Fire extinguishing agents and fire extinguishing structures for electric vehicles

Abstract

This invention provides a fire extinguishing structure for electric vehicles that allows for the supply of a highly effective fire extinguishing agent from an external source, even in various situations where electric vehicles are left on roads or other public places, and also allows for the entire battery to be immersed. [Solution] The fire extinguishing structure for electric vehicles allows for the injection of a water-additive fire extinguishing agent into the secondary battery structure installed in the electric vehicle. For example, in the case of a rectangular box-shaped secondary battery structure, a water-additive fire extinguishing agent can be injected into the secondary battery structure from the four corners using a fire extinguisher, fire hose, etc. The water-additive fire extinguishing agent contains, as a component of the fire extinguishing agent, a thermopolymerizable polymer with a structure to which soluble functional groups have been added, an alkali metal salt thereof, or an alkaline earth metal salt thereof, and in particular contains poly(methacrylic acid), an alkali metal salt thereof, or an alkaline earth metal salt thereof.

Description

Technical Field

[0001] The present invention relates to an extinguishing agent for extinguishing an electric vehicle capable of extinguishing a fire from a battery of the electric vehicle and an extinguishing structure of the electric vehicle.

Background Art

[0002] Many electric vehicles are equipped with a battery, for example, a plurality of secondary batteries such as a lithium-ion battery, and a traveling electric motor that drives drive wheels with the energy of this secondary battery, and travel using the secondary battery as a power source. In such an electric vehicle, in order to ensure safety such as impact protection for the secondary battery and electric shock protection for the human body, the secondary battery is housed in a sealed metal battery case (casing) having high rigidity strength. Further, in the battery case in which the secondary battery is sealed, a battery cooling device or the like is used to suppress heat generation generated from the secondary battery. Particularly in the battery cooling device, in order to ensure high cooling performance, a liquid cooling type, for example, a water cooling type structure in which a coolant is circulated between a heat absorption part arranged in the battery case and a heat radiation part arranged outside the battery is likely to be used.

[0003] For a fire from the secondary battery, it is effective to directly discharge a fire extinguishing liquid (extinguishing agent) such as water to the secondary battery. However, since the secondary battery is housed in a battery case that protects against electric shock, it is difficult to directly discharge water to the secondary battery from a fire truck or the like. Therefore, as a technique for extinguishing a fire of the secondary battery, in Patent Document 1, a part of a coolant circulation path in a water-cooled battery cooling device of the secondary battery is formed of a member having a low melting point. When ignition that causes a fire occurs, the coolant circulation path portion melts and breaks, and a fire extinguishing structure for injecting cooling water (coolant) for the secondary battery into the battery pack from this damaged portion has been proposed.

[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. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2009-54297 [Patent Document 2] Japanese Patent Publication No. 2011-65805 [Overview of the project] [Problems that the invention aims to solve]

[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. [Means for solving the problem]

[0009] In view of the above objectives, the present invention first provides a fire extinguishing agent for electric vehicles equipped with a secondary battery, comprising a water-added fire extinguishing agent containing, as a component of the fire extinguishing agent, 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 (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. [ka] (In the formula, X is hydrogen (H) or an alkyl group having 1 to 3 carbon atoms, and Y is COOH, SO3H, OCOOH, OSO3H, COO(CH2)) m COOH, COO(CH2) mSO3H, benzene ring-COOH, or benzene ring-SO3H, where n 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 an Mg salt (Invention 4).

[0013] In the above invention (Invention 1), it is preferable that the content of the thermally depolymerizable polymer having the water-soluble functional group in the water-additive 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 structure to which the water-soluble functional group is attached 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-additive 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 1-8), 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] Second, the present invention provides a fire extinguishing structure for an electric vehicle including a secondary battery structure comprising a secondary battery and a casing that externally wraps the secondary battery with a gap therebetween, 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 type fire extinguishing agent containing a thermally depolymerizable polymer having a water-soluble functional group, an alkali metal salt thereof, or an alkaline earth metal salt thereof (Invention 9).

[0019] According to such an invention (Invention 9), since a fire can be efficiently extinguished with a smaller amount of water discharge than when using water alone, when used in an electric vehicle, the space for the fire extinguishing agent can be made more compact.

[0020] In the above invention (Invention 9), a molded body containing a thermally depolymerizable polymer is disposed in the gap between the secondary battery and the casing, and the thermally depolymerizable polymer is preferably 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 such an invention (Invention 10), by having a thermally depolymerizable polymer present in the gap between the secondary battery and the casing, it is possible to prevent the flame from being released outside the vehicle, so that the driver or the person performing the fire extinguishing operation can approach the electric vehicle, and the fire extinguishing work can be speeded up.

[0022] In the above invention (Invention 9), it is preferable that the secondary battery structure has an injection port through which a fire extinguishing agent can be injected from the outside into the casing (Invention 11).

[0023] According to such an invention (Invention 11), by enabling the injection of a fire extinguishing agent from all sides of the secondary battery, it is possible to inject the fire extinguishing agent using a fire extinguisher or the like from the side opposite to the side where the flame or smoke is coming out.

[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 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. [Effects of the Invention]

[0028] The fire extinguishing structure for electric vehicles of the present invention is a fire extinguishing structure for electric vehicles 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 with a structure to which water-soluble functional groups are attached, an alkali metal salt thereof, or an alkaline earth metal salt thereof, and in particular a water-additive type fire extinguishing agent containing poly(methacrylic acid), an alkali metal salt thereof, or an alkaline earth metal salt thereof, so that a fire can be efficiently extinguished with a smaller amount of water discharged than when water is used alone, and therefore the space for the fire extinguishing agent can be made more compact when used in an electric vehicle. [Modes for carrying out the invention]

[0029] The present invention will be described in detail based on the following embodiments.

[0030] [Electric vehicles] In this embodiment, the electric vehicle to be extinguished is not limited to any vehicle that operates using electricity, and includes EVs, hybrid vehicles, etc. The power source is not limited to any vehicle that uses a secondary battery, and includes lithium-ion batteries, all-solid-state lithium-ion batteries, next-generation secondary batteries, etc.

[0031] [Water-additive type fire extinguishing agent] The water-additive fire extinguishing agent of this embodiment contains, as components of the fire extinguishing agent, a thermopolymerizable 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 (hereinafter, these may be referred to as polymer components).

[0032] (Polymer component) The thermally depolymerizable polymer with this water-soluble functional group is preferably structured as shown in the following chemical formula.

[0033] [ka]

[0034] (In the formula, X is hydrogen (H) or an alkyl group having 1 to 3 carbon atoms, Y is COOH, SO3H, OCOOH, OSO3H, COO(CH2)mCOOH, COO(CH2)mSO3H, benzene ring-COOH, or benzene ring-SO3H, n is a positive integer between 5 and 27,000, and m is a positive integer between 1 and 5.)

[0035] Poly(methacrylic acid) can be suitably used as a thermally depolymerizable polymer with such a water-soluble functional group structure.

[0036] Furthermore, as alkali metal salts of thermally depolymerizable polymers with water-soluble functional groups, sodium (Na) salts, potassium (K) salts, etc., can be used. In addition, as alkaline earth metal salts, calcium (Ca) salts, magnesium (Mg) salts, etc., can be used.

[0037] These polymer components are preferably those with a weight-average molecular weight (MW) of 1,000,000 or less, and particularly preferably 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 decrease the efficiency of polymer production. While there are no particular restrictions on the lower limit of the weight-average molecular weight (MW) as long as it is in polymer form, it should be 500 or more, and particularly 1,000 or more.

[0038] The water-added fire extinguishing agent of this embodiment is a water-added, or aqueous, solution of the polymer component 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 more preferably 0.1 to 5% by weight. If the polymer component content 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 is required to be sprayed. On the other hand, if it exceeds 20% by weight, not only is no further improvement in fire extinguishing performance not obtained, but the viscosity of the aqueous solution of the fire extinguishing agent increases, making it difficult to handle, which is undesirable.

[0039] In this embodiment of water-added fire extinguishing agents, a thermally depolymerizable polymer having a structure to which a water-soluble functional group such as poly(methacrylic acid) has been added, an alkali metal salt thereof, or an alkaline earth metal salt thereof may be used individually or in combination of two or more. When using two or more in combination, aqueous solutions of two or more of the two or more dissolved in the same solvent may be mixed, or two or more of the thermally depolymerizable polymer having a structure to which a water-soluble functional group has been added, an alkali metal salt thereof, or an alkaline earth metal salt thereof may be dissolved in the same aqueous solvent.

[0040] [External fire prevention material / Fire prevention material] While there are no restrictions on the fire prevention / ignition prevention material as long as it prevents flames from emanating from the secondary battery, as an effective material, it is preferable to place a molded body containing a thermodepolymer in the gap between the secondary battery and the casing in a secondary battery structure consisting of a secondary battery and a casing that encloses the secondary battery with a gap around it. As this thermodepolymer, 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 suitably used.

[0041] The copolymerized polymer described above may further contain various commonly used additives, to the extent that they do not impair its fire-preventing and ignition-preventing effects. Examples of additives include cross-linked rubber particles, ultraviolet absorbers, lubricants, antioxidants, mold release agents, antistatic agents, and flame retardants. Furthermore, the surface of the acrylic polymer may be coated with a material to enhance its functionality, to the extent that it does not impair the effects of the present invention.

[0042] The thermally depolymerizable polymers described above can be used in various forms, such as films, sheets, beads, pellets, and foams.

[0043] [Fire extinguishing structure for electric vehicles] In this embodiment, the fire extinguishing structure of the electric vehicle is designed to allow the aforementioned water-added 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-added 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. [Examples]

[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-additive type fire extinguishing agent] (Example 1, Comparative Example 1) A lithium-ion battery, designed for use in electric vehicles, was subjected to an overcharge test to ignite, followed by a fire extinguishing test while flames were still present. Overcharging the lithium-ion battery resulted in a violent explosion and ignition approximately 19 minutes later, with the flames continuing.

[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, as an alkali metal salt of a thermally depolymerizable polymer with a water-soluble functional group structure. The number of spray gun injections until extinguishing 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 was measured, 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] [Table 1]

[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 tests for external fire prevention materials and fire prevention materials] (Comparative Example 2) A PP resin container (internal dimensions: 80mm wide x 105mm long x 34mm deep, resin thickness 2mm, with the electrode side of an aluminum laminate lithium-ion battery placed on the 80mm wide side of the PP resin container, and an open top with five 10mm diameter holes on the 80mm wide side of the PP resin container) was prepared. A 1500mAh aluminum laminate lithium-ion battery (35mm wide x 75mm 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 4mm was placed over it, sealing the edges of the lid with heat-resistant tape to prevent any gaps, so that any ejection from the lithium-ion battery due to overcharging would only be released 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 40g of pelletized molded material (particle size 2mm to 5mm) of an acrylic polymer (polymer mainly composed of polymethyl methacrylate, 94% or more, with additives of 5% or less) contained in a flexible synthetic resin bag with a mesh diameter of 1mm.

[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 fire 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 are attached, 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 aforementioned water-soluble functional group structure has the structure shown by the following chemical formula. 【Chemistry 1】 (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 thermally depolymerizable polymers 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 which a fire extinguishing agent can be injected from the outside into the casing.

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