| abstract |
[PROBLEMS] In a coating method by a two-coat one-bake system in which an aqueous basecoat paint is coated, then a clearcoat paint is coated and these two coated films are simultaneously cured, an aqueous basecoat layer and clear The adhesion strength between the coat layers must be increased. [Solution] A coating method using a specific hardening agent in clear coat paint is provided. That is, the curing agent comprises (1) a derivative of 1,6-hexamethylene diisocyanate containing (i) a trimer but not substantially a diisocyanate monomer, and (ii) a reaction of a compound having both active hydrogen and a hydrophilic group Products; (2) the viscosity at 23 ° C is 1,000 mPa · s or less. The compounds having both active hydrogen and hydrophilic groups herein are compounds having an active hydrogen-containing group and a sulfo group represented by the following formula (I), and preferably the sulfo group in the curing agent is neutralized with a tertiary amine. <Formula I> XR-SO 3 H (wherein, X is an amino group, an alkylamino group, a cycloalkylamino group or a hydroxyl group, R is giim aliphatic and / or alicyclic hydrocarbons). |