Fire-resistant insulating sheet and method for manufacturing same

Abstract

Provided are a fire-resistant insulating sheet which can maintain shape retention properties at high temperatures, and a method for manufacturing same. The fire-resistant insulating sheet comprises a single layer having fire resistance and insulating properties and is a paper sheet containing inorganic fibers, organic fibers and inorganic particles. The average thickness is 0.60 mm or less, the basis weight is 100 g / m2 to 400 g / m2, the surface resistivity at room temperature is 4.0×109 Ω / □or more at 1000 V, the surface resistivity after heating to 1300°C is 4.0×109 Ω / □or more at an applied voltage of 1000 V.

Description

Fire-resistant insulating sheet and method for manufacturing the same

[0001] This disclosure relates to a fire-resistant insulating sheet and a method for manufacturing the same, and more particularly to a fire-resistant insulating sheet and a method for manufacturing the same that can be used for purposes such as insulating lithium-ion secondary batteries.

[0002] Insulating sheets are used to electrically insulate electrical components. For example, on circuit boards and cables where electronic components are integrated, it is necessary to protect the wires with insulating material to prevent them from electrically contacting each other. Also, in electric vehicles, hybrid vehicles, and storage batteries, energy storage devices are installed in which multiple battery cells are connected in series or parallel via metal busbars. Therefore, it is necessary to ensure insulation of the busbars to avoid unintended electrical conduction, and insulation is ensured by covering the busbars with a resin coating or wrapping them with mica tape.

[0003] In recent years, in addition to insulating properties, other functions required of such insulating materials include shape retention and maintenance of insulating properties at high temperatures. For example, in the automotive and stationary power supply systems that stack multiple secondary battery cells, the recent demands for higher output and higher capacity in the battery field have led to increased heat generation. As a result, the battery field requires materials that can maintain shape retention and insulating properties even at high temperatures when the battery cells malfunction.

[0004] Conventional materials used in this field include resin coatings and mica tapes. However, when these insulating materials are exposed to high temperatures, they can chip or crack, losing their original shape and consequently failing to provide proper insulation. Despite this, currently, no material exists that can maintain both shape retention and insulation properties at high temperatures.

[0005] Furthermore, as described in Patent Document 6, a method is known in which a laminate of inorganic heat insulating material and inorganic fiber sheet is placed on the busbar surface and then covered with insulating tape. However, because multiple materials (a laminate of inorganic heat insulating material and inorganic fiber sheet, and insulating tape) are used in a laminated manner, there is a problem in that the manufacturing process becomes complicated.

[0006] Japanese Patent Publication No. 2003-268139, Japanese Patent Publication No. 2015-527690, Japanese Patent Publication No. 2021-531631, Japanese Patent Publication No. 2019-96410, Japanese Patent Publication No. 2021-79555, Japanese Patent Publication No. 2023-170682

[0007] One objective of this disclosure is to provide an insulating sheet and a method for manufacturing the same that can maintain its shape retention and flexibility at high temperatures. Another objective is to provide a single-layer fire-resistant insulating sheet and a method for manufacturing the same that can maintain its insulating properties even at high temperatures. The description of these objectives and objectives in this disclosure does not preclude the existence of other objectives and objectives. Furthermore, one aspect of this disclosure is not required to solve all of these objectives. In addition, it is possible to extract other objectives from the description, drawings, and claims of this disclosure.

[0008] Furthermore, the objective is to provide a fire-resistant insulating sheet that has excellent fire resistance and even higher insulating properties. Means for solving the problem and the effects of the invention

[0009] The fire-resistant insulating sheet according to Form 1 is a fire-resistant insulating sheet consisting of one layer having fire resistance and insulating properties, and is a paper-made sheet containing inorganic fibers, organic fibers, and inorganic particles, with an average thickness of 0.60 mm or less and a basis weight of 100 g / m². 2 ~400g / m 2 Therefore, the surface resistivity at room temperature is 4.0 × 10⁻⁶ at 1000V. 9 The resistivity is greater than or equal to Ω / □, and the surface resistivity after firing at 1300°C is 4.0 × 10⁻¹⁰ at an applied voltage of 1000V. 9 It is greater than or equal to Ω / □.

[0010] Furthermore, the fire-resistant insulating sheet according to Form 2, in the above form, maintains its shape when fired at 1300°C, has a UL94 flammability test equivalent to V-0, and when wrapped around a 10 mm diameter stainless steel rod and heated at 900°C for 10 minutes, no cracks appear on the heated surface.

[0011] Furthermore, in any of the above embodiments, the fire-resistant insulating sheet according to Embodiment 3 has a thermal conductivity of 0.1 W / m·K or less and a temperature difference between the front and back surfaces of 230°C or more when heated with a 600°C burner.

[0012] Furthermore, the fire-resistant insulating sheet according to Embodiment 4 has a volume resistivity of 1 × 10 in any of the above embodiments. 12 Ω・m ~ 1 × 10 13 It is Ω・m.

[0013] Furthermore, in the fire-resistant insulating sheet according to form 5, the inorganic particles are made of a material with a melting point of 1400°C or higher, and the sheet contains 50% to 85% by weight of the inorganic particles.

[0014] Furthermore, the fire-resistant insulating sheet according to form 6 is a fire-resistant insulating sheet having fire resistance and insulating properties, and contains inorganic fibers, organic fibers, and inorganic particles with a melting point of 1400°C or higher in an amount of 50% to 85% by weight.

[0015] Furthermore, in any of the above embodiments, the fire-resistant insulating sheet according to Embodiment 7 is made of kaolin. With the above configuration, by using kaolin, which has excellent sintering strength, it is possible to suppress structural deterioration even at high temperatures, thereby achieving both shape retention and insulation properties.

[0016] Furthermore, in any of the above embodiments, the fire-resistant insulating sheet according to Embodiment 8 is characterized in that the inorganic particles are silica.

[0017] Furthermore, in any of the above embodiments, the fire-resistant insulating sheet according to Embodiment 9 is a wet-process papermaking sheet.

[0018] Furthermore, in any of the above embodiments, the fire-resistant insulating sheet according to Embodiment 10 includes at least aramid fibers among the organic fibers.

[0019] Furthermore, in any of the above embodiments, the fire-resistant insulating sheet according to embodiment 11 is wherein the inorganic fiber is silica fiber.

[0020] Furthermore, in any of the above embodiments, the fire-resistant insulating sheet according to Embodiment 12 has a volume resistivity of 3.00 × 10 before heating to 1300°C. 9 It is greater than or equal to Ω·cm.

[0021] Furthermore, the refractory insulation sheet according to Form 13 is a refractory insulation sheet consisting of a single layer having heat resistance and insulation properties, and is a papermaking sheet containing inorganic fibers, organic fibers, and inorganic particles. The average thickness is 0.40 mm or less, and the basis weight is 401 g / m 2 ~600 g / m 2 and the surface resistance at room temperature is 8.0×10 14 Ω or more and 1.0×10 17 Ω or less when the applied voltage is of 1000 V, and the volume resistivity at room temperature is 8.0×10 12 Ω·cm or more and 1.0×10 14 Ω·cm or less, and it does not break in the heating test of a burner at 1200 °C. Specifically, the flame does not penetrate in the 1200 °C burner test. Here, not allowing the flame to penetrate means a state where even if small cracks occur, the flame does not penetrate. By using this refractory insulation sheet for a bus bar coating material for a secondary battery, an upper cover material, etc., high insulation and fire resistance can be imparted to these bus bars and upper cover materials.

[0022] Furthermore, the refractory insulation sheet according to Form 14 has a surface resistance at room temperature of 1.0×10 15 Ω·cm or more and 1.0×10 17 Ω·cm or less in the above form.

[0023] Furthermore, the refractory insulation sheet according to Form 15 has a dielectric breakdown strength of AC 5.5 kV / mm or more and 10.0 kV / mm or less, DC 5.5 kV / mm or more and 13.0 kV / mm or less in any of the above forms.

[0024] Furthermore, the refractory insulation sheet according to Form 16 consists of at least two types of inorganic particles in any of the above forms.

[0025] Furthermore, the refractory insulation sheet according to Form 17 has at least one type of the inorganic particles being talc, and the blending amount of talc is 50% by weight or more and 78% by weight or less in any of the above forms.

[0026] Furthermore, in the refractory insulation sheet according to Form 18, in any of the above forms, at least one type of the inorganic particles is mica, and the blending amount of mica is 45% by weight or more and 85% by weight or less.

[0027] Furthermore, the manufacturing method of the refractory insulation sheet according to Form 19 is a manufacturing method of a refractory insulation sheet composed of a single layer having fire resistance and insulation properties. The method includes a step of blending inorganic fibers and organic fibers with inorganic particles at a rate of 70% by weight or more, dispersing them in water to form a slurry, and performing wet papermaking to obtain a sheet material with an average thickness of 0 .60 mm or less. The surface resistivity after heating to 1300°C is 4.0×10 9 Ω / □ or more when the applied voltage is 1000 V.

[0028] It is a schematic diagram showing an example of using a refractory insulation sheet for insulating a bus bar connected to a battery cell. It is a schematic diagram showing the state of a 600°C burner heating test. It is a schematic diagram showing the state of a shape retention confirmation test after firing in a wound state. It is a schematic diagram showing the state of a 1200°C burner heating test.

[0029] Hereinafter, embodiments of the present disclosure will be described based on the drawings. However, the embodiments shown below are examples for embodying the technical idea of the present disclosure, and the present disclosure is not limited to the following. Also, this specification does not specifically identify the members shown in the claims as the members of the embodiments. In particular, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments are not intended to limit the scope of the present disclosure only to those, but are merely illustrative examples unless specifically described. Note that the sizes and positional relationships of the members shown in each drawing may be exaggerated for clarity of explanation. Furthermore, in the following description, the same names and reference numerals indicate the same or similar members, and detailed descriptions will be omitted as appropriate. Furthermore, each element constituting the present disclosure may be configured such that a plurality of elements are constituted by the same member and one member serves as a plurality of elements, or conversely, the functions of one member may be shared by a plurality of members. In the present disclosure, the indefinite article (such as a or an) at the time of translation does not exclude the case where it is in the plural form. [Embodiment 1]

[0030] In circuit boards and cables that integrate electronic components, it is necessary to protect the wires from electrical contact with each other using insulating materials. In addition to insulating properties, insulating materials also need to maintain their shape at high temperatures. Depending on the components being insulated, some can reach high temperatures, and at high temperatures, the insulating material may chip or crack, making it impossible to maintain its original shape and resulting in a loss of proper insulating performance. For example, in the battery field, the recent demand for higher output and capacity has increased heat generation, and as a result, there is a need for materials that can maintain their shape and insulating properties even at 1300°C. However, currently, there are no materials that can maintain their shape and insulating properties at 1300°C.

[0031] In response to this, the inventors of the present invention, through diligent research, discovered that by using a filler with high heat resistance and a filler that exhibits high firing strength, the sheet can maintain its shape even after firing at 1300°C and retain its insulating properties from before firing, thus forming the fire-resistant insulating sheet according to the present embodiment.

[0032] The fire-resistant insulating sheet according to Embodiment 1 of this disclosure uses a lightweight and thin paper sheet made by a wet papermaking method, while incorporating a high proportion of inorganic particles with a melting point of 1400°C or higher, specifically 70% by weight or more, thereby realizing a fire-resistant insulating sheet that maintains heat resistance and insulation even at high temperatures. Such a fire-resistant insulating sheet can be appropriately used in applications where fire resistance, insulation, and shape retention are required even at high temperatures. For example, it can be used as a protective material to cover conductive objects in storage batteries and power supply devices so that insulation is maintained even if a fire occurs for any reason. It can also be incorporated into or wrapped around flammable energy storage devices such as lithium-ion secondary battery cells, lithium-ion secondary battery modules, and lithium-ion secondary battery packs.

[0033] As an example of using the fire-resistant insulating sheet according to Embodiment 1, Figure 1 shows an example in which the sheet is wrapped around a busbar connected to a battery cell for insulation. In this example, the metal busbar body 21, which is connected to one electrode 23 of the secondary battery cell 20, is insulated by wrapping the fire-resistant insulating sheet 10 around the area that is in contact with or facing other electrodes or parts of the secondary battery cell 20 that have a potential, as shown in the enlarged view of the main part. The number of times the fire-resistant insulating sheet 10 is wrapped is determined according to the required fire resistance and the thickness of the fire-resistant insulating sheet 10. In the example in Figure 1, it is wrapped twice. The busbar body 21 is made of a conductive material such as a metal plate, and a plate-shaped strip is bent in a stepped shape, with connection holes 22 opened at each end. The electrode 23 of the battery cell is inserted into one of the connection holes 22, and a terminal cap 24 is placed over it to secure it. In addition, an adjacent secondary battery cell or external equipment is connected to one of the connection holes 22 of the busbar body 21.

[0034] The busbar body 21 can be made into various shapes depending on the installation location of the secondary battery cells, such as an I-shape or an irregular shape with a curved section. (Fire-resistant insulating sheet 10)

[0035] Fire-resistant insulating sheets possess fire resistance or heat resistance and insulating properties. The volume resistivity is measured as 1.0 × 10⁻⁶. 9 Ω·cm or more, preferably 3.0 × 10 9 The density shall be Ω·cm or greater. Heat resistance will be discussed later. The fire-resistant insulating sheet is a wet-process paper sheet. This fire-resistant insulating sheet contains inorganic and organic fibers. The inorganic fibers function as fillers, and the organic fibers function as binders.

[0036] The thermal conductivity of the fire-resistant insulating sheet shall be 0.18 W / m·K or less, preferably 0.15 W / m·K or less, and more preferably 0.10 W / m·K or less. For measuring thin films with low thermal conductivity, for example, the improved transient planar heat source method can be used. In addition, the temperature difference between the front and back surfaces during the heating test with a 600°C burner shall be 230°C or more.

[0037] The 600°C burner heating test described here involves heating one side of the fire-resistant insulating sheet 10 (the first side; the lower side in Figure 2) to approximately 600°C using a heating means BN, as shown in Figure 2. In the 600°C heating test in Figure 2, the fire-resistant insulating sheet 10 was held in a 45° inclined position for the test. A burner can be used as the heating means BN. The heating surface is heated by the heating means BN, and the heating temperature is measured by the temperature sensor TS1, while a temperature sensor TS2 is placed on the temperature measuring surface on the back side of the heating surface (the second side; the upper side in Figure 2). Thermocouples can be used for temperature sensors TS1 and TS2. The thermocouples are fixed with clamps or the like and are in physical contact with the temperature measuring surface. In this state, the first side is heated by the heating means BN, and while confirming that the heating temperature is maintained with temperature sensor TS1, the temperature of the second side is measured with temperature sensor TS2. Then, the temperature difference ΔT between the front and back surfaces of the first and second surfaces is calculated 10 minutes after the start of the test. The higher this temperature difference, the better the heat insulation performance. In the fire-resistant insulating sheet according to this embodiment, the temperature difference ΔT between the front and back surfaces is set to 230°C to 400°C, preferably 250°C to 330°C.

[0038] The average thickness should be 0.30 mm to 0.60 mm or less, preferably 0.30 mm to 0.35 mm. By making the fire-resistant insulating sheet a thin film in this way, the flexibility of the sheet itself is increased, making it easier to wrap around objects to be protected, such as busbars with complex shapes.

[0039] The basis weight is 100 g / m². 2 ~400g / m 2 Preferably 160 g / m² 2 ~250g / m 2 (Inorganic particles)

[0040] Inorganic particles with a melting point of 1400°C or higher are used. Examples of such inorganic particles include silica, alumina, titanium oxide, sepiolite, zeolite, kaolin, and bentonite. Kaolin is preferably used. Furthermore, a refractory insulating sheet with a high kaolin content is preferable. Using kaolin, which has excellent sintering strength, provides a function that suppresses structural degradation even at high temperatures, thereby achieving both shape retention and insulation properties.

[0041] The inorganic particle content is 50% to 85% by weight, preferably 70% to 80% by weight. For example, kaolin is included at 70% by weight, more preferably 80% by weight. (Inorganic fiber)

[0042] Inorganic fibers can include silica fibers, alumina fibers, silicon carbide fibers, rock wool, rock fiber, and other rock-based fibers. (Organic fibers)

[0043] Organic fibers such as aramid fibers can be used. Specifically, para-aramid fibers, para-aramid pulp, meta-aramid pulp, polyphenylene sulfide fibers, PET fibers, flame-retardant PET fibers, flame-retardant rayon fibers, and natural fibers can be used. Natural fibers such as wood (coniferous and hardwood) pulp and cotton linters are natural cellulose fibers that can be used. The form of the fibers is not limited and they may be fibrillated. JIS P 8121 (2012) Canadian standard filtration rate method can be suitably used to determine the degree of fibrillation of the fibers. The blending ratio of organic fibers is preferably 0 to 40% by weight, and more preferably 5 to 20% by weight. If the ratio is below the upper limit of the above range, the amount of deformation during compression can be suppressed, and the decrease in heat resistance tends to be suppressed as well. Preferably, organic fibers with excellent flame retardancy or organic fibers containing flame retardants are used.

[0044] The basis weight is 100 g / m². 2 ~400g / m 2 Preferably, 160 g / m² 2 ~250g / m 2 Let's assume that.

[0045] The average thickness of the fire-resistant insulating sheet is 0.30 mm to 0.60 mm, preferably 0.30 mm to 0.35 mm. By making the fire-resistant insulating sheet a thin film in this way, the flexibility of the sheet itself is increased, making it easier to wrap around busbars and other objects with complex shapes.

[0046] Furthermore, it is preferable that the fire-resistant insulating sheet is not treated with a coating or other surface treatment. In particular, if a coating that hardens the surface of the fire-resistant insulating sheet is applied, the flexibility of the fire-resistant insulating sheet is lost, making it difficult to wind it into a roll shape, and reducing productivity and handling. Therefore, in the fire-resistant insulating sheet according to this embodiment, by not applying a coating treatment that hardens the surface, it is made easier to provide it in large areas such as in a roll shape, and the handling properties suitable for management and transportation are improved.

[0047] Furthermore, in addition to being constructed as a single layer, the fire-resistant insulating sheet may also be constructed as a laminated structure of multiple layers. This allows for the addition of different properties. For example, an additional layer with flame retardancy or fire-resistant properties may be added. By adding a material with excellent flame retardancy in this way, the spread of fire at high temperatures can be suppressed. For example, the additional layer may be composed of inorganic fillers such as silicate minerals, metal oxides, and graphite, inorganic fibers such as glass fibers, organic fibers with excellent flame retardancy such as aramid, and organic fibers containing flame retardants. [Method for manufacturing fire-resistant insulating sheet]

[0048] Wet papermaking can be used to manufacture such fire-resistant insulating sheets. For example, inorganic particles, inorganic fibers, and organic fibers are dispersed in water to form a papermaking slurry, which is then dewatered and dried on a wire mesh to obtain a wet-processed sheet. Known papermaking machines can be used, such as long-wire papermaking machines, cylinder papermaking machines, inclined short-wire papermaking machines, and twin-wire papermaking machines. Furthermore, the density of the sheet can be adjusted as needed using equipment such as wet presses and touch presses.

[0049] In this way, the precursor sheet, which is wet-processed with inorganic particles, inorganic fibers, and organic fibers, may be subjected to hot-pressing. For example, calendering may be performed further to increase the density of the wet-processed precursor sheet. In this case, the calendering process may be continuous with or independent of the wet-processing process. Known calendering devices can be used, such as metal rolls, resin rolls, rubber rolls, and double belt presses. The calendering device may be heated to increase density and processing efficiency. Preferably, the heating is performed in a temperature range below the melting point of the organic fibers being blended. This makes it possible to realize a fire-resistant insulating sheet with low compressive deformation while maintaining high heat insulation and heat resistance.

[0050] By combining inorganic particles and inorganic fibers with organic fibers in this way, heat resistance can be enhanced, and flame retardancy can be easily imparted. With a combination of inorganic materials alone, there are concerns that the material may break when secondary battery cells expand, or that heat resistance may decrease due to changes in thickness. In addition, it lacks flexibility, making it difficult to supply in large areas such as roll form due to strength limitations. In contrast, the fire-resistant insulating sheet according to this embodiment combines inorganic particles, inorganic fibers, and organic fibers to maintain a certain degree of flexibility to accommodate roll form, while suppressing changes in thickness and exhibiting high heat resistance. Furthermore, since it can be constructed as a single layer of paper sheet rather than by laminating multiple materials, manufacturing costs can be kept low.

[0051] Furthermore, the surface resistivity of the fire-resistant insulating sheet is 4.0 × 10 9 The resistance is Ω / □ or greater, and even after heating this fire-resistant insulating sheet to 1300°C as described later, the electrical resistance value remains 4.0 × 10 9 It is Ω / □ or greater. [Example]

[0052] Using the manufacturing methods described above, fire-resistant insulating sheets according to Examples 1 and 2 were prepared. Fire-resistant insulating sheets according to Comparative Examples 1 and 2 were also prepared. Each of these fire-resistant insulating sheets underwent heating tests at approximately 900°C, 1100°C, and 1300°C, after which their surface resistivity and shape retention were examined.

[0053] Specifically, in Example 1, inorganic paper was wet-processed using 70% by weight silica as inorganic particles, 15% by weight aramid fibers as organic fibers, and 15% by weight silica fibers as inorganic fibers. The resulting sheet was then impregnated with 25% by weight silica sol.

[0054] In Example 2, inorganic paper was wet-processed using 15% by weight of aramid fibers as organic fibers and 15% by weight of silica fibers as inorganic fibers, similar to Example 1, except that 70% by weight of kaolin was used as inorganic particles. However, unlike Example 1, silica sol impregnation was not performed.

[0055] On the other hand, as Comparative Example 1, we used WW-FMS-L, a commercially available mica sheet manufactured by Widework Co., Ltd. This mica sheet is said to contain mica and a few percent of silicone adhesive. The basis weight is 647 g / m². 2 The thickness was 0.33 mm.

[0056] As Comparative Example 2, a thermal calendered inorganic paper product was prepared using 80% by weight of vermiculite as inorganic particles, 10% by weight of aramid fiber as organic fibers, and 10% by weight of PET fiber. The conditions for the fire-resistant insulating sheets used in each example and comparative example are shown in Table 1. (Confirmation test of shape retention and insulating properties after firing)

[0057] First, as an indicator of the fire resistance performance of the fire-resistant insulating sheet, a heating test was conducted to measure the shape retention and surface resistivity after firing. Specifically, a 4cm x 4cm sample of the fire-resistant insulating sheet was prepared, placed in an alumina container, and then the alumina container containing the sample was placed in an electric furnace. In addition, to evaluate the shape retention after firing, it was checked whether the sample crumbled when lifted by hand after firing. A circle (○) was used if the sample did not crumble, a triangle (△) was used if the sample did not deform but stuck to the bottom of the alumina container and could not be cleanly removed, and a cross (×) was used if the sample stuck to the bottom of the alumina container and could not be removed.

[0058] After reaching the target temperature (approximately 900°C, 1100°C, or 1300°C) at a heating rate of 300°C / h, the sample was heated at the target temperature for 1 hour, then allowed to cool to room temperature, and removed from the electric furnace. Subsequently, the insulation resistance was measured using an insulation resistance meter IR4052-50 (HIOKI E.E. CORPORATION) at an applied voltage of 1000V, and the surface resistivity was calculated from the sample dimensions. The measurement limit of the insulation resistance meter is ≤4.0 x 10⁻¹⁰ in terms of surface resistivity. 9 It was Ω / m². (Thermal conductivity)

[0059] Thermal conductivity was measured using the modified transient planar heat source method in accordance with ASTM D7984 (2016). A C-Therm TCi thermal conductivity measuring device was used. A sample sheet was placed on a sensor unit with a built-in heater, and a 500g weight was placed on top of the sample. Heating was then started at a steady output, and the time change of the sensor temperature was measured. Thermal osmosis and thermal conductivity were then calculated using equation 1 of the following formula.

[0060] (Heat resistance confirmed by burner test)

[0061] A heating test using a burner was conducted as an indicator of the heat resistance performance of the fire-resistant insulating sheet. As shown in Figure 2, the inorganic powder sheet 10 was held in a 45° inclined position for the test. A burner can be used as the heating means BN. The heating surface is heated with the heating means BN, and the heating temperature is measured with the temperature sensor TS1, while the temperature sensor TS2 is placed on the temperature measuring surface on the back side of the heating surface (second surface; left side in the figure). Thermocouples can be used for temperature sensors TS1 and TS2. The thermocouples are fixed with clamps or the like and are in physical contact with the temperature measuring surface. In this state, the first surface is heated with the heating means BN, and while confirming that the heating temperature is maintained at 600°C with the temperature sensor TS1, the temperature of the second surface is measured with the temperature sensor TS2. Then, the temperature difference ΔT between the front and back surfaces of the first and second surfaces is calculated 10 minutes after the start of the test. The higher this temperature difference between the front and back surfaces, the better the heat resistance performance. (Confirmation test of shape retention after heating in a wrapped state)

[0062] Furthermore, the shape retention after firing when wrapped around busbars and electrodes was investigated. Here, as shown in Figure 3, a 130 mm x 280 mm sample of the fire-resistant insulating sheet 10 was wrapped around a 10 mm diameter stainless steel rod and fixed in place. The surface was then heated for 10 minutes using a heating means BN such as a burner, adjusting the flame while monitoring with a temperature sensor TS to reach approximately 900°C. After the test, it was checked whether there were any cracks on the heated surface.

[0063] A circle (○) indicates that no cracks occurred during wrapping and no cracks occurred after the test. A triangle (△) indicates that no cracks occurred during wrapping but cracks occurred after the test. A cross (×) indicates that cracks occurred during wrapping and the cracks increased further after heating.

[0064] Furthermore, the UL94 combustion test result is equivalent to V-0, indicating that the fire-resistant insulating sheet has high fire resistance and can protect the busbar from ignition from lithium-ion secondary battery cells that have experienced thermal runaway.

[0065] Table 1 shows the test results for electrical resistance and winding shape retention in each example and comparative example.

[0066]

[0067] As shown in Table 1, the fire-resistant insulating sheets according to Examples 1 and 2 exhibited a surface resistivity of 4.0 × 10⁻¹⁰ even after firing at approximately 900°C, 1100°C, and 1300°C, respectively, at an applied voltage of 1000V, which is the upper limit of measurement. 9 It was confirmed that a high surface resistivity of Ω / □ or more could be maintained. On the other hand, in Comparative Example 1, the surface resistivity at an applied voltage of 1000V was 1.0 × 10 at approximately 900°C. 9 Ω / □ or greater, at approximately 1100°C, is 2.0 × 10⁻⁶. 9 Ω / □, at 1300℃, is 4.0 × 10 9 In Comparative Example 2, the surface resistivity at an applied voltage of 1000V was 1.1 × 10⁻¹⁰ at 900°C, which is greater than or equal to Ω / □. 9 Ω / □, at 1100℃ it is 0.2 × 10⁻⁶ 9At Ω / □ and 1300°C, the sample could not be removed from the alumina container, making measurement impossible. At 900°C and 1100°C, the surface resistivity could not be maintained, suggesting that the insulating properties during firing were unstable. Furthermore, in Comparative Example 2, the values ​​were consistently lower than in Examples 1 and 2 from before firing to after firing.

[0068] Furthermore, in terms of shape retention, both Examples 1 and 2 were able to maintain their original shape at approximately 900°C, 1100°C, and 1300°C. They were also lightweight and could be made thinner. On the other hand, in Comparative Example 1, although the original shape was maintained at approximately 900°C and 1100°C, at 1300°C the sample deformed significantly, stuck to the bottom of the alumina container, and could not be cleanly removed, resulting in poor handling.

[0069] Furthermore, in the shape retention test during winding, no cracks were observed in Examples 1 and 2 and Comparative Example 2. On the other hand, in Comparative Example 1, cracks occurred during the winding stage, and the cracks increased further after heating, confirming a lack of flexibility.

[0070] Furthermore, fire-resistant insulating sheets according to Comparative Examples 3-5 and Examples 3-8 were prepared and subjected to heating tests using a burner. The specifications of these fire-resistant insulating sheets according to Comparative Examples 3-5 and Examples 3-8, and the results of the heating tests using a 1200°C burner are shown in Table 2 below. The volume resistivity and surface resistivity of the fire-resistant insulating sheets according to Comparative Examples 3-5 and Examples 3-8 were measured in accordance with JIS K6911.

[0071]

[0072] In the 1200°C burner test, as shown in Figure 4, the temperature at the position of the temperature sensor TS of the fire-resistant insulating sheet 10, heated by the flame from the burner (heating means BN), was adjusted to 1200°C. The evaluation of the 1200°C burner test in the table is as follows: ◎: No cracks occurred, and the flame did not penetrate. ○: Some small cracks occurred, but the flame did not penetrate. △: Many cracks occurred, and small holes were created, but the flame did not penetrate or tear. ×: The flame penetrated or tore.

[0073] As shown in Tables 2 and 3, Examples 3 to 8 exhibited excellent fire resistance, with no holes small enough to penetrate the flame appearing during the 1200°C burner test. On the other hand, Comparative Example 3 showed small holes. This is thought to be due to improved durability against high temperatures of 1200°C achieved by using kaolin and mica with higher fire resistance.

[0074] Furthermore, in Examples 3 to 8, the volume resistivity was 9.0 × 10⁻⁶. 12 It shows a value of Ω·cm or higher. This is thought to be due to an improvement in volume resistivity achieved by incorporating 80% or more by weight of highly electrically insulating inorganic particles such as kaolin, mica, and talc.

[0075] These materials provide fire-resistant insulating sheets with the fire resistance and electrical insulation properties required when used as fire-resistant insulating sheets to cover busbars or as upper cover materials installed on the inside of the upper surface (upper material) of battery modules that house secondary battery cells.

[0076] The fire-resistant insulating sheet of the present invention can be used as an insulating sheet sandwiched between objects that repeatedly expand and contract. For example, it can be suitably used as an insulating spacer interposed between secondary battery cells or secondary battery cell modules, as a buffer sheet interposed between explosion-proof valves and gas ducts, or as an insulating material to protect drive circuits such as ECUs. It can also be used in building applications as an insulating material, heat-resistant material, and other building materials to prevent the spread of fire.

[0077] 10...Fire-resistant insulating sheet 20...Secondary battery cell 21...Busbar body 22...Connection hole 23...Electrode 24...Terminal cap BN...Heating means TS, TS1, TS2...Temperature sensor

Claims

1. A fire-resistant insulating sheet consisting of one layer having heat resistance and insulating properties, comprising an inorganic fiber, an organic fiber, and an inorganic particle, having an average thickness of 0.60 mm or less and a basis weight of 100 g / m². 2 ~400g / m 2 Therefore, the surface resistivity at room temperature is 4.0 × 10 at 1000V. 9 The resistivity is greater than or equal to Ω / □, and the surface resistivity after firing at 1300°C is 4.0 × 10⁻¹⁰ at an applied voltage of 1000V. 9 A fire-resistant insulating sheet with a density of Ω / □ or greater.

2. A fire-resistant insulating sheet according to claim 1, wherein it maintains its shape when fired at 1300°C, has a UL94 flammability test equivalent to V-0, and when wrapped around a 10 mm diameter stainless steel rod and heated at 900°C for 10 minutes, no cracks appear on the heated surface.

3. A fire-resistant insulating sheet according to claim 1, wherein the thermal conductivity is 0.1 W / m·K or less and the temperature difference between the front and back surfaces during a heating test with a 600°C burner is 230°C or more.

4. A fire-resistant insulating sheet according to claim 1, wherein the volume resistivity is 1 × 10 12 Ω・m ~ 1 × 10 13 A fire-resistant insulating sheet with a density of Ω·m.

5. A fire-resistant insulating sheet according to claim 1, wherein the inorganic particles are made of a material having a melting point of 1400°C or higher, and the sheet contains 50% to 85% by weight of the inorganic particles.

6. A fire-resistant and insulating sheet having fire resistance and insulating properties, comprising inorganic fibers, organic fibers, and 50% to 85% by weight of inorganic particles having a melting point of 1400°C or higher.

7. A fire-resistant insulating sheet according to claim 1, wherein the inorganic particles are kaolin.

8. A fire-resistant insulating sheet according to claim 1, wherein the inorganic particles are silica.

9. A fire-resistant insulating sheet according to any one of claims 1 to 8, wherein the fire-resistant insulating sheet is a wet-process papermaking sheet.

10. A fire-resistant insulating sheet according to any one of claims 1 to 8, wherein the organic fibers include at least aramid fibers.

11. A fire-resistant insulating sheet according to any one of claims 1 to 8, wherein the inorganic fiber is silica fiber.

12. A fire-resistant insulating sheet according to any one of claims 1 to 8, wherein the volume resistivity before heating to 1300°C is 3.00 × 10 9 A fire-resistant insulating sheet with a thickness of Ω·cm or more.

13. A single-layer refractory insulation sheet having heat resistance and insulation properties, which is a papermaking sheet containing inorganic fibers, organic fibers, and inorganic particles, with an average thickness of 0.40 mm or less and a basis weight of 401 g / m 2 to 600 g / m 2 and having a surface resistance at room temperature of 8.0×10 14 Ω or more and 1.0×10 17 Ω or less when an applied voltage is 1000 V, and a volume resistivity at room temperature of 8.0×10 12 Ω·cm or more and 1.0×10 14 Ω·cm or less, and being a refractory insulation sheet that does not allow a flame to penetrate in a heating test with a 1200°C burner.

14. A fire-resistant insulating sheet according to claim 13, wherein the surface resistance at room temperature is 1.0 × 10⁻¹⁴ at an applied voltage of 1000 V. 15 Ω or more, 1.0×10 17 A fire-resistant insulating sheet with a resistance of Ω or less.

15. A fire-resistant insulating sheet according to claim 13 or 14, wherein the dielectric breakdown strength is AC 5.5 kV / mm or more and 10.0 kV / mm or less, and DC 5.5 kV / mm or more and 13.0 kV / mm or less.

16. A fire-resistant insulating sheet according to claim 13 or 14, wherein the inorganic particles consist of at least two types of inorganic particles.

17. A fire-resistant insulating sheet according to claim 15, wherein at least one of the inorganic particles is talc, and the amount of talc included is 50% by weight or more and 78% by weight or less.

18. A fire-resistant insulating sheet according to claim 15, wherein at least one of the inorganic particles is mica, and the amount of mica blended is 45% by weight or more and 85% by weight or less.

19. A method for manufacturing a fire-resistant insulating sheet consisting of one layer having fire resistance and insulating properties, comprising the steps of: blending inorganic fibers and organic fibers with 70% by weight or more inorganic particles, dispersing them in water to form a slurry, and wet-processing to obtain a sheet material with an average thickness of 0.60 mm or less, wherein the surface resistivity after heating to 1300°C is 4.0 × 10⁻⁶ at an applied voltage of 1000V. 9 A method for manufacturing a fire-resistant insulating sheet with a density of Ω・cm / □ or greater.

Images