CN105705597B

CN105705597B - Water-based paint compositions and coated article

Info

Publication number: CN105705597B
Application number: CN201480038672.XA
Authority: CN
Inventors: 古泽智
Original assignee: Kansai Paint Co Ltd
Current assignee: Kansai Paint Co Ltd
Priority date: 2013-08-27
Filing date: 2014-07-16
Publication date: 2018-04-13
Anticipated expiration: 2034-07-16
Also published as: JP5791846B2; WO2015029627A1; CN105705597A; JPWO2015029627A1

Abstract

The present invention provides a kind of water-based paint compositions, it is characterized in that, contain chlorine-free polyolefin-based resins (A), waterborne polyurethane resin (B), blocked polyisocyanate compound (C) and conductive pigment (D), and the acid number of waterborne polyurethane resin (B) is 1mgKOH/g~30mgKOH/g, and the time at a temperature of 20 DEG C untill film forming is 5 minutes~20 minutes.

Description

Aqueous coating composition and coated article

Technical Field

(Cross reference to related Art)

The present application claims the benefit of priority from the specification of japanese patent application No. 2013-175248, filed on 27/8/2013, which is incorporated by reference in its entirety into this specification.

(technical field)

The present invention relates to an aqueous coating composition and a coated article that can form a coating film having excellent chipping resistance, adhesion, polishability, and ethanol gasoline resistance, both with respect to metal parts and with respect to plastic parts.

Background

Generally, an automobile body has metal parts and plastic parts such as a bumper, which form the body.

In the coating of the automobile body, the following steps have been widely adopted: the plastic part is mounted on the metal part after coating with different paints and different coating processes suitable for the metal part and the plastic part.

However, in recent years, in order to reduce the facility cost in the manufacturing process of the automobile body and to make the color tones of the metal member and the plastic member uniform, a method of coating the metal member with the plastic member attached thereto has been demanded.

For example, patent document 1 discloses a method of coating an automobile body in which a polypropylene resin member is assembled with a metal steel plate.

However, the intermediate coating material disclosed in patent document 1 has no conductivity, and therefore, it is necessary to apply a conductive primer coating material to a polypropylene member. That is, in patent document 1, a conductive primer coating → an intermediate coating → a top coating are sequentially applied to a polypropylene member, and an intermediate coating → a top coating are sequentially applied to a metal member. That is, since the same coating material is not applied to all of the plastic member and the metal member in the same coating step, the cost reduction and color tone matching are not sufficient.

Patent document 2 discloses an aqueous coating composition containing a specific anionic urethane resin emulsion and a specific urethane resin. However, when the coating is applied to metal members and plastic members, even if chipping resistance and light transmittance are not problematic, it is difficult to say that adhesion to plastic members is sufficient compared to aqueous conductive primers.

Patent document 3 discloses an aqueous primer coating composition containing an aqueous polyolefin resin (a), at least 1 aqueous resin (B) selected from an aqueous polyurethane resin and an aqueous acrylic resin, a polyester resin (C), and a crosslinking agent (D) at a specific ratio. However, when the coating is applied to a metal member or a plastic member, even if there is no problem in adhesion to the plastic member, it is difficult to say that chipping resistance and light transmittance are sufficient compared with an aqueous intermediate coating.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2012-213692

Patent document 2: japanese patent laid-open publication No. 2005-330339

Patent document 3: WO2007/66827

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of these circumstances, and an object thereof is to provide an aqueous coating composition and a coated article capable of forming a coating film having excellent chipping resistance, adhesion, polishability, and ethanol gasoline resistance, both for metal parts and plastic parts.

Means for solving the problems

The present inventors have made intensive studies to achieve the above object and as a result, have found that the above object can be achieved by using an aqueous coating composition containing a non-chlorine polyolefin resin (a), a specific aqueous urethane resin (B), a blocked polyisocyanate compound (C) having a nonionic hydrophilic group, and a conductive pigment (D), and have completed the present invention.

Namely, the present invention provides the following aqueous coating composition and an article obtained by applying the aqueous coating composition.

In the first aspect of the present invention, there is provided an aqueous coating composition comprising a non-chlorine polyolefin resin (a), an aqueous polyurethane resin (B), a blocked polyisocyanate compound (C) having a nonionic hydrophilic group, and a conductive pigment (D), wherein the aqueous polyurethane resin (B) has an acid value of 1mgKOH/g to 35mgKOH/g, and the time required for film formation at a temperature of 20 ℃ is 5 minutes to 20 minutes.

In one embodiment, the blocked polyisocyanate compound (C) having a nonionic hydrophilic group is a blocked polyisocyanate compound having at least one blocked isocyanate group selected from the group consisting of a blocked isocyanate group represented by the following general formula (I), a blocked isocyanate group represented by the following general formula (II), and a blocked isocyanate group represented by the following general formula (III).

[ chemical formula 1]

[ in the formula (I), R¹、R²、R⁴And R⁵Independently represents a hydrocarbon group having 1 to 12 carbon atoms, R³Represents a linear or branched alkylene group having 1 to 12 carbon atoms.]

[ chemical formula 2]

[ in the formula (II), R²、R³、R⁴And R⁵And the above-mentioned R²、R³、R⁴And R⁵The same is true.]

[ chemical formula 3]

[ in the formula (III), R²、R³、R⁴And R⁵And the above-mentioned R²、R³、R⁴And R⁵Same as R⁶Represents a hydrocarbon group having 1 to 12 carbon atoms.]

In another embodiment, the aqueous coating composition further comprises a hydroxyl-containing acrylic resin.

In still another embodiment, the aqueous coating composition contains 10 to 60 mass% of the non-chlorine polyolefin resin (a), 10 to 50 mass% of the aqueous polyurethane resin (B), 5 to 40 mass% of the blocked isocyanate compound (C) having a nonionic hydrophilic group, and 0.5 to 40 mass% of the conductive pigment (D), based on the mass of the total resin solid content in the aqueous coating composition.

In a second aspect of the present invention, there is provided a method for forming a coating film by applying the aqueous coating composition described in any one of the above to a metal member and a plastic member as a substrate.

In a third aspect of the present invention, there is provided an article comprising a metal part and a plastic part of a substrate coated with a coating film of the aqueous coating composition described in any one of the above aspects.

Effects of the invention

The aqueous coating composition of the present invention can form a coating film having excellent chipping resistance, adhesion, and polishing properties and ethanol gasoline resistance, both for metal parts and plastic parts.

Detailed Description

Hereinafter, the aqueous coating composition of the present invention will be described in further detail.

In this specification, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise or clearly contradicts by context.

The aqueous coating composition of the present invention contains a non-chlorine polyolefin resin (a), a specific aqueous polyurethane resin (B), a blocked polyisocyanate compound (C) having a nonionic hydrophilic group, and a conductive pigment (D).

Non-chlorine polyolefin resin (A)

In the present invention, the non-chlorine polyolefin resin (a) has a polyolefin molecule as a main skeleton and is formed by introducing a hydrophilic group such as a carboxyl group into the polyolefin molecule, and the unsaturated carboxylic acid or acid anhydride-modified polyolefin (a) is generally preferred.

The unsaturated carboxylic acid or acid anhydride-modified polyolefin (a) can be usually obtained by graft copolymerizing an unsaturated carboxylic acid or acid anhydride to a polyolefin by a method known per se. Examples of the unsaturated carboxylic acid or anhydride that can be used for modification include aliphatic carboxylic acids or anhydrides thereof having 3 to 10 carbon atoms, which contain at least 1, preferably 1 polymerizable double bond in 1 molecule and do not contain chlorine, and specific examples thereof include: (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid, maleic anhydride and the like, and among them, maleic acid and maleic anhydride are particularly preferable. The graft copolymerization amount of the unsaturated carboxylic acid or its anhydride with respect to the polyolefin may vary depending on the physical properties desired for the modified polyolefin, but is usually in the range of 0.5 to 4% by weight, preferably 1 to 3% by weight, and more preferably 1.2 to 2.8% by weight, based on the weight of the solid content of the polyolefin.

On the other hand, the polyolefin used for modification includes, for example, an uncrosslinked polyolefin obtained by (co) polymerizing 1 or 2 or more species of olefins having 2 to 10 carbon atoms such as ethylene, propylene, butene, hexene, and the like, and a polyolefin containing propylene as a polymerization unit is particularly preferable. The weight fraction of propylene units in the modified polyolefin is usually in the range of 0.5 to 1, particularly preferably in the range of 0.7 to 0.99, and further particularly preferably in the range of 0.8 to 0.99, from the viewpoints of compatibility with other components, adhesion to form a coating film, and the like.

As the polyolefin, a known polyolefin which is not chlorinated can be used without limitation, but it is preferable to produce the polyolefin by (co) polymerizing an olefin using a single-site catalyst as a polymerization catalyst from the viewpoint of a narrow molecular weight distribution and excellent random copolymerization property of the obtained polyolefin.

The single-site catalyst is a polymerization catalyst having a uniform active site structure (single site), and among the single-site catalysts, a metallocene-based catalyst is particularly preferable. The metallocene catalyst is prepared by combining a metallocene (bis (cyclopentadienyl) metal complex or derivative thereof) which is a transition metal compound of groups IVB to VIB or VIII or a rare earth transition metal compound of group IIIB of the periodic Table of the elements having at least one conjugated five-membered ring ligand, a cocatalyst such as aluminoxane or boron for activating the metallocene, and an organoaluminum compound such as trimethylaluminum.

The (co) polymerization of olefins can be carried out by a method known per se, for example, by continuously adding an aluminum alkyl and a metallocene catalyst to a reaction vessel while supplying an olefin such as propylene or ethylene and hydrogen to the reaction vessel.

The unsaturated carboxylic acid-or acid anhydride-modified polyolefin (a) may be further subjected to acrylic modification. Examples of the acrylic unsaturated monomer usable for the acrylic modification include chlorine-free acrylic unsaturated monomers, for example, C1 to C20 alkyl esters of (meth) acrylic acid such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, and octadecyl (meth) acrylate; C1-C21 hydroxyalkyl esters of (meth) acrylic acid such as 2-hydroxyethyl (meth) acrylate and 3-hydroxypropyl (meth) acrylate; other acrylic monomers such as (meth) acrylic acid, glycidyl (meth) acrylate, (meth) acrylamide, and (meth) acrylonitrile, and further styrene, and these may be used alone or in combination of 2 or more.

In the present specification, "(meth) acrylic acid" means "acrylic acid or methacrylic acid", and "(meth) acrylate" means "acrylate or methacrylate".

The acrylic modification of the above-mentioned polyolefin can be carried out, for example, by: first, a chlorine-free acrylic unsaturated monomer reactive with the carboxyl group in the unsaturated carboxylic acid or acid anhydride-modified polyolefin produced as described above, for example, glycidyl (meth) acrylate or the like is reacted to introduce a polymerizable unsaturated group into the polyolefin, and then the acrylic unsaturated monomer alone or in combination of 2 or more is (co) polymerized with the polyolefin having the polymerizable unsaturated group introduced. The amount of the acrylic unsaturated monomer used in the acrylic modification of the polyolefin may vary depending on the physical properties desired for the modified polyolefin, but is usually preferably 30% by weight or less, particularly preferably in the range of 0.1 to 20% by weight, and further particularly preferably in the range of 0.15 to 15% by weight, based on the weight of the solid content of the obtained unsaturated carboxylic acid or acid anhydride-modified polyolefin (a), from the viewpoints of compatibility with other components, adhesion to form a coating film, and the like.

In the present invention, the unsaturated carboxylic acid or acid anhydride-modified polyolefin (a) may be further modified with a compound having a polyoxyalkylene chain. Examples of the polyoxyalkylene chain in the compound having a polyoxyalkylene chain include: polyoxyethylene chains, polyoxypropylene chains, capped chains of polyoxyethylene and polyoxypropylene, and the like.

The compound having a polyoxyalkylene chain generally preferably has a number average molecular weight in the range of 400 to 3,000, preferably 500 to 2,000. If the number average molecular weight is less than 400, the effect as a hydrophilic group may not be sufficiently exhibited, and the water resistance may be adversely affected, while if it exceeds 3,000, the solubility may be deteriorated by curing at room temperature, and the handling may be difficult.

The unsaturated carboxylic acid or acid anhydride-modified polyolefin (a) preferably has a melting point of 120 ℃ or less, preferably 60 to 110 ℃, more preferably 70 to 100 ℃, and a weight average molecular weight (Mw) of 10,000 to 230,000, preferably 50,000 to 200,000, more preferably 60,000 to 150,000, from the viewpoint of compatibility with other components, adhesion to a plastic part to be coated, interlayer adhesion to a top coating film layer, and the like.

In addition, the unsaturated carboxylic acid or acid anhydride-modified polyolefin (a) is desired to have a heat of fusion in the range of 1mJ/mg to 50mJ/mg, particularly 2mJ/mg to 50mJ/mg, from the viewpoint of adhesion to a plastic member to be coated, interlayer adhesion to a top coating film layer, and the like.

Here, the melting point and the heat of fusion of the unsaturated carboxylic acid or acid anhydride-modified polyolefin (a) can be measured by heating from-100 ℃ to 150 ℃ at a heating rate of 10 ℃/min using 20mg of the modified polyolefin by a differential scanning calorimetry apparatus "DSC-5200" (trade name, manufactured by Seiko electronics industries, Ltd.) the melting point and the heat of fusion can be measured by adjusting the melting point of the unsaturated carboxylic acid or acid anhydride-modified polyolefin (a) by changing the monomer composition of the polyolefin, particularly the amount of α -olefin monomer, and in the case where the heat of fusion is not easily determined, the heat of fusion can be measured by heating the measurement sample to 120 ℃ once, then cooling to room temperature at 10 ℃/min, and then leaving the sample to stand for 2 days or more.

The weight average molecular weight of the unsaturated carboxylic acid-or acid anhydride-modified polyolefin (a) is a value obtained by converting the weight average molecular weight measured by gel permeation chromatography into a polystyrene weight average molecular weight standard, and is measured at a column temperature of 135 ℃ and a flow rate of 1.0 ml/min using "HLC/GPC 150C" (manufactured by Waters corporation, 60cm × 1) as a gel permeation chromatography apparatus and o-dichlorobenzene as a solvent. The injection sample was prepared by dissolving at 140 ℃ for 1 to 3 hours so that the solution concentration of 5mg of polyolefin was obtained relative to 3.4ml of o-dichlorobenzene. As a column used for gel permeation chromatography, "GMHHR-H (S) HT" (trade name, manufactured by Tosoh Corp.).

Further, in the unsaturated carboxylic acid or acid anhydride-modified polyolefin (a), it is generally desirable that the ratio of the weight average molecular weight to the number average molecular weight (Mw/Mn) is in the range of 1.5 to 7.0, preferably in the range of 1.8 to 6.0, and more preferably in the range of 2.0 to 4.0, from the viewpoint of compatibility with other components, adhesion to form a coating film, and the like.

In the present invention, the non-chlorine polyolefin-based resin (a) can be dispersed in water by dispersing the unsaturated carboxylic acid or acid anhydride-modified polyolefin (a) described above in an aqueous medium, and usually can be dispersed in water by neutralizing a part or all of the carboxyl groups in the unsaturated carboxylic acid or acid anhydride-modified polyolefin (a) with an amine compound and/or with an emulsifier. From the viewpoint of improving water dispersibility, it is desirable to use water dispersion by neutralization and an emulsifier at the same time.

Examples of the amine compound used for neutralization include: tertiary amines such as triethylamine, tributylamine, dimethylethanolamine, and triethanolamine; secondary amines such as diethylamine, dibutylamine, diethanolamine, and morpholine; primary amines such as propylamine and ethanolamine. The amount of the amine compound used in the case of using the amine compound is preferably in the range of usually 0.1 to 1.0 molar equivalent to the carboxyl group in the unsaturated carboxylic acid-or acid anhydride-modified polyolefin (a).

Examples of the emulsifier include nonionic emulsifiers such as polyoxyethylene monooleyl ether, polyoxyethylene monostearyl ether, polyoxyethylene monolauryl ether, polyoxyethylene tridecyl ether, polyoxyethylene phenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene monooleate, sorbitan monolaurate, sorbitan monostearate, sorbitan trioleate, and polyoxyethylene sorbitan monolaurate, anionic emulsifiers such as sodium salts and ammonium salts of alkylsulfonic acid, alkylbenzenesulfonic acid, and alkylphosphoric acid, and polyoxyalkylene group-containing anionic emulsifiers having an anionic group and a polyoxyalkylene group such as a polyoxyethylene group or a polyoxypropylene group in 1 molecule, or polyoxyalkylene group-containing anionic emulsifiers having an anionic group and a polymerizable non-functional group in 1 molecule may be used Saturated group reactive anionic emulsifiers, and the like. These emulsifiers may be used alone or in combination of 2 or more.

The emulsifier is usually used in an amount of 1 to 20 parts by weight based on 100 parts by weight of the solid content of the unsaturated carboxylic acid-or acid anhydride-modified polyolefin (a).

The method for emulsifying the unsaturated carboxylic acid-or acid anhydride-modified polyolefin (a) is not particularly limited, and known methods such as phase inversion emulsification, D-phase emulsification, forced emulsification, gel emulsification, self-emulsification, reverse emulsification, and high-pressure emulsification can be used. Among them, a method of self-emulsification is preferable from the viewpoint of appearance and water resistance of the obtained coating film.

The aqueous dispersion of the unsaturated carboxylic acid-or acid anhydride-modified polyolefin (a) obtained as described above may be prepared into a non-chlorine polyolefin resin (a) containing an acrylic-modified unsaturated carboxylic acid-or acid anhydride-modified polyolefin by emulsion-polymerizing the acrylic unsaturated monomers listed in the description of acrylic modification in the presence of the water-dispersed unsaturated carboxylic acid-or acid anhydride-modified polyolefin (a).

In the present invention, the content of the non-chlorine polyolefin-based resin (a) is 10 to 60 mass%, preferably 20 to 50 mass%, and more preferably 25 to 50 mass% based on the total mass of the resin solid content in the coating composition, from the viewpoints of chipping resistance, adhesion, polishability, and ethanol gasoline resistance of the obtained coating film.

Aqueous polyurethane resin (B)

In the present invention, the aqueous polyurethane resin (B) is a polyurethane resin which can be dispersed in an aqueous medium containing water as a main solvent or a dispersion medium, and may be any of a water-soluble type, a colloidal dispersion type, an emulsion type and a slurry type as a form in the aqueous medium, but is preferably a colloidal dispersion type or an emulsion type.

As the aqueous urethane resin (B), a known aqueous urethane resin can be used, and for example, an aqueous urethane resin obtained by reacting a polyol such as a polyester polyol, a polycarbonate polyol or a polyether polyol or a low molecular weight hydroxyl group-containing compound with a polyisocyanate, and an aqueous urethane resin obtained by further optionally chain-extending a polyurethane in the presence of a low molecular weight compound having at least 2 active hydrogens in 1 molecule such as a diol or a diamine as a chain extender, can be stably dispersed or dissolved in an aqueous medium and used.

The polyol component is particularly preferably a polyester polyol or a polyether polyol in view of chipping resistance, adhesion, polishability, and alcohol gasoline resistance of the obtained coating film.

Examples of the polyester polyol used for producing the aqueous polyurethane resin (B) include: polyester polyols obtained by reacting an aliphatic diol such as 1, 4-butanediol or 1, 6-hexanediol with an aliphatic dicarboxylic acid such as adipic acid or sebacic acid; examples of the polycarbonate polyol include a polyester polyol obtained by reacting an aliphatic diol with an aromatic dicarboxylic acid such as terephthalic acid, and the like: polycarbonate polyols obtained by reacting diols such as 1, 6-hexanediol and 3-methyl-1, 5-pentanediol with carbonates such as dimethyl carbonate include, for example: polyalkylene glycols obtained by ring-opening polymerization of ethylene oxide, propylene oxide, and the like, such as polyethylene glycol, polypropylene glycol, and polybutylene glycol, and the like. Examples of the polyisocyanate include: aliphatic and alicyclic diisocyanates such as hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, and hydrogenated xylylene diisocyanate, and isocyanurate cycloadducts thereof. The polyisocyanate component is particularly preferably isophorone diisocyanate, from the viewpoint of chipping resistance, adhesion, polishability and ethanol gasoline resistance of the resulting coating film.

Examples of the diol as the chain extender include: ethylene glycol, 1, 4-butanediol, 1, 5-pentanediol, 3-methyl-1, 5-pentanediol, cyclohexanediol, and the like, and examples of the diamine include: ethylenediamine, propylenediamine, xylylenediamine, and the like.

As a method for stably dispersing or dissolving the aqueous urethane resin (B) in water, for example, the following method can be used.

(1) Carboxyl groups are introduced into polyurethane by using a carboxyl group-containing diol such as dimethylolpropionic acid or dimethylolbutyric acid as a raw material for producing polyurethane, and the polyurethane is rendered hydrophilic by neutralizing a part or all of the carboxyl groups and dispersed or dissolved in water by self-emulsification.

(2) A water-soluble polyurethane is produced using a hydrophilic polyol such as polyethylene glycol as a polyol which is a raw material for producing a polyurethane, and the water-soluble polyurethane is dispersed or dissolved in water.

(3) The polyurethane or terminal isocyanate group after the reaction is blocked with a blocking agent such as oxime, alcohol, phenol, thiol, amine, sodium hydrogen sulfite, etc., and the obtained polyurethane is forcedly dispersed in water with a nonionic and/or cationic emulsifier and a mechanical shearing force.

(4) The urethane prepolymer having a terminal isocyanate group is mixed with water/an emulsifier/a chain extender, and dispersion and high molecular weight are simultaneously carried out by a mechanical shearing force.

The aqueous polyurethane resin (B) is not limited to polyurethane obtained by a single production method, and a mixture of polyurethanes obtained by various methods may be used.

The acid value of the aqueous polyurethane resin (B) is in the range of 1mgKOH/g to 30mgKOH/g, preferably 3mgKOH/g to 25mgKOH/g, and more preferably 5mgKOH/g to 20mgKOH/g, from the viewpoint of chipping resistance, adhesion, polishability, and ethanol gasoline resistance of the resulting coating film.

The time required for the aqueous urethane resin (B) to form a film at a temperature of 20 ℃ is 5 to 20 minutes, preferably 10 to 20 minutes, and more preferably 12 to 18 minutes, from the viewpoints of chipping resistance, adhesion, polishability, and resistance to gasohol-containing oils of the obtained coating film.

Here, the time until film formation refers to the time required for the aqueous urethane resin to form a continuous film. The time until the film formation of the aqueous polyurethane resin was measured as follows.

An aqueous urethane resin solution having a solid content adjusted to 28% was coated on a PET film using a bar coater at room temperature of 20 ℃ and a humidity of 60% so that the wet film thickness was 40 μm. The starting point of the time measurement immediately after application was set, 0.3mL of ion-exchanged water was dropped from a 1cm height on the coating film at regular intervals using a dropper, the time at which the change in the diameter of the water droplet within 1 second immediately after the dropping was 1mm or less was set as the end point, and the time from the starting point to the end point was set as "the time until the film formation of the aqueous polyurethane resin".

The aqueous urethane resin (B) has an average particle diameter in an aqueous medium of preferably 70 to 250nm, more preferably 80 to 230nm, and still more preferably 100 to 200nm, from the viewpoint of chipping resistance, adhesion, polishability, and resistance to gasoline-containing oils of the resulting coating film.

In the present specification, the average particle diameter is a value measured at 20 ℃ after diluting with deionized water by a conventional method using a particle size distribution measuring apparatus using a dynamic light scattering method. As the particle size distribution measuring apparatus by the dynamic light scattering method, for example, "submicron particle analyzer N5" (trade name, manufactured by Beckman coulter Co., Ltd.) can be used.

In the aqueous coating composition of the present invention, the content of the aqueous urethane resin (B) is 10 to 50% by mass, preferably 10 to 40% by mass, and more preferably 15 to 30% by mass, based on the total mass of the resin solids in the coating composition, from the viewpoints of chipping resistance, adhesion, polishability, and ethanol gasoline resistance of the obtained coating film.

Blocked polyisocyanate Compound (C) having nonionic hydrophilic group

The blocked polyisocyanate compound (C) having a nonionic hydrophilic group is a compound in which a part of the isocyanate groups of a polyisocyanate compound having 2 or more isocyanate groups in 1 molecule is modified with a nonionic hydrophilic group, and the remaining part or all of the isocyanate groups are blocked with a blocking agent.

The blocked polyisocyanate compound (C) having a nonionic hydrophilic group can be obtained, for example, by reacting an active hydrogen-containing compound (C2) having a nonionic hydrophilic group and a blocking agent (C3) with an isocyanate group in a polyisocyanate compound (C1) having 2 or more isocyanate groups in 1 molecule (hereinafter, the blocked polyisocyanate compound having a nonionic hydrophilic group obtained as above is referred to as "(C1)").

When the isocyanate group in the polyisocyanate compound (c1) is reacted with the active hydrogen-containing compound (c2) having a nonionic hydrophilic group and the blocking agent (c3), the reaction sequence of the polyisocyanate compound (c1), the active hydrogen-containing compound (c2) having a hydrophilic group and the blocking agent (c3) is not particularly limited. Specifically, there may be mentioned: a method in which after the active hydrogen-containing compound (c2) having a hydrophilic group is reacted with a part of the isocyanate groups in the polyisocyanate compound (c1), the remaining isocyanate groups are blocked with a blocking agent (c 3); a method in which after a part of the isocyanate groups in the polyisocyanate compound (c1) is blocked with a blocking agent (c3), an active hydrogen-containing compound (c2) having hydrophilic groups is reacted with the remaining isocyanate groups; and a method of simultaneously reacting the active hydrogen-containing compound (c2) having a hydrophilic group and the blocking agent (c3) with an isocyanate group in the polyisocyanate compound (c1), and the like.

Polyisocyanate Compound (c1)

The polyisocyanate compound (c1) is a compound having at least 2 isocyanate groups in 1 molecule, and examples thereof include: aliphatic polyisocyanate, alicyclic polyisocyanate, aromatic aliphatic polyisocyanate, aromatic polyisocyanate, and a derivative of the polyisocyanate.

Examples of the aliphatic polyisocyanate include: aliphatic diisocyanates such as 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, and methyl 2, 6-diisocyanatohexanoate (common name: lysine diisocyanate); aliphatic triisocyanates such as 2-isocyanatoethyl 2, 6-diisocyanatohexanoate, 1, 6-diisocyanato-3-isocyanatomethylhexane, 1,4, 8-triisocyanatooctane, 1,6, 11-triisocyanatoundecane, 1, 8-diisocyanato-4-diisocyanatomethyloctane, 1,3, 6-triisocyanatohexane and 2,5, 7-trimethyl-1, 8-diisocyanato-5-isocyanatomethyloctane.

Examples of the alicyclic polyisocyanate include: alicyclic diisocyanates such as 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-cyclohexene diisocyanate (common name: hydrogenated TDI), 2-methyl-1, 3-cyclohexene diisocyanate, 1, 3-or 1, 4-bis (isocyanatomethyl) cyclohexane (common name: hydrogenated xylene diisocyanate) or a mixture thereof, methylenebis (4, 1-cyclohexanediyl) diisocyanate (common name: hydrogenated MDI), norbornane diisocyanate and the like; 1,3, 5-triisocyanatocyclohexane, 1,3, 5-trimethylisocyanatocyclohexane, 2- (3-isocyanatopropyl) -2, 5-bis (isocyanatomethyl) -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) -2-isocyanatomethyl-3- (3-isocyanatopropyl) -bicyclo (2.2.1) heptane Alicyclic triisocyanates such as propyl) -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.

Examples of the aromatic aliphatic polyisocyanate include: aromatic aliphatic diisocyanates such as methylenebis (4, 1-phenylene) diisocyanate (commonly known by the name MDI), 1, 3-or 1, 4-xylene diisocyanate or a mixture thereof, omega' -diisocyanato-1, 4-diethylbenzene, 1, 3-or 1, 4-bis (1-isocyanato-1-methylethyl) benzene (commonly known by the name tetramethylxylene diisocyanate) or a mixture thereof; and araliphatic triisocyanates such as 1,3, 5-triisocyanatomethylbenzene.

Examples of the aromatic polyisocyanate include: aromatic diisocyanates such as m-phenylene diisocyanate, p-phenylene diisocyanate, 4 ' -diphenyl diisocyanate, 1, 5-naphthalene diisocyanate, 2, 4-toluene diisocyanate (common name: 2,4-TDI), 2, 6-toluene diisocyanate (common name: 2,6-TDI), or a mixture thereof, 4 ' -toluidine diisocyanate, 4 ' -diphenyl ether diisocyanate, and the like; aromatic triisocyanates such as triphenylmethane-4, 4', 4 ″ -triisocyanate, 1,3, 5-triisocyanatobenzene, 2,4, 6-triisocyanatotoluene and the like; and aromatic tetraisocyanates such as 4,4 ' -diphenylmethane-2, 2 ', 5,5 ' -tetraisocyanate.

Further, as the derivatives of the polyisocyanate, for example, there can be mentioned: dimers, trimers, biurets, allophanates, uretdiones, uretonimines, isocyanurates, oxadiazinetriones, polymethylene polyphenyl polyisocyanates (crude MDI, condensation MDI), crude TDI, and the like of the above polyisocyanates.

The polyisocyanate and the derivative thereof may be used alone or in combination of 2 or more. Among these polyisocyanates, the polyisocyanate compound (C1) is preferably an aliphatic diisocyanate, an alicyclic diisocyanate, or a derivative thereof, because the obtained blocked polyisocyanate compound (C) having a nonionic hydrophilic group is less likely to be yellowed by heating. Among them, aliphatic diisocyanates and derivatives thereof are more preferable from the viewpoint of improving the flexibility property of the formed coating film.

Further, as the polyisocyanate compound (c1), a prepolymer produced by reacting the polyisocyanate and its derivative with a compound reactive with the polyisocyanate under a condition where the isocyanate group is excessive can be used. Examples of the compound reactive with the polyisocyanate include: examples of the compound having an active hydrogen such as a hydroxyl group and an amino group include a polyol, a low molecular weight polyester resin, an amine, and water.

Further, as the polyisocyanate compound (c1), a polymer of an isocyanate group-containing polymerizable unsaturated monomer or a copolymer of the isocyanate group-containing polymerizable unsaturated monomer and a polymerizable unsaturated monomer other than the isocyanate group-containing polymerizable unsaturated monomer may be used.

From the viewpoints of reactivity of the obtained blocked polyisocyanate compound (C) having a nonionic hydrophilic group and compatibility of the blocked polyisocyanate compound (C) with other coating components, the number average molecular weight of the polyisocyanate compound (C1) is preferably in the range of 300 to 20,000, more preferably in the range of 400 to 8,000, and still more preferably in the range of 500 to 2,000.

In addition, from the viewpoint of reactivity of the obtained blocked polyisocyanate compound (C) having a nonionic hydrophilic group and compatibility of the blocked polyisocyanate compound (C) having a nonionic hydrophilic group with other coating components, the average number of isocyanate functional groups in 1 molecule of the polyisocyanate compound (C1) is preferably in the range of 2 to 100. The lower limit is more preferably 3 from the viewpoint of improving the reactivity of the obtained blocked polyisocyanate compound (C) having a nonionic hydrophilic group. The upper limit is more preferably 20 from the viewpoint of preventing gelation in the production of the blocked polyisocyanate compound (C) having a nonionic hydrophilic group.

Active hydrogen-containing Compound having nonionic hydrophilic group (c2)

As the active hydrogen-containing compound having a nonionic hydrophilic group, for example, an active hydrogen-containing compound having a polyoxyalkylene group can be preferably used. Examples of the polyoxyalkylene group include: polyoxyethylene groups, polyoxypropylene groups, polyoxyethylene (oxypropylene) groups, and the like, and these may be used alone or in combination of 2 or more. Among them, from the viewpoint of storage stability of the obtained blocked polyisocyanate compound (C) having a nonionic hydrophilic group, an active hydrogen-containing compound having a polyoxyethylene group is preferable.

The active hydrogen-containing compound having a polyoxyethylene group has 3 or more continuous oxyethylene groups, preferably 5 to 100 continuous oxyethylene groups, and more preferably 8 to 45 continuous oxyethylene groups, from the viewpoints of storage stability of the obtained blocked polyisocyanate compound (C) having a nonionic hydrophilic group, water resistance of a coating film formed therefrom, and the like.

The active hydrogen-containing compound having a polyoxyethylene group may contain an oxyalkylene group other than an oxyethylene group in addition to a continuous oxyethylene group. Examples of the oxyalkylene group other than the oxyethylene group include: oxypropylene, oxybutylene, oxyhexenyl and the like. From the viewpoint of storage stability after water dispersion of the obtained blocked polyisocyanate composition, the molar ratio of the oxyethylene group in the oxyalkylene group in the active hydrogen-containing compound having a polyoxyethylene group is preferably in the range of 20 to 100 mol%, more preferably in the range of 50 to 100 mol%. If the molar ratio of oxyethylene groups in oxyalkylene groups is less than 20 mol%, hydrophilicity cannot be sufficiently imparted, and the storage stability of the resulting blocked polyisocyanate compound (C) having nonionic hydrophilic groups may be lowered.

In addition, the number average molecular weight of the active hydrogen-containing compound having a nonionic hydrophilic group is preferably in the range of 200 to 2,000 from the viewpoints of storage stability of the obtained blocked polyisocyanate compound (C) having a nonionic hydrophilic group and water resistance of the formed coating film. The lower limit of the number average molecular weight is more preferably 300, and still more preferably 400, from the viewpoint of the storage stability of the obtained blocked polyisocyanate compound (C) having a nonionic hydrophilic group. The upper limit is more preferably 1,500, and still more preferably 1,200, from the viewpoint of water resistance of a coating film formed from the aqueous coating composition of the present invention.

Examples of the active hydrogen-containing compound having a nonionic hydrophilic group include polyethylene glycol monoalkyl ethers such as polyethylene glycol monomethyl ether and polyethylene glycol monoethyl ether (also known as. omega. -alkoxypolyoxyethylene), polypropylene glycol monoalkyl ethers such as polypropylene glycol monomethyl ether and polypropylene glycol monoethyl ether (also known as. omega. -alkoxypolyoxypropylene),. omega. -alkoxypolyoxyethylene (oxypropylene) such as. omega. -ethoxypolyoxyethylene (oxypropylene), and polyethylene glycol (propylene glycol) monoalkyl ethers such as. omega. -ethoxypolyoxyethylene (oxypropylene), polyethylene glycol (propylene glycol) monomethyl ether, and polyethylene glycol (propylene glycol) monoethyl ether, polyethylene glycol, polypropylene glycol, polyethylene glycol (propylene glycol), α - (aminoalkyl) - ω -alkoxypolyoxyethylene, α - (aminoalkyl) - ω -alkoxypolyoxypropylene, and α - (aminoalkyl) - ω -alkoxypolyoxyethylene (oxypropylene), and these may be used alone or in combination of 2 or more.

In the present specification, "polyethylene glycol (propylene glycol)" refers to a copolymer of ethylene glycol and propylene glycol, and includes both a block copolymer and a random copolymer.

Further, as the commercially available product of the above-mentioned methoxy polyethylene glycol, for example, there can be mentioned: "UNIOX M-400", "UNIOX M-550", "UNIOX M-1000", and "UNIOX M-2000", manufactured by Nichigan oil Co., Ltd. Further, as the commercially available products of the polyethylene glycol, for example, there can be mentioned: "PEG # 200", "PEG # 300", "PEG # 400", "PEG # 600", "PEG # 1000", "PEG # 1500", "PEG # 1540" and "PEG # 2000" manufactured by Nichiyan oil Co., Ltd.

In the case where a part of the isocyanate groups in the polyisocyanate compound (C1) are reacted with the active hydrogen-containing compound having a nonionic hydrophilic group (C2), the reaction ratio of the isocyanate compound (C1) to the active hydrogen-containing compound having a nonionic hydrophilic group (C2) is preferably in the range of 0.03 to 0.6 mol in terms of 1 mol of the isocyanate groups in the polyisocyanate compound (C1), from the viewpoints of storage stability and curability of the obtained blocked polyisocyanate compound (C) having a nonionic hydrophilic group, and adhesion, smoothness, vividness, and water resistance of a coating film formed from the aqueous coating composition of the present invention. From the viewpoints of curability of the obtained blocked polyisocyanate compound (C) having a nonionic hydrophilic group and water resistance of a coating film formed from the aqueous coating composition of the present invention, the upper limit is more preferably 0.4, and still more preferably 0.3. The lower limit is more preferably 0.04, and still more preferably 0.05, from the viewpoints of storage stability of the obtained blocked polyisocyanate compound (C) having a nonionic hydrophilic group, and adhesion, smoothness, clearness and water resistance of a coating film formed from the aqueous coating composition of the present invention.

End capping agent (c3)

Examples of the blocking agent include: phenol, alcohol, active methylene, thiol, acid amide, acid imide, imidazole, urea, oxime, carbamate, amine, imine, etc., and these can be used alone or in combination of 2 or more. More specific blocking agents are shown below.

(1) A phenol series; phenol, cresol, ethylphenol, butylphenol, etc,

(2) An alcohol system; ethylene glycol, benzyl alcohol, methanol, ethanol, etc,

(3) An active methylene system; malonic diester, acetoacetic ester, isobutyrylacetic ester, etc,

(4) A thiol group; butanethiol, dodecanethiol, etc,

(5) Acid amide series; acetanilide, acetic acid amide, epsilon-caprolactam, delta-valerolactam, gamma-butyrolactam, and the like,

(6) Acid imide series; succinimide, maleimide, etc,

(7) An imidazole series; imidazole, 2-methylimidazole, etc,

(8) A urea line; urea, thiourea, ethylene urea, etc,

(9) An oxime system; formaldoxime, acetaldoxime, methylethylketoxime, cyclohexylketoxime, and the like,

(10) A carbamic acid series; phenyl N-phenylcarbamate, and the like,

(11) An amine system; diphenylamine, aniline, carbazole, etc,

(12) An imine system; ethyleneimine, polyethyleneimine, and the like.

The blocking reaction of the isocyanate group with the blocking agent (c3) may optionally use a reaction catalyst. Examples of the reaction catalyst include: metal hydroxides, metal alkoxides, metal carboxylates, metal acetoacetates, hydroxides of onium salts, onium carboxylates, metal salts of active methylene compounds, onium salts of active methylene compounds, aminosilanes, amines, phosphines, and other basic compounds. Among them, as the onium salt, ammonium salt, phosphonium salt and sulfonium salt are preferable. The amount of the reaction catalyst used is usually preferably in the range of 10ppm to 10,000ppm, more preferably 20ppm to 5,000ppm, based on the total solid content mass of the polyisocyanate compound (c1) and the blocking agent (c 3).

The blocking reaction of the isocyanate group by the blocking agent (c3) may be carried out at 0 to 150 ℃ or a solvent may be used. In this case, the solvent is preferably an aprotic solvent, and particularly preferably an ester, an ether, an N-alkylamide, a ketone, or the like. If the reaction proceeds as desired, the reaction can be stopped by neutralizing the basic compound as a catalyst by adding an acid component.

In the reaction for blocking an isocyanate group with the blocking agent (c3), the amount of the blocking agent (c3) used is not particularly limited, but is preferably 0.1 to 3 moles, more preferably 0.2 to 2 moles, based on 1 mole of an isocyanate group in the polyisocyanate compound (c 1). The blocking agent that has not reacted with the isocyanate group in the polyisocyanate compound (c1) may be removed after the end of the blocking reaction.

Among them, the end-capping agent (c3) is preferably an active methylene group, from the viewpoint of low-temperature curability of a coating film formed from the aqueous coating composition of the present invention.

From the viewpoint of stability of the aqueous coating composition of the present invention, particularly preferred embodiments of the blocked polyisocyanate compound having a nonionic hydrophilic group (C1) include: having the following general formula (IV)

[ chemical formula 4]

[ in the formula (IV), R¹Independently represent a hydrocarbon group having 1 to 12 carbon atoms, and may be the same or different.]

A blocked polyisocyanate compound having a blocked isocyanate group and a nonionic hydrophilic group (C1-1), and a compound having the following general formula (V)

[ chemical formula 5]

[ in the formula (V), R⁶And R⁷Independently represents a hydrocarbon group having 1 to 12 carbon atoms.]

A blocked polyisocyanate compound having a blocked isocyanate group and a nonionic hydrophilic group (C1-2).

Blocked polyisocyanate Compound having nonionic hydrophilic group (C1-1)

The blocked polyisocyanate compound having a nonionic hydrophilic group (C1-1) is a blocked polyisocyanate compound having a blocked isocyanate group represented by the general formula (IV).

Wherein,the blocking agent (c3) which is one of the raw materials of the blocked polyisocyanate compound is R, because an active methylene-based blocking agent compound which can be produced relatively easily can be used¹Preferably an alkyl group having 1 to 3 carbon atoms. Among them, R is a group selected from the group consisting of a blocked polyisocyanate compound having a nonionic hydrophilic group (C1) and a group consisting of a hydroxyl group, a carboxyl group, a sulfonic acid group¹An alkyl group having 2 or 3 carbon atoms is preferable, and R is R from the viewpoint of storage stability of the obtained blocked polyisocyanate compound (C1) having a nonionic hydrophilic group and smoothness and sharpness of a coating film formed from the aqueous coating composition of the present invention¹Isopropyl group is more preferred.

The blocked polyisocyanate compound (C1-1) having a nonionic hydrophilic group can be obtained, for example, by reacting the polyisocyanate compound (C1) and the active hydrogen-containing compound (C2) having a nonionic hydrophilic group with a dialkyl malonate having a hydrocarbon group having 1 to 12 carbon atoms as a blocking agent (C3).

Examples of the dialkyl malonate include: dimethyl malonate, diethyl malonate, di-n-propyl malonate, diisopropyl malonate, di-n-butyl malonate, diisobutyl malonate, di-sec-butyl malonate, di-tert-butyl malonate, di-n-pentyl malonate, di-n-hexyl malonate, di (2-ethylhexyl) malonate and the like, and these can be used singly or in combination of 2 or more. Among them, dimethyl malonate, diethyl malonate, di-n-propyl malonate, diisopropyl malonate, di-n-butyl malonate, diisobutyl malonate, di-sec-butyl malonate, and di-tert-butyl malonate are preferable, diethyl malonate, di-n-propyl malonate, and diisopropyl malonate are more preferable, and diisopropyl malonate is further preferable.

Blocked polyisocyanate Compound having nonionic hydrophilic group (C1-2)

The blocked polyisocyanate compound having a nonionic hydrophilic group (C1-2) is a blocked polyisocyanate compound having a blocked isocyanate group represented by the general formula (V).

Among these, the blocking agent (c3) which is one of the raw materials of the blocked polyisocyanate compound is R, because an active methylene-based blocking agent compound which can be produced relatively easily can be used⁶And R⁷Preferably an alkyl group having 1 to 3 carbon atoms. Among them, R is a group having a nonionic hydrophilic group, from the viewpoint of improving the compatibility of the obtained blocked polyisocyanate compound (C1) with other coating components⁶And R⁷An alkyl group having 2 or 3 carbon atoms is preferred, and R is R from the viewpoint of storage stability of the resulting blocked polyisocyanate compound (C1) having a nonionic hydrophilic group, smoothness and sharpness of a coating film formed from the aqueous coating composition of the present invention⁶And R⁷Isopropyl group is more preferred.

The blocked polyisocyanate compound (C1-2) having a nonionic hydrophilic group can be obtained, for example, by reacting the polyisocyanate compound (C1) and the active hydrogen-containing compound (C2) having a nonionic hydrophilic group with an acetoacetate ester having a hydrocarbon group having 1 to 12 carbon atoms or an isobutyrylacetate ester having a hydrocarbon group having 1 to 12 carbon atoms as a blocking agent (C3). Among them, the blocking agent (c3) is preferably obtained by reacting isobutyrylacetate having a hydrocarbon group having 1 to 12 carbon atoms as the blocking agent (c 3).

Examples of the acetoacetate ester include: methyl acetoacetate, ethyl acetoacetate, n-propyl acetoacetate, isopropyl acetoacetate, n-butyl acetoacetate, isobutyl acetoacetate, sec-butyl acetoacetate, tert-butyl acetoacetate, n-pentyl acetoacetate, n-hexyl acetoacetate, 2-ethylhexyl acetoacetate, phenyl acetoacetate, benzyl acetoacetate, etc., and these can be used alone or in combination of 2 or more. Among them, methyl acetoacetate, ethyl acetoacetate, and isopropyl acetoacetate are preferable.

Examples of the isobutyrylacetate include: methyl isobutyrylacetate, ethyl isobutyrylacetate, n-propyl isobutyrylacetate, isopropyl isobutyrylacetate, n-butyl isobutyrylacetate, isobutyl isobutyrylacetate, sec-butyl isobutyrylacetate, tert-butyl isobutyrylacetate, n-pentyl isobutyrylacetate, n-hexyl isobutyrylacetate, 2-ethylhexyl isobutyrylacetate, phenyl isobutyrylacetate, benzyl isobutyrylacetate, etc., which may be used alone or in combination of 2 or more. Among them, methyl isobutyrylacetate, ethyl isobutyrylacetate and isopropyl isobutyrylacetate are preferable.

In the present invention, in particular, from the viewpoint of stability in water, it is preferable to use, as the blocked polyisocyanate compound (C) having a nonionic hydrophilic group, a blocked polyisocyanate compound having a nonionic hydrophilic group obtained by further reacting a secondary alcohol (C4) with the above-mentioned blocked polyisocyanate compound (C1) (hereinafter, the blocked polyisocyanate compound having a nonionic hydrophilic group obtained as above is referred to as "(C2)").

Blocked polyisocyanate Compound having nonionic hydrophilic group (C2)

The blocked polyisocyanate composition (C2) having a nonionic hydrophilic group can be obtained by, for example, reacting the above-mentioned blocked polyisocyanate compound (C1) having a nonionic hydrophilic group with a secondary alcohol (C4) represented by the following general formula (VI).

[ chemical formula 6]

[ in the formula (VI), R²、R⁴And R⁵Independently represents a hydrocarbon group having 1 to 12 carbon atoms, R³Represents a linear or branched alkylene group having 1 to 12 carbon atoms.]

Secondary alcohol (c4)

The secondary alcohol (c4) is a compound represented by the above general formula (VI). Among them, R is R from the viewpoint of improving the reactivity of the blocked polyisocyanate compound having a nonionic hydrophilic group (C1) with the secondary alcohol (C4)²Preferably methyl. In addition, if R³、R⁴And R⁵When the number of carbon atoms is large, the polarity of the obtained blocked polyisocyanate compound (C2) having a nonionic hydrophilic group may be lowered, and the compatibility with other coating components may be lowered, so that R may be³Preferably an alkylene group having 1 to 3 carbon atoms, R⁴And R⁵Preferably methyl.

Examples of the secondary alcohol (c4) include: 4-methyl-2-pentanol, 5-methyl-2-hexanol, 6-methyl-2-heptanol, 7-methyl-2-octanol, and the like, which may be used alone or in combination of 2 or more. Among them, 4-methyl-2-pentanol having a lower boiling point is more preferable in terms of easier removal of the secondary alcohol (C4) when a part or all of the unreacted secondary alcohol (C4) is distilled off after the reaction of the blocked polyisocyanate compound (C1) having a nonionic hydrophilic group with the secondary alcohol (C4).

The blocked polyisocyanate compound having a nonionic hydrophilic group (C2) is particularly preferably used in view of stability of the aqueous coating composition of the present invention, and the following compounds (C2-1) and (C2-2) can be mentioned.

Blocked polyisocyanate Compound having nonionic hydrophilic group (C2-1)

Specific examples of the blocked polyisocyanate compound having a nonionic hydrophilic group (C2-1) include those described in the description of the blocked polyisocyanate compound having a nonionic hydrophilic group (C1) and those having the following general formula (IV)

[ chemical formula 7]

A blocked polyisocyanate compound (C1-1) having an isocyanate group and a nonionic hydrophilic group, and the secondary alcohol (C4).

In this case, R in the blocked isocyanate group in the blocked polyisocyanate compound (C1-1) having a nonionic hydrophilic group¹Is substituted with a group represented by the following general formula (VII).

[ chemical formula 8]

[ in the formula (VII), R²、R⁴And R⁵Independently represents a hydrocarbon group having 1 to 12 carbon atoms, R³Represents a linear or branched alkylene group having 1 to 12 carbon atoms.]

In this case, the obtained blocked polyisocyanate compound has a blocked isocyanate group represented by the following general formula (I) or a blocked isocyanate group represented by the following general formula (II).

[ chemical formula 9]

[ chemical formula 10]

The reaction between the blocked polyisocyanate compound having a nonionic hydrophilic group (C1-1) and the secondary alcohol (C4) is not particularly limited, and may be carried out, for example, by reacting R in the blocked isocyanate group in the blocked polyisocyanate compound having a nonionic hydrophilic group (C1-1)¹The method (4) may be a method in which at least one of the substituents is a group represented by the general formula (VII). Among them, R derived from the blocked polyisocyanate compound (C1-1) having a nonionic hydrophilic group is preferably subjected to heating, reduced pressure or the like¹A method in which a part or the whole of at least one alcohol is distilled off to the outside of the system to promote the reaction, thereby obtaining a blocked polyisocyanate compound having a blocked isocyanate group represented by the above general formula (I) or (II) and a nonionic hydrophilic group.

Specifically, the method for producing the alcohol comprises optionally reducing the pressure at a temperature of 20 to 150 ℃, preferably 75 to 95 ℃, and removing a part or all of the alcohol over a period of 5 minutes to 20 hours, preferably 10 minutes to 10 hours. If the temperature is too low, the exchange reaction of alkoxy groups in the blocked polyisocyanate compound having a nonionic hydrophilic group (C1-1) becomes slow, and the production efficiency is lowered, while if the temperature is too high, the decomposition of the blocked polyisocyanate compound having a nonionic hydrophilic group (C) is deteriorated drastically, and the curability may be lowered, which is not desirable.

Blocked polyisocyanate Compound having nonionic hydrophilic group (C2-2)

The blocked polyisocyanate compound having a nonionic hydrophilic group (C2-2) can be obtained, for example, by reacting the blocked polyisocyanate compound having a nonionic hydrophilic group (C1) described above with the following general formula (V)

[ chemical formula 11]

A blocked polyisocyanate compound (C1-2) having an isocyanate group and a nonionic hydrophilic group, and the secondary alcohol (C4).

In this case, R in the blocked isocyanate group in the above-mentioned blocked polyisocyanate compound having a hydrophilic group (C1-2)⁷Substituted with a group represented by the following general formula (VII).

[ chemical formula 12]

In this case, the resulting blocked polyisocyanate composition has a blocked isocyanate group represented by the following general formula (III).

[ chemical formula 13]

[ in the formula (III), R²、R³、R⁴And R⁵And said R²、R³、R⁴And R⁵Same as R⁶Represents a hydrocarbon group having 1 to 12 carbon atoms.]

The reaction between the blocked polyisocyanate compound having a nonionic hydrophilic group (C1-2) and the secondary alcohol (C4) is not particularly limited, and may be carried out, for example, by reacting R in the blocked isocyanate group in the blocked polyisocyanate compound having a nonionic hydrophilic group (C1-2)⁷Substitution with a group represented by the general formula (VII) may be carried out. Among them, R derived from the blocked polyisocyanate compound having a hydrophilic group (C1-2) is preferably subjected to heating, reduced pressure or the like⁷A method in which a part or the whole of the alcohol is distilled off to the outside of the system to promote the reaction, thereby obtaining a blocked polyisocyanate compound (C2-2) having a blocked isocyanate group represented by the above general formula (III) and a nonionic hydrophilic group.

Specifically, the method for producing the alcohol comprises optionally removing a part or all of the alcohol at a temperature of 20 to 150 ℃ and preferably 75 to 95 ℃ under reduced pressure for 5 minutes to 20 hours, preferably 10 minutes to 10 hours. If the temperature is too low, the exchange reaction of alkoxy groups in the blocked polyisocyanate compound having a nonionic hydrophilic group (C1-2) becomes slow, and the production efficiency decreases, while if the temperature is too high, the decomposition of the obtained blocked polyisocyanate compound having a nonionic hydrophilic group (C2) is deteriorated drastically, and the curability may decrease, which is not desirable.

In addition, from the viewpoint of reactivity and production efficiency of the obtained blocked polyisocyanate compound having a nonionic hydrophilic group (C), the blending ratio of the blocked polyisocyanate compound having a nonionic hydrophilic group (C1) and the secondary alcohol (C4) in the production of the blocked polyisocyanate compound having a nonionic hydrophilic group (C2) is preferably in the range of 5 to 500 parts by mass, more preferably in the range of 10 to 200 parts by mass, based on 100 parts by mass of the solid content of the blocked polyisocyanate compound having a nonionic hydrophilic group (C1). When the amount is less than 5 parts by mass, the reaction rate of the blocked polyisocyanate compound having a hydrophilic group (C1) with the secondary alcohol (C4) is sometimes too slow. When the amount exceeds 500 parts by mass, the concentration of the produced blocked polyisocyanate compound having a nonionic hydrophilic group (C2) becomes too low, and the production efficiency may be lowered.

In the reaction between the blocked polyisocyanate compound having a nonionic hydrophilic group (C1) and the secondary alcohol (C4), the polyol compound may be added to the blocked polyisocyanate compound having a nonionic hydrophilic group (C1) and the secondary alcohol (C4) to adjust the molecular weight of the blocked polyisocyanate compound having a nonionic hydrophilic group (C2), and then the removal operation may be performed.

Among the blocked polyisocyanate compounds (C) having a nonionic hydrophilic group, the compound (C2-1) or the compound (C2-2) is also particularly excellent in stability in water, and the reason is presumed to be as follows: since the isocyanate group has a nonionic hydrophilic group, it is relatively stable in water, and since the isocyanate group has a branched hydrocarbon group, it has low polarity and is not easily hydrolyzed.

[ chemical formula 14]

[ chemical formula 15]

[ chemical formula 16]

The number average molecular weight of the blocked polyisocyanate compound (C) having a nonionic hydrophilic group is preferably in the range of 600 to 30,000 from the viewpoints of compatibility with other coating components, smoothness, clearness, adhesion, water resistance, chipping resistance and the like of a coating formed from the aqueous coating composition of the present invention. The upper limit of the number average molecular weight is more preferably 10,000, and still more preferably 5,000, from the viewpoint of compatibility with other coating components and smoothness and sharpness of a coating film formed from the aqueous coating composition of the present invention. From the viewpoint of adhesion, water resistance and chipping resistance of a coating film formed from the aqueous coating composition of the present invention, the lower limit is more preferably 900, and still more preferably 1,000.

The blocked polyisocyanate compound (C) having a nonionic hydrophilic group may be previously mixed with a surfactant. In this case, the surfactant is preferably a nonionic surfactant from the viewpoint of stability of the aqueous coating composition of the present invention.

In the aqueous coating composition of the present invention, the content of the blocked polyisocyanate compound (C) having a nonionic hydrophilic group is preferably 5 to 40% by mass, more preferably 7 to 35% by mass, and still more preferably 10 to 30% by mass, based on the mass of the total resin solids in the coating composition, from the viewpoints of chipping resistance, adhesion, polishability, and gasohol resistance of the obtained coating film.

Conductive pigment (D)

The conductive pigment (D) used in the present invention is not particularly limited as long as it can impart conductivity to the formed coating film, and any of particle-like, flake-like, and fiber-like (including whisker-like) pigments can be used. Specifically, examples thereof include: conductive carbon such as conductive carbon black, carbon nanotube, carbon nanofiber, and carbon microcoil; metal powders of silver, nickel, copper, graphite, aluminum, and the like, and further, there may be mentioned: antimony-doped tin oxide, phosphorus-doped tin oxide, acicular titanium oxide surface-coated with tin oxide/antimony, antimony oxide, zinc antimonate, indium tin oxide, and a pigment in which the surface of a whisker of carbon or graphite is coated with tin oxide; a pigment in which a conductive metal oxide such as tin oxide or antimony-doped tin oxide is coated on the surface of a flaky mica; a pigment having conductivity and containing tin oxide and phosphorus on the surface of titanium dioxide particles. These may be used alone or in combination of 2 or more. Among them, conductive carbon can be particularly preferably used.

In the aqueous coating composition of the present invention, the content of the conductive pigment is preferably 0.5 to 40% by mass, more preferably 1 to 35% by mass, and still more preferably 3 to 30% by mass, based on the mass of the total resin solid content in the coating composition, from the viewpoint of the conductivity of the obtained coating film.

In one embodiment, the aqueous coating composition of the present invention contains 10 to 60 mass% of a non-chlorine polyolefin resin (a), 10 to 50 mass% of an aqueous urethane resin (B), 5 to 40 mass% of a blocked isocyanate compound (C) having a non-ionic hydrophilic group, and 0.5 to 40 mass% of a conductive pigment (D), based on the mass of the total resin solid content in the coating composition, and the aqueous urethane resin (B) has an acid value of 1 to 30mgKOH/g, and the time until film formation at a temperature of 20 ℃ is 5 to 20 minutes.

Other ingredients

The aqueous coating composition of the present invention contains the above-mentioned non-chlorine polyolefin resin (a), the specific aqueous polyurethane resin (B), the blocked polyisocyanate compound having a nonionic hydrophilic group (C), and the conductive pigment (D) as essential components, and may further contain resin components such as a hydroxyl group-containing acrylic resin, a hydroxyl group-containing polyester resin, a blocked polyisocyanate compound other than the component (C), a melamine resin, a phenol resin, a polycarbonate resin, and an epoxy resin as appropriate.

The hydroxyl group-containing acrylic resin may be a water-soluble or water-dispersible hydroxyl group-containing acrylic resin known per se which is used in the conventional water-based paint. The hydroxyl group-containing acrylic resin can be produced, for example, by copolymerizing a hydroxyl group-containing polymerizable unsaturated monomer and another polymerizable unsaturated monomer copolymerizable with the hydroxyl group-containing polymerizable unsaturated monomer by a method known per se, for example, solution polymerization.

The hydroxyl group-containing polymerizable unsaturated monomer is a compound having 1 or more hydroxyl groups and polymerizable unsaturated bonds in each molecule, and examples thereof include: monoesterified products of glycols such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate and polyethylene glycol mono (meth) acrylate and acrylic acid or methacrylic acid; and compounds obtained by ring-opening polymerization of epsilon-caprolactone with a monoester of the above polyol and acrylic acid or methacrylic acid.

The other polymerizable unsaturated monomer copolymerizable with the hydroxyl group-containing polymerizable unsaturated monomer may be appropriately selected and used in accordance with the desired characteristics of the hydroxyl group-containing acrylic resin. Specific examples of the monomer are listed below. These may be used alone or in combination of 2 or more.

(i) Alkyl or cycloalkyl (meth) acrylates: for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate, tricyclodecyl (meth) acrylate, and the like.

(ii) Polymerizable unsaturated monomer having isobornyl group: for example, isobornyl (meth) acrylate, and the like.

(iii) Polymerizable unsaturated monomer having adamantyl group: for example, adamantyl (meth) acrylate, and the like.

(iv) Polymerizable unsaturated monomer having tricyclodecenyl group: for example, tricyclodecenyl (meth) acrylate, and the like.

(v) Aromatic ring-containing polymerizable unsaturated monomers such as benzyl (meth) acrylate, styrene, α -methylstyrene, vinyltoluene and the like.

(vi) Polymerizable unsaturated monomer having alkoxysilyl group: for example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, gamma- (meth) acryloxypropyltrimethoxysilane, gamma- (meth) acryloxypropyltriethoxysilane, and the like.

(vii) Polymerizable unsaturated monomer having fluoroalkyl group: perfluoroalkyl (meth) acrylates such as perfluorobutylethyl (meth) acrylate and perfluorooctylethyl (meth) acrylate; fluoroolefins, and the like.

(viii) Polymerizable unsaturated monomers having a photopolymerizable functional group such as a maleimide group.

(ix) Vinyl compound (b): for example, N-vinyl pyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate, and the like.

(x) Polymerizable unsaturated monomer containing phosphoric group: for example, 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate, 2-acryloyloxypropyl acid phosphate, 2-methacryloyloxypropyl acid phosphate and the like.

(xi) Examples of the carboxyl group-containing polymerizable unsaturated monomer include (meth) acrylic acid, maleic acid, crotonic acid, and β -carboxyethyl acrylate.

(xii) Nitrogen-containing polymerizable unsaturated monomer: for example, an adduct of (meth) acrylonitrile, (meth) acrylamide, N-dimethylaminoethyl (meth) acrylate, N-diethylaminoethyl (meth) acrylate, N-dimethylaminopropyl (meth) acrylamide, methylenebis (meth) acrylamide, ethylenebis (meth) acrylamide, 2- (methacryloyloxy) ethyltrimethylammonium chloride, glycidyl (meth) acrylate and an amine, and the like.

(xiii) A polymerizable unsaturated monomer having at least 2 polymerizable unsaturated groups in 1 molecule: for example, allyl (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, and the like

(xiv) Examples of the epoxy group-containing polymerizable unsaturated monomer include glycidyl (meth) acrylate, β -methylglycidyl (meth) acrylate, 3, 4-epoxycyclohexylmethyl (meth) acrylate, 3, 4-epoxycyclohexylethyl (meth) acrylate, 3, 4-epoxycyclohexylpropyl (meth) acrylate, and allyl glycidyl ether.

(xv) (meth) acrylate having a polyoxyethylene chain with an alkoxy group at the molecular end.

(xvi) Polymerizable unsaturated monomer having sulfonic acid group: for example, 2-acrylamido-2-methylpropanesulfonic acid, 2-sulfoethyl (meth) acrylate, allylsulfonic acid, 4-styrenesulfonic acid, etc.; sodium salts and ammonium salts of these sulfonic acids, and the like.

(xvii) Polymerizable unsaturated monomer having ultraviolet-absorbing functional group: for example, 2-hydroxy-4- (3-methacryloxy-2-hydroxypropoxy) benzophenone, 2-hydroxy-4- (3-acryloxy-2-hydroxypropoxy) benzophenone, 2-dihydroxy-4- (3-methacryloxy-2-hydroxypropoxy) benzophenone, 2 ' -dihydroxy-4- (3-acryloxy-2-hydroxypropoxy) benzophenone, 2- (2 ' -hydroxy-5 ' -methacryloyloxyethylphenyl) -2H-benzotriazole and the like.

(xviii) Light-stable polymerizable unsaturated monomer: for example, 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-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 and the like.

(xix) Polymerizable unsaturated monomer having carbonyl group: for example, 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), and the like.

(xx) Polymerizable unsaturated monomer having acid anhydride group: for example, maleic anhydride and the like, itaconic anhydride, citraconic anhydride and the like.

The hydroxyl group-containing acrylic resin generally has a hydroxyl value of preferably 10 to 150, particularly preferably 50 to 100, an acid value of preferably 60 or less, particularly preferably 50 or less, and a weight average molecular weight of 1000 to 100000, particularly preferably 2000 to 60000.

In the present specification, the weight average molecular weight of the hydroxyl group-containing acrylic resin and the number average molecular weights of the hydroxyl group-containing polyester resin and the melamine resin are values obtained by converting the retention time (retention capacity) measured by Gel Permeation Chromatography (GPC) from the retention time (retention capacity) of standard polystyrene having a known molecular weight measured under the same conditions into the molecular weight of polystyrene. Specifically, using "HLC-8120 GPC" (trade name, manufactured by eastern cao corporation) as a gel permeation chromatography device, 4 total of "TSKgel G4000 HXL", "TSKgel G3000 HXL", "TSKgel G2500 HXL" and "TSKgel G2000 HXL" (trade name, manufactured by eastern cao corporation) as a chromatography column, and a differential refractive index meter as a detector, it was possible to perform the following steps in a mobile phase: tetrahydrofuran, measurement temperature: 40 ℃ and flow rate: measured under the condition of 1 mL/min.

In the aqueous coating composition of the present invention, the hydroxyl group-containing acrylic resin is used in an amount of 5 to 35% by mass, preferably 10 to 25% by mass, based on the total mass of the resin solids in the coating composition, from the viewpoints of chipping resistance, adhesion, polishability, and ethanol gasoline resistance of the obtained coating film.

The hydroxyl group-containing polyester resin may be a water-soluble or water-dispersible hydroxyl group-containing polyester resin known per se, which is used in the conventional water-based coating materials, and may be obtained, for example, by subjecting a polybasic acid and a polyhydric alcohol to an esterification reaction by a method known per se with an excess of hydroxyl groups. The polybasic acid is a compound having 2 or more carboxyl groups in 1 molecule, and examples thereof include: phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, 1, 4-cyclohexanedicarboxylic acid, pyromellitic acid, itaconic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, dimer acid, humic acid, succinic acid, chlorendic acid, anhydrides thereof, and the like. The polyol is a compound having 2 or more hydroxyl groups in 1 molecule, and examples thereof include: ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, butanediol, hexanediol, 2-ethyl-2-butyl-1, 3-propanediol, cyclohexanedimethanol, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, sorbitol, and the like. The introduction of the hydroxyl group can be performed, for example, by simultaneously using a polyol having 3 or more hydroxyl groups in 1 molecule. In addition, as the polyester resin, a fatty acid-modified polyester resin modified with a fatty acid such as soybean oil fatty acid, castor oil fatty acid, dehydrated castor oil fatty acid, or the like may be used. The polyester resin may be modified with an epoxy compound such as butyl glycidyl ether, alkylphenyl glycidyl ether, and glycidyl neodecanoate.

The hydroxyl group-containing polyester resin usually has a hydroxyl value of preferably 10mgKOH/g to 160mgKOH/g, particularly preferably 50mgKOH/g to 85mgKOH/g, an acid value of preferably 50mgKOH/g or less, particularly preferably 1mgKOH/g to 30mgKOH/g, and a number average molecular weight of preferably 1,000 to 20,000, particularly preferably 1,300 to 10,000.

In the aqueous coating composition of the present invention, the hydroxyl group-containing polyester resin is used in an amount of 2 to 20% by mass, preferably 5 to 15% by mass, based on the total mass of the resin solids in the coating composition, from the viewpoints of chipping resistance, adhesion, polishability, and ethanol gasoline resistance of the obtained coating film.

The blocked polyisocyanate compound other than the component (C) is a compound obtained by adding a blocking agent to the isocyanate group of the polyisocyanate compound. The blocked polyisocyanate compound produced by the addition is stable at ordinary temperature, but it is preferable that the blocking agent is dissociated and a free isocyanate group is produced again when the mixture is heated to a sintering temperature (usually about 80 to about 200 ℃) of the coating film. Examples of the blocking agent satisfying such requirements include: a blocking agent such as phenol-based, lactam-based, alcohol-based, ether-based, oxime-based, active methylene-based, thiol-based, acid amide-based, acid imide-based, amine-based, imidazole-based, pyrazole-based, etc.

The melamine resin is particularly preferably an alkyl-etherified melamine resin etherified with an alkyl group such as a methyl group, an ethyl group, an n-butyl group, an isobutyl group, a hexyl group, or a 2-ethylhexyl group. These melamine resins may further have methylol groups, imino groups, and the like. The melamine resin preferably has a number average molecular weight of 500 to 5,000 in general, and 800 to 3,000 in particular.

The aqueous coating composition of the present invention may further contain additives for coating materials such as coloring pigments, extender pigments, organic solvents, silane coupling agents, curing catalysts, tackifiers, defoamers, surface conditioners, film-forming aids, and the like.

Examples of the coloring pigment include: titanium oxide, carbon black, chrome yellow, loess, yellow iron oxide, hansa yellow, pigment yellow, chrome orange, molybdate red, permanent orange, umber, permanent red, brilliant carmine, fast violet, methyl violet lake, ultramarine, prussian blue, cobalt blue, phthalocyanine blue, pigment green, naphthol green, aluminum paste. These may be used alone or in combination of 2 or more.

Examples of the extender pigment include: talc, silica, calcium carbonate, barium sulfate, zinc white (zinc oxide), and the like. These may be used alone or in combination of 2 or more.

The organic solvent is not particularly limited, and examples thereof include organic solvents that can be dissolved or dispersed by mixing the above resin components, and examples thereof include aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, alcohol solvents, ester solvents, ketone solvents, and the like.

Examples of the silane coupling agent include: 2- (3, 4-epoxycyclohexyl) ethyltrialkoxysilane, 3-glycidoxypropyltrialkoxysilane, 3-glycidoxypropylmethyldialkoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldialkoxysilane, N-2- (aminoethyl) -3-aminopropyltrialkoxysilane, 3-aminopropylmethyldialkoxysilane, 3-mercaptopropylmethyldialkoxysilane, N-phenyl-3-aminopropyltrialkoxysilane, 3-ureidopropyltrialkoxysilane, 3-chloropropyltrialkoxysilane, bis (trialkoxysilylpropyl) tetrasulfide, bis (glycidoxypropyl) trialkoxysilane, bis (glycidoxypropyl, 3-isocyanatopropyltrialkoxysilanes, and the like. These may be used alone or in combination of 2 or more.

The aqueous coating composition of the present invention can be applied to the surface of a metal part or a plastic part of a substrate as described above. Therefore, a method for forming a coating film by applying the aqueous coating composition of the present invention to the surface of a metal member or a plastic member to be coated and an article comprising a coating film obtained by applying the aqueous coating composition of the present invention to the surface of a metal member or a plastic member to be coated are also included in the scope of the present invention. The object to be coated is not particularly limited, and examples thereof include: automobile outer panel sections such as passenger cars, trucks, motorcycles, and buses; automobile parts such as bumpers; and an outer panel portion of a home appliance such as a cellular phone and an audio device. The coated article containing the coating film of the present invention is not particularly limited, and examples thereof include: automobiles and home electrical appliances, etc.

Examples of the metal member include: iron, aluminum, brass, copper, tin, stainless steel, galvanized steel, and zinc alloy (Zn-Al, Zn-Ni, Zn-Fe, etc.) steel, and the like.

The metal member may be one having a surface treated by a phosphate treatment, a chromate treatment, a complex oxide treatment or the like, or one having an undercoat film formed of an undercoat paint formed thereon. Examples of the undercoat paint include electrodeposition paints, and among them, cationic electrodeposition paints are preferable.

As the material of the plastic member, for example, a polyolefin obtained by (co) polymerizing 1 or 2 or more kinds of olefins having 2 to 10 carbon atoms such as ethylene, propylene, butene, hexene, and the like is particularly preferable, and in addition to these, there can be mentioned: polycarbonate, ABS resin, urethane resin, polyamide, and the like. Examples of the plastic member include: plastic parts such as bumpers, spoilers, grilles, fenders, etc. in substrates. These plastic parts may be suitably subjected to degreasing treatment, washing treatment, and the like by a method known per se before application of the aqueous coating composition of the present invention.

The above-described metal parts and plastic parts can be assembled by known methods.

The application of the aqueous coating composition of the present invention is preferably carried out on the surfaces of metal parts and plastic parts by air spraying, airless spraying, dip coating, brush coating, etc., so that the dry film thickness is usually in the range of 1 to 20 μm, preferably 3 to 15 μm. After applying the composition, the obtained coating surface may be solidified at room temperature for about 30 seconds to 60 minutes, or may be preheated (preheated) at a temperature of about 40 ℃ to about 80 ℃ for about 1 minute to 60 minutes, or may be heated at a temperature of about 60 ℃ to about 140 ℃, preferably about 70 ℃ to about 120 ℃ for about 20 minutes to 40 minutes to solidify it, but in the present invention, in particular, top coating as the next step may be performed without preheating after applying the aqueous coating composition of the present invention, and preferably, solidification at room temperature (about 20 ℃ to about 35 ℃) for about 60 seconds to 10 minutes after applying the aqueous coating composition of the present invention is performed.

In the present invention, a top coating material may be applied to the surface of a coating film formed using the aqueous coating composition of the present invention. As the top coat paint, either a colored paint or a clear paint may be used alone for coating, or the colored paint may be used as a two-pass primer paint and the clear paint may be applied in this order. Further, a multilayer film is formed as a colored base coating film layer by applying, for example, a white two-coat primer and an interference pearlescent two-coat primer in this order to a coating film formed from the aqueous coating composition of the present invention.

As the colored coating material, a known colored coating material can be used, and a colored coating material containing a coloring component such as a coloring pigment, a luminescent pigment, or a dye, and a resin component such as a matrix resin or a crosslinking agent, and containing an organic solvent and/or water as a main solvent can be generally used.

Examples of the base resin used in the colored coating material include: resins having reactive functional groups such as hydroxyl, epoxy, carboxyl and silanol groups, such as acrylic resins, polyester resins and alkyd resins. Examples of the crosslinking agent include amino resins such as melamine resins and urea resins having a reactive functional group reactive with the functional group, and (blocked) polyisocyanates, polyepoxides, and polycarboxylic acids.

The colored coating composition may contain additives for coating materials such as extender pigments, curing catalysts, ultraviolet absorbers, surface conditioners, rheology control agents, antioxidants, defoaming agents, waxes, preservatives and the like.

The colored coating material may be applied to the coating film formed from the uncured or cured coating composition of the present invention so that the dry film thickness is usually in the range of 5 to 50 μm, preferably in the range of 5 to 30 μm, and more preferably in the range of 10 to 20 μm, and the obtained coating film surface is solidified at room temperature for 1 to 60 minutes or preheated at a temperature of about 40 to about 80 ℃ for about 1 to 60 minutes, or may be cured by heating at a temperature of about 60 to about 140 ℃, preferably at a temperature of about 80 to about 120 ℃ for about 20 to 40 minutes. In the present invention, particularly, it is preferable that the transparent coating can be performed without curing the colored two-pass primer after coating.

As the clear coating material, for example, an organic solvent-based or aqueous thermosetting coating material containing a resin component such as a matrix resin or a crosslinking agent, an organic solvent, water or the like and further containing an additive for coating materials such as an ultraviolet absorber, a light stabilizer, a curing catalyst, a coating surface adjuster, a rheology control agent, an antioxidant, an antifoaming agent, a wax or the like can be used, and the coating material has transparency to the extent that the lower layer coating film can be visually observed through the formed clear coating film.

Examples of the matrix resin include: resins such as acrylic resins, polyester resins, alkyd resins, fluorine resins, urethane resins, and silicon-containing resins containing at least 1 reactive functional group such as a hydroxyl group, a carboxyl group, a silanol group, and an epoxy group, and particularly, hydroxyl-containing acrylic resins are preferable. Examples of the crosslinking agent include: melamine resins, urea resins, (end-capped) polyisocyanate compounds, epoxy compounds, carboxyl group-containing compounds, acid anhydrides, alkoxysilane group-containing compounds, and the like having reactive functional groups reactive with these functional groups, and particularly, polyisocyanate compounds are preferred.

The application of the above clear coat can be carried out by: the clear coating material is applied to an uncured or cured colored base coating film so that the dry film thickness is usually in the range of 10 to 50 μm, preferably in the range of 20 to 45 μm, and the surface of the obtained coating film is cured for 1 to 60 minutes at room temperature or preheated for 1 to 60 minutes at a temperature of about 40 to about 80 ℃, and then cured by heating at a temperature of about 60 to about 140 ℃, preferably at a temperature of about 70 to about 120 ℃ for about 20 to 40 minutes.

The aqueous coating composition of the present invention can form a coating film having excellent chipping resistance, adhesion, polishing properties, and ethanol gasoline resistance to metal parts and plastic parts.

Examples

The present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention is not limited to these examples. In addition, "part(s)" and "%" are based on mass. In addition, the film thickness of the coating film is based on the cured coating film.

Production of non-chlorine polyolefin resin (A)

Production example 1

A mixture of 500 parts of a maleated polypropylene resin having a weight average molecular weight of 80000 (chlorination rate: 22%, maleic acid modification amount: 2.0%, acid value: 30mgKOH/g), 150 parts of N-heptane, and 50 parts of N-methylpyrrolidone was heated to 50 ℃ and 12 parts of dimethylethanolamine and 5 parts of "NOIGEN EA-140" (nonionic surfactant, product name of 1 st Industrial pharmaceutical Co., Ltd.) were added thereto, and the mixture was stirred at the same temperature for 1 hour, then 2000 parts of deionized water were slowly added thereto, and further stirred for 1 hour.

Subsequently, 600 parts in total of n-heptane and water were distilled off under reduced pressure at a temperature of 70 ℃ to obtain a non-chlorine based polyolefin resin dispersion (A-1) having a solid content of 23.6%.

Production example 2

In a 4-neck flask equipped with a stirrer, a condenser, a thermometer and a dropping funnel, 100g of maleic anhydride-grafted polypropylene (modified with 4 mass% maleic acid to polypropylene obtained using a metallocene catalyst, melting point 80 ℃, Mw of about 15 ten thousand and Mw/Mn of about 2.5) was heated and melted at 140 ℃, 15g of polyoxyethylene stearyl ether ("Newcol 1820", a polyoxyethylene compound having a hydroxyl group at one end, manufactured by japan emulsifier corporation) was added, and the reaction was carried out at 140 ℃ for 4 hours while stirring. After the reaction, the reaction mixture was cooled to 90 ℃ and deionized water was added thereto for filtration to obtain a non-chlorine polyolefin resin dispersion (A-2) having a solid content of 30%.

Production of aqueous urethane resin (B)

Production example 3

211.9 parts of polytetramethylene glycol (number average molecular weight 1000), 11.5 parts of α -dimethylolpropionic acid, 6.9 parts of trimethylolpropane, 112.2 parts of isophorone diisocyanate and 298.5 parts of methyl ethyl ketone were charged into a reaction vessel equipped with a thermometer, a stirrer and a reflux condenser, the reaction system was substituted with nitrogen, and then reacted at 80 ℃ while stirring to obtain an NCO-terminated urethane prepolymer having a free isocyanate group content of 3.2%, the obtained methyl ethyl ketone solution was cooled to 40 ℃, 493.2g of deionized water containing 5.2 parts of triethylamine was added to the solution and emulsified, 159.2 parts of a 5% ethylenediamine aqueous solution was added thereto, and after stirring for 60 minutes, the methyl ethyl ketone was distilled off while heating under reduced pressure, and the concentration was adjusted with deionized water to obtain an aqueous polyurethane dispersion (B-1) having a solid content of 35%, a film formation time of 15 minutes, an acid value of 14mgKOH/g and an average particle diameter of 120 nm.

Production examples 4 to 13

Each aqueous polyurethane resin dispersion was obtained by the same operation as in production example 3, except that the formulation was set as shown in table 1 in production example 3.

The formulation in table 1 is shown as a solid content, and (note 1) in table 1 is shown below.

(Note 1) production of polyester-polyol A

67 parts of polyethylene glycol (number average molecular weight 300), 49 parts of sodium salt of dimethyl 5-sulfoisophthalate and 0.2 part of dibutyltin oxide were charged into a reaction vessel, and the temperature was raised to 190 ℃ under a reduced pressure of 5mmHg, and transesterification was carried out for 6 hours while distilling off methanol to obtain a polyester polyol A having 5 sodium sulfonate groups on average in 1 molecule, a hydroxyl value of 29.6mgKOH/g, and a number average molecular weight of 3700.

[ Table 1]

TABLE 1

Production of blocked polyisocyanate Compound (C) having nonionic hydrophilic group

Production example 14

A reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, a nitrogen inlet, a dropping device and a simple solvent trap was charged with 275 parts of "Sumidule N-3300" (product name, manufactured by Suhua Bayer urethane Co., Ltd., polyisocyanate containing an isocyanurate structure derived from hexamethylene diisocyanate, about 100% of solid content, and 21.8% of isocyanate group content), "UNIOX M-550" (manufactured by Nichikoku Co., Ltd., polyethylene glycol monomethyl ether, and average molecular weight about 550) and 0.9 part of 2, 6-di-t-butyl-4-methylphenol, and the mixture was thoroughly mixed and heated at 130 ℃ for 3 hours under a nitrogen stream. Then, 550 parts of ethyl acetate and 1150 parts of diisopropyl malonate were added, 14 parts of a 28% methanol solution of sodium methoxide was added thereto under stirring in a nitrogen stream, and the mixture was stirred at 65 ℃ for 8 hours. The amount of isocyanate in the resulting resin solution was about 0.1 mol/kg. 3110 parts of 4-methyl-2-pentanol was added thereto, and the solvent was distilled off under reduced pressure for 3 hours while maintaining the temperature of the system at 80 ℃ to 85 ℃ to obtain 4920 parts of a blocked polyisocyanate composition solution (C-1). The simple solvent removal trap contained 585 parts isopropanol. The resulting blocked polyisocyanate composition solution (C-1) had a solid content concentration of about 60%.

Production example 15

A reaction vessel equipped with a thermometer, a thermostat, a stirring device, a reflux condenser, a nitrogen introduction tube, a dropping device and a simple solvent trap was charged with 275 parts of "Sumidule N-3300" (product name, manufactured by Suzuki Bayer urethane Co., Ltd., polyisocyanate containing an isocyanurate structure derived from hexamethylene diisocyanate, about 100% solid content, and 21.8% isocyanate group content), "UNIOX M-550" (manufactured by Nichikoku corporation, polyethylene glycol monomethyl ether, and having an average molecular weight of about 550), and 0.9 part of 2, 6-di-t-butyl-4-methylphenol, and the mixture was thoroughly mixed and heated at 130 ℃ for 3 hours in a nitrogen atmosphere. Then, 550 parts of ethyl acetate and 1150 parts of diisopropyl malonate were added, 14 parts of a 28% methanol solution of sodium methoxide was added under stirring in a nitrogen stream, and the mixture was stirred at 65 ℃ for 8 hours. The amount of isocyanate in the resulting resin solution was about 0.1 mol/kg. The resulting blocked polyisocyanate composition solution (C-2) had a solid content concentration of about 60%.

Production example 16

"Sumidule N-3300" 1610 parts and hydroxypivalic acid 236 parts were charged into a reaction vessel equipped with a thermometer, a thermostat, a stirring device, a reflux condenser, a nitrogen introduction tube, a dropping device, and a simple solvent trap, and thoroughly mixed with stirring, and heated at 130 ℃ for 3 hours under a nitrogen stream. Then, 550 parts of ethyl acetate and 930 parts of diisopropyl malonate were added, 14 parts of a 28% methanol solution of sodium methoxide was added under stirring in a nitrogen stream, and the mixture was stirred at 65 ℃ for 8 hours. The amount of isocyanate in the resulting resin solution was about 0.1 mol/kg. 2530 parts of 4-methyl-2-pentanol was added thereto, and the solvent was distilled off under reduced pressure for 3 hours while maintaining the temperature of the system at 80 ℃ to 85 ℃ to obtain 4450 parts of a blocked polyisocyanate composition solution (C-3). The simple solvent removal trap contained 475 parts of isopropanol. The resulting blocked polyisocyanate composition solution (C-3) had a solid content concentration of about 60%.

Production example 17

To a reaction vessel equipped with a thermometer, a thermostat, a stirring device, a reflux condenser, a nitrogen introduction tube, a dropping device, and a simple solvent trap were charged 480 parts of "Sumidule N-3300" (product name, polyisocyanate containing an isocyanurate structure derived from hexamethylene diisocyanate, about 100% solid content, and 21.8% isocyanate group content), 150 parts of ethyl acetate, and 365 parts of diisopropyl malonate, and while stirring under a nitrogen stream, 4 parts of a 28% methanol solution of sodium methoxide were added, and stirring was carried out at 65 ℃ for 8 hours. The amount of isocyanate in the resin solution obtained was 0.07 mol/kg. To this was added 870 parts of 4-methyl-2-pentanol, and while the temperature of the system was kept at 80 ℃ to 85 ℃ and the solvent was distilled off under reduced pressure for 3 hours, 120 parts of 4-methyl-2-pentanol was further added to obtain 1400 parts of a blocked polyisocyanate composition solution (C-4). The simple solvent removal catcher contains 183 parts of isopropanol. The resulting blocked polyisocyanate compound solution (C-4) had a solid content concentration of about 60%.

Further, (C-1) and (C-2) are solutions of blocked polyisocyanate compounds used in examples described later, and (C-3) and (C-4) are solutions of blocked polyisocyanate compounds used in comparative examples described later.

Production of hydroxyl-containing acrylic resin

Production example 18

35 parts of propylene glycol monopropyl ether was placed in a reaction vessel equipped with a thermometer, a thermostat, a 25785stirring device, a reflux condenser, a nitrogen introducing tube and a dropping device, and after the temperature was raised to 85 ℃, a mixture of 30 parts of methyl methacrylate, 20 parts of 2-ethylhexyl acrylate, 29 parts of n-butyl acrylate, 15 parts of 2-hydroxyethyl acrylate, 6 parts of acrylic acid, 15 parts of propylene glycol monopropyl ether and 2.3 parts of 2, 2' -azobis (2, 4-dimethylvaleronitrile) was dropped over 4 hours, followed by aging for 1 hour after completion of the dropping. Then, a mixture of 10 parts of propylene glycol monopropyl ether and 1 part of 2, 2' -azobis (2, 4-dimethylvaleronitrile) was added dropwise over 1 hour, followed by aging for 1 hour after the completion of the addition. Then, 7.4 parts of diethanolamine was added to the reaction solution to obtain a hydroxyl group-containing acrylic resin solution (E-1) having a solid content of 55%. The hydroxyl group-containing acrylic resin thus obtained had an acid value of 47mgKOH/g and a hydroxyl value of 72 mgKOH/g.

Production of hydroxyl-containing polyester resin

Production example 19

192 parts of adipic acid, 307 parts of hexahydrophthalic anhydride, 439 parts of 2-butyl-2-ethyl-1, 3-propanediol, 88.7 parts of 1, 6-hexanediol, and 36.0 parts of trimethylolpropane were charged into a reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, and a water separator, and the temperature was raised from 160 ℃ to 230 ℃ over 3 hours, and then the reaction was carried out while maintaining the temperature at 230 ℃ to obtain a desired acid value while removing the condensed water by distillation using the water separator. 20.2 parts of trimellitic anhydride was added to the reaction product, followed by addition reaction at 170 ℃ for 30 minutes, cooling to 50 ℃ or lower, neutralization with 2- (dimethylamino) ethanol, and slow addition of deionized water, whereby a hydroxyl group-containing polyester resin aqueous dispersion (F-1) having a solid content of 45% was obtained. The hydroxyl group-containing polyester resin had an acid value of 20mgKOH/g, a hydroxyl value of 60mgKOH/g, and a number average molecular weight of 1,700.

Preparation of coating composition

Example 1

An aqueous coating composition (1) was prepared by mixing and dispersing 35 parts (solid content) of a non-chlorine polyolefin resin dispersion (A-1), 20 parts (solid content) of an aqueous polyurethane resin dispersion (B-1), 20 parts (solid content) of a solution of a blocked polyisocyanate compound having a nonionic hydrophilic group (C-1), 10 parts (solid content) of a hydroxyl-containing acrylic resin solution (E-1), 15 parts (solid content) of a hydroxyl-containing polyester resin (F-1), 100 parts of a conductive pigment (D-1) ("Ketjen Black EC 600J", trade name, conductive carbon black pigment manufactured by Lyon Okaki K.K.; 5 parts of "JR-806" (product name, titanium white manufactured by Tayca Co., Ltd.) in a conventional manner, and diluting the solid content with deionized water to 20%.

Examples 2 to 14 and comparative examples 1 to 7

Aqueous coating compositions (2) to (21) were obtained in the same manner as in example 1, except that the blending composition was set as shown in table 2 in example 1.

The formulation in table 2 is shown as a solid content, and (note 2) in table 2 is shown below.

(Note 2) Water-based chlorinated polyolefin (A-3) (an aqueous dispersion of maleic acid-modified chlorinated polypropylene having an acid value of 35mgKOH/g and a chlorine content of 22% obtained by maleic acid modification)

Production of test coated sheet

As a metal member, a thermosetting epoxy resin-based cationic electrodeposition coating composition (trade name "ELECRON GT-10", manufactured by KANSHI paint Co., Ltd.) was electrodeposition-coated on a zinc phosphate-treated cold-rolled steel sheet (450 mm. times.300 mm. times.0.8 mm) so that the film thickness was 20 μm, and the coating was cured by heating at 170 ℃ for 30 minutes.

"TSOP-1 (TC-6)" (trade name, manufactured by Polygem corporation, Japan, 350 mm. times.10 mm. times.2 mm) was prepared as a plastic part.

Then, the surfaces of the metal parts and the plastic parts were wiped with gauze containing light gasoline to perform degreasing treatment. The steel sheet and the polypropylene sheet obtained as described above were disposed adjacent to each other to prepare a test sheet.

The coating compositions (1) to (21) prepared above were spray-coated on the test plate so that the dry film thickness was 10 μm, and after leaving the test plate at room temperature for 3 minutes, "WBC-713T #1F 7" (trade name, manufactured by Wako coating Co., Ltd., acrylic/melamine resin based water-based top coat paint, silver color) as a coloring two-pass primer was electrostatically coated so that the dry film thickness was 15 μm. Subsequently, "SOFLEX #500 CLEAR" (trade name, urethane acrylate organic solvent type CLEAR coating, manufactured by kansai coating corporation) as a CLEAR coating was electrostatically coated so that the dry film thickness was 30 μm, and after leaving at room temperature for 5 minutes, the coated plate was heated in an oven at 95 ℃ for 30 minutes to obtain a test coated plate having a multilayer coating film formed thereon. The multilayer coating film was subjected to various film performance tests as described below.

Film coating performance test

Polishing property: the polishing properties were evaluated by the following smoothness and sharpness.

Smoothness: the evaluation was carried out using a W1 value measured by "Wave Scan DOI" (trade name, BYK Gardner Co., Ltd.). The smaller the W1 value, the higher the smoothness of the coated surface.

Vividness: the evaluation was carried out using a W4 value measured by "Wave Scan DOI" (trade name, BYK Gardner Co., Ltd.). A smaller W4 value indicates a higher clearness of the coated surface.

Chipping resistance: a test piece was placed on a test piece holder of a flying stone tester (trade name "Q-G-R grit meter" (manufactured by QPanel Co., Ltd.), granite crushed stone having a grain size of No. 6 was brought into collision with 100G of the test piece at-20 ℃ at an angle of 90 degrees from a position 30cm away from the test piece by means of 480 to 520kPa compressed air, the obtained test piece was washed with water, dried, and a cloth-coated adhesive tape (manufactured by Nichiban corporation) was applied to the coated surface.

S: the proportion of the peeled area to the area of the test coated plate was less than 5%

A: the proportion of the stripping area to the area of the test coated plate is 5 to 10 percent

C: the proportion of the peeled area to the area of the test coated plate was 10%

Water-resistant adhesion: the test panels were immersed in warm water at 40 ℃ for 240 hours, taken out, dried at 20 ℃ for 12 hours, and then cut into a lattice shape with a knife so as to reach the bottom layer, thereby making 100 checkerboards of 2mm × 2mm in size. Subsequently, a transparent adhesive tape was bonded to the surface thereof, and the state of the residue of the checkerboard film was examined after the transparent adhesive tape was rapidly peeled off at 20 ℃.

S: 100 of the checkerboard film remained, and minor curling of the film was not produced at the edge cut by the knife

A: 100 of the tessellated film remained, producing a smaller curl of the film at the edge cut by the knife

B: 90-99 coating residues on the checkerboard

C: the number of the coated checkerboard film residues is 89 or less.

Alcohol-containing gasoline resistance: the description is made in terms of components.

Case of plastic parts: each test coating was immersed in a test solution containing 90/10 parts by weight of gasoline/methanol at 20 ℃, and the state of the coating surface that swelled and peeled off after 30 minutes had elapsed was observed and evaluated under the following criteria.

S: no abnormality at all,

A: expansion and peeling of less than 3mm,

B: 3-5 mm expansion, exfoliation,

C: swelling and peeling of 5mm or more,

Case of metal parts: each test coating was dipped in a test solution containing 90/10 parts by weight of gasoline/methanol at 40 ℃, and the state of the coating surface that swelled and peeled off after 60 minutes had elapsed was observed and evaluated by the same criteria as in the case of plastics.

[ Table 2]

TABLE 2

[ Table 3]

Table 2 (continuation)

[ Table 4]

Table 2 (continuation)

Claims

1. A method for forming a coating film by applying an aqueous coating composition to a metal member or a plastic member to be coated,

the aqueous coating composition comprises a non-chlorine polyolefin resin (A), an aqueous polyurethane resin (B), a blocked polyisocyanate compound (C) having a nonionic hydrophilic group, and a conductive pigment (D),

wherein the aqueous polyurethane resin (B) is obtained by reacting a polyol including a polyether polyol with a polyisocyanate, and has an acid value of 1mgKOH/g to 30mgKOH/g, and a time to film formation at a temperature of 20 ℃ is 5 minutes to 20 minutes.

2. The method according to claim 1, wherein the blocked polyisocyanate compound (C) having a nonionic hydrophilic group is a blocked polyisocyanate compound having at least one blocked isocyanate group selected from the group consisting of a blocked isocyanate group represented by the following general formula (I), a blocked isocyanate group represented by the following general formula (II), and a blocked isocyanate group represented by the following general formula (III),

[ chemical formula 1]

In the formula (I), R¹、R²、R⁴And R⁵Independently represents a hydrocarbon group having 1 to 12 carbon atoms, R³Represents a linear or branched alkylene group having 1 to 12 carbon atoms,

[ chemical formula 2]

In the formula (II), R²、R³、R⁴And R⁵And the above-mentioned R²、R³、R⁴And R⁵In the same way, the first and second,

[ chemical formula 3]

In the formula (III), R²、R³、R⁴And R⁵And the above-mentioned R²、R³、R⁴And R⁵Same as R⁶Represents a hydrocarbon group having 1 to 12 carbon atoms.

3. The method of claim 1, wherein the aqueous coating composition further comprises a hydroxyl-containing acrylic resin.

4. The method according to claim 1, wherein the aqueous coating composition comprises 10 to 60 mass% of the non-chlorine polyolefin resin (A), 10 to 50 mass% of the aqueous polyurethane resin (B), 5 to 40 mass% of the blocked isocyanate compound (C) having a nonionic hydrophilic group, and 0.5 to 40 mass% of the conductive pigment (D), based on the mass of the total resin solids in the aqueous coating composition.

5. An article comprising a coating film obtained by applying an aqueous coating composition to a metal member or a plastic member as a substrate,

6. The article according to claim 5, wherein the blocked polyisocyanate compound (C) having a nonionic hydrophilic group is a blocked polyisocyanate compound having at least one blocked isocyanate group selected from the group consisting of a blocked isocyanate group represented by the following general formula (I), a blocked isocyanate group represented by the following general formula (II), and a blocked isocyanate group represented by the following general formula (III),

[ chemical formula 4]

[ chemical formula 5]

[ chemical formula 6]

7. The article according to claim 5, wherein the aqueous coating composition further comprises a hydroxyl-containing acrylic resin.

8. The article according to claim 5, wherein the aqueous coating composition comprises 10 to 60 mass% of the non-chlorine polyolefin resin (A), 10 to 50 mass% of the aqueous polyurethane resin (B), 5 to 40 mass% of the blocked isocyanate compound (C) having a nonionic hydrophilic group, and 0.5 to 40 mass% of the conductive pigment (D), based on the mass of the total resin solids in the aqueous coating composition.