Aqueous coating composition, method for forming coating film, and method for forming multilayer coating film

Abstract

The purpose of the present invention is to provide an aqueous coating composition which has excellent storage stability and is capable of forming a coating film having excellent wear resistance, chipping resistance and glass adhesion even when cured at a relatively low temperature. The present invention is an aqueous coating material composition comprising: an aqueous dispersion of particles of a polyurethane resin (A) obtained from constituent components comprising a compound (a1) having a secondary amino group and an alkoxysilyl group and a urethane prepolymer (a2) having an isocyanate group; the compound (a1) having a secondary amino group and an alkoxysilyl group is obtained from constituent components including a compound (a11) containing a primary amino group and an alkoxysilyl group and a compound (a12) containing a polymerizable unsaturated group, and the content of the curing agent (B) is within the range of 5-50 mass% based on the total resin solid content in the aqueous coating composition.

Description

Technical Field

[0001] The present invention relates to a water-based coating composition, a coating film forming method and a multi-layer coating film forming method. Background Art

[0002] In automobile painting, a method of forming a multilayer coating film by a 3-coat 2-bake (3C2B) method is widely used, which is to apply an electrodeposition coating to the object, then apply a mid-coat → sintering and curing → apply a water-based base coating → preheating (preheating) → apply a clear coating → sintering and curing. In recent years, from the perspective of energy saving, a 3-coat 1-bake (3C1B) method is becoming popular, which is to omit the sintering and curing step after applying the mid-coat, and apply an electrodeposition coating to the object, then apply a water-based mid-coat → preheating (preheating) as needed → apply a water-based base coating → preheating (preheating) → apply a clear coating → sintering and curing.

[0003] Recently, in order to further reduce the energy used, it is required to further reduce the heating temperature in the above-mentioned sintering and solidification step.

[0004] However, when the heating temperature is low, the chipping resistance (the chipping phenomenon in which the coating film peels off due to the collision of small stones with the painted surface of the automobile body outer panel) and the resistance to the load applied to the bonding portion between the glass and the coating film, that is, the glass adhesion may be insufficient.

[0005] In addition, as the coating part of the automobile body, in the part where the appearance requirement is not high, research has been conducted to further reduce the painting man-hours. For example, a 1 coating 1 baking (1C1B) method has been studied, in which after applying the electrodeposition coating to the object to be coated, the water-based base coating is applied → preheating (preheating) → sintering and curing. In this case, the top coating film becomes a base coating film formed by the water-based base coating, so the base coating film is required to have high coating film properties such as wear resistance.

[0006] However, a coating composition having high coating performance even when heated at a relatively low temperature generally has high reactivity and sometimes has insufficient storage stability.

[0007] Patent document 1 describes an aqueous coating composition, characterized in that it is an aqueous coating composition comprising (A) an aqueous resin, (B) a melamine resin and (C) a weak acid catalyst, wherein the (A) aqueous resin has a hydroxyl value of 80 to 200 mgKOH / g in terms of resin solid content, the (B) melamine resin has an average imino number of 1.0 or more and an average methylol number of 0.5 or more per melamine nucleus, the mass ratio of the (A) aqueous resin to the (B) melamine resin in the aqueous coating composition is 90 / 10 to 60 / 40 in terms of solid content, and when the total of the (A) aqueous resin and the (B) melamine resin is 100 parts by mass, the content of the (C) weak acid catalyst is 0.1 to 10.0 parts by mass, and the aqueous coating composition is excellent in low temperature curing property and storage stability compared with conventional coatings.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2015-174958 Summary of the invention

[0011] Problem that the invention aims to solve

[0012] In the technique described in Patent Document 1, although the obtained water-based coating composition is excellent in low-temperature curability and storage stability, the formed coating film may have insufficient abrasion resistance, chipping resistance and glass adhesion.

[0013] An object of the present invention is to provide an aqueous coating composition which has excellent storage stability and can form a coating film having excellent abrasion resistance, chipping resistance and glass adhesion even when cured at a relatively low temperature.

[0014] Solutions for solving problems

[0015] The present inventors have conducted intensive studies to achieve the above-mentioned object, and as a result, have found that the above-mentioned object can be achieved according to the following aqueous coating composition, which is an aqueous coating composition comprising an aqueous dispersion of polyurethane resin (A) particles and a curing agent (B), wherein the aqueous dispersion of polyurethane resin (A) particles is obtained from constituent components comprising a compound (a1) having a secondary amino group and an alkoxysilyl group and an isocyanate group-containing urethane prepolymer (a2), wherein the compound (a1) having a secondary amino group and an alkoxysilyl group is obtained from constituent components comprising a compound (a11) having a primary amino group and an alkoxysilyl group and a compound (a12) containing a polymerizable unsaturated group, and the isocyanate group-containing urethane prepolymer (a2) is obtained from constituent components comprising a polyisocyanate component (a21) and a polyol component (a22), and the content of the curing agent (B) is in the range of 5 to 50% by mass based on the total resin solid content in the aqueous coating composition.

[0016] That is, the present invention relates to the following <1> ~ <11> .

[0017] <1> A water-based coating composition, characterized in that it is a water-based coating composition comprising a polyurethane resin (A) particle aqueous dispersion and a curing agent (B), wherein the polyurethane resin (A) particle aqueous dispersion is obtained from constituent components comprising a compound (a1) having a secondary amino group and an alkoxysilyl group and a urethane prepolymer (a2) containing an isocyanate group,

[0018] The compound (a1) having a secondary amino group and an alkoxysilyl group is obtained from components comprising a compound (a11) having a primary amino group and an alkoxysilyl group and a compound (a12) having a polymerizable unsaturated group, and the urethane prepolymer (a2) containing an isocyanate group is obtained from components comprising a polyisocyanate component (a21) and a polyol component (a22).

[0019] The content of the curing agent (B) is in the range of 5 to 50% by mass based on the total resin solid content in the aqueous coating composition.

[0020] <2> according to <1> In the water-based coating composition, the compound (a12) containing a polymerizable unsaturated group comprises a (meth)acrylate.

[0021] <3> according to <1> or <2> In the aqueous coating composition, the polyisocyanate component (a21) comprises an alicyclic polyisocyanate compound (a21-1).

[0022] <4> according to <1> ~ <3> The aqueous coating composition described above, wherein the polyol component (a22) comprises at least one selected from the group consisting of a polycarbonate polyol (a22-1) and a polyether polyol (a22-2).

[0023] <5> according to <1> ~ <4> The aqueous coating composition described in any one of the preceding claims, wherein the polyurethane resin (A) particle aqueous dispersion contains a chain extender (a3) ​​as a constituent component.

[0024] <6> according to <1> ~ <5> The aqueous coating composition described in any one of the preceding claims contains the polyurethane resin (A) particle aqueous dispersion in an amount within a range of 10 to 70% by mass based on the total resin solid content in the aqueous coating composition.

[0025] <7> according to <1> ~ <6> The aqueous coating composition described above, wherein the curing agent (B) comprises a polycarbodiimide compound (B1).

[0026] <8> according to <1> ~ <7> The aqueous coating composition described above further comprises at least one resin selected from the group consisting of an acrylic resin (C) and a polyester resin (D).

[0027] <9> A method for forming a coating film, characterized in that it comprises:

[0028] Step (I-1): Applying paint to the object <1> ~ <8> A step of forming an uncured colored coating film using the aqueous coating composition described in any one of the preceding claims;

[0029] Step (I-2): a step of curing the uncured colored coating film formed in the above step (I-1) by heating.

[0030] <10> A method for forming a multilayer coating film, characterized in that it comprises:

[0031] Step (II-1): a step of applying a mid-coat coating composition to a coating object to form an uncured mid-coat coating film;

[0032] Step (II-2): a step of applying a primer coating composition on the uncured intermediate coating film formed in the above step (II-1) to form an uncured primer coating film;

[0033] Step (II-3): a step of applying a clear coating composition on the uncured base coating film formed in the above step (II-2) to form an uncured clear coating film;

[0034] Step (II-4): a step of curing the uncured intermediate coating film formed in the step (II-1), the uncured base coating film formed in the step (II-2), and the uncured clear coating film formed in the step (II-3) by heating at one time,

[0035] At least one of the intermediate coating composition or the primer coating composition is <1> ~ <8> The aqueous coating composition described in any one of the above.

[0036] <11> according to <10> The multi-layer coating film forming method, wherein the intermediate coating composition and the primer coating composition are both <1> ~ <8> The aqueous coating composition described in any one of the above.

[0037] Effects of the Invention

[0038] According to the aqueous coating composition of the present invention, storage stability is excellent, and even when cured at a relatively low temperature, a coating film excellent in abrasion resistance, chipping resistance, and glass adhesion can be formed. DETAILED DESCRIPTION

[0039] Hereinafter, the present invention will be described in detail, but these are merely examples of preferred embodiments, and the present invention is not limited to these contents.

[0040] [Water-based coating composition]

[0041] The aqueous coating composition of the present invention is an aqueous coating composition comprising an aqueous dispersion of polyurethane resin (A) particles and a curing agent (B), wherein the aqueous dispersion of polyurethane resin (A) particles is obtained from components comprising a compound (a1) having a secondary amino group and an alkoxysilyl group and an isocyanate group-containing urethane prepolymer (a2), wherein the compound (a1) having a secondary amino group and an alkoxysilyl group is obtained from components comprising a compound (a11) having a primary amino group and an alkoxysilyl group and a compound (a12) containing a polymerizable unsaturated group, and the isocyanate group-containing urethane prepolymer (a2) is obtained from components comprising a polyisocyanate component (a21) and a polyol component (a22), and the content of the curing agent (B) is in the range of 5 to 50% by mass based on the total resin solid content in the aqueous coating composition.

[0042] [Polyurethane resin (A) particle aqueous dispersion]

[0043] The polyurethane resin (A) particle aqueous dispersion of the present invention is a polyurethane resin (A) particle aqueous dispersion obtained from constituent components including a compound (a1) having a secondary amino group and an alkoxysilyl group and an isocyanate group-containing urethane prepolymer (a2), wherein the compound (a1) having a secondary amino group and an alkoxysilyl group is obtained from constituent components including a compound (a11) having a primary amino group and an alkoxysilyl group and a compound (a12) containing a polymerizable unsaturated group, and the isocyanate group-containing urethane prepolymer (a2) is obtained from constituent components including a polyisocyanate component (a21) and a polyol component (a22).

[0044] It should be noted that the polyurethane resin (A) particle aqueous dispersion of the present invention may be an aqueous dispersion of modified polyurethane resin particles such as an acrylic modified polyurethane resin particle aqueous dispersion and a polyester modified polyurethane resin particle aqueous dispersion.

[0045] The polyurethane resin (A) particle aqueous dispersion can be produced by a conventionally known method for producing polyurethane resins, and is preferably produced by the following method (including the following production steps 1 to 4) from the viewpoint of production stability and the like.

[0046] Production process 1. The compound (a1) having a secondary amino group and an alkoxysilyl group is synthesized by reacting the compound (a11) having a primary amino group and an alkoxysilyl group with the compound (a12) having a polymerizable unsaturated group.

[0047] Production step 2. Synthesizing an isocyanate group-containing urethane prepolymer (a2) obtained from constituent components including a polyisocyanate component (a21) and a polyol component (a22).

[0048] Manufacturing process 3. The compound (a1) having a secondary amino group and an alkoxysilyl group obtained in the manufacturing process 1 is added to the isocyanate group-containing urethane prepolymer (a2) obtained in the manufacturing process 2, and the isocyanate group-containing urethane prepolymer (a2) and the compound (a1) having a secondary amino group and an alkoxysilyl group are reacted to obtain a polyurethane resin (A).

[0049] Production process 4. Deionized water is added to the polyurethane resin (A) to emulsify it to obtain an aqueous dispersion. If necessary, the aqueous dispersion is further subjected to a chain extension reaction and solvent removal to obtain an aqueous dispersion of polyurethane resin (A) particles.

[0050] [Manufacturing process 1]

[0051] The compound (a1) having a secondary amino group and an alkoxysilyl group is synthesized by reacting the compound (a11) having a primary amino group and an alkoxysilyl group with the compound (a12) having a polymerizable unsaturated group.

[0052] Examples of the compound (a11) containing a primary amino group and an alkoxysilyl group include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and N-2-(aminoethyl)-3-aminopropyltrimethoxysilane.

[0053] These primary amino group- and alkoxysilyl group-containing compounds (a11) can be used alone or in combination of two or more.

[0054] As the compound (a11) containing a primary amino group and an alkoxysilyl group, a commercially available product can be used. Examples of the trade names of the commercially available products include "KBM-903", "KBE-903", "KBM-602", "KBM-603" (these are trade names manufactured by Shin-Etsu Chemical Co., Ltd.), "Dynasylan AMEO", "Dynasylan AMMO", "Dynasylan DAMO", "Dynasylan DAMO-T" (these are trade names manufactured by Evonik Industries AG), "DOWSIL Z-6610 Silane", "DOWSIL Z-6611 Silane", "DOWSIL Z-6094 Silane", "XIAMETER OFS-6020 Silane" (these are trade names manufactured by Dow Toray Co., Ltd.), "A-1100", "A-1110", "A-1120", "A-2120" (these are trade names manufactured by Momentive Corporation), and the like.

[0055] From the viewpoint of chipping resistance of the formed coating film, etc., the compound (a11) containing a primary amino group and an alkoxysilyl group preferably includes a compound (a11-1) containing a primary amino group, a secondary amino group and an alkoxysilyl group.

[0056] Examples of the compound (a11-1) containing a primary amino group, a secondary amino group and an alkoxysilyl group include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane and N-2-(aminoethyl)-3-aminopropyltrimethoxysilane.

[0057] As the compound (a11-1) containing a primary amino group, a secondary amino group and an alkoxysilyl group, a commercially available product can be used. As the trade names of the commercially available products, "KBM-602", "KBM-603" (the above are manufactured by Shin-Etsu Chemical Co., Ltd., trade names), "Dynasylan DAMO", "Dynasylan DAMO-T" (the above are manufactured by Evonik Industries AG, trade names), "DOWSIL Z-6094 Silane", "XIAMETER OFS-6020 Silane" (the above are manufactured by Dow Toray Co., Ltd., trade names), "A-1120", "A-2120" (the above are manufactured by Momentive, trade names), etc. can be cited.

[0058] When the above-mentioned compound (a11) containing a primary amino group and an alkoxysilyl group includes a compound (a11-1) containing a primary amino group, a secondary amino group and an alkoxysilyl group, from the viewpoint of chipping resistance of the formed coating film, the content of the compound (a11-1) containing a primary amino group, a secondary amino group and an alkoxysilyl group is preferably in the range of 20 to 100 mass %, more preferably in the range of 50 to 100 mass %, and further preferably in the range of 90 to 100 mass %, based on the total solid content of the compound (a11) containing a primary amino group and an alkoxysilyl group.

[0059] The polymerizable unsaturated group is an unsaturated group capable of free radical polymerization, and specifically, for example, acryloyl, methacryloyl, vinyl, allyl, propenyl, isopropenyl, maleimide, vinyl ether, etc. Among these polymerizable unsaturated groups, acryloyl and methacryloyl are preferred, and acryloyl is particularly preferred from the viewpoint of excellent reactivity.

[0060] In addition, in this specification, "(meth)acrylate" means "acrylate and / or methacrylate". "(Meth)acrylic acid" means "acrylic acid and / or methacrylic acid". In addition, "(meth)acryloyl" means "acryloyl and / or methacryloyl". In addition, "(meth)acrylamide" means "acrylamide and / or methacrylamide".

[0061] Examples of the polymerizable unsaturated group-containing compound (a12) include monoesters of (meth)acrylic acid and a diol having 2 to 8 carbon atoms, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate, ε-caprolactone-modified monoesters of the monoesters, N-hydroxymethyl (meth)acrylamide, allyl alcohol, and (meth)acrylates having a polyoxyethylene chain with a hydroxyl group at the molecular end; and hydroxy-containing polymerizable unsaturated monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. (meth)acrylate alkyl or cycloalkyl esters such as 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 acrylate" (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd.), cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, and tricyclodecyl (meth)acrylate; polymerizable unsaturated monomers having an isobornyl group such as isobornyl (meth)acrylate; A polymerizable unsaturated monomer having an adamantyl group, such as adamantyl (meth)acrylate; a polymerizable unsaturated monomer having a tricyclodecenyl group, such as tricyclodecenyl (meth)acrylate; a polymerizable unsaturated monomer containing an aromatic ring, such as benzyl (meth)acrylate, styrene, α-methylstyrene, and vinyltoluene; a polymerizable unsaturated monomer having an alkoxysilyl group, such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(2-methoxyethoxy)silane, γ-(meth)acryloxypropyltrimethoxysilane, and γ-(meth)acryloxypropyltriethoxysilane; a polymerizable unsaturated monomer having a perfluorobutylethyl (meth)acrylate, a perfluorooctylethyl (meth)acrylate, and the like; Alkyl esters; polymerizable unsaturated monomers having fluoroalkyl groups such as fluoroolefins; polymerizable unsaturated monomers having photopolymerizable functional groups such as maleimide groups; vinyl compounds such as N-vinyl pyrrolidone, 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; 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 and amines;Epoxy-containing polymerizable unsaturated monomers such as glycidyl (meth)acrylate, β-methyl glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3,4-epoxycyclohexylethyl (meth)acrylate, 3,4-epoxycyclohexylpropyl (meth)acrylate, and allyl glycidyl ether; (meth)acrylates having a polyoxyethylene chain with an alkoxy group at the molecular end; glycerol di(meth)acrylate, 1,1,1-trimethylolethane di(meth)acrylate, allyl (meth)acrylate, ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,3-Butanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, pentaerythritol tetra(meth)acrylate, 1,1,1-trimethylolethane tri(meth)acrylate, 1,1,1-trimethylolpropane tri(meth)acrylate, methylenebis(meth)acrylamide, ethylenebis(meth)acrylamide, triallyl isocyanurate, diallyl terephthalate, divinylbenzene, polyethylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, etc.;

[0062] These polymerizable unsaturated group-containing compounds (a12) can be used alone or in combination of two or more.

[0063] From the viewpoints of the storage stability of the obtained aqueous coating composition, and the abrasion resistance, chipping resistance and glass adhesion of the formed coating film, the above-mentioned compound (a12) containing a polymerizable unsaturated group preferably comprises a (meth)acrylate, more preferably comprises an alkyl or cycloalkyl (meth)acrylate, further preferably comprises an alkyl (meth)acrylate having an alkyl group in the range of 2 to 6 carbon atoms, and particularly preferably comprises an alkyl (meth)acrylate having an alkyl group in the range of 3 to 6 carbon atoms.

[0064] Examples of the (meth)acrylate include monoesters of (meth)acrylic acid and a diol having 2 to 8 carbon atoms, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate, ε-caprolactone-modified monoesters of the monoesters, (meth)acrylates having a polyoxyethylene chain with a hydroxyl group at the molecular end, 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, and tert-butyl (meth)acrylate. 2-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, tridecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, "isostearyl acrylate" (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd.), cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, tricyclodecyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, tricyclodecenyl (meth)acrylate, benzyl (meth)acrylate, perfluorobutyl ethyl (meth)acrylate, Perfluorooctyl ethyl ester, β-carboxyethyl acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, nitrogen-containing polymerizable unsaturated monomers such as adducts of glycidyl (meth)acrylate and amines, glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3,4-epoxycyclohexylethyl (meth)acrylate, 3,4-epoxycyclohexylpropyl (meth)acrylate, (meth)acrylate having a polyoxyethylene chain with an alkoxy group at the molecular end; glycerol di(meth)acrylate, 1,1,1-trimethylolethane di(meth)acrylate ) acrylate, allyl (meth)acrylate, ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, pentaerythritol tetra(meth)acrylate, 1,1,1-trimethylolethane tri(meth)acrylate, 1,1,1-trimethylolpropane tri(meth)acrylate, polyethylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, and the like.

[0065] When the above-mentioned polymerizable unsaturated group-containing compound (a12) contains (meth)acrylate, from the viewpoints of storage stability of the obtained aqueous coating composition, abrasion resistance and glass adhesion of the formed coating film, the content of the (meth)acrylate is preferably in the range of 20 to 100 mass %, more preferably in the range of 50 to 100 mass %, and further preferably in the range of 90 to 100 mass %, based on the total solid content of the polymerizable unsaturated group-containing compound (a12).

[0066] Examples of the alkyl or cycloalkyl (meth)acrylate include 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 acrylate” (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd.), cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, and tricyclodecyl (meth)acrylate.

[0067] When the above-mentioned compound (a12) containing a polymerizable unsaturated group contains an alkyl (meth)acrylate or a cycloalkyl ester, from the viewpoints of the storage stability of the obtained aqueous coating composition, the abrasion resistance and glass adhesion of the formed coating film, etc., the content of the alkyl (meth)acrylate or the cycloalkyl ester is preferably in the range of 20 to 100 mass %, more preferably in the range of 50 to 100 mass %, and further preferably in the range of 90 to 100 mass %, based on the total solid content of the compound (a12) containing a polymerizable unsaturated group.

[0068] Examples of the alkyl (meth)acrylate having an alkyl group with a carbon number of 2 to 6 include ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, and n-hexyl (meth)acrylate.

[0069] When the above-mentioned compound (a12) containing a polymerizable unsaturated group contains an alkyl (meth)acrylate having an alkyl group with a carbon number in the range of 2 to 6, from the viewpoints of the storage stability of the obtained aqueous coating composition, the abrasion resistance and glass adhesion of the formed coating film, etc., the content of the alkyl (meth)acrylate having an alkyl group with a carbon number in the range of 2 to 6 is preferably in the range of 20 to 100 mass %, more preferably in the range of 50 to 100 mass %, and further preferably in the range of 90 to 100 mass %, based on the total solid content of the compound (a12) containing a polymerizable unsaturated group.

[0070] Examples of the alkyl (meth)acrylate having an alkyl group with a carbon number of 3 to 6 include n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, and n-hexyl (meth)acrylate.

[0071] In the case where the above-mentioned compound (a12) containing a polymerizable unsaturated group includes an alkyl (meth)acrylate having an alkyl group with a carbon number ranging from 3 to 6, from the viewpoints of the storage stability of the obtained aqueous coating composition, the abrasion resistance and glass adhesion of the formed coating film, etc., the content of the alkyl (meth)acrylate having an alkyl group with a carbon number ranging from 3 to 6 is preferably in the range of 20 to 100 mass %, more preferably in the range of 50 to 100 mass %, and further preferably in the range of 90 to 100 mass %, based on the total solid content of the compound (a12) containing a polymerizable unsaturated group.

[0072] The synthesis of the compound (a1) having a secondary amino group and an alkoxysilyl group is preferably performed at a temperature within a range of 30 to 100°C.

[0073] In the synthesis of the compound (a1) having a secondary amino group and an alkoxysilyl group, an organic solvent that does not interfere with the reaction of the compound (a11) containing a primary amino group and an alkoxysilyl group and the compound (a12) containing a polymerizable unsaturated group can be used as an organic solvent. As such an organic solvent, aromatic hydrocarbon solvents such as toluene and xylene, alicyclic hydrocarbon solvents such as cyclohexane and methylcyclohexane, ester solvents such as ethyl acetate and butyl acetate, etc. can be listed. Among them, alicyclic hydrocarbon solvents and ester solvents can be preferably used. These organic solvents can be used alone or in combination of two or more.

[0074] Furthermore, in the synthesis of the compound (a1) having a secondary amino group and an alkoxysilyl group, an antioxidant may be added as necessary.

[0075] Examples of the antioxidant include dibutylhydroxytoluene, hydroquinone, methylhydroquinone, and tert-butylhydroquinone.

[0076] The mass ratio (a11) / (a12) of the compound (a11) containing a primary amino group and an alkoxysilyl group and the compound (a12) containing a polymerizable unsaturated group in the above-mentioned compound (a1) having a secondary amino group and an alkoxysilyl group is preferably in the range of 25 / 75 to 60 / 40, more preferably in the range of 35 / 65 to 55 / 45, and still more preferably in the range of 40 / 60 to 50 / 50, based on 100 parts by mass of the total mass of the compound (a11) containing a primary amino group and an alkoxysilyl group and the compound (a12) containing a polymerizable unsaturated group, from the viewpoints of the storage stability of the obtained aqueous coating composition and the abrasion resistance, chipping resistance and glass adhesion of the formed coating film.

[0077] [Manufacturing process 2]

[0078] An isocyanate group-containing urethane prepolymer (a2) obtained from constituent components including a polyisocyanate component (a21) and a polyol component (a22) is synthesized.

[0079] The isocyanate group-containing urethane prepolymer (a2) may further contain, as necessary, a compound having an active hydrogen group and an ion-forming group as a water-dispersible group-imparting component.

[0080] [Polyisocyanate component (a21)]

[0081] Examples of the polyisocyanate component (a21) include alicyclic polyisocyanates (a21-1), aliphatic polyisocyanates, aromatic aliphatic polyisocyanates, aromatic polyisocyanates, and derivatives of the polyisocyanates.

[0082] As the polyisocyanate component (a21), it is preferred that an alicyclic polyisocyanate (a21-1) is contained from the viewpoints of the abrasion resistance and glass adhesion of the formed coating film.

[0083] Examples of the alicyclic polyisocyanate (a21-1) 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), 2-methyl-1,3-cyclohexylene diisocyanate, alicyclic diisocyanates such as 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane (common name: hydrogenated xylylene diisocyanate) or a mixture 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(isocyanato)cyclohexane; 2-(3-isocyanatopropyl)-2,6-bis(isocyanatomethyl)-bicyclo(2.2.1)heptane, 3-(3-isocyanatopropyl)-2,5-bis(isocyanatomethyl)-bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, 6-(2-isocyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, Alicyclic triisocyanates such as 2-(2-isocyanatoethyl)-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.

[0084] When the above-mentioned polyisocyanate component (a21) contains the above-mentioned alicyclic polyisocyanate (a21-1), from the viewpoints of abrasion resistance, chipping resistance and glass adhesion of the formed coating film, the content of the alicyclic polyisocyanate (a21-1) is preferably in the range of 50 to 100 mass %, more preferably in the range of 70 to 100 mass %, and further preferably in the range of 90 to 100 mass %, based on the total solid content of the polyisocyanate component (a21).

[0085] Examples of the aliphatic polyisocyanate 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 acid diisocyanate, 2,6-diisocyanatohexanoic acid methyl ester (common name: lysine diisocyanate), aliphatic triisocyanates such as 2,6-diisocyanatohexanoic acid 2-isocyanatoethyl ester, 1,6-diisocyanato-3-isocyanatomethylhexane, 1,4,8-triisocyanatooctane, 1,6,11-triisocyanatoundecane, 1,8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-triisocyanatohexane, 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyloctane, etc.

[0086] Examples of the aromatic aliphatic polyisocyanate include aromatic aliphatic diisocyanates such as methylenebis(4,1-phenylene) diisocyanate (common name: MDI), 1,3- or 1,4-phenylenediisocyanate or a mixture thereof, ω,ω'-diisocyanato-1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanato-1-methylethyl)benzene (common name: tetramethylphenylenediisocyanate) or a mixture thereof; and aromatic aliphatic triisocyanates such as 1,3,5-triisocyanatotoluene.

[0087] Examples of the aromatic polyisocyanate include aromatic diisocyanates such as m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 2,4-toluene diisocyanate (common name: 2,4-TDI) or 2,6-toluene diisocyanate (common name: 2,6-TDI) or a mixture thereof, 4,4'-toluidine diisocyanate, and 4,4'-diphenyl ether diisocyanate; 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.

[0088] In addition, examples of the derivatives of the polyisocyanates include dimers, trimers, biuret, allophanate, uretdione, ureaimines, isocyanurates, oxadiazinetriones, polymethylene polyphenyl polyisocyanates (crude MDI, polymeric MDI), crude TDI, etc. The polyisocyanates and their derivatives may be used alone or in combination of two or more.

[0089] The above-mentioned polyisocyanate may be used in the form of blocked isocyanate blocked with a blocking agent.

[0090] Examples of the end-capping agent include phenols such as phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxybiphenyl, 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, propanol, butanol, amyl alcohol, and lauryl alcohol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, and diethylene glycol monobutyl ether. ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, methoxymethanol and other ether series; benzyl alcohol, glycolic acid, methyl glycolate, ethyl glycolate, butyl glycolate, lactic acid, methyl lactate, ethyl lactate, butyl lactate, hydroxymethyl urea, hydroxymethyl melamine, diacetone alcohol, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate and other alcohol series; formamide oxime, acetamide oxime, acetone oxime, methyl ethyl ketone oxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime and other oxime series; dimethylmalonate Ester, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, acetylacetone and other active methylene series; butyl mercaptan, tert-butyl mercaptan, hexyl mercaptan, tert-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, methyl thiophenol, ethyl thiophenol and other thiol series; acetanilide, acetyl methoxyaniline, N-acetyl o-toluidine, acrylamide, methacrylamide, acetamide, stearamide, benzamide and other amide series; succinimide, phthalimide , maleimide and other imide series; diphenylamine, phenylnaphthylamine, dimethylaniline, N-phenyldimethylaniline, carbazole, aniline, naphthylamine, butylamine, dibutylamine, butylaniline and other amine series; imidazole series such as imidazole and 2-ethylimidazole; urea series such as urea, thiourea, ethylene urea, ethylene thiourea, diphenyl urea; carbamate series such as N-phenylcarbamate; imine series such as ethyleneimine and propyleneimine; sulfite series such as sodium bisulfite and potassium bisulfite; azole compounds, etc. Examples of the azole compounds include pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3,5-dimethylpyrazole, 3-methyl-5-phenylpyrazole and the like, and pyrazole derivatives; imidazole, benzimidazole, 2-methylimidazole, 2-ethylimidazole, 2-phenylimidazole and the like, and imidazoline derivatives such as 2-methylimidazoline and 2-phenylimidazoline.

[0091] When performing the above-mentioned blocking (making the blocking agent react), a solvent may be added as needed. The solvent used for the blocking reaction may be a solvent that is non-reactive to isocyanate groups, and examples thereof include ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate, and solvents such as N-methyl-2-pyrrolidone (NMP).

[0092] [Polyol component (a22)]

[0093] The polyol component (a22) is a compound having at least two hydroxyl groups in one molecule.

[0094] From the viewpoints of the storage stability of the obtained aqueous coating composition, and the abrasion resistance, crack resistance and glass adhesion of the formed coating film, the above-mentioned polyol component (a22) preferably contains at least one selected from polycarbonate polyol (a22-1) and polyether polyol (a22-2), and more preferably contains both polycarbonate polyol (a22-1) and polyether polyol (a22-2).

[0095] The polycarbonate polyol (a22-1) is a compound obtained by subjecting a known polyol component to a polycondensation reaction with a carbonylating agent by a conventional method. Examples of the polyol component include diol components and polyol components such as trivalent or higher alcohols.

[0096] Examples of the diol component include linear diols such as 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol; and 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-propylene glycol, 2-methyl-1,8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol and other branched diols; 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol and other alicyclic diols; p-xylene glycol, p-tetrachloroxylene glycol and other aromatic diols; diethylene glycol, dipropylene glycol and other ether diols, etc. These diol components can be used alone or in combination of two or more.

[0097] Examples of the trivalent or higher alcohol include glycerin, trimethylolethane, trimethylolpropane, a dimer of trimethylolpropane, pentaerythritol, etc. These trivalent or higher alcohols may be used alone or in combination of two or more.

[0098] As the carbonylating agent, a known carbonylating agent can be used. Specifically, as the carbonylating agent, for example, alkylene carbonate, dialkyl carbonate, diallyl carbonate, phosgene, etc. can be listed, and one of them or a combination of two or more can be used. Among them, as preferred substances, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, diphenyl carbonate, etc. can be listed.

[0099] The number average molecular weight of the polycarbonate polyol (a22-1) is preferably in the range of 1,000 to 5,000, more preferably in the range of 1,300 to 4,500, and even more preferably in the range of 1,500 to 3,500, from the viewpoint of chipping resistance of the formed coating film.

[0100] When the above-mentioned polyol component (a22) contains the above-mentioned polycarbonate polyol (a22-1), from the viewpoints of abrasion resistance, crack resistance and glass adhesion of the formed coating film, the content of the polycarbonate polyol (a22-1) is preferably in the range of 20 to 70 mass %, more preferably in the range of 25 to 60 mass %, and further preferably in the range of 30 to 50 mass %, based on the total solid content of the polyol component (a22).

[0101] As the above-mentioned polyether polyol (a22-2), the ring-opening (co)polymer of the alkylene oxide adduct of the low molecular weight polyol described later, alkylene oxide or cyclic ether (tetrahydrofuran, etc.) can be used. Specifically, for example, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, (block or random) copolymer of ethylene glycol-propylene glycol, polyhexamethylene glycol, polyoctamethylene glycol, etc. can be listed. The above-mentioned polyether polyol can be used alone or in combination of two or more.

[0102] From the viewpoints of the storage stability of the obtained aqueous coating composition, and the abrasion resistance, chipping resistance and glass adhesion of the formed coating film, the number average molecular weight of the above-mentioned polyether polyol (a22-2) is preferably in the range of 500 to 10,000, more preferably in the range of 1,000 to 5,000, and further preferably in the range of 1,600 to 4,000.

[0103] When the above-mentioned polyol component (a22) contains the above-mentioned polyether polyol (a22-2), from the viewpoints of abrasion resistance, crack resistance and glass adhesion of the formed coating film, the content of the polyether polyol (a22-2) is preferably in the range of 25 to 80 mass %, more preferably in the range of 30 to 70 mass %, and further preferably in the range of 40 to 60 mass %, based on the total solid content of the polyol component (a22).

[0104] From the viewpoint of storage stability of the obtained aqueous coating composition and chipping resistance of the formed coating film, the polyether polyol (a22-2) preferably contains polytetramethylene ether glycol.

[0105] When the above-mentioned polyether polyol (a22-2) contains polytetramethylene ether glycol, from the viewpoints of the storage stability of the obtained aqueous coating composition and the crack resistance of the formed coating film, the content of the polytetramethylene ether glycol is preferably in the range of 50 to 100 mass %, more preferably in the range of 70 to 100 mass %, and further preferably in the range of 90 to 100 mass %, based on the total solid content of the polyether polyol (a22-2).

[0106] When the polyol component (a22) comprises the polycarbonate polyol (a22-1) and the polyether polyol (a22-2), the mass ratio (a22-1) / (a22-2) of the polycarbonate polyol (a22-1) to the polyether polyol (a22-2) is preferably in the range of 10 / 90 to 90 / 10, more preferably in the range of 20 / 80 to 70 / 30, and further preferably in the range of 30 / 70 to 60 / 40, based on 100 parts by mass of the total mass of the polycarbonate polyol (a22-1) and the polyether polyol (a22-2).

[0107] The polyol component (a22) may contain other polyol components (a22-3) other than the polycarbonate polyol (a22-1) and the polyether polyol (a22-2).

[0108] As other polyol components (a22-3), for example, as low molecular weight polyols, 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-hexanediol, 2,5-hexanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, tricyclodecane dimethanol, 1,4-cyclohexanedimethanol, etc. can be used. These low molecular weight polyols can be used alone or in combination of two or more.

[0109] As other polyol components (a22-3), high molecular weight polyols such as polyester polyols and polyether ester polyols can be used. These high molecular weight polyols can be used alone or in combination of two or more.

[0110] As the polyester polyol, there can be cited polyester polyols obtained by polycondensing dicarboxylic acids (anhydrides) such as adipic acid, succinic acid, sebacic acid, glutaric acid, maleic acid, fumaric acid, and phthalic acid with low molecular weight polyols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octamethylene glycol, and neopentyl glycol under conditions of excess hydroxyl groups. Specifically, there can be cited, for example, ethylene glycol-adipic acid condensates, butanediol-adipic acid condensates, hexamethylene glycol-adipic acid condensates, ethylene glycol-propylene glycol-adipic acid condensates, and polylactone polyols obtained by ring-opening polymerization of lactones using glycols as initiators. These polyester polyols can be used alone or in combination of two or more.

[0111] Examples of the polyether ester polyol include those obtained by adding an ether group-containing polyol (the polyether polyol (a22-2) or diethylene glycol, etc.) or a mixture thereof with other diols to a dicarboxylic acid (anhydride) exemplified in the polyester polyol and reacting with an alkylene oxide, such as polytetramethylene glycol-adipic acid condensate, etc. These polyether ester polyols may be used alone or in combination of two or more.

[0112] [Compounds having both active hydrogen groups and ion-forming groups]

[0113] Examples of compounds having both an active hydrogen group and an ion-forming group 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 compounds can be used alone or in combination of two or more.

[0114] Among them, as the compound having both the active hydrogen group and the ion-forming group, a compound having two or more hydroxyl groups and one or more carboxyl groups in one molecule, or a compound having two or more hydroxyl groups and one or more sulfonic acid groups in one molecule can be preferably used.

[0115] In the present invention, compounds having both 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 (a22).

[0116] Examples of the compound having two or more hydroxyl groups and one or more carboxyl groups in one molecule include dimethylolpropionic acid, dimethylolacetic acid, dimethylolbutanoic acid, dimethylolheptanoic acid, dimethylolnonanoic acid, 1-carboxy-1,5-pentanediamine, dihydroxybenzoic acid, 3,5-diaminobenzoic acid and other alkanol carboxylic acid compounds; and half ester compounds of polyoxypropylene triol with maleic anhydride and / or phthalic anhydride.

[0117] Examples of the compound having two or more hydroxyl groups and one or more sulfonic acid groups in one molecule include 2-sulfonic acid-1,4-butanediol, 5-sulfonic acid-di-β-hydroxyethyl isophthalate, and N,N-bis(2-hydroxyethyl)aminoethylsulfonic acid.

[0118] In the case where the above-mentioned polyol component (a22) contains the above-mentioned compound having two or more hydroxyl groups and one or more carboxyl groups, from the viewpoint of the storage stability of the obtained aqueous coating composition, its content is preferably in the range of 1 to 30 mass %, more preferably in the range of 1 to 25 mass %, and further preferably in the range of 1 to 20 mass % relative to the total amount of the compounds constituting the polyol component (a22).

[0119] There is no particular limitation on the method for producing the isocyanate-containing urethane prepolymer (a2), and a conventionally known method can be applied. As a production method, for example, a polyisocyanate component (a21) and a polyol component (a22) are subjected to a urethanization reaction in an organic solvent, or a compound having both an active hydrogen group and an ion-forming group is further added as required to undergo a urethanization reaction, thereby synthesizing.

[0120] From the viewpoint of storage stability of the obtained aqueous coating composition, etc., the isocyanate group-containing urethane prepolymer (a2) preferably contains the compound having both an active hydrogen group and an ion-forming group.

[0121] In the urethanization reaction of the polyisocyanate component (a21) and the polyol component (a22), a catalyst may be used as necessary.

[0122] Examples of the catalyst include bismuth carboxylate compounds such as bismuth (III) tri(2-ethylhexanoate); organic tin compounds such as dibutyltin dilaurate, dibutyltin dioctoate, and stannous octoate; and tertiary amine compounds such as triethylamine and triethylenediamine.

[0123] The above-mentioned urethanization reaction is preferably carried out at 50 to 120°C.

[0124] In the synthesis of the above-mentioned isocyanate-containing urethane prepolymer (a2), as an organic solvent, an organic solvent that is inactive to isocyanate and does not hinder the urethane reaction can be used. As such an organic solvent, for example, aromatic hydrocarbon solvents such as toluene and xylene, ester solvents such as ethyl acetate and butyl acetate, ketone solvents such as acetone and methyl ethyl ketone, etc. can be listed. Among them, from the viewpoint of water dispersion stability, ketone solvents and ester solvents can be preferably used. These organic solvents can be used alone or in combination of two or more.

[0125] Regarding the content ratio of the polyisocyanate component (a21) and the polyol component (a22) in the isocyanate group-containing urethane prepolymer (a2), from the viewpoint of manufacturability, etc., the molar ratio of active hydrogen groups possessed by the polyol component (a22) / isocyanate groups possessed by the polyisocyanate component (a21) is preferably in the range of 1 / 1.01 to 1 / 3.0, and more preferably in the range of 1 / 1.05 to 1 / 2.0.

[0126] From the viewpoint of abrasion resistance, chipping resistance and glass adhesion of the formed coating film, the number average molecular weight of the above-mentioned isocyanate group-containing urethane prepolymer (a2) is preferably in the range of 1,000 to 20,000, more preferably in the range of 2,000 to 15,000, and further preferably in the range of 2,500 to 10,000.

[0127] It should be noted that in this specification, the average molecular weight is a value calculated from a chromatogram measured by gel permeation chromatography based on the molecular weight of standard polystyrene. The gel permeation chromatography uses "HLC8120GPC" (manufactured by TOSOH CORPORATION). As columns, four columns "TSKgel G-4000HXL", "TSKgel G-3000HXL", "TSKgel G-2500HXL", and "TSKgel G-2000HXL" (all manufactured by TOSOH CORPORATION, trade names) are used, and the mobile phase is tetrahydrofuran, the measurement temperature is 40°C, the flow rate is 1 mL / min, and the detector is RI.

[0128] [Manufacturing process 3]

[0129] The compound (a1) having a secondary amino group and an alkoxysilyl group obtained in the production step 1 is added to the isocyanate group-containing urethane prepolymer (a2) obtained in the production step 2, and the isocyanate group-containing urethane prepolymer (a2) and the compound (a1) having a secondary amino group and an alkoxysilyl group are reacted to obtain a polyurethane resin (A).

[0130] The reaction of the isocyanate group-containing urethane prepolymer (a2) and the compound (a1) having a secondary amino group and an alkoxysilyl group is preferably performed at a temperature within a range of 40 to 100°C.

[0131] The mass ratio (a1) / (a2) of the compound (a1) having a secondary amino group and an alkoxysilyl group to the isocyanate group-containing urethane prepolymer (a2) in the reaction between the isocyanate group-containing urethane prepolymer (a2) and the compound (a1) having a secondary amino group and an alkoxysilyl group is preferably in the range of 1 / 99 to 20 / 80, more preferably in the range of 2 / 98 to 10 / 90, and even more preferably in the range of 3 / 97 to 6 / 94, based on 100 parts by mass of the total mass of the isocyanate group-containing urethane prepolymer (a2) and the compound (a1) having a secondary amino group and an alkoxysilyl group. From the viewpoint of abrasion resistance and glass adhesion of the formed coating film, etc.

[0132] [Manufacturing process 4]

[0133] Deionized water is added to the polyurethane resin (A) to emulsify the polyurethane resin (A) to obtain an aqueous dispersion, and the aqueous dispersion is further subjected to a chain extension reaction and solvent removal as required to obtain an aqueous dispersion of polyurethane resin (A) particles.

[0134] When deionized water is added to the polyurethane resin (A), a neutralizing agent for the above-mentioned ion-forming groups may be added to the polyurethane resin (A) as needed.

[0135] As the neutralizing agent, there is no particular limitation as long as it can neutralize the ion-forming groups, and examples of the basic compound used for neutralization include organic amines such as ammonia, diethylamine, ethylethanolamine, diethanolamine, triethanolamine, monoethanolamine, monopropanolamine, isopropanolamine, ethylaminoethylamine, hydroxyethylamine, triethylamine, tributylamine, dimethylethanolamine, diethylenetriamine, N-methylmorpholine, and N-ethylmorpholine; or alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, etc. These neutralizing agents can be used alone or in combination of two or more.

[0136] The neutralizing agent is preferably used in such an amount that the pH of the polyurethane resin (A) particle aqueous dispersion is finally adjusted to about 6.0 to 9.0.

[0137] When the neutralizing agent is added to the polyurethane resin (A), the amount of the neutralizing agent added is preferably 0.1 to 1.5 equivalents, more preferably 0.3 to 1.2 equivalents, based on the acid groups such as carboxyl groups.

[0138] In order to improve the water dispersion stability of the polyurethane resin (A) particle water dispersion, an emulsifier such as a surfactant may be used.

[0139] As the emulsifier, known general anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, polymer surfactants, reactive surfactants, etc. can be used. When using them, anionic surfactants, nonionic surfactants or cationic surfactants are preferred because they are low in cost and can provide good emulsification.

[0140] Examples of the anionic surfactant include alkyl sulfates such as sodium dodecyl sulfate, potassium dodecyl sulfate, and ammonium dodecyl sulfate; sodium dodecyl polyethylene glycol ether sulfate; sodium sulforicinoleate; alkyl sulfonates such as alkali metal salts of paraffin sulfonates and ammonium salts of paraffin sulfonates; fatty acid salts such as sodium laurate, triethanolamine oleate, and triethanolamine rosinate; alkyl aryl sulfonates such as sodium benzene sulfonate and alkali metal sulfates of basic phenol hydroxyethylene; higher alkyl naphthalene sulfonates; naphthalenesulfonic acid formaldehyde condensates; dialkyl sulfosuccinates; polyoxyethylene alkyl sulfates; polyoxyethylene alkyl aryl sulfates, and the like.

[0141] Examples of the nonionic surfactant include ethylene oxide and / or propylene oxide adducts of alcohols having 1 to 18 carbon atoms, ethylene oxide and / or propylene oxide adducts of alkylphenols, and ethylene oxide and / or propylene oxide adducts of alkylene glycols and / or alkylenediamines.

[0142] Examples of the alcohol having 1 to 18 carbon atoms constituting the nonionic surfactant include methanol, ethanol, propanol, 2-propanol, butanol, 2-butanol, tert-butanol, amyl alcohol, isoamyl alcohol, tert-amyl alcohol, hexanol, octanol, decanol, lauryl alcohol, myristyl alcohol, palmityl alcohol, and stearyl alcohol. Examples of the alkylphenol include phenol, methylphenol, 2,4-di-tert-butylphenol, 2,5-di-tert-butylphenol, 3,5-di-tert-butylphenol, 4-(1,3-tetramethylbutyl)phenol, 4-isooctylphenol, 4-nonylphenol, 4-tert-octylphenol, 4-dodecylphenol, 2-(3,5-di-tert-butylphenol), and 4-(1,3-tetramethylbutyl)phenol. Examples of the alkylene glycol include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 2-methyl-1,3-propylene glycol, 2-butyl-2-ethyl-1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, and examples of the alkylene diamine include alkylene diamines in which the alcoholic hydroxyl groups of these alkylene diols are substituted with amino groups. The ethylene oxide and propylene oxide adducts may be random adducts or block adducts.

[0143] Examples of the cationic surfactant include primary and tertiary amine salts, pyridinium salts, alkylpyridinium salts, quaternary ammonium salts such as halogenated alkyl quaternary ammonium salts, etc. These surfactants may be used alone or in combination of two or more.

[0144] As the emulsification means, a general stirrer can be used for dispersion. However, in order to obtain a uniform aqueous dispersion having a finer particle size, a homomixer, a homogenizer, a disperser, a line mixer, etc. can be used.

[0145] When the chain extension reaction (molecular weight increase) is carried out, a chain extender (a3) ​​other than water may be added as needed to react the reaction product of the isocyanate group-containing urethane prepolymer (a2) and the compound (a1) having a secondary amino group and an alkoxysilyl group with the chain extender (a3).

[0146] The polyurethane resin (A) particle aqueous dispersion preferably contains the chain extender (a3) ​​as a constituent component from the viewpoints of abrasion resistance, glass adhesion, chipping resistance, and the like of the coating film to be formed.

[0147] As the chain extender (a3), a known chain extender having active hydrogen can be used. Specifically, for example, diamine compounds such as ethylenediamine, hexamethylenediamine, cyclohexanediamine, cyclohexylmethanediamine, and isophoronediamine, triamine compounds such as diethylenetriamine, tetraamine compounds such as triethylenetetramine, hydroxyethylhydrazine, hydroxyethyldiethylenetriamine, N-(2-aminoethyl)ethanol, 1,3-diamino-2-propanol, amino alcohol compounds such as 3-aminopropylene glycol, hydrazine, etc. can be cited.

[0148] From the viewpoint of storage stability of the resulting coating composition, etc., the chain extender (a3) ​​preferably contains a diamine compound such as ethylenediamine.

[0149] As the chain extender (a3), an amino alcohol compound such as N-(2-aminoethyl)ethanol may be used for the purpose of introducing a reactive functional group into the aqueous dispersion of polyurethane resin (A) particles.

[0150] The polyurethane resin (A) synthesized in the above-mentioned production steps 1 to 4 is synthesized as a dispersion in an aqueous solvent and has a particle form.

[0151] Here, the aqueous solvent refers to a solvent containing water as a main component (for example, a solvent in which 70 to 100% by mass of the solvent is water).

[0152] From the viewpoint of storage stability of the obtained aqueous coating composition, the average particle size of the polyurethane resin (A) particles 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 further preferably in the range of 50 to 140 nm.

[0153] The average particle size of the polyurethane resin (A) particles can be adjusted to the desired average particle size by adjusting the composition of the raw materials (polyisocyanate component, polyol component, amine component, etc.), the type of emulsifier, the amount of emulsifier, the feed distribution of the emulsifier, the type of neutralizer, the amount of neutralizer and other particle size control factors.

[0154] In this specification, the average particle size of the polyurethane resin (A) particles is a value measured at 20° C. using a particle size distribution measuring apparatus based on a dynamic light scattering method, after dilution with deionized water by a conventional method. As a particle size distribution measuring apparatus based on a dynamic light scattering method, for example, “ELSZ-2000” (trade name, manufactured by Otsuka Electronics Co., Ltd.) can be used.

[0155] From the viewpoints of abrasion resistance, chipping resistance and glass adhesion of the formed coating film, the hydroxyl value of the polyurethane resin (A) is preferably in the range of 0 to 45 mgKOH / g, more preferably in the range of 0 to 30 mgKOH / g, and further preferably in the range of 0 to 25 mgKOH / g.

[0156] From the viewpoint of storage stability of the obtained aqueous coating composition, the acid value of the polyurethane resin (A) is preferably in the range of 3 to 75 mgKOH / g, more preferably in the range of 5 to 60 mgKOH / g, and further preferably in the range of 10 to 40 mgKOH / g.

[0157] The solid content concentration in the polyurethane resin (A) particle water dispersion is preferably in the range of 20 to 50% by mass, more preferably in the range of 30 to 50% by mass. When the solid content concentration is 50% by mass or less, emulsification becomes easy and a water dispersion can be easily obtained. If the solid content concentration is 20% by mass or more, the solvent component decreases, so the solid content concentration of the water-based coating composition can be increased.

[0158] It should be noted that, in this specification, "solid content" refers to non-volatile components such as resin, curing agent, pigment, etc. that remain after drying at 110°C for 1 hour. The above-mentioned solid content can be obtained, for example, by measuring a sample in a heat-resistant container such as an aluminum foil cup, spreading the sample on the bottom of the container, drying at 110°C for 1 hour, and weighing the mass of the components remaining after drying.

[0159] In addition, in this specification, "solid content concentration" refers to the mass ratio of the above-mentioned solid components in the composition. Therefore, the solid content concentration of the composition can be calculated, for example, as follows: 1.0 g of the composition is weighed in a heat-resistant container such as an aluminum foil cup, the composition is spread on the bottom of the container, and then dried at 110°C for 1 hour, and the mass of the components in the composition remaining after drying is weighed, and the mass of the components remaining after drying is calculated to be the ratio of the mass of the components remaining after drying to the total mass of the composition before drying.

[0160] From the viewpoints of the storage stability of the obtained aqueous coating composition, and the abrasion resistance, chipping resistance and glass adhesion of the formed coating film, the content of the polyurethane resin (A) particles in the aqueous coating composition of the present invention is preferably in the range of 10 to 70% by mass, more preferably in the range of 15 to 60% by mass, and further preferably in the range of 20 to 55% by mass, based on the total resin solid content in the aqueous coating composition.

[0161] [Curing agent (B)]

[0162] The curing agent (B) is a compound that can react with the crosslinking functional groups in the polyurethane resin (A) particle aqueous dispersion and the desired acrylic resin (C) and polyester resin (D) described later to cure the aqueous coating composition. The curing agent (B) can be used alone or in combination of two or more.

[0163] Examples of the curing agent (B) include polycarbodiimide compounds, amino resins, polyisocyanate compounds, blocked polyisocyanate compounds, epoxy group-containing compounds, carboxyl group-containing compounds, hydrazide group-containing compounds, and semicarbazide group-containing compounds.

[0164] Among them, from the viewpoints of the storage stability of the obtained aqueous coating composition, and the abrasion resistance, chipping resistance and glass adhesion of the formed coating film, it is preferred to contain at least one selected from the group consisting of a polycarbodiimide compound (B1), an amino resin (B2), a polyisocyanate compound (B3) and a blocked polyisocyanate compound (B4), more preferably to contain at least one selected from the group consisting of a polycarbodiimide compound (B1), an amino resin (B2) and a blocked polyisocyanate compound (B4), and even more preferably to contain a polycarbodiimide compound (B1).

[0165] The polycarbodiimide compound (B1) is a compound having at least two carbodiimide groups in one molecule, and for example, a compound obtained by subjecting isocyanate groups of an isocyanate group-containing compound to a decarbonation reaction can be used.

[0166] As the polycarbodiimide compound (B1), a water-soluble or water-dispersible polycarbodiimide compound is preferably used from the viewpoints of the storage stability of the obtained aqueous coating composition, the abrasion resistance and glass adhesion of the formed coating film, etc. As the water-soluble or water-dispersible polycarbodiimide compound, any polycarbodiimide compound that can be stably dissolved or dispersed in an aqueous medium can be used without particular limitation.

[0167] Specific examples of the water-soluble polycarbodiimide compound include "CARBODILITE SV-02", "CARBODILITE V-02", "CARBODILITE V-02-L2", "CARBODILITE V-04" (all manufactured by Nisshinbo Co., Ltd., trade names), etc. Further, examples of the water-dispersible polycarbodiimide compound include "CARBODILITE E-01", "CARBODILITE E-02", "CARBODILITE E-05" (all manufactured by Nisshinbo Co., Ltd., trade names), etc.

[0168] When the curing agent (B) contains a polycarbodiimide compound (B1), the content of the polycarbodiimide compound (B1) is preferably in the range of 10 to 80% by mass, more preferably in the range of 15 to 70% by mass, and further preferably in the range of 20 to 65% by mass, based on the total solid content of the curing agent (B), from the viewpoints of abrasion resistance and glass adhesion of the formed coating film.

[0169] As the amino resin (B2), a partially methylolated amino resin or a completely methylolated amino resin obtained by a reaction between an amino component and an aldehyde component can be used. Examples of the amino component include melamine, urea, benzoguanamine, acetoguanamine, stereoguanamine, spiroguanamine, dicyandiamide, etc. Examples of the aldehyde component include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde, etc.

[0170] In addition, the methylol groups of the hydroxymethylated amino resins may be partially or completely etherified with appropriate alcohols. Examples of the alcohols used for etherification include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, 2-ethyl-1-butanol, and 2-ethyl-1-hexanol.

[0171] The amino resin (B2) is preferably a melamine resin. Particularly preferred are methyl-etherified melamine resins obtained by partially or completely etherifying the methylol groups of a partially or completely methylolated melamine resin with methanol, butyl-etherified melamine resins obtained by partially or completely etherifying the methylol groups of a partially or completely methylolated melamine resin with butanol, and methyl-butyl mixed etherified melamine resins obtained by partially or completely etherifying the methylol groups of a partially or completely methylolated melamine resin with methanol and butanol. More preferred are methyl-butyl mixed etherified melamine resins.

[0172] The weight average molecular weight of the melamine resin is preferably 400 to 6,000, more preferably 500 to 4,000, and even more preferably 600 to 3,000.

[0173] As the melamine resin, a commercially available product can be used. Examples of the trade names of the commercially available products 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 Allnex Japan Inc.), "Uvan 120", "Uvan 20HS", "Uvan 20SE60", "Uvan 2021", "Uvan 2028", and "Uvan 28-60" (all manufactured by Mitsui Chemicals, Inc.).

[0174] When the water-based coating composition of the present invention contains the above-mentioned melamine resin, the water-based coating composition may contain sulfonic acids such as p-toluenesulfonic acid, dodecylbenzenesulfonic acid, and dinonylnaphthalenesulfonic acid; neutralized salts of the sulfonic acid and amines; and neutralized salts of phosphate compounds and amines as curing catalysts.

[0175] When the curing agent (B) contains an amino resin (B2), the content of the amino resin (B2) is preferably in the range of 10 to 80% by mass, more preferably in the range of 15 to 70% by mass, and further preferably in the range of 20 to 65% by mass, based on the total solid content of the curing agent (B), from the viewpoints of the storage stability of the obtained aqueous coating composition, the abrasion resistance and glass adhesion of the formed coating film, etc.

[0176] The polyisocyanate compound (B3) is a compound having at least two isocyanate groups in one molecule, and examples thereof include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic aliphatic polyisocyanates, aromatic polyisocyanates, and derivatives of these polyisocyanates.

[0177] Examples of the aliphatic polyisocyanate 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 acid diisocyanate, 2,6-diisocyanatohexanoic acid methyl ester (common name: lysine diisocyanate), aliphatic triisocyanates such as 2,6-diisocyanatohexanoic acid 2-isocyanatoethyl ester, 1,6-diisocyanato-3-isocyanatomethylhexane, 1,4,8-triisocyanatooctane, 1,6,11-triisocyanatoundecane, 1,8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-triisocyanatohexane, 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyloctane, etc.

[0178] Examples of the alicyclic polyisocyanate 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), 2-methyl-1,3-cyclohexylene diisocyanate, 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane (common name: hydrogenated benzyl diisocyanate) or a mixture thereof, methylenebis(4,1-cyclohexanediyl)diisocyanate (common name: hydrogenated MDI), norbornane diisocyanate and other alicyclic diisocyanates; 1,3,5-triisocyanatocyclohexane, 1,3,5-trimethylisocyanatocyclohexane, 2-(3-isocyanatopropyl)-2,5-bis(isocyanatomethyl)cyclohexane )-bicyclo(2.2.1)heptane, 2-(3-isocyanatopropyl)-2,6-bis(isocyanatomethyl)-bicyclo(2.2.1)heptane, 3-(3-isocyanatopropyl)-2,5-bis(isocyanatomethyl)-bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, 6-(2-isocyanatoethyl)- alicyclic triisocyanates such as 2-(2-isocyanatoethyl)-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.

[0179] Examples of the aromatic aliphatic polyisocyanate include aromatic aliphatic diisocyanates such as methylenebis(4,1-phenylene) diisocyanate (common name: MDI), 1,3- or 1,4-phenylenediisocyanate or a mixture thereof, ω,ω'-diisocyanato-1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanato-1-methylethyl)benzene (common name: tetramethylphenylenediisocyanate) or a mixture thereof; and aromatic aliphatic triisocyanates such as 1,3,5-triisocyanatotoluene.

[0180] Examples of the aromatic polyisocyanate include aromatic diisocyanates such as m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 2,4-toluene diisocyanate (common name: 2,4-TDI) or 2,6-toluene diisocyanate (common name: 2,6-TDI) or a mixture thereof, 4,4'-toluidine diisocyanate, and 4,4'-diphenyl ether diisocyanate; 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.

[0181] Examples of the derivatives of the polyisocyanates include dimers, trimers, biuret, allophanate, uretdione, uretimine, isocyanurate, oxadiazinetrione, polymethylene polyphenyl polyisocyanate (crude MDI, polymeric MDI), and crude TDI of the polyisocyanates.

[0182] The above-mentioned polyisocyanates and their derivatives may be used alone or in combination of two or more. Among these polyisocyanates, aliphatic diisocyanates, alicyclic diisocyanates and their derivatives are preferred.

[0183] In addition, as the above-mentioned polyisocyanate compound, a prepolymer formed by reacting the above-mentioned polyisocyanate and its derivatives with a compound capable of reacting with the polyisocyanate under the condition of excessive isocyanate groups can be used. As the compound capable of reacting with the polyisocyanate, for example, compounds having active hydrogen groups such as hydroxyl and amino groups can be listed, and specifically, for example, polyols, low molecular weight polyester resins, amines, water, etc. can be used.

[0184] When the curing agent (B) contains a polyisocyanate compound (B3), the content of the polyisocyanate compound (B3) is preferably in the range of 10 to 80% by mass, more preferably in the range of 15 to 70% by mass, and further preferably in the range of 20 to 65% by mass, based on the total solid content of the curing agent (B).

[0185] 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 can be used.

[0186] The blocked polyisocyanate compound (B4) is a compound obtained by blocking the isocyanate groups of the polyisocyanate compound (B3) with a blocking agent.

[0187] Examples of the end-capping agent include phenols such as phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxybiphenyl, 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, propanol, butanol, amyl alcohol, and lauryl alcohol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, and diethylene glycol monobutyl ether. ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, methoxymethanol and other ether series; benzyl alcohol, glycolic acid, methyl glycolate, ethyl glycolate, butyl glycolate, lactic acid, methyl lactate, ethyl lactate, butyl lactate, hydroxymethyl urea, hydroxymethyl melamine, diacetone alcohol, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate and other alcohol series; formamide oxime, acetamide oxime, acetone oxime, methyl ethyl ketone oxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime and other oxime series; dimethylmalonate Ester, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, acetylacetone and other active methylene series; butyl mercaptan, tert-butyl mercaptan, hexyl mercaptan, tert-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, methyl thiophenol, ethyl thiophenol and other thiol series; acetanilide, acetyl methoxyaniline, N-acetyl o-toluidine, acrylamide, methacrylamide, acetamide, stearamide, benzamide and other amide series; succinimide, phthalimide , maleimide and other imide series; diphenylamine, phenylnaphthylamine, dimethylaniline, N-phenyldimethylaniline, carbazole, aniline, naphthylamine, butylamine, dibutylamine, butylaniline and other amine series; imidazole series such as imidazole and 2-ethylimidazole; urea series such as urea, thiourea, ethylene urea, ethylene thiourea, diphenyl urea; carbamate series such as N-phenylcarbamate; imine series such as ethyleneimine and propyleneimine; sulfite series such as sodium bisulfite and potassium bisulfite; azole compounds, etc. Examples of the azole compounds include pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3,5-dimethylpyrazole, 3-methyl-5-phenylpyrazole and the like, and pyrazole derivatives; imidazole, benzimidazole, 2-methylimidazole, 2-ethylimidazole, 2-phenylimidazole and the like, and imidazoline derivatives such as 2-methylimidazoline and 2-phenylimidazoline.

[0188] Among them, preferred end-capping agents include active methylene end-capping agents, pyrazole, or pyrazole derivatives.

[0189] When performing the blocking reaction (making the blocking agent react), a solvent may be added as needed. The solvent used for the blocking reaction may be a solvent that is non-reactive to the isocyanate group, and examples thereof include ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate, and solvents such as N-methyl-2-pyrrolidone (NMP).

[0190] In addition, as the above-mentioned blocking agent, hydroxycarboxylic acids having one or more hydroxyl groups and one or more carboxyl groups may be used, such as hydroxypivalic acid, dimethylolpropionic acid, etc. In particular, blocked polyisocyanate compounds obtained by neutralizing the carboxyl groups of the hydroxycarboxylic acids to impart water dispersibility after blocking the isocyanate groups with the above-mentioned hydroxycarboxylic acids may be preferably used.

[0191] When the curing agent (B) contains a blocked polyisocyanate compound (B4), the content of the blocked polyisocyanate compound (B4) is preferably in the range of 10 to 80% by mass, more preferably in the range of 15 to 70% by mass, and further preferably in the range of 20 to 65% by mass, based on the total solid content of the curing agent (B).

[0192] The above-mentioned curing agent (B) can be used alone or in combination of two or more.

[0193] The content of the curing agent (B) in the aqueous coating composition of the present invention is in the range of 5 to 50% by mass based on the total resin solid content in the aqueous coating composition. By making the content of the curing agent (B) in the range of 5 to 50% by mass, a coating film having excellent abrasion resistance, glass adhesion and chipping resistance can be formed.

[0194] From the viewpoints of abrasion resistance and glass adhesion of the formed coating film, the content of the curing agent (B) is preferably in the range of 7 to 50% by mass, more preferably in the range of 10 to 40% by mass, and further preferably in the range of 10 to 30% by mass, based on the total resin solid content in the aqueous coating composition.

[0195] The aqueous coating composition of the present invention may further contain at least one resin selected from the group consisting of an acrylic resin (C) and a polyester resin (D), as necessary.

[0196] [Acrylic resin (C)]

[0197] As the acrylic resin (C), a known water-soluble or water-dispersible acrylic resin that has been conventionally used in water-based coating materials can be used.

[0198] The acrylic resin (C) preferably has a crosslinkable functional group that can react with the curing agent (B). Examples of the crosslinkable functional group include a hydroxyl group, a carboxyl group, and an alkoxysilyl group.

[0199] The acrylic resin (C) can be produced, for example, by copolymerizing a polymerizable unsaturated monomer by a method known per se, for example, a solution polymerization method in an organic solvent, an emulsion polymerization method in water, or the like.

[0200] As the polymerizable unsaturated monomer, for example, the following monomers (i) to (xxi) etc. can be used. These polymerizable unsaturated monomers can be used alone or in combination of two or more.

[0201] (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, tert-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, tricyclodecyl (meth)acrylate, etc.

[0202] (ii) Polymerizable unsaturated monomer having an isobornyl group: isobornyl (meth)acrylate, etc.

[0203] (iii) Polymerizable unsaturated monomer having an adamantyl group: adamantyl (meth)acrylate, etc.

[0204] (iv) Polymerizable unsaturated monomer having a tricyclodecenyl group: tricyclodecenyl (meth)acrylate, etc.

[0205] (v) Polymerizable unsaturated monomers containing aromatic rings: benzyl (meth)acrylate, styrene, α-methylstyrene, vinyl toluene, etc.

[0206] (vi) Polymerizable unsaturated monomers having an alkoxysilyl group: vinyl trimethoxysilane, vinyl triethoxysilane, vinyl tri(2-methoxyethoxy)silane, γ-(meth)acryloxypropyl trimethoxysilane, γ-(meth)acryloxypropyl triethoxysilane, etc.

[0207] (vii) Polymerizable unsaturated monomers having a fluoroalkyl group: perfluoroalkyl (meth)acrylates such as perfluorobutyl ethyl (meth)acrylate and perfluorooctyl ethyl (meth)acrylate; fluoroolefins, and the like.

[0208] (viii) A polymerizable unsaturated monomer having a photopolymerizable functional group such as a maleimide group.

[0209] (ix) Vinyl compounds: N-vinyl pyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate, etc.

[0210] (x) Carboxyl-containing polymerizable unsaturated monomers: (meth)acrylic acid, maleic acid, crotonic acid, β-carboxyethyl (meth)acrylate, etc.

[0211] (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 and amine compounds, etc.

[0212] (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.

[0213] (xiii) Epoxy-containing polymerizable unsaturated monomers: glycidyl (meth)acrylate, β-methyl glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3,4-epoxycyclohexylethyl (meth)acrylate, 3,4-epoxycyclohexylpropyl (meth)acrylate, allyl glycidyl ether, etc.

[0214] (xiv) (meth)acrylate having a polyoxyethylene chain with an alkoxy group at the molecular end

[0215] (xv) Polymerizable unsaturated monomers having a sulfonic acid group: 2-acrylamide-2-methylpropanesulfonic acid, 2-sulfoethyl (meth)acrylate, allylsulfonic acid, 4-styrenesulfonic acid, etc.; sodium salts and ammonium salts of these sulfonic acids, etc.

[0216] (xvi) Polymerizable unsaturated monomers having a phosphoric acid group: acidic phosphoryloxyethyl (meth)acrylate, acidic phosphoryloxypropyl (meth)acrylate, acidic phosphoryloxypoly (oxyethylene) glycol (meth)acrylate, acidic phosphoryloxypoly (oxypropylene) glycol (meth)acrylate, etc.

[0217] (xvii) Polymerizable unsaturated monomers having ultraviolet 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.

[0218] (xviii) Light-stable 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-crotonyloxy-2,2,6,6-tetramethylpiperidine, 4-crotonylamino-2,2,6,6-tetramethylpiperidine, 1-crotonyl-4-crotonyloxy-2,2,6,6-tetramethylpiperidine, etc.

[0219] (xix) Polymerizable unsaturated monomers having a carbonyl group: acrolein, diacetone acrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate, formylstyrene, vinyl alkyl ketones having 4 to 7 carbon atoms (e.g., vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone), etc.

[0220] (xx) Polymerizable unsaturated monomers having anhydride groups: maleic anhydride, itaconic anhydride, citraconic anhydride, etc.

[0221] (xxi) Hydroxyl-containing polymerizable unsaturated monomers: monoesters of (meth)acrylic acid and diols having 2 to 8 carbon atoms, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; ε-caprolactone-modified monoesters of (meth)acrylic acid and diols having 2 to 8 carbon atoms; N-hydroxymethyl (meth)acrylamide; allyl alcohol; and (meth)acrylates having a polyoxyethylene chain with a hydroxyl group at the molecular end. Among them, the monomers belonging to the above-mentioned "(xvii) polymerizable unsaturated monomers having ultraviolet absorbing functional groups" are excluded from the above-mentioned "hydroxyl-containing polymerizable unsaturated monomers" even if they are monomers having a hydroxyl group.

[0222] When the acrylic resin (C) contains the hydroxyl-containing polymerizable unsaturated monomer as a constituent component of the acrylic resin (C), the proportion of the hydroxyl-containing polymerizable unsaturated monomer used is preferably in the range of 1 to 50% by mass, more preferably in the range of 2 to 40% by mass, and further preferably in the range of 3 to 30% by mass, based on the total amount of the monomer components.

[0223] When the acrylic resin (C) contains the carboxyl-containing polymerizable unsaturated monomer as a constituent component of the acrylic resin (C), the proportion of the carboxyl-containing polymerizable unsaturated monomer used is preferably in the range of 1 to 50% by mass, more preferably in the range of 1.5 to 40% by mass, and further preferably in the range of 2 to 30% by mass, based on the total amount of the monomer components.

[0224] When the acrylic resin (C) contains the alkoxysilyl-containing polymerizable unsaturated monomer as a constituent component of the acrylic resin (C), the proportion of the alkoxysilyl-containing polymerizable unsaturated monomer used is preferably in the range of 1 to 70% by mass, more preferably in the range of 1.5 to 60% by mass, and further preferably in the range of 2 to 40% by mass, based on the total amount of the monomer components.

[0225] From the viewpoints of curability, abrasion resistance, chipping resistance and glass adhesion of the formed coating film, the hydroxyl value of the acrylic resin (C) is preferably in the range of 1 to 200 mgKOH / g, more preferably in the range of 2 to 180 mgKOH / g, and further preferably in the range of 5 to 150 mgKOH / g.

[0226] From the viewpoint of storage stability of the obtained aqueous coating composition, the acid value of the acrylic resin (C) is preferably in the range of 1 to 150 mgKOH / g, more preferably in the range of 5 to 100 mgKOH / g, and even more preferably in the range of 5 to 80 mgKOH / g.

[0227] When the aqueous coating composition of the present invention contains the above-mentioned acrylic resin (C), the content of the acrylic resin (C) is preferably in the range of 2 to 70% by mass, more preferably in the range of 5 to 60% by mass, and further preferably in the range of 10 to 50% by mass, based on the total resin solid content in the aqueous coating composition.

[0228] [Polyester resin (D)]

[0229] As the polyester resin (D), a known water-soluble or water-dispersible polyester resin that has been conventionally used in water-based coatings can be used.

[0230] The polyester resin (D) preferably has a crosslinkable functional group that can react with the curing agent (B). Examples of the crosslinkable functional group include a hydroxyl group and a carboxyl group.

[0231] The polyester resin (D) can generally be produced by an esterification reaction or an ester exchange reaction between an acid component and an alcohol component.

[0232] As the acid component, a compound generally used as an acid component when producing a polyester resin can be used. Examples of the acid component include aliphatic polybasic acids, alicyclic polybasic acids, and aromatic polybasic acids.

[0233] The above-mentioned aliphatic polybasic acid is usually an aliphatic compound having two or more carboxyl groups in one molecule, an anhydride of the aliphatic compound, and an ester of the aliphatic compound. Examples of the aliphatic polybasic acid include aliphatic polycarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, octadecanedioic acid, citric acid, and butanetetracarboxylic acid; anhydrides of the aliphatic polybasic carboxylic acids; esters of lower alkyl groups having about 1 to 4 carbon atoms of the aliphatic polybasic carboxylic acids, and the like. The above-mentioned aliphatic polybasic acids may be used alone or in combination of two or more.

[0234] As the aliphatic polybasic acid, adipic acid and / or adipic anhydride is preferably used from the viewpoint of chipping resistance of the formed coating film.

[0235] The above-mentioned alicyclic polybasic acid is generally a compound having one or more alicyclic structures and two or more carboxyl groups in one molecule, an anhydride of the compound, and an ester of the compound. The alicyclic structure is mainly a 4- to 6-membered ring structure. Examples of the alicyclic polybasic acid 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; esters of lower alkyl groups having about 1 to 4 carbon atoms of the alicyclic polycarboxylic acids, and the like. The above-mentioned alicyclic polybasic acids can be used alone or in combination of two or more.

[0236] As the above-mentioned alicyclic polybasic acid, from the viewpoint of chipping resistance of the formed coating film, 1,2-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic anhydride, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, and 4-cyclohexene-1,2-dicarboxylic anhydride are preferably used, and among them, 1,2-cyclohexanedicarboxylic acid and / or 1,2-cyclohexanedicarboxylic anhydride are more preferably used.

[0237] The aromatic polybasic acid is usually an aromatic compound having two or more carboxyl groups in one molecule, an anhydride of the aromatic compound, and an ester of the aromatic compound, and examples thereof include aromatic polybasic carboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid, 4,4'-biphenyl dicarboxylic acid, trimellitic acid, and pyromellitic acid; anhydrides of the aromatic polybasic carboxylic acids; esters of lower alkyl groups having about 1 to 4 carbon atoms of the aromatic polybasic carboxylic acids, etc. The aromatic polybasic acids may be used alone or in combination of two or more.

[0238] As the aromatic polybasic acid, phthalic acid, phthalic anhydride, isophthalic acid, trimellitic acid, or trimellitic anhydride is preferably used.

[0239] In addition, acid components other than the above-mentioned aliphatic polybasic acid, alicyclic polybasic acid and aromatic polybasic acid can also be used. As the acid component, there is no particular limitation, and fatty acids such as coconut oil fatty acid, cottonseed oil fatty acid, hempseed 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, safflower oil fatty acid can be listed; monocarboxylic acids such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, benzoic acid, p-tert-butylbenzoic acid, cyclohexane acid, 10-phenyloctadecanoic acid; hydroxycarboxylic acids such as lactic acid, 3-hydroxybutyric acid, 3-hydroxy-4-ethoxybenzoic acid, etc. can be listed. These acid components can be used alone or in combination of two or more.

[0240] As the alcohol component, a polyol having two or more hydroxyl groups in one molecule can be preferably used. Examples of the polyol 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, and 1,2-pentanediol. , 1,5-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, tricyclodecane dimethanol, hydroxypivalic acid neopentyl glycol ester, hydrogenated bisphenol A, hydrogenated bisphenol F, dimethylol propionic acid and other diols; polylactone diols obtained by adding lactone compounds such as ε-caprolactone to these diols; 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, polytetramethylene ether glycol; trivalent or higher alcohols such as glycerol, trimethylolethane, trimethylolpropane, diglycerol, triglycerol, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, tri(2-hydroxyethyl)isocyanuric acid, sorbitol, mannitol; polylactone polyol compounds obtained by adding lactone compounds such as ε-caprolactone to these trivalent or higher alcohols; fatty acid esters of glycerol, etc.

[0241] In addition, alcohol components other than the above-mentioned polyols may also be used. The above-mentioned alcohol components are not particularly limited, and examples thereof include monohydric alcohols such as methanol, ethanol, propanol, butanol, stearyl alcohol, and 2-phenoxyethanol; 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 high-branched saturated fatty acid) with an acid; and the like.

[0242] The method for producing the polyester resin is not particularly limited and can be carried out according to a common method. For example, the polyester resin can be produced by heating the acid component and the alcohol component at about 150 to 250° C. for about 5 to 10 hours in a nitrogen gas stream to carry out an esterification reaction or an ester exchange reaction of the acid component and the alcohol component.

[0243] When the acid component and the alcohol component are subjected to an esterification reaction or an ester exchange reaction, they may be added to the reaction vessel at once, or one or both may be added in several portions. Alternatively, a hydroxyl-containing polyester resin may be synthesized first, and then an acid anhydride may be reacted with the obtained hydroxyl-containing polyester resin to perform half-esterification, thereby producing a carboxyl-containing polyester resin. Alternatively, a carboxyl-containing polyester resin may be synthesized first, and then the alcohol component may be added to produce a hydroxyl-containing polyester resin.

[0244] In the esterification or transesterification reaction, as a catalyst for accelerating the reaction, a known catalyst such as dibutyltin oxide, antimony trioxide, zinc acetate, manganese acetate, cobalt acetate, calcium acetate, lead acetate, tetrabutyl titanate, tetraisopropyl titanate, etc. can be used.

[0245] Furthermore, the polyester resin may be modified with a fatty acid, a monoepoxy compound, a polyisocyanate compound, an acrylic resin, or the like during or after the preparation of the resin.

[0246] Examples of the fatty acid include coconut oil fatty acid, cottonseed oil fatty acid, hempseed 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. Examples of the monoepoxy compound include "Cardura E10P" (trade name, manufactured by HEXION, a glycidyl ester of a synthetic highly branched saturated fatty acid).

[0247] In addition, examples of the polyisocyanate compound include aliphatic diisocyanate compounds such as lysine diisocyanate, hexamethylene diisocyanate, and trimethylhexane diisocyanate; alicyclic 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; aromatic diisocyanate compounds such as toluene diisocyanate, xylylene diisocyanate, and diphenylmethane diisocyanate; organic polyisocyanates such as lysine triisocyanate and other trivalent or higher polyisocyanates; adducts of these organic polyisocyanates with polyols, low molecular weight polyester resins, water, and the like; cyclized polymers (such as isocyanurates) and biuret-type adducts of these organic polyisocyanates. These polyisocyanate compounds can be used alone or in combination of two or more.

[0248] In addition, as a method for modifying the above-mentioned polyester resin with an acrylic resin, a known method can be used, for example, a method of polymerizing a mixture of a polyester resin containing a polymerizable unsaturated group and a polymerizable unsaturated monomer, a method of utilizing a reaction between a polyester resin and an acrylic resin, etc.

[0249] The hydroxyl value of the polyester resin (D) is preferably in the range of 1 to 250 mgKOH / g, more preferably in the range of 2 to 200 mgKOH / g, and further preferably in the range of 5 to 180 mgKOH / g.

[0250] The acid value of the polyester resin (D) is preferably in the range of 1 to 150 mgKOH / g, more preferably in the range of 2 to 100 mgKOH / g, and even more preferably in the range of 2 to 80 mgKOH / g.

[0251] The number average molecular weight of the polyester resin (D) is preferably in the range of 500 to 50,000, more preferably in the range of 800 to 30,000, and even more preferably in the range of 1,000 to 10,000.

[0252] When the aqueous coating composition of the present invention contains the above-mentioned polyester resin (D), the content of the polyester resin (D) is preferably in the range of 2 to 70% by mass, more preferably in the range of 5 to 50% by mass, and further preferably in the range of 10 to 40% by mass, based on the total resin solid content in the aqueous coating composition.

[0253] [Other ingredients]

[0254] The aqueous coating composition of the present invention may further contain an aqueous dispersion of polyurethane resin (A) particles, a curing agent (B), resins other than acrylic resin (C) and polyester resin (D), pigments, organic solvents, curing catalysts, dispersants, anti-settling agents, defoaming agents, thickeners, ultraviolet absorbers, light stabilizers, surface conditioners, etc. as needed.

[0255] Examples of the resin other than the above-mentioned polyurethane resin (A) particle aqueous dispersion, curing agent (B), acrylic resin (C) and polyester resin (D) include polyurethane resins other than the polyurethane resin (A) particle aqueous dispersion, acrylic-modified polyurethane resins other than the polyurethane resin (A) particle aqueous dispersion, polyester-modified polyurethane resins other than the polyurethane resin (A) particle aqueous dispersion, polyolefin resins, epoxy resins and the like.

[0256] Examples of the pigment include coloring pigments, extender pigments, and bright pigments. These pigments may be used alone or in combination of two or more.

[0257] When the aqueous coating composition of the present invention contains the above-mentioned pigment, the amount of the pigment blended 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 further preferably in the range of 3 to 120 parts by mass, based on 100 parts by mass of the total resin solid content in the aqueous coating composition.

[0258] Examples of the coloring pigment include titanium oxide, zinc oxide, carbon black, molybdenum red, Prussian blue, cobalt blue, azo pigments, phthalocyanine pigments, quinacridone pigments, isoindoline pigments, threne pigments, perylene pigments, dioxazine pigments, diketopyrrolopyrrole pigments, etc. Among them, titanium oxide and carbon black are preferably used.

[0259] When the aqueous coating composition of the present invention contains the above-mentioned coloring pigment, the amount of the coloring pigment blended 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 further preferably in the range of 15 to 120 parts by mass, based on 100 parts by mass of the total resin solid content in the aqueous coating composition.

[0260] Examples of the extender pigment include barium sulfate, talc, clay, kaolin, barium carbonate, calcium carbonate, silicon dioxide, alumina white, etc. As the extender pigment, barium sulfate and talc are preferably used from the viewpoint of coating stability and finished product quality.

[0261] When the aqueous coating composition of the present invention contains the above-mentioned extender pigment, the amount of the extender pigment blended 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 further preferably in the range of 10 to 120 parts by mass, based on 100 parts by mass of the total resin solid content in the aqueous coating composition.

[0262] In addition, examples of the bright pigment 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 them, aluminum pigments are preferably used. Aluminum pigments include non-leafing aluminum pigments and leafing aluminum pigments, and both can be used.

[0263] The bright pigment is preferably in the form of flakes. Also, as the bright pigment, a bright pigment having a length 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 is suitable.

[0264] When the aqueous coating composition of the present invention contains the above-mentioned bright pigment, the compounding amount of the bright 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 further preferably in the range of 3 to 25 parts by mass, based on 100 parts by mass of the total resin solid content in the aqueous coating composition.

[0265] Examples of the organic solvent 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 isopropyl alcohol, n-butanol, isobutyl alcohol, 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.

[0266] When the aqueous coating composition of the present invention is used, it can be diluted by adding water and / or an organic solvent or the like as necessary to adjust the viscosity to an appropriate level, and then applied.

[0267] The appropriate viscosity varies depending on the composition of the coating. For example, from the viewpoint of the appearance of the formed coating film, the viscosity after 1 minute at 60 rpm measured at a temperature of 20° C. with a B-type viscometer (sometimes referred to as "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 further preferably in the range of 500 to 1500 mPa·s. At this time, the viscometer used is "LVDV-I" (trade name, manufactured by Brookfield, B-type viscometer).

[0268] In the above, the coating solid content concentration of the aqueous coating composition of the present invention is usually about 5 to 70% by mass, preferably about 10 to 55% by mass.

[0269] In view of the abrasion resistance, chipping resistance and glass adhesion of the formed coating film, the gel fraction of the coating film formed from the aqueous coating composition of the present invention is preferably 85% or more, more preferably 87% or more, and even more preferably 90% or more.

[0270] In this specification, the gel fraction is measured by the following method.

[0271] First, the water-based coating composition of the present invention is applied to a polypropylene plate for gel fraction measurement so that the film thickness becomes 30 μm, and heated at 80° C. for 20 minutes to form a cured coating. Next, the formed cured coating is peeled off from the polypropylene plate and placed in a 300-mesh stainless steel mesh container whose mass (W1) has been measured in advance, and the total mass (W2) of the cured coating and the mesh container is measured. The mesh container containing the cured coating is placed in an equal mass mixed solvent of acetone and methanol heated to 50° C., and an extraction treatment is performed for 5 hours. After drying at 110° C. for 60 minutes, the total mass (W3) of the remaining cured coating and the mesh container is measured, and the insoluble coating residual rate (mass %) obtained according to the following formula is used as the gel fraction.

[0272] Gel fraction (mass %) = (W3-W1) / (W2-W1)×100

[0273] The aqueous coating composition of the present invention may be either a one-component coating or a multi-component coating, but is preferably a one-component coating from the viewpoints of eliminating the coating mixing step, being excellent in productivity, and being able to simplify the maintenance of coating machinery.

[0274] [Coating film forming method]

[0275] When the aqueous coating composition of the present invention forms a colored coating film on a coated object, it can be used as an aqueous coating composition for the colored coating film. The coating film formation method at this time can be carried out according to the following method I, for example.

[0276] <Method I>

[0277] A method for forming a coating film, characterized in that it comprises:

[0278] Step (I-1): a step of applying the aqueous coating composition to a coating object to form an uncured colored coating film;

[0279] Step (I-2): a step of curing the uncured colored coating film formed in the above step (I-1) by heating.

[0280] Examples of the coated objects include outer panels and inner panels of automobile bodies such as cars, trucks, motorcycles, and buses; automobile parts; and outer panels of household appliances such as mobile phones and audio equipment. Among them, outer panels, inner panels, and automobile parts of automobile bodies are preferred.

[0281] The materials of these coated objects are not particularly limited. Examples include metal materials such as iron, aluminum, brass, copper, tinplate, stainless steel, galvanized steel, zinc alloy (Zn-Al, Zn-Ni, Zn-Fe, etc.) steel; resins 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 FRPs; inorganic materials such as glass, cement, and concrete; wood; fiber materials such as paper and cloth, etc. Among them, metal materials and plastic materials are preferred.

[0282] In addition, the surface of the object to which the coating film is applied may be a surface treated by phosphate treatment, chromate treatment, composite oxide treatment or the like on the metal surfaces of the outer and inner panels of automobile bodies, automobile parts, household appliances, metal substrates such as steel sheets constituting them, etc.

[0283] A coating film may be further formed on an object that may or may not be subjected to a surface treatment. For example, a surface treatment may be applied to a coated object as a substrate as needed to form a base coating film thereon. For example, when the coated object is a car body, the base coating film may be formed using a base coating material that is generally used in the coating of the car body and is known per se.

[0284] As the base coating material for forming the base coating film, for example, an electrodeposition coating material can be used, and preferably a cationic electrodeposition coating material is used.

[0285] When the base coating film is formed on the above-mentioned object to be coated, a mid-coat film may be further formed thereon. For example, when the object to be coated is a car body, the mid-coat film may be formed using a known mid-coat coating material commonly used in the coating of the car body. The mid-coat film may be cured by heating or may not be cured by heating.

[0286] The above-mentioned water-based coating composition can be applied to the object by a method known per se, such as air spray coating, airless spray coating, rotary atomization coating, curtain coating, etc., and during coating, electrostatic application can be performed. Among them, air spray coating and rotary atomization coating are preferred. In addition, the coating method can be performed once to several times until the desired film thickness is obtained.

[0287] The amount of the aqueous coating composition applied is preferably an amount that gives a cured film thickness of the formed colored coating film of 5 to 40 μm, more preferably 7 to 35 μm, and even more preferably 10 to 30 μm.

[0288] The heating can be performed by known means, for example, a drying furnace such as a hot air furnace, an electric furnace, an infrared induction heating furnace, etc. The heating temperature is preferably in the range of 60 to 150° C., more preferably in the range of 70 to 120° C., and further preferably in the range of 75 to 100° 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.

[0289] [Multilayer coating film forming method]

[0290] The aqueous coating composition of the present invention can be used for forming a mid-coat film and / or a base coat film when forming a multilayer coating film comprising a mid-coat film, a base coat film and a clear coat film on an object such as an automobile body by a 3-coat 1-bake method.

[0291] The aqueous coating composition of the present invention can be formed into a multilayer coating film according to the following method II, for example.

[0292] <Method II>

[0293] A method for forming a multilayer coating film, characterized in that it comprises:

[0294] Step (II-1): a step of applying a mid-coat coating composition to a coating object to form an uncured mid-coat coating film;

[0295] Step (II-2): a step of applying a primer coating composition on the uncured intermediate coating film formed in the above step (II-1) to form an uncured primer coating film;

[0296] Step (II-3): a step of applying a clear coating composition on the uncured base coating film formed in the above step (II-2) to form an uncured clear coating film;

[0297] Step (II-4): A step of heating and curing the uncured middle coating film formed in the above step (II-1), the uncured base coating film formed in the above step (II-2), and the uncured clear coating film formed in the above step (II-3) at one time, wherein at least one of the above middle coating composition or the above base coating composition is the water-based coating composition of the present invention.

[0298] Method II includes the following method IIa, method IIb and method IIc.

[0299] When the aqueous coating composition of the present invention is used for forming the intermediate coating film, a multilayer coating film can be formed according to the following method IIa, for example.

[0300] <Method IIa>

[0301] A method for forming a multilayer coating film, comprising:

[0302] Step (IIa-1): a step of applying the aqueous coating composition of the present invention as a mid-coat coating composition to a coating object to form an uncured mid-coat coating film;

[0303] Step (IIa-2): a step of applying a primer coating composition on the uncured intermediate coating film formed in the above step (IIa-1) to form an uncured primer coating film;

[0304] Step (IIa-3): a step of applying a clear coating composition on the uncured base coating film formed in the above step (IIa-2) to form an uncured clear coating film;

[0305] Step (IIa-4): A step of heating and curing the uncured intermediate coating film formed in the above step (IIa-1), the uncured base coating film formed in the above step (IIa-2), and the uncured clear coating film formed in the above step (IIa-3) at one time.

[0306] As the above-mentioned coating object, the coating objects exemplified in the above-mentioned method I can be used.

[0307] In addition, the surface of the object to which the coating film is applied may be a surface treated by phosphate treatment, chromate treatment, composite oxide treatment or the like on the metal surfaces of the outer and inner panels of automobile bodies, automobile parts, household appliances, metal substrates such as steel sheets constituting them, etc.

[0308] A coating film may be further formed on an object that may or may not be subjected to a surface treatment. For example, a surface treatment may be applied to a coated object as a substrate as needed to form a base coating film thereon. For example, when the coated object is a car body, the base coating film may be formed using a base coating material that is generally used in the coating of the car body and is known per se.

[0309] As the base coating material for forming the base coating film, for example, an electrodeposition coating material can be used, and preferably a cationic electrodeposition coating material is used.

[0310] The above-mentioned water-based coating composition can be applied to the object by a method known per se, such as air spray coating, airless spray coating, rotary atomization coating, curtain coating, etc., and during coating, electrostatic application can be performed. Among them, air spray coating and rotary atomization coating are preferred. In addition, the coating method can be performed once to several times until the desired film thickness is obtained.

[0311] The amount of the aqueous coating composition applied is preferably an amount that gives a cured film thickness of the intermediate coating film to be formed of 5 to 40 μm, more preferably 7 to 35 μm, and even more preferably 10 to 30 μm.

[0312] As the above-mentioned primer coating composition, a composition prepared by coating a base resin such as an acrylic resin, polyester resin, alkyd resin, polyurethane resin, epoxy resin, etc. having crosslinking functional groups such as carboxyl and hydroxyl groups, an amino resin such as melamine resin and urea resin, a crosslinking agent such as a polyisocyanate compound that may be blocked, a pigment, a thickener and any other selected ingredients together can be used.

[0313] The coating method of the above-mentioned primer coating composition is not particularly limited, and for example, a wet coating film can be formed by a coating method such as air spray coating, airless spray coating, rotary atomization coating, curtain coating, etc. In these coating methods, electrostatic application can be performed as needed. Among them, air spray coating or rotary atomization coating is particularly preferred. The coating amount of the primer coating composition is usually preferably an amount of 5 to 40 μm in terms of cured film thickness, more preferably an amount of 7 to 35 μm, and further preferably an amount of 10 to 30 μm.

[0314] As the above-mentioned clear coating composition, any known thermosetting clear coating composition for coating automobile bodies, etc. can be used. Examples of the thermosetting clear coating composition include, for example, an organic solvent-based thermosetting coating composition, a water-based thermosetting coating composition, a powder thermosetting coating composition, etc., containing a base resin having a crosslinkable functional group and a curing agent. Among them, from the viewpoint of the finished appearance of the formed multilayer coating film, an organic solvent-based thermosetting coating composition containing a base resin having a crosslinkable functional group and a crosslinking agent is preferred.

[0315] Examples of the crosslinkable functional group possessed by the base resin include carboxyl, hydroxyl, epoxy, alkoxysilyl, etc. Examples of the type of base resin include acrylic resin, polyester resin, alkyd resin, polyurethane resin, epoxy resin, fluororesin, etc. Examples of the curing agent include polyisocyanate compounds, blocked polyisocyanate compounds, melamine resins, urea resins, carboxyl-containing compounds, carboxyl-containing resins, epoxy-containing resins, epoxy-containing compounds, etc.

[0316] The base resin / curing agent combination of the above-mentioned clear coating composition is preferably a hydroxyl-containing resin / polyisocyanate compound, a carboxyl-containing resin / epoxy-containing resin, a hydroxyl-containing resin / blocked polyisocyanate compound, a hydroxyl-containing resin / melamine resin, etc., and more preferably a hydroxyl-containing resin / polyisocyanate compound.

[0317] The clear coating composition may be a one-component coating or a multi-component coating such as a two-component polyurethane resin coating.

[0318] In addition, the above-mentioned clear coating composition may contain coloring pigments, bright pigments, dyes, etc. as needed to the extent that transparency is not impaired, and may also appropriately contain extender pigments, ultraviolet absorbers, light stabilizers, defoamers, thickeners, rust inhibitors, surface conditioners, etc.

[0319] The coating method of the clear coating composition is not particularly limited, and for example, a wet coating film can be formed by a coating method such as air spray coating, airless spray coating, rotary atomization coating, curtain coating, etc. In these coating methods, electrostatic application can be performed as needed. Among them, air spray coating or rotary atomization coating is particularly preferred. The coating amount of the clear coating composition is usually preferably an amount of 10 to 70 μm in terms of cured film thickness, and more preferably an amount of 20 to 50 μm.

[0320] In the case of air spray coating, airless spray coating and rotary atomization coating, it is preferred to use a solvent such as an organic solvent to appropriately adjust the viscosity of the clear coating composition to a viscosity range suitable for the coating, usually about 15 to 60 seconds, particularly about 20 to 50 seconds, in a Ford Cup No. 4 viscometer at 20°C.

[0321] The heating can be performed by known means, for example, a drying furnace such as a hot air furnace, an electric furnace, an infrared induction heating furnace, etc. The heating temperature is preferably in the range of 60 to 150° C., more preferably in the range of 70 to 120° C., and further preferably in the range of 75 to 100° 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.

[0322] When the aqueous coating composition of the present invention is used for forming the above-mentioned primer coating film, a multilayer coating film can be formed according to the following method IIb, for example.

[0323] <Method IIb>

[0324] A method for forming a multilayer coating film, comprising:

[0325] Step (IIb-1): a step of applying a mid-coat coating composition to a coating object to form an uncured mid-coat coating film;

[0326] Step (IIb-2): a step of applying the aqueous coating composition of the present invention as a primer coating composition on the uncured intermediate coating film formed in the above step (IIb-1) to form an uncured primer coating film;

[0327] Step (IIb-3): a step of applying a clear coating composition on the uncured base coating film formed in the above step (IIb-2) to form an uncured clear coating film;

[0328] Step (IIb-4): A step of heating and curing the uncured intermediate coating film formed in the above step (IIb-1), the uncured base coating film formed in the above step (IIb-2), and the uncured clear coating film formed in the above step (IIb-3) at one time.

[0329] As the above-mentioned coating object, the coating objects exemplified in the above-mentioned method I can be used.

[0330] In addition, the surface of the object to which the coating film is applied may be a surface treated by phosphate treatment, chromate treatment, composite oxide treatment or the like on the metal surfaces of the outer and inner panels of automobile bodies, automobile parts, household appliances, metal substrates such as steel sheets constituting them, etc.

[0331] A coating film may be further formed on an object that may or may not be subjected to a surface treatment. For example, a surface treatment may be applied to a coated object as a substrate as needed to form a base coating film thereon. For example, when the coated object is a car body, the base coating film may be formed using a base coating material that is generally used in the coating of the car body and is known per se.

[0332] As the base coating material for forming the base coating film, for example, an electrodeposition coating material can be used, and preferably a cationic electrodeposition coating material is used.

[0333] As the above-mentioned mid-coat coating composition, a composition prepared by coating a base resin such as an acrylic resin, polyester resin, alkyd resin, polyurethane resin, epoxy resin, etc. having cross-linking functional groups such as carboxyl and hydroxyl groups, an amino resin such as melamine resin and urea resin, a cross-linking agent such as a polyisocyanate compound that may be blocked, a pigment, a thickener and any other selected ingredients together can be used.

[0334] The coating method of the above-mentioned mid-coat coating composition is not particularly limited, and for example, a wet coating film can be formed by a coating method such as air spray coating, airless spray coating, rotary atomization coating, curtain coating, etc. In these coating methods, electrostatic application can be performed as needed. Among them, air spray coating or rotary atomization coating is particularly preferred. The coating amount of the mid-coat coating composition is usually preferably an amount of 5 to 40 μm in terms of cured film thickness, more preferably an amount of 7 to 35 μm, and further preferably an amount of 10 to 30 μm.

[0335] The above-mentioned water-based coating composition can be applied to the object by a method known per se, such as air spray coating, airless spray coating, rotary atomization coating, curtain coating, etc., and during coating, electrostatic application can be performed. Among them, air spray coating and rotary atomization coating are preferred. In addition, the coating method can be performed once to several times until the desired film thickness is obtained.

[0336] The amount of the aqueous coating composition applied is preferably an amount that gives a cured film thickness of the formed primer coating film of 5 to 40 μm, more preferably 7 to 35 μm, and even more preferably 10 to 30 μm.

[0337] As the clear coating composition, the clear coating composition exemplified in the above-mentioned method IIa can be used.

[0338] The coating method of the clear coating composition is not particularly limited, and for example, a wet coating film can be formed by a coating method such as air spray coating, airless spray coating, rotary atomization coating, curtain coating, etc. In these coating methods, electrostatic application can be performed as needed. Among them, air spray coating or rotary atomization coating is particularly preferred. The coating amount of the clear coating composition is usually preferably an amount of 10 to 70 μm in terms of cured film thickness, and more preferably an amount of 20 to 50 μm.

[0339] In the case of air spray coating, airless spray coating and rotary atomization coating, it is preferred to use a solvent such as an organic solvent to appropriately adjust the viscosity of the clear coating composition to a viscosity range suitable for the coating, usually about 15 to 60 seconds, particularly about 20 to 50 seconds, in a Ford Cup No. 4 viscometer at 20°C.

[0340] The heating can be performed by known means, for example, a drying furnace such as a hot air furnace, an electric furnace, an infrared induction heating furnace, etc. The heating temperature is preferably in the range of 60 to 150° C., more preferably in the range of 70 to 120° C., and further preferably in the range of 75 to 100° 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.

[0341] When the aqueous coating composition of the present invention is used for forming the intermediate coating film and the primer coating film, a multilayer coating film can be formed, for example, according to the following method IIc.

[0342] The aqueous coating composition of the present invention used for forming the intermediate coating film and the aqueous coating composition of the present invention used for forming the primer coating film may be the same as or different from each other.

[0343] <Method IIc>

[0344] A method for forming a multilayer coating film, comprising:

[0345] Step (IIc-1): a step of applying the aqueous coating composition of the present invention as a mid-coat coating composition to a coating object to form an uncured mid-coat coating film;

[0346] Step (IIc-2): a step of applying the aqueous coating composition of the present invention as a primer coating composition on the uncured intermediate coating film formed in the above step (IIc-1) to form an uncured primer coating film;

[0347] Step (IIc-3): a step of applying a clear coating composition on the uncured base coating film formed in the above step (IIc-2) to form an uncured clear coating film;

[0348] Step (IIc-4): A step of heating and curing the uncured intermediate coating film formed in the above step (IIc-1), the uncured base coating film formed in the above step (IIc-2), and the uncured clear coating film formed in the above step (IIc-3) at one time.

[0349] As the above-mentioned coating object, the coating objects exemplified in the above-mentioned method I can be used.

[0350] In addition, the surface of the object to which the coating film is applied may be a surface treated by phosphate treatment, chromate treatment, composite oxide treatment or the like on the metal surfaces of the outer and inner panels of automobile bodies, automobile parts, household appliances, metal substrates such as steel sheets constituting them, etc.

[0351] A coating film may be further formed on an object that may or may not be subjected to a surface treatment. For example, a surface treatment may be applied to a coated object as a substrate as needed to form a base coating film thereon. For example, when the coated object is a car body, the base coating film may be formed using a base coating material that is generally used in the coating of the car body and is known per se.

[0352] As the base coating material for forming the base coating film, for example, an electrodeposition coating material can be used, and preferably a cationic electrodeposition coating material is used.

[0353] The aqueous coating composition used for forming the intermediate coating film can be applied to the object by a method known per se, such as air spray coating, airless spray coating, rotary atomization coating, curtain coating, etc., and electrostatic application can be performed during coating. Among them, air spray coating and rotary atomization coating are preferred. In addition, the coating method can be performed once to several times until the desired film thickness is obtained.

[0354] The amount of the aqueous coating composition used for forming the intermediate coating film is preferably an amount to give a cured film thickness of 5 to 40 μm, more preferably 7 to 35 μm, and even more preferably 10 to 30 μm.

[0355] The aqueous coating composition used for forming the above-mentioned primer coating film can be applied to the object by a method known per se, such as air spray coating, airless spray coating, rotary atomization coating, curtain coating, etc., and during coating, electrostatic application can be performed. Among them, air spray coating and rotary atomization coating are preferred. In addition, the coating method can be performed once to several times until the desired film thickness is obtained.

[0356] The amount of the aqueous coating composition used for forming the primer film is preferably an amount to give a cured film thickness of the primer film to be formed of 5 to 40 μm, more preferably 7 to 35 μm, and even more preferably 10 to 30 μm.

[0357] As the clear coating composition, the clear coating composition exemplified in the above-mentioned method IIa can be used.

[0358] The coating method of the clear coating composition is not particularly limited, and for example, a wet coating film can be formed by a coating method such as air spray coating, airless spray coating, rotary atomization coating, curtain coating, etc. In these coating methods, electrostatic application can be performed as needed. Among them, air spray coating or rotary atomization coating is particularly preferred. The coating amount of the clear coating composition is usually preferably an amount of 10 to 70 μm in terms of cured film thickness, and more preferably an amount of 20 to 50 μm.

[0359] In the case of air spray coating, airless spray coating and rotary atomization coating, it is preferred to use a solvent such as an organic solvent to appropriately adjust the viscosity of the clear coating composition to a viscosity range suitable for the coating, usually about 15 to 60 seconds, particularly about 20 to 50 seconds, in a Ford Cup No. 4 viscometer at 20°C.

[0360] The heating can be performed by known means, for example, a drying furnace such as a hot air furnace, an electric furnace, an infrared induction heating furnace, etc. The heating temperature is preferably in the range of 60 to 150° C., more preferably in the range of 70 to 120° C., and further preferably in the range of 75 to 100° 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.

[0361] Example

[0362] Hereinafter, the present invention will be described in more detail by way of manufacturing examples, embodiments and comparative examples. However, the present invention is not limited thereto. In each example, unless otherwise specified, "parts" and "%" are based on a mass basis. In addition, the film thickness of the coating film is based on the cured coating film.

[0363] [Production of Compound (a1) Having a Secondary Amino Group and an Alkoxysilyl Group]

[0364] [Production Example 1]

[0365] 55.89 parts of n-butyl acrylate and 0.01 parts of dibutylhydroxytoluene were placed in a reaction container equipped with a thermometer, a thermostat, a stirring device and a reflux condenser, and the contents of the reaction container were stirred and mixed under air flow, and the temperature of the contents was raised to 50°C. Next, 44.1 parts of "KBM-602" (trade name, manufactured by Shin-Etsu Chemical Co., Ltd., N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane) was added dropwise over 2 hours to the reaction container maintained at the same temperature. After the addition was completed, 1.0 parts of butyl acetate was added to the reaction container, and the contents of the reaction container were aged for 2 hours. Next, the contents of the reaction container were discharged while being filtered with a 100-mesh nylon cloth, and the discharged product was left to stand in a constant temperature room at 50°C for 1 week to obtain a compound (a1-1) containing a secondary amino group and an alkoxysilyl group.

[0366] [Production Examples 2 to 12]

[0367] In Production Example 1, except that the compounding composition was as shown in the following Table 1, the same procedure as in Production Example 1 was carried out to obtain compounds (a1-2) to (a1-12) having a secondary amino group and an alkoxysilyl group.

[0368] It should be noted that in Table 1, compound (a1), compound (a11), compound (a11-1) and compound (a12) respectively refer to compound (a1) containing a secondary amino group and an alkoxysilyl group, compound (a11) containing an amino group and an alkoxysilyl group, compound (a11-1) containing a primary amino group, a secondary amino group and an alkoxysilyl group, and compound (a12) containing a polymerizable unsaturated group.

[0369] [Table 1]

[0370]

[0371] In addition, each component described in the table is as follows.

[0372] (Note 1) "KBM-603": Trade name, manufactured by Shin-Etsu Chemical Co., Ltd., N-2-(Aminoethyl)-3-aminopropyltrimethoxysilane

[0373] (Note 2) "KBM-903": Trade name, manufactured by Shin-Etsu Chemical Co., Ltd., 3-aminopropyltrimethoxysilane

[0374] [Production of Polyurethane Resin (A) Particle Aqueous Dispersion]

[0375] [Production Example 13]

[0376] In a reaction container equipped with a thermometer, a thermostat, a stirrer and a reflux condenser, 26.9 parts of "ETERNACOLL UH-200" (trade name, manufactured by Ube Industries, Ltd., polycarbonate diol having 1,6-hexanediol as the main skeleton, molecular weight 2000), 34.1 parts of "PTMG2000" (trade name, manufactured by Mitsubishi Chemical Corporation, polytetramethylene ether glycol, molecular weight 2000), 1.78 parts of 1,4-cyclohexanedimethanol, 4.8 parts of dimethylolpropionic acid, 0.04 parts of "Neostann U-600" (trade name, manufactured by Nitto Kasei Co., Ltd., bismuth-based catalyst) and 50.0 parts of methyl ethyl ketone were placed, and the contents of the reaction container were heated to 80° C. while stirring and mixing in an air stream, and then 9.3 parts of isophorone diisocyanate and 16.2 parts of dicyclohexylmethane-4,4'-diisocyanate were added dropwise to the reaction container over 30 minutes. Then, the content of the reaction container was reacted until the free isocyanate group content was kept at 1.6% or less, thereby obtaining a urethane prepolymer solution.

[0377] Next, the urethane prepolymer solution obtained above was cooled to 60°C, and 3.43 parts of the compound (a1-1) containing a secondary amino group and an alkoxysilyl group obtained in Production Example 1 was added dropwise to the reaction container over 10 minutes. After the addition was completed, the contents of the reaction container were aged for 20 minutes and cooled to room temperature.

[0378] Next, 2.5 parts of triethylamine and 142.6 parts of deionized water were added dropwise to the reaction container over 60 minutes. After the contents of the reaction container were emulsified, 17.8 parts of a 5% aqueous solution of ethylenediamine was added dropwise to the reaction container over 15 minutes to perform a chain extension reaction.

[0379] Then, the solvent was distilled off from the reaction container under reduced pressure, and the concentration of the contents of the reaction container was adjusted with deionized water to obtain an aqueous dispersion of polyurethane resin (A-1) particles having a solid content concentration of 35%, an acid value of 20 mgKOH / g, and an average particle size of 100 nm (measured at 20° C. using a particle size distribution measuring apparatus "ELSZ-2000" (trade name, manufactured by Otsuka Electronics Co., Ltd.) based on a dynamic light scattering method, diluted with deionized water).

[0380] [Production Examples 14 to 51]

[0381] In Production Example 13, except that the compounding composition was as shown in Table 2 below, the same procedure as in Production Example 13 was carried out to obtain polyurethane resin (A-2) to (A-39) particle water dispersions.

[0382] In addition, in Table 2, the compound (a1) containing a secondary amino group and an alkoxysilyl group and the urethane prepolymer (a2) containing an isocyanate group.

[0383] [Table 2-1]

[0384]

[0385] [Table 2-2]

[0386]

[0387] [Table 2-3]

[0388]

[0389] In addition, each component described in the table is as follows.

[0390] (Note 3) "ETERNACOLL UM-90 (3 / 1)": Trade name, manufactured by Ube Industries, Ltd., polycarbonate diol with 1,6-hexanediol and 1,4-cyclohexanedimethanol as main skeleton, molecular weight 900

[0391] (Note 4) "ETERNACOLL UC-100": Trade name, manufactured by Ube Industries, Ltd., polycarbonate diol with 1,4-cyclohexanedimethanol as the main skeleton, molecular weight 1000

[0392] (Note 5) “ETERNACOLL UP-200”: Trade name, manufactured by Ube Industries, Ltd., polycarbonate diol, molecular weight 2000

[0393] (Note 6) "Kuraray Polyol C-3090": Trade name, manufactured by KURARAY CO., LTD., polycarbonate diol, molecular weight 3000

[0394] (Note 7) "PTMG 3000": trade name, manufactured by Mitsubishi Chemical Corporation, polytetramethylene ether glycol, molecular weight 3000

[0395] (Note 8) "PTMG 1000": trade name, manufactured by Mitsubishi Chemical Corporation, polytetramethylene ether glycol, molecular weight 1000

[0396] (Note 9) “SANNIX PP-2000”: trade name, manufactured by Sanyo Chemical Co., Ltd., polypropylene glycol, molecular weight 2000)

[0397] [Production of acrylic resin (C)]

[0398] [Production Example 52]

[0399] 120 parts of deionized water and 0.8 parts of "ADEKA REASOAP SR-1025" (trade name, manufactured by ADEKA, emulsifier, active ingredient 25%) were added to a reaction container equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, a nitrogen inlet tube and a dropping device, and the contents of the reaction container were stirred and mixed under a nitrogen flow to raise the temperature of the contents to 80°C.

[0400] Next, 5% of the total amount of the monomer emulsion for the core described below and 2.5 parts of a 6% aqueous solution of ammonium persulfate were introduced into the reaction container, and the contents of the reaction container were kept at 80°C for 15 minutes. Then, the remaining amount of the monomer emulsion for the core was added dropwise to the reaction container kept at the same temperature over 3 hours, and after the addition was completed, the contents of the reaction container were aged for 1 hour. Next, the monomer emulsion for the shell described below was added dropwise over 1 hour, and after aging for 1 hour, 3.8 parts of a 5% aqueous solution of 2-(dimethylamino)ethanol was slowly added to the reaction container, and the contents of the reaction container were cooled to 30°C, and the contents of the reaction container were discharged while being filtered with a 100-mesh nylon cloth, to obtain a dispersion of acrylic resin (C-1) particles having an average particle size of 100 nm and a solid content of 30%. The obtained acrylic resin (C-1) particles had an acid value of 17.2 mgKOH / g and a hydroxyl value of 27.2 mgKOH / g.

[0401] Monomer emulsion for core:

[0402] 54 parts of deionized water, 3.1 parts of "ADEKA REASOAP 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 core monomer emulsion.

[0403] Monomer emulsion for shell:

[0404] 50 parts of deionized water, 1.8 parts of "ADEKA REASOAP 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 were mixed and stirred to obtain a monomer emulsion for a shell part.

[0405] [Production of polyester resin (D)]

[0406] [Production Example 53]

[0407] In a reaction vessel equipped with a thermometer, a thermostat, a stirring device, a reflux condenser and a water separator, 126 parts of trimesic acid, 1365 parts of "PTMG650" (trade name, manufactured by Mitsubishi Chemical Corporation, polytetramethylene ether glycol, molecular weight 650) and 37 parts of glycerol were placed, and the contents of the reaction vessel were heated between 160° C. and 230° C. over 3 hours, and then the contents were subjected to condensation reaction at 230° C. until the final acid value reached 3 mgKOH / g. Next, in order to add carboxyl groups to the obtained condensation reaction product, 77 parts of trimellitic anhydride were further added to the reaction vessel, and the contents of the reaction vessel were reacted at 170° C. for 30 minutes, and then 0.5 equivalents of 2-(dimethylamino)ethanol were added to the reaction vessel with respect to the acid groups, and the contents were further diluted with 2-ethyl-1-hexanol to obtain a polyester resin (D-1) solution having a solid content concentration of 70%. The obtained polyester resin (D-1) had an acid value of 32 mgKOH / g, a hydroxyl value of 117 mgKOH / g, a solid content concentration of 70%, and a number average molecular weight of 1,200.

[0408] [Production of Blocked Polyisocyanate Compound (B4)]

[0409] [Production Example 54]

[0410] In a reaction vessel equipped with a thermometer, a thermostat, a stirring device, a reflux condenser, a nitrogen inlet tube, a dropping device, and a simple trap for removing solvents, 360 parts of "Sumidur N-3300", 60 parts of "Uniox M-550" (manufactured by NOF Corporation, polyethylene glycol monomethyl ether, average molecular weight of about 550) and 0.2 parts of 2,6-di-tert-butyl-4-methylphenol were added, the contents of the reaction vessel were fully mixed, and the contents were heated at 130°C for 3 hours under a nitrogen stream. Next, 110 parts of ethyl acetate and 252 parts of diisopropyl malonate were added to the reaction vessel, and 3 parts of a 28% methanol solution of sodium methoxide were added to the reaction vessel while stirring the contents of the reaction vessel under a nitrogen stream, and the contents of the reaction vessel were stirred at 65°C for 8 hours. The amount of isocyanate in the obtained resin solution was 0.12 mol / kg. 683 parts of 4-methyl-2-pentanol were added to the reaction vessel, and the temperature of the system was maintained at 80-85°C while the solvent was distilled off under reduced pressure for 3 hours to obtain 1010 parts of an active methylene type blocked polyisocyanate compound (B4-1) solution. The solvent was removed in a simple trap containing 95 parts of isopropanol. The solid content concentration of the obtained active methylene type blocked polyisocyanate compound (B4-1) solution was about 60%.

[0411] [Production of Phosphoric Acid Group-Containing Dispersion Resin (R)]

[0412] [Production Example 55]

[0413] A mixed solvent of 27.5 parts of methoxypropanol and 27.5 parts of isobutyl alcohol was added to a reaction container equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, a nitrogen inlet tube and a dropping device, and the content of the reaction container was heated to 110° C. Then, 121.5 parts of a mixture containing 25 parts of styrene, 27.5 parts of n-butyl methacrylate, 20 parts of "isostearyl acrylate" (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd., branched higher alkyl acrylate), 7.5 parts of 4-hydroxybutyl acrylate, 15 parts of a phosphoric acid group-containing polymerizable unsaturated monomer (Note 1), 12.5 parts of 2-methacryloyloxyethyl acid phosphate, 10 parts of isobutyl alcohol and 4 parts of t-butyl peroxyoctanoate were added to the reaction container over 4 hours, and a mixture containing 0.5 parts of t-butyl peroxyoctanoate and 20 parts of isopropyl alcohol was added dropwise to the reaction container for 1 hour. Then, the contents of the reaction container were stirred and aged for 1 hour to obtain a 50% solid content concentration of a phosphoric acid group-containing dispersion resin (R-1) solution. The resin had an acid value of 83 mgKOH / g based on phosphoric acid groups, a hydroxyl value of 29 mgKOH / g, and a weight average molecular weight of 10,000.

[0414] (Note 1) Polymerizable unsaturated monomer containing a phosphoric acid group: 57.5 parts of monobutyl phosphate and 41 parts of isobutyl alcohol were added to a reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, a nitrogen inlet tube and a dropping device. After the contents of the reaction vessel were heated to 90°C, 42.5 parts of glycidyl methacrylate were added dropwise to the reaction vessel over 2 hours, and the contents of the reaction vessel were further stirred and aged for 1 hour. Then, 59 parts of isopropyl alcohol were added to the reaction vessel to obtain a phosphoric acid group-containing polymerizable unsaturated monomer solution having a solid content concentration of 50%. The acid value of the obtained monomer based on the phosphoric acid group was 285 mgKOH / g.

[0415] [Manufacturing of Pigment Dispersion Liquid (P)]

[0416] [Production Example 56]

[0417] 28.6 parts (solid content 20 parts) of the polyester resin (D-1) solution obtained in Production Example 53, 90 parts of "JR-806" (trade name, manufactured by TAYCA CORPORATION, rutile titanium dioxide), 30 parts of "BARIACE B-35" (trade name, manufactured by Sakai Chemical Industry Co., Ltd., barium sulfate powder), 0.8 parts of "Carbon MA100" (trade name, manufactured by Mitsubishi Chemical Corporation, carbon black) and 10 parts of deionized water were mixed in a container equipped with a stirring device, and the contents of the container were adjusted to pH 8.0 using 2-(dimethylamino)ethanol. Next, the obtained mixed solution was added to a wide-mouthed glass bottle, glass beads with a diameter of about 1.3 mmφ were added as a dispersion medium, and the mixture was sealed and dispersed for 30 minutes using a paint shaker to obtain a pigment dispersion (P-1).

[0418] [Production Example 57]

[0419] 66.7 parts (solid content 20 parts) of the acrylic resin (C-1) particle dispersion obtained in Preparation Example 52, 10 parts of "Carbon MA-100" (trade name, manufactured by Mitsubishi Chemical Corporation, carbon black) and 50 parts of deionized water were added to a container equipped with a stirring device, and the contents of the container were uniformly mixed, and the contents of the container were adjusted to pH 7.5 using 2-(dimethylamino)ethanol. Next, the obtained mixed solution was added to a wide-mouthed glass bottle, glass beads with a diameter of about 1.3 mmφ were added as a dispersion medium, and the bottle was sealed and dispersed for 4 hours using a paint shaker to obtain a pigment dispersion (P-2).

[0420] [Preparation of water-based coating composition]

[0421] [Example 1]

[0422] 128.6 parts (solid content 45 parts) of the polyurethane resin (A-1) particle aqueous dispersion obtained in Preparation Example 13, 50 parts (solid content 15 parts) of the acrylic resin (C-1) particle dispersion obtained in Preparation Example 52, 25 parts (solid content 10 parts) of "CARBODILITE SV02" (trade name, manufactured by Nisshinbo Co., Ltd., carbodiimide compound, solid content 40%, carbodiimide equivalent per unit solid content 429), and "CYMEL 325" (trade name, manufactured by Allnex Japan Inc., melamine resin, solid content concentration 80%), 6.25 parts (5 parts solid content), 8.3 parts (5 parts solid content) of the active methylene-type blocked polyisocyanate compound (B4-1) solution obtained in Preparation Example 54, and 159.4 parts (20 parts resin solid content) of the pigment dispersion (P-1) obtained in Preparation Example 56 were uniformly mixed to form a mixture, and to the mixture were added "UH-752" (trade name, manufactured by ADEKA Corporation, thickener, solid content concentration 28%), 2-(dimethylamino)ethanol and deionized water to obtain an aqueous coating composition No. 1 with a pH of 8.0, a solid content concentration of 48%, and a viscosity of 800 mPa·s after 1 minute at 60 rpm measured by a B-type viscometer at a temperature of 20°C.

[0423] [Examples 2 to 44 and Comparative Examples 1 to 4]

[0424] Aqueous coating compositions Nos. 2 to 44 and 89 to 92 were obtained in the same manner as in aqueous coating composition No. 1 of Example 1 except that the coating composition had been changed to the composition shown in Table 3 below.

[0425] [Example 45]

[0426] 85.7 parts (30 parts solid content) of the polyurethane resin (A-1) particle aqueous dispersion obtained in Preparation Example 13, 93.3 parts (28 parts solid content) of the acrylic resin (C-1) particle dispersion obtained in Preparation Example 52, 25 parts (10 parts solid content) of "CARBODILITE SV02" (trade name, manufactured by Nisshinbo Co., Ltd., carbodiimide compound, 40% solid content, carbodiimide equivalent per unit solid content 429), and CYMEL 325 (trade name, manufactured by Allnex Japan Inc., melamine resin, solid content concentration 80%), 6.25 parts (5 parts solid content) of the active methylene type blocked polyisocyanate compound (E4-1) solution obtained in Preparation Example 54, 8.3 parts (5 parts solid content) of the pigment dispersion (P-2) obtained in Preparation Example 57, and 4 parts (2 parts solid content) of the phosphoric acid group-containing acrylic resin (R-1) obtained in Preparation Example 55 were uniformly mixed to form a mixture, and to the mixture were added "UH-752" (trade name, manufactured by ADEKA Corporation, thickener, solid content concentration 28%), 2-(dimethylamino)ethanol and deionized water to obtain an aqueous coating composition No. 45 with a pH of 8.0, a solid content concentration of 25%, and a viscosity of 800 mPa·s after 1 minute at 60 rpm measured by a B-type viscometer at a temperature of 20°C.

[0427] [Examples 46 to 88 and Comparative Examples 5 to 8]

[0428] Aqueous coating compositions Nos. 46 to 88 and 93 to 96 were obtained in the same manner as in aqueous coating composition No. 45 of Example 45 except that the coating composition had been changed to the composition shown in Table 3 below.

[0429] [Gel fraction]

[0430] The gel fraction of each aqueous coating composition obtained in Examples 1 to 88 and Comparative Examples 1 to 8 was measured by the method described in the present specification. Table 3 shows the results of the gel fraction measurement.

[0431] [Storage stability test]

[0432] The storage stability of each aqueous coating composition obtained in Examples 1 to 88 and Comparative Examples 1 to 8 was evaluated based on the viscosity after 1 minute at 60 rpm measured using an "LVDV-I" (trade name, manufactured by Brookfield, Inc., a B-type viscometer) by the viscosity change rate expressed by the following formula between the viscosity immediately after production and the viscosity after standing at 40°C for 10 days.

[0433] Viscosity change rate (%)

[0434] =|(viscosity after standing at 40°C for 10 days / viscosity immediately after production)-1|×100

[0435] ◎ and ○ indicate passing. Table 3 shows the evaluation results.

[0436] ◎: The viscosity change rate is less than 50%.

[0437] ○: The viscosity change rate is 50% or more and less than 100%.

[0438] ×: The viscosity change rate is 100% or more.

[0439] [Abrasion resistance test]

[0440] On a cold-rolled steel sheet subjected to a zinc phosphate chemical conversion treatment, an electrodeposition coating of "ELECRON GT-10" (trade name, manufactured by Kansai Paint Co., Ltd., a cationic electrodeposition coating) was applied to a dry film thickness of 20 μm, thereby forming an electrodeposition coating film, and the electrodeposition coating film was heated at 170°C for 30 minutes to cure the electrodeposition coating film, thereby preparing a coated object for a wear resistance test. On the coated object for a wear resistance test, each aqueous coating composition obtained in Examples 1 to 88 and Comparative Examples 1 to 8 was used, and electrostatic coating was performed using a rotary atomization type electrostatic coating machine to form an uncured coating film by making the dry film thickness become 15 μm. The uncured coating film was left to stand for 3 minutes, and then, after preheating at 80°C for 3 minutes, the uncured coating film was heated at 80°C for 20 minutes to prepare a coated plate for a wear resistance test.

[0441] The weight before the wear test of the coated plate for the wear resistance test obtained above was measured, and then, it was installed in a "5130ABRASER" (trade name, manufactured by Toyo Seiki Co., Ltd., Taber-type wear tester), and a "CS-10CALIBRASE" (trade name, manufactured by TABER Co., Ltd., wear wheel) was used to wear each coating film under a load of 500 gf and a rotation number of 500 times. After the wear test, the weight after the wear test of the coated plate for the wear resistance test was measured, and the weight change (mg) was calculated by the following formula.

[0442] Weight change (mg) = weight before abrasion test - weight after abrasion test ◎ and ○ are acceptable.

[0443] ◎: Weight change is less than 20 mg.

[0444] ○: The weight change is 20 mg or more and less than 30 mg. ×: The weight change is 30 mg or more.

[0445] [Table 3-1]

[0446]

[0447] [Table 3-2]

[0448]

[0449] [Table 3-3]

[0450]

[0451] [Table 3-4]

[0452]

[0453] [Table 3-5]

[0454]

[0455] [Table 3-6]

[0456]

[0457] [Table 3-7]

[0458]

[0459] [Table 3-8]

[0460]

[0461] [Preparation of coated panels for multi-layer coating tests]

[0462] [Example 89]

[0463] On a cold-rolled steel sheet subjected to a zinc phosphate chemical conversion treatment, an uncured electrodeposition coating "ELECRON GT-10" (trade name, manufactured by Kansai Paint Co., Ltd., a cationic electrodeposition coating) was applied to a dry film thickness of 20 μm to form the uncured electrodeposition coating film, and the uncured electrodeposition coating film was heated at 170° C. for 30 minutes to cure the electrodeposition coating film, thereby producing a coated object.

[0464] On the above-mentioned coated object, the water-based coating composition No. 1 obtained in Example 1 as the intermediate coating composition was electrostatically coated using a rotary atomization type electrostatic coating machine to a dry film thickness of 25 μm to form a coating film, and the coating film was left for 5 minutes and then preheated at 80° C. for 3 minutes to form an uncured intermediate coating film. Next, on the uncured intermediate coating film, the water-based coating composition No. 45 obtained in Example 45 as the primer coating composition was electrostatically coated using a rotary atomization type electrostatic coating machine to a dry film thickness of 15 μm to form a coating film, and the coating film was left for 5 minutes and then preheated at 80° C. for 3 minutes to form an uncured primer coating film. On the above uncured primer coating film, electrostatic coating "KINO6510" (trade name, Kansai Paint Co., Ltd., hydroxyl / isocyanate-cured acrylic resin·polyurethane resin two-component organic solvent-based clear coating) was applied to make the cured film thickness 35 μm to form an uncured clear coating film. The coating film with the uncured clear coating layer was left for 7 minutes to form an uncured multilayer coating film including a mid-coat coating film, a primer coating film and a clear coating film. The uncured multilayer coating film was heated at 80°C for 30 minutes to sinter the mid-coat coating film, the primer coating film and the clear coating film at one time to prepare a coated plate for a multilayer coating film test.

[0465] [Examples 90 to 136, Comparative Examples 9 to 12]

[0466] In Example 89, except that the combination of the aqueous coating composition was changed to the combination shown in Table 4, the same procedure as in Example 89 was carried out to prepare coated plates for each multilayer coating film test.

[0467] [Glass Adhesion Test]

[0468] On the multilayer coating of each multilayer coating test plate obtained in the above-mentioned Examples 89 to 136 and Comparative Examples 9 to 12, a urethane adhesive (trade name "3740", manufactured by SUNSTAR, automotive windshield agent) was further applied so that the coating shape was 20 mm wide, 3 mm thick, and 100 mm long or more, and after covering it with release paper, it was evenly pressed with a flat plate. After removing the flat plate from each multilayer coating test plate, the polyurethane adhesive on each multilayer coating test plate was placed at a temperature of 23±2°C and a relative humidity of 50±5% for 72 hours to cure it, forming an adhesive layer. Then, the release paper was peeled off from each multilayer coating test plate. Next, each multilayer coating test plate was immersed in a constant temperature water bath set at 50°C for 240 hours and then immersed in water at 23°C for 1 hour and cooled. Thereafter, each multilayer coating test plate was subjected to the following peeling test.

[0469] The cured adhesive layer was stretched by hand in a direction of 90 degrees or more relative to the multilayer coating film, and the multilayer coating film was cut at an angle of about 60 degrees with a cutter at intervals of 2 to 3 mm until the coating film surface was reached. The peeling state after peeling the adhesive layer was evaluated according to the following criteria. ◎, ○+ and ○ were qualified. The evaluation results are shown in Table 4.

[0470] ⊚: No peeling of the adhesive layer was observed, and no exposure of the multilayer coating film was observed.

[0471] ○+: The multilayer coating film was not destroyed, and only the adhesive layer was peeled off due to cohesive failure, but the adhesion between the multilayer coating film and the adhesive layer was almost maintained.

[0472] ○: The multilayer coating film was cohesively broken and peeled off, and the width thereof was less than 1 mm from the portion cut with the cutter.

[0473] △: The multilayer coating film was peeled off due to cohesive failure, and the width thereof was 1 mm or more from the portion where the cutter was placed.

[0474] ×: Peeling was observed at the interface between the multilayer coating film and the adhesive layer.

[0475] [Crack resistance test]

[0476] The multilayer coating test panels obtained in Examples 89 to 136 and Comparative Examples 9 to 12 were placed on a test piece holding table of a flying stone tester "JA-400" (trade name, manufactured by Suga Test Instruments Co., Ltd., chipping resistance tester) and subjected to a pressure of 0.39 MPa (4 kgf / cm2) at a distance of 35 cm from the test panel at -20°C. 2 ) compressed air, 50 g of road crushed stone (S-5) described in JIS A5001 was made to collide with the test plate at an angle of 90 degrees. Then, the obtained test plate was washed with water and dried, and a cloth adhesive tape (made by Nichiban Co., Ltd.) was attached to the coated surface. After peeling it off, the degree of scratches on the coating film was visually observed, and the evaluation was performed according to the following criteria. ◎ and ○ were qualified. The evaluation results are shown in Table 4.

[0477] ◎: The size of the scratch is extremely small, and the electrodeposited surface and the base steel plate are not exposed.

[0478] ○: The size of the flaw is small, and the electrodeposited surface and the base steel plate are not exposed.

[0479] △: The size of the flaw is small, but the electrodeposited surface and the base steel sheet are exposed.

[0480] ×: The size of the flaw is quite large, and the base steel plate is also largely exposed.

[0481] [Table 4-1]

[0482] Table 4

[0483]

[0484] [Table 4-2]

[0485] Table 4 (Continued-1)

[0486]

[0487] [Table 4-3]

[0488] Table 4 (Continued-2)

[0489]

[0490] [Table 4-4]

[0491] Table 4 (Continued-3)

[0492]

[0493] [Table 4-5]

[0494] Table 4 (Continued-4)

[0495]

Claims

1. A water-based coating composition, characterized in that: The invention relates to an aqueous coating composition comprising a polyurethane resin (A) particle aqueous dispersion and a curing agent (B), wherein the polyurethane resin (A) particle aqueous dispersion is obtained from constituent components comprising a compound (a1) having a secondary amino group and an alkoxysilyl group and a urethane prepolymer (a2) containing an isocyanate group. The compound (a1) having a secondary amino group and an alkoxysilyl group is obtained from components including a compound (a11) containing a primary amino group and an alkoxysilyl group and a compound (a12) containing a polymerizable unsaturated group, and the urethane prepolymer (a2) containing an isocyanate group is obtained from components including a polyisocyanate component (a21) and a polyol component (a22). The content of the curing agent (B) is in the range of 5 to 50% by mass based on the total resin solid content in the aqueous coating composition.

2. The aqueous coating composition according to claim 1, wherein The polymerizable unsaturated group-containing compound (a12) includes a (meth)acrylate.

3. The aqueous coating composition according to claim 1 or 2, wherein: The polyisocyanate component (a21) contains an alicyclic polyisocyanate compound (a21-1).

4. The aqueous coating composition according to any one of claims 1 to 3, wherein The polyol component (a22) includes a polycarbonate polyol (a22-1) and a polyether polyol (a22-2).

5. The aqueous coating composition according to any one of claims 1 to 4, wherein The polyurethane resin (A) particle aqueous dispersion contains a chain extender (a3) ​​as a constituent component.

6. The aqueous coating composition according to any one of claims 1 to 5, wherein The polyurethane resin (A) particle water dispersion is contained in an amount within a range of 10 to 70% by mass based on the total resin solid content in the aqueous coating composition.

7. The aqueous coating composition according to any one of claims 1 to 6, wherein The curing agent (B) includes a polycarbodiimide compound (B1). 8 . The aqueous coating composition according to claim 1 , further comprising at least one resin selected from the group consisting of an acrylic resin (C) and a polyester resin (D).

9. A method for forming a coating film, characterized in that: It includes: Step (I-1): a step of applying the aqueous coating composition according to any one of claims 1 to 8 to a coating object to form an uncured colored coating film; Step (I-2): a step of curing the uncured colored coating film formed in the step (I-1) by heating.

10. A method for forming a multilayer coating film, characterized in that: It includes: Step (II-1): a step of applying a mid-coat coating composition to a coating object to form an uncured mid-coat coating film; Step (II-2): a step of applying a primer coating composition on the uncured intermediate coating film formed in the step (II-1) to form an uncured primer coating film; Step (II-3): a step of applying a clear coating composition on the uncured base coating film formed in the step (II-2) to form an uncured clear coating film; Step (II-4): a step of heating and curing the uncured intermediate coating film formed in the step (II-1), the uncured base coating film formed in the step (II-2), and the uncured clear coating film formed in the step (II-3) at one time, At least one of the intermediate coating composition and the primer coating composition is the aqueous coating composition according to any one of claims 1 to 8.

11. The method for forming a multilayer coating film according to claim 10, wherein: Both the intermediate coating composition and the base coating composition are the aqueous coating composition according to any one of claims 1 to 8.

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