Acrylic urethane composite resin, aqueous paint composition, and method for forming a multi-layer coating film

Abstract

To provide an acrylic urethane composite resin that is excellent in storage stability when being used as a component of an aqueous coating composition, in which a coating film formed from the aqueous coating composition is excellent in chipping resistance.SOLUTION: An acrylic urethane composite resin contains (A) a urethane resin part obtained from components containing (a1) a polyisocyanate component and (a2) (a2-1) a compound having two or more hydroxyl groups and one or more polymerizable unsaturated groups, and (a2-2) a polyol component containing polytetramethylene ether glycol, and (B) an acrylic resin part obtained from components containing (b1) a compound having one polymerizable unsaturated group and no or one hydroxyl group, and (b2) a compound having two or more polymerizable unsaturated groups, and no or one hydroxyl group.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an acrylic urethane composite resin, an aqueous paint composition, and a method for forming a multi-layer coating film.

Background Art

[0002] One of the performances required for an automotive multi-layer coating film is chipping resistance (chipping: coating film damage caused by small stones on the road jumping up and colliding with the coating film). For example, by softening the coating film to absorb the collision energy of small stones, etc., improvement in chipping resistance has been attempted.

[0003] Urethane resins have excellent physical properties and have thus been widely used as resins for paint applications for the purpose of improving coating film performances such as chipping resistance.

[0004] In addition, acrylic urethane composite resins are also used in the paint field, etc. for the purpose of synergistic effects between acrylic resins and urethane resins, improvement in compatibility when applied to acrylic resin-based paint compositions, and cost reduction of urethane resins. If an attempt is made to improve the above chipping resistance by softening the acrylic urethane composite resin, problems such as thickening and sedimentation may occur during storage of the paint composition, and problems with storage stability may arise.

[0005] Patent Document 1 discloses polyols (a1) composed of 86 to 96% by weight of polycarbonate diol and 14 to 4% by weight of anionic functional group-containing polyol, polyisocyanates (a2), and an acrylic compound (a3) having an active hydrogen-containing group as reaction components, and in the presence of water, general formula (1): CH2=CR 1 COOR 2 (wherein, R 1 is a hydrogen atom or a methyl group, and also R 2The document describes a water-based paint composition for steel plates that uses an aqueous dispersion of acrylic-polyurethane resin obtained by polymerizing a polymerization component (B) containing alkyl (meth)acrylates (b1) represented by ), which has excellent storage stability.

[0006] Furthermore, Patent Document 2 describes a step of (i) first charging an aqueous dispersion of at least one polyurethane, and then (ii) polymerizing a mixture of olefinic unsaturated monomers in the presence of the polyurethane from (i), wherein (a) a water-soluble initiator is used, (b) the olefinic unsaturated monomers are metered and supplied so as not to exceed a concentration of 6.0% by mass in the reaction solution relative to the total amount of olefinic unsaturated monomers used for polymerization during the entire reaction time, and (c) the mixture of olefinic unsaturated monomers comprises at least one copolymer (CP), and a 20 mg aqueous dispersion of at least one copolymer (CP) that can be produced by this step. It has been described that an aqueous paint composition comprising a linear hydroxy-functional reaction product (R) having an acid value of less than KOH / g, wherein the production of the linear hydroxy-functional reaction product (R) involves using at least one compound (v) having two functional groups (va) and an aliphatic or aromatic aliphatic hydrocarbyl group (vb) positioned between the functional groups and having 12 to 70 carbon atoms, exhibits excellent resistance to scratches caused by stones. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2008-189696 [Patent Document 2] Special Publication 2017-509725 [Overview of the project] [Problems that the invention aims to solve]

[0008] In the technology described in Patent Document 1, the chipping resistance of the formed coating film was sometimes insufficient.

[0009] Furthermore, in the technology described in Patent Document 2, the storage stability of the water-based paint composition was sometimes insufficient.

[0010] The object of the present invention is to provide an acrylic urethane composite resin that, when used as a component of an aqueous coating composition, exhibits excellent storage stability and the coating film formed from the aqueous coating composition exhibits excellent chipping resistance. [Means for solving the problem]

[0011] As a result of diligent research to achieve the above objective, the present inventors have found that the above objective can be achieved by an acrylic urethane composite resin (AB) comprising a urethane resin portion (A) obtained from a component comprising a polyisocyanate component (a1), a polyol component (a2) containing a compound having two or more hydroxyl groups and one or more polymerizable unsaturated groups (a2-1) and polytetramethylene ether glycol (a2-2), and an acrylic resin portion (B) obtained from a component comprising a compound having one polymerizable unsaturated group and no hydroxyl group or having one hydroxyl group (b1) and a compound having two or more polymerizable unsaturated groups and no hydroxyl group or having one hydroxyl group (b2).

[0012] In other words, the present invention is as follows: <1> ~ <8> This concerns... <1> (A)(a1) a polyisocyanate component, and (a2)(a2-1) a compound having two or more hydroxyl groups and one or more polymerizable unsaturated groups, and (a2-2) a polyol component containing polytetramethylene ether glycol, obtained from a constituent component, (B) An acrylic urethane composite resin comprising an acrylic resin portion obtained from a component comprising (b1) a compound having one polymerizable unsaturated group and no hydroxyl group or having one hydroxyl group, and (b2) a compound having two or more polymerizable unsaturated groups and no hydroxyl group or having one hydroxyl group. <2> The polyisocyanate component (a1) includes an alicyclic polyisocyanate (a1-1), <1> The acrylic urethane composite resin described above. <3> The content of the compound (b2) having two or more polymerizable unsaturated groups and having neither a hydroxyl group nor one hydroxyl group is within the range of 0.5 to 50% by mass, based on the total solid content of the acrylic resin portion (B). <1> or <2> The acrylic urethane composite resin described above. <4> The core-shell structure consists of a shell made of the urethane resin portion (A) and a core made of the acrylic resin portion (B). <1> ~ <3> Acrylic urethane composite resin as described in any one of the following. <5> <1> ~ <4> A water-based paint composition containing the acrylic urethane composite resin (AB) described in any one of the above. <6> Furthermore, it contains at least one resin selected from acrylic resin (C) and polyester resin (D). <5> The aqueous paint composition described above. <7> Furthermore, it contains a hardening agent (E), <5> or <6> The aqueous paint composition described above. <8> Step (1): On the object to be coated, <5> ~ <7> A step of applying an aqueous paint composition described in any one of the following to form a base coat film: Step (2): A step of applying a clear coat coating composition onto the base coat coating formed in step (1) to form a clear coat coating, and, A method for forming a multilayer coating film, comprising step (3): a step of simultaneously heating and curing the base coat coating film formed in step (1) and the clear coat coating film formed in step (2). [Effects of the Invention]

[0013] According to the acrylic urethane composite resin of the present invention, when the acrylic urethane composite resin is used as a component, an aqueous coating composition with excellent storage stability can be obtained, and when the aqueous coating composition is applied, a coating film with excellent chipping resistance can be obtained. [Modes for carrying out the invention]

[0014] Hereinafter, the present invention will be described in detail. These are examples of preferred embodiments, and the present invention is not limited to these contents.

[0015] [Acrylic urethane composite resin (AB)] The acrylic urethane composite resin (AB) of the present invention comprises a urethane resin portion (A) obtained from constituent components including a polyisocyanate component (a1), a polyol component (a2) containing a compound (a2-1) having two or more hydroxyl groups and one or more polymerizable unsaturated groups, and polytetramethylene ether glycol (a2-2), and an acrylic resin portion (B) obtained from constituent components including a compound (b1) having one polymerizable unsaturated group and no hydroxyl group or one hydroxyl group, and a compound (b2) having two or more polymerizable unsaturated groups and no hydroxyl group or one hydroxyl group. It is an acrylic urethane composite resin.

[0016] The acrylic urethane composite resin (AB) can be produced by a conventionally known method for producing an acrylic urethane composite resin. Among them, from the viewpoint of production stability and the like, it is preferably produced by the following method (comprising the following production steps 1 to 3).

[0017] Production step 1. First, in the presence of a compound (b1) having one polymerizable unsaturated group and no hydroxyl group or one hydroxyl group, and a compound (b2) having two or more polymerizable unsaturated groups and no hydroxyl group or one hydroxyl group, which are constituent components of the acrylic resin portion (B), the urethane resin portion (A) is synthesized.

[0018] Production step 2. Then, deionized water is added and emulsified to obtain an aqueous dispersion. If necessary, a chain extension reaction and solvent removal are further carried out.

[0019] Production step 3. Then, a polymerization initiator is added to the above aqueous dispersion and a polymerization reaction is carried out to obtain an acrylic urethane composite resin (AB) containing the urethane resin portion (A) and the acrylic resin portion (B).

[0020] Manufacturing process 1 First, the urethane resin portion (A) is synthesized in the presence of a compound (b1) having one polymerizable unsaturated group and no hydroxyl group or having one hydroxyl group, and a compound (b2) having two or more polymerizable unsaturated groups and no hydroxyl group or having one hydroxyl group, which are components of the acrylic resin portion (B).

[0021] Polymerizable unsaturated groups are unsaturated groups that can undergo radical polymerization. Specifically, examples include acryloyl groups, methacryloyl groups, vinyl groups, allyl groups, propenyl groups, isopropenyl groups, maleimide groups, vinyl ether groups, and the like. Of these polymerizable unsaturated groups, acryloyl groups and methacryloyl groups are preferred from the viewpoint of excellent reactivity, and acryloyl groups are particularly preferred.

[0022] Furthermore, in this specification, "(meth)acrylate" means "acrylate or methacrylate." "(meth)acrylic acid" means "acrylic acid or methacrylic acid." Also, "(meth)acryloyl" means "acryloyl or methacryloyl." Also, "(meth)acrylamide" means "acrylamide or methacrylamide."

[0023] Examples of compounds (b1) having one polymerizable unsaturated group and no hydroxyl group or having one hydroxyl group include compounds having one hydroxyl group and one polymerizable unsaturated group (b1-1), and compounds having one polymerizable unsaturated group but no hydroxyl group (b1-2).

[0024] Examples of the compound (b1-1) having one hydroxyl group and one polymerizable unsaturated group 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 forms of the monoesters; N-hydroxymethyl (meth)acrylamide; allyl alcohol; and hydroxyl group-containing polymerizable unsaturated monomers such as (meth)acrylates having polyoxyethylene chains with hydroxyl groups at the molecular ends.

[0025] These compounds (b1-1), each having one hydroxyl group and one polymerizable unsaturated group, can be used individually or in combination of two or more.

[0026] Examples of compounds (b1-2) that do not have a hydroxyl group but have one polymerizable unsaturated group include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, tridecyl (meth)acrylate, and lauryl (meth) Alkyl or cycloalkyl (meth)acrylates such as acrylate, stearyl (meth)acrylate, "isostearyl acrylate" (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd.), cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, tricyclodecanyl (meth)acrylate; polymerizable unsaturated monomers having an isobornyl group such as isobornyl (meth)acrylate; adamantyl group such as adamantyl (meth)acrylate Polymerizable unsaturated monomers containing a tricyclodecenyl group; polymerizable unsaturated monomers having a tricyclodecenyl group, such as tricyclodecenyl (meth)acrylate; polymerizable unsaturated monomers containing an aromatic ring, such as benzyl (meth)acrylate, styrene, α-methylstyrene, and vinyltoluene; polymerizable unsaturated monomers having an alkoxysilyl group, such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, γ-(meth)acryloyloxypropyltrimethoxysilane, and γ-(meth)acryloyloxypropyltriethoxysilane; Perfluoroalkyl (meth)acrylates such as perfluorobutylethyl (meth)acrylate and perfluorooctylethyl (meth)acrylate; polymerizable unsaturated monomers having fluorinated alkyl groups such as fluoroolefins; polymerizable unsaturated monomers having photopolymerizable functional groups such as maleimide groups; vinyl compounds such as N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, and vinyl acetate; polymerizable unsaturated monomers containing carboxyl groups such as (meth)acrylic acid, maleic acid, crotonic acid, and β-carboxyethyl acrylate;Examples include nitrogen-containing polymerizable unsaturated monomers such as (meth)acrylonitrile, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylamide, and adducts of glycidyl (meth)acrylate with amines; epoxy-group-containing polymerizable unsaturated monomers such as glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3,4-epoxycyclohexylethyl (meth)acrylate, 3,4-epoxycyclohexylpropyl (meth)acrylate, and allyl glycidyl ether; and (meth)acrylates having polyoxyethylene chains with alkoxy groups at the molecular ends.

[0027] These compounds (b1-2), which lack hydroxyl groups and have one polymerizable unsaturated group, can be used individually or in combination of two or more.

[0028] From the viewpoint of manufacturing stability and other factors, it is preferable that the compound (b1) having one polymerizable unsaturated group and no hydroxyl group or having one hydroxyl group includes a compound (b1-2) that does not have a hydroxyl group and has one polymerizable unsaturated group.

[0029] The content of the compound (b1) having one polymerizable unsaturated group and either no hydroxyl group or one hydroxyl group is preferably in the range of 5 to 95% by mass, more preferably in the range of 40 to 98% by mass, and even more preferably in the range of 50 to 98% by mass, based on the total solid content of the acrylic resin portion (B), from the viewpoint of manufacturing stability, etc.

[0030] Examples of compounds (b2) having two or more polymerizable unsaturated groups and either no hydroxyl group or one hydroxyl group include compounds having one hydroxyl group and two or more polymerizable unsaturated groups (b2-1), and compounds having two or more polymerizable unsaturated groups but no hydroxyl group (b2-2).

[0031] Examples of the compound (b2-1) having one hydroxyl group and two or more polymerizable unsaturated groups include glycerol di(meth)acrylate and 1,1,1-trishydroxymethylethane di(meth)acrylate.

[0032] These compounds (b2-1) having one hydroxyl group and two or more polymerizable unsaturated groups can be used individually or in combination of two or more.

[0033] Examples of compounds (b2-2) that do not have a hydroxyl group but have two or more polymerizable unsaturated groups include allyl (meth)acrylate, ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, and 1,6-hexanediol di(meth)acrylate. Examples include (meth)acrylate, pentaerythritol tetra(meth)acrylate, 1,1,1-trishydroxymethylethane tri(meth)acrylate, 1,1,1-trishydroxymethylpropane tri(meth)acrylate, methylenebis(meth)acrylamide, ethylenebis(meth)acrylamide, triallyl isocyanurate, diallyl terephthalate, divinylbenzene, polyethylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, and the like.

[0034] These compounds (b2-2) that do not have hydroxyl groups but have two or more polymerizable unsaturated groups can be used individually or in combination of two or more.

[0035] As for the compound (b2) having two or more polymerizable unsaturated groups and either no hydroxyl group or one hydroxyl group, it is preferable from the viewpoint of manufacturing stability, etc., to include a compound (b2-2) that does not have a hydroxyl group and has two or more polymerizable unsaturated groups.

[0036] The compound (b2) having two or more polymerizable unsaturated groups and either no hydroxyl group or one hydroxyl group has the function of imparting a crosslinked structure to the copolymer.

[0037] The content of the compound (b2) having two or more polymerizable unsaturated groups and having neither a hydroxyl group nor one hydroxyl group is preferably in the range of 0.5 to 50% by mass, more preferably in the range of 1.0 to 40% by mass, and even more preferably in the range of 2.0 to 20% by mass, based on the total solid content of the acrylic resin portion (B), from the viewpoint of the storage stability of the resulting aqueous paint composition.

[0038] Synthesis of the urethane resin part (A) The urethane resin portion (A) can be obtained from a component comprising a polyisocyanate component (a1), a polyol component (a2) containing a compound (a2-1) having two or more hydroxyl groups and one or more polymerizable unsaturated groups and polytetramethylene ether glycol (a2-2), and optionally a compound that further contains active hydrogen groups and ion-forming groups as water-dispersible group-granting components.

[0039] Polyisocyanate component (a1) Examples of the polyisocyanate component (a1) include alicyclic polyisocyanates (a1-1), aliphatic polyisocyanates, aromatic aliphatic polyisocyanates, aromatic polyisocyanates, and derivatives of said polyisocyanates.

[0040] As the polyisocyanate component (a1) mentioned above, it is preferable that it includes an alicyclic polyisocyanate (a1-1) from the viewpoint of storage stability of the resulting aqueous paint composition and chipping resistance of the formed coating film.

[0041] Examples of the above alicyclic polyisocyanates (a1-1) include 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (common name: isophorone diisocyanate), 4-methyl-1,3-cyclohexylene diisocyanate (common name: hydrogenated TDI), and 2-methyl-1,3-cyclohexylene Alicyclic diisocyanates such as diisocyanates, 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane (common name: hydrogenated xylylene diisocyanate) or mixtures thereof, methylenebis(4,1-cyclohexanediyl) diisocyanate (common name: hydrogenated MDI), norbornane diisocyanate; 1,3,5-triisocyanatocyclohexane, 1,3,5-trimethylisocyanatocyclohexane, 2-(3-isocyanatopropyl 2-(3-isocyanatopropyl)-2,5-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 2-(3-isocyanatopropyl)-2,6-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 3-(3-isocyanatopropyl)-2,5-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, 6-(2- Examples include alicyclic triisocyanates such as socyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, and 6-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane.

[0042] Examples of the aliphatic polyisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,4,4 or 2,2,4-trimethylhexamethylene diisocyanate, dimer diisocyanate, and 2,6-methyl diisocyanatohexanoate (common name: lysine). Examples include aliphatic diisocyanates such as diisocyanates; and aliphatic triisocyanates such as 2-isocyanatoethyl 2,6-diisocyanatohexanoate, 1,6-diisocyanato-3-isocyanatomethylhexane, 1,4,8-triisocyanatooctane, 1,6,11-triisocyanatoundecane, 1,8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-triisocyanatohexane, and 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyloctane.

[0043] Examples of the aforementioned aromatic aliphatic polyisocyanates include aromatic aliphatic diisocyanates such as methylenebis(4,1-phenylene) diisocyanate (common name: MDI), 1,3- or 1,4-xylylene diisocyanate or mixtures thereof, ω,ω'-diisocyanato-1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanato-1-methylethyl)benzene (common name: tetramethylxylylene diisocyanate) or mixtures thereof; and aromatic aliphatic triisocyanates such as 1,3,5-triisocyanatomethylbenzene.

[0044] Examples of the aromatic polyisocyanates include aromatic diisocyanates such as m-phenylenediisocyanate, p-phenylenediisocyanate, 4,4'-diphenyldiisocyanate, 1,5-naphthalenediisocyanate, 2,4-tolylenediisocyanate (common name: 2,4-TDI) or 2,6-tolylenediisocyanate (common name: 2,6-TDI) or mixtures thereof, 4,4'-toluidinediisocyanate, and 4,4'-diphenyletherdiisocyanate; aromatic triisocyanates such as triphenylmethane-4,4',4''-triisocyanate, 1,3,5-triisocyanatobenzene, and 2,4,6-triisocyanatotoluene; and aromatic tetraisocyanates such as 4,4'-diphenylmethane-2,2',5,5'-tetraisocyanate.

[0045] Furthermore, examples of derivatives of the polyisocyanate include dimers, trimers, biuret, allophanate, uretodione, uretoimine, isocyanurate, oxadiazinetrione, polymethylene polyphenyl polyisocyanate (crude MDI, polymeric MDI), crude TDI, and the like.

[0046] The above-mentioned polyisocyanates and their derivatives may be used individually or in combination of two or more types.

[0047] The above-mentioned polyisocyanates may also be used in the form of blocked isocyanates, which are blocked by a blocking agent.

[0048] Examples of the above-mentioned blocking agents include phenols such as phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxydiphenyl, butylphenol, isopropylphenol, nonylphenol, octylphenol, and methyl hydroxybenzoate; lactams such as ε-caprolactam, δ-valerolactam, γ-butyrolactam, and β-propiolactam; aliphatic alcohols such as methanol, ethanol, propyl alcohol, butyl alcohol, amyl alcohol, and lauryl alcohol; ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, and methoxymethanol; benzyl alcohol, glycolic acid, methyl glycolate, ethyl glycolate, butyl glycolate, lactic acid, methyl lactate, ethyl lactate, butyl lactate, methylolurea, methylolmelamine, diacetone alcohol, 2-hydroxyethyl acrylate, and 2-hydroxyethyl acrylate. Alcohol-based compounds such as droxyethyl methacrylate; oxime-based compounds such as formamide oxime, acetamide oxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, and cyclohexane oxime; active methylene-based compounds such as dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, and acetylacetone; butyl mercaptan, t-butyl mercaptan, hexyl mercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, and methylthiophenone. Mercaptan-based compounds such as ethylthiophenol; acid amide-based compounds such as acetanilide, acetanisidide, acetotoluid, acrylamide, methacrylamide, acetic acid amide, stearic acid amide, and benzamide; imide-based compounds such as succinimide, phthalimide, and maleimide; amine-based compounds such as diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine, and butylphenylamine; imidazole-based compounds such as imidazole and 2-ethylimidazole;Examples of azole compounds include urea-based compounds such as urea, thiourea, ethyleneurea, ethylenethiourea, and diphenylurea; carbamic acid ester compounds such as phenyl N-phenylcarbamate; imine-based compounds such as ethyleneimine and propyleneimine; sulfite-based compounds such as sodium bisulfite and potassium bisulfite; and azole compounds. Examples of the above-mentioned azole compounds include pyrazoles or pyrazole derivatives such as pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3,5-dimethylpyrazole, and 3-methyl-5-phenylpyrazole; imidazoles or imidazole derivatives such as imidazole, benzimidazole, 2-methylimidazole, 2-ethylimidazole, and 2-phenylimidazole; and imidazoline derivatives such as 2-methylimidazoline and 2-phenylimidazoline.

[0049] The above blocking process (reacting with the blocking agent) can be carried out by adding a solvent as needed. Suitable solvents for the blocking reaction are those that are not reactive with isocyanate groups. Examples include acetone, ketones such as methyl ethyl ketone, esters such as ethyl acetate, and solvents such as N-methyl-2-pyrrolidone (NMP).

[0050] Polyol component (a2) The polyol component (a2) is a compound having at least two hydroxyl groups in one molecule.

[0051] The above polyol component (a2) includes a compound (a2-1) having two or more hydroxyl groups and one or more polymerizable unsaturated groups, and polytetramethylene ether glycol (a2-2).

[0052] The compound (a2-1) having two or more hydroxyl groups and one or more polymerizable unsaturated groups imparts polymerizable unsaturated groups to the side chains of the urethane resin portion (A).

[0053] Examples of the compound (a2-1) having two or more hydroxyl groups and one or more polymerizable unsaturated groups include the reaction product of a glycidyl group-containing compound with (meth)acrylic acid, and the reaction product of a trifunctional or more polyol with (meth)acrylic acid.

[0054] As the compound (a2-1) having two or more hydroxyl groups and one or more polymerizable unsaturated groups, commercially available products can be used. Examples of commercially available product names include "Epoxy Ester 40EM", "Epoxy Ester 70PA", "Epoxy Ester 200PA", "Epoxy Ester 80MFA", "Epoxy Ester 3002M", "Epoxy Ester 3002A", "Epoxy Ester 3000MK", "Epoxy Ester 3000A" (all manufactured by Kyoeisha Chemical Co., Ltd.), "Denacol Acrylate DA-212", "Denacol Acrylate DA-314", "Denacol Acrylate DA-911M", "Denacol Acrylate DA-920", "Denacol Acrylate DA-931" (all manufactured by Nagase ChemteX Corporation), "Bremmer GLM", "Bremmer GLM-EX", "Bremmer GLM-R" (all manufactured by NOF Corporation).

[0055] As for the compound (a2-1) having two or more hydroxyl groups and one or more polymerizable unsaturated groups, it is preferable that it includes a compound having two or more hydroxyl groups and one polymerizable unsaturated group, from the viewpoint of storage stability of the resulting paint composition.

[0056] As the compound having two or more hydroxyl groups and one polymerizable unsaturated group as described above, commercially available products can be used. Examples of commercially available product names include "Bremmer GLM," "Bremmer GLM-EX," and "Bremmer GLM-R" (all manufactured by NOF Corporation).

[0057] The content of the compound (a2-1) having two or more hydroxyl groups and one or more polymerizable unsaturated groups is preferably in the range of 1.0 to 15% by mass, more preferably in the range of 2.0 to 10% by mass, and even more preferably in the range of 3.0 to 8.0% by mass, based on the total solid content of the polyol component (a2), from the viewpoint of the storage stability of the resulting aqueous coating composition and the chipping resistance of the formed coating film.

[0058] The aforementioned polytetramethylene ether glycol (a2-2) imparts flexibility to the urethane resin portion (A).

[0059] The number-average molecular weight of the above polytetramethylene ether glycol (a2-2) is preferably in the range of 500 to 10000, more preferably in the range of 1000 to 5000, and even more preferably in the range of 1600 to 4000, from the viewpoint of the chipping resistance of the formed coating film.

[0060] The content of the above-mentioned polytetramethylene ether glycol (a2-2) is preferably in the range of 20 to 85% by mass, more preferably in the range of 40 to 80% by mass, and even more preferably in the range of 70 to 80% by mass, based on the total solid content of the polyol component (a2), from the viewpoint of the storage stability of the resulting aqueous coating composition and the chipping resistance of the formed coating film.

[0061] The polyol component (a2) may include a compound having two or more hydroxyl groups and one or more polymerizable unsaturated groups (a2-1) and a polyol component other than polytetramethylene ether glycol (a2-2) (a2-3).

[0062] As polyol components other than the compound having two or more hydroxyl groups and one or more polymerizable unsaturated groups (a2-1) and polytetramethylene ether glycol (a2-2), for example, low molecular weight polyols such as ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexane glycol, 2,5-hexanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, tricyclodecanedimethanol, and 1,4-cyclohexanedimethanol can be used. These low molecular weight polyols can be used individually or in combination of two or more.

[0063] Furthermore, as polyol components other than the compound having two or more hydroxyl groups and one or more polymerizable unsaturated groups (a2-1) and polytetramethylene glycol (a2-2), high molecular weight polyols such as polycarbonate polyols, polyether polyols other than polytetramethylene ether glycol, polyester polyols, and polyether ester polyols can be used. These high molecular weight polyols can be used individually or in combination of two or more.

[0064] As a polyol component (a2-3) other than the compound having two or more hydroxyl groups and one or more polymerizable unsaturated groups (a2-1) and polytetramethylene glycol (a2-2), it is preferable to include a polycarbonate polyol from the viewpoint of storage stability of the resulting aqueous paint composition.

[0065] The above-mentioned polycarbonate polyol is a compound obtained by polycondensation reaction of a known polyol component with a carbonylating agent using a conventional method. Examples of polyol components include diol components and polyhydric alcohol components such as trihydric or higher alcohols.

[0066] The above diol components include linear diols such as 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol and 1,10-decanediol; 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 2-ethyl-1,6-hexanediol, 2,2-diethyl-1,3-propanediol, and 2-butyl-2-ethyl-1,3- Examples include branched diols such as propanediol, 2-methyl-1,8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, and 2-ethyl-1,3-hexanediol; alicyclic diols such as 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol; aromatic diols such as p-xylenediol and p-tetrachloroxylenediol; and ether diols such as diethylene glycol and dipropylene glycol. These diol components can be used individually or in combination of two or more.

[0067] Examples of trivalent or higher alcohols include glycerin, trimethylolethane, trimethylolpropane, trimethylolpropane dimers, and pentaerythritol. These trivalent or higher alcohols can be used individually or in combination of two or more.

[0068] Known carbonylating agents can be used. Specifically, examples include alkylene carbonates, dialkyl carbonates, diallyl carbonates, phosgene, etc., and one or more of these can be used in combination. Among these, preferred examples include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, diphenyl carbonate, etc.

[0069] Other polyether polyols besides the polytetramethylene ether glycol mentioned above can be alkylene oxide adducts of the low molecular weight polyols, ring-opening (co)polymers of alkylene oxides or cyclic ethers (such as tetrahydrofuran), etc. Specifically, examples include polyethylene glycol, polypropylene glycol, (block or random) copolymers of ethylene glycol-propylene glycol, polyhexamethylene glycol, polyoctamethylene glycol, etc.

[0070] Other polyether polyols besides the polytetramethylene ether glycol mentioned above can be used individually or in combination of two or more.

[0071] Examples of the polyester polyols mentioned above include those obtained by polycondensing a dicarboxylic acid (anhydride) such as adipic acid, succinic acid, sebacic acid, glutaric acid, maleic acid, fumaric acid, and phthalic acid with the low molecular weight polyols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octamethylenediol, and neopentyl glycol under conditions of excess hydroxyl groups. Specifically, examples include ethylene glycol-adipic acid condensate, butanediol-adipic acid condensate, hexamethylene glycol-adipic acid condensate, ethylene glycol-propylene glycol-adipic acid condensate, and polylactone polyols obtained by ring-opening polymerization of lactones using glycol as an initiator. These polyester polyols can be used individually or in combination of two or more.

[0072] Examples of the polyether ester polyol include ether group-containing polyols (such as polytetramethylene ether glycol, polyether polyols other than polytetramethylene ether glycol, or diethylene glycol) or mixtures thereof with other glycols, which are obtained by reacting an alkylene oxide with a (anhydrous) dicarboxylic acid, as exemplified in the polyester polyols above, for example, polytetramethylene glycol-adipic acid condensate. These polyether ester polyols can be used individually or in combination of two or more.

[0073] Compounds that possess both active hydrogen groups and ion-forming groups. Examples of compounds that possess both active hydrogen groups and ion-forming groups include compounds having two or more hydroxyl groups and one or more carboxyl groups in one molecule, compounds having two or more hydroxyl groups and one or more sulfonic acid groups in one molecule, and compounds having two or more amino groups and one or more carboxyl groups in one molecule. These can be used individually or in combination of two or more.

[0074] In particular, as compounds having both the active hydrogen group and the ion-forming group, compounds having two or more hydroxyl groups and one or more carboxyl groups in one molecule, and compounds having two or more hydroxyl groups and one or more sulfonic acid groups in one molecule can be suitably used.

[0075] In the present invention, compounds having two or more hydroxyl groups and ion-forming groups, such as compounds having two or more hydroxyl groups and one or more carboxyl groups in one molecule, and compounds having two or more hydroxyl groups and one or more sulfonic acid groups in one molecule, are included in the polyol component (a2).

[0076] Examples of compounds having two or more hydroxyl groups and one or more carboxyl groups in a single molecule include alkanol carboxylic acid compounds such as dimethylolpropionic acid, dimethylolacetic acid, dimethylolbutanoic acid, dimethylolheptanoic acid, dimethylolnonanoic acid, 1-carboxy-1,5-pentylenediamine, dihydroxybenzoic acid, and 3,5-diaminobenzoic acid, as well as half-ester compounds of polyoxypropylene triol with maleic anhydride and / or phthalic anhydride.

[0077] Examples of compounds having two or more hydroxyl groups and one or more sulfonic acid groups in a single molecule include 2-sulfonic acid-1,4-butanediol, 5-sulfonic acid-di-β-hydroxyethyl isophthalate, and N,N-bis(2-hydroxyethyl)aminoethylsulfonic acid.

[0078] As for the compound having both the active hydrogen group and the ion-forming group, it is preferable to use a compound having two or more hydroxyl groups and one or more carboxyl groups in one molecule, from the viewpoint of the flexibility of the coating film formed.

[0079] From the viewpoint of water dispersion stability and other factors, the urethane resin portion (A) preferably contains a compound having both an active hydrogen group and an ion-forming group.

[0080] When using a compound having two or more hydroxyl groups and one or more carboxyl groups, the amount used is preferably in the range of 1 to 30% by mass, more preferably in the range of 1 to 25% by mass, and even more preferably in the range of 1 to 20% by mass, relative to the total amount of compounds constituting the polyol component (a2), from the viewpoint of the storage stability of the resulting aqueous paint composition.

[0081] The method for producing the urethane resin portion (A) is not particularly limited, and conventionally known methods can be applied. For example, the production method involves reacting a polyisocyanate component (a1) and a polyol component (a2) in an organic solvent to form a urethane, or, if necessary, adding a compound having both an active hydrogen group and an ion-forming group and further reacting to form a urethane to synthesize a prepolymer. Furthermore, if necessary, the mixture may be reacted with a compound having one hydroxyl group and one polymerizable unsaturated group (b1-1) and / or a compound having one hydroxyl group and two or more polymerizable unsaturated groups (b2-1) to form a compound having a polymerizable unsaturated group at its terminus. Polymerization inhibitors may also be added if necessary.

[0082] A catalyst can be used as needed in the urethane formation reaction between the polyisocyanate component (a1) and the polyol component (a2) described above.

[0083] Examples of the catalysts mentioned above include bismuth carboxylic acid compounds such as tris(2-ethylhexanoic acid)bismuth(III); organotin compounds such as dibutyltin dilaurate, dibutyltin dioctoate, and stanus octoate; and tertiary amine compounds such as triethylamine and triethylenediamine.

[0084] The urethane formation reaction is preferably carried out at 50 to 120°C.

[0085] In the synthesis of the urethane resin portion (A), any organic solvent that is inert to isocyanate and does not interfere with the urethane formation reaction can be used. Examples of such organic solvents include aromatic hydrocarbon solvents such as toluene and xylene, ester solvents such as ethyl acetate and butyl acetate, and ketone solvents such as acetone and methyl ethyl ketone. Among these, ketone solvents and ester solvents can be preferably used from the viewpoint of water dispersion stability, etc.

[0086] These organic solvents can be used individually or in combination of two or more.

[0087] Furthermore, compounds having one polymerizable unsaturated group and no hydroxyl group or having one hydroxyl group (b1) and compounds having two or more polymerizable unsaturated groups and no hydroxyl group or having one hydroxyl group (b2) can be used as substitutes for solvents. When using these compounds as solvents, it is preferable to use compounds that do not have a hydroxyl group and have one polymerizable unsaturated group (b1-2) and / or compounds that do not have a hydroxyl group and have two or more polymerizable unsaturated groups (b2-2).

[0088] As the polymerization inhibitor, for example, known polymerization inhibitors such as phenolic hydroxyl group-containing compounds such as di-t-butylhydroxytoluene and methoxyphenol; carbonyl group-containing aromatic compounds such as benzoquinone; nitroso skeleton-containing compounds; and N-oxyl skeleton-containing compounds can be used.

[0089] From the viewpoint of manufacturability and other factors, the content ratio of the polyisocyanate component (a1) and the polyol component (a2) in the urethane resin portion (A) is preferably in the range of 1 / 1.01 to 1 / 3.0 in terms of the molar ratio of active hydrogen groups in the polyol component (a2) to isocyanate groups in the polyisocyanate component (a1), and more preferably in the range of 1 / 1.05 to 1 / 2.0.

[0090] The number-average molecular weight of the urethane resin portion (A) is preferably in the range of 2,000 to 20,000, more preferably in the range of 3,000 to 15,000, and even more preferably in the range of 4,000 to 10,000, from the viewpoint of the storage stability of the resulting aqueous paint composition and the chipping resistance of the formed coating film.

[0091] In this specification, the average molecular weight is calculated from the chromatogram measured by gel permeation chromatography, using the molecular weight of standard polystyrene as a reference. The gel permeation chromatograph used was "HLC8120GPC" (manufactured by Tosoh Corporation). Four columns were used: "TSKgel G-4000HXL", "TSKgel G-3000HXL", "TSKgel G-2500HXL", and "TSKgel G-2000HXL" (all product names manufactured by Tosoh Corporation). The measurements were performed under the following conditions: mobile phase; tetrahydrofuran, measurement temperature; 40°C, flow rate; 1 mL / min, detector; radioisotope (RI).

[0092] Manufacturing process 2 Next, deionized water is added and emulsified to obtain an aqueous dispersion. If necessary, further chain extension reactions and solvent removal are carried out.

[0093] When adding deionized water, a neutralizing agent for the ion-forming groups may be added as needed.

[0094] The neutralizing agent is not particularly limited as long as it can neutralize the ion-forming group. Examples of basic compounds for neutralization include ammonia, diethylamine, ethylethanolamine, diethanolamine, triethanolamine, monoethanolamine, monopropanolamine, isopropanolamine, ethylaminoethylamine, hydroxyethylamine, triethylamine, tributylamine, dimethylethanolamine, diethylenetriamine, N-methylmorpholine, N-ethylmorpholine, and other organic amines; or alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. These neutralizing agents can be used individually or in combination of two or more.

[0095] It is preferable to use the above-mentioned neutralizing agent in an amount such that the pH of the aqueous dispersion of acrylic urethane composite resin (AB) ultimately becomes approximately 6.0 to 9.0.

[0096] When adding the above-mentioned neutralizing agent, the amount of neutralizing agent added is preferably 0.1 to 1.5 equivalents relative to the acid group such as the carboxyl group, and more preferably 0.3 to 1.2 equivalents.

[0097] To improve the water dispersion stability of the acrylic urethane composite resin (AB), emulsifiers such as surfactants may be used.

[0098] As the emulsifier mentioned above, well-known anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, polymeric surfactants, reactive surfactants, etc., can be used. When using these, anionic surfactants, nonionic surfactants, or cationic surfactants are preferred because they are less expensive and provide good emulsification.

[0099] Examples of the above-mentioned anionic surfactants include alkyl sulfates such as sodium dodecyl sulfate, potassium dodecyl sulfate, and ammonium dodecyl sulfate; sodium dodecyl polyglycol ether sulfate; sodium sulfolycinolate; alkyl sulfonates such as alkali metal salts of sulfonated paraffins and ammonium salts of sulfonated paraffins; fatty acid salts such as sodium laurate, triethanolamine oleate, and toluethanolamine abietate; alkylaryl sulfonates such as sodium benzenesulfonate and alkali metal sulfates of alkaliphenol hydroxyethylene; high alkylnaphthalene sulfonates; naphthalene sulfonic acid formalin condensates; dialkyl sulfosuccinates; polyoxyethylene alkyl sulfate salts; and polyoxyethylene alkylaryl sulfate salts.

[0100] Examples of the nonionic surfactant include ethylene oxide and / or propylene oxide adducts of C1-C18 alcohols, ethylene oxide and / or propylene oxide adducts of alkylphenols, and ethylene oxide and / or propylene oxide adducts of alkylene glycols and / or alkylenediamines.

[0101] Examples of C1-C18 alcohols constituting the nonionic surfactant include methanol, ethanol, propanol, 2-propanol, butanol, 2-butanol, tertiary butanol, amyl alcohol, isoamyl alcohol, tertiary amyl alcohol, hexanol, octanol, decane alcohol, lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, etc. Examples of alkylphenols include phenol, methylphenol, 2,4-ditertiary butylphenol, 2,5-ditertiary butylphenol, 3,5-ditertiary butylphenol, 4-(1,3-tetramethylbutyl)phenol, 4-isooctylphenol, 4-nonylphenol, 4-tertiary octylphenol, 4-dodecyl butylphenol. Examples of alkylene glycols include silphenol, 2-(3,5-dimethylheptyl)phenol, 4-(3,5-dimethylheptyl)phenol, naphthol, bisphenol A, bisphenol F, etc. Examples of alkylene glycols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, etc. Examples of alkylenediamines include those alkylene glycols in which the alcoholic hydroxyl group is replaced with an amino group. The ethylene oxide and propylene oxide adducts may be either random adducts or block adducts.

[0102] Examples of cationic surfactants include primary to tertiary amine salts, pyridinium salts, alkylpyridinium salts, and quaternary ammonium salts such as alkyl quaternary ammonium halides.

[0103] These surfactants can be used individually or in combination of two or more.

[0104] As for the emulsification method, dispersion using a conventional stirrer is possible, but to obtain a more uniform aqueous dispersion with finer particle sizes, a homomixer, homogenizer, disperser, line mixer, etc., can be used.

[0105] When performing the chain extension reaction (increasing molecular weight), a chain extender other than water may be added as needed to react the urethane resin portion (A) with the chain extender. As the chain extender, any known chain extender having active hydrogen can be used. Specifically, examples include diamine compounds such as ethylenediamine, hexamethylenediamine, cyclohexanediamine, cyclohexylmethanediamine, and isophoronediamine; triamine compounds such as diethylenetriamine; tetraamine compounds such as triethylenetetraamine; and hydrazine.

[0106] As the chain extender, from the viewpoint of the storage stability of the resulting paint composition, triamine compounds such as diethylenetriamine, or amine compounds with three or more functions, can be suitably used.

[0107] Furthermore, from the viewpoint of the chipping resistance of the formed coating film, diamine compounds such as ethylenediamine can be suitably used as the chain extender.

[0108] Furthermore, for the purpose of introducing reactive functional groups into the acrylic urethane composite resin (AB), compounds having one or more amines and hydroxyl groups in a single molecule, such as hydroxyethylaminoethylamine, can also be suitably used.

[0109] Manufacturing process 3 Next, a polymerization initiator is added to the aqueous dispersion to carry out a polymerization reaction, thereby obtaining an acrylic urethane composite resin (AB) containing a urethane resin portion (A) and an acrylic resin portion (B).

[0110] Examples of polymerization initiators include organic peroxides such as benzoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, cumene hydroperoxide, tert-butyl peroxide, tert-butyl peroxylaurate, tert-butyl peroxyisopropyl carbonate, tert-butyl peroxyacetate, and diisopropylbenzene hydroperoxide; azobisisobutyronitrile, azobis(2,4-dimethylvaleronitrile), and azobis(2-methyl Examples of polymerization initiators include azo compounds such as propionnitrile, azobis(2-methylbutyronitrile), 4,4'-azobis(4-cyanobutanoic acid), dimethylazobis(2-methylpropionate), azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], azobis{2-methyl-N-[2-(1-hydroxybutyl)]-propionamide}, and 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamide]; and persulfates such as potassium persulfate, ammonium persulfate, and sodium persulfate. These polymerization initiators can be used individually or in combination of two or more. In addition, a reducing agent such as sugar, sodium formaldehyde sulfoxylate, or an iron complex can be used in combination with the above polymerization initiator as needed to form a redox initiator.

[0111] The amount of polymerization initiator used is generally preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and more preferably 5% by mass or less, and more preferably 3% by mass or less, based on the total amount of monomers used. The method of adding the polymerization initiator is not particularly limited and can be appropriately selected depending on its type and amount. For example, it can be included in the monomer mixture or aqueous medium in advance, added all at once during polymerization, or added dropwise.

[0112] The polymerization reaction can be carried out by conventionally known methods, such as emulsion polymerization in water or self-emulsification.

[0113] The acrylic urethane composite resin (AB) synthesized in the above manufacturing processes 1 to 3 is synthesized as a dispersion in an aqueous solvent and is considered to have a particulate form.

[0114] Here, an aqueous solvent refers to a solvent whose main component is water (for example, a solvent in which 70-100% by mass is water).

[0115] The average particle size of the above-mentioned acrylic urethane composite resin (AB) is preferably in the range of 10 to 5000 nm, more preferably in the range of 10 to 1000 nm, particularly preferably in the range of 20 to 500 nm, and even more preferably in the range of 50 to 140 nm, from the viewpoint of water dispersion stability and storage stability.

[0116] The average particle size of acrylic urethane composite resin (AB) can be adjusted to a desired average particle size by controlling particle size factors such as the composition of raw materials (polyisocyanate component, polyol component, amine component, etc.), the type of emulsifier, the amount of emulsifier, the proportion of emulsifier added, the type of neutralizing agent, and the amount of neutralizing agent.

[0117] In this specification, the average particle size of the acrylic urethane composite resin (AB) is the value measured at 20°C after dilution with deionized water using a dynamic light scattering particle size distribution analyzer. As a dynamic light scattering particle size distribution analyzer, for example, "ELSZ-2000" (product name, manufactured by Otsuka Electronics Co., Ltd.) can be used.

[0118] The acid value of the urethane resin portion (A) is preferably in the range of 3.0 to 75 mgKOH / g, more preferably in the range of 10.0 to 60 mgKOH / g, and even more preferably in the range of 20 to 40 mgKOH / g, from the viewpoint of the storage stability of the resulting aqueous paint composition.

[0119] The hydroxyl value of the acrylic resin portion (B) is preferably in the range of 0.5 to 90 mgKOH / g, more preferably in the range of 2.0 to 65 mgKOH / g, and even more preferably in the range of 10 to 45 mgKOH / g, from the viewpoint of the storage stability of the resulting aqueous paint composition and the chipping resistance of the formed coating film.

[0120] The acid value of the acrylic resin portion (B) is preferably in the range of 0.7 to 80 mgKOH / g, more preferably in the range of 3.5 to 40 mgKOH / g, and even more preferably in the range of 7.5 to 25 mgKOH / g, from the viewpoint of the storage stability of the resulting aqueous paint composition.

[0121] The hydroxyl value of the acrylic urethane composite resin (AB) is preferably in the range of 0 to 100 mg KOH / g, more preferably in the range of 0 to 50 mg KOH / g, and even more preferably in the range of 0 to 10 mg KOH / g, from the viewpoint of the chipping resistance of the formed coating film.

[0122] The acid value of the above-mentioned acrylic urethane composite resin (AB) is preferably in the range of 5 to 40 mg KOH / g, more preferably in the range of 5 to 30 mg KOH / g, and even more preferably in the range of 7.0 to 30 mg KOH / g, from the viewpoint of the storage stability of the resulting aqueous paint composition.

[0123] The mass ratio (B) / (A) of the acrylic resin portion (B) and the urethane resin portion (A) of the above-mentioned acrylic urethane composite resin (AB) is preferably in the range of 20 / 80 to 80 / 20, more preferably in the range of 30 / 70 to 70 / 30, and particularly preferably in the range of 40 / 60 to 60 / 40, from the viewpoint of the storage stability of the resulting aqueous paint composition and the chipping resistance of the formed coating film.

[0124] The solid content concentration in the aqueous dispersion of the acrylic urethane composite resin (AB) is preferably in the range of 20 to 50% by mass, and more preferably in the range of 30 to 50% by mass. When the solid content concentration is 50% by mass or less, emulsification is facilitated, and an aqueous dispersion can be easily obtained. When the solid content concentration is 20% by mass or more, the amount of solvent components is reduced, so the solid content concentration of the aqueous coating composition can be increased.

[0125] In this specification, "solid content" refers to non-volatile components such as resins, curing agents, and pigments that remain after drying at 110°C for 1 hour. The solid content can be determined, for example, by weighing 1.0 g of the sample into a heat-resistant container such as an aluminum foil cup, spreading the sample on the bottom surface of the container, drying it at 110°C for 1 hour, and then weighing the mass of the components remaining after drying.

[0126] Furthermore, in this specification, "solid content concentration" refers to the mass percentage of the solid content in the composition. Therefore, the solid content concentration of a composition can be calculated, for example, by measuring the composition into a heat-resistant container such as an aluminum foil cup, spreading the composition on the bottom surface of the container, drying it at 110°C for 1 hour, weighing the mass of the components remaining in the composition after drying, and determining the ratio of the mass of the components remaining after drying to the total mass of the composition before drying.

[0127] In the aqueous coating composition of the present invention, the content of the acrylic urethane composite resin (AB) is preferably in the range of 2 to 70% by mass, more preferably in the range of 5 to 50% by mass, and even more preferably in the range of 10 to 40% by mass, based on the amount of resin solids in the aqueous coating composition.

[0128] In the acrylic urethane composite resin (AB), by adjusting the composition of the urethane resin portion (A), the composition of the acrylic resin portion (B), the reaction conditions, etc., an aqueous dispersion of the acrylic urethane composite resin (AB) having a desired form, such as a core-shell structure comprising at least two layers, a core layer containing either the urethane resin portion (A) or the acrylic resin portion (B), and a shell layer containing either the urethane resin portion (A) or the acrylic resin portion (B), or a form in which part or all of the urethane resin portion (A) and the acrylic resin portion (B) are mixed, can be obtained.

[0129] Specifically, a core-shell structure refers to a structure in which components with different resin compositions exist within the same particle, resulting in a structure where the central part (core) and the outer shell (shell) are made of different resin compositions.

[0130] From the viewpoint of storage stability of the resulting aqueous paint composition and chipping resistance of the formed coating film, the above-mentioned acrylic urethane composite resin (AB) is preferably an acrylic urethane composite resin (AB') having a core-shell structure consisting of a shell portion made of the urethane resin portion (A) and a core portion made of the acrylic resin portion (B).

[0131] Acrylic urethane composite resin (AB') having a core-shell structure Acrylic urethane composite resins (AB') having a core-shell structure are typically synthesized as dispersions in aqueous solvents.

[0132] The acrylic urethane composite resin (AB') having a core-shell structure is preferably dispersed in water as particles having a structure in which the urethane resin portion (A) constituting the shell is positioned around the acrylic resin portion (B) constituting the core, acting as a dispersion stabilizer. In other words, it is preferable that it is dispersed in an aqueous solvent in a form having a core-shell structure with the urethane resin portion (A) constituting the shell on the outside and the acrylic resin portion (B) constituting the core on the inside. It is actually believed that the particles have almost such a morphology.

[0133] The above-described core-shell structure is typically a layered structure in which the core is completely covered by the shell. However, depending on the mass ratio of the core and shell, and other conditions, the shell may not be sufficient to form a layered structure. In such cases, it is not necessary to have a complete layered structure as described above, and a structure in which the shell covers only a portion of the core may be used.

[0134] As for the manufacturing method of the acrylic urethane composite resin (AB') having a core-shell structure, conventionally known methods for manufacturing acrylic urethane composite resins can be used, as long as the form having a core-shell structure can be obtained. For example, in manufacturing step 1 of the acrylic urethane composite resin (AB), by using a compound having both active hydrogen groups and ion-forming groups as a component of the urethane resin portion (A), the acrylic urethane composite resin (AB') having a core-shell structure can be manufactured.

[0135] As compounds having both an active hydrogen group and an ion-forming group, the compounds having both an active hydrogen group and an ion-forming group as exemplified by the acrylic urethane composite resin (AB) can be used, and these can be used individually or in combination of two or more.

[0136] In particular, as compounds having both the active hydrogen group and the ion-forming group, compounds having two or more hydroxyl groups and one or more carboxyl groups in one molecule, and compounds having two or more hydroxyl groups and one or more sulfonic acid groups in one molecule can be suitably used.

[0137] As the compounds having two or more hydroxyl groups and one or more carboxyl groups in a single molecule, the compounds having two or more hydroxyl groups and one or more carboxyl groups in a single molecule, as exemplified by the acrylic urethane composite resin (AB), can be used, and these can be used individually or in combination of two or more.

[0138] As the compound having two or more hydroxyl groups and one or more sulfonic acid groups in one molecule, the compounds having two or more hydroxyl groups and one or more sulfonic acid groups in one molecule, as exemplified by the acrylic urethane composite resin (AB), can be used, and these can be used alone or in combination of two or more.

[0139] As for the compound having both the active hydrogen group and the ion-forming group, it is preferable to use a compound having two or more hydroxyl groups and one or more carboxyl groups in its molecule, from the viewpoint of the storage stability of the resulting aqueous paint composition.

[0140] When the urethane resin portion (A) constituting the shell portion uses a compound having two or more hydroxyl groups and one or more carboxyl groups, the amount used is preferably in the range of 1 to 30% by mass, more preferably in the range of 1 to 25% by mass, and even more preferably in the range of 1 to 20% by mass, relative to the total amount of the compound constituting the polyol component (a2), from the viewpoint of the storage stability of the resulting aqueous paint composition.

[0141] The average particle size of the acrylic urethane composite resin (AB') having the core-shell structure is preferably in the range of 10 to 5000 nm, more preferably in the range of 10 to 1000 nm, particularly preferably in the range of 20 to 500 nm, and even more preferably in the range of 50 to 140 nm, from the viewpoint of water dispersion stability and storage stability.

[0142] The average particle size of an acrylic urethane composite resin (AB') having a core-shell structure can be adjusted to a desired average particle size by controlling particle size factors such as the composition of raw materials (polyisocyanate component, polyol component, amine component, etc.), the type of emulsifier, the amount of emulsifier, the proportion of emulsifier added, the type of neutralizing agent, and the amount of neutralizing agent.

[0143] The acid value of the urethane resin portion (A) constituting the shell portion is preferably in the range of 3.0 to 75 mgKOH / g, more preferably in the range of 10.0 to 60 mgKOH / g, and even more preferably in the range of 20 to 40 mgKOH / g, from the viewpoint of storage stability of the resulting aqueous paint composition.

[0144] The hydroxyl value of the acrylic resin portion (B) constituting the core is preferably in the range of 0.5 to 90 mgKOH / g, more preferably in the range of 2.0 to 65 mgKOH / g, and even more preferably in the range of 10 to 45 mgKOH / g, from the viewpoint of the storage stability of the resulting aqueous paint composition and the chipping resistance of the formed coating film.

[0145] The acid value of the acrylic resin portion (B) constituting the core portion described above is preferably in the range of 0.7 to 80 mgKOH / g, more preferably in the range of 3.5 to 40 mgKOH / g, and even more preferably in the range of 7.5 to 25 mgKOH / g, from the viewpoint of the storage stability of the resulting aqueous paint composition.

[0146] The hydroxyl value of the acrylic urethane composite resin (AB') having the core-shell structure is preferably in the range of 0 to 100 mgKOH / g, more preferably in the range of 0 to 50 mgKOH / g, and even more preferably in the range of 0 to 10 mgKOH / g, from the viewpoint of chipping resistance of the formed coating film.

[0147] The acid value of the acrylic urethane composite resin (AB') having the above-described core-shell structure is preferably in the range of 5 to 40 mgKOH / g, more preferably in the range of 5 to 30 mgKOH / g, and even more preferably in the range of 7.0 to 30 mgKOH / g, from the viewpoint of the storage stability of the resulting aqueous paint composition.

[0148] In the acrylic urethane composite resin (AB') having the above-described core-shell structure, the mass ratio (B) / (A) of the acrylic resin portion (B) constituting the core and the urethane resin portion (A) constituting the shell is preferably in the range of 20 / 80 to 80 / 20, more preferably in the range of 30 / 70 to 70 / 30, and particularly preferably in the range of 40 / 60 to 60 / 40, from the viewpoint of the storage stability of the resulting aqueous paint composition and the chipping resistance of the formed coating film.

[0149] The solid content concentration in the aqueous dispersion of the acrylic urethane composite resin (AB') having the above core-shell structure is preferably in the range of 20 to 50% by mass, and more preferably in the range of 30 to 50% by mass. When the solid content concentration is 50% by mass or less, emulsification is facilitated, and an aqueous dispersion can be easily obtained. When the solid content concentration is 20% by mass or more, the amount of solvent components is reduced, so the solid content concentration of the aqueous coating composition can be increased.

[0150] In the aqueous coating composition of the present invention, the content of the acrylic urethane composite resin (AB') having a core-shell structure is preferably in the range of 2 to 70% by mass, more preferably in the range of 5 to 50% by mass, and even more preferably in the range of 10 to 40% by mass, based on the amount of resin solids in the aqueous coating composition.

[0151] [Water-based paint composition] The aqueous coating composition of the present invention contains the acrylic urethane composite resin (AB), and optionally contains at least one resin selected from acrylic resin (C) and polyester resin (D), and a curing agent (E).

[0152] Acrylic resin (C) As the acrylic resin (C), any water-soluble or water-dispersible acrylic resin that has been conventionally used in water-based paints and is known for itself can be used.

[0153] The acrylic resin (C) preferably has crosslinkable functional groups that can react with the curing agent (E) described below. Examples of such crosslinkable functional groups include hydroxyl groups, carboxyl groups, epoxy groups, etc., and it is preferable that at least one of them is a hydroxyl group. Therefore, it is preferable to use a hydroxyl group-containing acrylic resin (C') as the acrylic resin (C).

[0154] Hydroxyl group-containing acrylic resin (C') Hydroxyl group-containing acrylic resin (C') can be produced, for example, by copolymerizing a hydroxyl group-containing polymerizable unsaturated monomer and other polymerizable unsaturated monomers copolymerizable with the hydroxyl group-containing polymerizable unsaturated monomer by methods known in themselves, such as solution polymerization in an organic solvent or emulsion polymerization in water.

[0155] The above-mentioned hydroxyl group-containing polymerizable unsaturated monomer is a compound having one or more hydroxyl groups and polymerizable unsaturated bonds in one molecule. Examples of the hydroxyl group-containing polymerizable unsaturated monomer 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 forms of the 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 ends. However, monomers that fall under "(xvii) polymerizable unsaturated monomers having UV-absorbing functional groups" as described later, even if they contain hydroxyl groups, should be defined in the present invention as "other polymerizable unsaturated monomers copolymerizable with the above-mentioned hydroxyl group-containing polymerizable unsaturated monomers," and are excluded from the above-mentioned "hydroxyl group-containing polymerizable unsaturated monomers." These can be used individually or in combination of two or more.

[0156] Other polymerizable unsaturated monomers copolymerizable with the above-mentioned hydroxyl group-containing polymerizable unsaturated monomers include, for example, the monomers (i) to (xx) listed below. These polymerizable unsaturated monomers can be used individually or in combination of two or more. (i) Alkyl or cycloalkyl (meth)acrylates: for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, tridecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, tricyclodecanyl (meth)acrylate, etc. (ii) Polymerizable unsaturated monomers having an isobornyl group: isobornyl (meth)acrylate, etc. (iii) Polymerizable unsaturated monomers having an adamantyl group: adamantyl (meth)acrylate, etc. (iv) Polymerizable unsaturated monomers having a tricyclodecenyl group: tricyclodecenyl (meth)acrylate, etc. (v) Polymerizable unsaturated monomers containing aromatic rings: benzyl (meth)acrylate, styrene, α-methylstyrene, vinyltoluene, etc. (vi) Polymerizable unsaturated monomers having an alkoxysilyl group: vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, γ-(meth)acryloyloxypropyltrimethoxysilane, γ-(meth)acryloyloxypropyltriethoxysilane, etc. (vii) Polymerizable unsaturated monomers having a fluorinated alkyl group: Perfluoroalkyl (meth)acrylates such as perfluorobutylethyl (meth)acrylate and perfluorooctylethyl (meth)acrylate; fluoroolefins, etc. (viii) A polymerizable unsaturated monomer having a photopolymerizable functional group such as a maleimide group. (ix) Vinyl compounds: N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate, etc. (x) Carboxylate-containing polymerizable unsaturated monomers: (meth)acrylic acid, maleic acid, crotonic acid, β-carboxyethyl (meth)acrylate, etc. (xi) Nitrogen-containing polymerizable unsaturated monomers: (meth)acrylonitrile, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylamide, methylenebis(meth)acrylamide, ethylenebis(meth)acrylamide, adducts of glycidyl (meth)acrylate with amine compounds, etc. (xii) Polymerizable unsaturated monomers having two or more polymerizable unsaturated groups in one molecule: allyl (meth)acrylate, ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, etc. (xiii) Polymerizable unsaturated monomers containing epoxy groups: glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3,4-epoxycyclohexylethyl (meth)acrylate, 3,4-epoxycyclohexylpropyl (meth)acrylate, allyl glycidyl ether, etc. (xiv) A (meth)acrylate having a polyoxyethylene chain with an alkoxy group at the molecular terminus. (xv) Polymerizable unsaturated monomers having a sulfonic acid group: 2-acrylamido-2-methylpropanesulfonic acid, 2-sulfoethyl (meth)acrylate, allylsulfonic acid, 4-styrenesulfonic acid, etc.; sodium salts and ammonium salts of these sulfonic acids, etc. (xvi) Polymerizable unsaturated monomers having a phosphate group: acid phosphooxyethyl (meth)acrylate, acid phosphooxypropyl (meth)acrylate, acid phosphooxypoly(oxyethylene) glycol (meth)acrylate, acid phosphooxypoly(oxypropylene) glycol (meth)acrylate, etc. (xvii) Polymerizable unsaturated monomers having UV-absorbing functional groups: 2-hydroxy-4(3-methacryloyloxy-2-hydroxypropoxy)benzophenone, 2-hydroxy-4-(3-acryloyloxy-2-hydroxypropoxy)benzophenone, 2,2'-dihydroxy-4-(3-methacryloyloxy-2-hydroxypropoxy)benzophenone, 2,2'-dihydroxy-4-(3-acryloyloxy-2-hydroxypropoxy)benzophenone, 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole, etc. (xviii) Photostable polymerizable unsaturated monomers: 4-(meth)acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-cyano-4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, 1-(meth)acryloyl-4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, 1-(meth)acryloyl-4-cyano-4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, 4-crotonoylamino-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, etc. (xix) Polymerizable unsaturated monomers having a carbonyl group: acrolein, diacetone acrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate, formyl styrene, vinyl alkyl ketones having 4 to 7 carbon atoms (e.g., vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone), etc. (xx) Polymerizable unsaturated monomers having an acid anhydride group: maleic anhydride, itaconic anhydride, citraconic anhydride, etc.

[0157] When producing the above-mentioned hydroxyl group-containing acrylic resin (C'), the proportion of the hydroxyl group-containing polymerizable unsaturated monomer used is preferably 1 to 50% by mass, more preferably 2 to 40% by mass, and even more preferably 3 to 30% by mass, based on the total amount of monomer components.

[0158] The hydroxyl group-containing acrylic resin (C') described above preferably has a hydroxyl value of 1 to 200 mg KOH / g, more preferably 2 to 180 mg KOH / g, and even more preferably 5 to 150 mg KOH / g, from the viewpoint of the curability, chipping resistance, adhesion, and finished appearance of the formed coating film.

[0159] Furthermore, the hydroxyl group-containing acrylic resin (C') is preferably 1 to 150 mg KOH / g, more preferably 5 to 100 mg KOH / g, and even more preferably 5 to 80 mg KOH / g, from the viewpoint of storage stability of the resulting aqueous paint composition and chipping resistance of the formed coating film.

[0160] When the aqueous paint composition contains the above-mentioned hydroxyl group-containing acrylic resin (C'), the content of the hydroxyl group-containing acrylic resin (C') is preferably 2 to 70% by mass, more preferably 5 to 50% by mass, and even more preferably 10 to 40% by mass, based on the amount of resin solids in the aqueous paint composition.

[0161] Polyester resin (D) As the polyester resin (D), any water-soluble or water-dispersible polyester resin that has been conventionally used in water-based paints and is known for itself can be used.

[0162] The polyester resin (D) preferably has crosslinkable functional groups that can react with the curing agent (E) described below. Examples of such crosslinkable functional groups include hydroxyl groups, carboxyl groups, epoxy groups, etc., and it is preferable that at least one of them is a hydroxyl group. Therefore, it is preferable to use a hydroxyl group-containing polyester resin (D') as the polyester resin (D).

[0163] Hydroxyl group-containing polyester resin (D') Hydroxyl group-containing polyester resin (D') can usually be produced by an esterification or transesterification reaction between an acid component and an alcohol component.

[0164] As the above-mentioned acid component, compounds commonly used as acid components in the manufacture of polyester resins can be used. Examples of such acid components include aliphatic polybasic acids, alicyclic polybasic acids, aromatic polybasic acids, and the like.

[0165] The above-mentioned aliphatic polybasic acids are generally aliphatic compounds having two or more carboxyl groups in one molecule, acid anhydrides of the aliphatic compounds, and esters of the aliphatic compounds. Examples of aliphatic polybasic acids include aliphatic polycarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanediic acid, dodecanediic acid, brassic acid, octadecanediic acid, citric acid, and butanetetracarboxylic acid; anhydrides of the aliphatic polycarboxylic acids; and esters of the aliphatic polycarboxylic acids of lower alkyl groups having approximately 1 to 4 carbon atoms. The above-mentioned aliphatic polybasic acids can be used alone or in combination of two or more types.

[0166] As the above-mentioned aliphatic polybasic acid, it is preferable to use adipic acid and / or adipic anhydride from the viewpoint of the smoothness of the coating film formed.

[0167] The above-mentioned alicyclic polybasic acids are generally compounds having one or more alicyclic structures and two or more carboxyl groups in one molecule, acid anhydrides of the same, and esters of the same. The alicyclic structure is mainly a 4- to 6-membered ring structure. Examples of alicyclic polybasic acids include alicyclic polycarboxylic acids such as 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, 3-methyl-1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, and 1,3,5-cyclohexanetricarboxylic acid; anhydrides of the alicyclic polycarboxylic acids; and esters of lower alkyl groups having approximately 1 to 4 carbon atoms of the alicyclic polycarboxylic acids. The above-mentioned alicyclic polybasic acids can be used alone or in combination of two or more.

[0168] As the above-mentioned alicyclic polybasic acid, from the viewpoint of the smoothness of the formed coating film, it is preferable to use 1,2-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid anhydride, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, and 4-cyclohexene-1,2-dicarboxylic acid anhydride, and among these, it is more preferable to use 1,2-cyclohexanedicarboxylic acid and / or 1,2-cyclohexanedicarboxylic acid anhydride.

[0169] The above-mentioned aromatic polybasic acids generally include aromatic compounds having two or more carboxyl groups in one molecule, acid anhydrides of the aromatic compounds, and esterified products of the aromatic compounds, such as aromatic polycarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, trimellitic acid, and pyromellitic acid; anhydrides of the aromatic polycarboxylic acids; and esterified products of the aromatic polycarboxylic acids of lower alkyl groups having approximately 1 to 4 carbon atoms. The above-mentioned aromatic polybasic acids can be used alone or in combination of two or more types.

[0170] As the above-mentioned aromatic polybasic acid, it is preferable to use phthalic acid, phthalic anhydride, isophthalic acid, trimellitic acid, or trimellitic anhydride.

[0171] Furthermore, acid components other than the above-mentioned aliphatic polybasic acids, alicyclic polybasic acids, and aromatic polybasic acids can also be used. Such acid components are not particularly limited and include, for example, fatty acids such as coconut oil fatty acid, cottonseed oil fatty acid, hemp seed oil fatty acid, rice bran oil fatty acid, fish oil fatty acid, tall oil fatty acid, soybean oil fatty acid, linseed oil fatty acid, tung oil fatty acid, rapeseed oil fatty acid, castor oil fatty acid, dehydrated castor oil fatty acid, and safflower oil fatty acid; monocarboxylic acids such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, benzoic acid, p-tert-butylbenzoic acid, cyclohexanoic acid, and 10-phenyloctadecanoic acid; and hydroxycarboxylic acids such as lactic acid, 3-hydroxybutanoic acid, and 3-hydroxy-4-ethoxybenzoic acid. These acid components can be used individually or in combination of two or more.

[0172] As the alcohol component, polyhydric alcohols having two or more hydroxyl groups in one molecule can be suitably used. Examples of such polyhydric alcohols include ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-butanediol, 2-methyl-1,3-propanediol, 3-methyl-1,2-butanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-pentanediol, and 1,5-butyl-2-ethyl-1,3-propanediol. Pentanediol, 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, tetramethylene glycol, 3-methyl-4,3-pentanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, tricyclodecanediethanol Examples include dihydric alcohols such as neopentyl glycol hydroxypivalate, hydrogenated bisphenol A, hydrogenated bisphenol F, and dimethylolpropionic acid; polylactone diols obtained by adding lactone compounds such as ε-caprolactone to these dihydric alcohols; ester diol compounds such as bis(hydroxyethyl) terephthalate; polyether diol compounds such as alkylene oxide adducts of bisphenol A, polyethylene glycol, polypropylene glycol, polybutylene glycol, and polytetramethylene ether glycol; trihydric or higher alcohols such as glycerin, trimethylolethane, trimethylolpropane, diglycerin, triglycerin, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, tris(2-hydroxyethyl)isocyanuric acid, sorbitol, and mannitol; polylactone polyol compounds obtained by adding lactone compounds such as ε-caprolactone to these trihydric or higher alcohols; and fatty acid esters of glycerin.

[0173] Furthermore, alcohol components other than the polyhydric alcohols mentioned above can also be used. Such alcohol components are not particularly limited and include, for example, monoalcohols such as methanol, ethanol, propyl alcohol, butyl alcohol, stearyl alcohol, and 2-phenoxyethanol; and alcohol compounds obtained by reacting monoepoxy compounds such as propylene oxide, butylene oxide, and "Cardura E10P" (trade name, manufactured by HEXION, a glycidyl ester of a synthetic highly branched saturated fatty acid) with an acid.

[0174] The method for producing hydroxyl group-containing polyester resin is not particularly limited and can be carried out according to conventional methods. For example, hydroxyl group-containing polyester resin can be produced by heating the acid component and the alcohol component in a nitrogen stream at approximately 150 to 250°C for approximately 5 to 10 hours to carry out an esterification reaction or transesterification reaction between the acid component and the alcohol component.

[0175] When carrying out the esterification or transesterification reaction of the above acid and alcohol components, they may be added to the reaction vessel all at once, or one or both may be added in several stages. Alternatively, a hydroxyl group-containing polyester resin may be synthesized first, and then the obtained hydroxyl group-containing polyester resin may be reacted with an acid anhydride to perform half-esterification to obtain a carboxyl group and hydroxyl group-containing polyester resin. Alternatively, a carboxyl group-containing polyester resin may be synthesized first, and then the above alcohol component may be added to obtain a hydroxyl group-containing polyester resin.

[0176] In the aforementioned esterification or transesterification reaction, known catalysts such as dibutyltin oxide, antimony trioxide, zinc acetate, manganese acetate, cobalt acetate, calcium acetate, lead acetate, tetrabutyl titanate, and tetraisopropyl titanate can be used as catalysts to accelerate the reaction.

[0177] Furthermore, the hydroxyl group-containing polyester resin can be modified with fatty acids, monoepoxy compounds, polyisocyanate compounds, acrylic resins, etc., during or after the preparation of the resin.

[0178] Examples of the above fatty acids include coconut oil fatty acids, cottonseed oil fatty acids, hemp seed oil fatty acids, rice bran oil fatty acids, fish oil fatty acids, tall oil fatty acids, soybean oil fatty acids, linseed oil fatty acids, tung oil fatty acids, rapeseed oil fatty acids, castor oil fatty acids, dehydrated castor oil fatty acids, and safflower oil fatty acids. As for the above monoepoxy compound, for example, "Cardura E10P" (trade name, manufactured by HEXION, a glycidyl ester of synthetic highly branched saturated fatty acids) can be suitably used.

[0179] Furthermore, examples of the polyisocyanate compounds include aliphatic diisocyanate compounds such as lysine diisocyanate, hexamethylene diisocyanate, and trimethylhexane diisocyanate; and lipid diisocyanate compounds such as hydrogenated xylylene diisocyanate, isophorone diisocyanate, methylcyclohexane-2,4-diisocyanate, methylcyclohexane-2,6-diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), and 1,3-(isocyanatomethyl)cyclohexane. Examples include cyclic diisocyanate compounds; aromatic diisocyanate compounds such as tolylene diisocyanate, xylylene diisocyanate, and diphenylmethane diisocyanate; organic polyisocyanates themselves, such as trivalent or higher polyisocyanates like lysine triisocyanate; adducts of these organic polyisocyanates with polyhydric alcohols, low molecular weight polyester resins, water, etc.; and cyclized polymers (e.g., isocyanurates) and biuret-type adducts of these organic polyisocyanates. These polyisocyanate compounds can be used individually or in combination of two or more.

[0180] Furthermore, known methods can be used to modify the hydroxyl group-containing polyester resin with acrylic resin. Examples include polymerizing a mixture of a polymerizable unsaturated group-containing polyester resin and a polymerizable unsaturated monomer, or reacting the hydroxyl group-containing polyester resin and the acrylic resin together.

[0181] The hydroxyl group-containing polyester resin (D') preferably has a hydroxyl value of 1 to 250 mgKOH / g, more preferably 2 to 200 mgKOH / g, and even more preferably 5 to 180 mgKOH / g.

[0182] Furthermore, if the hydroxyl group-containing polyester resin (D') also has carboxyl groups, its acid value is preferably 1 to 150 mg KOH / g, more preferably 2 to 100 mg KOH / g, and even more preferably 2 to 80 mg KOH / g.

[0183] Furthermore, the number-average molecular weight of the hydroxyl group-containing polyester resin (D') is preferably 500 to 50,000, more preferably 800 to 30,000, and even more preferably 1,000 to 10,000.

[0184] When the aqueous coating composition contains the above-mentioned hydroxyl group-containing polyester resin (D'), the content of the hydroxyl group-containing polyester resin (D') is preferably 2 to 70% by mass, more preferably 5 to 50% by mass, and even more preferably 10 to 40% by mass, based on the amount of resin solids in the aqueous coating composition.

[0185] Hardener (E) The curing agent (E) is a compound that reacts with the crosslinkable functional groups in the acrylic resin (C) and polyester resin (D) to cure the aqueous coating composition. The curing agent (E) can be used alone or in combination of two or more types.

[0186] Examples of curing agents (E) include amino resins, polyisocyanate compounds, blocked polyisocyanate compounds, epoxy group-containing compounds, carboxyl group-containing compounds, carbodiimide group-containing compounds, hydrazide group-containing compounds, and semicarbazide group-containing compounds.

[0187] In particular, from the viewpoint of water resistance, chipping resistance, and adhesion of the formed coating film, as well as storage stability of the resulting aqueous coating composition, amino resins (E1), polyisocyanate compounds (E2), and blocked polyisocyanate compounds (E3) that can react with hydroxyl groups, and carbodiimide group-containing compounds that can react with carboxyl groups are preferred, amino resins (E1), polyisocyanate compounds (E2), and blocked polyisocyanate compounds (E3) are more preferred, and amino resins (E1) and blocked polyisocyanate compounds (E3) are particularly preferred.

[0188] As the above amino resin (E1), a partially methylolated amino resin or a fully methylolated amino resin obtained by the reaction of an amino component and an aldehyde component can be used. Examples of amino components include melamine, urea, benzoguanamine, acetoganaamine, steroguanamine, spiloganamine, and dicyandiamide. Examples of aldehyde components include formaldehyde, paraformaldehyde, acetaldehyde, and benzaldehyde.

[0189] Furthermore, a methylolated amino resin can also be used in which the methylol group has been partially or completely etherified with a suitable alcohol. Examples of alcohols that can be used for etherification include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, 2-ethyl-1-butanol, and 2-ethyl-1-hexanol.

[0190] As the amino resin, melamine resin is preferred. Particularly preferred are methyl etherified melamine resins, in which the methylol groups of a partially or completely methylolated melamine resin are partially or completely etherified with methyl alcohol; butyl etherified melamine resins, in which the methylol groups of a partially or completely methylolated melamine resin are partially or completely etherified with butyl alcohol; and methyl-butyl mixed etherified melamine resins, in which the methylol groups of a partially or completely methylolated melamine resin are partially or completely etherified with methyl alcohol and butyl alcohol. Methyl-butyl mixed etherified melamine resin is more preferred.

[0191] The melamine resin described above preferably has a weight-average molecular weight of 400 to 6,000, more preferably 500 to 4,000, and even more preferably 600 to 3,000.

[0192] Commercially available melamine resins can be used. Examples of commercially available product names include "Cymel 202", "Cymel 203", "Cymel 238", "Cymel 250", "Cymel 251", "Cymel 303", "Cymel 323", "Cymel 324", "Cymel 325", "Cymel 327", "Cymel 350", "Cymel 385", "Cymel 1156", "Cymel 1158", "Cymel 1116", "Cymel 1130" (all manufactured by Ornex Japan Co., Ltd.), "Uban 120", "Uban 20HS", "Uban 20SE60", "Uban 2021", "Uban 2028", and "Uban 28-60" (all manufactured by Mitsui Chemicals, Inc.).

[0193] When the aqueous paint composition contains the above-mentioned melamine resin, the aqueous paint composition may contain, as a curing catalyst, a sulfonic acid such as p-toluenesulfonic acid, dodecylbenzenesulfonic acid, or dinonylnaphthalenesulfonic acid; a neutralized salt of the sulfonic acid with an amine; or a neutralized salt of a phosphate ester compound with an amine.

[0194] The polyisocyanate compound (E2) is a compound having at least two isocyanate groups in one molecule, and examples include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic aliphatic polyisocyanates, aromatic polyisocyanates, and derivatives of said polyisocyanates.

[0195] Examples of the above aliphatic polyisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, diisocyanate dimer, and methyl 2,6-diisocyanatohexanoate (common name: lysine). Examples include aliphatic diisocyanates such as diisocyanates; and aliphatic triisocyanates such as 2-isocyanatoethyl 2,6-diisocyanatohexanoate, 1,6-diisocyanato-3-isocyanatomethylhexane, 1,4,8-triisocyanatooctane, 1,6,11-triisocyanatoundecane, 1,8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-triisocyanatohexane, and 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyloctane.

[0196] Examples of the alicyclic polyisocyanates include 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (common name: isophorone diisocyanate), 4-methyl-1,3-cyclohexylene diisocyanate (common name: hydrogenated TDI), and 2-methyl-1,3-cyclohexylene diisocyanate. Alicyclic diisocyanates such as nate, 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane (common name: hydrogenated xylylene diisocyanate) or mixtures thereof, methylenebis(4,1-cyclohexanediyl) diisocyanate (common name: hydrogenated MDI), norbornane diisocyanate; 1,3,5-triisocyanatocyclohexane, 1,3,5-trimethylisocyanatocyclohexane, 2-(3-isocyanatopropyl)- 2,5-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 2-(3-isocyanatopropyl)-2,6-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 3-(3-isocyanatopropyl)-2,5-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, 6-(2-iso Examples include alicyclic triisocyanates such as cyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, and 6-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane.

[0197] Examples of the aforementioned aromatic aliphatic polyisocyanates include aromatic aliphatic diisocyanates such as methylenebis(4,1-phenylene) diisocyanate (common name: MDI), 1,3- or 1,4-xylylene diisocyanate or mixtures thereof, ω,ω'-diisocyanato-1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanato-1-methylethyl)benzene (common name: tetramethylxylylene diisocyanate) or mixtures thereof; and aromatic aliphatic triisocyanates such as 1,3,5-triisocyanatomethylbenzene.

[0198] Examples of the aromatic polyisocyanates include aromatic diisocyanates such as m-phenylenediisocyanate, p-phenylenediisocyanate, 4,4'-diphenyldiisocyanate, 1,5-naphthalenediisocyanate, 2,4-tolylenediisocyanate (common name: 2,4-TDI) or 2,6-tolylenediisocyanate (common name: 2,6-TDI) or mixtures thereof, 4,4'-toluidinediisocyanate, and 4,4'-diphenyletherdiisocyanate; aromatic triisocyanates such as triphenylmethane-4,4',4''-triisocyanate, 1,3,5-triisocyanatobenzene, and 2,4,6-triisocyanatotoluene; and aromatic tetraisocyanates such as 4,4'-diphenylmethane-2,2',5,5'-tetraisocyanate.

[0199] Furthermore, examples of derivatives of the polyisocyanate include dimers, trimers, biuret, allophanate, uretodione, uretoimine, isocyanurate, oxadiazinetrione, polymethylene polyphenyl polyisocyanate (crude MDI, polymeric MDI), crude TDI, and the like.

[0200] The polyisocyanates and their derivatives may be used individually or in combination of two or more. Among these polyisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and their derivatives are preferred.

[0201] Furthermore, as the polyisocyanate compound, a prepolymer obtained by reacting the above-mentioned polyisocyanate and its derivatives with a compound that can react with the polyisocyanate under conditions of excess isocyanate groups may be used. Examples of compounds that can react with the polyisocyanate include compounds having active hydrogen groups such as hydroxyl groups and amino groups, and specifically, for example, polyhydric alcohols, low molecular weight polyester resins, amines, water, etc. can be used.

[0202] Furthermore, as the polyisocyanate compound, a polymer of an isocyanate group-containing polymerizable unsaturated monomer, or a copolymer of the isocyanate group-containing polymerizable unsaturated monomer and a polymerizable unsaturated monomer other than the isocyanate group-containing polymerizable unsaturated monomer may be used.

[0203] The blocked polyisocyanate compound (E3) is a compound obtained by blocking the isocyanate group of the polyisocyanate compound (E2) with a blocking agent.

[0204] Examples of the above-mentioned blocking agents include phenols such as phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxydiphenyl, butylphenol, isopropylphenol, nonylphenol, octylphenol, and methyl hydroxybenzoate; lactams such as ε-caprolactam, δ-valerolactam, γ-butyrolactam, and β-propiolactam; aliphatic alcohols such as methanol, ethanol, propyl alcohol, butyl alcohol, amyl alcohol, and lauryl alcohol; ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, and methoxymethanol; benzyl alcohol, glycolic acid, methyl glycolate, ethyl glycolate, butyl glycolate, lactic acid, methyl lactate, ethyl lactate, butyl lactate, methylolurea, methylolmelamine, diacetone alcohol, 2-hydroxyethyl acrylate, and 2-hydroxyethyl acrylate. Alcohol-based compounds such as droxyethyl methacrylate; oxime-based compounds such as formamide oxime, acetamide oxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, and cyclohexane oxime; active methylene-based compounds such as dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, and acetylacetone; butyl mercaptan, t-butyl mercaptan, hexyl mercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, and methylthiophenone. Mercaptan-based compounds such as ethylthiophenol; acid amide-based compounds such as acetanilide, acetanisidide, acetotoluid, acrylamide, methacrylamide, acetic acid amide, stearic acid amide, and benzamide; imide-based compounds such as succinimide, phthalimide, and maleimide; amine-based compounds such as diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine, and butylphenylamine; imidazole-based compounds such as imidazole and 2-ethylimidazole;Examples of azole compounds include urea-based compounds such as urea, thiourea, ethyleneurea, ethylenethiourea, and diphenylurea; carbamic acid ester compounds such as phenyl N-phenylcarbamate; imine-based compounds such as ethyleneimine and propyleneimine; sulfite-based compounds such as sodium bisulfite and potassium bisulfite; and azole compounds. Examples of the above-mentioned azole compounds include pyrazoles or pyrazole derivatives such as pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3,5-dimethylpyrazole, and 3-methyl-5-phenylpyrazole; imidazoles or imidazole derivatives such as imidazole, benzimidazole, 2-methylimidazole, 2-ethylimidazole, and 2-phenylimidazole; and imidazoline derivatives such as 2-methylimidazoline and 2-phenylimidazoline.

[0205] Among these, preferred blocking agents include active methylene-based blocking agents, pyrazoles, or pyrazole derivatives.

[0206] When performing the blocking reaction (reacting with the blocking agent), a solvent may be added as needed. Suitable solvents for the blocking reaction are those that are not reactive with isocyanate groups. Examples include acetone, ketones such as methyl ethyl ketone, esters such as ethyl acetate, and solvents such as N-methyl-2-pyrrolidone (NMP).

[0207] Furthermore, as the blocking agent, hydroxycarboxylic acids having one or more hydroxyl groups and one or more carboxyl groups, such as hydroxypivalic acid and dimethylolpropionic acid, can also be used. In particular, a blocked polyisocyanate compound obtained by blocking the isocyanate group with the above-mentioned hydroxycarboxylic acid and then neutralizing the carboxyl group of the hydroxycarboxylic acid to impart water dispersibility can be suitably used.

[0208] Each of the above hardening agents (E) can be used individually or in combination of two or more types.

[0209] If the aqueous paint composition contains the curing agent (E), the content of the curing agent (E) is preferably 1 to 50% by mass, more preferably 5 to 45% by mass, and even more preferably 10 to 40% by mass, based on the amount of resin solids in the aqueous paint composition.

[0210] Other ingredients The aqueous coating composition of the present invention may further contain, if necessary, resins other than acrylic urethane composite resin (AB), acrylic resin (C), polyester resin (D), and curing agent (E), pigments, organic solvents, curing catalysts, dispersants, anti-settling agents, defoaming agents, thickeners, ultraviolet absorbers, light stabilizers, surface modifiers, etc.

[0211] Examples of resins other than the acrylic urethane composite resin (AB), acrylic resin (C), polyester resin (D), and curing agent (E) mentioned above include acrylic urethane composite resins other than acrylic urethane composite resin (AB), polyurethane resins, polyolefin resins, epoxy resins, and the like.

[0212] Examples of the above-mentioned pigments include coloring pigments, extender pigments, and luminosity pigments. These pigments can be used individually or in combination of two or more types.

[0213] When the aqueous coating composition of the present invention contains the above-mentioned pigment, the amount of the pigment is preferably in the range of 0.1 to 200 parts by mass, more preferably in the range of 1 to 150 parts by mass, and even more preferably in the range of 3 to 120 parts by mass, based on 100 parts by mass of resin solids in the aqueous coating composition.

[0214] Examples of the above-mentioned coloring pigments include titanium dioxide, zinc oxide, carbon black, molybdenum red, Prussian blue, cobalt blue, azo pigments, phthalocyanine pigments, quinacridone pigments, isoindoline pigments, surene pigments, perylene pigments, dioxazine pigments, and diketopyrrolopyrrole pigments. Among these, titanium dioxide and carbon black can be preferably used.

[0215] When the aqueous paint composition contains the above-mentioned coloring pigment, the amount of the coloring pigment is preferably in the range of 1 to 180 parts by mass, more preferably in the range of 5 to 150 parts by mass, and even more preferably in the range of 15 to 130 parts by mass, based on 100 parts by mass of resin solids in the aqueous paint composition.

[0216] Examples of the extender pigments include barium sulfate, talc, clay, kaolin, barium carbonate, calcium carbonate, silica, and alumina white. From the viewpoint of paint stability and finish, barium sulfate and talc can be suitably used as the extender pigment.

[0217] When the aqueous paint composition contains the above-mentioned extender pigment, the amount of the extender pigment is preferably in the range of 1 to 180 parts by mass, more preferably in the range of 5 to 140 parts by mass, and even more preferably in the range of 10 to 120 parts by mass, based on 100 parts by mass of resin solids in the aqueous paint composition.

[0218] Examples of the luminous pigments include aluminum (including vapor-deposited aluminum), copper, zinc, brass, nickel, glass flakes, aluminum oxide, mica, aluminum oxide coated with titanium oxide and / or iron oxide, and mica coated with titanium oxide and / or iron oxide. Among these, aluminum pigments are preferred. Aluminum pigments include non-leafing aluminum pigments and leafing aluminum pigments, and either can be used.

[0219] The above-mentioned lustrous pigment is preferably in the form of flakes. Furthermore, suitable lustrous pigments have a longitudinal dimension in the range of 1 to 100 μm, particularly 5 to 40 μm, and a thickness in the range of 0.001 to 5 μm, particularly 0.01 to 2 μm.

[0220] When the aqueous paint composition contains the above-mentioned luminous pigment, the amount of the luminous pigment is preferably in the range of 0.1 to 100 parts by mass, more preferably in the range of 1 to 50 parts by mass, and even more preferably in the range of 3 to 25 parts by mass, based on 100 parts by mass of resin solids in the aqueous paint composition.

[0221] Examples of the aforementioned organic solvents include ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ester solvents such as ethyl acetate, butyl acetate, methyl benzoate, ethyl ethoxypropionate, ethyl propionate, and methyl propionate; alcohol solvents such as isopropanol, n-butanol, isobutanol, and 2-ethylhexanol; ether solvents such as tetrahydrofuran, dioxane, and dimethoxyethane; glycol ether solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, and 3-methoxybutyl acetate; aromatic hydrocarbon solvents, aliphatic hydrocarbon solvents, and the like.

[0222] Water-based paint compositions can be applied by diluting them with water and / or organic solvents as needed and adjusting them to an appropriate viscosity.

[0223] The appropriate viscosity varies depending on the paint composition, but for example, the viscosity measured at 20°C using a B-type viscometer after 1 minute at 60 rpm (sometimes referred to as the "B60 value" in this specification) is preferably in the range of 100 to 3000 mPa·s, more preferably in the range of 300 to 2000 mPa·s, and even more preferably in the range of 500 to 1500 mPa·s, from the viewpoint of the storage stability of the resulting paint composition. The viscometer used in this case is the "LVDV-I" (product name, manufactured by Brookfield, a B-type viscometer).

[0224] Furthermore, in the above, the concentration of coating solids in the aqueous coating composition is usually preferably about 5 to 70% by mass, more preferably about 10 to 55% by mass.

[0225] The water-based paint composition may be either a one-component paint or a multi-component paint, but a one-component paint is preferred from the viewpoint of having no paint mixing process and having excellent productivity, as well as simplifying the maintenance of painting machinery.

[0226] Furthermore, when the acrylic urethane composite resin (AB) of the present invention is used as a component of an aqueous paint composition, the reason why the acrylic urethane composite resin (AB) exhibits excellent storage stability despite containing soft components is presumed to be as follows: The acrylic urethane composite resin (AB) of the present invention contains a compound (a2-1) having two or more hydroxyl groups and one or more polymerizable unsaturated groups as a component of the urethane resin portion (A). By copolymerizing the polymerizable unsaturated groups of the side chains of the urethane resin portion (A) with a compound (b1) having one polymerizable unsaturated group and no hydroxyl group or having one hydroxyl group, and a compound (b2) having two or more polymerizable unsaturated groups and no hydroxyl group or having one hydroxyl group, an acrylic urethane composite resin (AB) with a high crosslink density can be obtained, which is presumed to result in less swelling in aqueous solvents and excellent storage stability.

[0227] [Method for forming multi-layer coatings] The aqueous coating composition of the present invention is produced by the following steps (1) to (3): Step (1): A step of applying an aqueous paint composition to the object to be coated to form a base coat film. Step (2): A step of applying a clear coat coating composition onto the base coat coating formed in step (1) to form a clear coat coating, and, Step (3): A step of simultaneously heating and curing the base coat film formed in step (1) and the clear coat film formed in step (2). It can be suitably used as an aqueous coating composition in a multi-layer coating film formation method that includes [the specified element].

[0228] Examples of objects to be coated include the exterior and interior panels of automobile bodies such as passenger cars, trucks, motorcycles, and buses; automobile parts; and the exterior panels of household electrical appliances such as mobile phones and audio equipment. Of these, the exterior and interior panels of automobile bodies and automobile parts are preferred.

[0229] The materials of these objects to be coated are not particularly limited. Examples include metallic materials such as iron, aluminum, brass, copper, tinplate, stainless steel, galvanized steel, and zinc alloy (Zn-Al, Zn-Ni, Zn-Fe, etc.) plated steel; plastic materials such as polyethylene resin, polypropylene resin, acrylonitrile-butadiene-styrene (ABS) resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, epoxy resin, and various types of FRP; inorganic materials such as glass, cement, and concrete; wood; and fibrous materials such as paper and cloth. Of these, metallic and plastic materials are preferred.

[0230] Furthermore, the surfaces to which the coating film is applied may include metal surfaces such as the outer and inner panels of automobile bodies, automobile parts, household electrical appliances, and metal substrates such as steel plates that make up these, which may have undergone surface treatments such as phosphate treatment, chromate treatment, or composite oxide treatment.

[0231] A coating film may be formed on an object that has been surface-treated or not. For example, the substrate (the object to be coated) may be surface-treated as needed, and then a primer coating film may be formed on it. If the object to be coated is an automobile body, for example, this primer coating film can be formed using a primer paint that is known and commonly used in automobile body painting.

[0232] In particular, it is preferable that the object to be coated is a metal substrate which may or may not have undergone surface treatment, and that an undercoat film is formed on it using an electrodeposition paint, preferably a cationic electrodeposition paint. It is even more preferable that the undercoat film formed by the electrodeposition paint, preferably a cationic electrodeposition paint, is heat-cured.

[0233] If the object to be coated has a primer coat applied, an intermediate coating may be formed on top of it. This intermediate coating can be formed, for example, if the object to be coated is an automobile body, using a known intermediate coating paint that is commonly used in automobile body painting. This intermediate coating may or may not be heat-cured.

[0234] The aqueous coating composition can be applied to the object to be coated by known methods, such as air spray coating, airless spray coating, rotary atomization coating, and curtain coating, and electrostatic application may be performed during coating. Of these, air spray coating and rotary atomization coating are preferred. Furthermore, such coating methods can be carried out in one to several stages until the desired film thickness is obtained.

[0235] The amount of the above aqueous coating composition applied is preferably such that the cured film thickness of the formed base coat is 5 to 40 μm, more preferably 7 to 35 μm, and even more preferably 10 to 30 μm.

[0236] Any thermosetting clear coating composition known for use in painting automobile bodies and the like can be used as the clear coat coating composition. Examples of such thermosetting clear coating compositions include organic solvent-type thermosetting coating compositions containing a base resin having crosslinkable functional groups and a curing agent, aqueous thermosetting coating compositions, and powder thermosetting coating compositions. Among these, organic solvent-type thermosetting coating compositions containing a base resin having crosslinkable functional groups and a crosslinking agent are preferred from the viewpoint of the finished appearance of the multi-layer coating film that is formed.

[0237] Examples of crosslinkable functional groups in the above-mentioned base resin include carboxyl groups, hydroxyl groups, epoxy groups, and silanol groups. Examples of base resin types include acrylic resins, polyester resins, alkyd resins, urethane resins, epoxy resins, and fluororesins. Examples of curing agents include polyisocyanate compounds, blocked polyisocyanate compounds, melamine resins, urea resins, carboxyl group-containing compounds, carboxyl group-containing resins, epoxy group-containing resins, and epoxy group-containing compounds.

[0238] Preferred combinations of base resin / curing agent for the above clear coat coating composition include hydroxyl group-containing resin / polyisocyanate compound, carboxyl group-containing resin / epoxy group-containing resin, hydroxyl group-containing resin / blocked polyisocyanate compound, and hydroxyl group-containing resin / melamine resin, with hydroxyl group-containing resin / polyisocyanate compound being more preferred.

[0239] Furthermore, the above-mentioned clear coat paint composition may be a one-component paint or a multi-component paint such as a two-component urethane resin paint.

[0240] Furthermore, the above clear coat paint composition may contain, if necessary, coloring pigments, luminescence pigments, dyes, etc., to an extent that does not impair transparency, and may also contain, as appropriate, extender pigments, ultraviolet absorbers, light stabilizers, defoamers, thickeners, rust inhibitors, surface modifiers, etc.

[0241] The method of applying the clear coat coating composition is not particularly limited, but a wet coating can be formed by coating methods such as air spray coating, airless spray coating, rotary atomization coating, and curtain coating. Electrostatic application may be performed as needed in these coating methods. Of these, air spray coating or rotary atomization coating is particularly preferred. The amount of clear coating composition applied is usually preferably an amount that results in a cured film thickness of 10 to 70 μm, and more preferably an amount that results in a cured film thickness of 20 to 50 μm.

[0242] Furthermore, when performing air spray painting, airless spray painting, or rotary atomization painting, it is preferable to adjust the viscosity of the clear coating composition using an organic solvent or other solvent to a viscosity range suitable for the painting method, typically a viscosity range of about 15 to 60 seconds at 20°C, and particularly about 20 to 50 seconds, using a Ford Cup No. 4 viscometer.

[0243] The heating can be carried out by known means, for example, by drying furnaces such as hot air furnaces, electric furnaces, and infrared induction heating furnaces. The heating temperature is preferably in the range of 60 to 180°C, more preferably in the range of 70 to 170°C, and even more preferably in the range of 80 to 160°C. The heating time is not particularly limited, but is preferably in the range of 10 to 90 minutes, and more preferably in the range of 20 to 60 minutes.

[0244] In the multilayer coating film forming method of the present invention, when acrylic urethane composite resin (AB) is used as a component of the aqueous coating composition, the reason why the coating film formed from the aqueous coating composition exhibits excellent chipping resistance despite the high crosslinking density of the acrylic urethane composite resin (AB) is presumed to be because the urethane resin portion contains flexible polytetramethylene ether glycol, which mitigates the impact of flying stones and thus provides excellent chipping resistance. [Examples]

[0245] The present invention will be described in more detail below with reference to manufacturing 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 film thickness of the coating is based on the cured coating.

[0246] Manufacturing of acrylic urethane composite resin (AB') Example 1 In a reaction vessel equipped with a thermometer, thermostat, stirrer, and reflux condenser, 43.8 parts of n-butyl acrylate, 2.0 parts of allyl methacrylate, 24.0 parts of "PTMG3000" (trade name, manufactured by Mitsubishi Chemical Corporation, polytetramethylene ether glycol, molecular weight 3000), 0.3 parts of 1,4-cyclohexanedimethanol, 1.3 parts of "Bremmer GLM" (trade name, manufactured by NOF Corporation, glycerin monomethacrylate), 6.1 parts of dimethylolpropionic acid, 0.025 parts of p-methoxyphenol (polymerization inhibitor for unsaturated groups), and 0.004 parts of "Neostan U-600" (trade name, manufactured by Nitto Chemical Co., Ltd., bismuth-based catalyst) were charged. The mixture was heated to 80°C while stirring in an air stream, and then 8.6 parts of isophorone diisocyanate and 8.8 parts of dicyclohexylmethane-4,4'-diisocyanate were added dropwise over 30 minutes. The mixture was then heated to 100°C and reacted while maintaining the temperature until the free isocyanate group content was 13.4% or less. Next, 5.1 parts of 2-hydroxyethyl methacrylate were added and reacted until the free isocyanate group content was 2.0% or less, and then cooled to room temperature to obtain a diluted solution of acrylic monomer for a polyurethane prepolymer having acidic groups and terminal unsaturated groups.

[0247] Next, 3.6 parts of dimethylethanolamine and 127.8 parts of deionized water were added dropwise to the diluted acrylic monomer solution of the polyurethane prepolymer obtained above over a period of 60 minutes.

[0248] Next, the mixture was heated to 70°C while stirring in a nitrogen atmosphere. A polymerization initiator solution, prepared by dissolving 0.15 parts of "VA-057" (product name, manufactured by Wako Pure Chemical Industries, Ltd., polymerization initiator, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamide]) in 4.6 parts of deionized water, was added dropwise over 30 minutes. The mixture was then stirred for 3 hours to carry out the polymerization reaction of the acrylic resin components (polymerizable unsaturated groups). During this time, the temperature was controlled as needed.

[0249] The mixture was then cooled to room temperature, and the concentration was adjusted with deionized water to obtain an aqueous dispersion of acrylic urethane composite resin (AB'-1) having a core-shell structure consisting of a shell made of urethane resin and a core made of acrylic resin. The dispersion had a solid content of 40%, an acid value of 25 mg KOH / g, and an average particle size of 120 nm (measured at 20°C after dilution with deionized water using a dynamic light scattering particle size distribution analyzer "ELSZ-2000" (product name, manufactured by Otsuka Electronics Co., Ltd.)).

[0250] Examples 2-19, Comparative Examples 1-5 In Production Example 1, acrylic urethane composite resins (AB'-2) to (AB'-19) and (AB'-21) to (AB'-25) were obtained in the same manner as in Production Example 1, except that the compound composition was as shown in Table 1 below.

[0251] Example 20 In a reaction vessel equipped with a thermometer, thermostat, stirrer, and reflux condenser, 42.8 parts n-butyl acrylate, 2.0 parts allyl methacrylate, 25.0 parts "PTMG3000" (trade name, manufactured by Mitsubishi Chemical Corporation, polytetramethylene ether glycol, molecular weight 3000), 0.3 parts 1,4-cyclohexanedimethanol, 1.3 parts "Bremmer GLM" (trade name, manufactured by NOF Corporation, glycerin monomethacrylate), 5.9 parts dimethylolpropionic acid, 0.025 parts p-methoxyphenol (polymerization inhibitor for unsaturated groups), and 0.004 parts "Neostan U-600" (trade name, manufactured by Nitto Chemical Co., Ltd., bismuth-based catalyst) were charged. The mixture was heated to 80°C while stirring in an air stream, and then 8.6 parts isophorone diisocyanate and 8.6 parts dicyclohexylmethane-4,4'-diisocyanate were added dropwise over 30 minutes. The temperature was then raised to 100°C and the reaction was continued until the content of retained free isocyanate groups was 13.4% or less. Next, the mixture was cooled to room temperature, and 5.0 parts of 2-hydroxyethyl methacrylate were added to obtain a diluted solution of acrylic monomer for a polyurethane prepolymer having acid groups and isocyanate groups.

[0252] Next, 2.4 parts of dimethylethanolamine and 127.8 parts of deionized water were added dropwise to the diluted acrylic monomer solution of the polyurethane prepolymer obtained above over 60 minutes. After emulsification, 7.4 parts of a 5% ethylenediamine aqueous solution were added dropwise over 15 minutes to carry out the chain extension reaction.

[0253] Next, the mixture was heated to 70°C while stirring in a nitrogen atmosphere. A polymerization initiator solution, prepared by dissolving 0.15 parts of "VA-057" (product name, manufactured by Wako Pure Chemical Industries, Ltd., polymerization initiator, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamide]) in 4.6 parts of deionized water, was added dropwise over 30 minutes. The mixture was then stirred for 3 hours to carry out the polymerization reaction of the acrylic resin components (polymerizable unsaturated groups). During this time, the temperature was controlled as needed.

[0254] The mixture was then cooled to room temperature, and the concentration was adjusted with deionized water to obtain an aqueous dispersion of acrylic urethane composite resin (AB'-20) having a core-shell structure consisting of a shell made of urethane resin and a core made of acrylic resin. The dispersion had a solid content of 40%, an acid value of 25 mg KOH / g, and an average particle size of 140 nm (measured at 20°C after dilution with deionized water using a dynamic light scattering particle size distribution analyzer "ELSZ-2000" (product name, manufactured by Otsuka Electronics Co., Ltd.)).

[0255] [Table 1]

[0256] [Table 2]

[0257] [Table 3]

[0258] [Table 4]

[0259] The components listed in the table are as follows: (Note 1) "Epoxy Ester 70PA": Trade name, manufactured by Kyoeisha, acrylic acid adduct of propylene glycol diglycidyl ether, (Note 2) "Epoxy Ester 200PA": Trade name, manufactured by Kyoeisha, an acrylic acid adduct of tripropylene glycol diglycidyl ether. (Note 3) "PTMG2000": Product name, manufactured by Mitsubishi Chemical Corporation, polytetramethylene ether glycol, molecular weight 2000. (Note 4) "PTMG1000": Product name, manufactured by Mitsubishi Chemical Corporation, polytetramethylene ether glycol, molecular weight 1000. (Note 5) "Sannix PP-2000": Product name, manufactured by Sanyo Chemical Industries, Ltd., polypropylene glycol, molecular weight 2000) (Note 6) "PEG #600": Trade name, manufactured by NOF Corporation, polyethylene glycol, molecular weight 600, (Note 7) "ETERNACOLL UH-200": Trade name, manufactured by Ube Industries, polycarbonate diol, molecular weight 2000, (Note 8) "Kuraray Polyol C-3090": Trade name, manufactured by Kuraray Co., Ltd., polycarbonate diol, molecular weight 3000.

[0260] Production of hydroxyl group-containing acrylic resin (C') Production Example 1 Into a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, nitrogen inlet tube, and dropping device, 120 parts of deionized water and 0.8 parts of "ADEKA Raysoap SR-1025" (trade name, manufactured by ADEKA Corporation, emulsifier, active ingredient 25%) were charged, stirred and mixed under a nitrogen stream, and the temperature was raised to 80°C.

[0261] Next, 5% of the total amount of the following monomer emulsion for the core part and 2.5 parts of a 6% aqueous ammonium persulfate solution were introduced into the reaction vessel and held at 80°C for 15 minutes. Then, the remainder of the monomer emulsion for the core part was dropped into the reaction vessel maintained at the same temperature over three hours, and aging was carried out for 1 hour after the dropping was completed. Next, the following monomer emulsion for the shell part was dropped over 1 hour, aged for 1 hour, and then cooled to 30°C while gradually adding 3.8 parts of a 5% aqueous 2-(dimethylamino)ethanol solution to the reaction vessel, and discharged while filtering through a 100-mesh nylon cloth to obtain a hydroxyl group-containing acrylic resin (C'-1) particle dispersion with an average particle diameter of 100 nm and a solid content of 30%. The obtained hydroxyl group-containing acrylic resin particles had an acid value of 17.2 mgKOH / g and a hydroxyl value of 27.2 mgKOH / g.

[0262] Monomer emulsion for the core part: 54 parts of deionized water, 3.1 parts of "ADEKA Raysoap SR-1025", 1 part of allyl methacrylate, 10 parts of styrene, 35 parts of n-butyl acrylate, 10 parts of methyl methacrylate, 20 parts of ethyl acrylate, and 1 part of 2-hydroxyethyl methacrylate were mixed and stirred to obtain a monomer emulsion for the core part.

[0263] A monomer emulsion for the shell was obtained by mixing and stirring 50 parts of deionized water, 1.8 parts of "Adekaria Soap SR-1025", 0.04 parts of ammonium persulfate, 5.3 parts of 2-hydroxyethyl acrylate, 2.6 parts of methacrylic acid, 8 parts of ethyl acrylate, and 7.1 parts of methyl methacrylate.

[0264] Production of hydroxyl group-containing polyester resin (D') Manufacturing Example 2 In a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, and water separator, 126 parts trimesic acid, 1365 parts PTMG650 (trade name, manufactured by Mitsubishi Chemical Corporation, polytetramethylene ether glycol, molecular weight 650), and 37 parts glycerin were charged. The temperature was raised between 160°C and 230°C over 3 hours, and then the condensation reaction was carried out at 230°C until the final acid value reached 3 mg KOH / g. Next, to add carboxyl groups to the obtained condensation reaction product, 77 parts trimellitic anhydride were added and the reaction was carried out at 170°C for 30 minutes. Then, 0.5 equivalents of 2-(dimethylamino)ethanol were added relative to the acid groups, and the mixture was further diluted with 2-ethyl-1-hexanol to obtain a hydroxyl group-containing polyester resin (D'-1) solution with a solid content of 70%. The obtained hydroxyl group-containing polyester resin had an acid value of 32 mgKOH / g, a hydroxyl value of 117 mgKOH / g, a solids content of 70%, and a number-average molecular weight of 1200.

[0265] Production of blocked polyisocyanate compounds (E3) Manufacturing Example 3 In a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, nitrogen inlet tube, dropping device, and simple solvent removal trap, 360 parts of "Sumijoule N-3300," 60 parts of "Uniox M-550" (manufactured by NOF Corporation, polyethylene glycol monomethyl ether, average molecular weight approximately 550), and 0.2 parts of 2,6-di-tert-butyl-4-methylphenol were charged and thoroughly mixed, and heated at 130°C for 3 hours under a nitrogen stream. Next, 110 parts of ethyl acetate and 252 parts of diisopropyl malonate were charged, and while stirring under a nitrogen stream, 3 parts of a 28% methanol solution of sodium methoxide were added, and the mixture was stirred at 65°C for 8 hours. The amount of isocyanate in the resulting resin solution was 0.12 mol / kg. 683 parts of 4-methyl-2-pentanol were added to this, and the solvent was removed by distillation under reduced pressure for 3 hours while maintaining the system temperature at 80-85°C to obtain 1010 parts of the activated methylene-type blocked polyisocyanate compound (E3-1) solution. The simple solvent removal trap contained 95 parts of isopropanol. The solid content concentration of the obtained activated methylene-type blocked polyisocyanate compound (E3-1) solution was approximately 60%.

[0266] Production of phosphate group-containing dispersion resin (R) Manufacturing Example 4 A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, nitrogen inlet tube, and dropping device was filled with a mixed solvent of 27.5 parts methoxypropanol and 27.5 parts isobutanol, heated to 110°C, and 121.5 parts of a mixture consisting of 25 parts styrene, 27.5 parts n-butyl methacrylate, 20 parts isostearyl acrylate (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd., branched higher alkyl acrylate), 7.5 parts 4-hydroxybutyl acrylate, 15 parts phosphate-containing polymerizable unsaturated monomer (Note 1), 12.5 parts 2-methacryloyloxyethyl acid phosphate, 10 parts isobutanol, and 4 parts t-butyl peroxyoctanoate were added to the mixed solvent over 4 hours. A mixture consisting of 0.5 parts t-butyl peroxyoctanoate and 20 parts isopropanol was then added dropwise over 1 hour. After that, the mixture was stirred and aged for 1 hour to obtain a phosphate-containing dispersion resin (R-1) solution with a solid content of 50%. The acid value due to the phosphate group of this resin was 83 mgKOH / g, the hydroxyl value was 29 mgKOH / g, and the weight-average molecular weight was 10,000. (Note 1) Phosphate group-containing polymerizable unsaturated monomer: In a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, nitrogen inlet tube, and dropping device, 57.5 parts monobutyl phosphate and 41 parts isobutanol were added. After raising the temperature to 90°C, 42.5 parts glycidyl methacrylate were added dropwise over 2 hours, and the mixture was stirred and aged for another hour. Then, 59 parts isopropanol was added to obtain a phosphate group-containing polymerizable unsaturated monomer solution with a solid content of 50%. The acid value of the obtained monomer due to the phosphate group was 285 mgKOH / g.

[0267] Production of a luminous pigment dispersion (P) Manufacturing Example 5 In a stirring and mixing vessel, 19 parts (14 parts solids) of aluminum pigment paste "GX-180A" (trade name, manufactured by Asahi Kasei Metals, metal content 74%), 34.8 parts of 2-ethyl-1-hexanol, 10 parts (5 parts solids) of the phosphate group-containing dispersion resin (R-1) solution obtained in Production Example 4, and 0.2 parts of 2-(dimethylamino)ethanol were uniformly mixed to obtain a lustrous pigment dispersion (P-1).

[0268] Preparation of aqueous paint compositions Example 21 50 parts (20 parts solids) of acrylic urethane composite resin (AB'-1) obtained in Example 1, 100 parts (30 parts solids) of hydroxyl group-containing acrylic resin (C'-1) particle dispersion obtained in Production Example 1, 21.4 parts (15 parts solids) of hydroxyl group-containing polyester resin (D'-1) solution obtained in Production Example 2, 20 parts (20 parts solids) of "Cymel 350" (product name, manufactured by Mitsui Cytec Co., Ltd., methyl etherified melamine resin, weight-average molecular weight 550, solids 100%), and activated methylene type block resin obtained in Production Example 3 16.67 parts of polyisocyanate compound (E3-1) solution (10 parts solids) and 64 parts of the lustrous pigment dispersion (P-1) obtained in Production Example 5 (5 parts resin solids) were uniformly mixed. Further, "UH-752" (trade name, manufactured by ADEKA, thickener, solids concentration 28%), 2-(dimethylamino)ethanol, and deionized water were added to obtain aqueous paint composition No. 1 with a pH of 8.0, a solids concentration of 20%, and a viscosity of 800 mPa·s after 1 minute at 60 rpm measured with a B-type viscometer at 20°C.

[0269] Examples 22-40 and Comparative Examples 6-10 Water-based paint compositions No. 2 to No. 25 were obtained in the same manner as water-based paint composition No. 1 of Example 1, except that the paint composition was as shown in Table 2 below.

[0270] Storage stability test The storage stability of aqueous paint compositions No. 1 to 25 obtained in Examples 21 to 40 and Comparative Examples 6 to 10 was evaluated based on the viscosity measured at 60 rpm for 1 minute using an "LVDV-I" (product name, manufactured by Brookfield, a B-type viscometer), comparing the viscosity immediately after production with the percentage change in viscosity after standing at 40°C for 10 days. Viscosity change rate (%) = |(Viscosity after standing at 40°C for 10 days / Viscosity immediately after manufacturing) - 1| × 100 ◎ and ○ indicate a passing grade. The evaluation results are shown in Table 2. ◎: Viscosity change rate is less than 20%. ○: Viscosity change rate is 20% or more and less than 50%. ×: Viscosity change rate is 50% or more.

[0271]

Table 5

[0272]

Table 6

[0273]

Table 7

[0274]

Table 8

[0275] Preparation of test substrates Preparation of Test Specimen (O-1) Electrodeposition coating was performed on a cold-rolled steel sheet subjected to zinc phosphate conversion treatment with "Electron GT-10" (trade name, manufactured by Kansai Paint Co., Ltd., cationic electrodeposition paint) to a dry film thickness of 20 μm, and then heated at 170 °C for 30 minutes to cure the electrodeposition coating film, thereby preparing a test specimen (O-1).

[0276] Preparation of Test Specimen (O-2) Electrodeposition coating was performed on a cold-rolled steel sheet subjected to zinc phosphate conversion treatment with "Electron GT-10" (trade name, manufactured by Kansai Paint Co., Ltd., cationic electrodeposition paint) to a dry film thickness of 20 μm, and then heated and cured at 170 °C for 30 minutes to obtain an electrodeposition coating film. Next, an aqueous intermediate coating paint "WP-522H" (trade name, manufactured by Kansai Paint Co., Ltd., polyester resin - amino resin-based aqueous intermediate coating paint) was used to perform electrostatic coating with a rotary atomization type electrostatic coater to a cured film thickness of 30 μm, left for 5 minutes, and then preheated at 80 °C for 5 minutes to prepare a test specimen (O-2).

[0277] Preparation of test painted panels Example 41 Preparation of Test Coated Plate (S1) On the aforementioned test substrate (O-1), the aqueous paint composition No. 1 obtained in Example 21 was electrostatically coated using a rotary atomizing electrostatic coating machine to a cured film thickness of 15 μm, forming an uncured base coat film. After standing for 3 minutes, preheating at 80°C for 3 minutes, then "KINO6510" (product name, manufactured by Kansai Paint Co., Ltd., hydroxyl / isocyanate group curing type acrylic resin / urethane resin two-component organic solvent type clear coat paint) was electrostatically coated to a cured film thickness of 35 μm, forming an uncured clear coat film. After standing for 7 minutes, heating at 140°C for 30 minutes was performed to simultaneously bake the base coat film and the clear coat film, creating a test painted panel (S1-1).

[0278] Preparation of test painted board (S2) On the aforementioned test substrate (O-2), the aqueous paint composition No. 1 obtained in Example 21 was electrostatically coated using a rotary atomizing electrostatic coating machine to a cured film thickness of 15 μm, forming an uncured base coat film. After standing for 3 minutes, preheating at 80°C for 3 minutes was performed, and then "KINO6510" (product name, manufactured by Kansai Paint Co., Ltd., hydroxyl / isocyanate group curing type acrylic resin / urethane resin two-component organic solvent type clear coat paint) was electrostatically coated to a cured film thickness of 35 μm, forming an uncured clear coat film. After standing for 7 minutes, the intermediate coat film, base coat film, and clear coat film were simultaneously baked by heating at 140°C for 30 minutes to create a test painted panel (S2-1).

[0279] Examples 42-60, Comparative Examples 11-15 In Example 41, test coated panels (S1-2) to (S1-25) and (S2-2) to (S2-25) were prepared in the same manner as in Example 41, except that the combinations of aqueous paint composition and film thickness were as shown in Table 3.

[0280] Chipping resistance test Chipping resistance: The test coated plates obtained in Examples 41-60 and Comparative Examples 11-15 were placed on the specimen holder of the stone chip tester "JA-400" (product name, manufactured by Suga Test Machine Co., Ltd., chipping resistance test device). At -20°C, 50g of road crushed stone (S-5) as described in JIS A 5001 was impacted onto the test plate at a 90-degree angle using compressed air at 0.39 MPa (4 kgf / cm2) from a distance of 35 cm from the test plate. After that, the obtained test plates were washed with water, dried, and cloth adhesive tape (manufactured by Nichiban Co., Ltd.) was applied to the coated surface. After peeling it off, the degree of scratching of the coating film was visually observed and evaluated according to the following criteria. ◎ and ○ indicate a pass. The evaluation results are shown in Table 3. ◎: The scratch is extremely small, and the electrodeposited surface and the underlying steel plate are not exposed. ○: The scratch is small, and the electrodeposited surface or the base steel plate is not exposed. △: The scratch is small, but the electrodeposited surface or the underlying steel plate is exposed. ×: The scratch is quite large, and a significant portion of the bare steel plate is exposed.

[0281] [Table 9]

[0282] [Table 10]

[0283] [Table 11]

[0284] [Table 12]

Claims

1. (A) A urethane resin portion obtained from a constituent component comprising (a1) a polyisocyanate component, and (a2) (a2-1) a compound having two or more hydroxyl groups and one or more polymerizable unsaturated groups and (a2-2) a polyol component containing polytetramethylene ether glycol, (B) comprising an acrylic resin portion obtained from a component comprising (b1) a compound having one polymerizable unsaturated group and no hydroxyl group or having one hydroxyl group, and (b2) a compound having two or more polymerizable unsaturated groups and no hydroxyl group or having one hydroxyl group, The core-shell structure consists of a shell made of the urethane resin portion (A) and a core made of the acrylic resin portion (B). Aqueous dispersion of acrylic urethane composite resin.

2. The aqueous dispersion of the acrylic urethane composite resin according to claim 1, wherein the polyisocyanate component (a1) comprises an alicyclic polyisocyanate (a1-1).

3. An aqueous dispersion of an acrylic urethane composite resin according to claim 1 or 2, wherein the content of the compound (b2) having two or more polymerizable unsaturated groups and having neither a hydroxyl group nor one hydroxyl group is in the range of 0.5 to 50% by mass, based on the total solid content of the acrylic resin portion (B).

4. An aqueous coating composition containing an aqueous dispersion of an acrylic urethane composite resin according to any one of claims 1 to 3.

5. The aqueous paint composition according to claim 4, further comprising at least one resin selected from acrylic resin (C) and polyester resin (D).

6. The aqueous paint composition according to claim 4 or 5, further containing a curing agent (E).

7. Step (1): A step of applying the aqueous paint composition described in any one of claims 4 to 6 onto the object to be coated to form a base coat film. Step (2): A step of applying a clear coat coating composition onto the base coat coating formed in step (1) to form a clear coat coating, and, A method for forming a multilayer coating film, comprising step (3): a step of simultaneously heating and curing the base coat coating film formed in step (1) and the clear coat coating film formed in step (2).

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