Fire-extinguishing agent for electric vehicle and fire-extinguishing structure of electric vehicle

Abstract

In a fire-extinguishing structure of an electric vehicle according to the present invention, for example, in the case where a secondary battery structure installed in an electric vehicle is a rectangular box type, a water-added fire-extinguishing agent can be injected into the interior of the secondary battery structure from four corners thereof by means of fire extinguishers, fire-fighting water discharge, or the like. The water-added fire-extinguishing agent contains, as components of the fire-extinguishing agent, a heat-depolymerizable polymer having a structure to which a soluble functional group is imparted, an alkali metal salt thereof, or an alkaline earth metal salt thereof. In particular, the water-added fire-extinguishing agent contains poly(methacrylic acid), an alkali metal salt thereof, or an alkaline earth metal salt thereof. With such a fire-extinguishing structure of an electric vehicle, even in various situations in which the electric vehicle is left on a road or the like, the fire-extinguishing agent having a high fire-extinguishing effect from the outside can be supplied, and the whole battery can be immersed.

Description

Fire extinguishing agents and fire extinguishing structures for electric vehicles 【0001】 This invention relates to a fire extinguishing agent for electric vehicles and a fire extinguishing structure for electric vehicles, which can extinguish fires originating from the battery of an electric vehicle. 【0002】 Most electric vehicles are equipped with multiple secondary batteries, such as lithium-ion batteries, and electric motors that drive the drive wheels using the energy from these secondary batteries, and run on the secondary batteries as their power source. In such electric vehicles, the secondary batteries are housed in a sealed metal battery case (casing) with high rigidity and strength to ensure safety, such as protection from impact to the secondary batteries and protection from electric shock to the human body. In addition, battery cooling devices are used within the sealed battery case to suppress the heat generated by the secondary batteries. In particular, to ensure high cooling performance, battery cooling devices tend to use a liquid cooling system, such as a water cooling system, which circulates coolant between a heat absorption section located inside the battery case and a heat dissipation section located outside the battery. 【0003】 For fires originating from secondary batteries, directly spraying a fire extinguishing liquid (fire extinguishing agent) such as water onto the secondary battery is effective. However, because secondary batteries are housed in battery cases that protect them from electric shock, it is difficult to spray water directly onto them from fire trucks or other means. Therefore, as a technology for extinguishing fires in secondary batteries, Patent Document 1 proposes a fire extinguishing structure in which a portion of the coolant circulation path in a water-cooled battery cooling system for secondary batteries is formed from a material with a low melting point. When ignition that causes a fire occurs, the coolant circulation path portion melts and breaks, and the cooling water (coolant) used to cool the secondary battery is injected into the battery pack from this broken point. 【0004】Furthermore, Patent Document 2 proposes a fire extinguishing structure in which a fire extinguishing agent supply device is provided in a rapid charging device, and when the electric vehicle and the rapid charging device are connected for charging, the fire extinguishing agent supply device is connected to a passage that cools the electric vehicle's secondary battery, so that if the secondary battery catches fire during charging, the fire extinguishing agent (coolant) is supplied to the secondary battery from the fire extinguishing agent supply device installed in the rapid charging device through the connected passage. 【0005】 Japanese Patent Publication No. 2009-54297 Japanese Patent Publication No. 2011-65805 【0006】 Incidentally, in order to extinguish or suppress fires in the secondary batteries of electric vehicles, such as in collision accidents, various factors must be considered. This requires that the fire extinguishing agent can be supplied to the secondary battery even if the electric vehicle is left on the road, and that, in order to stabilize the battery, the entire secondary battery be immersed in the fire extinguishing agent, that is, that the entire inside of the battery pack be filled with the fire extinguishing agent. 【0007】 However, in the fire extinguishing structure described in Patent Document 1, in order to extinguish a fire in a secondary battery (including suppressing ignition), it is necessary to use a predetermined amount of coolant in a tank to cool the secondary battery beforehand, but there is a limit to the amount of coolant that can be stored. For this reason, it is difficult to immerse the entire secondary battery in the battery case, and there is a problem that sufficient fire extinguishing may not be achieved. Furthermore, in the fire extinguishing structure described in Patent Document 2, in which a fire extinguishing agent supply device attached to a rapid charging station is connected to an electric vehicle, the fire extinguishing function only works when the electric vehicle is stopped or parked at the rapid charging station. For this reason, there is a problem that it cannot cope with various situations, especially when the electric vehicle is left on the road due to an accident or the like. 【0008】 The present invention has been made in view of the above problems, and aims to provide a fire extinguishing structure for electric vehicles that can supply a highly effective fire extinguishing agent from the outside even in various situations such as when electric vehicles are left on the road, and that allows the entire battery to be immersed, as well as a fire extinguishing agent for electric vehicles that can be suitably applied to this fire extinguishing structure. 【0009】In view of the above objectives, the present invention first provides a fire extinguishing agent for electric vehicles equipped with a secondary battery, which comprises a water-added fire extinguishing agent containing, as a component of the fire extinguishing agent, a thermodepolymer having a structure to which water-soluble functional groups are attached, an alkali metal salt thereof, or an alkaline earth metal salt thereof (Invention 1). 【0010】 In the above invention (Invention 1), it is preferable that the pyropolymer with the water-soluble functional group attached has the structure represented by the following chemical formula. (In the formula, X is hydrogen (H) or an alkyl group having 1 to 3 carbon atoms, and Y is COOH or SO ３ H, OCOOH, OSO ３ H, COO (CH ２ ) ｍ COOH, COO(CH ２ ) ｍ SO ３ H, benzene ring-COOH or benzene ring-SO ３ H is a positive integer between 5 and 27,000, and m is a positive integer between 1 and 5. 【0011】 In the above invention (Invention 1), it is preferable that the alkali metal salt is a K salt or a Na salt (Invention 3). 【0012】 In the above invention (Invention 1), it is preferable that the alkaline earth metal salt is a Ca salt or a Mg salt (Invention 4). 【0013】 In the above invention (Invention 1), it is preferable that the content of the pyropolymer having the water-soluble functional group in the water-added fire extinguishing agent, its alkali metal salt, or its alkaline earth metal salt is 0.1 to 20% by weight (Invention 5). 【0014】 In the above invention (Invention 1), it is preferable that the weight-average molecular weight (MW) of the pyropolymer having the water-soluble functional group in the water-added fire extinguishing agent, its alkali metal salt, or its alkaline earth metal salt is 1,000,000 or less (Invention 6). 【0015】In the above invention (Invention 6), the water-added fire extinguishing agent may contain two or more types of thermopolymerizable polymers having a structure to which water-soluble functional groups are attached, alkali metal salts thereof, or alkaline earth metal salts thereof (Invention 7). 【0016】 In the above inventions (Inventions 1 to 7), it is preferable that the pyropolymer with the structure to which the water-soluble functional group is attached is poly(methacrylic acid) (Invention 8). 【0017】 According to these inventions (inventions 1 to 8), fires can be efficiently extinguished with a smaller volume of water than when water is used alone, so when used in an electric vehicle, the space required for the fire extinguishing agent can be designed to be more compact. 【0018】 Secondly, the present invention provides a fire extinguishing structure for an electric vehicle comprising a secondary battery structure consisting of a secondary battery and a casing that encloses the secondary battery with a gap between them, wherein a fire extinguishing agent can be injected into the secondary battery within the secondary battery structure from the outside, and the fire extinguishing agent is a water-added fire extinguishing agent containing a thermally depolymerizable polymer having a structure to which water-soluble functional groups are provided, an alkali metal salt thereof, or an alkaline earth metal salt thereof (Invention 9). 【0019】 According to this invention (Invention 9), a fire can be efficiently extinguished with a smaller volume of water than when water is used alone, so when used in an electric vehicle, the space required for the fire extinguishing agent can be made more compact. 【0020】 In the above invention (Invention 9), a molded body containing a pyrolytically polymerizable polymer is placed in the gap between the secondary battery and the casing, and it is preferable that the pyrolytically polymerizable polymer is a polymer (homopolymer or copolymer of two or more components) using one or more of methyl methacrylate (MMA) and α-methylstyrene (AMS) as monomer components (Invention 10). 【0021】According to this invention (Invention 10), by placing a thermopolymerizable polymer in the gap between the secondary battery and the casing, it is possible to prevent flames from being released outside the vehicle, allowing the driver or firefighter to approach the electric vehicle and expedite firefighting operations. 【0022】 In the above invention (Invention 9), it is preferable that the secondary battery structure has an inlet into the casing from which a fire extinguishing agent can be injected from the outside (Invention 11). 【0023】 According to this invention (Invention 11), by enabling the injection of fire extinguishing agent from all four sides of the secondary battery, the fire extinguishing agent can be injected using a fire extinguisher or the like from the opposite side of where the flames or smoke are coming from. 【0024】 In the above invention (Invention 9), the electric vehicle is equipped with a fire extinguisher for extinguishing a fire in the secondary battery, and it is preferable that the fire extinguishing agent of this fire extinguisher is the water-added fire extinguishing agent (Invention 12). 【0025】 According to this invention (Invention 12), by using a water-added fire extinguishing agent containing a thermopolymerizable polymer with a structure to which water-soluble functional groups are attached, an alkali metal salt thereof, or an alkaline earth metal salt thereof as the fire extinguishing agent for the fire extinguisher to be installed, the size of the fire extinguisher can be made more compact. 【0026】 In the above inventions (inventions 9 to 12), it is preferable that a cooling system for cooling the secondary battery is installed around the secondary battery structure, the cooling system is water-cooled, the water-additive type fire extinguishing agent is added to the cooling water of the cooling system, and the cooling water can be injected into the secondary battery structure if the secondary battery rapidly increases in temperature or if the secondary battery catches fire (invention 13). 【0027】 According to this invention (invention 13), the cooling water of the cooling system can be used directly as a fire extinguishing agent, and the space required for providing the fire extinguishing agent can be made more compact or reduced. 【0028】The fire extinguishing structure of the electric vehicle of the present invention is a fire extinguishing structure of an electric vehicle including a secondary battery structure composed of a secondary battery and a casing that has a gap with respect to the secondary battery and wraps it externally. The fire extinguishing agent can be injected into the secondary battery in the secondary battery structure from the outside. The fire extinguishing agent is a water-added type fire extinguishing agent containing a thermally depolymerizable polymer having a structure to which a water-soluble functional group is imparted, an alkali metal salt thereof, or an alkaline earth metal salt thereof, particularly a water-added type fire extinguishing agent containing poly(methacrylic acid), an alkali metal salt thereof, or an alkaline earth metal salt thereof. Therefore, a fire can be efficiently extinguished with a smaller amount of water discharged than when water is used alone. When used in an electric vehicle, the space for the fire extinguishing agent can be made compact. 【0029】 The present invention will be described in detail based on the following embodiments. 【0030】 [Electric vehicle] In the present embodiment, the electric vehicle to be extinguished is not limited as long as it is a vehicle that operates using electricity, and includes EV vehicles, hybrid vehicles, etc. The operating power source is not limited as long as a secondary battery is used, and includes lithium-ion batteries, all-solid-state lithium-ion batteries, next-generation secondary batteries, etc. 【0031】 [Water-added type fire extinguishing agent] The water-added type fire extinguishing agent of the present embodiment contains, as a component of the fire extinguishing agent, a thermally depolymerizable polymer having a structure to which a water-soluble functional group is imparted, an alkali metal salt thereof, or an alkaline earth metal salt thereof (hereinafter, these may be referred to as polymer components). 【0032】 (Polymer component) The thermally depolymerizable polymer having a structure to which the water-soluble functional group is imparted preferably has a structure represented by the following chemical formula. 【0033】 【0034】 (In the formula, X is hydrogen (H) or an alkyl group having 1 to 3 carbon atoms, and Y is COOH, SO ３ H, OCOOH, OSO ３ H, COO(CH ２ )mCOOH, COO(CH ２ )mSO ３H, benzene ring-COOH or benzene ring-SO ３ is H, n is a positive integer from 5 to 27,000, and m is a positive integer from 1 to 5.) 【0035】 As such a thermally depolymerizable polymer having a water-soluble functional group, poly(methacrylic acid) can be preferably used. 【0036】 Further, as the alkali metal salt of the thermally depolymerizable polymer having a water-soluble functional group, sodium (Na) salt, potassium (K) salt, etc. can be used. Further, as the alkaline earth metal salt, calcium (Ca) salt, magnesium (Mg) salt, etc. can be used. 【0037】 These polymer components preferably have a weight average molecular weight (MW) of 1,000,000 or less, particularly 100,000 or less. Those with a weight average molecular weight (MW) exceeding 1,000,000 not only have reduced solubility in water but also a decrease in the production efficiency of the polymer. Regarding the lower limit of the weight average molecular weight (MW), there is no particular limitation as long as it is in the form of a polymer, but it may be 500 or more, particularly 1,000 or more. 【0038】 The water-added fire extinguishing agent of this embodiment is a water-added type, that is, an aqueous solution, of the polymer component as described above. The content of the polymer component in this aqueous solution is preferably 0.1 to 20% by weight, particularly 0.1 to 10% by weight, and further 0.1 to 5% by weight. If the content of the polymer component is less than 0.1% by weight, sufficient fire extinguishing performance cannot be obtained, and a large amount (volume) of the aqueous solution of the fire extinguishing agent to be sprayed is required. On the other hand, if it exceeds 20% by weight, not only no further improvement effect of the fire extinguishing performance can be obtained, but also the viscosity of the aqueous solution of the fire extinguishing agent increases and the handleability decreases, which is not preferable. 【0039】Such a water-added fire extinguishing agent of the present exemplary embodiment may use a thermally depolymerizable polymer having a structure with a water-soluble functional group such as poly(methacrylic acid), its alkali metal salt, or its alkaline earth metal salt alone, or two or more of them may be used in combination. When two or more of them are used in combination, two or more aqueous solutions in which each is dissolved may be mixed, or two or more of a thermally depolymerizable polymer having a structure with a water-soluble functional group, its alkali metal salt, or its alkaline earth metal salt may be dissolved in the same water solvent. 【0040】 [Outer fire prevention material / Ignition prevention material] The outer fire prevention material / ignition prevention material is not limited as long as it is a material for preventing flames from coming out of the secondary battery. As an effective material, in a secondary battery structure including a secondary battery and a casing that has a gap and wraps around the secondary battery, it is preferable to dispose a molded body containing a thermally depolymerizable polymer in the gap between the secondary battery and the casing. As this thermally depolymerizable polymer, a polymer (homopolymer or copolymer of two or more components) using one or more of methyl methacrylate (MMA) and α-methylstyrene (AMS) as monomer components can be preferably used. 【0041】 The above copolymer may further contain various generally used additives as long as the outer fire prevention and ignition prevention effects are not impaired. Examples of the additives include crosslinked rubber particles, ultraviolet absorbers, lubricants, antioxidants, mold release agents, antistatic agents, flame retardants, etc. Also, on the surface of the acrylic polymer, a material coated for enhancing functionality may be used as long as the effects of the present invention are not impaired. 【0042】 The thermally depolymerizable polymers as described above can be used in various forms such as film, sheet, bead, pellet, and foam. 【0043】[Fire extinguishing structure for electric vehicles] In this embodiment, the fire extinguishing structure for electric vehicles is designed to allow the aforementioned water-additive type fire extinguishing agent to be injected into the secondary battery structure installed in the electric vehicle. For example, in the case of a rectangular box-shaped secondary battery structure, the water-additive type fire extinguishing agent can be injected into its interior from its four corners using a fire extinguisher, fire hose, etc. By allowing the fire extinguishing agent to be injected from all four sides of the secondary battery structure in this way, the fire extinguishing agent can be injected using a fire extinguisher or the like from the side opposite to where the flames or smoke are coming from. 【0044】 Furthermore, a cooling system for cooling the secondary battery structure may be provided. This cooling system is water-cooled and installed around the secondary battery structure. The cooling water contains a water-additive fire extinguishing agent consisting of a thermopolymerizable polymer with a water-soluble functional group, an alkali metal salt thereof, or an alkaline earth metal salt thereof. The structure may also include a system that injects this cooling water into the secondary battery structure if an abnormality occurs in the secondary battery, causing a rapid temperature rise or a fire to break out. For example, the container holding the cooling water could be designed to collapse by melting or other means when it reaches a predetermined temperature, so that the cooling water is released when the temperature of the secondary battery rises rapidly or the secondary battery catches fire. 【0045】 The present invention will be described in more detail based on the following specific examples, but the present invention is not limited to the following examples. 【0046】 [Performance Verification Test of Water-Added Fire Extinguishing Agent] (Example 1, Comparative Example 1) A lithium-ion battery, simulating a secondary battery structure for electric vehicles, was ignited through an overcharge test, and a fire extinguishing test was conducted while the flames were present. As a result of overcharging the lithium-ion battery, a violent explosion and ignition occurred approximately 19 minutes later, and the flames continued. 【0047】For this ongoing flame, a water-additive fire extinguishing agent (Example 1) was used, prepared by dissolving 4% by weight of potassium poly(methacrylate) salt as the solid content in an aqueous solution, which is an alkali metal salt of a thermally depolymerizable polymer with a water-soluble functional group structure. The number of spray gun injections until extinguishing the fire was measured, the required amount of extinguishing agent was calculated, and the presence or absence of re-flaming was checked. The results, along with the polymer component content of the extinguishing agent and the weight-average molecular weight of the polymer component used, are shown in Table 1. For comparison, a similar fire extinguishing test was conducted using water (Comparative Example 1), and the number of spray gun injections until extinguishing the fire, the required amount of extinguishing agent was calculated, and the presence or absence of re-flaming was checked. The results are also shown in Table 1. 【0048】 【0049】 As is clear from Table 1, the water-added fire extinguishing agent in Example 1 required less than 1 / 10 the amount of water needed to extinguish the fire compared to Comparative Example 1, which used water. It was also confirmed that there was no re-flaming and that it exhibited superior fire extinguishing capabilities. 【0050】 [Performance verification test of external fire prevention material and fire prevention material] (Comparative example 2) A PP resin container (internal dimensions: 80 mm wide x 105 mm long x 34 mm deep, resin thickness 2 mm, with the electrode side of an aluminum laminate lithium-ion battery placed on the 80 mm wide side of this PP resin container, and an open top with five 10 mm diameter holes on the 80 mm wide side of the PP resin container) was prepared. A 1500 mAh aluminum laminate lithium-ion battery (35 mm wide, 75 mm long) with a positive electrode ternary system was placed inside this PP resin container in a fully charged state, and a PP resin plate with a resin thickness of 4 mm was placed over it, and the periphery of the lid was sealed with heat-resistant tape to prevent gaps, so that ejected material from the lithium-ion battery due to overcharging would be released only through the five holes, thus creating a simulated secondary battery structure for electric vehicles. 【0051】 When a nail-piercing test was conducted on this secondary battery structure for electric vehicles, the lithium-ion battery was destroyed, and a violent fire was observed on the outside of the secondary battery structure. 【0052】(Example 2) A simulated secondary battery structure for electric vehicles was prepared by filling the gap between the PP resin container and the energy storage device container of the secondary battery structure for electric vehicles used in Comparative Example 1 with 40 g of pelletized molded material (particle size 2 mm to 5 mm) of an acrylic polymer (polymer mainly composed of polymethyl methacrylate, 94% or more, additives 5% or less) contained in a flexible synthetic resin bag with a mesh diameter of 1 mm. 【0053】 When this secondary battery structure for electric vehicles was subjected to a nail-piercing test under the same conditions as in Comparative Example 1, the lithium-ion battery was destroyed, but no ignition was observed on the outside of the secondary battery structure. 【0054】 This confirmed that polymers using one or more monomer components of methyl methacrylate (MMA) and α-methylstyrene (AMS) exhibit excellent fire prevention and ignition prevention effects.

Claims

1. A fire extinguishing agent for electric vehicles equipped with a secondary battery, comprising a water-additive type fire extinguishing agent containing, as a component of a thermally depolymerizable polymer having a structure to which water-soluble functional groups have been added, an alkali metal salt thereof, or an alkaline earth metal salt thereof.

2. The fire extinguishing agent for electric vehicles according to claim 1, wherein the thermally depolymerizable polymer having the water-soluble functional group has the structure shown by the following chemical formula. (In the formula, X is hydrogen (H) or an alkyl group having 1 to 3 carbon atoms, and Y is COOH or SO ３ H, OCOOH, OSO ３ H, COO (CH ２ ) ｍ COOH, COO(CH ２ ) ｍ SO ３ H, benzene ring-COOH or benzene ring-SO ３ H is a positive integer between 5 and 27,000, and m is a positive integer between 1 and 5.

3. The fire extinguishing agent for electric vehicles according to claim 1, wherein the alkali metal salt is a K salt or a Na salt.

4. The fire extinguishing agent for electric vehicles according to claim 1, wherein the alkaline earth metal salt is a Ca salt or a Mg salt.

5. The fire extinguishing agent for electric vehicles according to claim 1, wherein the content of the thermally depolymerizable polymer having the water-soluble functional group, its alkali metal salt, or its alkaline earth metal salt in the water-added fire extinguishing agent is 0.1 to 20% by weight.

6. The fire extinguishing agent for electric vehicles according to claim 1, wherein the weight-average molecular weight (MW) of the thermally depolymerizable polymer having the water-soluble functional group in the water-added fire extinguishing agent, the alkali metal salt thereof, or the alkaline earth metal salt thereof is 1,000,000 or less.

7. The fire extinguishing agent for electric vehicles according to claim 1, wherein the water-additive type fire extinguishing agent contains two or more types of thermodepolymers having a structure to which water-soluble functional groups are attached, alkali metal salts thereof, or alkaline earth metal salts thereof.

8. The fire extinguishing agent for an electric vehicle according to claim 1 of any one of claims 1 to 7, wherein the thermally depolymerizable polymer having the water-soluble functional group is poly(methacrylic acid).

9. A fire extinguishing structure for an electric vehicle, comprising a secondary battery structure consisting of a secondary battery and a casing that encloses the secondary battery with an air gap, wherein a fire extinguishing agent can be injected into the secondary battery within the secondary battery structure from the outside, and the fire extinguishing agent is a water-additive type fire extinguishing agent containing a thermally depolymerizable polymer having a structure to which water-soluble functional groups are attached, an alkali metal salt thereof, or an alkaline earth metal salt thereof.

10. The fire extinguishing structure for an electric vehicle according to claim 9, wherein a molded body containing a pyrolytically depolymerizable polymer is placed in the gap between the secondary battery and the casing, and the pyrolytically depolymerizable polymer is a polymer (homopolymer or copolymer of two or more components) using one or more of methyl methacrylate (MMA) and α-methylstyrene (AMS) as monomer components.

11. The fire extinguishing structure for an electric vehicle according to claim 9, wherein the secondary battery structure has an inlet into the casing from which a fire extinguishing agent can be injected from the outside.

12. The electric vehicle is equipped with a fire extinguisher for extinguishing a fire in the secondary battery, and the extinguishing agent of the fire extinguisher is the water-added type extinguishing agent, as described in claim 9.

13. A fire extinguishing structure for an electric vehicle according to any one of claims 9 to 12, wherein a cooling system for cooling the secondary battery is installed around the secondary battery structure, the cooling system is water-cooled, the water-additive type fire extinguishing agent is added to the cooling water of the cooling system, and the cooling water can be injected into the secondary battery structure if the secondary battery rapidly overheats or catches fire.

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