Aqueous intermediate coat composition

Abstract

The present invention relates to an aqueous intermediate coat composition comprising a first acrylic resin, a second acrylic resin, a polyester resin, a first polyurethane resin, a second polyurethane resin, and a melamine-based curing agent, wherein the first acrylic resin has a glass transition temperature of -15°C to 0°C, an acid value of 10 to 30 mgKOH / g, and a hydroxyl value of 10 to 20 mgKOH / g, the second acrylic resin has a glass transition temperature of -50°C to -20°C, an acid value of 10 to 30 mgKOH / g, and a hydroxyl value of 100 to 300 mgKOH / g, and the weight ratio of the first acrylic resin : the second acrylic resin is 3 to 60 : 1.

Description

Mercury intermediate composition

[0001] The present invention relates to a water-based intermediate composition, and more particularly, to a water-based intermediate composition capable of solving the problem of deterioration of physical properties occurring in a shortened coating method.

[0002] Recently, regulations on volatile organic compounds (VOCs) have been strengthened to protect the global environment, and the development of water-soluble paints to address these challenges is actively underway. Recently, automobile manufacturers have been preferring paint systems that are both environmentally friendly and economical, and various paint systems have been developed in response.

[0003] The 3C2B (3Coat2Bake) automotive painting system, which is generally used as a new car painting system, is the most common automotive painting system in which an electroplating paint is applied to the body, an intermediate coating is applied on top of it through an intermediate coating process, and then it is cured at 140 to 150°C for 20 to 30 minutes, and then a top coat base coat and a top coat clear coat are successively applied on top of it, and then it is dried at 140 to 150°C for 20 to 30 minutes.

[0004] Currently, an eco-friendly shortened painting process method introduced to the automobile industry is a waterborne 3C1B method (3Coat1Bake, 2HAB, 2 Preheat type) that omits the intermediate oven process, but in the present invention, a shortened waterborne 3C1B (Consolidated Waterborne 3C1B 1Bake, B1B2, 1HAB, 1Preheat type) that is a 3C1B with a shorter process than this is used, in which the intermediate drying oven (HAB) process is omitted after the intermediate painting, and the intermediate drying oven is passed through only once after the base coat to dry and then a clear coat is painted, thereby securing the optimal appearance and film properties.

[0005] The prior art was composed of acrylic resin and melamine hardener, so there was a problem that the appearance deteriorated and physical properties such as chipping resistance, impact resistance, and adhesion deteriorated due to the influence of the roughness of the undercoat.

[0006] [Prior Art Literature]

[0007] (Patent Document 1) Japanese Publication No. 2022-084372 (June 7, 2022)

[0008] The present invention aims to provide a water-based intermediate coating composition that can secure optimal appearance and film properties in a shortened coating method in which the intermediate drying oven (HAB) process is omitted after the intermediate coating, and a clear coat is applied after drying by passing the intermediate drying oven only once after the base coat.

[0009] The present invention provides an aqueous intermediate composition comprising a first acrylic resin, a second acrylic resin, a polyester resin, a first polyurethane resin, a second polyurethane resin, and a melamine-based curing agent, wherein the first acrylic resin has a glass transition temperature of -15 to 0°C, an acid value of 10 to 30 mgKOH / g, and a hydroxyl value of 10 to 20 mgKOH / g, and the second acrylic resin has a glass transition temperature of -50 to -20°C, an acid value of 10 to 30 mgKOH / g, and a hydroxyl value of 100 to 300 mgKOH / g, and a weight ratio of the first acrylic resin: the second acrylic resin is 3 to 60:1.

[0010] The aqueous intermediate composition according to the present invention can secure optimal appearance and film properties in a shortened coating method in which the intermediate drying oven (HAB) process is omitted after the intermediate coating, and the intermediate drying oven is passed through only once after the base coat is dried and then a clear coat is applied.

[0011] Hereinafter, various embodiments of the present invention will be described in detail.

[0012] In this specification, “weight average molecular weight (Mw)” and “number average molecular weight (Mn)” are measured by methods commonly known in the technical field to which the present invention belongs, and can be measured by methods such as GPC (gel permeation chromatography).

[0013] In this specification, the “glass transition temperature (Tg)” is measured by a method commonly known in the technical field to which the present invention belongs, and can be measured by, for example, thermomechanical analysis (TMA) or differential scanning calorimetry (DSC).

[0014] In this specification, functional groups such as “acid value (Av)” and “hydroxyl value (OHv)” are measured by methods commonly known in the technical field to which the present invention belongs, and can be measured by methods such as titration, for example.

[0015] In this specification, “viscosity” is measured by a conventional method known in the relevant technical field, and can be measured, for example, using a Brookfield viscometer or Gardner viscometer (bubble viscometer) at room temperature (25°C).

[0016] In this specification, “particle size (D50)” is measured by a conventional method known in the relevant technical field, and can be measured by, for example, laser light scattering (LLS).

[0017] The aqueous intermediate composition according to the present invention comprises a first acrylic resin, a second acrylic resin, a polyester resin, a first polyurethane resin, a second polyurethane resin, and a melamine-based curing agent.

[0018] In the conventional painting method, the intermediate coating film was painted in a thin film (20㎛±2), which resulted in problems such as deterioration of appearance, chipping resistance, impact resistance, and adhesion.

[0019] The aqueous intermediate composition according to the present invention uses two types of first acrylic resin and second acrylic resins having different physical properties, and two types of first polyurethane resin and second polyurethane resins having different physical properties to improve the smoothness of the intermediate coating film, thereby securing a high appearance, and at the same time imparting flexibility and elasticity to improve mechanical properties such as chipping resistance and impact resistance, in order to solve these conventional problems.

[0020] 1st acrylic resin

[0021] The first acrylic resin serves to improve the appearance properties and rheology of a coating film prepared from an aqueous intermediate composition containing the same.

[0022] The first acrylic resin may be directly synthesized according to a known method, or a commercially available product may be used. For example, the first acrylic resin may include units derived from one or more monomers selected from the group consisting of allyl methacrylate (AMA), methyl methacrylate (MMA), ethyl acrylate (EA), hydroethyl acrylate (HEA), and methacrylic acid (MAA). For example, the first acrylic resin may be prepared from a mixture including allyl methacrylate (AMA), methyl methacrylate (MMA), ethyl acrylate (EA), hydroethyl acrylate (HEA), and methacrylic acid (MAA) as monomers.

[0023] Additionally, the mixture may further comprise a divalent acrylic monomer. Divalent acrylic monomers include, for example, 1,4-Butanediol diacrylate, 1,4-Butanediol dimethacrylate, 1,5-pentanediol dimethacrylate, 1,6-Hexanediol diacrylate, 1,6-Hexanediol dimethacrylate, 1,9-Nonanediol dimethacrylate, 1,10-Decanediol dimethacrylate, ethylene glycol diacrylate, Examples include ethylene glycol dimethacrylate.

[0024] The first acrylic resin has a solid content (NV) of 30 to 70 wt% based on the total weight of the first acrylic resin. When the solid content of the first acrylic resin is within the above range, the storage stability of the resin may be improved and workability may be excellent. When the solid content of the first acrylic resin is below the above range, the viscosity may be excessively low, which may cause a problem in that the workability of the aqueous intermediate composition containing it may be insufficient. When the solid content of the first acrylic resin is above the above range, the viscosity of the first acrylic resin may be excessively high, which may result in poor stability during the reaction and poor dispersion stability, which may cause agglomeration over time.

[0025] The first acrylic resin has a viscosity of 10 to 200 cPs at 25°C. When the viscosity of the first acrylic resin at 25°C is within the above range, the viscosity of the aqueous intermediate composition is appropriate, thereby improving workability. When the viscosity of the first acrylic resin at 25°C is less than the above range, the viscosity of the aqueous intermediate composition is too low, which may cause problems such as poor formation of the produced coating film, resulting in poor paint flow, adhesion, and scratch resistance. When the viscosity exceeds the above range, the workability of the aqueous intermediate composition may be insufficient, which may cause problems such as poor appearance characteristics of the produced coating film.

[0026] The first acrylic resin has a glass transition temperature (Tg) of -15 to 0°C. When the glass transition temperature of the first acrylic resin is within the above range, the hardness and appearance properties of a coating film manufactured from a composition containing the same are improved. When the glass transition temperature of the first acrylic resin is below the above range, the drying speed and crosslinking density of the coating film are reduced, which causes a problem in that the hardness and appearance properties of the manufactured coating film are insufficient. When the glass transition temperature of the first acrylic resin is above the above range, the coating film becomes brittle, which may cause the appearance properties and chipping resistance of the manufactured coating film to be insufficient.

[0027] The first acrylic resin has an acid value (Av) of 10 to 30 mgKOH / g. When the acid value of the first acrylic resin is within the above range, the reactivity of the composition containing it can be adjusted to improve the appearance properties of the coating film manufactured therefrom. When the acid value of the first acrylic resin is below the above range, the resin stability is lowered, which causes a problem of lowering the storage properties of the manufactured aqueous intermediate composition. When the acid value exceeds the above range, the viscosity of the composition increases due to increased resin cohesion, which can cause problems of lowering workability and water resistance of the coating film.

[0028] The first acrylic resin has a hydroxyl value (OHv) of 10 to 20 mgKOH / g. When the hydroxyl value of the first acrylic resin is within the above range, the reactivity of the composition containing it can be adjusted to improve the appearance properties of the coating film manufactured therefrom. When the hydroxyl value of the first acrylic resin is below the above range, the resin stability is lowered, which causes a problem of lowering the storage properties of the manufactured aqueous intermediate composition. When the hydroxyl value exceeds the above range, the viscosity of the composition increases due to increased resin cohesion, which can cause problems of lowering workability and water resistance of the coating film.

[0029] The first acrylic resin may be in the form of an emulsion dispersed in a solvent such as deionized water. For example, the first acrylic resin may be in the form of an emulsion dispersed in a solvent and have a particle size (D50) of 80 to 150 nm. When the first acrylic resin is in the form of an emulsion dispersed in deionized water, it has the effect of reducing the volatile organic compound (VOC) content of the paint, and when the particle size (D50) is within the above range, the appearance and particle stability are good.

[0030] The first acrylic resin may be included in the aqueous intermediate composition in an amount of 21 to 30 wt%, or 23 to 27 wt%, based on the total weight of the aqueous intermediate composition. When the first acrylic resin is included within the above content range, it has the effect of improving the adhesion, durability, hardness, and scratch resistance of the coating film. When the content of the first acrylic resin is less than the above range, the drying property is reduced, which may cause a problem in that the adhesion, gloss, hardness, and durability of the coating film are reduced, and when the content exceeds the above range, the drying proceeds quickly, which may cause a problem in that the painting workability and paint flowability of the composition are insufficient, which may cause a problem in that the appearance and scratch resistance of the coating film are reduced.

[0031] Second acrylic resin

[0032] The second acrylic resin serves to control the rheology and hardness of a coating film prepared from an aqueous intermediate composition containing the same, thereby improving appearance properties, chipping resistance, impact resistance, and adhesion.

[0033] The second acrylic resin may be the same as described for the first acrylic resin, except as described below.

[0034] The second acrylic resin has a solid content (NV) of 40 to 70 wt% based on the total weight of the second acrylic resin. When the solid content of the second acrylic resin is within the above range, the storage stability of the resin may be improved and workability may be excellent. When the solid content of the second acrylic resin is below the above range, the viscosity may be excessively low, which may cause a problem in that the workability of the aqueous intermediate composition containing it may be insufficient. When the solid content of the second acrylic resin is above the above range, the viscosity of the second acrylic resin may be excessively high, which may result in poor stability during the reaction and poor dispersion stability, which may cause agglomeration over time.

[0035] The second acrylic resin has a Gardner viscosity of E to I at 25°C. When the viscosity of the second acrylic resin at 25°C is within the above range, the viscosity of the aqueous intermediate composition is appropriate, thereby improving workability. When the viscosity of the second acrylic resin at 25°C is less than the above range, the viscosity of the composition is too low, which may cause problems such as poor formation of the produced coating film, resulting in poor paint flow, adhesion, and scratch resistance. When the viscosity exceeds the above range, the workability of the composition may be insufficient, which may cause problems such as poor appearance characteristics of the produced coating film.

[0036] The second acrylic resin has a glass transition temperature (Tg) of -50 to -20°C, or -49 to -36°C. When the glass transition temperature of the second acrylic resin is within the above range, the hardness and appearance properties of a coating film manufactured from a composition containing the same are improved. When the glass transition temperature of the second acrylic resin is below the above range, the drying speed and crosslinking density of the coating film are reduced, which causes a problem in that the hardness and appearance properties of the manufactured coating film are insufficient, and when it exceeds the above range, the coating film becomes brittle, which may cause the appearance properties and chipping resistance of the manufactured coating film to be insufficient.

[0037] The second acrylic resin has an acid value (Av) of 10 to 30 mgKOH / g. When the acid value of the second acrylic resin is within the above range, the reactivity of the composition containing it can be adjusted to improve the appearance properties of the coating film manufactured therefrom. When the acid value of the second acrylic resin is below the above range, the resin stability is lowered, which causes a problem of reduced storage properties of the manufactured coating composition. When the acid value exceeds the above range, the viscosity of the composition increases due to increased resin cohesion, which can cause problems of reduced workability and water resistance of the coating film.

[0038] The second acrylic resin has a hydroxyl value (OHv) of 100 to 300 mgKOH / g. When the hydroxyl value of the second acrylic resin is within the above range, the reactivity of the composition containing it can be adjusted to improve the appearance properties of the coating film manufactured therefrom. When the hydroxyl value of the second acrylic resin is below the above range, the resin stability is lowered, which causes a problem of lowering the storage properties of the manufactured aqueous intermediate composition. When the hydroxyl value exceeds the above range, the viscosity of the composition increases due to increased resin cohesion, which can cause problems of lowering workability and water resistance of the coating film.

[0039] The second acrylic resin has a weight average molecular weight (Mw) of 7,000 to 30,000 g / mol. When the weight average molecular weight of the second acrylic resin is within the above range, the long-term physical properties of the manufactured coating film, such as durability, adhesion, hardness, and weather resistance, can be excellent. When the weight average molecular weight of the second acrylic resin is less than the above range, the molecular weight is small, so that the water resistance, weather resistance, and scratch resistance of the manufactured coating film are insufficient, and when the weight average molecular weight exceeds the above range, the flowability is reduced due to the increase in molecular weight, so that the workability of the aqueous intermediate composition containing it is poor, and the surface smoothness is poor, which may cause a problem that it is difficult to manufacture a coating film having an excellent appearance.

[0040] The second acrylic resin may be a water-soluble acrylic resin that dissolves in a solvent such as deionized water. If the second acrylic resin is a water-soluble acrylic resin, it has the effect of reducing the volatile organic compound (VOC) content of the paint.

[0041] The second acrylic resin may be included in the composition in an amount of 0.5 to 10 wt%, or 0.5 to 6 wt%, based on the total weight of the aqueous intermediate composition. When the second acrylic resin is included within the above content range, it has the effect of improving the adhesion, durability, hardness, and scratch resistance of the coating film. When the content of the second acrylic resin is less than the above range, the drying property is reduced, which may cause a problem in that the adhesion, gloss, hardness, and durability of the coating film are reduced, and when the content exceeds the above range, the drying proceeds quickly, which may cause a problem in that the painting workability and paint flow of the composition are insufficient, which may cause a problem in that the appearance and scratch resistance of the coating film are reduced.

[0042] polyester resin

[0043] Polyester resin plays a role in improving adhesion, water resistance and impact resistance by controlling the flexibility of a coating film manufactured from an aqueous intermediate composition containing the polyester resin.

[0044] A polyester resin can be prepared by reacting a carboxylic acid compound with a diol compound. For example, the polyester resin can be prepared by reacting at least one carboxylic acid compound selected from the group consisting of adipic acid (AA), isophthalic acid (IPA), trimaletic anhydride (TMA), alicyclic acids, phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, fumaric acid, maleic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and derivatives thereof; and at least one diol compound selected from the group consisting of 1,6-hexanediol (1,6-HD), neopentyl glycol (NPG), trimethylol propane (TMP), ethylene glycol, propylene glycol, diethylene glycol, butanediol, 1,4-hexanediol, and 3-methylpentanediol.

[0045] The polyester resin has a solids content (NV) of 60 to 90 wt% based on the total weight of the polyester resin. When the solids content of the polyester resin is within the above range, the storage stability of the resin is improved and workability may be excellent. When the solids content of the polyester resin is below the above range, the viscosity may be excessively low, which may cause the workability of the aqueous intermediate composition containing it to be insufficient. When the solids content of the polyester resin is above the above range, the viscosity of the polyester resin may be excessively high, which may reduce stability during the reaction.

[0046] The polyester resin may have a Gardner viscosity of Z to Z3 at 25°C. When the viscosity of the polyester resin at 25°C is within the above range, the viscosity of the aqueous intermediate composition is appropriate, thereby improving workability. When the viscosity of the polyester resin at 25°C is less than the above range, the viscosity of the composition is too low, which may cause problems such as poor formation of the produced coating film, resulting in reduced paint flow, adhesion, and scratch resistance. When the viscosity exceeds the above range, the workability of the composition may be insufficient, which may cause problems such as poor appearance characteristics of the produced coating film.

[0047] The polyester resin may have a glass transition temperature (Tg) of -40 to -20°C. When the glass transition temperature of the polyester resin is within the above range, the hardness and solvent resistance of a coating film manufactured from a composition containing the polyester resin are improved. When the glass transition temperature of the polyester resin is below the above range, the drying speed and crosslinking density of the coating film are reduced, which causes problems such as insufficient hardness and solvent resistance of the manufactured coating film. When the glass transition temperature exceeds the above range, the coating film becomes brittle, which may result in insufficient appearance characteristics and chipping resistance of the manufactured coating film.

[0048] The polyester resin has an acid value (Av) of 2 to 50 mgKOH / g. When the acid value of the polyester resin is within the above range, the storage stability and crosslinking density of the composition containing it are improved, resulting in good cold chipping resistance. When the acid value of the polyester resin is below the above range, the resin stability is reduced, resulting in a problem of reduced storage properties of the manufactured paint composition. When the acid value exceeds the above range, the viscosity of the composition increases due to increased resin cohesion, which may result in problems of reduced workability and water resistance of the coating film.

[0049] The polyester resin has a hydroxyl value (OHv) of 50 to 100 mgKOH / g. When the hydroxyl value of the polyester resin is within the above range, the composition containing it has improved storage stability and crosslinking density, resulting in good cold chipping resistance. When the hydroxyl value of the polyester resin is below the above range, the resin stability is reduced, resulting in a problem of reduced storage stability of the manufactured paint composition. When the hydroxyl value exceeds the above range, the viscosity of the composition increases due to increased resin cohesion, which may result in problems of reduced workability and water resistance of the coating film.

[0050] The polyester resin has a number average molecular weight (Mn) of 1,000 to 4,000 g / mol. When the number average molecular weight of the polyester resin is within the above range, the long-term physical properties of the manufactured coating film, such as durability, adhesion, hardness, and weather resistance, can be excellent. When the number average molecular weight of the polyester resin is less than the above range, the molecular weight is small, so that the water resistance, weather resistance, and scratch resistance of the manufactured coating film are insufficient. When the number average molecular weight of the polyester resin is greater than the above range, the flowability is reduced due to the increase in molecular weight, so that the workability of the aqueous intermediate composition containing it is poor, and the surface smoothness is poor, which may cause a problem that it is difficult to manufacture a coating film having an excellent appearance.

[0051] The polyester resin may be included in the composition in an amount of 1 to 10 wt%, or 2 to 7 wt%, based on the total weight of the aqueous intermediate composition. When the polyester resin is included within the above content range, excellent appearance, impact resistance, and cold chipping resistance can be secured. When the content of the polyester resin is less than the above range, the drying property is reduced, which may cause problems such as reduced adhesion, gloss, hardness, and durability of the coating film. When the content exceeds the above range, the drying proceeds quickly, which may cause problems such as reduced painting workability and paint flow of the composition, which may cause reduced appearance and scratch resistance of the coating film.

[0052] 1st polyurethane resin

[0053] The first polyurethane resin improves the drying properties of the aqueous intermediate composition containing the same, and improves the elasticity, impact resistance, and flexibility of the coating film produced from the composition.

[0054] The first polyurethane resin may be synthesized directly using a known method, or a commercially available product may be used. For example, the first polyurethane resin may be polyether polyurethane, polyester polyurethane, polycarbonate polyurethane, polyetherester polyurethane, polyethercarbonate polyurethane, polycaprolactone polyurethane, aliphatic hydrocarbon polyurethane, aromatic hydrocarbon polyurethane, etc.

[0055] The first polyurethane resin has a solid content (NV) of 30 to 60 wt% based on the total weight of the first polyurethane resin. When the solid content of the first polyurethane resin is within the above range, the storage stability of the resin and the storage stability of the aqueous intermediate composition are improved, and workability may be excellent. When the solid content of the first polyurethane resin is below the above range, the viscosity may be excessively low, which may cause a problem in that the workability of the aqueous intermediate composition containing it may be insufficient, and when the solid content of the first polyurethane resin is above the above range, the viscosity of the first polyurethane resin may be excessively high, which may result in poor stability during the reaction and poor dispersion stability, which may cause agglomeration over time.

[0056] The first polyurethane resin has a glass transition temperature (Tg) of -35 to -10°C. When the glass transition temperature of the first polyurethane resin is within the above range, the flexibility and hardness of the coating film are improved. When the glass transition temperature of the first polyurethane resin is below the above range, the drying speed of the aqueous intermediate composition is delayed, which causes problems such as insufficient solvent resistance and chipping resistance of the produced coating film. When the glass transition temperature exceeds the above range, the coating film may become brittle, resulting in insufficient appearance characteristics and hardness of the coating film.

[0057] The first polyurethane resin has an acid value (Av) of 5 to 30 mgKOH / g. When the acid value of the first polyurethane resin is within the above range, the reactivity of the composition containing the first polyurethane resin can be adjusted to improve the appearance properties of the coating film manufactured therefrom. When the acid value of the first polyurethane resin is below the above range, the resin stability is reduced, which causes a problem of reduced storability of the manufactured coating composition. When the acid value exceeds the above range, the viscosity of the composition increases due to increased resin cohesion, which can cause problems of reduced workability and water resistance of the coating film.

[0058] The first polyurethane resin may be in the form of a polyurethane resin dispersed in a solvent. The aqueous medium for dispersing the polyurethane resin may be an aqueous solvent or a mixed medium of water and a hydrophilic organic solvent. For example, the aqueous solvent may be tap water, ion-exchanged water, distilled water, or ultrapure water. In particular, ion-exchanged water may be used to prevent particles from becoming unstable due to the ease of obtaining water or the influence of salts. In addition, the hydrophilic organic solvent may be a lower monohydric alcohol such as methanol, ethanol, or propanol; a polyhydric alcohol such as ethylene glycol or glycerin; or an aprotic hydrophilic organic solvent such as N-methylmorpholine, dimethyl sulfoxide, or dimethylformamide. The first polyurethane resin may be in the form of a dispersion dispersed in deionized water, and may have a particle size (D50) of 50 to 200 nm.

[0059] The first polyurethane resin has a weight average molecular weight (Mw) of 15,000 to 35,000 g / mol. When the weight average molecular weight of the first polyurethane resin is within the above range, the aqueous intermediate composition exhibits excellent drying properties, cold-resistant chipping resistance, and impact resistance. When the weight average molecular weight of the first polyurethane resin is less than the above range, the molecular weight is low, which may cause a problem in that the mechanical properties of the produced coating film are deteriorated. When the weight average molecular weight exceeds the above range, the flowability is reduced due to an increase in molecular weight, which may cause the coating film to brittle, resulting in reduced smoothness and reduced scratch resistance.

[0060] The first polyurethane resin may be included in the composition in an amount of 7 to 15 wt%, or 9 to 13 wt%, based on the total weight of the aqueous intermediate composition. When the first polyurethane resin is included within the above content range, it has the effect of improving tensile strength, flexibility, elongation, adhesion, abrasion resistance, scratch resistance, and film smoothness. When the content of the first polyurethane resin in the composition is less than the above range, flexibility may decrease, which may cause problems such as decreased tensile strength and scratch resistance, and when it exceeds the above range, the viscosity of the composition may excessively increase, which may cause problems such as decreased workability and drying property, which may cause decreased appearance and mechanical properties.

[0061] Second polyurethane resin

[0062] The second urethane resin improves the workability of the aqueous intermediate composition containing the same, and improves the appearance properties, chipping resistance, impact resistance, and adhesion of the coating film manufactured from the composition.

[0063] The second polyurethane resin may be a urethane diol-based compound. For example, the second polyurethane resin may be a urethane diol obtained by reacting a primary amino alcohol such as aminoethanol or aminoisopropanol; or a primary diamine such as ethylenediamine, propylenediamine, 2-methyl-pentanediamine-(1,5) or hexanediamine-(1,6); with an alkylene carbonate such as ethylene or propylene carbonate.

[0064] The second polyurethane resin may have a solid content (NV) of 60 to 90 wt% based on the total weight of the second polyurethane resin. When the solid content of the second polyurethane resin is within the above range, the storage stability of the resin may be improved and workability may be excellent. When the solid content of the second polyurethane resin is below the above range, the viscosity may be excessively low, which may cause a problem in that the workability of the aqueous intermediate composition containing it may be insufficient, and when the solid content of the second polyurethane resin is above the above range, the viscosity of the second polyurethane resin may be excessively high, which may result in poor stability during the reaction.

[0065] The second polyurethane resin may have a viscosity of 1,000 to 6,000 cPs at 25°C. When the viscosity of the second polyurethane resin at 25°C is within the above range, the viscosity of the aqueous intermediate composition is appropriate, thereby improving workability. When the viscosity of the second polyurethane resin at 25°C is less than the above range, the viscosity of the composition may be too low, resulting in a problem of poor formation of the produced coating film, thereby deteriorating the paint flowability, adhesion, and scratch resistance. When the viscosity exceeds the above range, the workability of the composition may be insufficient, thereby causing a problem of poor appearance characteristics of the produced coating film.

[0066] The second polyurethane resin may have a hydroxyl value (OHv) of 200 to 450 mgKOH / g. When the hydroxyl value of the second polyurethane resin is within the above range, the gloss and appearance properties of the produced coating film are effectively improved. When the hydroxyl value of the second polyurethane resin is below the above range, the resin stability may be reduced, resulting in a problem of reduced storability of the produced coating composition. When the hydroxyl value exceeds the above range, the viscosity of the composition may increase due to increased resin cohesion, resulting in problems of reduced workability and water resistance of the coating film.

[0067] The second polyurethane resin may have a weight average molecular weight (Mw) of 200 to 600 g / mol. When the weight average molecular weight of the second polyurethane resin is within the above range, the long-term physical properties of the manufactured coating film, such as durability, adhesion, hardness, and weather resistance, may be excellent. When the weight average molecular weight of the second polyurethane resin is less than the above range, the molecular weight is small, so that the water resistance, weather resistance, and scratch resistance of the manufactured coating film are insufficient. When the weight average molecular weight of the second polyurethane resin is greater than the above range, the flowability is reduced due to the increase in molecular weight, so that the workability of the aqueous intermediate composition containing it is poor, and the surface smoothness is poor, which may cause a problem that it is difficult to manufacture a coating film having an excellent appearance.

[0068] The second polyurethane resin may be included in the composition in an amount of 0.5 to 10 wt%, or 0.5 to 6 wt%, based on the total weight of the aqueous intermediate composition. When the amount of the second polyurethane resin is within the above range, the flexibility and appearance of the coating film are improved. When the amount of the second polyurethane resin is less than the above range, the drying property is reduced, which may cause problems such as reduced adhesion, gloss, hardness, and durability of the coating film. When the amount exceeds the above range, the drying process proceeds quickly, which may cause problems such as reduced painting workability and paint flowability of the composition, which may cause reduced appearance and scratch resistance of the coating film.

[0069] Melamine-based hardener

[0070] The melamine-based curing agent acts to cure by crosslinking with each component of the aqueous intermediate composition, and improves the adhesion and hardness of a coating film manufactured from the aqueous intermediate composition containing the melamine-based curing agent.

[0071] The melamine-based curing agent may include a hydrophilic melamine resin containing an imino group. For example, the melamine-based curing agent may be in a liquid form containing a hydrophilic melamine resin containing an imino group. As another example, the melamine-based curing agent may be in a liquid form containing a hydrophilic melamine resin containing an imino group and having a solids content (NV) of 70 to 99 wt% based on the total weight of the melamine-based curing agent.

[0072] Commercially available melamine curing agents include Cymel-303, Cymel-325, Cymel-327, and Cymel-385 from Cytec, Resimene HM-2608, Resimene 718, and Resimene 717 from INEOS, and Luwipal 052 and 072 from BASF.

[0073] The melamine-based curing agent may have a Gardner viscosity of Y to Z2 at 25°C. When the viscosity of the melamine-based curing agent at 25°C is within the above range, the viscosity of the aqueous intermediate composition is appropriate, thereby improving workability. When the viscosity of the melamine-based curing agent at 25°C is less than the above range, the viscosity of the composition may be too low, resulting in problems such as poor formation of the produced coating film, which may deteriorate the paint flow, adhesion, and scratch resistance. When the viscosity exceeds the above range, the workability of the composition may be insufficient, which may result in problems such as poor appearance characteristics of the produced coating film.

[0074] The melamine-based curing agent may be included in the composition in an amount of 2 to 10 wt% or 3 to 7 wt% based on the total weight of the aqueous intermediate composition. When the amount of the melamine-based curing agent is within the above range, appropriate coating properties can be secured.

[0075] solvent

[0076] The aqueous intermediate composition according to the present invention may additionally include a solvent. The solvent serves to control the viscosity of the composition and reduce the generation of volatile organic compounds (VOCs). For example, the solvent may include one or more types of water selected from the group consisting of deionized water, pure water, ultrapure water, and distilled water. In addition to water, the solvent may additionally include an organic solvent.

[0077] The solvent may be included in the composition in an amount of 5 to 20 wt% based on the total weight of the aqueous intermediate composition. When the solvent content in the composition is within the above range, problems such as reduced water dispersibility of resins in the composition, reduced environmental friendliness, which is an advantage of water-based paints, and insufficient evaporation of water, resulting in coating defects such as pinholes and stains in the final coating can be prevented.

[0078] pigment

[0079] The aqueous intermediate composition according to the present invention may additionally include pigments. Pigments serve to enhance the mechanical strength of the resulting coating and impart color. For example, extender pigments increase the solids volume ratio of the aqueous intermediate composition and enhance the mechanical strength of the resulting coating. Examples of such extender pigments include calcium carbonate, magnesium carbonate, aluminum silicate, silica, and barium sulfate.

[0080] The water-based intermediate composition may use an effect pigment to impart a metallic effect to the coating, a coloring pigment to impart a color and hiding effect in combination with the coating forming material, or a combination thereof.

[0081] Examples of effect pigments include water-based aluminum flakes, mica pigments, or mixtures thereof. Examples of color pigments include inorganic oxide pigments, polycyclic organic pigments containing azo and VAT pigments, anthraquinone organic pigments, or mixtures thereof.

[0082] Examples of coloring pigments that can be used include carbon black and titanium dioxide.

[0083] The pigment may be included in the composition in an amount of 5 to 60 wt%, or 10 to 40 wt%, based on the total weight of the aqueous intermediate composition. When the pigment content in the aqueous intermediate composition is within the above range, problems such as insufficient mechanical properties and hiding power of the manufactured film, deterioration in the stability of the composition, and deterioration in the dispersibility of the pigment can be prevented.

[0084] additives

[0085] The aqueous intermediate composition according to the present invention may further comprise one or more additives selected from the group consisting of a softener, a thickener, a neutralizer, a catalyst, an ultraviolet absorber, a leveling agent, an antifoaming agent, a wetting agent, and a wax.

[0086] The additive may be included in the composition in an amount of 1 to 40 wt% or 5 to 20 wt% based on the total weight of the aqueous medium composition.

[0087] The solvent affects the smoothness of the coating being manufactured, provides storage stability to the water-based intermediate composition, lowers the minimum coating formation temperature, and controls the volatility of the solvent during the painting process.

[0088] Examples of the solubilizer include, but are not limited to, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, propylene glycol, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, n-propyl alcohol, i-propyl alcohol, n-butanol, propylene glycol monomethyl ether, butyl glycol, hexyl glycol, 2-ethylhexyl alcohol, butyl carbitol, and the like.

[0089] Thickeners serve to improve the flowability of aqueous medium compositions. For example, urethane thickeners or acrylic thickeners can be used.

[0090] Neutralizing agents improve the storage stability of aqueous intermediate compositions and control the pH (to a pH level of 7.5 to 9.0). Neutralizing agents include, for example, trialkylamines such as trimethylamine, triethylamine, and tributylamine; N,N-dialkylalkanolamines such as N,N-dimethylethanolamine, N,N-dimethylpropanolamine, N,N-dipropylethanolamine, and 1-dimethylamino-2-methyl-2-propanol; N-alkyl-N,N-dialkanolamines; and trialkanolamines such as triethanolamine; tertiary amine compounds such as ammonia; trimethylammonium hydroxide; sodium hydroxide; potassium hydroxide; and lithium hydroxide.

[0091] Catalysts prevent incomplete curing of aqueous intermediate compositions and improve the mechanical properties of coatings produced from them. Examples of catalysts include dodecylbenzene sulfonic acid type and amine-containing phosphate compounds.

[0092] UV absorbers block ultraviolet rays from reaching the manufactured coating, thereby improving the weatherability of the final coating.

[0093] The UV absorber may be a benzotriazole-based UV absorber. For example, the benzotriazole-based UV absorber is α-[3-[3-(2H-Benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxyphenyl]-1-oxapropyl]-ω-hydroxypoly(oxy-1,2-ethanediyl)). α-[3-[3-(2H-Benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxyphenyl]-1-oxapropyl]-ω-[3-[3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxyphenyl]-1-oxapropoxy]poly(oxy-1,2-ethanediyl)(α-[3-[3-(2H-Benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxyphenyl]-1-oxopropyl]-ω-[3-[3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxyphenyl]-1-oxopropoxy]poly(oxy-1,2-ethanediyl)), Examples include 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy-methyl ester.

[0094] Leveling agents serve to impart leveling and wettability to the manufactured coating film. Leveling agents may be cationic, anionic, or nonionic surfactants, and may include, for example, nonionic surfactants.

[0095] Defoaming agents suppress the formation of bubbles during paint production and suppress or eliminate pinholes and popping that occur during film formation. Any conventional defoaming agent suitable for use in paint compositions may be used without particular restrictions. Examples of commercially available defoaming agents include BYK-011, BYK-015, and BYK-072, Air Products' DF-21, Munzing's agitan 281, and Sannopco's Foamster-324.

[0096] Wetting agents serve to improve the leveling and wettability of a coating film prepared from a composition containing them, and are not particularly limited as long as they are commonly used in paint compositions. For example, wetting agents may include polyether-modified polysiloxane-based or acetylene alcohol-based wetting agents.

[0097] Wax serves to prevent problems such as sagging caused by slow drying of a coating film manufactured from a composition containing it, and is not particularly limited as long as it is commonly used in paint compositions. For example, waxes may include ethylene-vinyl-acetate waxes.

[0098] Mercury intermediate composition

[0099] The aqueous intermediate composition according to the present invention comprises a first acrylic resin and a second acrylic resin in a weight ratio of the first acrylic resin to the second acrylic resin of 3 to 60:1, 5 to 50:1, or 10 to 20:1. The first acrylic resin has a relatively high Tg, so that the coating film has good drying properties and thus has excellent appearance, gloss, and durability. The second acrylic resin has a low Tg and a high hydroxyl value (OHv), so that it has excellent effects of improving chipping resistance and impact resistance. Therefore, when the two types of acrylic resins are mixed and used, a synergistic effect can be produced. When the weight ratio of the first acrylic resin content to the second acrylic resin content is less than the above range, problems such as deterioration in appearance, deterioration in gloss, and deterioration in pencil hardness may occur. When the weight ratio exceeds the above range, problems in appearance, chipping resistance, and impact resistance may occur in the short-axis aqueous 3C1B coating method.

[0100] In the present invention, in order to solve the problems such as appearance degradation, chipping resistance, impact resistance, and adhesion that occur when the intermediate coating film is painted as a thin film (20㎛±2) in the existing water-based 3C1B method and the shortened water-based 3C1B method, a second polyurethane resin, which is a high-functional polyurethane diol resin, and a second acrylic resin, which is a high-functional acrylic resin, are used in the existing water-based intermediate coating composition to improve the smoothness of the intermediate coating film, thereby securing a high appearance, and at the same time, by imparting flexibility and elasticity, mechanical properties such as chipping resistance and impact resistance can be improved.

[0101] Meanwhile, the aqueous intermediate composition of the present invention can be used to produce a coating film with excellent appearance and mechanical properties, making it suitable as a paint for automotive parts and bodywork. Furthermore, the aqueous intermediate composition of the present invention is environmentally friendly and economical due to its high solids content and VOC reduction effect.

[0102] Hereinafter, the present invention will be described in more detail through examples. However, these examples are provided solely to aid understanding of the present invention and are not intended to limit the scope of the present invention in any way.

[0103] [Example]

[0104] Examples 1 to 6, Comparative Examples 1 to 14: Preparation of aqueous intermediate compositions

[0105] A modified intermediate composition was prepared by stirring and mixing each component as described in Tables 1 to 3.

[0106]

[0107]

[0108]

[0109] The manufacturers and product names of each ingredient used in the examples and comparative examples are shown in Table 4.

[0110]

[0111] [Test Example] Evaluation of the characteristics of manufactured coating films

[0112] After applying the water-based intermediate compositions of the examples and comparative examples on the electrodeposition-coated specimens, they were dried at room temperature for 15 minutes to form an intermediate coating film with a thickness of 20±2㎛. After that, a base coat (manufacturer: KCC, product name: WT3062, dry film thickness: 10-20㎛) was applied, and hot air was blown (HAB) at 80℃ for 3 minutes to evaporate the water remaining in the paint, and then an oil-based clear coat (manufacturer: KCC, product name: TT6830, dry film thickness: 30-50㎛) was applied, and the final coating film was produced by drying and curing in a general oven at 140℃ for 20-30 minutes.

[0113] The appearance characteristics and physical properties of the final coating were measured using the following methods, and the results are shown in Tables 5 to 7.

[0114] 1) Exterior of the coating

[0115] The horizontal / vertical appearance CF values ​​of the final coating were measured using an automotive appearance measuring device, Wave Scan DOI (BYK Gardner), and it was determined that the higher the CF value, the better the appearance characteristics of the coating.

[0116] It was judged as ◎-Excellent (CF 80 or higher / 70 or higher), ○-Good (CF 75∼79 / 65∼69), △-Average (CF 70∼75 or less / 60∼65 or less), ×-Poor (CF less than 70 / less than 60).

[0117] 2) Chipping resistance

[0118] After leaving the final coating at -20℃ for 3 hours, a method was used to strike the coating surface by pushing out a 50g chipping stone at a pressure of 5 bar using a 50g chipping stone.

[0119] When there are 10 or fewer damages of 1 mm or less in size, it is judged as “◎-Excellent”, when there are 10 or fewer damages of 1 mm to 2 mm or less in size, it is judged as “○-Good”, when there are 10 or fewer damages of 2 mm to 3 mm or less in size, it is judged as “△-Average”, and when there are 10 or more damages of 2 mm to 3 mm or more in size, it is judged as “×-Poor”.

[0120] 3) Impact resistance

[0121] The impact resistance was evaluated by observing cracks and peeling that occurred in the coating when dropped from a height of 20 cm or more using a 500 g weight.

[0122] If there were no cracks in the coating when the height of the weight was 50 cm or more, it was judged as “◎-Excellent”, if cracks in the coating occurred when the height of the weight was 30 to 50 cm or less, it was judged as “○-Good”, if cracks in the coating occurred when the height of the weight was 20 to 30 cm or less, it was judged as “△-Average”, and if cracks occurred when the height of the weight was less than 20 cm, it was judged as “×-Poor”.

[0123] 4) Adhesiveness

[0124] 100 square (2 mm wide × 2 mm long) checkerboards were made with a knife using crosscuts at 2 mm intervals, and then adhesive tape was used to remove them and measure the adhesiveness.

[0125] When the number of coating cracks in the crosscut line corners is less than 10, there is no peeling along a straight line, and there is no peeling of 50% or more of the checkerboard pattern, it is judged as “◎-Excellent”; when the coating cracks in the crosscut line corners are visible throughout, there is no peeling along a straight line, there is no peeling of 50% or more of the checkerboard pattern, and the total peeling area is less than 5%, it is judged as “○-Good”; when there is peeling along a straight line, there is no peeling of 50% or more of the checkerboard pattern, and the total peeling area is less than 5-15%, it is judged as “△-Average”; when there is a lot of peeling along a straight line, there are 20 or more cases where the checkerboard pattern is completely peeled, and the total peeling area is 15% or more, it is judged as “×-Poor”.

[0126] 5) Gloss

[0127] To measure the gloss (GLOSS, %) reflected from the final coating, a gloss meter (BYK Gardner) was used to measure the 20-degree gloss of the final coating (higher is better).

[0128] According to the measurement results, it was evaluated as ◎-Excellent (gloss 91 or higher), ○-Good (gloss 88 to less than 91), △-Average (gloss 85 to less than 88), ×-Poor (gloss less than 85).

[0129] 6) Pencil hardness

[0130] Measured using the pencil hardness method (hardness measurement without damaging the coating film using each pencil: 2B, B, HB, F, H, 2H). The measurement results are expressed as ◎-Excellent (HB or higher), ○-Good (B), ×-Poor (less than B).

[0131] 7) Water resistance

[0132] The final coating was immersed in a 40℃ constant temperature bath for 10 days, and then evaluated for adhesion and discoloration. Excellent adhesion and no discoloration were evaluated as "◎-Excellent", good adhesion and no discoloration were evaluated as "○-Good", and good adhesion but recovery after discoloration was evaluated as "△-Average". Poor adhesion or discoloration was evaluated as "×-Poor".

[0133] * Additional explanation: Water resistance (after immersion at 40℃ for 10 days) is evaluated for adhesion and discoloration. The adhesion evaluation is the same as 4) adhesion evaluation method.

[0134] 8) Content

[0135] A method for evaluating the chemical solvent resistance of the final coating is to place a cotton cloth soaked in xylene solvent on the coating and then scrape it with a fingernail at a force of 2 kg four times every minute. The time it takes for the lower coating surface to appear when scratching with the fingernail is recorded. The measurement results are evaluated as "◎-Excellent" if it takes 10 minutes or more, "○-Good" if it takes 7 to less than 10 minutes, "△-Average" if it takes 5 to less than 7 minutes, and "×-Poor" if it takes less than 5 minutes.

[0136] 9) Weather resistance

[0137] After 1,000 hours of exposure to WOM, gloss retention (20 degree gloss), adhesion, and color difference (X-Rite MA98) tests were conducted. After producing 100 2mm crosscuts and removing them using adhesive tape, if there were no problems, if the gloss retention was 97% or more, and the color difference value (△E) was 0.5 or less, it was evaluated as "◎-Excellent". If there was no fall off in the crosscutting area of ​​the blade, but the gloss retention was less than 93-97%, and the color difference value (△E) was 1.0 or less, it was evaluated as "○-Good". If there was no fall off in the crosscutting area of ​​the blade, but the gloss retention was less than 90-93%, and the color difference value (△E) was 1.0 or less, it was evaluated as "△-Average". If the fall off area was 10% or more, the gloss retention was less than 90%, and the color difference value (△E) was 1.0 or more, it was evaluated as "×-Poor".

[0138]

[0139]

[0140]

[0141] As shown in Tables 5 to 7, the aqueous intermediate composition of the example showed excellent or good results in both the appearance and the physical properties of the final coating film. On the other hand, the aqueous intermediate composition of the comparative example showed results inferior to those of the example in terms of the appearance and the physical properties of the final coating film.

[0142] Hereinafter, various embodiments of the present invention will be described.

[0143] [Item 1] An aqueous intermediate composition comprising a first acrylic resin, a second acrylic resin, a polyester resin, a first polyurethane resin, a second polyurethane resin, and a melamine-based curing agent, wherein the first acrylic resin has a glass transition temperature of -15 to 0°C, an acid value of 10 to 30 mgKOH / g, and a hydroxyl value of 10 to 20 mgKOH / g, and the second acrylic resin has a glass transition temperature of -50 to -20°C, an acid value of 10 to 30 mgKOH / g, and a hydroxyl value of 100 to 300 mgKOH / g, and a weight ratio of the first acrylic resin: the second acrylic resin is 3 to 60:1.

[0144] [Item 2] In Item 1, the first acrylic resin has a solid content of 30 to 70 wt% based on the total weight of the first acrylic resin, a viscosity at 25°C of 10 to 200 cPs, and a particle size (D50) of 80 to 150 nm, an aqueous intermediate composition.

[0145] [Item 3] In Item 1, the second acrylic resin has a solid content of 40 to 70 wt% based on the total weight of the second acrylic resin, a Gardner viscosity at 25°C of E to I, and a weight average molecular weight of 7,000 to 30,000 g / mol, an aqueous intermediate composition.

[0146] [Item 4] In Item 1, the polyester resin has a solid content of 60 to 90 wt% based on the total weight of the polyester resin, a Gardner viscosity at 25°C of Z to Z3, a glass transition temperature of -40 to -20°C, an acid value of 2 to 50 mgKOH / g, a hydroxyl value of 50 to 100 mgKOH / g, and a number average molecular weight of 1,000 to 4,000 g / mol, an aqueous intermediate composition.

[0147] [Item 5] In Item 1, the first polyurethane resin has a solid content of 30 to 60 wt% based on the total weight of the first polyurethane resin, a glass transition temperature of -35 to -10°C, an acid value of 5 to 30 mgKOH / g, a particle size (D50) of 50 to 200 nm, and a weight average molecular weight of 15,000 to 35,000 g / mol, an aqueous intermediate composition.

[0148] [Item 6] In Item 1, the second polyurethane resin is a urethane diol-based compound, has a solid content of 60 to 90 wt% based on the total weight of the second polyurethane resin, a viscosity at 25°C of 1,000 to 6,000 cPs, a hydroxyl value of 200 to 450 mgKOH / g, and a weight average molecular weight of 200 to 600 g / mol, an aqueous intermediate composition.

[0149] [Item 7] In Item 1, the melamine-based curing agent is an aqueous intermediate composition having a solid content of 70 to 99 wt% based on the total weight of the melamine-based curing agent and a Gardner viscosity at 25°C of Y to Z2.

[0150] [Item 8] An aqueous intermediate composition comprising, based on the total weight of the aqueous intermediate composition of Item 1, 21 to 30 wt% of the first acrylic resin, 0.5 to 10 wt% of the second acrylic resin, 1 to 10 wt% of the polyester resin, 7 to 15 wt% of the first polyurethane resin, 0.5 to 10 wt% of the second polyurethane resin, and 2 to 10 wt% of the melamine resin.

Claims

1. Contains a first acrylic resin, a second acrylic resin, a polyester resin, a first polyurethane resin, a second polyurethane resin, and a melamine-based curing agent. The first acrylic resin has a glass transition temperature of -15 to 0 ℃, an acid value of 10 to 30 mgKOH / g, and a hydroxyl value of 10 to 20 mgKOH / g. The second acrylic resin has a glass transition temperature of -50 to -20°C, an acid value of 10 to 30 mgKOH / g, and a hydroxyl value of 100 to 300 mgKOH / g. A water-based intermediate composition having a weight ratio of first acrylic resin to second acrylic resin of 3 to 60:

1.

2. In claim 1, A water-based intermediate composition in which the first acrylic resin has a solid content of 30 to 70 wt% based on the total weight of the first acrylic resin, a viscosity at 25°C of 10 to 200 cPs, and a particle size (D50) of 80 to 150 nm.

3. In claim 1, A second acrylic resin is an aqueous intermediate composition having a solid content of 40 to 70 wt% based on the total weight of the second acrylic resin, a Gardner viscosity at 25°C of E to I, and a weight average molecular weight of 7,000 to 30,000 g / mol.

4. In claim 1, A water-based intermediate composition, wherein the polyester resin has a solid content of 60 to 90 wt% based on the total weight of the polyester resin, a Gardner viscosity at 25°C of Z to Z3, a glass transition temperature of -40 to -20°C, an acid value of 2 to 50 mgKOH / g, a hydroxyl value of 50 to 100 mgKOH / g, and a number average molecular weight of 1,000 to 4,000 g / mol.

5. In claim 1, A first polyurethane resin has a solid content of 30 to 60 wt% based on the total weight of the first polyurethane resin, a glass transition temperature of -35 to -10°C, an acid value of 5 to 30 mgKOH / g, a particle size (D50) of 50 to 200 nm, and a weight average molecular weight of 15,000 to 35,000 g / mol, an aqueous intermediate composition.

6. In claim 1, A water-based intermediate composition in which the second polyurethane resin is a urethane diol-based compound, has a solid content of 60 to 90 wt% based on the total weight of the second polyurethane resin, a viscosity at 25°C of 1,000 to 6,000 cPs, a hydroxyl value of 200 to 450 mgKOH / g, and a weight average molecular weight of 200 to 600 g / mol.

7. In claim 1, A water-based intermediate composition having a solid content of 70 to 99 wt% based on the total weight of the melamine-based curing agent and a Gardner viscosity of Y to Z2 at 25°C.

8. In claim 1, An aqueous intermediate composition comprising, based on the total weight of the aqueous intermediate composition, 21 to 30 wt% of a first acrylic resin, 0.5 to 10 wt% of a second acrylic resin, 1 to 10 wt% of a polyester resin, 7 to 15 wt% of a first polyurethane resin, 0.5 to 10 wt% of a second polyurethane resin, and 2 to 10 wt% of a melamine resin.

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