Clay aerogel for low and medium frequency noise reduction, light weight and heat insulation and preparation method thereof

Abstract

The invention belongs to the technical field of heat insulation and sound absorption materials, and discloses clay aerogel for low and medium frequency noise reduction, light weight and heat insulation and a preparation method of the clay aerogel. According to the preparation method, sepiolite clay and calcium sulfate whiskers are taken as raw materials, epoxy resin, phytic acid and polyvinyl alcohol are taken as additives, and the clay aerogel with an ordered microstructure is obtained by controlling the growth direction of ice crystals through a directional freezing process. The optimal vibration unit structure is finally obtained by regulating and controlling the proportion of the sepiolite and the crystal whiskers and controlling the growth form of ice crystals, the material is endowed with excellent sound absorption, heat insulation and other properties, and the material has the characteristics of light weight, high strength and the like, and has important application prospects in the fields of building sound insulation, heat preservation and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sound-absorbing materials, and relates to a clay aerogel for medium-low frequency noise reduction and light heat insulation and a preparation method thereof. BACKGROUND

[0002] Building material functionalization is a market with great potential in China. With the improvement of building energy saving requirements and the development of energy saving technology, building thermal insulation materials and building sound insulation materials are also developing towards lightness, multifunctionality and energy saving and environmental protection. The application of low-frequency noise reduction materials is derived from low-frequency noise pollution in modern social life, usually refers to sound waves with a frequency below 1000 Hz (Hz), and has strong sound wave length and penetration, is closely related to industrial development and living noise. Long-term exposure to high-intensity low-frequency noise may cause physiological diseases such as hearing impairment, cardiovascular disease and nervous system decline. Many countries and regions have relevant noise control regulations to protect the health and quality of life of the public, and particularly emphasize the detection and control of low-frequency noise in noise control measures. Aerogel material as a new type of nanoscale light, multifunctional and environmentally friendly material has been widely concerned due to its unique properties, especially as a high-efficiency noise reduction, thermal insulation and sound insulation material has become a research hotspot.

[0003] Chinese patent CN115181322A discloses a sodium alginate / montmorillonite / natural latex aerogel and a preparation method thereof. Sodium alginate is used as a matrix, montmorillonite and natural latex are used as reinforcing materials, and sodium alginate / montmorillonite / natural latex aerogel is prepared by using chemical crosslinking technology and freeze-drying method. The complex crosslinking network structure is realized by crosslinking sodium alginate with calcium ions and vulcanizing natural latex at high temperature, and montmorillonite is used as a reinforcing material to improve the mechanical properties and sound absorption performance of the aerogel. However, the structure of the aerogel is layered stacking, which is not conducive to consuming low-frequency waves with long wavelengths, so the medium-low frequency noise reduction performance is limited to a certain extent, and cannot meet the medium-low frequency noise control below 1000 Hz.

[0004] Therefore, it is necessary to develop an aerogel with simple process, high strength, thermal insulation and suitable for low-frequency noise reduction, which has wide application prospect. SUMMARY

[0005] Sepiolite is a light clay mineral with a porous structure, which can be used as sound insulation material, and has the characteristics of high strength and excellent sound insulation performance compared with ordinary polymer sound insulation materials. At present, there are few reports on the application of sepiolite in the field of sound insulation and noise reduction. Sepiolite aerogel has a rich porous structure, which can form more and smaller vibration units, significantly increase the resistance of sound wave propagation, and is beneficial to consume low-frequency waves with long wavelength, thereby playing a sound insulation role. In addition, sepiolite itself has strong anti-vibration ability, which can effectively absorb the vibration of sound wave propagation, greatly reduce the reflection and emission of sound wave, thereby playing a sound insulation role. On the other hand, the light and porous structure of aerogel also makes it have good heat insulation performance, so it is a very promising noise reduction and light heat insulation material.

[0006] In order to overcome the shortcomings of the prior art, the present application provides a clay aerogel for middle and low frequency noise reduction and light heat insulation and a preparation method thereof, which takes sepiolite as a basic material, calcium sulfate whisker as a reinforcing material, polyvinyl alcohol, epoxy resin and bio-based phytic acid as additives, and obtains a clay aerogel with ordered vibration unit structure through a directional freezing process. The obtained clay aerogel has excellent properties such as high sound absorption coefficient, low thermal conductivity and high strength, and can be used for building energy-saving sound insulation and heat insulation.

[0007] The object of the present application is achieved by the following technical solutions: The first aspect of the present application provides a preparation method of a clay aerogel for middle and low frequency noise reduction and light heat insulation. Calcium sulfate whisker and modified sepiolite are dissolved in deionized water to uniformly ultrasonic disperse to obtain a clay solution. Polyvinyl alcohol is mixed with deionized water, stirred in a water bath at 80-90 DEG C, then epoxy resin is added and continuously stirred in a water bath until complete reaction to obtain a polymer solution. The clay solution and the polymer solution are mixed and stirred uniformly, then phytic acid is added and stirred uniformly to obtain a sol solution. Then the sol solution is poured into a mold, dried in a freeze dryer after directional freezing, then placed in a vacuum oven at 50-80 DEG C for 6-12 h, and finally the clay aerogel is obtained.

[0008] Further, the preparation method of the modified sepiolite is as follows: sepiolite and hydrochloric acid solution are mixed at a solid-liquid ratio of 1 g:10-20 mL at 70-80 DEG C, washed with deionized water to neutral after stirring, filtered, and dried to obtain acidified sepiolite. Then the acidified sepiolite is organically modified with an amino propyl triethoxysilane hydrolysate, washed with ethanol, filtered, and dried to obtain modified sepiolite. The amino propyl triethoxysilane hydrolysate is obtained by mixing amino propyl triethoxysilane, deionized water and ethanol at a mass ratio of 1:1: (1-10).

[0009] Further, the mass ratio of polyvinyl alcohol to epoxy resin is 1-10:1-5.

[0010] Further, the calcium sulfate whisker is anhydrous calcium sulfate whisker.

[0011] Further, the mass of the phytic acid is 10% to 20% of the mass of the polyvinyl alcohol.

[0012] Further, the mass ratio of the polyvinyl alcohol to the modified sepiolite is 1 to 5: 1 to 10.

[0013] Further, the mass ratio of the calcium sulfate whisker to the sepiolite is 1 to 10: 1 to 10.

[0014] Further, the directional freezing process is to place a mold on a copper sheet, place liquid nitrogen under the copper sheet, and control the cooling speed to make the ice crystals grow in one direction from bottom to top.

[0015] The second aspect of the present application provides a clay aerogel for low-frequency noise reduction and light heat insulation, which takes sepiolite as the main skeleton structure, and controls the skeleton spacing through the proportion of sepiolite and needle-shaped calcium sulfate whisker and a directional freezing process, to form a three-dimensional network porous structure with a vibration unit structure.

[0016] The third aspect of the present application provides an application of the clay aerogel for low-frequency noise reduction and light heat insulation in building thermal insulation, sound insulation and waterproofing.

[0017] The present application introduces calcium sulfate whisker into the modified sepiolite modified by acidification and organic modification, then adds polyvinyl alcohol, epoxy resin and clay to form a three-dimensional network cross-linked by hydrogen bond, and adds phytic acid and polyvinyl alcohol to form a bond to improve the structural stability. The directional freezing drying process controls the unidirectional growth of ice crystals to arrange the vibration unit structure in order, and obtains a high-performance composite clay aerogel with a special three-dimensional network structure. The content of calcium sulfate whisker can affect the diffusion degree of ice crystals, the irregular arrangement of calcium sulfate whisker can cause the diffusion of ice crystals to the surrounding, the greater the concentration of calcium sulfate whisker, the more significant the diffusion, and the growth and diffusion of ice crystals affect the order degree and spacing of the structure, and affect the micro-morphology of the material, thereby affecting its performance. The present application finally obtains the best vibration unit structure by controlling the content of calcium sulfate whisker and the directional freezing process. The special three-dimensional network microstructure makes the clay aerogel material have high sound absorption coefficient, low thermal conductivity and other properties, and realizes the effects of noise reduction and heat insulation.

[0018] The advantages and beneficial effects of the present application are: (1) The clay aerogel prepared by the present application has a controllable micro-morphology, and the microstructure of the aerogel is controlled by adjusting the proportion of sepiolite and calcium sulfate whisker; (2) The clay aerogel prepared by the method has optimal vibration unit structure, so that the clay aerogel has excellent sound absorption performance. The sepiolite disperses sound waves and air vibration into many smaller vibration units, thereby enhancing the hindering effect on the propagation of sound waves. The optimal vibration unit arrangement structure is obtained by regulating the micro-morphology of the calcium sulfate whisker, and the low-frequency wave noise reduction performance below 1000 Hz is effectively improved, so that the clay aerogel can be used for medium and low frequency noise reduction.

[0019] (3) The clay aerogel prepared by the method has the characteristics of light weight, high porosity, low thermal conductivity and high strength, and has density (0.1479~0.1904 g / cm 2 ), thermal conductivity (0.0367~0.0552 W·m -1 ·K -1 ), so that the clay aerogel has excellent heat insulation performance.

[0020] (4) The preparation process of the clay aerogel prepared by the method is simple, and the cost is low, so that the clay aerogel can be used in the fields of building energy-saving thermal insulation, sound insulation and the like. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Density and thermal conductivity test results of examples 1~3 and comparative examples; Figure 2 Scanning electron microscope images of the clay aerogels prepared in examples 1~3; Figure 3 Sound absorption coefficient test chart of the clay aerogels prepared in examples 1~3 and comparative examples; Figure 4 Stress-strain curves of examples 1~3. DETAILED DESCRIPTION

[0022] The application will be further described in detail below in combination with specific implementation examples. It should be understood that the following examples are only used to illustrate the application and are not limited to the scope of the application.

[0023] Example 1 A preparation method of a clay aerogel for low-frequency noise reduction, the steps are as follows: (1) Sepiolite modification: 20 g of sepiolite (SEP) was added to 300 mL of 1.5 mol / L hydrochloric acid solution according to the solid-liquid ratio of 1:15 (g / mL), and was stirred magnetically at 80 °C water bath environment for 1 h, washed with deionized water until neutral, filtered and dried for 12 h to obtain acidified sepiolite (a-SEP); Ammonia propyl triethoxysilane (KH550), deionized water and ethanol were mixed uniformly according to the ratio of 1:1:9, stirred at 30 °C water bath for 30 min, a-SEP was added to 100 mL of anhydrous ethanol and ultrasonic dispersed for 30 min to obtain a-SEP slurry which was uniformly dispersed, and the hydrolysis solution of KH550 was slowly added to the acidified sepiolite, and stirred at 80 °C for 1 h. After repeated washing with ethanol until neutral, filtration and vacuum drying at 80 °C for 12 h, the modified sepiolite (o-SEP) was obtained; (2) Preparation of clay aerogel: 8 g of o-SEP was dissolved in 30 g of deionized water by vigorous stirring, then 2 g of calcium sulfate whisker (CSW) was uniformly stirred in the o-SEP solution and ultrasonic dispersed for 30 min to obtain a uniformly dispersed clay solution; 4 g of polyvinyl alcohol (PVA) and 1.5 g of epoxy resin (EP) were mixed and dissolved in 34.5 g of deionized water, stirred at 85 °C water bath environment for 2 h, then cooled to room temperature, and then slowly added to the clay solution, finally 0.5 g of phytic acid was added and stirred uniformly, then the sol solution was poured into a mold, frozen with liquid nitrogen and copper sheet, stored in a refrigerator for 48 h, then placed in a vacuum freeze dryer, freeze dried for 72 h, and finally transferred to a vacuum oven, cured at 60 °C for 6-12 h, to obtain a clay aerogel.

[0024] Example 2 Preparation of clay aerogel: 6 g of o-SEP (same as in Example 1) was dissolved in 30 g of deionized water by vigorous stirring, then 4 g of calcium sulfate whisker (CSW) was uniformly stirred in the o-SEP solution and ultrasonic dispersed for 30 min to obtain a uniformly dispersed clay solution; 4 g of polyvinyl alcohol (PVA) and 1.5 g of epoxy resin (EP) were mixed and dissolved in 34.5 g of deionized water, stirred at 85 °C water bath environment for 2 h, then cooled to room temperature, and then slowly added to the clay solution, finally 0.5 g of phytic acid was added and stirred uniformly, then the sol solution was poured into a mold, frozen with liquid nitrogen and copper sheet, stored in a refrigerator for 48 h, then placed in a vacuum freeze dryer, freeze dried for 72 h, and finally transferred to a vacuum oven, cured at 60 °C for 6-12 h, to obtain a clay aerogel.

[0025] Example 3 Preparation of clay aerogel: 4 g of o-SEP (same as in Example 1) was weighed and dissolved in 30 g of deionized water with vigorous stirring. Then, 6 g of calcium sulfate whiskers (CSW) were weighed and uniformly stirred in the o-SEP solution and ultrasonically dispersed for 30 min to obtain a uniformly dispersed clay solution. 4 g of polyvinyl alcohol (PVA) and 1.5 g of epoxy resin (EP) were mixed and dissolved in 34.5 g of deionized water. The mixture was stirred in an 85°C water bath for 2 h, cooled to room temperature, and then slowly added to the clay solution. Finally, 0.5 g of phytic acid was added and stirred evenly. The sol was poured into a mold, directionally frozen with liquid nitrogen and a copper sheet, stored in a refrigerator for 48 h, and then placed in a vacuum freeze dryer for freeze drying for 72 h. After drying, the mixture was transferred to a vacuum oven and cured at 60°C for 6-12 h to obtain a clay aerogel.

[0026] Comparative Example Preparation of clay aerogel: 8 g of o-SEP (same as in Example 1) was weighed and dissolved in 32 g of deionized water with vigorous stirring, and ultrasonically dispersed for 30 min to obtain a uniformly dispersed clay solution; 4 g of polyvinyl alcohol (PVA) and 1.5 g of epoxy resin (EP) were mixed and dissolved in 34.5 g of deionized water, stirred in an 85°C water bath for 2 h, and then cooled to room temperature. The mixture was then slowly added to the clay solution, and finally 0.5 g of phytic acid was added and stirred evenly. The sol was poured into a mold, directionally frozen with liquid nitrogen and a copper sheet, stored in a refrigerator for 48 h, and then placed in a vacuum freeze dryer for freeze drying for 72 h. After drying, the mixture was transferred to a vacuum oven and cured at 60°C for 6-12 h to obtain a clay aerogel.

[0027] Performance test results: The thermal conductivity of the material at 25 °C was measured using a Xi'an Xiaxi hot wire thermal conductivity meter (TC3000). Figure 1 It can be seen that different ratios of sepiolite and calcium sulfate whiskers affect the density and thermal conductivity of the aerogel. The aerogel obtained in Example 2 has a lower thermal conductivity, which is attributed to its uniform and ordered pore structure, thus having excellent properties such as light weight and thermal insulation.

[0028] The micromorphology of the samples was analyzed using an SM-7800F ultra-high resolution thermal field emission scanning electron microscope from Hitachi, Japan. Figure 2 、 Figure 3 .like Figure 2 As shown, a to c correspond to the scanning electron micrographs of Examples 1 to 3, respectively. The skeleton structure is based on sepiolite, and the skeleton spacing is regulated by the ratio of sepiolite to needle-shaped calcium sulfate whiskers and the directional freezing process to form a three-dimensional network porous structure with a vibration unit structure. However, due to the different ratios of sepiolite and calcium sulfate whiskers, the pore spacing is also different. The results show that when the SEP content is 8 g and the CSW content is 2 g (Figure 2 In the middle a), the hole spacing is small, the hole distribution is uneven and there is a stacking phenomenon, when the sound wave enters the aerogel, the efficiency of sound energy consumption caused by air vibration friction is reduced due to too small gap; when the content of SEP is 6 g and the content of CSW is 4 g (b in the middle), Figure 2 In the middle b), the hole spacing is increased, the efficiency of sound energy consumption caused by air vibration friction is improved, in addition, it also shows a uniform porous structure, which further improves the efficiency of sound energy loss; when the content of SEP is 4 g and the content of CSW is 6 g (c), Figure 2 In the middle c), the hole spacing is too large to cause loose structure, and the hole size is increased, at this time, the sound wave is not easy to produce friction with the hole wall to consume sound energy, and the sound absorption coefficient decreases.

[0029] The sound absorption performance of the material was tested by Beijing Shengwang impedance tube test system (SW4661), and the results are shown in Figure 3 The aerogel obtained by the application has excellent sound absorption performance for sound waves in the wave band of 400-1000 Hz, and the sound absorption coefficient can be as high as 0.93.

[0030] The compressive strength of the material was tested by Mettler industrial system electronic universal testing machine, and the results are shown in Figure 4 It can be seen that the mechanical properties of the clay aerogel can be improved by increasing the content of calcium sulfate whiskers.

[0031] In summary, the aerogel obtained by the application has excellent properties such as light weight, heat preservation, high strength, etc.

[0032] Application Clay aerogel is a kind of light, high porosity, nano-porous solid material, which has extremely low thermal conductivity and excellent fireproof and soundproof performance. In the field of building, aerogel is widely used in energy saving, sound insulation and heat insulation. Its extremely low thermal conductivity effectively improves the building insulation effect and reduces energy consumption. Aerogel soundproof board is used for soundproofing of walls, ceilings and floors, which can reduce the interference of external noise on indoor environment and provide a more quiet indoor environment. At the same time, it is also helpful for energy saving and emission reduction, which meets the development trend of green building. Applied to building exterior wall and indoor partition, aerogel provides an efficient and environmentally friendly solution for building energy saving and sound insulation.

[0033] The above is only the preferred embodiment of the application, it should be pointed out that for those skilled in the art, without departing from the concept of the application, a number of modifications and improvements can be made, which belong to the protection scope of the application.

Claims

1. A method for preparing clay aerogel for medium and low frequency noise reduction and lightweight thermal insulation, characterized in that: Polyvinyl alcohol and deionized water were mixed and stirred in a water bath at 80°C-90°C. Epoxy resin was then added and stirred in a water bath until the reaction was complete to obtain a polymer solution. Modified sepiolite and calcium sulfate whiskers were dissolved in deionized water and ultrasonically dispersed to obtain a clay solution. The polymer solution was slowly added to the clay solution and phytic acid was added to prepare a uniform sol. The sol was then poured into a mold, directionally frozen, and then placed in a freeze dryer for drying. It was then cured in a vacuum oven at 50°C-80°C for 6-12 hours to obtain a clay aerogel.

2. The preparation method according to claim 1, characterized in that The modified sepiolite preparation method comprises: mixing sepiolite and hydrochloric acid solution at a solid-liquid ratio of 1 g:10-20 mL at 70°C-80°C, stirring, washing with deionized water until neutral, filtering, and drying to obtain acidified sepiolite, then organically modifying the acidified sepiolite with aminopropyltriethoxysilane hydrolyzate, washing with ethanol, filtering, and drying to obtain the modified sepiolite, wherein the aminopropyltriethoxysilane hydrolyzate is obtained by mixing aminopropyltriethoxysilane, deionized water, and ethanol in a ratio of 1:1:(1-10).

3. The preparation method according to claim 1, characterized in that The mass ratio of the polyvinyl alcohol to the epoxy resin is 1-10:1-5.

4. The preparation method according to claim 1, characterized in that The calcium sulfate whiskers are anhydrous calcium sulfate whiskers.

5. The preparation method according to claim 1, characterized in that The mass ratio of the calcium sulfate whiskers to the sepiolite is 1-10:1-10.

6. The preparation method according to claim 1, characterized in that The mass of the phytic acid is 10% to 20% of the mass of the polyvinyl alcohol.

7. The preparation method according to claim 1, characterized in that The mass ratio of the polyvinyl alcohol to the modified sepiolite is 1-5:1-10.

8. The preparation method according to claim 1, characterized in that The directional freezing process is to place the mold on a copper sheet, place liquid nitrogen under the copper sheet, and control the cooling rate to make ice crystals grow unidirectionally from bottom to top.

9. A clay aerogel for medium and low frequency noise reduction and lightweight thermal insulation obtained by the preparation method according to claims 1 to 8, characterized in that: The main skeleton structure is sepiolite, and the skeleton spacing is regulated by adjusting the ratio of sepiolite and needle-shaped calcium sulfate whiskers and the directional freezing process to form a three-dimensional network porous structure with a vibration unit structure.

10. Use of the clay aerogel for medium and low frequency noise reduction and lightweight thermal insulation according to claim 9 in building thermal insulation, sound insulation and waterproofing.

Images