Thermal insulation sheet and method for manufacturing the same

Abstract

The present invention provides a heat insulating sheet that can undergo further elastic deformation from a state of being compressed to a certain extent, and a method for manufacturing the same. [Solution] The heat-insulating sheet is a single-layer heat-resistant sheet made of paper containing inorganic fibers, organic fibers, inorganic particles, and a binder resin, with an average thickness of 0.7 mm to 1.6 mm, a thermal conductivity of 0.03 W / m·K to 0.08 W / m·K, and a difference in compression ratio of 8 to 13 points when compressed at 1 MPa and 2 MPa, respectively. The above configuration provides the advantage that the heat-insulating sheet can follow the expansion of the object. Furthermore, heat transfer can be slowed down without worrying about surface roughness.

Description

Technical Field

[0001] The present disclosure relates to a heat insulation sheet and a method for manufacturing the same, and more particularly to a heat insulation sheet and a method for manufacturing the same that can be used for heat insulation of, for example, lithium-ion secondary batteries.

Background Art

[0002] Heat insulation sheets for insulating heat-generating bodies are used in various applications. For example, in in-vehicle and stationary power supply devices in which a plurality of secondary battery cells are stacked, an increasing number of secondary battery cells are used because of the demand for higher output and higher capacity. In such a power supply device, there is a concern that some secondary battery cells may become hot for some reason (referred to as "thermal runaway" in the present disclosure), which may have an adverse effect on other adjacent secondary battery cells. Therefore, in order to protect the surrounding secondary battery cells during thermal runaway, it is required to thermally insulate adjacent secondary battery cells from each other. Specifically, a sheet-like heat insulating material (referred to as a "heat insulation sheet" in the present disclosure) called a separator or a spacer is interposed between adjacent secondary battery cells.

[0003] It is known that secondary battery cells expand during charging. When such a secondary battery cell expands, it is desirable to dispose an elastically deformable member between the secondary battery cells so as to follow the shape change of the secondary battery cell and prevent excessive pressure from being applied to the adjacent battery.

[0004] Therefore, in order to thermally insulate adjacent secondary battery cells from each other and prevent excessive pressure from being applied to adjacent secondary battery cells, it is known to use a sheet that is thermally insulating and elastically deformable between the secondary battery cells.

[0005] For example, a method of interposing a three-layer structure sheet in which both sides of a rubber elastic material on a flat plate are sandwiched between heat insulation sheets between adjacent secondary battery cells (Patent Document 1), or a method of utilizing the ease of deformation of convex portions to cause elastic deformation of the entire sheet is known (Patent Document 2).

Prior Art Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-13128 [Patent Document 2] Japanese Patent Publication No. 2024-55493 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] A known method for arranging multiple secondary battery cells within the housing of a secondary battery is to clamp the secondary battery cells with an elastically deformable heat insulating sheet in between, and then place the clamped, integrated secondary battery cells into the housing.

[0008] Therefore, the insulating sheet is required to be able to undergo further elastic deformation because the secondary battery cells expand due to charging while compressed to a certain extent by clamping.

[0009] However, when silicone foam, which is considered flexible, is compressed beyond a certain amount, the reaction force increases rapidly, making further elastic deformation difficult (Comparative Example 2).

[0010] Furthermore, although the mica sheet is thin, its low compressibility means that if the secondary battery cells expand after being placed inside the housing, it cannot follow the deformation (Comparative Example 1). Furthermore, the heat-insulating sheet described in Patent Document 1 has a three-layer structure, resulting in a large thickness, with the rubber sheet portion corresponding to the intermediate layer being 4 mm or more. Therefore, even if it can be compressed by 60%, the heat-insulating sheet will still be 1.6 mm or more thick, and the spacing between cells will be wide even when clamped. This necessitates either reducing the number of cells that can be placed in a given enclosure or increasing the size of the enclosure to accommodate more cells. Moreover, the manufacturing process involves laminating three layers on both sides of the rubber sheet (laminating heat-resistant sheets on both sides of the rubber sheet), resulting in low productivity.

[0011] On the other hand, the heat-insulating sheet described in Patent Document 2 has a complex uneven shape, resulting in low productivity.

[0012] One of the issues addressed by this disclosure is to provide a heat insulating sheet and a method for manufacturing the same that, by having a single layer of heat insulating sheet, and by keeping the thickness, heat insulating properties, and compressibility within predetermined ranges, allow a large number of clamped secondary battery cells to be arranged inside the housing, protect surrounding secondary battery cells when one secondary battery cell experiences thermal runaway, and be able to follow the deformation when secondary battery cells arranged inside the housing expand during charging, while also providing high productivity.

[0013] Another objective is to provide an insulating sheet and a method for manufacturing the same that improves heat resistance and fire resistance by maintaining the sheet's shape or preventing the formation of through-holes when heated with a burner.

[0014] Furthermore, the description of these objectives and problems in this disclosure does not preclude the existence of other objectives and problems. Also, one aspect of this disclosure is not required to solve all of these problems. Moreover, it is possible to extract other problems from the description, drawings, and claims of this disclosure. Means for solving the problems and effects of the invention.

[0015] An insulating sheet according to one embodiment of the present disclosure is a heat-resistant, single-layer insulating sheet comprising inorganic fibers, organic fibers, inorganic particles, and a binder resin, having an average thickness of 0.3 mm to 1.6 mm, a thermal conductivity of 0.03 W / m·K to 0.08 W / m·K, and a difference in compression ratio of 8 to 13 points when compressed at 1 MPa and 2 MPa, respectively. With the above configuration, the insulating sheet, which is compressed by a certain amount when clamped, has the advantage of being able to follow the expansion of the object thereafter. Furthermore, because of its low thermal conductivity, heat transfer from secondary battery cells can be suppressed.

[0016] Furthermore, in the above configuration, the insulation sheet has a compressibility of 30% to 65% when compressed at 1 MPa. With the above configuration, the distance between cells can be reduced by clamping multiple secondary battery cells, and many secondary battery cells can be arranged within the secondary battery housing.

[0017] Furthermore, in other forms of the heat insulating sheet, the temperature difference between the front and back surfaces of the heat insulating sheet when heated with a 600°C burner is 170°C to 220°C. With the above configuration, high heat insulating performance can be achieved.

[0018] Furthermore, in other forms of the heat insulating sheet, the shape of the heat insulating sheet is maintained when heated with a 600°C burner in any of the above forms. With the above configuration, even if the secondary battery cells become hot due to thermal runaway, the shape of the heat insulating sheet is maintained, so that heat transfer between secondary battery cells can be slowed down.

[0019] Furthermore, in any of the above forms, the heat insulating sheet is not penetrated when heated with an 800°C burner. With this configuration, even at 800°C, penetration by flames does not occur, and fire resistance can be achieved. Therefore, even if a secondary battery cell were to ignite due to thermal runaway, no holes would be created in the heat insulating sheet, and the shielding between adjacent secondary battery cells could be maintained, thus slowing down heat transfer between secondary battery cells.

[0020] Furthermore, in any of the above-mentioned forms of the heat insulating sheet, when heated with a 1000°C burner, the heat insulating sheet is not penetrated. With the above configuration, since it has fire resistance even at 1000°C, even if a secondary battery cell were to ignite due to thermal runaway, no holes would be created in the heat insulating sheet, and it would be possible to shield the space between adjacent secondary battery cells, thereby slowing down heat transfer between secondary battery cells.

[0021] Furthermore, the heat insulation sheet according to another form has a surface roughness of 3.0 μm to 5.5 μm in any of the above forms. With the above configuration, since air exists in the recesses with a rough surface, the advantage of suppressing heat transfer from the secondary battery cell can be obtained.

[0022] Furthermore, the heat insulation sheet according to another form has a thermal conductivity of 0.039 W / m·K to 0.063 W / m·K in any of the above forms.

[0023] Furthermore, the heat insulation sheet according to another form has an average thickness of 0.3 mm to 1.1 mm in any of the above forms.

[0024] Furthermore, the heat insulation sheet according to another form has a thickness of 0.3 mm to 0.6 mm when compressed at 1 MPa in any of the above forms.

[0025] Furthermore, the heat insulation sheet according to another form is a heat insulation sheet composed of a single layer having heat resistance, and is a paper sheet containing 23% to 43% by weight of inorganic fibers, 8% to 28% by weight of organic fibers, 32% to 48% by weight of inorganic particles, and 3% to 13% by weight of a binder resin, having an average thickness of 0.7 mm to 1.6 mm, a thermal conductivity of 0.03 W / m·K to 0.08 W / m·K, a difference in compression ratio when compressed at 1 MPa and 2 MPa of 8 points to 13 points, a compression ratio when compressed at 1 MPa of 30% to 65%, a temperature difference between the front and back of the heat insulation sheet when heated with a burner at 600 °C for 10 minutes of 170 °C to 220 °C, the shape of the heat insulation sheet being maintained when heated with a burner at 600 °C for 10 minutes, and a surface roughness of 3.0 μm to 5.5 μm. With the above configuration, even from a state where the heat insulation sheet has already been compressed by a certain amount, such as when arranged in a housing in a clamped state, it is possible to further compress the heat insulation sheet, and the advantage of being able to follow the expansion of the object can be obtained. Also, heat transfer can be slowed down without worrying about the surface roughness.

[0026] Furthermore, another form of heat-insulating sheet is a heat-resistant, single-layer heat-insulating sheet comprising 23% to 43% by weight of inorganic fibers, 8% to 28% by weight of organic fibers, 32% to 48% by weight of inorganic particles, and 3% to 13% by weight of binder resin, wherein the average thickness is 0.7 mm to 1.6 mm, the thermal conductivity is 0.035 W / m·K to 0.065 W / m·K, the difference in compression ratio when compressed at 1 MPa and 2 MPa is 8 to 13 points, the compression ratio when compressed at 1 MPa is 30% to 65%, the temperature difference between the front and back of the heat-insulating sheet when heated with a 600°C burner for 10 minutes is 170°C to 220°C, and when heated with a 1000°C burner for 10 minutes, the heat-insulating sheet does not penetrate, and the surface roughness is 3.0 μm to 5.5 μm. With the above configuration, even if the object ignites, the shielding between adjacent objects can be maintained, and the insulation sheet can follow the expansion of the object. In addition, heat transfer can be slowed down without worrying about surface roughness.

[0027] Furthermore, for other forms of thermal insulation sheets, the thickness when compressed at 1 MPa is 0.3 mm to 0.6 mm in any of the above forms.

[0028] Furthermore, in any of the above forms, the thermal insulation sheet comprises inorganic microballoons, shirasu balloons, diatomaceous earth, silicates, calcium silicate, aluminum hydroxide, and silicate minerals as inorganic particles.

[0029] Furthermore, in any of the above embodiments, the thermal insulation sheet comprises at least silicate minerals in the inorganic particles.

[0030] Furthermore, in any of the above embodiments, the thermal insulation sheet comprises at least one of the following inorganic fibers: glass fiber, ceramic fiber, alumina fiber, silica fiber, basalt fiber, glass wool, and rock wool.

[0031] Furthermore, in any of the above forms, the insulating sheet is further characterized in that the binder resin is acrylic resin.

[0032] Furthermore, in any of the above forms, the heat insulating sheet comprises natural fibers and synthetic fibers.

[0033] Furthermore, in any of the above forms, the heat insulating sheet is a wet papermaking sheet.

[0034] Furthermore, another method for manufacturing a heat-insulating sheet is a method for manufacturing a single-layer heat-insulating sheet having heat resistance, which includes the steps of: blending inorganic particles with inorganic fibers and organic fibers, dispersing them in water to form a slurry, and wet-processing the resulting sheet material having an average thickness of 0.3 mm to 1.6 mm and a surface roughness of 3.0 μm to 5.5 μm, thereby obtaining a sheet material with a thermal conductivity of 0.03 W / m·K to 0.08 W / m·K and a difference in compression ratio of 8 to 13 points when compressed at 1 MPa and 2 MPa, respectively. This provides the advantage that the heat-insulating sheet can follow the expansion of the object. In addition, heat transfer can be slowed down without worrying about surface roughness. [Brief explanation of the drawing]

[0035] [Figure 1] This shows how insulating sheets are placed between secondary battery cells. [Figure 2] This is a schematic diagram showing a burner heating test at 1000°C. [Figure 3] This is a schematic diagram showing a burner heating test at 600°C. [Figure 4] This graph shows the compressibility of the heat-insulating sheets for Examples 1-8 and Comparative Examples 1-2. [Modes for carrying out the invention]

[0036] The embodiments of this disclosure will be described below with reference to the drawings. However, the embodiments shown below are examples for concretizing the technical concept of this disclosure, and this disclosure is not limited to those shown below. Furthermore, this specification does not in any way limit the members shown in the claims to the members of the embodiments. In particular, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments are merely illustrative examples and are not intended to limit the scope of this disclosure to those components unless specifically stated otherwise. Note that the size and positional relationships of the members shown in each drawing may be exaggerated for clarity of explanation. Furthermore, in the following description, the same name and reference numeral indicate the same or similar members, and detailed explanations will be omitted as appropriate. Furthermore, each element constituting this disclosure may be configured such that multiple elements are made of the same member, with one member serving multiple elements, or conversely, the function of one member may be shared among multiple members. Note that in this disclosure, indefinite prefixes (such as a and an) are not excluded from being plural, especially in translation. [Embodiment 1]

[0037] The heat insulating sheet according to the embodiment of this disclosure is a lightweight and thin paper sheet obtained by a wet papermaking method, which has a single-layer structure while exhibiting high heat insulating properties and compressibility. Such a heat insulating sheet can be appropriately used in applications where heat insulating properties are required and compressibility is necessary to prevent the spread of fire. For example, it is suitable for applications where fire prevention is required from a safety standpoint when high temperatures are reached, such as during thermal runaway, in lithium-ion secondary batteries. Here, we describe an example in which a heat insulating sheet is used as a spacer interposed between adjacent secondary battery cells in a power supply device in which many prismatic secondary battery cells are stacked and connected in series or parallel. Such a power supply device is used as a power source for electric vehicles such as electric cars, hybrid cars, electric buses, trains, and electric carts, as a backup power source for factories and base stations, and as a storage battery for homes.

[0038] A power supply device according to Embodiment 1 is shown in the exploded perspective view of Figure 1. The power supply device 100 shown in this figure comprises a plurality of secondary battery cells 20 and an insulating sheet 10 interposed between the secondary battery cells 20. The secondary battery cells 20 have a bottomed cylindrical rectangular outer casing 21, and a plurality of them are stacked in a manner in which their main surfaces face each other. The stacking is done, for example, by covering both ends of the battery stack 25, which is made up of stacked secondary battery cells 20, with end plates 30, and fastening the end plates 30 together with fastening members. The battery stack 25 is also fixed on a base plate 40 as needed. The base plate 40 can function as a cooling plate by circulating a refrigerant inside, for example.

[0039] Each secondary battery cell 20 houses its electrode body inside the outer casing 21, and its open end is sealed with a sealing plate 22. In Figure 1, the sealing plate 22 located on the top surface of the outer casing 21 is provided with a pair of electrodes 23 and an explosion-proof valve 24. Multiple secondary battery cells 20 are electrically connected to each other in series and / or parallel by connecting the electrodes 23 with busbars. The explosion-proof valve 24 is a component that opens when it detects an increase in the internal pressure of the outer casing 21, and is used to discharge the high-pressure gas inside the outer casing 21. Each explosion-proof valve 24 is connected to a gas duct to guide the high-pressure gas to the outside as needed.

[0040] An insulating sheet 10 is placed between adjacent secondary battery cells 20. The insulating sheet 10, also known as a spacer or separator, insulates the outer casing 21 from short-circuiting between adjacent secondary battery cells 20.

[0041] During the assembly of such power supply units, the secondary battery cells constituting the battery module are constrained in the stacking direction. However, when the assembled power supply unit is used, the secondary battery cells expand and contract as it is charged and discharged. In this case, an insulating sheet is interposed between the secondary battery cells as a buffer material with thermal insulation properties to absorb the load caused by the expansion.

[0042] However, due to constraints during the assembly of the battery module, the cushioning material is already compressed. Therefore, further compression occurs when the secondary battery cells expand, requiring a corresponding deformation tolerance.

[0043] One possible cushioning material is a rubber sheet with a textured surface. While this cushioning material can provide sufficient compression to accommodate the expansion of secondary battery cells, its complex shape makes it difficult and time-consuming to manufacture.

[0044] On the other hand, a multi-layer structure, such as a three-layer structure of heat-resistant sheet / rubber sheet / heat-resistant sheet, could also be considered, but this presented a problem as it would require more effort to manufacture.

[0045] In contrast, the thermal insulation sheet according to this embodiment achieves a thermal insulation sheet with a compressibility and thermal conductivity within a predetermined range, while being composed of a single layer. This will be described in detail below. (Insulation sheet 10)

[0046] The insulation sheet possesses thermal insulation, heat resistance, and compressibility. Thermal conductivity is measured as 0.03 W / m·K to 0.08 W / m·K. Heat resistance and compressibility will be discussed later. The insulation sheet is a wet-process papermaking sheet. This insulation sheet contains inorganic fibers, organic fibers, and inorganic particles. The inorganic particles function as fillers, while the inorganic and organic fibers function as binders. (Inorganic particles)

[0047] Inorganic particles that can be used include inorganic microballoons, shirasu balloons, diatomaceous earth, silicates, calcium silicate, aluminum hydroxide, and silicate minerals. Suitable silicate minerals include talc, kaolin, and wollastonite. Other inorganic particles that can be used include silica, zirconia, alumina, and titanium oxide. Preferably, shirasu balloons, aluminum hydroxide, or talc are used as the inorganic particles. This allows for a reduction in thermal conductivity.

[0048] In particular, fire resistance can be further improved by using silicate minerals such as talc, kaolin, and wollastonite as inorganic particles.

[0049] The proportion of inorganic particles is 10% by weight or more, preferably 15% by weight or more. (Inorganic fibers)

[0050] Inorganic fibers such as glass fibers, ceramic fibers, alumina fibers, silica fibers, basalt fibers, glass wool, and rock wool can be used. Among these, glass fibers are preferred. This allows the compressibility and thermal insulation at 1 MPa and 2 MPa to be kept within a predetermined range.

[0051] The proportion of inorganic fibers is 20% by weight or more, preferably 25% by weight or more. (Organic fibers)

[0052] For organic fibers, it is preferable to use natural organic fibers. Natural cellulose fibers such as wood (coniferous and hardwood) pulp and cotton linters can be used. Wood pulp is particularly preferred.

[0053] Furthermore, synthetic fibers may be included in the organic fibers. Examples of synthetic fibers that can be used include para-aramid fibers, polyphenylene sulfide fibers, PET fibers, flame-retardant PET fibers, and flame-retardant rayon fibers.

[0054] The blending ratio of organic fibers is preferably 5 to 40% by weight, and more preferably 10 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 a flame retardant are used.

[0055] The basis weight is 100g / m². 2 ~400g / m 2 Preferably, 160 g / m² 2 ~200g / m 2 The basis weight was measured in accordance with JIS P 8124:2011. (Binder resin)

[0056] Furthermore, a binder resin may be included in the insulation sheet. This allows the binder resin to fix the fibers together at points, improving the handling properties of the insulation sheet. Acrylic resins are suitably used as such binder resins. Using a highly flexible resin provides advantages such as improved compressibility.

[0057] The average thickness of the heat insulating sheet is 0.3 mm to 1.7 mm, preferably 0.4 mm to 1.5 mm. By making the heat insulating sheet a thin film in this way, it can be used in a space-saving manner, and for example, when used as a heat insulating sheet for a power supply device, it avoids the situation where the device becomes large when heat insulating sheets are interposed between many secondary battery cells and laminated. The average thickness was measured and evaluated in accordance with JIS P 8118:2014.

[0058] Furthermore, maintaining a certain density suppresses deformation, particularly the reduction in thermal insulation performance due to changes in thickness. In particular, when used as an interposition between secondary battery cells, the secondary battery cells expand during use, and as a result of this expansion, the thermal insulation sheet is compressed, which can cause it to thin and reduce its thermal insulation performance. Therefore, the thermal insulation sheet according to this embodiment suppresses such changes in thickness by increasing its density, allowing it to maintain thermal insulation performance even when secondary battery cells expand.

[0059] The surface roughness of the heat-insulating sheet is preferably 3.0 μm to 5.5 μm. This provides the advantage of suppressing heat transfer by utilizing the air present in the recesses of the roughened surface. Surface roughness was measured in accordance with JIS B 0601:2001, using the 3D composite analysis function of a HIROX microscope. The magnification was 200x, the measurement range was 1.6 mm x 2 mm, and the average of three locations was set as N=1. Five locations (N=5) were measured on an A4 sample, and the average was taken. (Thermal insulation performance)

[0060] The thermal conductivity of the insulating sheet is 0.03 W / m·K to 0.08 W / m·K, preferably 0.04 W / m·K to 0.06 W / m·K. For thin films with low thermal conductivity, for example, the improved transient planar heat source method can be used. Here, the thermal conductivity was measured in accordance with ASTM D7984 (2016) using the improved transient planar heat source method with a thermal conductivity measuring device (product name Tci) manufactured by C-Therm.

[0061] The insulation sheet is constructed from a single layer. This allows for a thin, fire-resistant sheet that provides excellent insulation and fire resistance while simplifying the manufacturing process and improving handling. (Compression test)

[0062] The heat insulating sheet according to this embodiment exhibits a small change in compressibility during compression tests. This provides the advantage that, when interposed between secondary battery cells, the heat insulating sheet can follow the expansion and contraction of the object it is used with. For example, when a heat insulating sheet is used as a buffer between secondary battery cells in a power supply device in which secondary battery cells are stacked, even if the secondary battery cells expand or contract further while already fastened and constrained under a certain pressure, the difference in the compressibility of the heat insulating sheet is small, allowing it to absorb the deformation caused by expansion and contraction even in an already compressed state.

[0063] Specifically, the difference in compressibility when compressed at 1 MPa and 2 MPa is between 5 and 13 points. This compression test conformed to JIS K 7181, and the compression ratio of the insulation sheet was measured at a compression area of ​​50 mmΦ and a test speed of 0.1 mm / min using an Instron 5985 universal material testing machine when the compressive stress was 1 MPa and 2 MPa.

[0064] Furthermore, the compression ratio when compressed at 1 MPa is 30% to 65%. This allows for a narrower spacing between secondary battery cells when clamping them with an insulating sheet in between and placing them inside the enclosure, thus enabling the placement of a larger number of secondary battery cells within the enclosure. (Heating test)

[0065] A heating test is conducted to indicate the thermal insulation performance of the thermal insulation sheet. Specifically, as shown in Figures 2 and 3, one side of the thermal insulation sheet 100 (first side; right side in the figures) is heated to approximately 1000°C or approximately 800°C using a heating means BN. In the 1000°C heating test in Figure 2, the thermal insulation sheet 100 was held in a vertical position, and in the 600°C heating test in Figure 3, the thermal insulation sheet 100 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 measurement surface on the back side of the heating surface (second side; left side in the figures). 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 measurement surface. In this state, the first surface is heated by the heating means BN, and while the temperature sensor TS1 confirms that the heating temperature is maintained, the temperature of the second surface is measured by 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 thermal insulation performance. In the thermal insulation sheet according to this embodiment, the temperature difference ΔT between the front and back surfaces of the thermal insulation sheet when heated with a burner at approximately 600°C is set to 170°C to 220°C. This enables high thermal insulation performance.

[0066] Furthermore, even when heated with a burner flame at approximately 600°C for 10 minutes in the state shown in Figure 3, it was confirmed that no cracks or small holes (not penetrating) occurred in the insulation sheet due to the burner flame, and that the shape of the insulation sheet was maintained, confirming that it exhibits high heat resistance. As a result, it can maintain shape stability even at 600°C, and when interposed between secondary battery cells, even if the secondary battery cells experience thermal runaway at high temperatures due to some abnormality, the insulation sheet will not be damaged or disappear, and will maintain its insulation performance. In this shape retention test, sheets that did not develop cracks after heating were evaluated as ○, and those that developed cracks or small holes (not penetrating) around the flame were evaluated as ×.

[0067] Furthermore, it was confirmed that the insulation sheet was not penetrated even when heated for 10 minutes with a burner flame at approximately 800°C or approximately 1000°C in the state shown in Figure 2. This confirmed that the insulation sheet is not penetrated even at even higher temperatures and can exhibit high fire resistance. [Method for manufacturing insulation sheets]

[0068] Wet papermaking can be used to manufacture such thermal insulation sheets. For example, a wet papermaking sheet can be obtained by dispersing inorganic particles and organic fibers in water to form a papermaking slurry, which is then dewatered and dried on a wire mesh. 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.

[0069] By combining inorganic particles and organic fibers in this way, it is possible to enhance thermal insulation performance and easily impart flame retardancy. With a combination of inorganic materials alone, there are concerns that the material may break when secondary battery cells expand or that thermal insulation performance 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 thermal insulation sheet according to this embodiment combines inorganic particles and organic fibers to maintain a certain degree of flexibility to accommodate roll form while suppressing changes in thickness and exhibiting high thermal insulation performance. [Examples 1-8, Comparative Examples 1-2]

[0070] Thermal insulation sheets according to Examples 1 to 8 were prepared using the above manufacturing method. Thermal insulation sheets according to Comparative Examples 1 to 2 were also prepared. The basis weight of each example was measured in accordance with JIS P 8124 (2011). The thickness and density of the thermal insulation sheets were measured in accordance with JIS P 8118 (2014). Furthermore, the thermal conductivity was measured using the improved transient planar heat source method in accordance with ASTM D7984 (2016). A thermal conductivity measuring device TCi manufactured by C-Therm was used. In this case, a weight of 500 gf was placed on the sample to ensure close contact between the sample sheet and the sensor.

[0071] Specifically, in Example 1, 10% by weight of wood pulp (a natural fiber) and 15% by weight of PET fiber (a synthetic fiber) were used as organic fibers, 25% by weight of glass fiber (an inorganic fiber), 20% by weight of shirasu balloons and 25% by weight of aluminum hydroxide (inorganic particles), and 5% by weight of acrylic resin (a binder resin) were blended and dispersed in water to form a papermaking slurry. The resulting papermaking slurry was then wet-processed to produce a basis weight of 220 g / m². 2 We obtained an insulating sheet.

[0072] Similarly, in Example 2, 10% by weight of wood pulp (a natural fiber) and 5% by weight of PET fiber (a synthetic fiber) were used as organic fibers, 35% by weight of glass fiber (an inorganic fiber), 20% by weight of shirasu balloons and 20% by weight of aluminum hydroxide (inorganic particles), and 10% by weight of acrylic resin (a binder resin) were blended and dispersed in water to form a papermaking slurry. The resulting papermaking slurry was subjected to wet papermaking, resulting in a basis weight of 215 g / m². 2 We obtained an insulating sheet.

[0073] Furthermore, in Example 3, the same conditions as in Example 2 were used, except that the PET fiber was 10% by weight and the aluminum hydroxide was 15% by weight, to obtain the heat insulating sheet according to Example 3.

[0074] In Example 4, the same procedure was followed as in Example 3, except that the thickness was set to 0.4 mm.

[0075] In Example 5, 10% by weight of wood pulp (a natural fiber) and 5% by weight of PET fiber (a synthetic fiber) were used as organic fibers, 30% by weight of glass fiber (an inorganic fiber), 25% by weight of shirasu balloons and 20% by weight of talc (inorganic particles), and 10% by weight of acrylic resin (a binder resin) were mixed and dispersed in water to form a papermaking slurry. The resulting papermaking slurry was wet-processed to produce a basis weight of 250 g / m². 2 We obtained an insulating sheet.

[0076] In Example 6, the composition was the same as in Example 6, except that the glass fiber was 35% by weight and the shirasu balloon was 20% by weight.

[0077] In Example 7, the same procedure as in Example 1 was followed, except that the thickness of the heat-insulating sheet was set to 1.5 mm.

[0078] In Example 8, the same procedure as in Example 2 was followed, except that the thickness of the heat-insulating sheet was set to 1.5 mm.

[0079] On the other hand, in Comparative Example 1, a commercially available mica sheet with a thickness of 0.3 mm (Widework Co., Ltd. mica sheet: WW-FMS-L) was used.

[0080] In Comparative Example 2, a commercially available silicone foam with a thickness of 2.0 mm (manufacturer unknown) was used.

[0081] Table 1 shows the composition, properties, and results of compression and heating tests for each of these examples and comparative examples of thermal insulation sheets. Figure 4 shows the results of the compression tests performed on each example and comparative example.

[0082] [Table 1]

[0083] As shown in Table 1, each of the insulation sheets in Examples 1 to 8 was confirmed to exhibit high heat resistance. In particular, the temperature difference ΔT between the front and back surfaces in the first heating test, heated at approximately 1000°C, was 180°C or more, confirming high heat resistance. Furthermore, in the 600°C burner test, Examples 1 to 8 all maintained their shape, whereas Comparative Example 2, which was thicker at 2 mm, was penetrated by the flame and could not maintain its shape. Thus, it was confirmed that each example can exhibit high fire resistance even when thin, and that sufficient heat resistance can be maintained even with a single layer. By making the insulation sheet thin, it is easier to form a highly flexible roll shape, resulting in excellent portability and handling, and it can be supplied in larger areas. Also, when incorporated into a power supply device, the spacing between secondary battery cells can be narrowed, the module width can be reduced, or more secondary battery cells can be arranged, contributing to higher output and higher capacity. [Industrial applicability]

[0084] The heat insulating sheet and its manufacturing method of the present invention can be used as a heat insulating sheet sandwiched between heat-generating elements. For example, it can be suitably used as a heat 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 a heat insulating material to protect drive circuits such as ECUs. It can also be used in building applications as a heat insulating material or heat-resistant material to prevent the spread of fire. [Explanation of Symbols]

[0085] 100... Insulation sheet 10…Insulation sheet 20…Secondary battery cell 21…Outer can 22...Sealing plate 23...Electrode 24… Explosion-proof valve 25…Battery stack 30…End plate 40...Foundation plate BN…Heating means TS1, TS2... Temperature sensors

Claims

1. A heat-resistant, single-layer insulating sheet, Inorganic fibers and, Organic fibers and, Inorganic particles and Binder resin and It is a papermaking sheet that includes, The average thickness is 0.3 mm to 1.6 mm. The thermal conductivity is 0.03 W / m·K to 0.08 W / m·K. An insulating sheet where the difference in compression ratio when compressed at 1 MPa and 2 MPa is 8 to 13 points.

2. The heat insulating sheet according to claim 1, An insulating sheet with a compression ratio of 30% to 65% when compressed at 1 MPa.

3. The heat insulating sheet according to claim 1, An insulating sheet in which the temperature difference between the front and back surfaces of the insulating sheet when heated with a 600°C burner is 170°C to 220°C.

4. The heat insulating sheet according to claim 1, An insulating sheet that maintains its shape when heated with a 600°C burner.

5. The heat insulating sheet according to claim 1, An insulating sheet that does not penetrate when heated with an 800°C burner.

6. The heat insulating sheet according to claim 1, An insulating sheet that does not penetrate when heated with a 1000°C burner.

7. The heat insulating sheet according to claim 1, An insulating sheet with a surface roughness of 3.0 μm to 5.5 μm.

8. The heat insulating sheet according to claim 1, A fire-resistant and heat-insulating sheet with a thermal conductivity of 0.039 W / m·K to 0.063 W / m·K.

9. The heat insulating sheet according to claim 1, Fire-resistant and heat-insulating sheets with an average thickness of 0.3 mm to 1.1 mm.

10. The heat insulating sheet according to claim 1 An insulating sheet with a thickness of 0.3 mm to 0.6 mm when compressed at 1 MPa.

11. A heat-resistant, single-layer insulating sheet, 23% to 43% by weight of inorganic fibers, 8% to 28% by weight of organic fibers, 32% to 48% by weight of inorganic particles, A binder resin in an amount of 3% to 13% by weight, It is a papermaking sheet that includes, The average thickness is 0.7 mm to 1.6 mm. The thermal conductivity is 0.03 W / m·K to 0.08 W / m·K. The difference in compression ratio between compression at 1 MPa and 2 MPa is between 8 and 13 points. The compression ratio when compressed at 1 MPa is 30% to 65%. When heated with a 600°C burner for 10 minutes, the temperature difference between the front and back surfaces of the insulating sheet was 170°C to 220°C. When heated with a 600°C burner for 10 minutes, the shape of the insulating sheet is maintained. An insulating sheet with a surface roughness of 3.0 μm to 5.5 μm.

12. A heat-resistant, single-layer insulating sheet, 23% to 43% by weight of inorganic fibers, 8% to 28% by weight of organic fibers, 32% to 48% by weight of inorganic particles, A binder resin in an amount of 3% to 13% by weight, It is a papermaking sheet that includes, The average thickness is 0.7 mm to 1.6 mm. The thermal conductivity is 0.035 W / m·K to 0.065 W / m·K. The difference in compression ratio between compression at 1 MPa and 2 MPa is between 8 and 13 points. The compression ratio when compressed at 1 MPa is 30% to 65%. When heated with a 600°C burner for 10 minutes, the temperature difference between the front and back surfaces of the insulating sheet was 170°C to 220°C. When heated with a 1000°C burner for 10 minutes, the insulation sheet was not penetrated. An insulating sheet with a surface roughness of 3.0 μm to 5.5 μm. to.

13. The heat insulating sheet according to claim 11 An insulating sheet with a thickness of 0.3 mm to 0.6 mm when compressed at 1 MPa.

14. A heat insulating sheet according to any one of claims 1 to 13, An insulating sheet in which the inorganic particles include at least one of inorganic microballoons, shirasu balloons, diatomaceous earth, silicates, calcium silicate, aluminum hydroxide, and silicate minerals.

15. A heat insulating sheet according to any one of claims 1 to 13, The aforementioned inorganic particles comprise at least silicate minerals in this heat insulating sheet.

16. A heat insulating sheet according to any one of claims 1 to 13, An insulating sheet in which the inorganic fibers include at least one of glass fibers, ceramic fibers, alumina fibers, silica fibers, basalt fibers, glass wool, and rock wool.

17. A heat insulating sheet according to any one of claims 1 to 13, further, An insulating sheet with an acrylic resin binder.

18. A heat insulating sheet according to any one of claims 1 to 13, The aforementioned heat insulating sheet comprises natural fibers and synthetic fibers.

19. A heat insulating sheet according to any one of claims 1 to 13, The aforementioned heat insulating sheet is a wet-process papermaking sheet.

20. A method for manufacturing a heat-insulating sheet consisting of a single layer having heat resistance, A process in which inorganic particles are mixed with inorganic and organic fibers, dispersed in water to form a slurry, and then wet-processed to achieve an average thickness of 0.3 mm to 1.6 mm and a surface roughness of 3.0 μm to 5.5 μm, Includes, The thermal conductivity is 0.03 W / m·K to 0.08 W / m·K. A method for manufacturing an insulating sheet in which the difference in compression ratio when compressed at 1 MPa and 2 MPa is 8 to 13 points.

Images