Coating composition, coating film, and microchannel type heat exchanger using the same

Abstract

To provide a coating composition and a coating film having simultaneously long-term corrosion resistance and long-term hydrophilicity, and a microchannel type heat exchanger using the same.SOLUTION: A coating composition contains 10 to 40 wt.% of a hydrophilic resin, 1 to 10 wt.% of a metal compound, 0.5 to 5 wt.% of an amide-based crosslinking agent, 1 to 5 wt.% of a phosphoric acid-based compound, 0.1 to 3 wt.% of a preservative, and the balance water.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a coating composition capable of simultaneously imparting corrosion resistance and hydrophilic effects to the metal surface of a heat exchanger for heat exchange, a coating film, and a microchannel type heat exchanger using the same.

[0002] Related Art This application claims priority under Article 4 of the Paris Convention based on Korean Patent Application No. 10-2023-0098335 (filing date: July 27, 2023; DAS Code: D290), and the present invention is based on the contents disclosed in the Korean patent application. For reference, the contents of the specification, claims and drawings of the Korean patent application are incorporated herein by reference. [Background technology]

[0003] A heat exchange system is a system that is installed in an apparatus that uses heat exchange as its basic mechanism. For example, an air conditioner, a refrigerator, a dehumidifier, etc. are included in the category of an apparatus equipped with the heat exchange system, since they all achieve their intended results through heat exchange.

[0004] A typical device used in a heat exchange system is a heat exchanger. When a heat exchanger is continuously operated, moisture accumulates on the surface of the heat exchanger. For example, when a heat exchanger is used as an evaporator of an air conditioner, the temperature of the evaporator becomes lower than room temperature when the air conditioner is operated in cooling mode. As a result, condensed water accumulates on the surface of the evaporator.

[0005] When a heat exchanger is used for cooling in the summer, the surface temperature of the aluminum fins drops below the atmospheric dew point, causing water droplets to form on the fins. When water droplets form on the fins, the following three problems occur. The first is that the aluminum fins become susceptible to corrosion. The second is that the heat exchange efficiency decreases because the ventilation resistance increases and the air volume decreases. Finally, the third is that the water droplets on the fins' surface are sucked into the cooling air and splashed inside the room or car.

[0006] If the surface of the fin is hydrophilic, the water on the surface of the fin will be in the form of a water film rather than a spherical water droplet, so to solve the above problem, a hydrophilic coating is generally formed on the surface of the fin material. Also, a corrosion-resistant coating is provided between the fin material and the hydrophilic coating to prevent corrosion.

[0007] In this regard, Patent Document 1 (Korean Patent Publication No. 10-2020-0006436 (Publication Date: January 20, 2020)) relates to a "heat exchange system" and discloses a heat exchange system in which a chemical conversion layer and a hydrophilic coating layer are formed.

[0008] However, the above patent describes that the chemical conversion layer and hydrophilic coating layer are formed in areas of the base material surface where moisture remains for a long time in order to provide the antibacterial and odor removing functions of the heat exchange system, and the effect of improving corrosion resistance is very little.

[0009] In addition, Patent Document 2 [Korean Patent Registered No. 10-146350 (Announcement Date: November 18, 2014)] relates to a "material having a superhydrophobic surface and a manufacturing method thereof," and discloses a configuration in which a titanium dioxide layer is coated with a fluorine-containing compound to form superhydrophobicity on the surface of aluminum metal.

[0010] However, the above patent requires the formation of three or more layers on the surface of the material, i.e., a polydopamine coating layer, a titanium dioxide layer, and a fluorine-containing compound, resulting in a complicated process, and there is no confirmation as to whether the coating layer can be stably maintained in an environment with large temperature differences, such as an outdoor heat exchanger. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Korean Patent Publication No. 10-2020-0006436 [Patent Document 2] Korean Patent No. 10-146350 Summary of the Invention [Problem to be solved by the invention]

[0012] Therefore, an object of the present invention is to provide a coating composition capable of simultaneously imparting hydrophilicity and corrosion resistance to a substrate such as a metal, and a coating film formed therefrom.

[0013] Another object of the present invention is to provide a microchannel type heat exchanger that can improve the hydrophilicity and corrosion resistance by forming a coating film that has both hydrophilicity and corrosion resistance, thereby improving the drainage effect of condensed water in the microchannel type heat exchanger.

[0014] Yet another object of the present invention is to provide an indoor / outdoor unit for an air conditioner, which can improve the hydrophilicity and corrosion resistance by forming a coating film having both hydrophilicity and corrosion resistance, and can improve the drainage effect of condensed water in the indoor / outdoor unit of the air conditioner.

[0015] The object of the present invention is not limited to the object mentioned above, and other objects and advantages of the present invention not mentioned can be understood from the following description and can be more clearly understood from the embodiments of the present invention. Also, it can be easily understood that the object and advantages of the present invention can be realized by the means and combinations thereof as set forth in the claims. [Means for solving the problem]

[0016] [Preferred embodiment of the present invention] The present invention proposes the following as one embodiment of the invention. [Claim 1] A coating composition comprising: Hydrophilic resin 10%~40% by weight; Metal compound 1%~10% by weight; 0.5% to 5% by weight of amide-based crosslinking agent; 1% to 5% by weight of phosphoric acid compounds; 0.1% to 3% by weight of a preservative; and the balance being water. [Claim 2] 2. The coating composition according to claim 1, wherein the hydrophilic resin has a functional group including an acrylic group. [Claim 3] 2. The coating composition according to claim 1, wherein the metal compound contains at least two or more metal elements selected from the group consisting of chromium (Cr), zirconium (Zr) and titanium (Ti). [Claim 4] 2. The coating composition according to claim 1, wherein the amide-based crosslinking agent is one or more selected from the group consisting of formamide, sodium amide, nicotinamide, dimethylformamide, acetamide, acrylamide, polyacrylamide, potassium amide, oxamide, lithium diethylamide, dimethylformamide, benzamide, iodoacetamide, acetamide, arylamide, phenylacetamide, cyanoacetamide, dicyanoacetamide, dimethylacetamide, diethylchloroacetamide, dimethylformamide, glycine amide, isopropylacrylamide, methacrylamide, methylenebisacrylamide, nicotinamide, oleamide, oxamide, sulfonylamide, and thioacetamide. [Claim 5] 2. The coating composition according to claim 1, wherein the phosphoric acid compound is one or more selected from the group consisting of phosphoric acid, pyrophosphoric acid, polyphosphoric acid, potassium hydrogen orthophosphate, tetrasodium inorganic phosphate, disodium pyrophosphate, free potassium phosphate, phosphorus pentoxide, zinc phosphate, manganese phosphate, iron phosphate, trimetaphosphoric acid, tripolyphosphoric acid, and tetrapolyphosphoric acid. [Claim 6] 2. The coating composition according to claim 1, wherein the preservative is one or more selected from the group consisting of citric acid, lactic acid, and sorbic acid. [Claim 7] A coating film provided on a substrate, Hydrophilic resin 10%~40% by weight; Metal compound 1%~10% by weight; 0.5% to 5% by weight of amide-based crosslinking agent; 1% to 5% by weight of phosphoric acid compounds; 0.1% to 3% by weight of a preservative; and A coating film comprising a coating composition containing water as the balance. [Claim 8] The coating weight of the coating film is 0.10 g / m2 ~1.50g / m 2 The coating film according to claim 7, [Claim 9] A microchannel heat exchanger, a plurality of flat tubes having a plurality of flow passages formed therein; fins connecting the flat tubes for conducting heat; and a coating film formed on at least one of the flat tube and the fin; The coating film is Hydrophilic resin 10% to 40% by weight, Metal compound 1% to 10% by weight, 0.5% to 5% by weight of an amide crosslinking agent, 1% by weight to 5% by weight of a phosphoric acid compound, 0.1% to 3% by weight of a preservative, and A microchannel type heat exchanger comprising a coating composition containing water as the balance. [Claim 10] An indoor / outdoor unit of an air conditioner, a cabinet assembly having an intake port for drawing in room air; and a heat exchanger disposed inside the cabinet assembly for exchanging heat between the sucked indoor air and the refrigerant; The heat exchanger comprises a microchannel heat exchanger; At least one of the flat tubes and fins of the heat exchanger is provided with a coating film on the surface thereof, The coating film is Hydrophilic resin 10% to 40% by weight, Metal compound 1% to 10% by weight, 0.5% to 5% by weight of an amide crosslinking agent, 1% by weight to 5% by weight of a phosphoric acid compound, 0.1% to 3% by weight of a preservative, and An indoor / outdoor unit of an air conditioner, comprising a coating composition containing water as the balance. [Claim 11] An indoor / outdoor unit of an air conditioner, a cabinet assembly having an intake port for drawing in room air; and a heat exchange assembly disposed inside the cabinet assembly for exchanging heat between the drawn indoor air and the refrigerant; The heat exchange assembly comprises: A first heat exchanger of a microchannel type; A second heat exchanger of a microchannel type stacked on the upper side of the first heat exchanger; and a support disposed between the first heat exchanger and the second heat exchanger to join the first heat exchanger and the second heat exchanger together and to support the second heat exchanger; A coating film is provided on at least one surface of the flat tubes and fins of the first heat exchanger or the second heat exchanger, The coating film is Hydrophilic resin 10% to 40% by weight, Metal compound 1% to 10% by weight, 0.5% to 5% by weight of an amide crosslinking agent, 1% by weight to 5% by weight of a phosphoric acid compound, 0.1% to 3% by weight of a preservative, and An indoor / outdoor unit of an air conditioner, comprising a coating composition containing water as the balance. [Claim 12] An indoor / outdoor unit of an air conditioner, a cabinet assembly having an intake port for drawing in room air; and a heat exchange assembly disposed inside the cabinet assembly for exchanging heat between the drawn indoor air and the refrigerant; The heat exchange assembly comprises: A first heat exchanger of the microchannel type; and a second heat exchanger disposed behind the first heat exchanger; A coating film is provided on at least one surface of the flat tubes and fins of the first heat exchanger or the second heat exchanger, The coating film is Hydrophilic resin 10% to 40% by weight, Metal compound 1% to 10% by weight, 0.5% to 5% by weight of an amide crosslinking agent, 1% by weight to 5% by weight of a phosphoric acid compound, 0.1% to 3% by weight of a preservative, and An indoor / outdoor unit of an air conditioner, comprising a coating composition containing water as the balance.

[0017] In order to solve the above-mentioned technical problems, the present invention provides a coating composition that can simultaneously impart corrosion resistance and hydrophilicity to the surface of a substrate such as a metal, and the coating composition of the present invention particularly comprises (comprises; constitutes; constructs; sets; includes; contains; contains) a hydrophilic resin, a metal compound, an amide-based crosslinking agent, a phosphate-based compound, and a preservative.

[0018] Specifically, the coating composition of the present invention contains 10-40% by weight of a hydrophilic resin, 1-10% by weight of a metal compound, 0.5-5% by weight of an amide crosslinking agent, 1-5% by weight of a phosphoric acid compound, 0.1-3% by weight of a preservative, and water as the balance.

[0019] The present invention also provides a microchannel type heat exchanger including a plurality of flat tubes with a plurality of flow paths formed therein, fins connecting the flat tubes to conduct heat, and a coating film formed on at least one of the flat tubes and the fins, the coating film being formed from a composition containing 10 to 40 wt % of a hydrophilic resin, 1 to 10 wt % of a metal compound, 0.5 to 5 wt % of an amide-based crosslinking agent, 1 to 5 wt % of a phosphoric acid-based compound, 0.1 to 3 wt % of a preservative, and the remainder being water.

[0020] The present invention further provides an indoor / outdoor unit for an air conditioner, comprising: a cabinet assembly formed with an intake port for drawing in indoor air; and a heat exchanger disposed inside the cabinet assembly for exchanging heat between the drawn indoor air and a refrigerant, the heat exchanger comprising a microchannel type heat exchanger, and a coating film formed on at least one surface of flat tubes and fins of the heat exchanger, the coating film being formed from a composition containing 10 to 40 wt % hydrophilic resin, 1 to 10 wt % metal compound, 0.5 to 5 wt % amide-based crosslinking agent, 1 to 5 wt % phosphoric acid-based compound, 0.1 to 3 wt % preservative, and the remainder being water.

[0021] The present invention also provides an indoor / outdoor unit for an air conditioner, comprising: a cabinet assembly having an intake port for drawing in indoor air; and a heat exchange assembly disposed inside the cabinet assembly for heat exchange between the drawn indoor air and a refrigerant, the heat exchange assembly comprising: a first microchannel-type heat exchanger; a second microchannel-type heat exchanger stacked on the upper side of the first heat exchanger; and a support disposed between the first and second heat exchangers for integrally connecting the first and second heat exchangers and supporting the second heat exchanger, wherein a coating film is formed on at least one surface of flat tubes and fins of the first or second heat exchanger, and the coating film is formed from a composition containing 10 to 40% by weight of a hydrophilic resin, 1 to 10% by weight of a metal compound, 0.5 to 5% by weight of an amide-based crosslinking agent, 1 to 5% by weight of a phosphoric acid-based compound, 0.1 to 3% by weight of a preservative, and the remainder being water.

[0022] The present invention further provides an indoor / outdoor unit for an air conditioner, comprising: a cabinet assembly having an intake port for drawing in indoor air; and a heat exchange assembly disposed inside the cabinet assembly for heat exchange between the drawn indoor air and a refrigerant, the heat exchange assembly comprising a first heat exchanger of a microchannel type and a second heat exchanger disposed behind the first heat exchanger, wherein a coating film is formed on at least one surface of flat tubes and fins of the first heat exchanger or the second heat exchanger, the coating film being formed from a composition containing 10 to 40% by weight of a hydrophilic resin, 1 to 10% by weight of a metal compound, 0.5 to 5% by weight of an amide-based crosslinking agent, 1 to 5% by weight of a phosphoric acid-based compound, 0.1 to 3% by weight of a preservative, and the remainder being water. Effect of the Invention

[0023] Conventionally, at least two coating films are formed on the surface of a substrate to impart corrosion resistance and hydrophilicity to the surface of the substrate. However, the coating composition according to the present invention can provide a single coating film having both corrosion resistance and hydrophilicity, thereby improving the performance and lifespan of the product at a low cost.

[0024] In addition, the coating film according to the present invention may contain two or more metal compounds that exhibit corrosion resistance, thereby improving corrosion resistance. In addition, the coating film according to the present invention contains a phosphate compound and has a strong bond with substrates such as metals, so it can be applied to various metal materials.

[0025] The above-mentioned effects and specific effects of the present invention will be described in conjunction with the following description of the preferred embodiment of the invention. [Brief description of the drawings]

[0026] [Figure 1] 1 is a cross-sectional view showing a coating film according to the present invention. [Diagram 2] FIG. 1 is a schematic diagram showing the configuration of an air conditioner. [Diagram 3]1 is a perspective view showing a heat exchange assembly in an indoor / outdoor unit of an air conditioner according to the present invention; [Figure 4] 1 is a cross-sectional view showing a microchannel type heat exchanger according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The above-mentioned objects, features and advantages will be described in detail below with reference to the accompanying drawings, so that those skilled in the art to which the present invention pertains can easily implement the technical idea of ​​the present invention. In describing the present invention, if a detailed description of the known technology according to the present invention is deemed to make the gist of the present invention unclear, the detailed description will be omitted. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings are used to indicate the same or similar components.

[0028] Although the terms "first", "second", etc. are used to describe various components, it is understood that these components are not limited by these terms, and that these terms are used merely to distinguish one component from another, and that a first component may also be a second component unless otherwise specified.

[0029] Throughout the specification, unless otherwise specified to the contrary, each element may be singular or plural.

[0030] As used herein, singular expressions include plural expressions unless the context clearly indicates otherwise. Terms such as "comprise" or "include" in this application should not be interpreted as including all of the multiple components or multiple steps described in the specification, but should be interpreted as including some of the components or steps that may not be included, or may include additional components or steps.

[0031] The coating composition, coating film, and microchannel type heat exchanger using the same according to the present invention will be described below.

[0032] <Coating composition> First, the coating composition according to the present invention will be described.

[0033] The coating composition of the present invention can provide a single coating film that simultaneously has hydrophilicity and corrosion resistance.

[0034] Conventionally, in order to impart hydrophilicity and corrosion resistance to the surface of a substrate, two or more coating films are formed on the surface of the substrate, but currently known single coating films have a problem in that they cannot exhibit the required long-term hydrophilicity and long-term corrosion resistance.

[0035] Therefore, the present invention provides a novel coating composition that can simultaneously satisfy the required long-term hydrophilicity and long-term corrosion resistance, and the coating composition of the present invention contains 10 to 40 wt % of a hydrophilic resin, 1 to 10 wt % of a metal compound, 0.5 to 5 wt % of an amide-based crosslinking agent, 1 to 5 wt % of a phosphoric acid-based compound, 0.1 to 3 wt % of a preservative, and the remainder being water.

[0036] The content of each component of the coating composition of the present invention is the weight range of the composition in a liquid state before drying. The composition of each component contained in the composition is determined based on the bond energy between the components, and the bond energy increases with the content of the crosslinker, hydrophilic agent, and anti-corrosive agent in that order.

[0037] Specifically, the components of the composition of the present invention have inherent bond energy according to their chemical structures, and the higher the bond energy, the stronger the bond strength. Therefore, in order for the coating film formed from the composition to have sufficient bond strength, the crosslinker must be the most highly bonded, followed by the hydrophilic agent and the anti-corrosive agent.

[0038] As a result, in order to determine the content of each component in the composition of the present invention, the binding energy of the components contained in the composition was calculated to determine the optimized content of the components.

[0039] In addition, to ensure mass production of the product, the composition used to produce the coating film must have an appropriate viscosity, with a minimum of 20 cPs. If the viscosity is low, it is difficult to coat uniformly and ensure the amount of coating.

[0040] Furthermore, when the surface temperature of the aluminum fins installed in the heat exchanger falls below the atmospheric dew point, water droplets form on the surface of the fins, which causes the aluminum fins to corrode, increasing ventilation resistance and reducing airflow, resulting in a decrease in heat exchange efficiency and the problem that the water droplets on the surface of the fins are sucked into the cooling air and scattered inside the room or vehicle.

[0041] In order to solve the above-mentioned problems, a hydrophilic coating is usually formed on the surface of the fin material, and a corrosion-resistant coating can be provided between the fin material and the hydrophilic coating for corrosion resistance. As described above, a two-step coating process has been used in the past, which involves forming a hydrophilic coating film and then a corrosion-resistant coating film.

[0042] In the above-mentioned conventional techniques, a corrosion-resistant film and a hydrophilic film are formed, and in particular, in the case of a coating film having corrosion resistance, the coating film does not have hydrophilicity, and therefore the long-term hydrophilicity and long-term corrosion resistance are deteriorated, which may shorten the performance and lifespan of the product.

[0043] Moreover, the process of forming the two coating films reduces productivity and increases costs.

[0044] The coating composition according to the present invention can provide a single coating film having both corrosion resistance and hydrophilicity, thereby improving the performance and lifespan of products at a low cost. In other words, the present invention can provide a coating film having excellent hydrophilicity and corrosion resistance on the surface of a substrate by only one coating and drying process.

[0045] In addition, the coating composition according to the present invention provides corrosion resistance to the surface of the substrate by the metal compound, and the phosphate compound strongly bonds the metal compound to the substrate, thereby enhancing the corrosion resistance. In addition, the composition of the present invention uses a crosslinking agent having an amide group and a hydrophilic resin to strongly crosslink the corrosion-resistant agent and the hydrophilic agent.

[0046] Here, the coating composition may contain 10 to 40% by weight of a hydrophilic resin, and the hydrophilic resin may have a functional group including an acrylic group.

[0047] The hydrophilic resin may be one or more selected from the group consisting of acrylic acid, methacrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, cyclohexyl (meth)acrylate, ethylhexyl (meth)acrylate, (meth)acrylic ester monomers, 2-hydroxyethyl acrylate, and hydroxyethyl (meth)acrylate.

[0048] The content used in the present invention means weight %. In addition, since the coating film formed from the coating composition is in a state where water has been evaporated and removed, the content of each component in the coating film may be different from that of the coating composition.

[0049] If the content of the hydrophilic resin is less than 10% by weight, the hydrophilic effect in the coating film is small, resulting in a problem of reduced hydrophilicity. If the content of the hydrophilic resin is more than 40% by weight, the content of the metal compound relative to the crosslinking agent is relatively low, resulting in a problem of reduced corrosion resistance.

[0050] The metal compound is added to the coating composition to impart corrosion resistance, and preferably contains at least two or more metal elements selected from chromium (Cr), zirconium (Zr), and titanium (Ti), and most preferably contains chromium (Cr), zirconium (Zr), and / or titanium (Ti).

[0051] In this case, vanadium (V) is preferably not included among the elements of commonly used metal compounds since the substance itself has its own odor and there is a risk of odor being generated when the air conditioner is used.

[0052] The metal compound is added in an amount of 1 to 10% by weight. If the content is less than 1% by weight, the bonding strength between the substrate and the coating material is reduced, resulting in peeling of the coating film, whereas if the content is more than 10% by weight, the content of the hydrophilic resin is relatively low, resulting in reduced hydrophilicity of the coating film.

[0053] The amide crosslinking agent is included to enhance the durability of the coating film, and is preferably added in an amount of 0.5 to 5% by weight.

[0054] If the amide-based crosslinking agent is added in an amount of less than 0.5% by weight, the bonding strength between the hydrophilic component and the corrosion-resistant component is weak, and the hydrophilicity cannot be maintained for a long time. If the amount of the amide-based crosslinking agent is more than 5% by weight, the durability enhancing effect is small relative to the amount added, and the curing property of the coating composition is high, resulting in a hard coating film.

[0055] The amide-based crosslinking agent may be one or more selected from the group consisting of formamide, sodium amide, nicotinamide, dimethylformamide, acetamide, acrylamide, polyacrylamide, potassium amide, oxamide, lithium diethylamide, dimethylformamide, benzamide, iodoacetamide, acetamide, arylamide, phenylacetamide, cyanoacetamide, dicyanoacetamide, dimethylacetamide, diethylchloroacetamide, dimethylformamide, glycine amide, isopropylacrylamide, methacrylamide, methylenebisacrylamide, nicotinamide, oleamide, oxamide, sulfonylamide, and thioacetamide.

[0056] The phosphate compound is used to improve the bonding strength between the substrate and the coating film. The phosphate compound in the present invention means a compound containing phosphoric acid or a phosphate. The phosphate compound in the present invention can further strengthen the adhesion of the components of the coating film to the substrate, thereby improving the corrosion resistance and hydrophilicity of the coating film. In particular, since the phosphate compound has a strong bonding strength with metals, the composition of the present invention can be coated on most metal substrates including aluminum.

[0057] The phosphoric acid compound may be one or more selected from the group consisting of phosphoric acid, pyrophosphoric acid, polyphosphoric acid, potassium hydrogen orthophosphate, tetrasodium inorganic phosphate, disodium pyrophosphate, potassium glass phosphate, phosphorus pentoxide, zinc phosphate, manganese phosphate, iron phosphate, trimetaphosphoric acid, tripolyphosphoric acid, and tetrapolyphosphoric acid.

[0058] The phosphoric acid compound is preferably added in an amount of 1 to 5% by weight. If the phosphoric acid compound is added in an amount of less than 1% by weight, the bonding strength between the metal compound and the metal material decreases, resulting in a problem of reduced durability of the coating film and increased possibility of peeling of the coating film, whereas if the amount exceeds 5% by weight, the content of hydrophilic and corrosion-resistant components becomes relatively low, resulting in a problem of reduced hydrophilicity and corrosion resistance of the coating film.

[0059] Next, the composition of the present invention contains 0.1 to 3% by weight of a preservative. The preservative means a component that can impart a scent to the coating film and prevent odors caused by pollutants, etc.

[0060] The preservative can preferably be an organic acid, which may be, for example (preferably), one or more organic acids selected from the group consisting of citric acid, lactic acid, and sorbic acid, and most preferably, sorbic acid or a mixture of organic acids containing sorbic acid.

[0061] <Coating film> Next, the coating film formed from the above-mentioned coating composition of the present invention will be described in detail.

[0062] The coating film of the present invention is a coating film formed on a substrate, and is formed from a composition containing 10 to 40 wt % of a hydrophilic resin, 1 to 10 wt % of a metal compound, 0.5 to 5 wt % of an amide-based crosslinking agent, 1 to 5 wt % of a phosphoric acid-based compound, 0.1 to 3 wt % of a preservative, and the remainder being water.

[0063] The components of the composition are as described above.

[0064] Here, the coating amount of the coating film is 0.10 to 1.50 g / m 2 More preferably, the coating amount of the coating film is 0.10 to 1.50 g / m 2 may be also possible.

[0065] The coating amount is 0.10 g / m 2 If it is less than 1.50g / m, the effect of enhancing hydrophilicity is small, the amount of metal compounds is small, and the corrosion resistance effect is reduced, which may cause corrosion of the heat exchanger, and by-products formed by corrosion may be discharged to the outside when the air conditioner is in operation. 2If it exceeds this limit, the bonding strength with the metal material will be weakened, and the coating surface on the heat exchanger may become more likely to fall off.

[0066] The substrate may preferably be made of various metal materials, for example, aluminum, copper, stainless steel, nickel, or an alloy of two or more of these metals.

[0067] 1 is a cross-sectional view showing a coating film according to the present invention. Referring to FIG 1, a coating material 1000 includes a substrate 1100 and a coating film 1200 formed on one surface of the metal material 1100.

[0068] The coating film 1200 includes a hydrophilic resin 1220 , a metal compound 1240 , a phosphoric acid-based compound 1260 , and an amide-based crosslinking agent 1280 .

[0069] The metal compound 1240 exhibiting corrosion resistance may be of two types, and the metal compound 1240 includes a phosphoric acid compound 1260 to improve the bonding strength with the substrate 1100. The phosphoric acid compound 1260 has a strong bonding strength with metals, so the substrate 1100 that can be coated includes aluminum, and can be expanded to other metals. In addition, since the hydrophilic resin 1220 exhibiting hydrophilicity is included, a crosslinker 1280 having an amide group is included to harden the hydrophilic resin 1220 and bond with the corrosion resistant component.

[0070] The coating film 1200 according to the present invention, which will be described in more detail below, can be applied to the fins of a heat exchanger to allow heat exchange between the refrigerant pipe and the air around the fins, and multiple pieces can be provided to increase heat exchange efficiency.

[0071] FIG. 2 is a diagram showing the configuration of the air conditioner.

[0072] The air conditioner will be described taking as an example a stand type or ceiling type shown in the drawings. However, the type of air conditioner is not limited to this, and it can also be used as a wall-mounted type, or an integrated type without a division between an outdoor unit and an indoor unit, and it is clearly stated that the form is not limited to the drawings.

[0073] Referring to FIG. 2, an air conditioner includes an indoor unit 200 that discharges conditioned air into a room, and an outdoor unit 100 that is connected to the indoor unit 200 and disposed outside the room.

[0074] The outdoor unit 100 and the indoor unit 200 are connected by a refrigerant pipe, and the indoor unit 200 can discharge cold or hot air into the room by circulating the refrigerant. A plurality of the indoor units 200 may be provided and connected to the outdoor unit 100.

[0075] The air conditioner includes a plurality of indoor units 200 and at least one outdoor unit 100 connected to the plurality of indoor units 200. The plurality of indoor units 200 and the outdoor unit 100 may be connected by refrigerant piping, or may be connected by a cable capable of communication to transmit or receive control commands according to a predetermined communication method.

[0076] The indoor unit 200 includes an outlet port for discharging the air that has been heat exchanged. The outlet port may be provided with an airflow direction adjusting means for opening and closing the outlet port and controlling the direction of the air being discharged. The indoor unit 200 may also adjust the volume of air discharged from the outlet port. In this case, a number of vanes may be installed in the multiple air inlets and the multiple air outlets. The vanes may open and close at least one of the multiple air inlets and the multiple air outlets and may also guide the direction of air flow.

[0077] Also, the indoor unit 200 may further include a display unit that displays the operation state and setting information of the indoor unit 200, and an input unit for inputting setting data. When a user inputs an operation command for the air conditioner through the input unit, the outdoor unit 100 may operate in a cooling mode or a heating mode according to the input command. Also, the outdoor unit 100 supplies refrigerant to a plurality of indoor units 100, and the flow direction of air is guided along the discharge port of the indoor unit 100, thereby adjusting the indoor environment.

[0078] <Microchannel type heat exchanger> The present invention also provides a liquid ejection system comprising: a plurality of flat tubes each having a plurality of flow paths formed therein; fins connecting the flat tubes for heat transfer; and a corrosion-resistant and hydrophilic coating film formed on at least one of the flat tube and the fin. The coating film is formed from a composition containing 10 to 40 wt % of a hydrophilic resin, 1 to 10 wt % of a metal compound, 0.5 to 5 wt % of an amide-based crosslinking agent, 1 to 5 wt % of a phosphoric acid-based compound, 0.1 to 3 wt % of a preservative, and the remainder being water. This microchannel heat exchanger is provided.

[0079] The microchannel type heat exchanger according to the present invention will be described in more detail below, but it is possible to perform heat exchange between the flat tubes and the air around the fins, and a number of them can be provided to increase the heat exchange efficiency.

[0080] The present invention also provides a household or industrial appliance using the above-mentioned microchannel type heat exchanger. As a specific embodiment, the present invention provides various embodiments of indoor and outdoor air conditioner units using the above-mentioned microchannel type heat exchanger, although the present invention is not particularly limited thereto.

[0081] First, an indoor / outdoor unit of an air conditioner according to an embodiment of the present invention includes: a cabinet assembly having an intake port for drawing in indoor air; a heat exchanger disposed inside the cabinet assembly for exchanging heat between the intake indoor air and the refrigerant; The heat exchanger includes a microchannel heat exchanger; A coating film is formed on at least one surface of the flat tubes and fins of the heat exchanger, The coating film is formed from a composition containing 10 to 40% by weight of a hydrophilic resin, 1 to 10% by weight of a metal compound, 0.5 to 5% by weight of an amide-based crosslinking agent, 1 to 5% by weight of a phosphoric acid-based compound, 0.1 to 3% by weight of a preservative, and the remainder being water.

[0082] Next, an indoor / outdoor unit of an air conditioner according to another embodiment of the present invention is as follows: a cabinet assembly having an intake port for drawing in indoor air; a heat exchange assembly disposed inside the cabinet assembly for exchanging heat between the drawn indoor air and the refrigerant; The heat exchange assembly includes a first heat exchanger of a microchannel type, a second heat exchanger of a microchannel type stacked on the upper side of the first heat exchanger, and a support disposed between the first heat exchanger and the second heat exchanger to integrally couple the first heat exchanger and the second heat exchanger and to support the second heat exchanger, A coating film is formed on one or more surfaces of the flat tubes and fins of the first heat exchanger or the second heat exchanger, The coating film is formed from a composition containing 10 to 40% by weight of a hydrophilic resin, 1 to 10% by weight of a metal compound, 0.5 to 5% by weight of an amide-based crosslinking agent, 1 to 5% by weight of a phosphoric acid-based compound, 0.1 to 3% by weight of a preservative, and the remainder being water.

[0083] In addition, an indoor / outdoor unit of an air conditioner according to still another embodiment of the present invention includes: a cabinet assembly having an intake port for drawing in indoor air; a heat exchange assembly disposed inside the cabinet assembly for exchanging heat between the drawn indoor air and the refrigerant; The heat exchange assembly includes a first heat exchanger of a microchannel type and a second heat exchanger disposed behind the first heat exchanger; A coating film is formed on one or more surfaces of the flat tubes and fins of the first heat exchanger or the second heat exchanger, The first heat exchanger or the second heat exchanger includes a coating film formed on at least one of the flat tubes and the fins, The coating film is formed from a composition containing 10 to 40% by weight of a hydrophilic resin, 1 to 10% by weight of a metal compound, 0.5 to 5% by weight of an amide-based crosslinking agent, 1 to 5% by weight of a phosphoric acid-based compound, 0.1 to 3% by weight of a preservative, and the remainder being water.

[0084] FIG. 3 is a perspective view showing a heat exchange assembly according to an embodiment of the present invention which is applied to an indoor / outdoor unit of an air conditioner.

[0085] The heat exchange assembly 500 in the indoor / outdoor unit of the air conditioner according to the present invention can be operated as a single heat exchanger by stacking separately manufactured microchannel type first heat exchanger 501 and second heat exchanger 502 vertically.

[0086] The heat exchange assembly 500 may be configured such that one of the first and second heat exchangers 501 and 502 of a microchannel type is configured for parallel flow and the other is configured for counter flow.

[0087] The heat exchange assembly 500 has a large-area intake port formed on the rear surface covered by stacked microchannel-type first heat exchanger 501 and second heat exchanger 502, so that even if the area of ​​the intake port increases, it can be adequately accommodated without replacing the microchannel-type heat exchanger equipment.

[0088] When stacking two heat exchangers each having a height greater than its width, the heat exchange assembly 500 provides a stable connection structure through the support 510, and the piping connectors can be safely protected by inserting them into the support.

[0089] The heat exchange assembly 500 can eliminate pressure imbalance between the upper and lower refrigerants by stacking two heat exchangers each having a height greater than its width.

[0090] The first heat exchanger 501 and the second heat exchanger 502 may be manufactured to have the same structure.

[0091] 4 is a cross-sectional view showing a microchannel type heat exchanger according to the present invention. Taking the first heat exchanger 501 as an example, the detailed structure will be described.

[0092] The first heat exchanger 501 includes a first heat exchanger 530 that exchanges heat with air, and a second heat exchanger 540 that is stacked in a front-rear direction on the first heat exchanger 530 and exchanges heat with air. The first heat exchanger 530 and the second heat exchanger 540 are integrally manufactured in a furnace.

[0093] The first heat exchanger 530 and the second heat exchanger 540 are microchannel type heat exchangers, and are made of an aluminum material.

[0094] The first heat exchange unit 530 includes a plurality of flat tubes 550 each having a plurality of flow paths formed therein, fins 560 connecting the flat tubes 550 to conduct heat, a first lower head 570 coupled to one side of the plurality of flat tubes 550 and communicating with one side of the plurality of flat tubes 550 through which a refrigerant flows, a first upper header 580 coupled to the other side of the plurality of flat tubes 550 and communicating with the other side of the plurality of flat tubes 550 through which a refrigerant flows, and a baffle 590 formed in at least one of the first lower head 570 and the first upper header 580 to partition the inside so that the refrigerant does not flow.

[0095] A flow path through which a refrigerant flows is formed inside the flat tube 550, extending in the length direction. The flat tubes 550 are vertically arranged and stacked in the left-right direction, and a number of flow paths are formed inside the flat tubes 550. The refrigerant flows along the length direction of the flat tubes 550.

[0096] The left side of the flat tube 550 is inserted into and communicates with the first lower head 570. The right side of the flat tube 550 is inserted into and communicates with the first upper header 580.

[0097] The fins 560 are formed by bending and connect two stacked flat tubes 550 to conduct heat.

[0098] The flow path of air passing through the microchannel type heat exchanger 501 will be described as follows.

[0099] First, air passing through the indoor fan can move to the heat exchanger 501. Specifically, the air passing through the indoor fan can move to spaces formed between a number of fins 560. The air moving to the spaces can exchange heat with the refrigerant moving along the flat tubes 550.

[0100] In winter, frost may form on the outer surfaces of the fins 560. That is, the refrigerant moving along the flat tubes 550 and the air moved by the indoor fan may have different temperatures. And, the temperature difference between the refrigerant and the air may become larger in winter.

[0101] Therefore, the composite coating film according to the present invention may be formed on the fins 560 and the flat tubes 550. The composite coating film may entirely surround the outer surfaces of the fins 560 and the flat tubes 550.

[0102] The present invention will be described in more detail below with reference to coating films according to examples. These examples are presented only as examples to more fully explain the present invention. Therefore, the present invention is not limited to these examples.

[0103] [Example] <Examples 1 to 6> Coating film production 1.Air blowing for aluminum metal An air blowing step was performed to clean the surface of the aluminum metal.

[0104] 2. Preparation of the Coating Composition A coating composition was prepared by mixing a hydrophilic acrylic resin, a metal compound containing Cr and Zr, a phosphoric acid compound, an amide crosslinking agent, a preservative, and water.

[0105] Specifically, the hydrophilic resin used was a resin polymerized using hydroxy-ethyl-acrylate, methacrylic acid, acrylic acid, and polyoxyethylene ethyl phosphate.

[0106] The hydrophilic acrylic resin was added to ion-exchanged water at room temperature, and then zirconium hydrofluoric acid, chromium nitrate, and a crosslinking agent having an amide group were added in that order. Then, a phosphoric acid compound was added. Finally, sorbic acid was added to complete the preparation of the composition.

[0107] Table 1 below shows the specific contents of the components contained in the coating compositions of Examples 1 to 6.

[0108] [Table 1]

[0109] 3. Formation of coating film An aluminum specimen having a size of 10×10 cm and a thickness of 0.1 mm was prepared. The aluminum specimen was immersed in a paint bath containing the coating composition prepared according to the above example for 1 minute, and then natural decolorization was performed for 2 minutes using gravity. The specimen was then dried in a dryer at a temperature of 175° C. for 180 seconds to prepare a specimen with a coating film formed thereon.

[0110] <Comparative Example> Preparation of coating film according to comparative example 1. Preparation of coating composition according to comparative example 5g of potassium persulfate was added to 60g of ionized water, and completely dissolved at 70°C while stirring at 20 rpm to prepare a water-soluble ionic initiator solution, and then heated to 80°C. At 80°C, a mixed solution of 10g of 2-hydroxy-ethyl-acetate, 5g of methacrylic acid, and 55g of sodium 1-allyloxy-2-hydroxypropane-sulfonate was added dropwise to the water-soluble ionic initiator for 3 hours and the reaction was maintained for 1 hour. A solution of 5g of potassium persulfate was prepared by dissolving in 5g of ionized water, and then added dropwise for 30 minutes while stirring at 50 rpm, and further stirred for 10 minutes, and then the stirring speed was reduced to 20 rpm, and the reaction was maintained for 50 minutes, and polymerization was terminated to prepare a hydrophilic resin.

[0111] The hydrophilic resin prepared in the above Preparation Example was added to ion-exchanged water at room temperature, and then an amide-based crosslinking agent was added to the stirred preparation solution. Next, zirconium hydrofluoric acid, chromium nitrate, and sodium metavanadate were added in that order. Then, an epoxy silane compound catalyst was added first, followed by an amino silane compound catalyst. Finally, phytoncide was added to complete the preparation of the treatment solution.

[0112] [Table 2]

[0113] <Experimental Example> Experimental Example 1: Analysis of hydrophilicity of coating film The hydrophilicity of the coating film according to the present invention was analyzed, and the results are shown in Table 3 below.

[0114] First, the contact angle of water was measured before and after the coating film of the present invention was formed on the surface of aluminum.

[0115] The water contact angle was measured by dropping 10 μl of distilled water onto the surface and then measuring the contact angle.

[0116] Before the coating film according to the present invention is formed on the surface of aluminum, the contact angle of water is expressed as 81°, which means that water spreading is poor and the diameter of water spreading is small. However, when the composite coating film according to the present invention is formed on the surface of aluminum, the hydrophilicity is improved and water spreading is high, so that when distilled water is dropped on the surface, the contact angle is low at a maximum of 25° or less and the diameter of water spreading is large.

[0117] In addition, the hydrophilicity of the composite coating film according to the present invention was evaluated, and the results are shown in Table 3.

[0118] The coating amount was analyzed by calculating the coating amount per sample area using the weight difference before and after coating.

[0119] The hydrophilicity of the disk was evaluated by measuring the diameter of the water spread after dropping 10 μl of distilled water onto the disk immediately after forming the composite coating film.

[0120] The initial hydrophilicity was analyzed by repeating 10 cycles of immersion in distilled water for 10 minutes and drying for 10 minutes, and then dropping 10 μl of distilled water onto the surface of the coating film and measuring the water spreading diameter with a Vernier caliper.

[0121] The sustained hydrophilicity was analyzed by performing the above-mentioned cycle 300 times, dropping 10 μl of distilled water onto the surface of the coating film, and measuring the diameter of the water spread with a Vernier caliper.

[0122] [Table 3]

[0123] In Table 3 above, ◎: Water spread diameter is 10mm or more, ○: Water spread diameter 7~10mm, X: The water spread diameter is 7 mm or less.

[0124] The above Table 3 shows the results of measuring the hydrophilicity of the coating film according to the present invention depending on the amount of coating. Compared with the comparative example, it can be seen that the composite coating film according to the present invention has excellent disk hydrophilicity, initial hydrophilicity, and sustained hydrophilicity.

[0125] Experimental example 2: Analysis of corrosion resistance of coating film over time The corrosion resistance of the composite coating film according to the present invention was analyzed according to experimental time, and the results are shown in Table 4 below.

[0126] The corrosion resistance of the coating film was evaluated by an acid salt spray test (SWAAT, ASTM G85-A3) that mimics an acidic marine environment. The solution consisted of 14.2% NaC and 1% CH3COOH, and the acidity of the solution was pH 2.8-3.0. The cycle conditions consisted of 30 minutes (49°C) solution spray and 1 hour 30 minutes (49°C) wet atmosphere repeated.

[0127] In addition, to analyze the corrosion resistance, an acid salt spray test was performed for the time shown in Table 3 below, and the corrosion performance was evaluated by the Rating Number (RN) method of the coating film.

[0128] [Table 4]

[0129] In Table 4 above, ◎: RN9.8 or higher, ○:RN8~9.5, △:RN7~8, X:RN6 or below.

[0130] Referring to Table 4 above, when the grade index is expressed according to the corrosion area ratio of the coating film, the comparative examples all showed an RN of 8.0 or less (corroded area ratio of 0.10% or more and less than 0.25%), whereas the composite coating film according to the present invention showed an RN of 9.5 or more (corroded area ratio less than 0.02%) at all coating amounts.

[0131] Therefore, it can be seen that the composite coating film according to the present invention can maintain corrosion resistance for a long period of time.

[0132] Experimental Example 4: Evaluation of hydrophilicity by changing crosslinking agent The biggest difference between the coating compositions according to the examples of the present invention and the comparative examples is the type of crosslinking agent. The coating compositions according to the examples of the present invention use a phosphoric acid compound as an additional crosslinking agent, while the coating compositions according to the comparative examples use a silane compound as an additional crosslinking agent.

[0133] Thus, the examples of the present invention and the comparative examples using different crosslinking agents were subjected to a water rubbing test and a hydrophilicity test.

[0134] The water rubbing test involved rubbing the surface five times with a wet cloth to check for peeling of the coating and changes in hydrophilicity.

[0135] The hydrophilicity test was performed by dropping 0.1 μl of distilled water onto the surface of the sample and measuring the diameter of the water spread.

[0136] The test results are shown in Table 5 below.

[0137] [Table 5]

[0138] As can be seen from Table 5, in the comparative example using the silane compound, peeling of the coating occurred after the water rubbing test, and the hydrophilicity test showed a measurement of 5.7 mm.

[0139] In contrast, the examples of the present invention using a phosphoric acid-based compound showed no peeling of the coating film even after the water rubbing test, and the hydrophilicity test showed a measurement of 6.7 mm or more, confirming good hydrophilicity.

[0140] Although the present invention has been described above with reference to the illustrative drawings, the present invention is not limited to the embodiments and drawings disclosed in this specification, and it is clear that various modifications can be made by those skilled in the art within the scope of the technical concept of the present invention. Furthermore, even if the effects of the configuration of the present invention are not explicitly described and explained while the embodiments of the present invention are described above, it is natural that the effects that can be predicted by the configuration should also be recognized. [Explanation of symbols]

[0141] 1000 Coating Materials 1100 Base material 1200 Coating film 1220 Hydrophilic resin 1240 Metal compounds 1260 Phosphate compounds

Claims

1. A coating composition comprising: Hydrophilic resin 10% to 40% by weight; Metal compound 1% to 10% by weight; 0.5% to 5% by weight of an amide crosslinker; 1% to 5% by weight of a phosphoric acid compound; 0.1% to 3% by weight of a preservative; and the balance being water.

2. The coating composition according to claim 1 , wherein the hydrophilic resin has a functional group including an acrylic group.

3. 2. The coating composition according to claim 1, wherein the metal compound contains at least two or more metal elements selected from the group consisting of chromium (Cr), zirconium (Zr) and titanium (Ti).

4. 2. The coating composition according to claim 1, wherein the amide-based crosslinking agent is one or more selected from the group consisting of formamide, sodium amide, nicotinamide, dimethylformamide, acetamide, acrylamide, polyacrylamide, potassium amide, oxamide, lithium diethylamide, dimethylformamide, benzamide, iodoacetamide, acetamide, arylamide, phenylacetamide, cyanoacetamide, dicyanoacetamide, dimethylacetamide, diethylchloroacetamide, dimethylformamide, glycine amide, isopropylacrylamide, methacrylamide, methylenebisacrylamide, nicotinamide, oleamide, oxamide, sulfonylamide, and thioacetamide.

5. 2. The coating composition according to claim 1, wherein the phosphoric acid compound is one or more selected from the group consisting of phosphoric acid, pyrophosphoric acid, polyphosphoric acid, potassium hydrogen orthophosphate, tetrasodium inorganic phosphate, disodium pyrophosphate, free potassium phosphate, phosphorus pentoxide, zinc phosphate, manganese phosphate, iron phosphate, trimetaphosphoric acid, tripolyphosphoric acid, and tetrapolyphosphoric acid.

6. 2. The coating composition according to claim 1, wherein the preservative is one or more selected from the group consisting of citric acid, lactic acid, and sorbic acid.

7. A coating film provided on a substrate, Hydrophilic resin 10% to 40% by weight; Metal compound 1% to 10% by weight; 0.5% to 5% by weight of an amide crosslinker; 1% to 5% by weight of a phosphoric acid compound; 0.1% to 3% by weight of a preservative; and A coating film comprising a coating composition containing water as the balance.

8. The coating amount of the coating film is 0.10 g / m ２ ~1.50g / m ２ The coating film according to claim 7,

9. A microchannel heat exchanger, a plurality of flat tubes having a plurality of flow passages formed therein; fins connecting the flat tubes for thermal conduction; and a coating film formed on at least one of the flat tube and the fin; The coating film is Hydrophilic resin 10% to 40% by weight, metal compound 1% to 10% by weight, 0.5% to 5% by weight of an amide crosslinking agent, 1% to 5% by weight of a phosphoric acid compound, 0.1% to 3% by weight of a preservative, and A microchannel type heat exchanger comprising a coating composition containing water as the balance.

10. An indoor / outdoor unit of an air conditioner, a cabinet assembly having an intake port for drawing in room air; and a heat exchanger disposed inside the cabinet assembly for exchanging heat between the drawn indoor air and the refrigerant; The heat exchanger comprises a microchannel heat exchanger; At least one of the flat tubes and fins of the heat exchanger is provided with a coating film on the surface thereof, The coating film is Hydrophilic resin 10% to 40% by weight, metal compound 1% to 10% by weight, 0.5% to 5% by weight of an amide crosslinking agent, 1% to 5% by weight of a phosphoric acid compound, 0.1% to 3% by weight of a preservative, and An indoor / outdoor unit of an air conditioner, comprising a coating composition containing water as the balance.

11. An indoor / outdoor unit of an air conditioner, a cabinet assembly having an intake port for drawing in room air; and a heat exchange assembly disposed inside the cabinet assembly for exchanging heat between the drawn indoor air and the refrigerant; The heat exchange assembly comprises: A first heat exchanger of a microchannel type; A second heat exchanger of a microchannel type stacked on the upper side of the first heat exchanger; and a support disposed between the first heat exchanger and the second heat exchanger to couple the first heat exchanger and the second heat exchanger together and to support the second heat exchanger; A coating film is provided on at least one surface of the flat tubes and fins of the first heat exchanger or the second heat exchanger, The coating film is Hydrophilic resin 10% to 40% by weight, metal compound 1% to 10% by weight, 0.5% to 5% by weight of an amide crosslinking agent, 1% to 5% by weight of a phosphoric acid compound, 0.1% to 3% by weight of a preservative, and An indoor / outdoor unit of an air conditioner, comprising a coating composition containing water as the balance.

12. An indoor / outdoor unit of an air conditioner, a cabinet assembly having an intake port for drawing in room air; and a heat exchange assembly disposed inside the cabinet assembly for exchanging heat between the drawn indoor air and the refrigerant; The heat exchange assembly comprises: A first heat exchanger of the microchannel type; and a second heat exchanger disposed rearward of the first heat exchanger, A coating film is provided on at least one surface of the flat tubes and fins of the first heat exchanger or the second heat exchanger, The coating film is Hydrophilic resin 10% to 40% by weight, metal compound 1% to 10% by weight, 0.5% to 5% by weight of an amide crosslinking agent, 1% to 5% by weight of a phosphoric acid compound, 0.1% to 3% by weight of a preservative, and An indoor / outdoor unit of an air conditioner, comprising a coating composition containing water as the balance.

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