| abstract |
(57) [Summary] [Problem] To provide a new water-based surface treatment agent and a surface-treated metal material obtained thereby. SOLUTION: An acrylic resin, water and colloidal silica in an amount of 5 to 35% by mass in terms of solid content are contained, and the acrylic resin is represented by the following general formula (1) (a) in terms of solid content mass. (C) 15 to 76% by mass of a (meth) acrylate unsaturated monomer, (b) 2 to 10% by mass of an α, β-ethylenically unsaturated monomer having a carboxyl group in the molecule, A) 2 to 10% by mass of an α, β-ethylenically unsaturated monomer having a hydroxyl group in the molecule; (E) from 10 to 30% by weight of acrylonitrile and (f) from 0 to 10% by weight of an unsaturated monomer copolymerizable with these monomers. Having a glass transition temperature of 0 to An aqueous surface treatment agent at 30 ° C. is used. Embedded image |