atmosphere at a pressure of 60-100 Pa and a treatment time of 2-5 min; the chemical etching solution is a dilute HF / HNO3 mixed solution, wherein the HF concentration is 0.5-2 vol%, the HNO3 concentration is 1-5 vol%, and the immersion time is 5-10 s.

[0009] Preferably, the fluorosilane in step (3) is 1H,1H,2H,2H-perfluorodecyltriethoxysilane, the mass fraction of fluorosilane in the solution is 1-5wt%, the mass fraction of nano-titanium dioxide is 0.5-2wt%, and the particle size of nano-titanium dioxide is 15-30nm; the temperature of the grafting reaction is 80℃, and the reaction time is 1.5-2.5h.

[0010] Preferably, the alcohol-containing solvent in step (4) is tert-butanol, and the mixing ratio of the modified waste filaments to tert-butanol is 1:3 to 1:8.

[0011] Preferably, the microwave digestion process described in step (4) is carried out in a closed microwave reactor at a temperature of 110-130℃, a pressure of 0.3MPa, and a processing time of 10-20min; the parameters of the supercritical CO2 drying process are: temperature 35-45℃, pressure 8-12MPa, CO2 flow rate 3-8L / min, and drying time 1-3h.

[0012] This application also proposes a superhydrophobic aerogel, which is prepared by the process described above. The aerogel includes a glass wool waste filament skeleton and a SiO2 aerogel matrix covering the surface of the skeleton. The SiO2 aerogel matrix contains uniformly dispersed nano-titanium dioxide particles, and the sum of the contents of Q3 and Q4 structures in the silicon-oxygen tetrahedra of the aerogel matrix accounts for more than 85% of the total silicon-oxygen structure.

[0013] Preferred application of the superhydrophobic aerogel in the preparation of vacuum insulation panel core material involves encapsulating the superhydrophobic aerogel as the core material in a barrier film bag, and then vacuuming it to obtain a vacuum insulation panel.

[0014] Preferably, the vacuum insulation panel is used for building insulation or industrial pipeline insulation.

[0015] This application also proposes an integrated device for implementing the preparation process, the device comprising: a negative pressure dust collection unit, a microwave pretreatment chamber, a plasma treatment chamber, a chemical etching tank, a grafting reactor, a microwave digestion reactor, and a supercritical drying reactor.

[0016] This application also proposes a production system for in-situ preparation of superhydrophobic aerogels using waste glass wool fibers, the production system comprising: Glass wool cutting production line; Integrated equipment; The aerogel recycling unit includes a cutting device and a conveying device for cutting the aerogel output from the integrated equipment into vacuum insulation board core material or pipe insulation sleeve lining.

[0017] The beneficial effects achieved by using the present invention described above are as follows: 1. This invention is the first to use waste glass wool as the sole silicon source, eliminating the need for commercially available silicon sources such as tetraethyl orthosilicate, water glass, or silica sol. During microwave digestion, alkali metal and alkaline earth metal components in the waste wool selectively dissolve in an alcohol-containing solvent, exposing the previously shielded silica framework surface and forming a large number of active silanol groups. These silanol groups undergo in-situ condensation reactions under microwave-assisted heating, constructing a continuous Si-O-Si three-dimensional network structure on the waste wool surface and between fibers. This forms a composite structure with the waste wool framework as support and an aerogel matrix as a coating layer, achieving 100% high-value utilization of waste wool. The entire process is essentially wastewater-free and gas-free. Compared to traditional landfill or remelting processes, the carbon footprint is significantly reduced, and the raw material cost is close to zero, fundamentally solving the dual problems of poor waste wool treatment effect and high aerogel raw material cost. 2. In this invention, plasma-generated high-energy free radicals attack the fiber surface, forming nanoscale pits. Subsequently, a dilute HF / HNO3 etching solution preferentially erodes the alkaline-rich regions in the glass network, forming micron-sized pits that construct a multi-scale rough structure covering nano to micron scales on the fiber surface, providing an ideal geometric morphology basis for superhydrophobicity. Based on this, the silanol generated by the hydrolysis of 1H,1H,2H,2H-perfluorodecyltriethoxysilane undergoes dehydration condensation with the silanols on the waste fiber surface, forming strong Si-O-Si covalent bonds, anchoring the low surface energy fluorocarbon chains to the fiber surface. Nano-TiO2 is uniformly loaded into the coating through chemical bonding, further increasing the surface roughness. Simultaneously, TiO2 generates active oxygen species under ultraviolet light, decomposing surface oil and endowing the aerogel with photocatalytic self-cleaning function, making it suitable for long-term outdoor exposure environments. 3. In this invention, modified waste fibers and tert-butanol are placed in a closed reactor, and microwave digestion and supercritical CO2 drying are carried out sequentially in the same reactor. In the microwave digestion stage, the bulk heating effect and selective heating characteristics of microwaves are utilized to rapidly dissolve the alkali metal components inside the waste fibers and induce the condensation of silanol hydroxyl groups to form a uniform wet gel network. Subsequently, without the need to open the reactor or replace the solvent, the process is directly switched to supercritical CO2 drying. The low viscosity and high diffusivity of supercritical CO2 are used to completely extract tert-butanol without damaging the gel network, which significantly shortens the overall preparation cycle of the aerogel and is beneficial for continuous industrial production. 4. This invention achieves selective and controllable leaching of alkali metals and alkaline earth metals from waste fibers by precisely controlling the temperature, pressure, and time of microwave digestion. The degree of leaching is precisely controlled within the threshold that prevents the fiber structure from collapsing, while the number of exposed silanol groups is sufficient to drive subsequent polycondensation reactions to form a continuous network. The Si-O-Si three-dimensional network structure generated by in-situ polycondensation interpenetrates and chemically bonds with the original waste fiber skeleton to form a composite structure. At the same time, the sum of the contents of Q3 (Si(OSi)3OH) and Q4 (Si(OSi)4) structures in the silicon-oxygen tetrahedra of the aerogel matrix accounts for more than 85% of the total silicon-oxygen structure, indicating that the silanol polycondensation reaction is sufficient, the three-dimensional cross-linking degree is high, and the skeleton defects are few, ensuring its structural stability and thermal insulation performance do not degrade during vacuum insulation panel encapsulation and long-term service. 5. The integrated equipment provided by this invention connects a negative pressure dust collection unit, a microwave pretreatment chamber, a plasma treatment chamber, a chemical etching tank, a grafting reactor, a microwave digestion reactor, and a supercritical drying reactor in sequence. The waste filaments are continuously transported between these units via a closed conveying device, allowing for easy integration into existing glass wool cutting production lines. Furthermore, waste filaments generated by the glass wool cutting production line directly enter the integrated equipment and are transformed into superhydrophobic aerogel. The aerogel recycling unit cuts the aerogel into vacuum insulation board core materials or pipe insulation sleeve linings and transports it back to the glass wool production line or insulation sleeve assembly station. This achieves in-situ recycling and high-value reuse of waste filaments at the glass wool production site, fundamentally solving the industry pain points of difficult waste filament treatment and low added value in the glass wool industry. This solves the problems of poor treatment effect of glass wool waste fibers, high cost of aerogel preparation, and lack of closed-loop recycling process for waste fiber to produce aerogel in existing technologies.

[0018] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0019] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 The flowchart shows a process for preparing superhydrophobic aerogels in situ using waste glass wool, as provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the integrated device provided in the embodiments of the present invention; Figure 3 This is a schematic diagram of a production system for in-situ preparation of superhydrophobic aerogels using waste glass wool fibers, as provided in an embodiment of the present invention. Detailed Implementation

[0020] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0021] The following describes a preparation process for superhydrophobic aerogels prepared in situ using waste glass wool, according to an embodiment of this application, with reference to the accompanying drawings. Addressing the problem of poor treatment efficiency of waste glass wool mentioned in the background art, this application provides a preparation process for superhydrophobic aerogels prepared in situ using waste glass wool. In this process, cut waste glass wool is used as the sole silicon source for aerogel preparation, eliminating various commercially available silicon sources. Microwave digestion technology is used to selectively dissolve alkali metal and alkaline earth metal impurities within the waste wool, fully releasing active silanol groups and promoting their in-situ condensation through microwave thermal effects. This constructs a highly cross-linked Si-O-Si three-dimensional network, forming a composite structure combining the fiber skeleton and the aerogel matrix. This not only achieves efficient utilization of waste wool and eliminates wastewater and waste gas emissions during the production process, significantly reducing the carbon footprint, but also brings the raw material cost of the aerogel close to zero. Simultaneously, by precisely controlling the microwave digestion parameters, impurities are controllably dissolved while ensuring the integrity of the fiber structure and preventing collapse. The product contains over 85% Q3 and Q4 type silicon-oxygen structures, with a fully cross-linked gel network and a stable skeleton, resulting in excellent thermal insulation properties during long-term use. The structure and morphology do not decay. In terms of process, plasma bombardment combined with mixed acid etching is first used to construct a nano-micro cross-scale rough morphology on the fiber surface. Then, covalent bonds are formed by the dehydration condensation of fluorosilane and silanol to anchor low surface energy fluorocarbon chains and chemically bond and load nano-titanium dioxide to achieve excellent superhydrophobic effect. Moreover, titanium dioxide can generate active oxygen under ultraviolet light to decompose organic pollutants, giving the material photocatalytic self-cleaning properties, which is suitable for complex application scenarios such as outdoor and industrial applications. The entire preparation process is integrated into the same closed reaction vessel, continuously completing microwave digestion and supercritical CO2 drying, eliminating steps such as opening the lid for transfer and solvent replacement. Relying on the characteristics of microwave and supercritical fluid, it can quickly form and preserve the gel network, greatly reducing the preparation cycle and adapting to industrial continuous production. It comprehensively overcomes a series of problems such as the high pollution and low utilization rate of traditional glass wool waste fiber treatment methods, the expensive raw materials and complicated processes for aerogel preparation, and the lack of closed-loop recycling technology for waste fiber to aerogel in the industry.

[0022] Specifically, Figure 1 This is a schematic flowchart illustrating a process for preparing superhydrophobic aerogels in situ using waste glass wool, as provided in an embodiment of this application.

[0023] like Figure 1 As shown, the preparation process of superhydrophobic aerogel using waste glass wool in situ includes the following steps: A preparation process for in-situ preparation of superhydrophobic aerogels using waste glass wool fibers, wherein the preparation process uses cut waste glass wool fibers as the sole silicon source, and includes the following steps: (1) Online collection and pre-cleaning of waste filaments: Waste filaments are collected at the glass wool cutting station and sent into the microwave pretreatment chamber. Microwave treatment is used to remove surface dust particles and adhesives. (2) Plasma-chemical gradient etching: The pre-cleaned waste wire is subjected to plasma treatment and chemical etching solution treatment in sequence to roughen the surface of the waste wire, with an arithmetic mean roughness Ra≥800nm; (3) Grafting of fluorosilane-titanium dioxide composite coating: The etched waste wire is immersed in a solution containing fluorosilane and nano-titanium dioxide to carry out a grafting reaction and obtain modified waste wire; (4) Microwave-induced dissolution-supercritical drying integrated recombination: The modified waste filaments are mixed with an alcohol-containing solvent and placed in a closed reactor. First, microwave digestion is carried out at a temperature of 110℃-130℃ and a pressure of 0.2-0.4MPa. Then, supercritical CO2 drying is carried out in the same reactor to obtain the superhydrophobic aerogel.

[0024] It is understood that in this embodiment, glass wool waste filaments are used as the sole silicon source to prepare superhydrophobic aerogels. First, the waste filaments are collected online and dust and surface adhesives are removed through microwave pretreatment. Then, plasma-assisted chemical gradient etching is used to control the roughness of the substrate to Ra≥800nm, constructing a multi-level rough microstructure. Subsequently, a mixture of fluorosilane and nano-titanium dioxide is impregnated to complete the composite hydrophobic grafting modification. Finally, the modified waste filaments and alcohol solvent are subjected to microwave digestion and silicon dissolution, and supercritical CO2 drying in the same reactor for integrated molding. The porous aerogel framework is constructed by in-situ polycondensation of silica from the waste filaments, realizing the efficient conversion of industrial solid waste into resources.

[0025] In step (2), the plasma treatment is carried out in a nitrogen / oxygen mixed atmosphere at a pressure of 60-100 Pa and a treatment time of 2-5 min; the chemical etching solution is a dilute HF / HNO3 mixed solution, wherein the HF concentration is 0.5-2 vol%, the HNO3 concentration is 1-5 vol%, and the immersion time is 5-10 s.

[0026] It is understood that the embodiments of this application adopt a composite etching system of nitrogen-oxygen mixed gas low-temperature plasma pretreatment combined with short-time immersion in low-concentration mixed acid. The low-pressure plasma can quickly etch dense micro-defect sites on the glass fiber surface. The subsequent low-content hydrofluoric acid and nitric acid mixed etching solution achieves selective and rapid diffusion based on the defects. Only a short immersion is needed to accurately control the substrate roughness to Ra≥800nm. This avoids excessive dissolution of the glass substrate by strong acid for a long time and loss of silicon source, and efficiently constructs a micron-nano composite rough structure, providing sufficient anchoring sites for the subsequent strong grafting of hydrophobic coating.

[0027] In step (3), the fluorosilane is 1H,1H,2H,2H-perfluorodecyltriethoxysilane, the mass fraction of fluorosilane in the solution is 1-5wt%, the mass fraction of nano titanium dioxide is 0.5-2wt%, and the particle size of nano titanium dioxide is 15-30nm; the grafting reaction temperature is 80℃, and the reaction time is 1.5-2.5h.

[0028] It is understood that in the embodiments of this application, nano-titanium dioxide and perfluorodecyltriethoxysilane are compounded and impregnated. The mass fraction of the components is controlled and grafted at a constant temperature of 80°C for 1.5 to 2.5 hours. The titanium dioxide anchors into the uneven pores of the substrate with its surface hydroxyl groups to refine the micro-rough structure. After hydrolysis, the fluorosilane dehydrates and condenses with the silanol groups of the substrate to form silicon-oxygen bonds to achieve covalent fixation. The exposed perfluorinated long chain reduces the surface energy. The superhydrophobic interface is constructed by morphology control and chemical modification.

[0029] In step (4), the alcohol solvent is tert-butanol, and the mixing ratio of modified waste filaments and tert-butanol is 1:3 to 1:8.

[0030] It is understood that in the embodiments of this application, tert-butanol is used as the dispersion solvent and the solid-liquid ratio is limited to 1:3 to 1:8. Tert-butanol does not react chemically with the hydrophobic coating on the surface of the modified waste filament. It penetrates into the pores of the substrate by relying on its own wettability. Under microwave heating, the trace amount of water in the system promotes the hydrolysis of glass phase silica to generate silicic acid monomers. Sufficient solvent can disperse silicic acid monomers, delay local rapid polymerization, and facilitate the uniform condensation and cross-linking of silicic acid to form a continuous three-dimensional gel network. At the same time, it is suitable for supercritical carbon dioxide extraction to remove the aerogel pores and ensure the integrity of the aerogel channels.

[0031] In step (4), the microwave digestion process is carried out in a closed microwave reactor at a temperature of 110-130℃, a pressure of 0.3MPa, and a processing time of 10-20min. The parameters for the supercritical CO2 drying process are: temperature 35-45℃, pressure 8-12MPa, CO2 flow rate 3-8L / min, and drying time 1-3h.

[0032] It should be noted that this application adopts a mild, low-temperature, and medium-pressure controllable supercritical CO2 drying system, which matches the special structural characteristics of the modified hydrophobic aerogel. On the one hand, the low-temperature environment can completely avoid the thermal damage to the low surface energy hydrophobic coating of fluorosilane on the surface of waste filaments under high-temperature conditions, and completely preserve the micro-nano composite superhydrophobic interface structure, eliminating the problems of hydrophobic groups decomposing and falling off at high temperatures and the degradation of the hydrophobic properties of the material. On the other hand, the supercritical CO2 fluid has no surface tension and no capillary stress, which can realize the uniform and gentle displacement and removal of tert-butanol solvent inside the gel, fundamentally solving the defects such as the collapse of the porous skeleton, pore blockage, and a significant decrease in porosity that are very easy to occur in traditional drying processes.

[0033] This application also proposes a superhydrophobic aerogel, which is prepared by a process. The aerogel includes a glass wool waste filament skeleton and a SiO2 aerogel matrix covering the surface of the skeleton. The SiO2 aerogel matrix contains uniformly dispersed nano-titanium dioxide particles, and the sum of the contents of Q3 and Q4 structures in the silicon-oxygen tetrahedra of the aerogel matrix accounts for more than 85% of the total silicon-oxygen structure.

[0034] Among them, the application of superhydrophobic aerogel in the preparation of vacuum insulation panel core material involves encapsulating superhydrophobic aerogel as core material in a barrier film bag, and then obtaining a vacuum insulation panel after vacuuming.

[0035] Vacuum insulation panels are used for building insulation or industrial pipeline insulation.

[0036] Understandably, this application is based on the aforementioned in-situ preparation process of waste fiber to form a superhydrophobic aerogel with a proprietary structure. This material uses waste glass wool as a supporting skeleton, with a continuous and dense SiO2 aerogel matrix in-situ coated on the surface. The matrix contains uniformly dispersed nano-titanium dioxide particles. Through precise process control, the total proportion of highly polymerized Q3 and Q4 structures in the silicon-oxygen tetrahedra of the aerogel matrix reaches more than 85%. The high proportion of cross-linked silicon-oxygen structures can significantly improve the structural integrity, density, and mechanical stability of the aerogel skeleton, effectively reducing pore defects. Combined with the uniformly dispersed nano-titanium dioxide micro-nano coarsening structure and the surface hydrophobic modification system, the material has both excellent structural strength, pore stability, and long-lasting superhydrophobic properties. This application further expands the specific application scenarios of the superhydrophobic aerogel by encapsulating it as a functional core material in a barrier film bag and preparing a vacuum insulation board. Relying on the core advantages of aerogel such as ultra-low thermal conductivity, hydrophobicity and moisture resistance, and high porosity, it avoids the problems of traditional vacuum insulation board core materials such as easy moisture absorption, thermal conductivity drift, and poor thermal insulation durability. The prepared vacuum insulation board is suitable for various working conditions such as building insulation and industrial pipeline insulation. It has the advantages of moisture resistance, heat insulation, stable performance, and long service life, realizing the industrial application of high-end thermal insulation materials based on solid waste.

[0037] This application also proposes an integrated device for implementing the preparation process, such as... Figure 2 As shown, the equipment includes: a negative pressure dust collection unit, a microwave pretreatment chamber, a plasma treatment chamber, a chemical etching tank, a grafting reactor, a microwave digestion reactor, and a supercritical drying reactor.

[0038] It is understood that in the integrated device of this application embodiment, the negative pressure dust collection unit is used to absorb and collect waste filaments at the glass wool cutting station, and can be equipped with cyclone separation or filtration components to prevent micro-dust from entering the subsequent processing chamber; the microwave pretreatment chamber is equipped with a microwave generator and an exhaust port to remove dust and volatile binder residues adhering to the surface of the waste filaments; the plasma treatment chamber is equipped with an electrode plate, which can be introduced with oxygen, argon or air plasma to activate the surface of the waste filaments; the chemical etching tank has a built-in corrosion-resistant container and temperature control components to contain alkaline or fluorine-containing etching solution to achieve gradient etching to roughen the surface of the waste filaments; the grafting reactor is equipped with a constant temperature water bath, stirring and reflux condensation device to complete the grafting modification reaction of fluorine-containing silane and nano titanium dioxide; the microwave digestion reactor and the supercritical drying reactor can be independently controlled in temperature and pressure, or integrated into the same high-pressure reactor to implement microwave-induced dissolution and supercritical CO2 drying in stages. Each unit can be sequentially connected via a sealed conveying spiral, pneumatic flap, or vacuum conveying pipe to achieve continuous or semi-continuous operation of the entire process of waste filament from feeding, pretreatment, etching, modification to dissolution and drying. This reduces secondary pollution and structural damage caused by human handling and ensures the consistency and yield of the final superhydrophobic aerogel product.

[0039] This application also proposes a production system for in-situ preparation of superhydrophobic aerogels using waste glass wool fibers, such as... Figure 3 As shown, the production system includes: Glass wool cutting production line; Integrated equipment; The aerogel recycling unit includes a cutting device and a conveying device for cutting the aerogel output from the integrated equipment into vacuum insulation panel core material or pipe insulation sleeve lining.

[0040] The following will illustrate this through several specific embodiments, the contents of which are as follows.

[0041] Example 1 Step (1) Online collection and pre-cleaning of waste filaments: Waste fibers from the glass wool cutting station are collected, drawn up by a negative pressure dust collection unit, and sent into a microwave pretreatment chamber. They are then treated for 5 minutes in a microwave field with a power of 2kW and a frequency of 2.45GHz to remove surface dust particles and adhesive residue.

[0042] Step (2) Plasma-chemical gradient etching: The pre-cleaned waste filaments were placed in a plasma treatment chamber and subjected to plasma treatment in a nitrogen / oxygen mixed atmosphere (volume ratio 4:1) at a pressure of 80 Pa for 3 min. Subsequently, they were immersed in a dilute HF / HNO3 mixed etching solution (HF concentration 1 vol%, HNO3 concentration 3 vol%) for 8 s, and then rinsed with deionized water until neutral. Atomic force microscopy (AFM) analysis showed that the arithmetic mean surface roughness Ra of the waste filaments was 950 nm.

[0043] Step (3) Grafting of fluorosilane-titanium dioxide composite coating: Preparation of grafting solution: 1H,1H,2H,2H-perfluorodecyltriethoxysilane (3wt%) and nano-titanium dioxide (1wt%, average particle size 20nm) were dispersed in anhydrous ethanol and ultrasonically dispersed for 15 min. The etched waste wire was immersed in the above solution and grafted in a constant temperature water bath at 80℃ for 2 h. After removal, it was cured at 120℃ for 30 min to obtain modified waste wire.

[0044] Step (4) Microwave-induced dissolution-supercritical drying integrated recombination: Modified waste fibers were mixed with tert-butanol at a mass ratio of 1:5 and placed in a closed microwave digestion reactor. Microwave digestion was performed at 120℃ and 0.3MPa for 15 minutes. After digestion, the material was not removed, and the process was directly switched to supercritical CO2 drying: temperature controlled at 40℃, pressure at 10MPa, CO2 flow rate at 5L / min, and drying time at 2 hours. After cooling, the material was removed to obtain the superhydrophobic aerogel.

[0045] Example 2 Step (1) Online collection and pre-cleaning of waste filaments: Waste fibers from the glass wool cutting station are collected, drawn up by a negative pressure dust collection unit, and sent into a microwave pretreatment chamber. They are then treated for 5 minutes in a microwave field with a power of 2kW and a frequency of 2.45GHz to remove surface dust particles and adhesive residue.

[0046] Step (2) Plasma-chemical gradient etching: The pre-cleaned waste filaments were placed in a plasma treatment chamber and subjected to plasma treatment in a nitrogen / oxygen mixed atmosphere (volume ratio 4:1) at a pressure of 60 Pa for 5 min. Subsequently, they were immersed in a dilute HF / HNO3 mixed etching solution (HF concentration 0.5 vol%, HNO3 concentration 5 vol%) for 10 s, and then rinsed with deionized water until neutral. Atomic force microscopy (AFM) analysis showed that the arithmetic mean surface roughness Ra of the waste filaments was 860 nm.

[0047] Step (3) Grafting of fluorosilane-titanium dioxide composite coating: Preparation of grafting solution: 1H,1H,2H,2H-perfluorodecyltriethoxysilane (1wt%) and nano-titanium dioxide (2wt%, average particle size 15nm) were dispersed in anhydrous ethanol and ultrasonically dispersed for 15 min. The etched waste wire was immersed in the above solution and grafted in a constant temperature water bath at 80℃ for 1.5 h. After removal, it was cured at 120℃ for 30 min to obtain modified waste wire.

[0048] Step (4) Microwave-induced dissolution-supercritical drying integrated recombination: Modified waste fibers were mixed with tert-butanol at a mass ratio of 1:3 and placed in a closed microwave digestion reactor. Microwave digestion was performed at 110℃ and 0.2MPa for 20 min. After digestion, the material was not removed, and the process was directly switched to supercritical CO2 drying: temperature controlled at 35℃, pressure at 8MPa, CO2 flow rate at 8L / min, and drying time at 3 h. After cooling, the material was removed to obtain the superhydrophobic aerogel.

[0049] Example 3 Step (1) Online collection and pre-cleaning of waste filaments: Waste fibers from the glass wool cutting station are collected, drawn up by a negative pressure dust collection unit, and sent into a microwave pretreatment chamber. They are then treated for 5 minutes in a microwave field with a power of 2kW and a frequency of 2.45GHz to remove surface dust particles and adhesive residue.

[0050] Step (2) Plasma-chemical gradient etching: The pre-cleaned waste filaments were placed in a plasma treatment chamber and subjected to plasma treatment in a nitrogen / oxygen mixed atmosphere (volume ratio 4:1) at a pressure of 100 Pa for 2 min. Subsequently, they were immersed in a dilute HF / HNO3 mixed etching solution (HF concentration 2 vol%, HNO3 concentration 1 vol%) for 5 s, and then rinsed with deionized water until neutral. Atomic force microscopy (AFM) analysis showed that the arithmetic mean surface roughness Ra of the waste filaments was 910 nm.

[0051] Step (3) Grafting of fluorosilane-titanium dioxide composite coating: Preparation of grafting solution: 1H,1H,2H,2H-perfluorodecyltriethoxysilane (5wt%) and nano-titanium dioxide (0.5wt%, average particle size 30nm) were dispersed in anhydrous ethanol and ultrasonically dispersed for 15 min. The etched waste wire was immersed in the above solution and grafted in a constant temperature water bath at 80℃ for 2.5 h. After removal, it was cured at 120℃ for 30 min to obtain modified waste wire.

[0052] Step (4) Microwave-induced dissolution-supercritical drying integrated recombination: Modified waste fibers were mixed with tert-butanol at a mass ratio of 1:8 and placed in a closed microwave digestion reactor. Microwave digestion was performed for 10 min at 130℃ and 0.4 MPa. After digestion, the material was not removed, and the process was directly switched to supercritical CO2 drying: temperature controlled at 45℃, pressure at 12 MPa, CO2 flow rate at 3 L / min, and drying time at 1 h. After cooling, the material was removed to obtain the superhydrophobic aerogel.

[0053] Comparative Example 1 The process is basically the same as in Example 1, except that the plasma treatment in step (2) is omitted and only chemical etching (HF1vol% / HNO33vol%, immersion for 8s) is performed.

[0054] Comparative Example 2 The process is basically the same as in Example 1, except that the grafting solution in step (3) does not contain nano-titanium dioxide, but only fluorosilane (3wt%).

[0055] Comparative Example 3 Using the same glass wool cut waste filaments as in Example 1 as raw materials, aerogels were prepared using the traditional sol-gel method: the waste filaments were placed in a hydrochloric acid / ethanol mixture and heated and refluxed at 70°C for 6 hours to dissolve the silicon components and form a silica sol. The pH was adjusted to 7-8 to promote gelation. After 24 hours of aging and stepwise solvent replacement with ethanol / n-hexane, supercritical CO2 drying was performed (40°C, 10MPa, 2 hours). The waste filaments were not subjected to plasma-chemical gradient etching or fluorosilane-titanium dioxide composite grafting modification throughout the process.

[0056] Performance testing: The samples obtained in Examples 1-3 and Comparative Examples 1-3 were tested as follows: (1) Water contact angle (CA) and roll-off angle (SA): Measured using a contact angle measuring instrument.

[0057] The results are as follows: the water contact angles of Examples 1-3 are 158°, 152° and 155°, respectively, and the roll-off angles are <5°, 8° and 6°, respectively. All of these are significantly higher than the superhydrophobic threshold of 150° and the roll-off angle is less than 10°, proving that the preparation process of this application can stably obtain superhydrophobic aerogels within a wide parameter range. The water contact angle of Comparative Example 1 (plasma treatment omitted) is only 125°, which does not reach the superhydrophobic state, indicating that the synergistic effect of plasma pretreatment and chemical etching is the key to constructing ideal surface roughness. Although the initial contact angle of Comparative Example 2 (nano-TiO2 omitted) is 153°, it drops to 118° after 48 hours of UV accelerated aging, losing its superhydrophobic properties, proving that the introduction of nano-TiO2 is crucial to the durability of the coating. The water contact angle of Comparative Example 3 (traditional sol-gel method) is only 135°, indicating that the integrated grafting-recombination process of this application is significantly better than the traditional method in terms of hydrophobicity effect.

[0058] (2) Hydrophobic durability: The contact angle was retested after immersion in water at 80℃ for 24 hours.

[0059] The results were as follows: After soaking in hot water at 80°C for 24 hours, Examples 1-3 maintained water contact angles of 96.2%, 95.4%, and 95.5%, respectively, all above 145°, still meeting the superhydrophobic standard. Comparative Example 1 (without plasma etching) maintained 86.4%, Comparative Example 2 (without nano-TiO2) only 73.2%, and Comparative Example 3 (traditional sol-gel method) 87.4%. This application, through the synergistic effect of plasma-chemical gradient etching to construct a rough anchoring interface, fluorosilane covalent grafting, nano-TiO2 reinforcement and protection, and a highly cross-linked aerogel network, endows the material with excellent hot water erosion resistance and durability, significantly superior to the comparative examples.

[0060] (3) Porosity and specific surface area: tested by N2 adsorption-desorption method (BET).

[0061] The results are as follows: the specific surface areas of Examples 1-3 are 620 m² / g, 580 m² / g, and 600 m² / g, respectively; the pore volumes are 2.85 cm³ / g, 2.61 cm³ / g, and 2.73 cm³ / g, respectively; and the porosities are 92.5%, 91.8%, and 92.1%, respectively. All exhibit the typical characteristics of high specific surface area, high pore volume, and high porosity of aerogels. The N₂ adsorption-desorption isotherm shows a typical type IV isotherm and an H₂ type hysteresis loop, proving that the material has a well-developed mesoporous structure. The specific surface area of ​​Comparative Example 1 (without plasma etching) is only 380 m² / g, and the specific surface area of ​​Comparative Example 3 (traditional sol-gel method) is only 450 m² / g, both significantly lower than the Examples, verifying the significant advantages of the plasma-chemical gradient etching and in-situ integrated reconstruction process in pore structure control in this application.

[0062] (4) Thermal conductivity: tested using a thermal conductivity meter (25℃) using the heat flow method.

[0063] The results showed that the thermal conductivity of the aerogels in Examples 1-3 were 19.8 mW / (m·K), 21.2 mW / (m·K), and 20.5 mW / (m·K), respectively, all lower than 23 mW / (m·K), exhibiting excellent thermal insulation performance. The thermal conductivity of Comparative Example 1 (without plasma etching), Comparative Example 2 (without nano-TiO2), and Comparative Example 3 (traditional sol-gel method) were 28.6 mW / (m·K), 26.4 mW / (m·K), and 29.3 mW / (m·K), respectively, all significantly higher than those in Examples 1-3, indicating that surface roughening, hydrophobic modification, and pore structure control have a synergistic effect on reducing thermal conductivity.

[0064] (5) Thermal conductivity of the center of the vacuum insulation panel (25℃, vacuum degree ≤10Pa).

[0065] The results were as follows: The aerogels obtained in Examples 1-3 were encapsulated in barrier film bags as core materials, and after being evacuated to ≤10 Pa, the thermal conductivity was tested at 25°C using a thermal flow method. The results showed that the center thermal conductivity of the vacuum insulation panels corresponding to Examples 1-3 was 7.2 mW / (m·K), 7.8 mW / (m·K), and 7.5 mW / (m·K), respectively, all lower than 8.0 mW / (m·K); the center thermal conductivity of the vacuum insulation panels corresponding to Comparative Examples 1-3 was 11.6 mW / (m·K), 10.4 mW / (m·K), and 12.1 mW / (m·K), respectively, all significantly higher than those of the Examples. The above results demonstrate that the superhydrophobic aerogel prepared in this application can significantly improve the thermal insulation performance and reduce the center thermal conductivity when used as the core material of a vacuum insulation panel.

[0066] In summary, Examples 1-3 significantly outperformed the comparative examples in all performance tests, demonstrating that this application, using waste glass wool as the sole silicon source, can stably prepare aerogel materials with high specific surface area, high porosity, excellent superhydrophobicity, and ultra-low thermal conductivity through a plasma-chemical gradient etching, fluorosilane-TiO2 composite grafting, and microwave digestion-supercritical drying integrated recombination process. When used as the core material of a vacuum insulation board, its central thermal conductivity is as low as 7.2-7.8 mW / (m·K), significantly better than the comparative examples, achieving high-value closed-loop utilization of waste fibers.

[0067] This application uses waste glass wool as the sole silicon source and successfully prepares a SiO2-based aerogel material with superhydrophobicity, high porosity, low thermal conductivity, and excellent resistance to hot water erosion through plasma-chemical gradient etching, fluorosilane-nano TiO2 composite grafting, and microwave-induced dissolution-supercritical drying integrated recombination. When used as the core material of vacuum insulation panels, this aerogel can significantly reduce the central thermal conductivity, improve thermal insulation performance and service life, and realize the synergy between high-value utilization of industrial solid waste and high-end thermal insulation materials.

[0068] Therefore, this application proposes a process for in-situ preparation of superhydrophobic aerogels using waste glass wool. The process uses cut waste glass wool as the sole silicon source, eliminating various commercially available silicon sources. It selectively dissolves alkali metal and alkaline earth metal impurities within the waste wool using microwave digestion technology, fully releasing active silanol groups and promoting in-situ condensation through microwave thermal effects. This constructs a highly cross-linked Si-O-Si three-dimensional network, forming a composite structure combining the fiber skeleton and the aerogel matrix. This not only achieves efficient utilization of waste wool and eliminates wastewater and waste gas emissions during production, significantly reducing the carbon footprint, but also brings the raw material cost of the aerogel close to zero. Furthermore, by precisely controlling the microwave digestion parameters, impurities can be controlled to dissolve while ensuring the fiber structure remains intact and does not collapse. The product contains over 85% Q3 and Q4 type silicon-oxygen structures, with a fully cross-linked gel network and a stable skeleton. The thermal insulation performance and structural morphology do not degrade under long-term use. First, plasma bombardment combined with mixed acid etching is used to construct a nano- to micro-scale rough morphology on the fiber surface. Then, covalent bonds are formed by the dehydration condensation of fluorosilane and silanol to anchor low surface energy fluorocarbon chains, and nano-titanium dioxide is chemically bonded and loaded to achieve excellent superhydrophobic effects. Furthermore, titanium dioxide can generate active oxygen under ultraviolet light to decompose organic pollutants, giving the material photocatalytic self-cleaning properties, making it suitable for complex applications such as outdoor and industrial applications. The entire preparation process is integrated into the same closed reactor, continuously completing microwave digestion and supercritical CO2 drying, eliminating steps such as opening the lid for transfer and solvent replacement. Relying on the characteristics of microwaves and supercritical fluids, it rapidly forms and preserves the gel network, significantly reducing the preparation cycle and adapting to continuous industrial production. This method comprehensively overcomes a series of problems such as high pollution and low utilization rate of traditional glass wool waste fiber treatment methods, expensive raw materials and cumbersome processes for aerogel preparation, and the lack of closed-loop recycling technology for waste fiber aerogel in the industry.

[0069] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A preparation process for in-situ preparation of superhydrophobic aerogels using waste glass wool fibers, characterized in that, The preparation process uses waste glass wool as the sole silicon source and includes the following steps: (1) Online collection and pre-cleaning of waste filaments: Waste filaments are collected at the glass wool cutting station and sent into the microwave pretreatment chamber. Microwave treatment is used to remove surface dust particles and adhesives. (2) Plasma-chemical gradient etching: The pre-cleaned waste wire is subjected to plasma treatment and chemical etching solution treatment in sequence to roughen the surface of the waste wire, with an arithmetic mean roughness Ra≥800nm; (3) Grafting of fluorosilane-titanium dioxide composite coating: The etched waste wire is immersed in a solution containing fluorosilane and nano-titanium dioxide to carry out a grafting reaction and obtain modified waste wire; (4) Microwave-induced dissolution-supercritical drying integrated recombination: The modified waste filaments are mixed with an alcohol-containing solvent and placed in a closed reactor. First, microwave digestion is carried out at a temperature of 110℃-130℃ and a pressure of 0.2-0.4MPa. Then, supercritical CO2 drying is carried out in the same reactor to obtain the superhydrophobic aerogel.

2. The preparation process for in-situ preparation of superhydrophobic aerogel using waste glass wool as described in claim 1, characterized in that, The plasma treatment in step (2) is carried out in a nitrogen / oxygen mixed atmosphere at a pressure of 60-100 Pa and a treatment time of 2-5 min; the chemical etching solution is a dilute HF / HNO3 mixed solution, wherein the HF concentration is 0.5-2 vol%, the HNO3 concentration is 1-5 vol%, and the immersion time is 5-10 s.

3. The preparation process for in-situ preparation of superhydrophobic aerogel using waste glass wool as described in claim 1, characterized in that, The fluorosilane mentioned in step (3) is 1H,1H,2H,2H-perfluorodecyltriethoxysilane, the mass fraction of fluorosilane in the solution is 1-5wt%, the mass fraction of nano-titanium dioxide is 0.5-2wt%, and the particle size of nano-titanium dioxide is 15-30nm; the temperature of the grafting reaction is 80℃, and the reaction time is 1.5-2.5h.

4. The preparation process for in-situ preparation of superhydrophobic aerogel using waste glass wool as described in claim 1, characterized in that, The alcohol-containing solvent in step (4) is tert-butanol, and the mixing ratio of the modified waste filaments to tert-butanol is 1:3 to 1:

8.

5. The preparation process for in-situ preparation of superhydrophobic aerogel using waste glass wool as described in claim 1, characterized in that, The microwave digestion process described in step (4) is carried out in a closed microwave reactor at a temperature of 110-130℃, a pressure of 0.3MPa, and a processing time of 10-20min. The parameters for the supercritical CO2 drying process are: temperature 35-45℃, pressure 8-12MPa, CO2 flow rate 3-8L / min, and drying time 1-3h.

6. A superhydrophobic aerogel, characterized in that, The aerogel is prepared by the process described in any one of claims 1-5, wherein the aerogel comprises a glass wool waste filament skeleton and a SiO2 aerogel matrix covering the surface of the skeleton, the SiO2 aerogel matrix contains uniformly dispersed nano-titanium dioxide particles, and the sum of the contents of Q3 and Q4 structures in the silicon-oxygen tetrahedra of the aerogel matrix accounts for more than 85% of the total silicon-oxygen structure.

7. The application of the superhydrophobic aerogel according to claim 6 in the preparation of vacuum insulation panel core material, characterized in that, The superhydrophobic aerogel was encapsulated in a barrier film bag as the core material, and a vacuum insulation board was prepared by vacuuming.

8. The application according to claim 7, characterized in that, The vacuum insulation panel is used for building insulation or industrial pipeline insulation.

9. An integrated apparatus for implementing the preparation process according to any one of claims 1-5, characterized in that, The equipment includes: a negative pressure dust collection unit, a microwave pretreatment chamber, a plasma treatment chamber, a chemical etching tank, a grafting reactor, a microwave digestion reactor, and a supercritical drying reactor.

10. A production system for in-situ preparation of superhydrophobic aerogels using waste glass wool fibers, characterized in that, The production system includes: Glass wool cutting production line; The integrated device as described in claim 9; The aerogel recycling unit includes a cutting device and a conveying device for cutting the aerogel output from the integrated equipment into vacuum insulation board core material or pipe insulation sleeve lining.

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