Preparation method and application of flame-retardant sound-absorbing foam material

Abstract

This invention discloses a preparation method and application of a flame-retardant sound-absorbing foam material, belonging to the field of polymer foaming technology. The raw materials of this invention include polyolefin resin, polystyrene, rubber, foaming agent, flame retardant, hollow glass microspheres, dicumyl peroxide, foaming aid, and antioxidant. The preparation process includes steps such as intensive mixing and granulation, compounding and granulation, extrusion molding, electron irradiation crosslinking, preheating foaming, and secondary foaming. Compared with existing technologies, the foam material prepared by this invention has excellent mechanical properties, sound absorption properties, and flame-retardant properties, making it suitable for applications in rail transit, large shopping malls, KTVs, and other similar locations, with broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of polymer foaming technology, and in particular to a method for preparing and applying a flame-retardant sound-absorbing foam material. Background Technology

[0002] With the rapid development of the global economy, accelerated industrialization, and continuous urbanization, transportation, industrial production, and the construction of various large-scale infrastructures have developed rapidly. However, these advancements have also brought about serious noise pollution problems. The large amounts of noise generated by automobiles, high-speed trains, and large factories not only seriously affect people's physical and mental health but also bring many negative effects to the environment and ecosystems. Noise pollution has become one of the most pressing issues to be addressed in modern society.

[0003] Among numerous noise control technologies, the application of sound-absorbing materials is a key approach. Traditional sound-absorbing materials mainly include fiberglass, rock wool, and foam plastics, but these materials often suffer from problems such as high density, limited sound absorption performance, and flammability, making it difficult to meet the demands of modern industry and construction for efficient, lightweight, and flame-retardant sound-absorbing materials. In recent years, polyolefin foam materials have gradually gained attention due to their excellent properties such as light weight, heat insulation, thermal insulation, corrosion resistance, and sound absorption. However, most existing polyolefin foam materials have a closed-cell structure. Although they have excellent thermal insulation performance, their sound absorption performance is poor, and their flame-retardant properties are insufficient, limiting their application in places with high fire protection requirements (such as high-speed rail, large shopping malls, and automobiles).

[0004] To address these issues, researchers have conducted extensive research. For example, Chinese patent application publication number CN118480224 A discloses a lightweight foamed material with heat insulation and sound absorption properties, and its preparation method. This method involves mixing raw materials such as polyolefin resin, foaming agent, flame retardant, and foaming aids, followed by extrusion, irradiation crosslinking, and foaming treatment to prepare a foamed material with good mechanical properties. However, this invention still fails to fully resolve the shortcomings of polyolefin foamed materials in terms of sound absorption and flame retardancy.

[0005] Furthermore, open-cell polyolefin foam materials, due to their interconnected pores, can effectively absorb sound waves and convert sound energy into heat energy, thereby achieving noise reduction. However, these materials typically suffer from unstable pore structure, poor mechanical properties, and insufficient flame retardancy, limiting their widespread application. Therefore, developing a polyolefin foam material that combines excellent sound absorption, flame retardancy, and mechanical properties has become an urgent need in related fields. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention aims to provide a method for preparing and applying flame-retardant sound-absorbing foam materials. By optimizing the material formulation and preparation process, it overcomes the deficiencies of existing polyolefin foam materials in terms of sound absorption and flame retardancy, providing an efficient and environmentally friendly solution for noise pollution control and fire safety.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a flame-retardant sound-absorbing foam material, comprising the following raw materials in parts by weight: 20-60 parts polyolefin resin, 20-50 parts polyolefin copolymer, 10-30 parts polystyrene, 5-20 parts rubber, 1-20 parts foaming agent, 10-20 parts flame retardant, 0-10 parts filler, 1-5 parts dicumyl peroxide, 0.5-10 parts foaming aid, and 0.5-3 parts antioxidant.

[0009] A method for preparing a flame-retardant sound-absorbing foam material is as follows:

[0010] S1. According to the formula composition, the polyolefin copolymer and rubber are mixed and granulated in an internal mixer to obtain a high polar elastomer masterbatch.

[0011] S2. Mix and granulate the high polarity elastomer masterbatch, polyolefin resin, polystyrene, dicumyl peroxide, and antioxidant to obtain a mixed masterbatch;

[0012] S3. Mix the masterbatch, filler, foaming agent, flame retardant, and foaming aid, and extrude to obtain the master roll;

[0013] S4. Crosslink the master roll with electron irradiation;

[0014] S5. The cross-linked master roll is foamed in a horizontal furnace to obtain closed-cell polyolefin foam material.

[0015] S6. The closed-cell polyolefin foam material is foamed a second time to obtain a flame-retardant sound-absorbing foam material.

[0016] Preferably, the polyolefin resin is at least one of low-density polyethylene, high-density polyethylene, and polypropylene; and the polyolefin copolymer is an ethylene-vinyl acetate copolymer.

[0017] The low-density polyethylene melt index is 0.5-4.0 g / 10 min, the high-density polyethylene melt index is 0.5-6.0 g / 10 min, the polypropylene melt index is 2-15 g / 10 min, and the ethylene-vinyl acetate copolymer melt index is 0.5-8.0 g / 10 min.

[0018] The rubber is at least one of ethylene propylene rubber, nitrile rubber, styrene-butadiene rubber, and silicone rubber; the addition of rubber can promote the cross-linking of the master sheet, making the foam material have finer pores and better thermal insulation performance.

[0019] The foaming agent is at least one of azodicarbonamide, azobisisobutyronitrile, and barium azodicarbonate.

[0020] The flame retardant is at least one of phosphate esters and melamine polyphosphate.

[0021] The filler is at least one of hollow glass microspheres, modified microspheres, and nano-calcium carbonate;

[0022] The hollow glass microspheres have a particle size of 50-100 μm. Hollow glass microspheres can increase the porosity of the material, effectively improve the sound absorption performance of the composite material, and a small amount of addition can effectively improve the mechanical properties of the material.

[0023] The foaming aids are zinc oxide and zinc stearate.

[0024] The antioxidant is a compound of DSTP and 1010 in a weight ratio of 2-4:1-3.

[0025] In step S1, the mixing temperature is 90-120℃.

[0026] In step S2, the granulation temperature is set to 120-150℃.

[0027] In step S3, the extrusion temperature is set as follows: Zone 1 120-150℃, Zone 2 122-155℃, Zone 3 125-155℃, Zone 4 130-160℃, Zone 5 130-160℃, Zone 6 130-160℃, and the die head temperature is set as 125-140℃.

[0028] In step S4, the irradiation crosslinking energy is 35-100 keV.

[0029] In step S5, the preheating temperature is set to 140-160℃, the foaming temperature is set to 180-250℃, and the foaming time is 1-5 minutes.

[0030] In step S6, the secondary foaming temperature is set to 180-220℃, and the foaming time is 0.5-3 minutes.

[0031] The modified microspheres are prepared as follows:

[0032] Z1. Under stirring conditions, silica-alumina sol, water, and nitrogen-containing compounds are added to a beaker. The pH is adjusted to acidic with hydrochloric acid, followed by the addition of polyethylene glycol aqueous solution and stirring until homogeneous. Then, glutaraldehyde is added, stirred until homogeneous, and allowed to stand. The supernatant is removed by filtration, and the mixture is washed with water and anhydrous ethanol, dried, and then the composite microspheres are obtained. The composite microspheres are placed in a muffle furnace and calcined to obtain porous microspheres.

[0033] Z2. The porous microspheres were mixed and dispersed with anhydrous ethanol, a modifier and water were added, and the mixture was refluxed at high temperature. The sample was collected, washed with anhydrous ethanol, and dried to obtain the modified microspheres.

[0034] Preferably, the modified microspheres are prepared by the following method, in parts by weight:

[0035] Z1. Under stirring conditions, add 0.3-0.8 parts of silica-alumina sol, 50-70 parts of water, and 0.3-0.8 parts of nitrogen-containing compound to a beaker. Adjust the pH to 1-3 with 8-12 wt% hydrochloric acid. Then add 1-3 parts of 4-6 wt% polyethylene glycol aqueous solution and stir until homogeneous. Next, add 0.5-1 parts of glutaraldehyde, stir until homogeneous, and let stand for 5-10 hours. Filter to remove the supernatant, wash twice with water, then wash once with anhydrous ethanol. Finally, rinse at 60-80°C. The composite microspheres were dried at 0℃. The composite microspheres were then placed in a muffle furnace and calcined according to the following procedure: First stage, the temperature was increased from room temperature to 170-190℃ at a rate of 7-9℃ / min and held for 1-3 hours; Second stage, the temperature was increased to 230-270℃ at a rate of 4-6℃ / min and held for 1-3 hours; Third stage, the temperature was increased to 500-600℃ at a rate of 2-4℃ / min and held for 1-3 hours to obtain porous microspheres.

[0036] Z2. Mix 0.3-0.8 parts of porous microspheres and 20-40 parts of anhydrous ethanol evenly, add 1-3 parts of modifier and 1-3 parts of water, reflux at 70-90℃ for 1-5 hours, collect the sample, wash three times with anhydrous ethanol, and dry at 60-80℃ for 5-24 hours to obtain modified microspheres.

[0037] The nitrogen-containing compound is at least one of urea, melamine, and dicyandiamide.

[0038] The modifier is at least one of 3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and diethylenetriaminopropyltrimethoxysilane.

[0039] The functions of each substance in this invention are as follows:

[0040] Polyolefin resins and polyolefin copolymers serve as matrix materials, providing the basic mechanical properties and thermal stability of the materials.

[0041] Polystyrene improves the rigidity and processing performance of materials.

[0042] Rubber improves the elasticity and toughness of materials, promotes cross-linking of the master sheet, and makes the foam material's pores finer.

[0043] The foaming agent generates gas during the foaming process, forming a porous structure.

[0044] Flame retardants improve the flame retardant properties of materials, enabling them to meet fire safety requirements.

[0045] Hollow glass microspheres increase the porosity of materials, enhance sound absorption performance, and improve mechanical properties.

[0046] Dicumyl peroxide acts as a crosslinking agent, promoting the crosslinking reaction of materials and improving their thermal stability and mechanical properties.

[0047] Foaming aids assist in the decomposition of foaming agents and improve foaming effects.

[0048] Antioxidants prevent materials from oxidizing and degrading during processing and use, thus extending the material's service life.

[0049] Modified microspheres improve the porosity and sound absorption properties of materials through surface modification.

[0050] Nitrogen-containing compounds form a stable structure during high-temperature calcination, providing physical support and promoting cell connectivity.

[0051] Modifiers optimize the interfacial properties and pore structure of materials through chemical bonding.

[0052] Compared with existing technologies, it has the following advantages:

[0053] 1) This invention achieves a high porosity and sound absorption coefficient through optimized formulation and process. This characteristic gives it significant advantages in applications requiring high-efficiency sound absorption (such as high-speed rail, large shopping malls, KTVs, etc.).

[0054] 2) The flame retardant system and optimized formulation design used in this invention enable the foamed material to achieve a UL94-HF1 flame retardant rating. This improvement in flame retardant performance greatly expands the application range of the material in places with high fire safety requirements (such as rail transit, automotive interiors, etc.), and solves the problem of insufficient flame retardant performance of traditional polyolefin foamed materials.

[0055] 3) The foamed material prepared by this invention through a specific manufacturing process not only possesses excellent mechanical properties but also achieves a stable pore structure. This stable pore structure not only helps maintain efficient sound absorption performance but also avoids problems such as pore blockage or collapse, thereby extending the material's service life and improving its reliability in practical applications. Detailed Implementation

[0056] Main source of materials:

[0057] Low-density polyethylene, olefin melt index of 1.9g / 10min, grade: LD662, brand: Yanshan Petrochemical.

[0058] High-density polyethylene, melt index 3g / 10min, grade: FB0300, brand: LG Korea.

[0059] Polystyrene, item number: 525, Guangdong Zhonghai Nanlian Energy Co., Ltd.

[0060] Ethylene-vinyl acetate copolymer, melt index 2g / 10min, grade: EVA520F, brand: Toyo Soda.

[0061] Ethylene-vinyl acetate copolymer, melt index 3.5 g / 10 min, grade: EVA11-3.5, brand: Sinopec.

[0062] Polypropylene, melt index 3.5g / 10min, grade: 5014, brand: Daehan Oil & Chemical.

[0063] Ethylene propylene rubber, grade: 2650C, manufacturer (place of origin): Lanxess, Germany.

[0064] Nitrile rubber, grade: 20231118, Jingjiang Kanggaote New Material Technology Co., Ltd.

[0065] The phosphate ester is triisobutyl phosphate, CAS No.: 126-71-6, Shandong Guohua Chemical Co., Ltd.

[0066] Melamine polyphosphate, CAS No.: 15541-60-3, Jiangsu Runfeng Synthetic Technology Co., Ltd.

[0067] Hollow glass microspheres, porosity: 85%, specifications: 20-80 mesh, SiO2 content: 62%, Hebei Hengguang Mineral Products Co., Ltd.

[0068] Nano calcium carbonate, specification: 1250 mesh.

[0069] Melamine, product number: zy-1102, Zhongyan New Materials Co., Ltd.

[0070] Polyethylene glycol, model: PEG-400, brand: Russian Petrochemical.

[0071] Silica-alumina sol, model: FF-GL30W, particle size: 10-30 nm, Hangzhou Jiayou New Materials Co., Ltd.

[0072] PU foam sponge, item number: 20-65PPI, density: 20~35 (g / cm³)3 Jiangmen Fengrun Daily Necessities Co., Ltd.

[0073] All other raw materials used in the embodiments and comparative examples of this invention are commercially available products.

[0074] Example 1

[0075] The preparation method of a flame-retardant sound-absorbing foam material is as follows, in parts by weight:

[0076] S1. Formulation composition: 40 parts high-density polyethylene, 15 parts polystyrene, 30 parts ethylene-vinyl acetate copolymer, 10 parts ethylene propylene rubber, 12 parts azodicarbonamide, 8 parts flame retardant (the flame retardant is a compound of phosphate ester and melamine polyphosphate in a weight ratio of 2:5), 0.5 parts zinc oxide and 0.1 parts zinc stearate, 1.5 parts antioxidant (the antioxidant is a compound of DSTP and 1010 in a weight ratio of 3:2), and 1.5 parts dicumyl peroxide. The melt index of high-density polyethylene is 3 g / 10 min, and the melt index of ethylene-vinyl acetate copolymer is 2 g / 10 min. The ethylene-vinyl acetate copolymer and ethylene propylene rubber are granulated in a Banbury mixer according to the formulation composition. The mixing temperature is set to 100℃ to obtain a high-polarity elastomer masterbatch.

[0077] S2. Mix and granulate the high-polarity elastomer masterbatch, high-density polyethylene, polystyrene, dicumyl peroxide, and antioxidant. Set the granulation temperature to 125℃ to obtain the mixed masterbatch.

[0078] S3. Mix the masterbatch, azodicarbonamide, flame retardant, zinc oxide and zinc stearate, and extrude to obtain the master roll; set the temperature of the extruder zones 1-6 to 122℃, 125℃, 125℃, 128℃, 128℃ and 130℃, and the die temperature to 125℃.

[0079] S4. Perform electron crosslinking on the master roll with an irradiation crosslinking energy of 45 keV;

[0080] S5. The cross-linked master roll is preheated and foamed. The preheating temperature is set to 150℃, the foaming temperature is 210℃, and the foaming time is 2 minutes to obtain closed-cell polyolefin foam material.

[0081] S6. The closed-cell polyolefin foam material is foamed a second time at a foaming temperature of 185℃ for 1 minute to obtain a flame-retardant sound-absorbing foam material.

[0082] Example 2

[0083] The preparation method of a flame-retardant sound-absorbing foam material is as follows, in parts by weight:

[0084] S1. Formulation composition: 50 parts high-density polyethylene, 30 parts ethylene-vinyl acetate copolymer, 20 parts polystyrene, 15 parts nitrile rubber, 13 parts azodicarbonamide, 7 parts flame retardant (the flame retardant is a compound of phosphate ester and melamine polyphosphate in a weight ratio of 2:5), 1 part zinc oxide and 0.5 parts zinc stearate, 1.5 parts antioxidant (the antioxidant is a compound of DSTP and 1010 in a weight ratio of 3:2), and 1.2 parts dicumyl peroxide. The melt index of high-density polyethylene is 3 g / 10min, and the melt index of ethylene-vinyl acetate copolymer is 2 g / 10min. The ethylene-vinyl acetate copolymer and nitrile rubber are granulated in a Banbury mixer according to the formulation composition. The mixing temperature is set to 100℃ to obtain a high-polarity elastomer masterbatch.

[0085] S2. Mix and granulate the high-polarity elastomer masterbatch, high-density polyethylene, polystyrene, dicumyl peroxide, and antioxidant. Set the granulation temperature to 125℃ to obtain the mixed masterbatch.

[0086] S3. Mix the masterbatch, azodicarbonamide, flame retardant, zinc oxide and zinc stearate, and extrude to obtain the master roll; set the temperatures of zones 1-6 of the extruder to 130℃, 132℃, 132℃, 136℃, 136℃, and 136℃, and the die temperature to 130℃.

[0087] S4. Perform electron crosslinking on the master roll with an irradiation crosslinking energy of 80 keV;

[0088] S5. The cross-linked master roll is preheated and foamed. The preheating temperature is set to 150℃, the foaming temperature is 210℃, and the foaming time is 2 minutes to obtain closed-cell polyolefin foam material.

[0089] S6. The closed-cell polyolefin foam material is foamed a second time at a foaming temperature of 185℃ for 1 minute to obtain a flame-retardant sound-absorbing foam material.

[0090] Example 3

[0091] The preparation method of a flame-retardant sound-absorbing foam material is as follows, in parts by weight:

[0092] S1. Formulation Composition: The polyolefin resin includes 30 parts of low-density polyethylene and 20 parts of high-density polyethylene, 15 parts of polystyrene, 40 parts of ethylene-vinyl acetate copolymer, 10 parts of ethylene propylene rubber, 12 parts of azodicarbonamide, 10 parts of flame retardant (the flame retardant is a compound of phosphate ester and melamine polyphosphate in a weight ratio of 2:5), 5 parts of hollow glass microspheres, 1.5 parts of antioxidant (the antioxidant is a compound of DSTP and 1010 in a weight ratio of 3:2), 0.5 parts of zinc oxide and 0.3 parts of zinc stearate, and 1.5 parts of dicumyl peroxide; wherein the melt index of low-density polyethylene is 1.9 g / 10 min, the melt index of high-density polyethylene is 3 g / 10 min, and the melt index of ethylene-vinyl acetate copolymer is 3.5 g / 10 min; according to the formulation composition, the ethylene-vinyl acetate copolymer and ethylene propylene rubber are granulated by internal mixing in a mixer at a mixing temperature of 100℃ to obtain a high-polarity elastomer masterbatch;

[0093] S2. Mix and granulate the high polar elastomer masterbatch, polyolefin resin, polystyrene, dicumyl peroxide, and antioxidant. Set the granulation temperature to 140℃ to obtain the mixed masterbatch.

[0094] S3. Mix the masterbatch, hollow glass microspheres, azodicarbonamide, flame retardant, zinc oxide and zinc stearate, and extrude to obtain a master roll; set the temperatures of zones 1-6 of the extruder to 126℃, 128℃, 130℃, 130℃, 132℃ and 132℃, and the die temperature to 128℃.

[0095] S4. Perform electron cross-linking on the master roll with an irradiation cross-linking energy of 65 keV.

[0096] S5. The cross-linked master roll is preheated and foamed. The preheating temperature is set to 150℃, the foaming temperature is 230℃, and the foaming time is 2 minutes to obtain closed-cell polyolefin foam material.

[0097] S6. The closed-cell polyolefin foam material is foamed a second time at a foaming temperature of 190℃ for 1 minute to obtain a flame-retardant sound-absorbing foam material.

[0098] Example 4

[0099] The preparation method of a flame-retardant sound-absorbing foam material is as follows, in parts by weight:

[0100] S1. Formulation Composition: The polyolefin resin comprises 20 parts high-density polyethylene and 30 parts polypropylene, 15 parts polystyrene, 20 parts ethylene-vinyl acetate copolymer, 5 parts nitrile rubber, 10 parts azodicarbonamide, 10 parts flame retardant (the flame retardant is a compound of phosphate ester and melamine polyphosphate in a weight ratio of 2:5), 5 parts hollow glass microspheres, 0.8 parts zinc oxide and 0.5 parts zinc stearate, 2 parts antioxidant (the antioxidant is a compound of DSTP and 1010 in a weight ratio of 3:2), 1.3 parts dicumyl peroxide, and 1 part nano-calcium carbonate; the melt index of high-density polyethylene is 3 g / 10 min, the melt index of polypropylene is 3.5 g / 10 min, and the melt index of ethylene-vinyl acetate copolymer is 3.5 g / 10 min; according to the formulation composition, the ethylene-vinyl acetate copolymer and nitrile rubber are granulated by internal mixing in a mixer at a mixing temperature of 100℃ to obtain a high-polarity elastomer masterbatch;

[0101] S2. Mix and granulate the high polar elastomer masterbatch, polyolefin resin, polystyrene, dicumyl peroxide, and antioxidant. Set the granulation temperature to 140℃ to obtain the mixed masterbatch.

[0102] S3. Mix the masterbatch, hollow glass microspheres, nano calcium carbonate, azodicarbonamide, flame retardant, zinc oxide and zinc stearate, and extrude to obtain a master roll; set the temperatures of zones 1-6 of the extruder to 155℃, 157℃, 160℃, 160℃, 160℃ and 165℃, and the die temperature to 145℃.

[0103] S4. Perform electron cross-linking on the master roll with an irradiation cross-linking energy of 70 keV;

[0104] S5. The cross-linked master roll is preheated and foamed. The preheating temperature is set to 150℃, the foaming temperature is 230℃, and the foaming time is 2 minutes to obtain closed-cell polyolefin foam material.

[0105] S6. The closed-cell polyolefin foam material is foamed a second time at a foaming temperature of 200℃ for 1 minute to obtain a flame-retardant sound-absorbing foam material.

[0106] Example 5

[0107] The preparation method of a flame-retardant sound-absorbing foam material is as follows, in parts by weight:

[0108] S1. Formulation Composition: The polyolefin resin includes 30 parts of low-density polyethylene and 20 parts of high-density polyethylene, 15 parts of polystyrene, 40 parts of ethylene-vinyl acetate copolymer, 10 parts of ethylene propylene rubber, 12 parts of azodicarbonamide, 10 parts of flame retardant (the flame retardant is a compound of phosphate ester and melamine polyphosphate in a weight ratio of 2:5), 5 parts of modified microspheres, 1.5 parts of antioxidant (the antioxidant is a compound of DSTP and 1010 in a weight ratio of 3:2), 0.5 parts of zinc oxide and 0.3 parts of zinc stearate, and 1.5 parts of dicumyl peroxide; wherein the melt index of low-density polyethylene is 1.9 g / 10 min, and the melt index of ethylene-vinyl acetate copolymer is 3.5 g / 10 min; according to the formulation composition, the ethylene-vinyl acetate copolymer and ethylene propylene rubber are granulated by internal mixing in a mixer at a mixing temperature of 100℃ to obtain a high-polarity elastomer masterbatch;

[0109] S2. Mix and granulate the high polar elastomer masterbatch, polyolefin resin, polystyrene, dicumyl peroxide, and antioxidant. Set the granulation temperature to 140℃ to obtain the mixed masterbatch.

[0110] S3. Mix the masterbatch, modified microspheres, azodicarbonamide, flame retardant, zinc oxide and zinc stearate, and extrude to obtain a master roll; set the temperatures of zones 1-6 of the extruder to 126℃, 128℃, 130℃, 130℃, 132℃ and 132℃, and the die temperature to 128℃.

[0111] S4. Perform electron cross-linking on the master roll with an irradiation cross-linking energy of 65 keV.

[0112] S5. The cross-linked master roll is preheated and foamed. The preheating temperature is set to 150℃, the foaming temperature is 230℃, and the foaming time is 2 minutes to obtain closed-cell polyolefin foam material.

[0113] S6. The closed-cell polyolefin foam material is foamed a second time at a foaming temperature of 190℃ for 1 minute to obtain a flame-retardant sound-absorbing foam material.

[0114] The modified microspheres are prepared as follows, in parts by weight:

[0115] Z1. Under stirring conditions, 0.5 parts of silica-alumina sol, 60 parts of water, and 0.5 parts of melamine were added to a beaker. The pH was adjusted to 2 with 10 wt% hydrochloric acid. Then, 2 parts of 5 wt% polyethylene glycol aqueous solution were added and stirred evenly. Next, 0.85 parts of glutaraldehyde were added and stirred evenly. After standing for 8 hours, the supernatant was removed by filtration. The microspheres were washed twice with water and once with anhydrous ethanol. Finally, they were dried at 70°C to obtain composite microspheres. The composite microspheres were placed in a muffle furnace and calcined according to the following procedure: First stage: the temperature was increased from room temperature to 180°C at a rate of 8°C / min and held for 2 hours; Second stage: the temperature was increased to 250°C at a rate of 5°C / min and held for 2 hours; Third stage: the temperature was increased to 530°C at a rate of 3°C / min and held for 2 hours to obtain porous microspheres.

[0116] Z2. Mix 0.5 parts of porous microspheres and 30 parts of anhydrous ethanol evenly, add 2 parts of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and 2 parts of water, reflux at 80°C for 3 hours, collect the sample, wash three times with anhydrous ethanol, and dry at 70°C for 12 hours to obtain modified microspheres.

[0117] Example 6

[0118] The preparation method of a flame-retardant sound-absorbing foam material is basically the same as that in Example 5, except that the preparation method of the modified microspheres is different.

[0119] The modified microspheres are prepared as follows, in parts by weight:

[0120] Z1. Under stirring conditions, 0.5 parts of silica-alumina sol, 60 parts of water, and 0.5 parts of urea were added to a beaker. The pH was adjusted to 2 with 10 wt% hydrochloric acid. Then, 2 parts of 5 wt% polyethylene glycol aqueous solution were added and stirred evenly. Next, 0.85 parts of glutaraldehyde were added and stirred evenly. After standing for 8 hours, the supernatant was removed by filtration. The microspheres were washed twice with water and once with anhydrous ethanol. Finally, they were dried at 70°C to obtain composite microspheres. The composite microspheres were placed in a muffle furnace and calcined according to the following procedure: First stage: the temperature was increased from room temperature to 180°C at a rate of 8°C / min and held for 2 hours; Second stage: the temperature was increased to 250°C at a rate of 5°C / min and held for 2 hours; Third stage: the temperature was increased to 530°C at a rate of 3°C / min and held for 2 hours to obtain porous microspheres.

[0121] Z2. Mix 0.5 parts of porous microspheres and 30 parts of anhydrous ethanol evenly, add 2 parts of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and 2 parts of water, reflux at 80°C for 3 hours, collect the sample, wash three times with anhydrous ethanol, and dry at 70°C for 12 hours to obtain modified microspheres.

[0122] Example 7

[0123] The preparation method of a flame-retardant sound-absorbing foam material is basically the same as that in Example 5, except that the preparation method of the modified microspheres is different.

[0124] The modified microspheres are prepared as follows, in parts by weight:

[0125] Z1. Under stirring conditions, 0.5 parts of silica-alumina sol, 60 parts of water, and 0.5 parts of dicyandiamide were added to a beaker. The pH was adjusted to 2 with 10 wt% hydrochloric acid. Then, 2 parts of 5 wt% polyethylene glycol aqueous solution were added and stirred evenly. Next, 0.85 parts of glutaraldehyde were added and stirred evenly. After standing for 8 hours, the supernatant was removed by filtration. The microspheres were washed twice with water and once with anhydrous ethanol. Finally, they were dried at 70°C to obtain composite microspheres. The composite microspheres were placed in a muffle furnace and calcined according to the following procedure: First stage: the temperature was increased from room temperature to 180°C at a rate of 8°C / min and held for 2 hours; Second stage: the temperature was increased to 250°C at a rate of 5°C / min and held for 2 hours; Third stage: the temperature was increased to 530°C at a rate of 3°C / min and held for 2 hours to obtain porous microspheres.

[0126] Z2. Mix 0.5 parts of porous microspheres and 30 parts of anhydrous ethanol evenly, add 2 parts of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and 2 parts of water, reflux at 80°C for 3 hours, collect the sample, wash three times with anhydrous ethanol, and dry at 70°C for 12 hours to obtain modified microspheres.

[0127] Example 8

[0128] The preparation method of a flame-retardant sound-absorbing foam material is basically the same as that in Example 5, except that the preparation method of the modified microspheres is different.

[0129] The modified microspheres are prepared as follows, in parts by weight:

[0130] Z1. Under stirring conditions, 0.5 parts of silica-alumina sol, 60 parts of water, and 0.5 parts of melamine were added to a beaker. The pH was adjusted to 2 with 10 wt% hydrochloric acid. Then, 2 parts of 5 wt% polyethylene glycol aqueous solution were added and stirred evenly. Next, 0.85 parts of glutaraldehyde were added and stirred evenly. After standing for 8 hours, the supernatant was removed by filtration. The microspheres were washed twice with water and once with anhydrous ethanol. Finally, they were dried at 70°C to obtain composite microspheres. The composite microspheres were placed in a muffle furnace and calcined according to the following procedure: First stage: the temperature was increased from room temperature to 180°C at a rate of 8°C / min and held for 2 hours; Second stage: the temperature was increased to 250°C at a rate of 5°C / min and held for 2 hours; Third stage: the temperature was increased to 530°C at a rate of 3°C / min and held for 2 hours to obtain porous microspheres.

[0131] Z2. Mix 0.5 parts of porous microspheres and 30 parts of anhydrous ethanol evenly, add 2 parts of 3-aminopropyltriethoxysilane and 2 parts of water, reflux at 80°C for 3 hours, collect the sample, wash three times with anhydrous ethanol, and dry at 70°C for 12 hours to obtain modified microspheres.

[0132] Example 9

[0133] The preparation method of a flame-retardant sound-absorbing foam material is basically the same as that in Example 5, except that the preparation method of the modified microspheres is different.

[0134] The modified microspheres are prepared as follows, in parts by weight:

[0135] Z1. Under stirring conditions, 0.5 parts of silica-alumina sol, 60 parts of water, and 0.5 parts of melamine were added to a beaker. The pH was adjusted to 2 with 10 wt% hydrochloric acid. Then, 2 parts of 5 wt% polyethylene glycol aqueous solution were added and stirred evenly. Next, 0.85 parts of glutaraldehyde were added and stirred evenly. After standing for 8 hours, the supernatant was removed by filtration. The microspheres were washed twice with water and once with anhydrous ethanol. Finally, they were dried at 70°C to obtain composite microspheres. The composite microspheres were placed in a muffle furnace and calcined according to the following procedure: First stage: the temperature was increased from room temperature to 180°C at a rate of 8°C / min and held for 2 hours; Second stage: the temperature was increased to 250°C at a rate of 5°C / min and held for 2 hours; Third stage: the temperature was increased to 530°C at a rate of 3°C / min and held for 2 hours to obtain porous microspheres.

[0136] Z2. Mix 0.5 parts of porous microspheres and 30 parts of anhydrous ethanol evenly, add 2 parts of diethylenetriaminepropyltrimethoxysilane and 2 parts of water, reflux at 80°C for 3 hours, collect the sample, wash three times with anhydrous ethanol, and dry at 70°C for 12 hours to obtain modified microspheres.

[0137] Comparative Example 1

[0138] The preparation method of a flame-retardant sound-absorbing foam material is basically the same as that in Example 1, except that the raw materials used are different. The raw materials are 100 parts of high-density polyethylene with a melt index of 3 g / 10 min, 15 parts of azodicarbonamide, a flame retardant system of aluminum hydroxide and magnesium hydroxide compounded in a weight ratio of 4:1 and a dosage of 10 parts, 1.5 parts of zinc oxide and 0.5 parts of zinc stearate, and 1 part of nano calcium carbonate.

[0139] Comparative Example 2

[0140] Comparative Example 2 is a commercially available PU foam sponge.

[0141] Test Example 1

[0142] The performance indicators of Examples 1-9 and Comparative Examples 1-2 were tested using the following methods:

[0143] Apparent density: The apparent density test is based on the test method described in GB / T 6343-2009 "Determination of apparent density of foamed plastics and rubber";

[0144] Tensile strength: The tensile strength test is based on the test method described in GB / T 6344-2008 "Determination of tensile strength and elongation at break of flexible foam polymer materials";

[0145] Flame retardancy rating: The flame retardancy rating is tested based on the test method described in UL94 HF-1 "Horizontal flammability test for foam materials" standard;

[0146] Open cell ratio: The open cell ratio test is based on the test method described in ASTM D 2856-A, "Standard Method for Determination of Percentage of Open Cells in Rigid Foamed Plastics by Air Density Meter".

[0147] Sound absorption coefficient: The sound absorption coefficient is determined based on the method described in ISO 354 "Sound absorption measurement in reverberation chambers".

[0148] The test results are shown in the table below:

[0149] <![CDATA[Apparent density (kg / m 3 ).]]> Tensile strength (MPa) Flame retardant rating Open area ratio (%) Sound absorption coefficient Example 1 40 8.0 UL94-HF1 48 0.43 Example 2 50 6.0 UL94-HF1 55 0.47 Example 3 44 5.0 UL94-HF1 85 0.72 Example 4 42 4.8 UL94-HF1 78 0.65 Example 5 44 5.2 UL94-HF1 95 0.92 Example 6 46 5.1 UL94-HF1 68 0.78 Example 7 45 5.1 UL94-HF1 75 0.74 Example 8 44 4.8 UL94-HF1 85 0.85 Example 9 45 4.9 UL94-HF1 82 0.78 Comparative Example 1 40 10.0 UL94-HF1 12 0.18 Comparative Example 2 50 5.0 - 80 0.71

[0150] As can be seen from the data in the table above, the foamed material prepared by the present invention has better flame retardant properties; from Examples 1-4, it can be seen that Examples 3 and 4 have better sound absorption coefficients.

[0151] The test data from Examples 5-7 show that, under the condition of fixing the modifier N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, melamine, with its high-temperature stability (decomposition temperature > 350℃) and the rigid carbon nitride skeleton formed after calcination, achieves a 95% porosity and a sound absorption coefficient of 0.92, significantly better than urea (68% porosity / 0.78 sound absorption coefficient) and dicyandiamide (75% porosity / 0.74 sound absorption coefficient). The possible mechanism is that the three-dimensional carbon nitride skeleton formed by melamine calcination at 530℃ provides physical support during the foaming stage (230℃), promoting cell connectivity and optimizing sound wave scattering efficiency. In contrast, urea decomposes at a low temperature of 133℃, leading to premature gas escape in the preheating stage (150℃) and uneven cell merging; the residual linear urea-formaldehyde structure has poor thermal stability, and the pore walls are prone to collapse. Dicyandiamide decomposes at 210℃ with a slow gas release rate and generates toxic HCN, weakening the carbon layer quality. The high-temperature rigid skeleton support effect of melamine is the key to its excellent porosity and sound absorption performance, while urea and dicyandiamide cannot match its effect due to their decomposition defects.

[0152] Under the condition of fixing the nitrogen-containing compound (melamine), the chemical structure of the modifier has a significant impact on the performance of the flame-retardant sound-absorbing foam material. N-(2-aminoethyl)-3-aminopropyltrimethoxysilane achieves a dual anchoring mechanism during reflux through its primary amine (-NH2) and secondary amine (-NH-): the primary amine bonds to the silanol groups on the surface of the microspheres, and the secondary amine grafts to the phosphate groups (PO4³⁻) in the flame retardant, forming a stable PNC covalent network. This network not only optimizes the acoustic impedance matching, but also avoids pore blockage through the flexibility of the molecular chains, ensuring unobstructed multiple scattering paths of sound waves in the pores, thereby achieving the highest porosity (95%) and sound absorption coefficient (0.92). In contrast, KH-550 (monoamino) has a low grafting rate of the single primary amino group, resulting in poor compatibility with the polyolefin matrix. This leads to uneven microsphere dispersion, weak interfacial bonding, increased sound wave reflection at the pore walls, and decreased sound absorption efficiency (open porosity 85%, sound absorption coefficient 0.85). Diethylenetriaminepropyltrimethoxysilane, on the other hand, easily clogs the pore channels, reducing the open porosity. Simultaneously, its rigid structure hinders sound wave penetration, resulting in a significant attenuation of the sound absorption coefficient in the high-frequency range (>5kHz) (open porosity 82%, sound absorption coefficient 0.78).

[0153] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all formulations, processes and principles covered by the present invention are within the scope of protection of the present invention.

Claims

1. A process for the preparation of a flame-retardant acoustical foamed material, characterized in that, The method is as follows: S1, ethylene-vinyl acetate copolymer, rubber are mixed and granulated in an internal mixer to obtain high-polarity elastomer masterbatch according to the formula; S2, high-polarity elastomer masterbatch, polyolefin resin, polystyrene, dicumyl peroxide, antioxidant are mixed and granulated to obtain mixed masterbatch; S3, mixed masterbatch, filler, foaming agent, flame retardant, foaming aid are mixed and extruded to obtain master roll; S4, the master roll is subjected to electron irradiation crosslinking; S5, the crosslinked master roll is subjected to horizontal oven foaming to obtain closed-cell polyolefin foam material; S6, the closed-cell polyolefin foam material is subjected to secondary foaming to obtain flame-retardant sound-absorbing foam material. The flame-retardant sound-absorbing foam material comprises the following raw materials by weight: 20-60 parts of polyolefin resin, 20-50 parts of ethylene-vinyl acetate copolymer, 10-30 parts of polystyrene, 5-20 parts of rubber, 1-20 parts of foaming agent, 10-20 parts of flame retardant, 5 parts of filler, 1-5 parts of dicumyl peroxide, 0.5-10 parts of foaming aid, 0.5-3 parts of antioxidant; The filler is modified microspheres; The preparation method of the modified microspheres is as follows: Z1, under stirring, silica-alumina sol, water and nitrogen-containing compound are added into a beaker, the pH is adjusted to be acidic with hydrochloric acid, then polyethylene glycol aqueous solution is added, stirred uniformly, then glutaraldehyde is poured in, stirred uniformly, then left to stand, the supernatant is removed by filtration, washed with water and anhydrous ethanol, dried to obtain composite microspheres; the composite microspheres are placed in a muffle furnace for temperature rising calcination: in the first stage, the temperature is raised from room temperature to 170-190℃ at a rate of 7-9℃ / min and kept for 1-3 hours; in the second stage, the temperature is raised to 230-270℃ at a rate of 4-6℃ / min and kept for 1-3 hours; in the third stage, the temperature is raised to 500-600℃ at a rate of 2-4℃ / min and kept for 1-3 hours to obtain porous microspheres; Z2, the porous microspheres are mixed and dispersed with anhydrous ethanol, a modifier and water are added, the sample is collected under high-temperature reflux, washed with anhydrous ethanol and dried to obtain modified microspheres; The nitrogen-containing compound is melamine; the modifier is N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.

2. The method of claim 1, wherein the flame retardant sound absorbing foamed material is prepared by adding the flame retardant to the foaming agent. The polyolefin resin is at least one of low-density polyethylene, high-density polyethylene and polypropylene; The low-density polyethylene has a melt index of 0.5-4.0 g / 10 min, the high-density polyethylene has a melt index of 0.5-6.0 g / 10 min, the polypropylene has a melt index of 2-15 g / 10 min, and the ethylene-vinyl acetate copolymer has a melt index of 0.5-8.0 g / 10 min.

3. The preparation method of the flame-retardant sound-absorbing foam material as described in claim 1, characterized in that, The rubber is at least one of ethylene-propylene rubber, nitrile rubber, styrene-butadiene rubber and silicone rubber.

4. The method of making a fire-retardant acoustical foam material of claim 1 wherein, The foaming agent is azodicarbonamide; The foaming aid is zinc oxide and zinc stearate.

5. The preparation method of the flame-retardant sound-absorbing foam material as described in claim 1, characterized in that, The flame retardant is at least one of phosphate ester and melamine polyphosphate.

6. The method of making a fire-retardant acoustical foam material of claim 1 wherein, The antioxidant is a compound of DSTP and 1010 with a weight ratio of 2-4:1-3.

7. A fire-retardant acoustical foam material characterized by Prepared by the preparation method of any one of claims 1-6.

8. Use of a flame-retardant acoustical foamed material according to claim 7, characterized in that, Applied to rail transit and KTV sites.