Flame-retardant insulation material and method for manufacturing the same

Abstract

To provide a fire retardant heat insulation material, which has high heat insulation property capable of effectively blocking heat, fire retardancy to prevent firing, high strength, and excellent economy, and a manufacturing method thereof.SOLUTION: A fire retardant heat insulation material of the present invention is formed into a nonwoven fabric by mechanically connecting a sheet-like base material having oxygen index of 26 or more and a web formed by laminating short fibers having oxygen index of 26 or more on both surfaces of the sheet-like base material. A manufacturing method of the fire retardant heat insulation material of the present invention has a step to form the web by using the short fibers having oxygen index of 26 or more, a step to laminate the web on both surfaces of the sheet-like base material having oxygen index of 26 or more, and a step to form the nonwoven fabric by connecting the web and the sheet-like base material by a mechanical entanglement method.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a flame-retardant thermal insulation material and a method for producing the same, which can be applied to various uses requiring flame retardancy and thermal insulation properties, and is suitable as a thermal insulation material for preventing ignition of secondary battery cells, for example. [Background technology]

[0002] Thermal insulation materials are used in a wide range of fields, including housing, vehicles, aircraft, and packaging. Furthermore, thermal insulation materials that possess both thermal insulation and flame retardancy are used in a wide range of fields, such as by placing them around equipment that may generate heat and ignite, in order to prevent the spread of fire to other equipment. For example, they are used in vehicle mats, ceiling materials, dashboards, protective clothing and gloves for high-temperature work, and also by placing them between cells in automotive battery packs to prevent overheating and ignition of other cells.

[0003] For example, a vehicle insulation mat has been disclosed that is 10 to 100 mm thick, and is made by uniformly mixing glass fibers and carbon fibers with a small amount of low-melting-point organic fibers, and forming the entire sheet by passing hot air perpendicularly through the bulky cotton-like material (see, for example, Patent Document 1).

[0004] Furthermore, a thermal insulation material is disclosed that includes a composite layer containing fibers and silica aerogel, and resin supports arranged in the thickness direction within the composite layer. The purpose of this invention is to obtain a thermal insulation material that maintains its structure and suppresses deterioration of thermal conductivity under compressive stress, and it is disclosed that this thermal insulation material is placed between battery cells of an in-vehicle battery (see, for example, Patent Document 2).

[0005] Furthermore, a polymer foam is disclosed comprising a thermoplastic polymer matrix having dispersed air bubbles, an infrared attenuating agent dispersed in the matrix at an amount of 2% or more and 5% or less by weight, a brominated flame retardant dispersed in the matrix at an amount of 2.5 to 3.5% by weight, and an epoxy stabilizer dispersed in the matrix at an amount of at least 0.1% by weight. This invention is primarily intended for application in building and construction (see, for example, Patent Document 3).

[0006] Furthermore, the device comprises a base sheet formed by laminating a film on one or both sides of a cloth-like body made of linear elements, wherein at least one side of the base sheet is sequentially provided with a flame-retardant layer and an adhesive layer, and the storage modulus of the flame-retardant layer at 23°C is 2.0 × 10⁻⁶. 5 The Pa is greater than or equal to the storage modulus of the adhesive layer at 23°C, which is 5.0 × 10⁻⁶. 4 A flame-retardant adhesive tape having a Pa or higher and an oxygen index of 26 or higher has been disclosed (see, for example, Patent Document 4).

[0007] Furthermore, a multilayer thermal insulating material for thermally insulating a battery is disclosed, comprising a first coating layer, a second coating layer, and a compressible and / or flexible intermediate material disposed between the coating layers, the intermediate material having at least one heat-resistant fiber layer, wherein the fiber layer is formed from a needle nonwoven fabric and / or the coating layer is weak against bending, and the thermal insulating element as a whole is compressible and flexible. This invention is intended for use as thermal insulation for secondary batteries such as lithium-ion batteries (see, for example, Patent Document 5). [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2005-186857 [Patent Document 2] Japanese Patent Publication No. 2017-215014 [Patent Document 3] Patent No. 5785159 [Patent Document 4] Japanese Patent Application Laid-Open No. 2021-66891 [Patent Document 5] Japanese Patent Application Laid-Open No. 2021-507483 [Summary of the Invention] [Problems to be Solved by the Invention]

[0009] The heat insulation mat of the invention of Patent Document 1 has both incombustibility and heat insulation properties, but it is intended for railway vehicles. For example, it is difficult to use it as a heat insulation material between cells of a secondary battery pack such as a lithium-ion battery in terms of thickness. Furthermore, this invention also discloses a method of bonding a surface sheet made of a woven fabric or felt of inorganic fibers to a mat body with a thickness of 10 to 100 mm using an incombustible resin. However, since sufficient adhesive strength cannot be maintained by bonding with an incombustible resin, there is also a problem that the surface sheet is easily peeled off.

[0010] In the invention of Patent Document 2, polyethylene terephthalate can be used for the fibers of the composite layer, and polystyrene, polypropylene, etc. can be used for the resin struts. Therefore, the flame retardancy is not particularly considered, and there is a problem that it burns during ignition.

[0011] The invention of Patent Document 3 uses a brominated flame retardant as a flame retardant dispersed in a foamed polymer, which is based on the mechanism of preventing the progress of combustion by carbonizing the surface during combustion. However, since the upper limit temperature of use of this material is around 100°C, there is a problem that it cannot be used in a high temperature range of 100°C or higher.

[0012] Patent Document 4 relates to an invention of a flame retardant adhesive tape having a laminated structure of a base material sheet and a flame retardant layer, and imparting flame retardancy by making the oxygen index 26 or more as a whole. In this invention, there is no disclosure or suggestion regarding imparting heat insulation properties.

[0013] The invention described in Patent Document 5 has a structure in which fiber layers are provided on both sides of an intermediate layer, and coating layers are provided on the respective surfaces of these fiber layers. And it is stated that the intermediate layer is preferably a heat-resistant metal layer. The fiber layer is formed from a needle non-woven fabric, and it is described that a heat-resistant metal layer, a polyimide foil, etc. are used for the coating layer. With such a structure, it becomes a heat insulation element capable of heat insulation of a battery, but there is a cost problem due to its complicated structure.

[0014] Hybrid vehicles and electric vehicles are equipped with a battery pack having a module structure of a plurality of lithium-ion battery cells which are secondary batteries. Since lithium-ion batteries are chemically unstable, when short circuits or the like occur due to deterioration or some other cause, the secondary battery cells may generate heat and thermal runaway may occur. Then, heat is transmitted to adjacent secondary battery cells, and thermal runaway may occur one after another, leading to a major accident. In order to prevent this, a heat insulation material having not only heat insulation but also flame retardancy is required.

[0015] The present invention solves the above problems, and aims to provide a flame-retardant heat insulation material having high heat insulation capable of effectively blocking heat, flame retardancy for preventing ignition, and being high-strength and excellent in economy, and a manufacturing method thereof.

Means for Solving the Problems

[0016] In order to solve the above problems, the flame-retardant heat insulation material of the present invention mechanically bonds a sheet-like base material having an oxygen index of 26 or more and a web formed by laminating short fibers having an oxygen index of 26 or more on both sides of the sheet-like base material to form a non-woven fabric. This flame-retardant insulation material has a web made of laminated short fibers consisting of flame-resistant fibers, silica fibers, or alumina fibers, with the webs not chemically bonded to each other, and the bulk density of the flame-retardant insulation material, which is manufactured by bonding the web and a sheet-like substrate by mechanical entanglement, is 0.01 to 0.1 g / cm³. 3 That is It is characterized by this. By adopting such a structure, a flame-retardant heat insulation material made of a non-woven fabric having both flame retardancy and heat insulation can be obtained. It is possible to obtain a flame-retardant heat insulation material.

[0017] In this case, it is preferable that the tensile strength be 0.5 MPa or higher. If the tensile strength is 0.5 MPa or higher, stable operation can be performed without tearing, for example, when placed around secondary battery cells such as lithium-ion batteries. A tensile strength of 1 MPa or higher is preferable, and 3 MPa or higher is even preferable. If the tensile strength is less than 0.5 MPa, it will tear easily and stable operation cannot be performed. The tensile strength changes depending on the density of the mechanical bonding that entangles the fibers, but the upper limit of the tensile strength in this invention can be set to the tensile strength that is normally used for nonwoven fabrics, and is approximately 10 MPa or less.

[0018] In the above configuration, the sheet-like substrate is a cloth-like body (also called a cloth material) or film formed from glass fibers or filaments, or is made of polyester. Flame retardant Nonwoven fabrics may also be used. Sheet-like substrates made from these materials have an oxygen index of 26 or higher and are suitable for use as a base material for flame-retardant insulation materials because they have excellent heat insulation properties and flexibility.

[0019] In the above configuration, the short fibers may be flame-resistant fibers, silica fibers, or alumina fibers. Short fibers made of such materials have an oxygen index of 26 or higher and excellent heat insulation properties, making them suitable for use as a fiber layer laminated on both sides of a flame-retardant insulation material.

[0020] Next, the method for manufacturing the flame-retardant heat-insulating material of the present invention comprises the steps of: forming a web using short fibers with an oxygen index of 26 or higher; laminating this web onto both sides of a sheet-like substrate having an oxygen index of 26 or higher; and forming a nonwoven fabric by joining the web and the sheet-like substrate by a mechanical entanglement method. A method for manufacturing flame-retardant thermal insulation, wherein in the web formation step, flame-resistant fibers, silica fibers, or alumina fibers are used as short fibers and the webs are formed without chemical bonding to each other, and in the nonwoven fabric formation step, the entanglement density when bonding by mechanical entanglement is 80 to 200 times / cm³. 2 As such, the bulk density when used as a flame-retardant insulation material is 0.01 to 0.1 g / cm³. 3 so It is characterized by the following: In this case, the mechanical entanglement method may be needle punching or water jet punching.

[0021] By using this manufacturing method, no adhesives or other substances are used when manufacturing the nonwoven fabric, so flame-retardant insulation material with good reproducibility can be produced without compromising flame retardancy or heat insulation properties.

[0022] Furthermore, the secondary battery pack of the present invention comprises a storage compartment, a plurality of battery cells fixed within the storage compartment, and a flame-retardant heat-insulating sheet provided between the plurality of battery cells, characterized in that the flame-retardant heat-insulating sheet uses the flame-retardant heat-insulating material described above.

[0023] This secondary battery pack prevents fire even if one of the battery cells overheats and ignites for any reason, because the flame-retardant heat-insulating sheet surrounding it prevents heat from transferring to other battery cells. [Effects of the Invention]

[0024] According to the present invention, since a nonwoven fabric is used as a flame-retardant heat insulating material, in which short fibers with an oxygen index of 26 or higher are laminated on both sides of a sheet-like substrate with an oxygen index of 26 or higher, it is lightweight, has excellent heat resistance and flame retardancy, can secure the required tensile strength, and can also achieve high interlayer strength, thus proving highly effective when used in fields where flame retardancy and heat insulating properties are required. [Brief explanation of the drawing]

[0025] [Figure 1] This is a cross-sectional view showing an example of flame-retardant insulation material. [Figure 2] This is a cross-sectional view showing the flame-retardant heat insulating material of the present invention used as a heat insulating sheet in a secondary battery pack. [Modes for carrying out the invention]

[0026] Figure 1 is a cross-sectional view showing an example of the flame-retardant thermal insulation material of the present invention. The flame-retardant thermal insulation material 10 of the present invention is a nonwoven fabric in which short fibers 12 are laminated on both sides of a sheet-like substrate 11 to form a web, and these are then bonded together by a mechanical entanglement method. The sheet-like substrate, short fibers, manufacturing method, and flame-retardant thermal insulation material will be described in detail below. (Sheet-like substrate)

[0027] The sheet-like substrate 11 can take various forms, such as paper, nonwoven fabric, film, plate, or cloth. Its thickness is preferably in the range of 0.005 to 5 mm. A more preferable thickness is 0.015 to 1 mm, and a particularly preferable thickness is 0.05 to 0.5 mm. A thickness thinner than 0.005 mm is undesirable because it impairs handling. A thickness of 0.015 mm or more is more preferable because it greatly improves workability. A thickness of 0.05 mm or more is particularly preferable because it greatly improves workability. Furthermore, a thickness thicker than 5 mm is undesirable because it makes it difficult to increase the working speed of the mechanical entanglement method for forming the nonwoven fabric, thus reducing productivity. A thickness of 1 mm or less is more preferable because it increases productivity. A thickness of 0.5 mm or less is particularly preferable because it allows for further increased productivity while maintaining thermal insulation. Furthermore, the sheet-like substrate 11 can also be a laminated sheet made by laminating two or more materials. For example, it may be a laminate of paper-like material and cloth-like material.

[0028] Materials used for the sheet-like substrate 11 include, for example, cellophane, celluloid, synthetic paper, art paper, retroreflective sheets, glass fiber cloth, polyethylene cloth, and polypropylene cloth. Furthermore, elastic resins or thermoplastic resins can also be used as the material for the sheet-like substrate 11.

[0029] As the elastic resins mentioned above, styrene-butadiene rubber, acrylonitrile-butadiene rubber, olefin-based elastomer resins, styrene-based elastomer resins, urethane-based elastomer resins, polyester-based elastomer resins, and polyamide-based or aramid-based elastomer resins can be used.

[0030] As the thermoplastic resins mentioned above, thermoplastic resins such as high-pressure low-density polyethylene, high-density polyethylene, linear low-density polyethylene, ethylene-based polymers such as ethylene-vinyl acetate copolymer, polypropylene, propylene-α-olefin copolymer mainly composed of propylene, polyvinyl chloride, polyester, polyamide, polyimide, or acrylic resin can be used.

[0031] When manufacturing the sheet-like substrate 11 using these thermoplastic resins, it can be formed by T-die extrusion molding, casting molding, calendering, or inflation molding. Alternatively, the obtained sheet may be biaxially stretched before use. This is preferable because it allows for increased stiffness and tensile strength of the sheet-like substrate 11.

[0032] In the case of the above-mentioned fabric-like material, it can be manufactured by a known weaving method using a filament made of thermoplastic resin material such as a stretched thermoplastic resin monofilament, tape, yarn, split yarn, multifilament, or staple fiber. The term "filament" broadly refers to a long material that can form a sheet-like material, and includes ribbon-like materials, string-like materials, monofilaments, multifilaments, etc., which can be twisted as needed. The structure of the filament can be anything; it can be used as a tape by slitting a thermoplastic resin film to a predetermined width and uniaxially stretching it, and the cross-section can be round, oblong, square, polygonal, or other irregular shapes. Furthermore, flexibility can be increased by using a Danline, which is made by extruding a mixture of different resins into a filament and splitting the resins to create fibril. It is also possible to use a single filament as a weaving thread, or to use several filaments bundled together.

[0033] The fringe material can be woven into a fabric by plain weave, twill weave, diagonal weave, rib weave, double weave, gauze weave, etc. Furthermore, it can also be knitted into a fabric by warp knitting, weft knitting, raschel knitting, tricot knitting, etc. Known looms such as circular looms, through-looms, and waterjet looms can be used for weaving.

[0034] It may also be a cross-bonded fabric (sof) formed by arranging numerous linear structures made of thermoplastic resin material perpendicularly to each other to create a surface, and joining their intersections. Alternatively, it may be a knitted or braided fabric formed using linear structures made of the above-mentioned thermoplastic resin material.

[0035] The filaments used in manufacturing the cross-bonded fabric are mainly composed of a high-melting-point resin component with a melting point higher than the thermocompression temperature, but may also contain a low-melting-point resin component with a melting point lower than the thermocompression temperature. The resulting fabric can be used as a sheet-like substrate 11 as is, but it can also be made into a laminated resin sheet by laminating a film layer of thermoplastic resin.

[0036] In this invention, the sheet-like substrate 11 has an oxygen index of 26 or higher. Therefore, if the oxygen index of the material used is less than 26, a flame retardant can be added to raise the oxygen index to 26 or higher. Furthermore, even if the oxygen index is 26 or higher, a flame retardant may be added to further improve flame retardancy.

[0037] To achieve an oxygen index of 26 or higher, flame retardants known as flame retardants for adhesives can be used. Examples include halogenated flame retardants, halogenated flame retardants in combination with antimony trioxide, phosphorus-based flame retardants, metal hydroxyl group-based flame retardants, phosphinate metal salt-based flame retardants, nitrogen-containing compounds such as melamine cyanurate and triazine compounds, or sodium polyphosphate.

[0038] Examples of the halogen-based flame retardants mentioned above include brominated flame retardants such as tetrabromobisphenol A, hexabromocyclodecane, dibromodiphenyl oxide, tetrabromobisphenol A polycarbonate oligomer, brominated polystyrene, and ethylenebistetrabromophthalimide; chlorinated flame retardants such as chlorinated paraffin and perchlorocyclopentadecane; halogen-containing phosphate esters such as tris(tribromoneopentyl)phosphate and tris(chloropropyl)phosphate; and halogen-containing condensed phosphate esters such as "CR-504L," "CR-570," and "DAIGUARD-540" manufactured by Daihachi Chemical Industry Co., Ltd.

[0039] Examples of the phosphorus-based flame retardants mentioned above include non-halogenated phosphate esters such as trimethyl phosphate, triethyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, 2-naphthyl diphenyl phosphate, and cresyl di2,6-xylenyl phosphate; aromatic condensed phosphate esters such as "CR-733S," "CR-741," and "PX-200" manufactured by Daihachi Chemical Industry Co., Ltd.; and non-halogenated condensed phosphate esters such as "DAIGUARD-580," "DAIGUARD-610," and "DAIGUARD-880" manufactured by Daihachi Chemical Industry Co., Ltd. Examples of the above-mentioned metal hydroxyl group-based flame retardants include magnesium hydroxide and aluminum hydroxide.

[0040] Examples of the above-mentioned phosphinate metal salt-based flame retardants include Clariant's products, trade names "Exolit OP1230" and "Exolit OP930". For flame retardants in compound products (composite materials), a synergistic effect can be obtained by using flame retardants with different mechanisms of action in combination rather than using them alone. The phosphorus-based flame retardants exemplified above are preferred, and ammonium polyphosphate coated with melamine or the like is particularly preferred because it suppresses hydrolysis and has excellent resistance to moisture and heat.

[0041] The sheet-like substrate 11 in the present invention is not limited to the above materials and configuration, and may contain inorganic balloons or silica nanoparticles to further improve flame retardancy and heat insulation properties.

[0042] As the inorganic balloon mentioned above, at least one selected from shirasu balloons, silica balloons, fly ash balloons, barlite balloons, and glass balloons can be used. The average particle size of the inorganic balloon is preferably 1 μm or more and 100 μm or less, and more preferably 3 μm or more and 70 μm or less.

[0043] Furthermore, wet silica, dry silica, and aerogel can be used as the above-mentioned silica nanoparticles. Silica nanoparticles are spherical or nearly spherical silica particles with an average particle diameter of less than 1 μm, on the order of nanometers. If the average particle diameter of the silica nanoparticles is 1 nm or more and 100 nm or less, the heat insulation properties can be further improved, especially in the room temperature range. The average particle diameter of the silica nanoparticles is more preferably 2 nm or more, and even more preferably 3 nm or more. In addition, the average particle diameter of the silica nanoparticles is more preferably 50 nm or less, and even more preferably 10 nm or less.

[0044] The flame-retardant thermal insulation material 10 of the present invention may have different shapes and sizes depending on its intended use, but the ratio of the thickness of the sheet-like base material 11 used therein is preferably 3 to 50% of the total thickness of the flame-retardant thermal insulation material 10, and more preferably 5 to 40%. By setting the ratio of the sheet-like base material 11 to 3% or more, the flame-retardant thermal insulation material 10 is given appropriate strength and rigidity, and can be easily molded into the desired shape. Furthermore, if the sheet-like base material 12 is mixed in at a maximum of 50%, sufficient thermal insulation and flame retardancy can be provided. If the ratio of the thickness of the sheet-like base material 12 is greater than 50% of the total, the proportion of short fibers 12 decreases relatively, which is undesirable because it reduces the thermal insulation performance and flame retardancy performance. (Short fibers)

[0045] In the present invention, the short fiber 12 has an oxygen index of 26 or higher. In the present invention, as the short fiber 12, one or more inorganic or organic fibers selected from silica fibers, alumina fibers, basalt fibers, aramid fibers, polyarylate fibers, polybenzoxazole (PBO) fibers, polybenzthiazole fibers, polybenzimidazole (PBI) fibers, polyimide fibers, polyetherimide fibers, polyetheretherketone fibers, polyetherketone fibers, polyetherketoneketone fibers, polyamideimide fibers, and flame-resistant fibers can be used. All of these heat-resistant fibers can be conventionally known or manufactured according to known methods or similar methods.

[0046] Silica fibers are obtained by pickling glass fibers, for example, those composed of SiO2, Na2O, K2O, Al2O3, CaO, MgO, Fe2O3, B2O3, TiO2, and ZrO2, to remove the necessary amounts of components other than SiO2 and Al2O3. Silica fibers have superior heat resistance compared to glass fibers. The composition of silica fibers is 85-99% by weight of SiO2, 1-10% by weight of Al2O3, and 0-10% by weight of components other than SiO2 and Al2O3. Furthermore, when the composition of silica fibers is 90-98% by weight of SiO2, 2-5% by weight of Al2O3, and 0-5% by weight of components other than SiO2 and Al2O3, the flame resistance of the flame-retardant heat insulating material 10 of the present invention is even better, which is preferable. The fiber length of the silica fibers is 10-100 mm, with 20-75 mm being more preferable. Furthermore, the fineness of the silica fibers is preferably 0.5 to 10 dtex, and more preferably 1 to 5 dtex. When the fiber length and fineness of the modified silica fibers are within this range, a uniform fiber web can be obtained, for example, when using a dry process nonwoven fabric manufacturing method, thus enabling the production of a flame-resistant filter material with a uniform structure. An example of this is "BELCOTEX" manufactured by Belchem.

[0047] Alumina fibers typically have a diameter of 1 to 50 μm and a length of 0.5 to 500 mm. However, from the viewpoint of resilience and shape retention, fibers with a diameter of 3 to 8 μm and a length of 0.5 to 300 mm are particularly preferred. For example, Denka's product "Arsen" can be cited.

[0048] Here, flame-resistant fibers are mainly produced by firing acrylic fibers in an activated atmosphere such as air at 200-500°C, and are precursors to carbon fibers. Examples include OX from Zoltex, "Rastan" from Asahi Kasei, and "Pyromex" from Toho Tenax. Among the above flame-retardant short fibers, flame-resistant fibers that do not melt at high temperatures are preferred due to their low shrinkage and good processability.

[0049] As the short fibers 12, long fibers or short fibers cut to a desired fiber length can be used. Their fineness is preferably 0.1 to 10 dtex. The fiber length of the short fibers 12 in this invention is not particularly limited as described above and can be appropriately determined based on processability and heat insulation properties. However, a range of 1 to 20 mm is preferred. (Method of manufacturing flame-retardant insulation material)

[0050] The method for manufacturing the flame-retardant heat-insulating material 10 of the present invention comprises the steps of: forming a web using short fibers 12 with an oxygen index of 26 or higher; laminating this web onto both sides of a sheet-like substrate 11 having an oxygen index of 26 or higher; and forming a nonwoven fabric by joining the web and the sheet-like substrate by a mechanical entanglement method. The web can be manufactured using a known web-forming apparatus in accordance with conventional web-forming methods.

[0051] In this case, the mechanical entanglement method may be needle punching or water jet punching. By applying mechanical entanglement, the short fibers 12 can be entangled, thereby improving the abrasion resistance and interlayer strength of the flame-retardant insulation material 10.

[0052] If the mechanical confounding density is too low, the tensile strength and interlayer strength of the flame-retardant insulation material 10 will be insufficient. If it is too high, the bulk density will decrease, and the air volume ratio in the flame-retardant insulation material 10 will decrease, thus impairing the insulation effect. For this reason, 50 to 300 times / cm is recommended. 2 Preferably 80-200 times / cm 2 It is preferable to do so.

[0053] In the present invention, needle punching can be performed using a known needle punching apparatus and according to a known method. After needle punching, the flame-retardant heat insulating material 10 of the present invention can be obtained by drying in the same manner as in the conventional method.

[0054] Furthermore, a water jet punch is a device that has a large number of injection holes, for example, with a diameter of 0.05 to 2.0 mm, arranged in one or more rows with a hole spacing of 0.3 to 10 mm, and has an injection pressure of 90 to 250 kg / cm². 2 The process can be carried out using a water jet punching device that injects a high-pressure water stream as G, following the conventional water jet punching method. The distance between the injection hole and the web should be approximately 1 to 10 cm. After water jet punching, the flame-retardant heat insulating material 10 of the present invention can be obtained by drying it in the same manner as in the conventional method. (Flame-retardant insulation material)

[0055] In the present invention, the thickness of the flame-retardant heat insulating material 10 is not particularly limited and can be appropriately determined according to its purpose and application. However, from the viewpoint of economy and ease of processing, the thickness of the flame-retardant heat insulating material 10 is preferably 100 mm or less, more preferably 0.1 to 50 mm, and even more preferably 0.3 to 30 mm.

[0056] The total ratio (by weight) of the sheet-like base material 11 to the short fibers 12 may be 10 / 90~99 / 1, preferably 20 / 80~97 / 3, more preferably 25 / 75~95 / 5, and particularly preferably 30 / 70~90 / 10. With such a ratio, a flame-retardant heat-insulating material 10 with excellent heat resistance and flame retardancy can be obtained.

[0057] The flame-retardant heat-insulating material 10 of the present invention preferably has a bulk density in the range of 0.01 to 0.2 g / cm 3 from the viewpoints of flame retardancy, heat insulation, tensile strength, interlayer strength, processability, etc., more preferably in the range of 0.01 to 0.1 g / cm 3 and still more preferably in the range of 0.01 to 0.08 g / cm 3 , particularly preferably in the range of 0.02 to 0.05 g / cm 3 . Thus, by controlling the bulk density of the flame-retardant heat-insulating material 10, the proportion of air (oxygen) in the flame-retardant heat-insulating material 10 is controlled within a certain range, and excellent flame retardancy, heat insulation and tensile strength are imparted.

[0058] In addition, the flame-retardant heat-insulating material 10 of the present invention may be colored with a dye or a pigment as necessary. As a coloring method, the original yarn obtained by mixing a dye or a pigment with a polymer and spinning before spinning may be used as the short fiber 12, or the short fiber 12 colored by various methods may be used. Alternatively, the flame-retardant heat-insulating material 10 itself may be colored with a dye or a pigment.

[0059] Since the webs in the short fiber 12 of the flame-retardant heat-insulating material 10 of the present invention are not chemically adhered to each other, heat resistance of 500 °C or higher can also be imparted. Also, after use, the flame-retardant heat-insulating material 10 can be recovered, washed as necessary, etc., and then easily recycled by simply loosening the entangled short fibers 12.

[0060] Note that, in order to further improve the flame retardancy, tensile strength and interlayer strength of the flame-retardant heat-insulating material 10 of the present invention, an acrylic resin emulsion, a phosphate ester flame retardant, a halogen-based flame retardant or a hydrated metal compound or the like may be blended as necessary, and an acrylic resin emulsion or an acrylic resin solution obtained by blending a known flame retardant may be coated or impregnated.

[0061] Various additives can be added to the flame-retardant heat insulating material 10 of the present invention depending on the purpose. Examples of additives include antioxidants such as organophosphorus and thioether-based agents; light stabilizers such as hindered amine-based agents; ultraviolet absorbers such as benzophenone-based, benzotriazole-based, and benzoate-based agents; antistatic agents; dispersants such as bisamide-based, wax-based, and organometallic salt-based agents; lubricants such as amide-based and organometallic salt-based agents; flame retardants such as bromine-containing organic agents, phosphoric acid-based agents, melamine cyanurate-based agents, and antimony trioxide agents; stretching aids such as low-density polyethylene and linear low-density polyethylene; organic pigments; inorganic pigments; inorganic fillers; organic fillers; inorganic antibacterial agents such as metal ion-based agents and organic antibacterial agents.

[0062] The flame-retardant heat insulating material 10 of the present invention has a thermal conductivity of 0.20 W / m·K or less, preferably 0.15 W / m·K or less, more preferably 0.10 W / m·K or less, even more preferably 0.08 W / m·K or less, particularly preferably 0.05 W / m·K or less, and most preferably 0.03 W / m·K. As long as the thermal conductivity is within the above range, the flame-retardant heat insulating material 10 of the present invention can exhibit high heat insulating properties. (Rechargeable battery pack)

[0063] Figure 2 is a cross-sectional view showing the flame-retardant heat insulating material of the present invention used as a heat insulating sheet in a secondary battery pack. The secondary battery pack 15 of the present invention comprises a storage section 18, a plurality of battery cells 16 fixed within the storage section 18, and a flame-retardant heat insulating sheet 17 provided between the plurality of battery cells 16, wherein the flame-retardant heat insulating sheet 17 uses the flame-retardant heat insulating material of the present invention.

[0064] Even if one of the battery cells overheats and ignites for any reason, the flame-retardant heat-insulating sheet 17 surrounding it prevents heat conduction to the other battery cells 15, thus preventing ignition. (Examples)

[0065] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples. The measurement methods for each characteristic value in the following examples and comparative examples are as follows. (1) Thickness: Measured in accordance with JIS L-1096 with a load of 0.3 kPa. (2) Oxygen index: Measured at 23°C in accordance with JIS K-7201.

[0066] (3) Tensile strength: The longitudinal tensile strength was measured in accordance with JIS L-1096. From the viewpoint of processability, durability, and abrasion resistance, it is necessary to have a strength of 0.5 MPa or higher, preferably 1 MPa or higher, and more preferably 3 MPa or higher.

[0067] (4) High-temperature interlaminar strength: The interlaminar strength at 60°C was measured in accordance with JIS K-6854-3. From the viewpoint of processability and wear resistance, it is necessary to have a strength of 0.5 N / 50 mm or more, preferably 1 N / 50 mm or more, and more preferably 2 N / 50 mm or more. (5) Flame retardancy test: Conformed to the UL-94 5V flat plate test specimen vertical combustion test. (6) Thermal conductivity: Measured in accordance with JIS A-1412-2. First, two types of sheet-like substrates, as described below, were prepared.

[0068] The first sheet-like substrate (hereinafter referred to as "sheet-like substrate A") was prepared as follows. For the base layer, a flame-retardant polyamide resin was used, consisting of 90 parts by weight of polyamide A (nylon 6, grade 1020J, relative viscosity: 3.5, melting point 224°C, manufactured by Mitsubishi Engineering Plastics Co., Ltd.) and 10 parts by weight of a flame retardant (melamine cyanurate, manufactured by Mitsubishi Chemical Corporation). For the surface layer, polyamide B (nylon 6, grade 2420, relative viscosity: 3.5, melting point 195°C, manufactured by Mitsubishi Engineering Plastics Co., Ltd.) was used. Each of these was melt-kneaded at a cylinder setting temperature of 250°C to form pellets, which were then dried in a vacuum dryer at 120°C to obtain the respective polyamide resin pellets.

[0069] Next, these polyamide resin pellets were melted in a single-layer T-die molding machine at a cylinder setting temperature of 250°C, and then taken up while being cooled with a casting roll at 30°C to produce a three-layer polyamide film with a thickness of 100 μm, consisting of polyamide A / polyamide B / polyamide A (thickness ratio: 10:80:10).

[0070] The obtained polyamide film was slit to a predetermined width, then stretched fourfold on a hot plate at a temperature of 130-150°C, and further stretched 1.25 times in a hot air circulating oven at a temperature of 130-150°C. The resulting stretched filament had a fineness of 800 dtex and a yarn width of 3 mm.

[0071] The obtained uniaxially drawn yarn was woven into a plain weave using a through-zer loom with a thread count of 8 warp threads / 25.4 mm and 8 weft threads / 25.4 mm, and the uniaxially drawn yarns were heat-pressed together using a hot roll. The oxygen index of the sheet-like substrate A obtained in this way was 40 and the thickness was 0.25 mm.

[0072] The second sheet-like substrate (hereinafter referred to as "sheet-like substrate B") was prepared as follows: 40 parts by weight of vinyl chloride resin (Kanevinyl S1001N, manufactured by Kaneka Corporation), 8 parts by weight of adipic acid-based polyester plasticizer (ADEKA PN-446, manufactured by ADEKA Corporation), 1.0 part by weight of barium / zinc-based stabilizer (ADEKA AC-255, manufactured by ADEKA Corporation), 1.0 part by weight of ester-based lubricant (Chillstearate, manufactured by Kawaken Fine Chemicals Co., Ltd.), 35 parts by weight of silica nanoparticles (Enova IC3100, manufactured by Cabot Specialty Chemicals Inc.), and 15 parts by weight of glass balloons (Spherical 25P45, manufactured by Potters Barotini Co., Ltd.) were added and mixed in a ribbon blender. The obtained mixture was pre-kneaded in a pressure kneader at 150°C for 10 minutes, and then the resulting pre-kneaded material was melt-kneaded in a two-roll machine at a roll temperature of 160°C for 10 minutes. Next, a sheet-like substrate B with a thickness of approximately 50 μm was formed using the resulting molten mixture. The oxygen index of the obtained sheet-like substrate B was 33. (Example 1) In this embodiment, we primarily investigated the influence of the material of the sheet-like substrate.

[0073] The flame-retardant insulation material (hereinafter referred to as "insulation material A") relating to the first condition was prepared as follows. First, flame-resistant fibers (OX manufactured by Zoltex, oxygen index 55) were used as short fibers, with a basis weight of 150 g / m². 2 A web was fabricated. This web was laminated onto a sheet-like substrate A, and a needle density of 70 needles / cm² was applied according to a standard method. 2 After entanglement and fixation by needle punching at a needle depth of 12.0 mm, the material was dried according to a conventional method to obtain thermal insulation material A. The measured physical properties of the obtained thermal insulation material A are shown in Table 1.

[0074] The flame-retardant insulation material (hereinafter referred to as "insulation material B") relating to the second condition was prepared as follows. Instead of using sheet-like substrate A or sheet-like substrate B as the sheet-like substrate, a commercially available flame-retardant nonwoven fabric (Heim VH3501A, manufactured by Toyobo Co., Ltd., oxygen index 29) was used. Flame-resistant fibers (OX, manufactured by Zoltex, Inc., oxygen index 55) were used as the short fibers, with a basis weight of 150 g / m². 2 A web was fabricated. This web was laminated onto a flame-retardant nonwoven fabric, and a needle density of 70 needles / cm² was applied according to a standard method. 2 After entanglement and fixation by needle punching at a needle depth of 12.0 mm, the material was dried according to a conventional method to obtain thermal insulation material A. The measured physical properties of the obtained thermal insulation material A are shown in Table 1.

[0075] The flame-retardant insulation material (hereinafter referred to as "insulation material C") relating to the third condition was prepared as follows. First, flame-resistant fibers (OX manufactured by Zoltex, oxygen index 55) were used as short fibers, with a basis weight of 150 g / m². 2 A web was fabricated. This web was laminated onto a sheet-like substrate B, and a needle density of 70 needles / cm² was applied according to a standard method. 2 After entanglement and fixation by needle punching at a needle depth of 12.0 mm, the material was dried according to a conventional method to obtain thermal insulation material C. The measured physical properties of the obtained thermal insulation material C are shown in Table 1.

[0076] The first comparative example insulation material (hereinafter referred to as "Comparative Example A") was prepared as follows. Instead of using sheet-like substrate A or sheet-like substrate B as the sheet-like substrate, a commercially available general nonwoven fabric (Ecure 3501A, manufactured by Toyobo Co., Ltd., oxygen index 21) was used. Flame-resistant fibers (OX, manufactured by Zoltex, Inc., oxygen index 55) were used as the short fibers, with a basis weight of 150 g / m². 2 A web was fabricated. This web was laminated onto a general nonwoven fabric, and a needle density of 70 needles / cm² was applied according to a standard method. 2 Comparative Example A was obtained by confluence and fixation using needle punching at a needle depth of 12.0 mm, followed by drying according to a conventional method. The measured physical properties of the obtained Comparative Example A are shown in Table 1.

[0077] The second comparative example insulation material (hereinafter referred to as "Comparative Example B") was prepared as follows. In Comparative Example B, a sheet-like substrate was not used. Flame-resistant fibers (OX manufactured by Zoltex, oxygen index 55) were used as short fibers, with a basis weight of 150 g / m². 2 A web was fabricated. This web was then processed according to standard methods to achieve a needle density of 70 needles / cm². 2 Comparative Example B was obtained by confluence and fixation using needle punching at a needle depth of 12.0 mm, followed by drying according to a conventional method. The measured physical properties of the obtained Comparative Example B are shown in Table 1.

[0078] As can be seen from Table 1, the thermal insulation materials A, B, and C according to the present invention have a tensile strength of 1 MPa or more, an interlayer strength of 2 N / 50 mm or more, a thermal conductivity of 0.03 W / m·K, and cleared the flame retardancy test of 5 VA.

[0079] On the other hand, Comparative Example A had a tensile strength of 1 MPa or more, an interlaminar strength of 2 N / 50 mm, and a thermal conductivity of 0.03 W / m·K, but combustion occurred in the combustion test. Comparative Example B had a combustion strength of 5 VA and a thermal conductivity of 0.03 W / m·K, but its tensile strength and interlaminar strength were 0.3 MPa and 0.3 N / 50 mm, respectively, and it failed to achieve sufficient strength. (Example 2) In this example, the effect of the short fiber material was investigated.

[0080] The flame-retardant insulation material (hereinafter referred to as "insulation material D") relating to the fourth condition was prepared as follows. Sheet-like substrate A was used as the sheet-like substrate. Silica fibers (BELCOTEX110, manufactured by Belchem, with an oxygen index of 62) were used as the short fibers, with a basis weight of 150 g / m². 2 A web was fabricated. This web was laminated onto a sheet-like substrate A, and a needle density of 70 needles / cm² was applied according to a standard method. 2 After entanglement and fixation by needle punching at a needle depth of 12.0 mm, the material was dried according to a conventional method to obtain thermal insulation material D. The measured physical properties of the obtained thermal insulation material D are shown in Table 1.

[0081] The flame-retardant insulation material (hereinafter referred to as "insulation material E") relating to the fifth condition was prepared as follows. Sheet-like substrate A was used as the sheet-like substrate. Alumina fibers (Denka Co., Ltd. B97N1, oxygen index 60) were used as the short fibers, with a basis weight of 150 g / m². 2 A web was fabricated. This web was laminated onto a sheet-like substrate A, and a needle density of 70 needles / cm² was applied according to a standard method. 2 After entanglement and fixation by needle punching at a needle depth of 12.0 mm, the material was dried according to a conventional method to obtain thermal insulation material E. The measured physical properties of the obtained thermal insulation material E are shown in Table 1.

[0082] The third comparative example insulation material (hereinafter referred to as "Comparative Example C") was prepared as follows. Sheet substrate A was used as the sheet substrate. General polyester fiber yarn (2.8 dtex × 51 mm) was used as the short fiber, with a basis weight of 150 g / m². 2 A web was fabricated. This web was laminated onto a sheet-like substrate A, and a needle density of 70 needles / cm² was applied according to a standard method. 2 Comparative Example C was obtained by confluence and fixation using needle punching at a needle depth of 12.0 mm, followed by drying according to a conventional method. The measured physical properties of the obtained Comparative Example C are shown in Table 1.

[0083] As can be seen from Table 1, the thermal insulation materials D and E according to the present invention have a tensile strength of 3.5 MPa or more, an interlayer strength of 5.3 N / 50 mm or more, and a thermal conductivity of 0.03 W / m·K, and cleared the flame retardancy test of 5 VA. On the other hand, comparative example C had a tensile strength of 3.8 MPa, an interlayer strength of 3.0 N / 50 mm, and a thermal conductivity of 0.03 W / m·K, but combustion occurred in the combustion test. (Example 3) In this embodiment, we confirmed the effectiveness of using the water jet punch method instead of the needle punch method, which is a mechanical entanglement method.

[0084] The flame-retardant insulation material (hereinafter referred to as "insulation material F") relating to the sixth condition was prepared as follows. First, flame-resistant fibers (OX manufactured by Zoltex, oxygen index 55) were used as short fibers, with a basis weight of 150 g / m². 2 A web was fabricated. This web was laminated onto a sheet-like substrate A, and a needle density of 70 needles / cm² was applied according to a standard method. 2 After entanglement and fixation by water jet punching at a needle depth of 12.0 mm, the material was dried according to a conventional method to obtain thermal insulation material F. The measured physical properties of the obtained thermal insulation material F are shown in Table 1.

[0085] In this example, since we are comparing the needle punching method with the water jet punching method, we should compare it with insulation material A in Table 1. Comparing insulation material A and insulation material F, the tensile strength and interlaminar strength were slightly higher with the water jet punching method. On the other hand, a flame retardancy of 5VA was obtained in the flame retardancy test, and the same value was obtained for thermal conductivity. From these results, it was found that the water jet punching method yields slightly better properties than the needle punching method. (Example 4) In this example, the effects of the basis weight of flame-resistant fibers and the absence of short fibers were investigated.

[0086] The flame-retardant insulation material (hereinafter referred to as "insulation material G") relating to the seventh condition was prepared as follows. First, flame-resistant fibers (OX manufactured by Zoltex, oxygen index 55) were used as short fibers, with a basis weight of 50 g / m². 2A web was fabricated. This web was laminated onto a sheet-like substrate A, and a needle density of 70 needles / cm² was applied according to a standard method. 2 After entanglement and fixation by needle punching at a needle depth of 12.0 mm, the thermal insulation material G was obtained by drying according to a conventional method. The measured physical properties of the obtained thermal insulation material G are shown in Table 1.

[0087] The flame-retardant insulation material (hereinafter referred to as "insulation material H") relating to the eighth condition was prepared as follows. First, flame-resistant fibers (OX manufactured by Zoltex, oxygen index 55) were used as short fibers, with a basis weight of 1200 g / m². 2 A web was fabricated. This web was laminated onto a sheet-like substrate A, and a needle density of 70 needles / cm² was applied according to a standard method. 2 After entanglement and fixation by needle punching at a needle depth of 12.0 mm, the thermal insulation material H was obtained by drying according to a conventional method. The measured physical properties of the obtained thermal insulation material H are shown in Table 1.

[0088] The fourth comparative example (hereinafter referred to as "Comparative Example D") was prepared as follows. Sheet substrate A was used as the sheet substrate. In Comparative Example D, short fibers were not used, and therefore mechanical entanglement was not present, and the structure consisted only of sheet substrate A. The measured physical properties of the obtained Comparative Example D are shown in Table 1.

[0089] The fifth comparative example insulation material (hereinafter referred to as "Comparative Example E") was prepared as follows. First, flame-resistant fibers (OX manufactured by Zoltex, oxygen index 55) were used as short fibers, with a basis weight of 1200 g / m². 2 A web was fabricated. This web was laminated onto a sheet-like substrate A and fixed using a non-combustible adhesive (non-combustible bond AB-1BU manufactured by Alps Corporation) instead of entanglement by needle punching. Subsequently, it was dried according to a conventional method to obtain comparative example E. The measured physical properties of the obtained comparative example E are shown in Table 1.

[0090] As can be seen from Table 1, when comparing insulation materials A, G, and H, it was found that the tensile strength, interlaminar strength, thermal conductivity, and flame retardancy test results were not significantly affected by the basis weight. On the other hand, when comparing insulation material H with comparative example E of the same basis weight, it was found that comparative example E had a significantly lower interlaminar strength of 0.3 N / 50 mm. From these results, it was found that fixing by mechanical entanglement is preferable to using non-combustible adhesives, etc. Furthermore, comparative example D had a configuration in which short fibers were not provided on both sides of the sheet-like substrate A, and it was found that although the interlaminar strength was very high, the thermal conductivity was also high and it was combustible. From these results, it was found that covering both sides of the sheet-like substrate with short fibers has a significant effect on improving flame retardancy and heat insulation.

[0091] [Table 1]

[0092] Since the flame-retardant heat-insulating material of the present invention is in sheet form, it can be easily processed into appropriate sizes, shapes, etc., by applying known methods, etc., according to its purpose and application. Therefore, it can be used for a variety of applications.

[0093] In particular, when used in automotive secondary battery packs, it can not only prevent the spread of flames in the event of a fire originating from a secondary battery cell, secondary battery pack, or secondary battery module, but also prevent the fire from spreading from the secondary battery module to the outside.

[0094] The flame-retardant heat insulating material of the present invention can be used in all applications where flame retardancy and heat insulation are required. For example, it can be suitably used in interior materials for vehicles such as automobiles and freight cars, transportation equipment such as aircraft and ships, civil engineering and construction materials such as wall members, floor members and ceiling members, packaging materials such as refrigerated containers, bedding, or sound-absorbing materials.

[0095] In addition, it can be used in a wide range of applications, including automotive ceiling materials, rear packages, and door trims; dashboard insulators for automobiles, trains, and aircraft; various heat-insulating, heat-shielding, and thermal insulation materials; protective clothing, gloves, and hats for firefighting and high-temperature work; protective sheets for welding sites; weed control materials; speaker diaphragms; and laminated materials for electric carpets. [Industrial applicability]

[0096] The flame-retardant heat-insulating material of the present invention is in sheet form, making it flexible, easy to punch out into the required shape, and possessing both flame retardancy and heat-insulating properties, making it useful in a wide range of fields where heat shielding and heat insulation are required. [Explanation of Symbols]

[0097] 10. Flame-retardant insulation material 11 Base material 12 short fibers 15. Rechargeable battery pack 16 battery cells 17. Flame-retardant heat-insulating sheet 18 Storage compartment

Claims

1. A flame-retardant heat-insulating material for secondary batteries, comprising a sheet-like substrate made of a cloth-like body or film formed from glass fibers or filaments having an oxygen index of 26 or higher, and a web formed by laminating short fibers with an oxygen index of 26 or higher on both sides of the sheet-like substrate, formed as a nonwoven fabric by mechanical bonding, The aforementioned web is constructed by laminating flame-resistant fibers made of carbon fiber precursors, silica fibers, or alumina fibers as the short fibers, and the webs are not chemically bonded to each other. The bulk density of the flame-retardant heat-insulating material, which is manufactured by bonding the web and the sheet-like substrate by mechanical entanglement, is 0.01 to 0.1 g / cm³. ３ A flame-retardant heat-insulating material for secondary batteries, characterized by having a tensile strength of 0.5 MPa or more, a thermal conductivity of 0.05 W / m·K or less, a high-temperature interlaminar strength of 0.5 N / 50 mm or more, and simultaneously satisfying the UL-94 5V flat plate vertical combustion test.

2. A process of forming a web using short fibers with an oxygen index of 26 or higher, The process involves laminating the aforementioned web onto both sides of a sheet-like substrate made of a cloth-like material or film formed from glass fibers or filaments, which has an oxygen index of 26 or higher. A method for manufacturing a flame-retardant heat insulating material for secondary batteries, comprising the steps of forming a nonwoven fabric by mechanically entanglementing the web and the sheet-like substrate, In the process of forming the web, flame-resistant fibers made of carbon fiber precursors, silica fibers, or alumina fibers are used as the short fibers, and the webs are formed without chemical bonding to each other. In the process of forming the nonwoven fabric, the entanglement density when bonding by the mechanical entanglement method is set to 80 to 200 times / cm². ２ As such, the bulk density when used as the aforementioned flame-retardant insulation material is 0.01 to 0.1 g / cm³. ３ A method for manufacturing a flame-retardant heat-insulating material for secondary batteries, characterized by having a tensile strength of 0.5 MPa or more, a thermal conductivity of 0.05 W / m·K or less, a high-temperature interlaminar strength of 0.5 N / 50 mm or more, and simultaneously satisfying the UL-94 5V flat plate test specimen vertical combustion test.

3. The method for manufacturing a flame-retardant heat insulating material for a secondary battery according to claim 2, characterized in that the mechanical entanglement method is needle punching or water jet punching.

4. Storage compartment and Multiple battery cells fixed within the aforementioned storage compartment and The system includes a flame-retardant heat-insulating sheet provided between the plurality of battery cells, A secondary battery pack characterized in that the flame-retardant heat insulating sheet uses the flame-retardant heat insulating material described in claim 1.

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