Foamable rubber composition, rubber foam, method for manufacturing the same, and battery module

Abstract

To provide a foamable rubber composition that allows production of a heat insulating material having heat insulation performance and flame retardancy sufficient to prevent thermal chain reaction to adjacent battery cells and having flexibility sufficient to follow expansion and contraction of battery cells, a rubber foam prepared from the foamable rubber composition, a method for manufacturing the rubber foam, and a battery module.SOLUTION: A foamable rubber composition contains an unvulcanized rubber material, a foaming agent, and expandable graphite, wherein the foaming agent is at least one selected from expanded microballoons, unexpanded microballoons, and a chemical foaming agent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a foamable rubber composition, a rubber foam and a method for producing the same, and a battery module. [Background technology]

[0002] Automotive batteries used in electric vehicles, hybrid vehicles, etc. are composed of multiple battery cells. If a battery cell experiences thermal runaway due to a defect during manufacturing, a vehicle collision, or improper handling of the battery cell, a large amount of heat can be transferred to adjacent battery cells, causing a thermal chain reaction that can lead to fires and serious accidents. For this reason, it is common to install insulation between adjacent battery cells to prevent fires from spreading between them.

[0003] To improve the driving distance of automotive batteries when fully charged, it is necessary to increase the number of battery cells and increase battery capacity. However, increasing the number of battery cells narrows the gap between adjacent battery cells, which increases the risk of thermal chain reaction between adjacent battery cells. Therefore, there is a need to develop a thin-walled insulating material with excellent thermal insulation and flame retardancy that can prevent thermal chain reaction from occurring in adjacent battery cells even if a thermal runaway occurs in one battery cell.

[0004] Furthermore, when an automotive battery is charged and discharged, the multiple battery cells repeatedly expand and contract, so the insulating material provided between the battery cells must be flexible enough to accommodate the expansion and contraction of the battery cells. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 394612 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-137475 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to provide a foamed rubber composition that can be used to produce a heat insulating material that has sufficient heat insulating properties and flame retardancy to prevent thermal chain reaction to adjacent battery cells and is flexible enough to follow the expansion and contraction of battery cells, a rubber foam made from the foamed rubber composition, a method for producing a rubber foam, and a battery module. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a foamable rubber composition comprising an unvulcanized rubber raw material, a foaming agent, and expandable graphite, wherein the foaming agent is at least one of expanded microballoons, unexpanded microballoons, and a chemical foaming agent. The present invention also provides a rubber foam obtained by subjecting the foamable rubber composition to a vulcanization treatment and a foaming treatment. Furthermore, the present invention provides a method for producing a rubber foam, comprising a vulcanization step of heating the foamable rubber composition in a temperature range of 130 to 220°C. Furthermore, the present invention provides a battery module comprising a plurality of alternately stacked battery cells and an inter-cell insulating material, wherein the inter-cell insulating material is the above-mentioned rubber foam. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a foamed rubber composition that can be used to produce an insulating material that has sufficient heat insulating properties and flame retardancy to prevent thermal chain reaction to adjacent battery cells and is flexible enough to follow the expansion and contraction of battery cells, a rubber foam made from the foamed rubber composition, a method for manufacturing a rubber foam, and a battery module. [Brief explanation of the drawings]

[0009] [Figure 1]FIG. 1 is a schematic diagram showing the configuration of a main part of a battery module according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will be described. Aspect 1 of this embodiment is a foamable rubber composition containing an unvulcanized rubber raw material, a foaming agent, and expandable graphite, wherein the foaming agent is at least one of expanded microballoons, unexpanded microballoons, and a chemical foaming agent.

[0011] Aspect 2 of the present embodiment is a foamable rubber composition according to Aspect 1, characterized in that the rubber raw material is ethylene butene diene rubber. Aspect 3 of the present embodiment is the foamable rubber composition of Aspect 1 or Aspect 2, characterized in that the content of the foaming agent is 5 to 35 parts by mass per 100 parts by mass of the rubber raw material.

[0012] Aspect 4 of the present embodiment is a foamable rubber composition according to any one of Aspects 1 to 3, characterized in that the foaming agent is the unexpanded microballoons and / or the chemical foaming agent.

[0013] Aspect 5 of the present embodiment is the foamable rubber composition according to any one of Aspects 1 to 4, characterized in that the chemical foaming agent is a sulfonyl hydrazide foaming agent.

[0014] Aspect 6 of the present embodiment is a rubber foam obtained by subjecting the foamable rubber composition of any one of Aspects 1 to 5 above to a vulcanization treatment and a foaming treatment. Aspect 7 of the present embodiment is the rubber foam of Aspect 6 above, characterized in that the expansion rate is 50% or more.

[0015] Aspect 8 of the present embodiment is a method for producing a rubber foam, characterized by including a vulcanization step of heating the foamable rubber composition of any one of Aspects 1 to 5 above in a temperature range of 130 to 220°C. A ninth aspect of the present embodiment is the method for producing a rubber foam according to the eighth aspect, wherein the rubber foam has a volume change rate of 100% or more.

[0016] Aspect 10 of this embodiment is a battery module comprising a plurality of alternately stacked battery cells and inter-cell insulation, wherein the inter-cell insulation is the rubber foam of Aspect 6 or Aspect 7 above.

[0017] The foamable rubber composition according to the present embodiment contains an unvulcanized rubber raw material, a foaming agent, and expandable graphite. The rubber foam obtained by subjecting the foamable rubber composition according to the present embodiment to a vulcanization treatment and a foaming treatment has excellent heat insulating properties, flame retardancy, and flexibility, and therefore can be suitably used, for example, as a material for producing an inter-cell insulating material provided between battery cells of a battery module.

[0018] The rubber raw material in this embodiment is not particularly limited, and may be, for example, ethylene butene diene rubber (EBDM), ethylene propylene diene rubber (EPDM), butyl rubber (NBR), hydrogenated butyl rubber (HNBR), chloroprene rubber (CR), silicone rubber, urethane rubber, fluororubber, etc., and one or more of these may be used. The rubber raw material in this embodiment is preferably ethylene butene diene rubber (EBDM). With some rubber raw materials, the properties of the foamable rubber composition may not be fully exhibited at relatively low temperatures. However, when the rubber raw material contained in the foamable rubber composition is EBDM, the properties of the foamable rubber composition can be fully exhibited even at relatively low temperatures. Therefore, it is expected that the foamable rubber composition will be suitably used, for example, as a material for producing an inter-cell insulating material for a battery module used in cold regions.

[0019] The foaming agent in the present embodiment foams and expands when exposed to an atmosphere at a predetermined temperature or higher, and can form a rubber foam obtained by subjecting the foamable rubber composition to a vulcanization treatment and a foaming treatment into a porous (sponge-like) rubber foam having closed cells and / or open cells.

[0020] The foaming agent used in this embodiment may be at least one of expanded microballoons, unexpanded microballoons, and a chemical foaming agent, and is preferably unexpanded microballoons and / or a chemical foaming agent.

[0021] Examples of pre-expanded microballoons that can be used include commercially available products such as Expancel 920DE40d30, Expancel 920DE80d30, and Expancel 909DU80 (all manufactured by Nippon Phillite Co., Ltd.); Matsumoto Microsphere MFL-81GTA, Matsumoto Microsphere MFL-81GCA, Matsumoto Microsphere MFL-SEVVEN, Matsumoto Microsphere MFL-HD30CA, Matsumoto Microsphere MFL-HD60CA, and Matsumoto Microsphere MFL-100MCA (all manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.).

[0022] Examples of commercially available unexpanded microballoons that can be used include Matsumoto Microsphere HF-50D, Matsumoto Microsphere FD-190, Matsumoto Microsphere F-AC160D, and Matsumoto Microsphere F-AC170D (all manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.), and Expancel 053-40, Expancel 031-40, Expancel 007-40, Expancel 920-40, Expancel 909-80, and Expancel 930-120 (all manufactured by Nippon Phillite Co., Ltd.). Among these, Matsumoto Microsphere F-AC160D is preferred because it can be foamed well and can improve the expansion rate or volume change rate of the rubber foam.

[0023] Examples of chemical blowing agents that can be used include sulfonylhydrazide-based blowing agents (OBSH-based blowing agents) such as benzenesulfonylhydrazide, 4,4'-oxybis(benzenesulfonylhydrazide), toluenesulfonylhydrazide, and diphenylsulfone-3,3'-disulfonylhydrazide; azo-based blowing agents (ADCA-based blowing agents) such as azodicarbonamide, azobisisobutyronitrile, azodiaminobenzene, and azocyclohexylnitrile; and nitroso-based blowing agents (DPT-based blowing agents) such as N,N'-dinitrosopentamethylenetetramine and N,N'-dimethyl-N,N'-dinitrosoterephthalamide.

[0024] Examples of OBSH-based blowing agents that can be used include commercially available products such as NeoCelvon N5000 (manufactured by Eiwa Chemical Industry Co., Ltd.). Examples of ADCA-based blowing agents that can be used include commercially available products such as Cellmic CE and Cellmic C-191 (both manufactured by Sankyo Chemical Industry Co., Ltd.). Examples of DPT-based blowing agents that can be used include commercially available products such as Cellular D (manufactured by Eiwa Chemical Industry Co., Ltd.). Of these, the OBSH-based blowing agent NeoCelvon N5000 (4,4'-oxybis(benzenesulfonylhydrazide), manufactured by Eiwa Chemical Industry Co., Ltd.) and / or the ADCA-based blowing agent Cellmic CE (azodicarbonamide, manufactured by Sankyo Chemical Industry Co., Ltd.) are preferred because they enable good foaming and can improve the expansion rate or volume change rate of rubber foam.

[0025] In addition, when the foamable rubber composition according to the present embodiment contains the chemical foaming agent, it may contain a foaming aid together with the chemical foaming agent. Examples of the foaming aid that can be used include salicylic acid, phthalic acid, stearic acid, oxalic acid, uric acid, and derivatives thereof.

[0026] The foaming temperature of the unexpanded microballoons as the foaming agent in this embodiment and the foaming temperature (decomposition temperature) of the chemical foaming agent may be within a range of ±20° C. of the vulcanization temperature of the rubber raw material. If the foaming temperature (decomposition temperature) is within a range of ±20° C. of the vulcanization temperature of the rubber raw material, the foamable rubber composition can be vulcanized in the vulcanization temperature range of the rubber raw material, and at the same time, a foaming treatment can be performed to foam the foaming agent.

[0027] In the foamable rubber composition according to this embodiment, the content of the foaming agent is preferably 5 to 35 parts by mass, and particularly preferably 10 to 20 parts by mass, per 100 parts by mass of the rubber raw material. If the content of the foaming agent is less than 5 parts by mass per 100 parts by mass of the rubber raw material, the expansion rate (volume change rate) due to foaming of the foaming agent will be low, and the rubber foam obtained by vulcanizing and foaming the foamable rubber composition may have insufficient heat insulation and flexibility. If the content exceeds 35 parts by mass, the expansion rate or volume change rate due to foaming of the foaming agent will be too high, and the rubber foam obtained by vulcanizing and foaming the foamable rubber composition may have difficulty maintaining its shape and may have insufficient flexibility.

[0028] The expandable graphite in this embodiment is a conventionally known substance that has the property of expanding when heated. The expandable graphite is a graphite intercalation compound produced from a mixture of graphite powder, an inorganic acid such as concentrated sulfuric acid, and a strong oxidizing agent such as concentrated nitric acid, and is a type of crystalline compound that maintains the layered structure of carbon.

[0029] The expandable graphite in this embodiment includes expandable graphite SYZR (501, 501H, 502, 502H, 503, 801, 802, 803, 1002, 2002N, etc.; Shijiazhuang ADT Carbonic Material Commercially available products such as thermally expandable graphite TEG (5099, 60, etc.; manufactured by Air Water Inc.), thermally expandable graphite GREP-EG (manufactured by Suzuhiro Chemical Co., Ltd.), expandable graphite (grades No. 8099, 8099-LTE, 8099-LTE-u and 194, etc.; manufactured by Chuo Kasei Co., Ltd.), expandable graphite EXP (35, 50, 80, etc.; manufactured by Fuji Graphite Industries Co., Ltd.), expandable graphite (9532400, 9950200, 9550250, 955025L, etc.; manufactured by Ito Graphite Industries Co., Ltd.), and expandable graphite (SMF, EMF, SFF, etc.; manufactured by Chuetsu Graphite Industries Co., Ltd.) may also be used.

[0030] The expansion volume of expandable graphite (sometimes referred to as "expansion coefficient" or "degree of expansion") is not particularly limited, but may be, for example, 100 to 350 mL / g. If the expansion volume of expandable graphite is within the above numerical range, sufficient expansion performance can be obtained. The expansion volume of expandable graphite can be determined as the volume per 1 g when heated at 1000°C for 10 seconds.

[0031] In the foamable rubber composition according to the present embodiment, the content of expandable graphite is not particularly limited, but is preferably 10 to 150 parts by mass per 100 parts by mass of the rubber raw material. If the content of expandable graphite is less than 10 parts by mass per 100 parts by mass of the rubber raw material, when a rubber foam obtained by vulcanizing and foaming the foamable rubber composition is used as an inter-cell insulating material 12 provided between adjacent battery cells 11 in a battery module 10, the rubber foam may not expand sufficiently when thermal runaway occurs in the battery module 10 (battery cells 11), and sufficient thermal insulation and flame retardancy may not be obtained. If the content of expandable graphite exceeds 150 parts by mass, the rubber foam may expand too much when thermal runaway occurs, making it difficult for the expanded rubber foam to maintain its shape, and the rubber foam may collapse.

[0032] The foamable rubber composition according to the present embodiment may contain other components as necessary. Examples of other components that may be contained in the foamable rubber composition according to the present embodiment include various additives, release agents, extenders, colorants, etc. The various additives may be, for example, vulcanizing agents, vulcanization accelerators, vulcanization aids, antioxidants, plasticizers, reinforcing materials (carbon, silica, talc, etc.), coupling agents, UV stabilizers, antioxidants, deodorizers, flame retardants, weather resistance agents, antistatic agents, slip agents, ion exchange agents, etc. One or more additives arbitrarily selected from these may be contained in the foamable rubber composition, or two or more additives of the same type (for example, two or more plasticizers) may be contained in the foamable rubber composition.

[0033] The foamable rubber composition according to the present embodiment can be prepared by kneading the above-mentioned components by a conventional method. For example, the foamable rubber composition can be prepared by mixing and kneading the above-mentioned components using a mixing / kneading means such as a kneader, a roll mixer, a Banbury mixer, a tumbler mixer, or a Brabender mixer. Furthermore, if necessary, the above-mentioned components may be pre-kneaded before mixing and kneading.

[0034] The foamable rubber composition according to the present embodiment may or may not contain an elastomer (e.g., a thermoplastic elastomer). Examples of the elastomer include a vinyl chloride thermoplastic elastomer, a styrene thermoplastic elastomer, a polyolefin thermoplastic elastomer, and a polyester thermoplastic elastomer.

[0035] The foamable rubber composition according to the present embodiment is useful as a material for producing a rubber foam by vulcanizing and foaming the foamable rubber composition, since the foamable rubber composition can simultaneously vulcanize the rubber raw material and foam the foaming agent.

[0036] The rubber foam of this embodiment is obtained by subjecting the foamable rubber composition to a vulcanization treatment and a foaming treatment, and has a porous (sponge-like) structure with closed and / or open cells. The rubber foam of this embodiment has rubber elasticity due to the rubber raw materials contained in the foamable rubber composition used to produce it. Therefore, when the rubber foam of this embodiment is used, for example, as an inter-cell insulating material 12 disposed between multiple battery cells 11 in a battery module 10, the rubber foam can exhibit flexibility capable of following the expansion and contraction of the battery cells 11 associated with charging and discharging the battery module 10. Even if a battery cell 11 expands due to abnormal heat generation (thermal runaway), the rubber foam can generate a reaction force sufficient to prevent the battery cell 11 from contacting the adjacent battery cell 11, thereby suppressing thermal chain reaction to the adjacent battery cell 11. Furthermore, the rubber foam of this embodiment is formed into a porous (sponge-like) structure with closed and / or open cells by the foaming of the foaming agent contained in the foamable rubber composition and / or the expansion of the expandable graphite, thereby achieving excellent thermal insulation.

[0037] The expansion rate of the rubber foam in this embodiment is not particularly limited, but is preferably 50% or more, and particularly preferably 60% or more. The volume change rate of the rubber foam in this embodiment is not particularly limited, but is preferably 100% or more. When the expansion rate of the rubber foam is 50% or more or the volume change rate of the rubber foam is 100% or more, the rubber foam can have excellent heat insulation properties and flexibility. In this embodiment, the expansion rate is a value calculated using the following formula from the thickness of the foamable rubber composition molded into a sheet and the thickness of the rubber foam obtained by vulcanizing and foaming the sheet-like foamable rubber composition. The volume change rate is a value calculated using the following formula from the volume of the foamable rubber composition molded into a sheet and the volume of the rubber foam obtained by vulcanizing and foaming the sheet-like foamable rubber composition.

[0038] Expansion rate (%)=(AB) / B (1) In the above formula (1), A represents the "thickness (mm) of the rubber foam" and B represents the "thickness (mm) of the sheet-like foamable rubber composition". Volume change rate (%) = (CD) / D (2) In the above formula (2), C is the volume of the rubber foam (mm 3 )" and D represents the volume (mm 3 )".

[0039] The rubber foam of this embodiment is prepared by molding the rubber composition to form a film having a thickness of approximately 0.5 to 2 mm, and then vulcanizing the film with a vulcanizing agent. The temperature conditions for vulcanization may be any temperature at which the rubber raw materials contained in the rubber composition can be vulcanized, for example, 130 to 220°C, and preferably 140 to 200°C. The rubber foam of this embodiment is produced by vulcanizing the rubber raw materials contained in the rubber composition and foaming the foaming agent at the same time. By setting the foaming temperature of the foaming agent within a range of ±20°C of the vulcanization temperature of the rubber raw materials, the rubber raw materials can be vulcanized at the vulcanization temperature (130 to 220°C), and the foaming agent can be foamed at the same time. In other words, the vulcanization process and the foaming process can be performed simultaneously.

[0040] The rubber foam of the present embodiment described above has excellent heat insulating properties, flame retardancy, and flexibility, and can therefore be used, for example, as an insulating material between cells of a battery module. As shown in Fig. 1, a battery module 10 in this embodiment includes a plurality of battery cells 11 and a plurality of inter-cell insulating materials 12, and is configured by alternately stacking the battery cells 11 and the inter-cell insulating materials 12. The battery module in this embodiment has a storage section (not shown) that stores the alternately stacked battery cells 11 and the inter-cell insulating materials 12. The inter-cell insulating materials 12 included in the battery module 10 in this embodiment are rubber foams obtained by vulcanizing and foaming the foamable rubber composition according to this embodiment.

[0041] According to the battery module 10 of this embodiment, the rubber foam used as the inter-cell insulation material 12 is porous (sponge-like) with closed cells and / or open cells, and has excellent thermal insulation and flame retardancy, so that even if thermal runaway occurs in a battery cell 11, it can prevent a thermal chain reaction from occurring in adjacent battery cells 11. Furthermore, the rubber foam used as the inter-cell insulation material 12 has a reaction force against abnormal expansion due to thermal runaway in the battery cell 11, so it can effectively prevent a thermal chain reaction from occurring in adjacent battery cells 11. Furthermore, the rubber foam has excellent flexibility, so it can follow the expansion and contraction of the battery cells 11 when the battery module 10 is charged and discharged.

[0042] The above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention. [Example]

[0043] The present invention will be explained in more detail below by way of test examples, but the present invention is not limited to the following test examples.

[0044] [Test Example 1] Ethylene butene diene rubber (EBDM), expandable graphite (SYZR502H, manufactured by Shijiazhuang ADT Carbonic Material Factory), and foaming agents (Neocelbon N5000 (manufactured by Eiwa Chemical Industry Co., Ltd.), Cellmic CE (manufactured by Sankyo Kasei Co., Ltd.), Cellmic C-191 (manufactured by Sankyo Kasei Co., Ltd.), Matsumoto Microsphere FD-190 (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.), Matsumoto Microsphere F-AC160D (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.), or Matsumoto Microsphere F-AC170D (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.)), as well as various additives (vulcanization aids / processing aids (stearic acid 50S, manufactured by New Japan Chemical Co., Ltd.; Plastrodin J, manufactured by Fuso Chemical Co., Ltd.); zinc oxide (Nihon Foamable rubber compositions (Samples 1 to 6) were prepared containing: (Mitsui Mining & Smelting Co., Ltd.), reinforcing materials (Seast G-116, Tokai Carbon Co., Ltd.; Nipsil ER, Toso Silica Corporation), coupling agent (Silane Z-6062, Dow Toray Industries, Inc.), flame retardant (aluminum hydroxide B103, Nippon Light Metal Co., Ltd.), plasticizer (Process R-1000, ENEOS Corporation), vulcanizing agent (precipitated sulfur, Hosoi Chemical Industry Co., Ltd.), and vulcanization accelerators (Nocceler TT-P, Nocceler TRA (powder), Nocceler MP, Nocceler BZ-P, all manufactured by Ouchi Shinko Chemical Industry Co., Ltd.). The formulations of the foamable rubber compositions (each amount is expressed in parts by mass) are shown in Table 1. In addition, the "EBDM" in Test Example 1 is oil-extended (oil-extended EBDM), and the "EBDM blending amount" in Table 1 represents the parts by mass of oil-extended EBDM, with the amount of oil-extended EBDM being 30 parts by mass (30 phr) per 100 parts by mass of EBDM.

[0045] [Table 1]

[0046] Each foamable rubber composition was molded into a sheet having a thickness of 2 mm, and the sheet was placed in a thermostatic chamber at a predetermined temperature (see Tables 2 and 3) for a predetermined time (see Tables 2 and 3) to be subjected to a vulcanization treatment and a foaming treatment, thereby producing a rubber foam.

[0047] The thicknesses of the rubber foams of Samples 1 to 3 and the volumes of the rubber foams of Samples 4 to 6 obtained as described above were measured, and the expansion coefficients (%) of the rubber foams of Samples 1 to 3 and the volume change rates (%) of the rubber foams of Samples 4 to 6 were determined. The results are shown in Tables 2 and 3.

[0048] [Table 2]

[0049] [Table 3]

[0050] [Test Example 2] Ethylene butene diene rubber (EBDM), expandable graphite (SYZR502H, Shijiazhuang ADT Carbonic Material A foam rubber composition (Sample 1) containing a foaming agent (Matsumoto Microsphere F-AC160D (Matsumoto Yushi Pharmaceutical Co., Ltd.)) and various additives (vulcanization aids / processing aids (50S stearic acid, New Japan Chemical; Plastrodin J, Fuso Chemical Co., Ltd.; zinc oxide (type 2), Mitsui Mining & Smelting Co., Ltd.), reinforcing materials (Seast G-116, Tokai Carbon Co., Ltd.; Nipsil ER, Toso Silica Corporation), coupling agents (Silane Z-6062, Dow Toray Industries, Inc.), flame retardants (aluminum hydroxide B103, Nippon Light Metal Co., Ltd.), plasticizers (Process R-1000, ENEOS Corporation), vulcanizing agents (precipitated sulfur, Hosoi Chemical Co., Ltd.), and vulcanization accelerators (Noccela TT-P, Ouchi Shinko Chemical Industry Co., Ltd.; Valnoc R-10, Ouchi Shinko Chemical Industry Co., Ltd.) was used. 7 to 10) were prepared. The formulations of the foamable rubber compositions (each formulation amount is expressed in parts by mass) are shown in Table 4. Note that "EBDM" in Test Example 2 is oil-extended (oil-extended EBDM), and the "EBDM formulation amount" in Table 4 represents parts by mass of oil-extended EBDM, with the amount of oil-extended EBDM being 30 parts by mass (30 phr) per 100 parts by mass of EBDM.

[0051] [Table 4]

[0052] Each foamable rubber composition was molded into a 2 mm thick sheet, and the sheet was placed in a thermostatic chamber at a predetermined temperature (see Table 5) for a predetermined time (see Table 5) to undergo vulcanization and foaming treatment, producing a rubber foam. The volume of the rubber foam obtained as described above was measured, and the volume change rate (%) of the rubber foams of Samples 7 to 10 was determined. The results are shown in Table 5.

[0053] [Table 5]

[0054] [Test Example 3] Ethylene butene diene rubber (EBDM), expandable graphite (SYZR502H, Shijiazhuang ADT Carbonic Material Foamable rubber compositions (Samples 11 to 16) were prepared containing the foaming agent (CellMike CE, Sankyo Kasei Co., Ltd.), foaming aid (Cellpaste K5, Eiwa Kasei Kogyo Co., Ltd.), reinforcing material (Seat G-116, Tokai Carbon Co., Ltd.; Nipsil ER, Toso Silica Corporation), coupling agent (Silane Z-6062, Dow Toray Co., Ltd.), flame retardant (aluminum hydroxide B103, Nippon Light Metal Co., Ltd.), plasticizer 1 (Process R-1000, ENEOS Corporation), plasticizer 2 (DOA, J-Plus Co., Ltd.), vulcanizing agent (precipitated sulfur, Hosoi Chemical Industry Co., Ltd.), and vulcanization accelerators (Noccela TT-P, Noccela TRA (powder), Noccela MP, Noccela BZ-P, all manufactured by Ouchi Shinko Chemical Industry Co., Ltd.). The formulation of the foamable rubber composition (each formulation amount is expressed in parts by mass) is shown in Table 6. Note that "EBDM" in Test Example 3 is oil-extended (oil-extended EBDM), and the "EBDM formulation amount" in Table 6 represents parts by mass of oil-extended EBDM, with the amount of oil-extended EBDM being 30 parts by mass (30 phr) per 100 parts by mass of EBDM.

[0055] [Table 6]

[0056] Each foamable rubber composition was molded into a 2 mm thick sheet (50 mm × 25 mm), and the sheet was placed in a thermostatic chamber at a predetermined temperature (see Table 7) for a predetermined time (see Table 7) to undergo vulcanization and foaming treatment, producing a rubber foam. The volume of the rubber foam obtained as described above was measured, and the volume change rate (%) of the rubber foams of Samples 11 to 16 was determined. The results are shown in Table 7.

[0057] [Table 7]

[0058] [Test Example 4] A foam rubber composition (Sample 1) containing ethylene butene diene rubber (EBDM), expandable graphite (SYZR502H, manufactured by Shijiazhuang ADT Carbonic Material Factory), a foaming agent (Matsumoto Microsphere F-AC160D, manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.), and various additives (reinforcing material (Seast G-116, manufactured by Tokai Carbon Co., Ltd.; Nipsil ER, manufactured by Toso Silica Corporation), coupling agent (Silane Z-6062, manufactured by Dow Toray Industries, Inc.), flame retardant (aluminum hydroxide B103, manufactured by Nippon Light Metal Co., Ltd.), plasticizer 1 (Process R-1000, manufactured by ENEOS Corporation), plasticizer 2 (DOA, manufactured by J-Plus Corporation), vulcanizing agent (precipitated sulfur, manufactured by Hosoi Chemical Industry Co., Ltd.), and vulcanization accelerator (Noccela TT-P, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.); Valnoc R-10, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) was used. 17 to 24) were prepared. The formulations of the foamable rubber compositions (each formulation amount is expressed in parts by mass) are shown in Table 8. Note that "EBDM" in Test Example 4 is oil-extended (oil-extended EBDM), and the "EBDM formulation amount" in Table 8 represents parts by mass of oil-extended EBDM, with the amount of oil-extended EBDM being 30 parts by mass (30 phr) per 100 parts by mass of EBDM.

[0059] [Table 8]

[0060] Each foamable rubber composition was molded into a 2 mm thick sheet (50 mm × 25 mm), and the sheet was placed in a thermostatic chamber at a predetermined temperature (see Table 9) for a predetermined time (see Table 9) to undergo vulcanization and foaming treatment, thereby producing a rubber foam. The volume of the rubber foam obtained as described above was measured, and the volume change rate (%) of the rubber foams of Samples 17 to 24 was determined. The results are shown in Table 9.

[0061] [Table 9]

[0062] From the results of the above Test Examples 1 and 2, it was confirmed that good foaming was possible by vulcanizing and foaming foamable rubber compositions containing a chemical foaming agent or unexpanded microballoons, as in Samples 1 to 6 and Samples 8 to 10.

[0063] The results of Test Example 3 above confirmed that good foaming was possible in Samples 14 to 16, which had twice the compounding ratio (compounding ratio to EBDM) of the foaming agent (chemical foaming agent) compared to Samples 11 to 13. Furthermore, the results of Test Example 4 above also showed a similar tendency to Test Example 3 when unexpanded microballoons were used as the foaming agent.

[0064] Furthermore, when the cross sections of the rubber foams made from the foamable rubber compositions of Samples 1 to 6 and 8 to 24 were examined under a microscope, it was confirmed that they had good cell counts (closed cells and / or open cells). This clearly shows that the rubber foams have excellent heat insulating properties and flexibility, and it is presumed that if they are used as inter-cell insulating materials in a battery module, they will be able to follow the expansion and contraction of battery cells that accompany charging and discharging, and will be able to effectively prevent thermal chain reaction during thermal runaway. [Explanation of symbols]

[0065] 10...Battery module 11...Battery cell 12...Inter-cell insulation

Claims

1. The rubber composition contains an unvulcanized rubber material, a foaming agent, and expandable graphite, The foamable rubber composition is characterized in that the foaming agent is at least one of expanded microballoons, unexpanded microballoons, and a chemical foaming agent.

2. 2. The foamable rubber composition according to claim 1, wherein the rubber raw material is ethylene butene diene rubber.

3. 3. The foamable rubber composition according to claim 1, wherein the content of the foaming agent is 5 to 35 parts by mass per 100 parts by mass of the rubber raw material.

4. 3. The foamable rubber composition according to claim 1, wherein the foaming agent is the unexpanded microballoons and / or the chemical foaming agent.

5. 3. The foamable rubber composition according to claim 1, wherein the chemical foaming agent is a sulfonylhydrazide foaming agent.

6. A rubber foam obtained by subjecting the foamable rubber composition according to claim 1 or 2 to a vulcanization treatment and a foaming treatment.

7. 7. The rubber foam according to claim 6, wherein the expansion rate is 50% or more.

8. A method for producing a rubber foam, comprising a vulcanization step of heating the foamable rubber composition according to claim 1 or 2 at a temperature in the range of 130 to 220°C.

9. The method for producing a rubber foam according to claim 8, wherein the rubber foam has a volume change rate of 100% or more.

10. The battery pack includes a plurality of alternately stacked battery cells and an inter-cell insulating material, 7. A battery module, wherein the inter-cell heat insulating material is the rubber foam according to claim 6.

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