CHIPPING-RESISTANT TRANSPARENT COATING FILM AND FORMING METHOD THEREFOR

PROBLEM TO BE SOLVED: To prepare a chipping-resistant transparent coating film which allows utilization of the color, as it is, of an underlying formed by applying an environment-friendly water-dispersion-type transparent coating material with a sufficient thickness, is energy-saving by low-temperature drying and readily dried by humidification and achieves sufficient chipping resistance. SOLUTION: The subject method comprises preparing the chipping-resistant transparent coating film by mixing 100 pts.wt. of a urethane dispersion as a water-dispersed resin A with 10 pts.wt. of a polyisocyanate imparted with nonionic hydrophilic groups as a water-dispersible isocyanate B and 1 pt.wt. of a urethane-modified polyether compound as a thickener C, applying the resultant coating material to a film thickness of about 500 μm, drying it at low temperatures between about 50°C and about 60°C for about 10 min and humidifying at humidities of 80%±5% for about 10 min. When the average number of functional groups of B is set to be ≥2.5, and the number (n) of the alkyl group, CnH2n+1, in the side chain to be ≥5, the chipping-resistant transparent coating film obtained is transparent and excellent in the appearance of the coated surface, the adhesion of the over coating, chipping resistance and water whitening resistance. COPYRIGHT: (C)2006,JPO&NCIPI