A low-density sound-absorbing inorganic material and a method for producing the same

Abstract

The present application belongs to the technical field of sound-absorbing materials, and relates to a low-density sound-absorbing inorganic material and a preparation method thereof.The present application provides a low-density sound-absorbing inorganic material, which is composed of carbon fibers and basalt fibers and has a layered structure.The present application produces a layered structure by regulating the proportion of carbon fibers and basalt fibers and utilizing the linear density difference between the carbon fibers and the basalt fibers.The low-density sound-absorbing inorganic material provided by the present application has good sound-absorbing and noise-reducing performance at medium and low frequencies, and has the advantages of low density, low thermal conductivity and high noise-reducing coefficient.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sound-absorbing materials, and relates to a low-density sound-absorbing inorganic material and a preparation method thereof. BACKGROUND

[0002] Noise pollution has a great harm to people's physical and mental health, and effectively preventing noise pollution and reducing the harm of noise is a necessary measure to protect people's normal work and life. Sound-absorbing materials can be used to treat noise pollution from three aspects of noise source, propagation process and terminal victim protection, and are the most effective means for noise pollution. According to the sound-absorbing characteristics, sound-absorbing materials can be divided into porous sound-absorbing materials, resonant sound-absorbing materials and special structure sound-absorbing materials. The porous sound-absorbing materials have the characteristics of light weight and good sound-absorbing effect, and are one of the most widely used sound-absorbing materials at present, which are widely used in vehicles, broadcasting halls, theaters and other places. With the rapid development of the sound-absorbing material industry, only good sound-absorbing effect cannot fully meet the current market demand, and people have put forward higher requirements for sound-absorbing materials. The materials not only need to have good sound-absorbing performance, but also need to be light in weight. Therefore, in recent years, ultra-light high-efficiency sound-absorbing materials have become one of the global development hotspots.

[0003] Currently, the main lightweight and efficient sound-absorbing material is traditional non-woven sound-absorbing cotton, and researchers have also made corresponding research work in this regard and developed a series of sound-absorbing materials. CN108676139B provides a kind of polyurethane foam material, containing organic sound-absorbing material;The organic sound-absorbing material includes one or more of polymer micro powder, organic silicon microsphere, organic porous material and plant organic fiber porous material;The polyurethane foam material has a porous structure;The maximum pore of the porous structure is less than or equal to 5mm. The traditional foam sound-absorbing material is mostly porous structure, and the sound-absorbing performance of the porous structure depends on the pore size. Adjusting the pore size will inevitably affect the strength and other properties of the sound-absorbing material, which is difficult to meet the performance requirements of low density and high sound absorption. CN104441809B provides a kind of metal fiber foam aluminum composite layer plate and its preparation method, which includes at least one metal plate layer, at least one fiber layer and at least one foam aluminum layer;The fiber layer is alternately bonded with the foam aluminum layer by high-temperature-resistant polymer adhesive composite;The metal plate layer is used as the outermost layer and is bonded with the fiber layer by high-hardness polymer adhesive composite. The preparation method of the metal fiber foam aluminum composite layer plate is also disclosed, which mainly includes surface purification treatment of the metal plate layer and the foam aluminum layer, then coating the high-temperature-resistant and high-hardness polymer adhesive composite on the surface, and then bonding and curing the layers under pressure. The sound-absorbing material based on metal and fiber is difficult to meet the performance requirements of low density, and in addition, the existing fiber-based porous sound-absorbing material has the problems and defects of complex preparation process, large energy consumption, and difficult to adjust the pore size. In addition, with the promotion of the double carbon target, the development of lightweight thermal insulation materials has also become an important trend. The main raw materials of the current thermal insulation materials are silicate materials such as asbestos and perlite. However, silicate materials have relatively high density, and asbestos has high environmental and health risks. Carbon fiber, as a high-performance fiber, has small density and high performance, but has the characteristics of heat conduction and electrical conductivity, which poses great challenges in the preparation of thermal insulation materials. SUMMARY

[0004] The present application aims to provide a low-density and high-sound-absorbing inorganic material with a layered structure.

[0005] To meet the needs in the field, the present application provides a low-density sound-absorbing inorganic material and a preparation method thereof based on the above purpose.

[0006] In one aspect, the present application relates to a low-density sound-absorbing inorganic material, in which basalt fibers and carbon fibers are dispersed in a polyvinyl alcohol solution after being defibered and then foamed to form a layered structure.

[0007] The mass ratio of the basalt fibers to the carbon fibers is 7:3 to 3:7.

[0008] The content of the basalt fibers and the carbon fibers in the polyvinyl alcohol solution is 1.5-2wt%.

[0009] Further, the low-density sound-absorbing inorganic material provided by the present application has the basalt fiber with a length of 6-9 mm and a diameter of 9-13 μm.

[0010] The carbon fiber has a length of 6 mm and a diameter of 5-8 μm.

[0011] Further, the low-density sound-absorbing inorganic material provided by the present application has the polyvinyl alcohol solution with a mass concentration of polyvinyl alcohol of 2-3%.

[0012] Further, the low-density sound-absorbing inorganic material provided by the present application has a density of 0.013-0.015 g / cm 3 and a noise reduction coefficient of 0.44-0.63.

[0013] In another aspect, the present application relates to a preparation method of the low-density sound-absorbing inorganic material, which comprises: mixing basalt fiber and carbon fiber in a proportion, defibrating, vacuum filtering, placing in a polyvinyl alcohol solution, ultrasonic dispersing, foaming and drying to obtain the low-density sound-absorbing inorganic material.

[0014] Further, the preparation method of the low-density sound-absorbing inorganic material provided by the present application has the defibrating with 10,000-20,000 revolutions.

[0015] Further, the preparation method of the low-density sound-absorbing inorganic material provided by the present application has the foaming, which comprises: high-speed stirring to make air enter the reaction system, so that the air mass content in the reaction system is 50%-70%.

[0016] The high-speed stirring has a rotating speed of 3,000-4,000 r / min and a stirring time of 20-30 min.

[0017] Further, the preparation method of the low-density sound-absorbing inorganic material provided by the present application has a drying temperature of 90-100℃.

[0018] Compared with the prior art, the present application has the following beneficial effects or advantages:

[0019] (1) The present application uses basalt fiber and carbon fiber, utilizes the linear density difference of basalt fiber and carbon fiber, and controls the proportion of fibers to cause the arrangement number of basalt fiber and carbon fiber in xy plane and yz plane to be different, thereby producing a layered structure. The layered structure gives the material good sound absorption performance. The low-density sound-absorbing inorganic material provided by the present application has good sound absorption and noise reduction performance at low and medium frequencies, and has the advantages of low density, low thermal conductivity, and high noise reduction coefficient. In the traditional fiber-based foam material, a part of the fibers are cross-linked to form a three-dimensional network structure, and another part of the fibers are arranged in the z-axis to provide support for the material and facilitate the formation of foam. However, the composite foam prepared by the present application has a layered structure with a gathering feature. At low density, the overall structure is realized by the accumulation of fiber layers. It is this unique layered structure that makes the material have good sound absorption and thermal insulation performance.

[0020] (2) The length and linear density of the fibers and the air uptake amount in the system used in the present application will affect the structure. The difference in length and linear density of the fibers will affect the arrangement of the fibers in three-dimensional space, and different fiber ratios will also affect the arrangement of the fibers in three-dimensional space. It is found that when the air intake amount is in the range of 50% to 70%, a layered structure will appear.

[0021] (3) The present application starts from the raw materials themselves. Carbon fiber is originally used as a heat-conducting and electrically-conducting material in various fields, but after being compounded with basalt fiber through foaming molding technology, the prepared composite foam has good thermal insulation performance, so that carbon fiber can also be applied in the field of lightweight thermal insulation materials. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The figure is a sample of the low-density sound-absorbing inorganic material prepared in Example 1. a is a sample appearance figure; b is an internal cross-sectional figure after being cut; c is a sample appearance figure prepared by the comparative example; d is an internal cross-sectional figure after being cut by the comparative example.

[0023] Figure 2 The figure is the noise reduction coefficient detection result.

[0024] Figure 3 The figure is the thermal conductivity detection result. DETAILED DESCRIPTION

[0025] In the following, the technical solutions of the present application will be described in conjunction with examples. However, the present application is not limited to the following examples.

[0026] In order to make the skilled in the art better understand the technical solutions of the present application can be implemented, the following specific embodiments and the present application is further described with reference to the drawings, but the examples are not as a limitation of the present application.

[0027] The experimental methods and detection methods described in the following examples, if no special instructions, are conventional methods; the reagents and materials, if no special instructions, can be purchased on the market.

[0028] Example 1

[0029] The present embodiment provides a low-density sound-absorbing and heat-insulating material containing carbon fibers, the mass ratio of carbon fibers (CF) and basalt fibers (BF) is 7:3, and the total mass of the fibers accounts for 1.5% of the mass of the polyvinyl alcohol solution system.

[0030] S1: Take basalt fibers with a diameter of 13 μm and a length of 6 mm, and move them to a muffle furnace with a temperature of 350°C for calcination; take carbon fibers with a length of 5 mm and a diameter of 7 μm, and add them to a prepared sodium dodecylbenzenesulfonate solution with a concentration of 1.2×10 -3 mol / L, and stir and dry under heating in a water bath at 60°C.

[0031] S2: After drying the pretreated fibers, weigh them according to the ratio of CF:BF of 7:3, and perform defibration on a defibrator with 20000 revolutions, then add the treated fibers to a prepared PVA solution with a concentration of 3wt% for ultrasonic dispersion (400w, 20min), stir and mix the dispersed fibers in a high-speed stirrer, and pour them into a former when the air intake is 70%, and then filter water and dry at 100°C.

[0032] The low-density sound-absorbing inorganic material prepared in this embodiment is shown in Figure 1 , the density is 0.013 g / cm 3 , and the sound-absorbing and noise-reducing coefficient is 0.482.

[0033] Example 2

[0034] The present embodiment provides a low-density sound-absorbing and heat-insulating material containing carbon fibers, the mass ratio of carbon fibers (CF) and basalt fibers (BF) is 6:4, and the total mass of the fibers accounts for 1.6% of the mass of the polyvinyl alcohol solution system.

[0035] S1: Take basalt fibers with a diameter of 11 μm and a length of 7 mm, and move them to a muffle furnace with a temperature of 350°C for calcination; take carbon fibers with a length of 5 mm and a diameter of 7 μm, and add them to a prepared sodium dodecylbenzenesulfonate solution with a concentration of 1.2×10 -3mol / L sodium dodecyl benzene sulfonate solution, stirring under the heating of water bath at 60℃.

[0036] S2: After drying the pretreated fibers, weigh them according to the ratio of CF:BF of 6:4, and then perform defibration on the defibrator with 18000 rotations. After vacuum filtration, add the treated fibers into the prepared PVA solution with a concentration of 2.8wt% for ultrasonic dispersion (400w, 20min). Place the dispersed fibers in a high-speed blender for mixing and foaming. When the air intake reaches 65%, pour them into a former for water filtration and drying at 95℃.

[0037] The low-density sound-absorbing inorganic material prepared in this example has a density of 0.0133g / cm 3 and a sound-absorbing and noise-reducing coefficient of 0.506.

[0038] Example 3

[0039] This example provides a low-density sound-absorbing and heat-insulating material containing carbon fibers, with the mass ratio of carbon fibers (CF) to basalt fibers (BF) being 5:5, and the total mass of the fibers accounting for 1.7% of the mass of the polyvinyl alcohol solution system.

[0040] S1: Take basalt fibers with a diameter of 11μm and a length of 8mm, and move them to a muffle furnace with a temperature of 350℃ for calcination. Take carbon fibers with a length of 4mm and a diameter of 6μm, and add them to a prepared sodium dodecyl benzene sulfonate solution with a concentration of 1.2×10 -3 mol / L, and stir and dry under the heating of a water bath at 60℃.

[0041] S2: After drying the pretreated fibers, weigh them according to the ratio of CF:BF of 5:5, and then perform defibration on the defibrator with 16000 rotations. After vacuum filtration, add the treated fibers into the prepared PVA solution with a concentration of 2.6wt% for ultrasonic dispersion (400w, 20min). Place the dispersed fibers in a high-speed blender for mixing and foaming. When the air intake reaches 60%, pour them into a former for water filtration and drying at 95℃.

[0042] The low-density sound-absorbing inorganic material prepared in this example has a density of 0.014g / cm 3 and a sound-absorbing and noise-reducing coefficient of 0.538.

[0043] Example 4

[0044] This example provides a low-density sound-absorbing and heat-insulating material containing carbon fibers, with the mass ratio of carbon fibers (CF) to basalt fibers (BF) being 4:6, and the total mass of the fibers accounting for 1.8% of the mass of the polyvinyl alcohol solution system.

[0045] S1: Take basalt fibers with a diameter of 10 pm and a length of 9 mm, move them to a muffle furnace at a temperature of 350°C for calcination; take carbon fibers with a length of 6 mm and a diameter of 8 pm, and add them to a prepared sodium dodecyl benzene sulfonate solution with a concentration of 1.2 x 10 -3 mol / L, stir and wash under heating in a water bath at 60°C, and dry.

[0046] S2: After drying the pretreated fibers, weigh them according to the ratio of CF:BF of 4:6, perform defibration on the defibrator at 14000 revolutions, perform vacuum filtration on the treated fibers, add them to a prepared PVA solution with a concentration of 2.4 wt%, perform ultrasonic dispersion (400w, 20min), place the dispersed fibers in a high-speed blender for mixing and foaming, pour them into a former when the air intake reaches 55%, filter water, and dry at 90°C.

[0047] The low-density sound-absorbing inorganic material prepared in this example has a density of 0.0144 g / cm 3 , and a sound-absorbing and noise-reducing coefficient of 0.478.

[0048] Example 5

[0049] This example provides a low-density sound-absorbing and heat-insulating material containing carbon fibers, with the mass ratio of carbon fibers (CF) and basalt fibers (BF) being 3:7, and the total mass of the fibers accounting for 2% of the mass of the polyvinyl alcohol solution system.

[0050] S1: Take basalt fibers with a diameter of 9 pm and a length of 9 mm, move them to a muffle furnace at a temperature of 350°C for calcination; take carbon fibers with a length of 6 mm and a diameter of 8 pm, and add them to a prepared sodium dodecyl benzene sulfonate solution with a concentration of 1.2 x 10 -3 mol / L, stir and wash under heating in a water bath at 60°C, and dry.

[0051] S2: After drying the pretreated fibers, weigh them according to the ratio of CF:BF of 3:7, perform defibration on the defibrator at 12000 revolutions, perform vacuum filtration on the treated fibers, add them to a prepared PVA solution with a concentration of 2.2 wt%, perform ultrasonic dispersion (400w, 20min), place the dispersed fibers in a high-speed blender for mixing and foaming, pour them into a former when the air intake reaches 50%, filter water, and dry at 90°C.

[0052] The low-density sound-absorbing inorganic material prepared in this example has a density of 0.015 g / cm 3 , and a sound-absorbing and noise-reducing coefficient of 0.443.

[0053] Comparative Example 1

[0054] This comparative example provides a sound-absorbing and heat-insulating inorganic material.

[0055] S1: Take basalt fibers with a diameter of 13μm and a length of 6mm, with the total mass of the fibers accounting for 2% of the mass of the polyvinyl alcohol solution system. Transfer the crucible to a muffle furnace at a temperature of 350℃ for calcination.

[0056] S2: Weigh the pretreated basalt fibers and decompose them on a decomposition machine at 20,000 revolutions to disperse the fibers. After vacuum filtration, add the treated fibers to a prepared 2wt% PVA solution for ultrasonic dispersion (400w, 20min). Place the dispersed fibers on a high-speed mixer for mixing and foaming. When the air intake is 70%, pour the mixture into a molding machine to filter water and dry it at 95℃.

[0057] The sound-absorbing inorganic material prepared in this comparative example is as follows: Figure 2 As shown, its density is 0.0155 g / cm³. 3 The sound absorption and noise reduction coefficient is 0.427.

[0058] The sound absorption coefficients of Examples 1-2 and Comparative Example 1 were measured using a four-channel digital signal acquisition system and impedance tubes with diameters of 100 mm and 30 mm. The test frequency was 63-6300 Hz. The inorganic sound-absorbing materials prepared in Examples 1-2 and Comparative Example 1 were tested, and the test results are shown in Table 1.

[0059] Table 1. Sound absorption performance measurements of Examples 1-5 and Comparative Example 1

[0060]

[0061] As shown in Table 1, the noise reduction coefficient of the foam material increases significantly compared to Comparative Example 1 as the carbon fiber content decreases. When sound waves enter the foam, they are reflected between the fibers, and the sound energy is converted into heat energy through the friction and vibration of the fibers, thus achieving a sound absorption effect. When the fiber distribution has a layered structure, the sound wave propagation path becomes more tortuous, which is beneficial to improving the sound absorption and noise reduction performance of the material. This invention controls the arrangement of fibers inside the foam by controlling the air intake and the fiber ratio, so that the fibers self-crosslink and accumulate inside the foam to form a layered structure, increasing the sound wave reflection path and giving the foam superior sound absorption performance.

[0062] Carbon fiber generally has excellent thermal conductivity, so it is less used in thermal insulation materials. However, through the present technology, carbon fiber and basalt fiber are reasonably matched, and by controlling the difference in fiber density, the fibers are aggregated and present a layered structure during the material forming process, thereby facilitating the reduction of heat propagation. Therefore, even if a large amount of carbon fiber is used, the material still has good thermal insulation performance (i.e., a lower thermal conductivity).

[0063] Figure 1 a is a sample appearance diagram prepared according to a 1:1 ratio of carbon fiber and basalt fiber; Figure 1 b is an internal planing surface after being cut open, Figure 1 c is a basalt fiber foam in Comparative Example 1, Figure 1 d is a planing surface diagram of a basalt foam. Comparison Figure 1 b and Figure 1 d can directly observe the difference in the internal structure of the two foams. Using the foam forming method generally obtains a porous foam material, and the arrangement of the fibers of the material mostly tends to be in the Z direction (i.e., outside the X-Y plane), and the pores between the fibers are large, such as Figure 1 d. By using the present technology, the arrangement of the fibers of the material can be changed from the Z direction to a layered structure with fiber aggregation characteristics, thereby optimizing the structure of the material and greatly improving the performance.

[0064] Figure 2 The sound absorption coefficient of the sample is tested by using an impedance tube, and the test frequency is 63-6300 Hz. For a foam material, the higher the noise reduction coefficient (NRC) is, the more outstanding the sound absorption performance is. According to the experiment, it is found that when the fiber mixing ratio is 1:1, the noise reduction coefficient is the highest due to the excellent structural performance, which is 0.54.

[0065] Figure 3 The thermal conductivity of the sample is tested by using a thermal constant analyzer. For a foam material, the lower the thermal conductivity is, the more outstanding the thermal insulation performance is. According to the experiment, it is found that although the thermal conductivity increases as the content of carbon fiber increases, the composite foam still has good thermal insulation performance.

[0066] As described above, the present application can be well implemented. The above-described embodiments only describe the preferred embodiments of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various changes and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the scope of the present application.

Claims

1. A low-density sound-absorbing inorganic material, characterized in that, Basalt fiber and carbon fiber are dispersed in polyvinyl alcohol solution and then foamed to form a layered structure. Specifically, basalt fiber and carbon fiber are mixed in proportion and then dispersed, vacuum filtered, placed in polyvinyl alcohol solution, ultrasonically dispersed, foamed and dried to obtain low-density sound-absorbing inorganic material. The ratio of basalt fiber to carbon fiber by mass is 7:3 to 3:7; The content of basalt fiber and carbon fiber in polyvinyl alcohol solution is 1.5~2 wt%; The basalt fibers have a length of 6-9 mm and a diameter of 9-13 µm; the carbon fibers have a length of 6 mm and a diameter of 5-8 µm. The density of the low-density sound-absorbing inorganic material is 0.013~0.015 g / cm³. 3 The noise reduction coefficient is 0.44~0.63; The foaming process includes: high-speed stirring to introduce air into the reaction system, resulting in an air mass content of 50% to 70% in the reaction system; The high-speed stirring speed is 3000~4000 r / min, and the stirring time is 20~30 min.

2. The low-density sound-absorbing inorganic material according to claim 1, characterized in that, The polyvinyl alcohol concentration in the polyvinyl alcohol solution is 2-3%.

3. The low-density sound-absorbing inorganic material according to claim 1, characterized in that, The number of revolutions for the slack is 10,000 to 20,000.

4. The low-density sound-absorbing inorganic material according to claim 1, characterized in that, The drying temperature is 90~100℃.

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