Sound transmission composite fabric for vehicle and preparation method thereof

Abstract

The present application relates to the technical field of composite fabric, in particular to a sound-transmitting composite fabric for vehicles and a preparation method thereof.The present application comprises the following steps:Step 1: weaving 300D / 96F black DTY and 150D / 48F black DTY, and then performing water washing, setting and flame-retardant stiffening treatment to obtain a polyester weft-knitted fabric;Step 2: weaving 83D / 36F black DTY and 44D / 1F black DTY, and then performing water washing and setting treatment to obtain a polyester warp-knitted 3D mesh fabric;Step 3: compounding the polyester weft-knitted fabric and the polyester warp-knitted 3D mesh fabric through hot melt adhesive to obtain the sound-transmitting composite fabric for vehicles.The sound-transmitting composite fabric for vehicles prepared by the present application has excellent air permeability and flame-retardant performance, thereby effectively improving the comfort and safety inside the vehicle.

Description

Technical Field

[0001] This invention relates to the field of composite fabric technology, specifically to a sound-permeable composite fabric for automobiles and its preparation method. Background Technology

[0002] With the rapid development of the automotive industry, consumers are increasingly demanding higher levels of comfort, safety, and environmental performance in automobiles. Interior noise control has become a crucial factor in enhancing the driving experience, and sound-permeable composite fabrics, due to their combination of sound insulation, sound permeability, and lightweight properties, have garnered widespread attention in the field of automotive interior materials.

[0003] Sound-permeable composite fabrics are typically made by combining various functional materials through a special process, aiming to achieve controlled sound transmission and absorption. On the one hand, they need to possess a certain level of sound insulation to block external noise such as engine noise, tire noise, and wind noise from entering the vehicle; on the other hand, they need to allow the effective transmission of specific frequencies of sound (such as car audio sounds) to ensure the sound quality of the in-vehicle audio system. Simultaneously, to meet the requirements of lightweight vehicles, these fabrics also need to have low density and good mechanical properties.

[0004] However, existing sound-permeable composite fabrics often fail to simultaneously achieve high sound insulation performance and good sound permeability during their design. Some materials, while blocking external noise, may excessively absorb or reflect in-vehicle audio signals, leading to sound quality distortion or volume reduction; conversely, pursuing sound permeability may sacrifice sound insulation performance, failing to effectively reduce in-vehicle noise levels. Furthermore, most sound-permeable composite fabrics use flammable base materials such as polyester and polyurethane, and conventional flame-retardant finishing methods are mostly physical coatings or impregnations. Flame retardants are prone to migration and have poor washability, resulting in a significant decrease in flame-retardant performance after long-term use, making it difficult to meet the stringent long-term safety requirements of automotive interiors. While some highly efficient flame retardants (such as halogen-based ones) have excellent flame-retardant effects, they present environmental problems such as high VOC emissions and highly toxic smoke, failing to comply with in-vehicle health and environmental regulations.

[0005] Therefore, we propose a sound-permeable composite fabric for automobiles and its preparation method. Summary of the Invention

[0006] The purpose of this invention is to provide a sound-permeable composite fabric for automobiles and its preparation method, so as to solve the problems raised in the prior art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a sound-permeable composite fabric for automobiles includes the following steps: Step 1: Weave 300D / 96F black DTY and 150D / 48F black DTY, and after washing, setting and flame-retardant stiffening treatment, obtain polyester weft-knitted fabric. Step 2: Weave 83D / 36F black DTY and 44D / 1F black DTY, and after washing and setting, obtain polyester warp-knitted 3D mesh fabric. Step 3: Polyester weft-knitted fabric and polyester warp-knitted 3D mesh fabric are bonded together with hot melt adhesive to obtain automotive sound-permeable composite fabric.

[0008] In a more optimized scheme, the mass ratio of the 300D / 96F black DTY to the 150D / 48F black DTY is 2:1.

[0009] In a more optimized scheme, the mass ratio of the 83D / 36F black DTY to the 44D / 1F black DTY is 1:1.

[0010] A more optimized approach is to use a flame-retardant stiffening agent with a formulation of 400-600 g / L.

[0011] A more optimized approach is to prepare the flame-retardant stiffener as follows: Sodium dodecyl sulfate, methyl methacrylate, butyl acrylate, acrylic acid, and water are mixed evenly. A flame-retardant monomer is added, and the mixture is emulsified for 20-30 minutes at 40-50℃ and 450-550 rpm. The temperature is then raised to 65-75℃, and an initiator aqueous solution is added dropwise over 1-2 hours. During the reaction, [the following is used:] Adjust the pH of the solution to 6-7, add the solution dropwise, raise the temperature to 80-85℃, keep the temperature for 3-5 hours, cool to room temperature, filter, collect the filtrate, and obtain the flame retardant stiffener.

[0012] In a more optimized scheme, the flame retardant stiffener comprises the following raw materials: by weight, 10-30 parts flame retardant monomer, 10-20 parts methyl methacrylate, 5-10 parts butyl acrylate, 1-5 parts acrylic acid, 0.3-1.5 parts sodium dodecyl sulfate, 10-20 parts initiator aqueous solution, and 40-60 parts water.

[0013] In a more optimized scheme, the concentration of the initiator aqueous solution is 1-3 wt%, and the initiator is ammonium persulfate.

[0014] A more optimized approach is to prepare the flame-retardant monomer as follows: Step A: Mix p-aminophenol, cinnamaldehyde and anhydrous ethanol evenly, react at 60-70℃ for 3-5 hours, cool to room temperature, filter, wash and dry to obtain aromatic Schiff base; Step B: Mix aromatic Schiff base, DOPO and tetrahydrofuran evenly, react at 10-20℃ for 12-14h, filter, wash and dry to obtain modified DOPO. Step C: Under nitrogen protection, phenylphosphodichloro and tetrahydrofuran are mixed evenly. Under ice bath conditions, a mixed solution of modified DOPO, tetrahydrofuran and triethylamine is added dropwise over 50-60 minutes. The reaction is carried out at 0-5℃ for 1-2 hours, then raised to room temperature and reacted for 10-12 hours. Under ice bath conditions, a mixed solution of diethanolamine borate, tetrahydrofuran and triethylamine is added dropwise over 50-60 minutes. The reaction is carried out at 0-5℃ for 1-2 hours, then raised to room temperature and reacted for another 10-12 hours. After filtration, rotary evaporation, washing and drying, the flame-retardant monomer is obtained.

[0015] In a more optimized scheme, in step A, the mass ratio of p-aminophenol, cinnamaldehyde, and anhydrous ethanol is 1:(1.2-1.5):(8-10).

[0016] In a more optimized scheme, in step B, the mass ratio of aromatic Schiff base, DOPO and tetrahydrofuran is 1:(1-2):(4-6).

[0017] In a more optimized scheme, in step C, the molar ratio of phenylphosphodichloro, modified DOPO and diethanolamine borate is 1:1:(0.5-1.0).

[0018] In a more optimized scheme, in step C, the mass ratio of modified DOPO, tetrahydrofuran, and triethylamine is 1:(3-5):(0.8-1.0).

[0019] In a more optimized scheme, in step C, the mass ratio of diethanolamine borate, tetrahydrofuran, and triethylamine is 1:(3-5):(1-2).

[0020] A more optimized method for preparing the borate diethanolamine ester is as follows: Boric acid, diethanolamine and toluene are mixed evenly and refluxed at 115-125℃ until no more water is produced in the system. After vacuum distillation, washing and drying, the borate diethanolamine ester is obtained.

[0021] In a more optimized scheme, the mass ratio of boric acid, diethanolamine and toluene is 1:(3.5-4.0):(4-6).

[0022] A more optimized scheme is that the process conditions for the flame-retardant stiffening treatment are: two dips and two rolls, roll residue rate of 60-70%, rolling mill pressure of 0.2-0.3MPa, drying temperature of 100-120℃, time of 1-3min, baking temperature of 180-200℃, time of 2-4min.

[0023] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention discloses a sound-permeable composite fabric for automobiles and its preparation method. The sound-permeable composite fabric for automobiles is made by bonding polyester weft-knitted fabric and polyester warp-knitted 3D mesh fabric with hot melt adhesive, and can be used for the surface covering of automotive interiors. Compared with traditional leather surface materials, it has significantly better breathability and sound permeability: the polyester weft-knitted fabric itself has a loose structure and uniform pore distribution, which, combined with the three-dimensional mesh structure of the polyester warp-knitted 3D mesh fabric, forms a multi-layered, highly permeable breathable and sound-permeable channel after the two are combined, allowing gas and sound waves to pass through quickly with low loss; while traditional leather materials are mostly dense coating structures, which easily block the transmission path, resulting in poor breathability and significant sound wave attenuation.

[0024] 2. This invention discloses a sound-permeable composite fabric for automobiles and its preparation method. First, a Schiff base reaction is carried out between p-aminophenol and cinnamaldehyde, followed by a reaction with the pH bond of DOPO to obtain modified DOPO. Finally, by controlling the molar ratio of phenylphosphodichloro, modified DOPO, and diethanolamine borate to 1:1:(0.5-1.0), one -Cl group in phenylphosphodichloro reacts with the hydroxyl group on the modified DOPO to obtain a monochloro compound. Finally, the monochloro compound reacts with diethanolamine borate to obtain a flame-retardant monomer containing phosphorus, nitrogen, and boron. Through the synergistic enhancement of flame-retardant efficiency by phosphorus and nitrogen and the improvement of char layer stability by boron, a dual mechanism of "gas-phase flame retardancy + condensed-phase flame retardancy" is formed. Compared with traditional single phosphorus or halogen flame retardants, it has a higher flame retardant limit and better smoke suppression effect. At the same time, the flame-retardant monomer participates in the copolymerization reaction through carbon-carbon double bonds and is grafted onto the polymer chain, rather than being physically mixed, which solves the problem of easy migration of traditional flame retardants and meets the long-term use requirements of automotive fabrics. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Unless otherwise specified, all quantities below are by weight. It should be noted that there are no special restrictions on the manufacturers of the raw materials involved in this invention. Exemplary examples (in this embodiment) include 300D / 96F black DTY and 150D / 48F black DTY, both sourced from Xinzhanjiang Fiber Technology Co., Ltd.; 83D / 36F black DTY and 44D / 1F black DTY, both sourced from Jiangsu Hengli Chemical Fiber Co., Ltd.; hot melt adhesive: PUR hot melt adhesive, sourced from Fuller (China) Adhesives Co., Ltd.

[0027] Example 1: A method for preparing a sound-permeable composite fabric for automobiles, comprising the following processes: Step 1: 300D / 96F black DTY and 150D / 48F black DTY are woven at a mass ratio of 2:1 using a 30-inch 16-needle double-sided knitting machine, washed with water at a liquor ratio of 1:10 for 10 minutes, set at 140℃, and then placed in a 400g / L flame retardant stiffener for flame retardant stiffening treatment to obtain polyester weft-knitted fabric. Step 2: 83D / 36F black DTY and 44D / 1F black DTY are woven in a mass ratio of 1:1 through an 18-needle Karl Mayer RD7 double needle bed, washed with water at a liquor ratio of 1:10 for 10 minutes, and set at 140℃ to obtain polyester warp-knitted 3D mesh fabric. Step 3: Polyester weft-knitted fabric and polyester warp-knitted 3D mesh fabric are bonded together with hot melt adhesive to obtain automotive sound-permeable composite fabric; The preparation method of the flame retardant stiffener is as follows: Mix 0.3 parts sodium dodecyl sulfate, 10 parts methyl methacrylate, 5 parts butyl acrylate, 1 part acrylic acid, and 40 parts water until homogeneous. Add 10 parts flame retardant monomer and emulsify at 40℃ and 450 r / min for 20 min. Raise the temperature to 65℃ and add 10 parts of 1-3 wt% ammonium persulfate aqueous solution dropwise over 1 hour. During the reaction, use... The solution pH was adjusted to 6. After the addition was complete, the temperature was raised to 80°C and the reaction was maintained for 3 hours. The solution was then cooled to room temperature, filtered, and the filtrate was collected to obtain the flame retardant stiffener. The preparation method of flame-retardant monomers is as follows: Step A: Mix 10 parts of p-aminophenol, 12 parts of cinnamaldehyde and 80 parts of anhydrous ethanol evenly, react at 60°C for 3 hours, cool to room temperature, filter, wash and dry to obtain aromatic Schiff base. Step B: Mix 10 parts of aromatic Schiff base, 10 parts of DOPO and 40 parts of tetrahydrofuran evenly, react at 10°C for 12 hours, filter, wash and dry to obtain modified DOPO. Step C: Boric acid, diethanolamine and toluene are mixed evenly in a mass ratio of 1:3.5:4 and refluxed at 115°C until no more water is produced in the system. Toluene is removed by vacuum distillation, and the mixture is washed and dried to obtain diethanolamine borate. Under nitrogen protection, phenylphosphoryl dichloride and tetrahydrofuran were mixed uniformly at a mass ratio of 1:2. A mixed solution of modified DOPO, tetrahydrofuran, and triethylamine in a mass ratio of 1:3:0.8 was added dropwise over an ice bath, completing the addition over 50 minutes. The reaction was carried out at 0°C for 1 hour, then raised to room temperature and reacted for 10 hours. Then, under ice bath conditions, a mixed solution of diethanolamine borate, tetrahydrofuran, and triethylamine in a mass ratio of 1:3:1 was added dropwise, completing the addition over 50 minutes. The reaction was carried out at 0°C for 1 hour, then raised to room temperature and reacted for another 10 hours. After filtration, rotary evaporation, washing, and drying, the flame-retardant monomer was obtained; the molar ratio of phenylphosphoryl dichloride, modified DOPO, and diethanolamine borate was 1:1:0.5.

[0028] Example 2: A method for preparing a sound-permeable composite fabric for automobiles, comprising the following processes: Step 1: 300D / 96F black DTY and 150D / 48F black DTY are woven at a mass ratio of 2:1 using a 30-inch 16-needle double-sided knitting machine, washed with water at a liquor ratio of 1:10 for 12 minutes, set at 150℃, and then placed in a 500g / L flame retardant stiffener for flame retardant stiffening treatment to obtain polyester weft-knitted fabric. Step 2: 83D / 36F black DTY and 44D / 1F black DTY are woven in a mass ratio of 1:1 through an 18-needle Karl Mayer RD7 double needle bed, washed with water at a liquor ratio of 1:10 for 12 minutes, and set at 150℃ to obtain polyester warp-knitted 3D mesh fabric. Step 3: Polyester weft-knitted fabric and polyester warp-knitted 3D mesh fabric are bonded together with hot melt adhesive to obtain automotive sound-permeable composite fabric; The preparation method of the flame retardant stiffener is as follows: Mix 1 part sodium dodecyl sulfate, 15 parts methyl methacrylate, 8 parts butyl acrylate, 3 parts acrylic acid, and 50 parts water until homogeneous. Add 20 parts flame retardant monomer and emulsify at 45°C and 500 rpm for 25 minutes. Raise the temperature to 70°C and add 15 parts of 2wt% ammonium persulfate aqueous solution dropwise over 1.5 hours. During the reaction, use... Adjust the pH of the solution to 6.5, add the solution dropwise, heat to 80-85℃, keep the temperature for 3-5 hours, cool to room temperature, filter, collect the filtrate, and obtain the flame retardant stiffener. The preparation method of flame-retardant monomers is as follows: Step A: Mix 20 parts of p-aminophenol, 28 parts of cinnamaldehyde and 180 parts of anhydrous ethanol evenly, react at 65°C for 4 hours, cool to room temperature, filter, wash and dry to obtain aromatic Schiff base. Step B: Mix 20 parts of aromatic Schiff base, 30 parts of DOPO and 100 parts of tetrahydrofuran evenly, react at 15°C for 13 hours, filter, wash and dry to obtain modified DOPO. Step C: Boric acid, diethanolamine and toluene are mixed evenly in a mass ratio of 1:3.8:5 and refluxed at 120°C until no more water is produced in the system. Toluene is removed by vacuum distillation, and the mixture is washed and dried to obtain diethanolamine borate. Under nitrogen protection, phenylphosphoryl dichloride and tetrahydrofuran were mixed uniformly at a mass ratio of 1:3. A mixed solution of modified DOPO, tetrahydrofuran, and triethylamine in a mass ratio of 1:4:0.9 was added dropwise over an ice bath, completing the addition in 55 min. The reaction was carried out at 3°C ​​for 1.5 h, then raised to room temperature and reacted for 11 h. Under ice bath conditions, a mixed solution of diethanolamine borate, tetrahydrofuran, and triethylamine in a mass ratio of 1:4:1.5 was added dropwise, completing the addition in 55 min. The reaction was carried out at 3°C ​​for 1.5 h, then raised to room temperature and reacted for another 11 h. After filtration, rotary evaporation, washing, and drying, the flame-retardant monomer was obtained; the molar ratio of phenylphosphoryl dichloride, modified DOPO, and diethanolamine borate was 1:1:0.8.

[0029] Example 3: A method for preparing a sound-permeable composite fabric for automobiles, comprising the following processes: Step 1: 300D / 96F black DTY and 150D / 48F black DTY are woven at a mass ratio of 2:1 using a 30-inch 16-needle double-sided knitting machine, washed with water at a liquor ratio of 1:10 for 15 minutes, set at 160℃, and then placed in a 600g / L flame retardant stiffener for flame retardant stiffening treatment to obtain polyester weft-knitted fabric. Step 2: 83D / 36F black DTY and 44D / 1F black DTY are woven in a mass ratio of 1:1 through an 18-needle Karl Mayer RD7 double needle bed, washed with water at a liquor ratio of 1:10 for 15 minutes, and set at 160℃ to obtain polyester warp-knitted 3D mesh fabric. Step 3: Polyester weft-knitted fabric and polyester warp-knitted 3D mesh fabric are bonded together with hot melt adhesive to obtain automotive sound-permeable composite fabric; The preparation method of the flame retardant stiffener is as follows: Mix 1.5 parts sodium dodecyl sulfate, 20 parts methyl methacrylate, 10 parts butyl acrylate, 5 parts acrylic acid, and 60 parts water until homogeneous. Add 30 parts flame retardant monomer and emulsify at 50°C and 550 rpm for 30 minutes. Raise the temperature to 75°C and add 20 parts of 3wt% ammonium persulfate aqueous solution dropwise over 2 hours. During the reaction, use... The solution pH was adjusted to 7. After the addition was complete, the temperature was raised to 85°C and the reaction was maintained for 5 hours. The solution was then cooled to room temperature, filtered, and the filtrate was collected to obtain the flame retardant stiffener. The preparation method of flame-retardant monomers is as follows: Step A: Mix 30 parts of p-aminophenol, 45 parts of cinnamaldehyde and 300 parts of anhydrous ethanol evenly, react at 70°C for 5 hours, cool to room temperature, filter, wash and dry to obtain aromatic Schiff base. Step B: Mix 30 parts of aromatic Schiff base, 60 parts of DOPO and 180 parts of tetrahydrofuran evenly, react at 20°C for 14 hours, filter, wash and dry to obtain modified DOPO. Step C: Boric acid, diethanolamine and toluene are mixed evenly in a mass ratio of 1:4:6 and refluxed at 125°C until no more water is produced in the system. Toluene is removed by vacuum distillation, and after washing and drying, diethanolamine borate is obtained. Under nitrogen protection, phenylphosphoryl dichloride and tetrahydrofuran were mixed uniformly at a mass ratio of 1:4. A mixed solution of modified DOPO, tetrahydrofuran, and triethylamine in a mass ratio of 1:5:1 was added dropwise under ice bath conditions, completing the addition over 60 minutes. The reaction was carried out at 5°C for 2 hours, then raised to room temperature and reacted for 12 hours. Under ice bath conditions, a mixed solution of diethanolamine borate, tetrahydrofuran, and triethylamine in a mass ratio of 1:5:2 was added dropwise, completing the addition over 60 minutes. The reaction was carried out at 5°C for 2 hours, then raised to room temperature and reacted for another 12 hours. After filtration, rotary evaporation, washing, and drying, the flame-retardant monomer was obtained; the molar ratio of phenylphosphoryl dichloride, modified DOPO, and diethanolamine borate was 1:1:1.

[0030] Comparative Example 1: A method for preparing a sound-permeable composite fabric for automobiles, comprising the following processes: Compared with Example 2, Comparative Example 1 replaced the flame retardant monomer with the same mass of aromatic Schiff base, and the other steps were the same as in Example 2.

[0031] Comparative Example 2: A method for preparing a sound-permeable composite fabric for automobiles, comprising the following processes: The preparation method of flame-retardant monomers is as follows: Step A: Mix 20 parts of p-aminophenol, 28 parts of cinnamaldehyde and 180 parts of anhydrous ethanol evenly, react at 65°C for 4 hours, cool to room temperature, filter, wash and dry to obtain aromatic Schiff base. Step B: Mix 20 parts of aromatic Schiff base, 30 parts of DOPO and 100 parts of tetrahydrofuran evenly, react at 15°C for 13 hours, filter, wash and dry to obtain modified DOPO. Step C: Boric acid, diethanolamine and toluene are mixed evenly in a mass ratio of 1:3.8:5 and refluxed at 120°C until no more water is produced in the system. Toluene is removed by vacuum distillation, and after washing and drying, diethanolamine borate is obtained. Under nitrogen protection, phenylphosphoryl dichloride and tetrahydrofuran were mixed uniformly at a mass ratio of 1:3. A mixed solution of modified DOPO, tetrahydrofuran, and triethylamine in a mass ratio of 1:4:0.9 was added dropwise over an ice bath, completing the addition in 55 min. The reaction was carried out at 3°C ​​for 1.5 h, then raised to room temperature and reacted for 11 h. Then, under ice bath conditions, a mixed solution of diethanolamine borate, tetrahydrofuran, and triethylamine in a mass ratio of 1:4:1.5 was added dropwise, completing the addition in 55 min. The reaction was carried out at 3°C ​​for 1.5 h, then raised to room temperature and reacted for another 11 h. After filtration, rotary evaporation, washing, and drying, the flame-retardant monomer was obtained; the molar ratio of phenylphosphoryl dichloride, modified DOPO, and diethanolamine borate was 1:2:0.8. Compared with Example 2, in step C of Comparative Example 2, the molar ratio of phenylphosphodichloro and modified DOPO is 1:2, and the other steps are the same as in Example 2.

[0032] Experiment: Samples were prepared from the automotive sound-permeable composite fabrics obtained in Examples 1-3. The air permeability of these samples was tested and the results recorded. The test was conducted according to DIN EN ISO 9237:1995. Test area: Pressure drop: 200 Pa.

[0033] The test results are shown in Table 1.

[0034] Table 1. Test results of breathability of automotive sound-permeable composite fabric Take the automotive sound-permeable composite fabrics obtained in Examples 1-3 and Comparative Examples 1-2, prepare samples, test their flame retardant properties and record the test results: refer to FMVSS 302 for testing.

[0035] The test results are shown in Table 2.

[0036] Table 2 Flame retardancy test results of automotive sound-permeable composite fabric Based on the data in the table above, the following conclusions can be clearly drawn: the better the air permeability of the automotive sound-permeable composite fabric prepared by this invention, the higher the sound transmission rate, and it also has excellent flame-retardant properties. Compared with Examples 1-3, the flame-retardant properties of the products obtained in Comparative Examples 1 and 2 decreased, indicating that the flame-retardant monomer prepared by this invention has a better flame-retardant effect than aromatic Schiff bases. Furthermore, the performance of the flame-retardant monomer prepared by this invention is affected by its component ratio; selecting a component ratio within the stated range can produce materials with better flame-retardant effects.

[0037] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing a sound-permeable composite fabric for automobiles, characterized in that: Includes the following steps: Step 1: Weave 300D / 96F black DTY and 150D / 48F black DTY, and after washing, setting and flame-retardant stiffening treatment, obtain polyester weft-knitted fabric. The preparation method of the flame-retardant stiffening agent used in the flame-retardant stiffening process is as follows: Sodium dodecyl sulfate, methyl methacrylate, butyl acrylate, acrylic acid, and water are mixed evenly. A flame-retardant monomer is added, and the mixture is emulsified for 20-30 minutes at 40-50℃ and 450-550 rpm. The temperature is then raised to 65-75℃, and the initiator solution is added dropwise over 1-2 hours. During the reaction, [the following is used:] Adjust the pH of the solution to 6-7, add the solution dropwise, raise the temperature to 80-85℃, keep the temperature for 3-5 hours, cool to room temperature, filter, collect the filtrate, and obtain the flame retardant stiffener. Step 2: Weave 83D / 36F black DTY and 44D / 1F black DTY, and after washing and setting, obtain polyester warp-knitted 3D mesh fabric. Step 3: Polyester weft-knitted fabric and polyester warp-knitted 3D mesh fabric are bonded together with hot melt adhesive to obtain automotive sound-permeable composite fabric.

2. The method for preparing a sound-permeable composite fabric for automobiles according to claim 1, characterized in that: The mass ratio of the 300D / 96F black DTY to the 150D / 48F black DTY is 2:

1.

3. The method for preparing a sound-permeable composite fabric for automobiles according to claim 1, characterized in that: The mass ratio of the 83D / 36F black DTY to the 44D / 1F black DTY is 1:

1.

4. The method for preparing a sound-permeable composite fabric for automobiles according to claim 1, characterized in that: The process formula for the flame-retardant stiffening treatment is: 400-600g / L of flame-retardant stiffening agent.

5. The method for preparing a sound-permeable composite fabric for automobiles according to claim 1, characterized in that: The flame retardant stiffener comprises the following raw materials: by weight, 10-30 parts flame retardant monomer, 10-20 parts methyl methacrylate, 5-10 parts butyl acrylate, 1-5 parts acrylic acid, 0.3-1.5 parts sodium dodecyl sulfate, 10-20 parts initiator aqueous solution, and 40-60 parts water.

6. The method for preparing a sound-permeable composite fabric for automobiles according to claim 5, characterized in that: The preparation method of the flame-retardant monomer is as follows: Step A: Mix p-aminophenol, cinnamaldehyde and anhydrous ethanol evenly, react at 60-70℃ for 3-5 hours, cool to room temperature, filter, wash and dry to obtain aromatic Schiff base; Step B: Mix aromatic Schiff base, DOPO and tetrahydrofuran evenly, react at 10-20℃ for 12-14h, filter, wash and dry to obtain modified DOPO. Step C: Under nitrogen protection, phenylphosphodichloro and tetrahydrofuran are mixed evenly. Under ice bath conditions, a mixed solution of modified DOPO, tetrahydrofuran and triethylamine is added dropwise over 50-60 minutes. The reaction is carried out at 0-5℃ for 1-2 hours, then raised to room temperature and reacted for 10-12 hours. Under ice bath conditions, a mixed solution of diethanolamine borate, tetrahydrofuran and triethylamine is added dropwise over 50-60 minutes. The reaction is carried out at 0-5℃ for 1-2 hours, then raised to room temperature and reacted for another 10-12 hours. After filtration, rotary evaporation, washing and drying, the flame-retardant monomer is obtained.

7. The method for preparing a sound-permeable composite fabric for automobiles according to claim 6, characterized in that: In step C, the molar ratio of phenylphosphodichloro, modified DOPO and diethanolamine borate is 1:1:(0.5-1.0).

8. The method for preparing a sound-permeable composite fabric for automobiles according to claim 7, characterized in that: The preparation method of the borate diethanolamine ester is as follows: Boric acid, diethanolamine and toluene are mixed evenly and refluxed at 115-125℃ until no more water is produced in the system. After vacuum distillation, washing and drying, borate diethanolamine ester is obtained.

9. The method for preparing a sound-permeable composite fabric for automobiles according to claim 1, characterized in that: The process conditions for the flame-retardant stiffening treatment are as follows: two dips and two rolls, roll residue rate of 60-70%, rolling mill pressure of 0.2-0.3MPa, drying temperature of 100-120℃ for 1-3 min, and baking temperature of 180-200℃ for 2-4 min.

10. A sound-permeable composite fabric for vehicles prepared by the preparation method according to any one of claims 1-9.

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