Flame-retardant heat-insulation material

Abstract

To provide a flame-retardant insulation material which has a high heat insulation property for effectively insulating heat, a flame retardant property for preventing fire, and high strength and excellent cost effectiveness, and a manufacturing method thereof.SOLUTION: A material includes: a sheet-like base material having an oxygen index of 26 or more; and a heat insulation layer laminated on at least one face of the sheet-like base material. The heat insulation layer is composed of an inorganic heat insulation filler and an inorganic binder. Further, the inorganic heat insulation filler may be at least one selected from a flaky mica, a glass balloon, a fly ash balloon, a silas balloon, a perlite, a silica xerogel, and a silica aerogel. Also, the inorganic binder may be at least one selected from a silicone-based binder, a silica-based binder, an alumina-based binder, and zirconia-silica-based binder.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a flame-retardant heat insulating material that can be used in various applications requiring flame retardancy and heat insulation, and is suitable as an insulating material for preventing ignition of secondary battery cells, for example. [Background technology]

[0002] Thermal insulation materials are used in a wide range of areas in society, including homes, vehicles, aircraft, and packaging materials. Furthermore, thermal insulation materials that are flame-retardant in addition to insulating properties are used in a wide range of areas, such as being placed around equipment that may generate heat and catch fire to prevent the spread of heat to other equipment. Examples of such materials include vehicle mats, ceiling materials, dashboards, protective clothing and gloves for high-temperature work, and being placed between cells in automobile secondary battery packs to prevent overheating and ignition of other cells. A variety of materials and structures have been developed for such thermal insulation materials.

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

[0004] Another example is a thermal insulator that includes a composite layer containing fibers and silica aerogel and resin struts arranged in the thickness direction of the composite layer. This invention aims to obtain a thermal insulator that maintains its structure against compressive stress and suppresses deterioration of thermal conductivity, and it discloses that this thermal insulator is placed between battery cells of an automotive battery (see, for example, Patent Document 2).

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

[0006] The present invention further comprises a base sheet formed by laminating a film on one or both sides of a fabric-like material made of a filament, and a flame-retardant layer and a pressure-sensitive adhesive layer are sequentially provided on at least one side of the base sheet, and the storage modulus of the flame-retardant layer at 23°C is 2.0 × 10 5 The pressure-sensitive adhesive layer has a storage modulus of 5.0×10 Pa or more at 23°C. 4 A flame-retardant adhesive tape having a compressive strength of 100 Pa or more and an oxygen index of 26 or more has been disclosed (see, for example, Patent Document 4).

[0007] Furthermore, a mica sheet for high-temperature electrical insulation has been disclosed, which is characterized by comprising a synthetic laminated mica layer impregnated with a silicone resin, an adhesive layer, and a backing material layer, and containing aluminum hydroxide or magnesium hydroxide with a particle size of 50 μm or less in at least one of the above layers. This invention is intended for use as fire-resistant thermal insulation for fire-resistant bus ducts, fire-resistant electric wires, etc. (See, for example, Patent Document 5). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-186857 [Patent Document 2] Japanese Patent Application Publication No. 2017-215014 [Patent Document 3] Patent No. 5785159 [Patent Document 4] Patent Publication No. 2021-66891 [Patent Document 5] Patent No. 2790207 Summary of the Invention [Problem to be solved by the invention]

[0009] The insulating mat of the invention in Patent Document 1 is both non-flammable and insulating, but is intended for use in railway vehicles, and its thickness makes it difficult to use as insulating material between cells in a secondary battery pack such as a lithium-ion battery. This invention also discloses a method in which a surface sheet made of inorganic fiber woven fabric or felt is bonded to a 10-100 mm thick mat body with a non-flammable resin. However, bonding with a non-flammable resin does not provide sufficient adhesive strength, resulting in the surface sheet easily peeling off.

[0010] In the invention of Patent Document 2, the fibers of the composite layer can be made of polyethylene terephthalate, and the resin supports can be made of polystyrene, polypropylene, etc., so no particular consideration is given to flame retardancy, and there is a problem that the material will burn when ignited.

[0011] The invention of Patent Document 3 uses a brominated flame retardant dispersed in a foamable polymer, which is based on the mechanism that the surface carbonizes during combustion, preventing the progression of combustion. However, this material has an upper limit of usable temperature of around 100°C, so it cannot be used in high temperature ranges above 100°C.

[0012] Patent Document 4 is an invention relating to a flame-retardant pressure-sensitive adhesive tape having a laminated structure of a base sheet and a flame-retardant layer, and imparting flame retardancy by making the overall oxygen index equal to or greater than 26. This invention does not disclose or suggest imparting heat insulation properties.

[0013] The invention described in Patent Document 5 is a mica sheet for high-temperature electrical insulation with a three-layer structure consisting of a synthetic mica layer impregnated with silicone resin, an adhesive layer, and a backing layer, and is characterized in that at least one of the three layers contains aluminum hydroxide and magnesium hydroxide with a particle size of 50 μm or less. However, there is no disclosure or suggestion about the use of natural mica or flame retardancy.

[0014] Hybrid and electric vehicles are equipped with battery packs that have a modular structure consisting of multiple lithium-ion battery cells, which are secondary batteries. Because lithium-ion batteries are chemically unstable, if a short circuit occurs due to deterioration or some other reason, the secondary battery cell may generate heat and experience thermal runaway. This can then transfer heat to adjacent secondary battery cells, causing successive thermal runaways and leading to a major accident. To prevent this, insulation materials that are not only insulating but also flame-retardant are required.

[0015] The present invention is intended to solve the above-mentioned problems, and aims to provide a flame-retardant heat insulating material that has both high heat insulating properties that can effectively block heat and flame retardancy to prevent ignition, and that is high in strength and economical, as well as a method for producing the same. [Means for solving the problem]

[0016] In order to solve the above problems, the flame-retardant thermal insulation material of the present invention comprises a sheet-like substrate having an oxygen index of 26 or more and a thermal insulation layer laminated on at least one surface of the sheet-like substrate, the thermal insulation layer being composed of an inorganic thermal insulation filler and an inorganic binder. By adopting such a configuration, it is possible to obtain a sheet-like flame-retardant thermal insulation material that combines flame retardancy and thermal insulation properties.

[0017] In the above configuration, the inorganic heat insulating filler may be at least one selected from the group consisting of flaky mica, glass balloons, fly ash balloons, shirasu balloons, perlite, silica xerogel, and silica aerogel. By using such an inorganic heat insulating filler, a flame-retardant heat insulating material with low thermal conductivity and excellent heat insulating properties can be obtained.

[0018] Although good heat insulating properties can be obtained by using each of flaky mica, glass balloons, fly ash balloons, shirasu balloons, perlite, silica xerogel, and silica aerogel alone, a combination of these materials may also be used.

[0019] Furthermore, in the above configuration, the inorganic binder may be at least one selected from a silicone-based binder, a silica-based binder, an alumina-based binder, and a zirconia-silica-based binder. The inorganic binder is not limited to one type, and mixing multiple types may further improve the tensile strength when formed into a sheet. The type of material to be mixed may be selected taking into consideration the material, cost, the required tensile strength, thickness, etc. By using such materials, the flame retardancy of the insulating layer can be increased, thereby increasing the flame retardancy of the flame-retardant insulating material.

[0020] In the above-described configuration, the sheet-like substrate may be a woven or nonwoven fabric made of inorganic fibers or inorganic filaments, or a woven or nonwoven fabric made of organic fibers that has been given flame retardancy. By using such a sheet-like substrate, the flame retardancy of the sheet-like substrate itself can be increased, and the sheet can be made thinner. As a result, the flame-retardant heat insulating material can also be made thinner, making it easy to apply to various devices. For a sheet-shaped flame-retardant heat insulating material, important properties include tensile strength, high-temperature interlayer strength between the heat insulating layer and the sheet-shaped substrate, flame retardancy, and thermal conductivity.

[0021] The tensile strength is preferably 0.5 MPa or more. If the tensile strength is 0.5 MPa or more, stable work can be performed without tearing when the sheet is placed around a secondary battery cell such as a lithium-ion battery. The tensile strength is preferably 5 MPa or more, and more preferably 10 MPa or more. If the tensile strength is less than 0.5 MPa, the sheet is prone to tearing and stable work cannot be performed. The tensile strength varies depending on the combination of inorganic heat insulating filler, inorganic binder, and sheet-like substrate used and the thickness to be produced, but the upper limit of the tensile strength required to accommodate various applications is approximately 25 MPa. The high temperature interlaminar strength must be 0.5 N / 50 mm or more, preferably 3 N / 50 mm or more, and more preferably 5 N / 50 mm or more. The flame retardancy is required to pass the test method described below.

[0022] Furthermore, thermal conductivity is important for heat insulating properties, so a low value is desirable, and a value of 0.20 W / m K or less is required. It is 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 or less.

[0023] The secondary battery pack of the present invention comprises a storage section, a plurality of battery cells fixed within the storage section, and a flame-retardant heat insulating sheet disposed between the plurality of battery cells, the flame-retardant heat insulating sheet being made of the flame-retardant heat insulating material described above. Even if one of the battery cells generates heat and catches fire for some reason, the flame-retardant heat insulating sheet surrounding the battery cell prevents the heat from being transferred to the other battery cells, thereby preventing fire. [Effects of the Invention]

[0024] According to the flame-retardant insulating material of the present invention, an insulating layer consisting of an inorganic insulating filler and an inorganic binder is laminated on at least one surface of a sheet-like substrate having an oxygen index of 26 or more, so that it is lightweight, has excellent heat resistance and flame retardancy, and furthermore, can ensure the required tensile strength and can also increase interlayer strength, thereby providing great benefits when used in fields where flame retardancy and insulating properties are required. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a cross-sectional view showing an outline of a flame-retardant heat insulating material according to a first embodiment of the present invention. [Figure 2] FIG. 3 is a cross-sectional view showing an outline of a flame-retardant heat insulating material according to a second embodiment of the present invention. [Figure 3] 1 is a cross-sectional view showing a state in which the flame-retardant heat insulating material of the present invention is used as a flame-retardant heat insulating sheet for a secondary battery pack. DETAILED DESCRIPTION OF THE INVENTION

[0026] (First embodiment)

[0027] A flame-retardant thermal insulation material according to a first embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a cross-sectional view showing an example of a flame-retardant thermal insulation material according to this embodiment. The flame-retardant thermal insulation material 10 according to this embodiment has a configuration in which a thermal insulation layer 12 made of an inorganic thermal insulation filler and an inorganic binder is laminated on one surface of a sheet-like substrate 11.

[0028] The flame-retardant insulating material 10 can be produced, for example, by adding 180 parts by weight of toluene and 60 parts by weight of isopropyl alcohol to an inorganic insulating filler and an inorganic binder, stirring and mixing the mixture, casting the mixture onto a sheet-like substrate 11, drying (100°C x 5 minutes), and heat-curing (150°C x 8 hours).

[0029] Alternatively, the flame-retardant heat insulating material may be produced by separately forming the heat insulating layer 12 and then laminating it on at least one surface of the sheet-like substrate 11 having an oxygen index of 26 or more. In this case, the sheet-like substrate 11 and the heat insulating layer 12 may be laminated using an adhesive.

[0030] The adhesive is not particularly limited as long as it can firmly bond the sheet-like substrate 11 and the heat insulating layer 12 and is flame-retardant. Specific examples of adhesives with good properties include inorganic adhesives such as silica-based adhesives, ceramic, cement, solder, and water glass. Other examples include natural adhesives such as asphalt, gum arabic, albumin, lacquer, casein adhesives, natural rubber-based adhesives, natural rubber latex adhesives, starch-based adhesives, glue, fibrin adhesives, and rosin, acrylic resin-based adhesives, acrylic resin anaerobic adhesives, acrylic resin emulsion adhesives, acrylic resin adhesive tapes, α-olefin-based adhesives, urethane resin-based adhesives, urethane resin solvent-based adhesives, urethane resin emulsion adhesives, ether-based cellulose, ethylene-vinyl acetate resin emulsion adhesives, ethylene-vinyl acetate resin hot melt adhesives, epoxy resin-based adhesives, epoxy resin emulsion adhesives, vinyl chloride resin solvent-based adhesives, chloroprene rubber-based adhesives, vinyl acetate resin emulsion adhesives, cyanoacrylate-based adhesives, silicone-based adhesives, aqueous polymer-isocyanate-based adhesives, and sucrose-based adhesives. Any synthetic adhesive that has flame retardancy or has been imparted with flame retardancy can be used, such as ethylene-butadiene rubber solution-based adhesives, styrene-butadiene rubber latex adhesives, nitrile rubber-based adhesives, nitrocellulose adhesives, reactive hot melt adhesives, phenolic resin-based adhesives, modified silicone-based adhesives, polyamide resin hot melt adhesives, polyimide-based adhesives, polyurethane resin hot melt adhesives, polyolefin resin hot melt adhesives, polyvinyl acetate resin solution-based adhesives, polystyrene resin solvent-based adhesives, polyvinyl alcohol-based adhesives, polyvinylpyrrolidone resin-based adhesives, polyvinyl butyral resin-based adhesives, polybenzimidazole adhesives, polymethacrylate resin solution-based adhesives, melamine resin-based adhesives, urea resin-based adhesives, and resorcinol-based adhesives. Furthermore, synthetic adhesives are preferred from the standpoint of handleability and adhesiveness, and among these, α-olefin-based adhesives, epoxy resin-based adhesives, and cyanoacrylate-based adhesives that have flame retardancy or have been imparted with flame retardancy are more preferred.

[0031] The thickness of the flame-retardant thermal insulation material 10 according to this embodiment is not particularly limited and can be determined appropriately depending on the purpose and application. However, from the viewpoints of economy and ease of processing, the thickness of the flame-retardant thermal insulation material 10 is preferably 100 mm or less, more preferably 0.1 to 50 mm, and even more preferably 0.3 to 30 mm.

[0032] The total weight ratio of the sheet-like substrate 11 to the heat insulating layer 12 (sheet-like substrate / heat insulating layer) may be 10 / 90 to 99 / 1, preferably 20 / 80 to 97 / 3, more preferably 25 / 75 to 95 / 5, and particularly preferably 30 / 70 to 90 / 10. With such a ratio, a flame-retardant heat insulating material 10 having excellent heat resistance and flame retardancy can be obtained.

[0033] The flame-retardant heat insulating material 10 according to the present embodiment has a bulk density of 0.01 to 10 g / cm3 from the viewpoints of flame retardancy, heat insulating property, tensile strength, interlayer strength, processability, etc. 3 The range of 0.05 to 8 g / cm is preferable. 3 It is more preferable that the range is 0.08 to 5 g / cm. 3 , and particularly preferably 0.1 to 3 g / cm 3 It is desirable that the bulk density be within the above range. However, as long as the overall flame retardancy, tensile strength, and thermal conductivity meet the target values, there is no limitation to the above bulk density. However, if the bulk density of the flame-retardant thermal insulation material 10 is controlled within the above range, the proportion of air (oxygen) in the flame-retardant thermal insulation material 10 can be controlled within a certain range, making it easier to obtain excellent flame retardancy and thermal insulation.

[0034] The flame-retardant thermal insulation material 10 according to the present embodiment may be colored with a dye or pigment as needed. A coloring method may involve adding a colorant to the thermal insulation layer 12. Alternatively, the sheet-like substrate 11 may be colored. In this case, a dye-dyed yarn obtained by mixing a dye or pigment with a polymer and spinning the mixture before spinning may be used, or the sheet-like substrate 11 may be colored after being formed.

[0035] In addition, if necessary, the flame-retardant insulating material 10 of this embodiment may be coated or impregnated with an acrylic resin emulsion or acrylic resin solution containing a known flame retardant such as an acrylic resin emulsion, a phosphate ester-based flame retardant, a halogen-based flame retardant, or a hydrated metal compound, in order to further improve its flame retardancy, tensile strength, and interlayer strength.

[0036] Various additives can be added to the flame-retardant heat insulating material 10 according to the present embodiment depending on the purpose. Examples of additives include organic phosphorus and thioether antioxidants; hindered amine light stabilizers; benzophenone, benzotriazole, and benzoate ultraviolet absorbers; antistatic agents; bisamide, wax, and organometallic salt dispersants; amide and organometallic salt lubricants; bromine-containing organic, phosphoric acid, melamine cyanurate, and antimony trioxide flame retardants; stretching aids for low-density polyethylene and linear low-density polyethylene; organic pigments; inorganic pigments; inorganic fillers; organic fillers; and metal ion-based inorganic and organic antibacterial agents.

[0037] The inorganic heat insulating filler and inorganic binder for forming the heat insulating layer 12 of the flame-retardant heat insulating material 10 according to this embodiment, and the sheet-like substrate 11 will be described below. (inorganic heat insulating filler)

[0038] The inorganic insulating filler can be any suitable shape and composition as long as it has low thermal conductivity and provides insulating effects. Examples include silicate minerals such as sepiolite, talc, kaolin, mica powder, and sericite, magnesium carbonate, calcium carbonate, hard clay, calcined clay, barium sulfate, calcium silicate, wollastonite, sodium bicarbonate, synthetic silica such as white carbon and fused silica, natural silica such as diatomaceous earth, silica nanoparticles, aluminum hydroxide, magnesium hydroxide, and inorganic balloons such as glass beads, which may be used alone or in combination.

[0039] Preferably, the inorganic filler contains a balloon structure. A balloon structure refers to a structure containing a gas layer inside the bead. Examples of the gas layer include air, nitrogen, and rare gases. Examples of such inorganic balloons include glass balloons, fly ash balloons, silica balloons, and perlite. Among these, glass balloons are particularly preferred. The addition of these inorganic fillers exhibits effects such as maintaining the shape in a high-temperature atmosphere and improving heat insulation.

[0040] The particle size of the inorganic balloons is not particularly limited as long as they can be uniformly mixed with the inorganic binder, but the average particle size is preferably 1 μm or more and 100 μm or less, and more preferably 3 μm or more and 70 μm or less.

[0041] Furthermore, the silica nanoparticles may be wet silica, dry silica, aerogel, fumed silica, etc. Silica nanoparticles are spherical or nearly spherical silica particles with an average particle diameter of less than 1 μm, on the order of nanometers. When the average particle diameter of the silica nanoparticles is 1 nm or more and 100 nm or less, the heat insulating properties can be further improved, particularly in the room temperature 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. The average particle diameter of the silica nanoparticles is more preferably 50 nm or less, and even more preferably 10 nm or less.

[0042] Here, aerogel is obtained by drying a wet gel obtained by hydrolysis and condensation polymerization using the sol-gel method in a supercritical fluid or subcritical state. The obtained aerogel has a porous structure with pores of 5 to 30 nm in diameter, consisting of beads of 20 nm in average diameter, and has an apparent specific gravity of 0.03 to 0.3 g / cm3 and a specific surface area of ​​500 to 900 m3. 2 / g, with a solid content of 5% or less, and the remaining 95% or more surrounded by an air layer. Aerogel is sometimes distinguished as a substance obtained by drying with a supercritical fluid, while xerogel is a substance obtained by drying below the critical point, but in this invention, aerogel includes xerogel. Here, specific surface area refers to the surface area per unit weight.

[0043] Fumed silica is obtained by hydrolyzing a halogenated silane such as silicon tetrachloride in an oxyhydrogen flame (a so-called dry method). The obtained fumed silica has a porous structure with pore diameters of 10 nm to 100 nm, in which spherical particles with diameters of 10 to 30 nm are aggregated and fused together in a beaded shape, and has an apparent specific gravity of 0.03 to 0.1 g / cm. 3 , specific surface area 40~400m 2 / g and are aggregates with particle diameters of 100 to 400 nm.

[0044] The apparent density of silica gel is 0.7 to 1.3 g / cm 3 , specific surface area 300~800m 2 / g and has an average pore size of 1 nm to 10 nm. Silica aerogel and fumed silica differ from general silica gel in that they have a low apparent specific gravity. (inorganic binder)

[0045] The flame-retardant heat insulating material of the present invention can use various inorganic binders. Any inorganic substance capable of forming a film can be used as the inorganic binder. Examples include silicone-based binders, silica-based binders, alumina-based binders, zirconia-silica-based binders, smectites such as saponite, hectorite, and montmorillonite, vermiculites, kaolinite-serpentine such as kaolinite and halloysite, and natural clay minerals such as sepiolite. Other examples include colloidal silica, colloidal alumina and their modifications, synthetic inorganic polymer compounds, calcium sulfate, calcium silicate, water glass, Portland cement, alumina cement, alumina silicate, calcium oxide, and clay. These film-forming inorganic substances can be used alone or in combination.

[0046] The thickness of the heat insulating layer 12 formed using the inorganic heat insulating filler and inorganic binder is not particularly limited and can be determined appropriately depending on the purpose and application. However, from the viewpoints of economy and ease of processing, the thickness of the heat insulating layer 12 is preferably 100 mm or less, more preferably 0.1 to 50 mm, and even more preferably 0.3 to 30 mm.

[0047] The total weight ratio of the inorganic insulating filler to the inorganic binder may be 10 / 90 to 97 / 3, preferably 20 / 80 to 95 / 5, more preferably 25 / 75 to 92 / 8, and particularly preferably 30 / 70 to 90 / 10. With such a ratio, a flame-retardant insulating material with excellent heat resistance and flame retardancy can be obtained.

[0048] As described above, this heat insulating layer can be formed by not only the cast (flow coating) molding method, but also by general film molding methods such as T-die extrusion molding, inflation molding, and calendar molding.

[0049] The heat insulating layer 12 may be colored with dyes or pigments as needed. Note that the heat insulating layer 12 may be coated or impregnated with an acrylic resin emulsion or an acrylic resin solution containing a known flame retardant such as an acrylic resin emulsion, a phosphate ester flame retardant, a halogen-based flame retardant, or a hydrated metal compound, as needed, in order to further improve its flame retardancy and tensile strength.

[0050] Furthermore, various additives may be added to the heat insulating layer 12 depending on the purpose. Examples of additives include short fibers such as 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; organophosphorus and thioether antioxidants; hindered amine light stabilizers; benzophenone, benzotriazole, and benzoate ultraviolet absorbers; antistatic agents; bisamide, wax, and organic metal salt dispersants; amide and organic metal salt lubricants; bromine-containing organic, phosphoric acid, melamine cyanurate, and antimony trioxide flame retardants; stretching aids such as low-density polyethylene and linear low-density polyethylene; organic pigments; inorganic pigments; inorganic fillers; organic fillers; and metal ion-based inorganic and organic antibacterial agents.

[0051] The heat insulating layer 12 can be prepared, for example, by adding a volatile solvent, such as methyl ethyl ketone (MEK), toluene, or N,N-dimethylformamide, to the inorganic heat insulating filler and inorganic binder, thoroughly kneading them, and uniformly dispersing them. The kneading can be performed using, for example, a high-speed disperser, a vertical disperser, a kneader, a ball mill, a three-roll mill, a jet mill, an impeller, or the like. (sheet-shaped substrate)

[0052] The sheet-like substrate 11 can be in various shapes, such as paper, nonwoven fabric, film, plate, or cloth (woven fabric). Its thickness is preferably in the range of 0.005 to 5 mm. A more preferred thickness is 0.015 to 1 mm, and an even more preferred thickness is 0.05 to 0.5 mm. A thickness of less than 0.005 mm is undesirable because it reduces handling and workability. A thickness of 0.015 mm or more is more preferable because it significantly improves workability. A thickness of 0.05 mm or more is particularly preferable because it significantly improves workability. A thickness of more than 5 mm is undesirable because it reduces productivity when manufacturing the sheet-like substrate 11. 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 further increases productivity while maintaining heat insulation. The sheet-like substrate 11 may be a laminated sheet made by laminating two or more types of materials, for example, a laminate of a paper-like material and a cloth-like material.

[0053] Materials that are flame-retardant or have been imparted with flame retardancy can be used for the sheet-like substrate 11, such as cellophane, celluloid, synthetic paper, art paper, retroreflective sheeting, glass fiber cloth, polyethylene cloth, polypropylene cloth, etc. Furthermore, elastic resins or thermoplastic resins can also be used for the sheet-like substrate 11 as long as they are flame-retardant or have been imparted with flame retardancy.

[0054] The elastic resin may be styrene-butadiene rubber, acrylonitrile-butadiene rubber, olefin-based elastomer resin, styrene-based elastomer resin, urethane-based elastomer resin, polyester-based elastomer resin, polyamide-based or aramid-based elastomer resin, which has flame retardancy or has been imparted with flame retardancy.

[0055] The thermoplastic resin may be any of ethylene polymers such as high-pressure low-density polyethylene, high-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, etc., propylene polymers such as polypropylene and propylene-α-olefin copolymers containing propylene as the main component, polyvinyl chloride, polyester, polyamide, polyimide, acrylic resin, etc., which are either flame-retardant or have been made flame-retardant.

[0056] When producing the sheet-like substrate 11 from these thermoplastic resins, it can be formed by T-die extrusion molding, cast molding, calendar molding, or inflation molding. The obtained sheet may also be used after biaxial stretching. This is preferable because it can increase the stiffness and tensile strength of the sheet-like substrate 11.

[0057] The above-mentioned fabric-like materials can be produced by known weaving methods using filaments made of thermoplastic resin materials, such as drawn thermoplastic resin monofilaments, tapes, yarns, split yarns, multifilaments, or staple fibers. The term "filaments" broadly refers to long objects that can be formed into sheets, including ribbons, strings, monofilaments, multifilaments, and the like, which can be twisted as needed. The structure of the filaments can be any. They can be made into tapes by slitting a thermoplastic resin film to a predetermined width and uniaxially stretching it. They can also have cross sections of round, spheroidal, rectangular, polygonal, or other irregular shapes. Furthermore, suppleness can be enhanced by using Danline, which is a filament extruded from a mixture of different resins and fibrillated by splitting the resins. A single filament can be used as a weaving thread, or several filaments can be bundled together.

[0058] The filaments can be woven into a cloth-like material in a plain weave, twill weave, twill weave, rib weave, double weave, twill weave, etc. Furthermore, they can also be knitted into a cloth-like material in a warp knitting, weft knitting, raschel knitting, tricot knitting, etc. As a loom for weaving, a known loom such as a circular loom, a sluiser type loom, or a water jet type loom can be used.

[0059] The cross-bonded fabric may be a fabric made by arranging a large number of filaments made of a thermoplastic resin material in a line crosswise to form a sheet and joining the intersections. It may also be a knitted or braided fabric made using filaments made of the above-mentioned thermoplastic resin material. The filaments used to manufacture the cross-bonded fabric are primarily composed of a high-melting-point resin component having a melting point higher than the thermocompression temperature, but may also contain a low-melting-point resin component having a melting point lower than the thermocompression temperature. The resulting fabric-like material can be used as a sheet-like substrate 11 as is, or it can be made into a laminated resin sheet by laminating a thermoplastic resin film layer thereon.

[0060] In the present invention, the sheet-like substrate 11 has an oxygen index of 26 or more. Therefore, if the oxygen index of the material used is less than 26, a flame retardant is added to make the oxygen index 26 or more. Even if the oxygen index is 26 or more, a flame retardant may be added to further improve the flame retardancy.

[0061] The flame retardant used to achieve an oxygen index of 26 or more may be a known flame retardant for paper, nonwoven fabric, film, plate, or woven fabric. Examples include halogen-based flame retardants, a combination of a halogen-based flame retardant and antimony trioxide, phosphorus-based flame retardants, metal hydroxide-based flame retardants, metal phosphinate-based flame retardants, nitrogen-containing compounds such as melamine cyanurate and triazine compounds, and sodium polyphosphate.

[0062] Examples of the halogen-based flame retardants include bromine-based flame retardants such as tetrabromobisphenol A, hexabromocyclodecane, dibromodiphenyl oxide, tetrabromobisphenol A polycarbonate oligomer, brominated polystyrene, and ethylene bistetrabromophthalimide; chlorine-based 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 those sold under the trade names "CR-504L," "CR-570," and "DAIGUARD-540," manufactured by Daihachi Chemical Industry Co., Ltd.

[0063] Examples of the phosphorus-based flame retardant include non-halogen phosphate esters such as trimethyl phosphate, triethyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, 2-naphthyl diphenyl phosphate, and cresyl di-2,6-xylenyl phosphate; aromatic condensed phosphate esters such as those manufactured by Daihachi Chemical Industry Co., Ltd. under the trade names "CR-733S," "CR-741," and "PX-200"; and non-halogen condensed phosphate esters such as those manufactured by Daihachi Chemical Industry Co., Ltd. under the trade names "DAIGUARD-580," "DAIGUARD-610," and "DAIGUARD-880." Examples of the metal hydroxyl group-based flame retardant include magnesium hydroxide and aluminum hydroxide.

[0064] Examples of the metal phosphinate flame retardants include those manufactured by Clariant under the trade names "Exolit OP1230" and "Exolit OP930." For example, in the case of compound products (composite objects, composite materials), a synergistic effect can be achieved 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 inhibits hydrolysis and has excellent resistance to moist heat.

[0065] The sheet-like substrate 11 in the present invention is not limited to the above-mentioned materials and configuration, and may contain inorganic balloons or silica nanoparticles to further improve flame retardancy and heat insulation.

[0066] The flame-retardant thermal insulation material 10 of the present invention may vary in shape and size depending on the intended use. However, the thickness of the sheet-like substrate 11 used therein is preferably 3 to 50% of the total thickness of the flame-retardant thermal insulation material 10, more preferably 5 to 40%. By making the sheet-like substrate 11 3% or more, the flame-retardant thermal insulation material 10 is endowed with adequate strength and rigidity and can be easily molded into a desired shape. Furthermore, a maximum of 50% of the sheet-like substrate 11 can provide sufficient thermal insulation and flame retardancy. It is not preferable to make the thickness of the sheet-like substrate 11 greater than 50% of the total thickness because the proportion of the insulating layer 12 is relatively reduced, resulting in reduced thermal insulation and flame retardancy. (Modification of the first embodiment)

[0067] Hereinafter, a flame-retardant thermal insulation material according to a modification of the first embodiment will be described. Fig. 2 is a cross-sectional view showing an example of a flame-retardant thermal insulation material 20 according to the present embodiment. The flame-retardant thermal insulation material 20 of this modification has a configuration in which thermal insulation layers 22 made of an inorganic thermal insulation filler and an inorganic binder are laminated on both sides of a sheet-like substrate 21.

[0068] Such flame-retardant heat insulating material 20 can be produced, for example, by adding 180 parts by weight of toluene and 60 parts by weight of isopropyl alcohol to the inorganic heat insulating filler and inorganic binder, stirring and mixing the mixture, casting the mixture onto one side of sheet-like substrate 21, drying (100°C x 5 minutes), and then casting the mixture onto the other side in the same manner, drying (100°C x 5 minutes), and then heat curing (150°C x 8 hours). Alternatively, the material can be produced by slightly modifying the various manufacturing methods described in the first embodiment.

[0069] In this case, the heat insulating layers 22 formed on both sides may be made of the same material, or different materials may be used on each side. The thicknesses do not have to be the same. When different materials are used, the drying temperature and time, and the heat curing temperature and time should be set according to the respective materials. (Example)

[0070] 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 property value in the following examples and comparative examples are as follows. (1) Thickness: Measured in accordance with JIS L-1096 under a load of 1 kPa. (2) Oxygen index: Measured at 23°C in accordance with JIS K-7201. (3) Tensile strength: The tensile strength in the longitudinal direction was measured in accordance with JIS L-1096. From the viewpoints of processability, durability, and abrasion resistance, it must be 0.5 MPa or more, preferably 5 MPa or more, and more preferably 10 MPa or more. (4) High-temperature interlaminar strength: The interlaminar strength was measured at 60°C in accordance with JIS K-6854-3. From the viewpoint of processability and abrasion resistance, it must be 0.5 N / 50 mm or more, preferably 3 N / 50 mm or more, and more preferably 5 N / 50 mm or more. (5) Flame retardancy test: Compliant with UL-94 5V flat test piece vertical flame test. (6) Thermal conductivity: Measured in accordance with JIS A-1412-2.

[0071] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. The inorganic fillers used in the examples described below are shown in Table 1, the inorganic binders in Table 2, and the sheet-like substrates in Table 3.

[0072] As shown in Table 1, the inorganic fillers used were three types of glass balloons, one type each of fly ash balloons, shirasu balloons, perlite, silica aerogel, and flaky mica powder. The details of each inorganic filler are shown in Table 1.

[0073] As shown in Table 2, the inorganic binders used were silicone-based binders, silica-based binders, alumina-based binders, and zirconia-silica-based binders. A polyurethane-based binder was used as a comparative example. Details of each inorganic binder are shown in Table 2.

[0074] As shown in Table 3, the sheet-like substrates used were flame-resistant fiber woven fabric, basalt fiber woven fabric, basalt fiber nonwoven fabric, glass fiber woven fabric, silica fiber woven fabric, alumina fiber woven fabric, polyester flame-retardant nonwoven fabric, and polyethylene flame-retardant nonwoven fabric. A general nonwoven fabric was used as a comparative example. Details of each sheet-like substrate are shown in Table 3.

[0075] [Table 1]

[0076] [Table 2]

[0077] [Table 3] Example 1

[0078] In this example, glass balloons A were used as the inorganic filler, and the effects of varying the amount of glass balloons A mixed were evaluated. Example 1-1 contained 90 parts by weight of glass balloons A and 10 parts by weight of silicone-based binder. Example 1-2 contained 40 parts by weight of glass balloons A and 60 parts by weight of silicone-based binder. Example 1-3 contained 60 parts by weight of glass balloons A and 40 parts by weight of silicone-based binder. Example 1-4 contained 10 parts by weight of glass balloons A and 90 parts by weight of silicone-based binder. Comparative Example 1-1 contained 98 parts by weight of glass balloons A and 2 parts by weight of silicone-based binder. Comparative Example 1-2 contained 5 parts by weight of glass balloons A and 95 parts by weight of silicone-based binder. The curing agent was set according to the weight parts of the silicone-based binder, as shown in Table 4.

[0079] To the glass balloons A, silicone binder, and curing agent, 180 parts by weight of toluene and 60 parts by weight of isopropyl alcohol were added and mixed, and the mixture was cast onto a flame-resistant woven fabric sheet substrate, dried (100°C for 5 minutes), and heat-cured (150°C for 8 hours) to obtain a flame-retardant insulating material with a total thickness of 0.8 mm. Since the flame-resistant woven fabric sheet substrate was 0.4 mm thick, the insulating layer formed on one side of the flame-resistant woven fabric was 0.4 mm. The physical property evaluation results of the resulting flame-retardant insulating material are shown in Table 4.

[0080] The tensile strength was 16.0 MPa in Example 1-1, 21.0 MPa in Example 1-2, 19.0 MPa in Example 1-3, and 24.0 MPa in Example 1-4. These results confirmed that the tensile strength increased as the amount of glass balloon A, an inorganic filler, mixed decreased. Furthermore, all of Examples 1-1 to 1-4 cleared the target values.

[0081] Regarding high-temperature interlaminar strength, there was a tendency for strength to increase as the amount of glass balloon A mixed in decreased, but all targets were met. Flame retardancy test results also met all evaluation standards. Thermal conductivity also tended to increase as the amount of glass balloon A mixed in decreased, and in Example 1-4, the thermal conductivity was 0.2 W / m K, but still met the target value.

[0082] On the other hand, in Comparative Example 1-1, glass balloon A was used in an amount of 98 parts by weight. Although the tensile strength, flame retardancy, and thermal conductivity all met the target values, the high-temperature interlaminar strength was 0.3 N / 50 mm, which did not meet the target value of 0.5 N / 50 mm.

[0083] In addition, Comparative Example 1-2, in which glass balloon A was used at 5 parts by weight, met the standards for tensile strength, high-temperature interlaminar strength, and flame retardancy, but the thermal conductivity was 0.4 W / m K, which did not meet the target value of 0.2 W / m K.

[0084] [Table 4] Example 2

[0085] In this example, the effects of using various inorganic fillers were investigated. As shown in Table 5, the effects of using flaky mica powder, glass balloons B, glass balloons C, fly ash balloons, silica balloons, perlite, silica aerogel, and a mixed filler of glass balloons A and silica aerogel were investigated. Flame-retardant thermal insulation materials were prepared in the same manner as in Example 1, except that the inorganic filler was changed. Details of these materials and the evaluation results of the physical properties of the prepared flame-retardant thermal insulation materials are shown in Table 5.

[0086] As can be seen from Table 5, when various inorganic fillers were used in Examples 2-1 to 2-8, the target values ​​for tensile strength, high-temperature interlaminar strength, flame retardancy, and thermal conductivity were all met. As a result, it was confirmed that the flame-retardant insulating material obtained by mixing an inorganic filler having insulating properties with an inorganic binder, casting it onto a sheet substrate, drying (100°C x 5 minutes), and heat curing (150°C x 8 hours) has excellent properties. The total thickness of this flame-retardant insulating material is 0.8 mm, the thickness of the sheet substrate is 0.4 mm, and the thickness of the insulating layer formed on one side of the sheet substrate is also 0.4 mm.

[0087] [Table 5] Example 3

[0088] In this example, the effects of using various inorganic binders were investigated. Instead of the silicone-based binder used as the inorganic binder in Examples 1 and 2, a silica-based binder was used in Example 3-1, an alumina-based binder in Example 3-2, and a zirconia-silica-based binder in Example 3-3. Flame-retardant heat insulating materials were fabricated and their properties were evaluated. At the same time, a urethane-based binder was used in Comparative Example 3-1 to fabricate a flame-retardant heat insulating material, and its properties were evaluated.

[0089] In this example, a flame-retardant insulating material was produced in the same manner as in Example 1, except that no curing agent was used and the heat curing conditions were changed to 150°C x 1 hour. In this example, the total thickness of the flame-retardant insulating material was 0.8 mm, the thickness of the flame-resistant fiber woven fabric sheet substrate was 0.4 mm, and the thickness of the insulating layer formed on one side of the flame-retardant woven fabric sheet substrate was also 0.4 mm. Details of the inorganic filler, inorganic binder, and sheet substrate, as well as the results of evaluating the physical properties of the produced flame-retardant insulating material, are shown in Table 6.

[0090] Examples 3-1 to 3-3 all met the target values ​​for tensile strength, high-temperature interlaminar strength, flame retardancy, and thermal conductivity. These results demonstrate that good flame-retardant insulation can be obtained using not only silicone-based binders but also silica-based binders, alumina-based binders, and zirconia-silica-based binders. On the other hand, when a urethane-based binder was used, the target values ​​for tensile strength, high-temperature interlaminar strength, and thermal conductivity were met, but the flame retardancy test did not meet the standard values. Because the urethane-based binder is an organic material, it was found that the flame retardancy test could not be met even when the inorganic filler, glass balloon A, was used in an amount of 90 parts by weight and the urethane-based binder in an amount of 10 parts by weight.

[0091] [Table 6] Example 4

[0092] In this example, the effects of different materials for the sheet-like substrate were investigated. In Examples 1 to 3, flame-resistant fiber woven fabric was used as the sheet-like substrate, but in this example, Example 4-1 used basalt fiber woven fabric, Example 4-2 used basalt fiber nonwoven fabric, Example 4-3 used glass fiber woven fabric, Example 4-4 used silica fiber woven fabric, and Example 4-5 used alumina fiber woven fabric.

[0093] The manufacturing method of the flame-retardant insulating material was the same as in Example 1, and the total thickness of all flame-retardant insulating materials was 0.8 mm. However, in Example 4-1, the thickness of the basalt fiber woven fabric sheet substrate was 0.4 mm, and the thickness of the insulating layer formed on one side of it was also 0.4 mm. In Example 4-2, the thickness of the basalt fiber nonwoven fabric was 0.3 mm, and the thickness of the insulating layer was 0.5 mm. In Example 4-3, the thickness of the glass fiber woven fabric was 0.05 mm, and the thickness of the insulating layer was 0.75 mm. In Example 4-4, the thickness of the silica fiber woven fabric was 0.2 mm, and the thickness of the insulating layer was 0.6 mm. Furthermore, in Example 4-5, the thickness of the alumina fiber woven fabric was 0.3 mm, and the thickness of the insulating layer was 0.5 mm. Details of the inorganic filler, inorganic binder, and sheet substrate, as well as the physical property evaluation results of the prepared flame-retardant insulating materials, are shown in Table 7.

[0094] In this example, all of Examples 4-1 to 4-5 cleared the target values ​​for tensile strength, high-temperature interlaminar strength, flame retardancy, and thermal conductivity. As a result, it was confirmed that good properties can be obtained not only by using flame-resistant fiber woven fabrics but also by using various woven fabrics or nonwoven fabrics shown in Table 7 as the sheet-like substrate.

[0095] [Table 7] Example 5

[0096] This example describes the manufacture and properties of a flame-retardant heat insulating material that is a modification of the first embodiment. Various materials were used as the sheet-like substrate, and the effects of providing heat insulating layers on both sides were investigated.

[0097] In this example, Example 5-1 used a glass fiber woven fabric as the sheet-like substrate, and formed heat insulating layers consisting of glass balloons A and a silicone binder on both sides. The manufacturing method involved casting and coating one side of the glass fiber woven fabric and drying (100°C x 5 minutes), then casting and coating the other side in the same way and drying (100°C x 5 minutes), followed by heat curing (150°C x 8 hours) to obtain a flame-retardant heat insulating material with a total thickness of 0.8 mm.

[0098] In Example 5-2, a polyethylene flame-retardant woven fabric was used as the sheet-like substrate, and a heat-insulating layer was formed on both sides. In Example 5-3, a polyester flame-retardant nonwoven fabric was used as the sheet-like substrate, and a heat-insulating layer was formed on both sides. In Example 5-4, a glass fiber woven fabric was used as the sheet-like substrate, and a heat-insulating layer was formed on both sides using 45 parts by weight of glass balloon A and 45 parts by weight of silica aerogel. In Comparative Example 5-1, a general nonwoven fabric was used, and a heat-insulating layer was formed on both sides.

[0099] In Example 5-2 to Comparative Example 5-1, the method of forming the heat insulating layer on both sides was the same as in Example 5-1. The total thickness of the flame-retardant heat insulating materials was 0.8 mm, and the thickness of the heat insulating layer formed on both sides was set according to the thickness of the sheet-like substrate. Details of the inorganic filler, inorganic binder, and sheet-like substrate, as well as the evaluation results of the physical properties of the prepared flame-retardant heat insulating materials, are shown in Table 8.

[0100] The flame-retardant heat insulating materials of Examples 5-1 to 5-4 cleared the target values ​​for all of tensile strength, high-temperature interlayer strength, flame retardancy, and thermal conductivity. The polyethylene flame-retardant woven fabric has an oxygen index of 33, and the polyester flame-retardant nonwoven fabric has an oxygen index of 29, but these were also found to have good flame retardancy.

[0101] However, it was found that ordinary nonwoven fabrics with an oxygen index of 21 did not pass the flame retardancy test. This result confirmed that even if heat insulating layers were formed on both sides, if the oxygen index was less than 26, the fabric would not pass the flame retardancy test.

[0102] [Table 8] (Second embodiment)

[0103] 2 is a cross-sectional view showing the use of the flame-retardant thermal insulation material of the present invention as a thermal insulation sheet for a secondary battery pack. The secondary battery pack 30 of the present invention comprises a storage section 33, a plurality of battery cells 31 fixed in the storage section 33, and a flame-retardant thermal insulation sheet 32 ​​provided between the plurality of battery cells 31, and the flame-retardant thermal insulation sheet 32 ​​uses the flame-retardant thermal insulation material of the present invention.

[0104] Even if any of the battery cells generates heat and catches fire for some reason, the flame-retardant heat insulating sheet 32 ​​surrounding it prevents heat conduction to other battery cells 31, thereby preventing ignition.

[0105] Since the flame-retardant heat insulating material of the present invention is in the form of a sheet, it can be easily processed into an appropriate size, shape, etc. by applying a known method according to the purpose and use, and therefore can be used for a variety of purposes.

[0106] In particular, when used in a secondary battery pack for an automobile, if a fire breaks out from a secondary battery cell, secondary battery pack, or secondary battery module for some reason, it can not only prevent the flame from spreading, but also prevent the fire from spreading from the secondary battery module to the outside.

[0107] The flame-retardant heat insulating material of the present invention can be used in applications requiring both flame retardancy and heat insulating properties, such as interior materials for vehicles such as automobiles and freight cars, and transportation equipment such as aircraft and ships, civil engineering and construction materials such as wall members, floor members and ceiling members, packaging materials for refrigerated containers, bedding, and sound-absorbing materials.

[0108] In addition, it can be used for a wide range of applications, such as automobile ceiling materials, rear packages, door trim applications, dashboard insulators for automobiles, trains, and aircraft, various heat retaining materials, heat shielding materials, and heat insulating materials, protective clothing, protective gloves, and protective 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]

[0109] The flame-retardant heat insulating material of the present invention is in sheet form, so it is flexible and can be easily punched into the required shape, and because it has flame retardancy and heat insulating properties, it is useful in a wide range of fields where heat shielding or heat insulating properties are required. [Explanation of symbols]

[0110] 10, 20 Fire-retardant insulation 11, 21 Sheet substrate 12, 22 Insulation layer 30 Secondary battery pack 31 Battery Cells 32 Flame-retardant heat insulation sheet 33 Storage area

Claims

1. A sheet-like substrate having an oxygen index of 26 or more; a heat insulating layer laminated on at least one surface of the sheet-like substrate, A flame-retardant heat insulating material, wherein the heat insulating layer comprises an inorganic heat insulating filler and an inorganic binder.

2. 2. The flame-retardant insulating material according to claim 1, wherein the inorganic insulating filler is at least one selected from the group consisting of flaky mica, glass balloons, fly ash balloons, shirasu balloons, perlite, silica xerogel, and silica aerogel.

3. 2. The flame-retardant heat insulating material according to claim 1, wherein the inorganic binder is at least one selected from the group consisting of a silicone-based binder, a silica-based binder, an alumina-based binder, and a zirconia-silica-based binder.

4. 2. The flame-retardant heat insulating material according to claim 1, wherein the sheet-like substrate is a woven or nonwoven fabric made of inorganic fibers or inorganic filaments, or a woven or nonwoven fabric made of organic fibers and imparted flame retardancy.

5. A storage section and a plurality of battery cells fixed within the storage section; a flame-retardant heat insulating sheet disposed between the plurality of battery cells; A secondary battery pack, wherein the flame-retardant heat insulating sheet uses the flame-retardant heat insulating material according to any one of claims 1 to 4.

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