Thermal runaway prevention Sheet using the same

Abstract

The present invention is a thermal runaway prevention sheet comprising a flame retardant layer and a thermal insulation layer, wherein The above thermal runaway prevention sheet includes a heat dissipation layer that radiates a portion of the thermal energy in a second direction different from the first direction when thermal energy is incident in a first direction in which the above thermal runaway prevention sheet is laminated. The heat dissipation layer is characterized by having a thermal conductivity such that the thermal conductivity in the first direction is 0.1 to 8 W / mk and the thermal conductivity in the second direction is 50 to 200 W / mk.

Description

Technology Field

[0001] The present invention relates to an adhesive composition and a thermal runaway prevention sheet containing the same, which has low combustion persistence and excellent thermal insulation properties. Background Technology

[0002] Thermal runaway is a phenomenon in which the temperature of a battery cell rises excessively to an uncontrollable state. If the battery's thermal management fails and the internal temperature of the cell rises above a certain level, the electrolyte vaporizes, causing the internal pressure to increase.

[0003] In such situations, internal short circuits or ignition by flammable gases may occur, which promotes heat transfer to adjacent battery cells and results in the spread of fire. Major causes of thermal runaway include damage to the internal separator, failure of temperature control, and overcharging / overdischarging.

[0004] Various technical attempts are being made to prevent the spread of fire caused by thermal runaway in such batteries, especially secondary batteries.

[0005] Thermal runaway prevention technologies include methods for monitoring the temperature, voltage, and current of a battery and detecting abnormal conditions using a battery management system (BMS), maintaining the battery temperature appropriately through a thermal management system, preventing internal short circuits using heat-resistant thermal runaway prevention sheets, preventing overheating by increasing the chemical stability of battery materials, preventing overheating through safe cell design, and preventing overcharging and over-discharging of the battery using electronic circuits.

[0006] Among the methods described above, the present invention uses a thermal runaway prevention sheet, wherein the thermal runaway prevention sheet is made of a thin and light material to minimize space within the battery pack and can be placed between cells, while also requiring performance capable of withstanding a temperature of 350°C or lower, preferably 300°C or lower, at least 7 minutes in order to delay the escape time to prevent casualties in a cell located adjacent to the cell where the fire occurred.

[0007] As an alternative, a thermal runaway prevention sheet using ceramic-based flame-retardant materials, such as mica and glass fiber, which are non-flammable and have low thermal conductivity, has been proposed. However, even when using flame-retardant materials, there is a problem where the adhesive layer of the thermal runaway prevention sheet catches fire and spreads due to the flammability of the adhesive that is necessarily used for interlayer bonding containing the flame-retardant material during the manufacturing of the sheet.

[0008] Accordingly, Japanese Patent Publication No. JP2023-118245A (Patent Document 2) discloses elastomer-based adhesives such as rubber-based, acrylic-based, and silicone-based adhesives as flame-retardant adhesives used in thermal runaway prevention sheets. However, the adhesive disclosed in Patent Document 2 is a flammable or semi-flammable adhesive, and when the adhesive layer included in the manufactured thermal runaway prevention film is exposed to flames, the combustion persistence is high, so there is still a fire risk.

[0009] Therefore, there is a need to develop an adhesive composition with low combustion persistence and excellent thermal insulation properties, as well as a thermal runaway prevention sheet containing the same. Prior art literature

[0010] Republic of Korea Patent Registration No. 10-2560446, Japanese Published Patent Application No. JP2023-118245A The problem to be solved

[0011] One aspect of the present invention aims to provide an adhesive composition that has low combustion persistence and can be quickly extinguished even if combustion by a flame occurs.

[0012] Another aspect of the present invention aims to provide a thermal runaway prevention sheet comprising the adhesive composition described above, which has low combustion persistence and excellent thermal insulation properties. means of solving the problem

[0013] As a thermal runaway prevention sheet comprising a flame-retardant layer and an insulating layer,

[0014] The above thermal runaway prevention sheet includes a heat dissipation layer that radiates a portion of the thermal energy in a second direction different from the first direction when thermal energy is incident in a first direction in which the above thermal runaway prevention sheet is laminated.

[0015] The heat dissipation layer has a thermal conductivity such that the thermal conductivity in the first direction is 0.1 to 8 W / mk, and the thermal conductivity in the second direction is 50 to 200 W / mk.

[0016] When a flame of 1000 to 1300°C is radiated onto one side of the above thermal runaway prevention sheet and the temperature of the opposite side is measured, it is maintained at 200°C or lower until 10 minutes have elapsed.

[0017] The thickness (t5) of the heat dissipation layer is 0.1 to 1 mm.

[0018] The above heat dissipation layer includes expanded graphite and boron nitride.

[0019] The ratio of the expanded graphite and the boron nitride is included in a ratio of 80:20 to 95:5.

[0020] The structure comprises at least one insulating layer having a thickness of t2 that is laminated on one surface of the heat dissipation layer and suppresses heat transfer, at least one flame retardant layer having a thickness of t1 that is laminated on one surface of the heat dissipation layer or the first insulating layer and protects against flames, and at least one adhesive layer having a thickness of t4 that is printed with an area of ​​30% or less of the area of ​​the heat dissipation layer, the first insulating layer, or the flame retardant layer and bonds any two of the heat dissipation layer, the insulating layer, or the flame retardant layer.

[0021] The sum of the thicknesses of each layer (t1+t2+t4+t5) is 0.5 to 6.0 mm.

[0022] The above adhesive layer is made of a cured product of an adhesive composition that is applied in an amount of 1g over an area of ​​3cm2 and then radiated with a flame from a 1200-degree torch, so that the time taken from the moment it starts to catch fire until the moment it ends is less than 10 seconds.

[0023] The above adhesive composition is,

[0024] Binder resin comprising epoxy resin and acrylate resin;

[0025] Filler dispersed in the above binder;

[0026] A curing agent having an amine-based or epoxy group; and

[0027] A reactivity modifier comprising ethyl acetate or a halogenated organic compound is included, and the binder resin is included in an amount of 25 to 65 wt% of the entire adhesive composition. Effects of the invention

[0028] An adhesive composition according to one aspect of the present invention has low combustion persistence, so even if the adhesive is exposed to a flame and ignites, it is extinguished within a few seconds, thereby preventing the spread of fire and preventing defects in the thermal runaway prevention sheet.

[0029] A thermal runaway prevention sheet according to another aspect of the present invention has the effect of preventing chain thermal runaway while preventing the sheet from burning or igniting in the flames, by releasing heat to the outside of the battery pack even in the case of a thermal runaway fire in which high-temperature flames of about 1000 to 1300°C occur, such as in an electric vehicle battery, thereby maintaining the temperature of adjacent battery cells at 200°C or lower compared to conventional thermal runaway prevention sheets where heat transfer of 350 to 450°C occurs. Accordingly, the spread of fire and casualties can be prevented.

[0030] Accordingly, the thermal runaway prevention sheet according to the present invention can be used for the purpose of preventing fire caused by thermal runaway in application products such as EV Battery Electric Vehicle (secondary battery for electric vehicles), ESS Energy Storage System (electric energy storage system), and UPS Uninterruptible Power Supply (power supply unit). Brief explanation of the drawing

[0031] FIG. 1 is a cross-sectional view showing a thermal runaway prevention sheet according to an embodiment of the present invention. FIG. 2 is an exemplary diagram illustrating the printing pattern of the adhesive layer of a thermal runaway prevention sheet according to the present invention. FIG. 3 is a conceptual diagram illustrating the heat transfer mechanism of the heat dissipation layer included in the thermal runaway prevention sheet of the present invention. FIG. 4 is a thermal runaway prevention sheet according to various embodiments of the present invention. Figure 5 is a photograph of a combustion persistence test of an adhesive composition according to an embodiment of the present invention. Figure 6 is a photograph illustrating an experiment of the thermal runaway prevention sheet of the present invention. Specific details for implementing the invention

[0032] Before describing the present invention in detail below, it should be understood that the terms used in this specification are intended only to describe specific embodiments and are not intended to limit the scope of the invention, which is defined solely by the appended claims. Unless otherwise stated, all technical and scientific terms used in this specification have the same meaning as generally understood by those skilled in the art.

[0033] Throughout this specification and claims, unless otherwise noted, the terms "comprise," "comprising," and "comprising" mean including the mentioned article, step, or group of articles and steps, and are not used to mean excluding any other article, step, or group of articles or groups of steps.

[0034] Additionally, in the drawings, the width, length, thickness, angle, etc., of the components may be exaggerated for convenience. The drawings have been described from the observer's perspective, and when one component is described as being "above / below" or "on / below" another component, this includes not only the case where it is "immediately above / immediately below" the other component, but also the case where there is another component in between.

[0035] Meanwhile, various embodiments of the present invention may be combined with any other embodiments unless explicitly stated otherwise. Any feature indicated as particularly desirable or advantageous may be combined with any other features and features indicated as desirable or advantageous.

[0036] First aspect: Adhesive composition

[0037] The adhesive composition according to the present invention is an adhesive composition used as an adhesive layer provided in a printed form between a flame-retardant layer, an insulating layer, and a heat-dissipating layer constituting a thermal runaway prevention sheet. It is a composition that can function as an insulating layer due to the low thermal conductivity of the thermal runaway prevention sheet, maintains mechanical strength, has low combustion persistence during combustion, possesses a self-extinguishing function, and can prevent the spread of fire by being extinguished within a short period of time even when exposed to flames.

[0038] The adhesive composition according to the present invention comprises a binder resin, a curing agent, a filler, a reactivity modifier, and a tackiness modifier.

[0039] The binder resin plays a role in maintaining the adhesive strength of the thermal runaway prevention sheet by providing interlayer adhesion between the heat dissipation layer and the insulation layer of the thermal runaway prevention sheet through a curing reaction. In the present invention, the binder resin maintains tackiness through drying curing to maintain adhesion during the process, increases adhesive strength through thermal curing after lamination to stabilize the quality of the manufactured product, and essentially includes an acrylate-based resin to provide self-extinguishing and combustion persistence, and preferably includes an epoxy-based resin (including modified epoxy-based resin) and an acrylate-based resin (including modified acrylate-based resin).

[0040] At this time, it is preferable that the epoxy resin and the acrylate resin contain 90 to 110 parts by weight of the epoxy resin relative to 100 parts by weight of the acrylate resin.

[0041] Epoxy resins are not limited, but bisphenol A-based epoxy resins and rubber-modified epoxy resins may be used.

[0042] Acrylate-based resins such as acrylic acid-butyl acrylate-2-ethylhexyl acrylate-vinyl acetate, polymethyl methacrylate (PMMA), methacrylate copolymer, ethyl acrylate copolymer, polybutyl acrylate, polymethyl methacrylate (PMMA), polyethyl acrylate, styrene-acrylate copolymer, and acrylonitrile butadiene styrene (ABS) may be used.

[0043] Additionally, one or more types selected from the group derived from isocyanate-based, silane-based, modified silicone-based, vinyl acetate-based, and urethane-based materials may be used.

[0044] It is preferable that the binder resin be 25 to 65 weight percent of 100 weight percent of the total adhesive. If the binder resin is less than 25 weight percent, the adhesive performance may be reduced, and if it exceeds 65 weight percent, it burns due to a lack of flame resistance and does not burn out.

[0045] The curing agent acts as a curing agent that strengthens the network structure and improves durability. In the embodiments of the present invention, the curing agent is preferably an amine-based curing agent or a curing agent containing an epoxy group that can form crosslinks by reacting with other compounds.

[0046] Preferably, glycidyl ether or a polyfunctional epoxy monomer may be used. An example of a glycidyl ether is glycerol diglycidyl ether, and a bisphenol A-based epoxy resin may be used as the polyfunctional epoxy monomer.

[0047] The curing agent is included in an amount of 20 to 30 parts by weight per 100 parts by weight of the binder.

[0048] The filler is dispersed within the binder and serves to improve the thermal insulation properties of the adhesive. At least one filler selected from the group consisting of aluminum hydroxide, aluminum oxide, silicon-based compounds, calcium carbonate, magnesium oxide, zinc oxide, borides, and phosphorus-based flame retardant fillers may be used.

[0049] Preferably, molten silica powder may be used to reinforce mechanical properties and thermal stability, and Al(OH)3 may be used to provide flame retardancy and thermal stability.

[0050] The filler is included in an amount of 20 to 50 parts by weight per 100 parts by weight of the binder. If the filler content exceeds 50 wt%, the surface tackiness may be reduced when using the adhesive, resulting in reduced adhesive performance; if it is less than 20 wt%, gelation of the adhesive may occur, causing the viscosity to become too high, making printing difficult, and the combustion persistence may become too high.

[0051] Reactivity modifiers are additives that control physical and chemical properties by influencing reaction and curing. Ethyl acetate or halogenated organic compounds may be used to control reactivity and curability, such as 2-bromobutane, chloroacetic acid, bromoacetic acid, 2-chlorobutanoic acid, etc. Additionally, acetic acid, etc., may be added to adjust pH.

[0052] The reactivity modifier is included in an amount of 60 to 70 parts by weight per 100 parts by weight of binder.

[0053] Tackiness modifiers are included to impart appropriate tackiness to the adhesive and to enhance adhesion to various surfaces. While not limited to rosin esters, terpenes resins, C5 aliphatic resins, C9 aromatic resins, and hydrogenated hydrocarbon resins may be used.

[0054] The adhesive modifier is included in an amount of 2 to 8 parts by weight per 100 parts by weight of the binder.

[0055] Organic solvents play a role in maintaining viscosity and facilitating printing when using adhesive compositions. The type of organic solvent is not particularly limited, but one or more selected from the group consisting of alcohol compounds, ketone compounds, ester compounds, aromatic hydrocarbons, alkane compounds, chloride hydrocarbon compounds, ether compounds, amide compounds, sulfide hydrocarbon compounds, aldehyde compounds, nitrile hydrocarbon compounds, and carbonate compounds may be used. Preferably, methanol, toluene, or MEK (methyl ethyl ketone) may be used.

[0056] The organic solvent is included in an amount of 10 to 20 parts by weight per 100 parts by weight of the binder.

[0057] The cured adhesive forms an adhesive layer, and it is desirable that the thermal conductivity of the adhesive layer be 0.3 W / mK or less. If the thermal conductivity of the adhesive layer exceeds 0.3 W / mK, high thermal energy diffuses too rapidly, and there is a risk that battery cells adjacent to a battery cell in which thermal runaway has occurred will be exposed to high temperatures.

[0058] Meanwhile, the adhesive layer of the present invention burns rapidly when exposed to flame and is formulated in a minimal amount; it also possesses self-extinguishing performance upon combustion by imparting flame-retardant properties through flame-retardant fillers.

[0059] Second Aspect: Thermal Runaway Prevention Sheet

[0060] A thermal runaway prevention sheet according to another aspect of the present invention comprises an adhesive layer, a flame retardant layer, an insulating layer, and a heat dissipation layer. FIG. 1 is a cross-sectional view showing a thermal runaway prevention sheet according to an embodiment of the present invention.

[0061] The adhesive layer serves to maintain the mechanical strength of the thermal runaway prevention sheet and bonds the flame retardant layer and the insulation layer, the insulation layer and the insulation layer, the insulation layer and the heat dissipation layer, or the heat dissipation layer and the flame retardant layer. The adhesive layer is formed by printing and curing an adhesive composition according to the first aspect described above.

[0062] The adhesive composition used in the adhesive layer has been described in the first aspect, so a detailed description thereof is omitted.

[0063] The adhesive layer can also function as an insulating layer with a thermal insulation effect. Therefore, it is desirable that the thermal conductivity of the adhesive layer be 0.3 W / mK or less. If the thermal conductivity of the adhesive layer exceeds 0.3 W / mK, high thermal energy diffuses too rapidly, and there is a risk that battery cells adjacent to a battery cell in which thermal runaway has occurred will be exposed to high temperatures.

[0064] In addition, it is desirable to minimize the thickness (t2) of the adhesive layer to 5 to 40 μm. If the thickness is greater than the above, there are problems with flame retardant performance, and if it is smaller, there are problems with bonding and the production process.

[0065] FIG. 2 is an exemplary diagram illustrating the printing pattern of the adhesive layer of a thermal runaway prevention sheet according to the present invention. At this time, it is preferable to perform the printing of the adhesive using micro-gravure coating, gravure coating, or pattern printing. Minimizing the adhesive layer helps improve flame retardant performance.

[0066] In addition, the front printing and printing pattern formed by the adhesive are not limited, but it is desirable to minimize the printing to 30% or less of the thickness and area of ​​the flame retardant layer or the thermal insulation layer. This is to reduce the amount used as much as possible, as the adhesive contains organic materials and is unnecessary for non-combustible performance.

[0067] The flame retardant layer is provided on both outer sides of the sheet as a layer intended to prevent the sheet from igniting flames during thermal runaway. The thickness (t1) of the flame retardant layer is 0.05 to 2 mm, preferably 0.08 to 0.2 mm, and the area density is 200 to 400 g / m². 2 am.

[0068] For high flame resistance, the flame-retardant layer material includes mica, glass fiber, and a binder.

[0069] Mica provides excellent heat resistance and electrical insulation, and plays an important role as a flame-retardant material as its performance does not degrade even at high temperatures. Glass fibers enhance structural stability and improve thermal insulation, and are non-combustible, providing additional protection against fire. The binder combines the mica and glass fibers and is selected as a material that can withstand high temperatures while maintaining a composite structure and does not contribute to combustion; however, since the binder has lower flame resistance compared to the remaining components, it is included in an amount of 15% or less, preferably 10% or less.

[0070] At this time, it is preferable that mica and glass fiber be included in a weight ratio of 50:30 to 70:20. If the glass fiber content is lower than the above range, there are problems with strength or sheet formation, and if the glass fiber content is higher than the above range, there are problems with flame retardant performance.

[0071] The insulation layer is a layer for blocking thermal energy received from flames radiated to the flame retardant layer, and may be a first insulation layer or a second insulation layer depending on the material used for the thermal runaway prevention sheet.

[0072] The first insulating layer is a layer containing ceramic, wherein the thickness (t3) of the layer is 0.1 to 6 mm, more preferably 0.5 to 3 mm, the organic content is preferably less than 10 weight%, and the thermal conductivity is 0.1 W / mk or less.

[0073] The ceramic included in the first insulating layer is preferably at least one type selected from the group consisting of alumino-silica, alumina, and silicate. Alumino-silica is a material with excellent high temperature resistance and fire resistance, and has excellent thermal stability and durability, alumina exhibits strong heat resistance at high temperatures, and silicate provides fire resistance and heat resistance.

[0074] The second insulation layer is a layer containing graphite, wherein the thickness (t4) of the layer is 0.5 to 4.0 mm, more preferably 0.5 to 2.0 mm, and the organic content is preferably less than 10 weight%, and a non-combustible material is used.

[0075] The heat dissipation layer is a layer that releases a portion of the heat passing through the sheet to the outside. Figure 3 is a conceptual diagram explaining the heat transfer mechanism of the heat dissipation layer included in the thermal runaway prevention sheet of the present invention. The heat dissipation layer is a layer that prevents heat energy from passing through and being transferred in the first direction of the heat dissipation layer by dissipating a portion of the heat energy in the second direction, which is the lateral direction of the heat dissipation layer, even if heat energy is incident in the first direction, which is the direction in which the heat dissipation layer is stacked, when high temperature is generated in a specific battery cell.

[0076] At this time, the thickness (t5) of the heat dissipation layer is 0.1 to 1.0 mm, and preferably 0.5 to 1.0 mm. If the thickness of the heat dissipation layer is less than the above range, the heat dissipation capacity of the heat dissipation layer is reduced so that thermal energy can easily pass through in the first direction, and if it exceeds the above range, it occupies an excessive amount of space inside the battery pack.

[0077] In addition, the thermal conductivity of the heat dissipation layer in the first direction is 0.1 to 8.0 W / mk, preferably 0.5 to 3.0 W / mk, and the thermal conductivity in the second direction is 50 to 200 W / mk, preferably 100 to 150 W / mk.

[0078] If the thermal conductivity in the first direction is less than 0.1 W / mk, heat is transferred too slowly, causing heat to accumulate inside the heat dissipation layer and slowing down diffusion to the second direction, and if the thermal conductivity in the first direction exceeds 8.0 W / mk, there is no insulation effect between cells.

[0079] If the thermal conductivity in the second direction is less than 50 W / mk, it cannot dissipate heat as quickly as necessary, so there is no heat dissipation effect to remove heat from the cell, and if the thermal conductivity exceeds 200 W / mk, the excessively high thermal conductivity can cause economic problems such as increased material costs.

[0080] A preferred embodiment of the heat dissipation layer is a sheet comprising expanded graphite and boron nitride.

[0081] Expanded graphite is manufactured by heating graphite powder obtained by crushing natural graphite ore at high temperatures. Through the expansion process, the volume of the graphite increases significantly, becoming expanded graphite that is lighter than the original graphite while maintaining excellent thermal conductivity. It possesses a low coefficient of thermal expansion and high thermal conductivity, allowing it to efficiently dissipate heat.

[0082] Boron nitride (BN) powder is a white ceramic material with excellent thermal properties and electrical insulation characteristics. Its structure is similar to graphite, so it conducts heat well but does not conduct electricity, providing fire resistance to heat dissipation sheets and maintaining stability even at high temperatures.

[0083] A heat dissipation sheet can be manufactured through the processes of crushing, beneficiation, washing and drying, expansion, mixing, preforming, heating, and pressing. Specifically, natural graphite ore is crushed to produce particles with excellent thermal conductivity, the crushed graphite is selected and impurities are removed to obtain graphite powder, which is then washed and dried to increase purity. The graphite powder is expanded at high temperature to produce expanded graphite with increased volume, and then BN particles are mixed with the expanded graphite in a ratio of 80:20 to 95:5 and subjected to a ball milling process to impart refractory properties. Next, the mixture is heated to preform and formed into a sheet of a predetermined thickness using a compression roller. The formed sheet is then heated again at high temperature and pressed to adjust the thickness and remove internal air bubbles.

[0084] Referring again to FIG. 1, the operation of the thermal runaway prevention sheet of the present embodiment will be explained. Each layer of the thermal runaway prevention sheet according to one embodiment of the present invention, which is provided between the first battery cell where thermal runaway has occurred and the adjacent second battery cell, is shown separately, and the adhesive layer is omitted from the drawing.

[0085] If a fire occurs due to thermal runaway in the first battery cell and flames are radiated in the first direction to the flame retardant layer adjacent to the first battery cell, the flame retardant layer blocks the flames. At this time, high-temperature thermal energy is transferred to the 1-1 flame retardant layer.

[0086] Subsequently, the high-temperature thermal energy diffused into the flame retardant layer diffuses back into the insulation layer, and the insulation layer prevents or delays the transfer of thermal energy in the first direction.

[0087] Subsequently, when some of the thermal energy from the insulation layer reaches the heat dissipation layer, the heat dissipation layer having high thermal conductivity diffuses the thermal energy in a second direction and radiates it to the outside of the battery cell, thereby minimizing the flow of heat in the first direction and preventing or delaying the temperature rise of the flame retardant layer, thus preventing the temperature of the second battery cell from rising.

[0088] That is, the heat dissipation layer may diffuse heat to a thermal runaway sheet including an adjacent heat dissipation layer, thereby preventing the temperature of an adjacent battery cell from rising due to thermal runaway of the first battery cell.

[0089] FIG. 4 is a thermal runaway prevention sheet according to various embodiments of the present invention. According to this, various thermal runaway prevention sheets can be manufactured by combining a flame retardant layer, an adhesive layer, a heat dissipation layer, and an insulating layer.

[0090] Accordingly, the thermal runaway prevention sheet according to the present invention has a total thickness (t) of 0.6 to 10T and a specific gravity of 0.3 to 1.0, a flame retardant rating of UL 94 5VA-0 or higher, and when a flame of 1000 to 1300℃ is radiated on one side, the temperature of the other side is maintained at 200℃ or lower, and in a preferred embodiment, at 150℃ or lower for at least 10 minutes.

[0091] Preparation Example

[0092] (Preparation Example 1-1) Adhesive composition

[0093] 100 parts by weight of acrylic acid-butyl acrylate-2-ethylhexyl acrylate-vinyl acetate, 100 parts by weight of rubber-modified epoxy, 50 parts by weight of glycerol diglycidyl ether, 40 parts by weight of 2-bromobutane, 60 parts by weight of 2-chlorobutanoic acid, 30 parts by weight of chloroacetic acid, 10 parts by weight of acetic acid, and 40 parts by weight of bromoacetic acid are mixed and then dissolved at 180°C for 12 hours to prepare a binder resin.

[0094] 100g of binder resin, 30g of fused silica powder as a filler, and 10g of Al(OH)3 powder were added to a stirrer equipped with a saw blade impeller, and then stirred at 1,000 RPM for 30 minutes at room temperature.

[0095] Afterward, 33g of Takcyfier was added and stirred again at 1,000 RPM for 30 minutes. Then, 15.2g of MEK (methyl ethyl ketone) was added to adjust the viscosity, and the reaction mixture was aged at room temperature for 1 hour. After aging was complete, the reaction mixture was filtered through a 200-mesh filter to prepare an adhesive composition.

[0096] (Preparation Example 1-2) Adhesive composition

[0097] A binder resin is prepared by mixing 110 parts by weight of acrylic acid-butyl acrylate-2-ethylhexyl acrylate-vinyl acetate acrylate with 110 parts by weight of bisphenol A epoxy, 50 parts by weight of glycerol diglycidyl ether, 40 parts by weight of 2-bromobutane, 60 parts by weight of 2-chlorobutanoic acid, 30 parts by weight of chloroacetic acid, 10 parts by weight of acetic acid, and 40 parts by weight of bromoacetic acid, and then dissolving at 180°C for 12 hours.

[0098] 100g of binder resin, 35g of fused silica powder as a filler, and 10g of Al(OH)3 powder were added to a stirrer equipped with a saw blade impeller, and then stirred at 1,000 RPM for 30 minutes at room temperature.

[0099] Afterward, 33g of Takcyfier was added and stirred again at 1,000 RPM for 30 minutes. Then, 16g of MEK (methyl ethyl ketone) was added to adjust the viscosity, and the reaction mixture was aged at room temperature for 1 hour. After aging was complete, the reaction mixture was filtered through a 200-mesh filter to prepare an adhesive composition.

[0100] (Preparation Examples 1-3) Adhesive composition

[0101] A binder resin is prepared by mixing 110 parts by weight of urethane-modified acrylate, 110 parts by weight of bisphenol A epoxy, 50 parts by weight of glycerol diglycidyl ether, 40 parts by weight of 2-bromobutane, 60 parts by weight of 2-chlorobutanoic acid, 30 parts by weight of chloroacetic acid, 10 parts by weight of acetic acid, and 40 parts by weight of bromoacetic acid, and then dissolving at 180°C for 12 hours.

[0102] 100g of binder resin, 11g of fused silica powder and 10g of Al(OH)3 powder as fillers were added to a stirrer equipped with a saw blade impeller, and then stirred at 1,000 RPM for 30 minutes at room temperature.

[0103] Afterward, 33g of Takcyfier was added and stirred again at 1,000 RPM for 30 minutes. Then, 15g of MEK (methyl ethyl ketone) was added to adjust the viscosity, and the reaction mixture was aged at room temperature for 1 hour. After aging was complete, the reaction mixture was filtered through a 200-mesh filter to prepare an adhesive composition.

[0104] (Manufacturing Example 2) Manufacturing of a heat dissipation sheet

[0105] Natural graphite ore is crushed to produce particles with excellent thermal conductivity, and then graphite powder is obtained by classifying the graphite and removing impurities through a beneficiation process. Subsequently, this powder undergoes washing and drying, followed by processing in an expansion furnace heated at high temperatures to convert it into expanded graphite.

[0106] Boron Nitride (BN) particles are prepared with high-purity expanded graphite, and these are mixed in a ratio of 90:10 through a ball milling process to impart refractory properties.

[0107] This mixture undergoes a pre-forming process at 250°C and is formed into a sheet with a thickness of 1.5 mm using a compression roller. To remove air bubbles inside the sheet and to manufacture a heat dissipation sheet with well dispersed particles, the formed sheet undergoes a heating and pressing process at 350°C to adjust the thickness to 0.95 mm.

[0108] (Manufacturing Example 3) Manufacture of flame-retardant sheet

[0109] Prepare mica and glass fibers that provide fire resistance and structural strength. Mix them in a ratio of 50:30, and then add a ceramic silicon binder equivalent to 9.6% of the total weight.

[0110] This mixture is impregnated and molded into a sheet with a thickness of 0.1-0.2 mm. After the sheet is formed, it is dried at a certain temperature so that the binder is effectively bonded between the mica and the glass fibers.

[0111] (Manufacturing Example 4) Manufacture of the first insulation sheet

[0112] Ceramic fibers are manufactured by melting alumina (Al2O3) using a plasma arc to convert it into a liquid state and forming the ceramic material into thin fibers through drawing.

[0113] Subsequently, ceramic fibers are collected and aligned to form a sheet, fixed using a binder with a content of 6 wt% while applying pressure and heat, and cut into the desired size and shape to manufacture a ceramic sheet. The manufactured ceramic sheet has a thermal conductivity of 0.03 W / mk and a thickness of 0.5-2.0 mm.

[0114] (Manufacturing Example 5) Manufacture of the first insulation sheet

[0115] Silicon boride is melted using a plasma arc to convert it into a liquid state, and ceramic material is formed into a thin fiber shape by drawing to manufacture ceramic fibers.

[0116] Subsequently, ceramic fibers are collected and aligned to form a sheet, fixed using a binder with a content of 6 wt% while applying pressure and heat, and cut into the desired size and shape to manufacture a ceramic sheet. The manufactured ceramic sheet has a thermal conductivity of 0.08 W / mk and a thickness of 4 mm.

[0117] (Manufacturing Example 5) Manufacture of the second insulation sheet

[0118] High-purity graphite raw material is ground to a desired thickness ranging from 0.5 mm to 4.0 mm, and organic material is added to the ground graphite. The content of the organic material must be less than 10% of the total weight of the graphite insulation layer, which helps ensure non-combustible performance by minimizing the combustion of the organic material. The mixed graphite and organic material mixture is molded to adjust the thickness of the insulation layer to 0.5 mm to 4.0 mm or a more preferred range of 0.5 mm to 2.0 mm, and then the molded insulation layer is heat-treated at a high temperature to decompose and remove the organic material to manufacture a graphite sheet.

[0119] (Example)

[0120] According to the aforementioned manufacturing example of the present invention, a flame retardant sheet, an adhesive, a heat dissipation sheet, an adhesive, a first thermal insulation sheet, an adhesive, and a flame retardant sheet were laminated as shown in Table 1, and then a laminated thermal runaway prevention sheet was manufactured by rolling lamination at room temperature at 80 degrees for 24 hours.

[0121] At this time, the adhesive was printed between each layer within 30% of the thickness and area of ​​the first insulation sheet.

[0122] (Comparative Example 1)

[0123] In the reference example, a thermal runaway prevention sheet was used in which the heat dissipation layer included in the thermal runaway prevention sheet of the present invention was replaced with an insulating layer or a flame retardant layer.

[0124] A flame retardant sheet, a first thermal insulation sheet, and an adhesive were prepared according to the manufacturing example of the present invention. The flame retardant sheet, the adhesive, the first thermal insulation sheet, the adhesive, and the flame retardant sheet described above were laminated in order, and then rolled heated and compressed at 80°C to manufacture a thermal runaway prevention sheet.

[0125] At this time, the adhesive was printed between each layer within 30% of the thickness and area of ​​the first insulation sheet.

[0126] (Comparative Example 2)

[0127] A flame retardant sheet according to Manufacturing Example 2-1 of the present invention, a first insulation sheet according to Manufacturing Example 3-1, a second insulation sheet according to Manufacturing Example 3-2, and an adhesive according to Manufacturing Example 4 were prepared. The flame retardant sheet, adhesive, first insulation sheet, adhesive, second insulation sheet, adhesive, and flame retardant sheet described above were laminated in order, and then a thermal runaway prevention sheet was manufactured by roller heating and pressing at 80°C.

[0128] At this time, the adhesive was printed between each layer within 30% of the thickness and area of ​​the first insulation sheet.

[0129] (Comparative Example 3)

[0130] A flame retardant sheet according to Manufacturing Example 2-1 of the present invention, a first insulation sheet according to Manufacturing Example 3-1, a second insulation sheet according to Manufacturing Example 3-2, and an adhesive according to Manufacturing Example 4 were prepared. The flame retardant sheet, adhesive, first insulation sheet, adhesive, second insulation sheet, adhesive, first insulation sheet, adhesive, and flame retardant sheet described above were laminated in order, and then a thermal runaway prevention sheet was manufactured by roller heating and pressing at 80°C.

[0131] At this time, the adhesive was printed between each layer within 30% of the thickness and area of ​​the first insulation sheet.

[0132] (Comparative Example 4)

[0133] A flame retardant sheet according to Manufacturing Example 2-1 of the present invention, a second insulation sheet according to Manufacturing Example 3-2, and an adhesive according to Manufacturing Example 4 were prepared. The flame retardant sheet, adhesive, second insulation sheet, adhesive, flame retardant sheet, adhesive, second insulation sheet, adhesive, and flame retardant sheet described above were laminated in order, and then rolled heated and compressed at 80°C to produce a thermal runaway prevention sheet.

[0134] At this time, the adhesive was printed between each layer within 30% of the thickness and area of ​​the first insulation sheet.

[0136] Experimental Example

[0137] Experimental Example 1: Adhesive Composition-Flammability Test

[0138] After applying 1g of the adhesive composition to an area of ​​3cm² in the center of an experimental aluminum film dish, a flame was radiated using a 1200-degree torch, and the time taken from the moment the adhesive composition started to catch fire until the moment combustion ended was measured. At this time, Figure 5 shows a photograph of the combustion persistence test method of the adhesive composition according to the present invention.

[0139] Since a shorter duration of combustion duration may result in less fire spread due to thermal runaway when using adhesive, the evaluation results according to Experimental Example 1 were presented, and the criteria for determining combustion duration are as follows.

[0140] ◎ : Less than 5 seconds

[0141] ○ : 5 seconds or more but less than 10 seconds

[0142] △ : 10 seconds or more but less than 15 seconds

[0143] X : 15 seconds or more

[0145] Experimental Example 2: Adhesive Composition-Adhesion Performance Evaluation Experiment

[0146] The adhesive composition was coated onto a release film and laminated onto a glass plate at room temperature in the atmosphere. Then, the coating thickness (10~20 µm) and the solid residue rate (N / V, 60%) were measured to evaluate the 180-degree peel strength adhesive properties.

[0147] Adhesion performance is an indicator influenced by coating thickness and N / V (%). If the coating thickness is excessively thin, adhesion performance decreases, and if it is too thick, the flame retardancy of the product being used may decrease. Additionally, N / V (%) is the residual amount of solids remaining after drying the volatile components of the adhesive; if it is too low, the coating thickness decreases relative to the amount of adhesive input, which has the disadvantage of making process control difficult.

[0148] The evaluation criteria for adhesion performance are as follows. In this case, the indicator receiving the lower rating between coating thickness and N / V(%) was evaluated as the final result.

[0149] ◎ : Coating thickness 5~20㎛, N / V 50% or higher

[0150] ○: Coating thickness 20~30㎛ or 40~50㎛, N / V 55~65%

[0151] △ : Coating thickness 10~20㎛ or 50~60㎛, N / V 45~55%

[0152] X: Coating thickness less than 10㎛ or greater than 60㎛, N / V less than 45%

[0153] Experimental Example 3: Adhesive Composition-Printability Test

[0154] Printability is an indicator of the degree to which an adhesive can be easily sprayed from a printing nozzle or evenly distributed on a surface when used, and it is influenced by viscosity and Ti (Thixotropic Index).

[0155] If the viscosity is too high, there is a high risk of the process taking too long or the nozzle becoming clogged. In this case, the indicator receiving the lower evaluation between viscosity and Ti was used as the final result. Viscosity was measured at 5 rpm using a Cone & Plate Type Brookfield viscometer.

[0156] ◎ : Viscosity 100~1,000 cps, Ti <2

[0157] ○ : Viscosity 1,000~3,000 cps Ti 2 or higher - less than 3.0

[0158] △ : Viscosity 3,000~5,000 cps, Ti 3.0 or higher

[0159] X: Viscosity 5,000 cps or higher or exceeding 10,000 cps, Ti 3.0 or higher

[0160] The evaluation results of the combustion persistence, adhesive performance, and printability of the adhesive composition according to the present invention are shown in Table 1.

[0162] Evaluation results of adhesive combustion persistence, adhesion performance, and printability Combustion persistence Adhesion performance print performance Preparation Example 1-1 ◎ ◎ ◎ Preparation Example 1-2 ◎ ◎ ◎ Preparation Examples 1-3 ○ ○ ◎

[0163] Experimental Example 4: Thermal Runaway Prevention Sheet - Thermal Insulation Properties Evaluation Experiment

[0164] A thermal runaway prevention sheet is positioned vertically, and a flame of 1000 to 1100°C is radiated from one side or the opposite side using a torch, and the temperature change of the side opposite to the flame-radiated side is observed over time. At this time, FIG. 6 illustrates a photograph explaining an experiment of the thermal runaway prevention sheet of the present invention.

[0165] Table 2 shows the results of experiments conducted on the thermal runaway prevention sheet according to the present invention. According to the results, in all experiments, the flame retardant layer did not burn, and the temperature on the opposite side was 200°C or lower after 10 minutes of the experiment. However, the reference examples, such as the conventional silicone foam sheet, PU foam sheet, and sheet without a heat dissipation layer, were 300°C or lower, but exceeded 200°C.

[0166]

[0167] In Table 2, the silicone foam sheet, PU foam sheet, and sheet equipped with a flame retardant layer + insulation layer + flame retardant layer are reference examples.

[0168] Meanwhile, as a comparative example, various sheets were manufactured having a flame retardant layer, an insulating layer, and an adhesive layer without a heat dissipation layer.

[0169] The features, structures, effects, etc. exemplified in each of the aforementioned embodiments may be combined or modified and implemented in other embodiments by a person skilled in the art to which the embodiments belong. Therefore, details regarding such combinations and modifications should be interpreted as being included within the scope of the present invention.

Claims

Claim 1 A thermal runaway prevention sheet comprising at least one flame retardant layer, an insulating layer, and a heat dissipation layer, wherein the heat dissipation layer is a layer that radiates a portion of the thermal energy in a second direction different from the first direction when thermal energy is incident in a first direction in which the thermal runaway prevention sheet is laminated, and comprises expanded graphite and boron nitride, wherein the thermal conductivity in the first direction is 0.1 to 8 W / mk and the thermal conductivity in the second direction is 50 to 200 W / mk; wherein the flame retardant layer is provided on at least both sides of the outermost layer of the thermal runaway prevention sheet and comprises an adhesive layer that bonds any two of the flame retardant layer, the insulating layer, and the heat dissipation layer, wherein the adhesive layer comprises a flame-retardant inorganic filler in a binder resin, and 3 cm 2 A thermal runaway prevention sheet made of a cured adhesive composition, wherein the time taken from the moment a flame starts to burn until the moment combustion ends is less than 10 seconds after applying 1g to an area and radiating a flame with a 1200-degree torch. Claim 2 A thermal runaway prevention sheet according to claim 1, wherein a flame of 1000 to 1300°C is radiated onto one side of the thermal runaway prevention sheet and the temperature of the opposite side is maintained at 200°C or lower until 10 minutes have elapsed. Claim 3 In paragraph 2, the thermal runaway prevention sheet has a thickness (t5) of the heat dissipation layer of 0.1 to 1 mm. Claim 4 delete Claim 5 delete Claim 6 A thermal runaway prevention sheet according to claim 1, comprising: at least one insulating layer having a thickness t2 laminated on one surface of the heat dissipation layer and suppressing heat transfer; at least one flame retardant layer having a thickness t1 laminated on one surface of the heat dissipation layer or the insulating layer and protecting against flames; and at least one adhesive layer having a thickness t4, printed with an area of ​​30% or less of the area of ​​the heat dissipation layer, the insulating layer, or the flame retardant layer to bond any two of the heat dissipation layer, the insulating layer, or the flame retardant layer. Claim 7 In claim 6, a thermal runaway prevention sheet in which the sum of the thicknesses of each layer (t1+t2+t4+t5) is 0.5 to 6.0 mm. Claim 8 delete Claim 9 A thermal runaway prevention sheet according to claim 1, wherein the adhesive composition comprises: a binder resin comprising an epoxy resin and an acrylate resin; a filler dispersed in the binder; a curing agent having an amine-based or epoxy group; and a reactivity modifier comprising ethyl acetate or a halogenated organic compound, wherein the binder resin is included in an amount of 25 to 65 wt% of the total adhesive composition.

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