Multilayer film-forming method and coated article

A method of forming a multilayer coating film comprising the following steps 2-1, 2-2 and 2-3:

• step 2-1:
• a step of coating an article to be coated with a primer coating composition (X) and forming an uncured primer coating film on the article to be coated,
• step 2-2:
• a step of coating the article to be coated having the uncured primer coating film with an aqueous colored coating composition (Y2) for a top coating film, and forming an uncured top coating film thereover,
• step 2-3:
• a step of curing the uncured primer coating film and uncured top coating film by heating them,
• wherein the aqueous colored coating composition (Y2) comprises a hydroxyl-containing resin (A), and a blocked polyisocyanate compound (B) having at least one blocked isocyanate group selected from the group consisting of blocked isocyanate groups represented by the following formula (I):
• wherein R1, R2, R4 and R5 independently represent a C1-12 hydrocarbon group, and R3 represents a C1-12 straight-chain or branched alkylene group,
• blocked isocyanate groups represented by the following formula (II):
• wherein R2, R3, R4 and R5 have the same definitions as above,
• and blocked isocyanate groups represented by the following formula (III):
• wherein R2, R3, R4 and R5 have the same definitions as above, and R6 represents a C1-12 hydrocarbon group.

A method of forming a multilayer coating film comprising the following steps 3-1, 3-2 and 3-3:

• step 3-1:
• a step of coating an article to be coated with an aqueous colored coating composition (Y1) for a base coat and forming an uncured base coat coating film on the article to be coated,
• step 3-2:
• a step of coating the article to be coated having the uncured base coat coating film with an clear coating composition (Z), and forming a clear coating film thereover,
• step 3-3:
• a step of curing the uncured base coat coating film and uncured clear coating film by heating them,
• wherein the aqueous colored coating composition (Y1) comprises a hydroxyl-containing resin (A), and a blocked polyisocyanate compound (B) having at least one blocked isocyanate group selected from the group consisting of blocked isocyanate groups represented by the following formula (I):
• wherein R1, R2, R4 and R5 independently represent a C1-12 hydrocarbon group, and R3 represents a C1-12 straight-chain or branched alkylene group,
• blocked isocyanate groups represented by the following formula (II):
• wherein R2, R3, R4 and R5 have the same definitions as above,
• and blocked isocyanate groups represented by the following formula (III):
• wherein R2, R3, R4 and R5 have the same definitions as above, and R6 represents a C1-12 hydrocarbon group.