Composition for forming flame retardant coating layer of steel sheet, steel sheet, and method for manufacturing steel sheet

Abstract

A composition for forming a flame retardant coating layer of a steel sheet according to an embodiment of the present invention comprises 100 parts by weight of a resin, 1 to 100 parts by weight of silica, a composite oxide including two or more of Al, Si, Mg, and Fe in a total amount of 1 to 100 parts by weight, and 1 to 120 parts by weight of an inorganic flame retardant.

Description

Composition for forming a flame-retardant coating layer on a steel plate, steel plate and method for manufacturing a steel plate

[0001] One embodiment of the present invention relates to a composition for forming a flame-retardant coating layer on a steel plate, a steel plate, and a method for manufacturing a steel plate. More specifically, one embodiment of the present invention relates to a composition for forming a flame-retardant coating layer on a steel plate substrate for cans used as a cylindrical battery case for electric vehicles, which forms a flame-retardant coating layer to provide a flame-retardant effect in the event of high-temperature ignition caused by an abnormal increase in temperature within a battery cell, as well as to delay the transition to explosion due to thermal runaway.

[0002] With the recent rise in interest in eco-friendly energy, hybrid and electric vehicles utilizing batteries are garnering attention. In these cases, the battery is typically mounted in a battery pack, and the vehicle is powered by energy obtained from the pack. A battery pack consists of a battery module composed of multiple battery cells and a battery case that houses the battery module. Multiple battery cells within the pack are arranged in a stacked state to achieve high output. In various types of batteries, such as lithium batteries, phenomena of thermal runaway and ignition occur due to internal short circuits, overcharging, over-discharging, high-temperature environments, mechanical damage, and defects during the manufacturing process. In particular, as cases of fires caused by thermal runaway leading to material loss and human casualties frequently occur in the field of electric vehicles utilizing high-output lithium-ion batteries, the need for measures to prevent battery thermal runaway is increasing. Therefore, fire resistance of battery cells or battery packs, as well as heat resistance that prevents generated heat from dissipating to the outside, can be considered extremely important factors affecting safety. Inside a lithium-ion battery, a thin membrane called a separator is installed to prevent contact between the positive and negative electrodes. However, mechanical damage, high-temperature manufacturing defects in lithium plating, or other factors can damage this separator, potentially causing an internal short circuit. Thermal runaway is a phenomenon where a chain reaction occurs between the components within the battery cell; when the temperature rises abnormally, it forms a chain reaction in which chemical reactions occur sequentially inside. This chain reaction creates a cycle of temperature increase within the battery, and this cycle continues at extremely high temperatures until the battery is depleted.

[0003] To mitigate the risk of thermal runaway in such battery cans, a battery cell is disclosed in which at least a portion of the outer surface of the battery can is covered with a fire-resistant coating. Technology is known in which the fire-resistant coating is an ablative coating, an expansive coating, or an endothermic coating, or a polyurethane-based coating. However, when used in batteries, fire-resistant coatings fail to maintain their shape if ignition occurs, and they cannot be expected to exhibit sufficient fire resistance and thermal insulation for automotive applications.

[0004] One embodiment of the present invention provides a composition for forming a flame-retardant coating layer on a steel plate, a steel plate, and a method for manufacturing a steel plate. More specifically, one embodiment of the present invention provides a composition for forming a flame-retardant coating layer on a steel plate substrate for cans used as a cylindrical battery case for electric vehicles, which forms a flame-retardant coating layer on the substrate to provide a flame-retardant effect in the event of high-temperature ignition caused by an abnormal increase in temperature within a battery cell, as well as a steel plate for cans and a method for manufacturing a steel plate for cans.

[0005] A composition for forming a flame-retardant coating layer on a steel plate according to one embodiment of the present invention comprises 100 parts by weight of resin, 1 to 100 parts by weight of silica, 1 to 100 parts by weight of a composite oxide comprising two or more of Al, Si, Mg and Fe, and 1 to 120 parts by weight of an inorganic flame retardant.

[0006] A composition for forming a flame-retardant coating layer on a steel plate according to one embodiment of the present invention may further include 2 to 20 parts by weight of chromium oxide.

[0007] The resin may include one or more of epoxy resins, ester resins, melamine resins, siloxane resins, acrylic resins, phenolic resins, styrene resins, vinyl resins, ethylene resins, and urethane resins.

[0008] The resin may have an oxygen index of 20 or higher.

[0009] The average particle size of the silica can be 7 to 20 nm.

[0010] The composite oxide may include one or more of montmorillonite, kaolinite, illite, talc, and chlorite.

[0011] Inorganic flame retardants include aluminum hydroxide (Al(OH)3), antimony trioxide (Sb2O3), antimony pentoxide (Sb2O5), tin oxide (SnO2), zircon (ZrO2·SiO2), zirconia (ZrO2), boric acid (H3BO3), boron oxide (B2O3), zinc borate (2ZnO·2B2O3·3.5H2O), and ammonium polyphosphate ((NH4PO3) n (OH2)), molybdenum trioxide (MoO3), ammonium molybdenum oxide ((NH) 42 It may include one or more of Mo2O7), zinc molybdate (MoO4Zn), and calcium-zinc molybdate (Ca-Zinc Molybdate, Ca-MoO4Zn).

[0012] A steel plate according to one embodiment of the present invention comprises a steel plate substrate and a flame-retardant coating layer located on the surface of the steel plate substrate, wherein the flame-retardant coating layer comprises 100 parts by weight of resin, 1 to 100 parts by weight of silica, 1 to 100 parts by weight of a composite oxide comprising two or more of Al, Si, Mg and Fe, and 1 to 120 parts by weight of an inorganic flame retardant.

[0013] The flame-retardant coating layer may further include 2 to 20 parts by weight of chromium oxide.

[0014] A Ni plating layer may be interposed between the steel plate substrate and the flame-retardant coating layer.

[0015] A method for manufacturing a steel plate according to one embodiment of the present invention comprises the steps of: preparing a steel plate substrate; applying a composition for forming a flame-retardant coating layer to the surface of the steel plate substrate, comprising 100 parts by weight of resin, 1 to 100 parts by weight of silica, 1 to 100 parts by weight of a composite oxide comprising two or more of Al, Si, Mg and Fe, and 1 to 120 parts by weight of an inorganic flame retardant; and heat treating.

[0016] The composition for forming a flame-retardant coating layer may further include 2 to 20 parts by weight of chromium oxide.

[0017] It may further include a plating step of forming a Ni plating layer on a steel plate substrate.

[0018] The application step involves applying a composition for forming a flame-retardant coating layer at a concentration of 0.1 to 50.0 g / m² 2 It can be applied with an application amount of .

[0019] The heat treatment step can be performed at a temperature of 200 to 550°C for 10 to 200 seconds.

[0020] A composition for forming a flame-retardant coating layer according to one embodiment of the present invention improves flame-retardant properties and simultaneously possesses the characteristic of hindering combustion in the event of high-temperature ignition caused by abnormal phenomena of the electrolyte in the battery cell.

[0021] Therefore, it can significantly delay the thermal runaway phenomenon caused by abnormal temperature rise within the battery cell and significantly reduce the time for a rapid fire in the battery cell to spread to the main body.

[0022] FIG. 1 is a schematic diagram of a cross-section of a steel plate according to one embodiment of the present invention.

[0023] Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the present invention.

[0024] The technical terms used herein are for the reference of specific embodiments only and are not intended to limit the invention. The singular forms used herein include plural forms unless phrases clearly indicate otherwise. As used in the specification, the meaning of "comprising" specifies certain characteristics, areas, integers, steps, actions, elements, and / or components, and does not exclude the presence or addition of other characteristics, areas, integers, steps, actions, elements, and / or components.

[0025] When it is stated that one part is "above" or "on" another part, it may be directly above or on the other part, or other parts may be involved in between. In contrast, when it is stated that one part is "directly above" another part, no other parts are interposed in between.

[0026] Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

[0027] In one embodiment of the present invention, the meaning of including additional elements is that the remainder of iron (Fe) is replaced by an amount of the additional element.

[0028] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with relevant technical literature and the present disclosure, and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0029] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0030]

[0031] A composition for forming a flame-retardant coating layer of a steel sheet for a can according to one embodiment of the present invention comprises 100 parts by weight of resin, 1 to 100 parts by weight of silica, 1 to 100 parts by weight of a composite oxide comprising two or more of Al, Si, Mg and Fe, and 1 to 120 parts by weight of an inorganic flame retardant.

[0032] Each component is described in detail below. In one embodiment of the present invention, the weight part refers to a relative weight ratio based on 100 weight parts of resin, and is based on the solid content of each component. Solid content refers to the weight when each component is dried in a state free of volatile substances such as solvents. Specifically, assuming a heat treatment process when forming a flame-retardant coating layer, it refers to the weight remaining after heat treatment.

[0033]

[0034] Resin refers to a polymer compound and is a concept contrasted with monomer. Resin acts as a binder within the composition for forming a flame-retardant coating layer. If an appropriate amount of resin is not included, the adhesion of the flame-retardant coating layer may be compromised.

[0035] The resin may include one or more of epoxy resins, ester resins, melamine resins, siloxane resins, acrylic resins, phenolic resins, styrene resins, vinyl resins, ethylene resins, and urethane resins. More specifically, it may include one or more of polycarbonate, polyethylene terephthalate, acrylic-butadiene-styrene, and melamine resins. More specifically, it may include one or more of N-butylated melamine resin, iso-butylated melamine resin, methylated melamine, and urea-melamine resins. These resins are materials that minimize the emission of toxic substances even when the resin is burned.

[0036] The resin may be in an emulsion state with a number average molecular weight of 20,000 to 50,000, a Tg of 50 to 90 °C, and a solid fraction of 10 to 50%.

[0037] The resin may have an oxygen index of 20 or higher. Generally, the combustion characteristics of a resin are determined by its oxygen index; the higher the oxygen index, the more difficult combustion is, and the lower the value, the more easily combustion occurs. Therefore, flame retardancy can be further improved by using a resin with a high oxygen index. More specifically, the resin may have an oxygen index of 20 to 50.

[0038] A composition for forming a flame-retardant coating layer according to one embodiment of the present invention comprises 1 to 100 parts by weight of silica per 100 parts by weight of resin. The silica increases the strength and hardness of the flame-retardant coating layer itself through intramolecular network reactions during film drying after coating, thereby improving flame retardancy. Various types of silica can be used without limitation, and commercially available colloidal silica can also be used. More specifically, basic colloidal silica can be used.

[0039] Silica may be included in an amount of 1 to 100 parts by weight per 100 parts by weight of resin. If too little silica is added, the heat resistance improvement effect resulting from the addition of silica cannot be sufficiently obtained. If too much silica is added, the relative amount of resin decreases, which may lead to a decline in the adhesion of the flame-retardant coating layer. Specifically, silica may be included in an amount of 20 to 80 parts by weight per 100 parts by weight of resin, and more specifically, in an amount of 30 to 70 parts by weight per 100 parts by weight of resin. In this case, "parts by weight" refers to the relative weight based on the resin.

[0040] During the drying process of the film, silica undergoes a condensation reaction through a chain reaction of silica as shown in Reaction Scheme 1 below, forming a network structure such as -(HO-Si-O-Si)-n.

[0041] [Reaction Equation 1]

[0042] -(HO-Si-OH-) n + -(HO-Si-OH-) n = -(HO-Si-O-Si-OH) n + H2O (1)

[0043] However, using only such silica results in an overly uniform network structure, which limits the density of the flame-retardant coating layer. Consequently, there are limitations in imparting adhesion or flame retardancy between the steel substrate and the flame-retardant coating layer; to compensate for these insufficient physical properties, resins and composite oxides may be added.

[0044] The silica may be colloidal silica with an average particle size in the range of 7 to 20 nm. The composition may be prepared using a solution of silica with a solid fraction of 25 to 35 wt%. If the solid fraction is too small, a problem of reduced strength of the flame-retardant coating layer may occur. If the solid fraction is too large, a problem of reduced compatibility after manufacturing the coating agent may occur. More specifically, the solid fraction may be 28 to 32 wt%.

[0045] Silica is Na + The content may be 0.1 to 1.0 wt%. Na + If the content is too low, a problem may arise where the density of the film is reduced. Na + If the content is too high, an increase in cations within the coating agent may cause problems that impede the compatibility between components. More specifically, Na + The content may be 0.3 to 0.7 wt%.

[0046] A silica solution containing silica may have a pH of 9.5 to 10.5. If the pH is too low or too high, the pH difference of components other than silica in the coating composition may be extreme, and phase separation may occur. More specifically, the pH may be 9.5 to 10.0.

[0047] The silica may have a viscosity of 3.5 to 6.5 cp. If the viscosity is too low, problems may arise regarding the applicability of the coating composition. If the viscosity is too high, it may thicken during prolonged use, leading to aging problems. More specifically, the viscosity may be 4 to 6 cp. The viscosity can be measured using a Brookfield viscometer at a temperature of 20°C based on a 30% by weight silica solution.

[0048] The silica may have a specific gravity of 1.1 to 1.3. If the specific gravity is too low, it may be difficult to control the amount of coating composition applied. If the specific gravity is too high, sedimentation problems may occur after the coating agent is manufactured. More specifically, the specific gravity may be 1.15 to 1.25.

[0049] A composition for forming a flame-retardant coating layer according to one embodiment of the present invention comprises, in an amount of 1 to 100 parts by weight, a composite oxide comprising two or more of Al, Si, Mg, and Fe, per 100 parts by weight of resin. The composite oxide has a large difference in the coefficient of thermal expansion from the resin and silica, and thus plays a role in forming fine pores within the flame-retardant coating layer. These pores serve to provide a flame-retardant effect and slow down explosion propagation within the flame-retardant coating layer. If too little composite oxide is included, almost no pores are formed within the flame-retardant coating layer, and the flame-retardant effect and the effect of slowing down explosion propagation may be significantly reduced. If too much composite oxide is included, the solid fraction within the composition increases, which may cause aggregation and sedimentation phenomena between oxides. Specifically, 20 to 80 parts by weight of the composite oxide may be included per 100 parts by weight of resin. More specifically, 30 to 70 parts by weight of the composite oxide may be included per 100 parts by weight of resin.

[0050] A composite oxide containing two or more of Al, Si, Mg, and Fe may include one or more of montmorillonite, kaolinite, illite, talc, and chlorite. More specifically, montmorillonite (Montmorillonite, M x (Al 4-x Mg x )Si8O 20 It may include (OH)4).

[0051] Composite oxides containing two or more of Al, Si, Mg, and Fe have an average particle size of 10 2 nm to 10 5 It can be nm. If the average particle size of the complex oxide is too small, it is difficult to disperse evenly in the solution due to the electrostatic attraction of the particles themselves; conversely, if the average particle size is too large, precipitation occurs rapidly within the solution, making it difficult to achieve proper performance. The average particle size can be measured by dispersing the particles within the composition and using a laser scattering method.

[0052] A composition for forming a flame-retardant coating layer according to one embodiment of the present invention may include 1 to 120 parts by weight of an inorganic flame retardant per 100 parts by weight of resin. By adding an inorganic flame retardant that simultaneously possesses heat resistance and flame retardancy, combustion caused by chemical reactions between battery components can be hindered, thereby preventing the spread of fire or, even if a fire occurs, significantly slowing down its speed.

[0053] Inorganic flame retardants include aluminum hydroxide (Al(OH)3), antimony trioxide (Sb2O3), antimony pentoxide (Sb2O5), tin oxide (SnO2), zircon (ZrO2·SiO2), zirconia (ZrO2), boric acid (H3BO3), boron oxide (B2O3), zinc borate (2ZnO·2B2O3·3.5H2O), and ammonium polyphosphate ((NH4PO3) n (OH2)), molybdenum trioxide (MoO3), ammonium molybdenum oxide ((NH) 42 It may include one or more of Mo2O7), zinc molybdate (MoO4Zn), and calcium-zinc molybdate (Ca-Zinc Molybdate, Ca-MoO4Zn). More specifically, it may include one or more of aluminum hydroxide, magnesium oxide, and zinc borate.

[0054] Aluminum hydroxide, a representative inorganic flame retardant, exhibits flame retardancy through a physical flame retardant mechanism that acts as an endothermic reaction in which dehydration occurs at temperatures above 200°C, thereby cooling the solid phase and blocking flammable gases and fuel dilution through the generation of water vapor.

[0055] [Reaction Equation 2]

[0056] 2Al(OH)3→ Al2O3+ 3H2O (180 ~ 300 ℃, -1075 KJ / kg)

[0057] 2AlOOH → Al2O3+ H2O (400~450 ℃, -700 KJ / kg)

[0058] In addition, magnesium oxide (MgO) introduced in the present invention exhibits a flame-retardant effect through the following chemical reaction.

[0059] [Reaction Equation 3]

[0060] MgO + H2O → Mg(OH)2 (at room temperature)

[0061] Mg(OH)2→ MgO + H2O (300~490 ℃, -1220 KJ / kg)

[0062] Mg(OH)2 is a flame retardant that is stably used in plastic processing due to its high thermal decomposition temperature. The combustion gas suppression and flame retardation mechanism is as shown in Reaction Equation 3, and it exhibits a flame retardant effect by showing a dehydration reaction in the 300 to 490°C range when the battery temperature rises abnormally.

[0063] As shown in reaction equations 2 and 3, Mg(OH)2 has a decomposition initiation temperature that is more than 100°C higher than that of Al(OH)3, so different flame-retardant effects can be expected depending on the temperature difference. In particular, when the two are used in combination, in addition to sequential flame-retardant effects depending on temperature, complementary effects can be achieved in suppressing the rise in material temperature, reducing surface heat release, raising the ignition point, extending the ignition time, increasing the oxygen index, and promoting carbonization.

[0064] In addition to aluminum hydroxide and magnesium oxide, antimony-based and zinc-based flame retardants may also be used. Since the reaction between Sb2O3 and HCl is an endothermic reaction, it provides a cooling effect, and the reactant SbCl3 acts as a radical interceptor. Furthermore, SbOCl and SbCl3 keep halogens in the gaseous phase for longer, enhancing the reaction with H or OH radicals generated during a battery fire, which can significantly delay thermal runaway.

[0065] In addition, zinc borate (2ZnO·2B2O3·3.5H2O) can exhibit excellent flame retardant effects when introduced together with aluminum hydroxide as a halogen-free flame retardant (Reaction Formula 4), having characteristics such as suppressing smoke generation during battery fires and rapidly charring the burned resin.

[0066] [Reaction Equation 4]

[0067] 2ZnO·2B2O3·3.5H2O + HCl → ZnCl2+ B2O3+ H2O

[0068] 2ZnO·2B2O3·3.5H2O + Al(OH)3→ xAl2O3·yB2O3·zZnO + H2O

[0069] If too little inorganic flame retardant is included, it is difficult to obtain a sufficient combustion inhibition effect on oxide substances in the battery. If too much inorganic flame retardant is included, it may impede the battery charging and discharging effect. More specifically, 30 to 110 parts by weight of inorganic flame retardant may be included.

[0070] Chromium oxide may be additionally added to enhance the corrosion resistance of the flame-retardant coating layer and to neutralize silica. When chromium oxide is additionally included, it may be included in an amount of 2 to 20 parts by weight per 100 parts by weight of resin. If too little chromium oxide is included, the effect of enhancing corrosion resistance may not be sufficient, and it may also be difficult to properly perform the role of neutralizing silica. If too much chromium oxide is included, a problem may arise where the viscosity of the composition increases rapidly. Specifically, chromium oxide may be included in an amount of 5 to 15 parts by weight per 100 parts by weight of resin.

[0071] In addition to the aforementioned components, the composition for forming a flame-retardant coating layer may further include a solvent, and the addition of additional components is not limited. The solvent serves to facilitate the application of the composition and to uniformly disperse the components. The amount of solvent is not particularly limited, but may be included in an amount of 100 to 1,000 parts by weight per 100 parts by weight of resin.

[0072] FIG. 1 shows a schematic cross-sectional view of a steel plate (100) for a can according to one embodiment of the present invention. As shown in FIG. 1, the steel plate (100) for a can according to one embodiment of the present invention includes a steel plate substrate (10) and a flame-retardant coating layer (20) located on the steel plate substrate (10).

[0073] The steel plate substrate (10) can be any steel plate substrate (10) used in general can steel plates (100) without limitation. In one embodiment of the present invention, since the main configuration is to form a flame-retardant coating layer (20) of a special component on the steel plate substrate (10), a detailed description of the steel plate substrate (10) is omitted.

[0074] Additionally, the composition of the steel plate substrate (10) is described as follows.

[0075] The steel sheet substrate may contain, in weight percent, C: 0.02 to 0.07%, Si: 0.05% or less, Mn: 0.1 to 0.4%, Al: 0.01 to 0.06%, P: 0.02% or less, S: 0.015% or less, N: 0.006% or less, Mo: 0.02 to 0.15%, and the remainder being Fe and other unavoidable impurities. Since the description of each component of the steel sheet substrate (10) is the same as generally known, a detailed description is omitted.

[0076] A Ni plating layer (11) may be present on the steel plate substrate (10) to help secure corrosion resistance against the battery electrolyte and the atmosphere. That is, a Ni plating layer (11) may be interposed between the steel plate substrate (10) and the flame-retardant coating layer (20).

[0077] The thickness of the flame-retardant coating layer (20) can be 0.1 to 200 μm. If the thickness of the flame-retardant coating layer (20) is too thin, it is difficult to secure appropriate flame retardancy and heat resistance. If the thickness of the flame-retardant coating layer (20) is too thick, the total volume and weight of the can may increase. In one embodiment of the present invention, appropriate flame retardancy and heat resistance can be secured even if a thin flame-retardant coating layer (20) is formed. More specifically, the thickness of the flame-retardant coating layer (20) can be 1 to 100 μm.

[0078] The flame-retardant coating layer (20) may maintain the solid component and content ratio within the composition for forming the flame-retardant coating layer described above. Specifically, the flame-retardant coating layer (20) comprises 100 parts by weight of resin, 1 to 100 parts by weight of silica, 1 to 100 parts by weight of a composite oxide containing two or more of Al, Si, Mg, and Fe, and 1 to 120 parts by weight of an inorganic flame retardant. Since the reasons for limiting each component and its content are the same as those explained in the composition described above, a redundant explanation is omitted.

[0079] In addition, the flame-retardant coating layer (20) may further include 2 to 20 parts by weight of chromium oxide.

[0080] A method for manufacturing a steel sheet for a can according to one embodiment of the present invention may include the steps of: preparing a steel sheet substrate; applying a composition for forming a flame-retardant coating layer to the surface of the steel sheet substrate, comprising 100 parts by weight of resin, 1 to 100 parts by weight of silica, 1 to 100 parts by weight of a composite oxide comprising two or more of Al, Si, Mg, and Fe, and 1 to 120 parts by weight of an inorganic flame retardant; and heat treating.

[0081] It may further include a plating step of forming a Ni plating layer on a steel plate substrate.

[0082] First, a composition for forming a flame-retardant coating layer is applied onto a steel plate substrate. If a plating step is further included, the composition for forming a flame-retardant coating layer can be applied onto a Ni plating layer.

[0083] As the steel plate substrate and the composition for forming the flame-retardant coating layer are the same as those previously described, a repetitive explanation is omitted.

[0084] The composition for forming a flame-retardant coating layer before application can be maintained at a temperature of 10 to 30°C. If the temperature is lower than the aforementioned range, the viscosity increases, making it difficult to manage a uniform application amount. If the temperature is too high, the gelation phenomenon of the composition for forming a flame-retardant coating layer is accelerated, which may degrade the surface quality. More specifically, the composition for forming a flame-retardant coating layer before application can be maintained at a temperature of 15 to 25°C.

[0085] When applying a composition for forming a flame-retardant coating layer, the application amount is 0.1 to 50.0 g / m² 2 It can be applied within a specified range. If the application amount is too high, the flame-retardant coating layer becomes too thick, which may increase adhesion to the steel substrate and the overall weight and volume of the can. If the application amount is too low, the heat resistance and flame retardancy imparted by the flame-retardant coating layer may be weakened. More specifically, the application amount is 5.0 to 25.0 g / m² 2 It may be. The composition may be applied only to the inner surface of the can.

[0086] The heat treatment step can be performed at a temperature of 200 to 550°C for 10 to 200 seconds.

[0087]

[0088] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention, and the present invention is defined only by the scope of the claims set forth below.

[0089]

[0090] Experimental Example: Confirmation of properties according to metal type

[0091] A steel plate for cans plated with Ni on one side was prepared as a test material.

[0092] A composition for forming a flame-retardant coating layer was prepared comprising the components summarized in Table 1 below and 100 parts by weight of water. The composition for forming the flame-retardant coating layer was applied to the test material at a rate of 10 g / m² 2 After coating, the specimen was prepared by drying at 450°C for 30 seconds. Silica with an average particle size of 12 nm was used as the silica, and 100 parts by weight of a melamine-based emulsion resin (number average molecular weight 25,000, Tg 78°C, solid fraction 35%, oxygen index: 35) was used as the resin.

[0093] Evaluation Method for Heat Resistance and Flame Retardancy: A battery shape was completed by laminating materials such as a positive electrode, negative electrode, and separator inside a battery can coated with the aforementioned coating agent on its inner surface, and then injecting an electrolyte. Thermal runaway was induced by connecting a heating plate to the outer surface of the battery can to heat it. The heating plate, used as an external heat source, was set to heat at a temperature rise rate of approximately 6°C / min. A 70 Ah capacity battery can was placed on top of the heating plate, and K-Type thermocouples were attached to the outer and inner surfaces of the battery to record temperature changes. A Yokogawa MV1000 was used as the data collector for temperature measurement, and the effect of the flame-retardant coating agent was verified by measuring the rapid temperature change inside the battery and the ignition time (min). The battery temperature was measured at the point 20 minutes after heating the battery can at a temperature rise rate of 6°C / min using an external heat source. The ignition time was measured at the point when the internal temperature reached 270°C or higher.

[0094] Specimen Silica Composite Oxide Inorganic Flame Retardant Content (Parts by Weight) Type Content (Parts by Weight) Type Content (Parts by Weight) 150 Montmorillonite 50 Aluminum Hydroxide 50 250 Montmorillonite 50 Aluminum Hydroxide 100 350 Kaolinite 50 Aluminum Hydroxide (50%) + Magnesium Oxide (50%) 50 450 Kaolinite 50 Aluminum Hydroxide (50%) + Magnesium Oxide (50%) 100 550 Illite 50 Magnesium Oxide (50%) + Zinc Borate (50%) 50 650 Illite 50 Magnesium Oxide (50%) + Zinc Borate (50%) 100 750 Talc 50 Aluminum Hydroxide (30%) + Magnesium Oxide (30%) + Zinc Borate (40%) 50 850 Talc 50 Aluminum Hydroxide (30%) + Magnesium Oxide (30%) + Zinc Borate (40%) 100 90.5 Chilite 50 Aluminum Hydroxide 50 10 130 Chilite 50 Aluminum Hydroxide 100 11 50 Montmorillonite 0.5 Aluminum Hydroxide 50 12 50 Montmorillonite 130 Aluminum Hydroxide 100 13 50 Talc 50 - Not Added 14 50 Talc 50 Aluminum Hydroxide 0.5 15 50 Talc 50 Aluminum Hydroxide 130

[0095] Sample Battery Temperature (°C / 20 min) Ignition Time 113 2 26 min 51 sec Example 2 124 28 min 6 sec Example 3 126 27 min 38 sec Example 4 12 1 28 min 3 sec Example 5 12 2 28 min 2 sec Example 6 12 2 28 min 37 sec Example 7 13 1 29 min 59 sec Example 8 11 5 31 min 3 sec Example 9 21 6 23 min 01 sec Comparative Example 10 228 22 min 59 sec Comparative Example 11 239 22 min 12 sec Comparative Example 12 232 22 min 25 sec Comparative Example 13 220 20 min 30 sec Comparative Example 14 20 2 22 min 32 sec Comparative Example 15 198 23 min 57 sec Comparative Example

[0096]

[0097] As can be seen in Tables 1 and 2, in the case of the examples in which each component in the composition for forming the flame-retardant coating layer is appropriately included, it can be confirmed that heat resistance and flame retardancy are improved.

[0098] On the other hand, it can be confirmed that the comparative example, which does not contain the appropriate components, has inferior heat resistance and flame retardancy.

[0099]

[0100] The present invention is not limited to the above embodiments and can be manufactured in various different forms, and those skilled in the art will understand that the invention can be implemented in other specific forms without changing the technical concept or essential features of the invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

[0101] [Explanation of the symbol]

[0102] 100: Steel sheet for cans, 10: Steel sheet material,

[0103] 11: Ni plating layer, 20: Flame retardant coating layer

Claims

1. 100 parts by weight of resin, 1 to 100 parts by weight of silica, A composite oxide comprising two or more of Al, Si, Mg, and Fe in an amount of 1 to 100 parts by weight and A composition for forming a flame-retardant coating layer on a steel plate comprising 1 to 120 parts by weight of an inorganic flame retardant.

2. In Paragraph 1, A composition for forming a flame-retardant coating layer on a steel plate, further comprising 2 to 20 parts by weight of chromium oxide.

3. In Paragraph 1, The above resin is a composition for forming a flame-retardant coating layer on a steel plate comprising one or more of epoxy resin, ester resin, melamine resin, siloxane resin, acrylic resin, phenolic resin, styrene resin, vinyl resin, ethylene resin, and urethane resin.

4. In Paragraph 1, The above resin is a composition for forming a flame-retardant coating layer on a steel plate having an oxygen index of 20 or higher.

5. In Paragraph 1, A composition for forming a flame-retardant coating layer on a steel plate, wherein the average particle size of the silica is 7 to 20 nm.

6. In Paragraph 1, The above composite oxide is a composition for forming a flame-retardant coating layer on a steel sheet comprising one or more of montmorillonite, kaolinite, illite, talc, and chlorite.

7. In Paragraph 1, The above-mentioned inorganic flame retardants are aluminum hydroxide (Al(OH)3), antimony trioxide (Sb2O3), antimony pentoxide (Sb2O5), tin oxide (SnO2), zircon (ZrO2·SiO2), zirconia (ZrO2), boric acid (H3BO3), boron oxide (B2O3), zinc borate (2ZnO·2B2O3·3.5H2O), and ammonium polyphosphate ((NH4PO3) n (OH2)), molybdenum trioxide (MoO3), ammonium molybdenum oxide ((NH) 42 A composition for forming a flame-retardant coating layer on a steel sheet comprising one or more of Mo2O7), zinc molybdate (MoO4Zn), and calcium-zinc molybdate (Ca-Zinc Molybdate, Ca-MoO4Zn).

8. Steel plate substrate and It includes a flame-retardant coating layer located on the surface of the above-mentioned steel plate substrate, and The above flame-retardant coating layer comprises 100 parts by weight of resin, 1 to 100 parts by weight of silica, 1 to 100 parts by weight of a composite oxide containing two or more of Al, Si, Mg, and Fe, and 1 to 120 parts by weight of an inorganic flame retardant, for a steel plate.

9. In Paragraph 8, The above flame-retardant coating layer is a steel plate further comprising 2 to 20 parts by weight of chromium oxide.

10. In Paragraph 8, A steel plate having a Ni plating layer interposed between the above steel plate substrate and the above flame-retardant coating layer.

11. Step of preparing the steel plate substrate; A step of applying a composition for forming a flame-retardant coating layer to the surface of the above-mentioned steel plate substrate, comprising 100 parts by weight of resin, 1 to 100 parts by weight of silica, 1 to 100 parts by weight of a composite oxide comprising two or more of Al, Si, Mg, and Fe in total amount, and 1 to 120 parts by weight of an inorganic flame retardant; and A method for manufacturing a steel plate including a heat treatment step.

12. In Paragraph 11, A method for manufacturing a steel plate, wherein the composition for forming the flame-retardant coating layer further comprises 2 to 20 parts by weight of chromium oxide.

13. In Paragraph 11, A method for manufacturing a steel plate, further comprising a plating step of forming a Ni plating layer on the above-mentioned steel plate substrate.

14. In Paragraph 11, The above-mentioned application step involves applying a composition for forming a flame-retardant coating layer at a concentration of 0.1 to 50.0 g / m² 2 A method for manufacturing a steel plate by applying a coating amount.

15. In Paragraph 11, A method for manufacturing a steel plate in which the heat treatment step is performed at a temperature of 200 to 550℃ for 10 to 200 seconds.

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