Foamed cotton with high flame retardance and preparation method thereof

Abstract

The invention relates to the field of foamed cotton materials, and particularly discloses high-flame-retardance foamed cotton and a preparation method thereof. The foamed cotton with high flame retardance is prepared from the following raw materials in percentage by mass: 10 to 30 percent of alpha, omega-dihydroxy polysiloxane, 5 to 10 percent of vinyl silicone oil, 1 to 10 percent of hydrogen-containing silicone oil and 50 to 70 percent of flame retardant; the flame retardant comprises flame-retardant microspheres and layered filler in a mass ratio of 1: (1.3-2.3). The high-flame-retardance foamed cotton can be used for heat insulation between battery cells, has excellent flame retardance and heat insulation performance and good flexibility and is environmentally friendly.

Description

Technical Field

[0001] The present application relates to the field of foamed cotton materials, and more specifically, to a highly flame-retardant foamed cotton and a preparation method thereof. Background Art

[0002] In the rapidly developing field of electronic materials, especially in the assembly and encapsulation processes involved in the preparation process of lithium-ion batteries, efficient and safe thermal insulation materials play a crucial role. Thermal insulation between battery cells can not only effectively prevent the battery from catching fire and causing a fire in case of overheating or short circuit, improve the safety and stability of the battery, but also optimize the heat dissipation performance of the battery pack and extend the service life of the battery. As a lightweight, environmentally friendly, highly elastic and easy-to-process cushioning material, foamed cotton has become an ideal choice in the field of battery cell thermal insulation materials.

[0003] However, traditional foamed cotton materials usually have high flammability. When in high-temperature thermal runaway or in contact with an external fire source, they are prone to rapid combustion and release toxic smoke, which will not only accelerate the damage of the battery pack, but also pose a serious threat to personal safety.

[0004] In view of the above related technologies, the inventors found that most of the foamed cotton electronic materials on the market currently improve the flame retardancy of foamed cotton by adding flame retardants. For example, using halogen-based, phosphorus-based or nitrogen-based flame retardants to modify foamed cotton, although this can improve its flame retardancy level to a certain extent, these inorganic fillers often reduce the physical properties of foamed cotton materials, such as mechanical properties like flexibility and compression resilience, and even cause environmental pollution.

[0005] Therefore, how to improve the flame retardancy of foamed cotton without sacrificing its physical properties and environmental friendliness, so that it can provide a reliable thermal insulation barrier between battery cells, has become an urgent technical problem to be solved in the current field of electronic materials. Summary of the Invention

[0006] In order to improve the flame retardancy of foamed cotton and enable it to provide a reliable thermal insulation barrier between battery cells, the present application provides a highly flame-retardant foamed cotton and a preparation method thereof.

[0007] In the first aspect, the present application provides a highly flame-retardant foamed cotton, adopting the following technical solution: A highly flame-retardant foamed cotton, calculated by mass percentage, the raw materials include 10-30% of α,ω-dihydroxypolysiloxane, 5-10% of vinyl silicone oil, 1-10% of hydrogen-containing silicone oil and 50-70% of flame retardant; The flame retardant includes flame-retardant microspheres and layered fillers with a mass ratio of 1:(1.3-2.3).

[0008] By adopting the above technical solution, the spherical flame-retardant microspheres and the lamellar layered fillers can cooperate with each other and interweave in the foamed cotton matrix to form a three-dimensional flame-retardant system with the flame-retardant microspheres as the core.

[0009] This three-dimensional flame-retardant system can enable the flame-retardant microspheres to be orderly and evenly dispersed in the pores and channels of the complex spatial structure, which plays a lubricating role for the flame-retardant microspheres, significantly reducing the agglomeration phenomenon of the flame-retardant microspheres in the foamed cotton. At the same time, it provides effective physical protection for the flame-retardant microspheres, preventing the "popcorn" effect caused by the thermal expansion of the flame-retardant microspheres at high temperatures and ensuring the effective release of the flame retardant.

[0010] The lamellar layered fillers have a large specific surface area, and the complex and circuitous structure formed inside the foamed cotton can form a physical barrier inside the foamed cotton matrix, slowing down the penetration speed of heat and flame and significantly improving the heat insulation effect of the foamed cotton.

[0011] When encountering a flame, these layered structure fillers can expand to form a thicker and stable carbon layer, creating a more difficult obstacle for the propagation of oxygen and heat and prolonging the resistance time of the material in the flame. The flame-retardant microspheres can stably and effectively release the flame-retardant components in the carbon layer, ensuring the flame-retardant effect of the foamed cotton.

[0012] In addition, the addition of the layered fillers can form physical cross-linking points in the foamed cotton matrix, disperse stress, reduce the brittleness of the material, and effectively reduce the negative impact of the flame-retardant microspheres on the flexibility of the foamed cotton. When the foamed cotton is compressed, these physical cross-linking points can provide additional support, reduce the permanent deformation of the material, and enable the foamed cotton to maintain good compression resilience.

[0013] Optionally, the layered filler includes montmorillonite and expandable graphite with a mass ratio of 1:(1.5 - 3.5).

[0014] By adopting the above technical solution, both expandable graphite and montmorillonite have excellent flame-retardant effects. The lamellar structures of montmorillonite and expandable graphite can be evenly dispersed in the matrix of the foamed cotton during the foaming process. These lamellar structures significantly enhance the strength of the cell walls, making the cell walls of the foamed cotton not easily broken when subjected to external compression, thus maintaining good compression resilience.

[0015] Expandable graphite is an intercalation compound material formed by inserting acids, bases, or strongly oxidizing compounds into the interlayers of flake graphite as a carrier through an intercalation reaction. After heating, the interlayer compound begins to decompose and expand, generating a thrust along the c-axis direction of the graphite layer. Under the action of this thrust, the graphite intercalation compound can rapidly expand along the c-axis direction at the initial stage of combustion to form worm-like graphite, covering the surface of the foamed cotton to form a protective layer, and achieving the functions of blocking heat transfer, reducing the pyrolysis rate, isolating the fire source, and delaying or interrupting the spread of fire through the condensed-phase combustion mechanism.

[0016] Montmorillonite has a lamellar structure composed of two layers of silicon-oxygen tetrahedrons sandwiching a layer of aluminum-oxygen octahedrons, and it is a layered silicate clay mineral with excellent char-forming properties. The surface of montmorillonite is rich in hydrophilic groups, while expandable graphite has hydrophobicity. When the two are mixed, the hydrophobic property of expandable graphite can partially neutralize the hydrophilicity of montmorillonite, effectively balancing the compatibility problem between montmorillonite and the polymer matrix. Under this complementarity, a composite interface can be formed between montmorillonite and expandable graphite, which is more balanced in hydrophilic and hydrophobic properties, significantly improving the interaction between the layered filler and the polymer matrix, and forming a stable dispersion system in the foamed cotton matrix.

[0017] Under high-temperature conditions, expandable graphite will expand, and this expansion behavior can promote the mechanical locking between montmorillonite and the foamed cotton matrix, significantly enhancing the thermal barrier system established by the layered filler inside the foamed cotton, and significantly improving the heat insulation and flame retardant effects of the foamed cotton.

[0018] Optionally, the flame retardant microspheres are microcapsule structures with a core material wrapped by a wall material. By weight, the raw materials of the flame retardant microspheres include 12-21 parts of aluminum hypophosphite, 15-25 parts of phenyltrimethylsilane, 5-7 parts of hexamethyldisiloxane, and 2.5-4.5 parts of a crosslinking agent.

[0019] By adopting the above technical solution, aluminum hypophosphite contains a high amount of phosphorus and is an environmentally friendly halogen-free and non-toxic flame retardant, which can decompose to produce phosphoric acid during the combustion process, quickly promoting the formation of a carbon layer.

[0020] Using phenyltrimethylsilane and hexamethyldisiloxane as the wall materials of the flame retardant microspheres can prepare a hydrophobic microcapsule structure, which helps to improve the compatibility between the flame retardant microspheres and the silicon-based foamed cotton matrix, helps the flame retardant microspheres to better adapt to the flow and deformation of the substrate in the silicone rubber substrate, reduces the interfacial tension caused by the rigidity of the wall material, and thus improves the flexibility of the foamed cotton.

[0021] Optionally, the preparation method of the flame retardant microspheres includes the following steps: S1: Add aluminum hypophosphite to a solvent for dissolution to form a core material solution; S2: Add phenyltrimethylsilane and hexamethyldisiloxane to a solvent for dissolution, and stir evenly to form a wall material solution; S3: Add the core material solution to the wall material solution, ultrasonically stir for 30-60 min, then add a crosslinking agent, and continue ultrasonic treatment for 30-60 min to obtain a homogeneous emulsion; S4: Spray-dry and coagulate the homogeneous emulsion to form microcapsule structure particles, then heat to cure the inside of the microcapsule structure particles, and then grind and pass through a 150-200 mesh sieve to obtain the product.

[0022] Optionally, the flame retardant further includes zinc borate, and the mass of the zinc borate is 15-25% of the mass of the flame retardant microspheres.

[0023] By adopting the above technical solution, zinc borate has good smoke suppression and thermal stability. ZB can release crystal water at high temperature and form a viscous boric acid melt to delay the combustion process of the material and reduce the smoke release rate. While aluminum hypophosphite as the flame retardant microspheres of the core material will generate PH 3 , PH 3 is extremely easy to react with oxygen in the air to generate PO 2 · and PO· and other free radicals. These free radicals can capture H· and OH·, inhibit the progress of combustion, and play a role in gas-phase flame retardancy.

[0024] Under the flame retardant system formed by zinc borate and flame retardant microspheres, zinc borate reduces the combustion rate by forming a protective layer and releasing crystal water, and aluminum hypophosphite generates phosphate radicals to capture free radicals during the combustion process, further promoting the role of inhibiting combustion in the gas phase.

[0025] Optionally, the viscosity of the vinyl silicone oil at 25°C is 5000-8000 mPa·s.

[0026] Optionally, the hydrogen content of the hydrogen-containing silicone oil is 1.5-1.6 wt%.

[0027] In a second aspect, the present application provides a method for preparing a highly flame-retardant foam sponge, adopting the following technical solution: A method for preparing a highly flame-retardant foam sponge includes the following steps: S1: Prepare flame retardant microspheres, and mix montmorillonite and expandable graphite to form a layered filler; S2: Stir and mix α,ω-dihydroxy polysiloxane, vinyl silicone oil, flame retardant microspheres and the layered filler evenly to obtain a blend A; S3: Add hydrogen-containing silicone oil to the blend A, and quickly stir and mix evenly to obtain a blend B; S4: Add the blend B into a mold, let it stand for 20-30 min, and then start vulcanization and foaming. After 1-3 h of vulcanization and foaming molding, the product is obtained.

[0028] By adopting the above technical solution, using α,ω-dihydroxy polysiloxane and vinyl silicone oil as the base polymers, and hydrogen-containing silicone oil as the crosslinking agent and foaming agent for addition vulcanization and condensation foaming reactions to generate hydrogen, the prepared silicone rubber material has a uniform cell structure and strength, can effectively reduce by-products during the reaction, make the entire reaction time controllable and does not require secondary vulcanization heat treatment, and is environmentally friendly and pollution-free.

[0029] The process conditions of this application enable the prepared foamed silica gel to have uniform cell structure and good toughness, effectively avoiding the phenomenon of non-uniform cell sizes during multiple foaming processes.

[0030] Optionally, the following pretreatment is carried out before the montmorillonite and expandable graphite are mixed: Dissolve chitosan in water to form a solution; Add montmorillonite to the chitosan solution, heat to 60 - 70 °C, stir ultrasonically for 12 - 16 h, and obtain modified montmorillonite after drying and crushing.

[0031] By adopting the above technical solution, chitosan is used to modify the surface of montmorillonite. The hydrophobic groups in the chitosan molecule can interact with the hydrophilic groups on the surface of montmorillonite, reducing the hydrophilicity of the montmorillonite surface. At the same time, the chitosan molecules cover the surface of montmorillonite, reducing the exposure of hydrophilic groups such as hydroxyl groups on the montmorillonite surface, further reducing its hydrophilicity, and thus further enhancing the compatibility between montmorillonite and the foamed cotton matrix, enabling the flame retardant to be more evenly dispersed in the foamed cotton, and thus more effectively exerting its flame retardant effect.

[0032] The improved dispersibility of montmorillonite promotes the more uniform dispersion of other raw materials in the foamed cotton, which helps to form a denser cell structure, improve the density of the foamed cotton, and optimize the mechanical properties of the foamed cotton.

[0033] In summary, this application has the following beneficial effects: 1. This application uses spherical flame retardant microspheres and lamellar layered fillers as flame retardants. The two different structural types of flame retardant fillers cooperate with each other to form a three-dimensional flame retardant system with flame retardant microspheres as the core in the foamed cotton matrix, effectively enhancing the compatibility between the flame retardant and the silicone foamed matrix. This helps to form a stable and effective physical barrier system inside the foamed cotton matrix, significantly improving the heat insulation and flame retardant effects of the foamed cotton.

[0034] 2. The addition of the layered filler can form physical cross-linking points in the matrix of the foamed cotton, effectively dispersing the brittleness of the material. At the same time, it provides additional support for the foamed cotton when it is compressed, effectively ensuring that the foamed cotton maintains good flexibility and compression resilience.

[0035] 3. Using montmorillonite and expandable graphite as the layered filler, the hydrophobic property of expandable graphite can partially neutralize the hydrophilicity of montmorillonite, effectively balancing the influence of the poor compatibility between montmorillonite and the polymer matrix on the flame retardant performance of the layered filler, and helping to enhance the thermal barrier system established by the layered filler inside the foamed cotton, improving the heat insulation and flame retardant effects of the foamed cotton.

[0036] 4. The lamellar structures of montmorillonite and expandable graphite can form mechanical locking with each other and can be evenly dispersed in the matrix of the foamed cotton during the foaming process. These layered structures significantly enhance the strength of the cell walls, making the cell walls of the foamed cotton not easily broken when the foamed cotton is compressed by an external force, thus maintaining good compression resilience. Detailed implementation manners

[0037] The following examples further illustrate the present application in detail.

[0038] Raw materials Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available products, specifically: α,ω-dihydroxy polydimethylsiloxane, selected from Shouyue Chemical Technology, 107 silicone rubber GXJ007; Vinyl silicone oil, with a viscosity of 5000 - 8000 mPa·s at 25°C, selected from Zhonglianbang, CN-186; Hydrogen-containing silicone oil, with a hydrogen content of 1.5 - 1.6%, selected from Jipeng Silicon Fluoride Materials Co., Ltd., JP-202; Expandable graphite, selected from Qingdao Yanhai Carbon Materials Co., Ltd., EG-E300; Montmorillonite, selected from Xinhongli Chemical Industry, XHL0484; Aluminum hypophosphite, selected from Lianxiong Fine Chemicals, LXF-7784; Phenyltrimethylsilane, selected from Alpha, CAS768-32-1; Hexamethyldisiloxane, selected from Canos Technology, 8598479; Crosslinking agent, selected from Bosheng Chemical Industry, KH-602; Zinc borate, selected from Juepai Chemical Industry, ZR-001.

[0039] Preparation example of flame retardant microspheres Preparation example 1 The flame retardant microspheres have a microcapsule structure with a core material wrapped by a wall material. The raw materials and their dosages are shown in Table 1, where the crosslinking agent is the silane coupling agent KH-602.

[0040] Table 1 The preparation method of the above-mentioned flame retardant microspheres includes the following steps: S1: Under the condition of pH 5 - 6, mix aluminum hypophosphite with an aqueous solution at a material-liquid ratio of 1:3 and stir at 500 r / min for 15 min to form a core material solution; S2: Mix phenyltrimethylsilane and hexamethyldisiloxane, and mix them with 60% ethanol solution according to a material ratio of 1:4 for dissolution. Stir at 500 r / min for 10 min to form a wall material solution; S3: Add the core material solution to the wall material solution, ultrasonically stir for 30 min, then add a crosslinking agent, and continue ultrasonic treatment for 60 min to obtain a homogeneous emulsion; S4: Spray-dry and coagulate the homogeneous emulsion to form microcapsule-structured particles, then heat and dry them at 80 °C to cure the inside of the microcapsule-structured particles, and then grind them and pass through a 150-mesh sieve to obtain the product.

[0041] Preparation Example 2 Flame-retardant microspheres, different from Preparation Example 1 in that the raw materials and dosages are as shown in Table 1. Its preparation method includes the following steps: S1: Under the condition of pH 5-6, mix aluminum hypophosphite with an aqueous solution according to a material ratio of 1:3, and stir at 500 r / min for 15 min to form a core material solution; S2: Mix phenyltrimethylsilane and hexamethyldisiloxane, and mix them with 60% ethanol solution according to a material ratio of 1:4 for dissolution. Stir at 500 r / min for 10 min to form a wall material solution; S3: Add the core material solution to the wall material solution, ultrasonically stir for 45 min, then add a crosslinking agent, and continue ultrasonic treatment for 30 min to obtain a homogeneous emulsion; S4: Spray-dry and coagulate the homogeneous emulsion to form microcapsule-structured particles, then heat and dry them at 80 °C to cure the inside of the microcapsule-structured particles, and then grind them and pass through a 150-mesh sieve to obtain the product.

[0042] Preparation Example 3 Flame-retardant microspheres, different from Preparation Example 1 in that the raw materials and dosages are as shown in Table 1. Its preparation method includes the following steps: S1: Under the condition of pH 5-6, mix aluminum hypophosphite with an aqueous solution according to a material ratio of 1:3, and stir at 500 r / min for 15 min to form a core material solution; S2: Mix phenyltrimethylsilane and hexamethyldisiloxane, and mix them with 60% ethanol solution according to a material ratio of 1:4 for dissolution. Stir at 500 r / min for 10 min to form a wall material solution; S3: Add the core material solution to the wall material solution, ultrasonically stir for 60 min, then add a crosslinking agent, and continue ultrasonic treatment for 40 min to obtain a homogeneous emulsion; S4: Spray-dry and coagulate the homogeneous emulsion to form microcapsule-structured particles, then heat and dry them at 80 °C to cure the inside of the microcapsule-structured particles, and then grind them and pass through a 200-mesh sieve to obtain the product. Example

[0043] Example 1 A highly flame-retardant foamed cotton, the raw materials and their dosages are shown in Table 2. The flame retardant is flame-retardant microspheres and layered fillers with a mass ratio of 1:1.5. The flame-retardant microspheres are obtained from Preparation Example 1, and the layered filler is expandable graphite of montmorillonite with a mass ratio of 1:2; the vinyl silicone oil is a vinyl silicone oil with a viscosity of 5000 mPa·s at 25°C; the hydrogen content of the hydrogen-containing silicone oil is 1.5%.

[0044] Table 2 Component Example 1 Example 2 Example 3 Example 4 α,ω-dihydroxypolysiloxane / % 24 10 30 30 Vinyl silicone oil / % 5 10 10 6 Hydrogen-containing silicone oil / % 1 10 10 4 Flame retardant / % 70 70 50 60 The preparation method of the above-mentioned highly flame-retardant foamed cotton includes the following steps: S1: Mix montmorillonite and expandable graphite to form a layered filler; S2: Stir and mix α,ω-dihydroxypolysiloxane, vinyl silicone oil, flame-retardant microspheres and the layered filler evenly to obtain a blend A; S3: Add hydrogen-containing silicone oil to blend A and stir and mix evenly quickly to obtain blend B; S4: Add blend B to a mold, let it stand for 20 min, and then start vulcanization and foaming. After 3 h of vulcanization and foaming, the formed product is obtained.

[0045] Example 2 A highly flame-retardant foamed cotton, different from Example 1 in that the raw materials and their dosages are shown in Table 1. The flame retardant is flame-retardant microspheres and layered fillers with a mass ratio of 1:1.3; the vinyl silicone oil is a vinyl silicone oil with a viscosity of 6000 mPa·s at 25°C; the hydrogen content of the hydrogen-containing silicone oil is 1.6%; The preparation method of the above-mentioned highly flame-retardant foamed cotton includes the following steps: S1: Mix montmorillonite and expandable graphite to form a layered filler; S2: Stir and mix α,ω-dihydroxypolysiloxane, vinyl silicone oil, flame-retardant microspheres and the layered filler evenly to obtain a blend A; S3: Add hydrogen-containing silicone oil to blend A and stir and mix evenly quickly to obtain blend B; S4: Add blend B to a mold, let it stand for 30 min, and then start vulcanization and foaming. After 2 h of vulcanization and foaming, the formed product is obtained.

[0046] Example 3 A highly flame-retardant foamed cotton, different from Example 1 in that the raw materials and their dosages are shown in Table 1. The flame retardant is flame-retardant microspheres and layered fillers with a mass ratio of 1:1.8; the vinyl silicone oil is a vinyl silicone oil with a viscosity of 8000 mPa·s at 25°C; The preparation method of the above-mentioned highly flame-retardant foamed cotton includes the following steps: S1: Mix montmorillonite and expandable graphite to form a layered filler; S2: Stir and mix α,ω-dihydroxypolysiloxane, vinyl silicone oil, flame retardant microspheres and the layered filler evenly to obtain blend A; S3: Add hydrogen-containing silicone oil to blend A and quickly stir and mix evenly to obtain blend B; S4: Add blend B into a mold, let it stand for 30 min and then start vulcanization and foaming. After 1 h of vulcanization and foaming molding, it is obtained.

[0047] Example 4 A highly flame-retardant foamed cotton, different from Example 1 in that the raw materials and their dosages are shown in Table 1, wherein the flame retardant is flame retardant microspheres and layered filler with a mass ratio of 1:2.3, and other steps are the same as those in Example 1.

[0048] Example 5 A highly flame-retardant foamed cotton, different from Example 1 in that the flame retardant microspheres in the raw material flame retardant are obtained from Preparation Example 2, and other steps are the same as those in Example 1.

[0049] Example 6 A highly flame-retardant foamed cotton, different from Example 1 in that the flame retardant microspheres in the raw material flame retardant are obtained from Preparation Example 3, and other steps are the same as those in Example 1.

[0050] Example 7 A highly flame-retardant foamed cotton, different from Example 1 in that the layered filler in the raw material is montmorillonite and expandable graphite with a mass ratio of 1:1.5, and other steps are the same as those in Example 1.

[0051] Example 8 A highly flame-retardant foamed cotton, different from Example 1 in that the layered filler in the raw material flame retardant is montmorillonite and expandable graphite with a mass ratio of 1:3.5, and other steps are the same as those in Example 1.

[0052] Example 9 A highly flame-retardant foamed cotton, different from Example 1 in that the layered filler in the raw material flame retardant is only montmorillonite and expandable graphite is not added, and other steps are the same as those in Example 1.

[0053] Example 10 A highly flame-retardant foamed cotton, different from Example 1 in that the layered filler in the raw material flame retardant is only expandable graphite and montmorillonite is not added, and other steps are the same as those in Example 1.

[0054] Example 11 A highly flame-retardant foamed cotton, which is different from Example 1 in that the flame retardant in the raw materials is flame-retardant microspheres, layered fillers and zinc borate with a mass ratio of 1:1.5:0.15, and other steps are the same as those in Example 1.

[0055] Example 12 A highly flame-retardant foamed cotton, which is different from Example 1 in that the flame retardant in the raw materials is flame-retardant microspheres, layered fillers and zinc borate with a mass ratio of 1:1.5:0.25, and other steps are the same as those in Example 1.

[0056] Example 13 A highly flame-retardant foamed cotton, which is different from Example 1 in that montmorillonite is pretreated as follows before being mixed with expandable graphite to form layered fillers: Chitosan is mixed and dissolved in water according to a solid-liquid ratio of 1:5 to form a solution; Montmorillonite is added to the chitosan solution, heated to 60 °C, ultrasonically stirred for 16 h, dried and crushed to obtain modified montmorillonite; other steps are the same as those in Example 1.

[0057] Example 14 A highly flame-retardant foamed cotton, which is different from Example 1 in that montmorillonite is pretreated as follows before being mixed with expandable graphite to form layered fillers: Chitosan is mixed and dissolved in water according to a solid-liquid ratio of 1:5 to form a solution; Montmorillonite is added to the chitosan solution, heated to 70 °C, ultrasonically stirred for 12 h, dried and crushed to obtain modified montmorillonite; other steps are the same as those in Example 1.

[0058] Example 15 A highly flame-retardant foamed cotton, which is different from Example 14 in that the flame retardant in the raw materials is flame-retardant microspheres, layered fillers and zinc borate with a mass ratio of 1:1.5:0.25, and other steps are the same as those in Example 14.

[0059] Comparative example Comparative example 1 A highly flame-retardant foamed cotton, which is different from Example 1 in that the flame retardant in the raw materials is only flame-retardant microspheres, and other steps are the same as those in Example 1.

[0060] Comparative example 2 A highly flame-retardant foamed cotton, which is different from Example 1 in that the flame retardant in the raw materials is only layered fillers, and other steps are the same as those in Example 1.

[0061] Comparative example 3 A highly flame-retardant foamed cotton, which is different from Example 1 in that the flame retardant in the raw materials is aluminum hypophosphite, and other steps are the same as those in Example 1.

[0062] Performance detection test Performance detection tests related to flame retardancy, heat insulation and mechanical properties were carried out on a highly flame-retardant foam obtained from Examples 1-15 and Comparative Examples 1-3. Each test was carried out 3 times, and the average value of the 3 test result data was taken as the final result and recorded in Table 3.

[0063] 1. Flame retardancy: Referring to GB / T 2406-1993, the limiting oxygen index (LOI) of the highly flame-retardant foam of Examples 1-15 and Comparative Examples 1-3 was tested; Referring to UL94-2013, the flame retardant grade of the highly flame-retardant foam of Examples 1-15 and Comparative Examples 1-3 was tested; Referring to ISO 5660-1, using a cone calorimeter at an irradiation intensity of 35 kW / m 2 conditions, the combustion behavior was recorded and tested.

[0064] 2. Compression resilience: Referring to GB / T 18944.1-2003, the compression set of the highly flame-retardant foam of Examples 1-15 and Comparative Examples 1-3 was tested.

[0065] 3. Tensile strength: Referring to GB / T 6344-2008, the tensile strength of the highly flame-retardant foam of Examples 1-15 and Comparative Examples 1-3 was tested.

[0066] Table 3 It can be seen from the performance detection results of the examples and Comparative Examples 1-3 in Table 3 that the flame retardant grades of the highly flame-retardant foam prepared by using spherical flame retardant microspheres and lamellar fillers as flame retardants in this application all reach UL94V-0, the limiting oxygen index is ≥32.4%, the compression set is 3.1-3.8%, and the tensile strength is 0.51-0.64 MPa. This shows that a highly flame-retardant foam of this application has excellent heat insulation and flame retardant properties, and at the same time has good physical properties, and can provide a reliable heat insulation barrier between the battery cells.

[0067] It can be seen from the performance detection results of Examples 1-10 and Comparative Examples 1-2 that the spherical flame retardant microspheres and lamellar fillers cooperate with each other and interweave in the foam matrix to form a three-dimensional flame retardant system with flame retardant microspheres as the core. When encountering a flame, a stable and firm carbon layer is formed inside the foam, causing more difficult obstacles to the transmission of oxygen and heat, and effectively extending the resistance time of the material in the flame.

[0068] The complex spatial structure formed between the layered filler and the flame retardant microspheres enables the flame retardant microspheres to be dispersed orderly and uniformly in various pores and channels, significantly reducing the agglomeration of the flame retardant microspheres in the foamed cotton matrix, so that the flame retardant microspheres can stably and effectively release the flame retardant components in the carbon layer, ensuring the flame retardant effect of the foamed cotton. At the same time, the addition of the layered filler effectively disperses the brittleness of the material, provides additional support for the foamed cotton when it is compressed, and enables the foamed cotton to maintain good flexibility and compression resilience.

[0069] The mixture of montmorillonite and expandable graphite as the layered filler can effectively improve the hydrophobicity of the layered filler, thereby enhancing the compatibility between the layered filler and the foamed cotton matrix, and thus improving the heat insulation and flame retardant effect of the thermal barrier system established by the layered filler inside the foamed cotton.

[0070] According to the performance test results of Examples 1-8 and Examples 11-15, it can be seen that the addition of zinc borate significantly improves the flame retardancy and smoke suppression of the foamed cotton, and promotes the role of the foamed cotton in suppressing combustion in the gas phase.

[0071] Using chitosan to pretreat and coat the montmorillonite further reduces the influence of the hydrophilicity of the montmorillonite surface on its compatibility with the silicon matrix, enables the flame retardant to be more evenly dispersed in the foamed cotton, thus more effectively exerting its flame retardant effect, and at the same time improves the density of the foamed cotton and further optimizes the mechanical properties of the foamed cotton.

[0072] This specific embodiment is only an interpretation of the present application, and it is not a limitation of the present application. Those skilled in the art can make modifications without creative contributions to this embodiment according to needs after reading this specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A highly flame retardant foam, characterized in that: According to the percentage by mass, the raw materials include 10-30% of α,ω-dihydroxy polysiloxane, 5-10% of vinyl silicone oil, 1-10% of hydrogenated silicone oil and 50-70% of flame retardant; The flame retardant comprises flame retardant microspheres and layered fillers in a mass ratio of 1:(1.3-2.3).

2. The highly flame retardant foamed cotton according to claim 1, characterized in that: The layered filler comprises montmorillonite and expandable graphite in a mass ratio of 1:(1.5-3.5).

3. The highly flame retardant foamed cotton according to claim 1, characterized in that: The flame retardant microspheres are microcapsule structures in which the core material is wrapped by the wall material. The raw materials of the flame retardant microspheres include 12-21 parts of aluminum hypophosphite, 15-25 parts of phenyltrimethylsilane, 5-7 parts of hexamethyldisiloxane and 2.5-4.5 parts of a crosslinking agent in parts by weight.

4. The highly flame retardant foamed cotton according to claim 3, characterized in that: The method for preparing the flame retardant microspheres comprises the following steps: S1: adding aluminum hypophosphite into a solvent to dissolve it to form a core material solution; S2: adding phenyltrimethylsilane and hexamethyldisiloxane into a solvent to dissolve them, and stirring them to form a wall material solution; S3: adding the core material solution to the wall material solution, stirring ultrasonically for 30-60 min, then adding the crosslinking agent, and continuing ultrasonic treatment for 30-60 min to obtain a homogeneous emulsion; S4: The homogeneous emulsion is spray-dried and coagulated to form microcapsule structure particles, and then heated to solidify the inside of the microcapsule structure particles, and then ground and passed through a 150-200 mesh sieve to obtain.

5. The highly flame retardant foamed cotton according to claim 1, characterized in that: The flame retardant further comprises zinc borate, and the mass of the zinc borate is 15-25% of the mass of the flame retardant microspheres.

6. The highly flame retardant foamed cotton according to claim 1, characterized in that: The viscosity of the vinyl silicone oil at 25° C. is 5000-8000 mPa·s.

7. The highly flame retardant foamed cotton according to claim 1, characterized in that: The hydrogen content of the hydrogen-containing silicone oil is 1.5-1.6wt%.

8. A method for preparing a highly flame retardant foamed cotton according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: preparing flame retardant microspheres, mixing montmorillonite and expandable graphite to form a layered filler; S2: stirring and mixing α,ω-dihydroxy polysiloxane, vinyl silicone oil, flame retardant microspheres and layered filler to obtain blend A; S3: adding hydrogen-containing silicone oil to blend A, and rapidly stirring and mixing to obtain blend B; S4: Add blend B into the mold and let it stand for 20-30 minutes before vulcanization and foaming. After 1-3 hours of vulcanization and foaming, the molding is completed.

9. The method for preparing highly flame-retardant foamed cotton according to claim 8, characterized in that: The montmorillonite is pretreated as follows before mixing with expandable graphite: Dissolving chitosan in water to form a solution; The montmorillonite is added to the chitosan solution, heated to 60-70°C, ultrasonically stirred for 12-16 hours, and then dried and crushed to obtain the modified montmorillonite.

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