Flame-retardant car cover fabric with three-layer composite structure and preparation method of flame-retardant car cover fabric

Abstract

The invention belongs to the technical field of flame-retardant car clothing, and relates to a flame-retardant car clothing fabric with a three-layer composite structure and a preparation method thereof.The flame-retardant car clothing fabric comprises a silica gel foaming oxygen isolation outer layer, a glass fiber middle layer and a pre-oxidized fiber inner layer from outside to inside, and the glass fiber middle layer is made of plain cloth or twill woven by alkali-free glass fibers; the surface of the fiber is treated by a silane coupling agent, the pre-oxidized fiber inner layer is formed by weaving polyacrylonitrile-based pre-oxidized fiber in a twill mode, the glass fiber middle layer and the pre-oxidized fiber inner layer are pre-attached through a low-melting-point silicon resin adhesive, the surface of the glass fiber middle layer is evenly coated with silica gel foaming oxygen-isolating outer layer slurry, and the silica gel foaming oxygen-isolating outer layer slurry is coated with silica gel foaming oxygen-isolating outer layer slurry; a stable silica gel foaming oxygen isolation outer layer is formed through stepped heating drying tunnel treatment, and the flame-retardant car cover fabric of a three-layer composite structure is obtained. The limit oxygen index is larger than or equal to 35%, no molten drop exists in vertical combustion, the carbonization length is smaller than or equal to 50 mm, high temperature resistance is achieved, the structure is stable, mechanical properties are balanced, no halogen flame retardant is added, and safety and environment friendliness are achieved.

Description

Technical Field

[0001] This invention belongs to the field of flame-retardant car cover technology, specifically relating to a three-layer composite flame-retardant car cover fabric and its preparation method. Background Technology

[0002] With the increase in car ownership, outdoor parking lots, and vehicle transportation scenarios (land and sea), the risk of vehicles facing accidental damage such as high temperatures, open flames, and scratches has significantly increased. As a protective outer layer for automobiles, car covers must simultaneously meet basic protection and safety requirements in extreme environments (flame retardancy and high-temperature resistance). Currently, the mainstream car cover materials on the market are mainly polymers such as polyurethane (TPU) and polyethylene (PE). While these materials possess a certain degree of flexibility and abrasion resistance, their flame retardant properties are generally insufficient, easily melting and dripping when exposed to open flames, igniting surrounding materials. Some solutions that improve flame retardancy by adding halogenated flame retardants pose problems such as releasing toxic gases (e.g., dioxins) during combustion and causing secondary pollution after an accidental fire.

[0003] For special scenarios (such as racing cars, military vehicles, and high-end new energy vehicles), although there are solutions using single flame-retardant fibers (such as aramid, pre-oxidized fibers) or ceramic coating materials, the following drawbacks exist: 1. Limitations of single materials: For example, although pre-oxidized fibers are resistant to high temperatures, they are tough and brittle when used alone; although glass fibers are strong, they have a smooth surface and weak bonding with the substrate, and they are prone to breaking into short fibers when used alone, which may pose a risk of skin irritation or inhalation; although silicone has good temperature resistance, the mechanical strength of pure silicone layers is low and they are easily punctured by sharp objects; although ceramic fibers are lightweight, have good thermal insulation, thermal stability and chemical stability, they are not wear-resistant and impact-resistant, and are prone to breakage under the scouring of high-speed airflow, and cannot resist the erosion of molten slag.

[0004] 2. Insufficient composite structure design: Existing three-layer composite car covers mostly focus on wear resistance / waterproofing, such as "PU outer layer + sponge buffer layer + base fabric layer", without optimizing the synergistic effect of each layer of materials for flame retardant requirements, resulting in low overall flame retardant efficiency and easy damage to structural integrity at high temperatures.

[0005] Therefore, developing a high-performance flame-retardant car cover fabric that is functionally complementary through multiple layers and is environmentally friendly has significant application value. Summary of the Invention

[0006] The purpose of this invention is to provide a three-layer composite flame-retardant car cover fabric, which uses ultra-fine pre-oxidized fiber as raw material, giving the fabric excellent flame-retardant and high-temperature resistance properties. Through the composite process, the properties of glass fiber and silicone rubber are utilized to significantly improve the overall strength, waterproof, wear-resistant and heat-insulating properties of the fabric.

[0007] The technical solution adopted by the present invention to solve its technical problem is: a three-layer composite flame-retardant car cover fabric, which consists of a silicone foam oxygen barrier outer layer, a glass fiber middle layer and a pre-oxidized fiber inner layer from the outside to the inside. The glass fiber middle layer and the pre-oxidized fiber inner layer are bonded by hot pressing. The silicone foam oxygen barrier outer layer is formed by coating the glass fiber middle layer to form a wet film and then curing and foaming. The components of the silicone foam oxygen barrier outer layer by weight are: 90-120 parts of silicone rubber, 5-15 parts of foaming agent, 3-8 parts of crosslinking agent, 0.1-0.5 parts of catalyst, and 10-20 parts of functional filler. The wet film thickness of the silicone foam oxygen barrier outer layer is controlled at 0.1-0.3 mm. The flame retardancy is further improved by adding functional filler, while giving the surface hydrophobic and wear-resistant properties. The glass fiber interlayer is made of alkali-free glass fiber woven into plain or twill fabric. The fiber surface is treated with silane coupling agent to enhance the bonding force between the glass fiber interlayer and the silicone foam oxygen barrier outer layer and the pre-oxidized fiber inner layer. The inner layer of the pre-oxidized fiber is made of polyacrylonitrile-based pre-oxidized fiber in a twill weave.

[0008] Furthermore, the silicone rubber is one or a mixture of several of methyl silicone rubber, methyl vinyl silicone rubber, and methyl phenyl silicone rubber.

[0009] Furthermore, the foaming agent is an organosilicon foaming agent or an inorganic high-temperature foaming agent. The organosilicon foaming agent is a silane-modified azo compound, the inorganic high-temperature foaming agent is sodium bicarbonate, the crosslinking agent is hydrogen-containing silicone oil, the catalyst is a platinum catalyst, and the functional filler is one or a mixture of several of nano-aluminum hydroxide, nano-silica, and zinc borate.

[0010] Furthermore, the silane-modified azo compound (Si-RN=NC(CH3)2-CH3) is formed by modifying the cyano group (-CN) in the azobisisobutyronitrile (AIBN) molecule with a siloxane group (-R-Si(OCH3)3), wherein R is a C1-C8 alkylene group.

[0011] Furthermore, the alkali-free glass fiber monofilament has a diameter of 5-15μm, and the plain or twill fabric woven from it has a basis weight of 100-300g / m². The silane coupling agent is KH550 (γ-aminopropyltriethoxysilane).

[0012] Furthermore, the pre-oxidation degree of the polyacrylonitrile-based pre-oxidized fiber is 60%-80%, the fiber diameter is 10-20μm, and the weight after twill weaving is 150-400g / m².

[0013] Another object of the present invention is to provide a method for preparing a three-layer composite flame-retardant car cover fabric, comprising the following steps: (1) Preparation of glass fiber interlayer: Alkali-free glass fibers are woven into plain or twill fabrics, then immersed in an ethanol solution of silane coupling agent for 10 minutes, and dried at 70-80℃ for later use, which is the glass fiber interlayer. (2) Preparation of the pre-oxidized fiber inner layer: Polyacrylonitrile fibers are pre-oxidized to obtain polyacrylonitrile-based pre-oxidized fibers, with the degree of pre-oxidation controlled at 60-80%. The polyacrylonitrile-based pre-oxidized fibers are then woven into twill fabric, which is the inner layer of the pre-oxidized fibers. (3) Preparation of silicone foam oxygen-barrier outer layer slurry: The silicone rubber, foaming agent, crosslinking agent, catalyst, and functional filler are mixed in proportion and dispersed evenly by high-speed stirring to form a coatable paste or liquid slurry. (4) Three-layer composite molding: First, the glass fiber intermediate layer and the pre-oxidized fiber inner layer are pre-bonded with low melting point silicone resin adhesive, and pre-pressed at 80°C for 3 minutes to obtain a double-layer film. The silicone foam oxygen barrier slurry prepared in step (3) is uniformly coated on the surface of the glass fiber intermediate layer of the double-layer film using a scraping, roller coating or spraying process. The wet film thickness is controlled at 0.1-0.3 mm. The coated fabric is treated by a stepped heating oven to form a stable silicone foam oxygen barrier outer layer, and a three-layer composite fabric is obtained.

[0014] Furthermore, in step (1), the ethanol solution of the silane coupling agent has a mass concentration of 1-3%.

[0015] Furthermore, in step (2), the pre-oxidation process of polyacrylonitrile fibers adopts a stepped heating method: a. Bring the temperature from room temperature to 100℃, control the heating rate to 1-2℃ / min, stabilize for 10-30min, and remove moisture from the fiber surface; b. From 100℃ to 200℃, control the heating rate at 0.5-1℃ / min. This stage is the initial stage of the cyclization reaction. c. From 200℃ to 250-300℃, control the heating rate at 0.3-0.5℃ / min. This stage is the core cyclization and cross-linking stage. d. Maintain a constant temperature of 250-300℃ for 60-120 minutes to ensure the pre-oxidation degree is controlled at 60%-80%. During production, ensure uniform diffusion of surrounding oxygen. Apply stretching during pre-oxidation, with a stretching rate of 1%-3%. The constant temperature time depends on the target pre-oxidation degree. If the pre-oxidation degree is controlled at 60%~80%, the constant temperature time should be maintained at 60~120 minutes. Ensure uniform diffusion of surrounding oxygen during production to avoid localized overheating or incomplete oxidation. Applying appropriate stretching during pre-oxidation can guide the fiber molecular chains along the axial direction, improving the final fiber strength (if the stretching is too large, the fiber is prone to breakage due to cyclization shrinkage stress; if there is no stretching, the fiber structure is loose and the strength is low). A stretching rate of 1%-3% is recommended to maintain fiber morphological stability. Ultrafine pre-oxidized fibers inherently possess flame retardancy (limiting oxygen index LOI > 45%) and high-temperature resistance. As the core flame-retardant barrier of the inner layer of the car cover, and firmly bonded to the glass fiber intermediate layer through hot pressing, the overall impact resistance and strength are significantly improved.

[0016] Furthermore, in step (4), the softening point of the low-melting-point silicone resin adhesive is 120°C, and the coating amount is 5 g / m³. 2 The stepped heating oven process is as follows: pre-drying at 80-90℃ for 8-10 minutes to remove solvent, cross-linking and curing at 190-200℃ for 30-35 minutes to form an elastomer, and high-temperature foaming at 350-360℃ for 2-5 minutes to trigger expansion and carbonization, forming a stable silicone foam oxygen barrier layer.

[0017] The present invention has the following beneficial effects: 1. Significantly improved flame retardant performance: The flame retardant car cover fabric of this invention has a three-layer composite structure. The outer layer of silicone foam forms an oxygen barrier layer through expansion and carbonization. Air has a very low thermal conductivity, and the numerous pores in the coating are filled with air, forming a good heat insulation barrier with better heat insulation performance than ordinary silicone. The middle layer of glass fiber blocks heat transfer (thermal conductivity ≤0.2W / (m·K)), and the inner layer of pre-oxidized fiber is itself flame-retardant and heat-resistant. The three elements work together to make the overall limiting oxygen index of the fabric ≥35% (traditional TPU car cover <25%), with no dripping during vertical combustion and a carbonization length ≤50mm (National Standard GB / T5455-2014).

[0018] 2. High temperature resistance and structural stability: When the flame-retardant car cover fabric of the present invention is exposed to an 800°C flame for 30 minutes, the silicone foam oxygen barrier outer layer only shows slight surface discoloration (no melting drips), the glass fiber middle layer maintains its fiber shape (no powdering), and the pre-oxidized fiber inner layer maintains its strength (strength retention rate > 80%). The entire fabric does not crack or delaminate.

[0019] 3. Balanced mechanical properties: The flame-retardant car cover fabric of this invention has a three-layer composite structure. The ultra-fine pre-oxidized fiber provides flexibility (bending radius < 5cm), the glass fiber middle layer enhances impact resistance (impact energy absorption ≥ 10J), and improves overall strength (breaking strength ≥ 2000N, tear strength ≥ 100N), which is suitable for the complex curved surface of the vehicle.

[0020] 4. Safety and environmental protection: The three-layer composite structure of the flame-retardant car cover fabric of this invention does not contain halogen flame retardants. The combustion products are mainly carbon dioxide, water and inorganic oxides, which are non-toxic, safe and environmentally friendly. Detailed Implementation

[0021] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention. However, the scope of protection of the present invention is not limited to these embodiments. All changes or equivalent substitutions that do not depart from the concept of the present invention are included within the scope of protection of the present invention. Example 1

[0022] A flame-retardant car cover fabric with a three-layer composite structure, consisting of a silicone foam oxygen-barrier outer layer, a glass fiber middle layer, and a pre-oxidized fiber inner layer, from the outside to the inside.

[0023] (1) Preparation of glass fiber interlayer: Alkali-free glass fibers with a single filament diameter of 5μm are woven into plain or twill fabrics with a basis weight of 250g / m². They are then immersed in an ethanol solution of 2wt% silane coupling agent KH550 for 10 minutes and dried at 70℃ for later use, which is the glass fiber interlayer.

[0024] (2) Preparation of the pre-oxidized fiber inner layer: Polyacrylonitrile fibers are pre-oxidized to obtain polyacrylonitrile-based pre-oxidized fibers with a pre-oxidation degree of 80% and a fiber diameter of 20μm. Then, the polyacrylonitrile-based pre-oxidized fibers are woven into twill fabric with a weight of 150g / m², which is the inner layer of the pre-oxidized fibers. The pre-oxidation process for polyacrylonitrile fibers employs a stepped temperature increase: a. Bring the temperature from room temperature to 100℃, control the heating rate at 1.5℃ / min, stabilize for 10min, and remove moisture from the fiber surface; b. From 100℃ to 200℃, control the heating rate at 0.8℃ / min. This stage is the initial stage of the cyclization reaction. c. From 200℃ to 280℃, control the heating rate at 0.4℃ / min. This stage is the core cyclization and cross-linking stage. d. Maintain a constant temperature of 280℃ for 80 minutes to ensure that the degree of pre-oxidation is controlled at 80%. Ensure that the surrounding oxygen is evenly diffused during the production process. Apply stretching during the pre-oxidation process with a stretching rate of 2%.

[0025] (3) Preparation of silicone foam oxygen-barrier outer layer slurry: Coating preparation: 100 parts of methyl silicone rubber, 8 parts of sodium bicarbonate, 5 parts of hydrogen-containing silicone oil, 0.4 parts of platinum catalyst, and 20 parts of nano aluminum hydroxide are mixed in proportion and dispersed evenly by high-speed stirring to form a coatable paste or liquid slurry.

[0026] (4) Three-layer composite molding: First, the glass fiber interlayer and the pre-oxidized fiber inner layer are pre-bonded using a low-melting-point silicone resin adhesive. The softening point of the low-melting-point silicone resin adhesive is 120℃, and the application amount is 5g / m². 2 The double-layer film is obtained by pre-pressing at 80℃ for 3 minutes. The silicone foam oxygen barrier slurry prepared in step (3) is uniformly coated on the surface of the glass fiber intermediate layer of the double-layer film by scraping, rolling or spraying process. The wet film thickness is controlled at 0.3 mm. The coated fabric is treated by step heating oven, pre-drying at 80℃ for 10 minutes to remove solvent, cross-linking and curing at 200℃ for 30 minutes to form elastomer, and high-temperature foaming at 350℃ for 4 minutes to trigger expansion and carbonization, forming a stable silicone foam oxygen barrier outer layer, and obtaining a three-layer composite fabric.

[0027] The three-layer composite flame-retardant car cover fabric prepared in this embodiment has a tensile strength of 2260N, a tear strength of 114N, and after being exposed to an 800℃ flame for 30 minutes, the silicone foam oxygen barrier outer layer only shows slight surface discoloration. There is no melting dripping when burned vertically, the limiting oxygen index is 39%, and the char length determined based on the flammability test of GB / T5455-2014 is 35mm. Example 2

[0028] A flame-retardant car cover fabric with a three-layer composite structure, consisting of a silicone foam oxygen-barrier outer layer, a glass fiber middle layer, and a pre-oxidized fiber inner layer, from the outside to the inside.

[0029] (1) Preparation of glass fiber interlayer: Alkali-free glass fibers with a single filament diameter of 10μm are woven into plain or twill fabrics with a basis weight of 200g / m². They are then immersed in an ethanol solution of 1wt% silane coupling agent KH550 for 10 minutes and dried at 80℃ for later use, which is the glass fiber interlayer.

[0030] (2) Preparation of the pre-oxidized fiber inner layer: Polyacrylonitrile fibers are pre-oxidized to obtain polyacrylonitrile-based pre-oxidized fibers with a pre-oxidation degree of 75% and a fiber diameter of 15μm. Then, the polyacrylonitrile-based pre-oxidized fibers are woven into twill fabric with a weight of 300g / m², which is the inner layer of the pre-oxidized fibers. The pre-oxidation process for polyacrylonitrile fibers employs a stepped temperature increase: a. Bring the temperature from room temperature to 100℃, control the heating rate at 2℃ / min, stabilize for 20min, and remove moisture from the fiber surface. b. From 100℃ to 200℃, control the heating rate at 1℃ / min. This stage is the initial stage of the cyclization reaction. c. From 200℃ to 260℃, control the heating rate at 0.3℃ / min. This stage is the core cyclization and cross-linking stage. d. Maintain a constant temperature of 260℃ for 100 minutes to ensure that the degree of pre-oxidation is controlled at 75%. Ensure that the surrounding oxygen is evenly diffused during the production process. Apply stretching during the pre-oxidation process with a stretching rate of 2%.

[0031] (3) Preparation of silicone foam oxygen-barrier outer layer slurry: Coating preparation: 70 parts of methyl silicone rubber, 50 parts of methyl phenyl silicone rubber, 15 parts of silane-modified azo compound, 7 parts of hydrogen-containing silicone oil, 0.5 parts of platinum catalyst, 12 parts of nano aluminum hydroxide, and 6 parts of nano silica are mixed in proportion and dispersed evenly by high-speed stirring to form a coatable paste or liquid slurry.

[0032] (4) Three-layer composite molding: First, the glass fiber interlayer and the pre-oxidized fiber inner layer are pre-bonded using a low-melting-point silicone resin adhesive. The softening point of the low-melting-point silicone resin adhesive is 120℃, and the application amount is 5g / m². 2 The double-layer film is obtained by pre-pressing at 80℃ for 3 minutes. The silicone foam oxygen barrier slurry prepared in step (3) is uniformly coated on the surface of the glass fiber intermediate layer of the double-layer film by scraping, roller coating or spraying process. The wet film thickness is controlled at 0.1 mm. The coated fabric is treated by step heating oven, pre-drying at 85℃ for 8 minutes to remove solvent, cross-linking and curing at 190℃ for 35 minutes to form elastomer, and high-temperature foaming at 355℃ for 2 minutes to trigger expansion and carbonization, forming a stable silicone foam oxygen barrier outer layer, and obtaining a three-layer composite fabric.

[0033] The three-layer composite flame-retardant car cover fabric prepared in this embodiment has a tensile strength of 2340N, a tear strength of 119N, and after being exposed to an 800℃ flame for 30 minutes, the silicone foam oxygen barrier outer layer only shows slight surface discoloration. There is no melting dripping when burned vertically, the limiting oxygen index is 37%, and the char length determined based on the flammability test of GB / T5455-2014 is 33mm. Example 3

[0034] A flame-retardant car cover fabric with a three-layer composite structure, consisting of a silicone foam oxygen-barrier outer layer, a glass fiber middle layer, and a pre-oxidized fiber inner layer, from the outside to the inside.

[0035] (1) Preparation of glass fiber interlayer: Alkali-free glass fibers with a monofilament diameter of 15μm are woven into plain or twill fabrics with a basis weight of 100g / m². They are then immersed in an ethanol solution of 1wt% silane coupling agent KH550 for 10 minutes and dried at 75℃ for later use, which is the glass fiber interlayer.

[0036] (2) Preparation of the pre-oxidized fiber inner layer: Polyacrylonitrile fibers are pre-oxidized to obtain polyacrylonitrile-based pre-oxidized fibers with a pre-oxidation degree of 60% and a fiber diameter of 10μm. Then, the polyacrylonitrile-based pre-oxidized fibers are woven into twill fabric with a weight of 250g / m², which is the inner layer of the pre-oxidized fibers. The pre-oxidation process for polyacrylonitrile fibers employs a stepped temperature increase: a. Bring the temperature from room temperature to 100℃, control the heating rate to 1℃ / min, stabilize for 30min, and remove moisture from the fiber surface; b. From 100℃ to 200℃, control the heating rate at 0.5℃ / min. This stage is the initial stage of the cyclization reaction. c. From 200℃ to 300℃, control the heating rate at 0.5℃ / min. This stage is the core cyclization and cross-linking stage. d. Maintain a constant temperature of 300℃ for 60 minutes to ensure that the degree of pre-oxidation is controlled at 60%. Ensure that the surrounding oxygen is evenly diffused during the production process. Apply stretching during the pre-oxidation process with a stretching rate of 1%.

[0037] (3) Preparation of silicone foam oxygen-barrier outer layer slurry: Coating preparation: 110 parts of methyl vinyl silicone rubber, 10 parts of sodium bicarbonate, 3 parts of hydrogen-containing silicone oil, 0.2 parts of platinum catalyst, and 10 parts of zinc borate are mixed in proportion and dispersed evenly by high-speed stirring to form a coatable paste or liquid slurry.

[0038] (4) Three-layer composite molding: First, the glass fiber interlayer and the pre-oxidized fiber inner layer are pre-bonded using a low-melting-point silicone resin adhesive. The softening point of the low-melting-point silicone resin adhesive is 120℃, and the application amount is 5g / m². 2 The double-layer film is obtained by pre-pressing at 80℃ for 3 minutes. The silicone foam oxygen barrier slurry prepared in step (3) is uniformly coated on the surface of the glass fiber intermediate layer of the double-layer film by scraping, rolling or spraying process. The wet film thickness is controlled at 0.2 mm. The coated fabric is treated by step heating oven, pre-drying at 90℃ for 10 minutes to remove solvent, cross-linking and curing at 195℃ for 30 minutes to form elastomer, and high-temperature foaming at 355℃ for 5 minutes to trigger expansion and carbonization, forming a stable silicone foam oxygen barrier outer layer, and obtaining a three-layer composite fabric.

[0039] The three-layer composite flame-retardant car cover fabric prepared in this embodiment has a tensile strength of 2050N, a tear strength of 107N, and after being exposed to an 800℃ flame for 30 minutes, the silicone foam oxygen barrier outer layer only shows slight surface discoloration. There is no melting dripping when burned vertically, the limiting oxygen index is 37%, and the char length determined based on the flammability test of GB / T5455-2014 is 37mm. Example 4

[0040] A flame-retardant car cover fabric with a three-layer composite structure, consisting of a silicone foam oxygen-barrier outer layer, a glass fiber middle layer, and a pre-oxidized fiber inner layer, from the outside to the inside.

[0041] (1) Preparation of glass fiber interlayer: Alkali-free glass fibers with a monofilament diameter of 12μm are woven into plain or twill fabrics with a basis weight of 300g / m². They are then immersed in an ethanol solution of 3wt% silane coupling agent KH550 for 10 minutes and dried at 75℃ for later use, which is the glass fiber interlayer.

[0042] (2) Preparation of the pre-oxidized fiber inner layer: Polyacrylonitrile fibers are pre-oxidized to obtain polyacrylonitrile-based pre-oxidized fibers with a pre-oxidation degree of 70% and a fiber diameter of 15μm. Then, the polyacrylonitrile-based pre-oxidized fibers are woven into twill fabric with a weight of 400g / m², which is the inner layer of the pre-oxidized fibers. The pre-oxidation process for polyacrylonitrile fibers employs a stepped temperature increase: a. From room temperature to 100℃, control the heating rate to 1℃ / min, stabilize for 25min, and remove moisture from the fiber surface; b. From 100℃ to 200℃, control the heating rate at 0.6℃ / min. This stage is the initial stage of the cyclization reaction. c. From 200℃ to 250℃, control the heating rate at 0.3℃ / min. This stage is the core cyclization and cross-linking stage. d. Maintain a constant temperature of 250℃ for 120 minutes to ensure that the degree of pre-oxidation is controlled at 70%. Ensure that the surrounding oxygen is evenly diffused during the production process. Apply stretching during the pre-oxidation process with a stretching rate of 3%.

[0043] (3) Preparation of silicone foam oxygen-barrier outer layer slurry: Coating preparation: Mix 40 parts of methyl silicone rubber, 50 parts of methyl vinyl silicone rubber, 5 parts of silane-modified azo compound, 8 parts of hydrogen-containing silicone oil, 0.1 parts of platinum catalyst, 10 parts of nano aluminum hydroxide, and 5 parts of zinc borate in a certain proportion, and disperse them evenly by high-speed stirring to form a coatable paste or liquid slurry.

[0044] (4) Three-layer composite molding: First, the glass fiber interlayer and the pre-oxidized fiber inner layer are pre-bonded using a low-melting-point silicone resin adhesive. The softening point of the low-melting-point silicone resin adhesive is 120℃, and the application amount is 5g / m². 2 The double-layer film is obtained by pre-pressing at 80℃ for 3 minutes. The silicone foam oxygen barrier slurry prepared in step (3) is uniformly coated on the surface of the glass fiber intermediate layer of the double-layer film by scraping, roller coating or spraying process. The wet film thickness is controlled at 0.3 mm. The coated fabric is treated by step heating oven, pre-drying at 85℃ for 9 minutes to remove solvent, cross-linking and curing at 200℃ for 32 minutes to form elastomer, and high-temperature foaming at 360℃ for 3 minutes to trigger expansion and carbonization, forming a stable silicone foam oxygen barrier outer layer, and obtaining a three-layer composite fabric.

[0045] The three-layer composite flame-retardant car cover fabric prepared in this embodiment has a tensile strength of 2480N, a tear strength of 136N, and after being exposed to an 800℃ flame for 30 minutes, the silicone foam oxygen barrier outer layer only shows slight surface discoloration. There is no melting dripping when burned vertically, the limiting oxygen index is 41%, and the char length determined based on the flammability test of GB / T5455-2014 is 30mm.

[0046] This invention is not limited to the above-described embodiments. Anyone should know that any structural changes made under the guidance of this invention, and any technical solutions that are the same as or similar to this invention, fall within the protection scope of this invention.

[0047] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. A three-layer composite flame-retardant car cover fabric, characterized in that, From the outside in, the layers are: a silicone foam oxygen barrier outer layer, a glass fiber intermediate layer, and a pre-oxidized fiber inner layer. The glass fiber intermediate layer and the pre-oxidized fiber inner layer are bonded together by hot pressing. The silicone foam oxygen barrier outer layer is formed by coating the glass fiber intermediate layer to form a wet film and then curing and foaming. The components of the silicone foam oxygen barrier outer layer, by weight, include: 90-120 parts of silicone rubber, 5-15 parts of foaming agent, 3-8 parts of crosslinking agent, 0.1-0.5 parts of catalyst, and 10-20 parts of functional filler. The wet film thickness of the silicone foam oxygen barrier outer layer is controlled at 0.1-0.3 mm. The glass fiber interlayer is made of alkali-free glass fiber woven into plain or twill fabric, and the fiber surface is treated with silane coupling agent. The inner layer of the pre-oxidized fiber is made of polyacrylonitrile-based pre-oxidized fiber in a twill weave.

2. The flame-retardant car cover fabric with a three-layer composite structure as described in claim 1, characterized in that, The silicone rubber is one or a mixture of several of methyl silicone rubber, methyl vinyl silicone rubber, and methyl phenyl silicone rubber.

3. The flame-retardant car cover fabric with a three-layer composite structure as described in claim 1, characterized in that, The foaming agent is an organosilicon foaming agent or an inorganic high-temperature foaming agent. The organosilicon foaming agent is a silane-modified azo compound, and the inorganic high-temperature foaming agent is sodium bicarbonate. The crosslinking agent is hydrogen-containing silicone oil, the catalyst is a platinum catalyst, and the functional filler is one or a mixture of several of nano-aluminum hydroxide, nano-silica, and zinc borate.

4. The flame-retardant car cover fabric with a three-layer composite structure as described in claim 3, characterized in that, The silane-modified azo compound is formed by modifying the cyano group in the azobisisobutyronitrile molecule with a siloxane group.

5. The flame-retardant car cover fabric with a three-layer composite structure as described in claim 1, characterized in that, The alkali-free glass fiber monofilament has a diameter of 5-15μm, and the woven plain or twill fabric has a basis weight of 100-300g / m². The silane coupling agent is KH550.

6. The flame-retardant car cover fabric with a three-layer composite structure as described in claim 1, characterized in that, The pre-oxidation degree of the polyacrylonitrile-based pre-oxidized fiber is 60%-80%, the fiber diameter is 10-20μm, and the weight after twill weaving is 150-400g / m².

7. The method for preparing the three-layer composite flame-retardant car cover fabric as described in any one of claims 1-6, characterized in that, Includes the following steps: (1) Preparation of glass fiber interlayer: Alkali-free glass fibers are woven into plain or twill fabrics, then immersed in an ethanol solution of silane coupling agent for 10 minutes, and dried at 70-80℃ for later use, which is the glass fiber interlayer. (2) Preparation of the pre-oxidized fiber inner layer: Polyacrylonitrile fibers are pre-oxidized to obtain polyacrylonitrile-based pre-oxidized fibers, with the degree of pre-oxidation controlled at 60-80%. The polyacrylonitrile-based pre-oxidized fibers are then woven into twill fabric, which is the inner layer of the pre-oxidized fibers. (3) Preparation of silicone foam oxygen-barrier outer layer slurry: The silicone rubber, foaming agent, crosslinking agent, catalyst, and functional filler are mixed in proportion and dispersed evenly by high-speed stirring to form a coatable paste or liquid slurry. (4) Three-layer composite molding: First, the glass fiber intermediate layer and the pre-oxidized fiber inner layer are pre-bonded with low melting point silicone resin adhesive, and pre-pressed at 80°C for 3 minutes to obtain a double-layer film. The silicone foam oxygen barrier slurry prepared in step (3) is uniformly coated on the surface of the glass fiber intermediate layer of the double-layer film using a scraping, roller coating or spraying process. The wet film thickness is controlled at 0.1-0.3 mm. The coated fabric is treated by a stepped heating oven to form a stable silicone foam oxygen barrier outer layer, and a three-layer composite fabric is obtained.

8. The method for preparing the three-layer composite flame-retardant car cover fabric as described in claim 7, characterized in that, The ethanol solution of the silane coupling agent in step (1) has a mass concentration of 1-3%.

9. The method for preparing the flame-retardant car cover fabric with a three-layer composite structure as described in claim 7, characterized in that, In step (2), the pre-oxidation process of polyacrylonitrile fiber adopts a stepped heating method: a. Bring the temperature from room temperature to 100℃, control the heating rate to 1-2℃ / min, stabilize for 10-30min, and remove moisture from the fiber surface; b. From 100℃ to 200℃, control the heating rate at 0.5-1℃ / min. This stage is the initial stage of the cyclization reaction. c. From 200℃ to 250-300℃, control the heating rate at 0.3-0.5℃ / min. This stage is the core cyclization and cross-linking stage. d. Maintain a constant temperature of 250-300℃ for 60-120 minutes to ensure that the degree of pre-oxidation is controlled at 60%-80%. Ensure that the surrounding oxygen is evenly diffused during the production process. Apply stretching during the pre-oxidation process with a stretching rate of 1%-3%.

10. The method for preparing the three-layer composite flame-retardant car cover fabric as described in claim 7, characterized in that, In step (4), the softening point of the low-melting-point silicone resin adhesive is 120℃, and the coating amount is 5g / m². 2 The stepped heating oven process is as follows: pre-drying at 80-90℃ for 8-10 minutes to remove solvent, cross-linking and curing at 190-200℃ for 30-35 minutes to form an elastomer, and high-temperature foaming at 350-360℃ for 2-5 minutes to trigger expansion and carbonization, forming a stable silicone foam oxygen barrier layer.