Coating composition having heat insulating properties and coated metal sheet using the same

Abstract

The present invention provides a coating composition comprising a polymer resin; foam capsules; a plasticizer; and silica, wherein the coating composition comprises 0.1 to 10 parts by weight of the foam capsules; 5 to 40 parts by weight of the plasticizer; and 1 to 10 parts by weight of the silica, relative to 100 parts by weight of the polymer resin, the foam capsules being in the form of foam capsules containing a foaming agent within a thermoplastic plastic cell structure, and the weight ratio of the foam capsules to silica is 1:1 to 1:10. The coating composition also provides a coated metal sheet using the same.

Description

[Technical Field]

[0001] The present invention relates to a coating composition that has heat insulating properties due to closed pores formed by foaming, and to a dew condensation prevention steel plate having heat insulating properties, which is formed by applying the coating composition to a base metal plate and is used as the outer panels of home appliances, roofing materials for residential or factory buildings, walls, etc. [Background technology]

[0002] Condensation, as shown in Figure 1, refers to the phenomenon in which water droplets form on the surface of a home appliance such as a refrigerator or air conditioner, which has a large temperature difference between the inside and outside, or on the surface of an interior wall facing the outside, or on the interior surface of a structure such as a roof, when there is a large temperature difference between the inside and outside of a building in winter.

[0003] When condensation occurs in home appliances, buildings, and structures, it can cause mold to grow on the walls, freeze, and other phenomena, damaging the building structure.In the case of structures such as roofing materials for product production buildings, water droplets caused by condensation can fall inside the building and cause damage to products, etc.

[0004] Therefore, it is necessary to keep the living space comfortable and minimize energy loss, while preventing condensation to prevent interior and exterior materials of buildings from rotting or being damaged by moisture and to prevent losses in product production processes.

[0005] Generally, roofing materials and walls of buildings are made of highly insulating materials such as stone and wood, but steel is used for roofing materials of factories, other livestock barns, and temporary buildings for their ease and speed of construction and maintenance. However, steel requires additional insulation treatment because condensation and heat loss frequently occur due to the high thermal conductivity of metal.

[0006] Conventionally, various methods have been used to prevent condensation, including the use of adhesive to attach a 4-6mm thick insulating material such as sponge-like polyethylene to the steel plate. However, this method has had problems in practical use due to the limited adhesive strength of the adhesive and the complicated process.

[0007] In some cases, porous inorganic particles or glass beads are added to the polymer resin solution to prevent condensation through the pore effect. However, in such cases, when the steel sheet is wound into a coil using a continuous production method like steel, the glass beads can crack under the weight of the steel, resulting in the loss of insulation and anti-condensation effects. Furthermore, the addition of excessive inorganic particles or glass beads can make the coating hard, which can lead to cracking during press or bending processes. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2001-270031 Summary of the Invention [Problem to be solved by the invention]

[0009] Therefore, in order to solve the above problems, an object of one embodiment of the present invention is to provide a coating composition that contains a foaming agent in capsule form and has heat insulating properties due to closed pores formed by foaming of the foaming agent.

[0010] Another embodiment of the present invention is to provide a coated metal sheet coated with the above-described coating composition having heat insulating properties. [Means for solving the problem]

[0011] According to one embodiment of the present invention, there is provided a coating composition comprising a polymer resin; foam capsules; a plasticizer; and silica, wherein the coating composition comprises 0.1 to 10 parts by weight of the foam capsules; 5 to 40 parts by weight of the plasticizer; and 1 to 10 parts by weight of the silica, relative to 100 parts by weight of the polymer resin, the foam capsules being in the form of foam capsules containing a foaming agent within a thermoplastic cell structure, and the weight ratio of the foam capsules to the silica is 1:1 to 1:10.

[0012] According to another embodiment of the present invention, there is provided a coated metal sheet comprising a base metal sheet and an anti-condensation layer on at least one surface of the base metal sheet, wherein the anti-condensation layer comprises a porous coating layer and a pretreatment layer between the base metal sheet and the porous coating layer, and the porous coating layer contains the coating composition and has closed pores. [Effects of the Invention]

[0013] The coating film formed from the coating composition of the present invention contains closed pores formed by the foaming of the foaming agent contained inside the foam capsules, which minimizes the temperature difference between the inside and outside and prevents condensation. It also has an insulating effect by blocking external heat and cold and conversely preventing internal heat and cold from escaping, thereby saving energy.

[0014] In addition, the anti-condensation layer containing the coating composition according to the present invention has high emissivity and strength, and at the same time, has corrosion resistance that prevents corrosion of the base metal plate. [Brief explanation of the drawings]

[0015] [Figure 1] This is a diagram showing the principle behind the condensation phenomenon. [Figure 2] 1 is a cross-sectional view schematically showing a cross section of a coated metal sheet coated with a coating composition of the present invention. [Figure 3] 1 is a diagram illustrating the principle by which a coated metal sheet coated with the coating composition of the present invention exhibits a heat insulating effect. [Figure 4] 1 is a schematic diagram showing a method for evaluating the dew condensation prevention effect of the coating composition of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention may be modified in various ways, and the scope of the present invention is not limited to the following embodiments.

[0017] According to an embodiment of the present invention, there is provided a coating composition including a polymer resin, foam capsules, a plasticizer, and silica. A coating formed from the coating composition can form closed pores due to foaming of the foaming agent contained inside the foam capsules.

[0018] The coating composition according to one embodiment of the present invention may include, based on 100 parts by weight of the polymer resin, 0.1 to 10 parts by weight of the foam capsules; 5 to 40 parts by weight of the plasticizer; and 1 to 10 parts by weight of the silica.

[0019] More specifically, the coating composition of the present invention may contain, based on 100 parts by weight of the polymer resin, 0.1 to 5 parts by weight of the foam capsules; 10 to 30 parts by weight of the plasticizer; and 1 to 10 parts by weight of the silica.

[0020] The foam capsule may be in the form of a foam capsule containing a foaming agent in a thermoplastic cell structure, and the weight ratio of the foam capsule to silica may be 1:1 to 1:10.

[0021] More specifically, the weight ratio of the foam capsules to the silica may be 1:2 to 1:10.

[0022] More specifically, the weight ratio of the foam capsules to silica may be 1:2 to 1:5.

[0023] Each component of the coating composition of the present invention will now be described in more detail.

[0024] <Polymer resin> The polymer resin included in the coating composition according to an embodiment of the present invention may be a polyvinyl chloride resin that can be used to form a thick coating film using a liquid coating solution.

[0025] The polymer resin can be a polyvinyl chloride resin having a molecular weight of 3,000 to 6,000. If the molecular weight of the polymer resin is less than 3,000, the weather resistance of the coating layer may be reduced, and if the molecular weight is more than 6,000, the viscosity may increase sharply, reducing coating workability. In addition to polyvinyl chloride resin, the polymer resin can also be a polyurethane-based resin, but is not limited thereto.

[0026] <Plasticizer> The coating composition according to one embodiment of the present invention may include a plasticizer for adjusting the viscosity and workability of the polymer resin made of polyvinyl chloride.

[0027] The plasticizer used in the polyvinyl chloride resin may be one or more selected from the group consisting of bis(2-propylheptyl)phthalate (DPHP), bis(2-ethylhexyl)adipate (DEHA), dimethyl adipate (DMAD), monomethyl adipate (MMAD), dioctyl adipate (DOA), dibutyl sebacate (DBS), dibutyl maleate (DBM), diisobutyl maleate (DIBM), and trimethyl tert-butyl diisobutyrate.

[0028] The plasticizer may be included in an amount of 5 to 40 parts by weight, more preferably 10 to 30 parts by weight, based on 100 parts by weight of the polymer resin. If the plasticizer content is less than 5 parts by weight, the viscosity of the polyvinyl chloride solution may be too high, which may reduce workability, while if it exceeds 40 parts by weight, the viscosity may be too low or the coating film may be too brittle, making it difficult to maintain as an anti-condensation coating film for steel sheets.

[0029] <Foam capsule and silica> The coating composition according to one embodiment of the present invention may include foam capsules, which may contain a foaming agent within a thermoplastic cell structure.

[0030] The thermoplastic plastic forming the outer plastic cell structure of the foam capsule is an acrylonitrile copolymer-based plastic, more specifically, it can be made from a styrene-acrylonitrile copolymer, but is not limited thereto.

[0031] The foaming agent contained in the foam capsule may be azodicarbonamide (ADCA), p,p'-oxybisbenzenesulfonylhydrazide (OBSH), hydrazodicarbonamide (HDCA), dinitrosopentamethylenetetramine (DPT), etc., and preferably, an azodicarbonamide (ADCA)-based foaming agent may be used, but is not limited thereto.

[0032] The foam capsules mentioned above have a minimum of 200kg / cm after the foaming process. 2 It is preferable that the material can withstand a load of 200 kg / cm. 2 If the coating cannot support the load, the closed pores after coating production will not be able to support the load of the steel plate, which may result in pore destruction and weakened thermal insulation performance.

[0033] The average particle size of the foam capsules may be 1 to 20 μm. If the average particle size of the foam capsules is less than 1 μm, the size of the closed pores after foaming may be too small, making it difficult to obtain the insulating effect of the pores. On the other hand, if the average particle size of the foam capsules is more than 20 μm, the size of the closed pores after foaming may be too large, reducing the toughness of the coating film and causing a problem of deterioration in the physical properties of the coating film during processing.

[0034] In a coating composition according to one embodiment of the present invention, the foam capsules may be included in an amount of 0.1 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, and even more preferably 1 to 5 parts by weight, based on 100 parts by weight of the polymer resin. If the amount is less than 0.1 part by weight, closed pore formation due to foaming may be insufficient, resulting in poor heat insulation performance. If the amount is more than 10 parts by weight, the viscosity of the solution may increase during solution preparation, making the coating process difficult.

[0035] The coating composition according to one embodiment of the present invention may further include silica to improve the strength and emissivity of the coating, and the silica may be in the form of silica powder. In addition to silica, at least one of calcium carbonate (CaCO), titanium dioxide (TiO), and magnesium hydroxide (Mg(OH)) may also be used.

[0036] The average particle size of the silica powder may be 10 to 25 μm. If the average particle size of the silica is less than 10 μm, an excessive amount of silica is added to achieve the desired gloss, which may result in high viscosity and increased costs. If the average particle size exceeds 25 μm, the surface of the coating film may be too rough.

[0037] In a coating composition according to one embodiment of the present invention, the silica may be included in an amount of 1 to 10 parts by weight based on 100 parts by weight of the polymer resin. If it is included in an amount of less than 1 part by weight, it will not have an effect on improving the emissivity and strength of the coating, and if it is included in an amount of more than 10 parts by weight, the brittleness of the coating may increase, making it difficult to process and inhibiting the foaming properties of the coating.

[0038] In the coating composition of the present invention, the foam capsules and silica may be contained in a weight ratio of 1:1 to 1:10, more preferably 1:2 to 1:10, more preferably 1:2 to 1:8, and even more preferably 1:2 to 1:5.

[0039] If the weight ratio of silica to foam capsules is less than 1:1, foaming is relatively efficient, but the silica content is insufficient, making it difficult to expect an improvement in emissivity and the hardness of the coating film may become brittle.If it exceeds 1:10, the excessive silica makes the coating hardness too high, increasing the brittleness of the coating film and making it difficult to process, and limiting the formation of closed pores.

[0040] <Additives> The coating composition according to one embodiment of the present invention may contain other additives. Specific substances contained in the additives and their contents are generally known in the art and can be appropriately selected by a paint engineer when preparing the coating material. The type and content of the additives are not particularly limited.

[0041] For example, the additives may include one or more of pigments, antifoaming agents, leveling agents, dispersants, flame retardants, and UV stabilizers, and may be added in an amount of 1.0 to 10 parts by weight based on 100 parts by weight of the polymer resin, as needed.

[0042] In the coating composition according to one embodiment of the present invention, a pigment having a specific hue may be used as an additive for aesthetic purposes. The pigment may be black, red, yellow, or white pigments mixed in a predetermined mixing ratio to realize various hues.

[0043] Examples of the black pigment include carbon black, carbon nanotubes, graphite, and graphene, and may include at least one selected from the group consisting of ferric oxide (Fe2O3), titanium dioxide (TiO2), carbon black, carbon nanotubes, graphite, and graphene. An example of a red pigment is ferric oxide (Fe2O3). An example of a white pigment is titanium dioxide (TiO2). An example of a yellow pigment is strontium chromate.

[0044] The coating composition of the present invention may contain a solvent to adjust the viscosity. The solvent may be, for example, one or more solvents selected from the group consisting of toluene, xylene, isopropanol, solvent naphtha, cellosolve, cellosolve acetate, and butyl cellosolve. The solvent may be one or a mixture of two or more solvents. The content of the solvent added to the composition is not particularly limited and can be adjusted as needed to adjust the viscosity of the coating composition.

[0045] <Painted metal plate> According to another embodiment of the present invention, there is provided a coated metal sheet comprising a base metal sheet and an anti-condensation layer having thermal insulation properties on at least one surface of the base metal sheet. The anti-condensation layer may comprise a porous coating layer and a pretreatment layer between the base metal sheet and the porous coating layer. The porous coating layer is formed from a coating coated with the coating composition of the present invention and may include closed pores formed by foaming of a foaming agent contained within foam capsules of the coating composition of the present invention.

[0046] The coated metal sheet according to one embodiment of the present invention includes the porous coating layer in which closed pores are formed by the coating composition of the present invention, and therefore not only can it minimize the temperature difference between the outside and the inside to prevent condensation, as shown in Figure 3, but it also has an insulating effect of blocking external heat and cold and conversely preventing internal heat and cold from escaping, thereby achieving energy savings. Furthermore, the coated metal sheet of the present invention can have excellent corrosion resistance, high emissivity, and strength due to the condensation prevention layer including the porous coating layer formed on at least one surface of the base metal sheet.

[0047] Hereinafter, a coated metal sheet according to an embodiment of the present invention will be described in more detail with reference to FIG.

[0048] A coated metal plate according to an embodiment of the present invention may include a base metal plate and a dew condensation prevention layer formed on one or both sides of the base metal plate.

[0049] The coated metal sheet can be produced by applying a composition for forming the pretreatment layer to a base metal sheet, drying the composition, and then applying the coating composition thereon. In this case, the formation of pores by foaming of the foam capsules can be performed during drying and curing after coating the coating composition. The foaming, drying, and curing can be performed simultaneously.

[0050] The base metal plate may be one selected from the group consisting of cold-rolled steel plate, hot-rolled steel plate, galvanized steel plate, zinc alloy-plated steel plate, aluminum plate, and stainless steel, but is not limited thereto.

[0051] The thickness of the base metal plate may be, but is not limited to, 0.25 mm to 4.5 mm.

[0052] The anti-condensation layer may include a porous coating layer containing the coating composition of the present invention, and a pretreatment layer formed between the base metal plate and the porous coating layer to enhance the corrosion resistance of the base metal plate and the coating adhesion between the base metal plate and the porous coating layer.

[0053] The composition for forming the pretreatment layer may be an acrylic resin, an epoxy resin, a phenolic resin, a xylene resin, a polyester resin, a urethane resin, or the like, and preferably an acrylic resin. The acrylic resin may be, but is not limited to, a urethane acrylate or an epoxy acrylate.

[0054] The thickness of the pretreatment layer may be 0.1 to 1 μm. If the thickness of the pretreatment layer is less than 0.1 μm, the adhesion to the porous coating layer applied on the pretreatment layer may be insufficient, and if the thickness of the pretreatment layer is more than 1 μm, an excessive amount of resin composition may be required for the pretreatment layer treatment, which may be uneconomical.

[0055] The thickness of the porous coating layer may be 50 to 400 μm. If the thickness of the porous coating layer is less than 50 μm, the heat insulation, anti-condensation and energy saving effects may be weakened, and conversely, if the thickness exceeds 400 μm, the coating layer may become too thick, making it difficult to process the coated metal sheet, and the production may be uneconomical due to excessive costs.

[0056] The closed pores may have an average diameter of 5 to 50 μm. If the average diameter of the closed pores is less than 5 μm, the pore size is too small and it is difficult to obtain the insulating effect of the pores, and if the average diameter of the closed pores is more than 50 μm, the pore size in the coating film becomes too large, which may reduce the strength of the coating film and cause problems with the physical properties of the coating film during processing.

[0057] The porous coating layer may include closed pores formed by applying and foaming the coating composition according to one embodiment of the present invention.

[0058] More specifically, the coating composition according to one embodiment of the present invention may be applied to a base metal sheet, and then dried and cured at 185 to 240°C. The closed pores may be formed by the foam capsules contained in the coating composition of the present invention foaming during drying and curing.

[0059] If the drying and curing temperature is less than 185°C, the degree of foaming will be weak and the average diameter of closed pores will be small, which may make it difficult to obtain the insulating effect of the pores.If the drying and curing temperature is more than 240°C, the average diameter of closed pores may exceed 50μm or the foam capsules may be destroyed, causing the pores to open.

[0060] To produce a coated metal sheet according to one embodiment of the present invention, the coating composition of the present invention and / or the composition for forming the pretreatment layer can be applied to the base metal sheet by a conventionally known method. For example, flow coating, roll coating, curtain coating, knife coating, spin coating, bar coating, etc. can be used. Also, spraying, airless spraying, air spraying, brush coating, etc. can be used. These application methods can be automated, or manual application is also possible. [Example]

[0061] <Example> Examples and comparative examples of the present invention will be described below. However, the examples of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the examples described below.

[0062] 1. Manufacture of painted metal sheets Example 1 A coating composition was prepared by adding 100 g of polyvinyl chloride resin as a polymer resin, 20 g of bis(2-propylheptyl) phthalate (DPHP) as a plasticizer, 1 g of foam capsules, 5 g of silica, and 5 g of pigment (titanium dioxide, TiO2) and 10 g of solvent (solvent naphtha) as additives, followed by stirring.

[0063] The foamed capsules used were foamed capsules with an average particle size of 10 to 15 μm, which contained an azodicarbonamide foaming agent inside an outer shell made of styrene-acrylonitrile copolymer.

[0064] A 20×20 cm zinc-plated steel plate was prepared, and the urethane acrylate solution was applied to the zinc-plated steel plate to a thickness of 1 μm, and then cured at 150° C. to form a pretreatment layer.

[0065] To form a porous coating layer on the pretreatment layer, the prepared coating composition was applied to a thickness of 50 μm by bar coating and dried at 224° C. for 30 seconds to prepare a coated metal plate.

[0066] Example 2 A coated metal sheet was produced in the same manner as in Example 1, except that the coating composition was applied to a thickness of 100 μm.

[0067] Example 3 A coated metal sheet was produced in the same manner as in Example 1, except that the coating composition was applied to a thickness of 200 μm.

[0068] Example 4 A coated metal sheet was produced in the same manner as in Example 1, except that the coating composition was applied to a thickness of 400 μm.

[0069] Example 5 The coated metal plate was produced in the same manner as in Example 1 above, except that 1 g of silica was added when producing the coating composition so that the weight ratio of foam capsules to silica was 1:1.

[0070] Example 6 The coated metal plate was produced in the same manner as in Example 1 above, except that 2 g of silica was added when producing the coating composition so that the weight ratio of foam capsules to silica was 1:2.

[0071] Example 7 The coated metal plate was produced in the same manner as in Example 1 above, except that 3 g of silica was added when producing the coating composition so that the weight ratio of foam capsules to silica was 1:3.

[0072] Example 8 The coated metal plate was produced in the same manner as in Example 1 above, except that 10 g of silica was added when producing the coating composition so that the weight ratio of foam capsules to silica was 1:10.

[0073] Comparative Example 1 A galvanized steel plate measuring 20 x 20 cm was prepared.

[0074] Comparative Example 2 In the case of Comparative Example 2, a conventional, commercially mass-produced, 20 x 20 cm sized, general color-coated steel plate (a product of POSCOSTILLION) was used, and the coating film of the color-coated steel plate consisted of a 1 μm pretreatment layer, a 5 μm polyester resin primer layer, and a 20 μm polyester resin color coating layer.

[0075] Comparative Example 3 The coated metal plate was produced in the same manner as in Example 1 above, except that 11 g of silica was added when producing the coating composition so that the weight ratio of foam capsules to silica was 1:11.

[0076] 2. Evaluation criteria for coated metal sheets Coating film characteristics were evaluated according to coating film thickness for Examples 1 to 4 and Comparative Examples 1 and 2, and coating film characteristics were evaluated according to the content ratio of foaming agent to silica for Examples 1, 5 to 8 and Comparative Example 3. The evaluation criteria were as follows:

[0077] (1) Corrosion resistance Corrosion resistance was evaluated by spraying the evaluation test piece with 5% salt water at 35°C, and measuring the surface area of ​​the corroded part relative to the total surface area of ​​the coated metal plate after 720 hours to evaluate the degree of corrosion. [Failure]: After 720 hours, more than 5% of the total surface area of ​​the painted metal plate has corroded. [Good]: Less than 5% of the total surface area of ​​the painted metal plate corroded after 720 hours

[0078] (2) Anti-condensation property To evaluate the anti-condensation properties, boxes were made using the coated metal sheets produced in the examples and comparative examples of the present invention, as shown in Figure 4. The boxes were then filled with ice and the presence or absence of water droplets on the exterior surface was evaluated. Specifically, boxes measuring 200 mm (W) x 200 mm (D) x 200 mm (H) were made using the coated metal sheets produced in the examples and comparative examples. The boxes were then filled with ice and left for 30 minutes in an environment at room temperature (25°C) and a relative humidity of 50%, after which the presence or absence of water droplets on the surface of the boxes was evaluated. [Bad]: Water droplets adhere to the entire surface of the box. [Normal]: Water droplets adhere to some parts of the box surface [Good]: No water droplets adhere to the entire surface of the box.

[0079] (3) Thermal insulation Insulation is evaluated using the guarded hot plate method, where a painted metal plate is placed between a hot plate and a cold plate, and the amount of heat flowing from the top to the back of the steel plate is measured for one hour. The less heat that flows, i.e., the lower the thermal conductivity, the better the insulation performance.

[0080] (4) Emissivity The emissivity evaluation was carried out by measuring the emissivity of the steel sheet in the infrared wavelength band of 5 to 20 μm in accordance with the KS standard (KS L 2514), which is the emissivity measurement test regulation of the Korea Construction and Living Environment Testing Institute.

[0081] (5) Foaming The foaming ability of the foaming capsules contained in the coating composition was measured by visually inspecting the surface of the coating film with a 15x magnification lens after the foaming process. 2 Check for the presence of unfoamed areas. [Poor]: Unfoamed areas of 10% or more exist on the coating surface (area of ​​unfoamed areas 10% or less) [Normal]: Less than 10% of the coating surface is unfoamed (0%<unfoamed area<10%) [Good]: There are no unfoamed areas on the coating surface (area of ​​unfoamed areas is 0%)

[0082] (6) Paint film hardness The hardness of the coating was evaluated by scratching the cured coating with a fingernail 20 times in the same direction as the coating and 20 times at right angles to the direction of application, and then observing the scratches remaining on the coating. The observation results were evaluated using the following method. [Good]: No marks appear [Normal]: Traces will appear, but will disappear within 60 seconds. [Bad]: Marks appear

[0083] (7) Paint film processability The coating processability was evaluated based on whether or not cracks occurred in the entire area of ​​the processed coating after bending the coated coating 180 degrees. [Failure]: Paint cracks [Good]: No cracks on the coating

[0084] 3. Evaluation results of coated metal sheet properties (1) Evaluation results of coated metal sheet properties according to coating thickness For Examples 1 to 4 and Comparative Examples 1 and 2, coating film properties were evaluated according to coating film thickness.

[0085] 1) Corrosion resistance evaluation results The evaluation results of corrosion resistance are shown in Table 1 below.

[0086] [Table 1]

[0087] The corrosion resistance evaluation results showed that 100% of the total surface area of ​​the metal sheet was corroded in Comparative Example 1, and 10% of the total surface area of ​​the metal sheet was corroded in Comparative Example 2, while the corroded area was 0% in Examples 1 to 4 of the present invention. These results confirmed that the coated metal sheet of the present invention has excellent corrosion resistance.

[0088] 2) Evaluation results of condensation prevention The evaluation results of the condensation prevention properties are shown in Table 2 below.

[0089] [Table 2]

[0090] As a result of evaluating the condensation prevention property, condensation was observed on the entire surface of the boxes made from the coated metal sheets in Comparative Examples 1 and 2, but it was confirmed that no water droplets adhered to the entire surface of the boxes in Examples 1 to 4. The following results confirmed that the coated metal sheets of the present invention also have excellent condensation prevention properties.

[0091] 3) Thermal insulation evaluation results The evaluation results of the heat insulating properties are shown in Table 3 below.

[0092] [Table 3]

[0093] The evaluation results of the heat insulation showed that the metal sheets of Comparative Examples 1 and 2 had a thermal conductivity of 40 W / mK or more, while the heat conductivity of Examples 1 to 4 of the present invention was 2 W / mK or less. These results confirmed that the coated metal sheets of the present invention have excellent heat insulation performance.

[0094] 4) Emissivity evaluation The evaluation results of emissivity are shown in Table 4 below.

[0095] [Table 4]

[0096] The emissivity evaluation results showed that Comparative Example 1 had an emissivity of 0.55, and Comparative Example 2 had an emissivity of 0.80, while Examples 1 to 4 of the present invention all exhibited high emissivity of 0.90 or more. These results confirmed that the coated metal sheet of the present invention has excellent emissivity.

[0097] (2) Evaluation results of painted metal sheet properties according to the foaming agent and silica content ratio For Examples 1, 5 to 8 and Comparative Example 3, coating film properties were evaluated according to the content ratio of the foaming agent and silica.

[0098] The evaluation results are shown in Table 5 below.

[0099] [Table 5]

[0100] As a result of evaluating the coating film properties depending on the foaming agent and silica content ratio, in Comparative Example 3 where the foaming agent and silica ratio was 1:11, the excessive amount of silica contained in the coating composition increased the brittleness of the coating film, causing cracks. In addition, the silica restricted the formation of closed pores, resulting in a coating surface crack of 1 cm2. 2 It was measured that closed pores due to foam capsules were not formed in 10% or more of the area per unit area. On the other hand, in Examples 1 and 5 to 8 of the present invention, where the ratio of foaming agent to silica was 1:1 to 1:10, closed pores were normally formed, and it was measured that the coating had excellent corrosion resistance, anti-condensation properties, low thermal conductivity, above-average coating hardness, and good coating processability.

Claims

1. 1. A coating composition comprising: a polymeric resin; a foam capsule; a plasticizer; and silica, the coating composition contains, relative to 100 parts by weight of the polymer resin, 0.1 to 10 parts by weight of the foam capsules; 5 to 40 parts by weight of the plasticizer; and 1 to 10 parts by weight of the silica; The foam capsule is in the form of a foam capsule containing a foaming agent in a thermoplastic cell structure, The coating composition, wherein the weight ratio of the foam capsules to the silica is 1:1 to 1:

10.

2. The coating composition according to claim 1 , wherein the polymer resin is a polyvinyl chloride resin or a polyurethane resin.

3. 2. The coating composition of claim 1, wherein the plasticizer is one or more selected from the group consisting of bis(2-propylheptyl)phthalate (DPHP), bis(2-ethylhexyl)adipate (DEHA), dimethyl adipate (DMAD), monomethyl adipate (MMAD), dioctyl adipate (DOA), dibutyl sebacate (DBS), dibutyl maleate (DBM), diisobutyl maleate (DIBM), and trimethyltentanyl diisobutyrate.

4. 2. The coating composition according to claim 1, wherein the foamed capsules have an average particle size of 1 to 20 μm.

5. 2. The coating composition according to claim 1, further comprising one or more additives selected from the group consisting of a diluting solvent, a pigment, a surfactant, an antibacterial agent, an antifungal agent, a matting agent, an antifoaming agent, a thickener, an anti-settling agent, a leveling agent, a dispersant, a heat stabilizer, a wax component, and an ultraviolet absorber.

6. A coated metal plate including a base metal plate and an anti-condensation layer on at least one surface of the base metal plate, the condensation prevention layer includes a porous coating layer and a pretreatment layer disposed between the base metal plate and the porous coating layer; A coated metal sheet, wherein the porous coating layer contains the coating composition according to any one of claims 1 to 5 and has closed pores.

7. 7. The coated metal sheet according to claim 6, wherein the base metal sheet is selected from the group consisting of a cold-rolled steel sheet, a hot-rolled steel sheet, a zinc-plated steel sheet, a zinc alloy-plated steel sheet, an aluminum sheet, and a stainless steel sheet.

8. The coated metal sheet according to claim 6, wherein the base metal sheet has a thickness of 0.25 mm to 4.5 mm.

9. 7. The coated metal sheet according to claim 6, wherein the pretreatment layer is formed by applying a composition containing one or more selected from the group consisting of an acrylic resin, an epoxy resin, a phenolic resin, a xylene resin, a polyester resin, and a urethane resin to at least one surface of the base metal sheet.

10. The coated metal sheet according to claim 6, wherein the pretreatment layer has a thickness of 0.1 to 1 μm.

11. The coated metal sheet according to claim 6, wherein the closed pores have an average particle size of 5 to 50 μm.

12. The coated metal sheet according to claim 6, wherein the porous coating layer has a thickness of 50 to 400 μm.

Images