Silicone rubber composition for battery sealing material and battery sealing material

Abstract

To provide a silicone rubber composition for a battery sealing material that has enhanced flame retardancy relative to a conventional art.SOLUTION: A battery silicone rubber composition in an aspect of the present invention contains a flame retardant silicone rubber compound and a fibrous flame retardant, the fibrous flame retardant being contained in an amount of 5 to 60 pts.wt. assuming that the flame retardant silicone rubber compound is contained in an amount of 100 pts.wt., and the flame retardant silicone rubber compound being rated as V-0 or higher in accordance with UL94 standard.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a silicone rubber composition for a battery sealing material and a battery sealing material.

Background Art

[0002] Conventionally, in order to impart industrially desirable physical properties, compositions obtained by adding various additives to silicone rubber have been proposed (see, for example, Patent Documents 1 to 3).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, when silicone rubber is adopted for a sealing material used in a battery, it is preferable to impart flame retardancy to the silicone rubber. As a result of investigations by the present inventors, it has been found that there is still room for improving the flame retardancy in existing flame-retardant silicone rubber compounds.

[0005] One aspect of the present invention aims to provide a silicone rubber composition for a sealing material having improved flame retardancy compared to the prior art.

Means for Solving the Problems

[0006] In order to solve the above problems, a silicone rubber composition according to one aspect of the present invention contains a flame-retardant silicone rubber compound and a fibrous flame retardant. If the amount of the above flame-retardant silicone rubber compound is 100 parts by weight, then the amount of the above fiber-based flame retardant is 5 to 60 parts by weight. The above flame-retardant silicone rubber compound meets the UL94 standard of V-0 or higher. [Effects of the Invention]

[0007] According to one aspect of the present invention, a silicone rubber composition for sealing materials is provided that has improved flame retardancy compared to conventional materials. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram showing an example of a battery using a sealing material according to one aspect of the present invention. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described in detail below. However, the present invention is not limited to the embodiments described below, and various modifications are possible within the scope described. Embodiments that appropriately combine the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0010] In this specification, "A~B" representing a numerical range means "greater than or equal to A, and less than or equal to B."

[0011] [1. Silicone rubber composition for sealing materials] The silicone rubber composition for sealing materials according to the present invention contains a flame-retardant silicone rubber compound and a fibrous flame retardant. The components are described below.

[0012] [1.1. Flame-retardant silicone rubber compound] Flame-retardant silicone rubber compound is a composition in which various additives are blended with silicone rubber to impart flame retardancy. Flame-retardant silicone rubber compound has a flame retardancy of V-0 or higher according to the UL94 standard.

[0013] The UL94 standard is a globally adopted standard for evaluating the flame retardancy of plastic products. The UL94 standards, in order of increasing flame retardancy, are 5VA, 5VB, V-0, V-1, V-2, and HB. Therefore, flame-retardant silicone rubber compounds are classified as 5VA, 5VB, or V-0 according to the UL94 standard. In one embodiment, the flame-retardant silicone rubber compound is classified as V-0 according to the UL94 standard. The UL94 test methods are well known to those skilled in the art and therefore will not be described.

[0014] The flame-retardant silicone rubber compound contains silicone rubber. In one embodiment, the silicone rubber is an organopolysiloxane resin. In the organopolysiloxane resin, the number of units taking the organopolysiloxane structure among all units included in the main chain is preferably 50% or more, more preferably 70% or more, and even more preferably 90% or more. Specific examples of silicone rubber include methyl silicone rubber, vinylmethyl silicone rubber, phenylmethyl silicone rubber, and fluorinated silicone rubber. These silicone rubbers may be included individually or in combination of two or more types. In one embodiment, the flame-retardant silicone rubber compound contains vinylmethyl silicone rubber. Examples of additives included in the flame-retardant silicone rubber compound include platinum, platinum compounds, iron oxide, triazole compounds, and aluminum hydroxide. These additives may be included individually or in combination of two or more types. Many flame-retardant silicone rubber compounds are on the market, and there is a large amount of related patent literature. Therefore, a detailed explanation of the flame-retardant silicone rubber compound's composition will be omitted.

[0015] Examples of commercially available flame-retardant silicone rubber compounds include SILASTIC (TM) SH502U, SH502U A / B, SH1447 U A (all of which are from Dow Corning Toray Co., Ltd.); KE-5620W-U, KE-5620BL-U, KE-5612E-U, KE-3494, KE3490, KE3467, KE-4890, KE-40RTV, KE-1831, KE-1867, KE-1891, KE-1204-LTV, KE-1292, KE-1800, KE-1802 (all of which are from Shin-Etsu Chemical Co., Ltd.); ELASTOSIL (R) LR 3011 / 50 FR, LR 3001 / 55 FR, LR 3001 / 60 FR, LR 3170 / 40 (all of which are from Asahi Kasei Wacker Silicone Co., Ltd.); TSE2186U, TSE2183U, TSE2187U, TSE2184U, TCM5406U, XE20-A7016 (all of which are from Momentive Performance Materials Japan LLC).

[0016] Examples of patent documents disclosing flame-retardant silicone rubber compounds include JP-A-2004-149693, JP-A-2006-182911, and JP-A-2009-144024.

[0017] [1.2. Fiber-based flame retardants] Fiber-based flame retardants refer to flame retardants in fibrous form. In this specification, the "fibrous form" is intended to mean a shape with an aspect ratio (length / diameter) of 3 or more.

[0018] According to the findings of the present inventors, a silicone rubber composition obtained by combining a flame-retardant silicone rubber compound and a fiber-based flame retardant has improved flame retardancy compared to the flame-retardant silicone rubber compound itself. However, the effect of improving flame retardancy was not observed when other flame retardants (phosphorus-based flame retardants, particulate inorganic flame retardants, etc.) were blended (see the examples of the present application for details). That is, it can be said that the effect of the present invention was manifested by selecting a fiber-based flame retardant among various types of flame retardants.

[0019] The lower limit of the average fiber length of the fibrous flame retardant is preferably 50 μm or more, more preferably 70 μm or more, and even more preferably 100 μm or more. The upper limit of the average fiber length of the fibrous flame retardant is preferably 1500 μm or less, more preferably 1000 μm or less, and even more preferably 800 μm or less. The lower limit of the average diameter of the fibrous flame retardant is preferably 0.05 μm or more, more preferably 0.1 μm or more, even more preferably 0.15 μm or more, and particularly preferably 0.2 μm or more. The upper limit of the average diameter of the fibrous flame retardant is preferably 10.0 μm or less, more preferably 5.0 μm or less, even more preferably 3.0 μm or less, and particularly preferably 1.0 μm or less. The lower limit of the aspect ratio is preferably 5 or more, more preferably 50 or more, even more preferably 100 or more, and particularly preferably 150 or more. The upper limit of the aspect ratio is preferably 5000 or less, more preferably 4000 or less, even more preferably 1000 or less, particularly preferably 500 or less, and even more preferably 250 or less. The lower limit of the shot content of the fibrous flame retardant may be 0.1% by weight or more, 0.01% by weight or more, or substantially 0% by weight based on the weight of the fibrous flame retardant. Further, the upper limit of the shot content of the fibrous flame retardant is preferably 5% by weight or less, more preferably 1% by weight or less, and even more preferably 0.5% by weight or less based on the weight of the fibrous flame retardant. Here, the shot means non-fibrous particles that were not fibrillated in the production process of the fibrous flame retardant.

[0020] Examples of the fibrous flame retardant include man-made mineral fibers, natural mineral fibers, and synthetic organic fibers. Examples of man-made mineral fibers include rock wool, stone wool, slag wool, mineral wool, glass wool, and mineral glass wool. Examples of natural mineral fibers include wollastonite and potassium titanate fibers. Examples of synthetic organic fibers include aramid fibers. Among these, man-made mineral fibers are preferred. Among man-made mineral fibers, rock wool is preferred. In one embodiment, the fibrous flame retardant is an inorganic substance. In one embodiment, the fibrous flame retardant is not asbestos.

[0021] [1.3. Other Components] A silicone rubber composition for sealing materials according to one embodiment of the present invention may contain components other than those described above. An example of such a component is a curing agent.

[0022] A curing agent is a component that imparts rubber elasticity to a silicone rubber composition. A person skilled in the art can appropriately select a curing agent depending on the reaction mechanism required to impart rubber elasticity. Examples of reaction mechanisms by curing agents include crosslinking reactions, condensation reactions, and addition reactions.

[0023] Organic peroxides can be used to impart rubber elasticity through a crosslinking reaction. Examples of organic peroxides include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, dicumyl peroxide, cumyl-t-butyl peroxide, 2,5-dimethyl-2,5-di-t-butyl peroxyhexane, and di-t-butyl peroxide.

[0024] When rubber elasticity is imparted by a condensation reaction, silicon-containing crosslinking agents and curing catalysts can be used. Examples of silicon-containing crosslinking agents include alkoxysilanes, acetoxysilanes, and cyclic siloxanes. Examples of curing catalysts include metal carboxylate salts and organotin compounds.

[0025] When rubber elasticity is imparted by an addition reaction, organohydrogenpolysiloxanes and platinum-based catalysts can be used. Organohydrogenpolysiloxanes are polyorganosiloxanes in which, on average, two or more hydrogen atoms are bonded to silicon atoms per molecule.

[0026] Silicone rubber compositions may contain oils. Among oils, silicone oils are preferred, and modified silicone oils are more preferred. Silicone oil refers to an oil whose main component is polyorganosiloxane. Modified silicone oil refers to a silicone oil in which some of the methyl groups contained in dimethyl silicone oil are replaced with other functional groups. Examples of modified silicone oils include amino-modified silicone oil, epoxy-modified silicone oil, carboxyl-modified silicone oil, carbinol-modified silicone oil, (meth)acrylic-modified silicone oil, mercapto-modified silicone oil, phenol-modified silicone oil, polyether-modified silicone oil, methylstyryl-modified silicone oil, alkyl-modified silicone oil, higher fatty acid ester-modified silicone oil, higher alkoxy-modified silicone oil, fluorine-modified silicone oil, and aralkyl-modified silicone oil. Modified silicone oils include non-reactive modified silicone oils and reactive modified silicone oils. Among these, non-reactive modified silicone oils are preferred.

[0027] The silicone rubber composition may contain various additives known in the art. Examples of such additives include reinforcing fillers (silica, diatomaceous earth, quartz powder, mica, titanium oxide, etc.); bulking fillers (diatomaceous earth, quartz powder, mica, clay, glass beads, aluminum oxide, etc.); heat resistance improvers (carbon black, red iron oxide, alkali metal oxides, alkaline earth metal oxides, etc.); and pigments.

[0028] [1.4. Composition of Silicone Rubber Composition] Based on the total weight of the silicone rubber composition, the lower limit of the flame-retardant silicone rubber compound content is preferably 50% by weight or more, and more preferably 55% by weight or more. The upper limit of the flame-retardant silicone rubber compound content may be, for example, 98% by weight or less.

[0029] Based on the total weight of the silicone rubber composition, the lower limit of the silicone rubber polymer content is preferably 10% by weight or more, more preferably 15% by weight or more, and even more preferably 18% by weight or more. The upper limit of the silicone rubber polymer content may be, for example, 98% by weight or less.

[0030] If the silicone rubber composition contains rubber components other than silicone rubber, the proportion of silicone rubber in the total rubber components is preferably 50% by weight or more, more preferably 70% by weight or more, and even more preferably 90% by weight or more. In one embodiment, the silicone rubber composition does not contain rubber components other than silicone rubber. Examples of rubber components other than silicone rubber include fluororubber (FKM), natural rubber (NR), styrene-butadiene rubber (SBR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), butyl rubber (IIR), ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), urethane rubber (U), ethylene-acrylic rubber (AEM), and acrylic rubber (ACM).

[0031] The lower limit of the content of fibrous flame retardants in a silicone rubber composition is 5 parts by weight or more, preferably 15 parts by weight or more, and more preferably 20 parts by weight or more, based on the content of 100 parts by weight of the flame-retardant silicone rubber compound. If the lower limit of the content is within the above range, the silicone rubber composition tends to have sufficient flame retardancy. The upper limit of the content of fibrous flame retardants in a silicone rubber composition is 60 parts by weight or less, preferably 50 parts by weight or less, more preferably 45 parts by weight or less, and even more preferably 40 parts by weight or less, based on the content of 100 parts by weight of the flame-retardant silicone rubber compound. If the upper limit of the content is within the above range, the silicone rubber composition tends to have a softness suitable for use as a sealing material.

[0032] The lower limit of the oil content in a silicone rubber composition is preferably 0.1% by weight or more, more preferably 0.3% by weight or more, and even more preferably 0.5% by weight or more, based on the total weight of the silicone rubber composition. If the oil content is less than 0.1% by weight, the processability may decrease. The upper limit of the oil content in a silicone rubber composition is preferably 15% by weight or less, more preferably 10% by weight or less, and even more preferably 5% by weight or less, based on the total weight of the silicone rubber composition. If the oil content exceeds 15% by weight, the composition may become excessively soft or bleeding may occur.

[0033] The amounts of other components can be appropriately determined by those skilled in the art in accordance with common technical knowledge. For example, the amount of curing agent can be 0.2 to 5.0 parts by weight, assuming the amount of flame-retardant silicone rubber compound is 100 parts by weight.

[0034] [1.5. Physical Properties of Silicone Rubber Compositions] The Shore A hardness of the silicone rubber composition is preferably 85 or less, and more preferably 80 or less. If the Shore A hardness is within the above range, it can be said that it has a suitable softness for use as a sealing material. In this specification, Shore A hardness is measured using a Type A durometer based on JIS K6253. For more specific examples of measurement methods, please refer to the examples of this application. Note that the Shore A hardness of the silicone rubber composition is measured for the cured silicone rubber composition under normal conditions (without subjecting it to a heat resistance test or combustion test).

[0035] The compression set of the silicone rubber composition after the heat resistance test is preferably 50 or less, and more preferably 30 or less. If the compression set after the heat resistance test is within the above range, it can be said that the composition has sufficient elasticity even after exposure to high temperatures. In this specification, the compression set after the heat resistance test is measured in accordance with JIS K6262. For more specific examples of measurement methods, please refer to the embodiments of this application. Note that the compression set of the silicone rubber composition after the heat resistance test is measured on the cured silicone rubber composition.

[0036] The silicone rubber composition exhibits improved flame retardancy compared to the flame-retardant silicone rubber compound contained therein alone. In this specification, "improved flame retardancy" means that one or more (preferably two or more, more preferably all) of the following three conditions are met. For a method of conducting the flame retardancy test, refer to the examples of this application. • The time of smoke generation is getting later. The time of the flame outbreak is getting later. • The duration of the flame has been shortened.

[0037] [2. Sealing materials and batteries] A sealing material according to one aspect of the present invention comprises the above-described silicone rubber composition for sealing materials. In this specification, a sealing material is intended to be a molded article used interposed between two or more members. The two or more members may be members whose relative positions change or members that are relatively stationary. The sealing material has the function of sealing the movement of a fluid (gas, liquid, or mixture thereof).

[0038] The applications of the sealing material are not particularly limited. The sealing material according to one embodiment of the present invention has improved flame retardancy and is therefore preferable for use in products where flame retardancy is required. Examples of such products include batteries, vehicles, building materials, home appliances, and mobile devices.

[0039] The following describes an example of using a sealing material according to one embodiment of the present invention in a battery, with reference to Figure 1. The battery 10 comprises a sealing material 1, cells 2, a heat insulating material 3, and a container 4. The battery 10 is configured to extract power from two or more cells 2 (12 cells 2 in Figure 1). Note that in Figure 1, the components for extracting power from the cells 2 are omitted. A specific example of the battery 10 is a non-aqueous electrolyte secondary battery (such as a lithium-ion secondary battery).

[0040] The sealing material 1 is a sealing material according to one aspect of the present invention. The cell 2 is a power generation element in which a positive electrode, negative electrode, separator, electrolyte, etc., are packaged together. The heat insulating material 3 is a component that prevents heat from being transmitted from the cell 2. The container 4 is a component that houses the sealing material 1, the cell 2, and the heat insulating material 3.

[0041] The interior of container 4 is divided into two or more compartments by the insulation material 3. In Figure 1, it is divided into four compartments: A, B, C, and D. The two or more cells 2 are arranged in two or more of these compartments. In Figure 1, cells 2 are placed in all four compartments A to D, but there may be compartments where cells 2 are not placed. The sealing material 1 is placed to close the gap between the insulation material 3 and container 4.

[0042] For example, if cell 2 located in compartment A malfunctions and catches fire, the sealant 1 and insulation material 3 prevent the fire from spreading to compartment B. Since sealant 1 is a sealant according to one aspect of the present invention, its flame retardancy is improved compared to conventional sealants. Therefore, battery 10 is safer than conventional batteries.

[0043] [3. Silicone rubber composition for sealing material and method for manufacturing sealing material] The method for producing a silicone rubber composition for sealing materials according to one aspect of the present invention is not particularly limited. For example, a silicone rubber composition for sealing materials can be produced by kneading the components described in Section [1]. A kneader can be used to knead the components. Examples of kneaders include open rolls, kneaders, planetarium mixers, Banbury mixers, and extruders. The kneading temperature may be 25 to 200°C. The kneading time may be 1 minute to 1 hour.

[0044] The method for manufacturing a sealing material according to one aspect of the present invention is not particularly limited. For example, a sealing material can be manufactured by molding and curing the above-described silicone rubber composition for sealing materials. Examples of molding methods include injection molding, transfer molding, injection molding, compression molding, press working, and extrusion molding. The curing temperature may be 25 to 200°C. The curing time may be 10 seconds to 120 minutes.

[0045] The order of curing and molding is not particularly limited. The cured silicone rubber composition may be molded, the silicone rubber composition may be molded during the curing reaction, or the molded article may be cured after molding.

[0046] The cured molded body may be further cured. The secondary curing temperature may be 25 to 250°C. The secondary curing time may be 30 minutes to 4 hours.

[0047] [4. Summary] The present invention includes the following configuration. <1> It contains a flame-retardant silicone rubber compound and a fiber-based flame retardant. If the amount of the above flame-retardant silicone rubber compound is 100 parts by weight, then the amount of the above fiber-based flame retardant is 5 to 60 parts by weight. The above flame-retardant silicone rubber compound is a silicone rubber composition for sealing materials that meets the UL94 standard V-0 or higher. <2> The above-mentioned fiber-based flame retardant is characterized by containing one or more selected from the group consisting of artificial mineral fibers, natural mineral fibers, and synthetic organic fibers. <1> The silicone rubber composition for sealing materials described above. <3> The above-mentioned fiber-based flame retardant contains the above-mentioned artificial mineral fibers, The above artificial mineral fibers include rock wool. <2> The silicone rubber composition for sealing materials described above. <4> The above-mentioned fibrous flame retardant has a fiber length of 50 to 500 μm and a shot content of 5% by weight or less. <1> ~ <3> A silicone rubber composition for sealing materials as described in any of the following. <5> The content of the flame-retardant silicone rubber compound in the above-mentioned silicone rubber composition for sealing materials is 50% by weight or more. <1> ~ <4> A silicone rubber composition for sealing materials as described in any of the following. <6> Shore A stiffness is 85 or less. <1> ~ <5> A silicone rubber composition for sealing materials as described in any of the following. <7> <1> ~ <6> A sealing material comprising the silicone rubber composition for sealing materials described in any of the following. <8> Two or more cells, insulation material, container, <7> A battery comprising the sealing material described above, The two or more cells mentioned above, the insulating material mentioned above, and the sealing material mentioned above are stored in the container mentioned above. The above-mentioned insulation material is arranged to divide the container into two or more compartments. The two or more cells mentioned above are divided and arranged into two or more sections. The above sealing material is positioned to close the gap between the above insulating material and the above container. battery. <9> A battery comprising two or more cells, an insulating material, a container, and a sealing material, The above sealing material is <1> ~ <6> A battery comprising a silicone rubber composition for sealing materials as described in any of the following.

[0048] Furthermore, the present invention also includes the following configurations. [A1] A method for producing a silicone rubber composition for sealing materials, The process includes a step of mixing a flame-retardant silicone rubber compound and a fiber-based flame retardant. If the amount of the above flame-retardant silicone rubber compound is 100 parts by weight, then the amount of the above fiber-based flame retardant is 5 to 60 parts by weight. The above flame-retardant silicone rubber compound is manufactured using a method that meets the UL94 standard of V-0 or higher. [A2] A method for improving the flame retardancy of a flame-retardant silicone rubber compound, The process includes a step of mixing a flame-retardant silicone rubber compound and a fiber-based flame retardant. If the amount of the above flame-retardant silicone rubber compound is 100 parts by weight, then the amount of the above fiber-based flame retardant is 5 to 60 parts by weight. The above flame-retardant silicone rubber compound is V-0 or higher according to the UL94 standard. [Examples]

[0049] One embodiment of the present invention will be described in detail below with reference to examples. However, the present invention is not limited to these examples.

[0050] [Materials used] ● Flame-retardant silicone rubber compound • Flame-retardant silicone rubber compound A (KE-5612E-U, Shin-Etsu Chemical Co., Ltd., vinyl methyl silicone rubber compound, UL94 standard: V-0) • Flame-retardant silicone rubber compound B (SH502U, Dow-Toray Corporation, vinyl methyl silicone rubber compound, UL94 standard: V-0) ● Flame retardant • Fiber-based flame retardant A (rock wool, RS490ELS-Roxul1000, Rapinus, fiber length: 150-250 μm, shot content: 0.2% (average)) • Fiber-based flame retardant B (rock wool, FS021, JFE Rock Fiber Co., Ltd., shot content: 30-40%) • Fiber-based flame retardant C (aramid fiber, Twaron® 3091, Teijin Limited, fiber length: 650~1150μm) • Phosphorus-based flame retardant (Fireguard FCX-210, Teijin Limited) • Inorganic flame retardant (particulate aluminum hydroxide) ● Hardener • Hardener A (C-3, Shin-Etsu Chemical Co., Ltd., dicumyl peroxide) • Hardener B (RC4 50P, Dow-Toray Industries, Ltd., 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane)

[0051] [Examples 1-8, Comparative Examples 1-5] A vulcanized rubber sheet was prepared using the following procedure. This vulcanized rubber sheet will be used as the material for preparing test specimens in the tests described later. 1. Each component listed in Table 1 was kneaded in an open roll. The kneading temperature ranged from 20 to 100°C. The kneading time was 10 to 30 minutes. 2. An unvulcanized rubber sheet was prepared from the resulting mixture. 3. The unvulcanized rubber sheet was press-vulcanized at 165°C for 10 minutes. 4. Furthermore, secondary vulcanization was performed at 200°C for 4 hours. In this way, a vulcanized rubber sheet with a thickness of 2 mm was obtained.

[0052] [Test Method] [1. Hardness under normal conditions] In accordance with JIS K6253, the Shore A hardness of the silicone rubber composition was measured before subjecting it to a heat resistance test or combustion test. The specific procedure is as follows: 1. Three 2mm thick vulcanized rubber sheets were stacked together to form a test specimen. 2. Measurements were taken using a Type A durometer at 23°C and 50% relative humidity. The peak value of the durometer was defined as Shore A hardness.

[0053] [2. Heat Resistance Test] In accordance with JIS K6262, a heat resistance test was subjected to the silicone rubber composition, and then the compression set was measured. The specific procedure is as follows. 1. Three sheets with a diameter of 13 mm were cut from a 2 mm thick vulcanized rubber sheet. These three sheets were stacked together to form the test specimen. 2. The test specimens were compressed by 25% and held in air at 150°C for 70 hours. 3. The compression was released, and the compression set of the silicone rubber composition was calculated. Silicone rubber compositions with a small compression set value can be said to have high resilience even after being compressed for a long time.

[0054] [3.Dispersibility] The dispersibility of the fiber-based flame retardant was evaluated based on the appearance of the silicone rubber composition. The specific procedure is as follows. 1. The unvulcanized rubber sheet, prepared in the example or comparative example, was cut out using a cutter. 2. The degree of dispersion of fibrous flame retardants in the cross-section of the cut unvulcanized rubber sheet was measured using a filler dispersion meter (Dispersion Checker DCF50A, M&K Co., Ltd.). The measurement results were evaluated according to the following criteria. A higher degree of dispersion is preferable. 1: Dispersion less than 80% 2: Dispersion of 80% or more, but less than 90% 3:Dispersion degree of 90% or more

[0055] [4. Combustion Test] The silicone rubber composition was subjected to a combustion test to evaluate its flame retardancy and shape retention after combustion. The specific procedure is as follows: 1. A 10mm wide x 100mm long sheet was cut from a 2mm thick vulcanized rubber sheet to serve as a test specimen. 2. The test specimen was fixed to the jig, and the burner flame was adjusted so that the temperature of the combustion area reached 800°C. 3. The test specimen was exposed to a flame for 2 minutes. The time the flame was applied was defined as 0 seconds, and the time (in seconds) when smoke appeared and when the flame appeared were recorded. The duration (in seconds) from when the flame appeared until it was extinguished was also recorded. 4. After combustion, the deflection and appearance of the test specimen were visually inspected.

[0056] The criteria for judging the deflection and appearance of the test specimen after the combustion test are as follows: ●Sagging 1: There is a large deflection. 2: There is a moderate amount of deflection. 3: There is a slight sag. 4: There is no deflection (or only a very small deflection). ●Exterior 1: Defective. Numerous cracks, peeling, breaks, and shattering. 2: Normal. There is a large crack. 3: Good. There are small to moderate cracks. 4: Very good. Only whitening, no cracks (or only very small cracks). [Table 1] TIFF0007881241000002.tif179169 TIFF0007881241000003.tif215169

[0057] 〔result〕 The test results are shown in Table 1. Comparing Examples 1-5 with Comparative Example 1, it can be seen that the silicone rubber composition with added fiber-based flame retardant exhibits improved flame retardancy. Specifically, the time of smoke generation and flame generation was later in Examples 1-5 than in Comparative Example 1. In addition, the flame duration was shorter in Examples 1-5 than in Comparative Example 1.

[0058] The improvement in flame retardancy was observed even when the type of flame-retardant silicone rubber compound was changed (Example 6). Similarly, the improvement in flame retardancy was observed even when the type of fiber-based flame retardant was changed (Examples 7-9). In Comparative Examples 2 and 3, in which phosphorus-based flame retardants were added, a tendency for flame retardancy to decrease was observed. In Comparative Examples 4 and 5, in which inorganic flame retardants were added, the flame retardancy was equivalent to that of the examples, but the deflection and appearance after the combustion test were extremely poor.

[0059] Comparing the examples, the degree of improvement in flame retardancy was greater in Examples 2-5 than in Example 1. Therefore, from the viewpoint of flame retardancy, it is preferable to have a higher content of fibrous flame retardant than in Example 1 (for example, 15 parts by weight or more per 100 parts by weight of flame-retardant silicone rubber compound).

[0060] Furthermore, the Shore A hardness under normal conditions was lower in Examples 1-4 than in Example 5. Therefore, from the viewpoint of use in general sealing material applications, it is preferable to have a lower content of fibrous flame retardant than in Example 5 (for example, 45 parts by weight or less per 100 parts by weight of flame-retardant silicone rubber compound).

[0061] The dispersibility of the fibrous flame retardants in the silicone rubber composition was best with fibrous flame retardant A (Examples 1-6), followed by fibrous flame retardant B (Examples 7 and 8), and then fibrous flame retardant C (Example 9). Therefore, from the viewpoint of dispersibility, it is preferable that the fibrous flame retardant is rock wool. Similarly, from the viewpoint of dispersibility, it is preferable to have a low shot content of the fibrous flame retardant (for example, 0.5% by weight or less based on the weight of the fibrous flame retardant). [Industrial applicability]

[0062] The present invention can be used, for example, in sealing materials for batteries and the like. [Explanation of Symbols]

[0063] 1: Sealant 2: Cell 3: Insulation 4: Container 10:Battery

Claims

1. It contains a flame-retardant silicone rubber compound and a fiber-based flame retardant. If the amount of the above-mentioned flame-retardant silicone rubber compound is 100 parts by weight, then the amount of the above-mentioned fiber-based flame retardant is 5 to 60 parts by weight. The above flame-retardant silicone rubber compound is a silicone rubber composition for battery sealing materials that meets the UL94 standard of V-0 or higher.

2. The silicone rubber composition for battery sealing material according to claim 1, characterized in that it contains one or more fibrous flame retardants selected from the group consisting of artificial mineral fibers, natural mineral fibers, and synthetic organic fibers.

3. The above-mentioned fiber-based flame retardant contains the above-mentioned artificial mineral fibers, The above artificial mineral fibers include rock wool. The silicone rubber composition for battery sealing material according to claim 2.

4. The silicone rubber composition for battery sealing material according to claim 1, wherein the above-mentioned fibrous flame retardant has a fiber length of 50 to 500 μm and a shot content of 5% by weight or less.

5. The silicone rubber composition for battery sealing materials according to claim 1, wherein the content of the flame-retardant silicone rubber compound in the above-mentioned silicone rubber composition for battery sealing materials is 50% by weight or more.

6. The silicone rubber composition for battery sealing material according to claim 1, wherein the Shore A hardness is 85 or less.

7. A battery seal material comprising the silicone rubber composition for battery seal materials described in any one of claims 1 to 6.

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