METHOD OF FORMING A MULTILAYER COATING FILM

Abstract

Provided herein is a method of forming a multilayer coating film including coating, onto an object to be coated, a water-based primer coating composition, wet-on-wet coating a first water-based coloring coating composition, wet-on-wet coating a second water-based coloring coating composition, coating a clear coating composition, and simultaneous hardening of the formed multilayer coating film. The water-based primer coating composition contains a water-based polyolefin resin, a water-based polyurethane resin, a curing agent, and conductive carbon. The first and second water-based coloring coating compositions, each, as base resins, contain a core/shell-type emulsion including an acrylic resin core portion and a polyurethane resin shell portion. The clear coating composition contains a hydroxy-group-containing acrylic resin and a polyisocyanate compound.

Claims

1. A method of forming a multilayer coating film, the method comprising: a step of coating, onto an object to be coated, a water-based primer coating composition; a step of wet-on-wet coating a first water-based coloring coating composition; a step of wet-on-wet coating a second water-based coloring coating composition; a step of coating a clear coating composition; and a step of simultaneous hardening of the formed multilayer coating film, wherein: (1) the water-based primer coating composition contains components: (A) a water-based polyolefin resin with a melting point of 60-100 C. and a weight average molecular weight in the range of 50,000-250,000, (B) a water-based polyurethane resin having a glass transition temperature (Tg) of 100 to 70 C. and an elongation rate of 500% or more, (C) a curing agent, and (D) conductive carbon, (2) the first water-based coloring coating composition and second water-based coloring coating composition each contain a core/shell-type emulsion comprising an acrylic resin core portion and a polyurethane resin shell portion as base resins, and (3) the clear coating composition contains a hydroxy-group-containing acrylic resin and a polyisocyanate compound.

2. The method of forming a multilayer coating film of claim 1, wherein the mass ratio of water-based primer coating composition component (A) and component (B) is 20/80-80/20 as solid resin content, the mass ratio of component (C) and [component (A)+component (B)] is 1/100-30/100 as solid content, and the mass ratio of component (D) and [component (A)+component (B)+component (C)] is 2/98-20/80 as solid content.

3. The method of forming a multilayer coating film of claim 1, wherein aqueous primer coating composition component (B) is a colloidal dispersion-type or emulsion-type aqueous polyurethane resin.

4. The method of forming a multilayer coating film of claim 1, wherein aqueous primer coating composition component (B) is an aqueous polyurethane resin obtained by chain elongation using a polyester polyol, a polycarbonate polyol, or a polyurethane obtained by reacting a polyether polyol and a polyisocyanate.

5. The method of forming a multilayer coating film of claim 1, wherein the mass ratio of the core portion and the shell portion in the core/shell-type emulsion resin in the first water-based coloring coating composition and second water-based coloring coating composition base resin is between 20/80 and 80/20, the core portion acrylic resin has a hydroxyl group value of 10-85 mg KOH/g and an acid value of 0-30 mg KOH/g, the shell portion polyurethane resin has a hydroxyl group value of 20-80 mg KOH/g and an acid value of 10 to 60 mg KOH/g, and the mass ratio of constituent units based on dibasic acids and/or dihydric alcohols having 10 to 60 carbon atoms in the shell portion polyurethane resin is 10-50 parts by mass relative to the solid resin content of the polyurethane resin taken as 100 parts by mass.

6. The method of forming a multilayer coating film of claim 1, wherein the first water-based coloring coating composition and the second water-based coloring coating composition are each characterized by having a mass ratio of the core/shell-type emulsion of 5-80 mass % relative to 100 mass % for the resin solid content in the base resin.

7. The method of forming a multilayer coating film of claim 1, wherein the first water-based coloring coating composition contains a polyisocyanate compound and/or a polycarbodiimide as a curing agent.

8. The method of forming a multilayer coating film of claim 1, wherein aqueous primer coating composition component (B) is an aqueous polyurethane resin obtained by chain elongation using a polyester polyol, a polycarbonate polyol, or a polyurethane obtained by reacting a polyether polyol and a polyisocyanate and a low molecular weight compound having at least 2 active hydrogens in 1 molecule.

Description

EXAMPLES

[0117] The invention is described in more detail in the following examples but the invention is not limited to these examples. Moreover, in the examples, parts means mass % unless otherwise specified and % relating to the formulated amount and content means mass %.

Production Example 1: Production of Aqueous Dispersion P-1 of Non-Chlorinated Polyolefin Resin

[0118] The aqueous dispersion of non-chlorinated polyolefin resin used in the invention is manufactured using the following 3 processes.

(i) Stage 1: Production of Non-Chlorinated Polyolefin Resin

[0119] 110 mL Deionized water, 22.2 g magnesium sulfate heptahydrate, and 18.2 g sulfuric acid were charged into a 1,000 mL round-bottomed flask and dissolved with stirring. 16.7 g Commercially available granulated montmorillonite was added to this solution, it was heated to 100 C. and stirred for 2 hours. Thereafter, it was cooled to room temperature, the obtained slurry was filtered and a wet cake was recovered. The recovered cake was re-slurrified in a 1,000 mL round-bottomed flask with 500 mL desalted water and filtered. Drying was repeated twice. The finally obtained cake was dried overnight at 110 C. in a nitrogen atmosphere to obtain 13.3 g chemically treated montmorillonite. 20 mL Of a toluene solution of triethylaluminum (0.4 mmol/ml) was added to 4.4 g of the chemically treated montmorillonite and stirred at room temperature for 1 hour. 80 mL Toluene was added to this suspension and the supernatant was removed after stirring. After drying had been repeated twice, toluene was added and a clay slurry (slurry concentration=99 mg clay/mL) was obtained.

[0120] 0.2 mmol Triisobutyl aluminum was added to a separate flask, 19 mL of the obtained clay slurry and a toluene dilution of 131 mg (57 mol) dichloro[dimethylsilylene(cyclopentadienyl)(2,4-dimethyl-4H-5,6,7,8-tetrahydro-1-azulene) hafnium were added, and stirred for 10 minutes at room temperature to obtain a catalyst slurry.

[0121] Next, 11 L toluene, 3.5 mmol triisobutyl aluminum, and 2.64 L liquid propylene were introduced into a 24 L capacity induction-stirred autoclave. The entire amount of the abovementioned catalyst slurry was added at room temperature, it was heated to 62 C. and continuously stirred for 2 hours at the same temperature while maintaining a fixed total pressure of 0.65 MPa at the time of polymerization. After the completion of stirring, unreacted propylene was purged to stop polymerization. The autoclave was started, toluene solution from the polymer was completely recovered and 11 kg of an 11.0% toluene solution of the propylene polymer was obtained. The weight average molecular weight Mw of the obtained propylene polymer was 210,000.

(ii) Stage 2: Production of Maleic Anhydride Modified Non-Chlorinated Polyolefin Resin

[0122] 200 g Propylene polymer obtained in Stage 1 shown in the above (i) and 300 g toluene were added to a glass flask fitted with a reflux condensing tube, thermometer, and stirrer, the container was flushed with nitrogen gas and heated to 110 C. After heating, 12 g maleic anhydride was added, 6 g t-butyl peroxy isopropyl monocarbonate (NOF, Perbutyl I) was added, and stirring at the same temperature was continued for 7 hours to carry out the reaction. After completion of the reaction, the system was cooled to around room temperature, acetone was added and the precipitated polymer was filtered out. Further, precipitation/filtration using acetone was repeated and the finally obtained polymer was washed in acetone. After washing, a white, powdered maleic anhydride-modified polymer was obtained by vacuum drying the obtained polymer. The results of infrared absorption spectrum measurements of this modified polymer showed that the amount of the maleic anhydride moiety (graft rate) was 1.3% (0.13 mmol as a maleic anhydride moiety/1 g propylene polymer), the weight average molecular weight was 120,000, and the melting point measured using a differential scanning calorimeter (DS-50) was 80 C.

(iii) Stage 3: Production of an Aqueous Dispersion of Maleic Anhydride-Modified Non-Chlorinated Polyolefin Resin

[0123] 100 g maleic anhydride-modified propylene polymer (maleic anhydride content 13 mmol) obtained in Stage 2 shown in the above (ii) and 250 g toluene were added to a glass flask fitted with a reflux condensing tube, thermometer, and stirrer, and this was heated to 110 C. to fully dissolve the contents. Next, a solution of 30 g (30.0 mmol, corresponding to 30 parts by mass to 100 parts by mass propylene polymer) poly(oxyethylene/oxypropylene) block copolymer (molecular weight 1000) dissolved in 22.5 g toluene was added and reacted for 3 hours at 110 C.

[0124] Toluene was evaporated off under reduced pressure after cooling and 115 g of a yellow polymer was obtained. The results of infrared absorption spectrum analysis of the obtained product showed disappearance of a peak at around 1784 cm.sup.1 corresponding to maleic anhydride and it was confirmed that maleic anhydride-modified propylene polymer and polyether bonded. A graft copolymer with propylene grafted to the maleic anhydride-modified propylene polymer is formed. 160 g Tetrahydrofuran (THF) was added to 40 g of the obtained modified polymer and was allowed to completely dissolve at 65 C. 200 g pure water was added dropwise at the same temperature over 1 hour and a translucent pale yellow solution was obtained. This was cooled to 50 C., the pressure was gradually decreased from 0.03 MPa to 0.0045 MPa, THF and water were distilled off under reduced pressure until the solid resin content became 30% and a translucent, pale yellow water-based resin dispersion P-1 was obtained.

[0125] When the poly(oxyethylene/oxypropylene) block copolymer used in the examples was allowed to dissolve in water at 25 C. at a concentration of 10 mass %, the insoluble matter was 1 mass % or less and was hydrophilic polymer.

Production Example 2: Production of Water-Based Primer Coating Composition WP-1

[0126] 1.66 Parts conductive carbon black (tradename, Printex XE2B, Degussa KK), 12.55 parts titanium dioxide (tradename, JR 600-E, Tayca KK), 0.93 parts pigment dispersing agent (tradename, Disperbyk 191, BYK Chemie KK, solid content 98%, acid value 31 mg KOH/g, amine value 20 mg KOH/g) were added to 26.5 parts polyurethane resin (tradename, Impranil DLU, Covestro Japan Ltd, solid resin content 60%, Tg-83 C., elongation rate 800%), after dispersion in a dispersing machine, 21.0 parts of aqueous dispersion of non-chlorinated polyolefin resin P-1, 1.5 parts of a curing agent (tradename Duranate WM44-L70G, water-dispersible blocked polyisocyanate compound, Asahi Kasei KK, solid resin content 70%), 33.96 parts de-ionized water, 0.8 parts leveling agent (tradename BYK-348, BYK Chemie KK), and 1.1 parts thickening agent (Rheovis AS 5130, BASF Japan KK, solid content 30%) were added, mixed in a dissolver then dimethylethanolamine was added to adjust the pH to 7-8 to produce water-based primer coating composition WP-1.

Production Example 3: Production of Water-Based Primer Coating Compositions WP-2 to WP-21

[0127] Water-based coloring coating compositions WP-2 to WP-21 were obtained using the same method as in production example 2 based on combinations shown in Table 1.

TABLE-US-00001 TABLE 1 Water-based primer coating composition WP-1 WP-2 WP-3 WP-4 WP-5 A: polyolefin Aqueous dispersion 21 21 21 2.1 21 resin of non-chlorinated polyolefin resin P-1 B: polyurethane Impranil DLU 26.5 resin Acrit WBR-2181 (*1) 48.18 Pamarin UA-150 (*2) 53 Ucoat DA-100 (*3) 45.43 Takelac W6061 (*4) 53 Bayhydrol UH2952/1 (*5) Acrit WBR-2018 (*6) Takelac W6021 (*7) Lackstar 5215A (*8) C: curing DURANATE WM44-L70G 1.5 1.5 1.5 1.5 1.5 agent Mycoat775 (*9) D: conductive Printex XE2B 1.66 1.66 1.66 1.66 1.66 carbon Titanium JR600-E 12.55 12.55 12.55 12.55 12.55 dioxide Pigment Disperbyk 191 0.93 0.93 0.93 0.93 0.93 dispersing agent Leveling BYK-348 0.8 0.8 0.8 0.8 0.8 agent Thickening Rheovis AS S130 1.1 1.1 1.1 1.1 1.1 agent Deionized water 33.96 12.28 7.46 15.03 7.46 Total 100 100 100 100 100 A: polyolefin melting point ( C.) 80 80 80 80 80 resin Weight average 120,000 120,000 120,000 120,000 120,000 molecular weight B: polyurethane Glass transition 83 89 87 80 79 resin temperature ( C.) Elongation rate (%) 800 700 600 500 1000 A/B 28/72 28/72 28/72 28/72 28/72 C/(A + B) 5/100 5/100 5/100 5/100 5/100 D/(A + B + C) 7/93 7/93 7/93 7/93 7/93 Water-based primer coating composition WP-6 WP-7 WP-8 WP-9 A: polyolefin Aqueous dispersion 21 21 21 21 resin of non-chlorinated polyolefin resin P-1 B: polyurethane Impranil DLU resin Acrit WBR-2181 (*1) Pamarin UA-150 (*2) Ucoat DA-100 (*3) Takelac W6061 (*4) Bayhydrol UH2952/1 39.75 (*5) Acrit WBR-2018 (*6) 45.43 Takelac W6021 (*7) 53 Lackstar 5215A (*8) 33.61 C: curing DURANATE WM44-L70G 1.5 1.5 1.5 1.5 agent Mycoat775 (*9) D: conductive Printex XE2B 1.66 1.66 1.66 1.66 carbon Titanium JR600-E 12.55 12.55 12.55 12.55 dioxide Pigment Disperbyk 191 0.93 0.93 0.93 0.93 dispersing agent Leveling BYK-348 0.8 0.8 0.8 0.8 agent Thickening Rheovis AS S130 1.1 1.1 1.1 1.1 agent Deionized water 20.71 15.03 7.46 26.85 Total 100 100 100 100 A: polyolefin melting point ( C.) 80 80 80 80 resin Weight average 120,000 120,000 120,000 120,000 molecular weight B: polyurethane Glass transition 49 86 86 60 resin temperature ( C.) Elongation rate (%) 530 650 750 250 A/B 28/72 30/70 28/72 28/72 C/(A + B) 5/100 5/100 5/100 5/100 D/(A + B + C) 7/93 7/93 7/93 7/93 Water-based primer coating composition WP-10 WP-11 WP-12 WP-13 A: polyolefin Aqueous dispersion 21 14.8 24.67 29.6 resin of non-chlorinated polyolefin resin P-1 B: polyurethane Impranil DLU 26.5 29.6 24.67 22.2 resin Acrit WBR-2181 (*1) Pamarin UA-150 (*2) Ucoat DA-100 (*3) Takelac W6061 (*4) Bayhydrol UH2952/1 (*5) Acrit WBR-2018 (*6) Takelac W6021 (*7) Lackstar 5215A (*8) C: curing DURANATE WM44-L70G 1.5 1.5 1.5 agent Mycoat775 (*9) 2 D: conductive Printex XE2B 1.66 1.66 1.66 1.66 carbon Titanium JR600-E 12.55 12.55 12.55 12.55 dioxide Pigment Disperbyk 191 0.93 0.93 0.93 0.93 dispersing agent Leveling BYK-348 0.8 0.8 0.8 0.8 agent Thickening Rheovis AS S130 1.1 1.1 1.1 1.1 agent Deionized water 33.46 37.06 32.12 29.66 Total 100 100 100 100 A: polyolefin melting point ( C.) 80 80 80 80 resin Weight average 120,000 120,000 120,000 120,000 molecular weight B: polyurethane Glass transition 83 83 83 83 resin temperature ( C.) Elongation rate (%) 800 800 800 800 A/B 28/72 20/80 33/67 40/60 C/(A + B) 6/100 5/100 5/100 5/100 D/(A + B + C) 7/93 7/93 7/93 7/93 Water-based primer coating composition WP-14 WP-15 WP-16 WP-17 A: polyolefin Aqueous dispersion 59.2 62.9 21 21 resin of non-chlorinated polyolefin resin P-1 B: polyurethane Impranil DLU 7.4 5.55 26.5 26.5 resin Acrit WBR-2181 (*1) Pamarin UA-150 (*2) Ucoat DA-100 (*3) Takelac W6061 (*4) Bayhydrol UH2952/1 (*5) Acrit WBR-2018 (*6) Takelac W6021 (*7) Lackstar 5215A (*8) C: curing DURANATE WM44-L70G 1.5 1.5 0.32 3.1 agent Mycoat775 (*9) D: conductive Printex XE2B 1.66 1.66 1.66 1.66 carbon Titanium JR600-E 12.55 12.55 12.55 12.55 dioxide Pigment Disperbyk 191 0.93 0.93 0.93 0.93 dispersing agent Leveling BYK-348 0.8 0.8 0.8 0.8 agent Thickening Rheovis AS S130 1.1 1.1 1.1 1.1 agent Deionized water 14.86 13.01 35.14 32.36 Total 100 100 100 100 A: polyolefin melting point ( C.) 80 80 80 80 resin Weight average 120,000 120,000 120,000 120,000 molecular weight B: polyurethane Glass transition 83 83 83 83 resin temperature ( C.) Elongation rate (%) 800 800 800 800 A/B 80/20 85/15 28/72 28/72 C/(A + B) 5/100 5/100 1/100 10/100 D/(A + B + C) 7/93 7/93 7/93 6/94 Water-based primer coating composition WP-18 WP-19 WP-20 WP-21 A: polyolefin Aqueous dispersion 18.3 21 21 21 resin of non-chlorinated polyolefin resin P-1 B: polyurethane Impranil DLU 21.5 26.5 26.5 26.5 resin Acrit WBR-2181 (*1) Pamarin UA-150 (*2) Ucoat DA-100 (*3) Takelac W6061 (*4) Bayhydrol UH2952/1 (*5) Acrit WBR-2018 (*6) Takelac W6021 (*7) Lackstar 5215A (*8) C: curing DURANATE WM44-L70G 7.8 1.5 1.5 1.5 agent Mycoat775 (*9) D: conductive Printex XE2B 1.66 0.47 3.21 5 carbon Titanium JR600-E 12.55 3.55 24.27 37.65 dioxide Pigment Disperbyk 191 0.93 0.26 1.8 2.5 dispersing agent Leveling BYK-348 0.8 0.8 0.8 0.8 agent Thickening Rheovis AS S130 1.1 1.1 1.1 1.1 agent Deionized water 25.95 44.82 19.82 3.95 Total 90.59 100 100 100 A: polyolefin melting point ( C.) 80 80 80 80 resin Weight average 120,000 120,000 120,000 120,000 molecular weight B: polyurethane Glass transition 83 83 83 83 resin temperature ( C.) Elongation rate (%) 800 800 800 800 A/B 28/72 28/72 28/72 28/72 C/(A + B) 30/100 5/100 5/100 5/100 D/(A + B + C) 7/93 2/98 12/88 18/82 Various combinations of components shown in detail in Table 1 are described below. (*1) Acrit WBR-2181 (Taisei Fine Chemical Co., Ltd., solid resin content 33%, Tg-89 C., elongation rate 700%) (*2) Permarin UA-150 Sanyo Chemical Industries, Ltd., solid resin content 30%, Tg-87 C., elongation rate 600%) (*3) Ucoat DA-100 (Sanyo Chemical Industries, Ltd., solid resin content 35%, Tg-80 C., elongation rate 500%) (*4) Takelac W6061 (Mitsui Chemicals Ltd., solid resin content 30%, Tg-78 C., elongation rate 1000%) (*5) Bayhydrol UH2952/1 (Covestro Japan Ltd., solid resin content 40%, Tg-49 C., elongation rate 530%) (*6) Acrit WBR-2018 (Taisei Fine Chemical Co., Ltd., solid resin content 32.5%, Tg-86 C., elongation rate 660%) (*7) Takelac WS6021 (Mitsui Chemicals Ltd., solid resin content 30%, Tg-86 C., elongation rate 750%) (*8) Lackstar 5215A (DIC KK, solid resin content 47.3%, Tg-60 C., elongation rate 250%) (*9) Mycoat 775 (melamine resin, Allnex Japan KK, solid resin content 70%)

Production Example 4: Production of Polyester Resin Varnish PA-1

[0128] 54.0 Parts of dimer acid (tradename EMPOL 1008, Cognis KK, 36 carbon atoms), 8.0 parts of neopentyl glycol, 17.8 parts of isophthalic acid, 19.4 parts of 1,6-hexane diol, and 0.8 parts of trimethylolpropane were charged in a reaction vessel equipped with a reflux condensing tube, to which a reaction water separation tube was fitted, a nitrogen gas introduction device, a thermometer, and a stirring device, this heated to 120 C. so as to dissolve the raw materials and then heated to 160 C. while stirring. After maintaining a temperature of 160 C. for 1 hour, it was gradually heated to 230 C. over 5 hours. The temperature was maintained at 230 C. and the reaction continued, when the acid value of the resin reached 4 mg KOH/g the temperature was reduced to 80 C. or lower and 31.6 parts of methyl ethyl ketone were added to produce a polyester resin varnish PA-1 having characteristic values of a solid resin content of 74.6%, a hydroxyl group value of 62 mg KOH/g, an acid value of 4 mg KOH/g and a number average molecular weight of 1,800.

Production Example 5: Production of Polyurethane Resin WB-1

[0129] 78.3 Parts polyester resin solution PA-1, 7.8 parts dimethylolpropionic acid, 1.4 parts neopentyl glycol, and 40.0 parts methylethyl ketone were charge into a reactor fitted with a nitrogen gas delivery apparatus, a thermometer, and stirring apparatus, and after heating to 80 C. with stirring, 27.6 parts isophorone diisocyanate was added and reacted while keeping the components at 80 C. When the isocyanate value was 0.43 meq/g, 4.8 parts trimethylolpropane was added and the reaction was allowed to continue at 80 C. Then, when the isocyanate value was 0.01 meq/g, 33.3 parts butyl cellosolve was added to terminate the reaction. Subsequently, it was heated to 100 C. and methylethyl ketone was removed under reduced pressure. The temperature was reduced to 50 C., 4.4 parts of dimethylethanolamine was added to neutralize the acid groups, 147.9 parts deionized water was then added to produce a polyurethane resin (WB-1) having characteristic values of a solid resin content of 35.0%, a hydroxyl group value of 40 mg KOH/g, an acid value of 35 mg KOH/g, and a number average molecular weight of 4,900.

Production Example 6: Production of Core/Shell-Type Emulsion WC-1

[0130] 46.4 Parts polyurethane resin WB-1 and 33.1 parts de-ionized water were charged into a reactor fitted with nitrogen gas delivery apparatus, a thermometer, dropping funnel, and stirring apparatus, and after heating to 85 C. with stirring, a homogenous mixture of 4.9 parts styrene, 4.5 parts methyl methacrylate, 3.9 parts n-butyl acrylate, 3.0 parts 2-hydroxyethylmethacrylate, 3.8 parts propylene glycol monomethyl ether, and 0.24 parts the polymerization initiator t-butylperoxy-2-ethylhexanoate which was added dropwise at a constant rate over a period of 3.5 hours using the dropping funnel. Following completion of dropwise addition, the temperature was maintained at 85 C. for 1 hour, after which a polymerization initiator solution obtained by dissolving 0.03 parts of the polymerization initiator t-butylperoxy-2-ethylhexanoate in 0.14 parts of propylene glycol monomethyl ether was added as an additional catalyst, and after maintaining the temperature at 85 C. for a further 1 hour, the reaction was terminated to obtain a core/shell-type emulsion resin (WC-1) having a resin solid content of 32.5%. The hydroxyl group value of the core portion acrylic resin was 80 mg KOH/g and the acid value was 0 mg KOH/g.

Production Example 7: Production of 1st Water-Based Coloring Coating Composition WD-1

[0131] Using the water-based polyurethane resin WB-1 as a dispersion resin, 33.8 parts titanium dioxide (tradename TiPure R706, DuPont KK) and 0.4 parts carbon black (tradename MA-100, Mitsubishi Chemicals KK) were dispersed in a motor mill and a pigment paste was produced. Then, 25.5 parts core/shell-type emulsion WC-1 and 5.9 parts water-based polyurethane resin WB-1 and water-based acrylic resin (tradename SETAQUA6511, Nuplex Resins KK, acid value 8 mg KOH/g, hydroxyl group value 138 mg KOH/g, glass transition temperature 12 C., solid resin content 47%) were mixed in a dissolver and, after the resin base was prepared, the pigment paste created earlier was added and mixed. Finally, 6.6 parts polyisocyanate (tradename Bayhydur 3100, Sumika Bayer Urethane Co., Ltd., solid resin content 100%) was added and mixed to obtain the 1st water-based coloring coating composition WD-1. The content of water-based polyurethane resin WB-1 in the 1st water-based coloring coating composition WD-1 was set at 47.4 parts.

Production Example 8: Production of WD-2 1st Water-Based Coloring Coating Composition

[0132] The 1st water-based coloring coating composition WD-2 was obtained using the same method as in production example 7 based on combinations shown in Table 2.

TABLE-US-00002 TABLE 2 1st Water-based coloring coating composition WD-1 WD-2 Core/shell type emulsion WC-1 (solid resin content 25.5 25.5 32.5%) Water-based polyurethane resin WB-1 (solid resin 47.4 47.4 content 35.0%) Water-based acrylic resin (solid resin content 5.9 5.9 47.0%) Polyisocyanate (*10) 6.6 Polycarbodiimide (*11) 12.8 Titanium dioxide (*12) 33.8 32.4 Carbon black (*13) 0.4 0.4 Total 119.6 124.4 Core/shell-type emulsion 30% 30% Water-based polyurethane resin 60% 60% Water-based acrylic resin 10% 10% NCO/OH (molar ratio) 1.0 NCN/COOH (molar ratio) 1.0 P/B 1.0 1.0

Production Example 9: Production of WE-1 2nd Water-Based Coloring Coating Composition

[0133] Using water-based polyurethane resin WB-1 as a dispersion resin, 2.5 parts carbon black (tradename: MA-100, Mitsubishi Chemical KK) was dispersed in a motor mill and a pigment paste was prepared.

[0134] Then, 25.5 parts core/shell-type emulsion WC-1 and 5.9 parts water-based polyurethane resin WB-1 and water-based acrylic resin (tradename SETAQUA6511, Nuplex Resins KK, acid value 8 mg KOH/g, hydroxyl group value 138 mg KOH/g, glass transition temperature 12 C., solid resin content 47%) were mixed in a dissolver and, after the resin base was prepared, the pigment paste created earlier was added and mixed.

[0135] Finally, 6.6 parts of polyisocyanate (trade name: Bayhydur 3100, Sumika Bayer Urethane Co., Ltd., resin solid content 100%) was added and mixed and the 2nd water-based coloring coating composition WE-1 was obtained. The amount of water-based polyurethane resin WB-1 in the 2nd water-based coloring coating composition WE-1 was set at 47.4 parts.

Production Example 10: Production of WE-2 and WE-3 2nd Water-Based Coloring Coating Compositions

[0136] 2nd Water-based coloring coating compositions WE-2 and WE-3 were obtained using the same method as in production example 8 based on combinations shown in Table 3.

TABLE-US-00003 TABLE 3 2nd Water-based coloring coating composition WE-1 WE-2 WE-3 Core/shell type emulsion WC-1 (solid resin content 25.5 25.5 25.5 32.5%) Water-based polyurethane resin WB-1 (solid resin 47.4 47.4 47.4 content 35.0%) Water-based acrylic resin (solid resin content 5.9 5.9 5.9 47.0%) Polyisocyanate (*10) 6.6 Polycarbodiimide compound (*11) 12.8 Carbon black (*13) 2.5 2.4 2.1 Total 87.9 94.0 80.9 Core/shell type emulsion 30% 30% 30% Water-based polyurethane resin 60% 60% 60% Water-based acrylic resin 10% 10% 10% NCO/OH (molar ratio) 1.0 NCN/COOH (molar ratio) 1.0 P/B 0.1 0.1 0.1

[0137] Various combinations of components shown in in Tables 2-3 are described in detail below.

(*10) Polyisocyanate (trade name: Bayhydur 3100, Sumika Bayer Urethane Co., Ltd.)
(*11) Polycarbodiimide (trade name: Carbodilite V-02-L2, Nisshinbo Chemical Co., Ltd.)
(*12) Titanium dioxide (trade name: TiPure R706, DuPont Co. Ltd.)
(*13) Carbon black (trade name: MA-100, Mitsubishi Chemical Co. Ltd.)

Production Example 11: Production Example of CC-1 Clear Coating Composition

(i) Production of CA-1 Acrylic Resin Solution for Clear Coating

[0138] 24 Parts propylene glycol monomethyl ether was introduced into a four-necked flask fitted with a thermometer, a reflux condenser, a stirrer, and a dropping funnel and heated while being stirred under a current of nitrogen gas and maintained at 120 C. Next, 9.7 parts styrene, 26.6 parts ethylhexyl methacrylate, 27.3 parts 2-hydroxyethyl methacrylate, and 1.3 parts of the radical polymerizable monomer acrylic acid were mixed at 120 C. to homogeneity to form a monomer dropping component. In addition, 2.4 parts a,a-azobisisobutyronitrile was completely dissolved in 7 parts propylene glycol monomethyl ether with stirring to form an initiator dropping component. The monomer dropping component and the initiator dropping component were added using separate dropping funnels dropwise at a set rate at the same time over 3 hours. After completion of dropping, the same temperature was maintained for 1 hour, a solution prepared by completely dissolving 0.2 parts a,a-azobisisobutyronitrile in 1.5 parts propylene glycol monomethyl ether, as an additional catalyst, was added dropwise divided into several times within 30 minutes. Subsequently, the polymerization reaction was completed when maintained at 120 C. for 1 hour and acrylic resin solution CA-1 was obtained. The solid resin content of acrylic resin CA-1 was 67.5%, the hydroxyl group value was 174 mg KOH/g, the acid value was 10 mg KOH/g, and the weight average molecular weight was 6,000.

(ii) Production of CC-1 Clear Coating Material

[0139] 80 Parts acrylic resin solution CA-1 was charged into a reactor fitted with a stirrer, then 8 parts Solvesso #100 (tradename, Exon Mobil, aromatic naphtha), 3 parts xylene, 0.1 parts BYK-300 (tradename, BYK Chemical, surface regulator, 10 mass % xylene solution), 2.5 parts Tinuvin 292 (tradename, Ciba Specialty Chemicals Inc., photostabilizer, 20 mass % xylene solution), and 5 parts Tinuvin 900 (tradename, Ciba Specialty Chemicals Inc., ultraviolet absorbing agent, 20 mass % xylene solution) were added in succession with stirring and mixed to homogeneity. Next, 1 part Flownon SH-290 (tradename, Kyoeisha Chemical, viscosity adjuster, 10 mass % xylene solution) and 0.4 parts Neostann U-100 (tradename, Johoku Chemical, isocyanate curing catalyst, 1 mass % xylene solution) were added in succession with stirring and sufficiently stirred to form a homogenous mixture. Immediately before use, 40 parts Duranate THA-100 (tradename, Asahi Kasei Corp., HMDI-type isocyanurate-type polyisocyanate curing agent, solid resin content 75%, NCO 23.1 mass %) and 15 parts of a mixture of Solvesso #100/butyl acetate/propylene glycol monomethyl ether (mixing ratio: 60/20/20) to 100 parts the obtained mixture were added with stirring to obtain CC-1 clear coating material.

Example 1

[0140] A cationic electrodeposition coating material (tradename, CathoGuard No. 500, BASF Japan KK) was coated by electrostatic deposition on a zinc phosphate-treated mild steel plate to a thickness after drying of 20 m and then fired for 25 minutes at 175 C. to obtain an electrodeposition coated plate used in the present evaluation (hereinafter referred to as the electrodeposited plate).

[0141] Polypropylene SP-853 with its surface wiped with isopropyl alcohol was used as a plastic material.

[0142] Water-based primer coating material WP-1 was applied to the electrodeposition plate and the polypropylene material to a thickness after drying of 6-8 m. Thereafter, it was kept at room temperature for 5 minutes and the 1st water based coating WD-1 was coated to a thickness after drying of 20 m. Again, it was kept at room temperature for 5 minutes and the 2nd water based coating WE-1 was coated to a thickness after drying of 12 m. After coating, it was left for 5 minutes at room temperature and preheating at 80 C. for 5 minutes was carried out. After allowing the plate to cool to room temperature, a clear coat of coating material CC-1 was coated to a thickness after drying of 30 m. After coating, these were left for 10 minutes at room temperature, fired for 30 minutes at 80 C. to obtain evaluation plates.

[0143] The following coating film performance evaluation was carried out for the obtained evaluation plates.

(Appearance of Coating Film)

[0144] The appearance of the coating film on the obtained evaluation plate was observed visually and evaluated using the following standard.

: smoothness, gloss, vividness all good
: any of the smoothness, gloss, vividness slightly inferior
x: any of the smoothness, gloss, vividness notably inferior

(Adhesion)

[0145] Sections were introduced lengthwise and crosswise onto the obtained evaluation plates with a knife to obtain 100 squares at 2 mm intervals then they were evaluated according to the following standards by the number of squares remaining without coating film peeling when peeled off in one go from adhering cellophane tape.

: No peeling away of the coating film (as squares, 100/100)
: Some peeling away of the coating film (as squares, 95-99/100)
x: Almost all of the coating film peeled away (as squares, 0-94/100)

(Moisture Resistance)

[0146] An obtained evaluation plate was placed in a constant temperature and humidity chamber at 50 C. and 95% humidity and left for 240 hours. Thereafter, the coated plate was removed and abnormalities in appearance and extent of swelling of the coating film were investigated. 2 Hours after removal, adhesion was evaluated after the moisture resistance test using the same method as the abovementioned adhesion evaluation. The coating film appearance after the moisture resistance test were evaluated using the following standards.

: No abnormalities in the coating film.
: Fine bumps in the coating film and slightly abnormal appearance.
x: Coating film swelling and some appearance of abnormalities.

[0147] An evaluation of adhesion after the moisture test was carried out in the same way as the above adhesion evaluation.

(Chipping Resistance)

[0148] A test panel holder was fixed at a right angle to the stone outlet in a Suga Test Instruments Co., Ltd. flying stone test apparatus JA-400 (chipping test apparatus), 50 g of granite gravel having a particle size of No. 7 was sprayed onto the surface of a multilayer coating film using the sample plates under an air pressure of 0.4 MPa and at 20 C., the extent of appearance of scratches was observed visually and evaluated using the following standards.

: The size of scratches very small and upper coating film a little scratched
: The size of scratches fairly small and the water-based coating materials (product of the present invention) slightly exposed
: The size of scratches fairly small but the underlying steel plate exposed
x: The size of scratches fairly large but the underlying steel plate markedly exposed

Examples 2-21, Comparative Examples 1, 2

[0149] Evaluation plates were prepared using combinations of water-based primer coating composition, 1st water-based coloring coating composition, 2nd water-based coloring coating composition, and clear coating composition disclosed in Table 4-5 using the same method as in example 1 and an evaluation of the coating film performance was carried out. The results of an evaluation of coating film performance are summarized in Table 4-5.

TABLE-US-00004 TABLE 4 Example Example Example Example Example 1 2 3 4 5 Water-based primer coating WP-1 WP-2 WP-3 WP-4 WP-5 composition 1st Water-based coloring coating WD-1 WD-1 WD-1 WD-1 WD-1 composition 2nd Water-based coloring coating WE-1 WE-1 WE-1 WE-1 WE-1 composition Clear coating composition CC-1 CC-1 CC-1 CC-1 CC-1 Water-based primer coating composition A: polyolefin resin melting point 80 80 80 80 80 ( C.) weight average 120,000 120,000 120,000 120,000 120,000 molecular weight B: polyurethane glass 83 89 87 80 78 resin transition temperature ( C.) elongation rate 800 700 600 500 1000 composition A/B 28/72 28/72 28/72 28/72 28/72 C/(A + B) 5/100 5/100 5/100 5/100 5/100 D/(A + B + C) 7/93 7/93 7/93 7/93 7/93 Coating film quality Material: coating film electrodeposition appearance plate adhesion moisture resistance (coating film appearance) moisture resistance (adhesion) chipping resistance Material: coating film polypropylene appearance adhesion moisture resistance (coating film appearance) moisture resistance (adhesion) Example Example Example Example Example Example Example Example 6 7 8 9 10 11 12 13 Water-based primer coating WP-7 WP-8 WP-10 WP-11 WP-12 WP-13 WP-14 WP-15 composition 1st Water-based coloring coating WD-1 WD-1 WD-1 WD-1 WD-1 WD-1 WD-1 WD-1 composition 2nd Water-based coloring coating WE-1 WE-1 WE-1 WE-1 WE-1 WE-1 WE-1 WE-1 composition Clear coating composition CC-1 CC-1 CC-1 CC-1 CC-1 CC-1 CC-1 CC-1 Water-based primer coating composition A: polyolefin resin melting point 80 80 80 80 80 80 80 80 ( C.) weight average 120,000 120,000 120,000 120,000 120,000 120,000 120,000 120,000 molecular weight B: polyurethane g lass 86 86 83 83 83 83 83 83 resin transition temperature ( C.) elongation rate 660 750 800 800 800 800 800 800 composition A/B 30/70 28/72 28/72 20/80 33/67 40/60 80/20 85/15 C/(A + B) 5/100 5/100 6/100 5/100 5/100 5/100 5/100 5/100 D/(A + B + C) 7/93 7/93 7/93 7/93 7/93 7/93 7/93 7/93 Coating film quality Material: coating film electrodeposition appearance plate adhesion moisture resistance (coating film appearance) moisture resistance (adhesion) chipping resistance Material: coating film polypropylene appearance adhesion moisture resistance (coating film appearance) moisture resistance (adhesion) Example Example Example Example Example Example Example Example 14 15 16 17 18 19 20 21 Water-based primer coating WP-16 WP-17 WP-18 WP-19 WP-20 WP-21 WP-1 WP-1 composition 1st Water-based coloring coating WD-1 WD-1 WD-1 WD-1 WD-1 WD-1 WD-1 WD-1 composition 2nd Water-based coloring coating WE-1 WE-1 WE-1 WE-1 WE-1 WE-1 WE-2 WE-3 composition Clear coating composition CC-1 CC-1 CC-1 CC-1 CC-1 CC-1 CC-1 CC-1 Water-based primer coating composition A: polyolefin resin melting point 80 80 80 80 80 80 80 80 ( C.) weight average 120,000 120,000 120,000 120,000 120,000 120,000 120,000 120,000 molecular weight B: polyurethane g lass 83 83 83 83 83 83 83 83 resin transition temperature ( C.) elongation rate 800 800 800 800 800 800 800 800 composition A/B 28/72 28/72 28/72 28/72 28/72 28/72 28/72 28/72 C/(A + B) 1/100 10/100 30/100 5/100 5/100 5/100 5/100 5/100 D/(A + B + C) 7/93 6/94 7/93 2/98 12/88 18/82 7/93 7/93 Coating film quality Material: coating film electrodeposition appearance plate adhesion moisture resistance (coating film appearance) moisture resistance (adhesion) chipping resistance Material: coating film polypropylene appearance adhesion moisture resistance (coating film appearance) moisture resistance (adhesion)