A sandwich composite based on melamine foam and a method for producing the same

Abstract

The present application relates to the field of sound-absorbing materials, in particular to a sandwich composite material based on melamine foam and a preparation method thereof. The method comprises the following steps: coordination of Co and nanometer bacterial cellulose; preparation of Co-BC-melamine foam; and compounding of porous diatomite adhesive and Co-BC-melamine foam. In the present application, nanometer bacterial cellulose provides good porosity through its high specific surface area and micro-fiber structure. After coordination with cobalt acetylacetonate, cobalt ions are coordinated with the surface hydroxyl groups of nanometer bacterial cellulose to form a stable composite structure. The composite not only enhances the mechanical properties of the material, but also improves the porosity of the material, further improving the sound-absorbing effect. In addition, the natural properties of nanometer bacterial cellulose make it an excellent sound wave absorbing medium in the composite material, thus effectively improving the sound-absorbing capacity of the sandwich material.

Description

Technical Field

[0001] This invention relates to the field of sound-absorbing materials, specifically a sandwich composite material based on melamine foam and its preparation method. Background Technology

[0002] With the rapid development of modern industry and technology, noise pollution from various equipment and transportation vehicles has become increasingly serious. Noise has become the third largest pollution problem in the world after water pollution and air pollution. Long-term exposure to noise has many adverse effects on human health, such as tinnitus, insomnia, fatigue, and even cardiovascular diseases. In addition, noise not only harms human health, but also affects the service life of instruments, equipment and building structures.

[0003] Currently, solving the problem of noise pollution has become a global issue. There are three main methods for noise control: reducing the generation of noise sources, reducing noise by dissipating sound energy during sound wave propagation, and reducing the impact of noise through sound wave blocking measures. In particular, dissipating sound energy through sound-absorbing materials is currently the most effective means of mitigating noise hazards and improving human health. Sound-absorbing materials are widely used in noise control, especially in environments where noise sources such as household appliances, vehicles, and factory equipment generate noise, and have a significant noise reduction effect.

[0004] Common sound-absorbing materials include resonant sound-absorbing materials and porous sound-absorbing materials. Resonant sound-absorbing materials have a narrow absorption band and can effectively absorb sound waves of certain specific frequencies. They have good sound absorption performance in the low-frequency range, but their narrow absorption band limits their widespread application. At the same time, the structure of resonant sound-absorbing materials is usually more complex, making them more difficult to manufacture and process. Porous materials include natural fibers, melamine foam, polyurethane foam, aluminum foam, etc. They perform well in terms of sound absorption frequency range and stability, and have a wide range of material choices and relatively simple manufacturing processes. Therefore, they are widely used in noise control in industry, construction, and transportation. However, porous sound-absorbing materials usually have poor sound absorption performance in the low-frequency range (100-800Hz), and in order to obtain a satisfactory sound absorption coefficient, it is often necessary to increase their thickness and mass. Therefore, designing efficient sound-absorbing materials that can solve low-frequency sound absorption problems, are lightweight, and thin is extremely challenging. Summary of the Invention

[0005] To address the aforementioned technical deficiencies, this invention presents a method for preparing a sandwich composite material based on melamine foam. By preparing a porous diatomaceous earth binder to bond Co-BC-melamine foam, the resulting sandwich composite material exhibits excellent sound absorption performance in the high, medium, and low frequency ranges.

[0006] A method for preparing a sandwich composite material based on melamine foam includes the following steps:

[0007] S1: Co coordination with nanobacterial cellulose

[0008] The nanobacterial cellulose was oxidized with hydrogen peroxide and then dispersed in an ethanol solution to obtain a nanobacterial cellulose dispersion. Cobalt acetylacetone and acetic acid were added to the nanobacterial cellulose dispersion and magnetically stirred to obtain a Co-nanobacterial cellulose complex dispersion.

[0009] S2: Preparation of Co-BC-melamine foam

[0010] Melamine foam was subjected to high-temperature treatment in air, then immersed in a 3-mercaptopropyltrimethoxysilane solution prepared from 3-mercaptopropyltrimethoxysilane and ethanol solution, washed and dried to obtain silane-modified melamine foam. The silane-modified melamine foam was then immersed in a Co-nanobacterial cellulose complex dispersion for ultrasonic treatment, and after cyclic freezing and freeze-drying, Co-BC-melamine foam was obtained.

[0011] S3: Composite of porous diatomaceous earth binder and Co-BC-melamine foam

[0012] Diatomaceous earth is heat-treated and purified to obtain purified diatomaceous earth. The purified diatomaceous earth and sodium dodecylbenzene sulfonate are added to an aqueous polyurethane solution and mixed at high speed to obtain a porous diatomaceous earth adhesive. The porous diatomaceous earth adhesive is coated on the surface of Co-BC-melamine foam, and then another piece is used to stack and hot-press to obtain a melamine foam sandwich composite material.

[0013] Further, the coordination of S1Co with nanobacterial cellulose includes the following steps:

[0014] S1.1: Disperse and soak the nanobacterial cellulose in a 4-6% hydrogen peroxide solution, then let it stand at 50-70℃ for 1-2 hours, filter and wash with deionized water 3-4 times to obtain oxidized nanobacterial cellulose. Mix 2-3 parts by weight of oxidized nanobacterial cellulose, 0.3-0.4 parts by weight of polyvinyl alcohol and 80-100 parts by weight of ethanol solution in an ultrasonic disperser and ultrasonically treat with an ultrasonic power of 300-350W for 10-30 minutes to obtain nanobacterial cellulose dispersion.

[0015] S1.2: Add 1-1.5 parts by weight of cobalt acetylacetonate to the nanobacterial cellulose dispersion prepared in step S1.1, then add 0.1-0.5 wt% acetic acid, and magnetically stir at 150-200 rpm at 50-60℃ for 2-3 hours to obtain Co-nanobacterial cellulose complex dispersion.

[0016] Furthermore, the preparation of step S2Co-BC-melamine foam includes the following steps:

[0017] S2.1: Soak melamine foam in anhydrous ethanol, then place it in an ultrasonic cleaner and ultrasonically clean it for 15-20 minutes at an ultrasonic frequency of 25-30kHz. Then soak it in deionized water and ultrasonically clean it for 15-20 minutes at an ultrasonic frequency of 25-30kHz. Then place it in a muffle furnace and heat it to 180-200℃ at a heating rate of 5-10℃ / min in an air atmosphere. Hold it at this temperature for 2-2.5 hours and then let it cool naturally to room temperature to obtain pre-oxidized melamine foam.

[0018] S2.2: Mix 3-mercaptopropyltrimethoxysilane and ethanol solution in a volume ratio of 1:(40-60) in a container and stir until the 3-mercaptopropyltrimethoxysilane is completely dissolved. Let stand for 1-2 hours to obtain a 3-mercaptopropyltrimethoxysilane solution. Immerse the pre-oxidized melamine foam in the 3-mercaptopropyltrimethoxysilane solution for 1.5-2 hours. Every 20-30 minutes, take out the pre-oxidized melamine foam and stir it in the 3-mercaptopropyltrimethoxysilane solution for 1-2 minutes. Then take it out and rinse the surface with deionized water 2-3 times. Then place it in an oven at 60-80℃ and heat for 8-10 hours to obtain silane-modified melamine foam.

[0019] S2.3: The silane-modified melamine foam is completely immersed in the Co-nanobacterial cellulose complex dispersion prepared in step S1.2, and then placed in an ultrasonic water bath. It is ultrasonicated at 35-40 kHz for 30-40 minutes at a temperature of 45-50℃. After freezing at -25-20℃ for 6-8 hours, it is placed at room temperature for 10-12 hours. After 3-4 cycles, it is frozen in liquid nitrogen and finally transferred to a freeze dryer for freeze drying to obtain Co-BC-melamine foam.

[0020] Furthermore, the composite process of the porous diatomaceous earth binder and Co-BC-melamine foam in step S3 includes the following steps:

[0021] S3.1: Place 2-4 parts by weight of diatomaceous earth in a container, then place it in a constant temperature drying oven and heat it at 105-110℃ until the mass of the diatomaceous earth no longer changes, to obtain heat-treated diatomaceous earth. Mix the heat-treated diatomaceous earth with 8-12 parts by weight of a 6-8% hydrogen chloride solution, place it in a microwave oven and irradiate it with a power of 700-750W for 4-6 minutes. Wash it with distilled water until the pH of the washing distilled water is neutral. Then perform vacuum filtration and dry it at 105-110℃ for 10-12 hours to obtain purified diatomaceous earth.

[0022] S3.2: Add the purified diatomaceous earth obtained in step S3.1 and 0.03-0.04 parts by weight of sodium dodecylbenzenesulfonate to 60-65 parts by weight of aqueous polyurethane solution, then place it in a high-speed mixer and stir at 1200-1500 rpm for 50-60 minutes. Then add 0.1-0.5% of anti-settling agent, and then stir at 1800-2000 rpm for 25-30 minutes to obtain porous diatomaceous earth adhesive.

[0023] S3.3: Apply porous diatomaceous earth binder at a concentration of 600-800 g / m³. 2 Apply adhesive evenly to the upper surface of Co-BC-melamine foam according to the specified amount of adhesive. After the adhesive is applied, let it stand for 6-8 minutes to obtain adhesive-coated Co-BC-melamine foam. Then, take a piece of Co-BC-melamine foam and stack it on the upper surface of the adhesive-coated Co-BC-melamine foam. Hot press it at 100-120℃ and 0.1-0.2MPa for 8-10 minutes. After cooling, obtain melamine foam sandwich composite material.

[0024] Furthermore, the concentration of the ethanol solution in step S1.1 is 10-15%.

[0025] Furthermore, in step S2.1, the melamine foam has a diameter of 10 cm and a thickness of 2 cm.

[0026] Furthermore, in step S2.2, the concentration of the ethanol solution mixed with 3-mercaptopropyltrimethoxysilane is 96-98%.

[0027] Furthermore, the solid content of the aqueous polyurethane solution in step S3.2 is 40-45%.

[0028] Furthermore, the anti-settling agent in step S3.2 is water-based anti-settling agent 2521.

[0029] A sandwich composite material based on melamine foam is prepared by the above-mentioned method for preparing a sandwich composite material based on melamine foam.

[0030] The beneficial effects are as follows: 1. In this invention, nano-bacterial cellulose provides good porosity through its high specific surface area and micro-fiber structure, which helps to enhance the sound absorption performance of the composite material. After being combined with cobalt acetylacetonate, cobalt ions coordinate with the surface hydroxyl groups of nano-bacterial cellulose to form a stable composite structure. This composite not only enhances the mechanical properties of the material, but also improves the porosity of the material, further enhancing the sound absorption effect. The introduction of cobalt ions also helps to enhance the thermal stability and antibacterial properties of the composite material. These characteristics can ensure that the material maintains good sound absorption effect during long-term use and avoid performance degradation due to bacterial growth or environmental changes. In addition, the natural properties of nano-bacterial cellulose make it an excellent sound wave absorbing medium in the composite material, thus effectively improving the sound absorption capacity of the sandwich material.

[0031] 2. In this invention, porous diatomaceous earth possesses an extremely high specific surface area and abundant microporous structure, which can significantly improve the sound absorption performance of the composite material. Diatomaceous earth, when mixed with an aqueous polyurethane solution, forms an adhesive with strong bonding properties and creates a uniform coating on the surface of the composite material. The microporous structure and high specific surface area of ​​diatomaceous earth not only provide more sound wave absorption points but also help reduce sound wave reflection and propagation, thus improving the overall acoustic performance of the material. The aqueous polyurethane solution, as an adhesive, not only provides good adhesion, ensuring that diatomaceous earth particles are uniformly distributed in the composite material, but also possesses good low-frequency sound wave absorption capabilities. Combining the characteristics of diatomaceous earth and aqueous polyurethane, the pore structure of this composite material helps improve the sound wave absorption efficiency, enabling it to exhibit excellent sound absorption capabilities over a wide frequency range. Attached Figure Description

[0032] Figure 1 This is a flowchart illustrating the preparation method of the melamine foam-based sandwich composite material used in embodiments of the present invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1

[0035] A sandwich composite material based on melamine foam and its preparation method, such as Figure 1 As shown, it includes the following steps:

[0036] S1: Co coordination with nanobacterial cellulose

[0037] S1.1: The nanobacterial cellulose was dispersed and soaked in a 4% hydrogen peroxide solution, then allowed to stand at 50°C for 1 hour, filtered and rinsed 3 times with deionized water to obtain oxidized nanobacterial cellulose. 2 parts by weight of oxidized nanobacterial cellulose, 0.3 parts by weight of polyvinyl alcohol and 80 parts by weight of 10% ethanol solution were mixed and placed in an ultrasonic disperser and ultrasonically treated with an ultrasonic power of 300W for 10 minutes to obtain a nanobacterial cellulose dispersion.

[0038] S1.2: Add 1 part by weight of cobalt acetylacetonate to the nanobacterial cellulose dispersion prepared in step S1.1, then add 0.1 wt% acetic acid, and magnetically stir at 150 rpm at 50°C for 2 hours to obtain Co-nanobacterial cellulose complex dispersion.

[0039] S2: Preparation of Co-BC-melamine foam

[0040] S2.1: Soak melamine foam with a diameter of 10cm and a thickness of 2cm in anhydrous ethanol, then place it in an ultrasonic cleaner and ultrasonically clean it at an ultrasonic frequency of 25kHz for 15 minutes. Then soak it in deionized water and ultrasonically clean it at an ultrasonic frequency of 25kHz for 15 minutes. Then place it in a muffle furnace and heat it to 180℃ at a heating rate of 5℃ / min in an air atmosphere. After holding it at this temperature for 2 hours, allow it to cool naturally to room temperature to obtain pre-oxidized melamine foam.

[0041] S2.2: Mix 3-mercaptopropyltrimethoxysilane and a 96% ethanol solution at a volume ratio of 1:40 in a container and stir until the 3-mercaptopropyltrimethoxysilane is completely dissolved. Let stand for 1 hour to obtain a 3-mercaptopropyltrimethoxysilane solution. Immerse the pre-oxidized melamine foam in the 3-mercaptopropyltrimethoxysilane solution for 1.5 hours. Every 20 minutes, take out the pre-oxidized melamine foam and stir it in the 3-mercaptopropyltrimethoxysilane solution for 1 minute. Then take it out and rinse the surface twice with deionized water. Then place it in an oven at 60°C and heat for 8 hours to obtain silane-modified melamine foam.

[0042] S2.3: The silane-modified melamine foam was completely immersed in the Co-nanobacterial cellulose complex dispersion prepared in step S1.2, and then placed in an ultrasonic water bath. It was ultrasonicated at 35 kHz for 30 minutes at 45 ℃, frozen at -25 ℃ for 6 hours, and then placed at room temperature for 10 hours. After 3 cycles, it was frozen in liquid nitrogen and finally transferred to a freeze dryer for freeze drying to obtain Co-BC-melamine foam.

[0043] S3: Composite of porous diatomaceous earth binder and Co-BC-melamine foam

[0044] S3.1: Place 2 parts by weight of diatomaceous earth in a container, then place it in a constant temperature drying oven and heat it at 105°C until the mass of the diatomaceous earth no longer changes, to obtain heat-treated diatomaceous earth. Mix the heat-treated diatomaceous earth with 8 parts by weight of a 6% hydrogen chloride solution, place it in a microwave oven and irradiate it with a power of 700W for 4 minutes. Wash it with distilled water until the pH of the washing distilled water is neutral. Then perform vacuum filtration and dry it at 105°C for 10 hours to obtain purified diatomaceous earth.

[0045] S3.2: Add the purified diatomaceous earth obtained in step S3.1 and 0.03 parts by weight of sodium dodecylbenzenesulfonate to 60 parts by weight of an aqueous polyurethane solution with a solid content of 40%, then place it in a high-speed mixer and stir at 1200 rpm for 50 minutes. Then add 0.1% of aqueous anti-settling agent 2521, and then stir at 1800 rpm for 25 minutes to obtain a porous diatomaceous earth adhesive.

[0046] S3.3: Apply porous diatomaceous earth binder at a concentration of 600 g / m³. 2 The amount of adhesive applied is uniformly applied to the upper surface of Co-BC-melamine foam. After the adhesive is applied, it is left to stand for 6 minutes to obtain adhesive-coated Co-BC-melamine foam. Then, a piece of Co-BC-melamine foam is taken and stacked on the upper surface of the adhesive-coated Co-BC-melamine foam. It is then hot-pressed at 100℃ with a pressure of 0.1MPa for 8 minutes. After cooling, melamine foam sandwich composite material is obtained.

[0047] Example 2

[0048] A sandwich composite material based on melamine foam and its preparation method, such as Figure 1 As shown, it includes the following steps:

[0049] S1: Co coordination with nanobacterial cellulose

[0050] S1.1: The nanobacterial cellulose was dispersed and soaked in a 4% hydrogen peroxide solution, then allowed to stand at 50°C for 1 hour, filtered and rinsed 3 times with deionized water to obtain oxidized nanobacterial cellulose. 3 parts by weight of oxidized nanobacterial cellulose, 0.4 parts by weight of polyvinyl alcohol and 100 parts by weight of 10% ethanol solution were mixed and placed in an ultrasonic disperser and ultrasonically treated with an ultrasonic power of 300W for 10 minutes to obtain a nanobacterial cellulose dispersion.

[0051] S1.2: Add 1.5 parts by weight of cobalt acetylacetonate to the nanobacterial cellulose dispersion prepared in step S1.1, then add 0.1 wt% acetic acid, and magnetically stir at 150 rpm at 50°C for 2 hours to obtain Co-nanobacterial cellulose complex dispersion.

[0052] S2: Preparation of Co-BC-melamine foam

[0053] S2.1: Soak melamine foam with a diameter of 10cm and a thickness of 2cm in anhydrous ethanol, then place it in an ultrasonic cleaner and ultrasonically clean it at an ultrasonic frequency of 25kHz for 15 minutes. Then soak it in deionized water and ultrasonically clean it at an ultrasonic frequency of 25kHz for 15 minutes. Then place it in a muffle furnace and heat it to 180℃ at a heating rate of 5℃ / min in an air atmosphere. After holding it at this temperature for 2 hours, allow it to cool naturally to room temperature to obtain pre-oxidized melamine foam.

[0054] S2.2: Mix 3-mercaptopropyltrimethoxysilane and a 96% ethanol solution at a volume ratio of 1:60 in a container and stir until the 3-mercaptopropyltrimethoxysilane is completely dissolved. Let stand for 1 hour to obtain a 3-mercaptopropyltrimethoxysilane solution. Immerse pre-oxidized melamine foam in the 3-mercaptopropyltrimethoxysilane solution for 1.5 hours. Every 20 minutes, take out the pre-oxidized melamine foam and stir it in the 3-mercaptopropyltrimethoxysilane solution for 1 minute. Then take it out and rinse the surface twice with deionized water. Then place it in an oven at 60°C and heat for 8 hours to obtain silane-modified melamine foam.

[0055] S2.3: The silane-modified melamine foam was completely immersed in the Co-nanobacterial cellulose complex dispersion prepared in step S1.2, and then placed in an ultrasonic water bath. It was ultrasonicated at 35 kHz for 30 minutes at 45 ℃, frozen at -25 ℃ for 6 hours, and then placed at room temperature for 10 hours. After 3 cycles, it was frozen in liquid nitrogen and finally transferred to a freeze dryer for freeze drying to obtain Co-BC-melamine foam.

[0056] S3: Composite of porous diatomaceous earth binder and Co-BC-melamine foam

[0057] S3.1: Place 4 parts by weight of diatomaceous earth in a container, then place it in a constant temperature drying oven and heat it at 105°C until the mass of the diatomaceous earth no longer changes, to obtain heat-treated diatomaceous earth. Mix the heat-treated diatomaceous earth with 12 parts by weight of a 6% hydrogen chloride solution, place it in a microwave oven and irradiate it with a power of 700W for 4 minutes. Wash it with distilled water until the pH of the washing distilled water is neutral. Then perform vacuum filtration and dry it at 105°C for 10 hours to obtain purified diatomaceous earth.

[0058] S3.2: Add the purified diatomaceous earth obtained in step S3.1 and 0.04 parts by weight of sodium dodecylbenzenesulfonate to 65 parts by weight of an aqueous polyurethane solution with a solid content of 40%, then place it in a high-speed mixer and stir at 1200 rpm for 50 minutes. Then add 0.5% of aqueous anti-settling agent 2521, and then stir at 1800 rpm for 25 minutes to obtain a porous diatomaceous earth adhesive.

[0059] S3.3: Apply porous diatomaceous earth binder at 800g / m 2 The amount of adhesive applied is uniformly applied to the upper surface of Co-BC-melamine foam. After the adhesive is applied, it is left to stand for 6 minutes to obtain adhesive-coated Co-BC-melamine foam. Then, a piece of Co-BC-melamine foam is taken and stacked on the upper surface of the adhesive-coated Co-BC-melamine foam. It is then hot-pressed at 100℃ with a pressure of 0.1MPa for 8 minutes. After cooling, melamine foam sandwich composite material is obtained.

[0060] Example 3

[0061] A sandwich composite material based on melamine foam and its preparation method, such as Figure 1 As shown, it includes the following steps:

[0062] S1: Co coordination with nanobacterial cellulose

[0063] S1.1: The nanobacterial cellulose was dispersed and soaked in a 6% hydrogen peroxide solution, then allowed to stand at 70°C for 2 hours, filtered and rinsed 4 times with deionized water to obtain oxidized nanobacterial cellulose. 2 parts by weight of oxidized nanobacterial cellulose, 0.3 parts by weight of polyvinyl alcohol and 80 parts by weight of 15% ethanol solution were mixed and placed in an ultrasonic disperser and ultrasonically treated with an ultrasonic power of 350W for 30 minutes to obtain a nanobacterial cellulose dispersion.

[0064] S1.2: Add 1 part by weight of cobalt acetylacetonate to the nanobacterial cellulose dispersion prepared in step S1.1, then add 0.5 wt% acetic acid, and magnetically stir at 200 rpm at 60°C for 3 hours to obtain Co-nanobacterial cellulose complex dispersion.

[0065] S2: Preparation of Co-BC-melamine foam

[0066] S2.1: Melamine foam with a diameter of 10cm and a thickness of 2cm is immersed in anhydrous ethanol, then placed in an ultrasonic cleaner and ultrasonically cleaned at an ultrasonic frequency of 30kHz for 20 minutes. Then it is immersed in deionized water and ultrasonically cleaned at an ultrasonic frequency of 30kHz for 20 minutes. Then it is placed in a muffle furnace and heated to 200℃ at a heating rate of 10℃ / min in an air atmosphere. After holding at this temperature for 2.5 hours, it is naturally cooled to room temperature to obtain pre-oxidized melamine foam.

[0067] S2.2: Mix 3-mercaptopropyltrimethoxysilane and a 98% ethanol solution at a volume ratio of 1:40 in a container and stir until the 3-mercaptopropyltrimethoxysilane is completely dissolved. Let stand for 2 hours to obtain a 3-mercaptopropyltrimethoxysilane solution. Immerse pre-oxidized melamine foam in the 3-mercaptopropyltrimethoxysilane solution for 2 hours. Every 30 minutes, take out the pre-oxidized melamine foam and stir it in the 3-mercaptopropyltrimethoxysilane solution for 2 minutes. Then take it out and rinse the surface three times with deionized water. Then place it in an oven at 80°C and heat for 10 hours to obtain silane-modified melamine foam.

[0068] S2.3: The silane-modified melamine foam was completely immersed in the Co-nanobacterial cellulose complex dispersion prepared in step S1.2, and then placed in an ultrasonic water bath. It was ultrasonicated at 50°C and 40kHz for 40 minutes, frozen at -20°C for 8 hours, and then placed at room temperature for 12 hours. After 4 cycles, it was frozen in liquid nitrogen and finally transferred to a freeze dryer for freeze drying to obtain Co-BC-melamine foam.

[0069] S3: Composite of porous diatomaceous earth binder and Co-BC-melamine foam

[0070] S3.1: Place 2 parts by weight of diatomaceous earth in a container, then place it in a constant temperature drying oven and heat it at 110°C until the mass of the diatomaceous earth no longer changes, to obtain heat-treated diatomaceous earth. Mix the heat-treated diatomaceous earth with 10 parts by weight of 8% hydrogen chloride solution evenly, place it in a microwave oven and irradiate it with a power of 750W for 6 minutes, wash it with distilled water until the pH of the washing distilled water is neutral, then perform vacuum filtration and dry it at 110°C for 12 hours to obtain purified diatomaceous earth.

[0071] S3.2: Add the purified diatomaceous earth obtained in step S3.1 and 0.03 parts by weight of sodium dodecylbenzenesulfonate to 60 parts by weight of an aqueous polyurethane solution with a solid content of 45%, then place it in a high-speed mixer and stir at 1500 rpm for 60 minutes. Then add 0.1% of aqueous anti-settling agent 2521, and then stir at 2000 rpm for 30 minutes to obtain a porous diatomaceous earth adhesive.

[0072] S3.3: Apply porous diatomaceous earth binder at a concentration of 600 g / m³. 2 The amount of adhesive applied was uniformly applied to the upper surface of the Co-BC-melamine foam. After the adhesive was applied, it was left to stand for 8 minutes to obtain the coated Co-BC-melamine foam. Then, a piece of Co-BC-melamine foam was taken and stacked on the upper surface of the coated Co-BC-melamine foam. The foam was then hot-pressed at 120°C and 0.2 MPa for 10 minutes. After cooling, the melamine foam sandwich composite material was obtained.

[0073] Comparative Example 1: Compared with Example 1, the difference of Comparative Example 1 is that step S1.2 was removed and the subsequent Co-nanobacterial cellulose complex dispersion was replaced with an equal mass of nanobacterial cellulose dispersion. The remaining steps are the same as in Example 1. The melamine foam sandwich composite material obtained is referred to as Comparative Example 1.

[0074] Comparative Example 2: Compared with Example 1, Comparative Example 2 differs in that step S3.1 is removed, purified diatomaceous earth is not added in step S3.2 to obtain waterborne polyurethane adhesive, and the subsequent porous diatomaceous earth adhesive is replaced with an equal mass of waterborne polyurethane adhesive. The remaining steps are the same as in Example 1. The melamine foam sandwich composite material obtained is referred to as Comparative Example 2.

[0075] Sound absorption performance test: The melamine foam sandwich composite materials prepared in Examples 1-3 and Comparative Examples 1-2 were used. The sound absorption coefficient (NRC) of the melamine foam sandwich composite materials was tested by standing wave method using a Danish BK4206 dual impedance tube. The larger the NRC value, the better the sound absorption effect. The test frequencies were 500Hz, 1kHz, 2kHz, 3kHz, 5kHz, and 6kHz. Each material was tested three times, and the average value was taken. The test results are shown in Table 1.

[0076] Table 1: Sound absorption performance of melamine foam sandwich composite materials

[0077] Example 1 0.22 0.41 0.82 0.96 0.92 0.91 0.88 Example 2 0.24 0.43 0.85 0.97 0.93 0.92 0.9 Example 3 0.21 0.39 0.79 0.94 0.9 0.89 0.86 Comparative Example 1 0.16 0.33 0.71 0.83 0.84 0.81 0.75 Comparative Example 2 0.14 0.29 0.68 0.79 0.81 0.78 0.73

[0078] As can be seen from the data in Table 1 of Examples 1-3 and Comparative Example 1, when no cobalt acetylacetone was added to the nanobacterial cellulose dispersion, the sound absorption coefficient (NRC) of the melamine foam sandwich composite material decreased, which proves that cobalt acetylacetone can coordinate with nanobacterial cellulose, improve porosity, and enhance the sound absorption effect of the material.

[0079] As can be seen from the data in Table 1 of Examples 1-3 and Comparative Example 2, when purified diatomaceous earth was not added to the waterborne polyurethane adhesive, the sound absorption coefficient (NRC) of the melamine foam sandwich composite material decreased. This proves that diatomaceous earth, when mixed with the waterborne polyurethane solution, forms an adhesive with strong bonding properties and forms a uniform coating on the surface of the composite material. The microporous structure and high specific surface area of ​​diatomaceous earth not only provide more sound wave absorption points, but also help reduce sound wave reflection and propagation, thus improving the overall acoustic performance of the material.

[0080] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a sandwich composite material based on melamine foam, characterized in that, Includes the following steps: S1: Co coordination with nanobacterial cellulose The nanobacterial cellulose was oxidized with hydrogen peroxide and then dispersed in an ethanol solution to obtain a nanobacterial cellulose dispersion. Cobalt acetylacetone and acetic acid were added to the nanobacterial cellulose dispersion and magnetically stirred to obtain a Co-nanobacterial cellulose complex dispersion. S2: Preparation of Co-BC-melamine foam Melamine foam was soaked in anhydrous ethanol and then ultrasonically cleaned for 15-20 minutes at an ultrasonic frequency of 25-30 kHz. It was then soaked in deionized water and ultrasonically cleaned for another 15-20 minutes at the same frequency. Next, it was placed in a muffle furnace and heated to 180-200℃ at a rate of 5-10℃ / min in air, held at that temperature for 2-2.5 hours, and then allowed to cool naturally to room temperature to obtain pre-oxidized melamine foam. This pre-oxidized foam was then soaked in a 3-mercaptopropyltrimethoxysilane solution prepared from 3-mercaptopropyltrimethoxysilane and ethanol, cleaned, and dried to obtain silane-modified melamine foam. The silane-modified melamine foam was then immersed in a Co-nanobacterial cellulose complex dispersion for ultrasonic treatment. After cyclic freezing and lyophilization, Co-BC-melamine foam was obtained. S3: Composite of porous diatomaceous earth binder and Co-BC-melamine foam Diatomaceous earth is heat-treated and purified to obtain purified diatomaceous earth. The purified diatomaceous earth and sodium dodecylbenzene sulfonate are added to an aqueous polyurethane solution and then placed in a high-speed mixer and stirred at 1200-1500 rpm for 50-60 minutes. An anti-settling agent is then added, and the mixture is stirred at 1800-2000 rpm for 25-30 minutes to obtain a porous diatomaceous earth adhesive. The porous diatomaceous earth adhesive is coated on the surface of Co-BC-melamine foam, and then another piece of Co-BC-melamine foam is used for hot pressing to obtain a melamine foam sandwich composite material.

2. The method for preparing a sandwich composite material based on melamine foam according to claim 1, characterized in that, The coordination of S1Co with nanobacterial cellulose includes the following steps: S1.1: Disperse and soak the nano-bacterial cellulose in a 4-6% hydrogen peroxide solution, then let it stand at 50-70℃ for 1-2 hours, filter and wash with deionized water 3-4 times to obtain oxidized nano-bacterial cellulose. Mix 2-3 parts by weight of oxidized nano-bacterial cellulose, 0.3-0.4 parts by weight of polyvinyl alcohol and 80-100 parts by weight of ethanol solution in an ultrasonic disperser and ultrasonically treat with an ultrasonic power of 300-350W for 10-30 minutes to obtain nano-bacterial cellulose dispersion. S1.2: Add 1-1.5 parts by weight of cobalt acetylacetonate to the nano-bacterial cellulose dispersion obtained in step S1.1, then add 0.1-0.5 wt% acetic acid, and magnetically stir at 150-200 rpm at 50-60℃ for 2-3 hours to obtain Co-nanobacterial cellulose complex dispersion.

3. The method for preparing a sandwich composite material based on melamine foam according to claim 2, characterized in that, The preparation of step S2Co-BC-melamine foam includes the following steps: S2.1: Soak melamine foam in anhydrous ethanol, then place it in an ultrasonic cleaner and ultrasonically clean it for 15-20 minutes at an ultrasonic frequency of 25-30kHz. Then soak it in deionized water and ultrasonically clean it for 15-20 minutes at an ultrasonic frequency of 25-30kHz. Then place it in a muffle furnace and heat it to 180-200℃ at a heating rate of 5-10℃ / min in an air atmosphere. Hold it at this temperature for 2-2.5 hours and then let it cool naturally to room temperature to obtain pre-oxidized melamine foam. S2.2: Mix 3-mercaptopropyltrimethoxysilane and ethanol solution in a volume ratio of 1:(40-60) in a container and stir until the 3-mercaptopropyltrimethoxysilane is completely dissolved. Let stand for 1-2 hours to obtain a 3-mercaptopropyltrimethoxysilane solution. Immerse the pre-oxidized melamine foam in the 3-mercaptopropyltrimethoxysilane solution for 1.5-2 hours. Every 20-30 minutes, take out the pre-oxidized melamine foam and stir it in the 3-mercaptopropyltrimethoxysilane solution for 1-2 minutes. Then take it out and rinse the surface with deionized water 2-3 times. Then place it in an oven at 60-80℃ and heat for 8-10 hours to obtain silane-modified melamine foam. S2.3: The silane-modified melamine foam is completely immersed in the Co-nanobacterial cellulose complex dispersion prepared in step S1.2, and then placed in an ultrasonic water bath. It is ultrasonicated at 35-40 kHz for 30-40 minutes at a temperature of 45-50℃. After freezing at -25-20℃ for 6-8 hours, it is placed at room temperature for 10-12 hours. After 3-4 cycles, it is frozen in liquid nitrogen and finally transferred to a freeze dryer for freeze drying to obtain Co-BC-melamine foam.

4. The method for preparing a sandwich composite material based on melamine foam according to claim 3, characterized in that, Step S3, the composite of porous diatomaceous earth binder and Co-BC-melamine foam, includes the following steps: S3.1: Place 2-4 parts by weight of diatomaceous earth in a container, then place it in a constant temperature drying oven and heat it at 105-110℃ until the mass of the diatomaceous earth no longer changes, to obtain heat-treated diatomaceous earth. Mix the heat-treated diatomaceous earth with 8-12 parts by weight of a 6-8% hydrogen chloride solution, place it in a microwave oven and irradiate it with a power of 700-750W for 4-6 minutes, wash it with distilled water until the pH of the washing distilled water is neutral, then perform vacuum filtration and dry it at 105-110℃ for 10-12 hours to obtain purified diatomaceous earth. S3.2: Add the purified diatomaceous earth obtained in step S3.1 and 0.03-0.04 parts by weight of sodium dodecylbenzenesulfonate to 60-65 parts by weight of aqueous polyurethane solution, then place it in a high-speed mixer and stir at 1200-1500 rpm for 50-60 minutes. Then add 0.1-0.5% of anti-settling agent, and then stir at 1800-2000 rpm for 25-30 minutes to obtain porous diatomaceous earth adhesive. S3.3: Apply porous diatomaceous earth binder at a concentration of 600-800 g / m³. 2 Apply adhesive evenly to the upper surface of Co-BC-melamine foam according to the specified amount of adhesive. After the adhesive is applied, let it stand for 6-8 minutes to obtain adhesive-coated Co-BC-melamine foam. Then, take a piece of Co-BC-melamine foam and stack it on the upper surface of the adhesive-coated Co-BC-melamine foam. Hot press it at 100-120℃ and 0.1-0.2MPa for 8-10 minutes. After cooling, obtain melamine foam sandwich composite material.

5. The method for preparing a sandwich composite material based on melamine foam according to claim 2, characterized in that, The concentration of the ethanol solution in step S1.1 is 10-15%.

6. The method for preparing a sandwich composite material based on melamine foam according to claim 2, characterized in that, In step S2.1, the melamine foam has a diameter of 10cm and a thickness of 2cm.

7. The method for preparing a sandwich composite material based on melamine foam according to claim 5, characterized in that, In step S2.2, the concentration of the ethanol solution mixed with 3-mercaptopropyltrimethoxysilane is 96-98%.

8. The method for preparing a sandwich composite material based on melamine foam according to claim 5, characterized in that, The solid content of the aqueous polyurethane solution in step S3.2 is 40-45%.

9. The method for preparing a sandwich composite material based on melamine foam according to claim 5, characterized in that, The anti-settling agent in step S3.2 is water-based anti-settling agent 2521.

10. A sandwich composite material based on melamine foam, characterized in that, It is prepared by the method for preparing a sandwich composite material based on melamine foam as described in any one of claims 1-8.

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