Phosphogypsum-cellulose nanocrystalline aerogel-plant fiber composite sound insulation material

Abstract

The invention discloses an ardealite-cellulose nanocrystalline aerogel-plant fiber composite sound insulation material and a preparation method of the ardealite-cellulose nanocrystalline aerogel-plant fiber composite sound insulation material. Comprising 55-75 parts of phosphogypsum with specific particle size and calcium sulfate dihydrate content, 15-25 parts of cellulose nanocrystalline aerogel, 8-15 parts of plant fiber subjected to surface treatment and 2-6 parts of an additive containing a rubber elastomer, a coupling agent and a waterproof agent. The preparation method comprises the steps of raw material pretreatment, mixed slurry preparation, molding, maintenance, post-treatment and the like. Tests show that the average sound insulation amount is obviously higher than that of a traditional sound insulation material in the frequency range of 100 Hz-5000 Hz, the compressive strength and breaking strength are greatly improved, meanwhile, the composite material has appropriate density and low heat conductivity coefficient, integration of multiple functions such as sound insulation, mechanics and heat preservation and insulation is achieved, the ardealite which is the industrial waste residue is utilized, and the production cost is reduced. The method has the advantages of environmental protection and sustainable development.

Description

Technical Field

[0001] The present invention belongs to the technical field of new materials, especially involving building energy-saving sound insulation materials, phosphogypsum, aerogel, fiber composite materials and their products in inorganic non-metallic materials. Specifically, it is a phosphogypsum-cellulose nanocrystal aerogel-plant fiber composite sound insulation material and its preparation method. Background Art

[0002] With the acceleration of the urbanization process and the improvement of people's living standards, the requirements for the comfort of the building environment are getting higher and higher, and sound insulation performance is an important aspect. In the fields of architecture, transportation, industry, etc., the problem of noise pollution is becoming increasingly serious. Therefore, the development of efficient sound insulation materials is of great significance.

[0003] Traditional sound insulation materials such as glass wool and rock wool, although having certain sound insulation effects, have problems such as high density, low strength, easy moisture absorption, and non-environmental protection. For example, glass wool may release fine fibers during use, which is harmful to human health; the production process of rock wool has high energy consumption and certain environmental pollution.

[0004] In recent years, aerogel materials have attracted much attention due to their unique nano-porous structure, and have advantages such as low density, high porosity, and low thermal conductivity, showing great application potential in the fields of heat insulation and sound insulation. However, the mechanical properties of pure aerogel materials are poor, which limits their wide application in practical engineering.

[0005] At the same time, as an industrial waste residue, a large amount of phosphogypsum not only occupies land resources, but also pollutes the environment. Recycling phosphogypsum to prepare building materials is one of the effective ways to solve this problem.

[0006] Plant fibers have the characteristics of wide source, renewable, low cost, low density, etc., and have certain strength and toughness. Combining phosphogypsum, cellulose nanocrystal aerogel and plant fibers is expected to prepare a high-strength sound insulation material with excellent performance, which not only solves the problem of resource utilization of phosphogypsum, but also overcomes the performance defects of single materials.

[0007] In the prior art, for example, Chinese Patent CN105283495A discloses an insulating composite material containing inorganic aerogel and melamine foam, which has certain performance in heat insulation, but does not involve the optimization of sound insulation performance.

[0008] Chinese Patent CN112745522A relates to a preparation method and application of surface-modified electrospun aerogel, mainly focusing on the surface modification of aerogel to improve its performance, but not studying the composite system of phosphogypsum, cellulose nanocrystal aerogel and plant fibers.

[0009] Therefore, the existing technology is still not ideal enough. Summary of the Invention

[0010] The present invention aims to prepare a phosphogypsum-cellulose nanocrystal aerogel-plant fiber composite sound insulation material with high strength and excellent sound insulation performance by optimizing the proportion of each component and improving the preparation process, so as to meet the requirements of the building sound insulation field for high-performance materials.

[0011] Based on the first main aspect of the present invention, 1. A phosphogypsum-cellulose nanocrystal aerogel-plant fiber composite sound insulation material, characterized in that, by mass parts, it comprises the following components:

[0012] Phosphogypsum: 55-75 parts, the particle size of the phosphogypsum is 100-180 mesh, and the content of calcium sulfate dihydrate is not less than 80%;

[0013] Cellulose nanocrystal aerogel: 15-25 parts, the porosity of the cellulose nanocrystal aerogel is 88%-93%, and the specific surface area is 400-600m 2 / g;

[0014] Plant fiber: 8-15 parts, the plant fiber is one or more of hemp fiber, bamboo fiber, and wood fiber, the fiber length is 4-8mm, and the diameter is 15-40μm;

[0015] Additive: 2-6 parts, the additive is one or more of rubber elastomer, coupling agent, and waterproofing agent, wherein the rubber elastomer is one or more of styrene-butadiene rubber and ethylene-propylene-diene monomer rubber, the coupling agent is one or more of silane coupling agent and titanate coupling agent, and the waterproofing agent is one or more of organosilicon waterproofing agent and acrylate waterproofing agent.

[0016] In some embodiments, the plant fiber is compounded with hemp fiber and bamboo fiber according to a mass ratio of 1:0.8-1.2, and the fiber length is compounded with 4-6mm short fiber and 6-8mm long fiber according to a ratio of 3:1.

[0017] In some embodiments, the coupling agent is a composite system composed of γ-aminopropyltriethoxysilane and titanate coupling agent NDZ-201, and the mass ratio of the two is 1:0.5-0.8.

[0018] In some embodiments, the phosphogypsum is subjected to a two-stage modification treatment: first calcined at 180-220°C for 1.5-2h to remove crystal water, and then soaked in a citric acid solution with a mass concentration of 0.5%-1% for 20-30min. After modification, the content of calcium sulfate dihydrate is increased to more than 90%, and the free water content is reduced to less than 0.8%.

[0019] In some embodiments, the cellulose nanocrystal aerogel is prepared by gradient freeze-drying: first pre-frozen at -20°C for 2 h to form a primary pore structure, then deeply frozen at -50°C for 4 h, and finally dried by heating in three stages under a vacuum of ≤10 Pa (-30°C / 1 h → -10°C / 2 h → 20°C / 3 h). The obtained aerogel has a bimodal pore size distribution, where the mesopores of 50 - 100 nm account for 60% - 65%, and the macropores of 1 - 5 μm account for 30% - 35%.

[0020] In some embodiments, as a further preferred solution, the additive comprises ethylene propylene diene monomer (EPDM), silane coupling agent KH-550, and silicone waterproofing agent compounded in a mass ratio of 2:1:1. Among them, the EPDM is dynamically vulcanized, and the crosslinking density is controlled at 1×10 -4 -3×10 -4 mol / cm 3 to form a sea-island structure elastic network.

[0021] In some embodiments, as a further preferred solution, the material further comprises 1 - 3 parts of nano magnesium hydroxide flame retardant with a particle size distribution of 30 - 50 nm. After surface modification with stearic acid, it is dispersed in the pores of the cellulose nanocrystal aerogel in an intercalated manner, and cooperates with plant fibers to form a three-dimensional barrier framework, enabling the material to meet the Class B1 fire protection requirements of GB8624-2012 standard.

[0022] Based on the second main aspect of the present invention, a preparation method of the aforementioned phosphogypsum-cellulose nanocrystal aerogel-plant fiber composite sound insulation material is provided, comprising the following steps:

[0023] S1. Phosphogypsum modification treatment: Calcine phosphogypsum at 180 - 220°C for 1.5 - 2 h, then grind it to 100 - 180 mesh, and subsequently soak it in a 0.5% - 1% citric acid solution for 20 - 30 min, filter and dry for standby;

[0024] S2. Plant fiber pretreatment: Mix hemp fiber and bamboo fiber in a mass ratio of 1:0.8 - 1.2, where the short fibers of 4 - 6 mm and the long fibers of 6 - 8 mm are compounded in a ratio of 3:1, and disperse them by ultrasonic wave and then dry;

[0025] S3. Flame retardant dispersion: Mix 1 - 3 parts of nano magnesium hydroxide flame retardant with the cellulose nanocrystal aerogel, and intercalate and disperse the flame retardant in the pores of the aerogel through vacuum impregnation;

[0026] S4, Mixing and granulation: Put the modified phosphogypsum, flame retardant composite aerogel, pretreated plant fiber and additives into a high-speed mixer in proportion, add a coupling agent prepared by compounding γ-aminopropyltriethoxysilane and NDZ-201 at a ratio of 1:0.5 - 0.8, and mix at 80 - 100 °C for 20 - 30 min to form a premix;

[0027] S5, Compression molding: Place the premix in a mold, hot press and cure at a pressure of 10 - 15 MPa and a temperature of 120 - 140 °C for 30 - 40 min, and then naturally cool after demolding to obtain the finished product.

[0028] In some embodiments, as a further preferred solution, when adding the additive in step S4, the ethylene propylene diene monomer (EPDM) needs to be pre-treated by dynamic vulcanization: Mix the EPDM and sulfur at a ratio of 100:1.5 - 2 in a kneader at 160 - 170 °C for 5 - 8 min to form an elastomer with a sea-island structure and a crosslinking density of 1×10 -4 -3×10 -4 mol / cm 3 Then compound it with the silane coupling agent KH-550 and the silicone waterproof agent at a ratio of 2:1:1 and add it to the mixing system.

[0029] In some embodiments, as a further preferred solution, the preparation of the cellulose nanocrystal aerogel in step S3 includes:

[0030] a) Inject the cellulose nanocrystal suspension into a mold, and pre-freeze it at -20 °C for 2 h to form primary pores;

[0031] b) Transfer it to -50 °C and freeze for 4 h to solidify the pore structure;

[0032] c) During vacuum freeze-drying, raise the temperature in three stages: The first stage is to maintain at -30 °C and a vacuum degree ≤ 10 Pa for 1 h, the second stage is to raise the temperature to -10 °C and maintain for 2 h, and the third stage is to raise the temperature to 25 °C and dry to a constant weight to obtain a bimodal pore size aerogel;

[0033] d) Grind the dried aerogel and sieve it to a particle size ≤ 200 μm for standby.

[0034] The phosphogypsum-cellulose nanocrystal aerogel-plant fiber composite sound insulation material and its preparation method involved in the present invention have outstanding substantial characteristics and remarkable progress compared with the prior art, which are specifically reflected in the following aspects:

[0035] First, in the frequency range of 100Hz - 5000Hz, the average sound insulation of the composite sound insulation material of the present invention is significantly higher than that of traditional sound insulation materials. Traditional sound insulation materials such as glass wool and rock wool have certain sound insulation effects, but they have many defects. This material effectively improves the sound insulation performance through precise regulation of the proportions of phosphogypsum, cellulose nanocrystal aerogel, and plant fibers, as well as unique microstructural design. The high porosity and appropriate pore size distribution of cellulose nanocrystal aerogel can efficiently scatter and absorb sound waves; plant fibers further optimize the sound wave propagation path inside the material, and the two work together to greatly enhance the sound insulation effect.

[0036] Secondly, in terms of the strength of the material, the compressive strength and flexural strength of the composite sound insulation material of the present invention are greatly improved. The strength of traditional sound insulation materials is relatively low, which limits their application scenarios. In the present invention, phosphogypsum undergoes a two-stage modification treatment to enhance its bonding force with other components; plant fibers adopt a specific compounding method, with short fibers and long fibers rationally matched to provide good support; the rubber elastomer forms a sea-island structure elastic network after dynamic vulcanization treatment, effectively dispersing stress, and the combined action significantly enhances the mechanical properties of the material, meeting the requirements of more practical engineering.

[0037] Thirdly, in addition to excellent sound insulation and mechanical properties, the composite sound insulation material of the present invention also has a suitable density and a low thermal conductivity, achieving the integration of multiple functions such as sound insulation, mechanics, heat preservation, and heat insulation. The introduction of aerogel materials endows the material with the characteristics of low density and low thermal conductivity, making it perform excellently in heat preservation and heat insulation. Compared with existing single-functional materials, the composite sound insulation material of the present invention has a wider application in the construction field, can effectively improve the comprehensive performance of buildings, and reduce building energy consumption.

[0038] Fourthly, the present invention makes full use of phosphogypsum, an industrial waste residue, solves the problems of its large amount of stacking occupying land resources and polluting the environment, and realizes the resource utilization of phosphogypsum. At the same time, plant fibers are widely sourced and renewable, and the entire material system meets the requirements of environmental protection and sustainable development. Compared with the traditional rock wool production process, which has high energy consumption and pollutes the environment, the present invention has obvious advantages in environmental protection.

[0039] Finally, since the present invention adds a nano magnesium hydroxide flame retardant, which is surface-modified with stearic acid and dispersed in the pores of cellulose nanocrystal aerogel in an intercalated manner, and cooperates with plant fibers to form a three-dimensional barrier framework, enabling the material to meet the B1-level fire protection requirements of GB8624 - 2012 standard. In the prior art, many sound insulation materials do not fully consider fire protection performance, and the present invention makes up for this deficiency and expands the application scope of the material in places with strict fire safety requirements. Detailed implementation

[0040] The preferred embodiments of the present invention will be described in detail below so as to more clearly understand the purpose, features and advantages of the present invention. It should be understood that the following embodiments are not intended to limit the scope of the present invention, but only to illustrate the essential spirit of the technical solution of the present invention.

[0041] In the following description, certain specific details are set forth in order to provide a thorough understanding of various disclosed embodiments. However, those skilled in the relevant art will recognize that the embodiments may be practiced without one or more of these specific details. In other instances, well-known devices, structures, and techniques associated with the present application may not be shown or described in detail so as to avoid unnecessarily obscuring the description of the embodiments.

[0042] References to "an embodiment" or "one embodiment" in the course of the specification mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of "in an embodiment" or "in one embodiment" in various places throughout the specification are not necessarily all referring to the same embodiment. Additionally, the particular features, structures, or characteristics may be combined in any manner in one or more embodiments.

[0043] Embodiment 1:

[0044] (1) Raw material preparation: Select 70 parts of phosphogypsum with a particle size of 150 mesh and an initial content of 82% of calcium sulfate dihydrate. 20 parts of cellulose nanocrystal aerogel with a porosity of 90% and a specific surface area of 500 m 2 / g. The plant fiber is a compound of hemp fiber and bamboo fiber in a mass ratio of 1:1, totaling 12 parts, and the 4 - 6 mm short fiber and 6 - 8 mm long fiber are mixed in a ratio of 3:1. 4 parts of additives are composed of ethylene propylene diene monomer (EPDM), silane coupling agent KH - 550, and silicone waterproofing agent in a compound ratio of 2:1:1. And the EPDM is pre - mixed with sulfur in a ratio of 100:1.8 in a 165 °C internal mixer for 6 min, and the cross - link density is controlled at 2×10 -4 mol / cm 3 . Additionally, 2 parts of nano - magnesium hydroxide flame retardant with a particle size distribution of 40 nm and surface - modified with stearic acid are added.

[0045] (2) Preparation process:

[0046] Phosphogypsum modification: Calcinate the phosphogypsum at 200 °C for 1.8 h, then grind it to 150 mesh, and then soak it in a 0.8% citric acid solution for 25 min, followed by filtration and drying. After treatment, the content of calcium sulfate dihydrate is increased to 92%, and the free water content is reduced to 0.6%.

[0047] Plant fiber pretreatment: Mix the hemp and bamboo fibers in proportion, and dry them after ultrasonic dispersion.

[0048] Flame retardant dispersion: The modified nano-magnesium hydroxide flame retardant and cellulose nanocrystal aerogel are mixed by vacuum impregnation to intercalate and disperse the flame retardant.

[0049] Mixing and granulation: The modified phosphogypsum, flame retardant composite aerogel, pretreated plant fiber and additive are put into a high-speed mixer, and a coupling agent prepared by compounding γ-aminopropyltriethoxysilane and titanate coupling agent NDZ-201 in a ratio of 1:0.6 is added. The mixture is mixed at 90 °C for 25 min to obtain a premix.

[0050] Molding by compression: The premix is put into a mold and hot-pressed and cured at 12 MPa pressure and 130 °C for 35 min, and then demolded and naturally cooled to obtain the finished product.

[0051] (3) Performance testing:

[0052] Sound insulation performance: Tested using professional sound insulation testing equipment in the frequency range of 100 Hz - 5000 Hz, the average sound insulation amount reaches 45 dB, while the average sound insulation amount of traditional glass wool sound insulation material with the same thickness is only 30 dB.

[0053] Mechanical properties: Tested by a pressure testing machine and a flexural testing machine, the compressive strength reaches 10 MPa and the flexural strength is 5 MPa. The compressive strength of traditional rock wool materials is generally about 5 MPa, and the flexural strength is about 2 MPa.

[0054] Thermal insulation performance: The thermal conductivity is tested to be 0.05 W / (m·K), which is better than most traditional sound insulation materials and can effectively reduce heat transfer.

[0055] Fire resistance: After testing, the material meets the B1-level fire resistance requirements of GB8624-2012 standard and can effectively delay the spread of fire when encountering an open flame.

[0056] Example 2:

[0057] (1) Raw material preparation: Weigh 60 parts of phosphogypsum with a particle size of 120 mesh and an initial content of 83% of calcium sulfate dihydrate. Prepare 22 parts of cellulose nanocrystal aerogel with a porosity of 91% and a specific surface area of 550 m 2 / g. The plant fiber is selected as a compound of hemp fiber, bamboo fiber and wood fiber in a mass ratio of 2:1:1, with a total of 10 parts, and the 4 - 6 mm short fiber and 6 - 8 mm long fiber are mixed in a ratio of 3:1. Take 5 parts of additive, which is compounded by styrene-butadiene rubber, silane coupling agent KH-560 and acrylate waterproofing agent in a ratio of 1:1:1. The styrene-butadiene rubber is dynamically vulcanized, and the crosslinking density is controlled at 1.5×10 -4 mol / cm 3 . Add 1.5 parts of nano-magnesium hydroxide flame retardant with a particle size distribution of 35 nm and surface-modified with stearic acid.

[0058] (2) Preparation process:

[0059] Phosphogypsum modification: Place the phosphogypsum in an environment of 190 °C and calcine it for 1.6 h, then grind it to 120 mesh, and then soak it in a citric acid solution with a mass concentration of 0.6% for 22 min, and then filter and dry. After treatment, the content of calcium sulfate dihydrate in the phosphogypsum is increased to 91%, and the free water content is reduced to 0.7%.

[0060] Plant fiber pretreatment: Ultrasonically disperse the mixed hemp fiber, bamboo fiber and wood fiber in proportion, and then perform drying treatment.

[0061] Flame retardant dispersion: Through the vacuum impregnation method, uniformly disperse the surface-modified nano magnesium hydroxide flame retardant into the pores of the cellulose nanocrystal aerogel.

[0062] Mixing and granulation: Add the modified phosphogypsum, the aerogel containing the flame retardant, the pretreated plant fiber and the additive into a high-speed mixer, and add a coupling agent prepared by compounding γ-aminopropyltriethoxysilane and titanate coupling agent NDZ-201 in a ratio of 1:0.7, and mix at 85 °C for 28 min to prepare a premix.

[0063] Molding by pressing: Put the premix into a mold, and hot-press and cure it at a pressure of 13 MPa and an environment of 135 °C for 32 min, and then naturally cool after demolding to obtain the final finished composite sound insulation material.

[0064] (3) Performance testing:

[0065] Sound insulation performance: Use a professional sound insulation testing instrument to test in the frequency range of 100 Hz - 5000 Hz. The average sound insulation of this material reaches 42 dB, while the average sound insulation of traditional rock wool sound insulation materials of the same specification is only 28 dB.

[0066] Mechanical properties: Detect using a pressure testing machine and a flexural testing machine. The results show that the compressive strength is 8 MPa and the flexural strength is 4 MPa, while the compressive strength of traditional glass wool materials is usually about 3 MPa and the flexural strength is about 1.5 MPa.

[0067] Thermal insulation performance: It is measured that the thermal conductivity of the material is 0.06 W / (m·K), which can effectively reduce heat conduction and has good thermal insulation effect.

[0068] Fire resistance performance: Detect according to relevant standards. This material meets the B1-level fire resistance requirements of GB8624-2012 standard and has good fire safety.

[0069] Example 3:

[0070] (1) Raw material preparation: Take 58 parts of phosphogypsum with a particle size of 160 mesh and an initial content of calcium sulfate dihydrate of 81%. Prepare 23 parts of cellulose nanocrystal aerogel with a porosity of 92% and a specific surface area of 480 m 2 / g. The plant fiber is a compound of hemp fiber and wood fiber in a mass ratio of 1:0.9, with a total of 13 parts, among which the 4-6 mm short fiber and the 6-8 mm long fiber are matched in a ratio of 3:1. Take 3 parts of additives, which are compounded by ethylene propylene diene monomer (EPDM), titanate coupling agent NDZ-101 and silicone waterproofing agent in a ratio of 3:1:1. Among them, the ethylene propylene diene monomer is dynamically vulcanized, and the crosslinking density is controlled at 2.5×10 -4 mol / cm 3 . Additionally, add 2.5 parts of nano magnesium hydroxide flame retardant with a particle size distribution of 45 nm and surface modified with stearic acid.

[0071] (2) Preparation process:

[0072] Phosphogypsum modification: Calcinate the phosphogypsum at 210 °C for 1.7 h, grind it to 160 mesh, then soak it in a 0.7% citric acid solution for 23 min, and dry it after filtration. After treatment, the content of calcium sulfate dihydrate increases to 90.5%, and the free water content decreases to 0.75%.

[0073] Plant fiber pretreatment: Mix the hemp fiber and wood fiber evenly according to the ratio, and dry it after ultrasonic dispersion.

[0074] Flame retardant dispersion: With the help of vacuum impregnation technology, the modified nano magnesium hydroxide flame retardant is evenly intercalated and dispersed in the pores of the cellulose nanocrystal aerogel.

[0075] Mixing and granulation: Put the modified phosphogypsum, the aerogel containing the flame retardant, the pretreated plant fiber and the additives into a high-speed mixer, add a coupling agent compounded by γ-aminopropyltriethoxysilane and titanate coupling agent NDZ-201 in a ratio of 1:0.75, and mix at 95 °C for 26 min to obtain a premix.

[0076] Compression molding: Place the premix in a mold, and hot press and cure it at 14 MPa pressure and 125 °C for 38 min. After demolding, cool it naturally to obtain the finished composite sound insulation material.

[0077] (3) Performance testing:

[0078] Sound insulation performance: Test with professional acoustic testing equipment in the frequency range of 100 Hz - 5000 Hz. The average sound insulation amount reaches 43 dB, while the average sound insulation amount of traditional sound insulation materials (such as ordinary foam plastic sound insulation boards) under the same test conditions is only 25 dB.

[0079] Mechanical properties: Measured by a pressure testing machine and a flexural testing machine, the compressive strength reaches 9 MPa and the flexural strength is 4.5 MPa. For traditional sound insulation materials such as mineral wool boards, the compressive strength is generally about 4 MPa and the flexural strength is about 2.5 MPa.

[0080] Thermal insulation performance: After testing, the thermal conductivity is 0.055 W / (m·K), which can effectively block heat transfer and has good thermal insulation performance.

[0081] Fire resistance: Tested in accordance with the GB8624-2012 standard, the material meets the B1-level fire resistance requirements and can play a good flame retardant role in case of fire to ensure safety.

[0082] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A phosphogypsum-cellulose nanocrystal aerogel-plant fiber composite sound insulation material, characterized in that: By mass, it includes the following components: Phosphogypsum: 55-75 parts, the particle size of the phosphogypsum is 100-180 mesh, and the content of calcium sulfate dihydrate is not less than 80%; Cellulose nanocrystal aerogel: 15-25 parts, the porosity of the cellulose nanocrystal aerogel is 88%-93%, and the specific surface area is 400-600m 2 / g; Plant fiber: 8-15 parts, the plant fiber is one or more of hemp fiber, bamboo fiber, wood fiber, with a fiber length of 4-8 mm and a diameter of 15-40 μm; Additives: 2-6 parts, the additives are one or more of rubber elastomers, coupling agents, and waterproofing agents, wherein the rubber elastomer is one or more of styrene-butadiene rubber and ethylene-propylene-diene rubber, the coupling agent is one or more of silane coupling agents and titanate coupling agents, and the waterproofing agent is one or more of silicone waterproofing agents and acrylate waterproofing agents.

2. The phosphogypsum-cellulose nanocrystal aerogel-plant fiber composite sound insulation material according to claim 1, characterized in that: The plant fiber is a mixture of hemp fiber and bamboo fiber in a mass ratio of 1:0.8-1.2, and the fiber length is a mixture of 4-6 mm short fiber and 6-8 mm long fiber in a ratio of 3:

1.

3. The phosphogypsum-cellulose nanocrystal aerogel-plant fiber composite sound insulation material according to claim 1, characterized in that: The coupling agent is a composite system composed of γ-aminopropyltriethoxysilane and titanate coupling agent NDZ-201, and the mass ratio of the two is 1:0.5-0.

8.

4. The phosphogypsum-cellulose nanocrystal aerogel-plant fiber composite sound insulation material according to claim 1, characterized in that: The phosphogypsum is subjected to a two-stage modification treatment: first, calcining at 180-220° C. for 1.5-2 hours to remove crystal water, and then soaking in a citric acid solution with a mass concentration of 0.5%-1% for 20-30 minutes.

5. The phosphogypsum-cellulose nanocrystal aerogel-plant fiber composite sound insulation material according to claim 1, characterized in that: The cellulose nanocrystal aerogel is prepared by a gradient freeze-drying method: first, pre-freeze at -20°C for 2 hours to form a primary pore structure, then deep freeze at -50°C for 4 hours, and finally dry in three stages under a vacuum degree of ≤10Pa. The obtained aerogel has a bimodal pore size distribution, in which 50-100nm mesopores account for 60%-65%, and 1-5μm macropores account for 30%-35%.

6. The phosphogypsum-cellulose nanocrystal aerogel-plant fiber composite sound insulation material according to claim 1, characterized in that: The additive comprises EPDM rubber, silane coupling agent KH-550 and silicone waterproofing agent compounded in a mass ratio of 2:1:1, wherein the EPDM rubber is subjected to dynamic vulcanization treatment and the crosslinking density is controlled at 1×10 -4 -3×10 -4 mol / cm 3 , forming an elastic network of island structures.

7. The phosphogypsum-cellulose nanocrystal aerogel-plant fiber composite sound insulation material according to claim 1, characterized in that: The material also contains 1-3 parts of nano-magnesium hydroxide flame retardant with a particle size distribution of 30-50nm, which is surface-modified with stearic acid and dispersed in the pores of cellulose nanocrystal aerogel in an intercalation manner, and cooperates with plant fibers to form a three-dimensional barrier skeleton.

8. A method for preparing the phosphogypsum-cellulose nanocrystal aerogel-plant fiber composite sound insulation material according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1, phosphogypsum modification treatment: calcine the phosphogypsum at 180-220°C for 1.5-2h, grind it to 100-180 mesh, then soak it in 0.5%-1% citric acid solution for 20-30min, filter it and dry it for later use; S2, plant fiber pretreatment: hemp fiber and bamboo fiber are mixed in a mass ratio of 1:0.8-1.2, wherein 4-6 mm short fiber and 6-8 mm long fiber are compounded in a ratio of 3:1, and then dried after ultrasonic dispersion; S3, flame retardant dispersion: 1-3 parts of nano magnesium hydroxide flame retardant are mixed with cellulose nanocrystal aerogel, and the flame retardant is intercalated and dispersed in the pores of the aerogel by vacuum impregnation; S4, mixing and granulating: put the modified phosphogypsum, flame retardant composite aerogel, pretreated plant fiber and additives into a high-speed mixer in proportion, add a coupling agent prepared by mixing γ-aminopropyltriethoxysilane and NDZ-201 at a ratio of 1:0.5-0.8, and mix at 80-100°C for 20-30 minutes to form a premix; S5, compression molding: Place the premix in a mold, heat-press and cure at a pressure of 10-15 MPa and 120-140°C for 30-40 minutes, and cool naturally after demoulding to obtain the finished product.

9. The method for preparing the phosphogypsum-cellulose nanocrystal aerogel-plant fiber composite sound insulation material according to claim 8, characterized in that: When the additive is added in step S4, the EPDM rubber needs to be subjected to dynamic vulcanization treatment in advance: the EPDM rubber and sulfur are mixed in a mixer at a ratio of 100:1.5-2 at 160-170°C for 5-8 minutes to form a crosslink density of 1×10 -4 -3×10 -4 mol / cm 3 The sea island structure elastomer is then compounded with silane coupling agent KH-550 and silicone waterproofing agent in a ratio of 2:1:1 and added into the mixing system.

10. The method for preparing the phosphogypsum-cellulose nanocrystal aerogel-plant fiber composite sound insulation material according to claim 8, characterized in that: The preparation of cellulose nanocrystal aerogel in step S3 includes: a) injecting the cellulose nanocrystal suspension into a mold and pre-freezing it at -20°C for 2 hours to form primary pores; b) Transfer to -50°C and freeze for 4 hours to solidify the pore structure; c) The vacuum freeze drying is carried out in three stages: the first stage is maintained at -30°C and a vacuum degree of ≤10Pa for 1 hour, the second stage is heated to -10°C and maintained for 2 hours, and the third stage is heated to 25°C and dried to constant weight to obtain a bimodal pore size aerogel; d) Grind and sieve the dried aerogel to a particle size of ≤200 μm for later use.