Water-based two-component clear coating composition and automotive repair coating

Abstract

To provide an aqueous two-pack type clear coating composition from which a coating film excellent in scratch resistance and recoverability of glossiness lowered caused by scratches can be obtained.SOLUTION: An aqueous two-pack type clear coating composition contains a main agent (A) and a curing agent (B), wherein the main agent (A) contains a hydroxyl group-containing acrylic resin (a1) and an aqueous solvent (a2), the curing agent (B) contains an isocyanate compound (b1) and an organic solvent (b2) having no hydroxyl group, at least one of the side chain of the hydroxyl group-containing acrylic resin (a1) and the isocyanate compound (b1) has a soft segment part, the soft segment part contains at least one selected from the group consisting of chains represented by the following expressions (x), (y) and (z): (x) X1-(OC2H4)p-Y1, (y) -X2-(OC3H6)q-Y2 and (z) -X3-(CH2)r-Y3. In the expressions, each symbol has the same meaning in the specifications.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a water-based two-pack clear coating composition and an automotive refinish coating. [Background technology]

[0002] Conventionally, solvent-based paints have been used for automotive repair painting because they tend to improve image clarity and finished appearance. In recent years, growing concern about the environment has led to an increasing demand for water-based paints instead of solvent-based paints (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-22948 Summary of the Invention [Problem to be solved by the invention]

[0004] However, automotive repair coatings formed using the above-mentioned water-based paints are prone to scratches caused by car washing and the like.

[0005] An object of the present invention is to provide an aqueous two-pack clear coating composition that can provide a coating film, particularly a repair coating film, that is excellent in abrasion resistance and in the recovery of gloss reduced by abrasion. Another object of the present invention is to provide an automotive repair coating that contains the above aqueous two-pack clear coating composition. [Means for solving the problem]

[0006] The present invention provides the following aspects [1] to [8]. [1] Contains a base agent (A) and a curing agent (B), The main agent (A) is a hydroxyl group-containing acrylic resin (a1); an aqueous solvent (a2), The curing agent (B) is an isocyanate compound (b1); and (b2) an organic solvent having no hydroxyl group, at least one of the side chain of the hydroxyl group-containing acrylic resin (a1) and the isocyanate compound (b1) has a soft segment portion, The soft segment portion is The following formulas (x), (y) and (z): -X 1 -(OC2H4) p -Y 1 (x) -X 2 -(OC3H6) q -Y 2 (y) -X 3 -(CH2) r -Y 3 (z) [In the formula, p and q each independently represent an integer of 2 or more; r represents an integer of 6 or greater; When the side chain of the hydroxyl group-containing acrylic resin (a1) has a soft segment moiety, X 1 and X 2 each independently represents -C(=O)-; X 3 represents -C(=O)-O-, Y 1 -E 1 -OH(in the formula, E 1 is a single bond or a divalent organic group other than an oxyethylene group. Y 2 -E 2 -OH(in the formula, E 2 is a single bond or a divalent organic group other than an oxypropylene group. Y 3 -E 3 -OH(in the formula, E 3 is a single bond or a divalent organic group other than an alkylene group. When the isocyanate compound (b1) has the soft segment portion, X1 and X 2 each independently represents -NH-C(=O)-; X 3 represents -NH-C(=O)- or -NH-C(=O)-O-, Y 1 -E 1 -NCO(in the formula, E 1 is the same as above.) Y 2 -E 2 -NCO(in the formula, E 2 is the same as above.) Y 3 -E 3 -NCO(in the formula, E 3 is the same as above.) A water-based two-component clear coating composition comprising at least one selected from the group consisting of chains represented by the following formula:

[0007] [2] The aqueous two-pack clear coating composition according to the above [1], wherein the isocyanate compound (b1) comprises a hydrophilic isocyanate compound (b11) and a hydrophobic isocyanate compound (b12).

[0008] [3] The aqueous two-component clear coating composition according to the above [2], wherein the soft segment portion is contained at least in the hydrophobic isocyanate compound (b12).

[0009] [4] The aqueous two-component clear coating composition according to the above [3], wherein the ratio of the soft segment portion to the hydrophobic isocyanate compound (b12) is 40% by mass or more and 90% by mass or less.

[0010] [5] The solid content mass W of the hydrophilic isocyanate compound (b1) b1 and the solid content mass W of the hydrophobic isocyanate compound (b2) b2 Ratio to: W b1 / W b2The aqueous two-component clear coating composition according to [2] above, wherein the ratio of the total weight of the coating to the total weight of the paint is 99 / 1 to 76 / 24.

[0011] [6] The aqueous two-pack clear coating composition according to the above [1], wherein the main component (A) further contains a polyol compound (a3).

[0012] [7] The aqueous two-pack clear coating composition according to the above [1], further comprising a molybdenum compound (C).

[0013] [8] An automotive repair paint comprising the aqueous two-component clear paint composition described in [1] above. [Effects of the Invention]

[0014] According to the present invention, there is provided an aqueous two-pack clear coating composition that can provide a coating film, particularly a repair coating film, that is excellent in abrasion resistance and in the recovery of gloss that has been reduced due to abrasion. According to the present invention, there is also provided an automotive repair coating comprising the above aqueous two-pack clear coating composition. DETAILED DESCRIPTION OF THE INVENTION

[0015] [Water-based two-component clear coating composition] The aqueous two-component clear coating composition according to this embodiment (hereinafter sometimes simply referred to as the coating composition) is a two-component composition containing a main component (A) and a curing agent (B). The main component (A) contains a hydroxyl-containing acrylic resin (a1) and an aqueous solvent (a2). The curing agent (B) contains an isocyanate compound (b1) and an organic solvent (b2) that does not contain hydroxyl groups.

[0016] At least one of the side chain of the hydroxyl group-containing acrylic resin (a1) and the isocyanate compound (b1) has a soft segment portion.

[0017] The soft segment portion is The following formulas (x), (y) and (z): -X 1-(OC2H4) p -Y 1 (x) -X 2 -(OC3H6) q -Y 2 (y) -X 3 -(CH2) r -Y 3 (z) [In the formula, p and q each independently represent an integer of 2 or more; r represents an integer of 6 or greater; When the side chain of the hydroxyl group-containing acrylic resin (a1) has a soft segment moiety, X 1 and X 2 each independently represents -C(=O)-; X 3 represents -C(=O)-O-, Y 1 -E 1 -OH(in the formula, E 1 is a single bond or a divalent organic group other than OC2H4. Y 2 -E 2 -OH(in the formula, E 2 is a single bond or a divalent organic group other than OC3H6. Y 3 -E 3 -OH(in the formula, E 3 is a single bond, or a divalent organic group containing an oxygen atom, a nitrogen atom, or ◆〇〇. When the isocyanate compound (b1) has the soft segment portion, X 1 and X 2 each independently represents -NH-C(=O)-; X 3 represents -NH-C(=O)- or -NH-C(=O)-O-, Y 1 -E 1 -NCO(in the formula, E 1 is the same as above.) Y2 -E 2 -NCO(in the formula, E 2 is the same as above.) Y 3 -E 3 -NCO(in the formula, E 3 is the same as above.) The chain comprises at least one selected from the group consisting of:

[0018] The soft segment moiety acts like a spring in the coating film. Scratches are minute deformations of the coating film caused by external forces. Because the coating film obtained using the coating composition according to this embodiment contains the soft segment moiety, it is less likely to deform due to external forces. Furthermore, even if it does deform, the coating film can easily recover from the deformation. In other words, the coating film obtained using the coating composition according to this embodiment has excellent scratch resistance and gloss recovery (hereinafter simply referred to as gloss recovery) that has been reduced due to scratches. Therefore, the coating composition according to this embodiment is particularly suitable for forming repair coating films.

[0019] A repair coating is a coating formed on the peeled portion of an existing coating after the existing coating has been removed by grinding. Repair coatings are typically cured at temperatures lower than those of new car coatings (for example, 40°C or higher and 100°C or lower), and therefore tend to have poor physical properties. The repair coating obtained using the coating composition according to this embodiment has excellent scratch resistance and gloss recovery, and therefore can have physical properties comparable to those of existing coatings.

[0020] Hereinafter, the term "coating film" includes repair coating film. Repair paint is a paint used to form this repair coating film. Repair painting is painting that is applied to the peeled area after the existing coating film has been removed by grinding. Hereinafter, the term "painting" includes repair painting.

[0021] The soft segment portion may be contained in the side chain of the hydroxyl group-containing acrylic resin (a1), may be contained in the isocyanate compound (b1), or may be contained in both of them. The soft segment portion may be contained in the isocyanate compound (b1).

[0022] <Main ingredient (A)> The main component (A) contains a hydroxyl group-containing acrylic resin (a1) and an aqueous solvent (a2). The solid content of the main component (A) is not particularly limited. The solid content of the main component (A) is, for example, 30% by mass or more and 60% by mass or less.

[0023] (Hydroxyl group-containing acrylic resin (a1)) The hydroxyl group-containing acrylic resin (a1) improves various physical properties of the resulting coating film, such as appearance, weather resistance, and chemical resistance.

[0024] The hydroxyl-containing acrylic resin (a1) is in the form of an emulsion dispersed in an aqueous solvent (a2). The particle size of the hydroxyl-containing acrylic resin (a1) in the main component (A) is not particularly limited. In terms of ease of viscosity control and the appearance of the resulting coating film, the average particle size of the hydroxyl-containing acrylic resin (a1) may be 0.01 μm or more, or 0.05 μm or more. Similarly, the average particle size of the hydroxyl-containing acrylic resin (a1) may be 1.0 μm or less, or 0.5 μm or less. In one embodiment, the average particle size of the hydroxyl-containing acrylic resin (a1) is 0.01 μm or more and 1.0 μm or less. The average particle size is the 50% diameter (median diameter, D50) in the volume-based particle size distribution measured by dynamic light scattering.

[0025] The solids concentration of the hydroxyl-containing acrylic resin (a1) may be 30% by mass or more, 35% by mass or more, or 40% by mass or more of the total solids contained in the main component (A). The solids concentration of the hydroxyl-containing acrylic resin (a1) may be 95% by mass or less, 90% by mass or less, or 85% by mass or less of the total solids contained in the main component (A). In one embodiment, the solids concentration of the hydroxyl-containing acrylic resin (a1) is 30% by mass or more and 95% by mass or less of the total solids contained in the main component (A). When the solids concentration of the hydroxyl-containing acrylic resin (a1) is in the above range, the strength of the resulting coating film is likely to be increased.

[0026] The hydroxyl value of the hydroxyl-containing acrylic resin (a1) may be 5 mgKOH / g or more, or 50 mgKOH / g or more. The hydroxyl value of the hydroxyl-containing acrylic resin (a1) may be 200 mgKOH / g or less, or 150 mgKOH / g or less. In one embodiment, the hydroxyl value of the hydroxyl-containing acrylic resin (a1) is 5 mgKOH / g or more and 200 mgKOH / g or less. When the hydroxyl value of the hydroxyl-containing acrylic resin (a1) is within the above range, the strength of the resulting coating film is sufficiently high and water resistance is also likely to be improved.

[0027] The acid value of the hydroxyl-containing acrylic resin (a1) may be 5 mgKOH / g or more, or 10 mgKOH / g or more. The acid value of the hydroxyl-containing acrylic resin (a1) may be 100 mgKOH / g or less, or 50 mgKOH / g or less. In one embodiment, the acid value of the hydroxyl-containing acrylic resin (a1) is 5 mgKOH / g or more and 100 mgKOH / g or less. When the acid value of the hydroxyl-containing acrylic resin (a1) is within the above range, the water dispersibility of the hydroxyl-containing acrylic resin (a1) is improved, and the water resistance of the resulting coating film is also likely to be improved.

[0028] The number average molecular weight of the hydroxyl-containing acrylic resin (a1) may be 1,000 or more, 2,000 or more, or 3,000 or more. The number average molecular weight of the hydroxyl-containing acrylic resin (a1) may be 100,000 or less, 50,000 or less, or 10,000 or less. In one embodiment, the number average molecular weight of the hydroxyl-containing acrylic resin (a1) is 1,000 or more and 100,000 or less. When the number average molecular weight of the hydroxyl-containing acrylic resin (a1) is within the above range, an excessive increase in viscosity of the aqueous two-component clear coating composition is suppressed, and the appearance of the resulting coating film is improved, and its strength is also likely to be sufficiently high.

[0029] The hydroxyl value and acid value are both based on the solid content and can be measured in accordance with JIS K 0070. The number average molecular weight is a value measured using gel permeation chromatography and converted into a styrene homopolymer. The same applies hereinafter.

[0030] The hydroxyl group-containing acrylic resin (a1) can be obtained, for example, by emulsion polymerization of one or more raw material monomers. The emulsion polymerization is carried out by a method commonly used by those skilled in the art. Specifically, an emulsifier is mixed with an aqueous medium, optionally containing an organic solvent such as alcohol, and the resulting mixture is heated and stirred while the raw material monomers and polymerization initiator are added dropwise. Alternatively, an emulsion mixture in which the raw material monomers, emulsifier, and water are previously emulsified may be added dropwise to the aqueous medium. The aqueous medium may be the same as or different from the aqueous solvent (a2).

[0031] The hydroxyl group-containing acrylic resin (a1) can be obtained, for example, by emulsion polymerization of a raw material monomer mixture containing a (meth)acrylic acid alkyl ester monomer, an acid group-containing ethylenically unsaturated monomer, a hydroxyl group-containing ethylenically unsaturated monomer, and a styrene-based monomer.

[0032] <First soft segment> The hydroxyl group-containing acrylic resin (a1) may have a soft segment portion (hereinafter referred to as a first soft segment portion) in the side chain.

[0033] The first soft segment portion has the following formulae (x1), (y1), and (z1): -X 11 -(OC2H4) p1 -Y 11 (x1) -X 21 -(OC3H6) q1 -Y 21 (y1) -X 31 -(CH2) r1 -Y 31 (z1) [In the formula, p1 and q1 each independently represent an integer of 2 or more; r1 represents an integer equal to or greater than 6, X 11 and X 21 each independently represents -C(=O)-; X31 represents -C(=O)-O-, Y 11 -E 11 -OH(in the formula, E 11 is a single bond or a divalent organic group other than an oxyethylene group. Y 21 -E 21 -OH(in the formula, E 21 is a single bond or a divalent organic group other than an oxypropylene group. Y 31 -E 31 -OH(in the formula, E 31 is a single bond or a divalent organic group other than an alkylene group. The chain comprises at least one selected from the group consisting of:

[0034] The polyoxyethylene chain (-(OC2H4) p1 -) is a linear (-(OCH2CH2) p1 -), and may be branched (-(OCH(CH3)) p1 The polyoxyethylene chain may be linear (-(OCH2CH2) p1 -) may be used.

[0035] The polyoxypropylene chain (-(OC3H6) q1 -) is a straight chain (-(OCH2CH2CH2) q1 -), and may be branched (-(OCH(CH3)CH2) q1 -), or -(OCH2CH(CH3)) q1 The polyoxypropylene chain may be branched and may have a -(OCH(CH3)CH2) q1 -It may be.

[0036] The alkylene chain (-(CH2) r1-) may be linear, branched or cyclic. The alkylene chain may be linear.

[0037] The numbers of repeating units p1 and q1 are each independently an integer of 2 or greater, and r1 is an integer of 6 or greater. The upper limits of the numbers of repeating units p1, q1, and r1 may be appropriately set in consideration of the number average molecular weight of the hydroxyl group-containing acrylic resin (a1) and the proportion of the first soft segment portion in the hydroxyl group-containing acrylic resin (a1).

[0038] From the viewpoint of scratch resistance and gloss recovery, the numbers of repeating units p1 and q1 may each independently be 3 or more, or 4 or more. From the viewpoint of facilitating an improvement in the initial gloss value, the numbers of repeating units p1 and q1 may each independently be 10 or less, or 8 or less. In one embodiment, the numbers of repeating units p1 and q1 are each independently 3 or more and 10 or less. From the same viewpoint, the number of repeating units r1 may be 5 or more, or 8 or more. The number of repeating units r1 may be 15 or less, or 12 or less. In one embodiment, the number of repeating units r1 is 5 or more and 15 or less.

[0039] One bond of the polyoxyethylene chain, polyoxypropylene chain, and alkylene chain is X 11 , X 21 or X 31 The other bond of the polyoxyethylene chain, the polyoxypropylene chain, and the alkylene chain is bonded to Y 11 , Y 21 or Y 31 is bonded to.

[0040] Y 11 -E 11 -OH(in the formula, E 11is a single bond or a divalent organic group other than an oxyethylene group. ) Examples of divalent organic groups other than an oxyethylene group include hydrocarbon groups having 1 to 8 carbon atoms, groups containing carbon atoms and nitrogen atoms, oxypropylene groups, and ether bonds. The hydrocarbon group may be an aliphatic hydrocarbon group, may have an alicyclic hydrocarbon group, or may have an aromatic hydrocarbon group. The aliphatic hydrocarbon group may be linear or branched. E 11 may be a single bond.

[0041] Y 21 -E 21 -OH(in the formula, E 21 is a single bond or a divalent organic group other than an oxypropylene group. ) Examples of divalent organic groups other than an oxypropylene group include hydrocarbon groups having 1 to 8 carbon atoms, groups containing carbon atoms and nitrogen atoms, oxyethylene groups, and ether bonds. The hydrocarbon group is represented by E 11 E 21 may be a single bond.

[0042] Y 31 -E 31 -OH(in the formula, E 31 is a single bond or a divalent organic group other than an alkylene group. ) Examples of divalent organic groups other than alkylene groups include groups containing oxygen atoms and / or nitrogen atoms in addition to carbon atoms, and ether bonds. The divalent organic group other than an alkylene group may be an oxyalkylene group such as an oxyethylene group or an oxypropylene group. E 31 may be a single bond.

[0043] As mentioned above, the first soft segment has a terminal hydroxyl group. This hydroxyl group is used to react with the isocyanate group. This allows the coating film to have a spring function without reducing the crosslink density.

[0044] X 11 , X 21 and X 31One of the bonds of X is bonded to a polyoxyethylene chain, a polyoxypropylene chain, or an alkylene chain, as described above. 11 , X 21 and X 31 The other bond is bonded to, for example, a carbon atom constituting the main chain of the hydroxyl group-containing acrylic resin (a1).

[0045] X 11 and X 21 Each independently represents -C(=O)-. Specifically, X 11 and X 21 Each of these represents a divalent organic group in which one oxygen atom has been removed from an ester bond, and forms an ester bond together with the oxygen atom of the adjacent polyoxyethylene chain or polyoxypropylene chain.

[0046] X 31 represents -C(=O)-O-. Specifically, X 31 is an ester bond.

[0047] The hydroxyl-containing acrylic resin (a1) having a first soft segment portion can be obtained by using a raw material monomer containing a first soft segment portion. Examples of such raw material monomers include (meth)acrylates containing alkylene oxide groups having 2 and / or 3 carbon atoms and ε-caprolactone adducts of 2-hydroxyethyl (meth)acrylate. The proportion of the raw material monomer containing the first soft segment portion used is, for example, 30% to 60% by mass of the total raw material monomers. In this case, the proportion of the first soft segment portion in the hydroxyl-containing acrylic resin (a1) (hereinafter referred to as the proportion A) can also be 30% to 60% by mass.

[0048] The coating composition may contain multiple types of hydroxyl-containing acrylic resins (a1) having different first soft segment portions. The coating composition may contain a hydroxyl-containing acrylic resin (a1) having a first soft segment portion and a hydroxyl-containing acrylic resin (a1) not having a first soft segment portion. One hydroxyl-containing acrylic resin (a1) may have multiple different types of first soft segment portions.

[0049] (aqueous solvent (a2)) Examples of aqueous solvents include various types of water such as pure water, ion-exchanged water, tap water, and industrial water. The main agent (A) may contain an organic solvent in addition to the aqueous solvent. Examples of organic solvents include diethylene glycol dibutyl ether (dibutyl diglycol), dipropylene glycol dimethyl ether, ethyl diglycol acetate, propylene glycol methyl ether acetate, n-butyl alcohol, methoxypropanol, diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, and ethylene glycol monohexyl ether.

[0050] (Polyol compound (a3)) The coating composition may further contain a polyol compound (a3) ​​other than the hydroxyl group-containing acrylic resin (a1). Examples of the polyol compound (a3) ​​include polyester polyols, polyether polyols, polyurethane polyols, and polycarbonate polyols.

[0051] The number of hydroxyl groups per molecule of the polyol compound (a3) ​​may be 2 or more, and may be 3 or more. The number of hydroxyl groups per molecule of the polyol compound (a3) ​​may be 5 or less, and may be 4 or less. In one embodiment, the number of hydroxyl groups per molecule of the polyol compound (a3) ​​may be 2 or 3.

[0052] Solid mass W of hydroxyl group-containing acrylic resin (a1) a1 and the solid mass W of the polyol compound (a3) a2 Ratio to: W a1 / W a2 The ratio is 95 / 5 to 60 / 40. This gives the coating film high scratch resistance and gloss recovery.

[0053] From the viewpoint of scratch resistance, W a1 and W a2 When the total of the above is 100 parts by mass, the solid content mass W of the polyol compound (a3) ​​is a2 The amount of W may be 10 parts by mass or more, or 15 parts by mass or more. a1 and W a2 When the total of the above is 100 parts by mass, the solid content mass W of the polyol compound (a3) ​​is a2 may be 35 parts by mass or less, or may be 30 parts by mass or less.

[0054] The solid content concentration of the polyol compound (a3) ​​may be 5% by mass or more, 10% by mass or more, or 12% by mass or more of the total solid content contained in the main component (A). The solid content concentration of the polyol compound (a3) ​​may be 40% by mass or less, 35% by mass or less, or 32% by mass or less of the total solid content contained in the main component (A). In one embodiment, the solid content concentration of the polyol compound (a3) ​​is 5% by mass or more and 40% by mass or less of the total solid content contained in the main component (A).

[0055] <Polyol (a3) ​​Having Third Soft Segment Portion> The polyol compound (a3) ​​may have a third soft segment portion. This further improves the scratch resistance and gloss recovery of the coating film. The third soft segment portion includes at least one selected from the group consisting of chains represented by the following formulas (1), (2), and (3). The third soft segment portion acts like a spring in the coating film.

[0056] Equations (1), (2) and (3): -(OC2H4) a - (1) -(OC3H6) b - (2) -(OC(=O)OR) c - (3) (In the formula, a, b, and c each independently represent an integer of 2 or more, and R represents a hydrocarbon group having 1 to 8 carbon atoms.)

[0057] The coating composition may contain multiple polyol compounds (a3) ​​having different third soft segment portions, or may contain multiple different polyol compounds (a3) ​​having the same type of third soft segment portion. One polyol compound (a3) ​​may have multiple different types of third soft segment portions.

[0058] Formula (1):-(OC2H4) a The chain represented by - (polyoxyethylene chain) is a linear chain (-(OCH2CH2) a -), and may be branched (-(OCH(CH3)) a The polyoxyethylene chain may be linear (-(OCH2CH2) a -) may be used.

[0059] Formula (2):-(OC3H6) b The chain represented by - (polyoxypropylene chain) is a linear chain (-(OCH2CH2CH2) b -), and may be branched (-(OCH(CH3)CH2) b -), or -(OCH2CH(CH3)) bThe polyoxypropylene chain may be branched and may have a -(OCH(CH3)CH2) b -It may be.

[0060] Formula (3):-(OC(=O)OR) c In the chain (polycarbonate chain) represented by -, R represents a hydrocarbon group having 1 to 8 carbon atoms. The hydrocarbon group may be an aliphatic hydrocarbon group, may have an alicyclic hydrocarbon group, or may have an aromatic hydrocarbon group. The aliphatic hydrocarbon group may be linear or branched. R may be a linear or branched aliphatic hydrocarbon group having 4 to 6 carbon atoms.

[0061] The numbers of repeating units a, b, and c are not particularly limited as long as they are 2 or more. The numbers of repeating units a, b, and c may be appropriately set taking into consideration the number average molecular weight of the polyol compound (a3) ​​and the proportion of the third soft segment portion in the polyol compound (a3). From the viewpoint of abrasion resistance and gloss recovery, the numbers of repeating units a, b, and c may each independently be 3 or more. From the viewpoint of facilitating improvement of the initial gloss value, the numbers of repeating units a, b, and c may each independently be 12 or less, or may be 8 or less. In one embodiment, the numbers of repeating units a, b, and c are each independently 3 or more and 12 or less.

[0062] Specific examples of the polyol compound (a3) ​​having a third soft segment portion include polyether polyols and polycarbonate polyols. In terms of initial gloss value, the polyether polyol may be used.

[0063] Examples of polyether polyols include compounds in which ethylene oxide and / or propylene oxide are added to active hydrogen-containing compounds such as polyhydric alcohols, polyhydric phenols, and polycarboxylic acids. Examples of the active hydrogen atom-containing compound include water; dihydric alcohols such as ethylene glycol, diethylene glycol, trimethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-dihydroxymethylcyclohexane, and cyclohexylene glycol; glycerin, trioxyisobutane, 1,2,3-butanetriol, 1,2,3-pentanetriol, 2-methyl-1,2,3-propanetriol, 2-methyl-2,3,4-butanetriol, 2-ethyl-1,2,3-butanetriol, 2,3,4-pentanetriol, 2,3,4-hexanetriol, 4-propyl-3,4,5-heptanetriol, 2,4-dimethyl-2,3,4-pentanetriol, pentamethylglycerin, pentaglycerin, 1,2,4-butanetriol, 1,2,4-pentanetriol, and 1,2,4-pentanetriol. trihydric alcohols such as ethanol, trimethylolethane, and trimethylolpropane; tetrahydric alcohols such as pentaerythritol, 1,2,3,4-pentanetetrol, 2,3,4,5-hexanetetrol, 1,2,4,5-pentanetetrol, 1,3,4,5-hexanetetrol, diglycerin, and sorbitan; pentahydric alcohols such as adonitol, arabitol, xylitol, and triglycerin; hexahydric alcohols such as dipentaerythritol, sorbitol, mannitol, iditol, inositol, dulcitol, talose, and allose; octahydric alcohols such as sucrose; polyglycerin; polyhydric phenols such as pyrogallol, hydroquinone, and phloroglucin; bisphenols such as bisphenol A and bisphenol sulfone; aliphatic polycarboxylic acids such as succinic acid and adipic acid; and aromatic polycarboxylic acids such as phthalic acid, terephthalic acid, and trimellitic acid. These may be used alone or in combination of two or more.

[0064] Examples of polycarbonate polyols include reaction products of polyols (typically diols) with carbonylating agents. Examples of diols include aliphatic diols such as 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 2-ethyl-1,6-hexanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, and neopentyl glycol; alicyclic diols such as 1,3-cyclohexanediol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol; aromatic diols such as p-xylenediol and p-tetrachloroxylenediol; diethylene glycol; and dipropylene glycol. These may be used alone or in combination of two or more. Examples of the carbonylating agent include alkylene carbonates such as ethylene carbonate and propylene carbonate, dialkyl carbonates such as dimethyl carbonate, diethyl carbonate and dibutyl carbonate, and diaryl carbonates such as diphenyl carbonate. These may be used alone or in combination of two or more.

[0065] The polyol compound (a3) ​​may have two hydroxyl groups and a polyoxyethylene chain in one molecule, and a specific example of such a polyol compound (a3) ​​is polyoxyethylene glycol.

[0066] The polyol compound (a3) ​​may have two hydroxyl groups and a polyoxypropylene chain in one molecule, and a specific example of such a polyol compound (a3) ​​is polyoxypropylene glycol.

[0067] The polyol compound (a3) ​​may have two hydroxyl groups and a polycarbonate chain in one molecule, and specific examples of such polyol compounds (a3) ​​include polycarbonate diols.

[0068] The polyol compound (a3) ​​may have three hydroxyl groups and a polyoxyethylene chain in one molecule, and a specific example of such a polyol compound (a3) ​​is polyethylene glyceryl ether.

[0069] The polyol compound (a3) ​​may have three hydroxyl groups and a polyoxypropylene chain in one molecule, and a specific example of such a polyol compound (a3) ​​is polypropylene glyceryl ether.

[0070] The number average molecular weight of the polyol compound (a3) ​​may be 500 or more, or 600 or more, from the viewpoint of scratch resistance. The number average molecular weight of the polyol compound (a3) ​​may be 3,000 or less, or 1,500 or less, from the viewpoint of facilitating an improvement in initial gloss value. The number average molecular weight of the polyol compound (a3) ​​may be a theoretical value calculated from the hydroxyl value. In one embodiment, the number average molecular weight of the polyol compound (a3) ​​is 500 or more and 3,000 or less.

[0071] The hydroxyl value of the polyol compound (a3) ​​may be 56 mgKOH / g or more, 112 mgKOH / g or more, or 160 mgKOH / g or more. The hydroxyl value of the polyol compound (a3) ​​may be 330 mgKOH / g or less, or 280 mgKOH / g or less. In one embodiment, the hydroxyl value of the polyol compound (a3) ​​is 56 mgKOH / g or more and 330 mgKOH / g or less.

[0072] The proportion of the third soft segment portion in the polyol compound (a3) ​​(hereinafter referred to as the "occupancy proportion P") may be 60% by mass or more, 65% by mass or more, 75% by mass or more, or 82% by mass or more. The occupancy proportion P may be 99% by mass or less, 98% by mass or less, 97% by mass or less, or 95% by mass or less. In one embodiment, the occupancy proportion P is 60% by mass or more and 99% by mass or less. This makes it easier for the coating film to exhibit spring function.

[0073] The proportion P is calculated by dividing the mass of the third soft segment by the number average molecular weight of the polyol compound (a3). The mass of the third soft segment can be calculated from its structure and the number of repeating units. The number of repeating units can be calculated from the number average molecular weight of the polyol compound (a3).

[0074] (others) The main component (A) may optionally contain a resin that does not contain hydroxyl groups. In addition to the hydroxyl-containing acrylic resin (a1) and the aqueous solvent (a2), the main component (A) may optionally contain various additives. Examples of additives include dispersants, antifoaming agents, UV absorbers, hindered amine light stabilizers, antioxidants, viscosity modifiers, surface conditioners, film-forming aids, rust inhibitors, and thickeners.

[0075] (Method for preparing main agent (A)) The main component (A) can be prepared by mixing the above components by a method known to those skilled in the art, such as a kneading and mixing method using a kneader or roll, or a dispersion and mixing method using a sand grind mill or disperser.

[0076] <Curing agent (B)> The curing agent (B) contains an isocyanate compound (b1) and an organic solvent (b2) having no hydroxyl group. The solid content concentration of the curing agent (B) is not particularly limited. The solid content concentration of the curing agent (B) is, for example, 20% by mass or more and 70% by mass or less.

[0077] (Isocyanate compound (b1)) The isocyanate compound (b1) reacts with the hydroxyl groups of the hydroxyl-containing acrylic resin (a1) and the polyol compound (a3) ​​in the main component (A) to form a crosslinked structure.

[0078] The content of the isocyanate compound (b1) may be, for example, 20% by mass or more, or 30% by mass or more, of the total solid content of the curing agent (B).

[0079] The number average molecular weight of the isocyanate compound (b1) may be, for example, 500 or more, 700 or more, or 800 or more. In terms of facilitating an increase in crosslink density, the number average molecular weight of the isocyanate compound (b1) may be, for example, 3,000 or less, 2,500 or less, or 2,000 or less. In one embodiment, the number average molecular weight of the isocyanate compound (b1) is 500 or more and 3,000 or less.

[0080] The isocyanate compound (b1) is not particularly limited as long as it has an average of two or more isocyanate groups per molecule. The isocyanate compound (b1) may be hydrophilic from the viewpoint of compatibility with the main component (A).

[0081] <Hydrophilic isocyanate compounds (b11)> The hydrophilic isocyanate compound (b11) has, on average, two or more isocyanate groups in one molecule, as well as a hydrophilic group or hydrophilic moiety other than a hydroxyl group.

[0082] Examples of hydrophilic groups other than hydroxyl groups include at least one of a phosphate group and a sulfonic acid group. Examples of the hydrophilic moiety include a polyoxyalkylene chain. The oxyalkylene group has, for example, 2 to 4 carbon atoms. The hydrophilic isocyanate compound (b11) may have, as the hydrophilic moiety, a polyoxyalkylene chain having an oxyalkylene group having 2 and / or 3 carbon atoms.

[0083] The hydrophilic isocyanate compound (b11) can be obtained, for example, by reacting a conventionally known isocyanate compound (typically, a hydrophobic isocyanate compound (b12) described later) with a compound having a functional group (typically, a hydroxyl group) that reacts with an isocyanate group and a hydrophilic group or hydrophilic moiety other than a hydroxyl group.

[0084] <Hydrophobic isocyanate compounds (b12)> The isocyanate compound (b1) may contain a hydrophobic isocyanate compound (b12) in addition to the hydrophilic isocyanate compound (b11), which makes it easier to further increase the crosslink density.

[0085] The hydrophobic isocyanate compound (b12) is not particularly limited as long as it has an average of two or more isocyanate groups per molecule and is hydrophobic. The hydrophobic isocyanate compound (b12) does not have a hydroxyl group, the above-mentioned hydrophilic group, or a hydrophilic moiety. Examples of the hydrophobic isocyanate compound (b12) include aliphatic diisocyanates such as hexamethylene diisocyanate (HDI), pentamethylene diisocyanate, tetramethylene diisocyanate, and trimethylhexamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate and 4,4'-methylenebis(cyclohexyl isocyanate); aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate; and modified products thereof (for example, urethane compounds, carbodiimides, uretdione, uretonimine, biuret compounds, isocyanurate compounds, etc.).

[0086] Solid mass W of hydrophilic isocyanate compound (b11) b1 and the solid mass W of the hydrophobic isocyanate compound (b12) b2 Ratio to: W b1 / W b2 For example, the W may be 99 / 1 to 75 / 25, or 99 / 1 to 76 / 24. This can improve the crosslink density and initial gloss value. b1 and W b2 When the total of the above is 100 parts by mass, the solid content mass W of the hydrophobic isocyanate compound (b12) b2 The amount of W may be 2 parts by mass or more, or 4 parts by mass or more. b1 and W b2 When the total of the above is 100 parts by mass, the solid content mass W of the hydrophobic isocyanate compound (b12) b2 may be 20 parts by mass or less, or may be 10 parts by mass or less.

[0087] <Second soft segment> The isocyanate compound (b1) may have a soft segment portion (hereinafter referred to as a second soft segment portion).

[0088] When the hydrophilic isocyanate compound (b11) and the hydrophobic isocyanate compound (b12) are used in combination, the second soft segment portion may be in either isocyanate compound or in both. The second soft segment portion may be in the hydrophobic isocyanate compound (b12).

[0089] The second soft segment portion may be, for example, a compound represented by the following formulae (x2), (y2), and (z2): -X 12 -(OC2H4) p2 -Y 12 (x2) -X 22 -(OC3H6) q2 -Y 22 (y2) -X 32 -(CH2) r2 -Y 32 (z2) (In the formula, p2 and q2 each independently represent an integer of 2 or more; r2 represents an integer equal to or greater than 6, X 12 and X 22 each independently represents -NH-C(=O)-; X 32 represents -NH-C(=O)- or -NH-C(=O)-O-, Y 12 -E 12 -NCO(in the formula, E 12 is a single bond or a divalent organic group other than an oxyethylene group. Y 22 -E 22 -NCO(in the formula, E 22 is a single bond or a divalent organic group other than an oxypropylene group. Y 32 -E 32 -NCO(in the formula, E 32 is a single bond or a divalent organic group other than an alkylene group. The chain comprises at least one selected from the group consisting of:

[0090] The polyoxyethylene chain contained in the second soft segment portion represented by formula (x2) is a linear (-(OCH2CH2) p2 -), and may be branched (-(OCH(CH3)) p2 The polyoxyethylene chain may be linear (-(OCH2CH2) p2 -) may be used.

[0091] The polyoxypropylene chain contained in the second soft segment portion represented by formula (y2) is a linear (-(OCH2CH2CH2) q2 -), and may be branched (-(OCH(CH3)CH2) q2 -), or -(OCH2CH(CH3)) q2 The polyoxypropylene chain may be branched and may have a -(OCH(CH3)CH2) q2 -It may be.

[0092] The alkylene chain (-(CH2)) contained in the second soft segment portion represented by formula (z2) r2 -) may be linear, branched or cyclic. The alkylene chain may be linear.

[0093] The numbers of repeating units p2 and q2 are each independently an integer of 2 or greater, and r2 is an integer of 6 or greater. The upper limits of the numbers of repeating units p2, q2, and r2 may be appropriately set in consideration of the number average molecular weight of the isocyanate compound (b1) and the proportion of the second soft segment portion in the isocyanate compound (b1).

[0094] From the viewpoint of scratch resistance and gloss recovery, the numbers of repeating units p2 and q2 may each independently be 3 or more, or 4 or more. From the viewpoint of facilitating an improvement in the initial gloss value, the numbers of repeating units p2 and q2 may each independently be 10 or less, or 8 or less. In one embodiment, the numbers of repeating units p2 and q2 are each independently 3 or more and 10 or less. From the same viewpoint, the number of repeating units r2 may be 5 or more, or 8 or more. The number of repeating units r2 may be 15 or less, or 12 or less. In one embodiment, the number of repeating units r2 is 5 or more and 15 or less.

[0095] The isocyanate compound (b1) having a second soft segment portion is, for example, a reaction product of a hydrophilic isocyanate compound (b11) or a hydrophobic isocyanate compound (b12) with a compound having a functional group reactive with an isocyanate group and a second soft segment portion.

[0096] One bond of the polyoxyethylene chain, polyoxypropylene chain, and alkylene chain is X 12 , X 22 or X 32 The other bond of the polyoxyethylene chain, the polyoxypropylene chain, and the alkylene chain is bonded to Y 12 , Y 22 or Y 32 is bonded to.

[0097] Y 12 -E 12 -NCO(in the formula, E 12 is a single bond or a divalent organic group other than an oxyethylene group. ) As the divalent organic group other than an oxyethylene group, E 12 Examples include the same groups as those listed as E 12 may be a single bond.

[0098] Y 22 -E 22 -NCO(in the formula, E 22is a single bond or a divalent organic group other than an oxypropylene group. ) As the divalent organic group other than an oxypropylene group, E 21 Examples include the same groups as those listed as E 22 may be a single bond.

[0099] Y 32 -E 32 -NCO(in the formula, E 32 is a single bond or a divalent organic group other than an alkylene group. ) As the divalent organic group other than an alkylene group, E 31 Examples include the same groups as those listed as E 32 may be a single bond.

[0100] As mentioned above, the second soft segment has an isocyanate group at its terminal. This isocyanate group is used to react with the hydroxyl group of the main component (A). This allows the coating film to have spring properties without reducing the crosslink density.

[0101] X 12 , X 22 and X 32 One of the bonds of X is bonded to a polyoxyethylene chain, a polyoxypropylene chain, or an alkylene chain, as described above. 12 , X 22 and X 32 The other bond is bonded to, for example, an organic group having an isocyanate group at its terminal. The organic group is, for example, a hydrophilic isocyanate compound (b11) or a hydrophobic isocyanate compound (b12) from which one isocyanate group has been removed.

[0102] X 12 and X 22 Each independently represents -NH-C(=O)-. Specifically, X 12 and X 22 Each of these represents a divalent organic group in which one oxygen atom has been removed from a urethane bond, and together with the oxygen atom of the adjacent polyoxyethylene chain or polyoxypropylene chain, forms a urethane bond.

[0103] X 32 represents -NH-C(=O)- or -NH-C(=O)-O-. Specifically, X 32 is an amide bond or a urethane bond.

[0104] The isocyanate compound (b1) having the second soft segment portion represented by formula (x2) is, for example, a reaction product of a hydrophilic isocyanate compound (b11) or a hydrophobic isocyanate compound (b12) with polyoxyethylene glycol.

[0105] The isocyanate compound (b1) having the second soft segment portion represented by formula (y2) is, for example, a reaction product of a hydrophilic isocyanate compound (b11) or a hydrophobic isocyanate compound (b12) with polyoxypropylene glycol.

[0106] The isocyanate compound (b1) having the second soft segment represented by formula (z2) is, for example, a reaction product of a hydrophilic isocyanate compound (b11) or a hydrophobic isocyanate compound (b12) with a lactone polyol. Examples of the lactone polyol (B) include polybutyrolactone polyol, polyvalerolactone polyol, and polycaprolactone polyol.

[0107] The proportion of the second soft segment in the isocyanate compound (b1) containing it, for example, the hydrophobic isocyanate compound (b12) (hereinafter referred to as the "occupancy proportion I") may be 40% by mass or more, or 42% by mass or more. The occupancy proportion I may be 90% by mass or less, 80% by mass or less, or 60% by mass or less. In one embodiment, the occupancy proportion I is 40% by mass or more and 90% by mass or less. This makes it easier for the coating film to exhibit spring function.

[0108] The occupancy ratio I is calculated by dividing the mass of the second soft segment by the number average molecular weight of the isocyanate compound (b1) containing it, typically a hydrophobic isocyanate compound (b12). The mass of the second soft segment can be calculated from its structure and the number of repeating units. The number of repeating units can be calculated from the number average molecular weight of the isocyanate compound.

[0109] (organic solvent (b2)) The organic solvent (b2) is not particularly limited as long as it does not have a hydroxyl group. Examples of the organic solvent (b2) include 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, di ... diisobutyl ether, propylene glycol diallyl ether, propylene glycol diphenyl ether, dipropylene glycol dimethyl ether, dipropylene glycol di-n-butyl ether, dipropylene glycol diisobutyl ether, propylene glycol diisopropyl ether, propylene glycol diisopropyl ether, propylene glycol diphenyl ether, dipropylene glycol diethyl ether, dipropylene glycol di-n-butyl ether, dipropylene glycol diisobutyl ether, propylene glycol diisopropyl ether, propylene glycol diisopropyl ether, propylene glycol diisopropyl ether, propylene glycol diisopropyl ether, propylene glycol diphenyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol di-n-butyl ether, dipropylene glycol diisopropyl ether, propylene glycol diisopropyl ether, propylene glycol diisopropyl ether, propylene glycol diisopropyl ether, propylene glycol ether-based organic solvents such as butylene glycol diisobutyl ether, dipropylene glycol diallyl 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-butyl ether, 2-butoxyethyl diethoxyethyl ether, 2-butoxyethyl triethoxy ether, and 2-butoxyethyl tetraethoxyethyl ether; acetate-based organic solvents such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol mono-n-butyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol mono-n-butyl ether acetate, 3-methoxybutyl acetate, and propylene glycol monomethyl ether acetate;Examples of suitable organic solvents include ketone-based organic solvents such as acetone, methyl ethyl ketone, methyl amyl ketone, and methyl isobutyl ketone; and ester-based organic solvents such as ethyl acetate, butyl acetate, isobutyl acetate, methyl benzoate, ethyl ethoxypropionate, ethyl propionate, and methyl propionate. These may be used alone or in combination of two or more.

[0110] (others) The curing agent (B) may contain a curing agent other than the isocyanate compound (b1). The content of the other curing agent is, for example, 10 mass % or less of the total solid content of all the curing agents.

[0111] (Method for preparing curing agent (B)) The curing agent (B) can be prepared by mixing the above components by a method known to those skilled in the art, such as the same method as used to prepare the main component (A).

[0112] <Curing accelerator (C)> The coating composition may further contain a curing accelerator (C). The curing accelerator (C) controls the drying speed of the aqueous two-component clear coating composition, thereby improving the appearance and performance of the resulting coating film. The curing accelerator (C) may be contained in at least one of the main component (A) and the curing agent (B), and may be added during preparation of the coating composition.

[0113] The content of the curing accelerator (C) is, for example, 0.03 to 0.3 parts by mass per 100 parts by mass of the total solid content of the hydroxyl group-containing acrylic resin (a1) and the polyol compound (a3). The content of the curing accelerator (C) is determined arbitrarily within this range depending on the curing environment, etc.

[0114] The curing accelerator (C) is not particularly limited as long as it accelerates the reaction between hydroxyl groups and isocyanate groups. Examples of the curing accelerator (C) include amine compounds, metal compounds, and acids. Examples of amine compounds include tertiary amines such as triethylamine and triethylenediamine. Examples of metal compounds include tin compounds, bismuth compounds, molybdenum compounds, and zinc compounds. Examples of acids include sulfonic acids, inorganic acids, phosphate esters, oxyacids, and carboxylic acids. Among these, metal compounds are preferred. Molybdenum compounds are particularly preferred because they facilitate control of the drying rate and improve the appearance of the coating film. Additionally, molybdenum compounds are less likely to react with water and can therefore remain stable even in aqueous solvents.

[0115] Examples of molybdenum compounds include molybdenum oxide, molybdic acid, molybdates, phosphomolybdic acid, phosphomolybdates, and organic molybdenum compounds. Examples of molybdates include potassium molybdate, calcium molybdate, disodium molybdate(VI) dihydrate, lithium molybdate, magnesium molybdate, rubidium molybdate, cesium molybdate, cobalt(II) molybdate, manganese(II) molybdate, zinc molybdate, ammonium molybdate, hexaammonium molybdate tetrahydrate, and hexaammonium heptamolybdate tetrahydrate. Examples of phosphomolybdates include phosphomolybdic acid n-hydrate, sodium phosphomolybdate n-hydrate, and ammonium phosphomolybdate trihydrate. Examples of organic molybdenum compounds include molybdenum(IV) oxide bisacetylacetonate, bis(acetylacetonato)molybdenum(IV) oxide, molybdenum dioxide tetramethylheptadionate, tetraethylammonium molybdate, trimethylstannyl tetrabutylammonium molybdate, molybdenum alkoxide, molybdenum 2-ethylhexanoate, and molybdenum hexacarbonyl. These compounds may be used alone or in combination of two or more.

[0116] <Dilution component (D)> The coating composition may further contain a diluent component (D). The diluent component (D) is used to adjust the viscosity of the coating composition. Examples of the diluent component (D) include the same as those exemplified for the aqueous solvent (a2). The diluent component (D) may be the same as or different from the aqueous solvent (a2).

[0117] The amount of diluent component (D) mixed is appropriately determined taking into consideration the viscosity of the coating composition, the coating method, etc. The amount of diluent component (D) mixed is, for example, 10 to 70 parts by mass per 100 parts by mass of the total solid content of the hydroxyl group-containing resin (a1) and the polyol compound (a3).

[0118] The aqueous two-pack clear coating composition is prepared by a method commonly used by those skilled in the art, for example, by mixing the components in the same manner as in the preparation of the main component (A).

[0119] [Automotive repair paint] This embodiment includes an automotive repair paint containing the above-mentioned paint composition. The above-mentioned paint composition is excellent in abrasion resistance and gloss recovery, and is therefore suitable for use as an automotive repair paint.

[0120] [Manufacturing method for coated articles] A coated article can be obtained by applying the above coating composition to an object to be coated. The coated article is produced, for example, by a method comprising the steps of applying a coating composition onto an article to be coated to form an uncured coating film, and curing the uncured coating film.

[0121] Hereinafter, the method for producing a coated article will be described using the coating composition as an automobile repair coating as an example, although the present embodiment is not limited thereto.

[0122] (subject to be coated) The shape of the substrate is not particularly limited. The substrate may be flat or may have a three-dimensional shape. The material of the substrate is also not particularly limited. Examples of the material of the substrate include metal, resin, and glass. Examples of metal include iron, copper, aluminum, tin, zinc, and alloys thereof.

[0123] The metal substrate may be surface-treated. Examples of surface treatments include phosphate treatment, chromate treatment, zirconium conversion treatment, and composite oxide treatment. After the surface treatment, the metal substrate may be further coated with an electrodeposition paint. The electrodeposition paint may be either a cationic type or an anionic type.

[0124] Examples of resins include polypropylene resin, polycarbonate resin, urethane resin, polyester resin, polystyrene resin, ABS resin, vinyl chloride resin, and polyamide resin. It is preferable that a resin substrate be degreased.

[0125] Specific examples of the object to be coated include automobile bodies such as passenger cars, trucks, motorcycles, and buses, or parts thereof.

[0126] First, the target area and its surroundings are sanded as needed, and any irregularities are filled in with putty. The area is then sanded again. Next, a primer or repair primer (also called a primer surfacer) is applied. The primer and repair primer are not particularly limited and are selected appropriately depending on the type of paint to be applied over them. The primer and repair primer are, for example, water-based or solvent-based two-component urethane paints.

[0127] After the primer or primer surfacer is applied, the coating is cured, then polished and degreased. Curing is carried out, for example, at a temperature between 40°C and 70°C for 30 to 60 minutes. Polishing is carried out using sandpaper or similar.

[0128] Next, a repair base coat paint is applied. The base coat paint may be a curing type or a lacquer type. The curing type base coat paint forms a cured coating film by the curing reaction between the main agent and the curing agent as described above. The lacquer type base coat paint forms a cured coating film by the evaporation of the solvent. The base coat paint may be applied multiple times.

[0129] After application of the repair base coat paint, the paint film is cured under suitable curing conditions depending on the composition of the base coat paint.

[0130] Finally, the coating composition is applied. The coating method for the coating composition is not particularly limited. Examples of coating methods include air spray coating, airless spray coating, rotary atomization coating, and curtain coating. These methods may be combined with electrostatic coating. In the case of repairs, air spray coating is preferred because it is easy to apply localized coating. The coating of the coating composition may be performed multiple times.

[0131] The amount of coating composition to be applied is not particularly limited and is set appropriately depending on the performance required of the coating film. For example, the coating composition is applied so that the thickness of the coating film after curing is 5 μm or more and 70 μm or less.

[0132] The coating is then cured by heating at a temperature of 40° C. to 100° C. for 15 to 60 minutes, thereby obtaining a coated article. [Example]

[0133] Hereinafter, the present embodiment will be described in more detail using examples, but the present embodiment is not limited to these examples. In the examples, "parts" and "%" are by mass unless otherwise specified.

[0134] The components shown in Table 1 are as follows: Polyol A: Sannix GP-600, manufactured by Sanyo Chemical Industries, Ltd., polyoxypropylene glyceryl ether, containing a third soft segment portion represented by formula (2), b: 3, occupancy ratio P: approximately 85% by mass Polyol B: Sannix GP-1000, manufactured by Sanyo Chemical Industries, Ltd., polyoxypropylene glyceryl ether, containing a third soft segment portion represented by formula (2), b: 5, occupancy ratio P: approximately 90% by mass Polyol C: Sannix GP-1500, manufactured by Sanyo Chemical Industries, Ltd., polyoxypropylene glyceryl ether, containing a third soft segment portion represented by formula (2), b: 8, occupancy ratio P: approximately 94% by mass Polyol D: PEG-600, manufactured by Sanyo Chemical Industries, Ltd., polyoxypropylene glycol, containing a third soft segment portion represented by formula (2), b: 12, occupancy ratio P: approximately 97% by mass Polyol E: Duranol T5650E, manufactured by Asahi Kasei Chemicals Corporation, polyalkylene carbonate diol, containing a third soft segment portion represented by formula (3), c: 5, occupancy ratio P: approximately 88% by mass

[0135] Hydrophilic isocyanate compound A: Bayhydur 304, manufactured by Sumika Covestro Co., Ltd., contains polyoxypropylene chains, does not contain second soft segments Hydrophobic isocyanate compound A: Desmodur N3800, manufactured by Sumika Covestro Co., Ltd., containing a second soft segment portion represented by formula (z2), X 32 :-NH-C(=O)-, E 32 : Single bond, r2: 5, Occupancy ratio I: 43 mass% Hydrophobic isocyanate compound B: Sumidur N3300, manufactured by Sumika Covestro Co., Ltd., does not contain a second soft segment

[0136] [Example 1] (I) Preparation of coating composition The main component (A) was prepared by mixing nax E-CUBE WB (2:1) NN Clear (manufactured by Nippon Paint Co., Ltd., containing hydroxyl group-containing acrylic resin (a1), solids concentration approximately 38%), polyol A (polyol compound (a3)), and pure water (aqueous solvent (a2)) in the proportions shown in Table 1. In Table 1, the mixing proportion of pure water includes the amount of dilution water contained in nax E-CUBE WB (2:1) NN Clear.

[0137] The hydrophilic isocyanate compound A (isocyanate compound (b1)) and PMA (organic solvent (b2), propylene glycol monomethyl ether acetate) were mixed in the ratio shown in Table 1 to prepare the curing agent (B).

[0138] To the main component (A), 0.03 parts by mass of sodium molybdate (curing accelerator (C)) was added per 100 parts by mass of the total solids content of the hydroxyl group-containing acrylic resin (a1) and the polyol compound (a3). Subsequently, this main component (A), curing agent (B), and pure water (dilution component (D)) were mixed in the proportions shown in Table 1 to prepare the coating composition.

[0139] (II) Preparation of coated articles (II-1) Formation of the base coating A primer surfacer was prepared by mixing 100 parts of nax E-CUBE WB Primer Surface Vita Gray (main ingredient, manufactured by Nippon Paint, solids content approximately 56%), 12.5 parts of nax E-CUBE WB Water-Based Hardener (hardener, manufactured by Nippon Paint, solids content approximately 64%), and an appropriate amount of dilution water specifically for nax E-CUBE WB Clear Primer Surface (dilution component, manufactured by Nippon Paint).

[0140] The primer surfacer was applied to a 60 cm x 40 cm steel plate (substrate) using a spray gun and air-dried until the paint no longer adhered to the surface when touched with a finger. This application and drying process was repeated two more times. The steel plate was then placed in an oven set at 60°C and heated for 30 minutes to form a cured coating film. The surface of the resulting coating film was then polished. Finally, the surface of the coating film was degreased.

[0141] (II-2) Formation of water-based base coating A base coat paint was prepared by mixing 100 parts of nax E-CUBE WB412 Silent Black (main agent, manufactured by Nippon Paint Co., Ltd., solids content approximately 22%), 50 parts of nax E-CUBE WB911 S-binder (hardener, manufactured by Nippon Paint Co., Ltd., solids content approximately 26%), and 45 parts of nax E-CUBE WBR20 Standard Diluent (diluting component, manufactured by Nippon Paint Co., Ltd.).

[0142] The above base coat paint was applied to a substrate with a base coating film using an air spray gun, and air-dried until the paint no longer adhered to the surface when touched with a finger. This application and drying process was repeated two more times to form a base coat film (cured film thickness: 20 μm). In this way, an object to be coated having an undercoat film and a base coat film was prepared.

[0143] (II-3) Formation of clear coating film The above coating composition was applied three times using an air spray gun to a substrate having a primer coating and a base coat coating. Each application was performed with a one-minute interval between applications. The substrate was then left to stand for 15 minutes in an environment with a temperature of 23±2°C and a humidity of 50±2% RH. The substrate was then heated in an oven set to 70°C for 20 minutes to form a clear coating (cured film thickness: 50 μm).

[0144] [Examples 2 to 9, Comparative Examples 1 and 2] Coating compositions were prepared and coated articles were produced in the same manner as in Example 1, except that the types and / or mixing amounts of the polyol compound (a3) ​​and the isocyanate compound (b1) were changed as shown in Table 1.

[0145] [Evaluation method] The coated articles were evaluated by the following methods, and the evaluation results are shown in Table 1.

[0146] (1) Initial gloss value G0 The initial 20° gloss value of the cured clear coating was measured using a BYK Micro Trigloss. The gloss value G0 was calculated as the average of three measurements taken at different locations. The gloss value G0 was evaluated based on the following criteria:

[0147] Best: 20° gloss value of 85 or more Good: 20° gloss value is 80 or more and less than 85 Acceptable: 20° gloss value is 75 or more and less than 80 Poor: 20° gloss value less than 75

[0148] (2) Scratch resistance The scratch resistance test was carried out as follows. A mixture of 15 g of test dust (a mixture of seven types, particle size 27-31 μm) and 100 g of water was sprayed onto the platform of a mini car wash. The mini car wash was then rotated (45 rpm) and run back and forth once without running water, causing the test dust to adhere to the car wash brushes. A coated object (70 mm x 150 mm) was then fixed onto the platform. Approximately 5 g of foundry sand was then sprayed onto the coated object, and the mini car wash was then rotated (96 rpm) and run back and forth three times without running water. The coated object was then rinsed with water and dried.

[0149] The 20° gloss value of the coated article after the scratch resistance test was measured in the same manner as above. The gloss value was measured three times at different locations and the average value was taken as the gloss value G1 after the test. The ratio of the gloss value G1 after the test to the initial gloss value G0 (gloss retention) was calculated according to the following formula. The gloss value G0 was evaluated based on the following criteria. Gloss retention rate (%) = 100 x gloss value after test G1 / initial gloss value G0

[0150] Best: Gloss retention is 95% or more Good: Gloss retention is 90% or more but less than 95% Acceptable: Gloss retention is 80% or more but less than 90% Poor: Gloss retention is less than 80%

[0151] (3) Gloss recovery After the above scratch resistance test, the coated article was heated in an oven set at 80°C for 30 minutes. The 20° gloss value of the coated article after heating was measured in the same manner as above. The gloss values ​​were measured three times at different locations, and the average value was taken as the gloss value G2 after heating. The ratio of the gloss value G2 after heating to the initial gloss value G0 (gloss recovery rate) was calculated according to the following formula. The gloss value G2 was evaluated based on the following criteria. Gloss recovery rate (%) = 100 x gloss value after heating G2 / initial gloss value G0

[0152] Best: Gloss recovery rate is 95% or more Good: Gloss recovery rate is 90% or more but less than 95% Acceptable: Gloss recovery rate is 80% or more but less than 90% Poor: Gloss recovery rate is less than 80%

[0153] [Table 1] [Industrial Applicability]

[0154] The present invention provides a two-component aqueous clear coating composition that can produce a coating film that is excellent in abrasion resistance and in gloss recovery after abrasion. This two-component aqueous clear coating composition is suitable for automotive painting, particularly for automotive repair painting.

Claims

1. Contains a base agent (A) and a curing agent (B), The main agent (A) is a hydroxyl group-containing acrylic resin (a1); an aqueous solvent (a2); The curing agent (B) is an isocyanate compound (b1); and (b2) an organic solvent having no hydroxyl group, at least one of a side chain of the hydroxyl group-containing acrylic resin (a1) and the isocyanate compound (b1) has a soft segment portion, The soft segment portion is The following formulas (x), (y) and (z): -X １ -(OC ２ H ４ ) ｐ -Y １ (x) -X ２ -(OC ３ H ６ ) ｑ -Y ２ (y) -X ３ -(CH ２ ) ｒ -Y ３ (z) [In the formula, p and q each independently represent an integer of 2 or more; r represents an integer of 6 or more; When the side chain of the hydroxyl group-containing acrylic resin (a1) has the soft segment moiety, X １ and X ２ each independently represents —C(═O)—; X ３ represents —C(═O)—O—, Y １ Is, -E １ -OH (in the formula, E １ is a single bond or a divalent organic group other than an oxyethylene group. Y ２ Is, -E ２ -OH (in the formula, E ２ is a single bond or a divalent organic group other than an oxypropylene group; Y ３ Is, -E ３ -OH (in the formula, E ３ is a single bond or a divalent organic group other than an alkylene group. When the isocyanate compound (b1) has the soft segment portion, X １ and X ２ each independently represents —NH—C(═O)—; X ３ represents —NH—C(═O)— or —NH—C(═O)—O—, Y １ Is, -E １ -NCO (in the formula, E １ has the same meaning as above.) Y ２ Is, -E ２ -NCO (in the formula, E ２ has the same meaning as above.) Y ３ Is, -E ３ -NCO (in the formula, E ３ has the same meaning as above.) and at least one selected from the group consisting of chains represented by The isocyanate compound (b1) includes a hydrophilic isocyanate compound (b11) and a hydrophobic isocyanate compound (b12), When the hydrophobic isocyanate compound (b12) contains the soft segment portion, the hydrophobic isocyanate compound (b12) contains only the soft segment portion represented by formula (z).

2. 2. The aqueous two-component clear coating composition according to claim 1, wherein the ratio of the soft segment portion to the hydrophobic isocyanate compound (b12) is 40% by mass or more and 90% by mass or less.

3. The solid content mass W of the hydrophilic isocyanate compound (b11) ｂ１ and the solid content mass W of the hydrophobic isocyanate compound (b12) ｂ２ Ratio to: W ｂ１ / W ｂ２ 2. The aqueous two-pack clear coating composition according to claim 1, wherein the ratio of the total weight of the acrylic resin to the total weight of the acrylic resin is 99 / 1 to 76 / 24.

4. 2. The aqueous two-component clear coating composition according to claim 1, wherein the main component (A) further comprises a polyol compound (a3).

5. 2. The aqueous two-pack clear coating composition according to claim 1, further comprising a molybdenum compound (C).

6. An automotive refinish paint comprising the aqueous two-pack clear paint composition of claim 1.

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