WATER-BORNE COATING COMPOSITION SET AND MULTILAYER-COATING-FILM FORMING METHOD USING SAME

Abstract

Provided is a water-borne coating composition capable of forming a metallic coating film having high-design, and further capable of forming a coating film that exhibits good coating film properties. A water-borne coating composition set for forming a multilayer coating film, containing a first base coating composition that forms a first base coating film and a second base coating composition that forms a second base coating film, wherein the first base coating composition contains a first coating film-forming resin, a first curing agent, a first inorganic brightener, and a first hydrophobic association rheology control agent, the first inorganic brightener contains one or more species selected from the group consisting of silica, talc, calcium carbonate, kaolin, barium sulfate, and diatomaceous earth, the second base coating composition contains a second coating film-forming resin, a second curing agent, a second luster material, a second inorganic rheology control agent, a second hydrophobic association rheology control agent, and a second dispersant, and the second inorganic rheology control agent contains a layered material having a stacked structure of a large number of inorganic crystal layers stacked.

Claims

1. A water-borne coating composition set for forming a multilayer coating film having a first base coating film and a second base coating film, the water-borne coating composition set comprising a first base coating composition that forms the first base coating film and a second base coating composition that forms the second base coating film, wherein the first base coating composition comprises a first coating film-forming resin, a first curing agent, a first inorganic brightener, and a first hydrophobic association rheology control agent, the first inorganic brightener comprises one or more species selected from the group consisting of silica, talc, calcium carbonate, kaolin, barium sulfate, and diatomaceous earth, the second base coating composition comprises a second coating film-forming resin, a second curing agent, a second luster material, a second inorganic rheology control agent, a second hydrophobic association rheology control agent, and a second dispersant, and the second inorganic rheology control agent comprises a layered material having a stacked structure of inorganic crystal layers.

2. The water-borne coating composition set for forming a multilayer coating film according to claim 1, wherein the second luster material comprises a surface-treated luster material.

3. The water-borne coating composition set for forming a multilayer coating film according to claim 1, wherein the second luster material comprises a luster material having a scaly shape and having an aspect ratio of 5 to 2000.

4. The water-borne coating composition set for forming a multilayer coating film according to claim 1, wherein the second base coating composition contains the second inorganic rheology control agent in an amount of 1 part by mass or more and 7 parts by mass or less based on 100 parts by mass of a total resin solid content of the second coating film-forming resin and the second curing agent, and the second base coating composition contains the second hydrophobic association rheology control agent in an amount of 1 part by mass or more and 15 parts by mass or less based on 100 parts by mass of a total resin solid content of the second coating film-forming resin and the second curing agent.

5. The water-borne coating composition set for forming a multilayer coating film according to claim 1, wherein the second base coating composition further comprises a second inorganic brightener, and where an amount of the first inorganic brightener contained in the first base coating composition based on 100 parts by mass of a total resin solid content of the first coating film-forming resin and the first curing agent is represented by Am 1, and an amount of the second inorganic brightener contained in the second base coating composition based on 100 parts by mass of a total resin solid content of the second coating film-forming resin and the second curing agent is represented by Am2, a ratio (Am1)/(Am2) of Aml to Am2 is 2.0 or more.

6. The water-borne coating composition set for forming a multilayer coating film according to claim 1, wherein a nonvolatile content NV1 in the first base coating composition is 10% or more and 45% or less.

7. The water-borne coating composition set for forming a multilayer coating film according to claim 1, wherein a nonvolatile content NV2 in the second base coating composition is 3% or more and 18% or less.

8. The water-borne coating composition set for forming a multilayer coating film according to claim 1, wherein the first base coating composition further comprises at least one of a first luster material and a first inorganic rheology control agent.

9. The water-borne coating composition set for forming a multilayer coating film according to claim 1, wherein the second coating film-forming resin comprises at least one resin selected from among an acrylic resin, a urethane-based resin, and a polyester resin.

10. The water-borne coating composition set for forming a multilayer coating film according to claim 1, wherein the second inorganic rheology control agent comprises a silicate layered compound.

11. The water-borne coating composition set for forming a multilayer coating film according to claim 1, wherein at least one of the first hydrophobic association rheology control agent and the second hydrophobic association rheology control agent comprises a urethane-based hydrophobic association rheology control agent.

12. The water-borne coating composition set for forming a multilayer coating film according to claim 1, wherein the first base coating composition further comprises a first dispersant, and at least one of the first dispersant and the second dispersant comprises a polymer-type dispersant having at least one type of group selected from among anionic groups, cationic groups, and nonionic groups.

13. The water-borne coating composition set for forming a multilayer coating film according to claim 1, wherein the first inorganic brightener comprises an inorganic brightener having a positively charged surface.

14. The water-borne coating composition set for forming a multilayer coating film according to claim 5, wherein the second inorganic brightener comprises an inorganic brightener having a positively charged surface.

15. The water-borne coating composition set for forming a multilayer coating film according to claim 8, wherein the first inorganic rheology control agent has a thickness of 100 nm or less.

16. The water-borne coating composition set for forming a multilayer coating film according to claim 1, wherein the second inorganic rheology control agent has a thickness of 100 nm or less.

17. A method for forming a multilayer coating film using the water-borne coating composition set for forming a multilayer coating film according to claim 1, the method for forming a multilayer coating film comprising: a step of applying the first base coating composition to an article to be coated to form an uncured first base coating film; a step of applying the second base coating composition to the uncured first base coating film to form an uncured second base coating film; a step of applying a clear coating composition for forming a clear coating film to the uncured second base coating film to form an uncured clear coating film; and a step of simultaneously baking and curing the uncured first base coating film, the uncured second base coating film, and the uncured clear coating film to form a multilayer coating film, wherein a heat-cured first base coating film formed from the first base coating composition has a film thickness t1 of 1 μm or more and 35 μm or less, and a heat-cured second base coating film formed from the second base coating composition has a film thickness t2 of 1 μm or more and 20 μm or less.

18. The method for forming a multilayer coating film according to claim 17, wherein the film thickness t1 of the heat-cured first base coating film and the film thickness t2 of the heat-cured second base coating film have a relationship of (t1)≥(t2).

Description

EXAMPLES

[0297] The present disclosure will be described more specifically with reference to the following examples, but the present disclosure is not limited to them. In the examples, “parts” and “%” are on a mass basis unless otherwise indicated.

Examples 1 to 37, Comparative Examples 1 to 3

<Preparation of Resin Composition 1>

[0298] Resin composition 1 (main component) contained in the first and second base coating compositions was prepared. Specifically, the following items were used.

[0299] (1) Acrylic emulsion (average particle size: 150 nm, nonvolatile content: 20%, solid acid value: 20 mg KOH/g, hydroxyl value: 40 mg KOH/g) produced by Nippon Paint Co., Ltd., 236 parts

[0300] (2) 10% by mass aqueous solution of dimethylethanolamine, 10 parts

[0301] (3) Water-soluble acrylic resin (nonvolatile content: 30%, solid acid value: 40 mg KOH/g, hydroxyl value: 50 mg KOH/g) produced by Nippon Paint Co., Ltd., 28.3 parts

[0302] (4) “PRIMEPOL PX-1000” (bifunctional polyether polyol, number average molecular weight: 400, hydroxyl value: 278 mg KOH/g, primary/secondary hydroxyl value ratio=63/37, nonvolatile content: 100%) produced by Sanyo Chemical Industries, Ltd., 8.6 parts

[0303] (5) “CYMEL 204” (mixed alkylated melamine resin, nonvolatile content: 100%) produced by Mitsui Chemicals, Inc., 21.5 parts

[0304] (6) “NeoRez R-9603” (polycarbonate-based urethane emulsion, nonvolatile content: 33%) produced by Avecia, 26 parts

[0305] (7) Lauryl acid phosphate, 0.2 parts

[0306] (8) 2-Ethylhexanol, 60 parts

[0307] (9) Mono-2-ethylhexyl ether, 30 parts

[0308] In the resin composition, the total of the solid mass of the coating film-forming resin and the solid mass of the curing agent (i.e., the solid content of the main resin) was 100 parts by mass.

<Preparation of First Base Coating Composition>

[0309] The following components were blended with the resin composition 1 as shown in Table 1, and diluted with water, affording a first base water-borne coating composition.

[0310] In the table, the nonvolatile content (NV1), the PWC of the first luster material, and the PWC of the first inorganic brightener were calculated by the following formulas.

Nonvolatile content (NV1)=[(Mass of first base coating composition after drying)/mass of first base coating composition before drying)]×100 (%)

Mass concentration (PWC) of first luster material=(total mass of first luster material)/[(total mass of resin solid content of first coating film-forming resin and resin solid content of first curing agent)+(total mass of first luster material)]×100.

[0311] The mass concentration (PWC) of the first inorganic brightener was also calculated by replacing the first luster material in the (PWC) calculation formula of the first luster material with the first inorganic brightener.

(First Luster Material)

[0312] CP-315 (produced by Asahi Kasei Chemicals Corporation, aluminum pigment, thickness: 0.17 μm, average aspect ratio: 88)

(First Inorganic Brightener)

[0313] Barium sulfate (produced by Sakai Chemical Industry Co., Ltd., average particle size: 30 nm)

(First Hydrophobic Association Rheology Control Agent)

[0314] BYK-425 (urea-modified urethane compound, produced by BYK-Chemie GmbH, 1 part by mass based on 100 parts by mass of the solid content of the main resin)

<Preparation of Second Base Coating Composition>

[0315] The following components were blended with the resin composition 1 as shown in Table 1, and diluted with water, affording a second base water-borne coating composition.

[0316] In the tables, the nonvolatile content (NV2), the PWC of the second luster material, and the PWC of the second inorganic brightener were calculated in the same manner as the description of the preparation of the first base coating composition.

(Second Luster Material)

[0317] SB10 (produced by Asahi Kasei Chemicals Corporation, aluminum pigment, thickness: 0.06 μm, average aspect ratio: 170)

[0318] FD-508H (produced by Asahi Kasei Chemicals Corporation, aluminum pigment, thickness: 0.08 μm, average aspect ratio: 96)

[0319] FD-5090 (produced by Asahi Kasei Chemicals Corporation, aluminum pigment, thickness: 0.11 μm, average aspect ratio: 80)

[0320] WM2068 (produced by Toyo Aluminium K.K., aluminum pigment, thickness: 0.15 μm, average aspect ratio: 110)

[0321] WA3180 (produced by Asahi Kasei Chemicals Corporation, aluminum pigment, thickness: 0.25 μm, average aspect ratio: 55)

[0322] WS-3001 (produced by ECKART, aluminum pigment, thickness: 0.03 μm, average aspect ratio: 500)

(Second Inorganic Brightener)

[0323] Barium sulfate: BARIFINE BF-20 (produced by Sakai Chemical Industry Co., Ltd., average particle size: 30 nm)

(Second Inorganic Rheology Control Agent)

[0324] LAPONITE RD (synthetic hectorite-like substance produced by BYK-Chemie GmbH, thickness: from 0.9 nm to 1.0 nm)

[0325] LAPONITE EP (synthetic hectorite-like substance produced by BYK-Chemie GmbH, thickness: from 0.9 nm to 1.0 nm)

[0326] OPTIGEL WX (Na-substituted bentonite produced by BYK-Chemie GmbH)

[0327] In the tables, “LAPO” means LAPONITE, and “OPT” means OPTIGEL.

(Second Hydrophobic Association Rheology Control Agent)

[0328] BYK-425 (urea-modified urethane compound, produced by BYK-Chemie GmbH)

[0329] ADEKANOL UH550 (urethane compound, produced by ADEKA Corporation)

[0330] DISPARLON AQ021 (urethane compound, produced by Kusumoto Chemicals, Ltd.)

[0331] In the tables, “425” means BYK-425, “UH550” means ADEKANOL UH550, and “AQ021” means DISPARLON AQ021.

(Second Dispersant)

[0332] DISPERBYK-192 (produced by BYK-Chemie GmbH)

[0333] SURFYNOL-465 (produced by EVONIK)

[0334] SURFYNOL-440 (produced by EVONIK)

[0335] In the tables, “192” means DISPERBYK-192, “465” means SURFYNOL-465, and “440” means SURFYNOL-440.

[0336] DISPERBYK-192 is an anionic dispersant, and SURFYNOL is a nonionic dispersant (polyether adduct of acetylene diol compound).

<Production Example of Coating Film>

[0337] An SPCC-SD steel plate (dull steel plate) treated with zinc phosphate and measuring 70 mm by 150 mm by 0.8 mm thick was subjected to electrodeposition coating with a cationic electrodeposition coating material “POWERTOP U-50” produced by Nippon Paint Co., Ltd. so that a dry coating film thickness would be 20 μm. The resultant was baked at 160° C. for 30 minutes. Further, the coated sheet was further subjected to electrostatic deposition coating to have a dry film thickness of 35 pm with a gray intermediate coating material “ORGA P-30” (polyester melamine-based coating, produced by Nippon Paint Co., Ltd.), which had been diluted such that the viscosity thereof would be 25 seconds (measured at 20° C. using a No. 4 Ford cup). The resultant was baked at 140° C. for 30 minutes, and thus a substrate was prepared.

[0338] Then, the first base coating compositions of the respective Examples and Comparative Examples were applied to the obtained substrates with a Cartridge Bell (a rotary atomizing coater manufactured by ABB Industries) such that the dry film thicknesses shown in Table 1 would be achieved.

[0339] Then, following preheating at 80° C. for 3 minutes, the second base coating compositions were applied with a Cartridge Bell (a rotary atomizing coater manufactured by ABB Industries) such that the dry film thicknesses shown in Table 1 would be achieved.

[0340] Then, following preheating at 80° C. for 3 minutes, a clear coating material “MACFLOW O-1820 Clear” (epoxy curable acrylic resin-based coating, produced by Nippon Paint Co., Ltd.) was applied wet-on-wet with a rotary atomizing electrostatic coater such that a dry film thickness of 35 μm would be achieved.

[0341] After the application, baking was carried out at 140° C. for 30 minutes, affording the multilayer coating films according to the respective Examples and Comparative Examples.

<Evaluation>

[0342] Physical properties of the multilayer coating film, the first base coating composition, and the second base coating composition were evaluated based on the following criteria. The results are shown in Table 1.

(Settling Property)

[0343] A second base coating composition was placed in a 50 mL sample can and the state of settling attained after standing at room temperature for 10 days was evaluated based on the following criteria.

[0344] ∘: No pigment or the like has settled and no separation is observed at all.

[0345] Δ: A slight amount of pigment or the like has settled and the supernatant liquid is cloudy.

[0346] ×: Pigment or the like has settled and the supernatant liquid has become transparent.

(Dispersion Stability)

[0347] 250 mL of the second base coating composition obtained was placed in a 500 mL beaker, stirred at 30° C. for 7 days, and filtered through a 200 mesh filter, and then the degree of aggregation of the second luster material was evaluated. p ∘: The second luster material has not been aggregated.

[0348] ×: The second luster material has been aggregated.

(Sagging Property)

[0349] To a coated sheet having an electrodeposited coating film and an intermediate coating film (fanned from ORGA P-30) and having a hole sized 5 mm in diameter, a first base coating composition obtained and a second base coating composition obtained were applied by using a Cartridge Bell (a rotary atomizing coater manufactured by ABB Industries) such that a dry film thicknesses shown in the following table would be achieved. After preheating at 80° C. for 3 minutes, heat-curing was performed at 140° C. for 30 minutes, and then a sagging length under the hole was measured.

[0350] The smaller the numerical value, the better the sagging property; a result with a length of 5 mm or less leads to an evaluation that the sagging property is good (◯), and a result with a length of more than 5 mm is led to an evaluation that the sagging property was poor (×).

[0351] It should be noted that (Δ) means a case where the sagging property was good in one measurement and the sagging property was poor in another measurement even when the same coating composition was used.

(Hiding Property of Second Base Coating Composition)

[0352] Then, a second base coating composition obtained was applied to a black-and-white hiding test paper with a Cartridge Bell (a rotary atomizing coater manufactured by ABB Industries) such that a dry film thickness shown in the following table would be achieved. After preheating at 80° C. for 3 minutes, heat-curing was performed at 140° C. for 30 minutes. The degree of hiding of the obtained sample was visually evaluated.

[0353] A case where the base material has been hidden completely was rated as (∘), and a case where the base material has shown through was rated as (×).

[0354] In addition, a hiding property of (⊚) means that further improved hiding property is exhibited.

[0355] In addition, the hiding property of (Δ) means that there occurred both a case where the hiding property was (◯) and a case where the hiding property was (×) at a strictly limited site even when the same coating composition was used.

(Sanding-Mark Hiding Property)

[0356] On a substrate was formed an intermediate coating film (formed from the ORGA P-30), and the intermediate coating film of the resulting coated sheet was subjected to water-sanding with #800 sandpaper for water-sanding until a 60 degree gloss reached 50%. Subsequently, a first base coating film, a second base coating film, and a clear coating film were formed on the basis of the same procedure as in the production example of the coating film described above to form a composite coating film. Thereafter, the presence or absence of transfer of the sanding mark was visually examined.

[0357] Evaluation criteria are as follows.

[0358] ∘: No sanding mark was observed.

[0359] Δ: Slight sanding marks were observed.

[0360] ×: Sanding marks were observed on the entire surface.

(Metallic Feeling)

[0361] An electrodeposition coating film and an intermediate coating film were formed on a substrate. Further, a multilayer coating film having a first base coating film, a second base coating film, and a clear coating film was prepared thereon. For the resulting multilayer coating film, an FI value (flip-flop property) and a G value (grain feeling) were measured using a “BYK-mac” (manufactured by BYK-Gardner) and used as the evaluation of design. The higher the flip-flop property and the denser the grain feeling, the better the metallic feeling.

[0362] ⊚: FI value is 20 or more and G value is 3.0 or less.

[0363] ∘: FI value is 20 or more and G value is 3.5 or less.

[0364] Δ: FI value is 15 or more and G value is 4.0 or less.

[0365] ×: FI value is less than 15 or G value is 4.0 or more.

(Water-Resistant Adherability)

[0366] An electrodeposition coating film and an intermediate coating film were formed on a substrate. Further, a multilayer coating film having a first base coating film, a second base coating film, and a clear coating film was prepared thereon. After immersing the obtained specimen in water at 40° C. for 240 hours, the appearance of the coating film was visually observed and the adherability test described below was carried out. Evaluation criteria are as follows.

(High-Temperature Water-Resistant Adherability)

[0367] An electrodeposition coating film and an intermediate coating film were formed on a substrate. Further, a multilayer coating film having a first base coating film, a second base coating film, and a clear coating film was prepared thereon. After immersing the obtained specimen in water at 80° C. for 120 hours, the appearance of the coating film was visually observed and the adherability test described below was carried out. Evaluation criteria are as follows.

(Adherability Test)

[0368] Ten slits were cuts at 1 mm pitches in a longitudinal direction and a lateral direction, respectively, on the coating film of a specimen with a cutter, and a cellophane tape (registered trademark) (produced by Nichiban Co., Ltd.) was affixed thereon and then peeled off, and the number of peeled squares out of 100 squares was counted (also called cross-cut adhesion test). By this test, the presence or absence of delamination of the coating film was examined.

[0369] For example, when the result of the crosscut test is 100/100, this means that the peeled area of the coating film is 100%, indicating that the coating film has peeled off.

(Evaluation of Chipping Resistance)

[0370] An electrodeposition coating film and an intermediate coating film were formed on a substrate. Furthermore, a multilayer coating film having a first base coating film, a second base coating film, and a clear coating film formed from the base coating compositions of Examples and Comparative Examples was made thereon. The test board obtained was subjected to a chipping stone test under the conditions shown below using a Gravelometer KSS-1 (produced by Suga Test Instruments Co., Ltd.). (A hood of an automobile was assumed.)

<Test Methods>

[0371] Type of stone: Basalt No. 7

[0372] Stone size: 3 to 4 mm

[0373] Amount of stone: 100 g

[0374] Distance: 35 cm

[0375] Shot pressure: 0.3 MPa

[0376] Shot angle: 30°

[0377] Test temperature: -20° C.

[0378] The test board after the chipping test was evaluated visually according to the following criteria.

[0379] ◯: The maximum peeled part diameter is 1.0 mm or less.

[0380] Δ: The maximum peeled part diameter is more than 1.0 mm and 3.0 mm or less.

[0381] ×: The maximum peeled part diameter is more than 3.0 mm.

TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 First base Type of first CP-315 (thickness = ◯ ◯ ◯ ◯ ◯ ◯ coating luster material 0.17 μm, aspect ratio = 88) composition First luster 10 10 10 10 10 10 material PWC First inorganic Barium sulfate 20 20 20 20 20 20 brightener PWC Average particle size: 30 nm NV1 20 20 20 20 20 20 Second base Type of second SB10 (thickness = 0.06 μm, ◯ ◯ ◯ coating luster material aspect ratio = 170) composition FD-508H (thickness = ◯ 0.08 μm, aspect ratio = 96) FD-5090 (thickness = ◯ 0.11 μm, aspect ratio = 80) WM2068 (thickness = 0.15 μm, aspect ratio =110) WA3180 (thickness = 0.25 μm, aspect ratio = 55) WS-3001 (thickness = ◯ 0.03 μm, aspect ratio = 500) NV2 10 10 10 10 10 10 Second luster 30 30 30 30 20 30 material PWC Second inorganic Barium sulfate — — — — — — brightener PWC Average particle size: 30 nm Second inorganic Type/amount based on LAPO LAPO LAPO LAPO LAPO LAPO rheology control 100 parts by mass of resin RD/ RD/ RD/ RD/ RD/ RD/ agent solid content 5 PHR 5 PHR 5 PHR 5 PHR 5 PHR 5 PHR Second hydrophobic Type/amount based on 425/ 425/ 425/ 425/ 425/ 425/ association rheology 100 parts by mass of resin 3 PHR 3 PHR 3 PHR 3 PHR 3 PHR 3 PHR control agent solid content Anionic dispersant Type/amount based on 192/ 192/ 192/ 192/ 192/ 192/ 100 parts by mass of resin 3 PHR 3 PHR 3 PHR 3 PHR 3 PHR 3 PHR solid content Nonionic dispersant Type/amount based on 465/ 465/ 465/ 465/ 465/ 465/ 100 parts by mass of resin 10 PHR 10 PHR 10 PHR 10 PHR 10 PHR 10 PHR solid content Film thickness First base Dry film thickness (μm) 7 7 7 7 7 7 configuration Second base Dry film thickness (μm) 4 4 4 4 4 4 Properties of Settling property ◯ ◯ ◯ ◯ ◯ ◯ Second base Dispersion stability ◯ ◯ ◯ ◯ ◯ ◯ coating composition Coating Sagging property ◯ ◯ ◯ ◯ ◯ ◯ workability Hiding property ◯ ◯ ◯ ◯ Δ ◯ (second base) Sanding-mark ◯ ◯ ◯ ◯ ◯ ◯ hiding property Metallic FI 21.8 21.1 20.2 23.2 21.4 21.8 feeling Grainness 3.2 3.4 3.4 2.6 3.3 3.2 (G value) Evaluation ◯ ◯ ◯ ⊙ ◯ ◯ 40° C. Water Visual No No No No No No resistance observation abnormal- abnormal- abnormal- abnormal- abnormal- abnormal- ities ities ities ities ities ities Adherability 0/100 0/100 0/100 0/100 0/100 0/100 80° C. Water Visual No No No No No No resistance observation abnormal- abnormal- abnormal- abnormal- abnormal- abnormal- ities ities ities ities ities ities Adherability 0/100 0/100 0/100 0/100 0/100 0/100 Chipping resistance ◯ ◯ ◯ ◯ ◯ ◯ Example 7 Example 8 Example 9 Example 10 First base Type of first CP-315 (thickness = ◯ ◯ ◯ ◯ coating luster material 0.17 μm, aspect ratio = 88) composition First luster 10 10 10 10 material PWC First inorganic Barium sulfate 20 20 20 20 brightener PWC Average particle size: 30 nm NV1 20 20 20 20 Second base Type of second SB10 (thickness = 0.06 μm, ◯ ◯ ◯ ◯ coating luster material aspect ratio = 170) composition FD-508H (thickness = 0.08 μm, aspect ratio = 96) FD-5090 (thickness = 0.11 μm, aspect ratio = 80) WM2068 (thickness = 0.15 μm, aspect ratio =110) WA3180 (thickness = 0.25 μm, aspect ratio = 55) WS-3001 (thickness = 0.03 μm, aspect ratio = 500) NV2 10 10 10 10 Second luster 40 30 30 30 material PWC Second inorganic Barium sulfate — — 5 10 brightener PWC Average particle size: 30 nm Second inorganic Type/amount based on LAPO LAPO LAPO LAPO rheology control 100 parts by mass of resin RD/ RD/ RD/ RD/ agent solid content 5 PHR 5 PHR 5 PHR 5 PHR Second hydrophobic Type/amount based on 425/ 425/ 425/ 425/ association rheology 100 parts by mass of resin 3 PHR 3 PHR 3 PHR 3 PHR control agent solid content Anionic dispersant Type/amount based on 192/ 192/ 192/ 192/ 100 parts by mass of resin 3 PHR 3 PHR 3 PHR 3 PHR solid content Nonionic dispersant Type/amount based on 465/ 465/ 465/ 465/ 100 parts by mass of resin 10 PHR 10 PHR 10 PHR 10 PHR solid content Film thickness First base Dry film thickness (μm) 7 7 7 7 configuration Second base Dry film thickness (μm) 4 4 4 4 Properties of Settling property ◯ ◯ ◯ ◯ Second base Dispersion stability ◯ ◯ ◯ ◯ coating composition Coating Sagging property ◯ ◯ ◯ ◯ workability Hiding property ◯ ◯ ◯ ◯ (second base) Sanding-mark ◯ ◯ ◯ ◯ hiding property Metallic FI 18.8 21.8 20.4 17.6 feeling Grainness 3.6 3.2 3.4 3.4 (G value) Evaluation Δ ◯ ◯ Δ 40° C. Water Visual No No No No resistance observation abnormal- abnormal- abnormal- abnormal- ities ities ities ities Adherability 0/100 0/100 0/100 0/100 80° C. Water Visual No No No No resistance observation abnormal- abnormal- abnormal- abnormal- ities ities ities ities Adherability 0/100 0/100 0/100 0/100 Chipping resistance ◯ ◯ ◯ ◯

TABLE-US-00002 TABLE 2 Comparative Example 11 Example 12 Example 1 Example 13 Example 14 First base Type of first CP-315 (thickness = ◯ ◯ ◯ ◯ ◯ coating luster material 0.17 μm, aspect ratio = 88) composition First luster 10 10 10 10 10 material PWC First inorganic Barium sulfate 20 20 20 20 20 brightener PWC Average particle size: 30 nm NV1 20 20 20 20 20 Second base Type of second SB10 (thickness = 0.06 μm, ◯ ◯ ◯ ◯ ◯ coating luster material aspect ratio = 170) composition FD-508H (thickness = 0.08 μm, aspect ratio = 96) FD-5090 (thickness = 0.11 μm, aspect ratio = 80) WM2068 (thickness = 0.15 μm, aspect ratio =110) WA3180 (thickness = 0.25 μm, aspect ratio = 55) WS-3001 (thickness = 0.03 μm, aspect ratio = 500) NV2 5 10 15 13 10 Second luster 30 30 30 30 30 material PWC Second inorganic Barium sulfate — — — — — brightener PWC Average particle size: 30 nm Second inorganic Type/amount based on LAPO LAPO — LAPO LAPO rheology control 100 parts by mass of resin RD/ RD/ RD/ RD/ agent solid content 5 PHR 5 PHR 1 PHR 5 PHR Second hydrophobic Type/amount based on 425/ 425/ 425/ 425/ 425/ association rheology 100 parts by mass of resin 3 PHR 3 PHR 3 PHR 3 PHR 3 PHR control agent solid content Anionic dispersant Type/amount based on 192/ 192/ 192/ 192/ 192/ 100 parts by mass of resin 3 PHR 3 PHR 3 PHR 3 PHR 3 PHR solid content Nonionic dispersant Type/amount based on 465/ 465/ 465/ 465/ 465/ 100 parts by mass of resin 10 PHR 10 PHR 10 PHR 10 PHR 10 PHR solid content Film thickness First base Dry film thickness (μm) 7 7 7 7 7 configuration Second base Dry film thickness (μm) 4 4 4 4 4 Properties of Settling property ◯ ◯ X Δ ◯ second base Dispersion stability ◯ ◯ X ◯ ◯ coating composition Coating Sagging property ◯ ◯ ◯ ◯ ◯ workability Hiding property ◯ ◯ ◯ ◯ ◯ (second base) Sanding-mark ◯ ◯ ◯ ◯ ◯ hiding property Metallic FI 25.1 21.8 21.2 21.6 21.8 feeling Grainness 3.3 3.2 3.4 3.2 3.2 (G value) Evaluation ◯ ◯ ◯ ◯ ◯ 40° C. Water Visual No No No No No resistance observation abnormal- abnormal- abnormal- abnormal- abnormal- ities ities ities ities ities Adherability 0/100 0/100 10/100 0/100 0/100 80° C. Water Visual No No No No No resistance observation abnormal- abnormal- abnormal- abnormal- abnormal- ities ities ities ities ities Adherability 0/100 0/100 30/100 0/100 0/100 Chipping resistance ◯ ◯ ◯ ◯ ◯ Comparative Example 15 Example 16 Example 17 Example 2 First base Type of first CP-315 (thickness = ◯ ◯ ◯ ◯ coating luster material 0.17 μm, aspect ratio = 88) composition First luster 10 10 10 10 material PWC First inorganic Barium sulfate 20 20 20 20 brightener PWC Average particle size: 30 nm NV1 20 20 20 20 Second base Type of second SB10 (thickness = 0.06 μm, ◯ ◯ ◯ ◯ coating luster material aspect ratio = 170) composition FD-508H (thickness = 0.08 μm, aspect ratio = 96) FD-5090 (thickness = 0.11 μm, aspect ratio = 80) WM2068 (thickness = 0.15 μm, aspect ratio =110) WA3180 (thickness = 0.25 μm, aspect ratio = 55) WS-3001 (thickness = 0.03 μm, aspect ratio = 500) NV2 11 8 11 17 Second luster 30 30 30 30 material PWC Second inorganic Barium sulfate — — — — brightener PWC Average particle size: 30 nm Second inorganic Type/amount based on LAPO LAPO Opt WX/ LAPO rheology control 100 parts by mass of resin RD/ EP/ 5 PHR RD/ agent solid content 7 PHR 5 PHR 5 PHR Second hydrophobic Type/amount based on 425/ 425/ 425/ — association rheology 100 parts by mass of resin 3 PHR 3 PHR 3 PHR control agent solid content Anionic dispersant Type/amount based on 192/ 192/ 192/ 192/ 100 parts by mass of resin 3 PHR 3 PHR 3 PHR 3 PHR solid content Nonionic dispersant Type/amount based on 465/ 465/ 465/ 465/ 100 parts by mass of resin 10 PHR 10 PHR 10 PHR 10 PHR solid content Film thickness First base Dry film thickness (μm) 7 7 7 7 configuration Second base Dry film thickness (μm) 4 4 4 4 Properties of Settling property ◯ ◯ ◯ X second base Dispersion stability ◯ ◯ ◯ X coating composition Coating Sagging property ◯ ◯ ◯ ◯ workability Hiding property ◯ ◯ ◯ ◯ (second base) Sanding-mark ◯ ◯ ◯ ◯ hiding property Metallic FI 20.2 20.6 18.8 14.8 feeling Grainness 3.3 3.3 3.7 4.5 (G value) Evaluation ◯ ◯ Δ X 40° C. Water Visual No No No No resistance observation abnormal- abnormal- abnormal- abnormal- ities ities ities ities Adherability 0/100 0/100 0/100 0/100 80° C. Water Visual No No No No resistance observation abnormal- abnormal- abnormal- abnormal- ities ities ities ities Adherability 0/100 0/100 0/100 0/100 Chipping resistance ◯ ◯ ◯ ◯

TABLE-US-00003 TABLE 3 Example 18 Example 19 Example 20 Example 21 Example 22 First base Type of first CP-315 (thickness = ◯ ◯ ◯ ◯ ◯ coating luster material 0.17 μm, aspect ratio = 88) composition First luster 10 10 10 10 10 material PWC First inorganic Barium sulfate 20 20 20 20 20 brightener PWC Average particle size: 30 nm NV1 20 20 20 20 20 Second base Type of second SB10 (thickness = 0.06 μm, ◯ ◯ ◯ ◯ ◯ coating luster material aspect ratio = 170) composition FD-508H (thickness = 0.08 μm, aspect ratio = 96) FD-5090 (thickness = 0.11 μm, aspect ratio = 80) WM2068 (thickness = 0.15 μm, aspect ratio = 110) WA3180 (thickness = 0.25 μm, aspect ratio = 55) WS-3001 (thickness = 0.03 μm, aspect ratio = 500) NV2 15 10 7 10 12 Second luster 30 30 30 30 30 material PWC Second inorganic Barium sulfate — — — — — brightener PWC Average particle size: 30 nm Second inorganic Type/amount based on LAPO LAPO LAPO LAPO LAPO rheology control 100 parts by mass of resin RD/ RD/ RD/ RD/ RD/ agent solid content 5 PHR 5 PHR 5 PHR 5 PHR 5 PHR Second hydrophobic Type/amount based on 425/ 425/ 425/ UH550/ AQ021/ association rheology 100 parts by mass of resin 1 PHR 3 PHR 10 PHR 3 PHR 3 PHR control agent solid content Anionic dispersant Type/amount based on 192/ 192/ 192/ 192/ 192/ 100 parts by mass of resin 3 PHR 3 PHR 3 PHR 3 PHR 3 PHR solid content Nonionic dispersant Type/amount based on 465/ 465/ 465/ 465/ 465/ 100 parts by mass of resin 10 PHR 10 PHR 10 PHR 10 PHR 10 PHR solid content Film thickness First base Dry film thickness (μm) 7 7 7 7 7 configuration Second base Dry film thickness (μm) 4 4 4 4 4 Properties of Settling property ◯ ◯ Δ ◯ ◯ second base Dispersion stability ◯ ◯ ◯ ◯ ◯ coating composition Coating Sagging property ◯ ◯ ◯ ◯ ◯ workability Hiding property ◯ ◯ ◯ ◯ ◯ (second base) Sanding-mark ◯ ◯ ◯ ◯ ◯ hiding property Metallic FI 20.4 21.8 18.4 21.6 22.4 feeling Grainness 3.4 3.2 3.8 3.2 3.2 (G value) Evaluation ◯ ◯ Δ ◯ ◯ 40° C. Water Visual No No No No No resistance observation abnormal- abnormal- abnormal- abnormal- abnormal- ities ities ities ities ities Adherabilitv 0/100 0/100 0/100 0/100 0/100 80° C. Water Visual No No No No No resistance observation abnormal- abnormal- abnormal- abnormal- abnormal- ities ities ities ities ities Adherability 0/100 0/100 0/100 0/100 0/100 Chipping resistance ◯ ◯ ◯ ◯ ◯ Comparative Example 23 Example 24 Example 25 Example 3 First base Type of first CP-315 (thickness = ◯ ◯ ◯ ◯ coating luster material 0.17 μm, aspect ratio = 88) composition First luster 10 10 10 10 material PWC First inorganic Barium sulfate 20 20 20 — brightener PWC Average particle size: 30 nm NV1 20 20 20 20 Second base Type of second SB10 (thickness = 0.06 μm, ◯ ◯ ◯ ◯ coating luster material aspect ratio = 170) composition FD-508H (thickness = 0.08 μm, aspect ratio = 96) FD-5090 (thickness = 0.11 μm, aspect ratio = 80) WM2068 (thickness = 0.15 μm, aspect ratio = 110) WA3180 (thickness = 0.25 μm, aspect ratio = 55) WS-3001 (thickness = 0.03 μm, aspect ratio = 500) NV2 10 12 10 10 Second luster 30 30 30 30 material PWC Second inorganic Barium sulfate — — — — brightener PWC Average particle size: 30 nm Second inorganic Type/amount based on LAPO LAPO LAPO LAPO rheology control 100 parts by mass of resin RD/ RD/ RD/ RD/ agent solid content 5 PHR 5 PHR 5 PHR 5 PHR Second hydrophobic Type/amount based on 425/ 425/ 425/ 425/ association rheology 100 parts by mass of resin 3 PHR 3 PHR 3 PHR 3PHR control agent solid content Anionic dispersant Type/amount based on 192/ 192/ 192/ 192/ 100 parts by mass of resin 3 PHR 3 PHR 3 PHR 3PHR solid content Nonionic dispersant Type/amount based on 465/ 465/ 440/ 465/ 100 parts by mass of resin 10 PHR 15 PHR 10 PHR 10 PHR solid content Film thickness First base Dry film thickness (μm) 7 7 7 7 configuration Second base Dry film thickness (μm) 4 4 4 4 Properties of Settling property ◯ ◯ ◯ ◯ second base Dispersion stability ◯ ◯ ◯ ◯ coating composition Coating Sagging property ◯ ◯ ◯ ◯ workability Hiding property ◯ ◯ ◯ ◯ (second base) Sanding-mark ◯ ◯ ◯ Δ hiding property Metallic FI 21.8 21.4 20.6 16.2 feeling Grainness 3.2 3.3 3.3 4.5 (G value) Evaluation ◯ ◯ ◯ X 40° C. Water Visual No No No No resistance observation abnormal- abnormal- abnormal- abnormal- ities ities ities ities Adherabilitv 0/100 0/100 0/100 0/100 80° C. Water Visual No No No No resistance observation abnormal- abnormal- abnormal- abnormal- ities ities ities ities Adherability 0/100 0/100 0/100 0/100 Chipping resistance ◯ ◯ ◯ ◯

TABLE-US-00004 TABLE 4 Example Example Example Example Example Example 26 27 28 29 30 31 First base Type of first CP-315 (thickness = ◯ ◯ ◯ ◯ ◯ ◯ coating luster material 0.17 μm, aspect ratio = 88) composition First luster 10 10 10 10 10 10 material PWC First inorganic Barium sulfate 10 20 30 20 20 20 brightener PWC Average particle size: 30 nm NV1 20 20 20 20 20 20 Second base Type of second SB10 (thickness = 0.06 μm, ◯ ◯ ◯ ◯ ◯ ◯ coating luster material aspect ratio = 170) composition FD-508H (thickness = 0.08 μm, aspect ratio = 96) FD-5090 (thickness = 0.11 μm, aspect ratio = 80) WM2068 (thickness = 0.15 μm, aspect ratio = 110) WA3180 (thickness = 0.25 μm, aspect ratio = 55) WS-3001 (thickness = 0.03 μm, aspect ratio = 500) NV2 10 10 10 10 10 10 Second luster 30 30 30 30 30 30 material PWC Second inorganic Barium sulfate — — — — — — brightener PWC Average particle size: 30 nm Second inorganic Type/amount based on 100 parts LAPO LAPO LAPO LAPO LAPO LAPO rheology control by mass of resin solid content RD/ RD/ RD/ RD/ RD/ RD/ agent 5 PHR 5 PHR 5 PHR 5 PHR 5 PHR 5 PHR Second hydrophobic Type/amount based on 100 parts 425/ 425/ 425/ 425/ 425/ 425/ association rheology by mass of resin solid content 3 PHR 3 PHR 3 PHR 3 PHR 3 PHR 3 PHR control agent Anionic dispersant Type/amount based on 100 parts 192/ 192/ 192/ 192/ 192/ 192/ by mass of resin solid content 3 PHR 3 PHR 3 PHR 3 PHR 3 PHR 3 PHR Nonionic dispersant Type/amount based on 100 parts 465/ 465/ 465/ 465/ 465/ 465/ by mass of resin solid content 10 PHR 10 PHR 10 PHR 10 PHR 10 PHR 10 PHR Film thickness First base Dry film thickness (μm) 7 7 7 7 7 7 configuration Second base Dry film thickness (μm) 4 4 4 4 5 7 Properties of Settling property ◯ ◯ ◯ ◯ ◯ ◯ second base Dispersion stability ◯ ◯ ◯ ◯ ◯ ◯ coating composition Coating Sagging ◯ ◯ ◯ ◯ ◯ Δ workability property Hiding property ◯ ◯ ◯ ◯ ◯ ◯ (second base) Sanding-mark ◯ ◯ ◯ ◯ ◯ ◯ hiding property Metallic FI 20.2 21.8 20.6 21.8 20.4 18.4 feeling Grainness 3.1 3.2 3.4 3.2 3.4 3.8 (G value) Evaluation Δ ◯ ◯ ◯ Δ Δ 40° C. Waler Visual No No No No No No resistance observation abnormal- abnormal- abnormal- abnormal- abnormal- abnormal- ities ities ities ities ities ities Adherability 0/100 0/100 0/100 0/100 0/100 0/100 80° C. Water Visual No No No No No No resistance observation abnormal- abnormal- abnormal- abnormal- abnormal- abnormal- ities ities ities ities ities ities Adherability 0/100 0/100 0/100 0/100 0/100 0/100 Chipping resistance ◯ ◯ ◯ ◯ ◯ ◯ Example Example Example Example Example Example 32 33 34 35 36 37 First base Type of first CP-315 (thickness = ◯ ◯ ◯ ◯ ◯ ◯ coating luster material 0.17 μm, aspect ratio = 88) composition First luster 10 10 10 10 10 10 material PWC First inorganic Barium sulfate 20 20 20 20 20 20 brightener PWC Average particle size: 30 nm NV1 20 20 20 20 20 20 Second base Type of second SB10 (thickness = 0.06 μm, ◯ ◯ ◯ ◯ ◯ ◯ coating luster material aspect ratio = 170) composition FD-508H (thickness = 0.08 μm, aspect ratio = 96) FD-5090 (thickness = 0.11 μm, aspect ratio = 80) WM2068 (thickness = 0.15 μm, aspect ratio = 110) WA3180 (thickness = 0.25 μm, aspect ratio = 55) WS-3001 (thickness = 0.03 μm, aspect ratio = 500) NV2 10 10 10 10 10 10 Second luster 30 30 30 30 30 30 material PWC Second inorganic Barium sulfate — — — — — — brightener PWC Average particle size: 30 nm Second inorganic Type/amount based on 100 parts LAPO LAPO LAPO LAPO LAPO LAPO rheology control by mass of resin solid content RD/ RD/ RD/ RD/ RD/ RD/ agent 5 PHR 5 PHR 5 PHR 5 PHR 5 PHR 5 PHR Second hydrophobic Type/amount based on 100 parts 425/ 425/ 425/ 425/ 425/ 425/ association rheology by mass of resin solid content 3 PHR 3 PHR 3 PHR 3 PHR 3 PHR 3 PHR control agent Anionic dispersant Type/amount based on 100 parts 192/ 192/ 192/ 192/ 192/ 192/ by mass of resin solid content 3 PHR 3 PHR 3 PHR 3 PHR 3 PHR 3 PHR Nonionic dispersant Type/amount based on 100 parts 465/ 465/ 465/ 465/ 465/ 465/ by mass of resin solid content 10 PHR 10 PHR 10 PHR 10 PHR 10 PHR 10 PHR Film thickness First base Dry film thickness (μm) 3 5 7 10 12 15 configuration Second base Dry film thickness (μm) 4 4 4 4 4 4 Properties of Settling property ◯ ◯ ◯ ◯ ◯ ◯ second base Dispersion stability ◯ ◯ ◯ ◯ ◯ ◯ coating composition Coating Sagging ◯ ◯ ◯ ◯ ◯ Δ workability property Hiding property ◯ ◯ ◯ ◯ ◯ ◯ (second base) Sanding-mark Δ ◯ ◯ ◯ ◯ ◯ hiding property Metallic FI 22.6 21.2 21.8 18.6 17.2 15.4 feeling Grainness 3.5 3.3 3.2 3.4 3.7 3.9 (G value) Evaluation Δ ◯ ◯ ◯ Δ Δ 40° C. Waler Visual No No No No No No resistance observation abnormal- abnormal- abnormal- abnormal- abnormal- abnormal- ities ities ities ities ities ities Adherability 0/100 0/100 0/100 0/100 0/100 0/100 80° C. Water Visual No No No No No No resistance observation abnormal- abnormal- abnormal- abnormal- abnormal- abnormal- ities ities ities ities ities ities Adherability 0/100 0/100 0/100 0/100 0/100 0/100 Chipping resistance Δ ◯ ◯ ◯ ◯ ◯

[0382] With any water-borne coating composition set for forming a multilayer coating film according to the present disclosure, the orientation of a luster pigment is improved. Therefore, it is possible to form a superior metallic coating film that can suppress diffuse reflection of light and has sufficient highlight brightness.

[0383] A multilayer coating film formed from a composition set of the present disclosure is also superior in weather resistance.

[0384] In addition, any water-borne coating composition set for forming a multilayer coating film according to the present disclosure can form a coating film having good physical properties such as chipping resistance, water resistance, and high-temperature water resistance, and sanding-mark hiding property as coating workability.

[0385] Therefore, the water-borne coating composition set for forming a multilayer coating film according to the present disclosure can form a metallic multilayer coating film having superior design, especially superior metallic feeling, and good coating film physical properties.

[0386] Furthermore, since a multilayer coating film can be formed using wet-on-wet application, the number of coating film forming steps can be reduced, and an environmental load can be reduced.

[0387] On the other hand, since Comparative Example 1 does not contain the second inorganic rheology control agent according to the present disclosure, the second coating composition has poor settling property and poor dispersion stability. In addition, the obtained coating film was insufficient in both water resistance (40° C.) and high-temperature water resistance (80° C.).

[0388] In Comparative Example 2, since the second hydrophobic association rheology control agent according to the present disclosure is not contained, the second coating composition has poor settling property and poor dispersion stability. Furthermore, the metallic feeling satisfied the reference value for neither the FI value nor the G value.

[0389] In Comparative Example 3, since the first inorganic brightener was not contained, the G value did not satisfy the reference value, and the multilayer coating film was poor in metallic feeling.

INDUSTRIAL APPLICABILITY

[0390] With any water-borne coating composition set for forming a multilayer coating film according to the present disclosure, the orientation of a luster pigment is improved. Therefore, it is possible to form a superior metallic coating film that can suppress diffuse reflection of light and has sufficient highlight brightness. In addition, any water-borne coating composition set for forming a multilayer coating film according to the present disclosure can form a coating film having good physical properties such as chipping resistance, and sanding-mark hiding property as coating workability.

[0391] This application claims priority based on Japanese Patent Application No. 2019-232918, which was filed in Japan on Dec. 24, 2019, the disclosure of which application is incorporated herein by reference in its entirety.