Water-based paint compositions, coatings, and articles

Abstract

The object of the present invention is to provide a water-based paint that does not undergo phase separation during storage, even if the hydrophobic solvent content is zero or small, and that exhibits good water-resistant adhesion, water-resistant blistering, and sagging resistance of the coating film. [Solution] The solution comprises a coating resin, a curing agent, a viscous agent, and a pigment, wherein the viscous agent includes at least one selected from the group consisting of carboxyvinyl polymer and dieutan gum. Furthermore, the content of the viscous agent is 0.01 to 0.7% by mass relative to the total mass of the aqueous paint composition, and the steady-state value η1 of the predetermined viscosity of the aqueous paint composition is 0.10 Pa·s or more.

Description

[Technical Field]

[0001] This invention relates to aqueous coating compositions, coating films, and articles. [Background technology]

[0002] In recent years, due to VOC regulations on paints (e.g., China's GB standard), there has been a need to reduce the hydrophobic solvent content in paints (e.g., Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2024-141943 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, simply changing the solvent in the paint from a hydrophobic solvent to a water-based solvent can lead to phase separation during storage of the water-based paint, and can also reduce the water-resistant adhesion, blister resistance, and sagging resistance of the paint film.

[0005] Therefore, it is necessary to develop a paint that does not undergo phase separation during storage, even with zero or low hydrophobic solvent content, and that exhibits good water-resistant adhesion, water-resistant blistering, and sagging resistance of the paint film.

[0006] Therefore, the present invention aims to provide a water-based paint that does not undergo phase separation during storage, even if the hydrophobic solvent content is zero or small, and that exhibits good water-resistant adhesion, water-resistant blistering, and sagging resistance of the paint film. [Means for solving the problem]

[0007] The aqueous coating composition according to the present invention is It contains a film-forming resin, a curing agent, a viscous agent, and a pigment. The viscous agent comprises at least one selected from the group consisting of carboxyvinyl polymer and dieutan gum. The content of the viscous agent is 0.01 to 0.7% by mass relative to the total mass of the aqueous paint composition. The aqueous paint composition at 23°C and a shear rate of 10s -1 This is an aqueous paint composition in which the steady-state viscosity η1 measured during steady-state flow measurement of shear deformation is 0.10 Pa·s or higher. As a result, even if the hydrophobic solvent content is zero or small, phase separation does not occur during storage of the paint, and the water-resistant adhesion, water-resistant blistering resistance, and sagging resistance of the paint film are good.

[0008] In one embodiment of the aqueous coating composition according to the present invention, the VOC content [ρ(VOC)] of the aqueous coating composition is 420 g / L or less.

[0009] In one embodiment of the aqueous coating composition according to the present invention, the content of the organic solvent is 0 to 15% by mass based on 100% by mass of the coating composition.

[0010] In one embodiment of the aqueous coating composition according to the present invention, the film-forming resin comprises at least one selected from the group consisting of acrylic resins, urethane resins, and polyester resins.

[0011] In one embodiment of the aqueous coating composition according to the present invention, the curing agent comprises at least one selected from the group consisting of isocyanate-based curing agents, melamine-based curing agents, and carbodiimide-based curing agents.

[0012] In one embodiment of the aqueous coating composition according to the present invention, the aqueous coating composition has a steady-state value η1 of 0.10 to 0.90 Pa·s, 23℃, shear rate 1,000s -1 The steady-state viscosity η2 measured during steady-state flow measurement of shear deformation is 0.02 to 0.09 Pa·s.

[0013] In one embodiment of the aqueous paint composition according to the present invention, the non-volatile content (NV) of the aqueous paint composition is 1 to 80% by mass based on the total mass of the aqueous paint composition.

[0014] In one embodiment of the aqueous paint composition according to the present invention, the aqueous paint composition is an aqueous paint composition for liquid film discharge coating, liquid column discharge coating, or liquid droplet discharge coating.

[0015] In one embodiment of the aqueous paint composition according to the present invention, it further contains an alkali swelling type thickener.

[0016] The coating film according to the present invention is a coating film formed using any of the above aqueous paint compositions.

[0017] The article according to the present invention has the above coating film.

Effects of the Invention

[0018] According to the present invention, even if the content of the hydrophobic solvent is zero or small, phase separation does not occur during the storage of the aqueous paint, and an aqueous paint with good water resistance adhesion, water resistance swelling resistance, and stain resistance of the coating film can be provided.

Modes for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described. These descriptions are for the purpose of exemplifying the present invention and do not limit the present invention in any way.

[0020] In the present invention, two or more embodiments can be arbitrarily combined.

[0021] The materials, components, compounds, resins, curing agents, thickeners, and solvents described in this specification may each be used alone or in combination of two or more, unless otherwise specified.

[0022] In the present invention, paints and paint compositions can be used interchangeably.

[0023] In this invention, the term "solids content" is a concept that includes both solids content and non-volatile content. Furthermore, solids content may be referred to as NV.

[0024] In this specification, unless otherwise stated, numerical ranges are intended to include the upper and lower limits of that range. For example, 0.10 to 0.90 Pa·s means between 0.10 Pa·s and 0.90 Pa·s.

[0025] In the present invention, "even if the hydrophobic solvent content is zero or small" means that the invention is applicable when the hydrophobic solvent content is small (for example, 15% by mass or less relative to the total mass of the paint composition), and is not intended to exclude weak solvent-type paints and strong solvent-type paints that contain hydrophobic solvents.

[0026] In the present invention, at least one viscous agent selected from the group consisting of carboxyvinyl polymers and dieutan gum may be referred to as the first viscous agent.

[0027] In this invention, the alkali-swelling type viscosity agent may be referred to as the second viscosity agent.

[0028] In the present invention, the aqueous coating composition is measured at 23°C and a shear rate of 10s. -1 The steady-state viscosity η1 in steady-state flow measurement of shear deformation is determined by the method described in the examples.

[0029] In the present invention, the aqueous coating composition is measured at 23°C and a shear rate of 1000 s. -1 The steady-state viscosity η2 in steady-state flow measurement of shear deformation is determined by the method described in the examples.

[0030] (Water-based paint composition) The aqueous coating composition according to the present invention is It contains a film-forming resin, a curing agent, a viscous agent, and a pigment. The viscous agent comprises at least one selected from the group consisting of carboxyvinyl polymer and dieutan gum. The content of the viscous agent is 0.01 to 0.7% by mass relative to the total mass of the aqueous paint composition. The aqueous paint composition at 23°C and a shear rate of 10s -1 This is an aqueous paint composition in which the steady-state viscosity η1 measured during steady-state flow measurement of shear deformation is 0.10 Pa·s or higher.

[0031] In conventional paint compositions, viscosity is increased through the interaction of a hydrophobic solvent and a viscous agent, thereby providing the paint composition with resistance to sagging. However, simply changing the solvent in the paint from a hydrophobic solvent to an aqueous solvent is thought to reduce or eliminate the interaction between the hydrophobic solvent and the viscous agent, resulting in insufficient viscosity. Consequently, due to insufficient viscosity, the paint may sag during the drying of the paint film after application, reducing the smoothness of the film. In areas where the paint film is thin, water resistance decreases, allowing water to penetrate into or beneath the paint film, leading to reduced adhesion and blistering.

[0032] In response to this, the present inventors have found that by using a predetermined amount of a viscous agent selected from the group consisting of carboxyvinyl polymer and diutan gum, phase separation does not occur during storage of the water-based paint, and the water-resistant adhesion, water-resistant blistering, and sagging of the paint film are improved.

[0033] The following describes the essential components of the aqueous coating composition of the present invention: a film-forming resin, a curing agent, a specific viscous agent, and a pigment.

[0034] ·Coating film forming resin In the aqueous coating composition of the present invention, the film-forming resin is not particularly limited, and any film-forming resin used in known aqueous coating compositions can be used. Examples of film-forming resins include acrylic resins, polyester resins, alkyd resins, fluororesins, epoxy resins, urethane resins, polyether resins, polyolefin resins, polycarbonate resins, and melamine resins. Furthermore, as the resin component, polymer compounds containing or composed of inorganic components, such as silicone resins and alkoxysilane condensates, can also be used.

[0035] In one embodiment of the aqueous coating composition according to the present invention, the film-forming resin comprises at least one selected from the group consisting of acrylic resins, urethane resins, and polyester resins.

[0036] In one embodiment of the aqueous coating composition according to the present invention, the film-forming resin comprises an acrylic resin, a polyester resin, and a urethane resin, wherein the acrylic resin content is 5 to 40% by mass, the polyester resin content is 1 to 20% by mass, and the urethane resin content is 2 to 30% by mass, based on 100% by mass of the total solid content of the film-forming resin and curing agent. In another embodiment of the aqueous coating composition according to the present invention, the film-forming resin comprises an acrylic resin, a polyester resin, a urethane resin, and a polycarbonate resin, wherein the acrylic resin content is 5 to 40% by mass, the polyester resin content is 1 to 20% by mass, the urethane resin content is 2 to 30% by mass, and the polycarbonate resin content is 2 to 30% by mass, based on 100% by mass of the total solid content of the film-forming resin and curing agent.

[0037] The molecular weight of the film-forming resin is not particularly limited and can be adjusted as appropriate. The number-average molecular weight (Mn) of the film-forming resin is, for example, 5,000 to 30,000.

[0038] The hydroxyl value of the film-forming resin is not particularly limited and can be adjusted as appropriate. In one embodiment, the hydroxyl value of the film-forming resin is 20 to 180 mgKOH / g.

[0039] The acid value of the film-forming resin is not particularly limited and can be adjusted as appropriate. In one embodiment, the acid value of the film-forming resin is 10 to 80 mg KOH / g.

[0040] The film-forming resin may be an organic solvent type, a water-based type (water-soluble, water-dispersible, or emulsion), or a non-water-dispersible type.

[0041] The content of the film-forming resin is not particularly limited and can be adjusted as appropriate. In one embodiment, the solid content of the film-forming resin is 30 to 95% by mass relative to the total mass of solid content of the paint composition.

[0042] • Hardener The aqueous coating composition of the present invention contains a curing agent. The curing agent is not particularly limited, and any known curing agent can be appropriately selected and used. Examples include amine-based curing agents, carbodiimide-based curing agents, epoxy-based curing agents, isocyanate-based curing agents, and the like.

[0043] Examples of amine-based curing agents include melamine-based curing agents, guanamine-based curing agents, aziridine-based curing agents, oxazoline-based curing agents, and urea-based curing agents.

[0044] A melamine-based curing agent refers to a melamine in which one or more hydrogen atoms of the three amino groups (-NH2) are substituted with a methylol group (-CH2OH) or an alkoxymethyl group (-CH2OR (R: alkyl group, cycloalkyl group)). Examples of melamine-based curing agents include the fully alkyl etherified melamine resin, mixed alkyl etherified melamine resin, alkyl etherified melamine resin having a methylol group, methylolated melamine resin, alkyl etherified melamine resin having an imino group, methylolated melamine resin having an imino group, and polymers thereof, as described in Japanese Patent Application Publication No. 2022-141604.

[0045] Commercially available melamine-based hardening agents may be used. Examples of commercially available melamine-based hardening agents include the Cymel series, such as "Cymel 211" from Ornex Japan; the Nikalac series, such as "Nikarac (registered trademark) MW-390" from Sanwa Chemical Co., Ltd.; and the Amidia series, such as "Amidia J-820-60" from DIC Corporation.

[0046] As the guanamine-based curing agent, aziridine-based curing agent, oxazoline-based curing agent, and urea-based curing agent, known curing agents can be appropriately selected and used. As the guanamine-based curing agent, aziridine-based curing agent, oxazoline-based curing agent, and urea-based curing agent, for example, the curing agent described in Japanese Patent Application Publication No. 2022-141604 can be used.

[0047] Examples of carbodiimide-based curing agents include poly(4,4'-diphenylmethanecarbodiimide), poly(3,3'-dimethyl-4,4'-biphenylmethanecarbodiimide), poly(tolylcarbodiimide), poly(p-phenylenecarbodiimide), poly(m-phenylenecarbodiimide), poly(naphthylenecarbodiimide), poly(1,6-hexamethylenecarbodiimide), poly(1,4-tetramethylenecarbodiimide), and poly Examples include poly(1,3-cyclohexylenecarbodiimide), poly(1,4-cyclohexylenecarbodiimide), poly(1,3,5-triethylphenylenecarbodiimide), poly(4,4'-methylenebiscyclohexylcarbodiimide), poly(1,3-diisopropylphenylenecarbodiimide), poly(1-methyl-3,5-diisopropylphenylenecarbodiimide), and poly(isopropylphenylenecarbodiimide).

[0048] Commercially available carbodiimide-based curing agents may be used. Examples of commercially available carbodiimide-based curing agents include the CarbodiLite series, such as "CarbodiLite V-02" manufactured by Nisshinbo Chemical Co., Ltd.

[0049] As the epoxy curing agent, for example, any known curing agent can be appropriately selected and used. Examples of epoxy curing agents include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, trimethylolethane triglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, and the like.

[0050] Examples of isocyanate-based curing agents include aliphatic diisocyanates, alicyclic diisocyanates, aromatic diisocyanates, and dimers and trimers of these diisocyanates.

[0051] Examples of aliphatic diisocyanates include ethylene diisocyanate, butylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate.

[0052] Examples of alicyclic diisocyanates include dicyclohexylmethane-4,4'-diisocyanate, isophorone diisocyanate, 1,4-cyclohexane diisocyanate, norbornene methane diisocyanate, cyclohexane-1,4-diyrbis(methylene) diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated tetramethylxylylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated dimethyldiphenylmethane diisocyanate, and hydrogenated naphthalene diisocyanate.

[0053] Examples of aromatic diisocyanates include xylylene diisocyanate, tolylene diisocyanate, tetramethyl xylylene diisocyanate, diphenylmethane diisocyanate, dimethyl diphenylmethane diisocyanate, and naphthalene diisocyanate.

[0054] As an isocyanate-based curing agent, a blocked isocyanate in which the isocyanate groups of the isocyanate are blocked by a blocking agent may be used. Examples of blocked isocyanates include the active methylene-blocked polyisocyanate compound described in Japanese Patent Publication No. 2024-090534, the blocked polyisocyanate described in Japanese Patent Publication No. 2022-129736, and the blocked isocyanate resin described in International Publication No. 2017 / 217471.

[0055] Commercially available isocyanate-based curing agents may be used. Examples of commercially available isocyanate-based curing agents include the Takenate series, such as "Takenate WD-720" manufactured by Mitsui Chemicals; the Aquanate series, such as "Aquanate (registered trademark) 100" manufactured by Tosoh Corporation; and the Duranate series, such as "Duranate (registered trademark) WB40-100" manufactured by Asahi Kasei Corporation.

[0056] In one embodiment of the aqueous coating composition according to the present invention, the curing agent comprises at least one selected from the group consisting of isocyanate-based curing agents, melamine-based curing agents, and carbodiimide-based curing agents.

[0057] In an aqueous paint composition, the content of the curing agent may be, for example, 5 to 50% by mass with respect to 100% by mass of the total resin solids content of the film-forming resin and the curing agent. In one embodiment, the content of the curing agent is 5% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, or 45% by mass or more, with respect to 100% by mass of the total resin solids content of the film-forming resin and the curing agent. In another embodiment, the content of the curing agent is 50% by mass or less, 45% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less, with respect to 100% by mass of the total resin solids content of the film-forming resin and the curing agent.

[0058] • Viscosity agent The aqueous coating composition of the present invention uses a viscous agent comprising at least one selected from the group consisting of carboxyvinyl polymer and dieutan gum. This prevents phase separation during storage of the aqueous coating, resulting in good water-resistant adhesion, water-resistant blistering, and sagging resistance of the coating film. In the present invention, if the first viscous agent (carboxyvinyl polymer or dieutan gum) also corresponds to the alkali-swelling type viscous agent (second viscous agent) described later, that viscous agent is treated as the first viscous agent rather than the alkali-swelling type viscous agent.

[0059] Examples of carboxyvinyl polymers include polymers of acrylic acid (water-soluble polymers) that are designated as carbomers in INCI. The carboxyvinyl polymer is not particularly limited, and known carboxyvinyl polymers can be appropriately selected and used.

[0060] Commercially available carboxyvinyl polymers may be used. Examples of commercially available carboxyvinyl polymers include "Carbopol® 940", "Carbopol 941", "Carbopol 980", and "Carbopol 981" from Lubrizol Advanced Materials; "Hibis Wako® 103", "Hibis Wako 104", "Hibis Wako 105", and "Hibis Wako 105MD" from Fujifilm Wako Pure Chemical Industries; "Acpec® HV-501", "Acpec HV-504", "Acpec HV-505", "Acpec HV-505E", "Acpec HV-801EG", and "Acpec HV-805EG" from Sumitomo Seika Co., Ltd.; and "Syntalen K" and "Syntalen L" from 3V Sigma.

[0061] The dieutan gum is not particularly limited, and any known dieutan gum can be appropriately selected and used. In one embodiment, the dieutan gum consists of a repeating structure of units in which a main chain of glucose, glucuronic acid, glucose and rhamnose is attached to two rhamnose side chains.

[0062] Commercially available diyutan gum may be used. Examples of commercially available diyutan gum include the KELCO-VIS® series, Geovis series, KELCO-CARE® series, and KELCO-CRETE® series from CPKelco.

[0063] The amount of the first viscous agent in the aqueous paint composition is 0.01 to 0.70% by mass relative to the total mass of the aqueous paint composition. In one embodiment, the content of the first viscous agent is 0.01 to 0.50% by mass relative to the total mass of the aqueous paint composition. In another embodiment, the content of the first viscous agent is 0.01% by mass or more, 0.05% by mass or more, 0.10% by mass or more, 0.15% by mass or more, 0.20% by mass or more, 0.25% by mass or more, 0.30% by mass or more, 0.35% by mass or more, 0.40% by mass or more, 0.45% by mass or more, 0.50% by mass or more, 0.55% by mass or more, 0.60% by mass or more, or 0.65% by mass or more, relative to the total mass of the aqueous paint composition. In yet another embodiment, the content of the first viscous agent is 0.70% by mass or less, 0.65% by mass or less, 0.60% by mass or less, 0.55% by mass or less, 0.50% by mass or less, 0.45% by mass or less, 0.40% by mass or less, 0.35% by mass or less, 0.30% by mass or less, 0.25% by mass or less, 0.20% by mass or less, 0.15% by mass or less, 0.10% by mass or less, or 0.05% by mass or less, based on the total mass of the aqueous coating composition. In yet another embodiment, the content of the first viscous agent is 0.05 to 0.5% by mass, based on the total mass of the aqueous coating composition.

[0064] In an aqueous coating composition, the content of the first viscous agent may be, for example, 0.1 to 5.0 parts by mass per 100 parts by mass of the total solid content of the coating resin of the aqueous coating composition. In one embodiment, the content of the first viscous agent is 0.1 parts by mass or more, 0.5 parts by mass or more, 1.0 parts by mass or more, 1.5 parts by mass or more, 2.0 parts by mass or more, 2.5 parts by mass or more, 3.0 parts by mass or more, 3.5 parts by mass or more, 4.0 parts by mass or more, or 4.5 parts by mass or more, per 100 parts by mass of the total solid content of the coating resin. In another embodiment, the content of the first viscous agent is 5.0 parts by mass or less, 4.5 parts by mass or less, 4.0 parts by mass or less, 3.5 parts by mass or less, 3.0 parts by mass or less, 2.5 parts by mass or less, 2.0 parts by mass or less, 1.5 parts by mass or less, 1.0 part by mass or less, or 0.5 parts by mass or less, based on 100 parts by mass of the total solid content of the coating resin.

[0065] In an aqueous paint composition, when a first viscous agent and other viscous agents are used in combination as a viscous agent, the amount of solids of the first viscous agent relative to the total mass of solids of the viscous agents may be, for example, 6 to 90% by mass (preferably 15 to 75% by mass).

[0066] Pigments The pigment is not particularly limited, and known pigments used in paint compositions can be used. Examples of pigments include coloring pigments, extender pigments, flake pigments, and lustrous pigments.

[0067] The coloring pigment is not particularly limited, and any coloring pigment used in known paints can be used. Examples of coloring pigments include azo chelate pigments, insoluble azo pigments, condensed azo pigments, diketopyrrolopyrrole pigments, phthalocyanine pigments, indigo pigments, perinone pigments, perylene pigments, dioxane pigments, quinacridone pigments, isoindolinone pigments, metal complex pigments; lead yellow, yellow iron oxide, red iron oxide, carbon black, titanium dioxide, etc.

[0068] The extender pigment is not particularly limited, and any known extender pigment used in paints can be used. Examples of extender pigments include calcium carbonate, barium sulfate, clay, and talc.

[0069] The flake pigment is not particularly limited, and known flake pigments used in paints can be used. Examples of flake pigments include metallic flake pigments such as aluminum, copper, zinc, iron, nickel, tin, and aluminum oxide; graphite pigments; and glass flake pigments. In addition, for example, the optically coherent flake pigment described in Japanese Patent Application Publication No. 2024-140690 may be used.

[0070] The luminous pigment is not particularly limited, and any luminous pigment used in known paints can be used. Examples of luminous pigments include mica pigments such as interference mica, white mica, and colored mica; graphite pigments; glass flake pigments; and metallic pigments such as aluminum, copper, zinc, iron, nickel, tin, aluminum oxide, chromium oxide, and alloys containing these.

[0071] In an aqueous paint composition, the pigment content may be, for example, 1 to 150 parts by mass per 100 parts by mass of the resin solids of the film-forming resin and the curing agent.

[0072] Other ingredients The water-based paint composition may optionally contain other components in addition to the film-forming resin, curing agent, first viscosity agent, and pigment. Examples of other components include alkali-swelling viscosity agents (second viscosity agent), other viscosity agents, gloss agents, dispersants, curing catalysts, film-forming aids, ultraviolet absorbers, light stabilizers, antioxidants, defoamers, surface modifiers, pinhole inhibitors, rust inhibitors, and the like.

[0073] Alkaline swelling type viscosity Alkali-swelling viscous agents are acrylic polymers having acidic groups such as carboxyl groups, which swell when neutralized with alkaline substances (such as alkali metal hydroxides, alkali metal salts of carbonate, alkali metal salts of bicarbonate, ammonia, monoalkanolamines, dialkanolamines, or trialkanolamines), thereby imparting viscosity to aqueous paint compositions. Alkali-swelling viscous agents are usually insoluble in water under non-alkaline environments.

[0074] Examples of alkali-swelling type viscosity agents include polycarboxylic acid-based viscosity agents, polysulfonic acid-based viscosity agents, and polyphosphate-based viscosity agents.

[0075] Examples of commercially available alkaline swelling-type viscosity agents include the SN Thickener series from Sunopco, such as SN Thickener 615, 630, 636, and 640; the Primal series from Dow-Toray, such as Primal ASE-60; and "Viscalex HV30" from BASF.

[0076] In one embodiment, the aqueous paint composition comprises at least a first viscous agent and a second viscous agent. In another embodiment, the aqueous paint composition comprises at least the first viscous agent but does not contain the second viscous agent. In yet another embodiment, the aqueous paint composition comprises only the first viscous agent as the viscous agent.

[0077] In the present invention, at least one selected from the group consisting of urethane-associated viscous agents, cellulose-based viscous agents, amide-based viscous agents, inorganic layered compound-based viscous agents, and aminoplast-based viscous agents may be used as the third viscous agent.

[0078] Examples of urethane-associated viscous agents include urethane-modified polyether-type viscous agents.

[0079] Examples of commercially available urethane-associated viscosities include the Adekanol® UH series, such as Adekanol® UH-140S, 420, 450, 526, 540, and 550, manufactured by ADEKA Corporation; and SN Thickener 665T, manufactured by Sunnopco Corporation.

[0080] Examples of cellulose-based viscous agents include crystalline cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose.

[0081] Examples of commercially available cellulose-based viscosity agents include the Ceolus® series, such as the Ceolus® RC series manufactured by Asahi Kasei Corporation, and the Celosize® series, such as the Celosize QP 4400 and 52000H manufactured by Dow Chemical Corporation.

[0082] Examples of amide-based viscous agents include fatty acid amides, polyamides, acrylamides, long-chain polyaminoamides, aminoamides, and their salts (e.g., phosphates).

[0083] Examples of inorganic layered compound-based viscous agents include layered compounds such as montmorillonite, bentonite, and clay.

[0084] Examples of aminoplast-based viscosity modifiers include hydrophobic modified ethoxylate aminoplast-based association-type viscosity modifiers.

[0085] The amount of alkali-swelling type viscous agent (second viscous agent) in the aqueous coating composition is not particularly limited. In one embodiment, the content of the second viscous agent is 50 to 500 parts by mass per 100 parts by mass of the first viscous agent, in terms of solid content or active ingredients. In one embodiment, the content of the second viscous agent is 50 parts by mass or more, 100 parts by mass or more, 150 parts by mass or more, 200 parts by mass or more, 250 parts by mass or more, 300 parts by mass or more, 350 parts by mass or more, 400 parts by mass or more, or 450 parts by mass or more, per 100 parts by mass of the first viscous agent, in terms of solid content or active ingredients. In another embodiment, the content of the second viscous agent is 500 parts by mass or less, 450 parts by mass or less, 400 parts by mass or less, 350 parts by mass or less, 300 parts by mass or less, 250 parts by mass or less, 200 parts by mass or less, 150 parts by mass or less, or 100 parts by mass or less, per 100 parts by mass of the first viscous agent.

[0086] In this invention, a paint composition in which the most abundant dispersion medium is water is called an aqueous paint composition.

[0087] ·water When using water, conventionally known types of water can be appropriately selected and used. Examples of such water include tap water, distilled water, deionized water, and purified water.

[0088] When water is used, the water content of the aqueous paint composition may be adjusted as appropriate. For example, the water content of the aqueous paint composition is 20 to 80% by mass per 100% by mass of the aqueous paint composition. In one embodiment of the aqueous paint composition of the present invention, the water content is 20% or more by mass, 30% or more by mass, 40% or more by mass, 50% or more by mass, 60% or more by mass, 70% or more by mass, or 80% or more by mass per 100% by mass of the aqueous paint composition. In one embodiment of the aqueous paint composition of the present invention, the water content is 80% or less by mass, 70% or less by mass, 60% or less by mass, 50% or less by mass, 40% or less by mass, 30% or less by mass, or 20% or less by mass per 100% by mass of the aqueous paint composition.

[0089] • Organic solvents When using organic solvents, conventionally known organic solvents for paint compositions can be appropriately selected and used. Examples of organic solvents include alcohols such as methanol, ethanol, 2-propanol, and 1-butanol. In addition, solvents described in Japanese Patent Publication No. 2022-044364 can also be used.

[0090] The content of the organic solvent can be adjusted as appropriate. For example, it is 0 to 15% by mass, preferably 0 to 10% by mass, based on 100% by mass of the aqueous paint composition.

[0091] The aqueous coating composition of the present invention may be room-temperature drying type or heat-curing type. In one embodiment, the aqueous coating composition of the present invention is heat-curing type.

[0092] The aqueous coating composition of the present invention may be a one-component type or a two-component type.

[0093] In one embodiment of the aqueous coating composition according to the present invention, the temperature is 23°C and the shear rate is 10s. -1 The steady-state viscosity η1 (hereinafter sometimes simply referred to as "η1") measured during steady-state flow measurement of shear deformation is 0.10 to 0.90 Pa·s.

[0094] In one embodiment of the aqueous coating composition according to the present invention, at 23°C and a shear rate of 1,000 s, -1The steady-state viscosity η² (hereinafter sometimes simply referred to as "η²") measured during steady-state flow measurement of shear deformation is 0.02 to 0.09 Pa·s.

[0095] In one embodiment of the aqueous coating composition according to the present invention, the aqueous coating composition has an η1 of 0.10 to 0.90 Pa·s and an η2 of 0.02 to 0.09 Pa·s.

[0096] In a water-based paint composition, when η1 is between 0.10 and 0.90 Pa·s, phase separation does not occur during storage of the water-based paint, a uniform coating can be obtained, and the water-resistant adhesion and water-resistant blistering properties of the coating are good. Furthermore, when η1 is within this range, splashing of the water-based paint can be suppressed when transferring it to a container such as a tank, and the transfer time can be shortened. In one embodiment, η1 is 0.10 Pa·s or higher, 0.15 Pa·s or higher, 0.20 Pa·s or higher, 0.25 Pa·s or higher, 0.30 Pa·s or higher, 0.35 Pa·s or higher, 0.40 Pa·s or higher, 0.45 Pa·s or higher, 0.50 Pa·s or higher, 0.55 Pa·s or higher, 0.60 Pa·s or higher, 0.65 Pa·s or higher, 0.70 Pa·s or higher, 0.75 Pa·s or higher, 0.80 Pa·s or higher, or 0.85 Pa·s or higher. In another embodiment, η1 is 0.90 Pa·s or less, 0.85 Pa·s or less, 0.80 Pa·s or less, 0.75 Pa·s or less, 0.70 Pa·s or less, 0.65 Pa·s or less, 0.60 Pa·s or less, 0.55 Pa·s or less, 0.50 Pa·s or less, 0.45 Pa·s or less, 0.40 Pa·s or less, 0.35 Pa·s or less, 0.30 Pa·s or less, 0.25 Pa·s or less, 0.20 Pa·s or less, or 0.15 Pa·s or less.

[0097] In an aqueous paint composition, a pressure of η2 of 0.02 to 0.09 Pa·s results in good discharge performance of the aqueous paint. In particular, it is suitable for discharge using a paint jet, and it can suppress splashing and leakage of the aqueous paint into the surrounding area when dispensing with a dispenser or paint jet. In one embodiment, η2 is 0.02 Pa·s or more, 0.03 Pa·s or more, 0.04 Pa·s or more, 0.05 Pa·s or more, 0.06 Pa·s or more, 0.07 Pa·s or more, or 0.08 Pa·s or more. In another embodiment, η2 is 0.09 Pa·s or less, 0.08 Pa·s or less, 0.07 Pa·s or less, 0.06 Pa·s or less, 0.05 Pa·s or less, 0.04 Pa·s or less, or 0.03 Pa·s or less.

[0098] The following describes examples of how to adjust η1 and η2.

[0099] When the solid content (NV) of the water-based paint composition is similar, increasing the amount of the first viscous agent tends to increase η1 and η2 (1). In tendency (1), the tendency for η1 to increase is more pronounced than the tendency for η2 to increase. On the other hand, when the amount of the first viscous agent is similar, decreasing the solid content (NV) of the water-based paint composition tends to decrease η1 and η2 (2).

[0100] The non-volatile content (NV) in an aqueous coating composition can be adjusted as appropriate and is not particularly limited. For example, the NV in an aqueous coating composition is 1 to 80% by mass relative to the total mass of the aqueous coating composition. In one embodiment, the NV in an aqueous coating composition is 1% or more by mass, 3% or more by mass, 5% or more by mass, 10% or more by mass, 15% or more by mass, 20% or more by mass, 25% or more by mass, 30% or more by mass, 35% or more by mass, 40% or more by mass, 45% or more by mass, 50% or more by mass, 55% or more by mass, 60% or more by mass, 65% or more by mass, 70% or more by mass, or 75% or more by mass, relative to the total mass of the aqueous coating composition. In another embodiment, the NV in the aqueous coating composition is 80% by mass or less, 75% by mass or less, 70% by mass or less, 65% by mass or less, 60% by mass or less, 55% by mass or less, 50% by mass or less, 45% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less, based on the total mass of the aqueous coating composition. In yet another embodiment, the NV in the aqueous coating composition is 3 to 30% by mass, based on the total mass of the aqueous coating composition.

[0101] In one embodiment of the aqueous coating composition according to the present invention, the VOC content [ρ(VOC)] of the aqueous coating composition is 420 g / L or less.

[0102] Method for preparing a water-based paint composition The method for preparing the aqueous coating composition is not particularly limited, and known methods for preparing aqueous coating compositions can be used. For example, it can be prepared by mixing essential components such as a film-forming resin and a viscous agent, and other components as needed. Dispersers, ball mills, roll mills, planetary mixers, etc., can be used for mixing the components.

[0103] • Uses of water-based paint compositions The applications of the aqueous coating composition of the present invention are not particularly limited and can be used in the same applications as known aqueous coating compositions. Examples of applications for the aqueous coating composition include spray coating, electrostatic coating, liquid film discharge coating, liquid column discharge coating, or liquid droplet discharge coating. It can also be used for coating vehicles, buildings, home appliances, steel plates, and the like.

[0104] In one embodiment, liquid film discharge coating does not include curtain flow coating. Droplet discharge coating is a coating method described in Japanese Patent Application Publication No. 2022-044361 in which a paint composition in the form of droplets or liquid columns is controlled by turning the discharge on and off, and the direction of the droplets and liquid columns is controlled for application. In contrast, spray coating and electrostatic coating are coating methods in which the paint composition is split not by turning the discharge on and off, but by shearing with air or by centrifugal force, and droplets are applied without control over the direction of each droplet. Therefore, spray coating and electrostatic coating are not included in droplet discharge coating. In one embodiment, the aqueous paint composition of the present invention is an aqueous paint composition for spray coating or electrostatic coating. In one embodiment, the aqueous paint composition of the present invention is a paint composition for liquid film discharge coating or liquid column discharge coating.

[0105] (coating film) The coating film according to the present invention is a coating film using any of the above-mentioned aqueous coating compositions (for example, a cured film of an aqueous coating composition). This results in good water resistance, adhesion, and blister resistance of the coating film.

[0106] • Method for forming a coating film The method for forming the coating film is not particularly limited other than using the aqueous coating composition of the present invention, and known coating methods can be used. For example, dipping, brushes, rollers, roll coaters, air sprays, airless sprays, electrostatic coating machines, curtain flow coaters, roller curtain coaters, die coaters, and Durr's EcoPaintJet® jet dispensers can be used.

[0107] Jet dispensers include piezo-jet dispensers that control dispensing using a piezoelectric element, and electromagnetic jet dispensers that control dispensing using a solenoid valve. Examples of piezo-jet dispensers include the Stream Jet E series from SSI JAPAN. Examples of electromagnetic jet dispensers include the NOVADOT and JETTY from San-ei Tech.

[0108] The drying temperature after applying the water-based paint composition can be adjusted as appropriate depending on the solvent and other factors. For example, if drying is required in a short time, such as 10 seconds to 30 minutes, the temperature can be 30 to 200°C, with 40 to 160°C being preferred. If drying is required in a short time, energy rays such as ultraviolet light may be used. If drying is not required in a short time, drying may be done at room temperature, for example. Furthermore, for example, in the case of automobile bodies, preheating may be performed at around 80°C to increase the solid content concentration of the paint film, and then it may be baked at 70 to 160°C. In addition, for example, in the case of automobile repair (AR, lacquer), preheating may be performed at 50 to 60°C using a dryer, and the paint film may be cured by letting it stand at room temperature.

[0109] The film thickness of the coating can be adjusted as appropriate depending on the application, for example, the dry film thickness is 3 to 23 μm.

[0110] (Goods) The article of this embodiment is an article having the coating film of the present invention.

[0111] Articles having a coating are not particularly limited and include, for example, the interior and exterior of the bodies of vehicles such as automobiles and railway cars, aircraft fuselages, ship hulls and superstructures (outfittings); the interior, exterior and roof parts of buildings; furniture and fixtures; window glass of vehicles, aircraft, ships, and buildings; cases, containers, resin sheets, and films; housings and glass components of electrical appliances such as displays, monitors, and refrigerators; coatings applied to these; inorganic building materials such as various cements, ceramic building materials, lightweight foamed concrete, mortar, slate boards, roofs, tiles, and ALC; wood; various types of glass; and metal substrates such as steel plates, aluminum, and stainless steel. [Examples]

[0112] The present invention will be described in more detail below with reference to examples, but these examples are for illustrative purposes only and do not limit the present invention in any way. In the examples, "parts" and "%" are based on mass unless otherwise specified.

[0113] The materials used in the example are as follows: Surfactant: Product name "Newcol (registered trademark) 293" manufactured by Nippon Emulsifier Co., Ltd. Polyether polyol: Product name "Sannix GP-3000" manufactured by Sanyo Chemical Industries, Ltd. Dispersant: Anionic / nonionic dispersant, product name "Disperbyk 190" manufactured by Bic Chemie. Antifoaming agent: Product name "BYK-011" manufactured by Big Chemie Co., Ltd. Polyurethane resin: Polyether-based urethane emulsion, product name "Permarine UA-150" manufactured by Sanyo Chemical Industries, Ltd., resin solids content (NV) 30% by mass, indicated as "Permarine" in the table. Hardener: Imino-type melamine resin, product name "Cymel 211" manufactured by Ornex Japan Co., Ltd., referred to as "Cymel" in the table. Polycarbonate resin: Polycarbonate diol, product name "Duranole T5650E" manufactured by Asahi Kasei Corporation, referred to as "Duranole" in the table. Cationic electrodeposition paint: Product name "Power Top U-50" manufactured by Nippon Paint Co., Ltd. Gray undercoat paint: Polyester / melamine-based paint, product name "Olga P-30" manufactured by Nippon Paint Co., Ltd. Clear coating: Epoxy-curing acrylic resin-based paint, product name "Macflow O-1820 Clear" manufactured by Nippon Paint Co., Ltd. Cellophane tape: Made by Nichiban Co., Ltd.

[0114] The viscous agents used in the examples are as follows: Carboxyvinyl polymer 1: "Hibiscus Wako 103" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., indicated as "hv103" in the table. Carboxyvinyl polymer 2: "Hibiscus Wako 104" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., indicated as "hv104" in the table. Carboxyvinyl polymer 3: "Hibis Wako 105" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., indicated as "hv105" in the table. Diutan gum: "KELCO-VIS" manufactured by CPKelco, listed as "Diutan" in the table.

[0115] The viscosities used in the examples other than the first viscosity agent are as follows: Alkaline swelling type viscosity agent 1: Product name "Primal ASE-60" manufactured by Dow-Toray, indicated as "ASE60" in the table. Alkaline swelling viscosity agent 2: Product name "Viscalex HV30" manufactured by BASF, indicated as "HV30" in the table. Alkali-swelling viscosity agent 3: Product name "SN Thickener 613" manufactured by Sunopco, modified polyacrylic acid type, indicated as "613" in the table. Alkaline swelling type viscosity agent 4: Product name "SN Thickener 618" manufactured by Sunopco, modified sodium polyacrylate, indicated as "618" in the table. Alkaline swelling type viscosity agent 5: Product name "SN Thickener 630" manufactured by Sunopco, modified polyacrylic acid type, indicated as "630" in the table. Alkali-swelling viscosity agent 6: Product name "SN Thickener 634" manufactured by Sunopco, modified polyacrylic acid type, indicated as "634" in the table. Alkali-swelling viscosity agent 7: Product name "SN Thickener 636" manufactured by Sunopco, modified polyacrylic acid type, indicated as "636" in the table. Alkali-swelling viscosity agent 8: Product name "SN Thickener 641" manufactured by Sunopco, modified polyacrylic acid type, indicated as "641" in the table. Alkali-swelling viscosity agent 9: Product name "SN Thickener 640" manufactured by Sunopco, modified polyacrylic acid type, indicated as "640" in the table. Associative viscosity agent 1: Product name "SN Thickener 665T" manufactured by Sunopco, urethane-modified polyether type, indicated as "665T" in the table. Associative viscosity agent 2: Product name "SN Thickener 660T" manufactured by Sunopco, urethane-modified polyether type, indicated as "660T" in the table. Associative viscosity agent 3: Product name "ADEKA UH-814" manufactured by ADEKA Corporation, urethane associative type, indicated as "UH814" in the table. Cellulose-based viscosity agent: Ashland product name "Natrosol HE 3KB", hydrophobic modified hydroxyethylcellulose, indicated as "HE3KB" in the table. Amid-based viscosity agent: Product name "Disparon AQH-800" manufactured by Kusumoto Chemical Co., Ltd., polyamide amine salt / fatty acid amide, indicated as "AQH800" in the table.

[0116] The apparatus used in the example is as follows: Stress-controlled rheometer: Product name "MCR302" manufactured by Anton Paar. Rotary atomizing electrostatic coating machine: ABB cartridge bell

[0117] The components to be incorporated into the paint composition were manufactured as shown in the following manufacturing examples 1 to 4.

[0118] Manufacturing Example 1: Production of hydroxyl group-containing acrylic resin emulsion 445 parts by mass of water and 5 parts by mass of Newcol 293 were added to a conventional reactor for the production of acrylic resin emulsions, equipped with a stirrer, thermometer, dropping funnel, reflux condenser, and nitrogen inlet tube. The reactor temperature was raised to 75°C while stirring the mixture. Next, 5 parts by mass of styrene, 78.11 parts by mass of 2-ethylhexyl acrylate, 16.25 parts by mass of hydroxyethyl methacrylate, 0.64 parts by mass of acrylic acid, 240 parts by mass of water, and 30 parts by mass of Newcol 293 were mixed and emulsified using a homogenizer to obtain an emulsion. Next, 1 part by mass of ammonium persulfate (polymerization initiator) was dissolved in 50 parts by mass of water to obtain an aqueous solution. This emulsion was added dropwise to the reactor while stirring for 3 hours. In parallel with the addition of the emulsion, the aqueous solution of the polymerization initiator was added evenly to the reactor dropwise until the addition of the emulsion was completed. After the addition of the emulsion was completed, the reaction was continued at 80°C for another hour. Next, the product in the reactor was cooled. Then, an aqueous solution was prepared by dissolving 2 parts by mass of dimethylaminoethanol in 20 parts by mass of water. This aqueous solution was added to the reactor to adjust the pH of the mixture. A hydroxyl group-containing acrylic resin emulsion with an NV of 40.6% by mass was obtained.

[0119] Manufacturing Example 2: Production of hydroxyl group-containing polyester resin In a reactor equipped with a stirrer, thermometer, dropping funnel, reflux condenser, and nitrogen inlet tube, 25.6 parts by mass of isophthalic acid, 22.8 parts by mass of phthalic anhydride, 5.6 parts by mass of adipic acid, 19.3 parts by mass of trimethylolpropane, 26.7 parts by mass of neopentyl glycol, 17.5 parts by mass of ε-caprolactone, and 0.1 parts by mass of dibutyltin oxide were added. The mixture was then heated to 170°C while stirring. The temperature of the reactor was then raised to 220°C over 3 hours while removing the water produced by the condensation reaction. The water was removed until the acid value of the mixture in the reactor was 8 mg KOH / g. Next, 7.9 parts by mass of trimellitic anhydride was added to the mixture in the reactor. The reaction was then continued at 150°C for 1 hour to obtain a polyester resin with an acid value of 40 mg KOH / g. The temperature of the reactor was then cooled to 100°C. Next, 11.2 parts by mass of butyl cellosolve was added to the mixture in the reactor and stirred until homogenized. Then, the reactor temperature was cooled to 60°C. Next, 98.8 parts by mass of deionized water and 5.9 parts by mass of dimethylethanolamine were added to the mixture in the reactor. A hydroxyl group-containing polyester resin having the following characteristics was obtained. ·NV: 50% by mass • Solid content acid value: 40 mg KOH / g • Solid content hydroxyl value: 110 mg KOH / g ·Number average molecular weight (Mn): 2870 • Glass transition temperature (Tg): -3℃

[0120] Manufacturing Example 3: Production of Carbodiimide Compounds 3,930 parts by mass of 4,4-dicyclohexylmethane diisocyanate was reacted with 79 parts by mass of 3-methyl-1-phenyl-2-phosphorene-1-oxide (carbodiimide catalyst) at 180°C for 16 hours to obtain a carbodiimide compound. This compound has four carbodiimide groups per molecule and isocyanate groups at both ends. To the mixture containing this carbodiimide compound, 1,296 parts by mass of polyethylene glycol monomethyl ether and 2 parts by mass of dibutyltin dilaurate were added. The polyethylene glycol monomethyl ether has an average of 9 repeating units of oxyethylene groups. Next, the mixture was heated at 90°C for 2 hours to obtain a carbodiimide compound. This compound has isocyanate groups and hydrophilic groups at its ends. Next, 3,000 parts by mass of polyether polyol was added to the mixture. The mixture was reacted at 90°C for 6 hours. The disappearance of isocyanate groups in the reaction product was confirmed by IR. 18,800 parts by mass of deionized water were added to the reaction product and stirred. This yielded an aqueous dispersion of a carbodiimide compound with a resin solids content of 30% by mass.

[0121] Manufacturing Example 4: Manufacturing of Pigment Dispersion Paste 4.5 parts by mass of dispersant, 0.5 parts by mass of defoaming agent, 22.9 parts by mass of deionized water, and 72.1 parts by mass of rutile-type titanium dioxide were pre-mixed. Then, a glass bead medium was added to the mixture in paint conditioner. The mixture was then mixed and dispersed at room temperature until the particle size was 5 μm or less to obtain a pigment dispersion paste.

[0122] Preparation of base composition A Base composition A was prepared by mixing each component with deionized water according to the formulations shown in Table 1. The amount of deionized water was set to an amount that resulted in a non-volatile content (NV) of 24.1% by mass of base composition A.

[0123] Example 1: Preparation of an aqueous paint composition To 644.6 parts by mass of base composition A, carboxyvinyl polymer 1 and deionized water were mixed and stirred according to the formulations shown in Table 2 to obtain the aqueous coating composition of Example 1. The amount of deionized water was set to the amount at which the NV of the aqueous coating composition was calculated as shown in Table 2.

[0124] [Table 1]

[0125] [Table 2] In Tables 2-6, "Viscosity Solids (%)" represents the percentage of the viscosity content (by mass) relative to the total mass of the aqueous paint composition.

[0126] Examples 2-11 An aqueous paint composition was prepared in the same manner as in Example 1, except that the type or amount of the viscous agent was changed as shown in Table 2.

[0127] Comparison Examples 1-18 Aqueous paint compositions were prepared in the same manner as in Example 1, except that the type or amount of viscous agent was changed as shown in Tables 3 to 5. In Tables 3 to 5, "NE1" indicates that the evaluation was not performed because the evaluation of sagging resistance was unsatisfactory, "NE2" indicates that the evaluation was not performed because the paint had poor workability and could not be practically used as a paint, and "NE3" indicates that the evaluation was not performed because the paint separated.

[0128] [Table 3]

[0129] [Table 4]

[0130] [Table 5]

[0131] · Preparation of intermediate coat film On a zinc phosphate-treated SPCC-SD steel sheet (dull steel sheet) with a thickness of 0.8 mm and a size of 70 mm × 150 mm, cationic electrodeposition paint was electrodeposited so that the dry coating film would be 20 μm. Subsequently, the coating film was baked at 160 °C for 30 minutes. Then, the gray intermediate coat paint was diluted so that its viscosity would be 25 seconds (measured at 20 °C using a No. 4 Ford cup). And the diluted gray intermediate coat paint was electrostatically applied to the coated plate on which the electrodeposition coating was performed so that the dry film thickness would be 35 μm. Subsequently, the coating film was baked at 140 °C for 30 minutes to form an intermediate coat film. The steel sheet on which this electrodeposition coating film and intermediate coat film were formed was used as the object to be coated A for the evaluation described below.

[0132] For the aqueous coating compositions of each of the examples and comparative examples, the following measurements (1) were carried out and the evaluations (2) to (4) were carried out. The results are shown together in Tables 2 to 5.

[0133] (1) Viscosity (η1 and η2) For the aqueous coating compositions of each of the examples and comparative examples, using a stress-controlled rheometer, under the conditions of a 50 mm parallel plate, gap: 0.5 mm, measurement temperature: 23 °C, shear rate (dγ / dt) = 10 s -1 and 1000 s -1 steady-state flow measurements of shear deformation were carried out. The steady-state values of the viscosity (Pa·s) 30 seconds after the start of the measurement were taken as η1 and η2, respectively.

[0134] (2) VOC content For the aqueous coating compositions of each of the examples and comparative examples, the VOC content (g / L) was calculated by the following formula (1).

Equation

[0135] (3) Sagging resistance A water-based paint composition was applied to the intermediate coat film of substrate A using a sagging tester. Substrate A was immediately placed upright after application. At 23°C, the wet film thickness at which sagging did not occur was measured, and sagging resistance was evaluated according to the following criteria. A passing result indicates good sagging resistance. The results are shown in Tables 2-5. Passing criteria: The wet film thickness is 175 μm or greater. Failure: The wet film thickness is less than 175 μm.

[0136] (4) Separation of paint 20 mL of the water-based paint composition was placed in a sample tube and left to stand at 20°C for one month. After one month, the presence or absence of separation in the paint composition was visually observed. If there is no separation in the paint composition, it indicates that the paint properties are good. The results are shown in Tables 2-5.

[0137] • Coating preparation The aqueous coating compositions of each example and comparative example were applied to the intermediate coating film of the substrate A using a rotary atomizing electrostatic coating machine to a dry film thickness of 15 μm. Next, the wet coating film was preheated at 80°C for 5 minutes, and then a clear coating was applied wet-on-wet using a rotary atomizing electrostatic coating machine to a dry film thickness of 35 μm. After coating, the film was baked at 140°C for 30 minutes to obtain a multi-layer coating film.

[0138] The obtained multilayer coating was used as a test specimen, and the following evaluations (5) to (6) were performed. The results are shown in Tables 2 to 5.

[0139] (5) Water resistance and blister resistance The water resistance and blister resistance of the coating on the test specimens were evaluated by the following tests. The test specimens were immersed in 80°C water for 1 hour. Next, the specimens were transferred to room temperature water and allowed to cool for 10 minutes. Then, the specimens were removed from the water, and the appearance of the coating was visually observed and evaluated according to the following criteria. The results are shown in Tables 2-5. Pass: No blistering on the coating. Failure: The paint film has blisters.

[0140] (6) Water-resistant adhesion The water-resistant adhesion of the coating on the test specimens was evaluated by the following tests. The test specimens were immersed in 80°C water for 1 hour. Next, the specimens were transferred to room temperature water and allowed to cool for 10 minutes. Then, the specimens were removed from the water. Next, 10 vertical and 10 horizontal cuts were made in the coating of the specimens at 1 mm intervals using a cutter, and cellophane tape was applied and peeled off. The number of squares that remained intact without peeling was counted out of 100 squares. The results were then evaluated according to the following criteria. The results are shown in Tables 2-5. Pass: 100 squares remained, and there was no peeling of the paint film. Failure: The number of remaining squares was between 0 and 99, and there was peeling of the paint film.

[0141] Furthermore, the multilayer coatings obtained using the aqueous coating compositions of Examples 9 to 11 were used as test specimens and evaluated according to the following (7) to (8). The results are shown in Table 6.

[0142] (7) Long-term water resistance and blister resistance (5) Except for changing the immersion time in the water resistance and blistering test from 1 hour to 1 day, the water resistance and blistering test was conducted in the same manner and evaluated using the same criteria.

[0143] (8) Long-term water-resistant adhesion (6) Except for changing the immersion time for the water-resistant adhesion test from 1 hour to 1 day, the water-resistant adhesion test was conducted in the same manner and evaluated using the same criteria.

[0144] [Table 6]

[0145] According to the present invention, even with zero or small amounts of hydrophobic solvent content, a water-based paint can be provided that does not undergo phase separation during storage and exhibits good water-resistant adhesion, water-resistant blistering, and sagging resistance of the paint film. [Industrial applicability]

[0146] According to the present invention, even if the hydrophobic solvent content is zero or small, phase separation does not occur during storage of the water-based paint, and a water-based paint with good water-resistant adhesion, water-resistant blistering, and sagging properties of the paint film can be provided.

Claims

1. A water-based paint composition comprising a film-forming resin, a curing agent, a viscous agent, and a pigment, The viscous agent comprises at least one selected from the group consisting of carboxyvinyl polymer and dieutan gum. The content of the viscous agent is 0.01 to 0.7% by mass with respect to the total mass of the aqueous paint composition. The aqueous paint composition at 23°C and a shear rate of 10 s －１ A water-based paint composition in which the steady-state viscosity η1 measured during steady-state flow measurement of shear deformation is 0.10 Pa·s or higher.

2. The aqueous paint composition according to claim 1, wherein the VOC content [ρ(VOC)] of the aqueous paint composition is 420 g / L or less.

3. The aqueous paint composition according to claim 1, wherein the content of the organic solvent is 0 to 15% by mass based on 100% by mass of the aqueous paint composition.

4. The aqueous paint composition according to claim 1, wherein the film-forming resin comprises at least one selected from the group consisting of acrylic resins, urethane resins, and polyester resins.

5. The aqueous paint composition according to claim 1, wherein the curing agent comprises at least one selected from the group consisting of isocyanate-based curing agents, melamine-based curing agents, and carbodiimide-based curing agents.

6. The aqueous paint composition is The steady-state value η1 is 0.10 to 0.90 Pa·s, and 23°C, shear rate 1,000 s －１ The aqueous paint composition according to claim 1, wherein the steady-state viscosity η2 measured in steady-state flow measurement of shear deformation is 0.02 to 0.09 Pa·s.

7. The aqueous paint composition according to claim 1, wherein the non-volatile content (NV) of the aqueous paint composition is 1 to 80% by mass with respect to the total mass of the aqueous paint composition.

8. The aqueous paint composition according to claim 1, which is an aqueous paint composition for liquid film discharge coating, liquid column discharge coating, or liquid droplet discharge coating.

9. The aqueous paint composition according to claim 1, further comprising an alkaline swelling type viscosity agent.

10. A coating film using the aqueous coating composition described in claim 1.

11. An article having the coating film described in claim 10.

Images