阅读说明：本技术 形成多层涂膜的方法 (Method for forming multilayer coating film ) 是由 本间恭平 中岛久之 八木佑介 仓田祐介 小川刚志 于 2018-04-03 设计创作，主要内容包括：本发明使用各种第二水性底色漆提供一种具有优异的耐崩裂性和光滑度的多层涂膜。本发明是一种形成多层涂膜的方法,其包括依次将第一水性底色漆、第二水性底色漆和清漆施加至待涂覆的物体上,随后同时加热和固化这三层涂膜,其中第一水性底色漆包含玻璃化转变温度为-20℃或更低且重均分子量为30,000-500,000的水溶性或水分散性聚氨酯树脂,以及重均分子量为600或更高的可交联树脂。第一水性底色漆涂膜的断裂强度为2050N/cm<Sup>2</Sup>或更高,-20℃下的损耗正切(tanδ)为0.075或更高。三聚氰胺树脂从第二水性底色漆涂膜层向第一水性底色漆涂膜层的迁移量相对于100质量份的第一水性底色漆的总树脂固含量为3质量份以内。(The present invention provides a multilayer coating film having excellent chipping resistance and smoothness using various second aqueous base paints. The present invention is a method for forming a multilayer coating film, which comprises applying a first aqueous base coat, a second aqueous base coat and a clear coat in this order onto an object to be coated, followed by simultaneously heating and curing the three-layer coating film, wherein the first aqueous base coat comprises a water-soluble or water-dispersible polyurethane resin having a glass transition temperature of-20 ℃ or less and a weight-average molecular weight of 30,000-500,000, and a crosslinkable resin having a weight-average molecular weight of 600 or more. The first aqueous base coat coating film has a breaking strength of 2050N/cm2 or more and a loss tangent (tan. delta.) at-20 ℃ of 0.075 or more. The migration amount of the melamine resin from the second aqueous base coat coating layer to the first aqueous base coat coating layer is within 3 parts by mass relative to 100 parts by mass of the total resin solid content of the first aqueous base coat.)