Sheet, fireproof material using same, and secondary battery

Abstract

The problem to be solved by the invention is to provide a sheet that is flexible yet has excellent heat resistance at high temperatures, and a fire-resistant material and a secondary battery that use the same. The sheet of the present invention comprises: resin A having a limiting oxygen index of 25 or less in accordance with JIS K 7201-2 (2007); resin B having a limiting oxygen index of 25 or more in accordance with JIS K 7201-2 (2007); and insulating inorganic particles; wherein at least one of resin A and resin B is in the form of fibers, the fibers having a fiber length of 38 to 120 mm and a crimp number of 4.5 to 120.

Description

[Technical Field]

[0001] The present invention relates to a sheet having excellent heat resistance, and a fire-resistant material and a secondary battery using the same. [Background technology]

[0002] In recent years, hybrid and electric vehicles have been attracting attention from the perspective of environmental protection. In order for electric vehicles to become more widely used in society, performance improvements such as further improvements in efficiency and extended battery life, as well as improved safety and fuel economy, are required.

[0003] Battery modules and battery packages containing battery cells for in-vehicle secondary batteries are required to have certain flame retardancy, heat resistance, heat insulation, and electrical insulation properties, so it has been common to combine a heat-resistant metal casing with a heat-resistant and insulating mica sheet or the like.

[0004] For example, known nonwoven fabrics include a wet-laid nonwoven fabric with excellent flame retardancy, which is made by cutting flame-retardant rayon and polyphenylene sulfide fibers into short pieces, dispersing them in water, and then weaving them (see, for example, Patent Document 1), and a nonwoven fabric containing non-melting fibers with a limiting oxygen index of 27 or more and thermoplastic fibers with a limiting oxygen index of 30 or more (see, for example, Patent Document 2).Also known are spun yarns and nonwoven fabrics that are composites of flame-retardant fibers containing amorphous silica (see, for example, Patent Document 3), and a nonwoven fabric made of flame-resistant yarn and polyphenylene sulfide (see, for example, Patent Document 4). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-184839 [Patent Document 2] International Publication No. 2022 / 111424 [Patent Document 3] Special Publication No. 2008-522056 [Patent Document 4] International Publication No. 2019 / 188275 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in recent years, from the perspective of improving fuel efficiency by reducing the weight of battery packages and saving space in the packages, it is considered necessary for battery packaging materials to have the formability to conform to the shape of the battery.

[0007] In this regard, in the battery modules and battery packages having battery cells for the above-mentioned in-vehicle secondary batteries, although the shape of the metal casing can be designed by press molding or the like, the mica sheet combined with it has a high rigidity and may crack when bent, which poses a problem in terms of formability. In other words, a material that is flexible while maintaining flame retardancy and heat resistance against high-temperature burners, for example, at around 1000°C, is required.

[0008] As a flexible material, for example, the wet-laid nonwoven fabric disclosed in Patent Document 1 is thin and flexible, but its flame retardancy and heat resistance against a high-temperature burner at, for example, around 1000°C are insufficient. Furthermore, the nonwoven fabric disclosed in Patent Document 2 does not develop holes when heated with a high-temperature burner for 10 minutes, but cracks occur in the heated area and carbonization progresses, so suppression of embrittlement is required. The nonwoven fabric disclosed in Patent Document 3 does not develop holes when heated with a high-temperature burner for 10 minutes, but residues of carbonized flame-retardant fibers remain on the silica fibers, which still retain their fibrous shape, widening gaps in the nonwoven fabric and allowing flames to escape through these gaps. The nonwoven fabric disclosed in Patent Document 4 does not develop holes when heated with a 1000°C burner for 10 minutes, but decomposition of the polyphenylene sulfide carbide progresses in the center of the flame, thinning the carbonized film, and progressing embrittlement, so improvement of its flame retardancy and heat resistance is also required.

[0009] In view of the above-mentioned circumstances, an object of the present invention is to provide a sheet that is flexible yet has excellent heat resistance at high temperatures, and a fire-resistant material and a secondary battery that use the same. [Means for solving the problem]

[0010] To address the above-mentioned problems, the present invention employs the following means. (1) A sheet containing resin A, resin B, and inorganic particles, The resin A is non-meltable and has a limiting oxygen index according to JIS K 7201-2 (2007) of 25 or less, Resin B is thermoplastic and has a limiting oxygen index according to JIS K 7201-2 (2007) of 25 or more, At least one of the resin A and the resin B is in the form of a fiber, The fiber has a fiber length of 38 to 120 mm and a crimp number of 4.5 to 120 crimps, The sheet, wherein the inorganic particles are insulating. (2) The sheet according to (1) above, wherein the inorganic particles are contained in the resin A. (3) The sheet according to (1) or (2) above, wherein the resin A includes at least one selected from the group consisting of cellulose-based materials, thermosetting resins, and flame-retardant materials obtained by subjecting raw materials selected from acrylonitrile-based, pitch-based, cellulose-based, and phenol-based resins to a flame-retardant treatment. (4) The sheet according to any one of (1) to (3) above, wherein the inorganic particles contain at least one selected from silica and titanium dioxide. (5) The sheet according to any one of (1) to (4) above, wherein the resin A contains at least a cellulose-based material. (6) A sheet according to any one of (1) to (5) above, wherein the resin B comprises at least one selected from anisotropic melt polyester, poly(butylene terephthalate), poly(acrylonitrile butadiene styrene), polysulfone, poly(ether-ether-ketone), poly(ether-ketone-ketone), polyethersulfone, polyarylate, polyarylene sulfide, polyphenylsulfone, polyetherimide, polyamideimide, and copolymers thereof. (7) The sheet according to any one of (1) to (6) above, wherein the resin A is contained in an amount of 15 to 80% by mass of the mass of the sheet. (8) The sheet according to any one of (1) to (7) above, wherein the resin B is contained in an amount of 20 to 85% by mass of the mass of the sheet. (9) The sheet according to any one of (1) to (8) above, wherein the mass of the inorganic particles is 20 to 60% by mass of the mass of the resin A. (10) The density of the sheet is 50 to 800 kg / m 3 The sheet according to any one of (1) to (9) above, wherein (11) The sheet according to any one of (1) to (10) above, wherein the sheet is a dry-laid nonwoven fabric. (12) The surface resistance of the sheet, measured in accordance with JIS C 2139-3-2 (2018), after heating for 180 seconds with a Bunsen burner at 1000°C is 1.0 x 10 6 The sheet according to any one of (1) to (11) above, having a resistance of Ω or more. (13) A fire-resistant material using the sheet according to any one of (1) to (12) above. (14) A secondary battery using the sheet according to any one of (1) to (12) above as a fire-resistant material. [Effects of the Invention]

[0011] The sheet of the present invention has the above-mentioned constitution and is therefore flexible and highly heat-resistant. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of an apparatus for measuring heat resistance. [Figure 2] FIG. 2 is a schematic diagram showing an example of a cross section of a sheet of the present disclosure. [Figure 3] FIG. 3 is a schematic diagram showing an example of another embodiment of the cross section of the sheet of the present disclosure. [Figure 4] FIG. 4 is a schematic diagram showing a cross section of a fire-resistant material and a secondary battery using the sheet of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0013] The sheet of the present disclosure contains resin A having a limiting oxygen index of 25 or less in accordance with JIS K 7201-2 (2007), resin B having a limiting oxygen index of 25 or more in accordance with JIS K 7201-2 (2007), and insulating inorganic particles.

[0014] 《Limiting Oxygen Index》 The limiting oxygen index in this disclosure is determined in accordance with JIS K 7201-2 (2007). The limiting oxygen index is the volume percentage of the minimum amount of oxygen required to sustain combustion of a substance in a nitrogen-oxygen mixture, and the higher the limiting oxygen index, the more difficult it is to burn. Substances with a limiting oxygen index of 25 or higher according to JIS K 7201-2 (2007) are difficult to burn, and even if they ignite, the fire will quickly extinguish once the source of fire is removed. In some cases, the fire will be extinguished by carbonization. Conversely, the lower the limiting oxygen index, the easier it is to burn and the less likely it is that a carbonized residue will remain after combustion.

[0015] The limiting oxygen index is measured by hot pressing each resin raw material or dissolving it in an appropriate solvent and casting it into a sample measuring 80 to 150 mm in length, 10±0.5 mm in width, and 4±0.25 mm in thickness. If the measurement sample is too weak to stand on its own, it can be measured by fixing the measurement sample wound up on a stainless steel rod as described in JIS K7201-2 (2007). When measuring using a sheet sample, the evaluation should be carried out as follows. (1) Identification of each resin type: The resin species that make up the sheet are identified using a microscopic FT-IR (Fourier transform infrared spectrophotometer). (2) Separation and removal of each resin layer from the sheet: After identifying the resin type in (1) above, each resin layer is separated and removed using an acid, alkali, or an appropriate organic solvent depending on the resin type. The concentration of the acid, alkali, or organic solvent, as well as the treatment temperature and time for removal, can be adjusted as appropriate. When separating a thermoplastic resin from a non-melting resin, it is also possible to heat the mixture to near the melting point of the thermoplastic resin and filter and separate the non-melting resin.

[0016] (3) Measurement of limiting oxygen index: A sample is prepared from each of the separated resins as described above, and the limiting oxygen index is measured.

[0017] <Melting point / glass transition temperature> The melting point is a value measured by a method conforming to JIS K7121 (2012) and refers to the melting peak temperature when heated at 10°C / min under a nitrogen flow using a differential scanning calorimeter. The glass transition temperature is a value measured by a method conforming to JIS K7121 (2012) and refers to the inflection point or peak temperature in the endothermic / exothermic curve when heated at 10°C / min under a nitrogen flow using a differential scanning calorimeter.

[0018] Resin A Resin A has the above-mentioned limiting oxygen index of 25 or less. Preferably, the limiting oxygen index is 23 or less. By setting the limiting oxygen index within the range of the present disclosure, Resin A is efficiently oxidatively decomposed, making it easier to form a charcoal that combines insulating inorganic particles described below with Resin B. When Resin B combines insulating inorganic particles described below with Resin B to form a film, the charcoal contributes to maintaining the strength of the portion exposed to flame, further improving heat resistance. Furthermore, efficient oxidative decomposition of Resin A suppresses excessive carbonization of the portion exposed to flame, while the insulating properties of the inorganic particles make it easier to maintain the insulation of the portion exposed to flame.

[0019] Resin A is non-meltable. In this disclosure, non-meltable refers to a material that does not liquefy but maintains its shape when exposed to a flame at 700°C, or that burns or carbonizes. Even if a melting peak is observed in the above-mentioned differential scanning calorimetry analysis, if the material does not liquefy due to the progression of combustion or carbonization when exposed to a flame at 700°C, it is considered non-meltable in this disclosure.

[0020] Resin A preferably contains at least one selected from, for example, cellulose-based materials, thermosetting resins, and flame-retardant materials. These materials are preferably contained in an amount of 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, based on the mass of Resin A itself. Flame-retardant materials are preferably flame-retardant materials obtained by flame-retardant treatment using raw materials selected from acrylonitrile-based, pitch-based, cellulose-based, and phenol-based resins. Flame-retardant treatment refers to a process for imparting heat resistance by forming a ladder-like or cyclic structure having carbon atoms from raw materials selected from acrylonitrile-based, pitch-based, cellulose-based, and phenol-based resins. For example, in the case of acrylonitrile-based raw materials, flame-retardant treatment can be performed by heat treatment in air at a temperature of 200 to 300°C for 30 to 60 minutes. Examples of thermosetting resins include epoxy-based resins, unsaturated polyester-based resins, cross-linked acrylic resins, and vinyl ester-based resins. Thermosetting resins are cured by heat. These may be used alone or in combination of two or more.

[0021] Of the above, it is more preferable that resin A contains at least one of a cellulose-based material and a thermosetting resin. It is even more preferable that resin A contains at least a cellulose-based material that can be easily formed into a film or fiber using known methods. When using a cellulose-based material in the form of a film, for example, cellophane, which is obtained by dissolving wood pulp using known methods and regenerating it into a film, can be mentioned. When using a fibrous material, fibrous materials such as wood pulp, cotton, and hemp can be used as they are, or rayon, cupra, lyocell, and acetate obtained by modifying raw cellulose can be used.

[0022] The form of resin A preferably used in the present disclosure may be any of the above-mentioned film form, fiber form, and form impregnated into a fiber substrate. For example, resin A may be impregnated as shown in 202 in Figure 2, or may be in the form of fiber as shown in 302 in Figure 3. In the present disclosure, a fiber form is preferred because it allows for easy compounding with resin B, which will be described later.

[0023] When used in the form of fibers, the crimp number of the fibers is preferably in the range of 4.5 to 120, and more preferably in the range of 5.0 to 100. When the crimp number of the fibers is 4.5 or more, preferably 5.0 or more, the binding force between the fibers is strong when the fibers shrink when exposed to high temperatures, making them less likely to develop holes and improving heat resistance at high temperatures. Furthermore, the fibers are more resistant to friction, resulting in stronger mechanical properties for the sheet. Conversely, when the crimp number of the fibers is 120 or less, preferably 100 or less, the fibers are less entangled, improving flexibility. Furthermore, by maintaining the crimps in the fibers within the above range, appropriate frictional force is generated between the fibers, and the shrinkage of the heat-resistant sheet can be suppressed relative to the shrinkage of the fibers, resulting in a sheet that is less likely to develop holes or cracks when exposed to high temperatures and has excellent heat resistance. The crimp number in this disclosure is determined by the crimp number specified in JIS L 1015 (2010) 8.12. However, while the above measurement method calculates the number of crimps per 25 mm of fiber length, in this disclosure, the number of crimps is the number of ridges per fiber. Even if the fiber length is not 20 mm, the sample is attached to a piece of paper and measured according to JIS to determine the number of crimps per fiber.

[0024] The fiber length is preferably within the range of 38 to 120 mm, more preferably within the range of 40 to 115 mm, and even more preferably within the range of 42 to 110 mm. By keeping the fiber length within the above range, it becomes easy to form a dry nonwoven fabric by entangling a web formed by a carding or air-laid method using a needle punching method or a hydroentangling method after the web has been formed using the carding or air-laid method. By setting the fiber length to 38 mm or more, preferably 40 mm or more, and more preferably 42 mm or more, the mechanical properties of the sheet are improved, making it less likely to develop holes due to abrasion. Furthermore, by making the sheet bulky and thick, it is possible to obtain a sheet with excellent heat resistance. The fiber length is determined using the JIS L 1015 (2010) 8.4A method. The thickness of the single fiber is not particularly limited, but from the viewpoint of passability through the carding process, a single fiber fineness within the range of 0.1 to 10 dtex is preferred.

[0025] Examples of the form of the sheet when using a fiber form include woven fabrics, knitted fabrics (hereinafter sometimes referred to as "woven / knitted fabrics"), nonwoven fabrics, etc. In the case of woven / knitted fabrics, spun yarns obtained by spinning the above-mentioned staple fibers by a known method, or continuous filament yarns can also be used. In such cases, the compounding with resin B can be exemplified by a method in which fibers made of resin A are mixed and spun, or alternately woven and knitted into a woven / knitted fabric. In the case of nonwoven fabrics, if resin B is in a fibrous form, examples of the compounding method include a method in which the tows are aligned and then cut, or a method in which the respective resins are made into staple fibers and then mixed in an opening process, carding process, air mixing process, etc.

[0026] The proportion of resin A in the sheet of the present disclosure is preferably 15% by mass or more of the sheet mass, and more preferably 20% by mass or more. By setting the content of resin A at or above the above range, heat resistance is improved due to the influence of inorganic particles in the sheet. The upper limit is preferably 80% by mass or less, and more preferably 70% by mass or less. By setting the proportion of resin A at or below the above range, fire spread when exposed to flame is suppressed, a decrease in heat resistance can be suppressed, and hardening of the entire sheet due to inorganic particles can be suppressed. Note that when resin A contains inorganic particles, the mass including the inorganic particles is measured as the mass of resin A.

[0027] 《Inorganic particles》 The inorganic particles in the sheet of the present disclosure are insulating. In the present disclosure, the inorganic particles may be of one type or two or more types. In the present disclosure, insulating refers to a particle having a volume resistivity of 1.0 × 10 or more as measured according to JIS C 2139-3-1 (2018) (Measurement of resistance characteristics by application of DC voltage - volume resistance and volume resistivity). 6The test method is as described in the JIS, under the conditions described in 5.5.5 Conditioning and pretreatment of test specimens, that is, measurements were taken under the conditions of standard atmosphere B (23±2°C x 50±5% RH) described in JIS C 2142 (2016) (Solid electrical insulating materials - Standard conditions before and during tests) 8. Standard atmosphere. Specifically, measurements were taken using the method described in the examples below. There are no particular restrictions on insulating inorganic particles, but metal oxides can be cited as an example. A specific example of inorganic particles is silica (SiO2): volume resistivity = 1.0 x 10 14 Ω·m, alumina (Al2O3): volume resistivity = 1.0 × 10 16 Ω·m, silicon nitride (Si3N4): volume resistivity = 1.0 × 10 16 Ω m, magnesium oxide (MgO): volume resistivity = 1.0 × 10 14 Ω m, calcium oxide (CaO): volume resistivity = 1.0 × 10 14 Ω·m, titanium dioxide (TiO2): volume resistivity = 1.0 × 10 14 Ω m, zinc oxide (ZnO): volume resistivity = 1.0 × 10 15 Among these, it is preferable to use at least one selected from silica and titanium dioxide, which are less reactive with moisture in the air and are industrially available in a stable manner.

[0028] In the present disclosure, inorganic particles are preferably contained in resin A. This allows for a synergistic effect between the non-melting resin A and the insulating inorganic particles to be more fully realized, further improving heat resistance. Furthermore, the inorganic particles can be more effectively prevented from falling off the sheet, and flexibility can also be improved. To illustrate this with reference to the drawings, if the sheet is impregnated with resin A, the inorganic particles may be contained in resin A, as shown at 204 in FIG. 2. Furthermore, if resin A is in the form of fibers, the inorganic particles may be contained in the fibers, as shown at 304 in FIG. 3. The method for extracting inorganic particles contained in resin A and measuring their volume resistivity is as follows: First, a sufficient amount of resin A is extracted from the sheet, the resin component is burned off in a heating furnace at 900°C, and the resin is cooled. The mass of the residue after cooling is measured, and the resin is reheated and cooled for another 30 minutes to confirm that the mass loss rate is within 1% by mass before and after reheating. If the mass loss rate is greater than 1% by mass, the resin is reheated until the mass loss rate is within 1% by mass. The resulting residue is subjected to a pressure of 500 kgf / cm. 2 The volume resistivity is measured after molding the powder to a diameter of 100 mm and a thickness of 1 mm at a pressure of 1000 mm. If the amount of residue obtained is small, the thickness and area of ​​the molded product may be adjusted appropriately.

[0029] The mass of the inorganic particles is preferably 20% by mass or more of the mass of resin A, more preferably 25% by mass or more, and even more preferably 30% by mass or more, regardless of whether they are contained in resin A. As described above, it is preferable that the inorganic particles are contained in resin A at the above-mentioned mass% or more. Here, for example, 20% by mass of resin A means that the mass of the inorganic particles is 20% by mass relative to the total mass of resin A itself and the inorganic particles. Therefore, when all the inorganic particles are contained in resin A, the volume resistivity is calculated by dividing the mass measured after collecting the inorganic particles using the above-mentioned volume resistivity measurement method by the mass of resin A containing the inorganic particles. For inorganic particles not contained in resin A, the mass% is calculated by dividing the mass by the total mass of resin A and the inorganic particles. The amount of inorganic particles added in the manufacturing process may differ from the mass collected from the sheet as described above. In such cases, the mass collected from the sheet is used as the mass of the inorganic particles in the present disclosure. When the proportion of inorganic particles is above the above-mentioned range, when the sheet of the present disclosure is exposed to high temperatures, holes are less likely to form in high-temperature areas, and heat resistance tends to be improved. On the other hand, the proportion of inorganic particles is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less. When the proportion of inorganic particles is within the above range, for example, when inorganic particles are contained in resin A, the mechanical properties of resin A tend to be improved and it becomes easier to form a sheet.

[0030] The number-average particle size of the inorganic particles is preferably 0.1 μm or more, more preferably 0.2 μm or more. Having an inorganic particle size above the above range results in excellent handleability and reduced secondary aggregation. For example, when inorganic particles are contained in Resin A, the inorganic particles can be uniformly dispersed, resulting in stable heat resistance. On the other hand, the average particle size of the inorganic particles is preferably 5.0 μm or less, more preferably 2.0 μm or less. When the average particle size of the inorganic particles is below the above range, the mechanical properties of Resin A tend to improve and the resin A tends to be easily formed into a sheet. The number-average particle size is determined by imaging the inorganic particles using an optical microscope or scanning electron microscope and reading the particle size from a scale. If the inorganic particles are not perfectly round or spherical, the shortest axial length is considered to be the particle size. Images are taken from multiple locations, and the average particle size of 50 particles is calculated.

[0031] 《Resin B》 Resin B in the present disclosure exhibits thermoplastic properties. Its thermoplasticity allows it to flow onto the surface and gaps of the non-melting resin A as the temperature rises, facilitating its formation into a film. In the present disclosure, compounding with inorganic particles contributes to maintaining the strength of areas exposed to flames and improving heat resistance. Here, "thermoplastic" refers to a material that softens, flows, or melts as the temperature rises, and generally refers to a material that exhibits a melting point or glass transition temperature as determined by differential scanning calorimetry (DSC). Resin B preferably contains at least one selected from the group consisting of anisotropic melting polyesters, poly(alkylene terephthalates), poly(acrylonitrile butadiene styrene), polysulfones, poly(ether-ether-ketones), poly(ether-ketone-ketones), polyethersulfones, polyarylates, polyarylene sulfides, polyphenylsulfones, polyetherimides, polyamideimides, and copolymers thereof. The poly(alkylene terephthalate) is preferably poly(butylene terephthalate). These may be used alone or in combination of two or more kinds, and may contain additives.

[0032] Resin B has a limiting oxygen index of 25 or more, preferably 27 or more. Having a limiting oxygen index within the above range inhibits combustion in air and prevents excessive fire spread of Resin A. Furthermore, when carbonized Resin B and inorganic particles combine to form a film in the sheet, even better heat resistance is achieved.

[0033] Among the above, the most preferred resin B is polyarylene sulfide and its copolymers, particularly polyphenylene sulfide (hereinafter sometimes referred to as "PPS") and its copolymers (PPS and its copolymers will be hereinafter sometimes referred to as "PPS polymer"). Representative examples of PPS polymers include polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfide ketone, their random copolymers, block copolymers, and mixtures thereof. A particularly preferred PPS polymer is polyphenylene sulfide containing, as the main structural unit of the polymer, p-phenylene sulfide units represented by -(CH-S)-, preferably at 90 mol % or more. From the viewpoint of mass, polyphenylene sulfide containing 80 mass % or more, and even 90 mass % or more, of p-phenylene sulfide units is desirable. In particular, PPS polymers are most preferred because they contain sulfur atoms in the polymer structure, which generates sulfuric acid during thermal decomposition of the polymer or flame retardant, thereby exhibiting a mechanism for dehydrating and carbonizing the polymer substrate.

[0034] Furthermore, even if the limiting oxygen index of a polymer does not fall within the range specified in the present disclosure, it can be preferably used if the limiting oxygen index falls within the range specified in the present disclosure by mixing with a flame retardant. Of course, a polymer having a limiting oxygen index within the range specified in the present disclosure may also contain a flame retardant. As the flame retardant, it is preferable that the flame retardant contains sulfur molecules for the same reasons as those for the PPS polymer. From this perspective, sulfur-based flame retardants are preferred as the flame retardant.

[0035] The form of resin B preferably used in the present disclosure may be, like resin A, a film form, a fiber form, or a form impregnated into a fiber substrate, but a fiber form is preferred because it is easier to combine with resin A. The preferred fiber crimp number, fiber length, single fiber fineness, and sheet form are the same as those of the preferred fibers for resin A described above. Illustrative examples using figures include 203 in FIG. 2 and 303 in FIG. 3.

[0036] As described above, the resin B in the present disclosure is preferably a PPS polymer, and is preferably in the form of fiber. Here, a fiber made of a PPS polymer (hereinafter sometimes referred to as "PPS fiber") is a synthetic fiber made of a polymer whose main structural unit is -(C6H4-S)-. In the present disclosure, the undrawn PPS fiber and drawn yarn can be used in combination within the scope of the present disclosure. Of course, it is also possible to use a combination of a drawn yarn and an undrawn yarn of a fiber that satisfies the scope of the present disclosure instead of the PPS fiber.

[0037] The proportion of resin B in the sheet of the present disclosure is preferably 20% by mass or more of the sheet mass, and more preferably 30% by mass or more. By setting the content of resin B at or above the above range, excessive fire spread of resin A, which has a low limiting oxygen index, is suppressed, improving the heat resistance of the sheet. Conversely, the upper limit is preferably 85% by mass or less, and more preferably 80% by mass or less. By setting the content of resin B at or below the above range, the proportion of non-melting resin A becomes relatively high, suppressing excessive softening of the sheet due to a rise in temperature upon flame contact and making it less likely for holes to form in the flame contact area and its surrounding areas. Furthermore, a relatively large amount of inorganic particles makes the flame contact area less conductive.

[0038] In the present disclosure, at least one of the above-mentioned resin A and resin B is in the form of a fiber. By making them in the form of a fiber, the above-mentioned effects can be achieved. It is more preferable that both are in the form of a fiber. When they are in the form of a fiber, the fiber length and number of crimps of at least one of resin A and resin B are in the above-mentioned ranges. It is preferable that both are in the above-mentioned ranges.

[0039] <Resins other than Resin A and Resin B> In addition to resin A and resin B, one or more other resins may be added to the sheet to further impart specific performance or effects. For example, to improve the mechanical properties of the sheet, fibers other than vinylon fiber, resin B, such as polyester fiber or nylon fiber, may be used. Furthermore, adhesives for bonding resin A and resin B may also be added as resins other than resin A and resin B. The content of resins other than resin A and resin B is not particularly limited as long as it does not impair the effects of the present disclosure, but is preferably 20% by mass or less of the sheet mass, and more preferably 15% by mass or less. When using resins other than resin A and resin B, there is no particular limit as long as the desired performance is imparted, and the lower limit may be 0% by mass.

[0040] Seat The thickness of the sheet of the present disclosure is preferably 0.10 mm or more, as measured by a method conforming to JIS L-1913 (2010) Method A. When the sheet thickness is in the above range or more, the heat resistance is more excellent. On the other hand, the sheet thickness is preferably 5.00 mm or less. When the sheet thickness is in the above range or less, the flexibility is excellent, the entire package becomes thinner, and space-saving effects are obtained.

[0041] The basis weight of the sheet of the present disclosure is measured based on the mass per unit area as defined in JIS L-1913 (2010) 6.2. 2 It is stipulated that test pieces of a size of 30 cm or more must be taken. In this disclosure, the test piece is 30 cm square (90,000 mm 2 ) and measure the mass of the sample as 1m 2 Mass per unit (g / m 2 However, if the test piece is small, it may be cut into a rectangle of the largest possible size, measured with a steel ruler to determine the area, and the value obtained by dividing the sample mass by the area of ​​the sample may be used, as specified in JIS. The basis weight of the sheet is 50 g / m 2It is preferable that the weight is 80 g / m or more. 2 More preferably, it is 100 g / m or more. 2 It is more preferable that the basis weight is 500 g / m or more. When the basis weight is in the above range or more, the abrasion resistance and heat resistance are more excellent. On the other hand, the basis weight of the sheet is 500 g / m or more. 2 Preferably, it is 400 g / m or less. 2 More preferably, it is 300 g / m or less. 2 When the basis weight is within the above range, the sheet becomes more flexible and the package becomes lighter, resulting in the advantage of weight reduction.

[0042] The density of the sheet of the present disclosure can be determined by dividing the basis weight obtained by the above method by the thickness. 3 It is preferable that the saturation is 60 kg / m or more. 3 More preferably, it is 70 kg / m or more. 3 It is more preferable that the density is 800 kg / m or more. When the density is 800 kg / m or more, the sheet has excellent abrasion resistance, and the sheet is less likely to burn at high temperatures due to the small air layer, and the sheet also tends to have improved heat resistance. 3 Preferably, it is 700 kg / m or less. 3 More preferably, it is 600 kg / m or less. 3 When the density is within the above range or less, the flexibility of the sheet is superior.

[0043] The sheet of the present disclosure is preferably a dry nonwoven fabric for reasons such as the ease of adjusting the thickness and density, the ease of mixing resin A and resin B, and excellent performance. Examples of such a nonwoven fabric are 201 in Fig. 2 and 301 in Fig. 3.

[0044] The sheet of the present disclosure has a surface resistance of 1.0 × 10 in accordance with JIS C 2139-3-2 (2018) at a site after heating with a Bunsen burner at 1000 ° C for 180 seconds. 6It is preferable that the surface resistance is Ω or more. Since JIS recommends that measurements be made at three or more locations when the number of test specimens is not specified, it is preferable that measurements be made at three locations, and that all three locations be within the above range. By keeping the surface resistance within the above range, a sheet with excellent heat resistance can be obtained. The surface resistance tends to improve by increasing the mass of the resin A, resin B, and inorganic particles of the present disclosure, particularly the mass of the resin A and inorganic particles.

[0045] <<Sheet manufacturing method>> The method for producing the sheet of the present disclosure is not particularly limited, and the sheet can be produced by, for example, the following method, but is not limited thereto. The sheet of the present disclosure can be produced by combining resin A containing inorganic particles with resin B. For example, when one resin is in film form and the other resin is in fiber form, the fiber-form resin can be produced by combining the film-form resin with a fiber sheet formed by a known technique. When both resins are in fiber form, methods include a dry nonwoven fabric method in which the respective fibers are blended and a web is formed by a carding method or an air-laid method, and then a nonwoven fabric is formed by needle punching or hydroentangling, a method in which individual sheets are produced and then blended to form a sheet, and a method in which blended spun yarns or twisted filaments are used to form a woven or knitted fabric.

[0046] As a fiber manufacturing method, for example, a method for manufacturing PPS fiber, which is preferably used as resin B in the present disclosure, is preferably a method for melting a polymer having the above-mentioned phenylene sulfide structural unit at or above its melting point and spinning it through a spinneret to form a fiber. The spun fiber is generally an undrawn PPS fiber as is. Undrawn PPS fiber is largely amorphous and has a high breaking elongation. However, such fibers have poor thermal dimensional stability, so drawn yarns are commercially available that are oriented by hot drawing after spinning to improve the fiber strength and thermal dimensional stability. Several PPS fiber drawn yarns are available, including "TORCON" (registered trademark) (manufactured by Toray Industries, Inc.) and "PROCON" (registered trademark) (manufactured by Toyobo Co., Ltd.). Furthermore, a method for manufacturing flame-retardant rayon fiber containing inorganic particles, for example, as a cellulose-based fiber preferably used as resin A in the present disclosure, includes, but is not limited to, a method in which inorganic particles such as silica or titanium dioxide are added to a cellulose-containing viscose solution and the fiber is obtained by a two-bath tension spinning method. The method for imparting crimps is not particularly limited, and examples thereof include known methods such as mechanical pressing using a stuffing box or jet pressing using steam.

[0047] Examples of methods for producing sheets include dry nonwoven fabrics, in which short fibers are formed into a web by carding or air-laid methods and then needle-punched or hydroentangled to form a nonwoven fabric, and methods for producing woven or knitted fabrics using thread-like materials such as spun yarns or filaments. Sheet production using the dry nonwoven fabric method is preferred because of the ease of adjusting the density of the sheet by combining the blend ratio of resin A and resin B and the finishing process described below. Furthermore, when compounding a film-like resin with the resulting fiber sheet, methods such as coating and dipping are available.

[0048] The sheet thus obtained may be used as it is, or may be subjected to the following finishing process before use.

[0049] 《Finishing Process》 The obtained sheet may be used as is, or may be heat-set using a tenter or the like to suppress thermal shrinkage at high temperatures, or may be subjected to calendering to smooth and densify the surface. The setting temperature is preferably a temperature that is effective in suppressing high-temperature shrinkage, and is preferably 130 to 250°C, more preferably 150 to 230°C.

[0050] Calendering is primarily used to adjust the thickness of the sheet, i.e., its density. While the density is not particularly limited, if the density is too low, holes are likely to form when exposed to flame, reducing heat resistance at high temperatures. On the other hand, if the density is too high, the sheet becomes too hard, so it must be adjusted appropriately. The speed, pressure, and temperature of the calender are not limited as long as they do not impair the effects of the present disclosure.

[0051] <<Use of the sheet>> The sheet of the present disclosure thus obtained is flexible and has high heat resistance, and exhibits a fire spread prevention effect, particularly when combined with combustible materials, making it suitable for use as a fire-resistant material for applications requiring flame retardancy, such as clothing materials, wall materials, floor materials, ceiling materials, covering materials, etc. In particular, it can be suitably used as a fire-resistant protective clothing, a fire-spread prevention covering material for urethane sheet materials for automobiles and aircraft, etc., and a fire spread prevention material for bed mattresses.

[0052] Furthermore, since the sheet can suppress electrical conduction when exposed to high temperatures, it can be suitably used for heat-resistant insulation in high-temperature environments and in secondary batteries for automobiles. For example, it can also be suitably used as a fire-resistant material for battery modules and battery packages having battery cells of secondary batteries. [Example]

[0053] Next, the present disclosure will be specifically described based on examples. However, the present disclosure is not limited to these examples. Various modifications and alterations are possible within the scope of the technical scope of the present disclosure. The methods for measuring various properties used in the examples are as follows.

[0054] (Metsuke) In accordance with JIS L-1913 (2010) 6.2 Mass per unit area, the weight of a 30 cm square sample was measured as a test piece, and the area of ​​1 m 2 Weight per unit (g / m 2 ) is expressed as

[0055] (Thickness) Measurements were made in accordance with JIS L-1913 (2010) 6.1A method.

[0056] (density) The value obtained by dividing the above (basis weight) by (thickness) was recorded as the density.

[0057] (fineness) Measurements were made in accordance with JIS L 1015 (2010) 8.4A method.

[0058] (Number of crimps) Measurements were made in accordance with JIS L 1015 (2010) 8.12.1 Crimp count. JIS specifies the number of crimps per 25 mm, but here the number of crimps per fiber was used. Even when the fiber length was less than 20 mm, the sample was attached to a piece of paper and measurements were made in accordance with JIS.

[0059] (Heat resistance) Heat resistance was evaluated using a Bunsen burner with an inner diameter of 11 mm as follows. As shown in Figure 1, Bunsen burner 1 with a flame length L of 38 mm was placed vertically, and test specimen 2 was placed at a 45° angle to the horizontal. The heating time until the flame penetrated test specimen 2 was measured in seconds. Note that methane gas with a purity of 97% or higher was supplied to the Bunsen burner, and the air supply rate was adjusted to ensure the temperature of the tip of the flame was 1000°C. If the flame penetrated test specimen 2 within 180 seconds (3 minutes) of heating or if the fire spread throughout the entire test specimen, the test specimen was deemed "not heat resistant" and rated F. If the flame did not penetrate test specimen 2 or spread to the entire test specimen even after being exposed to flame for 180 seconds (3 minutes) or more, the test specimen was deemed "heat resistant." If the time until the flame penetrated was between 180 seconds (3 minutes) and 600 seconds (10 minutes), ...

[0060] (bending resistance) The bending resistance was evaluated using the 41.5-degree cantilever method (ISO method) of JIS L 1913 (general nonwoven fabric testing method, 2010). Measurements were taken at three random locations in each of the warp and weft directions, and the average value was recorded.

[0061] (bending resistance) Folding endurance was evaluated according to the JIS P 8115 (General Nonwoven Fabric Testing Method, 2001) folding endurance test method (MIT tester method). Using a No. 702 MIT folding endurance tester (manufactured by Mize Testing Instruments Co., Ltd.), a sample measuring 15 mm wide and 110 mm long was placed in a bending clamp with a radius of 0.38 mm. The bending clamp was adjusted (for thin fabrics or thick fabrics) depending on the sample thickness. The bending test was performed with a load of 1 kgf, a bending angle of 135°, and a test speed of 175 cpm, and the number of times the sample broke was recorded. If the sample did not break after 10,000 folds, it was recorded as "no break" and the condition of the sample was confirmed. Three randomly selected samples in each of the warp and weft directions were measured, and the average values ​​were recorded.

[0062] (Volume resistivity of inorganic particles) Measurement was performed using a method in accordance with JIS C 2139-3-1 (2018) (Measurement of resistance characteristics by applying DC voltage - Volume resistance and volume resistivity). Here, 5.5.3 states that in preparing the test specimen, the method should not change the state of the material and not damage the test specimen, and the specimen should have a simple shape such as a flat plate or tube. 5.5.1 General information states that unless otherwise specified, a length of 100 mm or more, a width of 100 mm or more, and a thickness of 1 ± 0.5 mm are recommended. Therefore, inorganic particles were measured at a pressure of 500 kgf / cm. 2The measurement sample was a 100 mm diameter, 1 mm thick specimen molded at a pressure of 100 V. The measurement was taken after 1 minute of application of a voltage of 100 V, the conditions for which are not specified in the individual specifications described in 5.2 Power Supply and Applied Voltage and 6.2 Volume Resistivity Measurement. Measurement was performed using a High Resistance Meter 4339B (Agilent Technologies) and its plate material measurement accessory 16008B (main electrode φ26 mm, guard electrode inner diameter φ38 mm, pressure during measurement 100 g). From the above measurement, the silica (SiO2) in the examples described below has a volume resistivity of 1.0 × 10 1 4 Ω·m, titanium dioxide (TiO2) has a volume resistivity of 1.0×10 14 Ω·m, and it was confirmed that both were insulating.

[0063] (sheet surface resistance) Using a 12.7 mm diameter propane Bunsen burner (manufactured by Tokyo Glass Instruments Co., Ltd.), a flame tip temperature adjusted to 1000°C was applied to the sheet for 180 seconds to prepare flame-exposed samples. Next, samples exposed to flame using the method described in the heat resistance evaluation section and samples not exposed to flame were measured under the conditions described in JIS C 2139-3-2 (2018) (Measurement of resistance characteristics by application of DC voltage - surface resistance and surface resistivity) 5.7 Test Procedure. Specifically, measurements were performed under the conditions described in JIS C 2142 (2016) (Solid electrical insulating materials - Standard conditions before and during test) 8. Standard atmosphere B (23 ± 2°C x 50 ± 5% RH), and samples were left in an environment of 25°C x 65% RH for 24 hours. Measurements were made in accordance with JIS C 2139-3-2 (2018) (Measurement of resistance characteristics by applying DC voltage - surface resistance and surface resistivity), using electrode C1 (inner diameter 50 mm) as described in 5.3.6 Electrode configuration C (concentric ring electrode), and the measurement voltage was 100 V, the recommended voltage for cases where no individual standard is specified as described in 5.2 Voltage. Specifically, a surface resistance measurement electrode SME-8301 (manufactured by Hioki E.E. Corporation) was connected to the Super Megohmmeter SM-8213, and measurements were made by pressing the measurement electrode against the sample. When the surface resistance (Ω) was 1.0 x 10 6The above cases were considered to be no continuity, and measurements were carried out on samples taken at three random locations.

[0064] (Resin A and Resin B content in the sheet) In this example, the content was calculated based on the amount of raw material used. When the content is measured using a sheet, the evaluation is performed as follows. (1) Identification of each resin type: The resin species were identified using a microscopic Fourier transform infrared spectrophotometer (FT-IR). (2) Separation and removal of each resin layer from the sheet: After identifying the resin type in (1) above, each resin layer was separated and removed using an acid, alkali, or an appropriate organic solvent depending on the resin type. The concentration of the acid, alkali, or organic solvent, as well as the treatment temperature and time for removal, can be adjusted as appropriate. When separating resin B from resin A, it is also possible to heat the mixture to near the melting point of resin B and then filter and separate resin A. (3) Measurement of the content of each resin: After identifying the resin type in (1) above, the mass of each resin was measured by sorting based on appearance or by separation using a dissolution method using a solvent suitable for each resin type, and the content ratio was calculated by dividing the mass of each resin by the sheet mass before carrying out (2) above.

[0065] (Content and composition of inorganic particles in resin A) The ash content of Resin A was measured according to JIS L 1015 (Testing Methods for Chemical Fiber Staples, 2010), and this value was taken as the content of inorganic particles. The obtained ash content was then subjected to elemental analysis using an energy dispersive micro-X-ray fluorescence analyzer, EDAX EAGLE II (manufactured by AMETEK Corporation), under the conditions of a rhodium cathode, a tube voltage of 35 kV, Cps 5000, and an analysis time of 100 seconds.

[0066] Next, the yarns used in the following examples and comparative examples will be described.

[0067] <PPS fiber drawn yarn 1> The drawn PPS fiber yarn 1 used was "TORCON" (registered trademark) manufactured by Toray Industries, Inc., product number S371, with a single fiber fineness of 2.2 dtex (diameter 14 μm) and a cut length of 51 mm. This PPS fiber has a limiting oxygen index of 34 and a melting point of 284°C, making it thermoplastic. The number of crimps was 12.0 crimps per 25 mm (12.0 / 25 × 51 = 24.5 crimps per short fiber).

[0068] <PPS fiber drawn yarn 2> The drawn PPS fiber yarn 2 used was "TORCON" (registered trademark) manufactured by Toray Industries, Inc., product number S307, with a single fiber fineness of 1.0 dtex (diameter 9 μm) and a cut length of 6 mm. This PPS fiber has a limiting oxygen index of 34 and a melting point of 284°C, making it thermoplastic. The number of crimps was 6.0 crimps per 25 mm (6.0 / 25 × 6 = 1.4 crimps per short fiber).

[0069] <PPS fiber drawn yarn 3> The drawn PPS fiber yarn 3 used was "TORCON" (registered trademark) manufactured by Toray Industries, Inc., product number S371, with a single fiber fineness of 2.2 dtex (diameter 14 μm) and a cut length of 38 mm. This PPS fiber has a limiting oxygen index of 34 and a melting point of 284°C, making it thermoplastic. The number of crimps was 12.0 crimps per 25 mm (12.0 / 25 × 38 = 18.2 crimps per short fiber).

[0070] <PPS fiber drawn yarn 4> As the drawn PPS fiber drawn yarn 4, a tow of "TORCON" (registered trademark) manufactured by Toray Industries, Inc., product number S307, with a single fiber fineness of 1.0 dtex (diameter 9 μm) was used to obtain short fibers with a cut length of 38 mm without passing through a crimper. This PPS fiber has a limiting oxygen index of 34 and a melting point of 284°C, making it thermoplastic. It was not passed through a crimper and had a crimp count of 0 crimps / 25 mm (0 / 25 x 38 = 0 crimps per short fiber).

[0071] <PPS fiber unstretched yarn 1> As the undrawn PPS fiber undrawn yarn 1, "TORCON" (registered trademark) manufactured by Toray Industries, Inc., product number S111, with a single fiber fineness of 2.2 dtex (diameter 14 μm) and a cut length of 51 mm was used. This PPS fiber has a limiting oxygen index of 34 and a melting point of 284°C, making it thermoplastic. The number of crimps was 6.0 crimps per 25 mm (6.0 / 25 × 51 = 12.2 crimps per short fiber).

[0072] <PPS fiber unstretched yarn 2> As the undrawn PPS fiber undrawn yarn 2, Toray Industries' "TORCON" (registered trademark), product number S111, with a single fiber fineness of 2.2 dtex (diameter 14 μm) and a cut length of 6 mm was used. This PPS fiber has a limiting oxygen index of 34 and a melting point of 284°C, making it thermoplastic. The number of crimps was 6.0 crimps per 25 mm (6.0 / 25 × 6 = 1.4 crimps per short fiber).

[0073] <PPS fiber unstretched yarn 3> As the undrawn PPS fiber undrawn yarn 3, "TORCON" (registered trademark) manufactured by Toray Industries, Inc., product number S111, with a single fiber fineness of 2.2 dtex (diameter 14 μm) and a cut length of 38 mm was used. This PPS fiber has a limiting oxygen index of 34 and a melting point of 284°C, making it thermoplastic. The number of crimps was 6.0 crimps per 25 mm (6.0 / 25 × 38 = 9.1 crimps per short fiber).

[0074] <PPS fiber unstretched yarn 4> As the undrawn PPS fiber undrawn yarn 4, a tow of Toray's "TORCON" (registered trademark), product number S111, with a single fiber fineness of 2.2 dtex (diameter 14 μm) was used to obtain short fibers with a cut length of 38 mm without passing through a crimper. This PPS fiber has a limiting oxygen index of 34 and a melting point of 284°C, making it thermoplastic. It was not passed through a crimper and had a crimp count of 0 crimps / 25 mm (0 / 25 x 38 = 0 crimps per short fiber).

[0075] <Flame-retardant rayon fiber 1> Flame-retardant rayon fiber 1 was "FR CORONA" (registered trademark) manufactured by Daiwabo Rayon Co., Ltd., with a single fiber fineness of 3.3 dtex (diameter 18 μm) and a cut length of 51 mm. This flame-retardant rayon fiber had a limiting oxygen index of 18, and the rayon component did not melt in air, making it non-meltable. The number of crimps was 6.8 crimps / 25 mm (6.8 / 25 × 51 = 13.9 crimps per short fiber). The proportion of inorganic particles contained in the flame-retardant rayon was 29.3 mass%. Elemental analysis revealed that the inorganic element was 100% silicon (Si). Since other inorganic elements were not detected below the detection limit, the inorganic particles were 100% SiO2. The average particle size of the inorganic particles contained in the fiber was 0.6 μm.

[0076] <Flame-retardant rayon fiber 2> (1) Production of viscose liquid A viscose stock solution containing 8.5% by mass of cellulose, 5.7% by mass of sodium hydroxide, and 2.6% by mass of carbon disulfide was prepared. Next, titanium dioxide (TA-300 manufactured by Fuji Titanium Kogyo Co., Ltd.) and a mixed solution of sodium hydroxide and water were added to the prepared viscose stock solution, and the composition of the viscose solution was adjusted to 7.2% by mass of cellulose and 7.4% by mass of sodium hydroxide, thereby obtaining a titanium dioxide-added viscose solution. The titanium dioxide content was 35% by mass relative to the mass of cellulose. (2) Spinning The titanium dioxide-added viscose solution was spun using a two-bath tension spinning method at a spinning speed of 50 m / min and a draw ratio of 50%, yielding a fiber with a fineness of 3.3 dtex. The first bath (spinning bath) contained 115 g / L of sulfuric acid and 350 g / L of sodium sulfate, and its temperature was 35°C. The second bath (hot water bath) had a temperature of 80°C. The titanium dioxide-added viscose solution was extruded through a nozzle to produce a rayon long fiber bundle containing titanium dioxide. (3) Crimping and cutting The long fiber bundle was passed through a crimper to create a crimp of 7.1 crimps per 25 mm, and then cut to a fiber length of 51 mm using a cutter. The number of crimps in the fiber was 7.1 / 25 x 51 = 14.5 crimps. The inorganic particle content of the resulting short cut fiber was measured and found to be 27.6 mass% in total, with 27.5 mass% TiO2 and 0.1 mass% Na2O. The limiting oxygen index was 20, and the rayon component does not melt in air, making it non-meltable. The average particle size of the inorganic particles contained in the fiber was 0.5 μm.

[0077] <Flame-retardant rayon fiber 3> The flame-retardant rayon fiber 3 used was "FR CORONA" (registered trademark) manufactured by Daiwabo Rayon, with a single fiber fineness of 3.3 dtex (diameter 18 μm) and a cut length of 5 mm. The limiting oxygen index of this flame-retardant rayon fiber was 18, and the rayon component does not melt in air, making it non-meltable. The number of crimps was 6.8 crimps / 25 mm (6.8 / 25 × 6 = 1.4 crimps per short fiber). The proportion of inorganic components contained in the flame-retardant rayon was 29.3 mass%. Elemental analysis revealed that the inorganic component was 100% silicon (Si), with no other inorganic components detected below the detection limit. The average particle size of inorganic particles contained in the fiber was 0.6 μm.

[0078] <Flame-retardant rayon fiber 4> The flame-retardant rayon fiber 4 used was "FR CORONA" (registered trademark) manufactured by Daiwabo Rayon Co., Ltd., with a single fiber fineness of 3.3 dtex (diameter 18 μm) and a cut length of 38 mm. This flame-retardant rayon fiber had a limiting oxygen index of 18, and the rayon component did not melt in air, making it non-meltable. The number of crimps was 6.8 crimps per 25 mm (6.8 / 25 × 38 = 10.3 crimps per short fiber). The proportion of inorganic particles contained in the flame-retardant rayon was 29.3 mass%. Elemental analysis revealed that the inorganic element was 100% silicon (Si). Since other inorganic elements were not detected below the detection limit, the inorganic particles were 100% SiO2. The average particle size of the inorganic particles contained in the fiber was 0.6 μm.

[0079] <Flame-retardant rayon fiber 5> (1) Production of viscose liquid A viscose stock solution containing 8.5% by mass of cellulose, 5.7% by mass of sodium hydroxide, and 2.6% by mass of carbon disulfide was prepared. Next, titanium dioxide (TA-300 manufactured by Fuji Titanium Kogyo Co., Ltd.) and a mixed solution of sodium hydroxide and water were added to the prepared viscose stock solution, and the composition of the viscose solution was adjusted to 7.2% by mass of cellulose and 7.4% by mass of sodium hydroxide, thereby obtaining a titanium dioxide-added viscose solution. The titanium dioxide content was 20% by mass relative to the mass of cellulose. (2) Spinning The titanium dioxide-added viscose solution was spun using a two-bath tension spinning method at a spinning speed of 50 m / min and a draw ratio of 50%, yielding a fiber with a fineness of 3.3 dtex. The first bath (spinning bath) contained 115 g / L of sulfuric acid and 350 g / L of sodium sulfate, and its temperature was 35°C. The second bath (hot water bath) had a temperature of 80°C. The titanium dioxide-added viscose solution was extruded through a nozzle to produce a rayon long fiber bundle containing titanium dioxide. (3) Cut The long fiber bundle was cut to a fiber length of 38 mm using a cutter without passing it through a crimper. The number of crimps in the fiber was 0 / 25 x 38 = 0 crimps, as it had not been passed through a crimper. The inorganic particle content of the resulting short cut fiber was measured and found to be 18.9 mass% in total, of which TiO2 was 18.8 mass% and Na2O was 0.1 mass%. The limiting oxygen index was 20, and the rayon component does not melt in air, making it non-meltable. The average particle size of the inorganic particles contained in the fiber was 0.5 μm.

[0080] [Example 1] (Nonwoven fabric production) The PPS fiber drawn yarn 1, PPS fiber undrawn yarn 1, and flame-retardant rayon fiber 1 obtained above were mixed in a fiber opener, then further mixed in a punching machine, and then passed through a carding machine to form a web. The obtained web was layered in a cross-lap machine and then felted in a needle punch machine to obtain a nonwoven sheet consisting of the PPS fiber drawn yarn, undrawn yarn, and flame-retardant rayon fiber. The mass mixture ratio of the PPS fiber drawn yarn, undrawn yarn, and flame-retardant rayon fiber in the nonwoven fabric was 40:30:30, and the basis weight was 203 g / m 2 , thickness 1.76mm, density 115kg / m 3 The structure of the obtained nonwoven fabric was roughly similar to that shown in Figure 3. (Heat resistance) For 600 seconds (10 minutes), the flame did not penetrate the nonwoven fabric, and it had sufficient flame and heat insulation properties, so its heat resistance was rated A. (bending resistance) The bending resistance measured by the cantilever method was 65 mm in the vertical direction and 70 mm in the horizontal direction, indicating that the nonwoven fabric was flexible. (bending resistance) Although slight fuzzing was observed at the folded portion even after 10,000 MIT folding cycles, the sample did not break in either the longitudinal or transverse directions, demonstrating good folding resistance. (sheet surface resistance) The surface resistance of all three test specimens was 1.0 x 10 before and after exposure to flame (3 minutes). 6 Ω or more, and no continuity was observed.

[0081] [Example 2] In Example 1, the mass mixing ratio of the PPS fiber stretched yarn, unstretched yarn, and flame-retardant rayon was changed to 60:30:10, and the weight was 201 g / m 2 , thickness 2.03mm, density 99kg / m 3 A nonwoven sheet of 1000g was obtained. This sheet did not develop any holes for 236 seconds, so its heat resistance was rated B. The bending resistance measured by the cantilever method was 71 mm in the vertical direction and 73 mm in the horizontal direction, making it a flexible nonwoven fabric. Furthermore, even after 10,000 MIT folding cycles, some fuzzing was observed at the folded area, but the sample did not break in either the vertical or horizontal direction, demonstrating good folding resistance. The surface resistance of the sheet was 1.0 x 10 6 No conduction was observed above Ω. The structure of the obtained nonwoven fabric was roughly similar to that shown in Figure 3.

[0082] [Example 3] In Example 1, the mass mixing ratio of the drawn yarn of PPS fiber, the undrawn yarn, and the flame-retardant rayon was changed to 10:5:85, and the basis weight was 205 g / m 2 , thickness 2.21mm, density 93kg / m 3 A nonwoven sheet of 1000g was obtained. Although this sheet experienced fire spread and residual flames on the flame-retardant rayon, and the area of ​​the flame spread became larger than the area in contact with the flame, no holes were formed after 450 seconds, so the heat resistance was rated B. The bending resistance measured by the cantilever method was 56 mm in the vertical direction and 58 mm in the horizontal direction, indicating that it was a flexible nonwoven fabric. Furthermore, even after 10,000 MIT folding cycles, some fuzzing was observed in the folded areas, but the sample did not break in either the vertical or horizontal directions, demonstrating good folding resistance. The surface resistance of the sheet was 1.0 x 10 both before and after contact with the flame. 6 No conduction was observed above Ω. The structure of the obtained nonwoven fabric was roughly similar to that shown in Figure 3.

[0083] [Example 4] A nonwoven fabric was produced under the same conditions as in Example 1, except that the flame-retardant rayon fiber 1 used in Example 1 was changed to the flame-retardant rayon fiber 2. The fibers constituting the nonwoven fabric were 1 PPS fiber oriented yarn, 1 PPS fiber unoriented yarn, and 2 flame-retardant rayon fibers, in a ratio of 40:30:30. The basis weight was 197 g / m 2 , thickness 1.78mm, density 111kg / m 3 It was. This nonwoven fabric had sufficient heat resistance for 600 seconds (10 minutes) without the flame penetrating the nonwoven fabric, and was therefore rated as heat resistance A. The bending resistance measured by the cantilever method was 71 mm in the vertical direction and 69 mm in the horizontal direction, indicating that the nonwoven fabric was flexible. Furthermore, even after 10,000 MIT folding cycles, some fuzzing was observed at the folded area, but the sample did not break in either the vertical or horizontal direction, demonstrating good folding resistance. The surface resistance of the sheet was 1.0 x 10 for all three test specimens both before and after exposure to flame (3 minutes). 6 The electrical resistance was Ω or more, and no electrical continuity was observed. The structure of the obtained nonwoven fabric was roughly similar to that shown in Figure 3.

[0084] [Example 5] The PPS fiber drawn yarn 1 and the PPS fiber undrawn yarn 1 obtained above were mixed in a 50:50 ratio using a fiber opener, then further mixed using a blow mill, and then passed through a carding machine to form a web. The obtained web was laminated using a cross-lap machine and then felted using a needle punch machine to produce a nonwoven fabric. The basis weight of the nonwoven fabric was 156 g / m 2 , thickness 1.55mm, density 101kg / m 3 It was. The obtained nonwoven fabric was dipped in a viscose liquid containing titanium dioxide particles prepared by the procedure in "(1) Production of viscose liquid" for flame-retardant rayon fiber 2, and the cellulose portion was regenerated in a bath of 115 g / L of sulfuric acid and 350 g / L of sodium sulfate to form a cellulose resin layer containing titanium dioxide particles, which was then dried. The cellulose resin containing titanium dioxide particles was formed into a sheet with a thickness of 4 mm, and a sample was taken at a length of 120 mm and a width of 10 mm to measure the limiting oxygen index, which was found to be 20. After drying, the nonwoven fabric sheet has a basis weight of 216 g / m 2 , thickness 1.50mm, density 144kg / m 3The composition of the nonwoven fabric sheet was 1 part oriented PPS fiber yarn, 1 part unoriented PPS fiber yarn, and 36 parts 36 parts 28 parts cellulose containing inorganic particles. The total content of inorganic particles in the cellulose was 29.8% by mass. The inorganic particle components were 29.5% by mass of TiO2 and 0.3% by mass of Na2O. The average particle size of the inorganic particles was 0.6 μm. The structure of the obtained nonwoven fabric was roughly similar to that shown in Figure 2. This nonwoven fabric sheet had sufficient heat resistance for 600 seconds (10 minutes) without the flame penetrating the nonwoven fabric, and was therefore rated as heat resistance A. The bending resistance measured by the cantilever method was flexible enough to bend the sheet to 113 mm in the vertical direction and 110 mm in the horizontal direction. Furthermore, even after 10,000 MIT folding tests, the sample did not break in either the vertical or horizontal direction, demonstrating good folding resistance. The surface resistance of the sheet was 1.0 x 10 for all three test specimens both before and after exposure to flame (3 minutes). 6 Ω or more, and no continuity was observed.

[0085] [Example 6] The nonwoven fabric obtained in Example 1 was treated using a double-sided heated metal roll thermal calender at a processing speed of 3 m / min, a heating temperature of 180°C, and a linear pressure of 150 kgf / cm to adjust the thickness. The obtained sheet had a basis weight of 216 g / m. 2 , thickness 0.45mm, density 480kg / m 3 It was. This nonwoven fabric sheet had sufficient heat resistance for 600 seconds (10 minutes) without the flame penetrating the nonwoven fabric, and was therefore rated as heat resistance A. The bending resistance measured by the cantilever method was flexible enough to bend 105 mm in the vertical direction and 101 mm in the horizontal direction. Furthermore, even after 10,000 MIT folding cycles, the sample did not break in either the vertical or horizontal direction, demonstrating good folding resistance. The surface resistance of the sheet was 1.0 x 10 for all three test specimens both before and after exposure to flame (3 minutes). 6 The electrical resistance was Ω or more, and no electrical continuity was observed. The structure of the obtained nonwoven fabric was roughly similar to that shown in Figure 3.

[0086] [Example 7] A nonwoven fabric was produced under the same conditions as in Example 1, except that the flame-retardant rayon fiber 1 used in Example 1 was changed to flame-retardant rayon fiber 4, the PPS fiber drawn yarn 1 was changed to PPS fiber drawn yarn 3, and the PPS fiber undrawn yarn 1 was changed to PPS undrawn yarn 3. The fibers constituting the nonwoven fabric were 3 oriented PPS fiber yarns, 3 unoriented PPS fiber yarns, and 4 flame-retardant rayon fiber, in a ratio of 40:30:30. The weight per unit area was 208 g / m 2 , thickness 1.43mm, density 145kg / m 3 It was. This nonwoven fabric had sufficient heat resistance for 600 seconds (10 minutes) without the flame penetrating the nonwoven fabric, and was therefore rated as heat resistance A. The bending resistance measured by the cantilever method was 58 mm in the vertical direction and 56 mm in the horizontal direction, indicating that the nonwoven fabric was flexible. Furthermore, even after 10,000 MIT folding cycles, some fuzzing was observed in the folded area, but the sample did not break in either the vertical or horizontal direction, demonstrating good folding resistance. The surface resistance of the sheet was 1.0 x 10 for all three test specimens both before and after exposure to flame (3 minutes). 6 The electrical resistance was Ω or more, and no electrical continuity was observed. The structure of the obtained nonwoven fabric was roughly similar to that shown in Figure 3.

[0087] [Table 1]

[0088] [Comparative Example 1] With reference to Patent Document 2 (WO 2022 / 111424), flame-retardant rayon fiber "DFG" (registered trademark) manufactured by Daiwabo Rayon Co., Ltd., with a fiber fineness of 3.3 dtex (diameter 18 μm) and a cut length of 51 mm, incorporating a phosphorus-based flame retardant, was used in place of the flame-retardant rayon fiber 1 in Example 1. This flame-retardant rayon fiber has a limiting oxygen index of 28, and the rayon component carbonizes in air, making it non-meltable. The number of crimps is 5.9 crimps per 25 mm (5.9 / 25 × 51 = 12.0 crimps per short fiber). This rayon incorporates a phosphorus-based flame retardant and does not contain inorganic particles. A nonwoven fabric was obtained in the same manner as in Example 1, using a blend ratio of the above-obtained drawn PPS fiber yarn 1 / undrawn PPS fiber yarn 1 / flame-retardant rayon of 40:30:30. The fabric had a basis weight of 200 g / m2 , thickness is 2.01mm, density is 100kg / m 3 It was. This nonwoven fabric cracked 125 seconds after exposure to flame, and flame penetrated through the cracks, giving it a heat resistance rating of F. The thickness of the nonwoven fabric in the flame-exposed area was not extremely thin, but carbonization had progressed excessively, and the carbonized area was prone to cracking. The bending resistance measured by the cantilever method was 60 mm in the vertical direction and 61 mm in the horizontal direction, indicating that the nonwoven fabric was flexible. Furthermore, after 10,000 MIT folding cycles, the sample did not break in either the vertical or horizontal direction, demonstrating good folding resistance. The surface resistance of the sheet was 1.0 x 10 before exposure to flame. 6 Although no conduction was observed, after exposure to flame (3 minutes), carbonization progressed and cracks were observed, so the surface resistance was 1.0 × 10 1 Conduction was achieved at Ω.

[0089] Comparative Example 2 With reference to Patent Document 3 (JP 2008-522056 A), a needle-punched nonwoven fabric was obtained using the flame-retardant rayon fiber used in Comparative Example 1, silica chop fiber KSF-75 (manufactured by Kowa Co., Ltd.) with a diameter of 7.5 μm and a cut length of 50 mm, 1 PPS fiber drawn yarn, and 1 PPS fiber undrawn yarn in a blend ratio of 25:15:40:20, respectively. The resulting nonwoven fabric had a basis weight of 197 g / m 2 , thickness 1.96mm, density 101kg / m 3 It was. This nonwoven fabric cracked 170 seconds after exposure to flame, allowing the flame to penetrate, and its heat resistance was rated F. At the flame-exposed area, PPS residue was present at the intersections of the silica fibers, which had melted and carbonized into balls, and the fibers that make up the nonwoven fabric were coarse, causing cracks to appear in the rough areas, allowing the flame to penetrate. The carbonized areas were prone to cracking. The bending resistance measured by the cantilever method showed flexibility, allowing bending at 135 mm in the vertical and 134 mm horizontal directions. After 10,000 MIT folding cycles, the sample did not break in either the vertical or horizontal directions, but some areas of the silica fibers had broken due to repeated bending were observed. The surface resistance of the sheet was 1.0 x 10 before exposure to flame. 6Although no electrical continuity was observed, after exposure to flame (3 minutes), carbonization of the flame-retardant rayon and PPS progressed, and the surface resistance of one specimen was 1.0 × 10 6 Although the resistance was above Ω, the remaining two specimens were 1.0 × 10 2 Variation was observed in Ω.

[0090] Comparative Example 3 With reference to Patent Document 1 (JP 2011-184839 A), a wet papermaking sample was prepared using the following fibers. The PPS fiber oriented yarn 2, PPS fiber unoriented yarn 2, and flame-retardant rayon fiber 3 obtained above were added to water in a ratio of 40:30:30. The mixture was stirred and dispersed for 1 minute using a household mixer adjusted to 3000 rpm. Next, the dispersion was added to a hand-made papermaking machine (manufactured by Kumagai Riki Kogyo Co., Ltd.) measuring 25 cm x 25 cm and 40 cm in height, with a 140-mesh hand-made papermaking screen installed at the bottom, and further water was added to adjust the fiber concentration to 0.1% by mass. Next, a wet paper web was obtained by dewatering. The total amount of fiber in the papermaking machine was adjusted to 6.25 g, and a 100 g / m 2 Two wet webs can be stacked to obtain a wet web of 200 g / m. 2 The wet web was made of. The obtained wet paper web was placed on a filter paper and dried in an oven at 130°C for 3 minutes, and then treated with a double-sided heated metal roll thermal calender at a processing speed of 3 m / min, a heating temperature of 180°C, and a linear pressure of 150 kgf / cm to adjust the thickness. The obtained sheet had a basis weight of 225 g / m. 2 , thickness 0.35mm, density 643kg / m 3 It was. This sheet cracked after 138 seconds and the flame penetrated, so its heat resistance was rated F. The bending resistance measured by the cantilever method was flexible enough to bend 145 mm in the vertical and 140 mm in the horizontal directions. The MIT folding endurance test showed that the sheet broke after 1,200 bendings in both the vertical and horizontal directions. The surface resistance of the sheet was 1.0 x 10 before contact with the flame. 6 Although no electrical continuity was observed, cracks appeared in the sheet after exposure to flame (3 minutes), and the resistance was 1.0×102 Conduction was measured at Ω. After drying, the flame-retardant rayon fibers were separated from the sheet, and the content of inorganic particles in the flame-retardant rayon was measured. It was found to be 19.2% by mass, confirming that the inorganic particles had fallen into the water during dispersion, stirring, and papermaking.

[0091] Comparative Example 4 With reference to Patent Document 4 (WO 2019 / 188275), a flame-retardant fiber (oxidized polyacrylonitrile fiber) manufactured by Zoltek Corporation with a fiber fineness of 2.2 dtex (diameter 13 μm) and a cut length of 51 mm was used as a non-melting fiber that does not contain inorganic particles, and was used in place of the flame-retardant rayon fiber 1 in Example 1. The limiting oxygen index of this flame-retardant fiber is 41. The number of crimps is 11.9 crimps / 25 mm (11.9 / 25 × 51 = 24.3 crimps per short fiber). This flame-retardant fiber does not contain inorganic particles. A nonwoven fabric was obtained in the same manner as in Example 1, using a mixture ratio of 1 oriented PPS fiber yarn, 1 unoriented PPS fiber yarn, and flame-resistant fiber of 40:30:30. The fabric weight was 197 g / m 2 , thickness 2.21mm, density 89kg / m 3 It was. Although this nonwoven fabric showed no holes after 10 minutes of exposure to flame, cracks appeared after 175 seconds, and the flame penetrated through the cracks, giving it a heat resistance rating of F. Excessive carbonization had progressed in the flame-exposed area, and the carbonized area was prone to cracking. The bending resistance measured by the cantilever method was 52 mm in the vertical direction and 50 mm in the horizontal direction, indicating that the nonwoven fabric was flexible. Furthermore, after 10,000 MIT folding cycles, the sample did not break in either the vertical or horizontal direction, demonstrating good folding resistance. The surface resistance of the sheet was 1.0 x 10 before exposure to flame. 6 Although the resistance was more than 1.0×10 Ω and no continuity was observed, after the flame was applied (for 3 minutes), carbonization had progressed and cracks had appeared, so the resistance was estimated to be 1.0×10 1 Conduction was achieved at Ω.

[0092] Comparative Example 5 A nonwoven fabric was produced under the same conditions as in Comparative Example 3, except that the flame-retardant rayon fiber 3 used in Comparative Example 3 was changed to flame-retardant rayon fiber 5, the PPS fiber drawn yarn 2 was changed to PPS fiber drawn yarn 4, and the PPS fiber undrawn yarn 2 was changed to PPS undrawn yarn 4. The fibers constituting the nonwoven fabric were 40:30:30 of oriented PPS fiber yarns, 4 of unoriented PPS fiber yarns, and 5 of flame-retardant rayon fiber. When the above fibers were added to water and stirred and dispersed for 1 minute in a household mixer adjusted to 3000 rpm, the fibers became entangled and clumped, making it difficult to obtain a uniform dispersion. Next, the dispersion was added to a 25cm x 25cm, 40cm high hand-made papermaking machine (manufactured by Kumagai Riki Kogyo Co., Ltd.) with a 140-mesh hand-made papermaking screen installed at the bottom, and further water was added to adjust the fiber concentration to 0.1% by mass. The wet paper web was then dewatered to obtain a wet paper web. The obtained wet paper web was uneven, with a mixture of clumped fiber aggregates and areas with visible holes. By adjusting the total amount of fiber in the papermaking machine to 6.25g, a 100g / m2 dispersion was obtained. 2 Two wet webs can be stacked to obtain a wet web of 200 g / m. 2 The wet web was made of. The obtained wet paper web was placed on a filter paper and dried in an oven at 130°C for 3 minutes, and then treated with a double-sided heated metal roll thermal calender at a processing speed of 3 m / min, a heating temperature of 180°C, and a linear pressure of 150 kgf / cm to adjust the thickness. The obtained sheet had a basis weight of 204 g / m. 2 , thickness 0.48mm, density 425kg / m 3 It was. This sheet had a lot of unevenness, and cracks appeared in the thinner parts after 24 seconds, allowing the flame to penetrate, so the heat resistance was rated F. The bending resistance measured by the cantilever method was flexible enough to bend 153 mm in the vertical direction and 158 mm in the horizontal direction. The MIT folding endurance test showed that the sheet broke after 300 bendings from the thinnest part of the sheet in both the vertical and horizontal directions. The surface resistance of the sheet was 1.0 x 10 before contact with the flame. 6 Although no electrical continuity was observed, cracks appeared in the sheet after exposure to flame (3 minutes), and the resistance was 1.0×10 1 Conduction was measured at Ω. After drying, the flame-retardant rayon fibers were separated from the sheet, and the content of inorganic particles in the flame-retardant rayon was measured, which revealed titanium dioxide of 18.2% by mass and sodium of 0.1% by mass.

[0093] [Reference example 1] The following evaluations were carried out using a 0.5 mm thick hard laminated mica board D581 manufactured by Okabe Mica Co., Ltd. The basis weight was 1020 g / m 2 , density is 2040 kg / m 3 It was. (Heat resistance) The flame did not penetrate the nonwoven fabric for 600 seconds (10 minutes), and the fabric had sufficient flame and heat insulation properties, so its heat resistance was rated A. (bending resistance) Since it was not possible to bend, the bending resistance could not be measured by the cantilever method. (bending resistance) It was difficult to bend at an angle of 135 degrees, making it impossible to measure. When bent by hand, the mica plate cracked. (sheet surface resistance) The surface resistance of all three test specimens was 1.0 x 10 before and after exposure to flame (3 minutes). 6 Ω or more, and no continuity was observed.

[0094] [Table 2] [Industrial Applicability]

[0095] The present disclosure is flexible and has high heat resistance, and therefore exhibits a fire spread prevention effect, particularly when combined with combustible materials, making it suitable for use in clothing materials, wall materials, floor materials, ceiling materials, covering materials, etc. that require flame retardancy, and is particularly suitable for use in fire-resistant protective clothing, fire spread prevention covering materials for urethane sheet materials for automobiles and aircraft, etc., and fire spread prevention for bed mattresses.

[0096] Furthermore, since the sheet contains insulating inorganic particles, it can suppress electrical conductivity when exposed to high temperatures, making it suitable for use as heat-resistant insulation in high-temperature environments and as a fire-resistant material for battery modules and battery packages that have battery cells for in-vehicle secondary batteries. [Explanation of symbols]

[0097] 101 Bunsen Burner 102 Test specimen L flame length 201 seats 202 Resin A 203 Resin B 204 Inorganic particles 301 seats 302 Resin A 303 Resin B 304 Inorganic particles 401 battery cells 402 Battery package case material 403 Fireproof materials

Claims

1. A sheet containing resin A, resin B, and inorganic particles, The resin A is non-meltable and has a limiting oxygen index according to JIS K 7201-2 (2007) of 25 or less, Resin B is thermoplastic and has a limiting oxygen index according to JIS K 7201-2 (2007) of 25 or more; At least one of the resin A and the resin B is in the form of a fiber, The fiber has a fiber length of 38 to 120 mm and a crimp number of 4.5 to 120 crimps, The sheet, wherein the inorganic particles are insulating.

2. The sheet according to claim 1 , wherein the inorganic particles are contained in the resin A.

3. 3. The sheet according to claim 1, wherein the resin A comprises at least one selected from the group consisting of a cellulose-based material, a thermosetting resin, and a flame-retardant product obtained by subjecting a raw material selected from acrylonitrile-based, pitch-based, cellulose-based, and phenol-based resins to a flame-retardant treatment.

4. 3. The sheet according to claim 1, wherein the inorganic particles include at least one selected from silica and titanium dioxide.

5. 3. The sheet according to claim 1, wherein the resin A contains at least a cellulose-based material.

6. The sheet according to claim 1 or 2, wherein the resin B comprises at least one selected from the group consisting of anisotropic melt polyester, poly(butylene terephthalate), poly(acrylonitrile butadiene styrene), polysulfone, poly(ether-ether-ketone), poly(ether-ketone-ketone), polyethersulfone, polyarylate, polyarylene sulfide, polyphenylsulfone, polyetherimide, polyamideimide, and copolymers thereof.

7. 3. The sheet according to claim 1, wherein the resin A is contained in an amount of 15 to 80% by mass of the mass of the sheet.

8. 3. The sheet according to claim 1, wherein the resin B is contained in an amount of 20 to 85% by mass of the mass of the sheet.

9. 3. The sheet according to claim 1, wherein the mass of the inorganic particles is 20 to 60% by mass of the mass of the resin A.

10. The density of the sheet is 50 to 800 kg / m ３ 3. The sheet according to claim 1 or 2, wherein

11. 3. The sheet according to claim 1, wherein the sheet is a dry-laid nonwoven fabric.

12. The sheet was heated at 1000°C with a Bunsen burner for 180 seconds, and the JIS Surface resistance conforming to C 2139-3-2 (2018) is 1.0 x 10 ６ The sheet according to claim 1 or 2, having a modulus of elasticity of Ω or more.

13. A fire-resistant material using the sheet according to claim 1 or 2.

14. A secondary battery using the sheet according to claim 1 or 2 as a fire-resistant material.

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