Flame-retardant gasket material, secondary battery cases and ECU cases

Abstract

To provide a gasket with excellent flame retardancy as a paper-based gasket sheet. [Solution] The non-metallic gasket material of the present invention contains organic fibers, an organic binder, and a metal hydroxide other than an alkali metal, with the proportion of the metal hydroxide being 100 parts by mass or more and 300 parts by mass or less per 100 parts by mass of the total of the organic fibers and the organic binder. The gasket material preferably has a flame retardancy rating of V-1 or higher according to the UL94 flammability test. The gasket material is preferably used for sealing around electronic components that are at risk of catching fire, such as secondary battery cases and ECU cases.

Description

[Technical Field]

[0001] The present invention relates to non-metallic gasket materials. [Background technology]

[0002] Non-aqueous electrolyte secondary batteries, such as lithium-ion secondary batteries, are widely used as portable power sources for personal computers and mobile devices, as well as for vehicle drive power sources, due to their light weight and high energy density. In particular, lithium-ion secondary batteries, which are lightweight and have high energy density, are favorably used as high-output power sources for driving vehicles such as electric vehicles (EVs), hybrid vehicles (HVs), and plug-in hybrid vehicles (PHVs). While batteries have become increasingly dense and have higher capacities in recent years, safety issues have arisen, such as the risk of battery combustion due to high temperatures and thermal runaway.

[0003] Battery components include a wide range of parts, including the battery, battery case, and cells, and the gasket material used to seal these components plays a role in preventing fluid leakage inside and outside the battery, as well as the intrusion of dust, etc. While sealing is important for ordinary automotive gasket components, gaskets used around the battery are required to be flame-retardant in addition to sealing to prevent fire from spreading from the battery.

[0004] As a gasket for use in a secondary battery case, Patent Document 1 proposes a seal molding material used to form a seal for sealing the electrolyte of a secondary battery, characterized in that the seal base material contains a plate-shaped filler. The seal base material is an ethylene-α-olefin copolymer rubber, and the filler is barium sulfate. The seal molded using the seal molding material may be formed into a desired shape, such as an O-ring, packing, or gasket used to seal the sealing part of a secondary battery. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-092658 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the sealing molding material described in Patent Document 1 is a rubber gasket. While rubber gaskets have the advantages of being elastic and having excellent conformability, they have low durability against compressive fracture when clamped by bolts or the like due to their low fiber content, and the scraps produced after punching cannot be recycled.

[0007] Known gaskets include liquid gaskets and metal gaskets. Liquid gaskets have the advantage of being easy to manufacture, but they have the disadvantage of requiring adhesive bonding, which makes gasket replacement difficult and reduces maintainability. Metal gaskets have the advantage of being durable, but they are relatively expensive, heavy, and difficult to process. Furthermore, they require adjustment of surface roughness and are often used under high surface pressure, which means that the body flange and sealing body flange require high rigidity.

[0008] Beater sheets are also known as gaskets. Beater sheets are produced using a papermaking process similar to that used for papermaking, and are lightweight and cost-effective. They also have the advantages of being easy to replace and maintain, being easy to process, having adequate gaps, and providing sufficient sealing performance even at low surface pressure.

[0009] However, to apply a gasket to a secondary battery case, it must be both sealing and flame-retardant. On the other hand, for beater sheets manufactured by papermaking, the choice of flame retardant is important, and making them flame-retardant is not easy. For this reason, there have been no examples of beater sheets being used as sealing materials for secondary battery cases.

[0010] An object of the present invention is to provide a gasket having excellent flame retardancy as a paper-based gasket sheet. [Means for solving the problem]

[0011] As a result of extensive research to solve the above problems, the present inventors discovered that by containing organic fibers, an organic binder, and a metal hydroxide other than an alkali metal, and by setting the proportion of the metal hydroxide within a predetermined range, it is possible to provide a gasket sheet using a papermaking system that has flame retardancy of V-1 or higher and also satisfies the other properties required of secondary battery cases (watertightness, airtightness, dustproofness, durability against compressive fracture, compatibility with metal flange surfaces, and resistance to settling), thereby completing the present invention. Specifically, the present invention provides the following.

[0012] A first aspect of the invention provides a non-metallic gasket material containing organic fibers, an organic binder, and a metal hydroxide other than an alkali metal, wherein the proportion of the metal hydroxide is 100 parts by mass or more and 300 parts by mass or less per 100 parts by mass of the total of the organic fibers and the organic binder.

[0013] The second feature of the invention is the first feature of the invention, and provides a nonmetallic gasket material having a flame retardancy rating of V-1 or higher according to the UL94 combustion test.

[0014] The gasket contains organic fibers, an organic binder, and a metal hydroxide other than an alkali metal, and has high sealing properties. Therefore, it has excellent watertightness, airtightness, and dustproofness. Furthermore, since the gasket contains an organic binder, it has excellent conformability to the flange surface. Furthermore, since the gasket contains organic fibers, it has excellent durability against compressive fracture caused by pinching by bolts, etc., and excellent tensile strength.

[0015] In addition, because the metal hydroxide content is 100 parts by mass or more per 100 parts by mass of the combined total of the organic fiber and organic binder, the flame retardancy rating of the gasket in the UL94 combustion test is V-1 or higher. On the other hand, because the metal hydroxide content is 300 parts by mass or less per 100 parts by mass of the combined total of the organic fiber and organic binder, the gasket does not impair its inherent requirements for use in secondary battery cases, such as sealing performance.

[0016] Therefore, according to the present invention, a gasket having excellent flame retardancy can be provided as a paper-based sheet. [Effects of the Invention]

[0017] According to the present invention, a gasket having excellent flame retardancy can be provided as a paper-based sheet. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram for explaining a method for evaluating air sealing properties. [Figure 2] FIG. 2 is a diagram showing the appearance of a gasket (punched product) used in evaluating the air sealing property. [Figure 3] FIG. 3 is a schematic diagram for explaining a method for evaluating the water-submersion sealability. [Figure 4] FIG. 4 is a diagram showing the appearance of a gasket (punched product) used in evaluating the water-submersion sealing property. DETAILED DESCRIPTION OF THE INVENTION

[0019] First, although the following disclosure, diagrams, and / or claims may be described as being presented alone or in combination with one or more other aspects, the subject matter of the immediate disclosure is not intended to be so limited. That is, the immediate disclosure, diagrams, and claims are intended to encompass the various aspects described herein, each alone or in one or more combinations with each other. For example, even if the immediate disclosure describes and illustrates a first, second, and third embodiment in such a way that the first embodiment is described and illustrated specifically in conjunction with the second embodiment, or the second embodiment is described and illustrated only in conjunction with the third embodiment, the immediate disclosure and illustrations are not so limited and may include only the first embodiment, only the second embodiment, only the third embodiment, or one or more combinations of the first, second, and / or third embodiments, such as the first and second embodiments, the first and third embodiments, the second and third embodiments, or the first, second, and third embodiments.

[0020] The use of the phrase "or" in this document shall mean a "non-exclusive" arrangement unless expressly specified otherwise. For example, when we say "item x is A or B," we mean either: (1) item x is either A or B, but not both; or (2) item x is both A and B. In other words, the word "or" is not used to define an "exclusive" arrangement.

[0021] Additionally, the phrases "comprising at least one of" and "comprising at least one of the following," when used in conjunction with a system or element, mean that the system or element includes one or more of the elements listed after the phrase. For example, if there are three types of elements, element 1 through element 3, the phrases "comprising at least one of" and "comprising at least one of the following" are to be interpreted as any of the following structural arrangements: a device including the first element, a device including the second element, a device including the third element, a device including the first and second elements, a device including the first and third elements, a device including the second and third elements, or a device including the first, second, and third elements.

[0022] A similar interpretation is intended when the phrase "used in at least one of the following" is used in this context. Furthermore, as used in this context, "and / or" is used as a verbal conjunction to indicate that one or more of the listed elements or conditions are included or occur. For example, a device including a first element, a second element, and / or a third element is to be interpreted as any of the following structural arrangements: a device including the first element, a device including the second element, a device including the third element, a device including the first element and the second element, a device including the first element and the third element, a device including the second element and the third element, or a device including the first element, the second element, and the third element.

[0023] In addition, the use of the phrase "and / or" in the text means a "non-exclusive" agreement, as stipulated in the Japanese Industrial Standards (JIS) "Format and preparation method of standard sheets JIS Z 8301."

[0024] An example of a preferred embodiment for carrying out the present invention will be described below. However, this is merely an example, and the technical scope of the present invention is not limited to this example.

[0025] <Non-metallic gasket material> The non-metallic gasket material according to the present invention contains at least organic fibers, an organic binder, and a hydroxide of a metal other than an alkali metal.

[0026] [Organic fiber] The organic fibers are used to increase the mechanical strength (e.g., tensile strength and compressive breaking strength) of the non-metallic gasket material. Since the gasket is provided as a paper-based sheet, the organic fibers preferably include pulp fibers (cellulose fibers).

[0027] The organic fibers may include not only pulp fibers (cellulose fibers) but also other organic fibers, such as plant fibers, synthetic fibers, carbon fibers, and recycled fibers, but are not limited to these examples.

[0028] Examples of plant fibers include cotton and hemp. Examples of synthetic fibers include polyamide fibers, aramid fibers, polyester fibers, polyurethane fibers, polyethylene fibers, acrylic fibers, and polyvinyl alcohol fibers. Examples of carbon fibers include PAN-based carbon fibers obtained by carbonizing PAN precursors (polyacrylonitrile fibers) and pitch-based carbon fibers obtained by carbonizing pitch precursors (pitch fibers obtained from coal tar or heavy petroleum fractions). Examples of recycled fibers include rayon.

[0029] The organic fibers may be used alone or in combination of two or more kinds.

[0030] Fibers include not only organic fibers but also inorganic fibers, such as alumina fibers, glass fibers, zirconia fibers, rock wool, basalt fibers, biosoluble fibers, silica fibers, and ceramic fibers.

[0031] Like organic fibers, inorganic fibers are also widely used as components contained in gaskets to increase mechanical strength, but in the present invention, organic fibers are preferred because they are superior in strength and have moderate flexibility and elasticity, making it easier to make uniform paper.

[0032] The lower limit of the average fiber diameter of the organic fibers is preferably 3 μm or more from the viewpoint of improving the mechanical strength of the gasket sheet, and more preferably 10 μm or more from the viewpoint of improving dispersibility in the gasket sheet.

[0033] Furthermore, from the viewpoint of smoothly and stably providing a gasket as a papermaking sheet, the upper limit of the average fiber diameter of the organic fibers is preferably 20 mm or less, more preferably 10 mm or less, and even more preferably 5 mm or less.

[0034] The average fiber diameter of organic fibers is defined as the value obtained by measuring the fiber diameters of organic fibers contained in an image taken using a scanning electron microscope and calculating the average value of the fiber diameters.

[0035] The content of organic fibers in the non-metallic gasket material is not particularly limited, but from the viewpoint of improving mechanical strength, the lower limit of the content is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the non-metallic gasket material.

[0036] Furthermore, from the viewpoint of imparting flame retardancy of V-1 or higher in the UL94 combustion test, the upper limit of the content is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less, per 100 parts by mass of the non-metallic gasket material.

[0037] In addition, in order to be able to provide the gasket as a papermaking sheet, the proportion of pulp fibers (cellulose fibers) out of 100 parts by mass of organic fibers is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, even more preferably 50 parts by mass or more, even more preferably 60 parts by mass or more, and particularly preferably 70 parts by mass or more.

[0038] [Organic binder] Organic binders are used to bond dissimilar materials such as organic fibers and fillers together to maintain mechanical strength, as well as to ensure watertightness by maintaining shape, and to give flexibility to the gasket, ensuring compatibility with the flange surface and resistance to settling.

[0039] The type of organic binder is not particularly limited, and examples thereof include NBR (nitrile rubber, thermal decomposition temperature: 550°C), SBR (styrene butadiene rubber, thermal decomposition temperature: approximately 600°C), CR (chloroprene rubber / neoprene, thermal decomposition temperature: approximately 200 to 260°C), silicone rubber (thermal decomposition temperature: approximately 400°C), natural rubber (NR, thermal decomposition temperature: approximately 200 to 250°C), fluororubber (FKM / Viton, thermal decomposition temperature: approximately 300°C), PU (polyurethane, thermal decomposition temperature: approximately 200°C), and acrylic rubber (ACM, thermal decomposition temperature: approximately 200°C).

[0040] In the case of a vehicle secondary battery case or ECU case, it is preferable that the case can withstand both high and low temperatures to accommodate the heat generated by the battery and the temperature range of the vehicle interior environment. Therefore, the organic binder preferably contains NBR (nitrile rubber) and / or SBR (styrene butadiene rubber). ECU stands for Electronic Control Unit.

[0041] The organic binder may be used alone or in combination of two or more kinds.

[0042] The content of the organic binder in the non-metallic gasket material is not particularly limited, but from the viewpoint of achieving the above-mentioned object, the lower limit of the content is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 7 parts by mass or more, per 100 parts by mass of the non-metallic gasket material.

[0043] Furthermore, from the viewpoint of imparting flame retardancy of V-1 or higher in the UL94 combustion test, the upper limit of the content is preferably 20 parts by mass or less, and more preferably 15 parts by mass or less, per 100 parts by mass of the non-metallic gasket material.

[0044] [Metal hydroxides other than alkali metals] Metal hydroxides other than alkali metals release water when heated and become oxides. Taking advantage of this property, metal hydroxides are used to impart flame retardancy to non-metallic gasket materials.

[0045] In addition to metal hydroxides other than alkali metals, phosphorus-based flame retardants, halogen-based flame retardants, silicone-based flame retardants, and other flame retardants are also known as flame retardants. However, even if a non-metallic gasket material contains a phosphorus-based flame retardant, halogen-based flame retardant, or silicone-based flame retardant, if it does not contain any metal hydroxides other than alkali metals, attempting to achieve a formulation suitable for a papermaking system such as that of the present invention is undesirable because, even if suitable flame retardancy is obtained, suitable adhesion cannot be achieved. Papermaking is carried out using aqueous raw materials, and if the raw materials of colloidal solutions such as binders do not adhere (adhere) well to fibers and powders when the raw materials are mixed, they will simply wash away with the water during papermaking. Components that wash away with the water do not remain on the sheet and therefore do not contribute to performance. In this specification, "adhesion" refers to the ability of a flame retardant to adhere to fibers and powders when the raw materials are mixed.

[0046] The metal hydroxide is not particularly limited as long as the constituent metal is not an alkali metal, and examples of the metal hydroxide include aluminum hydroxide, magnesium hydroxide, hydrotalcite, calcium hydroxide, manganese hydroxide, iron hydroxide, zinc hydroxide, and copper hydroxide.

[0047] Since it is believed that the dehydration action of metal hydroxides due to thermal decomposition imparts flame retardancy to non-metallic gasket materials, metal hydroxides that exhibit their dehydration action near the thermal decomposition temperature of the organic binder are preferred. From this perspective, the metal hydroxide preferably contains at least one selected from magnesium hydroxide, aluminum hydroxide, and hydrotalcite, more preferably at least one selected from magnesium hydroxide and aluminum hydroxide, and particularly preferably aluminum hydroxide.

[0048] The metal hydroxides may be used alone or in combination of two or more kinds.

[0049] The metal hydroxide is preferably in particulate form. To prevent permeation through the wire during papermaking, the lower limit of the average particle size of the metal hydroxide is preferably 1 μm or more, and more preferably 5 μm or more.

[0050] The upper limit of the average particle size of the metal hydroxide is preferably 50 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less. The size of the powder affects the unevenness of the sheet surface, and an excessively large powder particle size can be a factor in reducing the sealing properties.

[0051] The average particle size of the metal hydroxide is the 50% average particle size corresponding to the median value of the particle size distribution.

[0052] The metal hydroxide may be subjected to various surface treatments from the viewpoint of improving dispersibility, moldability, flame retardancy, etc. Examples of such surface-treated metal hydroxides include aluminum hydroxide treated with nitrate anions and aluminum hydroxide treated with high-temperature hydrothermal treatment from the viewpoint of improving dispersibility and moldability, and metal hydroxides that have been treated with phlogopite, silicone treatment, silicone polymer treatment, etc. from the viewpoint of improving flame retardancy include aluminum hydroxide treated with nitrate salts, aluminum hydroxide surface-treated with zinc stannate, magnesium hydroxide surface-treated with a nickel compound, etc.

[0053] The content of the metal hydroxide in the non-metallic gasket material is not particularly limited, but the lower limit of the content is preferably 15 parts by mass or more per 100 parts by mass of the non-metallic gasket material. A content limit of 15 parts by mass or more can impart flame retardancy of V-1 or higher in the UL94 flammability test. The lower limit of the content is more preferably 25 parts by mass or more, and even more preferably 35 parts by mass or more, per 100 parts by mass of the non-metallic gasket material. A content limit of 25 parts by mass or more can impart flame retardancy of V-0 or higher in the UL94 flammability test.

[0054] Furthermore, in order to avoid impairing the original performance of the gasket (mechanical strength, watertightness, heat resistance, flexibility, etc.), the upper limit of the metal hydroxide content is more preferably 70 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less, per 100 parts by mass of the non-metallic gasket material.

[0055] In addition, the proportion of the metal hydroxide is preferably 100 parts by mass or more per 100 parts by mass of the total of the organic fibers and the organic binder. This allows for imparting flame retardancy of V-1 or higher in the UL94 combustion test. Furthermore, the proportion of the metal hydroxide is more preferably 150 parts by mass or more per 100 parts by mass of the total of the organic fibers and the organic binder. This allows for imparting flame retardancy of V-0 or higher in the UL94 combustion test.

[0056] Furthermore, in order not to impair the original performance of the gasket (mechanical strength, watertightness, heat resistance, flexibility, etc.), the proportion of the metal hydroxide is preferably 300 parts by mass or less, and more preferably 250 parts by mass or less, per 100 parts by mass of the total of the organic fiber and organic binder.

[0057] [Other additives] The non-metallic gasket material may contain at least one other additive selected from the group consisting of fillers, crosslinking aids, vulcanizing agents, vulcanization aids, flocculants, antifoaming agents, dispersants, softeners, reinforcing agents, antioxidants, inorganic fillers, processing aids, activators, moisture absorbents, heat stabilizers, weather stabilizers, antistatic agents, colorants, lubricants, and thickeners, depending on the purpose. Each additive may be used alone, or two or more may be used in combination.

[0058] [Bulk specific gravity] Bulk specific gravity is a dimensionless number that represents the ratio of the mass of a substance to the volume, including voids. The bulk specific gravity of a non-metallic gasket material is preferably 1 or greater. A bulk specific gravity of 1 or greater can impart flame retardancy of V-1 or greater in the UL94 combustion test. Furthermore, a bulk specific gravity of 1.5 or greater is more preferable. A bulk specific gravity of 1.5 or greater can impart flame retardancy of V-0 or greater in the UL94 combustion test.

[0059] <Beater sheet manufacturing method> The method for producing a beater sheet is not particularly limited as long as it uses a general papermaking machine. For example, the production of a beater sheet is carried out through the steps of (1) raw material preparation, (2) papermaking, (3) dehydration, and (4) drying.

[0060] [Raw material preparation] In the raw material preparation step, a slurry for papermaking is prepared by dispersing organic fibers, filler, metal hydroxide powder, and an organic binder in a turbid liquid.

[0061] The organic fibers may be beaten before the raw material preparation step. For example, the fibers are fibrillated by mechanically beating them in the presence of water using a known refiner or beater. Fibrillation of the organic fibers strengthens the interaction between the fibers, thereby increasing the strength of the beater sheet.

[0062] [Papermaking] The papermaking slurry is then poured onto the wire to form a layer, producing a paper sheet, some of the water in the paper sheet passing through the wire and being removed.

[0063] 〔dehydration〕 The paper sheet is then transferred onto a felt body and passed through press rolls to apply pressure to dehydrate it. The dewatering process may be carried out while sucking water using suction dewatering equipment before and after the press rolls.

[0064] [Drying] The paper sheet after the dewatering process is transferred while being held on a canvas and brought into contact with the surfaces of multiple dryers to dry it. After the drying process, the paper sheet may be passed between calendar rolls and subjected to heated roll pressing. By using heated roll pressing, the surface smoothness and bulk specific gravity can be improved.

[0065] <Applications of non-metallic gasket materials> The non-metallic gasket material of the present invention can be used in any location where a sealing material is used. In particular, because of its excellent sealing properties and flame retardancy, the non-metallic gasket material of the present invention is preferably used for sealing around electronic components that are at risk of catching fire, such as secondary battery cases and ECU cases.

[0066] The secondary battery case includes a case body that accommodates a non-aqueous electrolyte and a sealing body that seals the opening of the case body. The space between the case body and the sealing body is sealed with the non-metallic gasket material of the present invention, and the non-metallic gasket material is sandwiched and fixed between the case body flange, the non-metallic gasket material, and the sealing body flange in this order. The secondary battery includes an electrode assembly and a non-aqueous electrolyte housed in the secondary battery case. The electrode assembly includes a positive electrode having a positive electrode active material and a negative electrode having a negative electrode active material.

[0067] The ECU case includes a case body and a sealing body that seals the opening of the case body. The non-metallic gasket material of the present invention seals the gap between the case body and the sealing body, and the non-metallic gasket material is sandwiched and fixed between the case body flange, the non-metallic gasket material, and the sealing body flange, in that order. The ECU contains components that make up the ECU inside the ECU case. ECUs are not limited to applications related to vehicle body components such as lights, doors, and keyless entry systems, but are also used in applications related to brake, engine, steering, and other control, as well as information-related applications such as audio, car navigation systems, and global positioning systems (GPS). [Example]

[0068] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0069] [Table 1] NBR: Nitrile rubber (copolymer of butadiene and acrylonitrile) SBR: Styrene butadiene rubber Non-halogen flame retardant: A commercially available flame retardant containing 50% huntite, 38% hydromagnesite, and 12% magnesium-calcium mixture.

[0070] <Creating a sheet> A non-metallic gasket material was prepared on a laboratory scale using the following procedure.

[0071] [Raw material preparation] First, the various raw materials contained in the non-metallic gasket material were weighed out in the proportions shown in Table 1 and dispersed in water to prepare a composition. The aramid fiber was beaten with a beater, and the pulp fiber was beaten with a pulper refiner.

[0072] [Paper making / dehydration] Next, the raw material was placed in a handsheet machine specified in JIS P 8222, and papermaking and dewatering were carried out in accordance with the same standard.

[0073] [Drying] After dehydration, the sheet was dried in a thermo-hygrostat at 80°C for 1 hour.

[0074] [Heat Roll] For the sample with pressure applied by a heated roll, the bulk density of the sheet was increased to 1.6 by applying temperature and pressure with the heated roll. The temperature was set to 130°C. For the sample without pressure, neither heating nor pressure was applied with the heated roll. The bulk density at that time was 1.1.

[0075] <Evaluation> The following evaluations were carried out, and the results are shown in Table 2. In Table 2, "-" indicates that the measurement was not performed. [Table 2]

[0076] [Flame retardancy] Flame retardancy was evaluated using a vertical flame test in accordance with the UL94 flame test, with test specimens measuring 13 mm wide x 125 mm long x 0.5 mm thick. In accordance with the UL94 flame test standard, the materials were rated as V-0, V-1, V-2, or Not-V.

[0077] [Air sealing properties] As shown in Figure 1, a gasket sheet with the shape shown in Figure 2 was sandwiched between two jigs and a surface pressure of 5.9 MPa was applied. Air was then flowed from bottom to top at an internal pressure of 98 kPa, and the amount of air leaking from the inside of the gasket to the outside of the gasket (air leak amount) was measured. If the air leak amount could be kept to 2.0 ml / min or less, it was marked as "Good", and if it could not be kept to 2.0 ml / min, it was marked as "Poor".

[0078] [Water-submersible sealability] As shown in Figure 3, a water-submersible sealability evaluation jig, which had the gasket sheet shown in Figure 4 assembled around a φ50 mm hole, was immersed in water to a depth of 800 mm, and the presence or absence of water intrusion into the jig after 30 minutes was evaluated. The surface pressure between the jig and the flange was 1.9 MPa. Cases where no water intrusion was observed were marked with "Good," and cases where water intrusion was observed were marked with "Poor."

[0079] [Thickness, bulk density, compression and recovery, tensile strength, stress relaxation rate] The thickness, bulk specific gravity, compressibility and recovery, tensile strength, and stress relaxation rate were measured in accordance with ASTM F104 TYPE7.

[0080] <Result> The gasket sheet of the example met the various requirements for secondary battery cases (watertightness, flame retardancy, airtightness, dustproofness, durability against compressive fracture, compatibility with metal flange surfaces, and resistance to settling).

[0081] On the other hand, when the flame retardant was not a metal hydroxide, the flame retardancy was reduced or the fixing property of the raw material was poor.

Claims

1. The composition contains organic fibers, an organic binder, and a hydroxide of a metal other than an alkali metal, The organic fibers include pulp fibers, and a ratio of the pulp fibers to 100 parts by mass of the organic fibers is 30 parts by mass or more; The metal hydroxide includes at least one selected from magnesium hydroxide, aluminum hydroxide, and hydrotalcite, the metal hydroxide is in a particulate form, and the average particle size of the metal hydroxide is 1 μm or more and 50 μm or less; the ratio of the metal hydroxide is 150 parts by mass or more and 300 parts by mass or less with respect to 100 parts by mass of the total of the organic fibers and the organic binder, A flame-retardant gasket material with a flame retardancy rating of V-0 or higher according to the UL94 combustion test.

2. The gasket material according to claim 1, which is for a secondary battery.

3. The battery includes a case body that accommodates a non-aqueous electrolyte solution and a sealing body that seals an opening of the case body, The gap between the case body and the sealing body is sealed by the gasket material according to claim 2, A secondary battery case in which the flange on the case body side, the gasket material, and the flange on the sealing body side are sandwiched and fixed in this order.

4. The gasket material according to claim 1, which is for an ECU.

5. The device includes a case body and a sealing body that seals an opening of the case body, An ECU case, wherein the gap between the case body and the sealing body is sealed with the gasket material according to claim 4.

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