A method for preparing nano-silica by controlled degradation of waste silicone rubber

Abstract

This invention belongs to the technical field of degrading waste silicone rubber, and discloses a method for preparing nano-silica through the controlled degradation of waste silicone rubber. The method involves crushing waste silicone rubber into particles, mixing them evenly with an aluminum-based catalyst in a crucible at a certain ratio, pouring the mixture into a reaction tube, and carrying out the degradation reaction on a heating platform at a temperature of 200–310°C for 10–70 minutes. After the reaction, the mixture is cooled to room temperature, and the product is then mixed with an appropriate amount of dilute hydrochloric acid. After washing and drying, silica nanoparticles are obtained. This invention selects an aluminum-based compound as a catalyst, which can activate the Si-C bonds in silicone rubber, facilitating the subsequent oxidation reaction with oxygen, thereby efficiently generating silica nanoparticles. This invention utilizes a catalyst capable of degrading waste silicone rubber to achieve the recycling and reuse of silicone rubber waste through a simple, low-cost, and low-energy process, reducing environmental pollution and resource waste caused by waste silicone rubber and turning waste into treasure.

Description

Technical Field

[0001] This invention belongs to the technical field of degrading waste silicone rubber, and more specifically, relates to a method for preparing nano-silica by controlling the degradation of waste silicone rubber. Background Technology

[0002] Silicone rubber polymer molecules are chain-like structures linked by Si-O bonds, and their main component is a high molar mass of linear polysiloxane. Because the Si-O-Si bond is the basic bond type, silicon atoms are mainly connected to methyl groups, and a very small number of unsaturated groups are introduced into the side chains. This results in weak intermolecular forces and a helical molecular structure, with methyl groups facing outwards and able to rotate freely. This gives silicone rubber better heat resistance, electrical insulation, and chemical stability than other ordinary rubbers. Silicone rubber has a temperature resistance range of -60 to 250℃, retaining flexibility even at -60℃, and possesses excellent hydrophobicity and insulation properties. It is widely used in medical, electronics, automotive, construction, household goods, and aerospace fields. With the increasing demand for silicone rubber materials in daily life, the amount of silicone rubber waste generated is also increasing.

[0003] Common methods for treating silicone rubber waste include crushing, reprocessing, and incineration. Alternatively, degrading waste silicone rubber into inorganic SiOC ceramics or silica nanoparticles enables recycling and reuse, thus addressing the environmental problems caused by silicone rubber waste. Hajj et al. pyrolyzed silicone rubber overnight at 600℃ in an aerobic environment, ground it into powder after cooling, and then pyrolyzed it again overnight at 600℃ to ensure the pyrolysis product was silica. To this end, the pyrolysis product was tested using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and... 29 Solid-state nuclear magnetic resonance (NMR) spectroscopy analysis of Si revealed that the pyrolysis product of silicone rubber at 600℃ is silica particles. This method involves heating the silicon atoms in the silicone rubber at high temperature to remove excess carbon, thereby forming silica particles (Raymond Hajj, Raphael Brunel, Rodolphe Sonnier, Claire Longuet). Ganachaud. Silicone-recycled pyrolyzed fillers for enhanced thermal-and flame-resistant silicone elastomers. Polymer Degradation and Stability 2022, 200, 109947). Liu et al. treated silicone rubber waste using high-temperature pyrolysis. The waste was placed in a muffle furnace and heated to 1000℃ at a rate of 10℃ / min, then held at 1000℃ for 1 hour. After high-temperature pyrolysis, the silicone rubber reacted with oxygen atoms in the air, forming a layer of deposited silica particles on its surface. Scanning electron microscopy-energy dispersive X-ray spectroscopy revealed that the atomic ratio of Si to O on the product surface was 1:2, consistent with the chemical composition of silica. Therefore, it was inferred that the particles deposited on the surface of the sintered silicone rubber were silica particles (TianLiu, Xingrong Zeng, Xuejun Lai, Hongqiang Li, Yanlin Wang. Remarkable improvement of organic-to-inorganic conversion of silicone rubber at elevated temperature through platinum-nitrogen catalytic system. Polymer Degradation and Stability 2020, 171, 109026).Chen et al. conducted pyrolysis reactions on silicone rubber (polydimethylsiloxane) and silicone rubber with added platinum catalyst and nitrogen-containing silane (γ-aminopropyltriethoxy). They found that at 900℃, the Si / O ratio of the degradation products of silicone rubber was closer to that of silica, while the Si / O ratio of the degradation products of silicone rubber with added platinum catalyst and nitrogen-containing silane (γ-aminopropyltriethoxy) was higher than that of silica under the same conditions. This indicates that the pyrolysis products of silicone rubber with added platinum catalyst and nitrogen-containing silane, compared to the pyrolysis products of pure silicone rubber, form a large amount of Si-C network rather than silica, while the latter is mainly silica. This is mainly because silicone rubber undergoes continuous oxidation reactions during high-temperature pyrolysis without the addition of a catalyst, forming silica, which corresponds precisely to the measured Si / O ratio of approximately 1 / 2 (Wanjuan Chen, Xingrong Zeng, Xuejun Lai, Hongqiang Li, Weizhen Fang, TianLiu. Synergistic effect and mechanism of platinum catalyst and nitrogen-containing silane on the thermal stability of silicone). rubber.ThermochimicaActa 2016,632,1-9).

[0004] In summary, traditional methods for treating waste silicone rubber mainly involve crushing it and using it directly as filler or for modification. Currently, the main method is to degrade silicone rubber waste into silica particles through high-temperature pyrolysis, but the temperatures are all above 500℃. This method has the disadvantages of high energy consumption and high cost, and lacks an environmentally friendly and effective way to recycle and reuse it. Therefore, there is an urgent need for a low-cost, low-energy, environmentally friendly and effective solution to achieve the recycling and reuse of silicone rubber waste. Summary of the Invention

[0005] To address the shortcomings and improvement needs of existing technologies, the present invention aims to provide a method for preparing nano-silica through the controlled degradation of waste silicone rubber. This invention achieves low-temperature, controllable degradation of silicone rubber waste into silica nanoparticles by uniformly mixing silicone rubber waste with an aluminum compound catalyst in an appropriate proportion. The aluminum compound, being a Lewis acid, can activate Si-C bonds, thereby efficiently eliminating them and facilitating subsequent oxidative cross-linking reactions with oxygen to generate silica nanoparticles. This invention achieves resource recycling and reuse of waste silicone rubber and possesses advantages such as low cost, low energy consumption, simple process, and high yield.

[0006] According to the purpose of this invention, a method for preparing nano-silica by controllable degradation of waste silicone rubber is first proposed, comprising the following steps:

[0007] (1) The waste silicone rubber was crushed into rubber particles and the aluminum-based catalyst was ground into powder;

[0008] (2) Mix the colloidal particles in step (1) with the catalyst evenly, react at a temperature of 200-310°C, and after the reaction is completed, cool naturally to room temperature and grind the product into powder.

[0009] (3) Take the powder obtained in step (2) and mix it with dilute hydrochloric acid, stir, filter and dry it, and then grind it to obtain the nano-silica.

[0010] Preferably, the particle size of the colloid particles in step (1) is 2 to 6 mm.

[0011] Preferably, the mass ratio of the colloidal particles to the aluminum-based catalyst is 1:(0.1-2).

[0012] Preferably, the aluminum-based catalyst is selected from one or more of Al2O3, Al(OH)3, Al2(SO4)3 and AlCl3.

[0013] Preferably, the reaction time in step (2) is 10 to 70 minutes.

[0014] Preferably, the concentration of the dilute hydrochloric acid is 0.1 to 1 mol / L.

[0015] According to another aspect of the present invention, the present invention also provides nano-silica prepared by the above method, wherein the nano-silica has a specific surface area of ​​64.7-115.6 m². 2 / g, the surface of the nano-silica has multiple micropores with a pore size of less than 2nm and mesopores with a pore size of 2-50nm.

[0016] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages:

[0017] (1) This invention selects a catalyst combined with pyrolysis to degrade silicone rubber. The catalyst used is one or more aluminum-based catalysts. Compared with the existing technology of obtaining silicon dioxide by high-temperature pyrolysis oxidation of silicone rubber, this invention activates the Si-C bond by adding an aluminum-based catalyst, which greatly reduces the degradation temperature of silicone rubber waste. In addition, the catalyst selected in this invention has a simple acquisition method and has an effective catalytic degradation effect. Compared with the existing technology, this invention has the advantages of simple raw materials, low cost and high efficiency, and provides a new idea for the recycling and reuse of waste silicone rubber.

[0018] (2) The reaction temperature in this invention is 200-310℃ and the reaction time is 10-70 min. Compared with the prior art, which requires a reaction temperature of 600℃ or 900℃ or even 1000℃ and a long pyrolysis time to degrade into silica particles, this invention has the obvious advantage of low energy consumption. Under the condition of aluminum-based catalyst, the degradation temperature of silicone rubber is reduced, and waste silicone rubber is degraded into silica nanoparticles with low energy consumption. This improves the recycling scheme of waste silicone rubber, not only realizing the recycling of silicone rubber waste, but also greatly saving resource consumption and contributing to social development and scientific progress.

[0019] (3) The degradation scheme designed in this invention is to crush the silicone rubber waste into rubber particles, mix it evenly with the catalyst in a crucible, and then pyrolyze it for a certain period of time to degrade the silicone rubber waste into silicon dioxide nanoparticles. Compared with the scheme in the prior art, this scheme has the advantage of simpler process, avoids cumbersome process flow, and greatly improves the degradation efficiency of waste silicone rubber. Attached Figure Description

[0020] Figure 1 Nitrogen adsorption-desorption curves and pore size distribution diagrams of silica nanoparticles prepared by reacting Al2O3 as a catalyst and silicone rubber waste as a raw material at 310℃ for 10 min were obtained. Figure 1 In the figure, 'a' represents the nitrogen adsorption-desorption curve between silica nanoparticles and silicone rubber. Figure 1 In the diagram, b represents the pore size distribution of silica nanoparticles and silicone rubber. The silicone rubber raw material is used as a control sample.

[0021] Figure 2 The nitrogen adsorption-desorption curves and pore size distribution diagrams of silica nanoparticles prepared by reacting Al(OH)3 as a catalyst and silicone rubber waste as a raw material at 280℃ for 20 min are shown. Figure 2 In the figure, 'a' represents the nitrogen adsorption-desorption curve between silica nanoparticles and silicone rubber. Figure 2 In the diagram, b represents the pore size distribution of silica nanoparticles and silicone rubber. The silicone rubber raw material is used as a control sample.

[0022] Figure 3 The nitrogen adsorption-desorption curves and pore size distribution diagrams of silica nanoparticles prepared by reacting Al2(SO4)3 as a catalyst and silicone rubber waste as a raw material at 260℃ for 30 min are shown. Figure 3 In the figure, 'a' represents the nitrogen adsorption-desorption curve between silica nanoparticles and silicone rubber. Figure 3 In the diagram, b represents the pore size distribution of silica nanoparticles and silicone rubber. The silicone rubber raw material is used as a control sample.

[0023] Figure 4 Nitrogen adsorption-desorption curves and pore size distribution diagrams of silica nanoparticles prepared by reacting AlCl3 as a catalyst and silicone rubber waste as a raw material at 240℃ for 40 min were obtained. Figure 4 In the figure, 'a' represents the nitrogen adsorption-desorption curve between silica nanoparticles and silicone rubber. Figure 4 In the diagram, b represents the pore size distribution of silica nanoparticles and silicone rubber.

[0024] Figure 5 X-ray diffraction and infrared spectra of silica nanoparticles prepared by reacting Al2O3 as a catalyst and silicone rubber waste as a raw material at 220℃ for 70 min are shown. Figure 5 In the diagram, 'a' represents the X-ray diffraction pattern of silica nanoparticles and silicone rubber. Figure 5 In the diagram, b represents the infrared spectrum of silica nanoparticles and silicone rubber.

[0025] Figure 6 X-ray diffraction and infrared spectra of silica nanoparticles prepared by reacting Al(OH)3 as a catalyst and silicone rubber waste as a raw material at 200℃ for 60 min are shown. Figure 6 In the diagram, 'a' represents the X-ray diffraction pattern of silica nanoparticles and silicone rubber. Figure 6 In the diagram, b represents the infrared spectrum of silica nanoparticles and silicone rubber.

[0026] Figure 7 X-ray diffraction and infrared spectra of silica nanoparticles prepared by reacting Al2(SO4)3 as a catalyst and silicone rubber waste as a raw material at 230℃ for 50 min are shown. Figure 7 In the diagram, 'a' represents the X-ray diffraction pattern of silica nanoparticles and silicone rubber. Figure 7 In the diagram, b represents the infrared spectrum of silica nanoparticles and silicone rubber.

[0027] Figure 8 X-ray diffraction pattern, infrared spectrum, and solid-state NMR spectrum of silica nanoparticles prepared by reacting AlCl3 as a catalyst and silicone rubber waste as a raw material at 250℃ for 30 min were obtained. Figure 8 In the diagram, 'a' represents the X-ray diffraction pattern of silica nanoparticles and silicone rubber. Figure 8 In the diagram, b represents the infrared spectrum of silica nanoparticles and silicone rubber. Figure 8 In the diagram, c represents the solid-state NMR spectrum of silica nanoparticles and silicone rubber.

[0028] Figure 9Scanning electron microscope (SEM) and transmission electron microscope (TEM) images of silica nanoparticles prepared by reacting AlCl3 as a catalyst and silicone rubber waste as a raw material at 270℃ for 20 min are shown. Figure 9 a and Figure 9 In the image, b is a scanning electron microscope image of silica nanoparticles. Figure 9 c and Figure 9 In the image, d represents a transmission electron microscope image of silica nanoparticles.

[0029] Figure 10 The image shows the X-ray diffraction pattern of the product of silicone rubber waste reacting at 300°C for 60 minutes without the addition of a catalyst. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0031] The waste silicone rubber used in this invention can be derived from scraps of silicone rubber products and silicone rubber gaskets.

[0032] The method for preparing nano-silica using low-temperature controllable degradation of waste silicone rubber in this invention can be carried out according to the following steps:

[0033] (1) The waste silicone rubber was crushed into rubber particles and the aluminum-based catalyst was ground into powder;

[0034] (2) Mix the colloidal particles in step (1) with the catalyst evenly, react at a temperature of 200-310°C, and after the reaction is completed, cool naturally to room temperature and grind the product into powder.

[0035] (3) Take the powder obtained in step (2) and mix it with dilute hydrochloric acid, stir, filter and dry it, and then grind it to obtain the nano-silica.

[0036] In some embodiments, the particle size of the colloid particles in step (1) is 2 to 6 mm.

[0037] In some embodiments, the mass ratio of the colloidal particles to the catalyst is 1:(0.1-2).

[0038] In some embodiments, the aluminum-based compound is selected from one or more of Al2O3, Al(OH)3, Al2(SO4)3 and AlCl3.

[0039] In some embodiments, the reaction time for step (2) is 10 to 70 minutes.

[0040] In some embodiments, the concentration of the dilute hydrochloric acid is 0.1 to 1 mol / L.

[0041] The following are specific examples:

[0042] Example 1

[0043] Silicone rubber waste was shredded into granules with a particle size of 2 mm. The granules were mixed evenly with Al2O3 catalyst at a mass ratio of 1:0.2 in a crucible, then poured into a reaction tube and placed on a heating platform. The mixture was reacted at 310°C for 10 min. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. After cooling, the product was ground into powder.

[0044] Take an appropriate amount of powder product and mix it with an appropriate amount of 0.1 mol / L dilute hydrochloric acid. Stir and stir for 1 hour. Then filter, dry, and grind into powder to obtain silica nanoparticles with a yield of 98%.

[0045] Figure 1 a and Figure 1 In the figures, b represents the nitrogen adsorption-desorption curves and pore size distribution diagrams of silica nanoparticles prepared by reacting Al2O3 as a catalyst to degrade silicone rubber waste at 300℃ for 10 min, respectively. Clearly, the silica nanoparticles prepared in this embodiment possess abundant micropores (<2 nm), mesopores (2–50 nm), and macropores (>50 nm), with a specific surface area of ​​87.2 m². 2 / g, while the specific surface area of ​​silicone rubber is 0.02m². 2 / g, and does not have micropores, mesopores or macropores.

[0046] Example 2

[0047] Silicone rubber waste was shredded into granules with a particle size of 3 mm. The granules were mixed evenly with Al(OH)3 catalyst at a mass ratio of 1:0.4 in a crucible, then poured into a reaction tube and placed on a heating platform. The mixture was reacted at 280°C for 20 min. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. After cooling, the product was ground into powder.

[0048] Take an appropriate amount of powder product and mix it with an appropriate amount of 0.2 mol / L dilute hydrochloric acid. Stir and stir for 2 hours. Then filter, dry, and grind into powder to obtain silica nanoparticles with a yield of 99%.

[0049] Figure 2 a and Figure 2In the figures, b represents the nitrogen adsorption-desorption curves and pore size distribution diagrams of silica nanoparticles prepared by degrading silicone rubber waste with Al(OH)3 as a catalyst at 280℃ for 20 min, respectively. Clearly, the degraded silica nanoparticles possess abundant micropores (<2 nm), mesopores (2–50 nm), and macropores (>50 nm), with a specific surface area of ​​94 m². 2 / g, while the specific surface area of ​​silicone rubber is 0.02m². 2 / g, and does not have micropores, mesopores or macropores.

[0050] Example 3

[0051] Silicone rubber waste was shredded into granules with a particle size of 4 mm. The granules were mixed evenly with Al2(SO4)3 catalyst at a mass ratio of 1:0.6 in a crucible, then poured into a reaction tube and placed on a heating platform. The mixture was reacted at 260°C for 30 min. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. After cooling, the product was ground into powder.

[0052] Take an appropriate amount of powder product and mix it with an appropriate amount of 0.3 mol / L dilute hydrochloric acid. Stir and stir for 3 hours. Then filter, dry, and grind into powder to obtain silica nanoparticles with a yield of 97%.

[0053] Figure 3 a and Figure 3 In the figures, b represents the nitrogen adsorption-desorption curves and pore size distribution diagrams of silica nanoparticles prepared by reacting Al2(SO4)3 as a catalyst with silicone rubber waste at 260℃ for 30 min. Clearly, the degraded silica nanoparticles possess abundant micropores (<2 nm), mesopores (2–50 nm), and macropores (>50 nm), with a specific surface area of ​​64.7 m². 2 / g, while the specific surface area of ​​silicone rubber is 0.02m². 2 / g, and does not have micropores, mesopores or macropores.

[0054] Example 4

[0055] Silicone rubber waste was shredded into granules with a particle size of 5 mm. The granules were mixed evenly with AlCl3 catalyst at a mass ratio of 1:0.8 in a crucible, then poured into a reaction tube and placed on a heating platform. The mixture was reacted at 240°C for 40 min. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. After cooling, the product was ground into powder.

[0056] Take an appropriate amount of powder product and mix it with an appropriate amount of 0.4 mol / L dilute hydrochloric acid. Stir and stir for 4 hours. Then filter, dry, and grind into powder to obtain silica nanoparticles with a yield of 98%.

[0057] Figure 4 a and Figure 4 In the figures, b represents the nitrogen adsorption-desorption curves and pore size distribution diagrams of silica nanoparticles and silicone rubber prepared by reacting AlCl3 as a catalyst at 240℃ for 40 min. Clearly, the degraded silica nanoparticles possess abundant micropores (<2 nm), mesopores (2–50 nm), and macropores (>50 nm), with a specific surface area of ​​115.6 m². 2 / g, while the specific surface area of ​​silicone rubber is 0.02m². 2 / g, and does not have micropores, mesopores or macropores.

[0058] Example 5

[0059] Silicone rubber waste was shredded into granules with a particle size of 4 mm. The granules were mixed evenly with Al2O3 catalyst at a mass ratio of 1:1 in a crucible, then poured into a reaction tube and placed on a heating platform. The reaction was carried out at 220°C for 70 min. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. After cooling, the product was ground into powder.

[0060] Take an appropriate amount of powder product and mix it with an appropriate amount of 0.5 mol / L dilute hydrochloric acid. Stir and stir for 3 hours. Then filter, dry, and grind into powder to obtain silica nanoparticles with a yield of 99%.

[0061] Figure 5 a and Figure 5 In the figures, 'b' represents the X-ray diffraction pattern and infrared spectrum of silica nanoparticles prepared by degrading silicone rubber waste at 220℃ for 70 min using Al2O3 as a catalyst, and silicone rubber. The X-ray diffraction pattern shows that the silicone rubber waste was successfully degraded into silica nanoparticles. The infrared spectrum shows that the degradation products contain no carbon-hydrogen bonds and only a very small number of silicon-carbon bonds, indicating that the silicone rubber waste was successfully degraded to generate silica nanoparticles.

[0062] Example 6

[0063] Silicone rubber waste was shredded into granules with a particle size of 3 mm. The granules were mixed evenly with Al(OH)3 catalyst at a mass ratio of 1:1.2 in a crucible, then poured into a reaction tube and placed on a heating platform. The mixture was reacted at 200°C for 60 min. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. After cooling, the product was ground into powder.

[0064] Take an appropriate amount of powder product and mix it with an appropriate amount of 0.6 mol / L dilute hydrochloric acid. Stir and stir for 2 hours. Then filter, dry, and grind into powder to obtain silica nanoparticles with a yield of 97%.

[0065] Figure 6 a and Figure 6In the figures, 'b' represents the X-ray diffraction pattern and infrared spectrum of silica nanoparticles prepared by degrading silicone rubber waste at 200℃ for 60 min using Al(OH)3 as a catalyst, and silicone rubber. The X-ray diffraction pattern shows that the silicone rubber waste was successfully degraded into silica nanoparticles. The infrared spectrum shows that the degradation products contain no carbon-hydrogen bonds and only a very small number of silicon-carbon bonds, indicating that the silicone rubber waste was successfully degraded to generate silica nanoparticles.

[0066] Example 7

[0067] Silicone rubber waste was shredded into granules with a particle size of 2 mm. The granules were mixed evenly with Al2(SO4)3 catalyst at a mass ratio of 1:1.5 in a crucible. The mixture was then poured into a reaction tube, placed on a heating platform, and reacted at 230°C for 50 min. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. After cooling, the product was ground into powder.

[0068] Take an appropriate amount of powder product and mix it with an appropriate amount of 0.7 mol / L dilute hydrochloric acid. Stir and stir for 1 hour. Then filter, dry, and grind into powder to obtain silica nanoparticles with a yield of 98%.

[0069] Figure 7 a and Figure 7 In the figures, 'b' represents the X-ray diffraction pattern and infrared spectrum of silica nanoparticles prepared by degrading silicone rubber waste at 230℃ for 50 min using Al2(SO4)3 as a catalyst, compared with silicone rubber. The X-ray diffraction pattern shows that the silicone rubber waste was successfully degraded into silica nanoparticles. The infrared spectrum shows that the degradation products contain no carbon-hydrogen bonds and only a very small number of silicon-carbon bonds, indicating that the silicone rubber waste was successfully degraded to generate silica nanoparticles.

[0070] Example 8

[0071] Silicone rubber waste was shredded into granules with a particle size of 4 mm. The granules were mixed evenly with AlCl3 catalyst at a mass ratio of 1:1.8 in a crucible, then poured into a reaction tube and placed on a heating platform. The mixture was reacted at 250°C for 30 min. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. After cooling, the product was ground into powder.

[0072] Take an appropriate amount of powder product and mix it with an appropriate amount of 0.8 mol / L dilute hydrochloric acid. Stir and stir for 3 hours. Then filter, dry, and grind into powder to obtain silica nanoparticles with a yield of 99%.

[0073] Figure 8In the diagram, a, b, and c represent the X-ray diffraction (XRD) pattern, infrared (IR) spectrum, and solid-state NMR spectrum of silica nanoparticles prepared by degrading silicone rubber waste at 250℃ for 30 min using AlCl3 as a catalyst, respectively. The XRD and NMR spectra show that the silicone rubber waste was successfully degraded into silica nanoparticles. The IR spectrum indicates that the degradation products contain no carbon-hydrogen bonds and only a very small number of silicon-carbon bonds, further confirming the successful degradation of the silicone rubber waste into silica nanoparticles.

[0074] Example 9

[0075] Silicone rubber waste was shredded into granules with a particle size of 6 mm. The granules were mixed evenly with AlCl3 catalyst at a mass ratio of 1:2 in a crucible, then poured into a reaction tube and placed on a heating platform. The mixture was reacted at 270°C for 20 min. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. After cooling, the product was ground into powder.

[0076] Take an appropriate amount of powder product and mix it with an appropriate amount of 1 mol / L dilute hydrochloric acid. Stir and stir for 4 hours. Then filter, dry, and grind into powder to obtain silica nanoparticles with a yield of 98%.

[0077] Figure 9 Scanning electron microscope (SEM) and transmission electron microscope (TEM) images of silica nanoparticles prepared by degrading silicone rubber waste at 270°C for 20 min using AlCl3 as a catalyst are shown. Figure 9 a and Figure 9 In the image, b is a scanning electron microscope image of the prepared silica nanoparticles. Figure 9 c and Figure 9 In the image, 'd' represents the transmission electron microscope (TEM) image of the prepared silica nanoparticles. Both the scanning electron microscope (SEM) and transmission electron microscope (TEM) images show that the size of the prepared silica nanoparticles is 20–30 nm.

[0078] Comparative Example 1

[0079] Silicone rubber waste was shredded into granules. 2.0g of granules was weighed, poured into a reaction tube, placed on a heating platform, and reacted at 300℃ for 60 minutes. After the reaction was completed, the product was allowed to cool naturally to room temperature. After cooling, the product was ground, but no changes were observed.

[0080] Figure 10 The image shows the X-ray diffraction pattern of the product after reacting silicone rubber at 300°C for 60 min without a catalyst. The X-ray diffraction pattern reveals that, even after reacting at 300°C for 60 min without a catalyst, the silicone rubber was not degraded, and the yield of silica nanoparticles was 0%. This confirms the high stability of silicone rubber and the highly efficient catalytic degradation activity of aluminum compounds.

[0081] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing nano-silica by controllable degradation of waste silicone rubber, characterized in that, Includes the following steps: (1) The waste silicone rubber is crushed into rubber particles and the aluminum-based catalyst is ground into powder; the aluminum-based catalyst is selected from one or more of Al2O3, Al(OH)3, Al2(SO4)3 and AlCl3; (2) Mix the colloidal particles from step (1) with the catalyst evenly, react at a temperature of 200~310 ℃, and after the reaction is completed, cool naturally to room temperature and grind the product into powder. (3) Take the powder obtained in step (2), mix it with dilute hydrochloric acid, stir, filter and dry it, and then grind it to obtain the nano-silica.

2. The method for preparing nano-silica by controllable degradation of waste silicone rubber according to claim 1, characterized in that, The particle size of the colloid in step (1) is 2~6 mm.

3. The method for preparing nano-silica by controllable degradation of waste silicone rubber according to claim 1, characterized in that, The mass ratio of the colloidal particles to the aluminum-based catalyst is 1:(0.1~2).

4. The method for preparing nano-silica by controllable degradation of waste silicone rubber according to claim 1, characterized in that, The reaction time for step (2) is 10~70 min.

5. The method for preparing nano-silica by controllable degradation of waste silicone rubber according to claim 1, characterized in that, The concentration of the dilute hydrochloric acid is 0.1~1 mol / L.

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