Water-based multi-liquid coating composition, coating film forming method, multi-color finish coating method, and coating repair method for coated objects

Abstract

To provide an aqueous multi-liquid type coating composition excellent in finishing properties such as dryness, handling workability (pot life / hand mixability or the like) of the coating material, storability, and weather resistance and gloss, optimum in coating to a relatively large coated matter, and a coating film forming method.SOLUTION: An aqueous multi-liquid type coating composition comprising a main agent (I) and a curing agent (II), in which the main agent (I) contains a hydroxy group-containing resin (A). The hydroxy group containing resin (A) contains a colloidal dispersion type acrylic resin (A1) and a water-soluble acrylic resin (A2). The colloidal dispersion type acrylic resin (A1) is contained by 50 mass% or larger relative to a total resin solid content contained in the main agent (I).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a water-based multi-liquid coating composition, a coating film forming method, a multi-color finish coating method, and a method for repair coating of a coated body, which are excellent in drying properties, coating workability, storage properties, weather resistance, and finish, and are particularly suitable for use in coating sites for relatively large objects such as railway cars, buses, trucks, construction machinery, ship hulls, buildings, structures, or industrial equipment. [Background technology]

[0002] Conventionally, thermosetting coating compositions containing a hydroxyl-containing resin such as a hydroxyl-containing acrylic resin, a crosslinking agent such as a melamine resin and / or a polyisocyanate compound, and a pigment have been widely used as coating compositions for coating automobile bodies such as passenger cars. However, in the coating process, a heating and drying temperature of about 140°C is usually required when a melamine resin is used as a crosslinking agent, and a heating and drying temperature of about 80°C is required even when a polyisocyanate compound is used as a crosslinking agent (Patent Document 1, Patent Document 2).

[0003] Large car bodies, vehicles, or parts such as railroad cars, trucks, buses, construction machinery, or industrial equipment have a larger coating area than automobile bodies such as passenger cars, so the drying ovens are inevitably large and require huge capital investment, and it may not be possible to ensure a sufficient and uniform heating and drying temperature for the entire object. Also, because the object is large, it takes a long time to cool it down when placed in a drying oven.

[0004] Furthermore, while organic solvent-based paint compositions are currently the norm for such coating compositions, from the standpoints of resource conservation and pollution control, there is a demand for the development of water-based coating compositions for the coating of such large substrates as well.

[0005] However, when painting such a large-area substrate, the large size of the substrate means that painting takes a long time, and so there is a demand for improvements in the storage stability of the paint itself (anti-settling ability of color pigments, viscosity change), as well as the ease of handling of the paint during painting, such as pot life (working time) and ease of hand mixing. In addition, compared to solvent-based paints, water-based paints not only take a long time to dry after painting, but also have many issues to address, such as finish quality and high weather resistance, and there are few paints that meet all of these requirements. In particular, improving the ease of handling of the paint, such as pot life and ease of hand mixing, can lead to problems such as poor drying, which can result in poor finish quality and weather resistance, and there has been a challenge in satisfying both of these requirements.

[0006] On the other hand, Patent Document 2 discloses an aqueous coating composition, in which the base agent contains a water-dispersible polymer polyol whose hydroxyl value, acid value and number average molecular weight are within a specific range, the curing agent contains a nonionic modified polyisocyanate and an ionic modified polyisocyanate, and the equivalent ratio (NCO / OH) with respect to the hydroxyl group is 0.5 to 3.0. This aqueous coating composition is intended for painting railroad cars, which are relatively large objects to be coated, and can reduce the amount of organic solvent used, and can form a coating film at room temperature. However, even this composition has problems in terms of paint handling workability, painting workability (finish, wettability), and weather resistance. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2014-152232 A [Patent Document 2] JP 2017-101126 A Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in consideration of the above circumstances, and aims to provide a water-based multi-component paint composition which is optimal even for painting relatively large substrates, and which has excellent drying properties, paint handling properties (pot life, ease of stirring by hand, etc.), storage properties, weather resistance, and finish properties such as gloss, a method for forming a coating film, a multi-color finish coating, and a method for repair coating of coated bodies. [Means for solving the problem]

[0009] As a result of extensive research, the present inventors have discovered that the above-mentioned problems can be solved.

[0010] The present invention includes the following embodiments: Item 1. An aqueous multi-liquid coating composition comprising a main agent (I) and a curing agent (II), wherein the main agent (I) contains a hydroxyl-containing resin (A), the hydroxyl-containing resin (A) contains a colloidal dispersion-type acrylic resin (A1) and a water-soluble acrylic resin (A2), and the colloidal dispersion-type acrylic resin (A1) is contained in an amount of 50 mass% or more based on the total resin solid content contained in the main agent (I).

[0011] Item 2. An aqueous multi-liquid coating composition comprising a main agent (I) and a curing agent (II), wherein the main agent (I) contains a hydroxyl-containing resin (A) and a color pigment (B), the hydroxyl-containing resin (A) contains a colloidal dispersion-type acrylic resin (A1) and a water-soluble acrylic resin (A2), and the colloidal dispersion-type acrylic resin (A1) is contained in an amount of 50 mass% or more relative to the total resin solid content contained in the main agent (I).

[0012] Item 3. The water-based multi-component coating composition according to Item 1 or 2, wherein the water-soluble acrylic resin (A2) is contained in an amount of 0.5 to 20 mass % based on the total resin solid content contained in the main component (I).

[0013] Item 4. The aqueous multi-component coating composition according to any one of Items 1 to 3, wherein the curing agent (II) contains an organic solvent (D), the organic solvent (D) contains an organic solvent (d1) having a boiling point of 190° C. or less, and the organic solvent (d1) is contained in an amount of 50 mass% or more based on the total mass of the organic solvent (D).

[0014] Item 5. The aqueous multi-liquid coating composition according to any one of Items 2 to 4, comprising surface-treated titanium oxide (b1) as the color pigment (B).

[0015] Item 6. The aqueous multi-liquid coating composition according to any one of Items 1 to 5, wherein the curing agent (II) contains a polyisocyanate compound (C) having an isocyanate group content of 10% by mass or more, and the equivalent ratio (NCO / OH) of the isocyanate group in the polyisocyanate compound (C) to the hydroxyl group in the hydroxyl group-containing resin (A) is within the range of 1.1 to 3.0.

[0016] Item 7. The curing agent (II) contains a polyisocyanate compound (C), and the polyisocyanate compound (C) contains a polyisocyanate compound having an isophorone skeleton in the molecule. The aqueous multi-component coating composition according to any one of Items 1 to 6.

[0017] Item 8. A method for forming a coating film, comprising coating an outermost coating film on a substrate with the aqueous multi-liquid coating composition according to any one of items 1 to 7 above.

[0018] Item 9. The method for forming a coating film according to claim 8, wherein the substrate is an industrial machine, a construction machine, a railroad vehicle, a large vehicle, a ship, a building, or a structure.

[0019] Item 10. A step (X) of applying an undercoat coating composition to an object to be coated to form an undercoat coating film; A step (Y) of applying a colored coating composition onto the undercoat coating to form a colored coating film; A coating film forming method further comprising a step (Z) of applying a clear coating material to form a clear coating film, The undercoat coating composition comprises: (X-1) Water-based paint composition containing epoxy resin (X-2) a putty composition containing an unsaturated polyester resin, (X-3) Urethane curing water-based paint composition At least one selected from the group consisting of: A method for forming a coating film, comprising the aqueous multi-component coating composition according to any one of claims 1 to 7.

[0020] Item 11. For the object to be coated, (1) a step of applying a first colored coating composition to form a base coating film; (2) A step of partially coating the base coating film with a second colored coating composition having a different color from the first colored coating composition to form a topcoat coating film; A multi-color finish coating method comprising: 8. A multicolor finish coating method, characterized in that the first colored coating composition and / or the second colored coating composition is the aqueous multi-component coating composition described in any one of items 1 to 7.

[0021] Item 12. A method for repairing a painted body, comprising applying the aqueous multi-liquid paint composition according to any one of items 1 to 7 to an old paint film or a damaged part of the painted body to form a paint film. Effect of the Invention

[0022] According to the present invention, it is possible to provide an aqueous multi-liquid coating composition that is optimal for coating relatively large substrates and has excellent coating workability and storage properties, and also has excellent paint handling workability such as pot life and hand mixing properties without impairing drying properties, finish properties such as gloss, and weather resistance. Furthermore, by using this coating composition to form a coating film, the coating film obtained has excellent weather resistance and finish properties, particularly under either drying conditions of heating or room temperature drying. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The aqueous multi-liquid coating composition according to the present invention is an aqueous coating, and "aqueous coating" is a term well known in the art, and in this specification, the water content in the total solvent of the aqueous multi-liquid coating composition is 30 to 90 mass %. From the viewpoint of the balance between drying property and finish property, the water content is preferably within the range of 35 to 80 mass %.

[0024] The aqueous multi-component paint composition of the present invention may be a clear paint that is substantially free of pigment, or an enamel paint that contains pigment, and when it is an enamel paint, it is desirable that the pigment be included in the aqueous multi-component paint composition.

[0025] The first embodiment of the aqueous multi-liquid coating composition of the present invention contains a color pigment (B) as an essential component, and can be distinguished from the clear coating composition of the second embodiment described below. It may be called a colored coating composition or an enamel coating. It will be explained in detail below.

[0026] <<Aqueous multi-component coating composition>> The aqueous multi-liquid coating composition according to the first aspect of the present invention comprises a main component (I) and a curing agent (II), and the main component (I) contains a hydroxyl-containing resin (A) and a color pigment (B). In particular, the hydroxyl-containing resin (A) comprises a colloidal dispersion type acrylic resin (A1) and a water-soluble acrylic resin (A2), and it is essential that the acrylic resin (A1) is contained in a specific amount or more relative to the total resin solid content contained in the main component (I).

[0027] <Main ingredient (I)> The base material (I) contains a hydroxyl group-containing resin (A) and a color pigment (B) as main components. Hydroxyl-containing resin (A) In the present invention, the hydroxyl-containing resin (A) contained in the main component (I) is a component that reacts with the polyisocyanate compound (C) described below to form a polyurethane film together.

[0028] The hydroxyl-containing resin (A) used in the present invention is a water-soluble resin or a water-dispersible resin, since it is applied to water-based paints. Here, in this specification, the "water-soluble" resin means that when the resin is mixed with water, the resin can be dissolved or semi-dissolved in water, and is in a different form from the "water-dispersible" resin. The water-dispersible resin is further divided into an emulsion type and a colloidal dispersion type. In this specification, the emulsion type is a form obtained by emulsion polymerization in the presence of an emulsifier using water as a solvent, or a form obtained by mechanically forcibly dispersing a resin that is completely insoluble in water in water. On the other hand, a form in which the polymerization reaction of the monomer mixture is carried out in the absence of a solvent or in the presence of a suitable organic solvent, the mixture is dropped and mixed in water, and the excess organic solvent is removed as necessary to disperse the mixture, or the excess organic solvent is removed as necessary after the polymerization reaction, and water is added to disperse the mixture, is called the colloidal dispersion type.

[0029] Colloidal dispersion type acrylic resin (A1) The hydroxyl-containing resin (A) in the present invention must contain 50% by mass or more of the colloidal dispersion type acrylic resin (A1) based on the total resin solid content contained in the main component (I). The content of the colloidal dispersion type acrylic resin (A1) can be 60% by mass or more, more than 70% by mass, and 75% by mass or more based on the total resin solid content contained in the main component (I) from the viewpoints of the drying property of the obtained coating film, finish properties such as gloss, weather resistance, and water resistance, and the upper limit is preferably 99.5% by mass or less, and 98% by mass or less.

[0030] Here, the total resin solids content contained in the main agent (I) refers to the total mass of components capable of forming a coating film excluding pigment components, and refers to the total mass of the non-volatile contents of the resin solids content of the hydroxyl-containing resin (A), the solids content of paint additives blended as necessary, and other resins blended as necessary, if any.

[0031] The colloidal dispersion type acrylic resin (A1) may be, for example, a copolymer of a hydroxyl group-containing polymerizable unsaturated monomer (a) and another polymerizable unsaturated monomer copolymerizable with the hydroxyl group-containing polymerizable unsaturated monomer (a).

[0032] The hydroxyl-containing polymerizable unsaturated monomer (a) is a compound having at least one hydroxyl group and at least one polymerizable unsaturated bond in one molecule, and specific examples thereof include monoesters of (meth)acrylic acid and dihydric alcohols having 2 to 8 carbon atoms, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; ε-caprolactone-modified monoesters of (meth)acrylic acid and dihydric alcohols having 2 to 8 carbon atoms; N-hydroxymethyl (meth)acrylamide; allyl alcohol; and (meth)acrylates having polyoxyethylene chains with hydroxyl groups at the molecular terminals. Among these, 2-hydroxyethyl methacrylate and / or 2-hydroxypropyl methacrylate are preferred in terms of drying properties and reactivity with a curing agent described later.

[0033] Examples of other monomers copolymerizable with the hydroxyl group-containing polymerizable unsaturated monomer (a) include carboxyl group-containing unsaturated monomers such as acrylic acid and methacrylic acid; methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, Alkyl ester compounds (straight-chain or branched alkyl (meth)acrylates) with acrylic acid or methacrylic acid, such as lauryl (meth)acrylate, isomyristyl (meth)acrylate, stearyl (meth)acrylate, and isostearyl acrylate (trade names, manufactured by Osaka Organic Chemical Industry Co., Ltd.); alicyclic alkyl (meth)acrylates, such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate; polymerizable organic siloxanes, such as polysiloxane mono(meth)acrylate; aralkyl (meth)acrylates, such as benzyl (meth)acrylate, p) acrylates; aromatic ring-containing polymerizable unsaturated monomers such as styrene and vinyl toluene; alkoxyalkyl (meth)acrylates such as 2-methoxyethyl (meth)acrylate; nitrogen-containing polymerizable unsaturated monomers such as (meth)acrylonitrile, (meth)acrylamide, and diacetone (meth)acrylamide; allyl (meth)acrylate, ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, pentaerythritol di(meth)acrylate, and 1,1,1-trishydroxymethylpropane Examples of the polymerizable unsaturated monomer include polymerizable unsaturated monomers having at least two polymerizable unsaturated groups in one molecule, such as aryl (meth)acrylate; vinyl monomers, such as vinyl acetate; epoxy group-containing polymerizable unsaturated monomers, such as glycidyl (meth)acrylate, allyl glycidyl ether, and 3,4-epoxycyclohexylmethyl (meth)acrylate; alkoxysilyl group-containing polymerizable unsaturated monomers, such as 3-methacryloyloxypropyltrimethoxysilane; and oxidative curing group-containing polymerizable unsaturated monomers, such as dicyclopentenyloxyethyl (meth)acrylate. These may be used alone or in combination of two or more.

[0034] In this specification, "(meth)acrylate" means "acrylate or methacrylate", "(meth)acrylic acid" means "acrylic acid or methacrylic acid", "(meth)acryloyl" means "acryloyl or methacryloyl", "(meth)acrylamide" means "methacrylamide or acrylamide", and "(meth)acrylonitrile" means "acrylonitrile or methacrylonitrile".

[0035] The method for preparing the colloidal dispersion type acrylic resin (A1) includes a method in which a monomer is polymerized by a conventionally known method such as solution polymerization in the absence of a solvent or in the presence of an organic solvent, and then dispersed in water as necessary. Conventionally known methods can be used as the method for dispersing in water. For example, a method can be used in which a part or all of the anionic groups such as carboxyl groups contained in the resin are neutralized and ionized with a basic compound such as an amine, thereby dispersing the resin in water, or a method can be used in which the resin is added to an aqueous medium containing a basic compound and dispersed.

[0036] As the polymerization method, any polymerization method can be used, such as the usual one-stage continuous uniform monomer dropping method, the core-shell polymerization method which is a multi-stage monomer feed method, or the power feed polymerization method in which the monomer composition fed during polymerization is continuously changed.

[0037] In the present invention, the colloidal dispersion type acrylic resin (A1) is preferably a colloidal dispersion type acrylic resin having a core-shell structure obtained by copolymerizing polymerizable unsaturated monomer components having different compositions in multiple stages, from the viewpoint of excellent storage stability of the main component (I).

[0038] Colloidal dispersion type acrylic resin (A1) is superior in water resistance and weather resistance compared with emulsion type acrylic resin because it does not use an emulsifier. Since it is not produced from an aqueous medium, it is easy to obtain fine particles with a relatively low molecular weight and small particle size, and when applied as a water-based paint, it is extremely excellent in paint handling workability such as hand mixing, and is excellent in drying and gloss. In addition, since the compatibility of the water-soluble acrylic resin described later with the color pigment and the hardener is also excellent, it is possible to obtain an extremely excellent coating film appearance even though it is a water-based paint, and since the reactivity with the polyisocyanate compound is also excellent, it is possible to obtain a coating film with extremely excellent weather resistance.

[0039] The hydroxyl value of the colloidal dispersion type acrylic resin (A1) is not particularly limited, but from the viewpoint of the balance of drying properties, finishing properties, weather resistance, and paint handling properties such as pot life and manual stirring properties, it is preferably within the range of 30 to 200 mgKOH / g, particularly preferably within the range of 50 to 160 mgKOH / g.

[0040] The acid value of the colloidal dispersion type acrylic resin (A1) is preferably less than 40 mgKOH / g, particularly within the range of 5 to 35 mgKOH / g, from the viewpoint of achieving both storage stability and drying properties of the coating material.

[0041] In this specification, the acid value and the hydroxyl value are both values ​​calculated as solid contents and are values ​​measured by a method in accordance with JIS K 0070.

[0042] The weight average molecular weight of the colloidal dispersion type acrylic resin (A1) is within the range of 1,000 to 100,000, particularly preferably within the range of 2,000 to 70,000.

[0043] In this specification, the weight average molecular weight is a value calculated in terms of polystyrene measured by gel permeation chromatography (GPC).

[0044] The glass transition temperature (hereinafter sometimes abbreviated as Tg) of the colloidal dispersion type acrylic resin (A1) is preferably 40°C or higher, more preferably 42 to 70°C, and particularly preferably within the range of 45 to 65°C, from the viewpoint of improving drying properties.

[0045] In this specification, the static glass transition temperature of the resin can be measured, for example, by placing a sample in a measuring cup, vacuum suctioning to completely remove the solvent, and then measuring the change in heat quantity in the range of -100°C to 150°C at a heating rate of 3°C / min using a differential scanning calorimeter "DSC-50Q" (Shimadzu Corporation, product name), and taking the first change point of the baseline on the low temperature side as the static glass transition temperature. From the viewpoint of finish properties such as water resistance, weather resistance, and gloss (smoothness), the colloidal dispersion type acrylic resin (A1) preferably has an average particle size in the range of 50 to 200 nm, more preferably in the range of 80 to 180 nm. In this specification, the average particle size is a value measured at room temperature (about 20°C) by diluting the sample with deionized water to a concentration suitable for measurement using a Coulter Counter N4 (product name, Beckman Coulter, Inc., particle size distribution measuring device).

[0046] The resin solid content of the acrylic resin (A1) is preferably about 35 to 65 mass % from the viewpoint of dispersion stability of the acrylic resin (A1) in water.

[0047] In this specification, the resin solid content (or simply the solid content) is a value calculated by placing about 2.0 g of a sample in an aluminum foil cup with a diameter of about 5 cm, heating it at 110°C for 1 hour, and measuring the residue (g) as the non-volatile content.

[0048] The acrylic resin (A1) may be a commercially available product. The commercially available product is not particularly limited, and examples thereof include MACRYNAL series (manufactured by Allnex) such as MACRYNAL SM 6825w / 37WA, MACRYNAL SM 6810w / 42WA, MACRYNAL VSM6299 / 42WA, BAYHYDROLL series (manufactured by Sumika Covestro Urethane Co., Ltd.) such as BARNOCK WD-551, BARNOCK series (manufactured by DIC), and NeoCryl series (manufactured by DSM) such as NeoCryl XK-555.

[0049] Water-soluble acrylic resin (A2) The water-soluble acrylic resin is a resin obtained by polymerizing a polymerizable unsaturated monomer having a hydrophilic functional group and other polymerizable unsaturated monomers using a polymerization initiator in the presence of a hydrophilic organic solvent, and can be in a dissolved (transparent) state in an aqueous medium. Therefore, it is clearly distinguished from the colloidal dispersion-type acrylic resin (A1) which is in a dispersed state in an aqueous medium.

[0050] The hydrophilic functional group-containing polymerizable unsaturated monomer is a compound having one or more hydrophilic functional groups and one or more polymerizable unsaturated bonds in one molecule. Examples of the hydrophilic functional group include a phosphate group, a sulfonic acid group, a carboxyl group, an amino group, an amide group, and a polyoxyalkylene chain.

[0051] Specific examples include N-substituted (meth)acrylamides, polyoxyalkylene chain-containing (meth)acrylates, dialkylaminoalkyl (meth)acrylates, and acid group-containing (meth)acrylates, and these can be used alone or in combination of two or more.

[0052] Among these, from the viewpoints of drying property, water resistance and weather resistance, acid group-containing polymerizable unsaturated monomers are preferred, and (meth)acrylic acid, maleic acid, phosphoric acid group-containing polymerizable unsaturated monomers and sulfonic acid-containing polymerizable unsaturated monomers are more preferred.

[0053] Examples of the phosphoric acid group-containing polymerizable unsaturated monomer include 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate, 2-acryloyloxypropyl acid phosphate, and 2-methacryloyloxypropyl acid phosphate.

[0054] Examples of the sulfonic acid group-containing polymerizable unsaturated monomer include 2-acrylamido-2-methylpropanesulfonic acid, allylsulfonic acid, styrenesulfonic acid sodium salt, sulfoethyl methacrylate, and its sodium salt and ammonium salt.

[0055] In particular, a water-soluble acrylic resin that uses a carboxyl group-containing polymerizable unsaturated monomer and a phosphoric acid group-containing polymerizable unsaturated monomer in combination as the acid group-containing polymerizable unsaturated monomer is preferred because it has the effect of improving the compatibility of the composition of the present invention when it is recoated.

[0056] As the hydroxyl group-containing polymerizable unsaturated monomer and other polymerizable unsaturated monomers copolymerizable with the hydrophilic functional group-containing polymerizable unsaturated monomer, those exemplified in the section on the acrylic resin (A1) can be suitably used.

[0057] In addition, it is preferable to neutralize the acid groups of the phosphoric acid group-containing water-soluble acrylic resin (A2) with a neutralizing agent. There are no particular limitations on the neutralizing agent as long as it can neutralize the carboxyl groups, and examples of such neutralizing agents include inorganic bases such as sodium hydroxide and potassium hydroxide, and organic amines such as trimethylamine, dimethylaminoethanol, 2-methyl-2-amino-1-propanol, triethylamine, and ammonia.

[0058] The hydrophilic organic solvent used in the polymerization is not strictly classified, but examples thereof include organic solvents that dissolve at least 20 g in 100 g of water at 20° C., and specifically, examples of the organic solvent include alcohol-based organic solvents such as methanol, ethanol, isopropanol, n-butanol, and isobutanol; ether-based organic solvents such as dioxane and tetrahydrofuran; ethylene glycol ether-based organic solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-propyl ether, ethylene glycol monoisopropyl ether, ethylene glycol mono n-butyl ether, ethylene glycol monoisobutyl ether, and ethylene glycol mono tert-butyl ether; diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono n-propyl ether, diethylene glycol mono diethylene glycol ether-based organic solvents such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono n-propyl ether, and propylene glycol monoisopropyl ether; dipropylene glycol ether-based organic solvents such as dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono n-propyl ether, and dipropylene glycol monoisopropyl ether; and ester-based organic solvents such as ethyl acetate, butyl acetate, isobutyl acetate, and 3-methoxybutyl acetate. These can be used alone or in combination of two or more.

[0059] The hydroxyl value of the water-soluble acrylic resin (A2) is not particularly limited, but from the viewpoint of a balance between the pot life, the ease of manual mixing, and other paint handling properties without impairing drying properties, finish properties, and weather resistance, it is preferably in the range of 1 to 200 mgKOH / g, particularly preferably in the range of 5 to 100 mgKOH / g.

[0060] The acid value of the water-soluble acrylic resin (A2) is preferably from 1 to less than 100 mgKOH / g, particularly from 5 to 60 mgKOH / g, from the viewpoints of achieving both storage stability and drying properties of the coating material and water resistance of the coating film.

[0061] The weight average molecular weight of the water-soluble acrylic resin (A2) is particularly preferably within the range of 1,000 to 500,000, 1,500 to 150,000, and more preferably 2,000 to 70,000.

[0062] The amount of the water-soluble acrylic resin (A2) contained in the main component (I) is preferably within a range of 0.5 to 20 mass %, more preferably 1 to 15 mass %, based on the total resin solid content contained in the main component (I) from the viewpoints of weather resistance and drying property.

[0063] Other resins Further, examples of the other resins include acrylic resins other than (A1) and (A2), silicone resins, urethane resins, fluororesins, epoxy resins, polyester resins, alkyd resins, etc., and mixed or modified resins thereof, such as acrylic-modified polyester resins, acrylic silicone resins, acrylic-modified epoxy resins, and epoxy ester resins, etc. These may be used alone or in combination of two or more.

[0064] Other resins may be used as long as they do not affect the storage stability, coating film performance, or weather resistance of the paint. From the viewpoint of weather resistance and storage stability of the paint, however, it is particularly preferable that the amount of such resin is 20 mass % or less, and more preferably less than 5 mass %, of the total resin solids in the main agent (I).

[0065] The usage ratio of the colloidal dispersion type acrylic resin (A1) and the water-soluble acrylic resin (A2) is within the range of 70 / 30 to 99 / 1, preferably 80 / 20 to 95 / 5, in terms of the mass ratio of solids, from the viewpoint of the balance between weather resistance and drying property.

[0066] Color pigment (B) The color pigment (B) contained in the main agent (I) can be any conventionally known pigment without any particular limitation.Specific examples thereof include metal oxide pigments such as titanium oxide and iron oxide, composite metal oxide pigments such as titanium yellow, carbon black, azo pigments, quinacridone pigments, diketopyrrolopyrrole pigments, perylene pigments, perinone pigments, benzimidazolone pigments, isoindoline pigments, isoindolinone pigments, metal chelate azo pigments, phthalocyanine pigments, indanthrone pigments, dioxane pigments, and indigo pigments; and lustrous pigments such as aluminum (including vapor-deposited aluminum), copper, zinc, brass, nickel, aluminum oxide, mica, aluminum oxide coated with titanium oxide or iron oxide, mica coated with titanium oxide or iron oxide, glass flakes, and hologram pigments; and the like, which can be used alone or in combination of two or more depending on the desired color and coating performance.

[0067] Among color pigments, titanium oxide, which is a white pigment, may be contained. In this case, from the viewpoint of weather resistance, it is preferable that the titanium oxide (b1) is surface-treated, and in particular, it is preferable that the surface of the titanium oxide particles is surface-treated with silicon dioxide and aluminum oxide. The surface-treated titanium oxide (b1) is preferably surface-treated with a ratio of 1.0 to 8.0 mass %, preferably 1.3 to 6.6 mass %, of silicon dioxide and 2.0 to 4.5 mass %, preferably 2.5 to 4.4 mass %, based on the mass of titanium oxide. The above ranges are desirable from the viewpoint of weather resistance and paint stability. The surface-treated ratios of silicon dioxide and aluminum oxide in the titanium oxide (b1) were determined by elemental analysis by energy dispersive X-ray analysis using EDX-700HS (manufactured by Shimadzu Corporation).

[0068] Examples of commercially available products of titanium oxide (b1) that have been subjected to such surface treatment include TI-SELECT TS-6200 (trade name, manufactured by Chemours Inc., SiO2 / Al2O3=2.4 / 3.4 (mass %)), TI-PURE R-960 (trade name, manufactured by Chemours Inc., SiO2 / Al2O3=6.5 / 3.5 (mass %)), TI-PURE R902+ (trade name, manufactured by Chemours Inc., SiO2 / Al2O3=1.4 / 4.3 (mass %)), and Typeque CR-95 (trade name, manufactured by Ishihara Sangyo Kaisha, Ltd., SiO2 / Al2O3=3.7 / 2.6 (mass %)).

[0069] The content of the color pigment (B) varies depending on the type of the color pigment, but is preferably 1 to 200 parts by mass, and more preferably 5 to 150 parts by mass, per 100 parts by mass of the resin solid content contained in the main component (I).

[0070] When titanium oxide (b1) is blended in the aqueous multi-component coating composition of the present invention, the blending ratio is desirably 10 to 150 parts by mass, preferably 40 to 120 parts by mass, per 100 parts by mass of the solid content of the hydroxyl-containing resin (A) contained in the main component (I) in terms of coating stability, coating film hardness, and weather resistance.

[0071] In addition, the pigment volume concentration (hereinafter sometimes abbreviated as PVC) of the color pigment (B) varies depending on the color pigment, but from the viewpoints of hiding power, finish property and weather resistance, the pigment volume concentration is preferably within the range of 1 to 20%, more preferably 3 to 16%.

[0072] Here, "Pigment Volume Concentration (PVC)" refers to the pigment volume concentration in the dried coating film. It is the volume percentage of the color pigment (B) contained, specifically the volume ratio of the pigment content to the total non-volatile content (total solid content) in the aqueous multi-liquid coating composition. More specifically, it can be calculated using the value obtained by dividing the mass of each component by its specific gravity (or true specific gravity).

[0073] <Hardening agent (II)> The curing agent (II) used in the present invention contains a curing agent component, and the curing agent component preferably contains a polyisocyanate compound (C). Polyisocyanate Compound (C) The polyisocyanate compound (C) is a compound having two or more free isocyanate groups in one molecule, and can be one that has been used in the production of polyurethane. In particular, it is preferable that the isocyanate group content is within a specific range. Specifically, from the viewpoint of water-resistant adhesion, it is suitable to use a compound having an isocyanate group content of 10% by mass or more, preferably 12 to 25% by mass, and more preferably 18 to 25% by mass.

[0074] In this specification, the isocyanate group content is the amount of isocyanate groups contained in a compound expressed as a mass fraction. The amount of isocyanate groups can be measured in accordance with JIS K 1603-1 (2007).

[0075] As the polyisocyanate compound, it is preferable to use a polyisocyanate compound (c1) for water-based paints, such as a hydrophilized polyisocyanate compound in which a hydrophilic group is introduced into the polyisocyanate compound, or a water-dispersible polyisocyanate compound in which the polyisocyanate compound can be dispersed in water using a surfactant. Examples of the hydrophilic group include an anionic group such as an acid group, and a nonionic group containing a polyoxyalkylene (polyether chain) unit. Examples of the acid group include a carboxyl group, a phosphoric acid group, and a sulfonic acid group.

[0076] Furthermore, the curing agent (II) may contain a hydrophobic polyisocyanate compound in addition to the polyisocyanate compound (c1) for the water-based coating material. As such a hydrophobic polyisocyanate compound, those generally used in solvent-based coating compositions may be used.

[0077] The polyisocyanate compound contained in the polyisocyanate compound for aqueous paint (c1) or the hydrophobic polyisocyanate compound can be one that has been used in the production of polyurethane. For example, aliphatic diisocyanates such as tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate; alicyclic diisocyanates such as 4,4'-methylenebis(cyclohexyl isocyanate) and isophorone diisocyanate; aromatic diisocyanates such as xylylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, and polyphenylmethane diisocyanate (hereinafter referred to as polymeric MDI); and similar compounds such as isocyanurate and biuret thereof, which can be used alone or in combination of two or more. Among these, those having an aliphatic diisocyanate and / or an alicyclic diisocyanate as at least a part of the components are particularly preferred, and polyisocyanate compounds having hexamethylene diisocyanate (HDI) and / or isophorone diisocyanate (IPDI) in the skeleton are particularly preferred. From the viewpoint of improving drying properties, it is preferred to contain a polyisocyanate compound containing an isophorone skeleton in the molecule.

[0078] These polyisocyanate compounds can be used alone or in combination of two or more. When two or more polyisocyanate compounds are used in the curing agent (II), it is preferable to adjust the blending amount so that the isocyanate group content in the curing agent (II) is, on average, 5% by mass or more, and more preferably within the range of 8 to 18% by mass, from the viewpoints of storage property and weather resistance.

[0079] The content of the polyisocyanate compound (C) in the above aqueous multi-liquid coating composition can be appropriately adjusted so that the equivalent ratio (NCO / OH) between the isocyanate group of the water-dispersible polyisocyanate compound (C) and the hydroxyl group of the hydroxyl group-containing resin (A) is generally within the range of 0.5 to 5.0, but from the viewpoint of curability and weather resistance, it is preferably within the range of 1.1 to 3.0, and more preferably within the range of 1.2 to 2.0. By making the equivalent ratio (NCO / OH) within the above preferred range, there is an advantage that the curing reactivity of the aqueous multi-liquid coating composition can be secured in a good range. Note that the above equivalent ratios are all calculated based on solid content.

[0080] Organic solvent (D) The curing agent (II) used in the present invention preferably contains an organic solvent (D).

[0081] The organic solvent (D) may be of the ketone, ester, ether, glycol ether, acetate, or the like type, and from the viewpoint of improving compatibility with the base resin, a water-soluble solvent is preferred.

[0082] From the viewpoint of adjusting the drying property and finishing property such as gloss, it is preferable that the curing agent (II) contains an organic solvent (D), and the organic solvent (D) contains an organic solvent (d1) having a boiling point of 190° C. or less in an amount of 50 mass % or more based on the total mass of the organic solvent (D). Furthermore, it is particularly preferable to adjust the content to be within the range of 55 to 100 mass % from the viewpoints of miscibility with the polyisocyanate compound (C) and the main component and finishing property.

[0083] From the viewpoint of improving the ease of manual mixing, it is particularly preferable that the organic solvent (D) contains one having a boiling point within the range of 130°C to 175°C.

[0084] Furthermore, from the viewpoint of the balance between drying properties, hand-mixing properties, and finish properties, the solubility of the organic solvent (d1) in water (20° C.) is preferably within the range of 0.5 to 100 g / 100 g of water, and particularly preferably within the range of 20 to 60 g / 100 g of water.

[0085] In the present invention, "solubility in water" means the weight (g) of a solvent that can be dissolved in 100 g of water at a measurement temperature of 20° C. Therefore, it is the same value as the weight % of a solvent that can be dissolved in 100% by weight of water.

[0086] Specific examples of such a preferable organic solvent (d1) include isoamyl acetate (boiling point 142°C, [solubility in water 20°C, 1.7g / 100g], no hydroxyl group), ethylene glycol monoethyl ether (also known as Cellosolve, boiling point 135°C, [100g or more / 100g], has a hydroxyl group), isopropyl glycol (also known as ethylene glycol monoisopropyl ether, boiling point 142°C, 100g or more / 100g], has a hydroxyl group), methoxypropyl acetate (also known as propylene glycol monomethyl ether acetate), acetate, boiling point 146°C, [19.8g / 100g], no hydroxyl group), ethylene glycol monomethyl ether propionate (boiling point 160°C, [18.5g / 100g], no hydroxyl group), ethoxypropyl acetate (boiling point 154°C, [9.5g / 100g], no hydroxyl group), 3-methoxybutyl acetate (synonym: methoxybutyl acetate, boiling point 171.3°C, [6.5g / 100g], no hydroxyl group), 3-methyl-3-methoxybutyl acetate (synonym: 3-methoxy-3-methylbutyl acetate, boiling point 18 8°C, [6.8g / 100g], no hydroxyl group), ethyl 3-ethoxypropionate (boiling point 169.7°C, [1.3g / 100g], no hydroxyl group), ethylene glycol monoisobutyl ether acetate (boiling point 160.5°C, [100g or more / 100g], no hydroxyl group), dipropylene glycol dimethyl ether (also known as dimethyl propylene diglycol, boiling point 171°C, [37g / 100g], no hydroxyl group), ethylene glycol monobutyl ether (also known as butyl cellosolve, boiling point 171.2°C, [10 0g or more / 100g, has hydroxyl group), cyclohexyl acetate (boiling point 174°C, [1.4g / 100g], no hydroxyl group), 3-methoxy-3-methylbutanol (boiling point 174°C, [100g or more / 100g], has hydroxyl group), ethylene glycol mono-t-butyl ether (boiling point 152°C, [100g or more / 100g], has hydroxyl group), propylene glycol mono-t-butyl ether (boiling point 151°C, [14.5g / 100g], has hydroxyl group), propylene glycol monobutyl ether (boiling point 170.2°C, [6.4g / 100g, has hydroxyl group), propylene glycol monopropyl ether (boiling point 150°C, [100g or more / 100g], has hydroxyl group), diethylene glycol dimethyl ether (boiling point 160°C, [100g or more / 100g], no hydroxyl group), diethylene glycol diethyl ether (boiling point 188.4°C, [100g or more / 100g], no hydroxyl group), ethylene glycol monoisoamyl ether (also known as 2-isopentyloxyethanol, boiling point 181°C, [100g or more / 100g], has hydroxyl group), and normal butyl propionate (also known as normal butyl propionate, boiling point 145°C, [0.2g / 100g], no hydroxyl group). Here, the value in [ ] indicates the solubility in water (20°C), and the "hydroxyl group-free" or "hydroxyl group-present" in ( ) indicates the presence or absence of a hydroxyl group in the molecule of the organic solvent.

[0087] Since the solvent may react with the polyisocyanate compound (C) described above, it is preferable to appropriately select a water-soluble solvent that does not have a hydroxyl group in the molecule from the viewpoint of storage stability.

[0088] More particularly, at least one selected from dipropylene glycol dimethyl ether, normal butyl propionate, and propylene glycol monomethyl ether acetate is preferred.

[0089] From the viewpoints of resistance to pinching, wetting and spreading onto a substrate, dust compatibility, and the like, the composition may contain an organic solvent having a boiling point of more than 190°C.

[0090] When an organic solvent having a boiling point of more than 190° C. is contained, the content is preferably within the range of 1 to 70% by mass, more preferably within the range of 10 to 50% by mass, based on the mass of the total solvent blended in the curing agent, from the viewpoints of popping resistance, dust compatibility and finish. Poor dust compatibility may cause defects in the finish, such as bumps, dullness and blackening.

[0091] Other ingredients The above-mentioned aqueous multi-liquid coating composition may contain other components, if necessary, in addition to the above-mentioned components. Examples of the other components include extender pigments, rust-preventive pigments such as aluminum tripolyphosphate, aluminum phosphomolybdate, and zinc phosphate, dispersants, curing catalysts, viscosity regulators, film-forming assistants, and additives commonly used in coating compositions (e.g., ultraviolet absorbers, light stabilizers, antioxidants, defoamers, surface conditioners, pinhole inhibitors, rust inhibitors, etc.).

[0092] Examples of the body pigment include calcium carbonate, clay, talc, mica, baryta, and silica. From the viewpoints of cost, film-forming properties, polishability, and the balance between the finish and coating performance after topcoat application, at least one selected from silica, calcium carbonate, talc, and baryta is particularly preferred, and talc and / or baryta is more particularly preferred.

[0093] These components can be added to the base agent (I) and / or the curing agent (II) in a manner that does not impair the various physical properties of the coating composition of the present disclosure.

[0094] <Adjustment method> The paint form of the multi-liquid water-based paint composition of the present invention can be a two-liquid composition of the main agent (I) containing the acrylic resin (A1) and the water-soluble acrylic resin (A2) and the curing agent (II). If necessary, it can contain components other than the main agent and the curing agent. Specific examples of the components other than the main agent and the curing agent include paint additives such as rheology control agents, diluent components containing water, siloxane bond forming components such as organic silane compounds and catalyst components thereof, and the like, which can be mixed together and used when mixing the main agent component and the curing agent component immediately before painting.

[0095] The multi-liquid type water-based paint composition of the present invention can be easily prepared by mixing the main agent (I) and the curing agent (II) immediately before painting. The composition of the present invention can be mixed by mechanical stirring such as a disperser if necessary, but even if it is mixed by hand, it is possible to obtain a coating film performance that is excellent in terms of finish and weather resistance.

[0096] In this specification, the term "immediately before painting" cannot be universally defined depending on the painting contractor or the painting site, but can refer to, for example, up to 3 hours before painting.

[0097] The solids concentration of the aqueous multi-component coating composition of the present invention obtained as described above is generally within the range of 5 to 50 mass%, preferably 10 to 40 mass%, which is suitable from the viewpoints of coating workability, hiding power, and finished appearance.

[0098] <<Coating film formation method>> The aqueous multi-component coating composition of the present invention can be applied to an article to be coated and then dried to obtain a coated article.

[0099] Examples of the substrate include metal substrates, plastic substrates, composite substrates thereof, wood, glass, cloth, concrete, ceramic materials, etc. Examples of the metal substrate include metals such as iron, steel, copper, aluminum, tin, zinc, etc., and alloys containing these metals, etc. The metal substrate may be plated with zinc, copper, chromium, etc., or may be surface-treated using a surface treatment agent such as chromate, zinc phosphate, or zirconium salt. Examples of the plastic substrate include polypropylene resin, polycarbonate resin, urethane resin, polyester resin, polystyrene resin, ABS resin, vinyl chloride resin, polyamide resin, etc. The surface of these metals or various plastic substrates may be surface-treated with a detergent or solvent, such as degreasing, phosphate treatment, chromate treatment, complex oxide treatment, cleaning, polishing, etc., and may further be coated with an undercoat coating film by a primer coating (undercoat coating composition).

[0100] <Undercoat> The undercoat coating film is a coating film formed under the coating film formed by the coating composition of the present invention, and the undercoat paint for forming the undercoat coating film is applied depending on the type and condition of the surface to be coated, etc. By providing an undercoat coating film between the coating film formed by the coating composition of the present invention, it is possible to improve adhesion to the surface to be coated, and the water resistance and impact resistance of the composite coating film.

[0101] The undercoat coating film may be a multi-layered film of two or more layers in order to improve adhesion. For example, when the substrate is a metal substrate, the undercoat coating film may be a coating film that can be obtained by applying a coating composition known in the coating field as a primer coating and / or an intermediate coating, and drying the coating composition.

[0102] As the constituent components of the undercoat paint constituting the undercoat coating film, specifically, for example, a paint composition containing a film-forming resin, a crosslinking agent, a coloring pigment, an extender pigment, a luster pigment, an anti-rust pigment, a conductive pigment, etc. can be suitably used, and further, the undercoat paint can appropriately contain paint additives such as an ultraviolet absorber, a light stabilizer, a curing catalyst, a plasticizer, an adhesion promoter, a compatibilizer, an antifoaming agent, a viscosity adjuster, an anti-rust agent, a surface conditioner, etc.

[0103] Examples of the extender pigment include talc, mica, barium sulfate, kaolin, calcium carbonate, clay, silica, quartz, and glass. Hollow particles such as glass balloons and plastic balloons can also be included. These extender pigment components can be used alone or in combination of two or more. From the standpoint of polishing workability, finish, and cost in undercoat applications, the above-mentioned extender pigment is preferably at least one selected from talc, barium sulfate, kaolin, clay, silica, and calcium carbonate, and particularly preferably contains talc.

[0104] Examples of the rust-preventive pigment include phosphate-based pigments such as zinc phosphate, calcium phosphate, zinc phosphite, potassium phosphite, and calcium phosphite; polyphosphate-based pigments such as aluminum dihydrogen tripolyphosphate; molybdate-based pigments such as zinc molybdate and calcium molybdate; phosphomolybdate-based pigments such as aluminum phosphomolybdate; borate-based pigments; metaborate-based pigments such as barium metaborate; zinc calcium cyanamide-based pigments; modified silica in which cations such as calcium, zinc, cobalt, lead, strontium, and barium are bound to porous silica particles; and pigments in which cations are bound by ion exchange. and inorganic rust-preventive pigments such as ion-exchanged silica; aluminum pyrophosphate; zinc oxide; and further benzothiazole compounds such as 1-(benzothiazole-2-ylthio)succinic acid and (2-benzothiazole-2-ylthio)succinic acid di-(C12-14 alkyl)ammonium salt; and organic rust-preventive agents such as ketocarboxylic acid-based compounds such as an addition product of 4-methyl-γ-oxo-benzenebutanoic acid and N-ethylmorpholine, and an addition product of 4-methyl-γ-oxo-benzenebutanoic acid and zirconium. These can be used alone or in combination of two or more.

[0105] Examples of main types of film-forming resins include acrylic resins, polyester resins, alkyd resins, urethane resins, polyolefin resins, epoxy resins, phenolic resins, polyamide resins, and modified resins thereof, hydroxyl group-containing resins, and alkyl silicates, which can be used alone or in combination of two or more.

[0106] The crosslinking may be caused by blending a curing agent, or may be substantially uncrosslinked without blending a curing agent, or may be caused by penetration of a crosslinking agent contained in the coating film of the upper layer.

[0107] From the viewpoint of improving rust prevention and polishability, the pigment component contained in the undercoat paint is preferably contained in an amount of 100 to 500 parts by mass, and more preferably 115 to 400 parts by mass, per 100 parts by mass of the film-forming resin contained in the base resin. In particular, the pigment component is preferably composed of a large amount of rust prevention pigment and extender pigment, and the ratio of other color pigments to the rust prevention pigment and extender pigment is within the range of 30 / 70 to 99 / 1, and preferably 40 / 60 to 95 / 5, in terms of the mass ratio of (rust prevention pigment and extender pigment) / (other color pigment).

[0108] The undercoat paint may be an organic solvent-based paint composition, an aqueous paint composition, or a solvent-free paint. However, taking into consideration the impact on the environment and human body, it is preferable to use a high solids content (solids content of 70% or more) organic solvent-based paint, aqueous paint, or solvent-free paint.

[0109] The substrate may be a molded article containing the above-mentioned substrate. Examples of the molded article include various molded articles such as automobile bodies, various vehicle bodies, and parts for home appliances. The above-mentioned aqueous coating composition can be particularly suitably used when the substrate is a metal substrate or the like that has a large heat capacity or is large and does not transfer heat sufficiently to the substrate in a heating furnace. Specific examples of such substrates include construction machinery (sometimes abbreviated as construction machinery, for example, bulldozers, scrapers, hydraulic excavators, excavators, transport machinery (railroad vehicles such as bullet trains, and large vehicles such as buses, trucks, and trailers), cranes and loading and unloading machinery, foundation construction machinery (diesel hammers, hydraulic hammers, etc.), tunnel construction machinery (boring machines, etc.), road rollers, etc.); industrial machinery such as low-voltage and heavy-voltage equipment, agricultural machinery, steel furniture, and machine tools, which are called general industrial use; ship hulls, buildings, and structures; and the like. In particular, industrial machinery, construction machinery, railroad vehicles, large vehicles, ship hulls, buildings, and structures are preferred.

[0110] The aqueous multi-liquid coating composition of the present invention may also be applied to a coating film (old coating film) already formed on the above-mentioned substrate or to a damaged part of the coated body. That is, the aqueous multi-liquid coating composition of the present invention can be applied to the damaged part of the old coating film or coated body to form a coating film. In this case, for example, the damaged part of the old coating film or coated body to be coated can be cleaned or sanded with sandpaper in advance, and the substrate can be pre-treated with a putty composition, primer surfacer, or other undercoat paint as necessary.

[0111] Since the present invention has extremely excellent drying properties and finish, it can be used, for example, in a colored top coat (for monocoats) used when forming the outermost coating film.

[0112] In this case, the drying method after the application of the aqueous multi-liquid coating composition is completed is not particularly limited, and as a drying method, a coating film can be obtained by drying at room temperature, but there is no problem even if the coating film is dried by heating or forced drying depending on the coating environment, etc. When drying by heating, the drying can be performed within a range of 25 to 80°C, preferably 40 to 60°C.

[0113] If necessary, air drying may be performed using a blower or the like. In room temperature drying, a coating film can be obtained by drying in an environment of, for example, 5 to 45° C. The relative humidity (hereinafter sometimes abbreviated as RH) during coating is preferably 80% or less, particularly preferably 70% or less.

[0114] In the case of the forced drying, in terms of the finish, the coating may be allowed to set (stand still) at room temperature for 2 to 30 minutes before heat curing.

[0115] The film thickness can be adjusted appropriately depending on the condition of the surface to be coated, but generally, a dry film thickness within the range of 5 to 150 μm, 10 to 100 μm, and particularly 7 to 60 μm is suitable.

[0116] The present invention can be suitably used as a base coating composition and / or a top coating composition because it provides excellent finish and drying properties even when multiple coatings are applied.

[0117] For example, a step (X) of applying an undercoat coating composition to a substrate to form an undercoat coating film; A step (Y) of applying a colored coating composition onto the undercoat coating to form a colored coating film; The present invention can be applied to a coating film forming method including the above.

[0118] In particular, as a primer coating composition, (X-1) Water-based paint composition containing epoxy resin (X-2) a putty composition containing an unsaturated polyester resin, (X-3) Urethane curing water-based primer surfacer and the colored coating composition is preferably the aqueous multi-liquid coating composition of the present invention.

[0119] It is particularly preferable that the undercoat film is formed of a multi-layer film of two or more layers from the viewpoint of improving the water resistance of the composite film.

[0120] As the constitution of the undercoat paint, those described in the above section <Undercoat paint film> can be suitably used.

[0121] A step (Z) may be provided in which a clear paint is applied on the colored base film to form a clear coating film.

[0122] The clear coating composition may be a conventionally known composition or the aqueous multi-liquid coating composition of the present invention, which will be described later.

[0123] From the viewpoints of corrosion resistance, water resistance, and weather resistance, it is also preferable to have a coating film configuration as described below.

[0124] 1.Substrate / Primer coating (X-1) / Primer coating (X-2) / Primer coating (X-3) / Top coating (Y) / Clear coating (Z) 2.Object to be coated / Undercoat film (X-1) / Undercoat film (X-3) / Colored paint film (Y) / Clear paint film (Z) 3.Object to be coated / Undercoat film (X-1) / Undercoat film (X-2) / Undercoat film (X-3) / Colored paint film (Y) / The thickness of each undercoat coating can be adjusted appropriately depending on the condition of the surface to be coated, but is generally within the range of 5 to 150 μm, 10 to 100 μm, and particularly 7 to 60 μm in terms of dry film thickness, except for the undercoat coating (X-2).

[0125] The putty composition (X-2) containing the unsaturated polyester resin can be applied in a relatively thick film, and the dry film thickness can generally be appropriately set within the range of 500 μm to 2000 μm (0.5 mm to 2 mm), particularly 700 μm to 1500 μm (0.5 mm to 1.2 mm).

[0126] For example, it can be suitably used in a multi-tone or more color finishing coating method. Specifically, the object to be coated is (1) a step of applying a first colored coating composition to form a base coating film; (2) A step of partially coating the base coating film with a second colored coating composition having a different color from the first colored coating composition to form a topcoat coating film; A multi-color finish coating method comprising: The first colored coating composition and / or the second colored coating composition may be the aqueous multi-component coating composition of the present invention.

[0127] When a second color coating composition or a clear coat described later is applied after the application of the aqueous multi-component coating composition of the present invention, the drying time after application of the aqueous multi-component coating composition of the present invention is preferably until the cured state reaches a semi-cured dry state or higher, from the viewpoint of the finish and weather resistance of the resulting process film.

[0128] In this specification, the semi-cured and dried state refers to the semi-cured and dried state defined in JIS K 5600-1-1 (2004), i.e., a coating film in a state where no scratches are left on the coating surface when the center of the coating surface is gently rubbed with a fingertip. On the other hand, a cured coating film in a less than semi-cured and dried state refers to a coating film that has not yet reached the above-mentioned cured and dried state, and is in a state where it is dry to the touch defined in JIS K 5600-1-1 or lower.

[0129] In this specification, the initial drying property refers to the time required for the coating film to reach the cured and dried state, and the shorter the initial drying property, the better the drying property, that is, the quicker the drying property.

[0130] The time required for the aqueous multi-component coating composition of the present invention to reach the semi-cured and dried state varies depending on the balance between the dry film thickness and the coating environment. For example, when the dry film thickness is 50 μm or less, the time can be less than 3 hours, or may be 1 to 2 hours.

[0131] Even when the aqueous multi-liquid coating composition is used for multi-color coating of two or more tones or when a top coat is applied, the composition dries in a relatively short time, which results in excellent work efficiency. In addition, in the case of a method of applying multiple coats, there is no particular problem even if it takes a long time, such as 3 hours or more, before applying multiple coats.

[0132] Furthermore, from the viewpoint of imparting weather resistance and antifouling properties, after step (2), a step (3) of subsequently applying a top clear coating composition to the entire surface and drying it to form an outermost clear coating film may be included.

[0133] As the top clear, conventionally known water-based paints, organic solvent-based paints, solventless paints, etc. can be used, and it is preferable to use an aqueous multi-liquid clear coating composition according to the second embodiment of the present invention described below.

[0134] The aqueous multi-component coating composition of the present invention can be applied by known coating methods such as spray coating, electrostatic coating, brush coating, roller coating, etc., but spray coating is preferred from the viewpoint of the finished appearance of the coating film.

[0135] When applying multiple coats of paint, if necessary, steps such as flash-off (leaving the paint film at room temperature after painting), air blowing at room temperature, or pre-heating at 60°C or less for 10 minutes or less may be carried out between each coat.

[0136] Since the present invention has extremely excellent drying properties and finish, it is suitable as a colored top coat (for monocoats) used when forming the outermost coating film.In addition, since it has excellent finish and drying properties even when overcoating, it can also be used suitably as a colored coating composition for multi-color coating of two or more tones.

[0137] The hiding rate of the dried coating of the aqueous multi-liquid coating composition of the present invention is more than 60%, preferably 80% or more, and more preferably 90% or more. Specifically, the hiding rate of the dried coating of the aqueous multi-liquid coating composition can be evaluated by measuring the hiding rate with a colorimeter. The measurement can be performed in accordance with JIS K 5600-4-1 "General Test Method for Paints (Hiding Power)" Method B (Hiding Rate Test Paper).

[0138] A second embodiment of the water-based multi-liquid coating composition of the present invention is a water-based multi-liquid clear coating composition that does not contain the color pigment (B) as an essential component, as described in detail below.

[0139] <<Water-based multi-liquid clear coating composition>> The aqueous multi-component clear coating composition according to the present invention is an aqueous multi-component clear coating composition comprising a main agent (I) and a curing agent (II), wherein the main agent (I) contains a hydroxyl-containing resin (A), the hydroxyl-containing resin (A) comprises a colloidal dispersion-type acrylic resin (A1) and a water-soluble acrylic resin (A2), and the colloidal dispersion-type acrylic resin (A1) accounts for 50 mass% or more of the total resin solid content contained in the main agent (I).

[0140] Everything is the same as in the first embodiment except that the color pigment (B) is not an essential component.

[0141] Here, the term "clear" refers to a dry coating that is transparent enough to show the pattern and color tone of the substrate. Specifically, the transparency of the dry coating of the aqueous multi-liquid clear coating composition can be evaluated by measuring the hiding rate with a colorimeter. In the present invention, it is particularly preferable that the hiding rate is 60% or less, and more preferably 50% or less.

[0142] In the second embodiment, the color pigment (B), which was an essential component in the first embodiment, is not contained at all, or the content of the color pigment (B) is preferably adjusted so that the content falls within the range defined as clear, specifically, the hiding ratio is 60% or less. That is, for example, colored clear and pearl clear can be classified as the second embodiment.

[0143] The water-based multi-liquid clear coating composition may contain, among the color pigments (B), glittering pigments such as interference pearls, which are called effect pigments.

[0144] When using the interference pearl pigment, the hiding power is lower than that of the primary color pigment, so it can be contained within the range that ensures the transparency of the coating film. For example, it can be contained in the range of 0.01 to 30 parts by mass, preferably 0.5 to 20 parts by mass, per 100 parts by mass of the resin solid content contained in the main agent (I).

[0145] As other coloring pigments, those listed in the section on coloring pigment (B) above can be contained. From the viewpoint of ensuring transparency, the amount of the coloring pigment may vary depending on the coloring pigment used, but as a guideline, the amount of the coloring pigment may be 30 parts by mass or less, preferably in the range of 0.01 to 10 parts by mass, and more preferably in the range of 0.05 to 5 parts by mass, per 100 parts by mass of the resin solid content contained in the main agent (I). EXAMPLES

[0146] The present invention will be described in more detail below with reference to Production Examples, Examples, and Comparative Examples. However, the present invention is not limited thereto. In each example, "parts" and "%" are based on mass unless otherwise specified. Furthermore, the thickness of the coating film is based on the cured coating film.

[0147] Acrylic resin manufacturing (Production Example 1) 400 parts of propylene glycol monopropyl ether was placed in a four-neck glass flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen inlet, and the temperature was raised to 120° C. under a nitrogen stream while stirring. When the temperature reached 120° C., mixed solution 1, which was a mixture of the monomer composition and polymerization initiator (12 parts of t-butylperoxy-2-ethylhexanoate) shown in the first-stage core part column in Table 1, was added dropwise over 4 hours, and the temperature was maintained at 120° C. for 1 hour after the end of the dropwise addition. While maintaining the temperature at 120°C, mixed solution 2, which was prepared by previously mixing the monomer composition shown in the second stage shell part column of Table 1 and a polymerization initiator (2.4 parts of t-butylperoxy-2-ethylhexanoate), was added dropwise to the flask over a period of 1 hour, and after completion of the addition, the temperature was maintained at 120°C for 1.5 hours to obtain an acrylic resin solution. The resin solid content of the obtained acrylic resin solution was 66.7%, and the weight average molecular weight was 14,000. Subsequently, propylene glycol monopropyl ether was distilled off under reduced pressure from the obtained acrylic resin solution until the solid content was 85%. This was cooled to 95°C, the pH was adjusted to 8.0 with dimethylethanolamine, and the mixture was stirred for 30 minutes. Further, deionized water was added dropwise over 2 hours while stirring so that the resin solid content was 50%, to obtain an aqueous dispersion of acrylic resin (A1-1) and a core-shell type colloidal dispersion. The weight average molecular weight, acid value per resin solid content, hydroxyl value, glass transition temperature, and average particle size of the aqueous dispersion of the obtained acrylic resin (A1-1) are shown in Table 1.

[0148] (Production Example 2) An aqueous dispersion of acrylic resin (A1-2) and a core-shell type colloidal dispersion were obtained in the same manner as in Preparation Example 1, except that the monomer composition and blending amounts of each copolymerization component in Preparation Example 1 were changed to those shown in the following Table 1. The weight average molecular weight, acid value and hydroxyl value per resin solid content, glass transition temperature, and average particle size of the aqueous dispersion of acrylic resin (A1-2) are also shown in Table 1.

[0149] (Production Example 3) In a 2-liter glass reaction vessel equipped with a stirrer, a thermometer, and a cooling tube, 300 parts of deionized water and 1 part of sodium dodecylbenzenesulfonate as an emulsifier for emulsion polymerization were charged, and after replacing the air inside with nitrogen, the inside temperature was raised to 82°C while stirring to dissolve. In a separate vessel, 320 parts of deionized water, 20 parts of sodium dodecylbenzenesulfonate, and 1 part of ammonium persulfate were added and thoroughly stirred, and the monomer composition and polymerization initiator shown in the first stage core part column in Table 1 were added thereto and stirred to prepare an emulsion, which was then continuously dropped into the previous reaction vessel over 2 hours. After the dropwise addition, the mixture was aged at the same temperature for 30 minutes, and then in a separate vessel, 160 parts of deionized water, 20 parts of sodium dodecylbenzenesulfonate, and 1 part of ammonium persulfate were added and thoroughly stirred, and the monomer mixture shown in the second stage shell part column in Table 1 was added and stirred to prepare an emulsion, which was then continuously dropped over a period of 2 hours. After the dropwise addition, the mixture was aged at the same temperature for 2 hours, then cooled to 40℃, and deionized water was added dropwise over 2 hours while stirring so that the resin solid content became 50%, to obtain an aqueous dispersion of hydroxyl-containing acrylic resin (A1-4) with an average particle size of 150 nm and a core-shell type emulsion. The hydroxyl value of the hydroxyl-containing acrylic resin was 103 mgKOH / g and the glass transition temperature was 62℃.

[0150] [Table 1]

[0151] (Production Example 4) A reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, a nitrogen inlet tube and a dropping device was charged with 35 parts of propylene glycol monopropyl ether and heated to 85 ° C., and then a mixture of 18 parts of methyl methacrylate, 29 parts of n-butyl acrylate, 35 parts of isobornyl acrylate, 10 parts of 2-hydroxyethyl acrylate, 6.5 parts of acrylic acid, 1.5 parts of 2-methacryloyloxyethyl acid phosphate, 15 parts of propylene glycol monopropyl ether and 2.3 parts of 2,2'-azobis (2,4-dimethylvaleronitrile) was added dropwise over 4 hours, and the mixture was aged for 1 hour after the end of the dropwise addition. After that, a mixture of 10 parts of propylene glycol monopropyl ether and 1 part of 2,2'-azobis (2,4-dimethylvaleronitrile) was added dropwise over 1 hour, and the mixture was aged for 1 hour after the end of the dropwise addition. Further, 7.4 parts of diethanolamine and propylene glycol monopropyl ether were added to obtain a colorless, transparent solution of a water-soluble acrylic resin (A2-1) containing carboxyl groups and phosphoric acid groups with a solid content of 50%. The obtained acrylic resin had an acid value of 50.6 mg KOH / g and a hydroxyl value of 5.8 mg KOH / g.

[0152] (Production Example 5) A reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, a nitrogen inlet tube and a dropping device was charged with 35 parts of propylene glycol monopropyl ether and heated to 85°C. Then, a mixture of 18 parts of methyl methacrylate, 15 parts of n-butyl acrylate, 35 parts of isobornyl acrylate, 10 parts of 2-hydroxyethyl acrylate, 2.0 parts of acrylic acid, 15 parts of propylene glycol monopropyl ether and 2.3 parts of 2,2'-azobis(2,4-dimethylvaleronitrile) and 40 parts of "NF Bisomer S20W" (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., polyethylene glycol monomethacrylate having a molecular weight of 2000, 50% water dilution product) (20 parts of active ingredient) were added dropwise in parallel over 4 hours, and the mixture was aged for 1 hour after the end of the dropwise addition. Then, a mixture of 10 parts of propylene glycol monopropyl ether and 1 part of 2,2'-azobis(2,4-dimethylvaleronitrile) was added dropwise over 1 hour, and the mixture was aged for 1 hour after the end of the dropwise addition. 7.4 parts of diethanolamine were added, and propylene glycol monopropyl ether was used to obtain a colorless, transparent solution of a water-soluble acrylic resin (A2-2) containing polyoxyalkylene groups as nonionic groups with a solid content of 50%. The obtained acrylic resin had an acid value of 15 mgKOH / g and a hydroxyl value of 48 mgKOH / g.

[0153] (Production Example 6) Production of hardener As a polyisocyanate compound, 50 parts of Bayhydur XP 2655 (100% solids), 28 parts of dipropylene glycol dimethyl ether (a water-soluble solvent without a hydroxyl group), 11 parts of ethylene glycol monobutyl ether acetate, and 11 parts of diethylene glycol monoethyl ether acetate were added and stirred for 30 minutes to prepare a hardener (II-1) with a solids content of 50%. The mass composition is shown in Table 2.

[0154] (Examples 7 to 13) Curing agents (II-2) to (II-8) were obtained in the same manner as in Production Example 6, except that the polyisocyanate compounds in Production Example 6 were as shown in Table 2. The mass blending is shown in Table 2.

[0155] [Table 2]

[0156] Preparation of coating composition Example 1 Water-soluble acrylic resin (A2-1) and TITANIX JR-903 (trade name, titanium white) were dispersed in a sand mill at a solid content ratio of 10:90 until the particle size reached 10 μm or less on a grain gauge, to obtain a dispersed paste. Thereafter, 100 parts by mass of the solid content of the dispersion paste, 180 parts (solid content 90.0 parts) of acrylic resin (A1-1) solution, 6.0 parts of BYK-348 (trade name, surface conditioner), 1.0 part of BYK-015 (trade name, surface conditioner), 1.0 part of ADEKA NOL UC-606 (trade name, light stabilizer), and 1.0 part of ACRYSOL ASE-60 (trade name, viscosity modifier) ​​were mixed and stirred for 15 minutes using a disper, and diethylethanolamine was added dropwise in an amount to give a pH of 7.6 to prepare a base material. Just before painting, the amounts of the base agent and the curing agent (II-1) obtained in Production Example 6 were adjusted so that the equivalent ratio of the hydroxyl value in the base agent to the isocyanate group (NCO) in the curing agent was NCO / OH=1.6, and the mixture was manually mixed with a spatula, and then 10 parts of deionized water was added to the base agent and further manually mixed. The storage stability of the base agent, the hand-stirring property of the water-based coating composition No. 1 after mixing with the hardener, and the pot life were evaluated. The evaluation results are shown in Table 3-1.

[0157] (Preparation of test panels) A commercially available lacquer primer surfacer is applied to a 300×150×2.0mm-sized electrodeposition-coated plate coated with an epoxy resin-based electrodeposition coating, with a thickness of 40 μm, as a base preparation, and after drying at room temperature for 30 minutes, it is polished with #400 waterproof abrasive paper. On this coated plate, the aqueous multi-liquid coating composition No. 1 of Example 1 is spray-coated on the entire surface so that the dry film thickness is 15 μm, and the plate is left horizontally for 30 minutes under the condition of room temperature (air temperature 23°C, humidity 50% RH), dried at 60°C for 30 minutes using an electric hot air dryer, and cooled to room temperature to obtain a test plate coated with the aqueous multi-liquid coating composition as a colored coating composition and as a top coat on the outermost surface.

[0158] (Examples 2 to 20, Comparative Examples 1 to 3) Water-based multi-liquid coating compositions Nos. 2 to 23 were obtained in the same manner as in Example 1, except that the formulation in Example 1 was changed to the contents shown in Tables 3-1 to 3-5 below. Furthermore, test panels were prepared in the same manner as in Example 1. Note that the resin formulation values ​​in the tables are solid contents. Furthermore, for Examples 1 to 20 and Comparative Examples 1 to 3, storage stability, hand mixing properties, pot life, drying properties, finish properties, and weather resistance were evaluated using the evaluation methods described below, and the evaluation results are shown in Tables 3-1 to 3-5.

[0159] [Table 3-1]

[0160] [Table 3-2]

[0161] [Table 3-3]

[0162] [Table 3-4]

[0163] [Table 3-5]

[0164] Details of each component in the table are as follows:

[0165] Acrylic Resin Acrylic resin A1-1: Colloidal dispersion type acrylic resin obtained in Production Example 1, Acrylic resin A1-2: Colloidal dispersion type acrylic resin obtained in Production Example 2, Acrylic resin A1-3: Bayhydrol A2470, product name, manufactured by Covestro, hydroxyl-containing acrylic resin, colloidal dispersion, resin solid content 45%, hydroxyl value 128 mg KOH / g (resin equivalent), acid value 10 mg KOH / g, Mw = 16,000, viscosity (23°C) 2250 mPa·s (dispersion medium: water), average particle size (D50) = 180 nm, Acrylic resin A1-4: Emulsion-type acrylic resin obtained in Production Example 3, Acrylic resin A2-1: the acid group-containing water-soluble acrylic resin obtained in Production Example 4, Acrylic resin A2-2: Water-soluble acrylic resin containing a polyoxyalkylene group as a nonionic group, obtained in Production Example 5.

[0166] Color pigments TITANIX JR-903: Product name, manufactured by Teika Co., Ltd., color pigment, white pigment, general-purpose titanium oxide, no surface treatment with silicon dioxide and aluminum oxide, TI-PURE R-960: Product name, manufactured by Du Pont Co., Ltd., color pigment, white pigment, modification amount SiO2 / Al2O3=6.5 / 3.5 (mass%), Phthalocyanine Blue: Color Pigment, Blue Pigment, Copper Phthalocyanine Blue, Carbon black: color pigment, black pigment.

[0167] Additives BYK-348: Product name, manufactured by BYK Japan, surface conditioner, polyether modified siloxane, weight average molecular weight 1,500, solid content 100% by mass, BYK-015: Product name, manufactured by BYK Japan, defoamer, polyether modified siloxane, weight average molecular weight 2,200, solid content 100%, ADEKA NOL UC-606: Trade name, manufactured by ADEKA Corporation, light stabilizer, hindered amine compound, solid content 57% by mass, ACRYSOL ASE-60: Trade name, manufactured by Dow Chemical, alkali swelling polyacrylic acid viscosity modifier, solids content 28%.

[0168] Polyisocyanate Compounds Bayhydur XP 2655: Trade name, manufactured by Sumika Covestro Urethane Co., Ltd., hexamethylene diisocyanate-based polyisocyanate compound having sulfonic acid groups and nurate skeleton, water-dispersible polyisocyanate, NCO content 21% by mass, solid content 100%, Duranate WR81-70P: Trade name, manufactured by Asahi Kasei Corporation, a hexamethylene diisocyanate and isophorone diisocyanate-based polyisocyanate compound having a nonionic hydrophilic group, weight average molecular weight 800 to 1200, NCO content 9.2%, solid content 70%, containing propylene glycol monomethyl ether acetate as an organic solvent, Bayhydur 304: Trade name, manufactured by Sumika Bayer, hexamethylene diisocyanate-based polyisocyanate compound having a nonionic hydrophilic group, water-dispersible polyisocyanate, NCO content 18%, solids content 100%.

[0169] Organic solvents Dipropylene glycol dimethyl ether: A glycol ether-based organic solvent without a hydroxyl group, with a molecular weight of 162 g / mol, boiling point of 171°C, and a solubility in water of 37 g / 100 g (20°C). n-Butyl propionate: An ester-based organic solvent without a hydroxyl group, with a molecular weight of 130.18 g / mol, boiling point of 145°C, and a solubility in water of 0.2 g / 100 g (20°C). Propylene glycol monomethyl ether acetate: also known as methoxypropyl acetate, an ester-based organic solvent without a hydroxyl group, molecular weight 132.2 g / mol, boiling point 146°C, solubility in water [19.8 g / 100 g]), Propylene glycol dimethyl ether: A glycol ether-based organic solvent without a hydroxyl group, with a molecular weight of 104 g / mol, boiling point of 97°C, and a solubility in water of 43.6 g / 100 g (20°C). Diethylene glycol isopropyl methyl ether: A glycol ether-based organic solvent without a hydroxyl group, with a molecular weight of 162 g / mol, boiling point of 179°C, and a solubility in water of 100 g or more / 100 g (20°C). DBE: A mixed solvent of DBE dibasic acid ester, dimethyl glutarate, dimethyl succinate and dimethyl adipate. Boiling point: 196-225°C. Solubility in water: 5.3g / 100g (20°C). Ethylene glycol monobutyl ether acetate: also known as butyriceroacetate, acetate-based organic solvent, molecular weight 160.2g / mol, boiling point 191.5℃, solubility in water 1.1g / 100g (20℃), Diethylene glycol monoethyl ether acetate: Also known as carbitol acetate, acetate-based organic solvent, molecular weight 176g / mol, boiling point 217.4, solubility in water 100g or more / 100g (20℃).

[0170] Test items In the present invention, it is important that all performances are excellent, and if any one of them is rated as failing "D", it is a failure.

[0171] Test item 1: Storage stability The base resin and hardener prepared in the above examples were stored at 40°C for one month, and the presence or absence of sedimentation, changes in appearance, color, and viscosity were evaluated. The evaluations were A, B, and C, which were pass, and D, which was fail. A: No sedimentation, separation, gelation, discoloration, or viscosity change was observed, and the result was very good. B: A small amount of sediment or separation is observed, but no gelation, discoloration, or viscosity change is observed. C: There is some sedimentation or separation, gelation, discoloration, viscosity change, etc., but it is at a level that can be tolerated by stirring. D: Significant sedimentation, separation, gelation, discoloration, viscosity change, etc. are observed, and there is clearly a problem.

[0172] Test item 2: Manual mixing For the coating compositions obtained in the examples and comparative examples, a sample (*1) was prepared in which the base agent and hardener were mixed by hand stirring, and a sample (*2) was prepared in which the base agent and hardener were mixed with a disperser at 1000 rpm for 3 minutes. The appearance of the coating composition was visually inspected after stirring for 15 minutes, and the hand stirring property of the base agent and hardener was evaluated. The evaluations were A and C, which were pass, and D, which was fail. A: Both *1 and *2 are in a homogeneous state and do not separate after standing. C: *2 is in a homogeneous state, but *1 shows some separation after standing. D: *1 and *2 are significantly separated.

[0173] Test item 3: Pot life (working time) The coating compositions obtained in the Examples and Comparative Examples were left to stand at 25°C, and their viscosities were measured at regular intervals using a Ford cup. The time it took to reach the coating limit viscosity was recorded as the pot life. The evaluations were A, B, and C, with A being pass and D being fail. A: The pot life is more than 2 hours. B: The pot life is 1 hour or more and less than 2 hours. C: The pot life is 30 minutes or more and less than 1 hour. D: The pot life is 30 minutes or less.

[0174] Test item 4: Drying Each test plate (substrate 1) was left at room temperature (20°C) for 30 minutes, and then the surface dryness of each test plate was checked by touching with a finger. The evaluation results were A, B, and C, which indicate pass, and D, which indicates fail. A: After 15 minutes, the surface was good with no tack. B: After 20 minutes, the surface is good with no tack. C: After 25 minutes, the surface was good with no tack. D: After 25 minutes, there is tack on the surface.

[0175] Test item 5: Finishability Test panels (for evaluating finish) coated with each aqueous multi-component coating composition as a topcoat were visually observed and evaluated for unevenness, shrinkage, popping, smoothness, gloss, etc. The evaluations were A, B, and C, indicating pass, and D, indicating fail. A: The appearance of the coating is very good. B: Almost no unevenness, wrinkles or shrinkage are observed, and the smoothness and gloss are good and there are no problems in practical use. C: A slight decrease in smoothness and loss of gloss are observed, but there is almost no unevenness, sideburns, or shrinkage, and the level is acceptable for practical use. D: There is a noticeable increase in unevenness, underarms, shrinkage and loss of shine, and there is clearly a problem.

[0176] Test item 6: Weather resistance (outdoor exposure test) Test pieces (test panels cut to a size of 100 x 300 mm) were attached at an angle of 4 degrees from vertical facing south on Okinoerabujima Island in Kagoshima Prefecture, and an exposure test was performed. The color difference (△E) from the initial painted panel was measured "2 months after the start of exposure," "18 months after the start of exposure," and "24 months after the start of exposure" in accordance with JIS Z8370 using a multi-light source spectrophotometer MSC-5N made by Suga Test Instruments Co., Ltd. The 60° gloss of each painted surface was measured in accordance with the specular gloss (60°) of JIS K5600-4-7 (1999), and evaluated according to the following criteria. A: No significant abnormalities were found in gloss or color difference. B: No abnormalities in color difference, but gloss tends to decrease. C: Color difference is large and gloss tends to decrease. D: Significant decrease in both color difference and gloss.

[0177] Example 21 A commercially available lacquer primer surfacer was applied to an electrodeposition-coated plate having a size of 300×150×2.0 mm coated with an epoxy resin-based electrodeposition coating material to a thickness of 40 μm as a base preparation, and then dried at room temperature for 30 minutes and polished with #400 waterproof abrasive paper. On this coated plate, the aqueous coating composition No. 10 described in Example 10 was spray-coated as a first colored coating composition to a dry film thickness of 40 μm on the entire surface, and the plate was left for 30 minutes under the conditions of room temperature (air temperature 23° C., humidity 50% RH). Then, the plate was masked with masking tape to form a line pattern, and the unmasked portion was spray-coated with the aqueous coating composition No. 17 of Example 17 as a second colored coating composition to a dry film thickness of 15 μm, and the plate was left for 30 minutes under the conditions of room temperature (air temperature 23° C., humidity 50% RH). After leaving it, the masking was removed, and "Retan PG Multi HX (Q) Clear" and its hardener (Kansai Paint Co., Ltd., organic solvent-based urethane hardening type paint composition) were mixed as a top clear paint composition in a main component hardener weight ratio (sometimes abbreviated as main hardening ratio) of 2:1, and spray-painted to a dry film thickness of 40 μm. The coated plate was then placed in a drying oven at 50°C (material reaching temperature 45°C), which is a large drying oven, for 30 minutes to heat and dry, and a test plate was obtained. The finish of the resulting multi-layer coating was good, and the weather resistance (24 months outdoor exposure) was also good at level A. It also dried quickly, so workability was good.

[0178] Example 22 A commercially available lacquer primer surfacer was applied to an electrodeposition-coated plate having a size of 300×150×2.0 mm coated with an epoxy resin-based electrodeposition coating material to a thickness of 40 μm as a base preparation, and after drying at room temperature for 30 minutes, it was polished with #400 waterproof abrasive paper. On this coated plate, the aqueous multi-liquid coating composition No. 10 described in Example 10 was spray-coated as a first colored coating composition to a dry film thickness of 15 μm on the entire surface, and left for 30 minutes under the conditions of room temperature (air temperature 23 ° C., humidity 50% RH). Then, the plate was masked with masking tape to form a line pattern, and the unmasked portion was spray-coated with the aqueous multi-liquid coating composition No. 17 of Example 17 as a second colored coating composition to a dry film thickness of 15 μm, and left for 30 minutes under the conditions of room temperature (air temperature 23 ° C., humidity 50% RH). After leaving it, the masking was removed, and "Retan WB Eco EV Clear Q" and its hardener (a water-based urethane curing paint composition manufactured by Kansai Paint Co., Ltd.) were mixed as a top clear paint composition in a main component hardener weight ratio (sometimes abbreviated as main hardening ratio) of 2:1, and spray-painted to a dry film thickness of 40μm. The coated plate was then placed in a drying oven at 50℃ (material reaching temperature 45℃) simulating a large drying oven for 30 minutes to heat and dry, and a test plate was obtained. The finish of the resulting multi-layer coating was good, and the weather resistance (24 months outdoor exposure) was also good at level A. It also dried quickly, making it easy to work with.

[0179] (Example 23) An electrocoated panel measuring 70 x 150 x 0.8 mm coated with an epoxy resin-based electrocoating paint was sanded with #240 paper, and on the coated panel with some of the steel plate exposed, a mixture of "Retan WB Eco EV ELS Plasafu L55" (Kansai Paint Co., Ltd., urethane curing water-based primer surfacer) with an NCO / OH ratio adjusted to 1.0 was mixed at a main hardness ratio of 100:10 and spray painted to a dry film thickness of 60 μm. It was then dried at 60°C for 30 minutes and then wet-sanded with #400 paper. After wiping off the moisture, the substrate was placed horizontally at 25°C and 40% relative humidity, and the aqueous multi-liquid coating composition No. 9 of Example 9 was spray-painted once as a colored coating composition, with the NCO:OH molar ratio adjusted to 1:1.6 and mixed until uniform. Air was then blown until the gloss of the base coating film was 25 or less to create a dried coating film. The same aqueous multi-liquid colored coating composition was spray-painted on the dried coating film, and air was blown until the gloss was 25 or less (second coating). The same aqueous colored coating composition was spray-painted on the dried coating film, and air was blown until the gloss was 25 or less (third coating). After coating, a base coat coating film with a dry film thickness of 15 μm was obtained. A top clear coating composition was prepared by mixing "Retan PG Multi HX(Q) Clear" and its hardener (Kansai Paint Co., Ltd., organic solvent-based urethane curing coating composition) at a main hardness ratio of 2:1, and the mixture was air-sprayed to a dry thickness of 40 μm. The coated plate was then held horizontally at room temperature for 20 minutes, and then dried at 60°C for 30 minutes using an electric hot air dryer and cooled to room temperature to obtain a clear coating. The resulting multi-layered coating plate (test plate) was subjected to the following performance tests. The finish of the resulting multi-layered coating was at level A, and the weather resistance (24 months outdoor exposure) was also at level A, making it excellent. The drying properties were also excellent, making the workability good.

[0180] Example 24 A commercially available lacquer primer surfacer was applied to an electrodeposition-coated plate having a size of 300×150×2.0 mm coated with an epoxy resin-based electrodeposition coating material to a thickness of 40 μm as a base preparation, and after drying at room temperature for 30 minutes, it was polished with #400 waterproof abrasive paper. On this coated plate, the aqueous multi-liquid coating composition No. 10 described in Example 10 was spray-coated as a first colored coating composition to a dry film thickness of 15 μm on the entire surface, and left for 30 minutes under the conditions of room temperature (air temperature 23 ° C., humidity 50% RH). Then, the plate was masked with masking tape to form a line pattern, and the unmasked portion was spray-coated with the aqueous multi-liquid coating composition No. 17 of Example 17 as a second colored coating composition to a dry film thickness of 15 μm, and left for 30 minutes under the conditions of room temperature (air temperature 23 ° C., humidity 50% RH). After leaving it, the masking was removed, and the main component and its curing agent were mixed in a ratio of 1:1.6 in the formulation described in Example 1 of Table 3-1 except that the pigment component was removed as the top clear coating composition to prepare water-based multi-liquid clear coating composition No. 23, which was spray-painted to a dry film thickness of 40 μm. The coated plate was then placed in a drying oven at 50 ° C (material reaching temperature 45 ° C), which is assumed to be a large drying oven, for 30 minutes to heat and dry, and a test plate was obtained. The finish of the obtained multi-layer coating film was good, and the weather resistance (24 months outdoor exposure) was also good at level A. In addition, the drying property was excellent, so the workability was also good.

[0181] (Example 25) An aluminum plate measuring 300 x 150 x 2.0 mm was coated with "Water-based Epotect Undercoat" (product name: water-based epoxy resin undercoat paint, manufactured by Kansai Paint Co., Ltd. The solid content of the pigment was 120 parts by mass per 100 parts by mass of the film-forming components contained in the main agent, (anti-rust pigment and extender pigment) / other pigment = 46 / 54) to a dry film thickness of 60 μ, and then "LUC Poly Putty" (product name: unsaturated polyester resin-containing putty composition, manufactured by Kansai Paint Co., Ltd.) was applied using a spatula to a hardened film thickness of 1000 μm as a base adjustment, and the surface of the coating was sanded with #400 waterproof sandpaper, degreased and washed, and then "Retan WB Eco EV ELS Plasma Surface" with an NCO / OH ratio adjusted to 1.0 was applied. L55" (trade name, Kansai Paint Co., Ltd., urethane curing water-based primer surfacer, pigment solid content is 250 parts by mass per 100 parts by mass of the film-forming components contained in the base, (anti-rust pigment and extender pigment) / other pigment = 80 / 20) was mixed at a main hardness ratio of 100:10, spray-painted to a dry film thickness of 60 μm, left at room temperature for 10 minutes, dried at 60 ° C for 30 minutes in a drying oven at 50 ° C (material reaching temperature 45 ° C) simulating a large drying oven, water-polished with # 400 paper, dried at room temperature, and degreased and washed using KAR Silicon Off. Next, the water-based multi-liquid coating composition No. 10 described in Example 10 was spray-painted as a colored coating composition on the entire surface to a dry film thickness of 45 μm, and left at room temperature (air temperature 23 ° C, humidity 50% RH) for 60 minutes. Then, "Retan WB Eco EV Clear Q" and its hardener (product name, Kansai Paint Co., Ltd., water-based urethane curing paint composition) were mixed as a top clear paint composition in a main component hardener weight ratio (sometimes abbreviated as main hardening ratio) of 2:1, and spray-painted to a dry film thickness of 40μm. The coated plate was then placed in a drying oven at 50℃ (material reaching temperature 45℃), which simulates a large drying oven, for 30 minutes to heat and dry, and a test plate was obtained. The finish of the resulting multi-layer coating was good, and the weather resistance (24 months outdoor exposure) was also good at level A. It also dried quickly, making it easy to work with.

Claims

1. An aqueous multi-liquid coating composition comprising a base agent (I) and a curing agent (II), The main component (I) contains a hydroxyl group-containing resin (A), The hydroxyl group-containing resin (A) is A colloidal dispersion type acrylic resin (A1), A water-soluble acrylic resin (A2), The colloidal dispersion type acrylic resin (A1) is contained in an amount of 50 mass% or more based on the total resin solid content contained in the main component (I), The glass transition temperature of the colloidal dispersion type acrylic resin (A1) is within the range of 42 to 70° C. Aqueous multi-component paint composition.

2. An aqueous multi-liquid coating composition comprising a base agent (I) and a curing agent (II), The main component (I) contains a hydroxyl group-containing resin (A) and a color pigment (B), The hydroxyl-containing resin (A) is A colloidal dispersion type acrylic resin (A1), A water-soluble acrylic resin (A2), The colloidal dispersion type acrylic resin (A1) is contained in an amount of 50 mass% or more based on the total resin solid content contained in the main component (I), The glass transition temperature of the colloidal dispersion type acrylic resin (A1) is within the range of 42 to 70° C. Aqueous multi-component paint composition.

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