Silicone rubber composition for sealing material, sealing material, and battery

Abstract

Provided is a silicone rubber composition for a sealing material, said composition exhibiting improved flame retardancy compared to the prior art. A silicone rubber composition according to one embodiment of the present invention contains a flame-retardant silicone rubber compound and a fibrous flame retardant. If the content of the flame-retardant silicone rubber compound is taken to be 100 parts by weight, the content of the fibrous flame retardant is 5-60 parts by weight. The flame-retardant silicone rubber compound is rated as V-0 or higher in UL94 specifications.

Description

Technical Field

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

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 employed 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 still remains 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 as compared with 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 includes a flame-retardant silicone rubber compound and a fibrous flame retardant. When the content of the above-mentioned flame-retardant silicone rubber compound is 100 parts by weight, the content of the above-mentioned fiber-based flame retardant is 5 to 60 parts by weight, The above-mentioned flame-retardant silicone rubber compound is V-0 or higher in the UL94 standard.

Advantages of the Invention

[0007] According to one aspect of the present invention, a silicone rubber composition for a sealing material with improved flame retardancy compared to the prior art is provided.

Brief Description of the Drawings

[0008]

Figure 1

Modes for Carrying Out the Invention

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

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

[0011] [1. Silicone Rubber Composition for Sealing Material] The silicone rubber composition for a sealing material according to one aspect of the present invention contains a flame-retardant silicone rubber compound and a fiber-based flame retardant. Hereinafter, each component will be described.

[0012] [1.1. Flame-Retardant Silicone Rubber Compound] The flame-retardant silicone rubber compound is a composition obtained by blending various additives into silicone rubber to impart flame retardancy. The flame-retardant silicone rubber compound has a flame retardancy of V-0 or higher in the UL94 standard.

[0013] The UL94 standard is a standard for evaluating the flame retardancy of plastic products and is widely adopted globally. The grades of the UL94 standard, in descending order of flame retardancy, are 5VA, 5VB, V-0, V-1, V-2, and HB. Therefore, the flame-retardant silicone rubber compound is 5VA, 5VB, or V-0 according to the UL94 standard. In one embodiment, the flame-retardant silicone rubber compound is V-0 according to the UL94 standard. Since the test methods of the UL94 standard are well-known among those skilled in the art, the description thereof is omitted.

[0014] The flame-retardant silicone rubber compound contains silicone rubber. In one embodiment, the silicone rubber is an organopolysiloxane resin. In the organopolysiloxane resin, it is preferable that 50% or more, more preferably 70% or more, and even more preferably 90% or more of the units having an organopolysiloxane structure among all the units contained in the main chain. Specific examples of the silicone rubber include methyl silicone rubber, vinyl methyl silicone rubber, phenyl methyl silicone rubber, and fluorinated silicone rubber. These silicone rubbers may be included alone or in combination of two or more. In one embodiment, the flame-retardant silicone rubber compound contains vinyl methyl silicone rubber. Examples of the additives contained in the flame-retardant silicone rubber compound include platinum, platinum compounds, iron oxide, triazole-based compounds, and aluminum hydroxide. These additives may be included alone or in combination of two or more. Many products of the flame-retardant silicone rubber compound are on the market, and there are also many related patent documents. Therefore, the detailed composition of the flame-retardant silicone rubber compound is omitted from the description.

[0015] Examples of commercially available flame-retardant silicone rubber compounds include SILASTIC (TM) SH502U, SH502U A / B, SH1447 U A (all of the above 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 the above 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 the above are from Asahi Kasei Wacker Silicone Co., Ltd.); TSE2186U, TSE2183U, TSE2187U, TSE2184U, TCM5406U, XE20-A7016 (all of the above 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 flame retardants other than fiber-based flame retardants (such as phosphorus-based flame retardants and particulate inorganic flame retardants) were blended (see the examples of the present application for details). That is, it can be said that the effect of the present invention is 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 fiberized in the manufacturing process of the fibrous flame retardant.

[0020] Examples of the fibrous flame retardant include artificial mineral fibers, natural mineral fibers, and synthetic organic fibers. Examples of artificial 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, artificial mineral fibers are preferred. Among artificial 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] The silicone rubber composition for a sealing material according to an embodiment of the present invention may contain components other than those described above. Examples of such components include curing agents.

[0022] A curing agent is a component that imparts rubber elasticity to the silicone rubber composition. A person skilled in the art can appropriately select a curing agent according to the reaction mechanism for imparting rubber elasticity. Examples of the reaction mechanism by the curing agent include crosslinking reaction, condensation reaction, and addition reaction.

[0023] When imparting rubber elasticity by a crosslinking reaction, an organic peroxide can be used. Examples of the organic peroxide include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, dicumyl peroxide, cumyl-t-butyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, and di-t-butyl peroxide.

[0024] When imparting rubber elasticity by a condensation reaction, a silicon-containing crosslinking agent and a curing catalyst can be used. Examples of the silicon-containing crosslinking agent include alkoxysilane, acetoxysilane, and cyclic siloxane. Examples of the curing catalyst include metal carboxylate and organotin compound.

[0025] When imparting rubber elasticity by an addition reaction, an organohydrogenpolysiloxane and a platinum-based catalyst can be used. An organohydrogenpolysiloxane is a polyorganosiloxane in which an average of two or more hydrogen atoms are bonded to silicon atoms per molecule.

[0026] The silicone rubber composition may contain oil. Among oils, silicone oil is preferred, and modified silicone oil is more preferred. Silicone oil refers to an oil mainly composed of polyorganosiloxane. Modified silicone oil refers to a silicone oil in which a part of the methyl groups contained in dimethyl silicone oil is 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 (such as silica, diatomaceous earth, quartz powder, mica, titanium oxide, etc.); extender fillers (such as diatomaceous earth, quartz powder, mica, clay, glass beads, aluminum oxide, etc.); heat resistance improvers (such as carbon black, red iron oxide, alkali metal oxides, alkaline earth metal oxides, etc.); and pigments.

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

[0029] Based on the total weight of the silicone rubber composition, the lower limit of the content of the silicone rubber polymer 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 content of the silicone rubber polymer can be, for example, 98% by weight or less.

[0030] When the silicone rubber composition contains a rubber component 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 a rubber component 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] Based on 100 parts by weight of the content of the flame-retardant silicone rubber compound, the lower limit of the content of the fibrous flame retardant in the 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. If the lower limit of the content is within the above range, the silicone rubber composition tends to have sufficient flame retardancy. Based on 100 parts by weight of the content of the flame-retardant silicone rubber compound, the upper limit of the content of the fibrous flame retardant in the 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. If the upper limit of the content is within the above range, the silicone rubber composition tends to have a softness suitable for a sealing material.

[0032] The lower limit of the oil content in the silicone rubber composition is preferably 0.1% by weight or more, more preferably 0.3% by weight or more, and still more preferably 0.5% by weight or more, based on the total weight of the silicone rubber composition. When the oil content is less than 0.1% by mass, the processability may deteriorate. The upper limit of the oil content in the silicone rubber composition is preferably 15% by weight or less, more preferably 10% by weight or less, and still more preferably 5% by weight or less, based on the total weight of the silicone rubber composition. When the oil content exceeds 15% by mass, it may become overly soft or bleed.

[0033] The compounding amounts of other components can be appropriately set by those skilled in the art according to common general knowledge. For example, when the content of the flame-retardant silicone rubber compound is 100 parts by weight, the content of the curing agent can be 0.2 to 5.0 parts by weight.

[0034] [1.5. Physical properties of the silicone rubber composition] 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 to have a suitable softness as a sealing material. In this specification, the Shore A hardness is measured using a Type A durometer based on JIS K6253. For an example of a more specific measurement method, 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 in the normal state (a state where no heat resistance test or combustion test is imposed).

[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 to have sufficient elasticity even after being exposed to high temperatures. In this specification, the compression set after the heat resistance test is measured based on JIS K6262. For an example of a more specific measurement method, refer to the examples of this application. Note that the compression set of the silicone rubber composition after the heat resistance test is measured for the cured silicone rubber composition.

[0036] The silicone rubber composition has improved flame retardancy compared to the flame-retardant silicone rubber compound contained therein alone. As used herein, "having improved flame retardancy" is intended to satisfy one or more (preferably two or more, more preferably all) of the following three conditions. For the method of conducting the flame retardancy test, refer to the examples of the present application. · The time of smoke generation is delayed. · The time of flame generation is delayed. · The flame duration is shortened.

[0037] [2. Sealing Material and Battery] The sealing material according to one aspect of the present invention contains the above-described silicone rubber composition for a sealing material. As used herein, the sealing material is intended to be a molded product 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, for example, a function of sealing the movement of a fluid (gas, liquid, or a mixture thereof).

[0038] The use of the sealing material is not particularly limited. Since the sealing material according to one embodiment of the present invention has improved flame retardancy, it is preferably used in products that require flame retardancy. Examples of such products include batteries, vehicles, housing building materials, household appliances, and mobile terminals.

[0039] Hereinafter, with reference to FIG. 1, a usage example in the case where the sealing material according to one embodiment of the present invention is applied to a battery will be described. The battery 10 includes a sealing material 1, cells 2, a heat insulating material 3, and a container 4. The battery 10 is configured to extract electric power from two or more cells 2 (12 cells 2 in FIG. 1). In FIG. 1, members for extracting electric power from the cells 2 are omitted. Specific examples of the battery 10 include non-aqueous electrolyte secondary batteries (such as lithium ion secondary batteries).

[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, a negative electrode, a separator, an electrolytic solution, etc. are packaged. The heat insulating material 3 is a member that prevents the heat generated by the cell 2 from being transmitted. The container 4 is a member that stores the sealing material 1, the cell 2, and the heat insulating material 3.

[0041] The inside of the container 4 is divided into two or more compartments by the heat insulating material 3. In FIG. 1, it is divided into four compartments: compartment A, compartment B, compartment C, and compartment D. Two or more cells 2 are divided and arranged in two or more of the two or more compartments. In FIG. 1, cells 2 are arranged in all four compartments A to D, but there may be a compartment in which no cell 2 is arranged. The sealing material 1 is arranged so as to block the gap between the heat insulating material 3 and the container 4.

[0042] For example, when the cell 2 arranged in compartment A malfunctions and catches fire, the sealing material 1 and the heat insulating material 3 prevent the spread of fire to compartment B. Since the sealing material 1 is a sealing material according to one aspect of the present invention, its flame retardancy is improved compared to conventional sealing materials. Therefore, the battery 10 has improved safety compared to conventional batteries.

[0043] [3. Method for Producing a Silicon Rubber Composition for Sealing Material and Sealing Material] The method for producing a silicon rubber composition for a sealing material according to one aspect of the present invention is not particularly limited. For example, a silicon rubber composition for a sealing material can be produced by kneading each component described in section [1]. A kneader can be used for kneading the components. Examples of kneaders include open rolls, kneaders, planetary 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 manufacturing method of the sealing material according to one aspect of the present invention is not particularly limited. For example, the sealing material can be manufactured by molding and curing the above-described silicone rubber composition for the sealing material. Examples of the molding method 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 silicone rubber composition after curing may be molded, the silicone rubber composition during the curing reaction may be molded, or the molded body after molding may be cured.

[0046] The cured molded body may be further secondarily 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 configurations. [1] A silicone rubber composition for a sealing material, comprising a flame-retardant silicone rubber compound and a fibrous flame retardant, wherein when the content of the flame-retardant silicone rubber compound is 100 parts by weight, the content of the fibrous flame retardant is 5 to 60 parts by weight, and the flame-retardant silicone rubber compound has a V-0 or higher rating in the UL94 standard. [2] The silicone rubber composition for a sealing material according to [1], wherein the fibrous flame retardant contains one or more selected from the group consisting of man-made mineral fibers, natural mineral fibers, and synthetic organic fibers. [3] The silicone rubber composition for a sealing material according to [2], wherein the fibrous flame retardant contains the man-made mineral fibers, and the man-made mineral fibers contain rock wool. The silicone rubber composition for a sealing material according to [2]. [4] The above fiber-based flame retardant is a silicone rubber composition for a sealing material according to any one of <1> to <3>, having a fiber length of 50 to 500 μm and a shot content of 5% by weight or less. <5> The silicone rubber composition for a sealing material according to any one of <1> to <4>, wherein the content of the flame-retardant silicone rubber compound in the silicone rubber composition for a sealing material is 50% by weight or more. <6> The silicone rubber composition for a sealing material according to any one of <1> to <5>, having a Shore A hardness of 85 or less. <7> A sealing material containing the silicone rubber composition for a sealing material according to any one of <1> to <6>. <8> A battery comprising two or more cells, a heat insulating material, a container, and the sealing material according to <7>, wherein the two or more cells, the heat insulating material, and the sealing material are stored in the container, the heat insulating material is arranged so as to divide the inside of the container into two or more compartments, the two or more cells are arranged separately in two or more of the two or more compartments, the sealing material is arranged so as to close the gap between the heat insulating material and the container. Battery. <9> A battery comprising two or more cells, a heat insulating material, a container, and a sealing material, wherein the sealing material contains the silicone rubber composition for a sealing material according to any one of <1> to <6>.

[0048] Further, the present invention also includes the following configurations. [A1] A method for producing a silicone rubber composition for a sealing material, comprising a step of mixing a flame-retardant silicone rubber compound and a fiber-based flame retardant, wherein when the blending amount of the flame-retardant silicone rubber compound is 100 parts by weight, the blending amount of the fiber-based flame retardant is 5 to 60 parts by weight. A manufacturing method of the above flame-retardant silicone rubber compound, which is V-0 or higher according to the UL94 standard. [A2] A method for improving the flame retardancy of a flame-retardant silicone rubber compound, comprising a step of mixing a flame-retardant silicone rubber compound and a fibrous flame retardant, when the compounding amount of the above flame-retardant silicone rubber compound is 100 parts by weight, the compounding amount of the above fibrous flame retardant is 5 to 60 parts by weight, and the above flame-retardant silicone rubber compound is V-0 or higher according to the UL94 standard.

Example

[0049] Hereinafter, an embodiment of the present invention will be specifically described by way of 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-based compound, UL94 standard: V-0) · Flame-retardant silicone rubber compound B (SH502U, Dow Corning Toray Co., Ltd., vinyl methyl silicone rubber-based compound, UL94 standard: V-0) ● Flame retardant · Fibrous flame retardant A (rock wool, RS490ELS-Roxul1000, Rapinus, fiber length: 150 - 250 μm, shot content: 0.2% (average)) · Fibrous flame retardant B (rock wool, FS021, JFE Rock Fiber Co., Ltd., shot content: 30 - 40%) · Fibrous flame retardant C (aramid fiber, Twaron (registered trademark) 3091, Teijin Limited, fiber length: 650 - 1150 μm) · Phosphorus-based flame retardant (Firegard FCX-210, Teijin Limited) · Inorganic flame retardant (particulate aluminum hydroxide) ● Curing agent · Hardening agent A (C-3, Shin-Etsu Chemical Co., Ltd., dicumyl peroxide) · Hardening agent B (RC4 50P, Dow-Toray Co., Ltd., 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane)

[0051] [Examples 1 to 8, Comparative Examples 1 to 5] Vulcanized rubber sheets were produced according to the following procedure. The vulcanized rubber sheets serve as materials for producing test pieces in the tests described later. 1. Each component listed in Table 1 was kneaded on an open roll. The temperature during kneading was 20 to 100 °C. The kneading time was 10 to 30 minutes. 2. An unvulcanized rubber sheet was produced from the obtained kneaded material. 3. The unvulcanized rubber sheet was press-vulcanized at 165 °C for 10 minutes. 4. Further, it was secondarily vulcanized 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 in the normal state] Based on JIS K6253, the Shore A hardness of the silicone rubber composition before subjecting it to a heat resistance test or a combustion test was measured. The specific procedure is as follows. 1. Three 2-mm-thick vulcanized rubber sheets were stacked to form a test piece. 2. Using a Type A durometer, the measurement was carried out at 23 °C and a relative humidity of 50%. The peak value of the durometer was taken as the Shore A hardness.

[0053] [2. Heat resistance test] Based on JIS K6262, the silicone rubber composition was subjected to a heat resistance test, and then the compression set was measured. The specific procedure is as follows. 1. From a 2-mm-thick vulcanized rubber sheet, three 13-mm-diameter sheets were cut out. The stack of these three sheets was used as a test piece. 2. The test piece was 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. A silicone rubber composition with a small value of compression set can be said to have a high resilience even after being compressed for a long time.

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

[0055] [4. Combustion test] A combustion test was conducted on the silicone rubber composition to evaluate its flame retardancy and shape retention after combustion. The specific procedure is as follows. 1. A sheet with a width of 10 mm × a length of 100 mm was cut out from a vulcanized rubber sheet with a thickness of 2 mm as a test piece. 2. The test piece was fixed to a jig, and the flame of the burner was adjusted so that the temperature at the combustion site reached 800 °C. 3. The test piece was exposed to the flame for 2 minutes. At this time, taking the time when the flame was first applied as 0 seconds, the time (seconds) when smoke was generated and the time (seconds) when the flame was generated were recorded. Also, the duration (seconds) from when the flame was generated until it was extinguished was recorded. 4. After combustion, the deflection and appearance of the test piece were visually confirmed.

[0056] The criteria for judging the deflection and appearance of the test piece after the combustion test are as follows. ● Deflection 1: There is a large deflection. 2: There is a medium deflection. 3: There is a small deflection. 4: There is no deflection (or only a minute deflection). ● Appearance 1: Defective. There are many cracks, peeling, breaks, pulverizations, etc. 2: Normal. There are large cracks. 3: Good. There are small or medium-sized cracks. 4: Very good. It is only whitened and has no cracks (or only minute cracks).

Table 1

[0057] 〔Results〕 The test results are shown in Table 1. Comparing Examples 1 to 5 with Comparative Example 1, it can be seen that the silicone rubber composition added with the fiber-based flame retardant has improved flame retardancy. That is, the smoke generation time and the flame generation time were later for Examples 1 to 5 than for Comparative Example 1. Also, the flame duration was shorter for Examples 1 to 5 than for Comparative Example 1.

[0058] The improvement in flame retardancy was also observed when changing the type of flame-retardant silicone rubber compound (Example 6). Similarly, the improvement in flame retardancy was also observed when changing the type of fiber-based flame retardant (Examples 7 to 9). In Comparative Examples 2 and 3 where a phosphorus-based flame retardant was added, conversely, there was a tendency for the flame retardancy to decrease. In Comparative Examples 4 and 5 where an inorganic-based flame retardant was 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 with each other, Examples 2 to 5 had a greater degree of improvement in flame retardancy than Example 1. Therefore, from the viewpoint of flame retardancy, it is preferable to increase the content of the fibrous flame retardant compared to Example 1 (for example, 15 parts by weight or more with respect to 100 parts by weight of the flame-retardant silicone rubber compound).

[0060] Also, Examples 1 to 4 had a lower Shore A hardness in the normal state than Example 5. Therefore, from the viewpoint of using it for general sealing material applications, it is preferable to reduce the content of the fibrous flame retardant compared to Example 5 (for example, 45 parts by weight or less based on 100 parts by weight of the flame-retardant silicone rubber compound).

[0061] Regarding the dispersibility of the fibrous flame retardant in the silicone rubber composition, fibrous flame retardant A was the most excellent (Examples 1 to 6), fibrous flame retardant B was the next best (Examples 7 and 8), and fibrous flame retardant C was the next best (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 that the shot content of the fibrous flame retardant is low (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, as a sealing material for batteries and the like.

Explanation of Symbols

[0063] 1: Sealing material 2: Cell 3: Heat insulating material 4: Container 10: Battery

Claims

1. A flame-retardant silicone rubber compound and a fibrous flame retardant, and when the content of the flame-retardant silicone rubber compound is 100 parts by weight, the content of the fibrous flame retardant is 15 to 60 parts by weight, The flame-retardant silicone rubber compound is V-0 or higher according to the UL94 standard, The flame-retardant silicone rubber compound contains an organopolysiloxane resin, A silicone rubber composition for a sealing material (however, excluding a composition consisting of rock wool, calcium carbonate, aluminum hydroxide, fibrous potassium titanate, titanium oxide, a modified silicone resin having a silicon-containing group only at the end of a polyalkylene oxide main chain, a silicone resin, tin octylate, laurylamine, di-2-ethylhexyl phthalate, an ultraviolet absorber, and an antioxidant).

2. The fibrous flame retardant contains one or more selected from the group consisting of man-made mineral fibers, natural mineral fibers, and synthetic organic fibers. The silicone rubber composition for a sealing material according to Claim 1.

3. The fibrous flame retardant contains the man-made mineral fiber, The man-made mineral fiber contains rock wool. The silicone rubber composition for a sealing material according to Claim 2.

4. The fibrous flame retardant has a fiber length of 50 to 500 μm and a shot content of 5% by weight or less. The silicone rubber composition for a sealing material according to Claim 1.

5. The content rate of the flame-retardant silicone rubber compound in the silicone rubber composition for a sealing material is 50% by weight or more. The silicone rubber composition for a sealing material according to Claim 1.

6. The silicone rubber composition for a sealing material according to Claim 1 has a Shore A hardness of 85 or less.

7. A sealing material containing the silicone rubber composition for a sealing material according to any one of Claims 1 to 6.

8. A battery including two or more cells, a heat insulating material, a container, and the sealing material according to Claim 7, The two or more cells, the heat insulating material, and the sealing material are stored in the container, The heat insulating material is arranged to divide the inside of the container into two or more compartments, The two or more cells are divided and arranged in two or more of the two or more compartments, The sealing material is arranged to block the gap between the heat insulating material and the container. Battery ​ ​ ​

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