JP7386680B2 - Water-based multi-component polyurethane coating composition - Google Patents

Description

The present invention relates to an aqueous multi-component polyurethane coating composition and a coating method for coating the same.

Urethane paints are widely used in paint applications because they can form coatings with excellent physical properties that combine toughness and flexibility through urethane bonds.

Urethane paints include (1) two-component urethane paints and (2) one-component urethane paints.

(1) A two-component urethane paint is a paint in which a base agent containing a polyol compound and a curing agent containing a polyisocyanate compound are measured and mixed in a fixed ratio immediately before painting. In this paint, the polyisocyanate compound has high reactivity and the crosslinking reaction between hydroxyl groups and isocyanate groups easily proceeds, so the paint film can be cured at room temperature. The two-component urethane paint is sometimes referred to as a low-temperature curing two-component urethane paint.

(2) A one-component urethane paint is a paint in which a blocked polyisocyanate whose reactivity is suppressed by masking the isocyanate groups with a blocking agent and a polyol compound coexist. While this coating has the advantage of not requiring the measurement and mixing of multiple liquids, it does require the isocyanate groups to be regenerated by dissociating the blocking agent in the blocked polyisocyanate, so the coating is usually removed after application. It needs to be heated at a high temperature. A one-component urethane paint is sometimes referred to as a heat-curable one-component urethane paint.

Therefore, (1) two-component urethane paint is usually used when the object to be painted is large, such as a building structure, or when there is a concern that the object may be deformed by heating, such as plastic.

Furthermore, since automobile bodies are equipped with parts that are sensitive to high temperatures, such as gasoline tanks, electrical components, and computers, it is difficult to bake the repair coating at high temperatures when repainting completed automobile bodies. . For this reason, two-component urethane paints are often used in repair paint compositions for refinishing automobiles.

In recent years, environmental pollution and the impact on the human body have become more of a consideration, and the use of water-based paints that use water as the main solvent instead of organic solvent-based paints has increased significantly. Development of compositions is needed. However, compared to organic solvent-based paints, water-based paints take longer to dry and have weaker water-resistant adhesion, but they cannot achieve the same performance as solvent-based paint compositions and finish properties such as unevenness, smoothness, and flaking. The current situation is that it is difficult to do so.

Patent Document 1 describes a water-based low-temperature-curing two-component urethane paint containing a compound containing at least one hydroxyl group, a free isocyanate group and/or a blocked isocyanate group, and at least one hydrolyzable silane group. An aqueous coating containing at least one catalyst for crosslinking silane groups is disclosed. According to the water-based coating agent described in Patent Document 1, it is possible to form a coating film with excellent gloss, scratch resistance, processability, and chemical resistance. It may not be.

Patent Document 2 discloses an aqueous two-component clear coating composition that includes a base agent containing multiple acrylic resin emulsions with different acid values, a polyisocyanate compound having an acid group, and a glycol ether organic solvent having no hydroxyl group. has been done. According to the aqueous two-component clear coating composition described in Patent Document 2, a coating film with a high-finished appearance that has smoothness even on a highly rough coated object and has excellent gloss and transparency. However, sufficient quality has not yet been obtained and problems remain with respect to the drying properties of the coating film. In particular, when it is necessary to polish a cured coating film that has been formed, the coating must be sufficiently dried until it has a hardness suitable for polishing, and improvements in this need are needed.

Special Publication No. 2014-508823 Unexamined Japanese Patent Publication No. 2018-2900

The problem to be solved by the present invention is to provide an aqueous coating composition that can provide a coating film with excellent hardness in a short drying time. Another object of the present invention is to provide a method for forming a multilayer coating film that provides a coating film with excellent water resistance and finish quality.

As a result of intensive studies to solve the above problems, the inventors have developed a first liquid containing a hydroxyl group-containing resin and water, and a polyisocyanate compound containing an isocyanate compound having three or more isocyanate groups and a molecular weight of 350 or less. The inventors have discovered that the above-mentioned problems can be solved by an aqueous multi-component polyurethane coating composition containing a second component, and have completed the present invention.
The present invention includes embodiments of the following aqueous multi-component polyurethane coating composition and coating method.
Item 1. An aqueous multi-component polyurethane coating composition containing a first liquid (A) containing a hydroxyl group-containing resin (a1) and water, and a second liquid (B) containing a polyisocyanate compound (b1), An aqueous multi-component polyurethane coating composition, wherein the isocyanate compound (b1) contains a polyisocyanate compound (b1-1) having three or more isocyanate groups and a molecular weight of 350 or less.
Item 2. Item 2. The aqueous multi-component polyurethane coating composition according to item 1, wherein the hydroxyl group-containing resin (a1) contains an aqueous dispersion of a hydroxyl group-containing acrylic resin having a glass transition temperature of 40° C. or higher.
Item 3. Item 2, wherein the aqueous dispersion of acrylic resin containing a hydroxyl group is a self-emulsifying aqueous dispersion of acrylic resin containing a hydrophilic group-containing polymerizable unsaturated monomer as a part of the constituent components. The aqueous multi-component polyurethane coating composition described in .
Item 4. The aqueous dispersion of hydroxyl group-containing acrylic resin is an aqueous dispersion of hydroxyl group-containing acrylic resin having a graft structure consisting of a main chain part and a side chain part, and constitutes either the main chain part or the side chain part. The polymerizable unsaturated monomer component (X) contains an epoxy group-containing polymerizable unsaturated monomer (x1), a hydroxyl group-containing polymerizable unsaturated monomer (x2), and another polymerizable unsaturated monomer (x3), and the other The polymerizable unsaturated monomer component (Y) constituting contains a carboxyl group-containing polymerizable unsaturated monomer (y1), a hydroxyl group-containing polymerizable unsaturated monomer (y2), and other polymerizable unsaturated monomers (y3). 4. The aqueous multi-component polyurethane coating composition according to item 2 or 3, characterized in that:
Item 5. Item 5. The aqueous multi-component polyurethane coating composition according to any one of Items 1 to 4, wherein the first liquid (A) contains a polyether polyol.
Item 6. Item 6. The aqueous multi-component polyurethane coating composition according to any one of Items 1 to 5, wherein the first liquid (A) has a nonvolatile content concentration in the range of 25 to 55% by mass.
Section 7. Item 7. The aqueous multi-component polyurethane paint according to any one of Items 1 to 6, wherein in the second liquid (B), the polyisocyanate compound (b1) further contains a hydrophilic polyisocyanate compound. Composition.
Section 8. In the second liquid (B), the proportion of the polyisocyanate compound (b1-1) having three or more isocyanate groups and having a molecular weight of 350 or less in the polyisocyanate compound (b1) is 10 to 90% by mass. Item 8. The aqueous multi-component polyurethane coating composition according to any one of Items 1 to 7.
Item 9. Item 8. The aqueous aqueous compound according to any one of Items 1 to 8, wherein in the second liquid (B), the polyisocyanate compound (b1-1) having three or more isocyanate groups and having a molecular weight of 350 or less is an aliphatic triisocyanate compound. Multi-component polyurethane coating composition.
Item 10. Item 10. The aqueous multi-component polyurethane coating composition according to any one of Items 1 to 9, wherein the nonvolatile content concentration of the second liquid (B) is within the range of 20 to 100% by mass.
Item 11. Item 11. The aqueous multi-component polyurethane coating composition according to any one of Items 1 to 10, which is a transparent coating composition.
Item 12. A coating method for coating an object to be coated with the aqueous multi-component polyurethane coating composition according to any one of Items 1 to 11.

According to the present invention, although it is an aqueous coating composition, a coating film with excellent hardness can be formed in a short time even when drying at room temperature or forced drying under relatively mild temperature conditions. Furthermore, the coating film formed using the coating composition of the present invention has excellent hardness, good water resistance, and a transparent finish, so it can be widely applied to various uses. .

In this specification, "the resin contains the monomer X that is its raw material" means that the resin is a (co)polymer of raw material monomers containing the monomer X, unless otherwise specified. means. Moreover, in this specification, a (co)polymer means a polymer or a copolymer.

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

The aqueous multi-component polyurethane coating composition of one embodiment of the present invention includes a first component (A) containing a hydroxyl group-containing resin (a1) and water, and a second component (B) containing a polyisocyanate compound (b1). ), wherein the polyisocyanate compound (b1) contains a polyisocyanate compound (b1-1) having three or more isocyanate groups and a molecular weight of 350 or less. do.
1. First liquid (A)
The first liquid (A) of the present invention is characterized by containing a hydroxyl group-containing resin (a1) and water.

The first liquid (A) of the present invention preferably has a nonvolatile content concentration of 25 to 55% by mass, particularly preferably 30 to 50% by mass, from the viewpoint of pot life and finish of the formed coating film. .

In this specification, the term "nonvolatile matter" refers to a residue after removing volatile components, and the residue may be either solid or liquid at room temperature. The non-volatile components refer to components remaining after volatile components are removed by treating a sample at 105° C. for 3 hours, for example.

1-1. Hydroxyl group-containing resin (a1)
Examples of the hydroxyl group-containing resin (a1) constituting the first liquid of the aqueous multi-component polyurethane coating composition according to the present invention include acrylic resin, polyester resin, alkyd resin, urethane resin, fluororesin, epoxy resin, and silicone resin. , polyether resin, acrylic silicone resin, vinyl acetate beoba resin, etc. Further, these may be used alone or in combination of two or more. Among these, it is preferable to contain at least one type of acrylic resin as the hydroxyl group-containing resin (a1). Further, the hydroxyl group-containing resin (a1) is preferably a water-soluble resin and/or a water-dispersible resin from the viewpoint of stability and workability of the base resin, and in particular, from the viewpoint of drying property and weather resistance, the hydroxyl group-containing resin (a1) is preferably a water-soluble resin and/or a water-dispersible resin. An aqueous dispersion (emulsion) of acrylic resin is preferred.

From the viewpoint of finishability, it is preferable that the hydroxyl group-containing resin (a1) is not a crosslinked resin particle. In the case of non-crosslinked resin particles, the weight average molecular weight of the resin can be measured with a gel permeation chromatography device. The hydroxyl group-containing resin (a1) preferably has a weight average molecular weight of 5,000 to 500,000, more preferably 10,000 to 100,000, from the viewpoint of water dispersion stability, finish, smoothness, polishability, coating hardness, etc. It is more preferable that the number is within the range of 10,000 to 30,000.

In this specification, the number average molecular weight and weight average molecular weight are determined using "HLC-8120GPC" (trade name, manufactured by Tosoh Corporation) as a gel permeation chromatography device, and one "TSKgel G4000HXL" as a column. A total of 4 tubes were used: 2 tubes of "TSKgel G3000HXL" and 1 tube of "TSKgel G2000HXL" (product names, both manufactured by Tosoh Corporation), a differential refractometer was used as a detector, and the mobile phase was tetrahydrofuran. , measurement temperature: 40° C., flow rate: 1 mL/min.

The average particle diameter of the resin particles contained in the hydroxyl group-containing resin (a1) is preferably within the range of 70 to 300 nm, particularly 100 to 200 nm, from the viewpoint of storage stability and finishing properties of the first liquid (A). ing.

In this specification, the average particle diameter is the value of the volume average particle diameter measured by the Coulter counter method at a measurement temperature of 20°C. Measurement by the Coulter counter method can be performed using, for example, "COULTER N4 type" (manufactured by Beckman Coulter, trade name).

The hydroxyl group-containing resin (a1) preferably has a hydroxyl value per resin solid content of 30 to 250 mgKOH/g, particularly 80 to 200 mgKOH/g, from the viewpoint of coating film properties, polishing properties, and drying properties. . In addition, the acid value per resin solid content is preferably 5 to 50 mgKOH/g, more preferably 10 to 40 mgKOH/g, and 15 to A range of 30 mgKOH/g is particularly preferred.

The glass transition temperature (hereinafter sometimes abbreviated as Tg) of the hydroxyl group-containing resin (a1) is preferably 40°C or higher, and 42 to The temperature is more preferably 70°C, and particularly preferably within the range of 45 to 65°C.

In this specification, the glass transition temperature (Tg) is a value calculated by the following formula.
1/Tg(K)=W ₁ /T ₁ +W ₂ /T ₂ +...W _n /T _n
Tg (℃) = Tg (K) - 273
In the formula, W ₁ , W ₂ , ... W _n is the mass fraction of each monomer, and T ₁ , T ₂ ... T _n is the glass transition temperature Tg (K) of the homopolymer of each monomer. . Note that the glass transition temperature of the homopolymer of each monomer is as described in POLYMER HANDBOOK Fourth Edition, J. Brandrup, E. h. Immergut, E. A. The glass transition temperature of monomers not described in the literature is the static glass transition when a homopolymer of the monomer is synthesized to have a weight average molecular weight of about 50,000. Temperature.

In this specification, the static glass transition temperature of a resin is measured using a differential scanning calorimeter "DSC-50Q model" (manufactured by Shimadzu Corporation, product name By measuring the change in heat value in the range of -100 to 150 °C at a heating rate of 3 °C/min using , can be measured.

The solubility parameter (SP value) of the hydroxyl group-containing resin (a1) is preferably within the range of 8.7 to 9.3 from the viewpoint of lowering the water absorption rate of the dried coating film and from the viewpoint of water resistance and adhesion. It is particularly preferably within the range of 8 to 9.2.

The solubility parameter ("SP value" is an abbreviation) represents a measure of intermolecular interaction of liquid molecules. The SP value of a homopolymer of polymerizable monomers is determined by J. Paint Technology, vol. 42, 176 (1970). The SP value of the copolymer of the polymerizable monomer mixture can be calculated and determined using the following formula.
SP value=SP ₁ ×fw ₁ +SP ₂ ×fw ₂ +……+SP _n ×fw _n
In the above formula, SP ₁ , SP ₂ , ...SP _n represent the SP value of the homopolymer of each polymerizable monomer, and fw ₁ , fw ₂ , ...... fw _n represent the SP value of the homopolymer of each polymerizable unsaturated monomer. It represents the mass fraction relative to the total amount of monomers.

In order to keep the solubility parameter of the hydroxyl group-containing resin (a1) within the above range, it is preferable that at least 10% by mass or more of monomers having an SP value of less than 9.3 are included in the copolymerization components, and 15 to 60% by mass. The content is more preferably within the range of 20 to 55% by mass, particularly preferably 20 to 55% by mass.

The amount of the hydroxyl group-containing resin (a1) in the first liquid (A) is 20 to 50 parts by weight when the entire weight of the first liquid (A) is 100 parts by weight. The amount is preferably from 25 to 45 parts by weight, particularly preferably from 25 to 45 parts by weight.

1-1-1. Hydroxyl group-containing acrylic resin emulsion component (a1-1)
The hydroxyl group-containing resin (a1) in the present invention contains a hydroxyl group-containing acrylic resin emulsion (a1-1), which is an aqueous dispersion of a hydroxyl group-containing acrylic resin, as a part of its components, since the hardness of the formed coating film is excellent. It is preferable to do so.

There are no restrictions on the water dispersion method for acrylic resin or the method for producing acrylic resin emulsion, but examples include a method in which a polymerizable unsaturated monomer component is emulsion polymerized in an aqueous solvent using a polymerization initiator in the presence of an emulsifier; A method of producing a resin by solution polymerization in an organic solvent and then forcibly dispersing it in water using an emulsifier.A method of producing a resin with hydrophilic groups by solution polymerization in an organic solvent and then dispersing it in water by self-emulsification. Examples include a method of dispersion.

The hydroxyl group-containing acrylic resin emulsion (a1-1) in the present invention is a polymerizable unsaturated monomer component containing a hydrophilic group-containing polymerizable monomer such as an anionic group, a cationic group, or a nonionic group in an organic solvent. The water dispersion obtained by emulsifying the hydrophilic group-containing acrylic resin obtained by solution polymerization by self-emulsification has excellent water dispersibility of the hydroxyl group-containing acrylic resin, storage stability of the first liquid, and water resistance. Preferable from this point of view. In particular, the emulsion obtained by this method is suitable because no emulsifier is used in the synthesis process and emulsification process, so no emulsifier remains and water resistance is potentially improved.

The hydroxyl group-containing acrylic resin emulsion (a1-1) in the present invention is an aqueous dispersion of a hydroxyl group-containing acrylic resin having a graft structure consisting of a main chain part and a side chain part. It is preferred from the viewpoint of excellent storage stability and water resistance. A hydroxyl group-containing acrylic resin having a graft structure consisting of a main chain part and a side chain part can be produced by the following method.
(1) In the first step, a copolymer is synthesized using the polymerizable unsaturated monomer component (X) that constitutes either the main chain portion or the side chain portion, and then in the second step, the copolymer that constitutes the other portion is synthesized. A copolymer is synthesized by adding a sexually unsaturated monomer component (Y).
(2) In the first step, a copolymer is synthesized using the polymerizable unsaturated monomer component (X) that constitutes either the main chain part or the side chain part, and separately, in the second stage, the other part is constituted. A copolymer of the polymerizable unsaturated monomer component (Y) is synthesized, and the copolymer synthesized in the second stage is added to the copolymer synthesized in the first stage to carry out copolymerization.
The hydroxyl group-containing acrylic resin emulsion (a1-1) in the present invention is preferably produced by the method (1) above.

The monomers for the first and second stages can be selected as appropriate; It is preferable to contain a monomer (x1), and the polymerizable unsaturated monomer component (Y) forming the second stage contains at least a part of the component a carboxyl group-containing polymerizable unsaturated monomer (y1). It is preferable. In that case, the amount of carboxyl groups contained in the polymerizable unsaturated monomer component (Y) with respect to 1 mole of epoxy groups contained in the polymerizable unsaturated monomer component (X) should be determined based on the storage stability, finishing properties, and From the viewpoint of polishing properties, the amount is preferably 1.5 to 30 mol, and particularly preferably adjusted within the range of 3 to 20 mol.

The usage ratio of the polymerizable unsaturated monomer component (X) and the polymerizable unsaturated monomer component (Y) is determined by the weight of the monomer component (X)/monomer component (Y) from the viewpoint of water dispersion stability and finishing properties of the emulsion. The ratio is preferably 60/40 to 95/5, particularly preferably 70/30 to 90/10.

Methods for dispersing resin in water include neutralizing some or all of the anionic groups such as carboxyl groups contained in the acrylic resin with a basic compound and dispersing it in water, or dispersing it in water containing a basic compound. It is also possible to add and disperse the acrylic resin in the medium. Specific examples of basic compounds that serve as neutralizing agents for hydroxyl group-containing acrylic resins include ammonia, diethylamine, ethylethanolamine, diethanolamine, triethanolamine, monoethanolamine, monopropanolamine, isopropanolamine, ethylamino Examples include organic amine compounds such as ethylamine, hydroxyethylamine, triethylamine, tributylamine, dimethylethanolamine, and diethylenetriamine; and alkali metal hydroxides such as caustic soda (NaOH) and caustic potash (KOH). Preference is given to using tertiary amines, especially tertiary amines.

Polymerizable unsaturated monomer component (X) forming the first stage
The polymerizable unsaturated monomer component (X) forming the first stage is an epoxy group-containing polymerizable unsaturated monomer (x1), a hydroxyl group-containing polymerizable unsaturated monomer (x2), and other polymerizable unsaturated monomers (x3). It is preferable to contain.

In the present invention, the epoxy group-containing polymerizable unsaturated monomer (x1) is reacted with a carboxyl group contained in the polymerizable unsaturated monomer component (Y) forming the second stage, which will be described later. ) is a monomer used to graft a copolymer with a polymerizable unsaturated monomer component (Y) to further improve the water dispersion stability of an acrylic resin emulsion. Specifically, for example, glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3,4-epoxycyclohexylethyl (meth)acrylate, 3,4- Examples include epoxycyclohexylpropyl (meth)acrylate, allyl glycidyl ether, and these can be used alone or in combination of two or more.

The proportion of the epoxy group-containing polymerizable unsaturated monomer (x1) in the polymerizable unsaturated monomer component (X) can be adjusted as appropriate as long as it is within the scope of the technical idea of the present invention, but in general, the proportion of the polymerizable unsaturated monomer (x1) The amount is preferably from 0.1 to 40% by weight, particularly preferably from 0.5 to 25% by weight, based on the total amount of component (X).

The hydroxyl group-containing polymerizable unsaturated monomer (x2) is a monomer that is copolymerized to introduce a hydroxyl group into the acrylic resin for reaction with the isocyanate compound described below and to improve the water dispersibility of the acrylic resin. . Specifically, for example, (meth)acrylic acids such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Monoesterified products with dihydric alcohols having 2 to 8 carbon atoms; ε-caprolactone modified products of monoesterified products of the (meth)acrylic acid and dihydric alcohols having 2 to 8 carbon atoms; allyl alcohol, etc. These can be used alone or in combination of two or more.

Other polymerizable unsaturated monomers (x3) are polymerizable unsaturated monomers other than the above monomers (x1) and monomers (x2), and those commonly used in the synthesis of acrylic resins can be widely used. Can be done. Specifically, for example, (meth)acrylates having an alkyl group having 1 to 2 carbon atoms such as methyl (meth)acrylate and ethyl (meth)acrylate; n-propyl acrylate, i-propyl acrylate, n-butyl acrylate; , i-butyl acrylate, tert-butyl acrylate and other acrylates having an alkyl group having 3 to 4 carbon atoms; n-hexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, tridecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, "isostearyl acrylate" (trade name, manufactured by Osaka Organic Chemical Co., Ltd.), cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate Alkyl or cycloalkyl (meth)acrylates having 6 or more carbon atoms such as acrylate, t-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, tricyclodecanyl (meth)acrylate; isobornyl (meth)acrylate, etc. Polymerizable unsaturated monomers having an isobornyl group; Polymerizable unsaturated monomers having an adamantyl group such as adamantyl (meth)acrylate; Polymerizable unsaturated monomers having a tricyclodecenyl group such as tricyclodecenyl (meth)acrylate Monomers: Aromatic ring-containing polymerizable unsaturated monomers such as benzyl (meth)acrylate, styrene, α-methylstyrene, vinyltoluene; Vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, vinyltris (2-methoxyethoxy)silane, vinyltriisopropoxysilane, γ-(meth)acryloyloxypropyltrimethoxysilane, γ-(meth)acryloyloxypropylmethyldimethoxysilane, γ-(meth)acryloyloxypropyltriethoxysilane, γ-(meth)acryloyloxypropylmethyldiethoxysilane, γ-(meth)acryloyloxypropyltri-n-propoxysilane, γ-(meth)acryloyloxypropyltriisopropoxysilane, vinyltriacetoxysilane, β-(meth)acryloyloxypropyltriisopropoxysilane, ) Polymerizable unsaturated monomers having a hydrolyzable silyl group such as acryloyloxyethyltrimethoxysilane; perfluoroalkyl (meth)acrylates such as perfluorobutylethyl (meth)acrylate and perfluorooctylethyl (meth)acrylate; Polymerizable unsaturated monomers having fluorinated alkyl groups such as olefins; Vinyl compounds such as N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, and vinyl acetate; 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl Phosphoric acid group-containing polymerizable unsaturated monomers such as acid phosphate, 2-acryloyloxypropyl acid phosphate, and 2-methacryloyloxypropyl acid phosphate; carboxyl groups such as (meth)acrylic acid, maleic acid, crotonic acid, and β-carboxyethyl acrylate Group-containing polymerizable unsaturated monomers: (meth)acrylonitrile, (meth)acrylamide, methylenebis(meth)acrylamide, ethylenebis(meth)acrylamide, 2-(methacryloyloxy)ethyltrimethylammonium chloride, glycidyl(meth)acrylate and amines nitrogen-containing polymerizable unsaturated monomers such as adducts with Saturated monomers; 2-acrylamido-2-methylpropanesulfonic acid, 2-sulfoethyl (meth)acrylate, allylsulfonic acid, 4-styrenesulfonic acid, etc.; polymerization with sulfonic acid groups such as sodium salts and ammonium salts of these sulfonic acids Polymerizable unsaturated monomers having an acid anhydride group such as maleic anhydride, itaconic anhydride, citraconic anhydride, etc., and these can be used alone or in combination of two or more.

In the present invention, the other polymerizable unsaturated monomer (x3) is a monomer whose homopolymer has a glass transition temperature of 30°C or higher as part of its components in order to obtain a coating film with excellent coating hardness. Preferably, it is desirable to include a monomer within the range of 40 to 130°C as part of the copolymerization component.

Specifically, the monomers having a glass transition temperature of 30° C. or higher for the homopolymer include styrene, methyl methacrylate, ethyl methacrylate, methacrylates having a branched alkyl group having 3 to 4 carbon atoms, such as i-propyl methacrylate, (Meth)acrylates having a cyclic alkyl structure such as i-butyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate, cetyl acrylate (also known as hexadecyl acrylate), benzyl methacrylate, etc. , others include isostearyl acrylate, stearyl methacrylate, etc. From the viewpoint of adhesion to the coated object and coating hardness, in particular, styrene, methyl methacrylate, methacrylate having a branched alkyl group having 3 to 4 carbon atoms. It is particularly preferred to use at least one selected monomer. Moreover, these monomers can be used alone or in combination.

When using a monomer having a glass transition temperature of 30° C. or higher, the amount used is within the range of 50 to 100% by mass, preferably 70 to 95% by mass in the other polymerizable unsaturated monomer (x3). From the viewpoint of coating film hardness, it is desirable that the

Polymerizable unsaturated monomer component (Y) forming the second stage
In particular, the hydroxyl group-containing acrylic resin that can be preferably applied to the present invention further includes a polymerizable unsaturated monomer component (Y) in addition to the polymerizable unsaturated monomer component (X) in at least one step of producing the hydroxyl group-containing acrylic resin as described above. is produced in at least two or more stages using as a copolymerization component.

The polymerizable unsaturated monomer component (Y) may contain a carboxyl group-containing polymerizable unsaturated monomer (y1), a hydroxyl group-containing polymerizable unsaturated monomer (y2), and other polymerizable unsaturated monomers (y3). preferable.

The carboxyl group-containing polymerizable unsaturated monomer (y1) introduces a water-dispersible group into the acrylic resin and also introduces a functional group that reacts with the epoxy group contained in the copolymer of the polymerizable unsaturated monomer component (X). It is a monomer used for Specific examples include (meth)acrylic acid, maleic acid, crotonic acid, and β-carboxyethyl acrylate, which can be used alone or in combination of two or more.

The usage ratio of the carboxyl group-containing polymerizable unsaturated monomer (y1) in the polymerizable unsaturated monomer component (Y) is preferably 5 to 60% by mass based on the total amount of the polymerizable unsaturated monomer component (Y), and 10% by mass. It is particularly preferable that the amount is in the range of 50% by mass.

The hydroxyl group-containing polymerizable unsaturated monomer (y2) is the same as the compounds listed in the hydroxyl group-containing polymerizable unsaturated monomer (x2), and can be used alone or in combination of two or more.

Other polymerizable unsaturated monomers (y3) are polymerizable unsaturated monomers other than the above-mentioned monomers (y1) and monomers (y2), and for example, the compounds listed under the above-mentioned other polymerizable unsaturated monomers (x3). These can be used alone or in combination of two or more.
The polymerizable unsaturated monomer component (X) constituting one of the main chain part and the side chain part is an epoxy group-containing polymerizable unsaturated monomer (x1), a hydroxyl group-containing polymerizable unsaturated monomer (x2), and other polymerizable monomers. The polymerizable unsaturated monomer component (Y) that contains the unsaturated monomer (x3) and constitutes the other is a carboxyl group-containing polymerizable unsaturated monomer (y1), a hydroxyl group-containing polymerizable unsaturated monomer (y2), and others. By containing the polymerizable unsaturated monomer (y3), it becomes easier to adjust the glass transition temperature of the hydroxyl group-containing resin (a1), adjust the hydroxyl value, adjust the reactivity of the monomer, etc., and dry in a short drying time. It is advantageous in that it produces a coating film with excellent hardness, and in terms of the dispersibility and storage stability of the resulting resin.

1-2. Polyether Polyol In the present invention, the first liquid (A) preferably contains a polyether polyol because a coating film with an excellent finished appearance can be obtained. The polyether polyol is a compound different from the hydroxyl group-containing resin (a1).

Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polyoxyalkylene glyceryl ether, which may be used alone or in combination of two or more. Among these, it is preferable to include polyoxyalkylene glyceryl ether from the viewpoint of improving the finish of the coating film.

The polyoxyalkylene structure in the polyoxyalkylene glyceryl ether can be selected from polyoxyethylene, polyoxypropylene, and polyoxybutylene, with polyoxypropylene being preferred.

The polyether polyol preferably has a number average molecular weight of 400 to 5000, particularly 500 to 1500, and a hydroxyl value of 30 to 400 mgKOH/g, particularly 100 to 350 mgKOH/g.

Commercially available polyether polyols include Sunix PP-1000, PP-2000, PP-3000, GP-600, GP-1000, GP-3000, GL-3000, FA-103, FA-703 (including Sanyo (manufactured by Kasei Kogyo Co., Ltd.), Exenol EL-1020, EL-2020, EL-3020, EL-510, EL-540, EL-3030, EL-5030, EL-823, EL-828, EL-830, EL-837 , EL-840, EL-850, EL-851B (manufactured by Asahi Glass Urethane Co., Ltd.), Preminol PML-3005, PML-3012, PML-4002, PML-5001, PML-7001 (all manufactured by Asahi Glass Urethane Co., Ltd.), etc. can be mentioned.

When the first liquid (A) contains a polyether polyol, its content should be 100% by weight of the nonvolatile content of the hydroxyl group-containing resin (a1) from the viewpoint of the balance between finishing properties, curability, and the hardness of the resulting coating film. It is suitably within the range of 0.5 to 40 parts by weight, preferably 1 to 25 parts by weight, more preferably 2 to 15 parts by weight.

1-3. Other components The first liquid (A) of the present invention includes a resin emulsion or water-soluble resin other than the hydroxyl group-containing resin (a1), a pigment component, a neutralizing agent, a rheology control agent, a surface conditioner, an antifoaming agent, and a curing agent. Catalysts, ultraviolet absorbers, light stabilizers, organic solvents, etc. can be added as necessary.

Among these, rheology control agents include, for example, polyamide rheology control agents such as fatty acid amide, polyamide, acrylamide, long chain polyaminoamide, aminoamide and their salts (e.g. phosphates); polyether polyol urethane preforms. Polymers, urethane-based rheology control agents such as urethane-modified polyether type viscosity modifiers; polycarboxylic acid-based rheology control agents such as high molecular weight polycarboxylic acids, high molecular weight unsaturated acid polycarboxylic acids, and their partially amidated products; hydroxyethyl cellulose , cellulose-based rheology control agents such as hydroxypropylcellulose; inorganic layered compound-based rheology control agents such as montmorillonite, bentonite, and clay; and aminoplast-based rheology control agents such as hydrophobically modified ethoxylate aminoplast. It may be used alone or in a mixture of two or more.

Commercial products of rheology control agents include polyamide rheology control agents such as "Disparon AQ-600" and "Disparon AQH-800" (trade name, manufactured by Kusumoto Kasei Co., Ltd.); "REOBYK H370", "REOBYK H400", " Aminoplast rheology control agents such as REOBYK H600 and RHEOBYK H600VF (manufactured by BYK Chemie); Polycarboxylic acid-based products such as "SN Thickener 613", "SN Thickener 617", "SN Thickener 618", "SN Thickener 630", "SN Thickener 634", "SN Thickener 636" (all product names, manufactured by San Nopco) Rheology control agents: "ADEKA NOL UH-814N", "UH-752", "UH-750", "UH-462" (all trade names, manufactured by ADEKA), "SN Thickener 621N", "SN Thickener 623N" ( Urethane rheology control agents such as "HEC Daicel SP600N" (product name, Daicel Chemical Co., Ltd.), "Reolate 244", "Reolate 278" (product names, manufactured by Elementis Japan Co., Ltd.); Cellulose-based rheology control agents such as "BENTONE HD" (trade name, manufactured by Elementis Japan Co., Ltd.); inorganic layered compound rheology control agents such as "BENTONE HD" (trade name, manufactured by Elementis Japan Co., Ltd.); etc., which can be used alone or in combination of two or more can do.

In the present invention, it is suitable to use a polycarboxylic acid rheology control agent and/or a nonionic rheology control agent as the rheology control agent from the viewpoint of the sagging resistance of the formed coating film.

Examples of nonionic rheology control agents include urethane rheology control agents, cellulose rheology control agents, layered compound rheology control agents, and aminoplast rheology control agents among the above-mentioned examples.

In the above rheology control agent, the mass of the active ingredient of the rheology control agent is 0.01 to 1.0 parts by mass, particularly 0.1 to 0.5 parts by mass, based on 100 parts by mass of nonvolatile components of the hydroxyl group-containing resin (a1). It is suitable to contain within the range of parts by mass.
It is particularly preferable to incorporate a curing catalyst into the aqueous coating composition of the present invention, since this may further improve the drying properties of the composition.
Examples of curing catalysts include organic tin compounds such as diacetyltin diacetate, dibutyltin dilaurate, dibutyltin diacetate, dioctyltin dilaurate, diacetyltin dioctoate, tin octylate, dibutyltin diacetate, and dibutyltin dioctoate; aluminum trimethoxy; organoaluminum compounds such as aluminum tris(acetylacetonate), aluminum tris(acetoacetate ethyl), aluminum diisopropoxy(acetoacetate ethyl), aluminum acetylacetonate; titanium tetra(monoethyl Organic titanium compounds such as titanium tetra(ethoxide), titanium tetra(monoethyl ethoxide), titanium tetra(monobutyl ethoxide), titanium tetrakis(acetylacetonate), and tetra-n-butyl titanate; zirconium tetra(monomethyl ethoxide), zirconium tetra Organic zirconium compounds such as (monoethyl ethoxide), zirconium tetra (monobutyl ethoxide), zirconium normal propylate, zirconium normal butyrate, zirconium tetrakis (acetylacetonate); organic zinc compounds such as zinc naphthenate; octylic acid Organic cobalt compounds such as cobalt and cobalt naphthenate; trimethylamine, triethylamine, 2-(dimethylamino)ethyl methacrylate, 1,4-diazabicyclo[2.2.2]octane, 1,8-diazabicyclo[5.4.0] Aliphatic amines such as -7-undecene, 1,5-diazabicyclo[4.3.0]-5-nonene, 1-methylpiperidine, 1-methylpyrrolidine, pyridine, 4-dimethylaminopyridine, 4-(1- Amine catalysts such as piperidyl) pyridine, N-methylimidazole, and N,N-dimethylaniline; lead, tin, zinc, and iron complexes of carboxylic acids; trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, Boric acid compounds such as boric acid esters such as triphenyl borate, tri(4-chlorophenyl) borate, and trihexafluoroisopropyl borate; molybdic acid, potassium molybdate, calcium molybdate, disodium molybdate (VI) Hydrate, ammonium molybdate, lithium molybdate, hexaammonium molybdate tetrahydrate, hexaammonium heptamolybdate tetrahydrate, magnesium molybdate, rubidium molybdate, cesium molybdate, cobalt (II) molybdate, Molybdate compounds or molybdate salts such as manganese(II) molybdate and zinc molybdate; molybdenum oxide; phosphomolybdate n-hydrate, sodium phosphomolybdate n-hydrate, ammonium phosphomolybdate trihydrate, etc. Phosphormolybdic acid compound or phosphomolybdate salt; molybdenum (IV) oxide bisacetylacetonate, bis(acetylacetonato) molybdenum (IV) oxide, molybdenum dioxide tetramethyl heptadionate, tetraethylammonium molybdate, trimethylstannyl molybdate -Organic molybdenum compounds such as tetrabutylammonium, molybdenum alkoxide, molybdenum 2-ethylhexanoate, and hexacarbonylmolybdenum can be used alone or in combination of two or more. Among these, organic zinc compounds and/or molybdenum compounds are particularly preferred from the viewpoint of consideration for the human body and the environment and the balance between curability and finish of the resulting coating film, and from the viewpoint of drying properties and coating film hardness. Therefore, molybdenum compounds are particularly preferred.
Further, when the first liquid (A) contains a curing catalyst, the content thereof is 0.01 to 1.00 parts by mass, particularly 0.01 to 1.00 parts by mass, based on 100 parts by mass of the nonvolatile content of the hydroxyl group-containing resin (a1). It is preferably within the range of 0.50 parts by mass.

2. Second liquid (B)
The second liquid (B) of the present invention is characterized by containing a polyisocyanate compound (b1).

The second liquid (B) of the present invention preferably has a nonvolatile content concentration of 20 to 100% by mass, preferably 30 to 90% by mass, from the viewpoint of painting workability, pot life, and finish quality of the formed coating film. The content is more preferably 40 to 80% by mass.

2-1. Polyisocyanate compound (b1)
The polyisocyanate compound (b1) in the present invention is characterized by containing a polyisocyanate compound (b1-1) having three or more isocyanate groups and having a molecular weight of 350 or less.

The amount of the polyisocyanate compound (b1) in the second liquid (B) is preferably 20 to 100 parts by weight in 100 parts by weight of the entire second liquid (B). It is preferably in the range of 30 to 80 parts by mass.

2-1-1. Polyisocyanate compound having 3 or more isocyanate groups and having a molecular weight of 350 or less (b1-1)
The second liquid (B) is characterized in that it contains a polyisocyanate compound (b1-1) having three or more isocyanate groups and having a molecular weight of 350 or less. Specifically, for example, 1,8-diisocyanato-4-isocyanatomethyloctane, 2-isocyanatoethyl (2S)-2,6-diisocyanatohexanoate (common name: lysine triisocyanate), 2,6 -Aliphatic triisocyanate compounds such as 2-isocyanatoethyl diisocyanatohexanoate, 1,6,11-triisocyanatoundecane, 1,3,5-triisocyanatocyclohexane, 1,3,5-trimethylisocyanate Examples include alicyclic triisocyanate compounds such as cyclohexane, aromatic triisocyanates such as 1,3,5-triisocyanatobenzene, and 2,4,6-triisocyanatotoluene, and these may be used alone or in combination. can be used in combination.

The polyisocyanate compound (b1-1) having three or more isocyanate groups and having a molecular weight of 350 or less is preferably an aliphatic triisocyanate compound from the viewpoint of pot life and finish of the formed coating film, and among them, 1, 8-Diisocyanato-4-isocyanatomethyloctane, 2-isocyanatoethyl (2S)-2,6-diisocyanatohexanoate (common name: lysine triisocyanate) is preferred, especially 1,8-diisocyanato-4-isocyanato Natomethyloctane is preferred.

In the present invention, the polyisocyanate compound (b1-1) having three or more isocyanate groups and having a molecular weight of 350 or less has a molecular weight within the range of 200 to 300, from the viewpoint of painting workability and finish quality of the formed coating film. It is preferably within the range of 230 to 280.

In the present invention, the polyisocyanate compound (b1-1) having three or more isocyanate groups and having a molecular weight of 350 or less has a viscosity of 1 to 50 mPa·s at 23°C from the viewpoint of coating workability and finish of the formed coating film. It is preferably within the range of 1 to 30 mPa·s, and more preferably within the range of 1 to 30 mPa·s.

In the aqueous multi-component polyurethane coating composition of the present invention, the polyisocyanate compound (b1-1) having a molecular weight of 350 or less and having 3 or more isocyanate groups has 3 or more isocyanate groups, so that the isocyanate groups are combined with each other when the coating film is cured. When the hydroxyl groups react, a three-dimensional network structure is formed. It is presumed that this results in a coating film with excellent hardness.

Further, the polyisocyanate compound (b1-1) having 3 or more isocyanate groups and having a molecular weight of 350 or less in the present invention has a solid content of 100% by mass of the polyisocyanate compound having 3 or more isocyanate groups and a molecular weight of 350 or less. In this case, the concentration of isocyanate groups is 36% by mass or more. Since this value is higher than that of commonly used polyisocyanate compounds, it is presumed that it has high reactivity. The aqueous multi-component polyurethane coating composition of the present invention forms a coating film in a short drying time due to the high isocyanate group concentration of the polyisocyanate compound (b1-1) with a molecular weight of 350 or less and having three or more isocyanate groups. It is assumed that it is possible.

In the present invention, the proportion of the isocyanate compound (b1-1) having three or more isocyanate groups and having a molecular weight of 350 or less in the polyisocyanate compound (b1) is determined by the coating workability, finish quality of the formed coating film, quick drying property, coating film From the viewpoint of hardness, it is preferably from 5 to 100% by mass, more preferably from 10 to 90% by mass, particularly preferably from 10 to 60% by mass, based on the total solid content of the polyisocyanate compound (b1). .

2-1-2. Other polyisocyanate compounds (b1-2)
The polyisocyanate compound (b1) in the present invention can contain a polyisocyanate compound (b1-2) other than the polyisocyanate compound having three or more isocyanate groups and a molecular weight of 350 or less. A polyisocyanate compound is a compound having two or more free isocyanate groups in one molecule, for example, an aliphatic polyisocyanate compound, an alicyclic polyisocyanate compound, an araliphatic polyisocyanate compound, an aromatic polyisocyanate compound. , derivatives of the polyisocyanate compound, etc., and these can be used alone or in combination of two or more.

Examples of the aliphatic polyisocyanate compounds include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1, Aliphatic diisocyanates such as 3-butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, dimer acid diisocyanate, methyl 2,6-diisocyanatohexanoate (common name: lysine diisocyanate), etc. can be mentioned.

Examples of the alicyclic polyisocyanate compound include 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (commonly used Name: Isophorone diisocyanate), 4,4'-methylenebis(cyclohexyl isocyanate), methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 1,3- or 1,4-bis(isocyanatomethyl) Alicyclic diisocyanates such as cyclohexane (common name: hydrogenated xylylene diisocyanate) or mixtures thereof, norbornane diisocyanate, such as 2-(3-isocyanatopropyl)-2,5-di(isocyanatomethyl)-bicyclo(2 .2.1) Heptane, 2-(3-isocyanatopropyl)-2,6-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 3-(3-isocyanatopropyl)-2, 5-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2 .1) Heptane, 6-(2-isocyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl) -2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo(2.2.1)-heptane, 6-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanato Examples include alicyclic triisocyanates such as (natopropyl)-bicyclo(2.2.1)heptane.

Examples of the araliphatic polyisocyanate compound include 1,3- or 1,4-xylylene diisocyanate or a mixture thereof, ω,ω'-diisocyanato-1,4-diethylbenzene, 1,3- or 1,4- Examples include aromatic aliphatic diisocyanates such as bis(1-isocyanato-1-methylethyl)benzene (common name: tetramethylxylylene diisocyanate) and mixtures thereof.

Examples of the aromatic polyisocyanate compound include m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 2,4'- or 4,4'-diphenylmethane diisocyanate, or mixtures thereof, 2,4- or 2,6-tolylene diisocyanate or mixtures thereof, aromatic diisocyanates such as 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, for example triphenylmethane-4,4' , 4'''-triisocyanate, and aromatic tetraisocyanates such as 4,4'-diphenylmethane-2,2',5,5'-tetraisocyanate.

Examples of the derivatives of the polyisocyanate compounds include dimers, trimers, biurets, allophanates, carbodiimides, uretdione, uretoimines, isocyanurates, oxadiazinetriones, polymethylene polyphenyl polyisocyanates (crude MDI, polymeric MDI), etc. ) and crude TDI.

In the polyisocyanate compound (b1) of the present invention, in addition to the polyisocyanate compound (b1-1) having three or more isocyanate groups and a molecular weight of 350 or less, from the viewpoint of coating workability, pot life, and finish of the formed coating film. It is preferable to contain other polyisocyanate compounds (b1-2), more preferably to contain a cyclized polymer of aliphatic diisocyanate such as hexamethylene diisocyanate, and the polyisocyanate compound is It is particularly preferable to include a hydrophilic polyisocyanate compound imparted with hydrophilicity by modification with a nonionic group.

A hydrophilic polyisocyanate compound can be prepared by reacting a polyisocyanate compound with a compound having both a functional group reactive with an isocyanate group and a hydrophilic group in the molecule.

Examples of the polyisocyanate compound for preparing the hydrophilic polyisocyanate compound include compounds listed as polyisocyanate compounds (b1-1) having a molecular weight of 350 or less having three or more of the above isocyanate groups, and compounds having three or more of the above isocyanate groups. Compounds listed as other polyisocyanate compounds (b1-2) other than polyisocyanate compounds with a molecular weight of 350 or less, or adducts of each of these polyisocyanate compounds with polyhydric alcohols, low molecular weight polyester resins, water, etc. Examples include cyclized polymers of each of the above-mentioned organic polyisocyanate compounds, and furthermore, isocyanate biuret bodies. Among them, aliphatic diisocyanates are preferred.

The hydrophilic groups of the compound having both a functional group reactive with the isocyanate group and a hydrophilic group in the molecule to be reacted with the polyisocyanate compound include carboxyl groups, phosphoric acid groups, sulfonic acid groups, etc. Examples include anionic groups and nonionic groups containing polyoxyalkylene units.

As the hydrophilic polyisocyanate compound, an anionic group-containing polyisocyanate compound is preferable from the viewpoint of coating film smoothness and coating film hardness, and a polyisocyanate compound having a sulfonic acid group and/or a phosphoric acid group as an anionic group is preferable. Particularly preferred.

In the present invention, the proportion of other polyisocyanate compounds (b1-2) other than the isocyanate compound having three or more isocyanate groups and a molecular weight of 350 or less in the polyisocyanate compound (b1) is determined by the coating workability and the finish of the formed coating film. From the viewpoint of properties, quick drying properties, and coating hardness, the amount is preferably 0 to 95% by mass, more preferably 10 to 90% by mass, and in the range of 40 to 90% by mass, based on the total solid content of the polyisocyanate compound (b1). It is particularly preferable that the

2-2. Others The second liquid (B) of the present invention includes a resin that does not react with the polyisocyanate compound (b1), a pigment component, a neutralizing agent, a rheology control agent, a surface conditioner, an antifoaming agent, a curing catalyst, an ultraviolet absorber, A light stabilizer, a dehydrating agent, etc. can be added as necessary.

The second liquid (B) of the present invention preferably contains an organic solvent from the viewpoint of coating workability and finish quality of the obtained coating film.

The organic solvent is preferably a compound without a hydroxyl group, and specifically, for example, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol divinyl ether, diethylene glycol ethyl methyl ether, diethylene glycol. Isopropyl methyl ether, diethylene glycol butyl methyl ether, triethylene glycol dimethyl ether, triethylene glycol divinyl ether, tetraethylene glycol diethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol di-n-propyl ether, propylene glycol diisopropyl ether, propylene Glycol di-n-butyl ether, propylene glycol diisobutyl ether, propylene glycol diallyl ether, propylene glycol diphenyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol di-n-butyl ether, dipropylene glycol diisobutyl ether, dipropylene glycol Allyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, tripropylene glycol di-n-butyl ether, tripropylene glycol diisobutyl ether, tripropylene glycol diallyl ether, butylene glycol dimethyl ether, butylene glycol diethyl ether, butylene glycol di-n- Glycol ether organic solvents such as butyl ether, 2-butoxyethyldiethoxyethyl ether, 2-butoxyethyltriethoxyether, 2-butoxyethyltetraethoxyethyl ether; ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol Acetate organic solvents such as mono-n-butyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol mono-n-butyl ether acetate, 3-methoxybutyl acetate, propylene glycol monomethyl ether acetate; acetone, methyl ethyl ketone, methyl amyl ketone, methyl isobutyl ketone Ester-based organic solvents such as ethyl acetate, butyl acetate, isobutyl acetate, methyl benzoate, ethyl ethoxypropionate, ethyl propionate, and methyl propionate. These can be used alone or in combination of two or more. Among them, from the viewpoint of the finish of the formed coating film, it is preferable that the organic solvent contains an organic solvent having a boiling point higher than that of water, particularly a compound having a boiling point of 150 to 250°C.

From the viewpoint of miscibility with the polyisocyanate compound (b1), that is, finishability, the amount of the organic solvent in the second liquid (B) is determined based on 100 parts by mass of the polyisocyanate compound (b1). is preferably in the range of 10 to 300 parts by weight, particularly 30 to 250 parts by weight.

3. Aqueous multi-component polyurethane coating composition The aqueous multi-component polyurethane coating composition of the present invention is a mixture obtained by mixing the first liquid (A) and the second liquid (B) immediately before use. It can be diluted appropriately and painted. The ratio of the first liquid (A) and the second liquid (B) to be used is 20 to 100 parts by mass, particularly 30 to 70 parts by mass of the second liquid (B) based on 100 parts by mass of the first liquid (A). A suitable ratio is such that

The aqueous multi-component polyurethane coating composition of the present invention can contain components other than the first component (A) and the second component (B). Specifically, the components other than the first liquid (A) and the second liquid (B) include, for example, a rheology control agent, a diluent containing water, a siloxane bond forming component such as an organic silane compound, and its catalyst. Can be mentioned. On the other hand, from the viewpoint of coating workability and storage stability, the aqueous multi-component polyurethane coating composition of the present invention is a water-based multi-component polyurethane coating composition in which the first component (A) is the main ingredient and the second component (B) is the curing agent. A two-component polyurethane coating composition is preferred.

The aqueous multi-component urethane paint composition of the present invention can be used as either a transparent paint or an opaque paint; however, since it can form a transparent finished appearance and a paint film with excellent hardness, it is preferable to use a clear paint film. The effect can be maximized when the composition is a transparent coating composition.

In addition, when the coating composition of the present invention is used as an opaque coating, the pigment to be used is not particularly limited, and examples thereof include pigments known in the coating field such as coloring pigments, extender pigments, and rust-preventing pigments. The type and amount can be adjusted depending on the purpose.

4. Coating method for aqueous multi-component polyurethane coating composition The aqueous multi-component polyurethane coating composition of the present invention comprises the first liquid (A), the second liquid (B), and optionally the first liquid ( A) and components other than the second liquid (B) can be mixed immediately before use, and the resulting mixture can be appropriately diluted and applied.

The substrate to which the aqueous multi-component polyurethane coating composition of the present invention is applied is not particularly limited, and includes, for example, metals such as aluminum, iron, stainless steel, zinc, copper, and tinplate; glass, concrete, slate plates, etc. Inorganic materials; organic materials such as plastics and vinyl chloride; wood, etc. The surface of these base materials may be further coated with a water-based or solvent-based paint. For example, the aqueous multi-component polyurethane coating composition of the present invention can be used to repair damaged coatings, although such coatings have been used to form coatings on substrates. Among these, the aqueous multi-component polyurethane coating composition of the present invention is preferably applied onto a colored coating.

Specific examples of objects to be coated with the above-mentioned base material include automobiles, motorcycles, and other motor vehicles, and their parts; trucks, buses, construction machinery, and railway vehicles, and other large vehicles and their parts; It is not limited.

Methods for applying the aqueous multi-component urethane coating composition of the present invention include, for example, air spray, airless spray, rotary atomization, brush, roller, hand gun, all-purpose gun, dipping, roll coater, curtain flow coater, and roller curtain. Coaters, die coaters, etc. can be used, and can be appropriately selected depending on the purpose of the object to be coated, and the coating may be applied multiple times.

The aqueous multi-component urethane coating composition of the present invention can form a coating film by drying at room temperature, forced drying, baking drying, etc. From the viewpoint of water resistance, it is preferable to perform forced drying or baking drying. Forced drying is particularly preferred from the viewpoint of product selectivity and energy reduction.

In the case of forced drying, it can be heated for 10 to 120 minutes under mild temperature conditions of 40 to 120 degrees Celsius, preferably 40 to 70 degrees Celsius, and then left at room temperature (5 to 45 degrees Celsius) to volatilize the solvent (setting time) may be provided as necessary. Air drying (ventilation) may also be used if necessary.
Setting can usually be carried out by leaving the coated object in a dust-free atmosphere at room temperature for 30 seconds to 60 minutes. The relative humidity (hereinafter sometimes abbreviated as RH) during setting is preferably 80% or less, particularly 70% or less.
For drying, an IR oven, an electric hot air dryer, etc. can be used.

The dry film thickness can be selected as appropriate depending on the application, but it can generally be in the range of 5 to 500 μm, more preferably 10 to 100 μm, and even more particularly 15 to 60 μm.

The coating composition of the present invention is particularly suitable for repair painting of automobiles and the like. Since a coating film with excellent hardness can be obtained in a short drying time, the surface can be polished at an early stage after the coating film is formed.

Examples of the polishing method include a method in which the repaired clear coating is wet-sanded using water-resistant abrasive paper, and then the polished surface is sequentially polished with a rough polishing compound and a final polishing compound.

The present invention will be further explained below with reference to Examples. Here, "parts" and "%" mean "parts by mass" and "% by mass", respectively.

Manufacturing example 1 of acrylic resin emulsion
Fifty parts of propylene glycol monopropyl ether was placed in a four-neck glass flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen inlet, and the temperature was raised to 120° C. under a nitrogen stream while stirring. When the temperature reached 120°C, a mixed solution of 1.5 parts of t-butylperoxy-2-ethylhexanoate was mixed in advance with the monomer formulation and polymerization initiator listed in the first stage column of Table 1 for 4 hours. After dropping, the temperature was maintained at 120° C. for 1 hour. Subsequently, while maintaining the temperature at 120°C, the monomer formulation described in the second stage column of Table 1 and 0.3 part of t-butylperoxy-2-ethylhexanoate were mixed in advance in the above flask. The mixed solution was added dropwise over 1 hour, and after the addition was completed, the mixture was maintained at 120°C for 1.5 hours to obtain an acrylic polyol solution. Subsequently, propylene glycol monopropyl ether was distilled off from the obtained acrylic polyol solution under reduced pressure until the nonvolatile content became 85%. This was cooled to 95°C, the pH was adjusted to 8.0 with dimethylethanolamine, and the mixture was stirred for 30 minutes. Further, deionized water was added dropwise over 2 hours to obtain a water dispersion (emulsion) of acrylic resin while stirring so that the nonvolatile content was 50%. The weight average molecular weight, acid value, hydroxyl value, and average particle diameter of the obtained acrylic resin emulsion (A1-1) are shown in Table 1 below.

Production examples 2 and 4
Acrylic resin emulsions (A1-2) and (A1-4) were obtained in the same manner as in Production Example 1, except that the monomer composition and blending amount of each copolymer component were as shown in Table 1 below. Ta.

Manufacturing example 3
Fifty parts of propylene glycol monopropyl ether was placed in a four-neck glass flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen inlet, and the temperature was raised to 120° C. under a nitrogen stream while stirring. When the temperature reached 120°C, a mixed solution of the monomer formulation listed in the first stage column of Table 1 and 1.5 parts of polymerization initiator t-butylperoxy-2-ethylhexanoate was added over 4 hours. After dropping, the temperature was maintained at 120° C. for 1 hour. Subsequently, while maintaining the temperature at 120° C., the monomer formulation described in the second stage column of Table 1 and 0.3 part of t-butylperoxy-2-ethylhexanoate were mixed in advance in the above flask. The mixed solution was added dropwise over a period of 1 hour, and after the addition was completed, the mixture was maintained at 120° C. for 1.5 hours to obtain an acrylic polyol solution. Subsequently, propylene glycol monopropyl ether was distilled off from the obtained acrylic polyol solution under reduced pressure until the nonvolatile content became 85%. This was cooled to 95° C., 5 parts of “Newcol 707SF” (Note 1) was added, and the mixture was stirred for 30 minutes. Furthermore, deionized water was added dropwise over 2 hours to obtain an acrylic resin emulsion (A1-3) while stirring so that the nonvolatile content was 50%.

Manufacturing example 5
Fifty parts of propylene glycol monopropyl ether was placed in a four-neck glass flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen inlet, and the temperature was raised to 120° C. under a nitrogen stream while stirring. When the temperature reached 120°C, a mixed solution of the monomer formulation listed in the first stage column of Table 1 and 1.8 parts of polymerization initiator t-butylperoxy-2-ethylhexanoate was added over 4 hours. After dropping, the temperature was maintained at 120° C. for 1 hour to obtain an acrylic polyol solution. Subsequently, propylene glycol monopropyl ether was distilled off from the obtained acrylic polyol solution under reduced pressure until the nonvolatile content became 85%. This was cooled to 95°C, the pH was adjusted to 8.0 with dimethylethanolamine, and the mixture was stirred for 30 minutes. Furthermore, deionized water was added dropwise over 2 hours to obtain an acrylic resin emulsion (A1-5) while stirring so that the nonvolatile content was 50%.

Note 1) "Nukol 707SF": Trade name, manufactured by Nippon Nyukazai Co., Ltd., polyoxyethylene polycyclic phenyl ether sulfate salt.

Manufacturing example 6
In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser, nitrogen inlet tube, and dropping device, add 85 parts of deionized water and “Adekaria Soap SR-1025” (trade name, manufactured by ADEKA, emulsifier, effective 0.8 part of component (25%) was added, stirred and mixed in a nitrogen stream, and heated to 80°C. Next, 5% of the total amount of the following monomer emulsion for the core part and 2.5 parts of a 6% ammonium persulfate aqueous solution were mixed into a reaction vessel and held at 80°C for 15 minutes. Thereafter, the remainder of the monomer emulsion for the core portion was dropped over 3 hours into a reaction vessel maintained at the same temperature, and after completion of the dropwise addition, aging was carried out for 1 hour. Next, the monomer emulsion for the shell part described below was added dropwise over 1 hour, and after aging for 1 hour, 3.8 parts of a 5% dimethylaminoethanol aqueous solution was gradually added to the reaction vessel while cooling to 30°C, and a 100-mesh The mixture was discharged while being filtered through a nylon cloth to obtain an acrylic resin emulsion (A1-6) with a solid content of 35%. The core portion of the obtained acrylic resin emulsion is crosslinked with a polymerizable unsaturated monomer (allyl methacrylate) having two or more polymerizable unsaturated groups in one molecule.
"Monomer emulsion for core part": 50 parts of deionized water, 3.1 parts of "Adekariasoap SR-1025", 1 part of allyl methacrylate, 10 parts of styrene, 28 parts of methyl methacrylate, 20 parts of ethyl acrylate, and 2-hydroxy A monomer emulsion for the core portion was obtained by mixing and stirring 18 parts of ethyl methacrylate.
"Monomer emulsion for shell part": 50 parts of deionized water, 1.8 parts of "Adekariasoap SR-1025", 0.04 parts of 6% ammonium persulfate aqueous solution, 3 parts of styrene, 10 parts of 2-hydroxyethyl methacrylate, A monomer emulsion for the shell portion was obtained by mixing and stirring 3 parts of methacrylic acid, 3 parts of ethyl acrylate, and 4 parts of methyl methacrylate.

Production of aqueous multi-component polyurethane coating composition Example 1
In a container, 70 parts of the acrylic resin emulsion (A1-1) with a nonvolatile content of 50% obtained in Production Example 1, 0.5 parts of "BYK-348" (Note 4), and 1 part of "BYK-015" (Note 5). part, "TINUVIN384-2" (Note 6) 1 part, "TINUVIN292" (Note 7) 0.5 part, "SN Thickener 621N" (Note 8) 0.5 part (non-volatile content 0.2 part), deionized 26 parts of water was blended, and dimethylethanolamine was added dropwise to the mixture under stirring at room temperature until the pH reached 7.6 to prepare a first liquid (A).
In another container, 12.5 parts of 1,8-diisocyanato-4-isocyanatomethyloctane, 12.5 parts of "Bihydur XP2655" (Note 10), 15 parts of dipropylene glycol dimethyl ether, 5 parts of ethylene glycol monobutyl ether acetate, A second solution (B) was prepared by adding 5 parts of diethylene glycol monoethyl ether acetate and mixing until uniform.
100 parts of the first liquid (A) and 50 parts of the second liquid (B) are mixed, and deionized water is added so that the nonvolatile content is 40%, and the mixture is stirred to obtain an aqueous solution. A multi-component polyurethane coating composition (X-1) was obtained.

Examples 2~ and Comparative Examples 1~3
In Example 1, water-based multi-component polyurethane coating compositions (X-2) to (X- 26) was obtained.

Note 2) "Sannix GP-600": Product name, manufactured by Sanyo Chemical Industries, Ltd., polyoxypropylene glyceryl ether, number average molecular weight 600, hydroxyl value 280 mgKOH/g, non-volatile content 100%
Note 3) "Sannix GP-3000": Product name, manufactured by Sanyo Chemical Industries, Ltd., polyoxypropylene glyceryl ether, number average molecular weight 3000, hydroxyl value 52.6 mgKOH/g, non-volatile content 100%
Note 4) "BYK-348": Product name, manufactured by BYK-Chemie Japan, polyether-modified siloxane, weight average molecular weight 1,500, non-volatile content 100%
Note 5) "BYK-015": Product name, manufactured by BYK-Chemie Japan, polyether-modified siloxane, weight average molecular weight 2,200, non-volatile content 100%
Note 6) "TINUVIN 384-2": Product name, manufactured by BASF, benzotriazole ultraviolet absorber, non-volatile content 95%, 1-methoxy-2-propyl acetate 5%,
Note 7) “TINUVIN 292”: Product name, manufactured by BASF, hindered amine light stabilizer, non-volatile content 100%
Note 8) "SN Thickener 621N": Product name, manufactured by San Nopco, nonionic rheology control agent, non-volatile content 30%
Note 9) Add dropwise in an amount to reach pH 7.6: Add all the components of the first liquid (A) and add dropwise while stirring at 23°C until the pH reaches 7.6 Note 10) "Bihydur XP2655": Product name , manufactured by Sumika Covestrourethane Co., Ltd., hexamethylene diisocyanate-based polyisocyanate having sulfonic acid groups, NCO content 21%, non-volatile content 100%
Note 11) "Byhydur 304": Trade name, manufactured by Sumika Covestrourethane Co., Ltd., hexamethylene diisocyanate-based polyisocyanate with ethylene oxide group, NCO content 18%, non-volatile content 100%
Note 12) "Desmodur N3900": Trade name, manufactured by Sumika Covestro Urethane Co., Ltd., hydrophobic polyisocyanate, cyclized polymer of hexamethylene diisocyanate, NCO content 23.5%, non-volatile content 100%
Note 13) Zinc compound: "K-KAT Japanese food

Evaluation Tests Tables 2 to 7 above list the results of the evaluation tests described below. In the present invention, it is important that all the performances are excellent, and if any one of them has a failing grade of "D", it is a failure.
<Object to be coated>
A painted board coated with a clear paint for automobile bodies was polished and degreased with #800 waterproof paper. Place this horizontally and apply a commercially available water-based colored base paint composition "Retan WB Eco Base" (trade name, water-based metallic base paint for automobile refinishing manufactured by Kansai Paint Co., Ltd.) under conditions of 25°C and 40% relative humidity. A colored base coating film with a total thickness of 15 μm was obtained by repeating the coating in three stages so that the color was as follows. After each stage of painting, air blowing was performed until the solvent volatilized and the gloss became low (specifically, the gloss level was about 25). The plate on which the metallic colored base coating film was formed was used as a coated object (V).

<Possible polishing time>
The coating compositions obtained in the Examples and Comparative Examples were air-sprayed onto the above-mentioned object (V) so that the dry film thickness was 40 μm, and then allowed to stand horizontally at room temperature for 20 minutes, and then dried with electric hot air. A plurality of test coated plates (for drying evaluation) with different drying times at 60°C were prepared for the same paint sample by varying the drying time at 60°C for 20 minutes, 30 minutes, and 40 minutes using a container. Next, the following polishing and repair method (*) was applied to each of the test coated plates (for drying evaluation), and from among them, the test coated plates (for drying evaluation) in good coating condition with no paper scratches or loss of gloss were selected. Selected. As for the evaluation, A, B, and C are passed, and D is failed.
A: It is possible to polish and repair the test coated plate with a drying time of 20 minutes or more.
B: It is possible to polish and repair the test coated plate with a drying time of 30 minutes or more.
C: Polishing and repair is possible with a test coated plate with a drying time of 40 minutes.
D: It is impossible to polish and repair the test coated plate with a drying time of 40 minutes.
(*Polishing repair method)
After wet-sanding each test coated plate (for drying evaluation) using #2000 water-resistant abrasive paper, polish it with a rough-polishing buff for 60 seconds using a rough-polishing compound to remove paper scratches caused by the water-resistant abrasive paper. Then, polishing was performed for 60 seconds using a finishing buff using a finishing compound to remove buffing scratches.

<Mixability of the first liquid and the second liquid>
Regarding the coating compositions obtained in Examples and Comparative Examples, we prepared a sample (*1) in which the first and second liquids were mixed by hand stirring, and a sample (*2) in which they were stirred for 3 minutes at 1000 rpm with a disper. . The miscibility of the first liquid and the second liquid was evaluated by visually observing the appearance of the coating composition after stirring and allowing it to stand for 15 minutes. As for the evaluation, A and C are passed, and D is failed.
A: Both sample (*1) and sample (*2) are in a uniform state and do not separate after standing.
C: Sample (*2) is in a homogeneous state, but sample (*1) is partially separated after being left still.
D: Both sample (*1) and sample (*2) are significantly separated.

<Pot life>
The coating compositions obtained in Examples and Comparative Examples were allowed to stand at 25° C., and the viscosity was measured using a Ford cup at specified time intervals, and the time required to reach the coating limit viscosity was defined as the pot life. As for the evaluation, A, B, and C are passed, and D is failed.
A: Pot life is 2 hours or more.
B: Pot life is 1 hour or more and less than 2 hours.
C: Pot life is 30 minutes or more and less than 1 hour.
D: Pot life is less than 30 minutes.

<Finishability>
The coating compositions obtained in the Examples and Comparative Examples were air-sprayed onto the object to be coated (V) so that the dry film thickness was 40 μm, and then the coated plate was kept horizontally at room temperature for 20 minutes. A test coated plate (for finish evaluation) was prepared by drying at 60°C for 30 minutes using an electric hot air dryer and cooling to room temperature. The appearance of the coating film, such as the appearance of wrinkles, smoothness, and gloss, was visually observed and evaluated. As for the evaluation, A, B, and C are passed, and D is failed.
A: The appearance of the coating film is very good.
B: Almost no unevenness, wrinkles, or wrinkles are observed, and the smoothness and gloss are good.
C: Deterioration in smoothness and slight glossiness are observed, but unevenness, wrinkles, and wrinkles are hardly observed, which is at a level that poses no problem in practical use.
D: Significant unevenness, armpits, wrinkles, and dull spots occur, and there is clearly a problem.

<Coating film hardness>
Using Fischerscope HM2000 (manufactured by FISCHER), an indenter was pressed into the surface of the test coated plate for finish evaluation, and the Martens hardness value obtained from the pressing depth and pressing force at that time was evaluated.
A: Martens hardness value is 20 N/mm ² or more.
B: Martens hardness value is 10 N/mm ² or more and less than 20 N/mm ² .
C: Martens hardness value is 5 N/mm ² or more and less than 10 N/mm ² .
D: Martens hardness value is less than 5 N/mm ² .

<Water resistance>
The test coated plate for finish evaluation was immersed in a constant temperature water bath at 40° C. for 10 days, taken out, and then left to stand for 1 hour, and the state of the coating film was visually evaluated.
A: No abnormality.
B: A very small amount of at least one abnormality such as shine, cracks, and blisters (or sometimes called blisters) is slightly observed.
C: At least one abnormality such as shine, cracks, and blisters is partially observed.
D: At least one abnormality such as shine, cracks, and blisters is significantly observed partially or over the entire surface of the coating.

<Storability>
The first liquid and the second liquid prepared in the example were each stored at 40° C. for one month, and changes in appearance and color were evaluated.
A: Very good, with no separation, gelation, discoloration, etc. observed.
B: Slight separation is observed, but gelation, discoloration, etc. are not observed.
C: Slight separation, gelation, discoloration, etc. are observed, but there is no problem with stirring.
D: Significant separation, gelation, discoloration, etc. were observed, and there was clearly a problem.

Claims (12)

An aqueous multi-component polyurethane coating composition containing a first liquid (A) containing a hydroxyl group-containing resin (a1) and water, and a second liquid (B) containing a polyisocyanate compound (b1), An aqueous multi-component polyurethane coating composition, wherein the isocyanate compound (b1) contains a polyisocyanate compound (b1-1) having three or more isocyanate groups and a molecular weight of 350 or less. The aqueous multi-component polyurethane coating composition according to claim 1, wherein the hydroxyl group-containing resin (a1) contains an aqueous dispersion of a hydroxyl group-containing acrylic resin having a glass transition temperature of 40° C. or higher. Claim characterized in that the water dispersion of the hydroxyl group-containing acrylic resin is a self-emulsifying water dispersion of the acrylic resin containing a hydrophilic group-containing polymerizable unsaturated monomer as a part of the constituent components. 2. The aqueous multi-component polyurethane coating composition according to 2. The aqueous dispersion of hydroxyl group-containing acrylic resin is an aqueous dispersion of hydroxyl group-containing acrylic resin having a graft structure consisting of a main chain part and a side chain part, and constitutes either the main chain part or the side chain part. The polymerizable unsaturated monomer component (X) contains an epoxy group-containing polymerizable unsaturated monomer (x1), a hydroxyl group-containing polymerizable unsaturated monomer (x2), and another polymerizable unsaturated monomer (x3), and the other The polymerizable unsaturated monomer component (Y) that constitutes contains a carboxyl group-containing polymerizable unsaturated monomer (y1), a hydroxyl group-containing polymerizable unsaturated monomer (y2), and other polymerizable unsaturated monomers (y3). The aqueous multi-component polyurethane coating composition according to claim 2 or 3, characterized in that: The aqueous multi-component polyurethane coating composition according to any one of claims 1 to 4, wherein the first liquid (A) contains a polyether polyol. The aqueous multi-component polyurethane coating composition according to any one of claims 1 to 5, wherein the first liquid (A) has a nonvolatile content concentration within a range of 25 to 55% by mass. The aqueous multi-component polyurethane according to any one of claims 1 to 6, wherein in the second liquid (B), the polyisocyanate compound (b1) further contains a hydrophilic polyisocyanate compound. Paint composition. In the second liquid (B), the proportion of the polyisocyanate compound (b1-1) having three or more isocyanate groups and having a molecular weight of 350 or less in the polyisocyanate compound (b1) is 10 to 90% by mass. The aqueous multi-component polyurethane coating composition according to any one of claims 1 to 7. In the second liquid (B), the polyisocyanate compound (b1-1) having a molecular weight of 350 or less and having three or more isocyanate groups is an aliphatic triisocyanate compound, according to any one of claims 1 to 8. Aqueous multi-component polyurethane coating composition. The aqueous multi-component polyurethane coating composition according to any one of claims 1 to 9, wherein the nonvolatile content concentration of the second liquid (B) is within the range of 20 to 100% by mass. The aqueous multi-component polyurethane coating composition according to any one of claims 1 to 10, which is a transparent coating composition. A coating method for coating an object to be coated with the aqueous multi-component polyurethane coating composition according to any one of claims 1 to 11.